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Liu, Shunqing, Xianwen Huang, Aizhao Zhou, Jun Hu i Wei Wang. "Soil-Rock Slope Stability Analysis by Considering the Nonuniformity of Rocks". Mathematical Problems in Engineering 2018 (8.11.2018): 1–15. http://dx.doi.org/10.1155/2018/3121604.
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Soil-rock slopes are widely distributed around the world, while the commonly adopted method by simplifying it as a uniform media tends to be excessively conservative. In this study, a slope stability analysis method considering the nonuniform characteristics of rocks was proposed. It was found that the distribution, relative position, and shape of rock have significant effect on slope stability. For the influence of distribution, large rocks at the foot of slope have the most significant effect on slope stability while the effect is insignificant when the rocks are on the slope surface. In terms of the relative position of rocks, four plastic expansion modes of bypass, diversion, inclusion, and penetration were put forward through the analysis on the expansion mode of the plastic zone. Moreover, rock shape also has influence on slope stability.
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Guo, Jin Quan, Fen Lan Ou, Jian Feng Zhong, Shun Cong Zhong, Xiao Xiang Yang i Li Gang Yao. "Damage Detection of Cantilever Beams Based on Derivatives of Mode Shapes". Applied Mechanics and Materials 488-489 (styczeń 2014): 817–20. http://dx.doi.org/10.4028/www.scientific.net/amm.488-489.817.
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For the small crack detection (crack ration less than 5%), the derivatives of mode shapes of cantilever beams were used for crack detection in the beams. These derivatives consist of the slope, curvature and rate of curvature, which are the first, second and third derivatives of the displacement mode shape respectively. The presence of a crack results in a slight change in the mode shape of a structure which is manifested as a small discontinuity in the response at the crack location. It is hard to detect small cracks in beams using the direct data of mode shape change. But when the first, second and third derivatives of the displacement mode shape, that is the slope, curvature and rate of curvature, respectively, of the cracked cantilever beam provide a progressively better indication of the presence of a crack. However, `noise' effects due to the difference approximation error also begin to be magnified at higher derivatives so that it is not advantageous to go beyond the third derivatives of mode shapes. For the intact beam, these derivatives are smooth curves. So the local peaks or discontinuity on the slope, curvature and rate of curvature modal curves can be used to indicate abnormal mode shape changes at those positions. In this way, these local peak positions can be used to detect and locate cracks in the structure. The modal responses of the damaged and intact cantilever beams used were computed using the finite element method.
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He, Hongjia, Scott A. Banks i Adam H. Biedrzycki. "Anatomical variations of the equine femur and tibia using statistical shape modeling". PLOS ONE 18, nr 6 (30.06.2023): e0287381. http://dx.doi.org/10.1371/journal.pone.0287381.
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The objective of this study was to provide an overarching description of the inter-subject variability of the equine femur and tibia morphology using statistical shape modeling. Fifteen femora and fourteen tibiae were used for building the femur and tibia statistical shape models, respectively. Geometric variations in each mode were explained by biometrics measured on ±3 standard deviation instances generated by the shape models. Approximately 95% of shape variations within the population were described by 6 and 3 modes in the femur and tibia shape models, respectively. In the femur shape model, the first mode of variation was scaling, followed by notable variation in the femoral mechanical-anatomical angle and femoral neck angle in mode 2. Orientation of the femoral trochlear tubercle and femoral version angle were described in mode 3 and mode 4, respectively. In the tibia shape model, the main mode of variation was also scaling. In mode 2 and mode 3, the angles of the coronal tibial plateau and the medial and lateral caudal tibial slope were described, showing the lateral caudal tibial slope angle being significantly larger than the medial. The presented femur and tibia shape models with quantified biometrics, such as femoral version angle and posterior tibial slope, could serve as a baseline for future investigations on correlation between the equine stifle morphology and joint disorders due to altered biomechanics, as well as facilitate the development of novel surgical treatment and implant design. By generating instances matching patient-specific femorotibial joint anatomy with radiographs, the shape model could assist virtual surgical planning and provide clinicians with opportunities to practice on 3D printed models.
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Roy, Koushik. "Structural Damage Identification Using Mode Shape Slope and Curvature". Journal of Engineering Mechanics 143, nr 9 (wrzesień 2017): 04017110. http://dx.doi.org/10.1061/(asce)em.1943-7889.0001305.
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Bazardehi, Sayyed Roohollah Kazemi, i Mohammad Ali Kouchakzadeh. "Detection of delamination in composite laminated plates using filtered mode shapes". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 226, nr 12 (21.03.2012): 2902–11. http://dx.doi.org/10.1177/0954406212442052.
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Filtered mode shapes are used to detect the presence, location, size and shape of the delaminations in composite laminated plates with various boundary conditions. This method is the extension of a previous study by the authors on the delamination detection in the beams using irregularities of the mode shapes. The mode shapes are filtered to separate the smooth and irregular parts. Presence and situation of delamination affects these separated parts, and these effects are used to detect the delamination. Here, two new indicators, named ‘slope of smooth part’ and ‘irregularities in the slope of smooth part’, are introduced to increase the clarity of detected damage and reduce the noisy effects. The former one is obtained by differentiating the smooth part of the mode shape and the latter by applying the filter on the slope of smooth part for another time. Using this method and the mentioned indicators, delaminations may be detected in the plates using the data of just the damaged structure. This is considered as an important advantage of the method as we do not need the intact structure data. The method is validated utilizing the numerical data for a delaminated plate model. This method lacks the ability to locate the position of delamination through the thickness and the delamination should not be too close to the edges of the plate.
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Peng, Pu, Ze Li, Xiaoyan Zhang, Wei Zhang i Wushu Dong. "Efficient Method for Calculating Slope Failure Risk Based on Element Failure Probability". Applied Sciences 13, nr 8 (11.04.2023): 4806. http://dx.doi.org/10.3390/app13084806.
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The finite element method (FEM) and the limit equilibrium method (LEM) are commonly used for calculating slope failure risk. However, the FEM needs to carry out post-processing to estimate slope sliding surface, while the LEM requires assumption of the shape and location of the sliding surface in advance. In this paper, an element failure risk method (EFR) for calculating soil slope failure risk is proposed based on element failure probability (EFP) acquired by plastic limit analysis. The proposed method does not require any assumptions about failure modes. Firstly, the non-common-node triangle element is used to discrete the slope then the random field is generated based on the Cholesky decomposition midpoint method. According to the reliability stochastic programming model and solution strategy, the external overload coefficient, bulk overload coefficient, slope stability coefficient and velocity field of the slope under each random field are obtained, according to which the failure of the element is judged and the failure risk of the slope is calculated. In order to verify the correctness of the proposed method, two classical slopes are systematically analyzed. The research shows that compared with the traditional slope failure risk analysis method, the greatest advantage of the proposed method is that it can capture all failure modes of the slope and greatly simplify the calculation of the slope failure consequences of each failure mode. An efficient upper bound method (UBM) parallel program is prepared, which greatly improves the calculation efficiency.
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Campos, Luiz M. B. C., i Manuel J. S. Silva. "On the Generation of Harmonics by the Non-Linear Buckling of an Elastic Beam". Applied Mechanics 2, nr 2 (15.06.2021): 383–418. http://dx.doi.org/10.3390/applmech2020022.
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The Euler–Bernoulli theory of beams is usually presented in two forms: (i) in the linear case of a small slope using Cartesian coordinates along and normal to the straight undeflected position; and (ii) in the non-linear case of a large slope using curvilinear coordinates along the deflected position, namely, the arc length and angle of inclination. The present paper starts with the exact equation in a third form, that is, (iii) using Cartesian coordinates along and normal to the undeflected position like (i), but allowing exactly the non-linear effects of a large slope like (ii). This third form of the equation of the elastica shows that the exact non-linear shape is a superposition of linear harmonics; thus, the non-linear effects of a large slope are equivalent to the generation of harmonics of a linear solution for a small slope. In conclusion, it is shown that: (i) the critical buckling load is the same in the linear and non-linear cases because it is determined by the fundamental mode; (ii) the buckled shape of the elastica is different in the linear and non-linear cases because non-linearity adds harmonics to the fundamental mode. The non-linear shape of the elastica, for cases when powers of the slope cannot be neglected, is illustrated for the first four buckling modes of cantilever, pinned, and clamped beams with different lengths and amplitudes.
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Qiao, Zhong Liang, Bao Xue Bo, Si Yu Zhang, Xin Gao, Peng Lu, Hui Li, Yi Qu i Guo Jun Liu. "808 nm Semiconductor Lasers with Tailored Gain for Mode Shape". Applied Mechanics and Materials 84-85 (sierpień 2011): 603–6. http://dx.doi.org/10.4028/www.scientific.net/amm.84-85.603.
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We implement the concept of the distributed electrode, which allows to improve the modal behavior of lasers and to reduce spatial-hole burning effects by preferentially localizing current injection in the center of the structure, hence discriminating the optical mode. We report the first realization of distributed electrode lasers emitting at 808 nm with the measured full width at half maximum (FWHM) angle of the minimal horizontal angle as 3.8° while the maximum continuous-wave output power is up to 4 W and high slope efficiencies as high as 0.95 W/A.
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Manucharyan, Georgy E., Andrew F. Thompson i Michael A. Spall. "Eddy Memory Mode of Multidecadal Variability in Residual-Mean Ocean Circulations with Application to the Beaufort Gyre". Journal of Physical Oceanography 47, nr 4 (kwiecień 2017): 855–66. http://dx.doi.org/10.1175/jpo-d-16-0194.1.
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AbstractMesoscale eddies shape the Beaufort Gyre response to Ekman pumping, but their transient dynamics are poorly understood. Climate models commonly use the Gent–McWilliams (GM) parameterization, taking the eddy streamfunction to be proportional to an isopycnal slope s and an eddy diffusivity K. This local-in-time parameterization leads to exponential equilibration of currents. Here, an idealized, eddy-resolving Beaufort Gyre model is used to demonstrate that carries a finite memory of past ocean states, violating a key GM assumption. As a consequence, an equilibrating gyre follows a spiral sink trajectory implying the existence of a damped mode of variability—the eddy memory (EM) mode. The EM mode manifests during the spinup as a 15% overshoot in isopycnal slope (2000 km3 freshwater content overshoot) and cannot be explained by the GM parameterization. An improved parameterization is developed, such that is proportional to an effective isopycnal slope , carrying a finite memory γ of past slopes. Introducing eddy memory explains the model results and brings to light an oscillation with a period ≈ 50 yr, where the eddy diffusion time scale TE ~ 10 yr and γ ≈ 6 yr are diagnosed from the eddy-resolving model. The EM mode increases the Ekman-driven gyre variance by γ/TE ≈ 50% ± 15%, a fraction that stays relatively constant despite both time scales decreasing with increased mean forcing. This study suggests that the EM mode is a general property of rotating turbulent flows and highlights the need for better observational constraints on transient eddy field characteristics.
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Barahim, Adnan A., i Khalid A. Al-Suba’i. "Slope Stability Assessment of The Garin Majjed Archeological Village Area, East of Yemen". Thamar University Journal of Natural & Applied Sciences 3, nr 3 (28.01.2023): 39–47. http://dx.doi.org/10.59167/tujnas.v3i3.1281.
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The stability assessment of sedimentary rock slopes of the area surround Garin Majjed archeological village which lay on cuesta shape hill in Wadi Dawa'an - East of Yemen was carried out. All important factors affecting slope stability in the area such as differential weathering, rainfall and runoff, sewage, discontinuities trends and inclinations, slope face orientation, and mechanical properties of rocks and joints filling materials were evaluated. Direct shear test of joints filling materials showed that the friction angle (Φ) values range between 11˚ and 31˚ and cohesion (C) Values between 0.00 and 0.5 MPa. The compressive strength (cσ) values of the nodular limestone rocks is 66 MPa and for shaley marly sandstone it is 12 MPa. It was found that rock fall is the main mode of failure in the area, while secondary toppling and/ or plane sliding are probable to occur. Some remedial measures are proposed to protect the slopes like erect well seal drainage path, supporting the toe of the dip slope and the overhanging parts, as well as grouting of joints by convenient filling material.
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Jiang, Xin, Zhongguo John Ma i Wei-Xin Ren. "Crack Detection from the Slope of the Mode Shape Using Complex Continuous Wavelet Transform". Computer-Aided Civil and Infrastructure Engineering 27, nr 3 (22.09.2011): 187–201. http://dx.doi.org/10.1111/j.1467-8667.2011.00734.x.
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Bonovas, Markos, Kostas Belibassakis i Eugen Rusu. "Multi-DOF WEC Performance in Variable Bathymetry Regions Using a Hybrid 3D BEM and Optimization". Energies 12, nr 11 (1.06.2019): 2108. http://dx.doi.org/10.3390/en12112108.
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In the present work a hybrid boundary element method is used, in conjunction with a coupled mode model and perfectly matched layer model, for obtaining the solution of the propagation/diffraction/radiation problems of floating bodies in variable bathymetry regions. The implemented methodology is free of mild-slope assumptions and restrictions. The present work extends previous results concerning heaving floaters over a region of general bottom topography in the case of generally shaped wave energy converters (WECs) operating in multiple degrees of freedom. Numerical results concerning the details of the wave field and the power output are presented, and the effects of WEC shape on the optimization of power extraction are discussed. It is demonstrated that consideration of heave in combination with pitch oscillation modes leads to a possible increase of the WEC performance.
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Kisley, Michael A., i George L. Gerstein. "The Continuum of Operating Modes for a Passive Model Neuron". Neural Computation 11, nr 5 (1.07.1999): 1139–54. http://dx.doi.org/10.1162/089976699300016386.
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Whether cortical neurons act as coincidence detectors or temporal integrators has implications for the way in which the cortex encodes information—by average firing rate or by precise timing of action potentials. In this study, we examine temporal coding by a simple passive-membrane model neuron responding to a full spectrum of multisynaptic input patterns, from highly coincident to temporally dispersed. The temporal precision of the model's action potentials varies continuously along the spectrum, depends very little on the number of synaptic inputs, and is shown to be tightly correlated with the mean slope of the membrane potential preceding the output spikes. These results are shown to be largely independent of the size of postsynaptic potentials, of random background synaptic activity, and of shape of the correlated multisynaptic input pattern. An experimental test involving membrane potential slope is suggested to help determine the basic operating mode of an observed cortical neuron.
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Klymak, Jody M., Matthew H. Alford, Robert Pinkel, Ren-Chieh Lien, Yung Jang Yang i Tswen-Yung Tang. "The Breaking and Scattering of the Internal Tide on a Continental Slope". Journal of Physical Oceanography 41, nr 5 (1.05.2011): 926–45. http://dx.doi.org/10.1175/2010jpo4500.1.
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Abstract A strong internal tide is generated in the Luzon Strait that radiates westward to impact the continental shelf of the South China Sea. Mooring data in 1500-m depth on the continental slope show a fortnightly averaged incoming tidal flux of 12 kW m−1, and a mooring on a broad plateau on the slope finds a similar flux as an upper bound. Of this, 5.5 kW m−1 is in the diurnal tide and 3.5 kW m−1 is in the semidiurnal tide, with the remainder in higher-frequency motions. Turbulence dissipation may be as high as 3 kW m−1. Local generation is estimated from a linear model to be less than 1 kW m−1. The continental slope is supercritical with respect to the diurnal tide, implying that there may be significant back reflection into the basin. Comparing the low-mode energy of a horizontal standing wave at the mooring to the energy flux indicates that perhaps one-third of the incoming diurnal tidal energy is reflected. Conversely, the slope is subcritical with respect to the semidiurnal tide, and the observed reflection is very weak. A surprising observation is that, despite significant diurnal vertical-mode-2 incident energy flux, this energy did not reflect; most of the reflection was in mode 1. The observations are consistent with a linear scattering model for supercritical topography. Large fractions of incoming energy can reflect depending on both the geometry of the shelfbreak and the phase between the modal components of the incoming flux. If the incident mode-1 and mode-2 waves are in phase at the shelf break, there is substantial transmission onto the shelf; if they are out of phase, there is almost 100% reflection. The observations of the diurnal tide at the site are consistent with the first case: weak reflection, with most of it in mode 1 and almost no reflection in mode 2. The sensitivity of the reflection on the phase between incident components significantly complicates the prediction of reflections from continental shelves. Finally, a somewhat incidental observation is that the shape of the continental slope has large regions that are near critical to the dominant diurnal tide. This implicates the internal tide in shaping of the continental slope.
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Tian, Yang, Dacian Tomus, Aijun Huang i Xinhua Wu. "Melt pool morphology and surface roughness relationship for direct metal laser solidification of Hastelloy X". Rapid Prototyping Journal 26, nr 8 (23.06.2020): 1389–99. http://dx.doi.org/10.1108/rpj-08-2019-0215.
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Purpose Limited research has attempted to reveal the different modes of the melt pool formation in additive manufacturing. This paper aims to study the mechanisms of surface roughness formation, especially on the aspect of melt pool formation which determine the surface profile and consequently significantly influence the surface roughness. Design/methodology/approach In this study, the conditions under which different modes of melt pool formation (conduction mode and keyhole mode) occur for the case of as-fabricated Hastelloy X using direct metal laser solidification (DMLS) are derived and validated experimentally. Top surfaces of uni-directionally built samples under various processing conditions are cut, grinded, polished and etched to reveal their individual melt pool morphologies. Similarly, up-skin (slope angle < 90°) and down-skin (slope angle > 90°) melt pool morphologies are also investigated to compare the differences. Surface tension gradients and resultant Marangoni flow, which dominate the melt flow in the melt pool, is also calculated to help better evaluate the melt pool shape forming. Findings Two types of melt pool formation modes are dominating in DMLS: conduction mode and keyhole mode. Melt pool formed by conduction mode generally has an aspect ratio of 1:2 (depth vs width) and is in elliptical shape. Appropriate selection of scanning laser power and speed are required to maintain a low characteristic length and width ratio to prevent ballings. Melt pool formed by keyhole mode has an aspect ratio of 1:1 or less. High-energy contour promotes formation of key-hole-shaped melt pool which fills the gaps between layers and smoothens the up-skin surface roughness. Low-energy contour scan is necessary for down-skin surface to form small melt pool profiles and achieve low Ra. Originality/value This paper provides valuable insight into the origins of surface quality problem of DMLS, which is a very critical issue for upgrading the process for manufacturing real components. This paper helps promote the understanding of the attributes and capabilities of this rapidly evolving three-dimensional printing technology and allow appropriate control of processing parameters for successful fabrication of components with sound surface quality.
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Kuo, Ting-Tzu, Ying-Chung Chen, Ting-Chang Chang, Kai-Chun Chang, Chien-Hung Yeh, Fong-Min Ciou, Yu-Shan Lin i in. "Abnormal trend in hot carrier degradation with fin profile in short channel FinFET devices at 14 nm node". Semiconductor Science and Technology 37, nr 4 (25.02.2022): 045010. http://dx.doi.org/10.1088/1361-6641/ac557f.
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Abstract This study investigates the impact of fin profiles under hot carrier stress, which defines different base widths: wide-base samples with the smallest slope, medium-base samples, and narrow-base samples with a larger slope. The performance of the narrow samples is better than the medium samples, regardless of transconductance, on-state current, subthreshold swing or drain-induced barrier lowering, demonstrating that the narrow profile samples’ mobility and gate control are better. In long channel devices, the trend of hot carrier degradation (HCD) is in agreement with previous references, and is dependent on the transverse electric field and the fin shapes. However, this trend does not exist for short-channel devices. Positive bias stress and technology computer aided design simulation are applied for investigation and to clarify the reasons for this abnormal HCD trend. Finally, by fitting the multiple vibrational excitation (MVE) mechanism, the slope of the trend lines in the short channel devices are found to indeed match the bending mode. In other words, the disappearance of the general trend between the HCD and fin profiles is caused by the change in the mechanism in the short-channel device. Because the MVE mechanism is independent from the electric field, the narrow profile fin shape more effectively promotes gate control and better performance without affecting the reliability in short channel devices. These results can provide a clear direction for fin shape designers in the future.
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Xue, Gang, i Feng Ge Li. "Study on the Damage Detection of RC Frame Beams Based on the Vibration Mode Slope Change Rate". Advanced Materials Research 163-167 (grudzień 2010): 2868–72. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.2868.
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Based on the mechanism of the relative change rate of mode shape (RD), a new damage identification quantity called the vibration mode slope change rate (RD’) is proposed. The new quantity is analyzed with the fundamental principles of function differential method. Dynamic test is carried on 5 RC frame beams, which are subjected to an increasing static load in the middle to introduce cracks. After each load step, unloading, and an experimental dynamic monitoring is performed on the beam, then reloading to the next step. Modal analysis is carried out on frame beams under each load step, and modal displacements are given, the vibration mode slope change rate graphs of the RC beams are calculated, which can be used to detect multiple-damages. By means of SAP2000, the comparison analyses between RD and RD’ indicate that RD’ can effectively avoid the careless judges and misjudge in the damage identification of frame beams.
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Han, Jae-hyeok, Seongnoh Ahn, Hyungchul Yoon i Jongwon Jung. "Analysis of Dynamic p-y Curve Characteristics According to Mode Shape of Structure Using Shaking Table Tests". Journal of the Korean Society of Hazard Mitigation 21, nr 5 (31.10.2021): 245–50. http://dx.doi.org/10.9798/kosham.2021.21.5.245.
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In the seismic design of pile foundations, a p-y curve representing the nonlinear behavior of the ground considering the dynamic load of the earthquake is required. Recently, p-y curve analyses reflecting the soil-structure interaction have been conducted, but studies on multilayer structures have not been investigated extensively. In this study, the p-y curve characteristics were analyzed, considering the influence of the ground-structure interaction based on the mode shape of the structure (no structure, single-story structure, and three-story structure) through shake table tests. It was found that (1) the bending moment and pile displacement increased with input acceleration, and (2) the maximum soil resistance and pile displacement occurred at the natural frequencies of each structure were observed. In addition, the bending moment, soil resistance, and p-y curve slope were higher in the single-story structure than in the three-story structure. The findings indicate that the seismic design simulated for a single-story structure is conservative.
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Zhu, Shanshan, i Jinlian Hu. "Multi-Modal Contractive Forces of Wools as Actuator". Polymers 12, nr 7 (30.06.2020): 1464. http://dx.doi.org/10.3390/polym12071464.
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Wool has a long history of use in textiles throughout human civilization. Many smart functions such as reversible shape changes to various stimuli have been demonstrated in the last few years. However, the force-related characteristics are still imperfectly recognized, although they are expected to be used as actuators due to their biological origins and broad applications. Herein, we investigated the feasibility of wools in performing actuating ability through its intrinsic structures and fabrication methods. The diverse modes of contractive forces were obtained in wool materials including platform-like, double-peak, and slope-like shapes, where a molecular model was also presented to trace the origins of stress evolution. After that, a polymeric blend was created to modify the wool materials and a dissimilar performance of stress production was achieved, a square stress mode with stable manner and maintenance, for broad applications in a more efficient way. It is believed that these actuating properties extracted from natural hairs have a large potential in current smart applications and lay down new inspiration in designing actuators.
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Wang, Lei, Rongjian Li, Shibin Zhang, Rongjin Li, Weishi Bai i Huiping Xiao. "Function of a Deep-Buried Isolated Trench and Its Effect on Cracking Failure Characteristics of a Slope under Artificial Rainfall". Water 14, nr 7 (31.03.2022): 1123. http://dx.doi.org/10.3390/w14071123.
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When tests are conducted on the field slope under artificial rainfall, because artificial rainfall is often limited to implementation in the mode of local rainfall, there is a boundary constraint effect between the rainfall area and the non-rainfall area, which is manifested in the lateral infiltration of rainwater and the slope deformation retardation of non-rainfall area to the rainfall area. Firstly, a deep-buried isolated trench was proposed to solve these boundary constraints. Then, field cracking tests and the corresponding numerical simulation were conducted under rainfall. In the end, the response of water content and the cracking failure characteristics of the slope were analyzed during rainfall, and the effect of a deep-buried isolated trench on the cracking characteristics of the slope was evaluated. The results indicate that the proposed deep-buried isolated trench measure can effectively eliminate the deformation retardation resulting from the adjacent non-rainfall area so a through-crack parallel to the slope shoulder that extended on both sides of the boundary of the rainfall slope was observed at the slope crest and a cracking failure in the shape of the overall downward cutting was realized. As the crack occurred, the rainwater infiltration further aggravated expansion of depthwise cracks, and a local sliding zone was formed in the upper part of the slope. The deep-buried isolated trench solves the boundary constraints, such as lateral infiltration of rainwater and deformation retardation, and can provide an effective technical measure for the field slope test under artificial rainfall.
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Shimamoto, Akira, Hiroshi Ohkawara, Jeong Hwan Nam i Jai Sug Hawong. "Calculation of Stress Intensity Factor under Mixed Mode Biaxial Tensile Load by Photoelastic Hybrid Method". Key Engineering Materials 452-453 (listopad 2010): 837–40. http://dx.doi.org/10.4028/www.scientific.net/kem.452-453.837.
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In this study, the photoelastic experiment hybrid method was introduced and applied to the fracture problems of the isotropic polycarbonate plate with a central crack under the uniaxial and equibiaxial tensile load. The influences of equibiaxial tensile load on the isochromatic fringes and stress fields, stress intensity factors near the mixed mode crack-tip were investigated. As the results, without relation to the inclined angle of crack, the asymmetric isochromatic fringes around the crack propagation line under uniaxial tensile load has become symmetric and the slope of isochromatic fringe loop has inclined toward crack surface when an equal lateral tensile load was added. Furthermore, the distribution of all stress components have changed from asymmetric shape to symmetric shape, and only the range of compressive stress of σχ/σ0 have changed as compared with the mode I condition under unaxial load with β = 0°. When an equal lateral tensile load was added to uniaxial load, the value of stress intensity factors are little changed when β = 0° but the values of KI /K0 are increased and KII /K0 are become zero, that is, mode I situation when β = 15°~45°.
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Arciprete, Fabrizio, Ernesto Placidi, Rita Magri, Massimo Fanfoni, Adalberto Balzarotti i Fulvia Patella. "Role of As in the Anisotropic Positioning of Self-Assembled InAs Quantum Dots". MRS Proceedings 1551 (2013): 3–9. http://dx.doi.org/10.1557/opl.2013.892.
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ABSTRACTProgress in tailoring the size, shape and positioning of Quantum Dots on the substrate is crucial for their potential applications in new optoelectronic devices for nano-photonics as well as in quantum information and computation. Using Molecular Beam Epitaxy in pulsed deposition mode we demonstrate that the nucleation of InAs Quantum Dots can be selectively guided on the GaAs(001) surface by a suitable choice of the kinetic parameters for the growth of both the GaAs buffer layer and the InAs Quantum Dots. By developing a two-species rate-equation kinetic model we show that the positioning of the Quantum Dots on only one side of mounds of the GaAs buffer can be traced back to the very small As flux gradient between the two mound slopes $\left( {\Delta F_A /F_A \approx 1 - 5\% } \right)$ caused by the proper tilting of the incoming As flux. Such gradient originates, at the relatively high growth-temperature, a net cation flow from one slope of the mound to the other that is responsible for the selective growth.
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Athanassoulis, M. A., i K. Belibassakis. "A novel coupled-mode theory with application to hydroelastic analysis of thick, non-uniform floating bodies over general bathymetry". Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 223, nr 3 (25.06.2009): 419–38. http://dx.doi.org/10.1243/14750902jeme150.
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A new coupled-mode system of horizontal equations is presented for the hydroelastic analysis of large floating bodies or ice sheets of general, finite thickness, lying over variable bathymetry regions. The present method is based on the theory of shear deformable plates (or beams), and is derived by an enhanced representation of the elastic displacement field, containing additional elastic vertical modes and permitting shear strain and stress to vanish on both the upper and lower boundaries of the thick floating plate. This model extends existing third-order plate theories to plates and beams of general shape. The presented coupled-mode system of horizontal differential equations is obtained by means of a variational principle composed of the one-field functional of the elastodynamics in the plate region, and a pressure functional in the water region. The wave potential in the water column is represented by means of a local-mode series expansion containing an additional mode providing the appropriate correction term on the bottom boundary, when the slope is not mild. In the above sense, the proposed method extends previous approaches concerning hydroelastic problems based on thin-plate theory. The focus of this work is on the scattering of linear, coupled, hydroelastic waves propagating through an inhomogeneous sea ice environment, containing ice sheets of variable thickness and a non-mildly-sloped interface. Numerical results are presented in the simple two-dimensional case, showing that the presented approach efficiently models the hydroelastic problem and is able to provide accurate results when only a few terms are used in the expansion. Ideas for extending the proposed method to three dimensions are also discussed.
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Yang, Tong, Yuming Men, Cassandra J. Rutherford i Zhen Zhang. "Static and Dynamic Response of Micropiles Used for Reinforcing Slopes". Applied Sciences 11, nr 14 (8.07.2021): 6341. http://dx.doi.org/10.3390/app11146341.
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To study the static and dynamic response of micropile-reinforced slopes, static model tests and shaking table tests were performed. The failure modes, the pile-slope interaction, the displacement, and the static/dynamic earth pressure distributions were analyzed based on static and dynamic model tests with a prescribed sliding surface. The test results indicated: (1) The micropile failure mode is mainly bending failure under both loading conditions. As far as the damage to the pile body is concerned, under static loading, the rear row piles showed more damage than the middle row piles followed by the front row piles. Under dynamic loading, the damage of the rear row piles was approximately the same as the middle row piles, which was greater than the front row piles; (2) The earth pressures in front of and behind each row of micropiles and the axial force of the pile body distributed triangularly for both loading conditions, with the bending moment of the pile body distributed in an “S” shape; (3) The landslide thrust experienced by the micropiles has a relatively large group effect. The group effect or shear ratio parameters are recommended for each loading case; (4) The interaction between the micropiles and the soil landslide presents evident progressive failure and load transfer between the rows.
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Tang, Xiao Song, Ying Ren Zheng i Jian Ping Xin. "Experimental Study and Numerical Simulation on the Large-Sized Models of Micro Anti-Slide Piles". Advanced Materials Research 919-921 (kwiecień 2014): 670–77. http://dx.doi.org/10.4028/www.scientific.net/amr.919-921.670.
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Micro antislide pile is more and more widely used in the emergent repair of landslide. But systematic and complete understanding about its antislide and failure mechanism is still insufficient; in addition, the theoretical study lags far behind the practical application. Through largesized physical model experiment and numerical simulation, the paper analyses the failure mechanism and failure mode of micro antislide piles in soil slope. The experiment and numerical simulation prove the fine antislide effects of micro piles, which allows large displacement of sliding mass and can delay the collapse of slope effectively, so it is applicable for emergent repair. The deformation of micro antislide pile is “S” shape, which is the tensile failure and shearcompression failure of concrete by bending deformation. At the same time, tensileshear failure happens on the reinforced bars. The largest shear of pile is located on the sliding surface and all the largest bending moment is above the sliding surface. The bending moment on the first row of plies is the largest followed by the third row and that on the second row is the smallest.
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Belibassakis, Kostas, Markos Bonovas i Eugen Rusu. "A Novel Method for Estimating Wave Energy Converter Performance in Variable Bathymetry Regions and Applications". Energies 11, nr 8 (11.08.2018): 2092. http://dx.doi.org/10.3390/en11082092.
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A numerical model is presented for the estimation of Wave Energy Converter (WEC) performance in variable bathymetry regions, taking into account the interaction of the floating units with the bottom topography. The proposed method is based on a coupled-mode model for the propagation of the water waves over the general bottom topography, in combination with a Boundary Element Method for the treatment of the diffraction/radiation problems and the evaluation of the flow details on the local scale of the energy absorbers. An important feature of the present method is that it is free of mild bottom slope assumptions and restrictions and it is able to resolve the 3D wave field all over the water column, in variable bathymetry regions including the interactions of floating bodies of general shape. Numerical results are presented concerning the wave field and the power output of a single device in inhomogeneous environment, focusing on the effect of the shape of the floater. Extensions of the method to treat the WEC arrays in variable bathymetry regions are also presented and discussed.
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Chen, Li Hua, Yue Sun i Wei Zhang. "Study of Vibration Characteristics of Cantilever Rectangular Plate with Side Crack". Applied Mechanics and Materials 226-228 (listopad 2012): 113–18. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.113.
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In this paper, the vibration characteristics of the cantilever rectangular plate with side crack are studied in the way of analysis, which including natural frequency and mode shape. The influences of different parameters of crack, such as the locations and lengths of crack, to the vibration characteristics of the cantilever rectangular plate are investigated. The modal function of the crack plate consists two parts, which are (1) the modal function of intact cantilever rectangular plate from beam functions combination method and (2) corner functions presenting the discontinuity of displacement and slope along the crack. The natural frequencies and modal shapes can be obtained when taking the modal function into the method of Ritz. At last, the effects of the crack location and crack length on the vibration characteristics are investigated, and it could provide the theoretical basis for engineering application and the relevant study.
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van Hateren, Johannes Albert, Unze van Buuren, Sebastiaan Martinus Arens, Ronald Theodorus van Balen i Maarten Arnoud Prins. "Identifying sediment transport mechanisms from grain size–shape distributions, applied to aeolian sediments". Earth Surface Dynamics 8, nr 2 (12.06.2020): 527–53. http://dx.doi.org/10.5194/esurf-8-527-2020.
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Abstract. The way in which sediment is transported (creep, saltation, suspension), is traditionally interpreted from grain size distribution characteristics. However, the grain size range associated with transitions from one transport mode to the other is highly variable because it depends on the amount of transport energy available. In this study we present a novel methodology for determination of the sediment transport mode based on grain size and shape data from dynamic image analysis. The data are integrated into grain size–shape distributions, and primary components are determined using endmember modelling. In real-world datasets, primary components can be interpreted in terms of different transport mechanisms and/or sediment sources. Accuracy of the method is assessed using artificial datasets with known primary components that are mixed in known proportions. The results show that the proposed technique accurately identifies primary components, with the exception of those primary components that only form minor contributions to the samples (highly mixed components). The new method is tested on sediment samples from an active aeolian system in the Dutch coastal dunes. Aeolian transport processes and geomorphology of these type of systems are well known and can therefore be linked to the spatial distribution of endmembers to assess the physical significance of the method's output. The grain size–shape distributions of the aeolian dune dataset are unmixed into three primary components. The spatial distribution of these components is constrained by geomorphology and reflects the three dominant aeolian transport processes known to occur along a beach–dune transect: bedload on the beach and in notches that were dug by man through the shore-parallel foredune ridge, modified saltation on the windward and leeward slope of the intact foredune, and suspension in the vegetated hinterland. The three transport modes are characterised by distinctly different trends in grain shape with grain size: with increasing size, bedload shows a constant grain regularity, modified saltation a minor decrease in grain regularity, and suspension a strong decrease in grain regularity. These trends, or in other words, the shape of the grain size–shape distributions, can be used to determine the transport mode responsible for an aeolian sediment deposit. Results of the method are therefore less ambiguous than those of traditional grain size distribution endmember modelling, especially if multiple transport modes occur or if primary components overlap in terms of grain size but differ in grain shape.
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Wang, Qiang, Lili Zeng, Jian Li, Ju Chen, Yunkai He, Jinglong Yao, Dongxiao Wang i Weidong Zhou. "Observed Cross-Shelf Flow Induced by Mesoscale Eddies in the Northern South China Sea". Journal of Physical Oceanography 48, nr 7 (lipiec 2018): 1609–28. http://dx.doi.org/10.1175/jpo-d-17-0180.1.
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AbstractCross-shelf flow induced by mesoscale eddies has been investigated in the northern South China Sea (NSCS) using velocity observations from Long Ranger ADCP moorings. Mesoscale eddies influenced the three mooring stations during almost all the observation period. Four quadrants have been defined with the mooring location as the origin, and it is found that warm (cold) mesoscale eddies induce onshore (offshore) movement in the eastern two quadrants and offshore (onshore) movement in the western two quadrants. When an eddy propagates past a mooring station, net cross-shelf flow at the mooring station can be induced by asymmetry in the horizontal and vertical structure of the eddy and by its evolution. As an eddy propagates westward, its shape changes continually and the vertical modes also transform from high to lower modes, which contributes to the net cross-shelf flow. Based on the quasigeostrophic potential vorticity equation, it is confirmed that the net cross-shelf flow is mainly induced by the eddy evolution and suppressed by nonlinear effect. Because of dispersion characteristics of the mesoscale eddy, barotropic mode will restructure at the baroclinic mode area after separating from the baroclinic mode, which will be enhanced by topography slope.
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Ramírez-Velásquez, Iliana María, Álvaro H. Bedoya-Calle, Ederley Vélez i Francisco J. Caro-Lopera. "Dissociation Mode of the O–H Bond in Betanidin, pKa-Clusterization Prediction, and Molecular Interactions via Shape Theory and DFT Methods". International Journal of Molecular Sciences 24, nr 3 (2.02.2023): 2923. http://dx.doi.org/10.3390/ijms24032923.
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Betanidin (Bd) is a nitrogenous metabolite with significant bioactive potential influenced by pH. Its free radical scavenging activity and deprotonation pathway are crucial to studying its physicochemical properties. Motivated by the published discrepancies about the best deprotonation routes in Bd, this work explores all possible pathways for proton extractions on that molecule, by using the direct approach method based on pKa. The complete space of exploration is supported by a linear relation with constant slope, where the pKa is written in terms of the associated deprotonated molecule energy. The deprotonation rounds 1, …, 6 define groups of parallel linear models with constant slope. The intercepts of the models just depend on the protonated energy for each round, and then the pKa can be trivially ordered and explained by the energy. We use the direct approximation method to obtain the value of pKa. We predict all possible outcomes based on a linear model of the energy and some related verified assumptions. We also include a new measure of similarity or dissimilarity between the protonated and deprotonated molecules, via a geometric–chemical descriptor called the Riemann–Mulliken distance (RMD). The RMD considers the cartesian coordinates of the atoms, the atomic mass, and the Mulliken charges. After exploring the complete set of permutations, we show that the successive deprotonation process does not inherit the local energy minimum and that the commutativity of the paths does not hold either. The resulting clusterization of pKa can be explained by the local acid and basic groups of the BD, and the successive deprotonation can be predicted by using the chemical explained linear models, which can avoid unnecessary optimizations. Another part of the research uses our own algorithm based on shape theory to determine the protein’s active site automatically, and molecular dynamics confirmed the results of the molecular docking of Bd in protonated and anionic form with the enzyme aldose reductase (AR). Also, we calculate the descriptors associated with the SET and SPLET mechanisms.
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Wang, Zhaonian, Jiangbing Du, Weihong Shen, Jiacheng Liu i Zuyuan He. "Efficient Design for Integrated Photonic Waveguides with Agile Dispersion". Sensors 21, nr 19 (7.10.2021): 6651. http://dx.doi.org/10.3390/s21196651.
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Chromatic dispersion engineering of photonic waveguide is of great importance for Photonic Integrated Circuit in broad applications, including on-chip CD compensation, supercontinuum generation, Kerr-comb generation, micro resonator and mode-locked laser. Linear propagation behavior and nonlinear effects of the light wave can be manipulated by engineering CD, in order to manipulate the temporal shape and frequency spectrum. Therefore, agile shapes of dispersion profiles, including typically wideband flat dispersion, are highly desired among various applications. In this study, we demonstrate a novel method for agile dispersion engineering of integrated photonic waveguide. Based on a horizontal double-slot structure, we obtained agile dispersion shapes, including broadband low dispersion, constant dispersion and slope-maintained linear dispersion. The proposed inverse design method is objectively-motivated and automation-supported. Dispersion in the range of 0–1.5 ps/(nm·km) for 861-nm bandwidth has been achieved, which shows superior performance for broadband low dispersion. Numerical simulation of the Kerr frequency comb was carried out utilizing the obtained dispersion shapes and a comb spectrum for 1068-nm bandwidth with a 20-dB power variation was generated. Significant potential for integrated photonic design automation can be expected.
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Wang, Weiwei, Xinxi Liu, Weidong Hu, Hua Luo i Guanghui Wang. "Active Earth Pressure for Sloping Finite Soil While Accounting for Shear Stress and Curved Slip Surface". Geofluids 2022 (15.09.2022): 1–10. http://dx.doi.org/10.1155/2022/1481386.
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Calculating the earth pressure of the sloping soil having finite width behind the retaining wall is difficult for stability calculation. Thus, a novel method to calculate the active pressure of cohesionless sloping finite soil behind a retaining wall was developed to investigate. Taking cohesionless soil as the research object and considering the principal stress rotation of soil, the resultant force for active earth pressure, action point position, and earth pressure distribution of sloping finite soil was obtained based on assumptions of the translational mode of the rigid retaining wall and cycloidal slip surface. The accuracy of the proposed method was verified by model tests. The influence of the slope height ratio l / H and slope angle α on earth pressure was analyzed in this study. The result revealed that the horizontal component of the active earth pressure distribution curve for sloping finite soil was linear in area I and nonlinear with a drum shape in area II. There was a noticeable change at the junction of the two areas. The resultant force of earth pressure and the height of action point of resultant force increased and tended to reach a certain value as the aspect ratio l / H increased. When l / H ≥ 0.4 , the height of the action point of resultant force tended to be two-fifths the height of the wall. The resultant force and the height of the action point decreased linearly as the slope bottom angle increased.
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Zhang, Yie Yie, Ling Qiong Kong i Jie Shi. "Finite Element Analysis and Structural Optimization of Mine Man-Car Skip Underframe". Advanced Materials Research 842 (listopad 2013): 591–95. http://dx.doi.org/10.4028/www.scientific.net/amr.842.591.
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Mine man-car skip underframe is one of key components of mine hoisting system, in order to obtain the optimal structure and function characteristics, the finite element analysis method based on ANSYS is used to make static and modal analysis for the mine slope ramp man-car skip underframe. Static analysis shows that: The strength of underframe under typical working conditions meets requirements, but the stress surplus is relatively large. Modal analysis indicates that: It's prone to have bend and torsional deflection between the 4th and 5th beam, and the free modal shape has saltation. According to the above finite element analysis results, corresponding structure optimization is made on the underframe section size and the position of beams. The optimizing results show that: The stress amplitude of structural optimized underframe increases by 16.9%, the stress surplus effectively reduces, and the weight of underframe decreases by 10.6%. The free modal shape is more smooth, vibration mode has no saltation, and the dynamic performance is improved.
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Arifjanov, Aybek, Maqsud Otaxonov, Luqmon Samiev i Shamshodbek Akmalov. "Hydraulic calculation of horizontal open drainages". E3S Web of Conferences 97 (2019): 05039. http://dx.doi.org/10.1051/e3sconf/20199705039.
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In article analysed the factors influencing the hydraulic processes which arise in the open horizontal drainage systems. Open drainages plays important role in order to improve the ameliorative condition of the agricultural area, salt washing on the soil. It is emphasized that the deep drainage in our region has a good effect on the soil condition and salt removing. At present, efforts are being made to improve the productivity of the collectors to clean and built. As example the collector drainage systems in Syrdarya region are listed. It is observed that the motion mode of open drainage flows is physically identical. Due to the complexity of equations in the unstable motion mode, the drainage water flow scheme in the collectors reflects the hydraulic calculation of the movement. Researches were provided in open agricultural drainage system of Syrdarya region and analysis have been done in natural field conditions. It has been noted when slope of the drainage bed is equal to i<0,0005 intensity of deformation were very high, when slope was between 0,0005<i<0,0011 intensity of deformation of collector bed was equal to the minimum level. In this article provided hydraulic calculation for Syrdarya region drainage system for choosing dynamical stable shape of bed. Those hydraulic calculations and projections ensure collectors with long time period of exploitation condition. Calculation and analyses were done with taking account trapezoidal capacity of the stream in drainage system, and the results of studies on increasing the flow efficiency are reflected. Analysed that when slope will increase until 20% discharge capacity will increase because of high average flow velocity increased by 7-8 times and discussed difference of them. As a result of the hydraulic calculation, the slope of the drainage increased from i-0,00048 to i-0,0006, the fact that the flow capacity increased by 25% due to the increase because of flow velocity.
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Lemenkova, Polina. "Distance-based vegetation indices computed by SAGA GIS: A comparison of the perpendicular and transformed soil adjusted approaches for the LANDSAT TM image". Poljoprivredna tehnika 46, nr 3 (2021): 49–60. http://dx.doi.org/10.5937/poljteh2103049l.
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Landsat-TM of 2001 covering Iceland (15.5°W-21°W, 64.5°N-67°N) was processed using SAGA GIS for testing distance-based Vegetation Indices (VIs): four approaches of Perpendicular Vegetation Index (PVI) and two approaches of Transformed Soil Adjusted Vegetation Index TSAVI. The PVI of vegetation from the soil background line indicated healthiness as a leaf area index (LAI). The results showed that the reflectance for vegetation has a linear relation with soil background line. Four PVI models and two TSAVI shown coefficients of determination with LAI. The dataset demonstrate variations in the calculated coefficients. The mode in the histograms of the PVI based on four different algorithms show the difference:-7.1,-8.36, 2.78 and 7.0. The dataset for the two approaches of TSAVI: first case ranges in 4.4.-80.6 with a bell-shape mode of a histogram (8.09 to 23.29) for the first algorithm and an irregular shape for the second algorithm with several modes starting from 0.11 to 0.2 and decreasing to 0.26. SAGA GIS permits the calculation of PVI and TSAVI by computed NDVI based on the intersection of vegetation and soil background. Masking the NIR and R, a linear regression of grids was performed using an equation embedded in SAGA GIS. The advantages of the distance-based PVI and TSAVI consists in the adjusted position of pixels on the soil brightness line which refines it comparing to the slope-based VIs. The paper demonstrates SAGA GIS application in agricultural studies.
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Wang, Huan You, Qiao Lai Tan i Gui Jin. "V-Defect and Dislocation Analysis in InGaN Multiple Quantum Wells on Patterned Sapphire Substrate". Key Engineering Materials 787 (listopad 2018): 37–41. http://dx.doi.org/10.4028/www.scientific.net/kem.787.37.
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InGaN/GaN multiquantum well (MQW) structures have been grown on cone-shaped patterned sapphire substrates (CPSS) by metalorganic chemical vapor deposition (MOCVD). From the transmission electron microscopy (TEM) results, we found that most of the threading dislocations (TDs) in the trench region of the CPSS were bent by lateral growth mode. Also the staircase-like TDs were observed near the slant region of the cone pattern, they converged at the slope of the cone patterned region by staircase-upward propagation, which seems to effectively prevent TDs from vertical propagation in the trench region. The associated dislocation runs up into the overgrown GaN layer and MQW, and some (a+c) dislocations were shown to decompose inside the multi-quantum well, giving rise to a misfit segment in the c-plane and a V-shape defect. From cross-sectional TEM, we found that all V defects are not always connected with TDs at their bottom, some V defects are generated from the stacking mismatch boundaries induced by stacking faults which are formed within the MQW due to the strain relaxation.
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Zhang, Zhaopeng, Chaoyu Chang i Zhiyi Zhao. "Influence of the Slope Shape on Seismic Stability of a Slope". Advances in Civil Engineering 2020 (14.08.2020): 1–8. http://dx.doi.org/10.1155/2020/8827072.
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The slope shape is one of the most intuitive factors affecting the seismic stability of a slope. However, current research on this subject is mainly focused on statistical analysis and seismic response law, and the influence on seismic stability evaluation of the slope is rarely discussed. Furthermore, slope shapes are often simplified for easy numerical model building. In view of this, five slope models with different slope shapes are considered, and the time-history analysis method and Newmark method are chosen to evaluate the seismic stability of these slope models under different amplitudes. The purpose of this paper is to compare the seismic stability of slopes with different slope shapes and to study the feasibility of simplifying the slope shape when evaluating the seismic stability of a slope.
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Das, Prosenjit, Sk Tanbir Islam, Sudip K. Samanta i Santanu Das. "Microscale deformation behavior of rheocast Al–7Si–0.3 Mg alloy". Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications 230, nr 6 (3.08.2016): 1041–61. http://dx.doi.org/10.1177/1464420715595056.
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In the present work, microscale deformation behavior, plastic strain localization, and plastic instability of rheocast Al–Si–Mg (A356) alloy have been investigated using micromechanical approach. For this purpose, two-dimensional microscale models (representative volume elements) have been developed using actual microstructure of the cast samples made under three different process conditions. Microstructure of the above-mentioned alloy consists of two different phases, such as aluminum-rich primary phase and silicon-rich eutectic phase. In line with that, composite micromechanical models have been developed to analyze them within the finite element framework. Rheocasting has been performed using cooling slope with two different slope angles of 45° and 60°, and comparison has been made with the conventional cast samples of the alloy that has been cast directly from the superheated molten state. Different boundary conditions have been assumed to perform finite element based simulation, using a popular finite element solver ABAQUS, depending upon the position of representative volume elements on the cylindrical tensile specimen. Under uniaxial tensile loading, ductile failure mode is predicted in the form of plastic strain localization due to incompatible deformation between the phases. This indicates inhomogenity of microstructure that determines the damage initiation process within this material, as there is no damage or failure criterion specified during the finite element analysis. Grain size, shape, and orientation of the primary aluminum phase are found to play a vital role on deformation behavior and failure mode of the materials investigated in this study.
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Li, Zhaoqi, Jie Dong, Tao Jiang, Kai Feng, Siwu Cheng, Yuqian Liu, Guoxiang Zhang i Xuewei Tian. "Experimental Study on the Dynamic Fracture Characteristics of Mortar–Rock Interface Zones with Different Interface Inclinations and Shapes". Materials 16, nr 15 (4.08.2023): 5475. http://dx.doi.org/10.3390/ma16155475.
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There has been little research on the impact resistance of mortar–rock slope protection structures. To ensure that the mortar–rock interface has good adhesion properties under the action of impact loading, in this paper, based on fracture mechanics theory, a theoretical impact model was established for mortar–rock binary material. Dynamic fracture tests were carried out on mortar–rock interfaces using the split-Hopkinson pressure bar (SHPB) system. The Brazilian disc (CSTBD) specimen was prepared with one half in granite and the other half in mortar. The specimen used for the dynamic impact test was 48 mm in diameter and 25 mm thick. The effects caused by the change in interface inclination and interface shape on the dynamic fracture mode were discussed. The dynamic model parameters were obtained for different inclination angles and interfaces. The results show that both the interface inclination and interface shape have significant effects on the dynamic mechanical properties of the mortar–rock binary material. The fracture modes of the mortar–rock specimens can be classified into three types. When the interface inclination is 0°, the specimen shows shear damage with an interface fracture; when the interface inclination is in the range of 0–90°, the dynamic splitting strength of the mortar–rock material increases with increasing interface inclination, and the interface undergoes composite fracture; and when the interface inclination is 90°, the dynamic splitting strength of the specimen reaches its peak, and the interface undergoes tensile fracture. The mortar–rock interface damage follows the M-C criterion. The roughness of the interface shape has a large influence on the dynamic splitting strength of the specimens. The rougher the interface shape, the higher the interface cleavage strength and the higher the peak load that causes the material to damage. The results of this study can provide a reference for the design of mortar–rubble structures to meet the demand for impact resistance and have strong engineering application value.
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Polifke, W., A. Fischer i T. Sattelmayer. "Instability of a Premix Burner With Nonmonotonic Pressure Drop Characteristic". Journal of Engineering for Gas Turbines and Power 125, nr 1 (27.12.2002): 20–27. http://dx.doi.org/10.1115/1.1519267.
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Instabilities in combustion systems have frequently been reported to occur when slight changes in operating conditions lead to significant and abrupt changes in flame shape or flame position, i.e., changes in the mode of flame stabilization. The present paper offers an explanation and mathematical model of this observation. The analysis rests on the assumption that changes in the mode of flame stabilization are accompanied by a significant variation of the pressure drop across burner and flame, such that the pressure drop-flow rate characteristic locally displays a negative slope. In the limit of low frequencies (Helmholtz mode), it is then straightforward to show that an oscillatory instability can result from such behavior. An analytical stability criterion is derived, relating the nondimensionalized gradient of the pressure drop characteristic to the Helmholtz number of the burner. The physical mechanism of the instability is explained, and it is observed that the Rayleigh criterion need not be satisfied for this kind of instability to occur. In order to extend the stability analysis to higher frequencies, the transfer matrix for a burner with nonmonotonic pressure drop is derived in the limit of low Mach number and negligible fluctuations of the rate of heat release. The transfer matrix is employed in stability analysis based on a linear acoustic model of a combustion system. Experimental results obtained with an externally premixed swirl burner are presented. The pressure drop characteristic, the observed onset of instability and the instability frequency match the model predictions very well.
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Campos, L. M. B. C. "On a pitch control law for a constant glide slope through windshears". Aeronautical Journal 93, nr 928 (październik 1989): 290–300. http://dx.doi.org/10.1017/s0001924000022090.
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SummaryThe equations of motion of an aircraft flying at a constant glide slope (Fig. 3), in the presence of arbitrary head- or tailwinds, and up- or downflows is considered. The equations are integrated analytically, in the case of an aircraft initially on a steady flight, perturbed by winds of ‘moderate’ strength, in the sense that the wind velocity is not negligible compared to the aircraft's steady speed, but the ratio of their squares is much smaller than unity. The case of an approach through a downburst (Fig. 1), leads to winds which can be simplified to a one-period sinusoidal wind along the flight path, changing from head- to tailwind, at the peak of a superimposed downflow (Fig. 2), of half-period sinusoidal shape, and this is discussed in some detail. Data sheets are presented for three combinations of amplitudes of the head-to-tailwind and downflow; each contains plots of the scheduling of incidence that exactly cancels windshear effects, and of the groundspeed a'nd airspeed profiles which will keep the aircraft flying along the original glide slope. Each plot is given for a range of values of the windshear susceptibility parameter, representing aircraft with small or large inertia, with high or low approach speeds, including light aircraft, jet fighters and large transports; the cancellation of windshear effects isachievable only if the incidence schedule lies wholly below the stall limit. Since the rotational inertia of the aircraft is neglected, the short period mode is absent, and the pitch control acts to cancel the ‘phugoid’ instability induced on the aircraft by the wind profiles typical of a microburst.
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Amani, Mohamad, i Arezoo Safaviyan. "Sub-Basins Prioritization Using Morphometric Analysis-Remote Sensing Technique and GIS-Golestan-Iran". International Letters of Natural Sciences 38 (maj 2015): 56–65. http://dx.doi.org/10.18052/www.scipress.com/ilns.38.56.
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Sub-basins prioritization is one of the most important resolutions of development sustainability and natural resources comprehended management. In this study, 11 sub-basins of Lohender in east Golstan province about 272/63cm Prioritized using computation and morphometric analysis and using GIS and RS techniques. Erosion mode in each sub-basin specified through Sediment Yield Index approximation. In morphometric analysis, parameters like canal length, bifurcation ratio, discharge density, sub-basins shape coefficient, round coefficient, stretch coefficient and compressive coefficients were computed thus these parameters divided to two classifications: linear coefficients and figurative coefficient. In order to study annual sediment index, from fields applied maps, land coverage, slope, soil type and topographic map scale 1:50000 were used. Finally, each sub-basin Priority determined due to Sediment Yield Index (SYI) and total average of morphometric parameters. According to morphometric parameters, the BS sub-basin and according to SYI parameter, A5 sub-basin showed more critical mode and combination of both showed that B2 sub-basin showed the worst situation.
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Amani, Mohamad, i Arezoo Safaviyan. "Sub-Basins Prioritization Using Morphometric Analysis-Remote Sensing Technique and GIS-Golestan-Iran". International Letters of Natural Sciences 38 (6.05.2015): 56–65. http://dx.doi.org/10.56431/p-21x716.
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Sub-basins prioritization is one of the most important resolutions of development sustainability and natural resources comprehended management. In this study, 11 sub-basins of Lohender in east Golstan province about 272/63cm Prioritized using computation and morphometric analysis and using GIS and RS techniques. Erosion mode in each sub-basin specified through Sediment Yield Index approximation. In morphometric analysis, parameters like canal length, bifurcation ratio, discharge density, sub-basins shape coefficient, round coefficient, stretch coefficient and compressive coefficients were computed thus these parameters divided to two classifications: linear coefficients and figurative coefficient. In order to study annual sediment index, from fields applied maps, land coverage, slope, soil type and topographic map scale 1:50000 were used. Finally, each sub-basin Priority determined due to Sediment Yield Index (SYI) and total average of morphometric parameters. According to morphometric parameters, the BS sub-basin and according to SYI parameter, A5 sub-basin showed more critical mode and combination of both showed that B2 sub-basin showed the worst situation.
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Koco, Entela, Eleni Soilemezi, Panagiota Sotiriou, Savvoula Savvidou, Matthew Tsagourias, Ioannis Pnevmatikos i Dimitrios Matamis. "Ultrasonographic assessment of diaphragmatic contraction and relaxation properties: correlations of diaphragmatic displacement with oesophageal and transdiaphragmatic pressure". BMJ Open Respiratory Research 8, nr 1 (wrzesień 2021): e001006. http://dx.doi.org/10.1136/bmjresp-2021-001006.
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Transdiaphragmatic (Pdi) and oesophageal pressures (Pes) are useful in understanding the pathophysiology of the respiratory system. They provide insight into respiratory drive, intrinsic positive end-expiratory pressure, diaphragmatic fatigue and weaning failure.BackgroundThe use of Pdi and Pes in clinical practice is restricted due to the invasiveness of the technique and the cumbersome equipment needed. On the other hand, diaphragmatic displacement is non-invasively and easily assessed with M-mode ultrasound.PurposeWe observed striking similarities in shape and magnitude between M-mode diaphragmatic displacement, Pes and Pdi pressures. The study aimed to evaluate if the information provided by these two pressures could be obtained non-invasively from the diaphragmatic displacement curve.Material and methodsIn 14 consecutive intubated patients undergoing a weaning trial, simultaneous recordings of Pes and Pdi pressures and the diaphragmatic displacement were assessed while breathing spontaneously and during a sniff-like manoeuvre. Moreover, the slope of the diaphragmatic displacement curve during relaxation was compared with the maximal relaxation rate (MRR) obtained from the Pdi curve.ResultsMore than 200 breaths were analysed in pairs. Diaphragmatic displacement significantly correlated with Pdi (R2=0.33, p<0.001) and Pes (R2=0.44, p<0.001), and this correlation further improved during sniff (R2=0.47, p<0.001) and (R2=0.64, p<0.001), respectively. Additionally, a significant correlation was found between the relaxation slope derived from the diaphragmatic displacement curve and the MRR derived from the Pdi curve, both in normal breathing (R2=0.379, p<0.001) and during the sniff manoeuvre (R2=0.71, p<0.001).ConclusionsM-mode diaphragmatic displacement parameters correlate well with the ones obtained from oesophageal pressure and Pdi, particularly during sniffing. Diaphragmatic displacement assessment possibly offers an alternative non-invasive solution for understanding and clinically monitoring the diaphragmatic contractile properties and weaning failure due to diaphragmatic fatigue.
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MESOT, J., A. KAMINSKI, H. M. FRETWELL, S. ROSENKRANZ, J. C. CAMPUZANO, M. R. NORMAN, H. DING, M. RANDERIA i K. KADOWAKI. "PROXIMITY OF THE METAL-INSULATOR/MAGNETIC TRANSITION AND ITS IMPACT ON THE ONE-ELECTRON SPECTRAL FUNCTION: A DOPING-DEPENDENT ARPES STUDY". International Journal of Modern Physics B 14, nr 29n31 (20.12.2000): 3596–601. http://dx.doi.org/10.1142/s0217979200004118.
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The doping dependence of the low-temperature spectral function is precisely determined from angle resolved photoemision (ARPES) measurements. It is found that, as the doping decreases, the maximum of the superconducting gap increases, but the slope of the gap near the nodes decreases. Though consistent with d-wave symmetry, the gap with underdoping cannot be fit by the simple cos(kx)-cos(ky) form. We suggest that this arises due to the increasing importance of long range interactions as one approaches the insulator. It is also shown that the shape of the spectral function at the (π, 0) point below T c can be explained by the interaction of the electrons with a collective mode whose energy matches that of the magnetic resonance as obtained by inelastic neutron scattering data, and points to the intimate relation of magnetic correlatins to high Tc superconductivity.
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Scott, Robert B., i Faming Wang. "Direct Evidence of an Oceanic Inverse Kinetic Energy Cascade from Satellite Altimetry". Journal of Physical Oceanography 35, nr 9 (1.09.2005): 1650–66. http://dx.doi.org/10.1175/jpo2771.1.
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Abstract Sea surface height measurements from satellites reveal the turbulent properties of the South Pacific Ocean surface geostrophic circulation, both supporting and challenging different aspects of geostrophic turbulence theory. A near-universal shape of the spectral kinetic energy flux is found and provides direct evidence of a source of kinetic energy near to or smaller than the deformation radius, consistent with linear instability theory. The spectral kinetic energy flux also reveals a net inverse cascade (i.e., a cascade to larger spatial scale), consistent with two-dimensional turbulence phenomenology. However, stratified geostrophic turbulence theory predicts an inverse cascade for the barotropic mode only; energy in the large-scale baroclinic modes undergoes a direct cascade toward the first-mode deformation scale. Thus if the surface geostrophic flow is predominately the first baroclinic mode, as expected for oceanic stratification profiles, then the observed inverse cascade contradicts geostrophic turbulence theory. The latter interpretation is argued for. Furthermore, and consistent with this interpretation, the inverse cascade arrest scale does not follow the Rhines arrest scale, as one would expect for the barotropic mode. A tentative revision of theory is proposed that would resolve the conflicts; however, further observations and idealized modeling experiments are needed to confirm, or refute, the revision. It is noted that no inertial range was found for the inverse cascade range of the spectrum, implying inertial range scaling, such as the established K−5/3 slope in the spectral kinetic energy density plot, is not applicable to the surface geostrophic flow.
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Scalo, John M. "The Initial Mass Function of Massive Stars in Galaxies: Empirical Evidence". Symposium - International Astronomical Union 116 (1986): 451–66. http://dx.doi.org/10.1017/s0074180900149411.
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Observational constraints on the form of the high-mass stellar IMF are reviewed. The evidence includes star counts in the solar neighborhood, individual and composite star clusters, and nearby galaxies, and arguments based on integrated light and chemical evolution modeling. There is no convincing evidence for any systematic variations of the shape of the high-mass IMF. However, the various determinations are very uncertain, and do not allow any firm estimate of the logarithmic slope of the upper IMF; the appropriate value is somewhere between −1.3 and −2.3, with region-to-region variations smaller than about ±0.5. A number of lines of evidence suggest that the lower mass limit or mode mass of the IMF increases with increasing star formation rate, reaching perhaps 10–15 m⊙ in some starburst galaxies. It is also possible that the upper mass limit depends on metallicity, based on variations in excitation conditions of HII regions.
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Li, Xingyue, Betty Sovilla, Chenfanfu Jiang i Johan Gaume. "The mechanical origin of snow avalanche dynamics and flow regime transitions". Cryosphere 14, nr 10 (12.10.2020): 3381–98. http://dx.doi.org/10.5194/tc-14-3381-2020.
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Abstract. Snow avalanches cause fatalities and economic damage. Key to their mitigation is the understanding of snow avalanche dynamics. This study investigates the dynamic behavior of snow avalanches, using the material point method (MPM) and an elastoplastic constitutive law for porous cohesive materials. By virtue of the hybrid Eulerian–Lagrangian nature of the MPM, we can handle processes involving large deformations, collisions and fractures. Meanwhile, the elastoplastic model enables us to capture the mixed-mode failure of snow, including tensile, shear and compressive failure. Using the proposed numerical approach, distinct behaviors of snow avalanches, from fluid-like to solid-like, are examined with varied snow mechanical properties. In particular, four flow regimes reported from real observations are identified, namely, cold dense, warm shear, warm plug and sliding slab regimes. Moreover, notable surges and roll waves are observed peculiarly for flows in transition from cold dense to warm shear regimes. Each of the flow regimes shows unique flow characteristics in terms of the evolution of the avalanche front, the free-surface shape, and the vertical velocity profile. We further explore the influence of slope geometry on the behavior of snow avalanches, including the effect of slope angle and path length on the maximum flow velocity, the runout angle and the deposit height. Unified trends are obtained between the normalized maximum flow velocity and the scaled runout angle as well as the scaled deposit height, reflecting analogous rules with different geometry conditions of the slope. It is found that the maximum flow velocity is mainly controlled by the friction between the bed and the flow, the geometry of the slope, and the snow properties. We reveal the crucial effect of both flow and deposition behaviors on the runout angle. Furthermore, our MPM modeling is calibrated and tested with simulations of real snow avalanches. The evolution of the avalanche front position and velocity from the MPM modeling shows reasonable agreement with the measurement data from the literature. The MPM approach serves as a novel and promising tool to offer systematic and quantitative analysis for mitigation of gravitational hazards like snow avalanches.
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Tripathi, Jay Prakash, i Sanjoy Ghoshal. "Combining inertia and constriction technique in the PSO applied to fault identification in a hydraulic system". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 231, nr 14 (22.03.2016): 2730–40. http://dx.doi.org/10.1177/0954406216640302.
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A novel methodology for simultaneous parametric fault isolation and mode switching identification in the spool motion of a Directional Control Valve (DCV), under multi fault assumption, has been reported in this paper. The shape of the profile traversed by the DCV spool was assumed to be trapezoidal in both healthy and faulty condition, but the slope of trapezoidal may change due to fault. Under this assumption, the real valued fault parameter and binary mode switching were identified by real valued Particle Swarm Optimization (PSO) alone instead of a combined real and binary valued PSO (Hybrid PSO). A novel PSO algorithm by combining the concepts of varying inertia weight (both increasing and decreasing trend) and constriction factor has been proposed in the article to achieve more accurate identification. Its validity was examined using an existing heuristic formula and by conducting several tests on a benchmark function used for fault identification. Superior improvement was observed in the identification with increasing inertia weight than that of widely used decreasing inertia weight, when combined with the constriction coefficient. A high pressure hydraulic circuit used in dumper and several other lifting machines was used as a simulation example.
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Bagnulo, Stefano, Zuri Gray, Mikael Granvik, Alberto Cellino, Ludmilla Kolokolova, Karri Muinonen, Olga Muñoz, Cyrielle Opitom, Antti Penttilä i Colin Snodgrass. "Optical Spectropolarimetry of Binary Asteroid Didymos–Dimorphos before and after the DART Impact". Astrophysical Journal Letters 945, nr 2 (1.03.2023): L38. http://dx.doi.org/10.3847/2041-8213/acb261.
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Abstract We have monitored the Didymos–Dimorphos binary asteroid in spectropolarimetric mode in the optical range before and after the DART impact. The ultimate goal was to obtain constraints on the characteristics of the ejected dust for modeling purposes. Before impact, Didymos exhibited a linear polarization rapidly increasing with phase angle, reaching a level of ∼5% in the blue and ∼4.5% in the red. The shape of the polarization spectrum was anticorrelated with that of its reflectance spectrum, which appeared typical of an S-class asteroid. After impact, the level of polarization dropped by about 1 percentage point (pp) in the blue band and about 0.5 pp in the red band, then continued to linearly increase with phase angle, with a slope similar to that measured prior to impact. The polarization spectra, once normalized by their values at an arbitrary wavelength, show very little or no change over the course of all observations before and after impact. The lack of any remarkable change in the shape of the polarization spectrum after impact suggests that the way in which polarization varies with wavelength depends on the composition of the scattering material, rather than on its structure, be this a surface or a debris cloud.