Journal articles on the topic 'Flow control features'
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Kim, Dong Kwan. "Enhancing code clone detection using control flow graphs." International Journal of Electrical and Computer Engineering (IJECE) 9, no. 5 (October 1, 2019): 3804. http://dx.doi.org/10.11591/ijece.v9i5.pp3804-3812.
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Code clones are syntactically or semantically equivalent code fragments of source code. Copy-and-paste programming allows software developers to improve development productivity, but it could produce code clones that can introduce non-trivial difficulties in software maintenance. In this paper, a code clone detection framework is presented with a feature extractor and a clone classifier using deep learning. The clone classifier is trained with true and false clones and then is tested with a test dataset to evaluate the performance of the proposed approach to clone detection. In particular, the proposed approach to clone detection uses Control Flow Graphs (CFGs) to extract features of a given code snippet. The selected features are used to compute similarity scores for comparing two code fragments. The clone classifier is trained and tested with similarity scores that quantify the degree of how similar two code fragments are. The experimental results demonstrate that using CFG features is a viable methodology in terms of the effectiveness of clone detection for both syntactic and semantic clones.
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Keshkeh, Kinan, Aman Jantan, and Kamal Alieyan. "A MACHINE LEARNING CLASSIFICATION APPROACH TO DETECT TLS-BASED MALWARE USING ENTROPY-BASED FLOW SET FEATURES." Journal of Information and Communication Technology 21, No.3 (July 17, 2022): 279–313. http://dx.doi.org/10.32890/jict2022.21.3.1.
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Transport Layer Security (TLS) based malware is one of the most hazardous malware types, as it relies on encryption to conceal connections. Due to the complexity of TLS traffic decryption, several anomaly-based detection studies have been conducted to detect TLS-based malware using different features and machine learning (ML) algorithms. However, most of these studies utilized flow features with no feature transformation or relied on inefficient flow feature transformations like frequency-based periodicity analysis and outliers percentage. This paper introduces TLSMalDetect, a TLS-based malware detection approach that integrates periodicity-independent entropy-based flow set (EFS) features generated by a flow feature transformation technique to solve flow feature utilization issues in related research. EFS features effectiveness was evaluated in two ways: (1) by comparing them to the corresponding outliers percentage and flow features using four feature importance methods, and (2) by analyzing classification performance with and without EFS features. Moreover, new Transmission Control Protocol features not explored in literature were incorporated into TLSMalDetect, and their contribution was assessed. This study’s results proved EFS features of the number of packets sent and received were superior to related outliers percentage and flow features and could remarkably increase the performance up to ~42% in the case of Support Vector Machine accuracy. Furthermore, using the basic features, TLSMalDetect achieved the highest accuracy of 93.69% by Naïve Bayes (NB) among the ML algorithms applied. Also, from a comparison view, TLSMalDetect’s Random Forest precision of 98.99% and NB recall of 92.91% exceeded the best relevant findings of previous studies. These comparative results demonstrated the TLSMalDetect’s ability to detect more malware flows out of total malicious flows than existing works. It could also generate more actual alerts from overall alerts than earlier research.Transport Layer Security (TLS) based malware is one of the most hazardous malware types, as it relies on encryption to conceal connections. Due to the complexity of TLS traffic decryption, several anomaly-based detection studies have been conducted to detect TLS-based malware using different features and machine learning (ML) algorithms. However, most of these studies utilized flow features with no feature transformation or relied on inefficient flow feature transformations like frequency-based periodicity analysis and outliers percentage. This paper introduces TLSMalDetect, a TLS-based malware detection approach that integrates periodicity-independent entropy-based flow set (EFS) features generated by a flow feature transformation technique to solve flow feature utilization issues in related research. EFS features effectiveness was evaluated in two ways: (1) by comparing them to the corresponding outliers percentage and flow features using four feature importance methods, and (2) by analyzing classification performance with and without EFS features. Moreover, new Transmission Control Protocol features not explored in literature were incorporated into TLSMalDetect, and their contribution was assessed. This study’s results proved EFS features of the number of packets sent and received were superior to related outliers percentage and flow features and could remarkably increase the performance up to ~42% in the case of Support Vector Machine accuracy. Furthermore, using the basic features, TLSMalDetect achieved the highest accuracy of 93.69% by Naïve Bayes (NB) among the ML algorithms applied. Also, from a comparison view, TLSMalDetect’s Random Forest precision of 98.99% and NB recall of 92.91% exceeded the best relevant findings of previous studies. These comparative results demonstrated the TLSMalDetect’s ability to detect more malware flows out of total malicious flows than existing works. It could also generate more actual alerts from overall alerts than earlier research.
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Zare, A., T. T. Georgiou, and M. R. Jovanović. "Stochastic Dynamical Modeling of Turbulent Flows." Annual Review of Control, Robotics, and Autonomous Systems 3, no. 1 (May 3, 2020): 195–219. http://dx.doi.org/10.1146/annurev-control-053018-023843.
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Advanced measurement techniques and high-performance computing have made large data sets available for a range of turbulent flows in engineering applications. Drawing on this abundance of data, dynamical models that reproduce structural and statistical features of turbulent flows enable effective model-based flow control strategies. This review describes a framework for completing second-order statistics of turbulent flows using models based on the Navier–Stokes equations linearized around the turbulent mean velocity. Dynamical couplings between states of the linearized model dictate structural constraints on the statistics of flow fluctuations. Colored-in-time stochastic forcing that drives the linearized model is then sought to account for and reconcile dynamics with available data (that is, partially known statistics). The number of dynamical degrees of freedom that are directly affected by stochastic excitation is minimized as a measure of model parsimony. The spectral content of the resulting colored-in-time stochastic contribution can alternatively arise from a low-rank structural perturbation of the linearized dynamical generator, pointing to suitable dynamical corrections that may account for the absence of the nonlinear interactions in the linearized model.
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Nishioka, Toshiaki. "Flow Features to Control Thermally Induced Convection in a Vertical Laminar Flow Cleanroom." Journal of the IEST 35, no. 6 (November 1, 1992): 17–24. http://dx.doi.org/10.17764/jiet.2.35.6.q5p725u054361928.
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This paper presents results of a flow simulation study of convection heat currents above a heat source in a vertical laminar flow (VLF) cleanroom as determined both experimentally and computationally. Typical clcanroom operations have numerous pieces of equipment that generate heat— thus the importanec of this study. The experiment was carried out in a full-scale mockup of a cleanroom. Temperature distributions above an electrical hot plate were measured for 12 airflow velocities and four heat source levels. The results showed that when the mean downward airflow velocity was 0.20 m/s or greater, the plume of heated air was completely suppressed and rose only 30 cm above the heat source. The relation between the convection current zone and the Richardson number was determined. Computer models simulating the turbulent incompressible fluid flow in a Cartesian coordinate system were applid to analyze the three-dimensional heat currents inside the VLF cleanroom and to prediet the temperature and velocity distributions. The velocity distributions clearly indicated the magnitude of the area within which the heat current disturbed the vertical flow. Comparisons between the experimental findings and the calculated results provided significant information on how to apply the computer simulation to a practical design.
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Li, Cong, Jie Liu, Xiaohua Yang, Shiyu Yan, and Meng Li. "Metamorphic Relation Recognition Method Based on Control Flow Graph Features." Journal of Physics: Conference Series 2219, no. 1 (April 1, 2022): 012058. http://dx.doi.org/10.1088/1742-6596/2219/1/012058.
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Abstract Metamorphic testing is an effective method to solve Oracle problems. It is used to test software which is no expected output or the expected output is difficult to construct. However, finding a suitable and effective metamorphic relation in the program is still a very difficult task, usually obtained by domain experts through manual analysis, which greatly reduces the efficiency of software testing. In this work we define a function parameter metamorphic relation from the operation of the function parameter sequence, and preset 10 function parameter metamorphic relation. Because functions with the same structure usually have the same function parameter metamorphic relation, we extract node features and independent path features from the control flow graph, and then create a classification model to judge the similarity between functions. Our experiment includes the evaluation of the prediction model and the prediction of the metamorphic relation on the real function. Good experimental results shows that this method can provides a new way to automated discovery of metamorphic relation.
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New, T. H., Y. X. Chan, G. C. Koh, M. C. Hoang, and Shengxian Shi. "Effects of Corrugated Aerofoil Surface Features on Flow-Separation Control." AIAA Journal 52, no. 1 (January 2014): 206–11. http://dx.doi.org/10.2514/1.j052398.
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Choi, Haecheon, Hyungmin Park, Woong Sagong, and Sang-im Lee. "Biomimetic flow control based on morphological features of living creatures." Physics of Fluids 24, no. 12 (December 2012): 121302. http://dx.doi.org/10.1063/1.4772063.
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CHOU, SHIH-CHIEN, and YING-KAI WEN. "ASSOCIATION-BASED INFORMATION FLOW CONTROL IN OBJECT-ORIENTED SYSTEMS." International Journal of Software Engineering and Knowledge Engineering 14, no. 03 (June 2004): 291–322. http://dx.doi.org/10.1142/s0218194004001658.
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Controlling information flows to prevent information leakage within an application is essential. According to the maturity of object-oriented techniques, many models were developed for the control in object-oriented systems. Since objects may be dynamically instantiated during program execution, controlling information flows among objects is difficult. Our research revealed that association is useful in the control. We developed an association-based information flow control model for object-oriented systems. It precisely controls information flows among objects through associations and constraints. It also offers features such as controlling method invocation through argument sensitivity, allowing declassification, allowing purpose-oriented method invocation, and precisely controlling write access. This paper proposes the model and the implementation of the model, which is composed of the language AbFlow (association-based flow) and its supporting environment.
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Yaremenko, Oksana. "CUSTOMS LOGISTICS: CONCEPTS, FUNCTIONS, FEATURES." HERALD OF KHMELNYTSKYI NATIONAL UNIVERSITY 300, no. 6 (December 3, 2021): 32–36. http://dx.doi.org/10.31891/2307-5740-2021-300-6-5.
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The article investigates the approaches to the definition of the term customs logistics. It is established that there is no generally accepted point of view on the content of the concept, its subject field among scientists and practitioners. Customs logistics is considered as a scientific direction, and as a practical activity, and as a functional area of logistics, and as part of the logistics chain, and as a set of logistics processes of participants in foreign economic activity. Given the complex structure and multiplicity of approaches to the interpretation of the term, and applying a systematic approach to disclose the content of customs logistics, it is proposed to understand customs logistics as a scientific and practical activity aimed at regulating customs goods and information and financial flows and protecting national interests, finding a balance of interests and ensuring the security and development of entities. The object-subject field of customs logistics is primarily export-import trade flows. They are accompanied by information flows: outgoing (from customs to the central authority), incoming (on the contrary), accompanying (documents for the goods). In this case, the implementation of foreign trade operations implies that the financial flow is divided into two parts: the first includes payments paid to the supplier for the goods (its feature is that it is governed by the laws of most states and international agreements); the second part includes customs duties, through which the state regulates the volume, range and direction of movement of export-import trade flows. Customs logistics integrates such important functions of customs activity, tariff-regulating, information-analytical, control-passing and financial-economic. The purpose of logistics of customs activity is first of all in the effective logistical organization of all types of the flows observed in customs business and their acceleration. This refers to commodity, information and financial flows, which together form an integrated commodity-information-financial flow, which has the duty to control such structures of the customs service as customs posts and customs, in particular when crossing this integrated flow of the customs border . The integrated nature of customs and logistics flows corresponds to the complex structure of customs logistics, which includes component, regional and functional structure.
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Ashill, P. R., J. L. Fulker, and K. C. Hackett. "A review of recent developments in flow control." Aeronautical Journal 109, no. 1095 (May 2005): 205–32. http://dx.doi.org/10.1017/s0001924000005200.
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Abstract This paper reviews and highlights recent developments of certain aspects of flow control concerned with reducing the drag of, and delaying flow separation on, wings and bodies over which the flow is turbulent. The study is restricted to devices that extend beyond the viscous sub-layer but are on a smaller scale than geometric features of the aircraft (e.g. wing chord). The review is mainly concerned with developments within the UK, although significant developments in other countries are discussed. The review discusses types of flow that need to be controlled, basic features of flow control devices and applications. It concludes with recommendations for future research.
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Abouelazayem, Shereen, Ivan Glavinić, Thomas Wondrak, and Jaroslav Hlava. "Flow Control Based on Feature Extraction in Continuous Casting Process." Sensors 20, no. 23 (December 1, 2020): 6880. http://dx.doi.org/10.3390/s20236880.
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The flow structure in the mold of a continuous steel caster has a significant impact on the quality of the final product. Conventional sensors used in industry are limited to measuring single variables such as the mold level. These measurements give very indirect information about the flow structure. For this reason, designing control loops to optimize the flow is a huge challenge. A solution for this is to apply non-invasive sensors such as tomographic sensors that are able to visualize the flow structure in the opaque liquid metal and obtain information about the flow structure in the mold. In this paper, ultrasound Doppler velocimetry (UDV) is used to obtain key features of the flow. The preprocessing of the UDV data and feature extraction techniques are described in detail. The extracted flow features are used as the basis for real time feedback control. The model predictive control (MPC) technique is applied, and the results show that the controller is able to achieve optimum flow structures in the mold. The two main actuators that are used by the controller are the electromagnetic brake and the stopper rod. The experiments included in this study were obtained from a laboratory model of a continuous caster located at the Helmholtz-Zentrum Dresden Rossendorf (HZDR).
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Leslie, Daniel C., Christopher J. Easley, Erkin Seker, James M. Karlinsey, Marcel Utz, Matthew R. Begley, and James P. Landers. "Frequency-specific flow control in microfluidic circuits with passive elastomeric features." Nature Physics 5, no. 3 (February 1, 2009): 231–35. http://dx.doi.org/10.1038/nphys1196.
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Wallasch, Thomas-Martin. "Transcranial Doppler Ultrasonic Features in Episodic Tension-Type Headache." Cephalalgia 12, no. 5 (October 1992): 293–96. http://dx.doi.org/10.1046/j.1468-2982.1992.1205293.x.
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In a pilot study we used transcranial Doppler ultrasound (TCD) to measure cerebral blood flow velocities in 21 headache-free episodic tension-type headache sufferers and in the same number of age- and sex-matched control subjects. We found increased blood flow velocities in the anterior, middle and posterior cerebral arteries and a decreased pulsality index in the middle and posterior cerebral arteries in tension-type headache sufferers compared to controls. Vascular bruits were significantly more frequent in the basal cerebral arteries of the patients compared to controls. There were no significant asymmetries of blood flow velocities in corresponding arteries. The findings suggest a multifactorial pathogenesis in episodic tension type headache including vascular abnormalities.
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Dearing, S., S. Lambert, and J. Morrison. "Flow control with active dimples." Aeronautical Journal 111, no. 1125 (November 2007): 705–14. http://dx.doi.org/10.1017/s0001924000004887.
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Abstract The long-term goal is to design and manufacture optimal ‘on-demand’ vortex generators, ‘dimples’ that can produce vortices of prescribed strength and duration for the real-time control of aerodynamic flows that are either undergoing transition or are fully turbulent, attached or separating. Electro-active polymers (EAP) are ideal for a dimple control surface, offering high strain rate, fast response, and high electromechanical efficiency. EAP can also be used as the basis of a resistanc – or capacitance – change pressure sensor, development of which has just begun. In terms of manufacture, inkjet printing of EAP also offers a paradigm shift such that a monolithic control surface is a very real possibility. Important features for integration into a control system are robustness and a predictable, repeatable motion. With these objectives in mind, the suitability of EAP-based actuators is assessed both mechanically and aerodynamically. The ultimate goal is to integrate these devices, along with shear-stress and pressure sensors and distributed control, also under development, into a flexible ‘smart skin’ which could be incorporated into an airframe structure. The response of a laminar boundary layer to forcing is investiagted using mechanical dimples.
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Han, Jinguang, Maoxuan Bei, Liqun Chen, Yang Xiang, Jie Cao, Fuchun Guo, and Weizhi Meng. "Attribute-Based Information Flow Control." Computer Journal 62, no. 8 (May 13, 2019): 1214–31. http://dx.doi.org/10.1093/comjnl/bxz018.
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Abstract Information flow control (IFC) regulates where information is permitted to travel within information systems. To enforce IFC, access control encryption (ACE) was proposed to support both the no read-up rule and the no write-down rule. There are some problems in existing schemes. First, the communication cost is linear with the number of receivers. Second, senders are not authenticated, namely an unauthorized sender can send a message to a receiver. To reduce communication cost and implement sender authentication, we propose an attribute-based IFC (ABIFC) scheme by introducing attribute-based systems into IFC. Our ABIFC scheme captures the following features: (i) flexible IFC policies are defined over a universal set of descriptive attributes; (ii) both the no read-up rule and the no write-down rule are supported; (iii) the communication cost is linear with the number of required attributes, instead of receivers; (iv) receivers can outsource heavy computation to a server without compromising data confidentiality; (v) authorized senders can control release their attributes when sending messages to receivers. To the best of our knowledge, it is the first IFC scheme where flexible policies are defined over descriptive attributes and outsourced computation is supported.
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Schädler, Rainer, Anestis I. Kalfas, Reza S. Abhari, Gregor Schmid, Tilmann auf dem Kampe, and Sanjay B. Prabhu. "Novel high-pressure turbine purge control features for increased stage efficiency." Journal of the Global Power and Propulsion Society 1 (July 21, 2017): 68MK5V. http://dx.doi.org/10.22261/68mk5v.
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AbstractRim seals throttle flow and have shown to impact the aerodynamic performance of gas turbines. The results of an experimental investigation of a rim seal exit geometry variation and its impact on the high-pressure turbine flow field are presented. A one-and-a-half stage, unshrouded and highly loaded axial turbine configuration with 3-dimensionally shaped blades and non-axisymmetric end wall contouring has been tested in an axial turbine facility. The exit of the rotor upstream rim seal was equipped with novel geometrical features which are termed as purge control features (PCFs) and a baseline rim seal geometry for comparison. The time-averaged and unsteady aerodynamic effects at rotor inlet and exit have been measured with pneumatic probes and the fast-response aerodynamic probe (FRAP) for three rim seal purge flow injection rates. Measurements at rotor inlet and exit reveal the impact of the geometrical features on the rim seal exit and main annulus flow field, highlighting regions of reduced aerodynamic losses induced by the modified rim seal design. Measurements at the rotor exit with the PCFs installed show a benefit in the total-to-total stage efficiency up to 0.4% for nominal and high rim seal purge flow rates. The work shows the potential to improve the aerodynamic efficiency by means of a well-designed rim seal exit geometry without losing the potential to block hot gas ingestion from the main annulus.
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KOTAPATI, RUPESH B., RAJAT MITTAL, OLAF MARXEN, FRANK HAM, DONGHYUN YOU, and LOUIS N. CATTAFESTA. "Nonlinear dynamics and synthetic-jet-based control of a canonical separated flow." Journal of Fluid Mechanics 654 (May 11, 2010): 65–97. http://dx.doi.org/10.1017/s002211201000042x.
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A novel flow configuration devised for investigation of active control of separated airfoil flows using synthetic jets is presented. The configuration consists of a flat plate, with an elliptic leading edge and a blunt trailing edge, at zero incidence in a free stream. Flow separation is induced on the upper surface of the airfoil at the aft-chord location by applying suction and blowing on the top boundary of the computational domain. Typical separated airfoil flows are generally characterized by at least three distinct frequency scales corresponding to the shear layer instability, the unsteadiness of the separated region and the vortex shedding in the wake, and all these features are present in the current flow. Two-dimensional Navier–Stokes simulations of this flow at a chord Reynolds number of 6 × 104 have been carried out to examine the nonlinear dynamics in this flow and its implications for synthetic-jet-based separation control. The results show that there is a strong nonlinear coupling between the various features of the flow, and that the uncontrolled as well as the forced flow is characterized by a variety of ‘lock-on’ states that result from this nonlinear coupling. The most effective separation control is found to occur at the highest forcing frequency for which both the shear layer and the separated region lock on to the forcing frequency. The effects of the Reynolds number on the scaling of the characteristic frequencies of the separated flow and its subsequent control are studied by repeating some of the simulations at a higher Reynolds number of 1 × 105.
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Mabey, D. G. "Design features which influence flow separations on aircraft." Aeronautical Journal 92, no. 920 (December 1988): 409–15. http://dx.doi.org/10.1017/s0001924000016547.
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Summary Features of aircraft which influence flow separations, and hence the onset of buffeting, should be always of interest to an aerodynamicist. The present compilation of such features is based on notes made during a visit to the USAF Aircraft Museum in Dayton, Ohio. Although two low-speed aircraft with high aspect ratio wings are considered, the emphasis is primarily on transonic and supersonic military aircraft, with wings of lower aspect ratio. Some recommendations are made to stimulate research into improved methods to control flow separation, particularly for future transonic and supersonic aircraft.
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Pack, L. G., and A. Seifert. "Effects of sweep on the dynamics of active separation control." Aeronautical Journal 107, no. 1076 (October 2003): 617–29. http://dx.doi.org/10.1017/s000192400001383x.
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Abstract A series of active flow control experiments were recently conducted at high Reynolds numbers on a wall mounted ‘Hump’. The model simulates the upper surface of a 20% thick Glauert-Goldschmied type airfoil at zero incidence. The flow over the model is turbulent since the tunnel sidewall boundary-layer flows over it, eliminating laminar-turbulent transition from the problem. The main motivation for the experiments was to generate a comprehensive data base for validation of unsteady numerical simulation as a first step in the development of a design tool, without which it would not be possible to effectively utilise the great potential of unsteady flow control. This paper focuses on the dynamics of several key features of the baseline as well as the controlled two- and three-dimensional flows. It was found that the two-dimensional separated flow contains unsteady waves centered on a reduced frequency (Strouhal number based on the length of the separated region and free-stream velocity) of 0·8, while in the three-dimensional separated flow, reduced frequencies of 0·3 and 1·0 are active. Several scenarios of resonant wave interaction take place over the separated shear-layer and in the pressure recovery regions. The unstable reduced frequency bands for periodic excitation are centered on 1·5 and 5, but these reduced frequencies are based on the length of the baseline bubble that shortens due to the excitation. The conventional swept wing-scaling works well for the coherent wave features. Reproduction of these dynamic effects by a numerical simulation would provide benchmark validation.
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Yu, Bo, Lin Yang, Shu Hui Chen, and Lin Ru Ma. "A Review of Information Flow Control in Composite Services." Applied Mechanics and Materials 336-338 (July 2013): 2348–53. http://dx.doi.org/10.4028/www.scientific.net/amm.336-338.2348.
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Service computing facilitates resource sharing and business collaboration for cross-domain partiers by universal service description and discovery. The multi-domain nature of service oriented environments introduces challenging security issues, especially with regard to information flow control which controls the flow of privacy resources. This paper presents a state-of-the-art review of information flow control technology in service oriented environments. We review the research background and classifications of information flow control, and discuss architecture and existing technologies of both centralized and distributed information flow approach. We outline the features, advantages and limitations of existing information flow control approaches. The analysis results show that the research of collaboration and dynamic nature are important, but insufficient to secure information flow.
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Jain, Rahil, and Barry Lutz. "Frequency tuning allows flow direction control in microfluidic networks with passive features." Lab on a Chip 17, no. 9 (2017): 1552–58. http://dx.doi.org/10.1039/c7lc00058h.
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Rodrigues, Hillary Peter. "Fluid control: Orchestrating blood flow in the Durgā Pūjā." Studies in Religion/Sciences Religieuses 38, no. 2 (June 2009): 263–92. http://dx.doi.org/10.1177/000842980903800204.
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Tantric rituals are often concerned with the manipulation of life fluids. The Bengali Durgā Pūjā, an annual worship celebration for the Hindu Great Goddess, is an example of an essentially Tantric ritual with orthodox Vedic and Puranic features. Although the overt rationales for the ritual have undergone changes over the centuries, from its martial origins to socio-economic display, the liturgy offers an underlying rationale that reveals its Tantric interests. Ritual features, symbolic elements, and the states and statuses of the actors during the enactment of the Durgā Pūjā demonstrate its concern with orchestrating the flow of female reproductive fluids through a ritual manipulation of the divine feminine. This paper will articulate the most salient of those aspects. Although often overlooked, because of its non-Tantric façade, the Bengali Durga Pūjā points us to a valuable resource for the study of Hindu Śākta Tantrism.
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Brion, V., J. Dandois, R. Mayer, P. Reijasse, T. Lutz, and L. Jacquin. "Laminar buffet and flow control." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 234, no. 1 (January 31, 2019): 124–39. http://dx.doi.org/10.1177/0954410018824516.
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An experimental investigation of the transonic flow past the laminar OALT25 airfoil has been conducted to analyze the impact of laminar flow upon the shock wave dynamics and the existence of a laminar buffet like phenomenon. Tests have been carried out at freestream Mach numbers varying in the range of 0.7–0.8, angle of attack from 0.5° to 4°, and with two tripping configurations at the upper surface of the wing. The (airfoil) chord based Reynolds number is about three million. Results obtained from pressure taps and sensors measurements, as well as Schlieren visualizations of the flow reveal the presence of a laminar buffet phenomenon in sharp contrast with the turbulent phenomenon, as it features a freestream- and chord-based normalized frequency of about unity while turbulent buffet occurs for a frequency close to 0.07 (Jacquin et al., AIAA J 2009; 47). A low-frequency mode, at a frequency of about 0.05 is also present in the laminar situation, notably lower than the high-frequency component. The latter exhibits strong oscillations of the shock foot and vertical wavelike deformations of the shock wave and the former moves the shock back and forth over a small portion of chord, quite similar to the turbulent phenomenon. The mean flow past the laminar wing is characterized by a laminar separation bubble under the shock foot, which likely contributes much to the novel dynamics revealed by the present experiments. Two control strategies of the unsteady shock wave are implemented, one consisting of three-dimensional bumps and one consisting of steady jets blowing transversely to the freestream. It is found that bumps provide a significant reduction of the buffet intensity in the laminar situation. The jets are able to completely remove the flow unsteadiness in both laminar and turbulent conditions.
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Guillamat, Pau, Jordi Ignés-Mullol, and Francesc Sagués. "Control of active liquid crystals with a magnetic field." Proceedings of the National Academy of Sciences 113, no. 20 (May 2, 2016): 5498–502. http://dx.doi.org/10.1073/pnas.1600339113.
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Living cells sense the mechanical features of their environment and adapt to it by actively remodeling their peripheral network of filamentary proteins, known as cortical cytoskeleton. By mimicking this principle, we demonstrate an effective control strategy for a microtubule-based active nematic in contact with a hydrophobic thermotropic liquid crystal. By using well-established protocols for the orientation of liquid crystals with a uniform magnetic field, and through the mediation of anisotropic shear stresses, the active nematic reversibly self-assembles with aligned flows and textures that feature orientational order at the millimeter scale. The turbulent flow, characteristic of active nematics, is in this way regularized into a laminar flow with periodic velocity oscillations. Once patterned, the microtubule assembly reveals its intrinsic length and time scales, which we correlate with the activity of motor proteins, as predicted by existing theories of active nematics. The demonstrated commanding strategy should be compatible with other viable active biomaterials at interfaces, and we envision its use to probe the mechanics of the intracellular matrix.
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Wu, Fei, Changjiang Zheng, Chen Zhang, Junze Ma, and Kai Sun. "Multi-View Multi-Attention Graph Neural Network for Traffic Flow Forecasting." Applied Sciences 13, no. 2 (January 4, 2023): 711. http://dx.doi.org/10.3390/app13020711.
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The key to intelligent traffic control and guidance lies in accurate prediction of traffic flow. Since traffic flow data is nonlinear, complex, and dynamic, in order to overcome these issues, graph neural network techniques are employed to address these challenges. For this reason, we propose a deep-learning architecture called AMGC-AT and apply it to a real passenger flow dataset of the Hangzhou metro for evaluation. Based on a priori knowledge, we set up multi-view graphs to express the static feature similarity of each station in the metro network, such as geographic location and zone function, which are then input to the multi-graph neural network with the goal of extracting and aggregating features in order to realize the complex spatial dependence of each station’s passenger flow. Furthermore, based on periodic features of historical traffic flows, we categorize the flow data into three time patterns. Specifically, we propose two different self-attention mechanisms to fuse high-order spatiotemporal features of traffic flow. The final step is to integrate the two modules and obtain the output results using a gated convolution and a fully connected neural network. The experimental results show that the proposed model has better performance than eight other baseline models at 10 min, 15 min and 30 min time intervals.
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Asim, Taimoor, Rakesh Mishra, Antonio Oliveira, and Matthew Charlton. "Effects of the geometrical features of flow paths on the flow capacity of a control valve trim." Journal of Petroleum Science and Engineering 172 (January 2019): 124–38. http://dx.doi.org/10.1016/j.petrol.2018.09.050.
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Bichhawat, Abhishek, Vineet Rajani, Deepak Garg, and Christian Hammer. "Permissive runtime information flow control in the presence of exceptions." Journal of Computer Security 29, no. 4 (June 18, 2021): 361–401. http://dx.doi.org/10.3233/jcs-211385.
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Information flow control (IFC) has been extensively studied as an approach to mitigate information leaks in applications. A vast majority of existing work in this area is based on static analysis. However, some applications, especially on the Web, are developed using dynamic languages like JavaScript where static analyses for IFC do not scale well. As a result, there has been a growing interest in recent years to develop dynamic or runtime information flow analysis techniques. In spite of the advances in the field, runtime information flow analysis has not been at the helm of information flow security, one of the reasons being that the analysis techniques and the security property related to them (non-interference) over-approximate information flows (particularly implicit flows), generating many false positives. In this paper, we present a sound and precise approach for handling implicit leaks at runtime. In particular, we present an improvement and enhancement of the so-called permissive-upgrade strategy, which is widely used to tackle implicit leaks in dynamic information flow control. We improve the strategy’s permissiveness and generalize it. Building on top of it, we present an approach to handle implicit leaks when dealing with complex features like unstructured control flow and exceptions in higher-order languages. We explain how we address the challenge of handling unstructured control flow using immediate post-dominator analysis. We prove that our approach is sound and precise.
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Yang, Jin. "Urban Traffic Flow Prediction with Deep Neural Network." Security and Communication Networks 2022 (June 1, 2022): 1–10. http://dx.doi.org/10.1155/2022/8711873.
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It is critical to realize accurate collecting, visualization, rule mining, and prediction analysis of the traffic flow operating state in order for the intelligent transportation system to achieve exact management and control of traffic flow. Traffic flow prediction is primarily concerned with traffic data on roadways, which has both temporal and spatial correlations. Aiming at the spatiotemporal characteristics, this paper studies two aspects and designs a traffic flow prediction model with a deep neural network. First, this work proposes a traffic flow spatial feature learning algorithm with the combination of graph convolutional neural network and attention mechanism. Distinct weights are assigned to the degree of mutual impact between different nodes, and node adaptive learning is implemented at the same time, which modifies the standard parameter sharing mode, allowing for improved expressive ability and spatial feature extraction. Secondly, a learning algorithm for temporal characteristics of traffic flow based on the temporal convolutional network is proposed, which ensures that the dimensions of input and output data are consistent through causal convolution. The dilated convolution can flexibly control the receptive field by setting the sampling interval and can also extract temporal features well for long-length spatiotemporal sequence data. Finally, a spatiotemporal graph attention-based traffic flow prediction approach is constructed. To learn features, learn parameters for multiple modes and improve the model effect, this model employs a combination of graph convolutional neural networks and an attention mechanism. It uses a temporal convolutional network to expand the receptive field, better capture temporal features, and finally add residual connections to prevent problems such as overfitting caused by too deep network layers.
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kamal, Farrukh, and Naeem Arbab. "Micro Grid Automation with Unique Features of Power Flow Control by using SCADA." International Journal of Engineering Works 07, no. 06 (June 12, 2020): 238–46. http://dx.doi.org/10.34259/ijew.20.706238246.
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Pagliara, Stefano, and Michele Palermo. "Rock grade control structures and stepped gabion weirs: Scour analysis and flow features." Acta Geophysica 61, no. 1 (July 27, 2012): 126–50. http://dx.doi.org/10.2478/s11600-012-0066-0.
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Chern, Ming-Jyh, and Chih-Cheng Wang. "Control of Volumetric Flow-Rate of Ball Valve Using V-Port." Journal of Fluids Engineering 126, no. 3 (May 1, 2004): 471–81. http://dx.doi.org/10.1115/1.1760536.
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The control of volume flow rate in a ball valve is very important when a ball valve is utilized in a piping system. It is difficult to linearly control the flow rate in a ball valve without external devices. V-ports are employed to achieve this purpose. In order to investigate the effects of V-port on the volume flow rate and flow features, 3-D numerical simulations and experiments were conducted to observe the flow patterns and to measure performance coefficients when V-ports with various angles were used in a piping system. Three V-ports with angles 30 deg, 60 deg, and 90 deg were studied. It was found that V-ports with angles 30 deg and 60 deg make the flow rate proportional to the valve opening. However, V-ports increase the pressure loss between the inlet and the exit of a ball valve. In addition, V-ports with a small angle such as 30 deg increase the possibility of cavitation compared with flows without V-ports.
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Kadish, Shai, David Schmid, Jarryd Son, and Edward Boje. "Computer Vision-Based Classification of Flow Regime and Vapor Quality in Vertical Two-Phase Flow." Sensors 22, no. 3 (January 27, 2022): 996. http://dx.doi.org/10.3390/s22030996.
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This paper presents a method to classify flow regime and vapor quality in vertical two-phase (vapor-liquid) flow, using a video of the flow as the input; this represents the first high-performing and entirely camera image-based method for the classification of a vertical flow regime (which is effective across a wide range of regimes) and the first image-based tool for estimating vapor quality. The approach makes use of computer vision techniques and deep learning to train a convolutional neural network (CNN), which is used for individual frame classification and image feature extraction, and a deep long short-term memory (LSTM) network, used to capture temporal information present in a sequence of image feature sets and to make a final vapor quality or flow regime classification. This novel architecture for two-phase flow studies achieves accurate flow regime and vapor quality classifications in a practical application to two-phase CO2 flow in vertical tubes, based on offline data and an online prototype implementation, developed as a proof of concept for the use of these models within a feedback control loop. The use of automatically selected image features, produced by a CNN architecture in three distinct tasks comprising flow-image classification, flow-regime classification, and vapor quality prediction, confirms that these features are robust and useful, and offer a viable alternative to manually extracting image features for image-based flow studies. The successful application of the LSTM network reveals the significance of temporal information for image-based studies of two-phase flow.
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Gao, Chuanqiang, Weiwei Zhang, Jiaqing Kou, Yilang Liu, and Zhengyin Ye. "Active control of transonic buffet flow." Journal of Fluid Mechanics 824 (July 5, 2017): 312–51. http://dx.doi.org/10.1017/jfm.2017.344.
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Transonic buffet is a phenomenon of aerodynamic instability with shock wave motions which occurs at certain combinations of Mach number and mean angle of attack, and which limits the aircraft flight envelope. The objective of this study is to develop a modelling method for unstable flow with oscillating shock waves and moving boundaries, and to perform model-based feedback control of the two-dimensional buffet flow by means of trailing-edge flap oscillations. System identification based on the ARX algorithm is first used to derive a linear model of the input–output dynamics between the flap rotation (the control input) and the lift and pitching moment coefficients (system outputs). The model features a pair of unstable complex-conjugate poles at the characteristic buffet frequency. An appropriate reduced-order model (ROM) with a lower dimension is further obtained by a balanced truncation method that keeps the pair of unstable poles in the unstable subspace but truncates the dynamics in the stable subspace. Based on this balanced ROM, two kinds of feedback control are designed by pole assignment and linear quadratic methods respectively. These independent designs, however, result in similar suboptimal static output feedback control laws. When introduced in numerical simulations, they are both able to completely suppress the buffet instability. Furthermore, the resulting controllers are even able to stabilize buffet flows with nonlinear disturbances and in off-design flow conditions, thus implying their robustness. The analysis of the feedback control laws indicates that parameters (frequency and phase) corresponding to the ‘anti-resonance’ of the linear input–output model are vital for optimal control. The best performance is obtained when the control operates close to the ‘anti-resonance’, which is supported by the optimal frequency and the phase of the open-loop control as well as by the optimal phase of the closed-loop control.
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Li, Biaohui, Jinhao Zhang, and Nan Jiang. "Influence of Synthetic Jets on Multiscale Features in Wall-Bounded Turbulence." Actuators 11, no. 7 (July 18, 2022): 199. http://dx.doi.org/10.3390/act11070199.
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This experimental research focuses on the impacts of submerged synthetic jets on a fully-developed turbulent boundary layer (TBL) under a drag reduction working case. Two-dimensional velocity vectors in the flow field are captured with the aid of a particle image velocimetry (PIV) system. Proper orthogonal decomposition (POD) analyses provide evidence that synthetic jets notably attenuate the induction effect of prograde vortex on the low-speed fluid in large-scale fluctuation velocity field, thereby weakening the bursting process of near-wall turbulent events. Furthermore, the introduced perturbance redistributes the turbulent kinetic energy (TKE) and concentrates the TKE onto small-scale coherent structures. Modal time coefficients in various orders of POD are divided into components of multiple frequency bands by virtue of complementary ensemble empirical mode decomposition (CEEMD). It is found that the turbulence signals are shifted from low-frequency to high-frequency bands thanks to synthetic jets, thus revealing the relationship between scales and frequency bands. One further method of scale decomposition is proposed, that is, the large-scale fluctuating flow field will be obtained after removing the high-frequency noise data with the help of continuous mean square error (CMSE) criterion.
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Yang, Bing. "Numerical Simulation of Fluid Flow Features of Mechanical Mixer with Automatic Variable Frequency Control." International Journal of Heat and Technology 39, no. 1 (February 28, 2021): 319–27. http://dx.doi.org/10.18280/ijht.390135.
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For many engineering fields, it is of practical significance to construct and reasonably simplify the solid-liquid two-phase flow model in the cylinder of mechanical mixer. However, the existing studies have not considered how the control technology affects the fluid features in the mixer. From the angle of automatic variable frequency control, this paper carries out a numerical simulation of the fluid flow features in mechanical mixer. Firstly, the authors constructed the system structure for the mixer with automatic variable frequency control, and summarized the basic devices and the number of input/output points of the system. Then, the relationship between the force energy and control frequency of the mixing cylinder was detailed. Afterwards, the Euler-Euler two fluid model was introduced to numerically simulate the solid-liquid two-phase flow in the cylinder of the mixer, which contains both solid particles and liquid, followed by the establishment of control equation, the drag model, and the turbulence model. The proposed model was proved effective through experiments. The research findings provide a reference for the relevant research and the optimal design of the drive module of mixers.
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Pattyn, Frank, Sang De Brabander, and Ann Huyghe. "Basal and thermal control mechanisms of the Ragnhild glaciers, East Antarctica." Annals of Glaciology 40 (2005): 225–31. http://dx.doi.org/10.3189/172756405781813672.
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AbstractThe Ragnhild glaciers are three enhanced-flow features situated between the Sør Rondane and Yamato Mountains in eastern Dronning Maud Land, Antarctica. We investigate the glaciological mechanisms controlling their existence and behavior, using a three-dimensional numerical thermomechanical ice-sheet model including higher-order stress gradients. This model is further extended with a steady-state model of subglacial water flow, based on the hydraulic potential gradient. Both static and dynamic simulations are capable of reproducing the enhanced ice-flow features. Although basal topography is responsible for the existence of the flow pattern, thermomechanical effects and basal sliding seem to locally soften and lubricate the ice in the main trunks. Lateral drag is a contributing factor in balancing the driving stress, as shear margins can be traced over a distance of hundreds of kilometers along west Ragnhild glacier. Different basal sliding scenarios show that central Ragnhild glacier stagnates as west Ragnhild glacier accelerates and progressively drains the whole catchment area by ice and water piracy.
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Ou, Jishun, Jingxin Xia, Yao-Jan Wu, and Wenming Rao. "Short-Term Traffic Flow Forecasting for Urban Roads Using Data-Driven Feature Selection Strategy and Bias-Corrected Random Forests." Transportation Research Record: Journal of the Transportation Research Board 2645, no. 1 (January 2017): 157–67. http://dx.doi.org/10.3141/2645-17.
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Urban traffic flow forecasting is essential to proactive traffic control and management. Most existing forecasting methods depend on proper and reliable input features, for example, weather conditions and spatiotemporal lagged variables of traffic flow. However, the feature selection process is often done manually without comprehensive evaluation and leads to inaccurate results. For that challenge, this paper presents an approach combining the bias-corrected random forests algorithm with a data-driven feature selection strategy for short-term urban traffic flow forecasting. First, several input features were extracted from traffic flow time series data. Then the importance of these features was quantified with the permutation importance measure. Next, a data-driven feature selection strategy was introduced to identify the most important features. Finally, the forecasting model was built on the bias-corrected random forests algorithm and the selected features. The proposed approach was validated with data collected from three types of urban roads (expressway, major arterial, and minor arterial) in Kunshan City, China. The proposed approach was also compared with 10 existing approaches to verify its effectiveness. The results of the validation and comparison show that even without further model tuning, the proposed approach achieves the lowest average mean absolute error and root mean square error on six stations while it achieves the second-best average performance in mean absolute percentage error. Meanwhile, the training efficiency is improved compared with the original random forests method owing to the use of the feature selection strategy.
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Zhang, Tongtong, Jie Liu, Xiaohua Yang, Shiyu Yan, and Meng Li. "Metamorphic Relations Recognition Method Based on Node Features and Path Features." Journal of Physics: Conference Series 2219, no. 1 (April 1, 2022): 012059. http://dx.doi.org/10.1088/1742-6596/2219/1/012059.
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Abstract The classification model of the metamorphic relations of the scientific computing program has four categories, of which the code model occupies an important position. We redefine a metamorphic relations, which is single-line metamorphic relations and it exists in the nuclear power program. And it is more comprehensive compared to other metamorphic relations to reflect the internal logic of the program, while node features and path features can maximize the logical structure of the programs. Based on the above situation, we started from the code layer to study the metamorphic relations, put the control flow chart as the bridge of the code and metamorphic relations, extract node features and path features control flowchart and transform the identification problem of metamorphic relations into the problem of predictive model classification. Apply the identified single-line metamorphic relations to the nuclear power field and detect the effectiveness of the software program. The results show that the method is used to enrich the study of the metamorphic relations with the code level, and further improve the degree of automation of metamorphic tests.
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Zheng, Ming Gang, and Nan Wei. "Research on Cooling Control System of Flue Gas Based on Fuzzy Control." Applied Mechanics and Materials 610 (August 2014): 497–500. http://dx.doi.org/10.4028/www.scientific.net/amm.610.497.
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High-temperature flue gas in the factory has three features: high flow, strong corrosive and high temperature. It must be cooled to the rated temperature of different working conditions. There are nonlinear, time-varying issues and difficult to establish accurate mathematical model in the control of pump water quantity. We put PLC as the core to design the cooling control system which adjusts the pump water quantity by frequency changer based on fuzzy control theory.
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BANERJEE, ANINDYA, and DAVID A. NAUMANN. "Stack-based access control and secure information flow." Journal of Functional Programming 15, no. 2 (March 2005): 131–77. http://dx.doi.org/10.1017/s0956796804005453.
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Access control mechanisms are often used with the intent of enforcing confidentiality and integrity policies, but few rigorous connections have been made between information flow and runtime access control. The Java virtual machine and the .NET runtime system provide a dynamic access control mechanism in which permissions are granted to program units and a runtime mechanism checks permissions of code in the calling chain. We investigate a design pattern by which this mechanism can be used to achieve confidentiality and integrity goals: a single interface serves callers of more than one security level and dynamic access control prevents release of high information to low callers. Programs fitting this pattern would be rejected by previous flow analyses. We give a static analysis that admits them, using permission-dependent security types. The analysis is given for a class-based object-oriented language with features including inheritance, dynamic binding, dynamically allocated mutable objects, type casts and recursive types. The analysis is shown to ensure a noninterference property formalizing confidentiality and integrity.
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Yue, Meng, Qingxin Yan, Han Zheng, and Zhijun Wu. "Cross-Plane DDoS Attack Defense Architecture Based on Flow Table Features in SDN." Security and Communication Networks 2022 (September 30, 2022): 1–16. http://dx.doi.org/10.1155/2022/7409083.
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Software-Defined Networking (SDN) actualizes the separation of control and forwarding and innovates network functionalities with a logically centralized controller. Contemporary SDN infrastructure exposes the potential bottlenecks which are prone to engage in distributed denial of service attack (DDoS) thus posing an ever-increasing threat. This paper adopts the idea of “cross-plane collaboration” accomplishing DDoS attack defense and incorporates a two-phase project deploying the lightweight detection mechanism in data layer and the fine-grained filtering model in control layer. The coadjutant detection mechanism introduces a novel three-dimensional entropy consisting of five flow table features performing real-time feature detection; the defense strategy schedules an attack classification algorithm based on neural network by means of extracting four flow rule features designed to locate compromised interfaces occupied by malicious traffic. Extensive experiments are implemented to demonstrate the method we proposed brings excellent superiority. The detection rate of the classification filtering model is 99.4%, and it is real-time, with a detection time of 0.51s. In addition, the method of cross-layer defense reduces the CPU utilization of the controller.
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Strelnikov, G. A., A. D. Yhnatev, N. S. Pryadko, and S. S. Vasyliv. "Gas flow control in rocket engines." Technical mechanics 2021, no. 2 (June 29, 2021): 60–77. http://dx.doi.org/10.15407/itm2021.02.060.
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In the new conditions of application of launch vehicle boosters, space tugs, etc., modern rocket engines often do not satisfy the current stringent requirements. This calls for fundamental research into processes in rocket engines for improving their efficiency. In this regard, for the past 5 years, the Department of Thermogas Dynamics of Power Plants of the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine has conducted research on gas flow control in rocket engines to improve their efficiency and functionality. Mechanisms of flow perturbation in the nozzle of a rocket engine by liquid injection and a solid obstacle were investigated. A mathematical model of supersonic flow perturbation by local liquid injection was refined, and new solutions for increasing the energy release rate of the liquid were developed. A numerical simulation of a gas flow perturbed by a solid obstacle in the nozzle of a rocket engine made it possible to verify the known (mostly experimental) results and to reveal new perturbation features. In particular, a significant increase in the efficiency of flow perturbation by an obstacle in the transonic region was shown up, and some dependences involving the distribution of the perturbed pressure on the nozzle wall, which had been considered universal, were refined. The possibility of increasing the efficiency of use of the generator gas picked downstream of the turbine of a liquid-propellant rocket engine was investigated, and the advantages of a new scheme of gas injection into the supersonic part of the nozzle, which provides both nozzle wall cooling by the generator gas and the production of lateral control forces, were substantiated. A new concept of rocket engine thrust vector control was developed: a combination of a mechanical and a gas-dynamic system. It was shown that such a thrust vector control system allows one to increase the efficiency and reliability of the space rocket stage flight control system. A new liquid-propellant rocket engine scheme was developed to control both the thrust amount and the thrust vector direction in all planes of rocket stage flight stabilization. New approaches to the process organization in auxiliary elements of rocket engines on the basis of detonation propellant combustion were developed to increase the rocket engine performance.
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Cui, Xiaotong, Nan Jiang, Xiaobo Zheng, and Zhanqi Tang. "Active control of multiscale features in wall-bounded turbulence." Acta Mechanica Sinica 36, no. 1 (November 5, 2019): 12–21. http://dx.doi.org/10.1007/s10409-019-00907-5.
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Abstract This study experimentally investigates the impact of a single piezoelectric (PZT) actuator on a turbulent boundary layer from a statistical viewpoint. The working conditions of the actuator include a range of frequencies and amplitudes. The streamwise velocity signals in the turbulent boundary layer flow are measured downstream of the actuator using a hot-wire anemometer. The mean velocity profiles and other basic parameters are reported. Spectra results obtained by discrete wavelet decomposition indicate that the PZT vibration primarily influences the near-wall region. The turbulent intensities at different scales suggest that the actuator redistributes the near-wall turbulent energy. The skewness and flatness distributions show that the actuator effectively alters the sweep events and reduces intermittency at smaller scales. Moreover, under the impact of the PZT actuator, the symmetry of vibration scales’ velocity signals is promoted and the structural composition appears in an orderly manner. Probability distribution function results indicate that perturbation causes the fluctuations in vibration scales and smaller scales with high intensity and low intermittency. Based on the flatness factor, the bursting process is also detected. The vibrations reduce the relative intensities of the burst events, indicating that the streamwise vortices in the buffer layer experience direct interference due to the PZT control.
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He, Zhong Hai, Yi Hao Du, and Zhao Xia Wu. "Generation of Respiratory Flow Having Fractal Signal Feature." Advanced Materials Research 366 (October 2011): 211–14. http://dx.doi.org/10.4028/www.scientific.net/amr.366.211.
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In this paper how to generate respiratory flow that has fractal signal feature is introduced. Physiological signal have fractal feature have been verified by many researchers, such as heart beat rate, interbreath interval. Mechanical ventilators are used to provide life support for patients with respiratory failure. But these machines can damage the lung, causing them to collapse. On the other hand, fractal feature can be used as an indication of health situation; as a result in patient simulation the physiological signal should also have fractal features. The fractal feature is generated by fractional Brownian motion simulation. The fractal dimension is decided by Hurst exponent in routine. The algorithm is realized by R language and result is input into LabVIEW which have friendly interface and easy for simulation control usage. The method can be used in design of mechanical ventilator and medical patient simulator.
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Bi, Henry H., and John Nolt. "Toward a Formal Semantics for Control-Flow Process Models." Journal of Database Management 23, no. 2 (April 2012): 72–97. http://dx.doi.org/10.4018/jdm.2012040104.
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A number of information systems have been developed to automate business processes. For process modeling, verification, and automation in information systems, a formal semantics of control-flow process models is needed. Usually process modeling languages (e.g., BPMN, EPC, IDEF3, UML, and WfMC standards) are used to represent control-flow process models. When these process modeling languages are developed, their informal semantics are typically described using examples, but their formal semantics are not defined. Although many different semantics for control-flow process models have been proposed, the existing semantics specifications have limitations because they do not support certain desirable features. In this paper, we propose a new formal semantics for control-flow process models. We show that it is more accurate, complete, and applicable than the existing semantics specifications.
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Ullah, Amin, Khan Muhammad, Javier Del Ser, Sung Wook Baik, and Victor Hugo C. de Albuquerque. "Activity Recognition Using Temporal Optical Flow Convolutional Features and Multilayer LSTM." IEEE Transactions on Industrial Electronics 66, no. 12 (December 2019): 9692–702. http://dx.doi.org/10.1109/tie.2018.2881943.
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SAMIMY, M., M. DEBIASI, E. CARABALLO, A. SERRANI, X. YUAN, J. LITTLE, and J. H. MYATT. "Feedback control of subsonic cavity flows using reduced-order models." Journal of Fluid Mechanics 579 (May 2, 2007): 315–46. http://dx.doi.org/10.1017/s0022112007005204.
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Development, experimental implementation, and the results of reduced-order model based feedback control of subsonic shallow cavity flows are presented and discussed. Particle image velocimetry (PIV) data and the proper orthogonal decomposition (POD) technique are used to extract the most energetic flow features or POD eigenmodes. The Galerkin projection of the Navier–Stokes equations onto these modes is used to derive a set of nonlinear ordinary differential equations, which govern the time evolution of the eigenmodes, for the controller design. Stochastic estimation is used to correlate surface pressure data with flow-field data and dynamic surface pressure measurements are used to estimate the state of the flow. Five sets of PIV snapshots of a Mach 0.3 cavity flow with a Reynolds number of 105 based on the cavity depth are used to derive five different reduced-order models for the controller design. One model uses only the snapshots from the baseline (unforced) flow while the other four models each use snapshots from the baseline flow combined with snapshots from an open-loop sinusoidal forcing case. Linear-quadratic optimal controllers based on these models are designed to reduce cavity flow resonance and are evaluated experimentally. The results obtained with feedback control show a significant attenuation of the resonant tone and a redistribution of the energy into other modes with smaller energy levels in both the flow and surface pressure spectra. This constitutes a significant improvement in comparison with the results obtained using open-loop forcing. These results affirm that reduced-order model based feedback control represents a formidable alternative to open-loop strategies in cavity flow control problems even in its current state of infancy.
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Wallasch, Thomas-Martin. "Transcranial Doppler Ultrasonic Features in Chronic Tension-Type Headache." Cephalalgia 12, no. 6 (December 1992): 385–86. http://dx.doi.org/10.1111/j.1468-2982.1992.00385.x.
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We studied vascular features in patients suffering from chronic headache of the tension-type by means of transcranial Doppler ultrasound (TCD). Blood flow velocities of the basal cerebral arteries and the submandibular extracranial part of the internal carotid artery were compared between 20 chronic tension-type headache sufferers and the same number of age- and sex-matched control subjects. There were no significant differences of ultrasonic features between the groups. Changes in blood flow velocities do not seem to be involved in the pathogenetic mechanisms of chronic tension-type headache.
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Bhagat, Apurva, Harshal Gijare, and Nishanth Dongari. "Modeling of a reaction control jet interacting with high-speed cross-flow in slip flow regime." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 13 (April 15, 2019): 5029–44. http://dx.doi.org/10.1177/0954410019836901.
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Numerical investigation of a sonic reaction control jet interacting with the high-speed cross-flow has been carried out over a generic missile body. Simulations are performed in the early-hypersonic slip flow regime for air, CO2, and helium jet gases. An open source computational fluid dynamics tool, OpenFOAM is used to model the steady state, three-dimensional compressible Navier–Stokes equations with k-ω shear stress transport turbulence model. The conventional computational fluid dynamics solver is extended with additional features, such as transport of species, nonequilibrium boundary conditions for velocity slip and temperature jump, and a heat load calculation utility based on the sliding friction effect. The extended solver is validated with the direct simulation Monte Carlo results for the case of a sonic argon jet injected into hypersonic nitrogen cross-flow. The extended solver is able to accurately capture all the qualitative flow features like separation shock, bow shock, and barrel shock, and it also improves heat load predictions in the slip flow regime. The main objective of the present work is to study the effect of rarefaction and change in jet gas species on the complex flow topology, heat load distribution, and spread of jet gas on the missile body. Heat load predictions are found to be strongly dependent on the slip velocity of molecules in addition to the temperature gradient near the wall. The strength of a bow shock and a barrel shock is higher for helium jet, compared to air and CO2 jets, which spread more along the missile body, and weaker shocks and reduced heat load is generated. The current work is significant from the perspective of the thermal design of spacecraft surfaces and positioning of the optical sensors.
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Ortloff, Charles R. "Inka Hydraulic Engineering at the Tipon Royal Compound (Peru)." Water 14, no. 1 (January 4, 2022): 102. http://dx.doi.org/10.3390/w14010102.
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The Inka site of Tipon had many unique hydraulic engineering features that have modern hydraulic theory counterparts. For example, the Tipon channel system providing water to the Principal Fountain had a channel contraction inducing critical flow as determined by CFD analysis- this feature designed to induce flow stability and preserve the aesthetic display of the downstream Waterfall. The Main Aqueduct channel sourced by the Pukara River had a given flow rate to limit channel overbank spillage induced by a hydraulic jump at the steep-mild slope transition channel location as determined by use of modern CFD methods- this flow rate corresponds to the duplication of the actual flow rate used in the modern restoration using flow blockage plates placed in the channel to limit over-bank spillage. Additional hydraulic features governing the water supply to agricultural terraces for specialty crops constitute further sophisticated water management control systems discussed in detail in the text.