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Kim, Youngjun, Jinwoo Park i Yeunwoong Kyung. "Mobility-Aware Hybrid Flow Rule Cache Scheme in Software-Defined Access Networks". Electronics 11, nr 1 (5.01.2022): 160. http://dx.doi.org/10.3390/electronics11010160.
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Due to the dynamic mobility feature, the proactive flow rule cache method has become one promising solution in software-defined networking (SDN)-based access networks to reduce the number of flow rule installation procedures between the forwarding nodes and SDN controller. However, since there is a flow rule cache limit for the forwarding node, an efficient flow rule cache strategy is required. To address this challenge, this paper proposes the mobility-aware hybrid flow rule cache scheme. Based on the comparison between the delay requirement of the incoming flow and the response delay of the controller, the proposed scheme decides to install the flow rule either proactively or reactively for the target candidate forwarding nodes. To find the optimal number of proactive flow rules considering the flow rule cache limits, an integer linear programming (ILP) problem is formulated and solved using the heuristic method. Extensive simulation results demonstrate that the proposed scheme outperforms the existing schemes in terms of the flow table utilization ratio, flow rule installation delay, and flow rules hit ratio under various settings.
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Shen, Yi, Chunming Wu, Dezhang Kong i Qiumei Cheng. "Flow Table Saturation Attack against Dynamic Timeout Mechanisms in SDN". Applied Sciences 13, nr 12 (16.06.2023): 7210. http://dx.doi.org/10.3390/app13127210.
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Software-defined networking (SDN) enables dynamic management and flexible network control by employing reactive rule installation. Due to high power consumption and cost, current OpenFlow switches only support a limited number of flow rules, which is a major limitation for deploying massive fine-grained policies. This bottleneck can be exploited by attackers to launch saturation attacks to overflow the flow table. Moreover, flow table overflow can occur in the absence of malicious attackers. To cope with this, researchers have developed many proposals to relieve the load under benign conditions. Among them, the dynamic timeout mechanism is one of the most effective solutions. We notice that when the SDN controller adopts dynamic timeouts, existing flow table saturation attacks can fail, or even expose the attackers, due to inaccurate inferring results. In this paper, we extract the common features of dynamic timeout strategies and propose an advanced flow table saturation attack. We explore the definition of flow rule lifetime and use a timing-based side-channel to infer the timeout of flow rules. Moreover, we leverage the dynamic timeout mechanisms to proactively interfere with the decision of timeout values and perform an attack. We conduct extensive experiments in various settings to demonstrate its effectiveness. We also notice that some replacement strategies work differently when the controller assigns dynamic timeouts. The experiment results show that the attack can incur significant network performance degradation and carry out the attack in a stealthy manner.
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MEDDERS, STEPHEN C., EDWARD B. ALLEN i EDWARD A. LUKE. "USING RULE STRUCTURE TO EVALUATE THE COMPLETENESS OF RULE-BASED SYSTEM TESTING: A CASE STUDY". International Journal of Software Engineering and Knowledge Engineering 20, nr 07 (listopad 2010): 975–86. http://dx.doi.org/10.1142/s0218194010005006.
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Rule-based systems are typically tested using a set of inputs which will produce known outputs. However, one does not know how thoroughly the software has been exercised. Traditional test-coverage metrics do not account for the dynamic data-driven flow of control in rule-based systems. Our literature review found that there has been little prior work on coverage metrics for rule-based systems. This paper proposes test-coverage metrics for rule-based systems derived from metrics defined by prior work, and presents an industrial scale case study. We conducted a case study to evaluate the practicality and usefulness of the proposed metrics. The case study applied the metrics to a system for computational fluid-dynamics models based on a rule-based application framework. These models were tested using a regression-test suite. The data-flow structure built by the application framework, along with the regression-test suite, provided case-study data. The test suite was evaluated against three kinds of coverage. The measurements indicated that complete coverage was not achieved, even at the lowest level definition. Lists of rules not covered provided insight into how to improve the test suite. The case study illustrated that structural coverage measures can be utilized to measure the completeness of rule-based system testing.
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Ashrafi, Mohammad, Lloyd H. C. Chua i Chai Quek. "The applicability of Generic Self-Evolving Takagi-Sugeno-Kang neuro-fuzzy model in modeling rainfall–runoff and river routing". Hydrology Research 50, nr 4 (28.03.2019): 991–1001. http://dx.doi.org/10.2166/nh.2019.146.
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Abstract Recent advancements in neuro-fuzzy models (NFMs) have made possible the implementation of dynamic rule base systems. This is in comparison with static applications commonly seen in global NFMs such as the Adaptive-Network-Based Fuzzy Inference System (ANFIS) model widely used in hydrological modeling. This study underlines key differences between local and global NFMs with an emphasis on rule base dynamics, in the context of two common flow forecast applications. A global NFM, ANFIS, and two local NFMs, Dynamic Evolving Neural-Fuzzy Inference System (DENFIS) and Generic Self-Evolving Takagi-Sugeno-Kang (GSETSK), were tested. Results from all NFMs compared favorably when benchmarked against physically based models. Rainfall–runoff modeling is a complex process which benefits from the advanced rule generation and pruning mechanisms in GSETSK, resulting in a more compact rule base. Although ANFIS resulted in the same number of rules, this came about at the expense of having the need for a large training dataset. All NFMs generated a similar number of rules for the river routing application, although local NFMs yielded better results for forecasts at longer lead times. This is attributed to the fact that the routing procedure is less complex and can be adequately modeled by static NFMs.
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Sharma, Pankaj, i Ajai Jain. "Effect of routing flexibility and sequencing rules on performance of stochastic flexible job shop manufacturing system with setup times: Simulation approach". Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 231, nr 2 (8.08.2016): 329–45. http://dx.doi.org/10.1177/0954405415576060.
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Routing flexibility is a major contributor towards flexibility of a flexible job shop manufacturing system. This article focuses on a simulation-based experimental study on the effect of routing flexibility and sequencing rules on the performance of a stochastic flexible job shop manufacturing system with sequence-dependent setup times while considering dynamic arrival of job types. Six route flexibility levels and six sequencing rules are considered for detailed study. The performance of manufacturing system is evaluated in terms of flow time related and due date–related measures. Results reveal that routing flexibility and sequencing rules have significant impact on system performance, and the performance of a system can be increased by incorporating routing flexibility. Furthermore, the system performance starts deteriorating as the level of route flexibility is increased beyond a particular limit for a specified sequencing rule. The statistical analysis of the results indicates that when flexibility exists, earliest due date rule emerges as a best sequencing rule for maximum flow time, mean tardiness and maximum tardiness performance measures. Furthermore, smallest setup time rule is better than other sequencing rules for mean flow time and number of tardy jobs performance measures. Route flexibility level two provides best performance for all considered measures.
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PRIORE, PAOLO, DAVID DE LA FUENTE, ALBERTO GOMEZ i JAVIER PUENTE. "DYNAMIC SCHEDULING OF MANUFACTURING SYSTEMS WITH MACHINE LEARNING". International Journal of Foundations of Computer Science 12, nr 06 (grudzień 2001): 751–62. http://dx.doi.org/10.1142/s0129054101000849.
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A common way of scheduling jobs dynamically in a manufacturing system is by means of dispatching rules. The drawback of this method is that the performance of these rules depends on the state the system is in at each moment, and no one rule exists that overrules the rest in all the possible states that the system may be in. It would therefore be interesting to use the most appropriate rule at each moment. To achieve this goal, a scheduling approach which uses machine learning is presented in this paper. The methodology proposed in this paper may be divided into five basic steps. Firstly, definition of the appropriate control attributes for identifying the relevant manufacturing patterns. In second place, creation of a set of training examples using different values of the control attributes. Subsequently, acquiring of heuristic rules by means of a machine learning program. Then, using of the previously calculated heuristic rules to select the most appropriate dispatching rules, and finally testing of the performance of the approach. The approach that we propose is applied to a flow shop system and to a classic job shop configuration. The results demonstrate that this approach produces an improvement in the performance of the system when compared to the traditional method of using dispatching rules.
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Yu, Chenxu, i Sundaram Gunasekaran. "Correlation of Dynamic and Steady Flow Viscosities of Food Materials". Applied Rheology 11, nr 3 (1.06.2001): 134–40. http://dx.doi.org/10.1515/arh-2001-0008.
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AbstractEight commercial foods representing a wide range of viscosities (i.e. honey, condensed milk, mayonnaise, tomato ketchup, cream cheese, yogurt, process and Mozzarella cheeses) were investigated. Their steady shear viscosity and dynamic complex viscosity were determined by rheological measurements at two temperatures using a Bohlin-CVO rheometer. Based on experimental data, shear rate dependence of steady flow apparent viscosity and frequency dependence of dynamic viscosity was established and compared. It was determined that for condensed milk, tomato ketchup and mayonnaise, a modified Cox-Merz relation could be established. For cream cheese, a generalized Cox-Merz relation was proposed; and for yogurt, a deviation from the Cox-Merz rule was found. For Mozzarella and process cheeses a sharp drop in steady shear viscosity was noticed between 1~10 s-1 shear rate range. The Cox-Merz rule was not applicable for these cheese samples.
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Ma, Wei, Fei Ma i Rong Guo. "Experimental research on the dynamic instability characteristic of a pressure relief valve". Advances in Mechanical Engineering 11, nr 3 (marzec 2019): 168781401983353. http://dx.doi.org/10.1177/1687814019833531.
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This article presents detailed experimental results of the influencing factors of flow rate, set pressure, and inlet pipe length of a pressure relief valve. In order to analyze the influence of different flow rates on the instability characteristics of pressure relief valve, the multi-stage output of pump flow is realized. In terms of modeling, we investigated the theory concerning instability in the system: the 3% rule boundary. Data analyses on typical stable, cycling, and chatter instability conditions are conducted. The stable boundaries of the 3% rule and the quarter-wave model are drawn, which are consistent with the experimental results.
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Zhao, Wenshuang, Nan Jiang, Xinkai Yu, Yunhai Chen i Xinke Zhao. "A Correlation Analysis Method for Geographical Object Flows from a Geoeconomic Perspective". Sustainability 14, nr 15 (25.07.2022): 9085. http://dx.doi.org/10.3390/su14159085.
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Geographic object flow is the reason behind the relationship of geographic units. There are interactions in the process of dynamic change of a geographic object flow, and its regularity, which can reflect the relationship or pattern of geographic units in a region. In this paper, an association rule mining method for the geographic object flow linkage process is studied from a geoeconomics perspective. Additionally, an association rule mining algorithm with hierarchical constraints is proposed. Data segmentation is performed according to the time series characteristics of geographic object flow data. The basic attributes for the association rule mining are determined based on the basic parameters of geographic object flows, and a database for the association rule mining is formed according to the characteristics of the hierarchical structure of the geographic object flows. Based on the obtained data, the association rule mining algorithm with hierarchical constraints obtained using a parent–child matrix is improved by adding the Apriori algorithm. With the Indo-Pacific region as an example, the trade flow association rules for 25 countries in the region from 2010 to 2021 are selected. In addition, a mathematical statistical analysis of the strongly associated mined trade flows and geoeconomic factors is conducted in terms of both a basic feature analysis of trade flow associations and a country-oriented trade flow association analysis by considering domain knowledge. The effectiveness of the method has been evaluated from various perspectives such as correlation analysis, mathematical statistics, and comparison with the findings of existing studies and proved the validity of the method.
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Tian, Jun-fang, Zhen-zhou Yuan, Bin Jia i Wang Tao. "Dynamic Congested Traffic States of Density Difference Lattice Hydrodynamic Model with On-Ramp". Discrete Dynamics in Nature and Society 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/941238.
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The density difference lattice hydrodynamic model with on-ramp is proposed. Stochastic and deterministic rules for the on-ramp flow entering into the main road are designed. Under the stochastic rule, various empirical spatiotemporal patterns can be well reproduced, such as the pinned localized cluster (PLC) and homogeneous synchronized traffic (HST). Under the deterministic rule, four new types of congested traffic states, such as the stationary oscillatory congested traffic (OCT) upstream of on-ramp and the stationary and localized OCT emerging in HST, are identified for the first time. Comparisons with the macroscopic speed gradient model are carried out, and some advantages of our model are clarified. To our knowledge, it is the first research showing that the lattice hydrodynamic model could reproduce various congested patterns induced by the on-ramp system.
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Anees, V. V. Muhammed, K. P. Abdul Nazar i R. Sridharan. "Simulation Modelling and Analysis of Due Date Assignment Methods and Scheduling Decision Rules in a Flexible Manufacturing System". Advances in Science and Technology 106 (maj 2021): 99–108. http://dx.doi.org/10.4028/www.scientific.net/ast.106.99.
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This paper presents the salient details of a simulation-based study conducted to analyze the effect of due date assignment methods and scheduling decision rules on the performance of a flexible manufacturing system. A typical FMS is considered for investigation in the present study. Three endogenous due date setting methods and one exogenous method are examined in the present study. The scheduling rules considered for experimentation include processing time based rules and due date based rules in addition to the unbiased first-in-first-out rule. The performance measures evaluated in the present study are mean flow time, standard deviation of flow time, mean tardiness, standard deviation of tardiness, percentage of tardy jobs and average flow allowance. Analysis of the simulation results reveal that the dynamic due date setting methods provide better system performance.
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Chen, Xi, i Guo Xin Wang. "Research on Dynamic Scheduling Technology in Job Shop with Tool Flow". Applied Mechanics and Materials 313-314 (marzec 2013): 685–88. http://dx.doi.org/10.4028/www.scientific.net/amm.313-314.685.
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To solve the tool flow and part flow interaction problems in job-shop scheduling, a kind of dynamic scheduling technology in job shop with tool flow is proposed. A new method of decision point calculation and a new heuristic approach for job selection named tools-minimally-occupied (TMO) are proposed. According to the method and the rule, the problems of when and how to select the parts in the dynamic scheduling are solved. The technology is proved to be effective by examples.
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Zhang, Z. J., i F. Stern. "Free-Surface Wave-Induced Separation". Journal of Fluids Engineering 118, nr 3 (1.09.1996): 546–54. http://dx.doi.org/10.1115/1.2817793.
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Free-surface wave-induced separation is studied for a surface-piercing NACA 0024 foil over a range of Froude numbers (0, .2, .37, .55) through computational fluid dynamics of the unsteady Reynolds-averaged Navier-Stokes and the continuity equations with the Baldwin-Lomax turbulence model, exact nonlinear kinematic and approximate dynamic free-surface boundary conditions, and a body/free-surface conforming grid. The flow conditions and uncertainty analysis are discussed. A topological rule for a surface-piercing body is derived and verified. Steady-flow results are presented and analyzed with regard to the wave and viscous flow and the nature of the separation.
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Agnetis, A., G. Oriolo, D. Pacciarelli i F. Rossi. "A Dynamic Lookahead Dispatching Rule in a Flexible Flow Line for Automobile Assembly". IFAC Proceedings Volumes 26, nr 2 (lipiec 1993): 493–96. http://dx.doi.org/10.1016/s1474-6670(17)48517-x.
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Rahaman, Md Masiur, Bensingh Dhas, D. Roy i J. N. Reddy. "A dynamic flow rule for viscoplasticity in polycrystalline solids under high strain rates". International Journal of Non-Linear Mechanics 95 (październik 2017): 10–18. http://dx.doi.org/10.1016/j.ijnonlinmec.2017.05.010.
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Shi, Yong Gui. "Research on Element Model of Enterprise Network". Advanced Materials Research 472-475 (luty 2012): 3140–43. http://dx.doi.org/10.4028/www.scientific.net/amr.472-475.3140.
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Enterprise network is a group of interconnected enterprises and institutions, which connected with information technology. In the process of sharing resources, exchanging resources and transferring resources, they formed a variety of relations based on the same background of social culture and mutual trust in order to respond to market changes quickly. As a kind of special social network, enterprise network also has four basic elements of the social networks, which namely the structure elements, resource elements, rule elements and dynamic elements. Structural elements is the most intuitive expression form of enterprise network, including the structure of enterprise network agents and the relation between enterprise network agents; rule elements affects or determines the behavior rules of enterprise network agents, which also affects the flow of resource elements in enterprise network; resource element is the resources that belong to enterprise network agents or they access to; dynamic elements is the external environment that affects the enterprise network.
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Korelstein, Leonid, Vladimir Tarasevich i Elena Yudovina. "Centrifugal pump dynamic simulation experience for waterhammer calculation". E3S Web of Conferences 219 (2020): 01006. http://dx.doi.org/10.1051/e3sconf/202021901006.
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Dynamic model of centrifugal pump with induction motor on the base of Suter curves is described. The model is implemented in surge model of PASS/Hydrosystem software. The ways to provide consistency between transient and steady state flow models are proposed. A rule of thumb is described to preliminarily estimate if pump start-up and shut down can produce significant pressure picks that require detailed simulation.
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Hong, Wei Bo, Ke Ping Zhang i Ya Ping Yao. "Numerical Simulation of the Influence of Gear Rotation Speed on the Gear Pump Flow Field". Applied Mechanics and Materials 741 (marzec 2015): 232–36. http://dx.doi.org/10.4028/www.scientific.net/amm.741.232.
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Gear pump has simple structure, long service life, strong self-priming capacity, high working reliability and other characteristics, which is widely used in various kinds of mechanical equipment. In order to study the influence of gear rotational speed on the internal fluid flow field change rule, the computational fluid dynamics software Fluent was used to simulate the gear pump flow field, while dynamic grid technique was carried on the numerical simulation of the gear pump under different rotation speed, and flow field characteristics were analysed. The results showed that with the increase of gear rotation speed, the area of pump fluid velocity mutation decreased, the area of pressure mutation reduced, and the larger volume of fluid closed to balance.
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Dau, Quan Van, Anongrit Kangrang i Kittiwet Kuntiyawichai. "Probability-Based Rule Curves for Multi-Purpose Reservoir System in the Seine River Basin, France". Water 15, nr 9 (30.04.2023): 1732. http://dx.doi.org/10.3390/w15091732.
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Multiple reservoir operation is of paramount importance due to tradeoffs in water supply and their cost functions. Understanding this complexity is important for optimizing water supply and increasing synergies gained from the joint operation. Therefore, this study aimed to develop a conceptual framework for addressing the effects of climate change on water security under the operating rules of the multiple reservoir system in northern France. A dynamic programming approach (DP) was employed to find the cost–benefit analysis that best fit with the objectives of reservoir operation, while the space rule was applied to balance the available space in each reservoir of a parallel system. A finite-horizon optimal regulation was then adopted for determining daily reservoir storage based on probability-based rule curves. The results indicated that the predicted inflow during the drawdown–refill cycle period to the Marne and Pannecière reservoirs would be the largest and lowest, respectively. The proposed upper rule curves during high-flow conditions suggested that the release from Aube reservoir should be postponed from July to August until September. At 50- and 100-year return periods, quite a high release rate from Seine and Marne reservoirs was observed during the dry season. A decrease in future water supply from Pannecière reservoir was found during summer, while the withdrawal in November could cause excessive water in the Seine tributary and Paris City. Under low-flow conditions in all return periods, the proposed lower rule curves recommended that the reservoir storage should go below the current operating rule, with a clear difference in July (the largest in Marne and the smallest in Pannecière) and almost no difference in November. Moreover, the web-based support system IRMaRA was developed for revising operating rules of four main reservoirs located in the Seine River Basin. The novelty of this modeling framework would contribute to the practice of deriving optimal operating rules for a multi-reservoir system by the probability-based rule curve method. Based on the evaluation of the effects of applying the estimated reservoir storage capacity under different return periods, both less overflow and water shortage represented by different levels of quantity and severity can be expected compared to the existing target storage at specified control points. Finally, the obtained finding revealed that the application of dynamic programming for reservoir optimization would help in developing a robust operating policy for tackling the effects of climate change.
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Kalateh, F., i F. Hosseinejad. "Dynamic Analysis of Porous Media using Generalized Plasticity Model and Non-Darcy Flow Rule". Journal of Computational Methods In Engineering 38, nr 1 (1.08.2019): 101–18. http://dx.doi.org/10.29252/jcme.38.1.101.
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Lodree, Emmett, Wooseung Jang i Cerry M. Klein. "A new rule for minimizing the number of tardy jobs in dynamic flow shops". European Journal of Operational Research 159, nr 1 (listopad 2004): 258–63. http://dx.doi.org/10.1016/s0377-2217(03)00404-1.
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Eskandarinejad, A., i A. H. Shafiee. "Pseudo-dynamic analysis of seismic stability of reinforced slopes considering non-associated flow rule". Journal of Central South University of Technology 18, nr 6 (grudzień 2011): 2091–99. http://dx.doi.org/10.1007/s11771-011-0948-3.
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Martínez-Ruvalcaba, A., E. Chornet i D. Rodrigue. "Dynamic Rheological Properties of Concentrated Chitosan Soltions". Applied Rheology 14, nr 3 (1.06.2004): 140–47. http://dx.doi.org/10.1515/arh-2004-0009.
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AbstractA detailed analysis of the dynamic flow properties of chitosan in solution at different temperatures (25 - 45°C), chitosan concentration (0.5% - 2.0%), solvent type (acetic, lactic, and hydrochloric acid), and ionic strength (0 and 0.2M NaCl) has been undertaken. The storage modulus, G’, loss modulus, G’’ and complex viscosity, η* have been determined over a wide range of frequencies and the results are presented using master curves. For the conditions studied, at low frequencies chitosan solutions show a constant complex viscosity which decreases as frequency increases. Likewise, storage modulus, G’ and loss modulus, G’’ increase as frequency increases with G’’ being always greater than G’ (η’ > η’’) indicating that viscous effects are more important than elastic effects. For modelling the oscillatory-shear results we used the generalized Maxwell model. Two empirical equations were used to correlate the data: Cox-Merz rule for viscosity and Laun's rule for primary normal stress difference. Both relations were found to represent our data for the experimental conditions studied.
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Abdelwahab, Amira, i Nesma Youssef. "Performance Evaluation of Sequential Rule Mining Algorithms". Applied Sciences 12, nr 10 (21.05.2022): 5230. http://dx.doi.org/10.3390/app12105230.
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Data mining techniques are useful in discovering hidden knowledge from large databases. One of its common techniques is sequential rule mining. A sequential rule (SR) helps in finding all sequential rules that achieved support and confidence threshold for help in prediction. It is an alternative to sequential pattern mining in that it takes the probability of the following patterns into account. In this paper, we address the preferable utilization of sequential rule mining algorithms by applying them to databases with different features for improving the efficiency in different fields of application. The three compared algorithms are the TRuleGrowth algorithm, which is an extension sequential rule algorithm of RuleGrowth; the top-k non-redundant sequential rules algorithm (TNS); and a non-redundant dynamic bit vector (NRD-DBV). The analysis compares the three algorithms regarding the run time, the number of produced rules, and the used memory to nominate which of them is best suited in prediction. Additionally, it explores the most suitable applications for each algorithm to improve the efficiency. The experimental results proved that the performance of the algorithms appears related to the dataset characteristics. It has been demonstrated that altering the window size constraint, determining the number of created rules, or changing the value of the minSup threshold can reduce execution time and control the number of valid rules generated.
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Zhang, Yanqin, Zhiquan Zhang, Xiangbin Kong, Rui Li i Hui Jiang. "Application of dynamic mesh technology in the oil film flow simulation for hydrostatic bearing". Industrial Lubrication and Tribology 71, nr 1 (14.01.2019): 146–53. http://dx.doi.org/10.1108/ilt-08-2017-0222.
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Purpose The purpose of this paper was to obtain the lubrication characteristics of heavy hydrostatic bearing in heavy equipment manufacturing industry through theoretical analysis and numerical simulation. Design/methodology/approach This paper discusses the influence of oil film thickness variation on velocity field, outlet-L and outlet-R flow velocity under the hydrostatic bearing running in no-load 0 N, load 400 KN, full load 1,500 KN and rotating speeds of 10 r/min, 20 r/min, 30 r/min, 40 r/min, 50 r/min and 60 r/min, by using dynamic mesh technology and FLUENT software. Findings When the working table rotates clockwise, in the change process of oil film thickness, the fluid flow pattern of the lubricating oil at the edge of the sealing oil is the rule of laminar flow, and the oil cavity has a vortex. The outlet-R flow velocity becomes higher and higher by increasing the bearing load and working table speed, and the flow velocity increases with the decrease in oil film thickness; the outlet-L flow velocity increases with the decrease in oil film thickness under low rotating speed (less than 10 r/min) condition and decreases with the decrease of oil film thickness under high rotating speed (more than 60 r/min) condition. Originality/value The influence of the oil film thickness on the flow state distribution of the oil film was analyzed under different working conditions, and the influence rules of oil film thickness on the flow velocity of hydrostatic bearing oil pad was obtained by using dynamic mesh technology.
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Gao, Mingxia. "A Node Model Capturing Turning Lane Capacity and Physical Queuing for the Dynamic Network Loading Problem". Mathematical Problems in Engineering 2012 (2012): 1–14. http://dx.doi.org/10.1155/2012/542459.
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An analytical dynamic node-based model is proposed to represent flows on a traffic network and to be utilized as an integral part of a dynamic network loading (DNL) process by solving a continuous DNL problem. The proposed model formulation has an integrate base to be structured with a link load computing component, where physical queuing and its influence were explicitly taken into account by dividing a link into two parts: running part and queuing part. The solution to the model is obtained by a hybridization algorithm of simulation and analytical approach, where an iteration process is conducted to update time-dependent network flow conditions after a reasonable discretization of the problem. The performance of the proposed model, as a DNL model, is tested on a sample network. It is seen that the proposed model provides consistent approximations to link flow dynamics. The dynamic node model proposed in this paper is unique in that it explicitly models directional queue in each turning lane and the First-In-First-Out (FIFO) rule at lane level rather than link level is pursued.
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Zhang, Wei, Cai Xia Ma i Shuang Xia Niu. "Discussig of Electricity Embedded Software Testing Technology". Applied Mechanics and Materials 401-403 (wrzesień 2013): 1674–79. http://dx.doi.org/10.4028/www.scientific.net/amm.401-403.1674.
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Focusing on the feature of embedded software in power industry and to ensure its high reliability, the authors of this article introduced a comprehensive and effective testing technique based on the theory and practice of embedded test, with two phases: static test and dynamic unit test. It focus on the coding rule checking, quality metrics, analysis, flow control and data flow analysis and coverage analysis techniques.
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Zhong, Fusheng, i Anlin Wang. "Rule Optimization of Self-organization Control of Traffic Signals in Urban Net Based on Hydrodynamic". MATEC Web of Conferences 237 (2018): 03004. http://dx.doi.org/10.1051/matecconf/201823703004.
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Prior researchers indicate that hydrodynamics models of traffic-flow is lack of description of changing mechanism under urban traffic, and self-organization control system can not explain the dynamic characteristics of urban traffic flow clearly. The aim of the paper is to puts forward an optimized method on control rules that make the united application of hydrodynamics and self-organization system in signal control. The parameter sets of control rules are built from parameter sets of road network which are evolution under hydrodynamic equations such as the length of each lane, phase, queue length and so on .With the aim of the maximum traffic volume at each intersection in the road network, the control rules optimize its parameter sets to adapt to the dynamic change. By means of the computer simulation, the application of signal self-organizing control under hydrodynamic is proved effective in urban traffic.a
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Heger, Jens, Jürgen Branke, Torsten Hildebrandt i Bernd Scholz-Reiter. "Dynamic adjustment of dispatching rule parameters in flow shops with sequence-dependent set-up times". International Journal of Production Research 54, nr 22 (28.04.2016): 6812–24. http://dx.doi.org/10.1080/00207543.2016.1178406.
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Jiang, Wei Jin, Luo Zhong, Qing Feng Li i Xiao Qing Deng. "MAS-Based Supply Chain Dynamic Collaboration Resource Sharing". Advanced Materials Research 282-283 (lipiec 2011): 474–77. http://dx.doi.org/10.4028/www.scientific.net/amr.282-283.474.
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In order to study the law of emergence and its internal attributable causes according to the resources owned by agents that interacts with each other in the complex adaptive system about the supply chain, at the beginning the resources which the agents in the supply chain draw are defined as followings: the resources outside system, the resources in the system, the resources that other else agents own, and the dynamic resources the agent itself own, the multi-compartment agent of resources. The operating points of eight resources owned by agents interact with each other are controlled through eight random numbers, the direction, degree, speed and stability of resources flow during interaction among agents are described respectively by matching capability, matching speed and matching time; Furthermore, the evolution process about the resources among agents interacting is described by rules of GEF(Global Evaluate Function) and LEF(Local Evaluate Function), resources flow model of complex system about the supply chain is established; Eventually, through simulating respectively in the Swarm platform both the proposed model and the simple model that doesn’t cunsder the multi-compartment agent but the linear sum of all resources, it is found that the former describes the change rule of the resource more accurately in the supply chain system. It means that syncretizing eight resources, which interact and inter-constrain in the system, to an indiscerptible one is the attributable cause of the emergence.
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Dong, Xing, Wei Yang i Hai Lu Zhang. "Numerical Simulation in Nozzle Outflow of Post-Mixed Water-Jet Peening". Applied Mechanics and Materials 448-453 (październik 2013): 1173–78. http://dx.doi.org/10.4028/www.scientific.net/amm.448-453.1173.
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In order to achieve movement rule of post-mixed water jet outflow field, post-mixed water jet peening nozzle flow field were simulated by FLUENT software, according to their turbulent characteristics, the mathematical model adopted Euler model, turbulence model adopted the standard kε model. Analyzed the peening pressure and peening standoff distance on the influence of outflow field of liquid-solid two phases-flow axial dynamic pressure and axial velocity, the results show that in different peening pressure, water flow field and pill flow field of axial velocity and the axial dynamic pressure both are symmetrical distribution, and their value increased with the increase of peening pressure to raise, decreases with the increase of peening standoff distance, even, with the increase of length of pill nozzle water flow field of axial velocity decreases, and pill flow field of axial velocity increases. When the peening pressure is 14 MPa, peening standoff distance is 30 mm, length of pill nozzle is 55 mm, maximum axial dynamic pressure of the outflow field is 3.18 MPa, the maximum axial velocity of water flow field and pill flow field respectively are 71.3 m/s and 69.6 m/s.
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Maggiani, Giovanni Battista, i Maria Giovanna Mora. "A dynamic evolution model for perfectly plastic plates". Mathematical Models and Methods in Applied Sciences 26, nr 10 (25.08.2016): 1825–64. http://dx.doi.org/10.1142/s0218202516500469.
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We consider the dynamic evolution of a linearly elastic-perfectly plastic thin plate subject to a purely vertical body load. As the thickness of the plate goes to zero, we prove that the three-dimensional evolutions converge to a solution of a certain reduced model. In the limiting model admissible displacements are of Kirchhoff–Love type. Moreover, the motion of the body is governed by an equilibrium equation for the stretching stress, a hyperbolic equation involving the vertical displacement and the bending stress, and a rate-independent plastic flow rule. Some further properties of the reduced model are also discussed.
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Wiskott, Laurenz, i Terrence Sejnowski. "Constrained Optimization for Neural Map Formation: A Unifying Framework for Weight Growth and Normalization". Neural Computation 10, nr 3 (1.04.1998): 671–716. http://dx.doi.org/10.1162/089976698300017700.
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Computational models of neural map formation can be considered on at least three different levels of abstraction: detailed models including neural activity dynamics, weight dynamics that abstract from the neural activity dynamics by an adiabatic approximation, and constrained optimization from which equations governing weight dynamics can be derived. Constrained optimization uses an objective function, from which a weight growth rule can be derived as a gradient flow, and some constraints, from which normalization rules are derived. In this article, we present an example of how an optimization problem can be derived from detailed nonlinear neural dynamics. A systematic investigation reveals how different weight dynamics introduced previously can be derived from two types of objective function terms and two types of constraints. This includes dynamic link matching as a special case of neural map formation. We focus in particular on the role of coordinate transformations to derive different weight dynamics from the same optimization problem. Several examples illustrate how the constrained optimization framework can help in understanding, generating, and comparing different models of neural map formation. The techniques used in this analysis may also be useful in investigating other types of neural dynamics.
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Schaeffer, David G., i Michael Shearer. "Scale-invariant initial value problems in one-dimensional dynamic elastoplasticity, with consequences for multidimensional nonassociative plasticity". European Journal of Applied Mathematics 3, nr 3 (wrzesień 1992): 225–54. http://dx.doi.org/10.1017/s0956792500000814.
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This paper solves a class of one-dimensional, dynamic elastoplasticity problems for equations which describe the longitudinal motion of a rod. The initial conditions U(x, 0) are continuous and piecewise linear, the derivative ∂U/∂x(x, 0) having just one jump at x = 0. Both the equations and the initial data are invariant under the scaling Ũ(x, t) = α−1U(αx, αt), where α > 0; hence the term scale-invariant. Both in underlying motivation and in solution, this problem is highly analogous to the Riemann problem from gas dynamics. These ideas are applied to the Sandler–Rubin example of non-unique solutions in dynamic plasticity with a nonassociative flow rule. We introduce an entropy condition that re-establishes uniqueness, but we also exhibit problems regarding existence.
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Sekacheva, A. A., L. G. Pastukhova, A. S. Noskov i E. R. Butakova. "Experimental Study of Hydromechanical System Pipeline Dynamic Characteristics". Proceedings of Higher Educational Institutions. Маchine Building, nr 7 (748) (lipiec 2022): 90–100. http://dx.doi.org/10.18698/0536-1044-2022-7-90-100.
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The article considers vibration resistance of hydromechanical system pipelines characterizing the reliability of their operation. As a rule, vibrations and noise in pipelines are caused by pressure pulsations in the flow of the working medium and structural vibrations from superchargers propagating along the pipeline structure. An experimental analysis of vibroacoustic parameters of a real complex pipeline system with a supercharger was performed to study its dynamic behavior. At this stage of the study, the stationary process of pump operation forming a turbulent flow in the pipeline, was researched. In the course of the physical experiment, a spectral analysis was performed and vibroacoustic spectra were built at the selected control points of a separate straight section of the pipeline in the frequency range of 0.5 ... 400.0 Hz. An analysis of the change in dynamic parameters along the length of a straight section was made at various flow rates of the working fluid. The influence of the operating parameters of the supercharger (supply and pressure) on the vibroacoustic characteristics of the pipeline was studied. It was found that transverse oscillations are of greater importance in the formation of the dynamic behavior of the studied area. It is determined that with increasing the flow rate, the relative vibrational displacement of the pipeline along the X axis (longitudinal vibrations) also increases.
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Ip, Bill, W. D. Hibler i Greg Flato. "The Effect Of Rheology On Seasonal Sea-Ice Simulations". Annals of Glaciology 14 (1990): 340. http://dx.doi.org/10.3189/s0260305500009046.
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On the seasonal time scales relevant to numerical investigations of climate, the rheology used in large-scale sea ice models significantly affects the ice thickness build-up and ice velocity fields. Plastic rheologies with a normal flow rule have been used to-date in seasonal dynamic thermodynamic simulations. These rheologies have proved useful in simulating discontinuous slip near the coast while still supplying relatively robust velocity fields in the central Arctic Basin. However, as indicated by limited numerical sensitivity studies with different types of elliptical yield curves, the amount of shear strength significantly affects the ice build-up and can possibly cause a stoppage of the ice outflow through Fram Strait. In addition to the shear strength issue, there is also the possibility that non-normal flow rule rheologies, such as the Mohr Coulomb failure criterion used in soil mechanics, may cause somewhat different types of flow patterns, especially in the Fram Strait region. However, to date no seasonal simulations with such non-normal flow rule rheologies have been carried out.In order to investigate the role of different rheologies on the large-scale flow patterns in the Arctic Basin, a more general numerical scheme than that of Hibler (1979) is developed, which allows the simulation of the dynamic thermodynamic behavior of sea ice with a wide variety of different non linear rheologies. Using this numerical scheme, comparative simulations are carried out to seasonal equilibrium with several variations of the Mohr Coulomb rheology and compared to the more standard Elliptical yield curve results. In particular, the main control Mohr Coulomb case is a capped rheology in which the shear strength is taken to be proportional to the compressive stress. In this capped case only shear flow is allowed until a maximum allowable compressive stress is reached. This cap strength is parameterized to be a function of the ice thickness and compactness. For comparison, a simulation with a very large cap strength is also carried out, and an experiment with a similar compressive cap but much lower shear strength. Overall the results are analyzed to determine the sensitivity of the ice build-up to flow rule and shear strength magnitude. In addition special attention is given to the character of the flow and stoppage (if any) through Fram Strait.
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Ip, Bill, W. D. Hibler i Greg Flato. "The Effect Of Rheology On Seasonal Sea-Ice Simulations". Annals of Glaciology 14 (1990): 340. http://dx.doi.org/10.1017/s0260305500009046.
Pełny tekst źródłaStreszczenie:
On the seasonal time scales relevant to numerical investigations of climate, the rheology used in large-scale sea ice models significantly affects the ice thickness build-up and ice velocity fields. Plastic rheologies with a normal flow rule have been used to-date in seasonal dynamic thermodynamic simulations. These rheologies have proved useful in simulating discontinuous slip near the coast while still supplying relatively robust velocity fields in the central Arctic Basin. However, as indicated by limited numerical sensitivity studies with different types of elliptical yield curves, the amount of shear strength significantly affects the ice build-up and can possibly cause a stoppage of the ice outflow through Fram Strait. In addition to the shear strength issue, there is also the possibility that non-normal flow rule rheologies, such as the Mohr Coulomb failure criterion used in soil mechanics, may cause somewhat different types of flow patterns, especially in the Fram Strait region. However, to date no seasonal simulations with such non-normal flow rule rheologies have been carried out. In order to investigate the role of different rheologies on the large-scale flow patterns in the Arctic Basin, a more general numerical scheme than that of Hibler (1979) is developed, which allows the simulation of the dynamic thermodynamic behavior of sea ice with a wide variety of different non linear rheologies. Using this numerical scheme, comparative simulations are carried out to seasonal equilibrium with several variations of the Mohr Coulomb rheology and compared to the more standard Elliptical yield curve results. In particular, the main control Mohr Coulomb case is a capped rheology in which the shear strength is taken to be proportional to the compressive stress. In this capped case only shear flow is allowed until a maximum allowable compressive stress is reached. This cap strength is parameterized to be a function of the ice thickness and compactness. For comparison, a simulation with a very large cap strength is also carried out, and an experiment with a similar compressive cap but much lower shear strength. Overall the results are analyzed to determine the sensitivity of the ice build-up to flow rule and shear strength magnitude. In addition special attention is given to the character of the flow and stoppage (if any) through Fram Strait.
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Liu, Qing, Mu Qing Wu i Ting Ting Zhang. "Cooperative Spectrum Sensing Based on Biological Learning Mechanism in Dynamic Electromagnetic Environment". Applied Mechanics and Materials 195-196 (sierpień 2012): 234–39. http://dx.doi.org/10.4028/www.scientific.net/amm.195-196.234.
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Cognitive Radio is an intelligent radio that should be adapted to the time-varying environment. However, an adaptive fusion rule has been investigated by a rather limited work. In this paper, we present a new approach which is derived from the inspiration of human learning mechanism based on conditioning in behavioural theory. The framework and algorithmic flow are introduced. Moreover, the proposed method is proven to perform well in the dynamic circumstance by the result of the simulation.
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Xu, Xiang Min, i Xi Fan Yao. "Application of Ontology in Event-Driven Job-Shop Scheduling Problems". Applied Mechanics and Materials 775 (lipiec 2015): 458–63. http://dx.doi.org/10.4028/www.scientific.net/amm.775.458.
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Aiming at the flexible flow-shop scheduling problem of cloud manufacturing, this paper introduces event driven concept and apply ontologies to Job-Shop scheduling problem FT46. The inference of ontology models allows the system to gain the dynamic information of workshop, and then rule engine is used to match event patterns to optimize the job shop scheduling problem.
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Liang, Xin Rong, i Di Qian Wang. "Fuzzy Logic Based Traffic Density Control via Ramp Metering". Applied Mechanics and Materials 97-98 (wrzesień 2011): 888–91. http://dx.doi.org/10.4028/www.scientific.net/amm.97-98.888.
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In this work, we apply fuzzy logic method to address the traffic density control problem in a macroscopic level freeway environment with ramp metering. The second-order traffic flow model is firstly formulated. Then traffic density is selected as the control variable in place of traffic occupancy. Based on the traffic flow model and in conjunction with nonlinear feedback theory, a fuzzy logic based traffic density controller is designed. The ramp metering rate is determined by the fuzzy control according to density tracking error and error variation. Triangle curves are used for the membership functions of the fuzzy variables. The rule base including 56 fuzzy rules is also established. Finally, the fuzzy logic based feedback controller is simulated in Matlab software. Simulation results show that this method has good dynamic and steady-state performance, and can achieve an almost perfect tracking performance.
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Wang, Chun Lin, Tian Fang Zhang, Chun Lei Zhao i Dong Liu. "3-D Numerical Simulation on Unsteady Turbulent Flow of Rotational Flow Self-Priming Pump". Advanced Materials Research 562-564 (sierpień 2012): 899–902. http://dx.doi.org/10.4028/www.scientific.net/amr.562-564.899.
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The three-dimensional unsteady turbulent flow of rotational flow self-priming pump was simulated by using Reynolds time-averaged N-S equations and the standard k-ε turbulent model, sliding mesh model of static-dynamic coupled models and SIMPLE arithmetic. The static pressure distribution of the pump central rotative surface and relative velocity of the impeller central rotative surface in a complete application cycle were analyzed. The rule of instantaneous head in a impeller channel cycle was studied, and the positions of maximal head and minimal head were analyzed. It revealed that the unsteady method can truly simulate the changes of the rotational flow self-priming pump interior flow, and the unsteady characteristic of interior flow in rotational flow self-priming pump is obvious and it changes as the relative position of impeller and volute change. The change is periodical, and its frequency is relate to the impeller number and the rotate speed of the pump.
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Zhang, Lin, Jian Lu, Man Long, Shu-bin Li i Jialin Zhou. "A Cascading Failures Perspective Based Mesoscopic Reliability Model of Weighted Public Transit Network considering Congestion Effect and User Equilibrium Evacuation". Mathematical Problems in Engineering 2018 (2018): 1–13. http://dx.doi.org/10.1155/2018/9292375.
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To establish the optimal route layout estimation technology based on reliability optimization, a more accurate and realistic reliability model of a weighted public transit network (PTN) is the indispensable basis. This paper establishes a cascading failures (CFs) perspective based mesoscopic reliability model for measuring PTN survivability. First, a modeling method for abstracting weighted PTN and determining its initial passenger flow and bearing capacity is proposed, making the network passenger flow pattern follow the aggregated flow pattern. Second, three basic concepts (time step, congestion effect of a road section, and CFs judging method) for establishing the CFs model are defined to clarify the overall evolution process of CFs. Furthermore, the aggregated passenger flow evacuation that exists in an emergency occurring at a station (i.e., failure load dynamic redistribution (FLDR)) is considered as a conscious dynamic game process through following the user equilibrium rule. As a result, a novel CFs model that considers congestion effect and user equilibrium evacuation is obtained. Finally, based on the collected data of Jinan’s PTN, a case simulation analysis is conducted to verify the adaptability of this model through showing a significantly different dynamics characteristic with the existing FLDR patterns and to provide optimization direction for effectively controlling PTN survivability, that is, guide the transformation among varying FLDR patterns through some technical measures or traffic policies.
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Sakhno, N. H., K. V. Avramov i B. V. Uspensky. "Dynamic instability of a compound nanocomposite shell". Kosmìčna nauka ì tehnologìâ 27, nr 5 (2021): 60–70. http://dx.doi.org/10.15407/knit2021.05.060.
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Free oscillations and dynamic instability due to supersonic airflow pressure are investigated in a functional-gradient compound composite conical-cylindrical shell made of a carbon nanotubes-reinforced material. Nanocomposite materials with a linear distribution of the volumetric fraction of nanotubes over the thickness are considered. Extended mixture rule is used to estimate nanocomposite’s mechanical characteristics. A high-order shear deformation theory is used to represent the shell deformation. The assumed-mode technique, along with a Rayleigh-Ritz method, is applied to obtain the equations of the structure motion. To analyze the compound structure dynamics, a new system of piecewise basic functions is suggested. The pressure of a supersonic flow on the shell is obtained by using the piston theory. An example of the dynamic analysis of a nanocomposite conical-cylindrical shell in the supersonic gas flow is considered. The results of its modal analysis using the Rayleigh-Ritz technique are close to the natural frequencies of the shell obtained by finite element analysis. In this case, finite element analysis can only be used for shells made of material with a uniform distribution of nanotubes over the thickness. The dependence of the natural frequencies of a compound shell on the ratio of the lengths of the conical and cylindrical parts is studied. The dependence of the critical pressure of a supersonic flow on the Mach numbers and the type of carbon nanotubes reinforcement is investigated. Shells with a concentration of nanotubes predominantly near the outer and inner surfaces are characterized by higher values of natural frequencies and critical pressure than the shells with a uniform distribution of nanotubes or with a predominant concentration of nanotubes inside the shell.
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Wang, Yang, Wen Fu Wu i Ya Qiu Zhang. "Research on Correlation between the Pressure and the Grain Moisture Content in the Rectangular Silo". Advanced Materials Research 1073-1076 (grudzień 2014): 1828–31. http://dx.doi.org/10.4028/www.scientific.net/amr.1073-1076.1828.
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In the process of grain drying, the pressure of grain formation has a certain rule when the grains flow in the silo. In the project, we research on the method of the saturated pressure would measure grain moisture in the silo. The dynamic and static pressure is set up the simulation equation in the rectangular silo. We explore dynamic and static pressure change regularity and analysis the trend of the dynamic and static pressure with height in the rectangular silo.The results show that with the increase of filling height, dynamic and static pressure has gradually becoming saturated trend. At the same time, we study on the correlation between the saturated pressure and moisture content. When the grain reaches a certain height, the pressure achieves the ultimate value.
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Wei, Xian Min. "Design and Implementation of Dynamic Query Component Based on Neural Network". Advanced Materials Research 171-172 (grudzień 2010): 736–39. http://dx.doi.org/10.4028/www.scientific.net/amr.171-172.736.
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This paper analyzed the principles of learning and associative memoryof artificial neural network, while combining with component-based software engineering (CBSE) development ideas, and designed dynamic data query component. To Innovatively and effectively combinate neural network (Instar rule) with the data query concretely. Dynamic data query components mainly consist of five group elements, in addition to system interface group element as a characteristic group element, the other as functional group elements. Under control flow, around the user's service request to analyze data profiling and query information feedback. In addition, dynamic data query component of internal work processes is briefly described. The design will be of practical value for the database management system.
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Sitahong, Adilanmu, Yiping Yuan, Ming Li, Junyan Ma, Zhiyong Ba i Yongxin Lu. "Designing Dispatching Rules via Novel Genetic Programming with Feature Selection in Dynamic Job-Shop Scheduling". Processes 11, nr 1 (27.12.2022): 65. http://dx.doi.org/10.3390/pr11010065.
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Genetic Programming (GP) has been widely employed to create dispatching rules intelligently for production scheduling. The success of GP depends on a suitable terminal set of selected features. Specifically, techniques that consider feature selection in GP to enhance rule understandability for dynamic job shop scheduling (DJSS) have been successful. However, existing feature selection algorithms in GP focus more emphasis on obtaining more compact rules with fewer features than on improving effectiveness. This paper is an attempt at combining a novel GP method, GP via dynamic diversity management, with feature selection to design effective and interpretable dispatching rules for DJSS. The idea of the novel GP method is to achieve a progressive transition from exploration to exploitation by relating the level of population diversity to the stopping criteria and elapsed duration. We hypothesize that diverse and promising individuals obtained from the novel GP method can guide the feature selection to design competitive rules. The proposed approach is compared with three GP-based algorithms and 20 benchmark rules in the different job shop conditions and scheduling objectives. Experiments show that the proposed approach greatly outperforms the compared methods in generating more interpretable and effective rules for the three objective functions. Overall, the average improvement over the best-evolved rules by the other three GP-based algorithms is 13.28%, 12.57%, and 15.62% in the mean tardiness (MT), mean flow time (MFT), and mean weighted tardiness (MWT) objective, respectively.
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WU, J. J., H. J. SUN i Z. Y. GAO. "CAPACITY ASSIGNMENT MODEL TO DEFENSE CASCADING FAILURES". International Journal of Modern Physics C 20, nr 07 (lipiec 2009): 991–99. http://dx.doi.org/10.1142/s0129183109014126.
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How to alleviate the damages of cascading failures triggered by the overload of edges/nodes is common in complex networks. To describe the whole cascading failures process from edges overloading to nodes malfunctioning and the dynamic spanning clustering with the evolvement of traffic flow, we propose a capacity assignment model by introducing an equilibrium assignment rule of flow in artificially created scale-free traffic networks. Additionally, the capacity update rule of node is given in this paper. We show that a single failed edge may undergo the cascading failures of nodes, and a small failure has the potential to trigger a global cascade. It is suggested that enhancing the capacity of node is particularly important for the design of any complex network to defense the cascading failures. Meanwhile, it has very important theoretical significance and practical application worthiness in the development of effective methods to alleviate the damage of one or some failed edges/nodes.
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Campolucci, Paolo, Aurelio Uncini i Francesco Piazza. "A Signal-Flow-Graph Approach to On-line Gradient Calculation". Neural Computation 12, nr 8 (1.08.2000): 1901–27. http://dx.doi.org/10.1162/089976600300015196.
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A large class of nonlinear dynamic adaptive systems such as dynamic recurrent neural networks can be effectively represented by signal flow graphs (SFGs). By this method, complex systems are described as a general connection of many simple components, each of them implementing a simple one-input, one-output transformation, as in an electrical circuit. Even if graph representations are popular in the neural network community, they are often used for qualitative description rather than for rigorous representation and computational purposes. In this article, a method for both on-line and batch-backward gradient computation of a system output or cost function with respect to system parameters is derived by the SFG representation theory and its known properties. The system can be any causal, in general nonlinear and time-variant, dynamic system represented by an SFG, in particular any feedforward, time-delay, or recurrent neural network. In this work, we use discrete-time notation, but the same theory holds for the continuous-time case. The gradient is obtained in a straightforward way by the analysis of two SFGs, the original one and its adjoint (obtained from the first by simple transformations), without the complex chain rule expansions of derivatives usually employed. This method can be used for sensitivity analysis and for learning both off-line and on-line. On-line learning is particularly important since it is required by many real applications, such as digital signal processing, system identification and control, channel equalization, and predistortion.
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Riazantseva, M. O., V. P. Budaev, L. M. Zelenyi, G. N. Zastenker, G. P. Pavlos, J. Safrankova, Z. Nemecek, L. Prech i F. Nemec. "Dynamic properties of small-scale solar wind plasma fluctuations". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, nr 2041 (13.05.2015): 20140146. http://dx.doi.org/10.1098/rsta.2014.0146.
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The paper presents the latest results of the studies of small-scale fluctuations in a turbulent flow of solar wind (SW) using measurements with extremely high temporal resolution (up to 0.03 s) of the bright monitor of SW (BMSW) plasma spectrometer operating on astrophysical SPECTR-R spacecraft at distances up to 350 000 km from the Earth. The spectra of SW ion flux fluctuations in the range of scales between 0.03 and 100 s are systematically analysed. The difference of slopes in low- and high-frequency parts of spectra and the frequency of the break point between these two characteristic slopes was analysed for different conditions in the SW. The statistical properties of the SW ion flux fluctuations were thoroughly analysed on scales less than 10 s. A high level of intermittency is demonstrated. The extended self-similarity of SW ion flux turbulent flow is constantly observed. The approximation of non-Gaussian probability distribution function of ion flux fluctuations by the Tsallis statistics shows the non-extensive character of SW fluctuations. Statistical characteristics of ion flux fluctuations are compared with the predictions of a log-Poisson model. The log-Poisson parametrization of the structure function scaling has shown that well-defined filament-like plasma structures are, as a rule, observed in the turbulent SW flows.
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Zhao, Xusheng, Jie Cao, Bo Wang i Xuelin Yang. "Experiment Study of Outburst Pulverized Coal-Gas Two-Phase Flow and Characteristic Analysis of Outburst Wave". Geofluids 2021 (18.06.2021): 1–11. http://dx.doi.org/10.1155/2021/8186230.
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Coal and gas outburst is still a major safety problem in the process of coal production in China. Correctly understanding of the migration law of outburst high gas and pulverized coal is an important basis for accurately predicting the occurrence time and possible scope of outburst. To reveal the airflow disturbance characteristics and coal-gas flow rule in coal and gas outburst process, outburst coal-gas migration simulations under different gas pressures were conducted using a self-developed visual outburst dynamic effect test device. The results showed that coal-gas flow state at the outburst port is divided into subcritical flow, critical flow, and supercritical flow state. The pulverized coal-gas flow migration in the roadway space can be divided into coal gas two-phase flow area, air compression area, and undisturbed area. Under the experimental conditions, the maximum propagation velocities of wave are 342.22~359.21 m/s, and the coal gas two-phase flow is far less than the propagation velocities of outburst wave, just 3.68~33.33 m/s. When the outburst energy is large, multiple compression waves can superimpose to form shock waves. The peak value of the wave does not necessarily appear in the first boosting range. The presence of pulverized coal leads to a faster attenuation of shock wave, but it makes a greater dynamic destructive force at the same speed.