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Barron, Yonit. "The Delay Time Profile of Multistage Networks with Synchronization". Mathematics 11, n.º 14 (23 de julho de 2023): 3232. http://dx.doi.org/10.3390/math11143232.
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The interaction between projects and servers has grown significantly in complexity; thus, applying parallel calculations increases dramatically. However, it should not be ignored that parallel processing gives rise to synchronization constraints and delays, generating penalty costs that may overshadow the savings obtained from parallel processing. Motivated by this trade-off, this study investigates two special and symmetric systems of split–join structures: (i) parallel structure and (ii) serial structure. In a parallel structure, the project arrives, splits into m parallel groups (subprojects), each comprising n subsequent stages, and ends after all groups are completed. In the serial structure, the project requires synchronization after each stage. Employing a numerical study, we investigates the time profile of the project by focusing on two types of delays: delay due to synchronization overhead (occurring due to the parallel structure), and delay due to overloaded servers (occurring due to the serial structure). In particular, the author studies the effect of the number of stages, the number of groups, and the utilization of the servers on the time profile and performance of the system. Further, this study shows the efficiency of lower and upper bounds for the mean sojourn time. The results show that the added time grows logarithmically with m (parallelism) and linearly with n (seriality) in both structures. However, comparing the two types of split–join structures shows that the synchronization overhead grows logarithmically undr both parallelism and seriality; this yields an unexpected duality property of the added time to the serial system.
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Lee, Jung-Han. "A Novel Meander Split Power/Ground Plane Reducing Crosstalk of Traces Crossing Over". Electronics 8, n.º 9 (17 de setembro de 2019): 1041. http://dx.doi.org/10.3390/electronics8091041.
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In this paper, a novel meander split power/ground plane is proposed for reducing crosstalk between parallel lines crossing over it. The working mechanism of the meander split scheme is investigated by simulations and measurements. The LC equivalent circuit and transmission line model are developed for modeling interactions between the meander split and the signal lines. The proposed meander structure enhances electromagnetic coupling between split planes. The capacitive coupling across the split ensures signal integrity and magnetic coupling between adjacent finger shaped structures suppresses lateral wave propagation along the split gap, which in turn helps suppress the crosstalk. The effectiveness of the meander split remains valid over very wide frequency ranges (up to 9 GHz). Experimental results show that the proposed structure improves the signal quality and reduces the near/far end crosstalk over 30 dB and 50% in the frequency domain and time domain, respectively.
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RAUBER, THOMAS, e GUDULA RÜNGER. "A DATA RE-DISTRIBUTION LIBRARY FOR MULTI-PROCESSOR TASK PROGRAMMING". International Journal of Foundations of Computer Science 17, n.º 02 (abril de 2006): 251–70. http://dx.doi.org/10.1142/s0129054106003814.
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Multiprocessor task (M-task) programming is a suitable parallel programming model for coding application problems with an inherent modular structure. An M-task can be executed on a group of processors of arbitrary size, concurrently to other M-tasks of the same application program. The data of a multiprocessor task program usually include composed data structures, like vectors or arrays. For distributed memory machines or cluster platforms, those composed data structures are distributed within one or more processor groups. Thus, a concise parallel programming model for M-tasks requires a standardized distributed data format for composed data structures. Additionally, functions for data re-distribution with respect to different data distributions and different processor group layouts are needed to glue program parts together. In this paper, we present a data re-distribution library which extends the M-task programming with Tlib, a library providing operations to split processor groups and to map M-tasks to processor groups.
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Zhu, Hong, Song Zhang e Chul Ahn. "Sample size considerations for split-mouth design". Statistical Methods in Medical Research 26, n.º 6 (24 de agosto de 2015): 2543–51. http://dx.doi.org/10.1177/0962280215601137.
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Split-mouth designs are frequently used in dental clinical research, where a mouth is divided into two or more experimental segments that are randomly assigned to different treatments. It has the distinct advantage of removing a lot of inter-subject variability from the estimated treatment effect. Methods of statistical analyses for split-mouth design have been well developed. However, little work is available on sample size consideration at the design phase of a split-mouth trial, although many researchers pointed out that the split-mouth design can only be more efficient than a parallel-group design when within-subject correlation coefficient is substantial. In this paper, we propose to use the generalized estimating equation (GEE) approach to assess treatment effect in split-mouth trials, accounting for correlations among observations. Closed-form sample size formulas are introduced for the split-mouth design with continuous and binary outcomes, assuming exchangeable and “nested exchangeable” correlation structures for outcomes from the same subject. The statistical inference is based on the large sample approximation under the GEE approach. Simulation studies are conducted to investigate the finite-sample performance of the GEE sample size formulas. A dental clinical trial example is presented for illustration.
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Khan, Adeena, Waleed M. S. Fawzy, Syed S. Habib e Mamoona Sultan. "Novel and pragmatic exploration of variation in glottic parameters in non-parallel versus parallel vocal cord CT planes with potential reporting pitfalls". PLOS ONE 18, n.º 10 (30 de outubro de 2023): e0293659. http://dx.doi.org/10.1371/journal.pone.0293659.
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Oblique orientation of vocal cord demands strict compliance, by technicians and clinicians, to the recommended parallel plane CT scan of larynx. Repercussions of non-compliance has never been investigated before. We aimed to observe influence of non-parallel vocal cord plane CT scan on qualitative and quantitative glottic parameters, keeping parallel plane CT as a standard for comparison. Simultaneous identification of potential suboptimal imaging sequelae as a result of unformatted CT plane was also identified. In this study we included 95 normal adult glottides and retrospectively analyzed their anatomy in two axial planes, non-parallel plane ① and parallel to vocal cord plane ②. Qualitative (shape, structures at glottic level) and quantitative (anterior commissure ACom, vocal cord width VCw, anteroposterior AP, transverse Tr, cross-sectional area CSA) glottic variables were recorded. Multivariate statistical analysis was used to predict pattern and their impact on glottic anatomy. Plane ① displayed supraglottic features in glottis; adipose (90.5%) and split thyroid laminae (70.6%). Other categorical variables: atypical shape, submental structures and multilevel vertebral crossing were also in majority. All glottic dimensions varied significantly between two planes with most in ACom (-5.8mm) and CSA (-15.0 mm2). In contrast, plane ② manifested higher VCw (>73%), Tr (66.3%), CSA (64.2%) and AP (44.2%) measurements. On correlation analysis, variation in ACom, CSA, Tr was positively associated with VC or plane obliquity (p<0.05). This variability was more in obese and short necked subjects. Change in one parameter also modified other significantly i.e., ACom versus AP and CSA versus Tr. Results indicated statistically significant change in subjective and objective anatomical parameters of glottis on non-application of appropriate CT larynx protocol for image analysis hence highlighting importance of image reformation.
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Blelloch, Guy, Daniel Ferizovic e Yihan Sun. "Joinable Parallel Balanced Binary Trees". ACM Transactions on Parallel Computing 9, n.º 2 (30 de junho de 2022): 1–41. http://dx.doi.org/10.1145/3512769.
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In this article, we show how a single function, join , can be used to implement parallel balanced binary search trees ( BSTs ) simply and efficiently. Based on join , our approach applies to multiple balanced tree data structures, and a variety of functions for ordered sets and maps. We describe our technique as an algorithmic framework called join-based algorithms . We show that the join function fully captures what is needed for rebalancing trees for a variety of tree algorithms, as long as the balancing scheme satisfies certain properties, which we refer to as joinable trees. We discuss four balancing schemes that are joinable: AVL trees, red-black trees, weight-balanced trees, and treaps. We present a variety of tree algorithms that apply to joinable trees, including insert , delete , union , intersection , difference , split , range , filter , and so on, most of them also parallel. These algorithms are generic across balancing schemes. Many algorithms are optimal in the comparison model, and we provide a general proof to show the efficiency in work for joinable trees. The algorithms are highly parallel, all with polylogarithmic span (parallel dependence). Specifically, the set-set operations union , intersection , and difference have work \( O(m\log (\frac{n}{m}+1)) \) and polylogarithmic span for input set sizes \( n \) and \( m\le n \) . We implemented and tested our algorithms on the four balancing schemes. In general, all four schemes have quite similar performance, but the weight-balanced tree slightly outperforms the others. They have the same speedup characteristics, getting around 73 \( \times \) speedup on 72 cores (144 hyperthreads). Experimental results also show that our implementation outperforms existing parallel implementations, and our sequential version achieves close or much better performance than the sequential merging algorithm in C++ Standard Template Library (STL) on various input sizes.
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Chen, Shuang, Zongqian Shi, Jiajia Sun, Shenli Jia, Mingjie Zhong e Yuxin Ma. "High-throughput particle focusing and separation in split-recombination channel". Journal of Micromechanics and Microengineering 32, n.º 2 (14 de janeiro de 2022): 025007. http://dx.doi.org/10.1088/1361-6439/ac4644.
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Abstract Inertial microfluidic has been widely applied to manipulate particles or bio-sample based on the inertial lift force and Dean Vortices. This technology provides significant advantages over conventional technologies, including simple structure, high throughput and freedom from an external field. Among many inertial microfluidic systems, the straight microchannel is commonly used to produce inertial focusing, which is a phenomenon that particles or cells are aligned and separated based on their size under the influence of inertial lift force. Besides the inertial lift force, flow drag forces induced by the geometrical structures of microchannel can also affect particle focusing. Herein, a split-recombination microchannel, consisting of curved and straight channels, is proposed to focus and separate particles at high flow rate. As compared with the straight channel, the particle focusing in the split-recombination channel is greatly improved, which results from the combined effects of the inertial lift force, the curvature-induced Dean drag force and the structure of split and recombination. Moreover, the distribution of different-sized particles in designed microchannel is investigated. The results indicate that the proposed microchannel not only enhances the particle focusing but also enables the separation of different-sized particles with high throughput. Finally, it is discovered that the larger length of straight channel and curvature radius of curved channel can result in a more efficient particle separation. Another important feature of designed split-recombination microchannel is that it can be arranged in parallel to handle large-volume samples, holding great potential in lab-on-a-chip applications.
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Mosbah, Said, Chemseddine Zebiri, Djamel Sayad, Issa Elfergani, Mohamed Lamine Bouknia, Samira Mekki, Rami Zegadi, Merih Palandoken, Jonathan Rodriguez e Raed A. Abd-Alhameed. "Compact and Highly Sensitive Bended Microwave Liquid Sensor Based on a Metamaterial Complementary Split-Ring Resonator". Applied Sciences 12, n.º 4 (18 de fevereiro de 2022): 2144. http://dx.doi.org/10.3390/app12042144.
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In this paper, we present the design of a compact and highly sensitive microwave sensor based on a metamaterial complementary split-ring resonator (CSRR), for liquid characterization at microwave frequencies. The design consists of a two-port microstrip-fed rectangular patch resonating structure printed on a 20 × 28 mm2 Roger RO3035 substrate with a thickness of 0.75 mm, a relative permittivity of 3.5, and a loss tangent of 0.0015. A CSRR is etched on the ground plane for the purpose of sensor miniaturization. The investigated liquid sample is put in a capillary glass tube lying parallel to the surface of the sensor. The parallel placement of the liquid test tube makes the design twice as efficient as a normal one in terms of sensitivity and Q factor. By bending the proposed structure, further enhancements of the sensor design can be obtained. These changes result in a shift in the resonant frequency and Q factor of the sensor. Hence, we could improve the sensitivity 10-fold compared to the flat structure. Subsequently, two configurations of sensors were designed and tested using CST simulation software, validated using HFSS simulation software, and compared to structures available in the literature, obtaining good agreement. A prototype of the flat configuration was fabricated and experimentally tested. Simulation results were found to be in good agreement with the experiments. The proposed devices exhibit the advantage of exploring multiple rapid and easy measurements using different test tubes, making the measurement faster, easier, and more cost-effective; therefore, the proposed high-sensitivity sensors are ideal candidates for various sensing applications.
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Rashid, Mahmood A., Swakkhar Shatabda, M. A. Hakim Newton, Md Tamjidul Hoque e Abdul Sattar. "A Parallel Framework for Multipoint Spiral Search in ab Initio Protein Structure Prediction". Advances in Bioinformatics 2014 (16 de março de 2014): 1–17. http://dx.doi.org/10.1155/2014/985968.
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Protein structure prediction is computationally a very challenging problem. A large number of existing search algorithms attempt to solve the problem by exploring possible structures and finding the one with the minimum free energy. However, these algorithms perform poorly on large sized proteins due to an astronomically wide search space. In this paper, we present a multipoint spiral search framework that uses parallel processing techniques to expedite exploration by starting from different points. In our approach, a set of random initial solutions are generated and distributed to different threads. We allow each thread to run for a predefined period of time. The improved solutions are stored threadwise. When the threads finish, the solutions are merged together and the duplicates are removed. A selected distinct set of solutions are then split to different threads again. In our ab initio protein structure prediction method, we use the three-dimensional face-centred-cubic lattice for structure-backbone mapping. We use both the low resolution hydrophobic-polar energy model and the high-resolution 20×20 energy model for search guiding. The experimental results show that our new parallel framework significantly improves the results obtained by the state-of-the-art single-point search approaches for both energy models on three-dimensional face-centred-cubic lattice. We also experimentally show the effectiveness of mixing energy models within parallel threads.
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Deng, Xida, Ge Dong, Xuan Dai e Jinxiang Deng. "Compact Full Ka-Band Waveguide Directional Coupler Based on Rectangular Aperture Array with Stairs". Micromachines 12, n.º 7 (25 de junho de 2021): 745. http://dx.doi.org/10.3390/mi12070745.
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This article presents a compact 3 dB waveguide directional coupler with full waveguide bandwidth. It consists of a pair of rectangular waveguides with stairs structures in the coupling region. The waveguides are placed parallel to each other along their broad wall, which has a rectangular aperture array. The compact size, broad bandwidth, good in-band coupling flatness, and good return loss are achieved by using the proposed structure. For verification purposes, a prototype of the proposed coupler was designed, manufactured, and measured. The experimental results show that over the full waveguide bandwidth a return loss of input port better than 17.46 dB, coupling strength varying between −2.74 dB and −3.80 dB, power-split unbalance within 0.76 dB, and an isolation better than 20.82 dB were obtained. The length of the coupling region was only 15.82 mm.
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Mansy, Hussein, Pan-Mei Yang e David R. Williams. "Quantitative measurements of three-dim ensional structures in the wake of a circular cylinder". Journal of Fluid Mechanics 270 (10 de julho de 1994): 277–96. http://dx.doi.org/10.1017/s0022112094004271.
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The fine scale three-dimensional structures usually associated with streamwise vortices in the near wake of a circular cylinder have been studied at Reynolds numbers ranging from 170 to 2200. Spatially continuous velocity measurements along lines parallel to the cylinder axis were obtained with a scanning laser anemometer. To detect the streamwise vortices in the amplitude modulated velocity field, it was necessary to develop a spatial decomposition technique to split the total flow into a primary flow component and a secondary flow component. The primary flow is comprised of the mean flow and Strouhal vortices, while the secondary flow is the result of the three-dimensional streamwise vortices that are the essence of transition to turbulence. The three-dimensional flow amplitude increases in the primary vortex formation region, then saturates shortly after the maximum amplitude in the primary flow is reached. In the near-wake region the wavelength decreases approximately like Re−0.5, but increases with downstream distance. A discontinuous increase in wavelength occurs below Re = 300 suggesting a fundamental change in the character of the three-dimensional flow. At downstream distances (x/D = 10-20), the spanwise wavelength decreases from 1.42D to 1.03D as the Reynolds number increases from 300 to 1200.
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Kraftmakher, G., e V. Butylkin. ""Cut wires grating – single longitudinal wire" planar metastructure to achieve microwave magnetic resonance in a single wire". Advanced Electromagnetics 1, n.º 2 (26 de setembro de 2012): 16. http://dx.doi.org/10.7716/aem.v1i2.14.
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Here we present metastructures containing cut-wire grating and a single longitudinal cut-wire orthogonal to grating’s wires. Experimental investigations at microwaves show these structures can provide strong magnetic resonant response of a single nonmagnetic cut-wire in dependence on configuration and sizes in the case when metastructures are oriented along the direction of wave propagation and cut-wires of grating are parallel to the electric field of a plane electromagnetic wave. It is suggested a concept of magnetic response based on antiparallel resonant currents excited by magnetic field of surface polaritons in many spatial LC-circuits created from cut-wire pairs of a grating and section of longitudinal cut-wire. Three separately observed resonant effects connected with grating, LC-circuits and with longitudinal cut-wire have been identified applying measurements in waveguides, cutoff waveguides and free space. To tune and mark resonance split cut-wires are loaded with varactor diodes.
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Muldarisnur, M., e F. Marlow. "Polarization angular-resolved transmission spectroscopy of opal films". Journal of Nonlinear Optical Physics & Materials 25, n.º 02 (junho de 2016): 1650015. http://dx.doi.org/10.1142/s0218863516500156.
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In this paper, we investigated the angular behavior of light transmission through opal films over a broad range of wavelengths and angles. The opal films were prepared using the capillary deposition method (CDM). The observation of many well-defined diffraction peaks indicates that the CDM results in opal films with high quality. Peaks overlapping at normal incidence split when samples are rotated. The angular shift of these peaks was found to satisfy the kinematical diffraction theory very well. Furthermore, the variation of intensity with incident angle can be interpreted in terms of a simplified dynamical diffraction theory. Moreover, the presence of two differently oriented domains in CDM-made opal films is essential in discussing the measured spectra. These domains can be assigned to parallel microscopic stripes of ABC and ACB type fcc structures. Angular-resolved spectroscopy with polarized incident light shows interesting polarization dependence of light propagation inside opals.
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Wang, Yaqian, e Xiaohong Jiao. "Dual Heuristic Dynamic Programming Based Energy Management Control for Hybrid Electric Vehicles". Energies 15, n.º 9 (28 de abril de 2022): 3235. http://dx.doi.org/10.3390/en15093235.
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This paper investigates an adaptive dynamic programming (ADP)-based energy management control strategy for a series-parallel hybrid electric vehicle (HEV). This strategy can further minimize the equivalent fuel consumption while satisfying the battery level constraints and vehicle power demand. Dual heuristic dynamic programming (DHP) is one of the basic structures of ADP, combining reinforcement learning, dynamic programming (DP) optimization principle, and neural network approximation function, which has higher accuracy with a slightly more complex structure. In this regard, the DHP energy management strategy (EMS) is designed by the backpropagation neural network (BPNN) as an Action network and two Critic networks approximating the control policy and the gradient of value function concerning the state variable. By comparing with the existing results such as HDP-based and rule-based control strategies, the equivalent consumption minimum strategy (ECMS), and reinforcement learning (RL)-based strategy, simulation results verify the robustness of fuel economy and the adaptability of the power-split optimization of the proposed EMS to different driving conditions.
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Miau, J. J., C. R. Chen e J. H. Chou. "A vertically oscillating plate disturbing the development of a boundary layer". Journal of Fluid Mechanics 298 (10 de setembro de 1995): 1–22. http://dx.doi.org/10.1017/s0022112095003211.
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A vertically oscillating plate in a boundary layer regulates the vorticity flux rate with respect to time and displaces the vorticity away from the wall. These phenomena are discussed for non-dimensional frequencies of the oscillating plate K = 0, 0.006, 0.01 and 0.02. The velocity data obtained by a split-fibre probe near the wall in the region immediately downstream of the oscillating plate lead to a discussion on the behaviour of the flow structures with respect to the non-dimensional frequency. The physical understanding deduced is complementary to the findings of a smoke-wire flow visualization conducted in this study. An integral analysis of the momentum equation indicates that the mean vorticity flux rate of the present flow is composed of contributions from both the parallel shear layer and the curving streamline. This analysis further suggests that the mean vorticity flux rate can be obtained through a combination of pressure measurements at the wall and in the irrotational region of the flow.
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Samelson, R. M. "Lyapunov, Floquet, and singular vectors for baroclinic waves". Nonlinear Processes in Geophysics 8, n.º 6 (31 de dezembro de 2001): 439–48. http://dx.doi.org/10.5194/npg-8-439-2001.
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Abstract. The dynamics of the growth of linear disturbances to a chaotic basic state is analyzed in an asymptotic model of weakly nonlinear, baroclinic wave-mean interaction. In this model, an ordinary differential equation for the wave amplitude is coupled to a partial differential equation for the zonal flow correction. The leading Lyapunov vector is nearly parallel to the leading Floquet vector f1 of the lowest-order unstable periodic orbit over most of the attractor. Departures of the Lyapunov vector from this orientation are primarily rotations of the vector in an approximate tangent plane to the large-scale attractor structure. Exponential growth and decay rates of the Lyapunov vector during individual Poincaré section returns are an order of magnitude larger than the Lyapunov exponent l ≈ 0.016. Relatively large deviations of the Lyapunov vector from parallel to f1 are generally associated with relatively large transient decays. The transient growth and decay of the Lyapunov vector is well described by the transient growth and decay of the leading Floquet vectors of the set of unstable periodic orbits associated with the attractor. Each of these vectors is also nearly parallel to f1. The dynamical splitting of the complete sets of Floquet vectors for the higher-order cycles follows the previous results on the lowest-order cycle, with the vectors divided into wave-dynamical and decaying zonal flow modes. Singular vectors and singular values also generally follow this split. The primary difference between the leading Lyapunov and singular vectors is the contribution of decaying, inviscidly-damped wave-dynamical structures to the singular vectors.
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Liu, Qiang, Baoyan Song e Junlu Wang. "Second-degree branch structure blockchain expansion model". International Journal of Distributed Sensor Networks 18, n.º 3 (março de 2022): 155014772110647. http://dx.doi.org/10.1177/15501477211064755.
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The blockchain runs in a complex topological network which is affected by the principle of consensus, and data storage between nodes needs to maintain global consistency in the entire network, which causes the data storage inefficient. At the same time, the information exchange between large-scale communication node groups leads to the problems of bandwidth expropriation and excessive network load. In response to these problems, this article proposes a second-degree branch structure blockchain expansion model. First, a ternary storage structure is established. Data use the way of fully integrated storage, multi-cell storage, and fully split storage, and data are classified and stored in parallel between the structures. Second, a second-degree branch chain model is constructed. The main chain forks into multiple sub-chains, and a free competition chain structure and a Z-type chain structure are defined; a two-way rotation mechanism is introduced to realize the integration and transition between chain structures. Finally, a set of malicious attacks is simulated to realize the security constraints of the blockchain, to verify the security of the second-degree branch chain model. Experiment shows that the second-degree branch structure expansion model proposed in this article has great advantages in data storage efficiency and network load.
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Geng, Stefan, Andreas Meier e Thomas Schulte. "Model-Based Optimization of a Plug-In Hybrid Electric Powertrain with Multimode Transmission". World Electric Vehicle Journal 9, n.º 1 (13 de junho de 2018): 12. http://dx.doi.org/10.3390/wevj9010012.
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Plug-in hybrid electric vehicles are developed in order to reduce the fuel consumption and the emission of carbon dioxide. Besides the series, parallel and power split configurations are commonly used for conventional hybrid electric vehicles, and multimode transmissions are used for plug-in hybrid electric vehicles, which are able to switch between different modes like parallel or series operation of the combustion engine and electric motor. Several concepts have already been discussed and presented. These concepts comprise novel structures and multi-speed operation for the combustion engine and the electric motor, respectively. For improving the fuel and energy consumption, model-based optimizations of multimode transmissions are performed. In the first step of the optimization, the optimal number of gears and transmission ratios, as well as the corresponding fuel and energy savings, are estimated. Based on these results, a new multimode transmission concept with two-speed transmissions for the combustion engine and the electric motor has been developed. The knowledge of the concrete concept enables the further optimizations of the transmission ratios and the transmission control. In order to prove the benefit of the new and optimized transmission concept, powertrain simulations have been carried out. The new powertrain concept is compared to a powertrain concept with single-speed transmissions for the internal combustion engine (ICE) and electric motor operation. The new transmission concept enables a significant improvement of the fuel consumption.
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Zerbe, Eva-Maria, Oliver Moers, Peter G. Jones e Armand Blaschette. "Zwischenmolekulare Wechselwirkungen in den Kristallstrukturen von 4-Halogenbenzolsulfonamiden (Halogen = Fluor, Chlor, Brom, Iod) und 4-Methylbenzolsulfonamid / Intermolecular Interactions in the Crystal Structures of 4-Halobenzenesulfonamides (Halogen = Fluorine, Chlorine, Bromine, Iodine) and 4-Methylbenzenesulfonamide". Zeitschrift für Naturforschung B 60, n.º 2 (1 de fevereiro de 2005): 125–38. http://dx.doi.org/10.1515/znb-2005-0201.
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Low-temperature single-crystal X-ray structures of the following 4-X-benzenesulfonamides have been studied in order to compare the effects of the 4-substituents on the molecular packings: X = F (1, orthorhombic, Pbca, Z′ = 1, structure previously reported), X = Cl (2, monoclinic, P21/n, Z′ = 1), X = Br (3, isostructural with 2), X = Me (4, isomorphous with 2 and 3, room-temperature structure previously reported, accurate redetermination in this work), X = I (5, monoclinic, Pc, Z′ = 2 molecules with markedly different conformations). As a common feature, the five structures display molecular layers comprising an internal polar lamella of H2NSO2 groups engaged in N-H···O hydrogen bonding, and hydrophobic peripheral regions consisting of the 4-X-substituted phenyl rings. Whereas each molecule in 1 - 4 is linked to four adjacent congeners by ordinary two-centre hydrogen bonds, the sterically demanding iodo substituent in 5 causes all N-H···O interactions to split up into longer N-H(···O)2 three-centre bonds that are used to connect each molecule to six adjacent molecules. Important packing differences between 1 and the other structures appear to emanate from the high electronegativity of fluorine. In 2- 5, the polar lamellae are approximately planar, and the aromatic groups protrude obliquely (2 - 4) or vertically (5) from the lamellae to form translationgenerated parallel stacks separated by broad voids. Contiguous layers are packed via stack-void interlocking, thus creating high packing density and, concomitantly for 2, 3 and 5, interlayer halogen bonds of the type Cl···O, Br···O or I···N, respectively; none of the four structures exhibits π···π stacking interactions between aromatic rings or short halogen-halogen contacts. This simple packing architecture does not hold in the case of 1. Here, the polar lamella adopts a zigzag profile with acute angles of ca. 60°, allowing high packing density to be achieved by intralayer π···π stacking between parallel rows of geometrically convergent aryl rings. The electronegative fluorine atoms, efficiently shielded from the polar lamellae, are segregated into the regions between adjacent layers and form short F···F interlayer contacts about crystallographic centres of inversion.
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Vasilyak, L. M., O. D. Volpyan, A. I. Kuzmichev, Yu A. Obod, V. Ya Pecherkin e P. A. Privalov. "Resonant reflection of plane microwave electromagnetic waves by the linear dielectric-ring structures". Industrial laboratory. Diagnostics of materials 88, n.º 2 (22 de fevereiro de 2022): 49–53. http://dx.doi.org/10.26896/1028-6861-2022-88-2-49-53.
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Artificial materials with negative magnetic and dielectric permittivity have unique electrodynamic properties that are not present in natural materials. We present the results of studying of the main magnetic LC resonance induced by a plane electromagnetic wave of GHz range in the linear structures of subwavelength dielectric ring elements with a high relative permittivity. The dielectric constant of the ring material (capacitor ceramics) is 160. Resonant scattering on the main magnetic mode and wave properties of linear structures consisting of subwavelength dielectric elements in the form of flat thin rings were studied. A single ring or ring structures were arranged in such a way that the vectors of the electric and magnetic fields of a plane incident electromagnetic wave were parallel to the plane of the ring, whereas the wave vector was perpendicular to the plane of the ring. Linear structures consisting of two or three rings were oriented along the magnetic vector of the incident wave. The magnetic field probe was placed on the line of the axis of symmetry of the ring and structures relative to the wave vector at the side of the structures most distant from the antenna. The spectra of transmitted radiation were measured during resonant excitation of magnetic fields in a system of dielectric rings in the near (distance — 2 mm) and remote (distance — 30 mm) zones from the ring. It is shown that in the near wave zone, splitting of the resonant frequency occurs due to mutual inductance and interaction of the rings. As the number of rings increases, the number of additional peaks also increases. A bandwidth of ~200 MHz with an amplitude 25 dB greater than the amplitude of the incident electromagnetic wave in the specified spectrum appears between the split levels. In the far zone, the transmitted radiation at the resonance frequency for a single ring practically does not change due to the splitting of this resonance frequency due to the interaction of the rings in the structure. The results obtained can be used in the development of new materials.
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Godinez, Felipe, Raphael Tomi-Tricot, Bruno Quesson, Matthias Barthel, Gunthard Lykowsky, Greig Scott, Reza Razavi, Joseph Hajnal e Shaihan Malik. "An 8 channel parallel transmit system with current sensor feedback for MRI-guided interventional applications". Physics in Medicine & Biology 66, n.º 21 (1 de novembro de 2021): 21NT05. http://dx.doi.org/10.1088/1361-6560/ac2fbe.
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Abstract Background. Parallel transmit (pTx) has introduced many benefits to magnetic resonance imaging (MRI) with regard to decreased specific absorption rates and improved transmit field homogeneity, of particular importance in applications at higher magnetic field strengths. PTx has also been proposed as a solution to mitigating dangerous RF induced heating of elongated conductive devices such as those used in cardiac interventions. In this work we present a system that can augment a conventional scanner with pTx, in particular for use in interventional MRI for guidewire safety, by adjusting the amplitude and phase of each channel right before the start of the imaging pulses. Methods. The pTx system was designed to work in-line with a 1.5 T MRI while the RF synthesis and imaging control was maintained on the host MR scanner. The add-on pTx system relies on the RF transmit signal, unblanking pulse, and a protocol driven trigger from the scanner. The RF transmit was split into multiple fully modulated transmit signals to drive an array of custom transceiver coils. The performance of the 8-channel implementation was tested with regards to active and real-time control of RF induced currents on a standard guidewire, heating mitigation tests, and anatomical imaging in sheep. Results. The pTx system was intended to update RF shims in real-time and it was demonstrated that the safe RF shim could be determined while the guidewire is moved. The anatomical imaging demonstrated that cardiac anatomy and neighbouring superficial structures could be fully characterized with the pTx system inline. Conclusion. We have presented the design and performance of a real-time feedback control pTx system capable of adding such capabilities to a conventional MRI with the focus of guidewire imaging in cardiac interventional MRI applications.
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Gkantou, Michaela, Magomed Muradov, George S. Kamaris, Khalid Hashim, William Atherton e Patryk Kot. "Novel Electromagnetic Sensors Embedded in Reinforced Concrete Beams for Crack Detection". Sensors 19, n.º 23 (26 de novembro de 2019): 5175. http://dx.doi.org/10.3390/s19235175.
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This paper investigates the possibility of applying novel microwave sensors for crack detection in reinforced concrete structures. Initially, a microstrip patch antenna with a split ring resonator (SRR) structure was designed, simulated and fabricated. To evaluate the sensor’s performance, a series of structural tests were carried out and the sensor responses were monitored. Four reinforced concrete (RC) beam specimens, designed according to the European Standards, were tested under three-point bending. The load was applied incrementally to the beams and the static responses were monitored via the use of a load cell, displacement transducers and crack width gauges (Demec studs). In parallel, signal readings from the microwave sensors, which were employed prior to the casting of the concrete and located along the neutral axis at the mid-span of the beam, were recorded at various load increments. The microwave measurements were analysed and compared with those from crack width gauges. A strong linear relationship between the crack propagation and the electromagnetic signal across the full captured spectrum was found, demonstrating the technique’s capability and its potential for further research, offering a reliable, low-cost option for structural health monitoring (SHM).
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Balić-Žunić, Tonči, Martha G. Pamato e Fabrizio Nestola. "Redetermination and new description of the crystal structure of vanthoffite, Na6Mg(SO4)4". Acta Crystallographica Section E Crystallographic Communications 76, n.º 6 (1 de maio de 2020): 785–89. http://dx.doi.org/10.1107/s2056989020005873.
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The crystal structure of vanthoffite {hexasodium magnesium tetrakis[sulfate(VI)]}, Na6Mg(SO4)4, was solved in the year 1964 on a synthetic sample [Fischer & Hellner (1964). Acta Cryst. 17, 1613]. Here we report a redetermination of its crystal structure on a mineral sample with improved precision. It was refined in the space group P21/c from a crystal originating from Surtsey, Iceland. The unique Mg (site symmetry \overline{1}) and the two S atoms are in usual, only slightly distorted octahedral and tetrahedral coordinations, respectively. The three independent Na atoms are in a distorted octahedral coordination (1×) and distorted 7-coordinations intermediate between a `split octahedron' and a pentagonal bipyramid (2×). [MgO6] coordination polyhedra interchange with one half of the sulfate tetrahedra in <011> chains forming a (100) meshed layer, with dimers formed by edge-sharing [NaO7] polyhedra filling the interchain spaces. The other [NaO7] polyhedra are organized in a parallel layer formed by [010] and [001] chains united through edge sharing and bonds to the remaining half of sulfate groups and to [NaO6] octahedra. The two types of layers interconnect through tight bonding, which explains the lack of morphological characteristics typical of layered structures.
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Abdel-Hakim, Khaled, Tetsuo Nishimura, Michikatsu Takai e Harumi Sakahara. "Review of Monoisocentric Split-Field Technique for Conventional and IMRT Treatment in Head and Neck Cancers: Technical Limitations and Approaches for Optimization". Technology in Cancer Research & Treatment 4, n.º 1 (fevereiro de 2005): 107–13. http://dx.doi.org/10.1177/153303460500400114.
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The importance of treatment planning of head and neck malignancies arises from the necessity to achieve homogenous doses to localized target volume surrounded by normal structures, which can produce acute and long-term morbidity. In many radiotherapy departments, a commonly employed strategy is a 3-field technique. Bilateral parallel-opposed fields are matched to anterior lower neck field. In recent years, Intensity Modulated Radiotherapy (IMRT) is used to radiate head and neck tumors. When the target extends to the lower neck regions, abutment of upper IMRT and lower neck fields is required. Field matching represents a technical challenge for the medical physicist, medical engineer, and radiation oncologist to treat multiple fields while avoiding their overlap on the spinal cord. The monoisocentric split field technique has recently become a common technique to achieve matchline homogenous dose while respecting normal tissue tolerance. The aim of this work is to review merits, limitations, and recent approaches to optimize matchline dose in monoisocentric technique in conventional and intensity modulated radiotherapy for head and neck cancers. Although the technique has many advantages, it is subjected to some systematic and random errors due to equipment and patient setup inaccuracies. To decrease the magnitude of matchline inhomogeneities, customized penumbra generator or multileaf collimator have been used. Both methods are viable and represent alternative approaches to the problem of field matching using the asymmetric jaws.
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Pan, Tao, Yanan Zhang, Hui Wang, Jun Wu, Xing Kang, Lifu Qian, Jinyun Chen, Dingqi Rao, Jianping Jiang e Baowei Zhang. "The reanalysis of biogeography of the Asian tree frog,Rhacophorus(Anura: Rhacophoridae): geographic shifts and climatic change influenced the dispersal process and diversification". PeerJ 5 (21 de novembro de 2017): e3995. http://dx.doi.org/10.7717/peerj.3995.
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Rapid uplifts of the Tibetan Plateau and climate change in Asia are thought to have profoundly modulated the diversification of most of the species distributed throughout Asia. The ranoid tree frog genusRhacophorus, the largest genus in the Rhacophoridae, is widely distributed in Asia and especially speciose in the areas south and east of the Tibetan Plateau. Here, we infer phylogenetic relationships among species and estimate divergence times, asking whether the spatiotemporal characteristics of diversification withinRhacophoruswere related to rapid uplifts of the Tibetan Plateau and concomitant climate change. Phylogenetic analysis recovered distinct lineage structures inRhacophorus, which indicated a clear distribution pattern from Southeast Asia toward East Asia and India. Molecular dating suggests that the first split within the genus date back to the Middle Oligocene (approx. 30 Ma). TheRhacophoruslineage through time (LTT) showed that there were periods of increased speciation rate: 14–12 Ma and 10–4 Ma. In addition, ancestral area reconstructions supported Southeast Asia as the ancestral area ofRhacophorus. According to the results of molecular dating, ancestral area reconstructions and LTT we think the geographic shifts, the staged rapid rises of the Tibetan Plateau with parallel climatic changes and reinforcement of the Asian monsoons (15 Ma, 8 Ma and 4–3 Ma), possibly prompted a burst of diversification inRhacophorus.
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Fonseka, H. Aruni, Yunyan Zhang, James A. Gott, Richard Beanland, Huiyun Liu e Ana M. Sanchez. "Multiple radial phosphorus segregations in GaAsP core-shell nanowires". Nano Research 14, n.º 1 (30 de setembro de 2020): 157–64. http://dx.doi.org/10.1007/s12274-020-3060-x.
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AbstractHighly faceted geometries such as nanowires are prone to form self-formed features, especially those that are driven by segregation. Understanding these features is important in preventing their formation, understanding their effects on nanowire properties, or engineering them for applications. Single elemental segregation lines that run along the radii of the hexagonal cross-section have been a common observation in alloy semiconductor nanowires. Here, in GaAsP nanowires, two additional P rich bands are formed on either side of the primary band, resulting in a total of three segregation bands in the vicinity of three of the alternating radii. These bands are less intense than the primary band and their formation can be attributed to the inclined nanofacets that form in the vicinity of the vertices. The formation of the secondary bands requires a higher composition of P in the shell, and to be grown under conditions that increase the diffusivity difference between As and P. Furthermore, it is observed that the primary band can split into two narrow and parallel bands. This can take place in all six radii, making the cross sections to have up to a maximum of 18 radial segregation bands. With controlled growth, these features could be exploited to assemble multiple different quantum structures in a new dimension (circumferential direction) within nanowires.
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Hatert, Frédéric, Edward S. Grew, Pietro Vignola, Nicola Rotiroti, Fabrizio Nestola, Paul Keller, Maxime Baijot et al. "Crystal chemistry and nomenclature of fillowite-type phosphates". Canadian Mineralogist 59, n.º 4 (1 de julho de 2021): 781–96. http://dx.doi.org/10.3749/canmin.2000043.
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ABSTRACT The crystal chemistries of five samples of minerals belonging to the fillowite group were structurally investigated: (A) fillowite from the Buranga pegmatite, Rwanda; (B) fillowite from the Kabira pegmatite, Uganda; (C) johnsomervilleite from Loch Quoich, Scotland; (D) johnsomervilleite from the Malpensata pegmatite, Italy; and (E) chladniite from the Sapucaia pegmatite, Minas Gerais, Brazil. Their crystal structures were refined in space group R (No. 148), using single-crystal X-ray diffraction data, to R1 values of (A) 3.79%, (B) 3.52%, (C) 4.14%, (D) 4.04%, and (E) 5.59%. Unit-cell parameters are: (A) a = 15.122(1), c = 43.258(4) Å; (B) a = 15.125(1), c = 43.198(3) Å; (C) a = 15.036(2), c = 42.972(9) Å; (D) a = 15.090(2), c = 43.050(9) Å; and (E) a = 15.1416(6), c = 43.123(2) Å. The asymmetric unit contains 15 cation sites with coordinations ranging from V to IX, as well as six P sites. The complex structure can be split into three types of chains running parallel to the c axis. These chains are composed of edge- and face-sharing polyhedra. Detailed cation distributions were determined for all five samples, and their comparison allowed us to establish the general formula A3BC11(PO4)9 for fillowite-type phosphates, where A represents the group of sites mainly occupied by Na, B the Ca sites, and C the sites containing the divalent cations Fe2+, Mn, and Mg. This formula was accepted by the CNMNC, and the four valid mineral species occurring in the fillowite group are fillowite (C = Mn), johnsomervilleite (C = Fe2+), chladniite (C = Mg), and galileiite (B and C = Fe2+). Stornesite-(Y) is discredited, since this mineral corresponds to Y-bearing chladniite.
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Müller, Jens. "Wide Band Measurement of Dielectric Properties of Electronic Assembly Materials Inside an LTCC Fluidic Structure". Journal of Microelectronics and Electronic Packaging 11, n.º 2 (1 de abril de 2014): 64–69. http://dx.doi.org/10.4071/imaps.400.
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Assembly materials such as underfillers or glob top epoxies are typically not specified regarding their dielectric properties for frequencies higher than 1 MHz. However, their behavior should be known for a wider frequency range in order to implement the appropriate parameters for RF and microwave simulations and designs. Typical methods to measure permittivity and loss tangent are based on parallel plate capacitor measurement with an impedance or network analyzer (up to about 1 GHz), S-parameter measurement of filled waveguides, coaxial transmission lines, or resonance methods (e.g., split post resonator, slit cavity resonator, ring resonator, open resonator). Most of these methods require specific sophisticated sample preparation. The paper describes a novel method based on suspended or inverted microstrip evaluation in a 3D LTCC structure. Suspended and inverted microstrip lines have lower insertion losses than standard microstrip lines due to the air gap between the line and the ground plane (reduced dielectric losses). Low loss structures are necessary to be able to measure low loss dielectrics. Such suspended or inverted microstrip lines can be easily achieved in LTCC by implementing a cavity structure. Inlets and outlets allow for the cavity to be filled with fluids after an initial S-parameter measurement of line properties (i.e., impedance, insertion loss, phase velocity). Measuring is repeated once the assembly material is cured. The change in impedance, phase velocity, and insertion contains the information about the material under test. Its properties are derived by curve fitting methods with a 3D electromagnetic field simulator. It is also possible to implement line resonators instead of through lines. In the latter case, the resonant frequency shift and the quality factor contains the material information. The procedure is demonstrated on a multilayer LTCC substrate based on low loss DP 9k7 and a commercial underfill material.
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Müller, Jens. "Wide Band Measurement of Dielectric Properties of Electronic Assembly Materials Inside a LTCC Fluidic Structure". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2013, CICMT (1 de setembro de 2013): 000041–46. http://dx.doi.org/10.4071/cicmt-tp22.
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Assembly materials like underfillers or glob top epoxies are typically not specified regarding their dielectric properties for frequencies higher than 1 MHz. However, their behavior should be known for a wider frequency range in order to implement the right parameters for RF and microwave simulations and designs. Typical methods to measure permittivity and loss tangent are based on parallel plate capacitor measurement with an impedance or network analyzer (up to about 1 GHz), S-parameter measurement of filled wave guides or coaxial transmission lines or resonance methods (e.g. split post resonator, slit cavity resonator, ring resonator, open resonator). Most of these methods require specific sophisticated sample preparation. The paper describes a novel method based on suspended or inverted microstrip evaluation in a 3D LTCC structure. Suspended and inverted microstrip lines have lower insertion losses than standard microstrip lines due to the air gap between the line and the ground plane (reduced dielectric losses). Low loss structures are necessary to be able to measure low loss dielectrics. Such suspended or inverted microstrip lines can be easily achieved in LTCC by implementing a cavity structure. In- and outlets allow filling the cavity with fluids after an initial S-parameter measurement of line properties (impedance, insertion loss, phase velocity). Measuring is repeated once the assembly material is cured. The change in impedance, phase velocity and insertion contains the information about the material under test. Its properties are derived by curve fitting methods with a 3D electromagnetic field simulator. It is also possible to implement line resonators instead of through lines. In the latter case, the resonant frequency shift and the quality factor contains the material information. The procedure is demonstrated on a multilayer LTCC substrate based on low loss DP 9k7 and a commercial underfill material.
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Kovalevsky, V. N., A. V. Mysi e V. I. Sushkova. "Theoretical aspects of block stone blasting method". Gornye nauki i tekhnologii = Mining Science and Technology (Russia) 9, n.º 2 (1 de agosto de 2024): 97–104. http://dx.doi.org/10.17073/2500-0632-2023-12-187.
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Block stone excavation is a key aspect of the building materials industry, important for providing construction with durable materials and when giving aesthetic solutions to various structures and design elements. However, when excavating stone (using drilling and blasting), it is necessary to maintain its integrity for further processing and use. The conditions required for applying the method of blasting separation (split off) of stone blocks from hard rock mass were considered, which is important for improving the quality of blasted stone blocks. The rational parameters of stone block blasting with Granilen elastic tubular charges (Granilen ETCs) are presented. An approach to the preliminary assessment of stone block fracturing zone under various explosive loading regimes was determined. The relationship between the consumption of explosives and fracturing of stone blocks at possible blasthole spacing was considered. The mechanism of creating an extended rupture plane in a rock mass was studied. The decisive role of stress waves in the formation of an extended main rupture along the line of blasthole charges was established. It was shown that it is possible to localize the zone of induced fracturing by regulating the conditions for the interaction of stress waves. The results of numerical modeling of stress fields at blasting a single charge and a two-charge Granilen ETC system are presented, which made it possible to assess zones of induced fracturing and the conditionsfor the formation of a main rupture. Blasting effectiveness increases significantly due to the orientation of the expected stone block separation line parallel to the plane of the best rupture, taking into account the anisotropy of the physical and mechanical properties of granites. The study confirms the feasibility of increasing the yield of commodity blocks when selecting rational blasting parameters.
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English, L. T. P., V. H. Galvan e C. R. Pullinger. "Geological setting of gold-silver mineralization in the La India mining district, Nicaragua". Naturalis Scientias 01, n.º 01 (2024): 41–45. http://dx.doi.org/10.62252/nss.2024.1003.
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La India gold mining district covers a 50 km² area of fault-fill gold-silver mineralized quartz-adularia veins on the western margin of a Tertiary volcanic arc in western Nicaragua. Historic mining records and modern mineral exploration data, which to-date has defined a mineral endowment of over 2.3 Moz gold, provide a wealth of geological information. This paper draws on these observations and data to describe and classify the gold-silver mineralisation at La India, identify the geological controls, and interpret the timing of mineralisation within the regional tectonic setting. The district-scale gold-silver mineralisation at La India occurs in two adjacent geological settings with distinct mineralization characteristics and exploration potential: (1) an upland area of strongly faulted felsic to andesitic volcanics where the historic mine workings are located, and (2) an adjacent downthrown graben, the Sebaco Graben, where a thick sequence of andesite is preserved overlying the felsic volcanic sequence. Gold mineralisation is classified as rift margin-type low-sulphidation epithermal gold-silver fault and fracture-fill vein mineralization. In the historic mining area erosion has exposed the top of the high-grade epithermal zone. Minimal erosion in the Sebaco Graben means that the epithermal system is fully preserved at depth, with localised hydrothermal sinter outcrops, sporadic low-grade mineralised veins and a phreatic breccia pipe exposed at surface. Apart from the one phreatic breccia, the gold-silver mineralisation occurs in quartz veins and breccias that filled brittle faults and associated fractures and fissures which developed in an extensional tectonic setting. The structures containing the gold-silver mineralisation were formed as normal and trans-tensional faults with orientations consistent with southwest-directed extension: (1) a predominant northwest to north-northwest set parallel to the subducting plate; (2) secondary but locally extensive east-west, and (3) tertiary shorter and narrower northeast and north-striking veins. A district-scale north-northwest orientated through-going structure linking the major gold-silver deposits in the historic mining area is interpreted as a deep crustal conduit for the gold-silver bearing hydrothermal fluids. Other, as yet unidentified basement feeder structures may have fed mineralised corridors in the east and west of the district. The gold-silver mineralisation is best developed where structures pass through competent felsic volcanics and welded tuffs in the historic mine area, and also in the overlying andesite flows in the Sebaco Graben. Gold-silver mineralisation is less well developed where the structure passes through less competent unwelded tuffs and volcanic agglomerates. Gold-silver mineralisation is interpreted as occurring shortly before or at 8-10 Ma at the end of a long period of slab-rollback induced extension and arc volcanism. Post-mineralisation block faulting split the La India district into the upthrown, and subsequently eroded historic mine area where epithermal mineralisation is largely exposed at surface, and the well-preserved downthrown blocks such as the Sebaco graben where much of the gold-silver mineralisation is still hidden several hundred metres below surface.
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Stepišnik, Tomaž, e Dragi Kocev. "Semi-supervised oblique predictive clustering trees". PeerJ Computer Science 7 (3 de maio de 2021): e506. http://dx.doi.org/10.7717/peerj-cs.506.
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Semi-supervised learning combines supervised and unsupervised learning approaches to learn predictive models from both labeled and unlabeled data. It is most appropriate for problems where labeled examples are difficult to obtain but unlabeled examples are readily available (e.g., drug repurposing). Semi-supervised predictive clustering trees (SSL-PCTs) are a prominent method for semi-supervised learning that achieves good performance on various predictive modeling tasks, including structured output prediction tasks. The main issue, however, is that the learning time scales quadratically with the number of features. In contrast to axis-parallel trees, which only use individual features to split the data, oblique predictive clustering trees (SPYCTs) use linear combinations of features. This makes the splits more flexible and expressive and often leads to better predictive performance. With a carefully designed criterion function, we can use efficient optimization techniques to learn oblique splits. In this paper, we propose semi-supervised oblique predictive clustering trees (SSL-SPYCTs). We adjust the split learning to take unlabeled examples into account while remaining efficient. The main advantage over SSL-PCTs is that the proposed method scales linearly with the number of features. The experimental evaluation confirms the theoretical computational advantage and shows that SSL-SPYCTs often outperform SSL-PCTs and supervised PCTs both in single-tree setting and ensemble settings. We also show that SSL-SPYCTs are better at producing meaningful feature importance scores than supervised SPYCTs when the amount of labeled data is limited.
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Xu, Tao, Ge Fu, Huai Yuan Tan, Hong Zhang e Xin Ran Liu. "Structured Big Data Management System Supported Cross-Domain Query". Applied Mechanics and Materials 631-632 (setembro de 2014): 1033–38. http://dx.doi.org/10.4028/www.scientific.net/amm.631-632.1033.
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We design a structured big data management system which can deal with large-scale structured datasets and supports the cross-domain collaborative query. The system employs the HDFS as the storage layer. And it realizes a scheduling engine in reference with the splitting technology of the massive parallel processing (MPP) database. Using this engine, tasks can be split and distributed to different sub-nodes for parallel execution. Through cross-domain querymodule, users can execute SQL commands on the datasets of different datacenters or network domains. Meanwhile, the system supports the distributed deployment, so as to reduce the construction cost by making full use of existing software and hardware resources and equipments. We test the system functions and performance on a 80 nodes cluster, and compares with Hive. The result suggested that system performance is improved by 2-3 times than Hive and the function designed can be performed correctly.
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Quenneville, Pierre, Alain Charron e Karl Van Dalen. "Effect of end distance on the resistance of split ring connectors in timber joints loaded in compression". Canadian Journal of Civil Engineering 20, n.º 5 (1 de outubro de 1993): 863–71. http://dx.doi.org/10.1139/l93-112.
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An experimental program was undertaken to verify the end distance requirements in the Canadian standard for engineering design in wood for split ring connectors in joints loaded in compression. In a laboratory study, 48 joints of the Douglas fir-larch species group using 63 mm diameter split rings, 45 joints of the Douglas fir-larch species group using 102 mm diameter split rings, and 51 joints of the spruce-pine-fir species group using 63 mm diameter split rings were loaded to failure in compression. The split ring end distance varied between 50 and 200 mm for joints with 63 mm diameter split rings and between 80 and 220 mm for joints with 102 mm diameter split rings. Tests were also carried out to verify the cleavage strength of the wood and the strength of the wood in compression parallel-to-grain for each of the specimens. Results show that the end distance does not have any significant effect on the resistance of split ring connectors in joints with members loaded in compression. Key words: split ring, compression, end distance, timber, resistance.
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Hayes, Michael J. "Surficial Physical Sedimentary Structures of Bahia la Choya". Paleontological Society Special Publications 2 (1987): 52–61. http://dx.doi.org/10.1017/s247526220000472x.
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I observed and measured the orientations of common physical sedimentary structures on the beach and spit, estero, tidal channel, and inner and outer tidal flats of Bahia la Choya. The spit is characterized by wind ripples and the beach typically displays swash marks. Mudcracks typify the high marsh portions of the estero while the meandering estero channel contains ripples and megaripples. The inner and outer tidal flats are dominated by small, ebb-oriented, straight-crested to undulatory current ripples. The current ripples are often superimposed on flood-oriented ridges and runnels of the outer flat. Rill marks, tool marks, and current crescents occur sporadically. Ebb-oriented megaripples, small current ripples, and primary current lineations occur in the tidal channel.Ripple crests trend from N15E - N40E on the southern tidal flats to N10W - N20W on the northern flats. The crests roughly parallel the shoreline and are normal to tidal currents.
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Mikhalevich, Valeria I. "New insight into the systematics and evolution of the foraminifera". Micropaleontology 59, n.º 6 (2013): 493–527. http://dx.doi.org/10.47894/mpal.59.6.01.
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A new suprageneric classification of the Foraminifera is here presented based on fundamentally new concepts of their evolution and classification. The predominant significance is given to the shell morphology as the most conservative feature, while the wall composition and shell wall ultrastructure are considered as having important but nevertheless subordinate meaning. Foraminifera are regarded as a phylum that includes five classes: Astrorhizata Saidova 1981, Spirillinata Mikhalevich 1992, Miliolata Saidova 1981, Nodosariata Mikhalevich 1992 and Rotaliata Mikhalevich 1980. Each of the five classes unite forms that can be characterized by a complex of common features of their shell morphology reflecting the building plan of the organism (number of chambers, their form, the predominant mode of coiling, position and character of the aperture and its inner structures, the presence or absence of additional apertures, the presence or absence of integrative systems and their peculiarities, and some other features – all of them having evolutionary significance). Each of these classes represents independent and well-outlined phyletic lines. Some characters of the cell structure and nuclear apparatus are also used as taxonomic features of some higher-ranking taxa where the accumulated data permit. Isomorphic agglutinated forms differing from their calacareous analogues in their shell wall composition are separated as subclasses within the appropriate classes: the subclasses Ammodiscana Mikhalevich 1980, Miliamminana Mikhalevich 1980, Hormosinana Mikhalevich 1992, Textulariana Mikhalevich 1980 within the Spirillinata, Miliolata, Nodosariata and Rotaliata correspondingly (the latter also includes two calcareous subclasses – the Rotaliana Mikhalevich 1980 and Globigerinana Mikhalevich 1980).Within the class Astrorhizata, subclasses with organic (Lagynana Mikhalevich 1980) and agglutinated (Astrorhizana Saidova 1981) shell walls are included. In total, the phylum Foraminifera embraces 73 orders, 27 suborders, 98 superfamilies, 499 families and 368 subfamilies among which 2 orders (Cymbaloporida, Cassigerinellida), one suborder Duostominina, two families (Cymbaloporettidae, Haynesinidae), and two subfamilies (Cushmanellinae and Tristixinae) are described as new. The composition of the classes and subclasses is also partially revised. The largest changes were made within the classes Spirillinata, Miliolata and Nodosariata: thus the Fusulinids were included into the Miliolata, the Chapmaninids - into the Spirillinata, the Stilostomellids, Pleurostomellids and Paleozoic Nodosariids – into the Nodosariata. The former suborder Textulariina (= Textulariacea Ehrenberg 1838 sensu lata Loeblich and Tappan 1987) was shown to be heterogenous and its representatives are split out into several subclasses of the different classes according to their shell morphology. The composition of the subclasses is here given up to the family level; most of the subclasses need further revision at the family and generic level. Under the new approach the morphologically similar agglutinated and calcareous shells within each class could be regarded as closely related rather than convergent forms. The rise and development of the classes took place independently and in parallel in each of the phylogenetic lines examined.
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Wang, Mengxiang, Qi Zong e Haibo Wang. "An Experimental Study on Mechanical Properties and Fracture Characteristics of Saturated Concrete under Coupling Effect of Low Temperature and Dynamic Load". Geofluids 2022 (20 de setembro de 2022): 1–13. http://dx.doi.org/10.1155/2022/5201061.
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Concrete is widely used in bridge foundation, water supply, and drainage engineering. On the one hand, the saturated concrete is always in the saturated state. In the cold winter, northeast China and the alpine region suffer from freezing disaster. On the other hand, it has to continue to bear the dynamic load action of vehicles and running water, which makes the stress state of saturated concrete more complicated under the coupling action of low temperature and dynamic load. In order to study the mechanical properties and fracture characteristics of saturated concrete under the coupling effect of low temperature and dynamic load, the impact compression tests of concrete under normal temperature 20°C, -5°C, -10°C, and -15°C were carried out with a diameter of 74 mm split Hopkinson pressure bar (SHPB). The stress-strain characteristics, energy dissipation, and failure modes of specimens under different low temperatures were studied. From a detailed point of view, the failure mechanism of low-temperature water-saturated concrete is expounded. The results show that under the same dynamic load, the dynamic stress-strain curve of saturated concrete changes obviously with the change of low temperature. The dynamic compressive strength of the natural specimen at room temperature is high while that of the water-saturated specimen is low, and the dynamic compressive strength is opposite at low temperature. At the same temperature, the energy time-history curves of concrete in the saturated state are different from those in the natural state, mainly in the plastic section. The energy time-history curves of saturated concrete are different at different temperatures, and the energy dissipation rate of saturated concrete increases linearly with the decrease of temperature. Under the experimental conditions, the dynamic strength of saturated concrete increases linearly with the decrease of temperature, and the peak strain of saturated concrete decreases linearly with the increase of temperature. With the decrease of temperature, the fragmentation of saturated concrete under the impact of the same air pressure gradually increases, and the integrity of the specimen gradually improves. Low temperature can improve the impact resistance of saturated concrete, which is consistent with the failure law of natural state concrete. The water-saturated low-temperature state of the concrete void is filled with ice crystal particles; for low-temperature water-saturated concrete in the impact of the dynamic load, the microstructure is affected by the ice crystal structure which is not easy to change; the specimen along the axial force direction microdefect development produces a crack, the crack along the parallel to the pressure direction of cracking, through the two ends of the specimen, and finally produces axial splitting tensile damage. The research results have important theoretical significance for the safety design of low temperature saturated concrete structures.
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Manasyan, Anahit, e Taron Simonyan. "Legal Symbolism and Constitutional Policy in Contemporary Reality of Changes". Studia Politologiczne, n.º 61/2021 (1 de outubro de 2021): 152–85. http://dx.doi.org/10.33896/spolit.2021.61.8.
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The article tries to bring to the light the role of symbolism in the organized human life, in general, and the contemporary societies with the accelerating changes almost in all social structures, in particular. The rational of symbolism in changing socio-political and legal environment creates complexity of the issue, which has been studied in the article, taking into account the methodology of complex system theory. The interconnectivity and interdependency of law, morality and politics create the picture of synergy of different social norms with each other in changing environment. Their positive synergy is able to create a perception of the ‘ethical state’ – the focal point of equilibrium expressed in the attractor of future admired development. In the legal perspective, the symbol of that attractor appears to be the constitution as the society’s and the nation’s symbol of coexistence based on the values of mutual past, necessary present and admired future. It is substantiated that the Constitution is the phenomenon, representing a concrete constitutional idea and constitutional identity, and should be the one to be considered as such in a lot of people’s minds if we intend to have a proper constitutional system and values. Hence, the Constitution is not just a document with a highest legal force, but also a symbol of a concrete constitutional system, and from this viewpoint the Basic Law has a symbolic significance. The authors substantiate that the mentioned significance of the Constitution makes it clear that constitutional policy in any state should be established and implemented in a manner, obviously demonstrating an attitude towards the Constitution, in the frames of which it is considered as a symbol of a concrete constitutional system. The most important circumstance in this context is to never transform the Constitution (directly or indirectly) from a symbol to an instrument in the hands of both the people and the state power and the whole constitutional policy of the state should be based on the discussed essential idea. Moreover, according to the authors the Constitution should not be subject to amendment parallel to every change of political situation of the state or formation of a new political majority merely conditioned by the mentioned changes. The Constitution has a fundamental role from the aspect of regulating social relations, has symbolic significance and can’t be used just as a tool for solving ongoing political problems.
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Al-Shamarti, Ahlam Dhahir Mohsin. "PLOT AND STRUCTURE IN A CRITICAL EXAMINATION OF "KING LEAR" BY WILLIAM SHAKESPEARE". American Journal Of Social Sciences And Humanity Research 4, n.º 8 (1 de agosto de 2024): 207–28. http://dx.doi.org/10.37547/ajsshr/volume04issue08-16.
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Known for its complicated character interactions and complex narrative, William Shakespeare's tragedy King Lear is the subject of this paper's critical analysis of the play's structure and plot. The analysis centers on the ways in which Shakespeare enhances the play's thematic resonance through the utilization of structural components, subplots, and parallel narratives. Shakespeare explores themes of power, insanity, familial devotion, and human suffering by intertwining King Lear and Gloucester's narratives. The symmetrical split of the play into acts and scenes reflects the fall into anarchy that occurs when Lear's power crumbles. The structural elements are also considered in this analysis, as they add to the dramatic tension by emphasizing the inevitable disaster through the pace of events. Dramatic irony and foreshadowing are also examined in the article; these devices are fundamental to the structural intricacy of the play and help the audience become more invested in the tragedy as it unfolds. Based on what we know now, King Lear's structural aspects are more than just plot devices; they are fundamental to the play's thematic development and provide light on the human condition via Shakespeare's expert use of the plot.
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Rots, Jan G., e Max A. N. Hendriks. "Elastic-Brittle Fraction Model for Robust Post-Peak Analysis of Masonry Structures". Key Engineering Materials 624 (setembro de 2014): 27–39. http://dx.doi.org/10.4028/www.scientific.net/kem.624.27.
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The paper presents a model that splits the material cross section into a number of parallel fractions each of them having a different elastic-perfectly brittle characteristic. The idea is that the summation of all parallel fractions provides an approximation of the overall continuum softening curve. Softening is interpreted as a gradual reduction of the cross-sectional area, which it actually is from a physical point of view. Disorder and heterogeneity are introduced by assigning the fractions i different values of Young’s modulus Ei , strength fi and area Ai such that the overall fracture energy is consumed properly. The model blends well with a scaled sequentially linear solution procedure at global level tracing structural failure via successive snapping/cracking of critical fractions. Examples are included for tension, compression, combined tension-shear and combined tension-compression. The tension-shear case shows the ability of the model to capture a gradually shifting crack orientation. Preliminary structural examples are included in this paper and further results will be presented at the conference. These relate to push-over analysis of Groningen masonry building stock subjected to man-induced earthquakes from gas depletion, a currently serious problem in The Netherlands. The results show an increased robustness and stability of the post-peak response as compared to conventional incremental-iterative procedures.
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Sieder, Raimund, e Reinhard Brandner. "Probabilistic Models for the Tensile Properties of Split Boards and Their Application for the Prediction of Bending Properties of Engineered Timber Products Made of Norway Spruce". Buildings 12, n.º 8 (1 de agosto de 2022): 1143. http://dx.doi.org/10.3390/buildings12081143.
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The main strength and elastic properties of structural timber products, such as glued laminated timber (glulam; GLT) and cross-laminated timber (CLT), are usually described via load-bearing models, which use the tensile properties parallel to the grain of the base material boards and finger joints as input parameters. These load-bearing models assume that the strength-graded boards will retain their full dimensions in the final product. In some applications or use cases, however, the structural timber products are split lengthwise, e.g., split/resawn glulam, or comprise a random share of in width randomly lengthwise split lamellas. As a result of splitting, the material properties assigned to these boards during the grading process in their full cross-sections are no longer valid. Examples of such structural timber products are the novel flex_GLT-beams which are cut out from large dimensional multi-laminated timber panels. In the following paper, the bending properties and system effects of resawn glulam and flex_GLT-beams are described by means of a 3D stochastic-numerical beam model that uses probabilistic models to create the input values for unsplit and split boards as well as finger joints. The models are successfully validated by our own tests and tests from literature and applied in numerous parameter studies.
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Jablonowski, Christiane, Michael Herzog, Joyce E. Penner, Robert C. Oehmke, Quentin F. Stout, Bram van Leer e Kenneth G. Powell. "Block-Structured Adaptive Grids on the Sphere: Advection Experiments". Monthly Weather Review 134, n.º 12 (1 de dezembro de 2006): 3691–713. http://dx.doi.org/10.1175/mwr3223.1.
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Abstract A spherical 2D adaptive mesh refinement (AMR) technique is applied to the so-called Lin–Rood advection algorithm, which is built upon a conservative and oscillation-free finite-volume discretization in flux form. The AMR design is based on two modules: a block-structured data layout and a spherical AMR grid library for parallel computer architectures. The latter defines and manages the adaptive blocks in spherical geometry, provides user interfaces for interpolation routines, and supports the communication and load-balancing aspects for parallel applications. The adaptive grid simulations are guided by user-defined adaptation criteria. Both statically and dynamically adaptive setups that start from a regular block-structured latitude–longitude grid are supported. All blocks are logically rectangular, self-similar, and independent data units that are split into four in the event of refinement requests, thereby doubling the horizontal resolution. Grid coarsenings reverse this refinement principle. Refinement and coarsening levels are constrained so that there is a uniform 2:1 mesh ratio at all fine–coarse-grid interfaces. The adaptive advection model is tested using three standard advection tests with increasing complexity. These include the transport of a cosine bell around the sphere, the advection of a slotted cylinder, and a smooth deformational flow that describes the roll-up of two vortices. The latter two examples exhibit very sharp edges and gradients that challenge not only the numerical scheme but also the AMR approach. The adaptive simulations show that all features of interest are reliably detected and tracked with high-resolution grids. These are steered by either a threshold- or gradient-based adaptation criterion that depends on the characteristics of the advected tracer field. The additional resolution clearly helps preserve the shape and amplitude of the transported tracer while saving computing resources in comparison to uniform-grid model runs.
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Zeng, Yan, Wei Wang, Yong Ding, Jilin Zhang, Yongjian Ren e Guangzheng Yi. "Adaptive Distributed Parallel Training Method for a Deep Learning Model Based on Dynamic Critical Paths of DAG". Mathematics 10, n.º 24 (16 de dezembro de 2022): 4788. http://dx.doi.org/10.3390/math10244788.
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AI provides a new method for massive simulated data calculations in molecular dynamics, materials, and other scientific computing fields. However, the complex structures and large-scale parameters of neural network models make them difficult to develop and train. The automatic parallel technology based on graph algorithms is one of the most promising methods to solve this problem, despite the low efficiency in the design, implementation, and execution of distributed parallel policies for large-scale neural network models. In this paper, we propose an adaptive distributed parallel training method based on the dynamic generation of critical DAG (directed acyclic graph) paths, called FD-DPS, to solve this efficiency problem. Firstly, the proposed model splits operators with the dimension of the tensor, which can expand the space available for model parallelism. Secondly, a dynamic critical path generation method is employed to determine node priority changes in the DAG of the neural network models. Finally, the model implements the optimal scheduling of critical paths based on the priority of the nodes, thereby improving the performance of parallel strategies. Our experiments show that FD-DPS can achieve 12.76% and 11.78% faster training on PnasNet_mobile and ResNet_200 models, respectively, compared with the MP-DPS and Fast methods.
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Saafi, Houssem, Med Amine Laribi e Said Zeghloul. "Design of a 4-DoF (degree of freedom) hybrid-haptic device for laparoscopic surgery". Mechanical Sciences 12, n.º 1 (12 de fevereiro de 2021): 155–64. http://dx.doi.org/10.5194/ms-12-155-2021.
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Abstract. This paper presents a novel kinematics architecture with 4 DoFs (degrees of freedom) intended to be used as a haptic interface for laparoscopic surgery. The proposed architecture is a result of an association of serial and parallel kinematics chains, with each one handling a part of the whole device DoF. The serial chain allows one to handle the translation and self-rotation and the parallel chain handles the two tilt motions, and this in a disjoint way as the natural gesture of the surgeon. The proposed hybrid-haptic device (HH device) benefits from the split DoF to ensure a good kinematic performance, large workspace, as well as gravity compensation. The kinematics study of the HH device is presented and followed by the optimal dimensional synthesis and the gravity compensation model.
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Yang, Guoliang, Jingjiu Bi e Linian Ma. "Dynamic Compression Damage Energy Consumption and Fractal Characteristics of Shale". Shock and Vibration 2019 (23 de setembro de 2019): 1–7. http://dx.doi.org/10.1155/2019/5792841.
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Studying the relationship between energy consumption and crushed size of shale under different loading conditions is the key to efficient shale cracking. The split Hopkinson pressure bar system was used to study the dynamic mechanical properties of shale under parallel- and vertical-bedding loading, and energy dissipation in the impact tests was calculated. Relationships between the average crushed size of shale fracture products and energy dissipation and between the fractal dimension and dissipated energy were studied using fractal theory. The experimental results showed that the dynamic compressive strength of shale under parallel- and vertical-bedding conditions had an obvious positive correlation with the strain rate. Dissipative energy of the shale samples under loading in both directions increased with the increase of strain rate. The increase of the strain rate enhanced crushing of the sample. The vertical-bedding shale samples had stronger ability to absorb energy and more internal crack propagation. Dissipative energies of the shale samples in the parallel- and vertical-bedding impact tests were positively related to the fractal dimension. The fractal dimension increased with the increase of dissipative energy during sample failure; with further increase in the dissipative energy, its effect on the change of fractal dimension gradually weakened.
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Wang, Yanhong, Rui Jiang, Yu (Marco) Nie e Ziyou Gao. "Impact of Information on Topology-Induced Traffic Oscillations". Transportation Science 55, n.º 2 (março de 2021): 475–90. http://dx.doi.org/10.1287/trsc.2020.1032.
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Previous studies have shown traffic oscillations can be induced by special network topology. In the simplest case, a network of two intersections connected by two parallel roads would produce oscillatory traffic, when the split of drivers between the two roads falls into certain range. To understand how traffic information may affect such oscillations, a subset of drivers is allowed to be “reactive” in this study; that is, their route choice varies according to information about prevailing traffic conditions on the roads. We show that, depending on the ratio of reactive drivers, the system displays six new decaying, periodic oscillatory, or stable patterns. All solutions are obtained analytically in closed form and validated by macroscopic traffic simulation. Of all the solutions discovered, only one both is stable and fully utilizes the road space between the two intersections, and hence it is more desirable than the other solutions. The findings reveal the link between information provision and topology-induced oscillations, which may help practitioners design strategies that contribute to mitigating the adverse impact of such oscillations.
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Wang, Lei, Hongming Su, Shiguan Chen e Yue Qin. "Nonlinear Dynamic Constitutive Model of Frozen Sandstone Based on Weibull Distribution". Advances in Civil Engineering 2020 (29 de junho de 2020): 1–10. http://dx.doi.org/10.1155/2020/6439207.
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To obtain the dynamic mechanical properties of frozen sandstone at different temperatures (i.e., 20°C, −10°C, −20°C, and −30°C), dynamic uniaxial compression tests of saturated sandstone are conducted using a split-Hopkinson pressure bar. The experimental results demonstrated that the brittleness of the saturated sandstone increased and its plasticity weakened with a decrease in temperature. The peak strength and dynamic elastic modulus of the sandstone were positively correlated with its strain rate. The peak stress was most sensitive to the strain rate at −10°C, and the elastic modulus was most sensitive to the strain rate at −30°C. According to the evident segmentation characteristics of the obtained stress-strain curve, a viscoelastic dynamic constitutive model considering the strain rate effect and temperature effect is developed; this model combines a nonlinear (or linear) body and a Maxwell body in parallel with a damage body. The applicability of the constitutive model is also verified using experimental data. The fitting results were demonstrated to be in good agreement with the experimental results. Furthermore, the fitting results serve as reference for the study of the constitutive model of weakly cemented soft rock and the construction of roadway freezing methods.
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Anderson, Austin, Petros Potikas e Katerina Potika. "CoDiS: Community Detection via Distributed Seed Set Expansion on Graph Streams". Information 14, n.º 11 (1 de novembro de 2023): 594. http://dx.doi.org/10.3390/info14110594.
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Community detection has been (and remains) a very important topic in several fields. From marketing and social networking to biological studies, community detection plays a key role in advancing research in many different fields. Research on this topic originally looked at classifying nodes into discrete communities (non-overlapping communities) but eventually moved forward to placing nodes in multiple communities (overlapping communities). Unfortunately, community detection has always been a time-inefficient process, and datasets are too large to realistically process them using traditional methods. Because of this, recent methods have turned to parallelism and graph stream models, where the edge list is accessed one edge at a time. However, all these methods, while offering a significant decrease in processing time, still have several shortcomings. We propose a new parallel algorithm called community detection with seed sets (CoDiS), which solves the overlapping community detection problem in graph streams. Initially, some nodes (seed sets) have known community structures, and the aim is to expand these communities by processing one edge at a time. The innovation of our approach is that it splits communities among the parallel computation workers so that each worker is only updating a subset of all the communities. By doing so, we decrease the edge processing throughput and decrease the amount of time each worker spends on each edge. Crucially, we remove the need for every worker to have access to every community. Experimental results show that we are able to gain a significant improvement in running time with no loss of accuracy.
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Richa, Jean Pierre, Jean-Emmanuel Deschaud, François Goulette e Nicolas Dalmasso. "AdaSplats: Adaptive Splatting of Point Clouds for Accurate3D Modeling and Real-Time High-Fidelity LiDAR Simulation". Remote Sensing 14, n.º 24 (10 de dezembro de 2022): 6262. http://dx.doi.org/10.3390/rs14246262.
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LiDAR sensors provide rich 3D information about their surroundings and are becoming increasingly important for autonomous vehicles tasks such as localization, semantic segmentation, object detection, and tracking. Simulation accelerates the testing, validation, and deployment of autonomous vehicles while also reducing cost and eliminating the risks of testing in real-world scenarios. We address the problem of high-fidelity LiDAR simulation and present a pipeline that leverages real-world point clouds acquired by mobile mapping systems. Point-based geometry representations, more specifically splats (2D oriented disks with normals), have proven their ability to accurately model the underlying surface in large point clouds, mainly with uniform density. We introduce an adaptive splat generation method that accurately models the underlying 3D geometry to handle real-world point clouds with variable densities, especially for thin structures. Moreover, we introduce a fast LiDAR sensor simulator, working in the splatted model, that leverages the GPU parallel architecture with an acceleration structure while focusing on efficiently handling large point clouds. We test our LiDAR simulation in real-world conditions, showing qualitative and quantitative results compared to basic splatting and meshing techniques, demonstrating the interest of our modeling technique.
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Bweupe, Arthur S., e Balimu Mwiya. "Quality Management In Ready-Mix Concrete Production In Zambia". Journal of Construction Business and Management 7, n.º 1 (30 de agosto de 2024): 1–15. http://dx.doi.org/10.15641/jcbm.7.1.1508.
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The construction industry, a significant contributor to global economies, is projected to yield substantial economic output by 2030 of around $135 trillion. Central to construction is concrete, a widely used material. Ready-mix concrete (RMC), a specialised form of concrete, is gaining prominence due to its rapid setting and superior quality. In Zambia, the increasing demand for RMC highlights the need for stringent quality management to hedge potential structural risks. This study aimed to determine the quality management in ready-mix concrete production in Zambia. Employing a parallel convergent mixed-methods research design to achieve the objectives, qualitative data was collected through semi-structured interviews and desk study and quantitative data was gathered through a structured questionnaire and an observation checklist. The findings of the study reveal that while guidelines exist, adherence varies. Regulatory bodies for standards, engineering and construction play pivotal roles in overseeing RMC quality. However, their execution faces inconsistencies and challenges due to limited resources and a lack of sense of responsibility. Quality control practices were investigated unveiling variations in forward, immediate, and retrospective control phases. Notable trends in proper storage and equipment calibration showed a commitment to precision. Immediate control practices, encompassing sampling and non-compliance management, demonstrated both positive aspects and areas for improvement. Retrospective control showed commitment to comprehensive strength testing and minimal towards split cylinder testing and on-site slump evaluation. In the realm of quality assurance (QA), RMC facilities show substantial adherence to documented QA standard operating procedures and thorough raw material inspections. However, deficiencies in batching and mixing practices and limited adoption of modern weighing systems require improvement. The study recommends creating an industry association for collaboration, enhancing standardised practices, introducing third-party quality audits, and proposing compulsory RMC standards to boost progress in the Zambian RMC industry. Key Words: Quality Management, Ready Mix Concrete, Observation, Desk Study, Zambia.