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Sample records for hydrodynamic clutch control

  1. Virtual Clutch Controller for Clutch-to-Clutch Shifts in Planetary-Type Automatic Transmission

    Directory of Open Access Journals (Sweden)

    Yunjiang Cheng

    2015-01-01

    Full Text Available It is known that the shift processes of the four types of clutch-to-clutch shifts can theoretically be divided into two phases which are torque phase and inertia phase, but the execution orders are different. Two virtual clutch controllers are designed with the same eight states which include all control processes for these shifts. An equivalent method is proposed so that AT can be controlled just like DCT by adopting the torque ratios of oncoming clutch and offgoing clutch of each gear. The powertrain system model and the shift controller are established on Matlab/Simulink platform. The clutch-to-clutch shift processes have been studied based on the virtual clutch controller by software-in-the-loop simulations. Some typical problems in the clutch-to-clutch shift control are discussed and several control methods are compared to solve these problems.

  2. Dynamic Analysis and Control of the Clutch Filling Process in Clutch-to-Clutch Transmissions

    Directory of Open Access Journals (Sweden)

    Wei Guo

    2014-01-01

    Full Text Available Clutch fill control in clutch-to-clutch transmissions influences shift quality considerably. An oncoming clutch should be applied synchronously with the release of an offgoing clutch to shift gear smoothly; therefore, the gap between the piston and clutch plates should be eliminated when the torque capacity is near zero at the end of the clutch fill phase. Open-loop control is typically implemented for the clutch fill because of the cost of pressure sensor. Low control precision causes underfill or overfill to occur, deteriorating shift quality. In this paper, a mathematical model of an electrohydraulic clutch shift control system is presented. Special dynamic characteristic parameters for optimal clutch fill control are subsequently proposed. An automatic method for predicting initial fill control parameters is proposed to eliminate distinct discrepancies among transmissions caused by manufacturing or assembling errors. To prevent underfill and overfill, a fuzzy adaptive control method is proposed, in which clutch fill control parameters are adjusted self-adaptively and continually. Road vehicle test results proved that applying the fuzzy adaptive method ensures the consistency of shift quality even after the transmission’s status is changed.

  3. Model reference control of conceptual clutched train substituted for vehicular friction clutch

    Directory of Open Access Journals (Sweden)

    Huang Wei

    2016-01-01

    Full Text Available In order to essentially reduce heat generation and frictional dissipation carried by friction clutch engagement, conceptual design of clutched train combined with hydrostatic braking system is proposed as a novel substitution for vehicular friction clutch. Potential collateral merits of clutched train may improve service life and control accuracy since less friction heat generated during synchronization process. Parameter of clutched train is obtained by Genetic Algorithm optimization aiming at axial space-saving and light weight. Control-oriented model of proposed concept is derived and used in Model Reference Control development. Based on optimum parameter of clutched train, simulation result has shown the functionality of clutched train on vehicle standing-start, and well-behaved Model Reference Control on smoothing clutched train synchronization process.

  4. Control of gear shifts in dual clutch transmission powertrains

    Science.gov (United States)

    Walker, Paul D.; Zhang, Nong; Tamba, Richard

    2011-08-01

    To achieve the best possible responses during shifting in dual clutch transmissions it is commonplace to integrate clutch and engine control, while the clutch is used to match speeds between the engine and wheels via reduction gears, poor engine control can lead to extended engagement times and rough/harsh shift transients. This paper proposes a method for combined speed and torque control of vehicle powertrains with dual clutch transmissions for both the engine and clutches. The vehicle powertrain is modelled as a simple four degree of freedom system with reduction gears and two clutches. Including a detailed clutch hydraulic model, comprising of the direct acting solenoids and clutch piston with the hydraulic fluid modelled as a compressible fluid. Powertrain control is realised through control of clutch solenoids and manipulation of the engine throttle input. Sensitivity study of clutch performance evaluating inaccurate torque estimation demonstrated variance in the response of the hydraulic system, with an indicative simulation of poor estimation resulting in increased powertrain vibration during and after shifting. Simulations are conducted to demonstrate the capacity for this method of engine and clutch control to further reduce shift transients developed in dual clutch transmission powertrains. The obtained results also show that the adoption of torque based control techniques for both the clutch and engine, which makes use of the estimated target clutch torque, significantly improves the powertrain response as a result of reduction in the lockup discontinuities.

  5. Generic control flow for the four types of clutch-to-clutch shifts

    Directory of Open Access Journals (Sweden)

    Yunjiang Cheng

    2016-05-01

    Full Text Available It is known that the clutch-to-clutch shifts in both planetary-type automatic transmission and dual clutch transmission can be divided into four types, which are power-on upshift, power-on downshift, power-off upshift, and power-off downshift. In previous studies, many control methods of clutch-to-clutch shifts are analyzed, but the control flows of the four types are different. In this article, the principle of these shifts is analyzed in detail. The concept of oncoming clutch’s torque ability is proposed. A generic control flow is designed, which divides the shift processes of the four types into the same three phases, and the control algorithm in transmission control unit and the calibration process can be simplified. The powertrain system model and the shift controller are established on MATLAB/Simulink platform. The generic control flow is verified by software-in-the-loop simulations. The simulation results show that the proposed generic control flow can control the four types of shifts properly.

  6. DETERMINATION ANALYSIS OF TEMPERATURE REGIMES, FUNCTIONAL CHARACTERISTICS AND SLIDING CURVES OF A HYDRODYNAMIC CLUTCH

    Directory of Open Access Journals (Sweden)

    Božidar V Krstić

    2010-01-01

    Full Text Available Analysis of output quality of power transmitters is possible in position when characteristics are determined earlier. This is the reason why we focused on determination of these characteristics for a concrete power hydro-transmitter. This means that the investigation task primarily consisted of determination of functional characteristics, defining of the sliding curves and temperature regimes of a concrete hydrodynamic clutch. Results of velocity and pressure field investigations in the working space of this clutch, obtained by use of the same test setup, are the basis for determination and analysis of the functional characteristics, sliding curves and temperature regimes. In this work we also analyzed function of the hydrodynamic transmitter in assembly with an internal combustion engine, as well as a process of acceleration and deceleration of a vehicle with this assembly in it.

  7. Adaptive Clutch Engaging Process Control for Automatic Mechanical Transmission

    Institute of Scientific and Technical Information of China (English)

    LIU Hai-ou; CHEN Hui-yan; DING Hua-rong; HE Zhong-bo

    2005-01-01

    Based on detail analysis of clutch engaging process control targets and adaptive demands, a control strategy which is based on speed signal, different from that of based on main clutch displacement signal, is put forward. It considers both jerk and slipping work which are the most commonly used quality evaluating indexes of vehicle starting phase. The adaptive control system and its reference model are discussed profoundly.Taking the adaptability to different starting gears and different road conditions as examples, some proving field test records are shown to illustrate the main clutch adaptive control strategy at starting phase. Proving field test gives acceptable results.

  8. Optimal torque coordinating control of the launching with twin clutches simultaneously involved for dry dual-clutch transmission

    Science.gov (United States)

    Zhao, Z. G.; Chen, H. J.; Zhen, Z. X.; Yang, Y. Y.

    2014-06-01

    As for the self-developed six-speed dry dual-clutch transmission (DCT), the optimal torque-coordinated control strategy between engine and dual clutches is proposed to resolve the problem of launching with twin clutches simultaneously involved based on the minimum value principle. Focusing on the sliding friction phase of the launching process, dynamics equations of dry DCT with two intermediate shafts are firstly established, and then the optimal transmitting torque variation rate and the driven plate's rotating speed of dual clutches are deduced by using the minimum value principle, in which the jerk intensity and friction work are taken as the performance indexes, and the terminal constraints of state variables are determined according to the driver's launching intention. Besides, the separating conditions of non-target gear clutch and the torque distributing relations of twin clutches are derived from the launching control targets that guarantee the approximately equal friction extent of two clutches and no power cycle. After the synchronisation of driving and driven plates of on-coming clutch, the output torque of engine is smoothly switched to the driver's demand level. Furthermore, launching the simulation model of the dry DCT vehicle is set up on the Matlab/Simulink platform. Simulation results indicate that the proposed launching control strategy not only can effectively reflect the driver's intention and extend the life span of twin clutches, but also obtain an excellent launching quality. Finally, the torque control laws of two clutches obtained through the simulation are transformed into clutch position control laws for the future realisation in the real car, and the closed-loop position controls of twin clutches in the launching process are conducted on the test bench with two sets of clutch actuator, obtaining preferable tracking effects.

  9. Simulation and control of an electro-hydraulic actuated clutch

    Science.gov (United States)

    Balau, Andreea-Elena; Caruntu, Constantin-Florin; Lazar, Corneliu

    2011-08-01

    The basic function of any type of automotive transmission is to transfer the engine torque to the vehicle with the desired ratio smoothly and efficiently and the most common control devices inside the transmission are clutches and hydraulic pistons. The automatic control of the clutch engagement plays a crucial role in Automatic Manual Transmission (AMT) vehicles, being seen as an increasingly important enabling technology for the automotive industry. It has a major role in automatic gear shifting and traction control for improved safety, drivability and comfort and, at the same time, for fuel economy. In this paper, a model for a wet clutch actuated by an electro-hydraulic valve used by Volkswagen for automatic transmissions is presented. Starting from the developed model, a simulator was implemented in Matlab/Simulink and the model was validated against data obtained from a test-bench provided by Continental Automotive Romania, which includes the Volkswagen wet clutch actuated by the electro-hydraulic valve. Then, a predictive control strategy is applied to the model of the electro-hydraulic actuated clutch with the aims of controlling the clutch piston displacement and decreasing the influence of the network-induced delays on the control performances. The simulation results obtained with the proposed method are compared with the ones obtained with different networked controllers and it is shown that the strategy proposed in this paper can indeed improve the performances of the control system.

  10. OPTIMAL CONTROL APPLIED IN AUTOMATIC CLUTCH ENGAGEMENTS OF VEHICLES

    Institute of Scientific and Technical Information of China (English)

    Sun Chengshun; Zhang Jianwu

    2004-01-01

    Start-up working condition is the key to the research of optimal engagement of automatic clutch for AMT.In order to guarantee an ideal dynamic performance of the clutch engagement,an optimal controller is designed by considering throttle angle,engine speed,gear ratio,vehicle acceleration and road condition.The minimum value principle is also introduced to achieve an optimal dynamic performance of the nonlinear system compromised in friction plate wear and vehicle drive quality.The optimal trajectory of the clutch engagement can be described in the form of explicit and analytical expressions and characterized by the deterministic and accurate control strategy in stead of indeterministic and soft control techniques which need thousands of experiments.For validation of the controller,test work is carried out for the automated clutch engagements in a commercial car with an traditional mechanical transmission,a hydraulic actuator,a group of sensors and a portable computer system.It is shown through experiments that dynamic behaviors of the clutch engagement operated by the optimal control are more effective and efficient than those by fuzzy control.

  11. Precision Tension Control System Using Magnetic Particle Clutch

    Institute of Scientific and Technical Information of China (English)

    王春香; 杨汝清; 王永章; 路华

    2004-01-01

    The control of the stability of the filament tension is one of the crucial techniques ensuring the component quality of the composite materials. The open-loop tension control system, with industrial control computer as the core,magnetic particle clutch as the actuator, equipped with compensation technique is researched and manufactured.It can assure the tension control stability of the yarn in filament winding process and increase the control precision of the whole system.

  12. Position control system using ER clutch and piezoactuator

    Science.gov (United States)

    Choi, Seung-Bok; Han, Sang-Soo

    2003-08-01

    This paper presents ultra precision positioning system consisting of electrorheological(ER) clutch and piezoelectric actuators using dual servo control mechanism. ER clutch and ball screw are adopted for a coarse positioning stage, and magnification device driven by multi-stack piezoelectric actuator is manufactured for a fine positioning stage. After deriving the dynamic modeling for coarse motion stage, a sliding mode controller is designed to achieve robust control performance. In addition, conventional PID controller incorporated with the hysteresis nonlinearity of the piezoelectric actuator is designed to construct a feed-back with feed-forward control scheme for precise and fast positioning of the fine motion stage. Step regulating control performance of the proposed dual servo system is evaluated via experimental works to verify the effectiveness of the proposed position control system.

  13. Automated Clutch of AMT Vehicle Based on Adaptive Generalized Minimum Variance Controller

    National Research Council Canada - National Science Library

    Ze Li; Xinhao Yang

    2014-01-01

    ... of the automated clutch of automatic mechanical transmission vehicle. In this paper, an adaptive generalized minimum variance controller is applied to the automated clutch, which is driven by a brushless DC motor...

  14. A new method for speed control of a DC motor using magnetorheological clutch

    Science.gov (United States)

    Nguyen, Quoc Hung; Choi, Seung-Bok

    2014-03-01

    In this research, a new method to control speed of DC motor using magnetorheological (MR) clutch is proposed and realized. Firstly, the strategy of a DC motor speed control using MR clutch is proposed. The MR clutch configuration is then proposed and analyzed based on Bingham-plastic rheological model of MR fluid. An optimal designed of the MR clutch is then studied to find out the optimal geometric dimensions of the clutch that can transform a required torque with minimum mass. A prototype of the optimized MR clutch is then manufactured and its performance characteristics are experimentally investigated. A DC motor speed control system featuring the optimized MR clutch is designed and manufactured. A PID controller is then designed to control the output speed of the system. In order to evaluate the effectiveness of the proposed DC motor speed control system, experimental results of the system such as speed tracking performance are obtained and presented with discussions.

  15. Sliding Mode Control Approach for Electrically Controllable Clutch of AMT Based on the Feedback Linearization

    Institute of Scientific and Technical Information of China (English)

    程东升; 张建武; 叶晓峰; 黄维纲

    2003-01-01

    A sliding mode control approach based on the feedback linearization is proposed for the electrically controllable clutch of AMT vehicles. The nonlinear dynamic model for the hydraulic actuator associated with clutch is established. By means of the exact feedback linearization procedure of differential geometry, an equivalent, fully controllable and linear model is derived via a homomorphic transformation for the AMT clutch system.Furthermore, a sliding mode control is introduced to improve robustness. The tracking tests are performed using the sliding mode control on a Santana LX passenger car, and the experimental results prove that this nonlinear controller is of fine robustness and high degree of tracking accuracy.

  16. Supervisor control strategy of synchronizer for wet DCT based on online estimation of clutch drag torque

    Science.gov (United States)

    Lu, Tongli; Li, Hongkui; Zhang, Jianwu; Hao, Hongtao

    2016-01-01

    The objective of this paper is to improve the performance of the synchronizer control strategy by considering the effect of clutch drag torque. The research of synchronization process in wet dual clutch transmission is performed in this paper. The significant effect of clutch drag torque is analyzed by adding a complex clutch drag torque module to synchronizer model. This paper focuses on the development of original estimation method of clutch drag torque. The estimation method offers an effective way to obtain accurate clutch drag torque, and it is applied to develop a new supervisor control strategy. Results have demonstrated that the estimation method has satisfied efficiency and accuracy and the control strategy improves the performance of the synchronizer mechanism significantly.

  17. Electrorheological clutch for robotics applications: validation of mathematical model and preliminary control study

    Science.gov (United States)

    Tan, Kim P.; Stanway, Roger; Johnson, Andrew R.; Bullough, William A.; Tozer, Richard C.

    2001-08-01

    There is much current interest in the development of smart fluid clutches for use in the design of high speed machinery. In this paper, the authors employ an ER clutch mechanism in a robotic application. This clutch mechanism consists of twin ER clutches which are driven in opposite directions by two electric motors. By controlling the electric field applied to each clutch, it is possible to control the angular displacement of a robot arm. Before considering control, an established mathematical model is validated. The purpose of this model validation is to help design a control strategy for accurate positioning of the robot arm. Through the use of a Simulink program and a digital controller, both the simulated and experimental angular displacements are compared and shown to be in close agreement. Finally, the displacement response of the ER- driven and DC servo-actuatored robot arm are compared and conclusions are drawn as to the suitability of the ER clutch mechanism as a robotic actuator.

  18. The Design of Miniature Electronic Control Unit for Variable Speed Hydrodynamic Clutch%调速型液力偶合器微型电控单元设计

    Institute of Scientific and Technical Information of China (English)

    刘丹丹; 邵万珍; 类延磊; 姜文震

    2015-01-01

    With variable speed hydraulic coupling for the study, according to the characteristics of their work to design a miniature electronic control unit for hydraulic coupling automation control. In this paper, using the FPGA programmable logic controller chip to deploy peripher-al circuits. Completed the detection of the variable speed hydraulic coupling on oil well pump and turbine speed, automatic control design. Hardware circuit comprises a signal acquisition module, a signal processing module, and a driving external device control module. The PID regulation technology has the characteristics of small overshoot on the speed and temperature, fast response and accurate.%以调速型液力偶合器为研究对象,根据其工作特点设计一套用于液力偶合器自动化控制的微型电控单元。该文采用FPGA可编程逻辑控制芯片,部署外围电路。完成调速型液力偶合器对油温、油压以及泵轮和涡轮速度的检测、自动控制偶合器的输出转速设计。硬件电路包括信号采集模块、信号处理模块以及驱动外部设备控制模块。采用PID调节技术,控制参数的超调量小、响应速度快、准确。

  19. Self-adaptive optimal control of dry dual clutch transmission (DCT) during starting process

    Science.gov (United States)

    Zhao, Zhiguo; He, Lu; Zheng, Zhengxing; Yang, Yunyun; Wu, Chaochun

    2016-02-01

    An optimal control based on the minimum principle is proposed to solve the problems with the starting process of the self-developed five-speed dry dual clutch transmission (DCT). For the slipping phase, the minimum principle and improved engine constant speed control are adopted to obtain the optimal clutch and engine torques and their rotating speeds, with the minimum jerk intensity and friction work as optimization indices. For the stable running phase, the engine torque is converted to the driver's level of demand. The Matlab/Simulink software platform was used to simulate the DCT vehicle in the starting stage. The simulation and related analysis were conducted for different engine speeds and intentions of the driver. The results showed that the proposed clutch starting control strategy not only reduces the level of jerk and the frictional energy loss but also follows the different starting intentions of the driver. The optimum clutch engagement principle was transformed into the clutch position principle, and a test was carried out on the test bench to validate the effectiveness of the optimum clutch position curve.

  20. Coordinated Control of Downshift Powertrain of Combined Clutch Transmissions for Electric Vehicles

    Directory of Open Access Journals (Sweden)

    Junqiu Li

    2014-01-01

    Full Text Available To improve the shift quality of electric vehicles equipped with two-gear automatic transmissions, the coordinated control of the combined clutch and the motor is proposed. The dynamic model of shift process is built up, the dynamic characteristics of each phase of downshift process are analyzed, and linear quadratic optimal control is used to optimize the shift process. As a result, the optimal trajectories of the motor torque and oil pressure of the combined clutch are obtained. Compared to the clutch control only, the simulation results indicate that shift quality is improved remarkably by employing the proposed coordinated control. Specifically, the shift jerk and sliding friction work are decreased by 43% and 44%, respectively, with accelerator pedal angle 50%. In contrast, the reduced percentages are 57% and 89% when accelerator pedal is not depressed.

  1. Control of a haptic gear shifting assistance device utilizing a magnetorheological clutch

    Science.gov (United States)

    Han, Young-Min; Choi, Seung-Bok

    2014-10-01

    This paper proposes a haptic clutch driven gear shifting assistance device that can help when the driver shifts the gear of a transmission system. In order to achieve this goal, a magnetorheological (MR) fluid-based clutch is devised to be capable of the rotary motion of an accelerator pedal to which the MR clutch is integrated. The proposed MR clutch is then manufactured, and its transmission torque is experimentally evaluated according to the magnetic field intensity. The manufactured MR clutch is integrated with the accelerator pedal to transmit a haptic cue signal to the driver. The impending control issue is to cue the driver to shift the gear via the haptic force. Therefore, a gear-shifting decision algorithm is constructed by considering the vehicle engine speed concerned with engine combustion dynamics, vehicle dynamics and driving resistance. Then, the algorithm is integrated with a compensation strategy for attaining the desired haptic force. In this work, the compensator is also developed and implemented through the discrete version of the inverse hysteretic model. The control performances, such as the haptic force tracking responses and fuel consumption, are experimentally evaluated.

  2. Oscillations control of a transmission belt by Excitation Clipping using Clutch Clamping Control (E4C)

    Science.gov (United States)

    Temporelli, Robin; Micheau, Philippe

    2017-04-01

    A transmission belt deals with non-linear phenomena such as parametric excitations that can bring the belt in an instability region resulting in large transverse oscillations. These oscillations can cause belt life deflection, noise and unexpected vibration on its environment. The present study proposes a new strategy to control oscillations of a transmission belt subject to periodic tension fluctuations. Indeed, for a transmission belt, periodic torque fluctuations cause periodic belt tension fluctuations which can be a source of excitation for the belt and resulting in belt oscillations under certain conditions. The presence of a clutch between the belt end-point and the source of torque fluctuations offers a means to clip torque fluctuations and thus to clip belt excitation. In keeping with this notion, belt oscillations can be controlled by an Excitation Clipping using Clutch Clamping Control (E4C) strategy. Through an example of a transmission belt subject to periodic tension fluctuations, the E4C strategy is presented and a new analytical model of belt behavior with its E4C strategy is constructed. Free belt oscillations (E4C is not activated) and controlled belt oscillations (E4C is activated) are observed through an experimental setup and predicted owing to the new analytical model. Finally, the E4C strategy leads to frequency unlocking that successfully removes belt oscillations. This new analytical model furthermore provides an accurate prediction of belt behavior with its E4C strategy.

  3. Torque Control of a Rehabilitation Teaching Robot Using Magneto-Rheological Fluid Clutches

    Science.gov (United States)

    Hakogi, Hokuto; Ohaba, Motoyoshi; Kuramochi, Naimu; Yano, Hidenori

    A new robot that makes use of MR-fluid clutches for simulating torque is proposed to provide an appropriate device for training physical therapy students in knee-joint rehabilitation. The feeling of torque provided by the robot is expected to correspond to the torque performance obtained by physical therapy experts in a clinical setting. The torque required for knee-joint rehabilitation, which is a function of the rotational angle and the rotational angular velocity of a knee movement, is modeled using a mechanical system composed of typical spring-mass-damper elements. The robot consists of two MR-fluid clutches, two induction motors, and a feedback control system. In the torque experiments, output torque is controlled using the spring and damper coefficients separately. The values of these coefficients are determined experimentally. The experimental results show that the robot would be suitable for training physical therapy students to experience similar torque feelings as needed in a clinical situation.

  4. Powertrain dynamics and control of a two speed dual clutch transmission for electric vehicles

    Science.gov (United States)

    Walker, Paul; Zhu, Bo; Zhang, Nong

    2017-02-01

    The purpose of this paper is to demonstrate the application of torque based powertrain control for multi-speed power shifting capable electric vehicles. To do so simulation and experimental studies of the shift transient behaviour of dual clutch transmission equipped electric vehicle powertrains is undertaken. To that end a series of power-on and power-off shift control strategies are then developed for both up and down gear shifts, taking note of the friction load requirements to maintain positive driving load for power-on shifting. A mathematical model of an electric vehicle powertrain is developed including a DC equivalent circuit model for the electric machine and multi-body dynamic model of the powertrain system is then developed and integrated with a hydraulic clutch control system model. Integral control of the powertrain is then performed through simulations on the develop powertrain system model for each of the four shift cases. These simulation results are then replicated on a full scale powertrain test rig. To evaluate the performance of results shift duration and vehicle jerk are used as metrics to demonstrate that the presented strategies are effective for shift control in electric vehicles. Qualitative comparison of both theoretical and experimental results demonstrates reasonable agreement between simulated and experimental outcomes.

  5. Fuzzy Determination of Target Shifting Time and Torque Control of Shifting Phase for Dry Dual Clutch Transmission

    Directory of Open Access Journals (Sweden)

    Zhiguo Zhao

    2014-01-01

    Full Text Available Based on the independently developed five-speed dry dual clutch transmission (DDCT, the paper proposes the torque coordinating control strategy between engine and two clutches, which obtains engine speed and clutch transferred torque in the shifting process, adequately reflecting the driver intention and improving the shifting quality. Five-degree-of-freedom (DOF shifting dynamics model of DDCT with single intermediate shaft is firstly established according to its physical characteristics. Then the quantitative control objectives of the shifting process are presented. The fuzzy decision of shifting time and the model-based torque coordinating control strategy are proposed and also verified by simulating under different driving intentions in up-/downshifting processes with the DCT model established on the MATLAB/Simulink. Simulation results validate that the shifting control algorithm proposed in this paper can not only meet the shifting quality requirements, but also adapt to the various shifting intentions, having a strong robustness.

  6. Intelligent clutch control with incremental encoder to improve wear issues of an intercept pendulum in real time

    Science.gov (United States)

    Jalba, C. K.; Diekmann, R.; Epple, S.

    2017-01-01

    A pendulum impact tester is a technical device which is used to perform plasticity characterizations of metallic materials. Results are calculated based on fracture behavior under pendulum impact loadings according to DIN 50115, DIN 51222/EN 10045. The material is held at the two ends and gets struck in the middle. A mechanical Problem occurs when testing materials with a very high impact toughness. These specimen often do not break when hit by the pendulum. To return the pendulum to its initial position, the operator presses a service button. After a delay of approximately 2 seconds a clutch is activated which connects the arm of the pendulum with an electric motor to return it back upright in start position. At the moment of clutch activation, the pendulum can still swing or bounce with any speed in any direction at any different position. Due to the lack of synchronization between pendulum speed and constant engine speed, the clutch suffers heavy wear of friction. This disadvantage results in considerable service and repair costs for the customer. As a solution to this problem this article presents a customized technical device to significantly increase the lifetime of the clutch. It was accomplished by a precisely controlled activation of the clutch at a point of time when pendulum and motor are at synchronized speed and direction using incremental encoders.

  7. Torque coordinating robust control of shifting process for dry dual clutch transmission equipped in a hybrid car

    Science.gov (United States)

    Zhao, Z.-G.; Chen, H.-J.; Yang, Y.-Y.; He, L.

    2015-09-01

    For a hybrid car equipped with dual clutch transmission (DCT), the coordination control problems of clutches and power sources are investigated while taking full advantage of the integrated starter generator motor's fast response speed and high accuracy (speed and torque). First, a dynamic model of the shifting process is established, the vehicle acceleration is quantified according to the intentions of the driver, and the torque transmitted by clutches is calculated based on the designed disengaging principle during the torque phase. Next, a robust H∞ controller is designed to ensure speed synchronisation despite the existence of model uncertainties, measurement noise, and engine torque lag. The engine torque lag and measurement noise are used as external disturbances to initially modify the output torque of the power source. Additionally, during the torque switch phase, the torque of the power sources is smoothly transitioned to the driver's demanded torque. Finally, the torque of the power sources is further distributed based on the optimisation of system efficiency, and the throttle opening of the engine is constrained to avoid sharp torque variations. The simulation results verify that the proposed control strategies effectively address the problem of coordinating control of clutches and power sources, establishing a foundation for the application of DCT in hybrid cars.

  8. STUDY ON CONTROL STRATEGY OF CLUTCH STARTING FOR CAR WITH A METAL PUSHING BELT-PLANETARY GEAR CONTINUOUSLY VARIABLE TRANSMISSION SYSTEM

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The automatic control of clutch starting in car with a metal pushing belt-planetary gear continuously variable transmission (CVT) is a complex problem. A suited control strategy is required to realize quick and smooth start. A simulation state space equation is established on clutch starting control of a car with CVT by bond graph theory. According to the fuzzy control method with the expert system, a fuzzy control system of car starting process to weaken the jerk motion is introduced. The simulation results indicate that the jerk motion of clutch starting is below 10 m/s3.

  9. Sliding Mode Variable Structure Control and Real-Time Optimization of Dry Dual Clutch Transmission during the Vehicle’s Launch

    OpenAIRE

    Zhiguo Zhao; Haijun Chen; Qi Wang

    2014-01-01

    In order to reflect driving intention adequately and improve the launch performance of vehicle equipped with five-speed dry dual clutch transmission (DCT), the issue of coordinating control between engine and clutch is researched, which is based on the DCT and prototype car developed independently. Four-degree-of-freedom (DOF) launch dynamics equations are established. Taking advantage of predictive control and genetic algorithm, target tracing curves of engine speed and vehicle velocity are ...

  10. Dynamo efficiency controlled by hydrodynamic bistability.

    Science.gov (United States)

    Miralles, Sophie; Herault, Johann; Herault, Johann; Fauve, Stephan; Gissinger, Christophe; Pétrélis, François; Daviaud, François; Dubrulle, Bérengère; Boisson, Jean; Bourgoin, Mickaël; Verhille, Gautier; Odier, Philippe; Pinton, Jean-François; Plihon, Nicolas

    2014-06-01

    Hydrodynamic and magnetic behaviors in a modified experimental setup of the von Kármán sodium flow-where one disk has been replaced by a propeller-are investigated. When the rotation frequencies of the disk and the propeller are different, we show that the fully turbulent hydrodynamic flow undergoes a global bifurcation between two configurations. The bistability of these flow configurations is associated with the dynamics of the central shear layer. The bistable flows are shown to have different dynamo efficiencies; thus for a given rotation rate of the soft-iron disk, two distinct magnetic behaviors are observed depending on the flow configuration. The hydrodynamic transition controls the magnetic field behavior, and bifurcations between high and low magnetic field branches are investigated.

  11. Research methodology simplification for teaching purposes illustrated by clutch automatic control device testing

    Science.gov (United States)

    Wojs, J.

    2016-09-01

    The paper proves that simplified, shorter examination of an object, feasible in laboratory classes, can produce results similar to those reached in scientific investigation of the device using extensive equipment. A thorough investigation of an object, an automatic clutch device in this case, enabled identifying the magnitudes that most significantly affect its operation. The knowledge of these most sensitive magnitudes allows focusing in the teaching process on simplified measurement of only selected magnitudes and verifying the given object in the positive or negative.

  12. Dynamic Temperature Rise Mechanism and Some Controlling Factors of Wet Clutch Engagement

    Directory of Open Access Journals (Sweden)

    Zhang Zhigang

    2016-01-01

    Full Text Available The friction transmission model of wet clutch is established to analyze the friction transmission mechanism of its engagement. The model is developed by applying both the average flow model and the elastic contact model between the friction disk and separator plate. The key components during wet clutch engagement are the separator plate, friction disk, and lubricant. The one-dimension transient models of heat transfer in radial direction for the three components are built on the basis of the heat transfer theory and the conservation law of energy. The friction transmission model and transient heat transfer models are coupled and solved by using the Runge-Kutta numerical method, and the radial temperature distribution and their detailed parametric study for the three components are conducted separately. The simulation results show that the radial temperature for the three components rises with the increase of radius in engagement. The changes in engagement pressure, lubricant viscosity, friction lining permeability, combined surface roughness RMS, equivalent elasticity modulus, difference between dynamic and static friction coefficients, and lubricant flow have important influence on the temperature rise characteristics. The proposed models can get better understanding of the dynamic temperature rise characteristics of wet clutch engagement.

  13. DYNAMIC ANALYSIS OF A VEHICLE CLUTCH

    Directory of Open Access Journals (Sweden)

    Emin GÜLLÜ

    2003-03-01

    Full Text Available In this study as a first step of an ongoing investigation, a dynamic model was developed to analyse motion and power transmission phenomen in mechanical clutches used commonly in motor vehicles . The control of a driver on clutch and speed pedals was reflected in the model. The movement of clutch disk with constant speed and acceleration can be investigated by using the model. In addition, the control of speeding by driver was included to the model via a certain scenario. During clutch engagement and after, the effects of loading torques in different gears on the time of perfect engagement and on the speed of the vehicle were investigated.

  14. Dynamic Coordinated Shifting Control of Automated Mechanical Transmissions without a Clutch in a Plug-In Hybrid Electric Vehicle

    Directory of Open Access Journals (Sweden)

    Xinlei Liu

    2012-08-01

    Full Text Available On the basis of the shifting process of automated mechanical transmissions (AMTs for traditional hybrid electric vehicles (HEVs, and by combining the features of electric machines with fast response speed, the dynamic model of the hybrid electric AMT vehicle powertrain is built up, the dynamic characteristics of each phase of shifting process are analyzed, and a control strategy in which torque and speed of the engine and electric machine are coordinatively controlled to achieve AMT shifting control for a plug-in hybrid electric vehicle (PHEV without clutch is proposed. In the shifting process, the engine and electric machine are well controlled, and the shift jerk and power interruption and restoration time are reduced. Simulation and real car test results show that the proposed control strategy can more efficiently improve the shift quality for PHEVs equipped with AMTs.

  15. Power-on Downshift Control for Clutch-to-clutch Automatic Transmission%离合器-离合器式自动变速器动力降档过程控制

    Institute of Scientific and Technical Information of China (English)

    万国强; 李克强; 罗禹贡; 黄英

    2015-01-01

    Power-on downshift is an effective way for the vehicle to achieve rapid acceleration and overtake. To achieve smooth power-on downshift, not only the clutch hydraulic pressure should be accurately controlled, but also the engine torque should be properly controlled. Based on the DEUTZ BF4M 1013 turbo-charged electronic unit pump diesel engine and the Allison S2000 clutch-to-clutch automatic transmission, an integrated powertrain control strategy for the power-on downshift process is proposed. First of all, the dynamics model of the downshift process is derived using the Lagrange method. Then the method for controlling the oncoming clutch and the offgoing clutch is obtained, and the coordinated engine control based on the turbine speed is proposed. The experimental study is carried out on the test bench. The experimental results show that the shift time is less than 1 s, and the shift jerk of the power-on downshift process is smaller than 10 m/s3. The proposed integrated powertrain control strategy for the power-on downshift process can be used for the practical engineering application.%动力降档是实现车辆快速提速、超车等的有效技术途径.在保证换档品质的前提下,实现动力降档,不仅需要自动变速器进行精确的离合器油压控制,而且需要发动机进行有效的转矩协调控制.针对由DEUTZ BF4M1013涡轮增压单体泵柴油机和Allison S2000离合器-离合器换档式液力自动变速器组成的动力传动系统,基于Lagrange方程建立换档过程的动力学模型,通过对降档过程各个阶段的详细分析,得到动力降档过程结合离合器和分离离合器的搭接控制时序以及控制油压的变化规律,制定基于涡轮轴转速闭环的发动机协调控制策略,在台架上进行试验验证.试验结果表明,动力降档过程的时间小于1 s,冲击度小于10 m/s3.制定的控制策略不仅实现了动力降档,而且保证了换档品质,能够进行工程实际应用.

  16. Sliding Mode Variable Structure Control and Real-Time Optimization of Dry Dual Clutch Transmission during the Vehicle’s Launch

    Directory of Open Access Journals (Sweden)

    Zhiguo Zhao

    2014-01-01

    Full Text Available In order to reflect driving intention adequately and improve the launch performance of vehicle equipped with five-speed dry dual clutch transmission (DCT, the issue of coordinating control between engine and clutch is researched, which is based on the DCT and prototype car developed independently. Four-degree-of-freedom (DOF launch dynamics equations are established. Taking advantage of predictive control and genetic algorithm, target tracing curves of engine speed and vehicle velocity are optimally specified. Sliding mode variable structure (SMVS control strategy is designed to track these curves. The rapid prototyping experiment and test are, respectively, conducted on the DCT test bench and in the chassis dynamometer. Results show that the designed SMVS control strategy not only effectively embodies the driver’s intention but also has strong robustness to the vehicle parameter’s variations.

  17. Electromagnetic clutches and couplings

    CERN Document Server

    Vorob'Yeva, T M; Fry, D W; Higinbotham, W

    2013-01-01

    Electromagnetic Clutches and Couplings contains a detailed description of U.S.S.R. electromagnetic friction clutches, magnetic couplings, and magnetic particle couplings. This book is divided into four chapters. The first chapter discusses the design and construction of magnetic (solenoid-operated) couplings, which are very quick-acting devices and used in low power high-speed servo-systems. Chapter 2 describes the possible fields of application, design, construction, and utilization of magnetic particle couplings. The aspects of construction, design, and utilization of induction clutches (sli

  18. Estimation of torque transmitted by clutch during shifting process for dry dual clutch transmission

    Science.gov (United States)

    Zhao, Zhiguo; He, Lu; Yang, Yunyun; Wu, Chaochun; Li, Xueyan; Karl Hedrick, J.

    2016-06-01

    The key toward realizing no-impact gear shifting for dual clutch transmission (DCT) lies in the coordination control between the engine and dual clutches, as well as the accurate closed-loop control of torque transmitted by each clutch and the output torque of the engine. However, the implementation and control precision of closed-loop control are completely dependent on the effective measurement or estimation of the instant transmission torque of the clutch. This study analyzes the DCT shifting process, and builds a three-dimensional (3D) clutch model and mathematical model of a DCT vehicle powertrain system. The torque transmitted by a twin clutch during the upshifting process is estimated by applying the unscented Kalman filter (UKF) algorithm. Then, the torque estimation algorithm is verified using a DCT prototype vehicle installed with a torque sensor on the drive half-shaft. The experimental results show that the designed UKF torque estimation algorithm can estimate the transmission torques of two clutches in real time; further, it can be directly used for DCT shift control and improving the shifting quality.

  19. Shift Optimal Control of Dual Clutch Type Automatic Transmission%双离合器式自动变速器换档优化控制研究

    Institute of Scientific and Technical Information of China (English)

    张洁

    2012-01-01

    The friction problem in the process of car shift was studied to reduce the friction loss. Aiming at the problem that in the shift process of double clutch type automatic transmission, pressure waves heavily, causing the output torque fluctuating violently and large friction loss, the paper put forward a shift optimization control strategy of dual clutch type automatic transmission. By establishing a double clutch dynamic model and physical shift rule mod-el, the optimized P1D pressure control algorithm was used to control the pressure changes in the process of the shift, make the pressure reach an optimal control state and reduce hardware friction. The experimental results show that the optimization control strategy can sharply reduce the friction consumption in shift process.%研究汽车换挡过程中的摩擦问题,降低摩擦损耗.针对双离合器式自动变速器换档过程,压力突变很大,造成车辆的输出转矩发生剧烈波动,硬件摩擦损耗很大的问题,提出一种双离合器式自动变速器换档优化控制策略,通过建立双离合器物理动力学模型和构建换档规律模型,运用优化的压力控制PID算法,控制在汽车换挡过程中的压力变化,使得压力能够达到一个最优的控制状态,减少硬件摩擦.实验结果表明,换档优化控制策略能够大幅降低换挡过程的摩擦消耗,取得了不错的效果.

  20. A Novel Approach for Enhancement of Automobile Clutch Engagement Quality Using Mechatronics Based Automated Clutch System

    Science.gov (United States)

    Tripathi, K.

    2013-01-01

    In automated manual clutch (AMC) a mechatronic system controls clutch force trajectory through an actuator governed by a control system. The present study identifies relevant characteristics of this trajectory and their effects on driveline dynamics and engagement quality. A new type of force trajectory is identified which gives the good engagement quality. However this trajectory is not achievable through conventional clutch control mechanism. But in AMC a mechatronic system based on electro-hydraulic or electro-mechanical elements can make it feasible. A mechatronic system is presented in which a mechatronic add-on system can be used to implement the novel force trajectory, without the requirement of replacing the traditional diaphragm spring based clutch in a vehicle with manual transmission.

  1. Thermal mechanical analysis of sprag clutches

    Science.gov (United States)

    Mullen, Robert L.; Zab, Ronald Joseph; Kurniawan, Antonius S.

    1992-01-01

    Work done at Case Western Reserve University on the Thermal Mechanical analysis of sprag helicopter clutches is reported. The report is presented in two parts. The first part is a description of a test rig for the measurement of the heat generated by high speed sprag clutch assemblies during cyclic torsional loading. The second part describes a finite element modeling procedure for sliding contact. The test rig provides a cyclic torsional load of 756 inch-pounds at 5000 rpm using a four-square arrangement. The sprag clutch test unit was placed between the high speed pinions of the circulating power loop. The test unit was designed to have replaceable inner ad outer races, which contain the instrumentation to monitor the sprag clutch. The torque loading device was chosen to be a water cooled magnetic clutch, which is controlled either manually or through a computer. In the second part, a Generalized Eulerian-Lagrangian formulation for non-linear dynamic problems is developed for solid materials. This formulation is derived from the basic laws and axioms of continuum mechanics. The novel aspect of this method is that we are able to investigate the physics in the spatial region of interest as material flows through it without having to follow material points. A finite element approximation to the governing equations is developed. Iterative Methods for the solution of the discrete finite element equations are explored. A FORTRAN program to implement this formulation is developed and a number of solutions to problems of sliding contact are presented.

  2. Road deicing salt irreversibly disrupts osmoregulation of salamander egg clutches.

    Science.gov (United States)

    Karraker, Nancy E; Gibbs, James P

    2011-03-01

    It has been postulated that road deicing salts are sufficiently diluted by spring rains to ameliorate any physiological impacts to amphibians breeding in wetlands near roads. We tested this conjecture by exposing clutches of the spotted salamander (Ambystoma maculatum) to three chloride concentrations (1 mg/L, 145 mg/L, 945 mg/L) for nine days, then transferred clutches to control water for nine days, and measured change in mass at three-day intervals. We measured mass change because water uptake by clutches reduces risks to embryos associated with freezing, predation, and disease. Clutches in controls sequestered water asymptotically. Those in the moderate concentrations lost 18% mass initially and regained 14% after transfer to control water. Clutches in high concentration lost 33% mass and then lost an additional 8% after transfer. Our results suggest that spring rains do not ameliorate the effects of deicing salts in wetlands with extremely high chloride concentrations.

  3. A novel brewing process via controlled hydrodynamic cavitation

    CERN Document Server

    Albanese, Lorenzo; Meneguzzo, Francesco; Pagliaro, Mario

    2016-01-01

    This paper describes a completely new brewing equipment and process based upon controlled hydrodynamic cavitation, providing significant advantages in terms of lowered capital cost, reduced production time, enhanced energy and production efficiency, food safety, while preserving beer organoleptic qualities. Experiments carried out on real microbrewery volume scale using the new and conventional technology unquestionably confirm the relevance of the new findings. Impacts of these discoveries are potentially far reaching, as beer is the worldwide most widely consumed alcoholic beverage, therefore highly relevant to health, environment the economy and even to local identities.

  4. 离合器操纵特性影响因素试验研究%Experimental Study on the Factors Affecting Clutch Control Characteristics

    Institute of Scientific and Technical Information of China (English)

    孙晓清; 胡志远; 周含露

    2012-01-01

    Using clutch pedal analysis system, clutch pedal characteristics at different engine speed are tested under cold and warm condition as well as clutch in its end of life cycle. The results show that: with the increase of engine speed, the disengage curve of clutch pedal characteristic moves downward, the maximum disengagement force decreases, at the same time, engage curve moves upward and hysteresis of clutch pedal is decreasing, feedback effect becomes better; compared with warm vehicle condition, the maximum disengagement force and hysteresis force in cold vehicle are bigger. Compared with new clutch, there are about 50% increases in maximum disengagement force and hysteresis force of clutch pedal at the end of clutch life cycle.%利用离合器踏板特性分析系统,测试了某轿车冷车、热车及离合器生命周期末期时不同发动机工作转速下离合器的踏板特性.结果表明,随发动机转速的增加,离合器分离过程的踏板特性曲线呈整体下移趋势,离合器的最大分离力降低,同时离合器回位过程的踏板特性呈整体上移趋势,离合器踏板的迟滞力减小,回馈效果变好;与热车状态相比,离合器冷车状态时的最大分离力较高,且迟滞力略高;与新离合器相比,处于生命周期末期的离合器的最大分离力和迟滞力均增加约50%.

  5. Analysis Groove Characteristics of Friction Dishes in Wet Speeding Clutch

    Institute of Scientific and Technical Information of China (English)

    HongYue; LiuJin; JinShiliang

    2004-01-01

    The impacts of different groove shapes, numbers, and angle of friction dish on transmitting torque, speed, push pressure in wet speeding clutch are discussed in this paper. Since the wet speeed governing clutch works within hydrodynamic lubrication mixture lubrication. boundary, lubrication and contact situation, the oils combining with a-hydrocarbon or polyester are getting widely used as lubricant.The power-law fluid model with Patir-Cheng average flow model, GT asperity contact model and oil film inertia are applied for average Reynolds equation setting, In order to investigate the relationship between average push pressure within hydrodynamic lubrication and mixture lubrication, average transmitting torque and output speed, the numeral calculation and analysis are presented. According to calculation, it is found that the groove shape, groove angle and groove numbers affect the average transfer torque and push pressure with the speed rate.

  6. An Hourglass Control Algorithm for Lagrangian Smooth Particle Hydrodynamics

    CERN Document Server

    Ganzenmüller, Georg C

    2014-01-01

    This paper presents a stabilization scheme which addresses the rank-deficiency problem in meshless collocation methods for solid mechanics. Specifically, Smooth-Particle Hydrodynamics (SPH) in the Total Lagrangian formalism is considered. This method is rank-deficient in the sense that the SPH approximation of the deformation gradient is not unique with respect to the positions of the integration points. The non-uniqueness can result in the formation of zero-energy modes. If undetected, these modes can grow and completely dominate the solution. Here, an algorithm is introduced, which effectively suppresses these modes in a fashion similar to hour-glass control mechanisms in Finite-Element methods. Simulations utilizing this control algorithm result exhibit much improved stability, accuracy, and error convergence properties. In contrast to an alternative method which eliminates zero-energy modes, namely the use of additional integration points, the here presented algorithm is easy to implement and computationa...

  7. Road deicing salt irreversibly disrupts osmoregulation of salamander egg clutches

    Energy Technology Data Exchange (ETDEWEB)

    Karraker, Nancy E., E-mail: karraker@hku.hk [Department of Environmental and Forest Biology, State University of New York, College of Environmental Science and Forestry, Syracuse, NY 13210 (United States); Gibbs, James P. [Department of Environmental and Forest Biology, State University of New York, College of Environmental Science and Forestry, Syracuse, NY 13210 (United States)

    2011-03-15

    It has been postulated that road deicing salts are sufficiently diluted by spring rains to ameliorate any physiological impacts to amphibians breeding in wetlands near roads. We tested this conjecture by exposing clutches of the spotted salamander (Ambystoma maculatum) to three chloride concentrations (1 mg/L, 145 mg/L, 945 mg/L) for nine days, then transferred clutches to control water for nine days, and measured change in mass at three-day intervals. We measured mass change because water uptake by clutches reduces risks to embryos associated with freezing, predation, and disease. Clutches in controls sequestered water asymptotically. Those in the moderate concentrations lost 18% mass initially and regained 14% after transfer to control water. Clutches in high concentration lost 33% mass and then lost an additional 8% after transfer. Our results suggest that spring rains do not ameliorate the effects of deicing salts in wetlands with extremely high chloride concentrations. - Road deicing salts irreversibly disrupts osmoregulation of salamander egg clutches.

  8. THERMAL ANALYSIS OF FRICTIONAL DISK IN SPEEDING WET CLUTCH

    Institute of Scientific and Technical Information of China (English)

    Hong Yue; Liu Jin; Wang Yungeng

    2004-01-01

    Multi-frictional disks are employed to transmit the torque in speeding wet clutch, and the oil thickness within frictional disks could be adjusted for practical output speeding.As oil combined with α-hydrocarbon or polyester is getting widely used as lubricant and the speeding wet clutch works within hydrodynamic lubrication, mixture lubrication, boundary lubrication and contact situation, established the thermal analysis model for investigating the behavior of frictional disks in speeding wet clutch, which covers the power-law fluid model, Patir-Cheng average flow model, GT asperity contact model, oil film inertia and heat effects, mean energy equation, and heat conduction equation.The formulas in the model are deduced.The numeral calculation and analysis for hydrodynamic lubrication and mixture lubrication are executed.Relationships and variations among transmitting torque, mean push pressure, output speed, and load are presented.Thermal effect should be considered during the hydrodynamic lubrication and larger transmitting torque makes earlier entrance to mixture lubrication.

  9. Active control of magneto-hydrodynamic instabilities in hot plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Igochine, Valentin (ed.) [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)

    2015-04-01

    Written and edited by leading plasma physics researchers. Provides a toolkit for scientists and engineers aiming to optimize plasma performance. Comprehensive treatment of different plasma instabilities. During the past century, world-wide energy consumption has risen dramatically, which leads to a quest for new energy sources. Fusion of hydrogen atoms in hot plasmas is an attractive approach to solve the energy problem, with abundant fuel, inherent safety and no long-lived radioactivity. However, one of the limits on plasma performance is due to the various classes of magneto-hydrodynamic instabilities that may occur. The physics and control of these instabilities in modern magnetic confinement fusion devices is the subject of this book. Written by foremost experts, the contributions will provide valuable reference and up-to-date research reviews for ''old hands'' and newcomers alike.

  10. Active control of magneto-hydrodynamic instabilities in hot plasmas

    CERN Document Server

    2015-01-01

    During the past century, world-wide energy consumption has risen dramatically, which leads to a quest for new energy sources. Fusion of hydrogen atoms in hot plasmas is an attractive approach to solve the energy problem, with abundant fuel, inherent safety and no long-lived radioactivity.  However, one of the limits on plasma performance is due to the various classes of magneto-hydrodynamic instabilities that may occur. The physics and control of these instabilities in modern magnetic confinement fusion devices is the subject of this book. Written by foremost experts, the contributions will provide valuable reference and up-to-date research reviews for "old hands" and newcomers alike.

  11. Fault Diagnosis and Tolerant Control for Dual Clutch Transmission%双离合器自动变速器故障诊断及容错控制

    Institute of Scientific and Technical Information of China (English)

    余健飞; 吴光强

    2011-01-01

    针对双离合器自动变速器的系统组成,应用冗余法、搭建诊断电路法、极值法,制定包括传感器、执行机构、控制器和被控对象在内的故障诊断策略,并开发了车辆行驶状态下的在线综合故障诊断程序.将各故障分为不同等级,提出相应的容错控制方法,使车辆在发生故障时能最大限度地保持继续行驶的能力.最后,对部分典型故障下的双离合器自动变速器起步及换挡模型进行仿真,验证了所提出的故障诊断及容错控制策略的有效性.%According to system constructions of dual clutch transmission ( DCT), by using redundancy method,building diagnosis circuit method and extremum method, fault diagnosis strategies are proposed for sensors, actuators, controllers and controlled objects. A comprehensive on-line fault diagnosis program is also designed for vehicles on the running state. Tolerant control strategies are established based on different fault types so that vehicles can furthest keep running capacity. Finally, simulations for some typical faults are applied on a DCT starting and shifting model, and the effectiveness of the proposed fault diagnosis and tolerant control strategies is verified.

  12. 基于微分几何的离合器接合过程速度跟踪滑模控制%Sliding Mode Control for Speed Tracking Based on Differential Geometry during Clutch Engaging Process

    Institute of Scientific and Technical Information of China (English)

    赵韩; 邱明明; 黄康

    2015-01-01

    Aimed at nonlinearity,external disturbances and parameter uncertainty of the clutch control system,a sliding mode control was put forward based on differential geometry for speed track-ing during clutch engaging process.Considering the uncertainty of system parameters and external dis-turbances and other uncertain factors,a single clutch dynamic system model was established,feedback linearization was used based on differential geometry method,the control law was obtained,and then a sliding mode controller was designed based on reaching law control method for the clutch control sys-tem with disturbance.The stability of the system was proved by using Lyapunov theory.The simula-tion results show that the controller can make the process of clutch engagement speed tracking accura-cy and robustness.%针对离合器控制系统中存在的非线性、外部干扰和参数不确定问题,提出了基于微分几何的离合器接合过程速度跟踪滑模控制方法。考虑系统参数的不确定性和外界干扰等不确定因素,建立了单个离合器起步动力学模型;基于微分几何的反馈线性化方法,得出系统的控制律;采用基于趋近律的滑模控制方法,设计了存在不确定干扰的离合器控制系统滑模控制器。利用 Lyapunov 理论对系统的稳定性进行了证明。仿真结果表明该控制器使离合器接合过程的速度跟踪精度高,且鲁棒性好。

  13. Study of hydrodynamic model in sluice controlled river networks

    Science.gov (United States)

    Li, Yan; Zeng, Fantang

    2010-05-01

    Shiqi river network ,is situated in the Zhongshan city of Guangdong province in the P.R.China. The river network covers approximately 702.55km2 ,with a total river length of over 500km and extending over 34km from north to south and over 46km from east to west. The river network overlaps with the most densely populated and economically developed region in the Pear River Delta Economic Zone. In 2008 the region had a population of 1 846.9 thousands And a GDP of more than 8 2500 million RMB. All branches of the river network are encircled by the main rivers of Pear River Delta(PRD) network. With the economic and social development, all natural connections with the external rivers are controlled by the sluices, water body exchanges between the Shiqi river network and external rivers are significantly changed by human activities. The overall objective the research is to develop a tool for the local Environmental Protection Bureau to Understand and quantify the impact of the artificial construction on the hydrological cycle. The developed model can accurate representation of the water levels and flows in the study area, to allow accurate representation of the transport of pollutants. The river network topography is derived directly from the available database. Only the "major" rivers were included in the model, because cross-section data for the "minor" rivers are currently not available. In general, the 1D hydrodynamic model is provided with flow boundary conditions ("Q") at its upstream boundaries and with water level boundary conditions ("z") at its downstream boundaries. For all boundaries of Shiqi river network, there are no flow records available, all records are water level. To reflect the hydrodynamic process accurately, the author developed a new methods to set the hydrodynamic model's boundary. For each boundary, the boundary condition is "Z" when the sluice is open, and the boundary condition is "Q" while it is closed. The open or close condition is identified

  14. Engagement Model of Dry Friction Clutch with Diaphragm Spring

    Directory of Open Access Journals (Sweden)

    Trinoy Dutta

    2014-11-01

    Full Text Available The duration of engagement of automotive clutch plays an important role in the driving comfort and smooth launching of the vehicle. It is a transient phenomenon controlled by many variables like dynamics of release bearing and linkage, relation between release bearing travel and pressure plate lift, the clamp load developed with respect to cushion deflection and inertia of driver and driven shafts. Modern automobiles employ diaphragm spring clutch, which is advantageous in terms of less overall height and weight, number of components, low release load and increased service life. The non-linear characteristics of the diaphragm spring can be exploited favorably in achieving smooth engagement process. In this paper a mathematical model of transient engagement dynamics is developed correlating the parameters like spring characteristics, clamp load characteristics, pressure plate lift and release bearing travel characteristics, clutch pedal kinematics during engagement, vehicle driveline dynamics during startup, etc. The engagement duration of the clutch can be simulated along with the clamp load build up and torque transmission to the driveline using this model. Results of simulation are also included here which were verified through actual tests. This analysis should be useful in design of release mechanism for achieving smooth clutch engagement and to compare various clutches on the duration of slippage.

  15. How hydrodynamics control algal blooms in the Ythan estuary, Scotland

    Science.gov (United States)

    Champangern, Khruewan; Hoey, Trevor; Thomas, Rhian

    2016-04-01

    The Ythan estuary, northeast Scotland, was designated in 2000 as a Nitrate Vulnerable Zone (NVZ) under the European Commission (EC) Nitrates Directive. Much of the catchment is intensively farmed and water quality has been adversely affected by nutrients from agricultural fertilizers. As a result, algal mats develop annually on tidal flats where sediment from upstream and from the adjacent dune systems is deposited. Understanding the patterns of water (river and ocean) circulation in the estuary as well as understanding how nutrients and sediments are transported in the estuary is crucial for understanding the role of several factors (elevation; sediment characteristics; nutrient flux) control the locations and scale of annual algal blooms. In order to understand those controls, study of interactions between hydrodynamic factors and water quality, in particular chlorophyll levels, at different time scales has been carried out. The results from the study reveal complex seasonal and event-scale relationships of river flow with the amount of chlorophyll, which provide an initial comprehension of controls over the concentrations of chlorophyll in the estuary. The concentration of chlorophyll changes, whether increasing or decreasing, with regards to changes in river flow. During high flow events, high amounts of chlorophyll are found when the tide is low. During low flow events, high amounts of chlorophyll are found at high tides. These phenomena reveal that both river flow and tidal cycle affect the amount of chlorophyll in the estuary. In addition, the Delft3d flow model, which has been extensively applied to many coastal and estuarine studies is used to simulate hydrodynamic patterns in the estuary during high flow and low flow events. The model is composed of 36,450 fine resolution grids and the upstream/ downstream boundary that represents water level is based on time-series data from river flow and tidal measurements. The bathymetry used for the model domain is

  16. Optimized wet clutches:simulation and tribotesting

    OpenAIRE

    2006-01-01

    Wet clutches are used in a variety of different machinery. Wet clutches and brakes are frequently used to distribute torque in vehicle drive-trains. The clutches can be located in e.g. automatic transmissions or limited slip differentials. Their frictional behavior is of great importance for the overall vehicle behavior and has to be thoroughly investigated when designing new wet clutch applications. Frictional behavior is normally investigated in test rigs where complete friction discs are t...

  17. Lattice hydrodynamic model based traffic control: A transportation cyber-physical system approach

    Science.gov (United States)

    Liu, Hui; Sun, Dihua; Liu, Weining

    2016-11-01

    Lattice hydrodynamic model is a typical continuum traffic flow model, which describes the jamming transition of traffic flow properly. Previous studies in lattice hydrodynamic model have shown that the use of control method has the potential to improve traffic conditions. In this paper, a new control method is applied in lattice hydrodynamic model from a transportation cyber-physical system approach, in which only one lattice site needs to be controlled in this control scheme. The simulation verifies the feasibility and validity of this method, which can ensure the efficient and smooth operation of the traffic flow.

  18. Uncoupling clutch size, prolactin, and luteinizing hormone using experimental egg removal.

    Science.gov (United States)

    Ryan, Calen P; Dawson, Alistair; Sharp, Peter J; Williams, Tony D

    2015-03-01

    Clutch size is a key avian fitness and life history trait. A physiological model for clutch size determination (CSD), involving an anti-gonadal effect of prolactin (PRL) via suppression of luteinizing hormone (LH), was proposed over 20 years ago, but has received scant experimental attention since. The few studies looking at a PRL-based mechanistic hypothesis for CSD have been equivocal, but recent experiments utilizing a pharmacological agent to manipulate PRL in the zebra finch (Taeniopygia guttata) found no support for a role of this hormone in clutch size determination. Here, we take a complementary approach by manipulating clutch size through egg removal, examining co-variation in PRL and LH between two breeding attempts, as well as through experimentally-extended laying. Clutch size increased for egg removal females, but not controls, but this was not correlated with changes in PRL or LH. There were also no differences in PRL between egg removal females and controls, nor did PRL levels during early, mid- or late-laying of supra-normal clutches predict clutch size. By uncoupling PRL, LH and clutch size in our study, several key predictions of the PRL-based mechanistic model for CSD were not supported. However, a positive correlation between PRL levels late in laying and days relative to the last egg (clutch completion) provides an alternative explanation for the equivocal results surrounding the conventional PRL-based physiological model for CSD. We suggest that females coordinate PRL-mediated incubation onset with clutch completion to minimize hatching asynchrony and sibling hierarchy, a behavior that is amplified in females laying larger clutches.

  19. Optimal Robust Control of Shifting Process for Hybrid Electric Car with Dry Dual Clutch Transmission%干式DCT变速HEV换档过程鲁棒优化控制

    Institute of Scientific and Technical Information of China (English)

    赵治国; 吴朝春; 杨云云; 陈海军

    2016-01-01

    Taking the hybrid electric vehicle equipped with dual clutch transmission(DCT) as the object and considering the characteristics of fast responding and high accuracy of integrated starter and generator(ISG) motor speed and torque, the robust control issue of torque coordination between twin clutches and power sources when ISG intervene with the gear-shifting process are investigated. The different dynamics models in the different phases of whole shifting process are established; Then, the power sources' synthesizing torque is optimally determined under the consideration of the responding characteristic of clutch actuators in the torque phase and the model uncertainty & external disturbance(measurement noise and engine torque’s lag) in the inertia phase; Afterwards, in the torque transition phase, the engine torque is switched into the level of driver demand and ISG torque is slowly come down. Finally, the torques of the power sources are distributed based on the optimization of system efficiency. The simulation results on the Simulink software platform illustrate that the proposed control strategies possess the capabilities of strong anti-uncertainty and anti-disturbance. And the following bench test results further show that it can also effectively address the coordinating control problems between the twin clutches and power sources, ensure that the vehicle has good quality in shift.%针对双离合器自动变速器(Dual clutch transmission,DCT)变速弱混合动力轿车,考虑到起动发电一体化电机(Integrated starter and generator,ISG)转矩响应特性较快、转速/转矩控制精度高等特点,对其介入到换档过程时不同动力源输出转矩和离合器传递转矩协调鲁棒控制问题进行研究。建立体现DCT换档切换过程阶段差异性的动力学模型;考虑转矩相的离合器执行机构的响应能力和惯性相的模型不确定性和外界干扰(转速量测噪声和发动机转矩响应滞后),优化

  20. Hydrodynamic size distribution of gold nanoparticles controlled by repetition rate during pulsed laser ablation in water

    Science.gov (United States)

    Menéndez-Manjón, Ana; Barcikowski, Stephan

    2011-02-01

    Most investigations on the laser generation and fragmentation of nanoparticles focus on Feret particle size, although the hydrodynamic size of nanoparticles is of great importance, for example in biotechnology for diffusion in living cells, or in engineering, for a tuned rheology of suspensions. In this sense, the formation and fragmentation of gold colloidal nanoparticles using femtosecond laser ablation at variable pulse repetition rates (100-5000 Hz) in deionized water were investigated through their plasmon resonance and hydrodynamic diameter, measured by Dynamic Light Scattering. The increment of the repetition rate does not influence the ablation efficiency, but produces a decrease of the hydrodynamic diameter and blue-shift of the plasmon resonance of the generated gold nanoparticles. Fragmentation, induced by inter-pulse irradiation of the colloids was measured online, showing to be more effective low repetition rates. The pulse repetition rate is shown to be an appropriate laser parameter for hydrodynamic size control of nanoparticles without further influence on the production efficiency.

  1. 双离合器自动变速器控制系统软件架构设计%Software Architecture Design of Dual Clutch Transmission Control System

    Institute of Scientific and Technical Information of China (English)

    司建玉; 吴光强

    2011-01-01

    From the view of software development mode and architecture, the control system of dual clutch transmission (DCT) is analyzed. Based on the kernel of the embedded real time operating system fxC/OS- TJ ?the software architecture of DCT control system is established. The complicated control of DCT shifting process is implemented by using finite state machine (FSM), and DCT control system is developed according to the software architecture of control system. In the platform of DCT hardware-in-the-loop simulation, the function and performance of control system software are tested. The results show that the software can not only ensure the real-time requirements of DCT control system, but also enhance its stability and scalability.%从软件开发方式与架构设计的角度对双离合器自动变速器(dual clutch transmission,D(T)控制系统进行了深入剖析,并以嵌入式实时操作系统μC/OS-Ⅱ内核为基础,构建了DCT控制系统软件架构.通过引入有限状态机(finite state machine,FSM)实现了DCT的复杂换挡过程控制,以此为基础开发了DCT多任务控制系统.基于DCT硬件在环仿真试验台对所设计开发的控制系统软件进行了功能及性能验证.验证结果表明,设计开发的DCT控制系统软件既满足了系统对实时性的要求,又提高了系统的可靠性和扩展性.

  2. On Dynamic Transmitting Property of Circular Plate MR Clutch

    Science.gov (United States)

    Guo, Chongzhi; Guo, Jiangchuan; Guo, Yu; Ma, Ziyang

    This study focuses on the analysis of relationship between the current density and the torque of a circular plate Magneto-Rheological (MR) clutch. In order to get the expression of magnetic induction intensity, the Finite Element Method(FEM) is used for the magnetic analysis on the given geometry of circular plate MR clutch under different current density. With some reasonable assumptions, the discrete values of the magnetic induction intensity along some defined paths are obtained. The fitted expression of magnetic induction intensity is derived from discrete points and the analysis of these discrete data. Based on the expression and the Bingham model which is used to describe the constitutive characteristics of the MR fluids flow between two circular plates subject to an applied magnetic field induced by current density, the mathematical model to transmit the torque is established. From the model and the fit expression, the relationship of the torque and the current density is deduced. The numerical results show that the torque transferred under magnetic induction density by control current density is increased smoothly as the current density is increased except a very short time after initial start. Results also indicate that the torque can be controlled continuously by changing the current density. The analysis provides the theoretical foundation for the design of the MR clutch, and the equation of the torque provides the information by which the torque transmitted by the clutch can be manipulated accurately through adjusting the current density.

  3. Hydrodynamic control of microphytoplankton bloom in a coastal sea

    Science.gov (United States)

    Murty, K. Narasimha; Sarma, Nittala S.; Pandi, Sudarsana Rao; Chiranjeevulu, Gundala; Kiran, Rayaprolu; Muralikrishna, R.

    2017-08-01

    The influence of hydrodynamics on phytoplankton bloom occurrence/formation has not been adequately reported. Here, we document diurnal observations in the tropical Bay of Bengal's mid-western shelf region which reveal microphytoplankton cell density maxima in association with neap tide many times more than what could be accounted for by solar insolation and nutrient levels. When in summer, phytoplankton cells were abundant and the cell density of Guinardia delicatula reached critical value by tide caused zonation, aggregation happened to an intense bloom. Mucilaginous exudates from the alga due to heat and silicate stress likely promoted and stable water column and weak winds left undisturbed, the transient bloom. The phytoplankton aggregates have implication as food resource in the benthic region implying higher fishery potential, in carbon dioxide sequestration (carbon burial) and in efforts towards improving remote sensing algorithms for chlorophyll in the coastal region.

  4. Hydrodynamic control of microphytoplankton bloom in a coastal sea

    Indian Academy of Sciences (India)

    K Narasimha Murty; Nittala S Sarma; Sudarsana Rao Pandi; Gundala Chiranjeevulu; Rayaprolu Kiran; R Muralikrishna

    2017-08-01

    The influence of hydrodynamics on phytoplankton bloom occurrence/formation has not been adequately reported. Here, we document diurnal observations in the tropical Bay of Bengal’s mid-western shelf region which reveal microphytoplankton cell density maxima in association with neap tide many times more than what could be accounted for by solar insolation and nutrient levels. When in summer, phytoplankton cells were abundant and the cell density of Guinardia delicatula reached critical value by tide caused zonation, aggregation happened to an intense bloom. Mucilaginous exudates from the alga due to heat and silicate stress likely promoted and stable water column and weak winds left undisturbed, the transient bloom. The phytoplankton aggregates have implication as food resource in the benthic region implying higher fishery potential, in carbon dioxide sequestration (carbon burial) and in efforts towards improving remote sensing algorithms for chlorophyll in the coastal region.

  5. Adaptive density dependence of avian clutch size

    NARCIS (Netherlands)

    Both, C; Tinbergen, JM; Visser, ME

    2000-01-01

    In birds, the annual mean clutch size is often negatively correlated with population density. This relationship is at least in part due to adjustment by individuals. We investigated whether this response is adaptive in two ways. First we used an optimality model to predict how optimal clutch size

  6. A fly-wheel drive with controlled-torque clutch for a reactors cooling circuit pumps; Entrainement des pompes du circuit de refrigeration d'un reacteur par volant a embrayage sous couple controle

    Energy Technology Data Exchange (ETDEWEB)

    Riettini, A. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

    1964-10-15

    After a theoretical study on the slowing down of a centrifugal pump, the motion equations have been checked by means of experimental tests. In order to have important slowing down times (which is the case of the cooling pumps of a research reactor) it is necessary to add a fly-wheel. To prevent troubles when starting, a block pump-fly-wheel with clutch under controlled torque was developed. It is so possible to start the fly-wheel progressively without increasing too much power of the driving motor. (author) [French] Apres une etude theorique sur le mouvement de ralentissement d'une pompe centrifuge, les equations du mouvement ont ete verifiees par des essais pratiques. Pour obtenir des temps de ralentissement importants (cas des pompes de refrigeration d'un reacteur de recherche) il est necessaire d'y adjoindre un volant d'inertie. Pour eviter les inconvenients au demarrage, on a etudie un ensemble pompe-volant avec embrayage sous couple controle. Cette solution permet de lancer progressivement le volant sans augmentation appreciable de la puissance du moteur d'entrainement. (auteur)

  7. Research on Servo Performance of Heavy Duty Truck Clutch Operating System with Hydraulic Control and Gas Power-assistance%重型货车离合器液压气助力操纵系统随动性能研究

    Institute of Scientific and Technical Information of China (English)

    陈德鑫; 李松松; 吴亚军

    2012-01-01

    In this paper, according to the bond graph theory, a calculation model for the clutch operating system with hydraulic control and gas power—assistance of a heavy duty vehicle is established in AMESim. Through this model, the key factors and key structural design parameters that affect the servo performance of the system are analyzed. Results show that preload of the line diameter and pressure control valve exerts great influence on pump retraction time. Moreover, the retraction time of the operating system is greatly influenced by diameter of the exhaust port of the power—assist pump, preload of the hydraulic controlled pressure valve as well as preload of the pressure control valve. Finally, with regard to actual malfunction cases of the servo performance of the clutch operating system, causes for failures in different malfunction models are found.%基于键合图理论,采用AMESim软件建立了某重型车离合器液压气助力操纵系统的计算模型,并利用该模型分析了影响离合器操纵系统随动性能的关键因素及关键结构设计参数.结果表明,管路直径、气压控制阀的预紧力对总泵回位时间影响显著;助力泵排气口直径、液控气压阀预紧力以及气压控制阀的预紧力对操纵系统回位时间影响显著.针对离合器操纵系统随动性能问题的实际故障案例,找到了不同故障模式的失效原因.

  8. Master equation-based analysis of a motor-clutch model for cell traction force.

    Science.gov (United States)

    Bangasser, Benjamin L; Odde, David J

    2013-12-01

    Microenvironmental mechanics play an important role in determining the morphology, traction, migration, proliferation, and differentiation of cells. A stochastic motor-clutch model has been proposed to describe this stiffness sensitivity. In this work, we present a master equation-based ordinary differential equation (ODE) description of the motor-clutch model, from which we derive an analytical expression to for a cell's optimum stiffness (i.e. the stiffness at which the traction force is maximal). This analytical expression provides insight into the requirements for stiffness sensing by establishing fundamental relationships between the key controlling cell-specific parameters. We find that the fundamental controlling parameters are the numbers of motors and clutches (constrained to be nearly equal), and the time scale of the on-off kinetics of the clutches (constrained to favor clutch binding over clutch unbinding). Both the ODE solution and the analytical expression show good agreement with Monte Carlo motor-clutch output, and reduce computation time by several orders of magnitude, which potentially enables long time scale behaviors (hours-days) to be studied computationally in an efficient manner. The ODE solution and the analytical expression may be incorporated into larger scale models of cellular behavior to bridge the gap from molecular time scales to cellular and tissue time scales.

  9. Effects of hydrodynamic interactions and control within a point absorber array on electrical output

    DEFF Research Database (Denmark)

    Nambiar, Anup J.; Forehand, David I.M.; Kramer, Morten

    2015-01-01

    the WECs and the total power extracted by the array can be modified. In this paper, different resistive and reactive PTO control strategies, applied to a time-domain wave-to-wire model of a three-float Danish Wavestar device, are compared. The time-domain modelling approach, as opposed to the frequency...... and farms of WECs. The total power extracted by an array of WECs is influenced by the hydrodynamic interactions between them, especially when the WECs are spaced very closely. By control of the power take-off (PTO) forces and moments acting on the WECs within the array, the hydrodynamic interactions between...

  10. Design of hydrodynamically confined microfluidics: controlling flow envelope and pressure.

    Science.gov (United States)

    Christ, Kevin V; Turner, Kevin T

    2011-04-21

    Closed-channel microfluidic devices are widely used in a number of chemical and biological applications; however, it is often difficult to interact with samples, such as cells, that are enclosed inside them. Hydrodynamically confined microflows (HCMs) allow microfluidic-type flows to be generated in open liquid environments, such as Petri dishes, thus greatly increasing the flexibility of microfluidic approaches. HCMs have previously been used for protein patterning and selective cell treatment applications, but the underlying fluid mechanics is not fully understood. Here, we examine the effect of device geometry and flow parameters on the properties of the flow envelope and pressure drop of several two-port HCM devices using a combination of experiments and modeling. A three-port device, which allows for different flow envelope shapes to be generated, is also analyzed. The experimental results agree well with the 3-D computational fluid dynamics simulations, with the majority of the measurements within 10% of the simulations. The results presented provide a framework for understanding the fluid mechanics of HCMs and will aid in the design of HCM devices for a broad range of applications.

  11. 混合动力车辆无离合器操作换档动态协调控制方法%Dynamic coordinated control method of gear shifting without clutch operation for hybrid electric vehicle

    Institute of Scientific and Technical Information of China (English)

    王俊; 王庆年; 王鹏宇; 曾小华

    2014-01-01

    In order to decrease gear shifting impact,shorten gear shifting time and improve vehicle accelerating performance,a dynamic coordinated control method of gear shifting without clutch operation for hybrid electric vehicle was proposed based on dual-motor hybrid electric powertrain. The driven motor of automatic transmission input shaft was controlled to fast realize rotate speed synchronization in gear shifting process without clutch operation so as to shorten gear shifting time.The driven motor of automatic transmission output shaft was controlled to prevent clutch from over wearing because of frequent separation and combination,and the continuous torque output of driving system was achieved by using motor torque on the output shaft of transmission to reduce the impact degree in gear shifting.Test result shows that vehicle driving force keeps stable in gear shifting because of the dynamic coordinated control method.Compared with the traditional gear shifting method, clutch impact degree reduces by about 60%, and vehicle accelerating performances improve by 5. 53% and 5.94% under 0-50 and 0-60 km·h-1 accelerating conditions,respectively.1 tab,19 figs,18 refs.%为减小混合动力车辆换档过程中产生的冲击,缩短换档时间与提高车辆的加速性能,基于一种双电机混合动力系统构型,提出了无离合器操作的换档协调控制方法。通过控制自动变速器输入轴处的电机,实现无离合器操作换档过程中变速器输入轴的转速快速同步,缩短换档时间。为了防止离合器频繁分离与结合导致过度的磨损,控制自动变速器输出轴处的电机,在换档过程中通过驱动力补偿来保证整个系统的转矩输出连续,减小换档过程的冲击度。试验结果表明:应用无离合器操作换档协调控制方法能够确保车辆在换档过程中驱动力的连续输出,与传统的换档方式相比,冲击度降低了约60%,车辆在0~50 km·h-1与0

  12. Egg clutch dehydration induces early hatching in red-eyed treefrogs, Agalychnis callidryas

    Directory of Open Access Journals (Sweden)

    María José Salica

    2017-07-01

    Full Text Available Terrestrial eggs have evolved repeatedly in tropical anurans exposing embryos to the new threat of dehydration. Red-eyed treefrogs, Agalychnis callidryas, lay eggs on plants over water. Maternally provided water allows shaded eggs in humid sites to develop to hatching without rainfall, but unshaded eggs and those in less humid sites can die from dehydration. Hatching responses of amphibian eggs to dry conditions are known from two lineages with independent origins of terrestrial eggs. Here, we experimentally tested for dehydration-induced early hatching in another lineage (Agalychnis callidryas, Phyllomedusidae, representing a third independent origin of terrestrial eggs. We also investigated how dehydration affected egg and clutch structure, and egg mortality. We collected clutches from a pond in Gamboa, Panama, and randomly allocated them to wet or dry treatments at age 1 day. Embryos hatched earlier from dry clutches than from wet clutches, accelerating hatching by ∼11%. Clutch thickness and egg diameter were affected by dehydration, diverging between treatments over time. Meanwhile, mortality in dry clutches was six-fold higher than in control clutches. With this study, early hatching responses to escape mortality from egg dehydration are now known from three anuran lineages with independent origins of terrestrial eggs, suggesting they may be widespread. Further studies are needed to understand how terrestrial amphibian eggs can respond to, or will be affected by, rapid changes in climate over the next decades.

  13. Shifting Process Control of AMT Based on Virtual Clutch Technology for Hybrid Electric Vehicle%基于“虚拟离合器”的混合动力车辆AMT换挡过程控制

    Institute of Scientific and Technical Information of China (English)

    沈文臣; 胡宇辉; 于会龙; 席军强; 陈慧岩

    2014-01-01

    Automatic mechanical transmission(AMT) is the core plant of a single shaft parallel hybrid electric system, whose acceleration, economy, lifetime and reliability largely depend on the rapid, accurate control of AMT’s shifting process. The shifting process control of AMT based on virtual clutch technology is proposed and above all, the five sequential process of the mentioned method are expounded in detail, in which the primary control problems of every stage are put forward. According to the system’s structure, the dynamic model considering the driving shaft’s torsional vibration in the drivetrain is built up and the approximate mathematical model of the transmitted torque in AMT that can be used in shifting process control is deduced. This model is validated in trial that it can control the torque transmitted in AMT and weaken the oscillation of the output shaft’s rotate speed after shifting into neutral gear. Vehicle trial shows that virtual clutch technology aimed at zero torque transmitted in transmission is able to apply on the shifting process control of AMT. The application of this technology can realize the gear shift of AMT without clutch manipulation, effectively decrease the time of power interrupt during shifting process, reduce the oscillation of vehicle speed and improve the shifting quality of AMT system.%自动机械变速器(Automaticmechanicaltransmission,AMT)是单轴并联混合动力系统中的核心部件,对其换挡过程的快速、精确控制直接决定着混合动力系统的加速性、经济性、使用寿命以及可靠性。一种基于“虚拟离合器”技术的混合动力系统AMT换挡过程控制方法可以充分保证其性能。该方法的五个时序进行详细论述,并分别提出各个阶段的核心控制问题。基于该单轴并联混合动力系统的结构特点,建立以考虑传动系统中驱动轴扭转振动特性的动力学模型,在此基础上,推导出可用于换挡过程控制

  14. Intraspecific variation in nutrient reserve use during clutch formation by Lesser Scaup

    Science.gov (United States)

    Esler, Daniel N.; Grand, James B.; Afton, Alan D.

    2001-01-01

    We studied nutrient reserve dynamics of female Lesser Scaup (Aythya affinis) to identify sources of intraspecific variation in strategies of nutrient acquisition for meeting the high nutritional and energetic costs of egg formation. We collected data from interior Alaska and combined these with data for Lesser Scaup from midcontinent breeding areas (Afton and Ankney 1991), allowing a rangewide analysis for the species. We found little evidence that nutrient reserve use differed between Alaskan and midcontinent Lesser Scaup, except that subarctic birds used a small amount of protein reserves when forming eggs, whereas midcontinent birds did not. Mineral reserves contributed relatively little to the clutch, but endogenous lipid accounted for approximately two-thirds of the lipid in the clutch. Levels of endogenous lipid and protein at initiation of clutch formation declined with date of initiation. Also, absolute amounts of lipid and protein reserves used declined through the season, corresponding to smaller clutch sizes. Our data are consistent with a seasonally variable threshold of lipid reserves for initiation of clutch formation and considerable reliance on lipid reserves, suggestive of lipid control of productivity via effects on clutch size and initiation dates. However, our data cannot refute the hypothesis that clutch size or initiation dates are set by other factors that in turn dictate the amount of lipid reserves that are stored and used. Despite uncertainty regarding the role of nutrient limitations on productivity, maintenance of adequate food resources on winter, migration, and breeding areas should be a management concern, given the high costs of clutch formation by Lesser Scaup, evidence of recent population declines, and potential links between nutrition and productivity.

  15. Environmental influences on egg and clutch sizes in lentic- and lotic-breeding salamanders

    Directory of Open Access Journals (Sweden)

    Jon M. Davenport

    2010-12-01

    Full Text Available Recent research indicates that social and environmental factors influence egg and clutch sizes in amphibians. However, most of this work is based on the reproductively diverse order Anura (frogs and toads, whereas less research has been conducted on Caudata (salamanders and Gymnophiona (caecilians. Researchers have suggested that a relationship exists between social and environmental factors and egg and clutch sizes in salamanders, but studies controlling for phylogenetic context are lacking. We could not identify a sufficient number of comparisons for social influences on egg and clutch sizes; therefore, we focused on environmental influences for this study. Data on egg size, clutch size, environmental factors, and phylogenies for salamanders were assembled from the scientific literature. We used independent, pair-wise comparisons to investigate the association of larval salamander habitat and egg size and the association of larval salamander habitat with clutch sizes within a phylogenetic framework. There is a significant association between larval habitat and egg size; specifically, stream-breeding species produce larger eggs. There is no significant association between larval habitat and clutchsize. Our study confirms earlier reports that salamander egg size is associated with larval environments, but is the first to use phylogenetically independent contrasts to account for the lack of phylogenetic independence of the traits measured (egg size and clutch size associated with many of the diverse lineages. Our study shows that environmental selection pressure can be quite strong on one aspect of salamander reproduction—egg size.

  16. New control strategy for the lattice hydrodynamic model of traffic flow

    Science.gov (United States)

    Zhu, Chenqiang; Zhong, Shiquan; Li, Guangyu; Ma, Shoufeng

    2017-02-01

    The new delayed-feedback control strategy is applied for lattice hydrodynamic model of traffic flow by considering the control signal of the variation rate of the optimal velocity. The linear stability condition is derived in the frequency-domain with control theory. Then, different feedback gains under the periodic boundary scenery and on-ramp scenery are simulated. The periodic boundary scenery provides an initial small disturbance situation on the circle road, while the on-ramp scenery reproduces the disturbance triggered by the on-ramp on the open road. Both the theoretical analysis and simulations show that this new control signal has a positive effect to suppress traffic jams.

  17. Hydrodynamic Controls on Acoustical and Optical Water Properties in Tropical Reefs

    Science.gov (United States)

    2013-09-30

    change, coral bleaching and the future of the world’s coral reefs . Mar. Freshw. Res., 50, 839-866. McKee and Cunningham, 2005. Evidence for wavelength...the dominant hydrodynamic controls across different reef environments? Tropical coral health can be significantly affected by sedimentation that can...collaborative field work by the PIs, carried out in collaboration with UCSD SIO (PI: Terrill) and the Coral Reef Research Foundation in Koror (PI

  18. Wear forms of heterogeneous electro-rheological fluids working in a hydraulic clutch system

    Science.gov (United States)

    Ziabska, E.; Duchowski, J.; Olszak, A.; Osowski, K.; Kesy, A.; Kesy, Z.; Choi, S. B.

    2017-09-01

    The paper presents experimental results concerning the wear of heterogeneous electro-rheological (ER) fluids operating as working fluids in a complex clutch system consisting of a hydrodynamic clutch and a cylinder viscous clutch. The change of electric field intensity in the clutches results in change of sheer stress values in working fluids what causes the change of transmitted torque. This work shows that the most important factors affecting the wear of the ER fluid are the electric field of high intensity, the accompanying electrical breakdown, and the high temperature of the silicone oil. In addition, the water from the humid air absorbed mainly by hygroscopic particles influences a significant impact on the wear of the working fluid. Various forms of wear particles of the fluid depending on the prevailing conditions such as working mode are observed from the microscopic aspects. It is observed that the particles are flattened, rolled out or smashed into smaller fragments, partially melted, wrinkled and glued or caked. In addition, it is identified that the partial destruction of silicone oil is occurred due to the damage of the hydrocarbon chains, as evidenced by the decrease in its viscosity and the presence of the particle matter newly containing silicon.

  19. Can selection on nest size from nest predation explain the latitudinal gradient in clutch size?

    Science.gov (United States)

    Biancucci, L.; Martin, T.E.

    2010-01-01

    1. Latitudinal variation in clutch sizes of birds is a well described, but poorly understood pattern. Many hypotheses have been proposed, but few have been experimentally tested, and none have been universally accepted by researchers. 2. The nest size hypothesis posits that higher nest predation in the tropics favours selection for smaller nests and thereby constrains clutch size by shrinking available space for eggs and/or nestlings in the nest. We tested this hypothesis with an experiment in a tropical forest and a comparative study between temperate and tropical field sites. 3. Specifically, we tested if: (i) predation increased with nest size; (ii) tropical birds had smaller nests controlled for body size; and (iii) clutch size was explained by nest size controlled for body size. 4. Experimental swapping of nests of different sizes showed that nest predation increased with nest size in the tropical site. Moreover, nest predation rates were higher in species with larger nests in both sites. However, nest size, corrected for body mass and phylogeny, did not differ between sites and was not related to clutch size between sites. 5. Hence, nest predation can exert selection on nest size as predicted by the hypothesis. Nest size increased with adult body mass, such that adult size might indirectly influence reproductive success through effects on nest size and nest predation risk. Ultimately, however, selection from nest predation on nest size does not explain the smaller clutch sizes typical of the tropics.

  20. Leg-robot with MR clutch to realize virtual spastic movements

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, T; Oda, K; Yamaguchi, S; Furusho, J [Osaka University, Yamadaoka, Suita, Osaka 565-0871 (Japan)], E-mail: kikuchi@mech.eng.osaka-u.ac.jp

    2009-02-01

    In this study, we propose a leg-robot with an MR clutch to realize virtual haptic control for spastic movements of brain-injured patients. This system can be used in the practical training for trainees of physical therapy. Additionally, we will study to figure out the physiological mechanism of spastic movements of human with the process to simulate patientlike spastic motion by this robot. In this paper, basic structure and mechanism of the leg-robot with the MR clutch are explained. Finally, experimental results of some kinds of haptic control for spastic movements are described.

  1. Torque coordinating optimal control for dry dual clutch transmission in shifting process%干式双离合器变速器换挡过程的转矩协调最优控制

    Institute of Scientific and Technical Information of China (English)

    赵治国; 王琪; 陈海军; 刁威振

    2013-01-01

    A torque coordinating optimalcontrol strategy was developed using different driving intentions in different shifting process phases for a six-speed Dry Dual-Clutch-Transmission (DDCT) of a self-developed car. A simulation model was set up on the Matlab/Simulink software platform and then used to simulate the control strategy for DDCT shifting process. The sub-divided phases included the quadratic optimal control adopted in torque phase;the ignition parameters and fuel supply controlin inertia phase;the control factor mapping method, which relfects driving intension, both in micro-slipping phase and in demanded torque switching phase. The results show that shift jerks are within-2 m/s3 while the total frictional energy losses are within 2 kJ in shift process. Therefore, this control strategy relfects driving intentions and meets the demand of shift quality.%对于某一自主开发汽车的六速干式双离合器变速器(DDCT),提出了对不同驾驶意图、分阶段采取不同措施的转矩协调最优控制策略:在转矩相阶段,运用二次型最优控制确定了离合器转矩变化率;在惯性相阶段,采用发动机点火参数与燃油供给调节控制以缩短惯性相时间;在微滑摩阶段及需求转矩切换阶段,建立了体现驾驶意图的控制因子映射。并在Matlab/Simulink软件平台上,搭建了DDCT换挡过程模型,进行仿真试验。结果表明:换挡过程中的换挡冲击在-2 m/s3以内,产生的总滑摩功在2 kJ以内;因而,该控制策略能体现驾驶员的换挡意图,且满足换挡品质需求。

  2. A moving control volume approach to computing hydrodynamic forces and torques on immersed bodies

    Science.gov (United States)

    Nangia, Nishant; Johansen, Hans; Patankar, Neelesh A.; Bhalla, Amneet Pal Singh

    2017-10-01

    We present a moving control volume (CV) approach to computing hydrodynamic forces and torques on complex geometries. The method requires surface and volumetric integrals over a simple and regular Cartesian box that moves with an arbitrary velocity to enclose the body at all times. The moving box is aligned with Cartesian grid faces, which makes the integral evaluation straightforward in an immersed boundary (IB) framework. Discontinuous and noisy derivatives of velocity and pressure at the fluid-structure interface are avoided and far-field (smooth) velocity and pressure information is used. We re-visit the approach to compute hydrodynamic forces and torques through force/torque balance equations in a Lagrangian frame that some of us took in a prior work (Bhalla et al., 2013 [13]). We prove the equivalence of the two approaches for IB methods, thanks to the use of Peskin's delta functions. Both approaches are able to suppress spurious force oscillations and are in excellent agreement, as expected theoretically. Test cases ranging from Stokes to high Reynolds number regimes are considered. We discuss regridding issues for the moving CV method in an adaptive mesh refinement (AMR) context. The proposed moving CV method is not limited to a specific IB method and can also be used, for example, with embedded boundary methods.

  3. Formulation optimization of hydrodynamically balanced oral controlled release bioadhesive tablets of tramadol hydrochloride.

    Science.gov (United States)

    Singh, Bhupinder; Rani, Ashu; Babita; Ahuja, Naveen; Kapil, Rishi

    2010-01-01

    The directly compressible floating-bioadhesive tablets of tramadol were formulated using varying amounts Carbopol 971P (CP) and hydroxy-propylmethyl cellulose (HPMC), along with other requisite excipients. In vitro drug release profile, floatational characteristics and ex vivo bioadhesive strength using texture analyzer were determined, and systematically optimized using a 3(2) central composite design (CCD). The studies indicated successful formulation of gastroretentive compressed matrices with excellent controlled release, mucoadhesion and hydrodynamic balance. Comparison of the dissolution profiles of the optimized formulation, with optimal composition of CP:HPMC :: 80.0:125.0, with that of the marketed controlled release formulation other indicated analogy of drug release performance with each other. Validation of optimization study using eight confirmatory experimental runs indicated very high degree of prognostic ability of CCD with mean  SEM of â0.06%  0.37. Further, the study successfully unravels the effect of the polymers on the selected response variables.

  4. Modeling of fluid-induced vibrations and identification of hydrodynamic forces on flow control valves

    Institute of Scientific and Technical Information of China (English)

    Samad Mehrzad; Ilgar Javanshir; Ahmad Rahbar Ranji; Seyyed Hadi Taheri

    2015-01-01

    Dynamics and vibration of control valves under flow-induced vibration are analyzed. Hydrodynamic load characteristics and structural response under flow-induced vibration are mainly influenced by inertia, damping, elastic, geometric characteristics and hydraulic parameters. The purpose of this work is to investigate the dynamic behavior of control valves in the response to self-excited fluid flow. An analytical and numerical method is developed to simulate the dynamic and vibrational behavior of sliding dam valves, in response to flow excitation. In order to demonstrate the effectiveness of proposed model, the simulation results are validated with experimental ones. Finally, to achieve the optimal valve geometry, numerical results for various shapes of valves are compared. Rounded valve with the least amount of flow turbulence obtains lower fluctuations and vibration amplitude compared with the flat and steep valves. Simulation results demonstrate that with the optimal design requirements of valves, vibration amplitude can be reduced by an average to 30%.

  5. Design of energy-efficient MRF-based clutches with defined fail-safe behavior for integration in hybrid powertrains

    Science.gov (United States)

    Erbis, Vadim; Hegger, Christian; Güth, Dirk; Maas, Jürgen

    2015-04-01

    Drag losses in the powertrain are a serious deficiency for any energy-efficient application, especially for hybrid electrical vehicles. A promising approach for fulfilling requirements like efficiency, wear, safety and dynamics is the use of an innovative MRF-based clutch design for the transmission of power that is based on magnetorheological fluids (MRF). MRF are smart fluids with the particular characteristics of changing their apparent viscosity significantly under influence of the magnetic field. Their characteristics are fast switching times and a smooth torque control in the powertrain. In this paper, a novel clutch concept is investigated that facilitates the controlled movement of the MRF from an active torque-transmitting region into an inactive region of the shear gap. This concept enables a complete disengagement of the fluid engaging surfaces in a way that viscous drag torque can be eliminated. Therefore, a simulation based design for such MRF-based clutches is used to design the required magnetic excitation systems for enabling a well-defined safety behavior by the fluid control. Based on this approach, an MRF-based clutch is developed in detail which provides a loss-reduced alternative to conventional disengagement devices in the powertrain. The presented MRF-based clutch enables a investigation of different systems in one design by changing the magnetic excitation. Especially, different possibilities for the fail-safe behavior of the MRF-based clutch are considered to ensure a well-defined condition in electrical or hybrid powertrains in case of a system failure.

  6. Theoretical research on hydroviscous speed-adjusting clutch in soft-start of belt conveyor

    Institute of Scientific and Technical Information of China (English)

    ZHOU Man-shan; ZHANG Yuan

    2005-01-01

    Through research on the application of hydroviscous speed-adjusting clutch in belt conveyor, this paper concluded that hydroviscous speed-adjusting clutch has many advantages such as controllable start and stop, overload protection and multi-motor power equilibrium. But its theory when used in large power fan and pump could not meet the needs of belt conveyor soft-start operation. Focusing on the theoretical analysis of the lubrication oil flow needed by the transmission procedure to form the oil-film. Put forward concrete calculation methods of lubrication flow and how to decide number of oil-films used in belt conveyor.

  7. Clutch size declines with elevation in tropical birds

    Science.gov (United States)

    Boyce, A.J.; Freeman, Benjamin G.; Mitchell, Adam E.; Martin, Thomas E.

    2015-01-01

    Clutch size commonly decreases with increasing elevation among temperate-zone and subtropical songbird species. Tropical songbirds typically lay small clutches, thus the ability to evolve even smaller clutch sizes at higher elevations is unclear and untested. We conducted a comparative phylogenetic analysis using data gathered from the literature to test whether clutch size varied with elevation among forest passerines from three tropical biogeographic regions—the Venezuelan Andes and adjacent lowlands, Malaysian Borneo, and New Guinea. We found a significant negative effect of elevation on variation in clutch size among species. We found the same pattern using field data sampled across elevational gradients in Venezuela and Malaysian Borneo. Field data were not available for New Guinea. Both sets of results demonstrate that tropical montane species across disparate biogeographic realms lay smaller clutches than closely related low-elevation species. The environmental sources of selection underlying this pattern remain uncertain and merit further investigation.

  8. Camouflage and Clutch Survival in Plovers and Terns

    Science.gov (United States)

    Stoddard, Mary Caswell; Kupán, Krisztina; Eyster, Harold N.; Rojas-Abreu, Wendoly; Cruz-López, Medardo; Serrano-Meneses, Martín Alejandro; Küpper, Clemens

    2016-01-01

    Animals achieve camouflage through a variety of mechanisms, of which background matching and disruptive coloration are likely the most common. Although many studies have investigated camouflage mechanisms using artificial stimuli and in lab experiments, less work has addressed camouflage in the wild. Here we examine egg camouflage in clutches laid by ground-nesting Snowy Plovers Charadrius nivosus and Least Terns Sternula antillarum breeding in mixed aggregations at Bahía de Ceuta, Sinaloa, Mexico. We obtained digital images of clutches laid by both species. We then calibrated the images and used custom computer software and edge detection algorithms to quantify measures related to three potential camouflage mechanisms: pattern complexity matching, disruptive effects and background color matching. Based on our image analyses, Snowy Plover clutches, in general, appeared to be more camouflaged than Least Tern clutches. Snowy Plover clutches also survived better than Least Tern clutches. Unexpectedly, variation in clutch survival was not explained by any measure of egg camouflage in either species. We conclude that measures of egg camouflage are poor predictors of clutch survival in this population. The behavior of the incubating parents may also affect clutch predation. Determining the significance of egg camouflage requires further testing using visual models and behavioral experiments. PMID:27616020

  9. Camouflage and Clutch Survival in Plovers and Terns

    Science.gov (United States)

    Stoddard, Mary Caswell; Kupán, Krisztina; Eyster, Harold N.; Rojas-Abreu, Wendoly; Cruz-López, Medardo; Serrano-Meneses, Martín Alejandro; Küpper, Clemens

    2016-09-01

    Animals achieve camouflage through a variety of mechanisms, of which background matching and disruptive coloration are likely the most common. Although many studies have investigated camouflage mechanisms using artificial stimuli and in lab experiments, less work has addressed camouflage in the wild. Here we examine egg camouflage in clutches laid by ground-nesting Snowy Plovers Charadrius nivosus and Least Terns Sternula antillarum breeding in mixed aggregations at Bahía de Ceuta, Sinaloa, Mexico. We obtained digital images of clutches laid by both species. We then calibrated the images and used custom computer software and edge detection algorithms to quantify measures related to three potential camouflage mechanisms: pattern complexity matching, disruptive effects and background color matching. Based on our image analyses, Snowy Plover clutches, in general, appeared to be more camouflaged than Least Tern clutches. Snowy Plover clutches also survived better than Least Tern clutches. Unexpectedly, variation in clutch survival was not explained by any measure of egg camouflage in either species. We conclude that measures of egg camouflage are poor predictors of clutch survival in this population. The behavior of the incubating parents may also affect clutch predation. Determining the significance of egg camouflage requires further testing using visual models and behavioral experiments.

  10. Studies on centrifugal clutch judder behavior and the design of frictional lining materials

    Science.gov (United States)

    Li, Tse-Chang; Huang, Yu-Wen; Lin, Jen-Fin

    2016-01-01

    This study examines the judder behavior of a centrifugal clutch from the start of hot spots in the conformal contact, then the repeated developments of thermoelastic instability, and finally the formation of cyclic undulations in the vibrations, friction coefficient and torque. This behavior is proved to be consistent with the testing results. Using the Taguchi method, 18 kinds of frictional lining specimens were prepared in order to investigate their performance in judder resistance and establish a relationship between judder behavior and the Ts/Td (Ts: static torque; Td: dynamic torque) and dμ/dVx (μ: friction coefficient; Vx: relative sliding velocity of frictional lining and clutch drum) parameters. These specimens are also provided to examine the effects and profitability with regard to the centrifugal clutch, and find the relative importance of the various control factors. Theoretical models for the friction coefficient (μ), the critical sliding velocity (Vc) with clutch judder, and the contact pressure ratio p* /pbar (p*: pressure undulation w.r.t. pbar; pbar: mean contact pressure) and temperature corresponding to judder behavior are developed. The parameters of the contact pressure ratio and temperature are shown to be helpful to explain the occurrence of judder. The frictional torque and the rotational speeds of the driveline, clutch, and clutch drum as functions of engagement time for 100 clutch cycles are obtained experimentally to evaluate dμ/dVx and Ts/Td. A sharp rise in the maximum p* /pbar occurred when the relative sliding velocity reached the critical velocity, Vc. An increase in the maximum p* /pbar generally led to an increase of the (initially negative) dμ/dVx value, and thus the severity of judder. The fluctuation intensity of dμ/dVx becomes a governing factor of the growth of dμ/dVx itself in the engagement process. The mean values of dμ/dVx and Ts/Td for the clutching tests with 100 cycles can be roughly divided into three groups

  11. Inner wrinkling control in hydrodynamic deep drawing of an irregular surface part using drawbeads

    Institute of Scientific and Technical Information of China (English)

    Meng Bao; Wan Min; Wu Xiangdong; Yuan Sheng; Xu Xudong; Liu Jie

    2014-01-01

    Inner wrinkling phenomenon is more likely to develop during hydrodynamic deep draw-ing (HDD) of complicated component-forms due to the higher demand for controlling deformation sequences. Aiming at the problems in control of inner wrinkling for an irregular surface part featured with both concavity and convex, this research proposes an optimal design method of drawbead parameters to change the material flow. According to theoretical analysis of the mechanism of inner wrinkling, optimizing cavity pressure only is unreasonable to form a wrinkle-free deep-drawn part, so semi-circular drawbeads are employed. The effects of layout and height of drawbeads on forming results are discussed, and a process window is established based on evaluation indicators including the anti-wrinkle coefficient and the minimum wall thickness. Experiments are carried out to validate the process window, and the wall thickness and the wrinkle height are measured and compared with numerical findings. The results show that the anti-wrinkle ability of drawbeads weakens with increasing oblique angle and distance from the die center, while the wall thickness increases with increasing oblique angle and distance, and the inner wrinkling can be completely suppressed by drawbeads arranged in zones I and II with optimum penetration.

  12. Inner wrinkling control in hydrodynamic deep drawing of an irregular surface part using drawbeads

    Directory of Open Access Journals (Sweden)

    Meng Bao

    2014-06-01

    Full Text Available Inner wrinkling phenomenon is more likely to develop during hydrodynamic deep drawing (HDD of complicated component-forms due to the higher demand for controlling deformation sequences. Aiming at the problems in control of inner wrinkling for an irregular surface part featured with both concavity and convex, this research proposes an optimal design method of drawbead parameters to change the material flow. According to theoretical analysis of the mechanism of inner wrinkling, optimizing cavity pressure only is unreasonable to form a wrinkle-free deep-drawn part, so semi-circular drawbeads are employed. The effects of layout and height of drawbeads on forming results are discussed, and a process window is established based on evaluation indicators including the anti-wrinkle coefficient and the minimum wall thickness. Experiments are carried out to validate the process window, and the wall thickness and the wrinkle height are measured and compared with numerical findings. The results show that the anti-wrinkle ability of drawbeads weakens with increasing oblique angle and distance from the die center, while the wall thickness increases with increasing oblique angle and distance, and the inner wrinkling can be completely suppressed by drawbeads arranged in zones I and II with optimum penetration.

  13. A magnetorheological clutch for efficient automotive auxiliary device actuation

    Directory of Open Access Journals (Sweden)

    F. Bucchi

    2013-01-01

    Full Text Available In this paper the results of a project funded by Regione Toscana aimed at reducing the power absorption of auxiliary devices in vehicles are presented. In particular the design, testing and application of a magnetorheological clutch (MR is proposed, aimed at disengaging the vacuum pump, which draws in air from the power-brake booster chamber, in order to reduce the device power absorption. Several clutch preliminary studies done to choose the clutch geometry and the magnetic field supply are illustrated. The final choice consisted in an MR clutch with permanent magnet, which satisfied size, torque and fail-safe specifications. The clutch characteristics, in terms of torque versus slip, were obtained experimentally for three different clutch prototypes on an ad-hoc developed test bench.As result of a preliminary simulation, a comparison between the power absorption of a current production vacuum pump, an innovative vacuum pump and both vacuum pumps coupled with the MR clutch is presented. The New European Driving Cycle is considered for simulating the vacuum pump operation both in urban and highway driving. Results show that the use of the innovative vacuum pump reduces the device consumption of about 35%, whereas the use of MR clutch coupled with the innovative vacuum pump reduces it up to about 44% in urban driving and 50% in highway driving.

  14. Hourglass control for Smooth Particle Hydrodynamics removes tensile and rank-deficiency instabilities. Hourglass control for SPH

    Science.gov (United States)

    Ganzenmüller, G. C.; Sauer, M.; May, M.; Hiermaier, S.

    2016-05-01

    We present a stabilization scheme for elastoplastic Smooth-Particle Hydrodynamics (SPH) which overcomes two major challenges: (i) the tensile instability inherent to the updated Lagrangian approach is suppressed and (ii) the rank-deficiency instability inherent to the nodal integration approach is cured. To achieve these goals, lessons learned from the Finite-Element Method are transferred to SPH. In particular, an analogue of hourglass control is derived for SPH, which locally linearizes the deformation field to obtain stable and accurate solutions, without the need to resort to stabilization via excessive artificial viscosity. The resulting SPH scheme combines the ability of updated Lagrangian SPH to model truly large deformations with the accuracy and stability needed to faithfully perform simulations. This claim is supported by the analysis of problematic cases and the simulation of an impact scenario.

  15. Hydrodynamic controls on oxygen dynamics in a riverine salt wedge estuary, the Yarra River estuary, Australia

    Science.gov (United States)

    Bruce, L. C.; Cook, P. L. M.; Teakle, I.; Hipsey, M. R.

    2014-04-01

    Oxygen depletion in coastal and estuarine waters has been increasing rapidly around the globe over the past several decades, leading to decline in water quality and ecological health. In this study we apply a numerical model to understand how salt wedge dynamics, changes in river flow and temperature together control oxygen depletion in a micro-tidal riverine estuary, the Yarra River estuary, Australia. Coupled physical-biogeochemical models have been previously applied to study how hydrodynamics impact upon seasonal hypoxia; however, their application to relatively shallow, narrow riverine estuaries with highly transient patterns of river inputs and sporadic periods of oxygen depletion has remained challenging, largely due to difficulty in accurately simulating salt wedge dynamics in morphologically complex areas. In this study we overcome this issue through application of a flexible mesh 3-D hydrodynamic-biogeochemical model in order to predict the extent of salt wedge intrusion and consequent patterns of oxygen depletion. The extent of the salt wedge responded quickly to the sporadic riverine flows, with the strength of stratification and vertical density gradients heavily influenced by morphological features corresponding to shallow points in regions of tight curvature ("horseshoe" bends). The spatiotemporal patterns of stratification led to the emergence of two "hot spots" of anoxia, the first downstream of a shallow region of tight curvature and the second downstream of a sill. Whilst these areas corresponded to regions of intense stratification, it was found that antecedent conditions related to the placement of the salt wedge played a major role in the recovery of anoxic regions following episodic high flow events. Furthermore, whilst a threshold salt wedge intrusion was a requirement for oxygen depletion, analysis of the results allowed us to quantify the effect of temperature in determining the overall severity and extent of hypoxia and anoxia. Climate

  16. Hydrodynamic control of phytoplankton loss to the benthos in an estuarine environment

    Science.gov (United States)

    Jones, N.L.; Thompson, J.K.; Arrigo, K.R.; Monismith, Stephen G.

    2009-01-01

    Field experiments were undertaken to measure the influence of hydrodynamics on the removal of phytoplankton by benthic grazers in Suisun Slough, North San Francisco Bay. Chlorophyll a concentration boundary layers were found over beds inhabited by the active suspension feeders Corbula amurensis and Corophium alienense and the passive suspension feeders Marenzellaria viridis and Laonome sp. Benthic losses of phytoplankton were estimated via both the control volume and the vertical flux approach, in which chlorophyll a concentration was used as a proxy for phytoplankton biomass. The rate of phytoplankton loss to the bed was positively correlated to the bed shear stress. The maximum rate of phytoplankton loss to the bed was five times larger than estimated by laboratory-derived pumping rates for the active suspension feeders. Reasons for this discrepancy are explored including a physical mechanism whereby phytoplankton is entrained in a near-bed fluff layer where aggregation is mediated by the presence of mucus produced by the infaunal community. ?? 2009, by the American Society of Limnology and Oceanography, Inc.

  17. Size-Controlled Fabrication of Polyaniline Microfibers Based on 3D Hydrodynamic Focusing Approach.

    Science.gov (United States)

    Yoo, Imsung; Song, Simon; Uh, Kyungchan; Lee, Chan Woo; Kim, Jong-Man

    2015-07-01

    Owing to the relatively high conductivity and unique redox behavior, polyaniline (PANI) has been one of the most technologically promising conducting polymers. Although various methodologies have been developed, fabrication of PANI microfibers has been a challenging task owing to the poor solubility in most organic solvents. By taking advantage of a microfluidic technology and organic soluble acid labile t-Boc-protected PANI (t-Boc-PANI) as the conducting polymer precursor, fabrication of PANI microfibers in a size-controlled manner is possible. Introduction of a THF solution containing t-Boc-PANI, and dodecylbenzenesulfonic acid (DBSA) as a core flow, and water as a sheath flow into a microfluidic channel with a 3D hydrodynamic focusing effect results in crystallization of the polymer fiber. By changing the flow rate, linear PANI microfibers that range from 16.2 to 39.4 μm in diameter are readily obtained. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Hydrodynamic Data for Manoeuvring and Control of an AUV Determined by Tank Tests and Free-Sailing Trials

    DEFF Research Database (Denmark)

    Aage, Christian

    1998-01-01

    Autonomous Underwater Vehicles (AUV's) can be used for a large number of subsea acitivities in different modes of operation varying from the ROV-mode with on-line control and power supply from the surface, to the true AUV-mode where the vehicle performs its pre-programmed tasks with full autonomy.......For any mode of operation a complete set of hydrodynamic data will be required for the optimum design of the steering and manoeuvring equipment and strategies. Precise track-keeping and fast obstacle avoidance are important qualities of an underwater vehicle. The data necessary to investigate...... these properties and to program the control systemm comprise added mass and inertia coefficients, damping, lift and drag coefficients of the vehicle and its control surfaces, as well as resistance and propulsion characteristics. Only few hydrodynamic data for AUVs have yet been published, so dedicated tests...

  19. Hydrodynamic parameters estimation from self-potential data in a controlled full scale site

    Science.gov (United States)

    Chidichimo, Francesco; De Biase, Michele; Rizzo, Enzo; Masi, Salvatore; Straface, Salvatore

    2015-03-01

    A multi-physical approach developed for the hydrodynamic characterization of porous media using hydrogeophysical information is presented. Several pumping tests were performed in the Hydrogeosite Laboratory, a controlled full-scale site designed and constructed at the CNR-IMAA (Consiglio Nazionale delle Ricerche - Istituto di Metodologia per l'Analisi Ambientale), in Marsico Nuovo (Basilicata Region, Southern Italy), in order to obtain an intermediate stage between laboratory experiments and field survey. The facility consists of a pool, used to study water infiltration processes, to simulate the space and time dynamics of subsurface contamination phenomena, to improve and to find new relationship between geophysical and hydrogeological parameters, to test and to calibrate new geophysical techniques and instruments. Therefore, the Hydrogeosite Laboratory has the advantage of carrying out controlled experiments, like in a flow cell or sandbox, but at field comparable scale. The data collected during the experiments have been used to estimate the saturated hydraulic conductivity ks [ms-1] using a coupled inversion model working in transient conditions, made up of the modified Richards equation describing the water flow in a variably saturated porous medium and the Poisson equation providing the self-potential ϕ [V], which naturally occurs at points of the soil surface owing to the presence of an electric field produced by the motion of underground electrolytic fluids through porous systems. The result obtained by this multi-physical numerical approach, which removes all the approximations adopted in previous works, makes a useful instrument for real heterogeneous aquifer characterization and for predictive analysis of its behavior.

  20. Circulating breeding and pre-breeding prolactin and LH are not associated with clutch size in the zebra finch (Taeniopygia guttata).

    Science.gov (United States)

    Ryan, Calen P; Dawson, Alistair; Sharp, Peter J; Meddle, Simone L; Williams, Tony D

    2014-06-01

    Clutch size is a fundamental predictor of avian fitness, widely-studied from evolutionary and ecological perspectives, but surprisingly little is known about the physiological mechanisms regulating clutch size variation. The only formal mechanistic hypothesis for avian clutch-size determination predicts an anti-gonadal effect of circulating prolactin (PRL) via the inhibition of luteinizing hormone (LH), and has become widely-accepted despite little experimental support. Here we investigated the relationship between pre-breeding and breeding plasma PRL and LH and clutch-size in captive-breeding female zebra finches (Taeniopygia guttata). Using a repeated-measures design, we followed individual females from pre-breeding, through multiple breeding attempts, and attempted to decrease PRL using the D2-receptor agonist, bromocriptine. Clutch size was independent of variation in pre-breeding PRL or LH, although pre-breeding LH was negatively correlated with the time between pairing and the onset of laying. Clutch size was independent of variation in plasma PRL on all days of egg-laying. Bromocriptine treatment had no effect on plasma PRL, but in this breeding attempt clutch size was also independent of plasma PRL. Finally, we found no evidence for an inverse relationship between plasma PRL and LH levels, as predicted if PRL had inhibitory effects via LH. Thus, our data fail to provide any support for the involvement of circulating PRL in clutch size determination. These findings suggest that alternative models for hormonal control of avian clutch size need to be considered, perhaps involving downstream regulation of plasma PRL at the level of the ovary, or other hormones that have not been considered to date.

  1. The Application of Laser Processing on Clutch Manufacture

    Institute of Scientific and Technical Information of China (English)

    ZHU Qigen

    2006-01-01

    The first multi-function laser processing system in the domestic for clutch manufacture, with abilities of cutting, jointing and heat treatment, was reported in this paper. One external optical path, double laser heads, adjust device by manual operation, automatically track were employed in this system. Also the other parts of vehicles can be fabricated by this system, as well as clutches. The special processing to manufacture the clutches of heavy vehicles, which was developed by the project of this laser processing system, achieved the international standards and satisfied the economic development and nation defense in the domestic.

  2. Method for use of hydraulically or electrically controlled solenoids under failed on conditions

    Science.gov (United States)

    Bolenbaugh, Jonathan M.; Naqi, Syed

    2014-07-08

    A method to operate a clutch device in an electro-mechanical transmission mechanically-operatively coupled to an internal combustion engine and at least one electric machine includes, in response to a failure condition detected within a flow control device configured to facilitate flow of hydraulic fluid for operating the clutch device, selectively preventing the flow of hydraulic fluid from entering the flow control device and feeding the clutch device. Synchronization of the clutch device is initiated when the clutch device is intended for activation, and only if the clutch device is synchronized, the flow of hydraulic fluid is selectively permitted to enter the flow control device to activate the clutch device.

  3. Variable-Speed Simulation of a Dual-Clutch Gearbox Tiltrotor Driveline

    Science.gov (United States)

    DeSmidt, Hans; Wang, Kon-Well; Smith, Edward C.; Lewicki, David G.

    2012-01-01

    This investigation explores the variable-speed operation and shift response of a prototypical two-speed dual-clutch transmission tiltrotor driveline in forward flight. Here, a Comprehensive Variable-Speed Rotorcraft Propulsion System Modeling (CVSRPM) tool developed under a NASA funded NRA program is utilized to simulate the drive system dynamics. In this study, a sequential shifting control strategy is analyzed under a steady forward cruise condition. This investigation attempts to build upon previous variable-speed rotorcraft propulsion studies by 1) including a fully nonlinear transient gas-turbine engine model, 2) including clutch stick-slip friction effects, 3) including shaft flexibility, 4) incorporating a basic flight dynamics model to account for interactions with the flight control system. Through exploring the interactions between the various subsystems, this analysis provides important insights into the continuing development of variable-speed rotorcraft propulsion systems.

  4. Stresses and Deformations Analysis of a Dry Friction Clutch System

    Directory of Open Access Journals (Sweden)

    O.I. Abdullah

    2013-06-01

    Full Text Available The friction clutch is considered the essential element in the torquetransmission process. In this paper, the finite element method is used to study the stresses and deformations for clutch system (pressure plate, clutch disc and flywheel due to the contact pressure of diaphragm spring and the centrifugal force during the full engagement of clutch disc (assuming no slipping between contact surfaces. The investigation covers the effect of the contact stiffness factor FKN on the pressure distribution between contact surfaces, stresses and deformations. The penalty and Augmented Lagrangian algorithms have been used to obtain the pressure distribution between contact surfaces. ANSYS13 software has been used to perform the numerical calculation in this paper.

  5. Modeling and Stability Analysis of Wedge Clutch System

    Directory of Open Access Journals (Sweden)

    Jian Yao

    2014-01-01

    Full Text Available A wedge clutch with unique features of self-reinforcement and small actuation force was designed. Its self-reinforcement feature, associated with different factors such as the wedge angle and friction coefficient, brings different dynamics and unstable problem with improper parameters. To analyze this system, a complete mathematical model of the actuation system is built, which includes the DC motor, the wedge mechanism, and the actuated clutch pack. By considering several nonlinear factors, such as the slip-stick friction and the contact or not of the clutch plates, the system is piecewise linear. Through the stability analysis of the linearized system in clutch slipping phase, the stable condition of the designed parameters is obtained as α>arctan⁡(μc. The mathematical model of the actuation system is validated by prototype testing. And with the validated model, the system dynamics in both stable and unstable conditions is investigated and discussed in engineering side.

  6. Investigation of energy-efficient MRF-based clutches for hybrid powertrains

    Science.gov (United States)

    Hegger, Christian; Maas, Jürgen

    2016-04-01

    The requirements for transmission and coupling elements in hybrid powertrains are rising continuously. On this occasion a novel clutch-design is investigated and validated in this contribution. The transmission of power is based on magnetorheological fluids (MRF) including a fluid movement control for enabling a drag torque-free operation for an increased energy efficient operation. Drag losses in powertrains are a serious deficiency for an energy-efficient application. MRFs are highly qualified for the utilization in powertrains considering their particular characteristics of changing their apparent viscosity significantly under influence of a magnetic field by fast switching times and a smooth torque control. The proposed MRF-clutch with three different variations of the fluid movement control is designed based on a numerical model and validated by experimental measurements with a realized prototype. The main aspects during the investigation are focused on the coupling functions under the influence of high rotational speeds up to 6000 min-1 and also the safety behavior of the different variations by the fluid control in case of a system failure. The theoretical and experimental investigation demonstrates the suitability for an integration of clutches based on MRF in electrical or hybrid powertrains as an alternative to conventional coupling elements.

  7. Asbestos exposures of mechanics performing clutch service on motor vehicles.

    Science.gov (United States)

    Cohen, Howard J; Van Orden, Drew R

    2008-03-01

    A study was conducted to assess historical asbestos exposures of mechanics performing clutch service on motor vehicles. For most of the 20th century, friction components used in brakes and manual transmission clutches contained approximately 25-60% chrysotile asbestos. Since the late 1960s, asbestos exposure assessment studies conducted on mechanics performing brake service have frequently reported levels below the current OSHA permissible exposure limit (PEL) of 0.1 fiber/cc (flcc). Although there is a robust asbestos exposure data set for mechanics performing brake service, there are almost no data for mechanics removing and replacing clutches in manual transmission vehicles. Personal and area airborne asbestos samples were collected during the removal of asbestos-containing clutches from 15 manual transmissions obtained from salvage facilities by an experienced mechanic. Clutch plates and debris were analyzed for asbestos using EPA and ISO published analytical methods. More than 100 personal and area air samples were collected and analyzed for asbestos fibers using NIOSH methods 7400 and 7402. A separate study involved a telephone survey of 16 automotive mechanics who began work prior to 1975. The mechanics were asked about the duration, frequency, and methods used to perform clutch service. Wear debris in the bell housing surrounding clutches had an average of 0.1% chrysotile asbestos by weight, a value consistent with similar reports of brake debris. Asbestos air sampling data collected averaged 0.047 flcc. Mechanics participating in the telephone survey indicated that clutch service was performed infrequently, the entire clutch assembly was normally replaced, and there was no need to otherwise handle the asbestos-containing clutch plates. These mechanics also confirmed that wet methods were most frequently used to clean debris from the bell housing. Combining the asbestos exposure that occurred when mechanics performed clutch service, along with the duration

  8. Modeling and Prototyping of Automatic Clutch System for Light Vehicles

    Science.gov (United States)

    Murali, S.; Jothi Prakash, V. M.; Vishal, S.

    2017-03-01

    Nowadays, recycling or regenerating the waste in to something useful is appreciated all around the globe. It reduces greenhouse gas emissions that contribute to global climate change. This study deals with provision of the automatic clutch mechanism in vehicles to facilitate the smooth changing of gears. This study proposed to use the exhaust gases which are normally expelled out as a waste from the turbocharger to actuate the clutch mechanism in vehicles to facilitate the smooth changing of gears. At present, clutches are operated automatically by using an air compressor in the four wheelers. In this study, a conceptual design is proposed in which the clutch is operated by the exhaust gas from the turbocharger and this will remove the usage of air compressor in the existing system. With this system, usage of air compressor is eliminated and the riders need not to operate the clutch manually. This work involved in development, analysation and validation of the conceptual design through simulation software. Then the developed conceptual design of an automatic pneumatic clutch system is tested with proto type.

  9. Post-mating clutch piracy in an amphibian.

    Science.gov (United States)

    Vieites, David R; Nieto-Román, Sandra; Barluenga, Marta; Palanca, Antonio; Vences, Miguel; Meyer, Axel

    2004-09-16

    Female multiple mating and alternative mating systems can decrease the opportunity for sexual selection. Sperm competition is often the outcome of females mating with multiple males and has been observed in many animals, and alternative reproductive systems are widespread among species with external fertilization and parental care. Multiple paternity without associated complex behaviour related to mating or parental care is also seen in simultaneously spawning amphibians and fishes that release gametes into water. Here we report 'clutch piracy' in a montane population of the common frog Rana temporaria, a reproductive behaviour previously unknown in vertebrates with external fertilization. Males of this species clasp the females and the pair deposits one spherical clutch of eggs. No parental care is provided. 'Pirate' males search for freshly laid clutches, clasp them as they would do a female and fertilize the eggs that were left unfertilized by the 'parental' male. This behaviour does not seem to be size-dependent, and some males mate with a female and perform clutch piracy in the same season. Piracy affected 84% of the clutches and in some cases increased the proportion of eggs fertilized, providing direct fitness benefits both for the pirate males and the females. Sexual selection--probably caused by a strong male-biased sex ratio--occurs in this population, as indicated by size-assortative mating; however, clutch piracy may reduce its impact. This provides a good model to explore how alternative mating strategies can affect the intensity of sexual selection.

  10. Realization of a MRF-safety-clutch for high torsional moments based on a novel ball-clutch design

    Science.gov (United States)

    Matthias, M.; Seipel, B.; Jackel, M.; Kloepfer, J.

    2012-04-01

    This paper describes the development of a safety-clutch by using magnetorheological fluids (MRF) to switch the transmission torque between a motor and a generator in a bus-like vehicle. The clutch is based on a new design combining an axial MRF-actuator and a ball coupling mechanism. This so called "MRF-ball-clutch" avoids the disadvantages of traditional bell- or disc-MRF-clutch designs where the torque is transmitted by the MRF which leads to a self-heating due to the shearing forces in the fluid and a more or less significant drag torque caused by limitations of the relation between minimal and maximal transmittable torque. The safety clutch based on the new MRF-clutch design requires a minimum of power consumption and allows switching high torsional moments in a very compact, lightweight and robust design. The work was done within the Fraunhofer System Research for Electromobility FSEM, founded by the German Federal Ministry of Research and Technology.

  11. Cryptic female choice: frogs reduce clutch size when amplexed by undesired males.

    Science.gov (United States)

    Reyer, H U; Frei, G; Som, C

    1999-10-22

    In species with internal fertilization, females can 'cryptically' choose (e.g. through sperm selection) which individuals sire their offspring, even when their overt preferences for copulatory partners are overrun by male-male competition and sexual coercion. The experiment presented here reveals that control of paternity after copulation has begun is also possible in species with external fertilization. Females of the hybridogenetic Rana essonae-Rana esculenta (LL-LR) waterfrog complex adjust their clutch size in response to mate type: they release fewer eggs when amplexed by hybrid LR males who--jeopardize successful reproduction--than when amplexed by parental LL males. This reduction in the number of eggs laid can increase a female's residual reproductive value through a second mating in the same breeding season or a larger clutch size in the next year. We argue that cryptic female choice through clutch size adjustment (i) may have evolved more often than previously assumed, and (ii) can arise even where females mate only once during a reproductive period.

  12. Effective clutch-system development; Effiziente Entwicklung von Kupplingssystemen

    Energy Technology Data Exchange (ETDEWEB)

    Welter, R.; Zink, M.; Shead, R.

    2001-04-01

    Although there is a trend to automatisation in the vehicle drive train manually operated clutches will keep an important market share in the near future. This is because technical and commercial expectations of the car manufacturers have led to numerous innovative solutions. An example for this is the self adjusting clutch (SAC) or the market introduction of hydraulic clutch actuation over the last years. Further potential can be achieved, if the clutch and the release components are regarded as an unified technical system and are consequently analysed by a clutch specialist. (orig.) [German] Fahrzeuge mit fussbetaetigter Einscheibentrockenkupplung werden trotz stetig steigender Automatisierung im Antriebsstrang auch in Zukunft noch einen bedeutenden Marktanteil besitzen. Dieser konnte bislang nicht zuletzt dadurch behauptet werden, dass den gestiegenen technischen und kommerziellen Erwartungen immer neue innovative Detailloesungen entgegen gesetzt wurden. Hierzu gehoert beispielsweise die selbsteinstellende Kupplung oder die breite Einfuehrung der Kupplungshydraulik in den letzten Jahren. Dieser Beitrag der LuK zeigt weiter fuehrende Potenziale auf. Diese ergeben sich, wenn die Kupplung und die Betaetigung als ein zusammenhaengendes technisches System begriffen wird. (orig.)

  13. Noise reduction of punch press mechanical clutch engagement

    Institute of Scientific and Technical Information of China (English)

    CHEN Wei; SUN Chang-qing; LI Yun-liang

    2005-01-01

    Among the noises of the punch press, blanking noise and engaging noise of the clutch should be paid most attention to. The latter is generated by the engagement impacts of the rotating key on the spline bush. In order to absorb the pressing energy and reduce the noise radiated, polyurethane cushions were added to the spline bush keyways and the clutch running noise reduction has reached 10.7 dB(A). Considering such factors as the running characteristics of the punch press clutch, the demand for cushioning performance and the demand of the clutch temperature field for damping materials, the temperature field of the rigid clutch spline bush was simulated to find out whether the temperature of polyurethane go beyond its critical application temperature, using the finite element method. According to the characteristic that the deforming memory alloy can restore the remembered shape with the temperature rising, the actual temperature of the spline bush was measured. Consequently, the theoretical temperature turned out to be close to the measured temperature.

  14. A hybrid ultrasonic motor and electrorheological fluid clutch actuator for force-feedback in MRI/fMRI.

    Science.gov (United States)

    Chapuis, Dominique; Gassert, Roger; Burdet, Etienne; Bleuler, Hannes

    2008-01-01

    This paper presents a safe, electrically powered MR-compatible actuator with a large range of output impedance, which can be used at the entry of the scanner bore. This actuator is composed of an ultrasonic motor (USM) and a torque-controlled electrorheological fluid clutch which modulates the output torque of the USM. This paper describes the developments on the electrorheological fluid (ERF) clutch and its high voltage driver. The performances of the ERF brake constituting the clutch are evaluated, and its torque range is adapted using an epicyclic differential. The transmissible torque of the ERF clutch, i.e., the maximum system output torque, is 94.4 mNm and its drag torque is 2.6 mNm. The MR compatibility of the complete hybrid actuator is shown in extensive tests including subtraction of images and comparison of signal-to-noise ratios in powered and unpowered conditions. This novel MR-compatible actuator may be used to study the neural control of the hand.

  15. Validation of dynamic torque response of an electrorheological (ER) clutch

    Science.gov (United States)

    Tan, K. P.; Stanway, R.; Bullough, W. A.

    2006-02-01

    It is now well established that using actuators, which have faster speeds of response than d.c. servomotors, can solve the positional errors of the robot arms. One of the possible robotic actuators can be an electro-rheological (ER) clutch. To justify this objective, the authors measured the output torque response of a co-axial ER clutch. However, due to the dynamic inefficiency of a torque transducer, the measured torque response is inaccurate for analytical studies. Therefore, this measured torque is signal processed by using the transfer functions of this torque sensor and a filter to yield the ER torque response. The validity of this ER torque is investigated by comparing the numerical errors between the measured torque and its inverse torque response. From the torque error analysis, it is concluded that the ER clutch can be an actuator to improve the positioning accuracies of the robot arms.

  16. Developing Additive Technology for Wet Dual Clutch Transmissions

    Institute of Scientific and Technical Information of China (English)

    Ramnath Iyer; Samuel H.Tersigni; Philippe Ezanno; Christopher S.Cleveland

    2012-01-01

    Wet dual clutch transmissions(W-DCTs) show overall benefits including excellent fuel efficiency,wide torque capacity range,long durability,driving comfort and sportiness.Many breakthroughs have been made to further improve the fuel efficiency by design innovations and introductions of new hardware.Each W-DCT has its unique design and hardware.It demands the lubricant to provide excellent wet clutch friction performance and anti-shudder friction durability,good synchronizer friction performance and durability,high load-carrying ability,excellent bearing performance,strong anti-corrosion performance,high thermal and oxidative stability,excellent material compatibility,etc.Particularly,the requirement of the wet clutch friction performance in W-DCT is much more severe than conventional ATFs and CVTFs.We report here our latest W-DCTF technologies developed for different W-DCT applications.DCTF-1 was optimized for a two-sump W-DCT application with the clutch lining material of friction material A(FM-A).DCTF-1 shows high and stable dynamic friction,static friction,particularly,high quasi-static friction without any shudder tendency in GK tests.DCTF-2 was designed for a one-sump W-DCT application with the same clutch lining material of FM-A.DCTF-2 completes 42,000 cycles of the severe GTI chassis dynamometer vehicle test without any issues,which is comparable to the factory fill fluid DCTF-FF.DCTF-3 was developed for a one-sump W-DCT application with a different clutch lining material of FM-B.DCTF-3 shows high and stable dynamic friction in the severe newly developed SAE DCT test procedure.DCTF-3 also gives excellent LVFA durability of over 720 h in the JASO M349 test procedure on FM-B.

  17. Research on Drag Torque Prediction Model for the Wet Clutches

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Considering the surface tension effect and centrifugal effect, a mathematical model based on Reynolds equation for predicting the drag torque of disengage wet clutches is presented. The model indicates that the equivalent radius is a function of clutch speed and flow rate. The drag torque achieves its peak at a critical speed. Above this speed, drag torque drops due to the shrinking of the oil film. The model also points out that viscosity and flow rate effects on drag torque. Experimental results indicate that the model is reasonable and it performs well for predicting the drag torque peak.

  18. Ergonomic assessment of drivers in MF285 and MF399 tractors during clutching using algometer

    Directory of Open Access Journals (Sweden)

    Hossein Fallahi

    2016-03-01

    The results showed that the clutching forces for MF285 and MF399 tractors were 340 N and 290 N, respectively. The knee angle of the drivers of the two tractors was statistically different at the one percent level of significance. The reduction of pain threshold after 30 and 60 s clutching and also 60 s rest after clutching in MF285 tractor, for all three muscles, were more than those of MF399 tractor. The impact of clutching on the average decreases of pain threshold, for all drivers and all clutching periods, during and after clutching, in the Quadratus lumborum muscle was more than the other two muscles, in both tractors. In order to reduce the clutching force for MF285 tractor some modifications is suggested. In this regard the force transfer joint between the pedal and the clutch release linkage may be replaced with one made of cast iron.

  19. The influence of clutch and brood sizes on nesting success of the biscutate swift, Streptoprocne biscutata (Aves: Apodidae

    Directory of Open Access Journals (Sweden)

    Mauro Pichorim

    2011-04-01

    Full Text Available The nesting success of three colonies of Streptoprocne biscutata (Sclater, 1866, and the influence of clutch and brood size on nesting success of species were studied. Overall, apparent nesting success was 58% and Mayfield nesting success was 53%. Nest survival during incubation (64% was lower than during the nestling period (83%. During incubation, clutches were lost to rain, desertion, predation, egg ejection, egg damage, and egg disappearance. During the nestling period, losses occurred due to offspring disappearance, nestling death by starvation, predation and falling. During both incubation and nestling periods, predation was low, while egg ejections and nestling starvation were the main causes of nest failure. Nest survival during incubation was directly proportional to clutch size, while during the nestling period it was inversely proportional to the brood size. Apparently, there seemed to be an advantage to having more eggs during incubation. However, if all eggs were to hatch during unfavorable weather the nest success could be low. These results suggest that when the breeding pairs face adversity during incubation, they control the brood size by ejecting part of the clutch.

  20. Some Design-Objectives and Design-Guidelines for Automotive Friction Clutch Based on Clutch Engagement Dynamics

    Science.gov (United States)

    Tripathi, K.

    2014-01-01

    Dynamics of the driveline and the vehicle during clutch engagement is a complex phenomenon. Time domain analysis of different state variables is performed through numerical solution of sixth-order driveline model using an indigenous computer program. The study revealed that different design objectives like driver and passenger comfort, smoothness of engagement, wear of friction surfaces, power loss, and heat generation are in mutual conflict, with respect to the sub-ranges of operational parameters. The overall outcome of this study is presented in the form of a matrix, relating the sub-ranges of operational parameters with engagement quality parameters, which may be used as a guideline for clutch design for different design objectives. The engagement quality parameters may also be used for building a cost function for overall optimization of clutch.

  1. Relativistic hydrodynamics

    CERN Document Server

    Luciano, Rezzolla

    2013-01-01

    Relativistic hydrodynamics is a very successful theoretical framework to describe the dynamics of matter from scales as small as those of colliding elementary particles, up to the largest scales in the universe. This book provides an up-to-date, lively, and approachable introduction to the mathematical formalism, numerical techniques, and applications of relativistic hydrodynamics. The topic is typically covered either by very formal or by very phenomenological books, but is instead presented here in a form that will be appreciated both by students and researchers in the field. The topics covered in the book are the results of work carried out over the last 40 years, which can be found in rather technical research articles with dissimilar notations and styles. The book is not just a collection of scattered information, but a well-organized description of relativistic hydrodynamics, from the basic principles of statistical kinetic theory, down to the technical aspects of numerical methods devised for the solut...

  2. Hydrodynamic Effects on Modeling and Control of a High Temperature Active Magnetic Bearing Pump with a Canned Rotor

    Energy Technology Data Exchange (ETDEWEB)

    Melin, Alexander M [ORNL; Kisner, Roger A [ORNL; Fugate, David L [ORNL; Holcomb, David Eugene [ORNL

    2015-01-01

    Embedding instrumentation and control Embedding instrumentation and control (I\\&C) at the component level in nuclear power plants can improve component performance, lifetime, and resilience by optimizing operation, reducing the constraints on physical design, and providing on-board prognostics and diagnostics. However, the extreme environments that many nuclear power plant components operate in makes embedding instrumentation and control at the component level difficult. Successfully utilizing embedded I\\&C requires developing a deep understanding of the system's dynamics and using that knowledge to overcome material and physical limitations imposed by the environment. In this paper, we will develop a coupled dynamic model of a high temperature (700 $^\\circ$C) canned rotor pump that incorporates rotordynamics, hydrodynamics, and active magnetic bearing dynamics. Then we will compare two control design methods, one that uses a simplified decoupled model of the system and another that utilizes the full coupled system model. It will be seen that utilizing all the available knowledge of the system dynamics in the controller design yield an order of magnitude improvement in the magnitude of the magnetic bearing response to disturbances at the same level of control effort, a large reduction in the settling time of the system, and a smoother control action.

  3. A conceptual framework for clutch size evolution in songbirds

    Science.gov (United States)

    Martin, Thomas E.

    2014-01-01

    Causes of evolved differences in clutch size among songbird species remain debated. I propose a new conceptual framework that integrates aspects of traditional life history theory, while including novel elements, to explain evolution of clutch size among songbirds. I review evidence that selection by nest predation on length of time that offspring develop in the nest creates a gradient in offspring characteristics at nest-leaving (fledging), including flight mobility, spatial dispersion, and self-feeding rate. I postulate that this gradient has consequences for offspring mortality rates and parental energy expenditure per offspring. These consequences then determine how reproductive effort is partitioned among offspring, while reproductive effort evolves from age-specific mortality effects. Using data from a long-term site in Arizona, as well as from the literature, I provide support for hypothesized relationships. Nestling development period consistently explains fledgling mortality, energy expenditure per offspring, and clutch size while accounting for reproductive effort (i.e., total energy expenditure) to thereby support the framework. Tests in this paper are not definitive, but they document previously unrecognized relationships and address diverse traits (developmental strategies, parental care strategies, energy requirements per offspring, evolution of reproductive effort, clutch size) that justify further investigations of hypotheses proposed here.

  4. New dual clutch transmission for tractors; Neues Doppelkupplungsgetriebe fuer Traktoren

    Energy Technology Data Exchange (ETDEWEB)

    Seeger, Joerg [John Deere Werke, Mannheim (Germany)

    2012-10-15

    John Deere presented its new 6R series of tractors at Agritechnica 2011. The tractors are available since the summer of this year, with a double clutch transmission, a completely new type of transmission for agricultural machinery. This transmission concept combines the advantages of mechanical manual transmissions (high efficiency) and stepless transmissions (convenient driving and operation). (orig.)

  5. Theoretical hydrodynamics

    CERN Document Server

    Milne-Thomson, L M

    2011-01-01

    This classic exposition of the mathematical theory of fluid motion is applicable to both hydrodynamics and aerodynamics. Based on vector methods and notation with their natural consequence in two dimensions - the complex variable - it offers more than 600 exercises and nearly 400 diagrams. Prerequisites include a knowledge of elementary calculus. 1968 edition.

  6. Hydrodynamic bearings

    CERN Document Server

    Bonneau, Dominique; Souchet, Dominique

    2014-01-01

    This Series provides the necessary elements to the development and validation of numerical prediction models for hydrodynamic bearings. This book describes the rheological models and the equations of lubrication. It also presents the numerical approaches used to solve the above equations by finite differences, finite volumes and finite elements methods.

  7. Ship Hydrodynamics

    Science.gov (United States)

    Lafrance, Pierre

    1978-01-01

    Explores in a non-mathematical treatment some of the hydrodynamical phenomena and forces that affect the operation of ships, especially at high speeds. Discusses the major components of ship resistance such as the different types of drags and ways to reduce them and how to apply those principles for the hovercraft. (GA)

  8. Radiation Hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Castor, J I

    2003-10-16

    The discipline of radiation hydrodynamics is the branch of hydrodynamics in which the moving fluid absorbs and emits electromagnetic radiation, and in so doing modifies its dynamical behavior. That is, the net gain or loss of energy by parcels of the fluid material through absorption or emission of radiation are sufficient to change the pressure of the material, and therefore change its motion; alternatively, the net momentum exchange between radiation and matter may alter the motion of the matter directly. Ignoring the radiation contributions to energy and momentum will give a wrong prediction of the hydrodynamic motion when the correct description is radiation hydrodynamics. Of course, there are circumstances when a large quantity of radiation is present, yet can be ignored without causing the model to be in error. This happens when radiation from an exterior source streams through the problem, but the latter is so transparent that the energy and momentum coupling is negligible. Everything we say about radiation hydrodynamics applies equally well to neutrinos and photons (apart from the Einstein relations, specific to bosons), but in almost every area of astrophysics neutrino hydrodynamics is ignored, simply because the systems are exceedingly transparent to neutrinos, even though the energy flux in neutrinos may be substantial. Another place where we can do ''radiation hydrodynamics'' without using any sophisticated theory is deep within stars or other bodies, where the material is so opaque to the radiation that the mean free path of photons is entirely negligible compared with the size of the system, the distance over which any fluid quantity varies, and so on. In this case we can suppose that the radiation is in equilibrium with the matter locally, and its energy, pressure and momentum can be lumped in with those of the rest of the fluid. That is, it is no more necessary to distinguish photons from atoms, nuclei and electrons, than it is

  9. Bacterial hydrodynamics

    CERN Document Server

    Lauga, Eric

    2015-01-01

    Bacteria predate plants and animals by billions of years. Today, they are the world's smallest cells yet they represent the bulk of the world's biomass, and the main reservoir of nutrients for higher organisms. Most bacteria can move on their own, and the majority of motile bacteria are able to swim in viscous fluids using slender helical appendages called flagella. Low-Reynolds-number hydrodynamics is at the heart of the ability of flagella to generate propulsion at the micron scale. In fact, fluid dynamic forces impact many aspects of bacteriology, ranging from the ability of cells to reorient and search their surroundings to their interactions within mechanically and chemically-complex environments. Using hydrodynamics as an organizing framework, we review the biomechanics of bacterial motility and look ahead to future challenges.

  10. Nanoflow hydrodynamics

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt; Dyre, Jeppe C.; Daivis, Peter J.;

    2011-01-01

    We show by nonequilibrium molecular dynamics simulations that the Navier-Stokes equation does not correctly describe water flow in a nanoscale geometry. It is argued that this failure reflects the fact that the coupling between the intrinsic rotational and translational degrees of freedom becomes...... important for nanoflows. The coupling is correctly accounted for by the extended Navier-Stokes equations that include the intrinsic angular momentum as an independent hydrodynamic degree of freedom. © 2011 American Physical Society....

  11. Control Theory with Applications to Naval Hydrodynamics: The First David W. Taylor Lectures -- April 1972

    Science.gov (United States)

    1975-12-01

    by Bucy and Joseph; this lecture considers only the linear problem. Astrom , K. J., "Introduction to Stochastic Control Theory," Academic Press, Inc...Optimal Filter 62 REFERENCES 1. Astrom , K. J., "Introduction to Stochastic Control Theory," Academic Press, Inc., New York (1970). 2. Kaiman, R. E

  12. Research on Dynamic Performance of Power Shift Clutch

    Directory of Open Access Journals (Sweden)

    Wang Li

    2016-01-01

    Full Text Available Smooth shift and low shift shock are needed to improve power shift quality and comfort of construction vehicle. And higher dynamic performance of power shift clutch is needed. In this paper, the dynamic mathematical model and simulation model of the clutch engagement process were established, the factors affecting the shift quality were analyzed qualitatively and quantitatively. The simulation model of the transmission system was established based on the software AMESim, the corresponding vehicle tests were performed, and the shifting quality was improved by changing key parameters. Analysis results illustrate that the proposed mathematical model and simulation model are correct and effective and can be used to predict and evaluate construction vehicle shift-feel, which are the theoretical basis for analysis and research on the static and dynamic characteristics of the dynamic shifting process in the future.

  13. Compact MR fluid clutch device for human-friendly actuator

    Energy Technology Data Exchange (ETDEWEB)

    Kikuchi, T; Ikeda, K; Otsuki, K; Kakehashi, T; Furusho, J [Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)], E-mail: kikuchi@mech.eng.osaka-u.ac.jp

    2009-02-01

    In this paper, we describe a design method and experimental results of a newly developed MR Fluid clutch which has a multi-layered disks and micro-size (50 micro meters) gaps of MR Fluid. The micro-size gap works for the reduction of magnetic resistance, amount of power supply and size of the total system. Static torques of the device was predictable with conventional magnetostatic analyses. Additionally, dynamic test shows that its response time is about 20 milliseconds.

  14. Extending the molecular clutch beyond actin-based cell motility

    Science.gov (United States)

    Havrylenko, Svitlana; Mezanges, Xavier; Batchelder, Ellen; Plastino, Julie

    2014-10-01

    Many cell movements occur via polymerization of the actin cytoskeleton beneath the plasma membrane at the front of the cell, forming a protrusion called a lamellipodium, while myosin contraction squeezes forward the back of the cell. In what is known as the ‘molecular clutch’ description of cell motility, forward movement results from the engagement of the acto-myosin motor with cell-matrix adhesions, thus transmitting force to the substrate and producing movement. However during cell translocation, clutch engagement is not perfect, and as a result, the cytoskeleton slips with respect to the substrate, undergoing backward (retrograde) flow in the direction of the cell body. Retrograde flow is therefore inversely proportional to cell speed and depends on adhesion and acto-myosin dynamics. Here we asked whether the molecular clutch was a general mechanism by measuring motility and retrograde flow for the Caenorhabditis elegans sperm cell in different adhesive conditions. These cells move by adhering to the substrate and emitting a dynamic lamellipodium, but the sperm cell does not contain an acto-myosin cytoskeleton. Instead the lamellipodium is formed by the assembly of major sperm protein, which has no biochemical or structural similarity to actin. We find that these cells display the same molecular clutch characteristics as acto-myosin containing cells. We further show that retrograde flow is produced both by cytoskeletal assembly and contractility in these cells. Overall this study shows that the molecular clutch hypothesis of how polymerization is transduced into motility via adhesions is a general description of cell movement regardless of the composition of the cytoskeleton.

  15. Design and Test of an Automotive Clutch Actuation

    OpenAIRE

    Meloni, Michele

    2012-01-01

    This thesis builds on the analysis of a automatic system for automotive automatic clutches. In this field of study there are some constraint to take into account and through them it is possible to find the best technological solution. The system under consideration is characterized as electromechanical, with an electric motor brush DC and reduction system very complex. The system was modeled using the Bond-Graph technique which allowed the drafting of the dynamical system equations, in state ...

  16. Clutch size in the tropical scincid lizard Emoia sanfordi, a species endemic to the Vanuatu Archipelago.

    Science.gov (United States)

    Hamilton, Alison Madeline; Eckstut, Mallory Elizabeth; Klein, Elaine Renee; Austin, Christopher Cowell

    2008-08-01

    The majority of species in the scincid genus Emoia (Squamata: Scincidae) have a fixed clutch size of two eggs per clutch and produce between two and four clutches per year. One lineage within Emoia, the Emoia samoensis species group, consists of 13 species occurring in Melanesia and the islands of the southwestern Pacific Ocean, and exhibits variation in clutch size, with previously reported clutch sizes of two to five eggs. Little is known about reproduction in several members of this lineage including Emoia sanfordi, a large-bodied lizard endemic to the archipelago of Vanuatu in the South Pacific. We analyzed reproduction and clutch size in E. sanfordi females and discovered that there is a substantial amount of intraspecific variation, with clutch size ranging from two to seven eggs, with a modal clutch size of five eggs. Females were reproductively active throughout the study period of June through October and appear to be laying multiple clutches. The variation in clutch size seen in E. sanfordi is congruent with the variation previously reported within other closely related species.

  17. Brood parasites lay eggs matching the appearance of host clutches.

    Science.gov (United States)

    Honza, Marcel; Šulc, Michal; Jelínek, Václav; Požgayová, Milica; Procházka, Petr

    2014-01-07

    Interspecific brood parasitism represents a prime example of the coevolutionary arms race where each party has evolved strategies in response to the other. Here, we investigated whether common cuckoos (Cuculus canorus) actively select nests within a host population to match the egg appearance of a particular host clutch. To achieve this goal, we quantified the degree of egg matching using the avian vision modelling approach. Randomization tests revealed that cuckoo eggs in naturally parasitized nests showed lower chromatic contrast to host eggs than those assigned randomly to other nests with egg-laying date similar to naturally parasitized clutches. Moreover, egg matching in terms of chromaticity was better in naturally parasitized nests than it would be in the nests of the nearest active non-parasitized neighbour. However, there was no indication of matching in achromatic spectral characteristics whatsoever. Thus, our results clearly indicate that cuckoos select certain host nests to increase matching of their own eggs with host clutches, but only in chromatic characteristics. Our results suggest that the ability of cuckoos to actively choose host nests based on the eggshell appearance imposes a strong selection pressure on host egg recognition.

  18. Fluid durability in a high speed electro-rheological clutch

    Science.gov (United States)

    Johnson, A. R.; Makin, J.; Bullough, W. A.; Firoozian, R.; Hosseini-Sianaki, A.

    1993-10-01

    The durability of an electro-rheological (ER) fluid was investigated by running a high speed ER clutch under different conditions and periods of operation. The tests involved running the clutch at 3000 rpm for a total period of twelve hours over a five day period. The tests subjected the fluid to a centripetal acceleration of 3000 m/sq s, and were conducted with and without an excitation field of 2 kV/mm, and with and without shearing the fluid at shear rates up to 9500/s. The condition of the fluid was assessed periodically by measuring the torque response of the clutch to a step application of voltage in respect of both magnitude and speed of response. Results at the two pole 50 Hz synchronous speed of 3000 rpm indicated that the particles in the fluid were centrifuged over the prolonged test periods. The application of a voltage across the fluid had a negligible effect on this particle migration. The effect of particle migration due to centrifugal and electro-static effects indicate future development requirements for these smart materials.

  19. Drag Torque Prediction Model for the Wet Clutches

    Institute of Scientific and Technical Information of China (English)

    HU Jibin; PENG Zengxiong; YUAN Shihua

    2009-01-01

    Reduction of drag torque in disengaged wet clutch is one of important potentials for vehicle transmission improvement. The flow of the oil film in clutch clearance is investigated. A three-dimension Navier-Stokes(N-S) equation based on laminar flow is presented to model the drag torque. Pressure and speed distribution in radial and circumferential directions are deduced. The theoretical analysis reveals that oil flow acceleration in radial direction caused by centrifugal force is the key reason for the shrinking of oil film as constant feeding flow rate. The peak drag torque occurs at the beginning of oil film shrinking. A variable is introduced to describe effective oil film area and drag torque after oil film shrinking is well evaluated with the variable. Under the working condition, tests were made to obtain drag torque curves at different clutch speed and oil viscosity. The tests confirm that simulation results agree with test data. The model performs well in the prediction of drag torque and lays a theoretical foundation to reduce it.

  20. Experimental evidence of how the fractal structure controls the hydrodynamic resistance on granular aggregates moving through water

    Science.gov (United States)

    Maggi, Federico

    2015-09-01

    A comprehensive set of experiments was carried out to investigate the effect of the fractal architecture of granular aggregates on the free-fall acceleration through a still water column. Test aggregates were first generated numerically with a method that allowed to control the fractal dimension d and, next, three stochastic replicates were lithographically fabricated for each of six values of d ranging between 1.9 and 2.7. The recorded position, velocity and acceleration served to analyze their dynamics in the Reynolds and Galilei number space, and to calculate the momentum rate of change and the intensity of drag (viscous and impact) and inertial forces (added mass and Basset-Bousinnesq). Analysis of these forces highlighted a strong dependence on d; additionally, integration of these forces in the particle momentum equation allowed to identify an additional resistance Rx that showed a strong correlation with d. A correlation analysis of Rx with various scaling laws combining velocity and acceleration suggested that Rx could be described by a nonlinear drag force and a force intermediate between drag and inertia. It was therefore concluded that irregular granular fractal aggregates accelerating in water are subject to highly complex and nonlinear hydrodynamic effects caused by surface roughness and volume porosity, and that these effects have tight connection with the internal and external fractal characteristics of the aggregates.

  1. Introduction to Hydrodynamics

    CERN Document Server

    Jeon, Sangyong

    2015-01-01

    We give a pedagogical review of relativistic hydrodynamics relevant to relativistic heavy ion collisions. Topics discussed include linear response theory derivation of 2nd order viscous hydrodynamics including the Kubo formulas, kinetic theory derivation of 2nd order viscous hydrodynamics, anisotropic hydrodynamics and a brief review of numerical algorithms. Emphasis is given to the theory of hydrodynamics rather than phenomenology.

  2. Finite Element Analysis of Temperature Field in Automotive Dry Friction Clutch

    Directory of Open Access Journals (Sweden)

    O.I. Abdullah

    2012-12-01

    Full Text Available The friction clutch design is strongly dependent upon the frictional heat generated between contact surfaces during the slipping at beginning of engagement. Because of that the frictional heat generated firstly will reduce the performance of clutch system and then will lead to premature failure in some cases. Finite element method was used to investigate aneffect of thermal load type on the temperature field of the clutch system. Two-dimensional axisymmetric model was used to study the temperature distribution for the clutch system (pressure plate, clutch disc and flywheel during heating phase (slipping period and in the cooling phase (full engagement period. Depending on basic friction clutch design two types of thermal loads were applied; load type A (uniform pressure and load type B (uniform wear. Repeated engagements made at regular interval wereconsidered in this work. ANSYS13 has been used to perform the numerical calculation in this paper.

  3. Hydrodynamic directional control of liquid metal droplets within a microfluidic flow focusing system

    Science.gov (United States)

    Gol, Berrak; Kurdzinski, Michael E.; Tovar-Lopez, Francisco J.; Petersen, Phred; Mitchell, Arnan; Khoshmanesh, Khashayar

    2016-04-01

    Here, we investigate the directional control of Galinstan liquid metal droplets when transferring from the high-viscosity glycerol core into the parallel low-viscosity NaOH sheath streams within a flow focusing microfluidic system. In the presence of sufficient flow mismatch between the sheath streams, the droplets are driven toward the higher velocity interface and cross the interface under the influence of surface tension gradient. A minimum flow mismatch of 125 μl/min is required to enable the continuous transfer of droplets toward the desired sheath stream. The response time of droplets, the time required to change the direction of droplet transfer, is governed by the response time of the syringe pump driven microfluidic system and is found to be 3.3 and 8.8 s when increasing and decreasing the flow rate of sheath stream, respectively.

  4. Finite Element Analysis of Temperature Field in Automotive Dry Friction Clutch

    OpenAIRE

    O.I. Abdullah; J. Schlattmann

    2012-01-01

    The friction clutch design is strongly dependent upon the frictional heat generated between contact surfaces during the slipping at beginning of engagement. Because of that the frictional heat generated firstly will reduce the performance of clutch system and then will lead to premature failure in some cases. Finite element method was used to investigate aneffect of thermal load type on the temperature field of the clutch system. Two-dimensional axisymmetric model was used to study the tempe...

  5. Clutch size evolution under sexual conflict enhances the stability of mating systems.

    Science.gov (United States)

    Smith, H G; Härdling, R

    2000-11-07

    Models of optimal clutch size often implicitly assume a situation with uniparental care. However, the evolutionary conflict between males and females over the division of parental care will have a major influence on the evolution of clutch size. Since clutch size is a female trait, a male has little possibility of directly influencing it. However, the optimal clutch size from a female's perspective will depend on the amount of paternal care her mate is expected to provide. The sexual conflict over parental care will in its turn be affected by clutch size, since a larger clutch makes male care more valuable. Hence, there will be joint evolution of mating system and clutch size. In this paper, we demonstrate that this joint evolution will tend to stabilize the mating system. In a situation with conventional sex roles, this joint evolution might result in either increased clutch size and biparental care or reduced clutch size and uniparental female care. Under some circumstances the initial conditions might determine which will be the outcome. These results demonstrate that it may be difficult to deduce whether biparental care evolved because of few opportunities for breeding males increasing their fitness by attracting additional mates or because of the importance of male care for offspring fitness by studying prevailing mating systems using, for example, male removals or manipulation of males' opportunities for finding additional mates. In general terms, we demonstrate that models of life-history evolution have to consider the social context in which they evolve.

  6. Submarine hydrodynamics

    CERN Document Server

    Renilson, Martin

    2015-01-01

    This book adopts a practical approach and presents recent research together with applications in real submarine design and operation. Topics covered include hydrostatics, manoeuvring, resistance and propulsion of submarines. The author briefly reviews basic concepts in ship hydrodynamics and goes on to show how they are applied to submarines, including a look at the use of physical model experiments. The issues associated with manoeuvring in both the horizontal and vertical planes are explained, and readers will discover suggested criteria for stability, along with rudder and hydroplane effectiveness. The book includes a section on appendage design which includes information on sail design, different arrangements of bow planes and alternative stern configurations. Other themes explored in this book include hydro-acoustic performance, the components of resistance and the effect of hull shape. Readers will value the author’s applied experience as well as the empirical expressions that are presented for use a...

  7. Particle fluxes in the NW Iberian coastal upwelling system: Hydrodynamical and biological control

    Science.gov (United States)

    Zúñiga, D.; Villacieros-Robineau, N.; Salgueiro, E.; Alonso-Pérez, F.; Rosón, G.; Abrantes, F.; Castro, C. G.

    2016-07-01

    To better understand sources and transport of particulate material in the NW Iberian coastal upwelling system, a mooring line dotted with an automated PPS 4/3 sediment trap was deployed off Cape Silleiro at the base of the photic zone. The samples were collected from November 2008 through June 2012 over sampling periods of 4-12 days. Our study represents the first automated sediment trap database for the NW Iberian margin. The magnitude and composition of the settling material showed strong seasonal variability with the highest fluxes during the poleward and winter mixing periods (averages of 12.9±9.6 g m-2 d-1 and 5.6±5.6 g m-2 d-1 respectively), and comparatively lower fluxes (3.6±4.1 g m-2 d-1) for the upwelling season. Intensive deposition events registered during poleward and winter mixing periods were dominated by the lithogenic fraction (80±3%). They were associated to high energy wave-driven resuspension processes, due to the occurrence of south-westerly storms, and intense riverine inputs of terrestrial material from Minho and Douro rivers. On the other hand, during the spring - summer upwelling season, the share of biogenic compounds (organic matter, calcium carbonate (CaCO3), biogenic silica (bSiO2)) to downward fluxes was higher, reflecting an increase in pelagic sedimentation due to the seasonal intensification of primary production and negligible river inputs and wave-driven resuspended material. Otherwise, the large variations of biogenic settling particles were mainly modulated by upwelling intensity, which by means of upwelling filaments ultimately controlled the offshore transport of the organic carbon fixed by primary producers towards the adjacent ocean. Based on the average downward flux of organic carbon (212 mg C m-2 d-1) and considering an average primary production of 1013 mg C m-2 d-1 from literature, we estimated that about 21% of the fixed carbon is vertically exported during the upwelling season.

  8. Modeling and Testing of Hydrodynamic Damping Model for a Complex-shaped Remotely-operated Vehicle for Control

    Institute of Scientific and Technical Information of China (English)

    Cheng Chin; Michael Lau

    2012-01-01

    In this paper,numerical modeling and model testing of a complex-shaped remotely-operated vehicle (ROV) were shown.The paper emphasized the systematic modeling of hydrodynamic damping using the computational fluid dynamic software ANSYS-CFXTM on the complex-shaped ROV,a practice that is not commonly applied.For initial design and prototype testing during the developmental stage,small-scale testing using a free-decaying experiment was used to verify the theoretical models obtained from ANSYS-CFXTM.Simulation results are shown to coincide with the experimental tests.The proposed method could determine the hydrodynamic damping coefficients of the ROV.

  9. 3-D Modelling of Megaloolithid Clutches: Insights about Nest Construction and Dinosaur Behaviour

    Science.gov (United States)

    Vila, Bernat; Jackson, Frankie D.; Fortuny, Josep; Sellés, Albert G.; Galobart, Àngel

    2010-01-01

    Background Megaloolithid eggs have long been associated with sauropod dinosaurs. Despite their extensive and worldwide fossil record, interpretations of egg size and shape, clutch morphology, and incubation strategy vary. The Pinyes locality in the Upper Cretaceous Tremp Formation in the southern Pyrenees, Catalonia provides new information for addressing these issues. Nine horizons containing Megaloolithus siruguei clutches are exposed near the village of Coll de Nargó. Tectonic deformation in the study area strongly influenced egg size and shape, which could potentially lead to misinterpretation of reproductive biology if 2D and 3D maps are not corrected for bed dip that results from tectonism. Methodology/Findings Detailed taphonomic study and three-dimensional modelling of fossil eggs show that intact M. siruguei clutches contained 20–28 eggs, which is substantially larger than commonly reported from Europe and India. Linear and grouped eggs occur in three superimposed levels and form an asymmetric, elongate, bowl-shaped profile in lateral view. Computed tomography data support previous interpretations that the eggs hatched within the substrate. Megaloolithid clutch sizes reported from other European and Indian localities are typically less than 15 eggs; however, these clutches often include linear or grouped eggs that resemble those of the larger Pinyes clutches and may reflect preservation of incomplete clutches. Conclusions/Significance We propose that 25 eggs represent a typical megaloolithid clutch size and smaller egg clusters that display linear or grouped egg arrangements reported at Pinyes and other localities may represent eroded remnants of larger clutches. The similarity of megaloolithid clutch morphology from localities worldwide strongly suggests common reproductive behaviour. The distinct clutch geometry at Pinyes and other localities likely resulted from the asymmetrical, inclined, and laterally compressed titanosaur pes unguals of the female

  10. High renesting rates in arctic-breeding Dunlin (Calidris alpina): A clutch-removal experiment

    Science.gov (United States)

    Gates, H. River; Lanctot, Richard B.; Powell, Abby N.

    2013-01-01

    The propensity to replace a clutch is a complex component of avian reproduction and poorly understood. We experimentally removed clutches from an Arctic-breeding shorebird, the Dunlin (Calidris alpina arcticola), during early and late stages of incubation to investigate replacement clutch rates, renesting interval, and mate and site fidelity between nesting attempts. In contrast to other Arctic studies, we documented renesting by radiotracking individuals to find replacement clutches. We also examined clutch size and mean egg volume to document changes in individual females’ investment in initial and replacement clutches. Finally, we examined the influence of adult body mass, clutch volume, dates of clutch initiation and nest loss, and year on the propensity to renest. We found high (82–95%) and moderate (35–50%) rates of renesting for early and late incubation treatments. Renesting intervals averaged 4.7–6.8 days and were not different for clutches removed early or late in incubation. Most pairs remained together for renesting attempts. Larger females were more likely to replace a clutch; female body mass was the most important parameter predicting propensity to renest. Clutches lost later in the season were less likely to be replaced. We present evidence that renesting is more common in Arctic-breeding shorebirds than was previously thought, and suggest that renesting is constrained by energetic and temporal factors as well as mate availability. Obtaining rates of renesting in species breeding at different latitudes will help determine when this behavior is likely to occur; such information is necessary for demographic models that include individual and population-level fecundity estimates.

  11. Hydrodynamics of dip-coated thin films in the presence of evaporation, and, Surfactant structures controlling spontaneous dewetting

    Science.gov (United States)

    Qu, Dan

    In this dissertation, we discuss the investigation of two problems in dynamic wetting: the hydrodynamics of dip-coated, finite-length films of evaporative fluids and the surfactant structures controlling the spontaneous dewetting of a surfactant solution. While films pulled from non-volatile fluids on a vertical substrate are essentially infinite in length, films pulled from volatile fluids have a finite length. We examine such finite films using three well-controlled oligomer liquids as well as surfactant solutions. We find that the finite length of the film is controlled by a global balance between mass lost by evaporation and mass input by viscous forces. While the attendant thermally driven Marangoni flows have small impact on the mass balance, they do alter the velocity field in the film in the direction parallel to the substrate. Using measured film profiles, wit have developed a novel method to determine the combined effects of evaporation and Marangoni flow on velocity and pressure fields in the film. This method is independent of any specific model of the evaporation process. In preliminary studies with surfactant solutions, we observed strong effects of solutal Marangoni flows on dip-coated films. For the second problem, we examine the structures of self-assemblies left on a solid as a contact line spontaneously retreats across a surface during an autophobing event. We find that surfactants of a continuous structural gradient are deposited: from molecules lying down on the surface with low packing densities in a region never touched by the solution, to molecules standing up with higher packing densities in a region where the contact line has moved slowly. Despite significant free volumes within the self-assemblies, we see no evidence of clustering of molecules. We see a clear correlation between contact line speed and the surfactant structures. We show that the dynamics during at least a later period of the autophobing event is dominated by the time

  12. Modeling and simulation of Cobot based on double over-running clutches

    Institute of Scientific and Technical Information of China (English)

    DONG Yu-hong; ZHANG Li-xun

    2008-01-01

    In order to analyze characteristics of Cobot cooperation with a human in a shared workspacce, the model of a non-holonormic constraint joint mechanism and its control model were constructed based on double o-ver-running clutches. The simulation analysis was carried out and it validated passive and constraint features of the joint mechanism. In terms of Cobot components, the control model of Cobot following a desired trajectory was built up. The simulation studies illustrate that the Cobot can track a desired trajectory and possess passive and constraint features; a human supplies operation force that makes Cobot move, and a computer system con-trois its motion trajectory. So it can meet the requirements of Cobot collaboration with an operator. The Cobot model can be used in applications of material moving, parts assembly and some situations requiring man-ma-chine cooperation and so on.

  13. Research and Development of Automatic Clutch System of Small Passenger Car%小型乘用车自动离合器研制

    Institute of Scientific and Technical Information of China (English)

    田春林; 邱占浩; 王晓军

    2015-01-01

    针对自动变速器成本高、油耗高、维修复杂,而手动变速器操作复杂,驾驶员易疲劳的问题,研发了自动离合器系统。用电动机构取代离合器踏板功能,而保留其它原有操纵机构。把电动机旋转运动转化为控制离合器总泵的直线运动,通过离合器工作泵间接控制离合器分离叉,从而控制离合器分离、接合。自动离合器系统将自动挡和手动挡相结合,不但可以自动变速,又保留变速杆。自动离合器系统有成本低、维护方便、富有驾驶乐趣等特点。%In view of the problems of the high cost, high fuel consumption and complex maintenance of the automatic transmission as well as the complicated operation of manual transmission and the easy fatigue of drivers, an automatic clutch system is researched and developed, in which the clutch pedal function is replaced by electric mechanism and the other original steering mechanisms are kept. The rotary motion of motor is converted to the linear movement to control the clutch master and the clutch release fork is controlled indi-rectly by the clutch pump so as to control the clutch’ s separation and connection. The automatic clutch system, with the combination of automatic transmission and manual transmission, can realize the automatic transmission function and keep the gear lever. Automatic clutch system has the features of low cost and convenient maintenance, having driving pleasure.

  14. Females paired with new and heavy mates reduce intra-clutch differences in resource allocation.

    Directory of Open Access Journals (Sweden)

    Maud Poisbleau

    Full Text Available Reproductive investment affects both offspring and parental fitness and influences the evolution of life histories. Females may vary their overall primary reproductive effort in relation to the phenotypic characteristics of their mate. However, the effects of male quality on differential resource allocation within clutches have been largely neglected despite the potential implications for mate choice and population dynamics, especially in species exhibiting biparental care and brood reduction. Female southern rockhopper penguins Eudyptes chrysocome paired with heavy mates reduced intra-clutch variation in egg and albumen masses. Females paired with new mates also reduced intra-clutch variation in yolk androgen levels. Since both an increased mass and increased androgen concentrations positively influence chick survival under sibling competition, the chances of fledging the whole clutch are likely to be higher for newly formed pairs with heavy males than for previously formed pairs with light males. Interestingly, total clutch provisioning did not vary with male quality. We show for the first time that females vary intra-clutch variation in resource allocation according to male quality. In species with brood reduction, it may be more adaptive for females to modulate the distribution of resources within the clutch according to breeding conditions, than to change their total clutch provisioning.

  15. Effect of clutch surface changes on the computerized pantographic reproducibility index and the Fischer angle.

    Science.gov (United States)

    Dupas, P H; Picart, B; Graux, F; Lefevre, C

    1987-05-01

    This study of eight patients compared the pantographic numeric data obtained with a concave clutch with those obtained with a flat clutch. The slight alterations that resulted were insignificant and varied with each patient. The only difference between Depoorter's study and this one is the manual calculation of the EPRI compared with the computerized calculation of CPRI. Small variation was found in the value of the Fischer angle when the studies were compared. As shown in Depoorter's work, the shape of the clutch does not produce any significant changes in the recording of the posterior determinants. This conclusion is confirmed by this study for both the CPRI and the value of the Fischer angle. The concave clutch and the flat clutch reproduced similar results in both studies. By altering the central bearing pin and obtaining the same interclutch distance for both clutches, we obtained results in this study that refute the findings of Scortecci that a concave clutch was superior to a flat clutch.

  16. Fitness cost of incubation in great tits (Parus major) is related to clutch size

    NARCIS (Netherlands)

    de Heij, Maaike E.; van den Hout, Piet J.; Tinbergen, Joost M.

    2006-01-01

    Life-history theory predicts that parents produce the number of offspring that maximizes their fitness. In birds, natural selection on parental decisions regarding clutch size may act during egg laying, incubation or nestling phase. To study the fitness consequences of clutch size during the

  17. Females Paired with New and Heavy Mates Reduce Intra-Clutch Differences in Resource Allocation

    Science.gov (United States)

    Poisbleau, Maud; Dehnhard, Nina; Demongin, Laurent; Parenteau, Charline; Quillfeldt, Petra; Eens, Marcel

    2013-01-01

    Reproductive investment affects both offspring and parental fitness and influences the evolution of life histories. Females may vary their overall primary reproductive effort in relation to the phenotypic characteristics of their mate. However, the effects of male quality on differential resource allocation within clutches have been largely neglected despite the potential implications for mate choice and population dynamics, especially in species exhibiting biparental care and brood reduction. Female southern rockhopper penguins Eudyptes chrysocome paired with heavy mates reduced intra-clutch variation in egg and albumen masses. Females paired with new mates also reduced intra-clutch variation in yolk androgen levels. Since both an increased mass and increased androgen concentrations positively influence chick survival under sibling competition, the chances of fledging the whole clutch are likely to be higher for newly formed pairs with heavy males than for previously formed pairs with light males. Interestingly, total clutch provisioning did not vary with male quality. We show for the first time that females vary intra-clutch variation in resource allocation according to male quality. In species with brood reduction, it may be more adaptive for females to modulate the distribution of resources within the clutch according to breeding conditions, than to change their total clutch provisioning. PMID:23967280

  18. Fitness cost of incubation in great tits (Parus major) is related to clutch size

    NARCIS (Netherlands)

    de Heij, Maaike E.; van den Hout, Piet J.; Tinbergen, Joost M.

    2006-01-01

    Life-history theory predicts that parents produce the number of offspring that maximizes their fitness. In birds, natural selection on parental decisions regarding clutch size may act during egg laying, incubation or nestling phase. To study the fitness consequences of clutch size during the incubat

  19. Stress Analysis and Optimization of a Piaggio Ape Clutch Plate with different Friction Materials

    Directory of Open Access Journals (Sweden)

    B.Sreedher

    2014-11-01

    Full Text Available clutch plate is one of the important part in the power transmission systems. Good design of clutch provides better engine performance. Clutch is device which is used to engage or disengage of gears and it transfers the rotary motion of one shaft to the other shaft when desired. In automobiles friction clutches are widely used in power transmission applications. To transmit maximum torque in friction clutches selection of the friction material is one of the important tasks. In this thesis a model of Piaggio Ape clutch plate has been generated in Pro-E Cre0-5 and then imported in ANSYS for power transmission applications. We have conducted structural analysis by varying the friction surfaces material and keeping base material aluminium same. By seeing the results, Comparison is done for both materials to validate better lining material for Piaggio Ape clutch plate by doing analysis on clutch with help of ANSYS software for find out which material is best for the lining of friction surfaces.

  20. Thermo-mechanical Analysis of the Dry Clutches under Different Boundary Conditions

    Directory of Open Access Journals (Sweden)

    O.I. Abdullah

    2014-06-01

    Full Text Available The high thermal stresses, generated between the contacting surfaces of the clutch system (pressure plate, clutch disc and flywheel due to the frictional heating during the slipping, are considered to be one of the main reasons of clutch failure. A finite element technique has been used to study the transient thermoelastic phenomena of a dry clutch. The effect of the boundary conditions on the contact pressure distribution, the temperature field and the heat flux generated along the frictional surfaces are investigated. Analysis has been completed using two dimensional axisymmetric model that was used to simulate the clutch elements. ANSYS software has been used to perform the numerical calculation in this paper.

  1. Nonlinear behavior analysis of spur gear pairs with a one-way clutch

    Science.gov (United States)

    Gill-Jeong, Cheon

    2007-04-01

    Nonlinear behavior analysis of a paired spur gear system with a one-way clutch was used to verify whether a one-way clutch is effective for reducing torsional vibration. The dynamic responses were studied over a wide frequency range by speed sweeping to check the nonlinear behavior using numerical integration. The gear system with a one-way clutch showed typical nonlinear behavior, such as softening nonlinearity and jump phenomena. The oscillating component of the dynamic transmission error was reduced over the entire frequency range compared to a system without a one-way clutch, and double-side contact could be prevented, even with very small backlash. Installing a one-way clutch on both sides of the gear system was more effective at mitigating the negative effects of various parameter changes than installing one only on the input or output side.

  2. Sustainable Improvement of Urban River Network Water Quality and Flood Control Capacity by a Hydrodynamic Control Approach-Case Study of Changshu City

    Science.gov (United States)

    Xie, Chen; Yang, Fan; Liu, Guoqing; Liu, Yang; Wang, Long; Fan, Ziwu

    2017-01-01

    Water environment of urban rivers suffers degradation with the impacts of urban expansion, especially in Yangtze River Delta. The water area in cites decreased sharply, and some rivers were cut off because of estate development, which brings the problems of urban flooding, flow stagnation and water deterioration. The approach aims to enhance flood control capability and improve the urban river water quality by planning gate-pump stations surrounding the cities and optimizing the locations and functions of the pumps, sluice gates, weirs in the urban river network. These gate-pump stations together with the sluice gates and weirs guarantee the ability to control the water level in the rivers and creating hydraulic gradient artificially according to mathematical model. Therefore the flow velocity increases, which increases the rate of water exchange, the DO concentration and water body self-purification ability. By site survey and prototype measurement, the river problems are evaluated and basic data are collected. The hydrodynamic model of the river network is established and calibrated to simulate the scenarios. The schemes of water quality improvement, including optimizing layout of the water distribution projects, improvement of the flow discharge in the river network and planning the drainage capacity are decided by comprehensive Analysis. Finally the paper introduces the case study of the approach in Changshu City, where the approach is successfully implemented.

  3. Hydrodynamics of fossil fishes.

    Science.gov (United States)

    Fletcher, Thomas; Altringham, John; Peakall, Jeffrey; Wignall, Paul; Dorrell, Robert

    2014-08-07

    From their earliest origins, fishes have developed a suite of adaptations for locomotion in water, which determine performance and ultimately fitness. Even without data from behaviour, soft tissue and extant relatives, it is possible to infer a wealth of palaeobiological and palaeoecological information. As in extant species, aspects of gross morphology such as streamlining, fin position and tail type are optimized even in the earliest fishes, indicating similar life strategies have been present throughout their evolutionary history. As hydrodynamical studies become more sophisticated, increasingly complex fluid movement can be modelled, including vortex formation and boundary layer control. Drag-reducing riblets ornamenting the scales of fast-moving sharks have been subjected to particularly intense research, but this has not been extended to extinct forms. Riblets are a convergent adaptation seen in many Palaeozoic fishes, and probably served a similar hydrodynamic purpose. Conversely, structures which appear to increase skin friction may act as turbulisors, reducing overall drag while serving a protective function. Here, we examine the diverse adaptions that contribute to drag reduction in modern fishes and review the few attempts to elucidate the hydrodynamics of extinct forms.

  4. Design and experimental evaluation of yoked hand-clutching for a lever drive chair.

    Science.gov (United States)

    Sarigul-Klijn, Yasemin; Smith, Brendan W; Reinkensmeyer, David J

    2017-05-16

    Lever-drive wheelchairs lower physical strain but are less maneuverable than push-rim wheelchairs. Here, we study a possible solution in which the user simultaneously actuates clutches mounted between the levers and wheels each stroke via a clutch handle attached to one lever; this solution is of particular interest for user groups with only one functional hand. First, to demonstrate maneuverability, we show how this "yoked clutch" allows an experienced user to maneuver a constrained space. Then, we compared the difficulty of learning a yoked clutch chair to a conventional lever-drive transmission (i.e. a one-way bearing). Twenty-two unimpaired novice adults navigated a figure-eight track during six training sessions over two weeks. Participant mean speed improved roughly 60% for both chairs, with similar exponential improvement time constants (3 days) and final speeds. However, speed improvement mostly took place overnight rather than within the session for hand-clutching, and the physiological cost index was also about 40% higher. These results indicate that while hand-clutching is no more difficult to learn than a lever-drive, it is reliant on overnight improvement. Also, its increased maneuverability comes with decreased efficiency. We discuss how the yoked clutch may be particularly well suited for individuals with stroke during inpatient rehabilitation.

  5. Design and analysis of logarithmic spiral type sprag one-way clutch

    Institute of Scientific and Technical Information of China (English)

    刘志辉; 严宏志; 曹煜明

    2015-01-01

    A complete mathematical model for logarithmic spiral type sprag one-way clutch design and analysis is given. It assumes that the motion of all clutch components can be expressed by a model of epicyclic gearing. It takes advantage of Hunt-Crossley contact impact theory to calculate the contact forces between sprags and races, and it can be used for optimization of design and comparison with other types of sprag clutches. A good deal of analysis shows that the parameters of the steady windup angle, the steady contact force, the natural frequency and natural cycle of clutch have nothing to do with the initial velocity of outer race, while the parameters of the maximum transient windup angle, the maximum transient impact force and the steady engagement time increase linearly in the mode of engaging operation of clutch. It is also shown that the strut angle has great influence on the dynamic engagement performance of clutch. The parameters of the steady windup angle, the maximum transient windup angle, the steady engaging time, the steady contact force, the maximum transient impact force and the natural cycle of clutch decrease linearly nearly with the inner strut angle, while the natural frequency of the system increases linearly with the inner strut angle.

  6. Clutch size in populations and species of cnemidophorines (Squamata: Teiidae on the eastern coast of Brazil

    Directory of Open Access Journals (Sweden)

    VANDERLAINE A. MENEZES

    2014-06-01

    Full Text Available We analyzed some reproductive aspects of 16 coastal populations, belonging to five lizard species (A. ocellifera, A. abaetensis, A. nativo, A. littoralis and C. lacertoides from different restinga habitats along the eastern coast of Brazil. This study aimed to evaluate to what extent the reproductive aspects vary geographically and among species. For each female, we recorded the number of vitellogenic follicles, size and color of the largest follicle, presence and size of corpora lutea, and number and size of oviductal eggs. Clutch size of almost all coastal populations/species of Ameivula had little variation and most clutches were composed of two eggs. There was a significant relationship between female size and the mean clutch size when females from different species were pooled. Mean egg volume, among species, varied from 420 to 655 mm3. Relative clutch mass varied from 0.129 to 0.159 and did not differ significantly among species. We concluded that the five coastal species studied (four bisexuals and one parthenogenetic had similar reproductive characteristics. Most of them presented multiple clutches, low clutch size and low relative clutch mass, similar to other species in the genus and to unisexual and bisexual species of the Teiidae family.

  7. Driveline Torsional Analysis and Clutch Damper Optimization for Reducing Gear Rattle

    Directory of Open Access Journals (Sweden)

    Huwei Wu

    2016-01-01

    Full Text Available This paper describes a research work on driveline modeling, torsional vibration analysis, and clutch damper parameters optimization for reducing transmission gear rattle on the vehicle creeping condition. Firstly, major driveline components, including quasi-transient engine, multistage stiffness clutch damper, detailed manual transmission and differential mechanism, and LuGre tire, are modeled, respectively. Secondly, powertrain system modeling adopting a two-stage stiffness clutch damper is constructed and analyzed. Transient responses predicted by the model show that the driveline undergoes severe torsional vibration and transmission gear rattle phenomenon. By analysis, it is concluded that the clutch damper works jumping between the first- and second-stage stiffness, which results in this problem for the creeping condition. Then, a three-stage stiffness clutch damper is proposed innovatively to solve this problem. It is shown that severe driveline vibration and gear rattle phenomenon are inhibited effectively. Finally, it draws a conclusion that clutch damper parameters could have a great effect on driveline vibration and gear rattle phenomenon and a three-stage stiffness clutch damper could be utilized to solve gear rattle phenomenon efficiently on the vehicle creeping condition.

  8. Design Modification & Failure Analysis of a Driven Plate/Friction Plate of a Clutch using FEA.

    Directory of Open Access Journals (Sweden)

    Marella. Veerendra

    2014-10-01

    Full Text Available Clutch is device which is used to transmit power one component to another. It is a device used to connect the driving shaft to a driven shaft, so that the driven shaft may be started or stopped at will, without stopping the driving shaft. A clutch thus provides an interruptible connection between two rotating shafts Clutches allow a high inertia load to be stated with a small power. The engine power transmitted to the system through the clutch. The failure of such a critical component during service can stall the whole application. The objective of present project is to do analysis on driven plate of a clutch which is often fails during the operation. In this present research work analysis is conducted on driven plate of a clutch used in TATA Vehicle. There are so many complaints are noted against the failure of clutch during heavy loads. The driven main plate failed normally during its operation due to cyclic loading. For this reason we designed the driven plate and modeled in Pro-E and analyzed using FEA package in the process of designing and analyzing the actual design is changed to lower down the failure values. And the design may suggest to the company.

  9. Evolution of parental incubation behaviour in dinosaurs cannot be inferred from clutch mass in birds.

    Science.gov (United States)

    Birchard, Geoffrey F; Ruta, Marcello; Deeming, D Charles

    2013-08-23

    A recent study proposed that incubation behaviour (i.e. type of parental care) in theropod dinosaurs can be inferred from an allometric analysis of clutch volume in extant birds. However, the study in question failed to account for factors known to affect egg and clutch size in living bird species. A new scaling analysis of avian clutch mass demonstrates that type of parental care cannot be distinguished by conventional allometry because of the confounding effects of phylogeny and hatchling maturity. Precociality of young but not paternal care in the theropod ancestors of birds is consistent with the available data.

  10. OPTIMAL TORQUE CONTROL STRATEGY FOR PARALLEL HYBRID ELECTRIC VEHICLE WITH AUTOMATIC MECHANICAL TRANSMISSION

    Institute of Scientific and Technical Information of China (English)

    GU Yanchun; YIN Chengliang; ZHANG Jianwu

    2007-01-01

    In parallel hybrid electrical vehicle (PHEV) equipped with automatic mechanical transmission (AMT), the driving smoothness and the clutch abrasion are the primary considerations for powertrain control during gearshift and clutch operation. To improve these performance indexes of PHEV, a coordinated control system is proposed through the analyzing of HEV powertrain dynamic characteristics. Using the method of minimum principle, the input torque of transmission is optimized to improve the driving sinoothness of vehicle. Using the methods of fuzzy logic and fuzzy-PID, the engaging speed of clutch and the throttle opening of engine are manipulated to ensure the smoothness of clutch engagement and reduce the abrasion of clutch friction plates. The motor provides the difference between the required input torque of transmission and the torque transmitted through clutch plates. Results of simulation and experiments show that the proposed control strategy performs better than the contrastive control system, the smoothness of driving and the abrasion of clutch can be improved simultaneously.

  11. 基于AMESim的离合器操纵系统建模及随动性能仿真分析%Modeling and Servo Performance Analysis of Clutch Operating System Based on AMESim

    Institute of Scientific and Technical Information of China (English)

    陈德鑫; 吴亚军; 石兴磊

    2013-01-01

    Servo performance of clutch operating system is one the important factors affecting vehicle performance and handling qualities.In this paper,according to the bond graph theory,a clutch operating system simulation model of heavy vehicle with hydraulic control and gas power-assistance is established in AMESim.Through testing,verify the correctness of this model.Using this modal,simulated servo performance of the clutch operating system,and analyzed quantitative the reason of the clutch pedal hard and abnormal wear under shifting of "continuous two clutch" conditions.%离合器操纵系统的随动性能是影响车辆性能和操纵品质的重要因素之一.该文利用键合图理论,基于AMESim软件建立了重型车离合器液压气助力操纵系统的仿真模型.通过相关试验,验证了仿真模型的正确性.利用该模型,对离合器操纵系统进行了随动性能仿真,并且定量地分析了导致“连续两脚离合器”换档工况下离合器踏板沉重以及离合器异常磨损的原因.

  12. Study on the Engaging Process of Saving Energy Clutch in ISG Hybrid Electric Vehicle%ISG型混合动力汽车节能离合器的接合过程研究

    Institute of Scientific and Technical Information of China (English)

    李彤; 樊军; 董平

    2011-01-01

    The basic structure of ISG hybrid electric vehicle (HEV) and the function of saving energy clutch were introduced. Based on the dynamics analysis of the clutch engaging process, the formula of jerk degree was deduced. Analyzing the 4 phases of the clutch engaging process, the control principle of the clutch engagement speed was summed up. This method was applied to study Jinga-ng HEV. It is proven that changing the clutch engagement speed can reduce the degree of jerk.%介绍ISG型混合动力汽车的基本结构和节能离合器的功能.对接台过程进行动力学分析,得出节能离合器冲击度的计算公式.根据节能离合器接合特性,总结了接合速度的控制原则.通过金刚混合动力汽车的试验证明:降低节能离合器的接合速度,能够减小离合器接合时的冲击度,降低该混合动力汽车在工况转换时的冲击.

  13. Warmer springs, laying date and clutch size of tree sparrows Passer montanus in Croatia

    Institute of Scientific and Technical Information of China (English)

    Z. DOLENEC; P. DOLENEC; A.P. MΦLER

    2011-01-01

    Global surface air temperatures increased during the past 100 years. Many long-term studies of birds have reported a climatic influence on breeding performance. We analysed long-term changes in first laying date and clutch size for first clutches of sedentary, hole-nesting and socially monogamous tree sparrows Passer montanus during 1980-2009 in northwestern Croatia. Laying date advanced and spring temperature increased significantly during the study. Date of laying was significantly correlated with mean air spring temperature and advanced by 8.6 days during the 30 years period. Laying date was delayed in extremely cold, but not in extremely warm springs compared to years with normal temperatures. These results suggest that current climate change including extreme change does not have negative effects on timing of laying or clutch size. In contrast to laying date, clutch size did not vary systematically during the study period or with mean spring air temperature changes.

  14. Vibration isolation analysis of clutches based on trouble shooting of vehicle accelerating noise

    Science.gov (United States)

    Liu, Xue-Lai; Shangguan, Wen-Bin; Jing, Xingjian; Ahmed, Waizuddin

    2016-11-01

    Vehicle accelerating noise is a troublesome issue commonly existing in automobiles, leading to negative passenger experience. Considering real experimental results and practical issues, a nonlinear 3-degree of freedom (DOF) torsional model of the clutch system is developed for reducing abnormal noise during vehicle accelerating. In this model, the nonlinear characteristics of the multi-staged clutch damper and the gear backlash are carefully studied. This greatly facilitates the analysis of the vibration transmission characteristics of the clutch and helps understanding of the influence of each critical physical parameter on noise generation. To reduce the accelerating noise, an optimization method for the clutch dynamics is proposed, based on the parameter analysis results, and the effectiveness is validated both in simulations and experiments.

  15. CHINESE JOURNAL OF MECHANICAL ENGINEERING RELIABILITY AND OPTIMIZATION DESIGN OF NEW ROLLER ORIENTATION CLUTCH

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The mechanical reliability and optimization theory on the method of reliability-optimization design for the new roller orientation clutch is provided. The result of reliability-optimization design is compared with the result of the conventional design method.

  16. New Energy-Efficient Electromagnetic Clutch for Automotive Air Conditioning Compressors

    OpenAIRE

    Baumgart, Rico; van der Seylberg, Frank; Aurich, Joerg; von Unwerth, Thomas

    2012-01-01

    Even if the air conditioning is switched off, the internal combustion engine in today’s cars continues to drive the common compressor. To avoid resulting power losses, the automotive industry aspires to apply electromagnetic clutches. When the air conditioning is used, however, CO2-emission increases significantly because the electromag-netic coil consumes electricity. The CO2-reduction per year is consequently very low, which is why new compressor clutches were developed that do not require ...

  17. Spiralling out of control: 3D hydrodynamical modelling of the colliding winds in $\\eta\\thinspace$Carinae

    CERN Document Server

    Parkin, E R; Corcoran, M F; Hamaguchi, K

    2010-01-01

    Three dimensional (3D) adaptive-mesh refinement (AMR) hydrodynamical simulations of the wind-wind collision between the enigmatic super-massive star \\etacar and its mysterious companion star are presented which include radiative driving of the stellar winds, gravity, optically-thin radiative cooling, and orbital motion. Simulations with static stars with a periastron passage separation reveal that the preshock companion star's wind speed is sufficiently reduced that radiative cooling in the postshock gas becomes important, permitting the runaway growth of non-linear thin shell (NTSI) instabilities which massively distort the WCR. However, large-scale simulations which include the orbital motion of the stars, show that orbital motion reduces the impact of radiative inhibition, and thus increases the acquired preshock velocities. As such, the postshock gas temperature and cooling time see a commensurate increase, and sufficient gas pressure is preserved to stabilize the WCR against catastrophic instability grow...

  18. Hydrodynamic effects on coalescence.

    Energy Technology Data Exchange (ETDEWEB)

    Dimiduk, Thomas G.; Bourdon, Christopher Jay; Grillet, Anne Mary; Baer, Thomas A.; de Boer, Maarten Pieter; Loewenberg, Michael (Yale University, New Haven, CT); Gorby, Allen D.; Brooks, Carlton, F.

    2006-10-01

    The goal of this project was to design, build and test novel diagnostics to probe the effect of hydrodynamic forces on coalescence dynamics. Our investigation focused on how a drop coalesces onto a flat surface which is analogous to two drops coalescing, but more amenable to precise experimental measurements. We designed and built a flow cell to create an axisymmetric compression flow which brings a drop onto a flat surface. A computer-controlled system manipulates the flow to steer the drop and maintain a symmetric flow. Particle image velocimetry was performed to confirm that the control system was delivering a well conditioned flow. To examine the dynamics of the coalescence, we implemented an interferometry capability to measure the drainage of the thin film between the drop and the surface during the coalescence process. A semi-automated analysis routine was developed which converts the dynamic interferogram series into drop shape evolution data.

  19. A kinetic clutch governs uncoiling by type IB topoisomerases

    Science.gov (United States)

    Neuman, Keir

    2013-03-01

    Type IB topoisomerases (Top1B) are essential enzymes that relax excessive DNA supercoiling associated with replication and transcription and are important drug targets for cancer chemotherapy. The natural compound camptothecin (CPT) and the cancer chemotherapeutics derived from it, irinotecan and topotecan, are highly specific inhibitors of human nuclear Type IB topoisomerase (nTop1). We employed a magnetic-tweezers based single-molecule DNA supercoil relaxation assay to measure the torque dependence of human nuclear Top1 relaxation (nTop1) and inhibition by CPT. For comparison, we examined the human mitochondrial (Top1mt) topoisomerase and an N-terminal deletion mutant of nTop1 (Top68). Despite substantial sequence homology in their core domains, nTop1 and Top1mt exhibit dramatic differences in sensitivity to torque and CPT, with Top68 betraying intermediate characteristics. In particular, nTop1 displays nearly torque-independent religation probability, distinguishing it from other Top1B enzymes studied to date. Kinetic modeling reveals a hitherto unobserved torque-independent transition linking the DNA rotation and religation phases of the enzymatic cycle. The parameters of this transition determine the torque sensitivity of religation, and the efficiency of CPT binding. This ``kinetic clutch'' mechanism explains the molecular basis of CPT sensitivity and more generally provides a framework with which to interpret Top1B activity and inhibition.

  20. Sliding Mode Observation and Estimation of Clutch Transmitted Torque for Dry Dual Clutch Transmission during Starting%干式DCT起步离合器传递转矩滑模观测估计

    Institute of Scientific and Technical Information of China (English)

    赵治国; 何露; 杨云云; 吴朝春

    2015-01-01

    By studying the five-speed dry DCT and analyzing the starting process of vehicle equipped with dry type DCT, we establish the dynamics & control strategy of the vehicle during the starting process. Meanwhile the clutch torque transmitted during the starting process is estimated utilizing the high order sliding mode observer based on unknown input reconstruction. The simulation results show that the sliding mode observer and the unknown input reconstruction can estimate the clutch torque effectively for vehicle equipped with DCT in the starting process.%以5速干式DCT为研究对象,分析干式DCT车辆起步过程,搭建车辆起步过程动力学及控制策略模型,同时基于未知输入重构并运用高阶滑模观测器对起步过程离合器传递转矩进行仿真估计。仿真结果表明,采用高阶滑模观测器以及未知输入重构能较好估计出DCT车辆起步过程离合器实际传递的转矩。

  1. 恶劣环境下的电磁离合器结构设计%Structure design of electromagnetic clutch under adverse circumstances

    Institute of Scientific and Technical Information of China (English)

    冯定; 檀便友; 袁咏心; 吴力; 张红

    2012-01-01

    高造斜率井眼轨迹控制工具是一种控制大位移井井眼轨迹的井下工具,工作环境复杂,它的关键传动部件电磁离合器还要受到高造斜工具结构的限制,所以工作条件更加恶劣.首先阐述了该特殊电磁离合器的恶劣工作环境,然后根据恶劣环境的要求校核首选的摩擦片式电磁离合器,摩擦片式电磁离合器不能传递额定扭矩.选择牙嵌式电磁离合器后,为了满足不停轴啮合的要求,对衔铁齿环进行了特殊设计,并验证了该设计的工作可靠性.%The trajectory control tool for high build-up rate well,is tool underground used to control the wellbore trajectory of the extended reach well.lt works in a complex environment,which critical transmission components electromagnetic clutch is also subject to the limitations of high build-up rate tool, therefore its working environment is even worse.First the poor working conditions of the special electromagnetic clutch was described in it,then in accordance with the severe environment,the preferred electromagnetic clutch of friction plate type was checked,which can not transmit rated torqueAfier selecting the slipping toothed electromagnetic clutch,special design of armature ring gear was made to check the reliability of the design in order to meet the requirements of meshing when the axis is turning.

  2. Coupled Hydrodynamic-Water Quality Model for Pollution Control Scenarios in El-Burullus Lake (Nile Delta, Egypt

    Directory of Open Access Journals (Sweden)

    A. El-Adawy

    2014-01-01

    Full Text Available El-Burullus Lake is affected by increasing and extensive human activities, rapid social-economic development and the construction of fish ponds nearby. This has significantly impacted the health of the lake eco-system. On the foundation of the two-dimensional depth averaged hydrodynamic model, distributions of the salinity, Dissolved Oxygen (DO, Biochemical Oxygen Demand (BOD, Chemical Oxygen Demand (COD and Ammonium (NH4 were modeled. The heat flux model was also utilized to enhance the accuracy of the calculations in the water quality modeling stage. The calibration and the verification of this model were based on spatially distributed water quality measurements during the period 2010-2011. The correlation coefficients between measured and simulated salinity was found to be 0.79 in January 2011 and 0.84 in August 2010 with a mean errors of 1.3407 and 2.0727 ppt in August 2010 and January 2011 respectively. The results generally agree with the observations, but this indicates that more measurements are needed to verify the predictability of the simulations. In addition, Delft-3D model has been applied in evaluating the feasibility of adding a new artificial inlet or diversion of some drains. The model proved to be an effective tool for the water dynamics, water quality simulation and evaluating different scenarios of such shallow Lake.

  3. Controlled hydrodynamic conditions on the formation of iron oxide nanostructures synthesized by electrochemical anodization: Effect of the electrode rotation speed

    Science.gov (United States)

    Lucas-Granados, Bianca; Sánchez-Tovar, Rita; Fernández-Domene, Ramón M.; García-Antón, Jose

    2017-01-01

    Iron oxide nanostructures are of particular interest because they can be used as photocatalysts in water splitting due to their advantageous properties. Electrochemical anodization is one of the best techniques to synthesize nanostructures directly on the metal substrate (direct back contact). In the present study, a novel methodology consisting of the anodization of iron under hydrodynamic conditions is carried out in order to obtain mainly hematite (α-Fe2O3) nanostructures to be used as photocatalysts for photoelectrochemical water splitting applications. Different rotation speeds were studied with the aim of evaluating the obtained nanostructures and determining the most attractive operational conditions. The synthesized nanostructures were characterized by means of Raman spectroscopy, Field Emission Scanning Electron Microscopy, photoelectrochemical water splitting, stability against photocorrosion tests, Mott-Schottky analysis, Electrochemical Impedance Spectroscopy (EIS) and band gap measurements. The results showed that the highest photocurrent densities for photoelectrochemical water splitting were achieved for the nanostructure synthesized at 1000 rpm which corresponds to a nanotubular structure reaching ∼0.130 mA cm-2 at 0.54 V (vs. Ag/AgCl). This is in agreement with the EIS measurements and Mott-Schottky analysis which showed the lowest resistances and the corresponding donor density values, respectively, for the nanostructure anodized at 1000 rpm.

  4. Numerical Modeling Analysis of Hydrodynamic and Microbial Controls on DNAPL Pool Dissolution and Detoxification: Dehalorespirers in Co-culture

    Energy Technology Data Exchange (ETDEWEB)

    Wesseldyke, Eric S.; Becker, Jennifer G.; Seagren, Eric A.; Mayer, Alex S.; Zhang, Changyong

    2015-04-01

    Dissolution of dense non-aqueous phase liquid (DNAPL) contaminants like tetrachloroethene (PCE) can be “bioenhanced” via biodegradation, which increases the concentration gradient at the DNAPL–water interface. Model simulations were used to evaluate the impact of ecological interactions between different dehalorespiring strains and hydrodynamics on the bioenhancement effect and the extent of PCE dechlorination. Simulations were performed using a two-dimensional coupled flow-transport model, with a DNAPL pool source and two microbial species, Dehalococcoides mccartyi 195 and Desulfuromonas michiganensis, which compete for electron acceptors (e.g., PCE), but not for their electron donors. Under biostimulation, low vx conditions, D. michiganensis alone significantly enhanced dissolution by rapidly utilizing aqueous-phase PCE. In co-culture under these conditions, D. mccartyi 195 increased this bioenhancement modestly and greatly increased the extent of PCE transformation. Although D. michiganensis was the dominant population under low velocity conditions, D. mccartyi 195 dominated under high velocity conditions due to bioclogging effects.

  5. Variation in clutch size in relation to nest size in birds

    Science.gov (United States)

    Møller, Anders P; Adriaensen, Frank; Artemyev, Alexandr; Bańbura, Jerzy; Barba, Emilio; Biard, Clotilde; Blondel, Jacques; Bouslama, Zihad; Bouvier, Jean-Charles; Camprodon, Jordi; Cecere, Francesco; Charmantier, Anne; Charter, Motti; Cichoń, Mariusz; Cusimano, Camillo; Czeszczewik, Dorota; Demeyrier, Virginie; Doligez, Blandine; Doutrelant, Claire; Dubiec, Anna; Eens, Marcel; Eeva, Tapio; Faivre, Bruno; Ferns, Peter N; Forsman, Jukka T; García-Del-Rey, Eduardo; Goldshtein, Aya; Goodenough, Anne E; Gosler, Andrew G; Góźdź, Iga; Grégoire, Arnaud; Gustafsson, Lars; Hartley, Ian R; Heeb, Philipp; Hinsley, Shelley A; Isenmann, Paul; Jacob, Staffan; Järvinen, Antero; Juškaitis, Rimvydas; Korpimäki, Erkki; Krams, Indrikis; Laaksonen, Toni; Leclercq, Bernard; Lehikoinen, Esa; Loukola, Olli; Lundberg, Arne; Mainwaring, Mark C; Mänd, Raivo; Massa, Bruno; Mazgajski, Tomasz D; Merino, Santiago; Mitrus, Cezary; Mönkkönen, Mikko; Morales-Fernaz, Judith; Morin, Xavier; Nager, Ruedi G; Nilsson, Jan-Åke; Nilsson, Sven G; Norte, Ana C; Orell, Markku; Perret, Philippe; Pimentel, Carla S; Pinxten, Rianne; Priedniece, Ilze; Quidoz, Marie-Claude; Remeš, Vladimir; Richner, Heinz; Robles, Hugo; Rytkönen, Seppo; Senar, Juan Carlos; Seppänen, Janne T; da Silva, Luís P; Slagsvold, Tore; Solonen, Tapio; Sorace, Alberto; Stenning, Martyn J; Török, János; Tryjanowski, Piotr; van Noordwijk, Arie J; von Numers, Mikael; Walankiewicz, Wiesław; Lambrechts, Marcel M

    2014-01-01

    Nests are structures built to support and protect eggs and/or offspring from predators, parasites, and adverse weather conditions. Nests are mainly constructed prior to egg laying, meaning that parent birds must make decisions about nest site choice and nest building behavior before the start of egg-laying. Parent birds should be selected to choose nest sites and to build optimally sized nests, yet our current understanding of clutch size-nest size relationships is limited to small-scale studies performed over short time periods. Here, we quantified the relationship between clutch size and nest size, using an exhaustive database of 116 slope estimates based on 17,472 nests of 21 species of hole and non-hole-nesting birds. There was a significant, positive relationship between clutch size and the base area of the nest box or the nest, and this relationship did not differ significantly between open nesting and hole-nesting species. The slope of the relationship showed significant intraspecific and interspecific heterogeneity among four species of secondary hole-nesting species, but also among all 116 slope estimates. The estimated relationship between clutch size and nest box base area in study sites with more than a single size of nest box was not significantly different from the relationship using studies with only a single size of nest box. The slope of the relationship between clutch size and nest base area in different species of birds was significantly negatively related to minimum base area, and less so to maximum base area in a given study. These findings are consistent with the hypothesis that bird species have a general reaction norm reflecting the relationship between nest size and clutch size. Further, they suggest that scientists may influence the clutch size decisions of hole-nesting birds through the provisioning of nest boxes of varying sizes. PMID:25478150

  6. Elasto-hydrodynamic lubrication

    CERN Document Server

    Dowson, D; Hopkins, D W

    1977-01-01

    Elasto-Hydrodynamic Lubrication deals with the mechanism of elasto-hydrodynamic lubrication, that is, the lubrication regime in operation over the small areas where machine components are in nominal point or line contact. The lubrication of rigid contacts is discussed, along with the effects of high pressure on the lubricant and bounding solids. The governing equations for the solution of elasto-hydrodynamic problems are presented.Comprised of 13 chapters, this volume begins with an overview of elasto-hydrodynamic lubrication and representation of contacts by cylinders, followed by a discussio

  7. Elementary classical hydrodynamics

    CERN Document Server

    Chirgwin, B H; Langford, W J; Maxwell, E A; Plumpton, C

    1967-01-01

    Elementary Classical Hydrodynamics deals with the fundamental principles of elementary classical hydrodynamics, with emphasis on the mechanics of inviscid fluids. Topics covered by this book include direct use of the equations of hydrodynamics, potential flows, two-dimensional fluid motion, waves in liquids, and compressible flows. Some general theorems such as Bernoulli's equation are also considered. This book is comprised of six chapters and begins by introducing the reader to the fundamental principles of fluid hydrodynamics, with emphasis on ways of studying the motion of a fluid. Basic c

  8. Within- and among-clutch variation of organohalogenated contaminants in eggs of great tits (Parus major)

    Energy Technology Data Exchange (ETDEWEB)

    Steen, E. van den [Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk (Belgium)]. E-mail: evi.vandensteen@ua.ac.be; Dauwe, T. [Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk (Belgium); Covaci, A. [Toxicological Centre, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk (Belgium); Jaspers, V.L.B. [Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk (Belgium); Pinxten, R. [Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk (Belgium); Eens, M. [Department of Biology, University of Antwerp, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk (Belgium)

    2006-11-15

    In this study we investigated the variation of organohalogenated compounds, such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs), within and among clutches of a small insectivorous songbird, the great tit (Parus major), and determined whether egg laying order affects the concentrations of these compounds. PCBs were the major organohalogenated contaminants in the eggs of great tits (mean 4778 ng/g lipid weight), while PBDEs (mean 204 ng/g lipid weight) and DDTs (mean 601 ng/g lipid weight) were found at much lower concentrations. Within-clutch variability of PCBs, PBDEs, and DDTs residues in the egg samples was small (7%, 3%, and 22%, respectively) compared to among-clutch variability (93%, 97%, and 78%, respectively). The small within-clutch variability may be in part related to the small home range of great tits and low spatial heterogeneity of the contaminants. We found no laying order effects on the concentrations of PCBs, PBDEs, and DDTs. Our results show that random egg samples of great tits are suitable as a biomonitoring tool for contamination with persistent organohalogenated pollutants in terrestrial environments. - A single egg represents the contamination levels of PCBs, PBDEs, and DDTs of the entire clutch in great tits.

  9. Analysis of differently sized prototypes of an MR clutch by performance indices

    Science.gov (United States)

    Bucchi, Francesco; Forte, Paola; Franceschini, Alessandro; Frendo, Francesco

    2013-10-01

    In this paper we investigate the torque performances of three prototypes of a magnetorheological clutch, whose operation is based on the relative movement of a permanent magnet with respect to a gap filled with magnetorheological fluid, are discussed. The clutch was already been presented by the authors in other papers. The analysed prototypes are based on the same layout and have different sizes (i.e. outer diameter and overall length). Two new performance indices are introduced to evaluate the clutch design, and are proposed as an alternative to the usually employed turn-up ratio for evaluating MR clutches and brakes. Measurements of the transmitted torque in different operating conditions were carried out on a purpose-built test bench. A brushless motor drove the primary shaft of the clutch, while the transmitted torque was measured by a torque-meters up to 1500 rpm. The experimental results are discussed and compared to those expected on the basis of simulations, showing a fairly good agreement. Some geometric parameters were found to have a great influence on the magnet shielding in the disengaged configuration.

  10. Geochemical and hydrodynamic controls on arsenic and trace metal cycling in a seasonally stratified US sub-tropical reservoir

    Energy Technology Data Exchange (ETDEWEB)

    Brandenberger, Jill M.; Louchouarn, Patrick; Herbert, Bruce; Tissot, Philippe

    2004-10-01

    contaminants downstream of the U mine pits and tailings. As in Lyssy pond, arsenic (and other oxyanions) in Lake Corpus Christi's water column are not affected by the abundant presence of Fe-rich particles but instead behave conservatively throughout the entire period of study. A quantitative mass balance model, constructed using monthly hydrological data for the reservoir, provides quantitative evidence of seasonal evaporative concentration of as in surface waters demonstrating the predominance of hydrodynamic constraints, over geochemical ones, on the cycling of this metal in selected aquatic systems.

  11. Quasiparticle anisotropic hydrodynamics

    CERN Document Server

    Alqahtani, Mubarak

    2016-01-01

    We study an azimuthally-symmetric boost-invariant quark-gluon plasma using quasiparticle anisotropic hydrodynamics including the effects of both shear and bulk viscosities. We compare results obtained using the quasiparticle method with the standard anisotropic hydrodynamics and viscous hydrodynamics. We consider the predictions of the three methods for the differential particle spectra and mean transverse momentum. We find that the three methods agree for small shear viscosity to entropy density ratio, $\\eta/s$, but show differences at large $\\eta/s$. Additionally, we find that the standard anisotropic hydrodynamics method shows suppressed production at low transverse-momentum compared to the other two methods, and the bulk-viscous correction can drive the primordial particle spectra negative at large $p_T$ in viscous hydrodynamics.

  12. Count your eggs before they invade: identifying and quantifying egg clutches of two invasive apple snail species (Pomacea.

    Directory of Open Access Journals (Sweden)

    Colin H Kyle

    Full Text Available Winning the war against invasive species requires early detection of invasions. Compared to terrestrial invaders, aquatic species often thrive undetected under water and do not garner notice until too late for early action. However, fortunately for managers, apple snails (Family Ampullariidae, Genus Pomacea provide their own conspicuous sign of invasion in the form of vibrantly colored egg clutches. Managers can potentially use egg clutches laid in the riparian zone as a means of early detection and species identification. To facilitate such efforts, we quantified differences in characteristics (length, width, depth, mass, egg number of field-laid clutches for the two most common invasive species of apple snail, P. canaliculata and P. maculata, in native and non-native populations. Pomacea canaliculata native and non-native populations differed noticeably only in width. Native P. maculata clutches possessed significantly greater width, mass and eggs numbers compared with native P. canaliculata. Non-native P. maculata clutches significantly exceeded all other populations in all measured characteristics. Consequently, these traits may successfully distinguish between species. Fecundity data also allowed us to develop models that accurately estimated the number of eggs per clutch for each species based on clutch dimensions. We tested one, two and three dimensional models of clutches, including rendering a clutch as either a complete ellipsoid or an ellipsoid intersected by a cylinder to represent the oviposition site. Model comparisons found the product of length and depth, with a different function for each population, best predicted egg number for both species. Comparisons of egg number to clutch volume and mass implied non-native P. canaliculata may be food limited, while non-native P. maculata appeared to produce such enormous clutches by having access to greater nutrients than the native population. With these new tools, researchers and

  13. Research on Gear Shifting Process without Disengaging Clutch for a Parallel Hybrid Electric Vehicle Equipped with AMT

    Directory of Open Access Journals (Sweden)

    Hui-Long Yu

    2014-01-01

    Full Text Available Dynamic models of a single-shaft parallel hybrid electric vehicle (HEV equipped with automated mechanical transmission (AMT were described in different working stages during a gear shifting process without disengaging clutch. Parameters affecting the gear shifting time, components life, and gear shifting jerk in different transient states during a gear shifting process were deeply analyzed. The mathematical models considering the detailed synchronizer working process which can explain the gear shifting failure, long time gear shifting, and frequent synchronizer failure phenomenon in HEV were derived. Dynamic coordinated control strategy of the engine, motor, and actuators in different transient states considering the detailed working stages of synchronizer in a gear shifting process of a HEV is for the first time innovatively proposed according to the state of art references. Bench test and real road test results show that the proposed control strategy can improve the gear shifting quality in all its evaluation indexes significantly.

  14. New directions in the psychology of optimal performance in sport: flow and clutch states.

    Science.gov (United States)

    Swann, Christian; Crust, Lee; Vella, Stewart A

    2017-08-01

    Csikszentmihalyi's conceptualisation of flow is the primary framework for understanding the psychology of optimal experience and performance in sport. However, emerging evidence suggests a more dynamic, multi-state perspective. This review focuses primarily on recent studies highlighting a second, overlapping 'clutch' state which - in addition to flow - underlies optimal performance in sport. We also examine how the nature of goals ('open' or 'fixed') athletes pursue influence the experience of flow and clutch respectively. This new, integrated model of psychological states underlying optimal performance raises questions around conceptualisation and methodology employed in the field to date. These implications are outlined, and recommendations are provided for more critical and accurate measurement of both flow and clutch as overlapping, yet distinct, states. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Organochlorines and heavy metals in Herring Gull (Larus argentatus) eggs and chicks from the same clutch

    Energy Technology Data Exchange (ETDEWEB)

    Becker, P.H. (Institut fur Vogelforschung Vogelwarte Helgoland (West Germany)); Sperveslage, H. (Veterinaeruntersuchungsamt, Oldenburg (West Germany))

    1989-05-01

    In an earlier paper the authors investigated the intraclutch variability in levels of toxic pollutants and compared this contamination with that of the female Herring Gull (Larus argentatus) after production of the clutch in question. In the present study, they examine the concentrations of contaminants in chicks as compared with one egg of the same clutch. Such studies are important with regard to the question as to which ontogenetic stage is most endangered by toxic pollutants. Some investigations concerning this problem have already been carried out, but they don't refer to samples taken from the same clutches. Chicks receive contaminants mainly from two sources: from the egg, which reflects directly the contamination of the breeding female as well as from the food. Moreover the concentrations of pollutants in chicks vary with growth-dependent body distribution and with a decline of the lipid content.

  16. Regional drivers of clutch loss reveal important trade-offs for beach-nesting birds

    Directory of Open Access Journals (Sweden)

    Brooke Maslo

    2016-09-01

    Full Text Available Coastal birds are critical ecosystem constituents on sandy shores, yet are threatened by depressed reproductive success resulting from direct and indirect anthropogenic and natural pressures. Few studies examine clutch fate across the wide range of environments experienced by birds; instead, most focus at the small site scale. We examine survival of model shorebird clutches as an index of true clutch survival at a regional scale (∼200 km, encompassing a variety of geomorphologies, predator communities, and human use regimes in southeast Queensland, Australia. Of the 132 model nests deployed and monitored with cameras, 45 (34% survived the experimental exposure period. Thirty-five (27% were lost to flooding, 32 (24% were depredated, nine (7% buried by sand, seven (5% destroyed by people, three (2% failed by unknown causes, and one (1% was destroyed by a dog. Clutch fate differed substantially among regions, particularly with respect to losses from flooding and predation. ‘Topographic’ exposure was the main driver of mortality of nests placed close to the drift line near the base of dunes, which were lost to waves (particularly during storms and to a lesser extent depredation. Predators determined the fate of clutches not lost to waves, with the depredation probability largely influenced by region. Depredation probability declined as nests were backed by higher dunes and were placed closer to vegetation. This study emphasizes the scale at which clutch fate and survival varies within a regional context, the prominence of corvids as egg predators, the significant role of flooding as a source of nest loss, and the multiple trade-offs faced by beach-nesting birds and those that manage them.

  17. Comparison of Applied Forces on Selective Joints and Muscles of Drivers During Clutching of MF285 and MF399 Tractors

    Directory of Open Access Journals (Sweden)

    H Fallahi

    2015-03-01

    Full Text Available In this research, the imposed forces on three muscles including: Gastrocnemius muscle, Trapezius muscle and Quadratus lumborum of the tractor drivers during clutching have been studied. The sample included 30 persons and the research was conducted on two domestic tractors including: MF285 and MF399 models. The clutching forces for these tractors were measured as 340 N and 290 N, respectively. The difference between drivers’ knee angle of the two tractors was proved significant at the one percent level. The decrease of pain threshold after 30 seconds and 60 seconds clutching and 60 seconds rest after clutching in MF285 tractor in all three muscles were more than that of MF399 tractor. The impact of clutching on the average decrease of pain threshold, among all the drivers, and for all time intervals, during and after clutching in the Quadratus lumborum muscle for both tractors was more than the other two muscles. In order to reduce the imposed force of clutching for MF285 tractor, some modifications is suggested. In this regard the force transfer joint between the pedal and the disc in the mechanism of clutching can be replaced with one made of cast iron.

  18. Family Planning in the Great Tit (Parus major) : Optimal Clutch Size as Integration of Parent and Offspring Fitness

    NARCIS (Netherlands)

    Tinbergen, Joost M.; Daan, Serge

    Fitness variations due to natural variation in the size of the first clutch and its laying date were estimated using Fisher's reproductive value for both the clutch (Vc) and the parent (Vp) in a population of great tits. In order to test the hypothesis that individual birds maximize their

  19. Role of hydrodynamic factors in controlling the formation and location of unconformity-related uranium deposits: insights from reactive-flow modeling

    Science.gov (United States)

    Aghbelagh, Yousef Beiraghdar; Yang, Jianwen

    2017-03-01

    The role of hydrodynamic factors in controlling the formation and location of unconformity-related uranium (URU) deposits in sedimentary basins during tectonically quiet periods is investigated. A number of reactive-flow modeling experiments at the deposit scale were carried out by assigning different dip angles and directions to a fault and various permeabilities to hydrostratigraphic units). The results show that the fault dip angle and direction, and permeability of the hydrostratigraphic units govern the convection pattern, temperature distribution, and uranium mineralization. A vertical fault results in uranium mineralization at the bottom of the fault within the basement, while a dipping fault leads to precipitation of uraninite below the unconformity either away from or along the plane of the fault, depending on the fault permeability. A more permeable fault causes uraninite precipitates along the fault plane, whereas a less permeable one gives rise to the precipitation of uraninite away from it. No economic ore mineralization can form when either very low or very high permeabilities are assigned to the sandstone or basement suggesting that these units seem to have an optimal window of permeability for the formation of uranium deposits. Physicochemical parameters also exert an additional control in both the location and grade of URU deposits. These results indicate that the difference in size and grade of different URU deposits may result from variation in fluid flow pattern and physicochemical conditions, caused by the change in structural features and hydraulic properties of the stratigraphic units involved.

  20. 线控离合器接合性能影响因素的研究%A Research on the Factors Affecting the Engagement Performance of Clutch-by-wire

    Institute of Scientific and Technical Information of China (English)

    王阳阳

    2012-01-01

    A structure of clutch-by-wire (CBW) is proposed and its transmitting chain is analyzed. With jerk as the evaluation indicator of the engagement performance of clutch, the two key parameters affecting the engagement performance of clutch are found; the rate of change of the travel of the left end of pull rod with respect of the rotation angle of worm gear and the angular velocity of worm gear. Finally the effects of the structural parameters of clutch (the rotation angle of worm gear and the motor speed) on the engagement performance of CBW are analyzed, laying a foundation for the further study on the control strategy of CBW.%提出一种线控离合器的结构,并对其传动链进行分析.以冲击度作为离合器接合性能的评价指标,得出起步工况下影响线控离合器接合性能的两个关键参数是拉杆行程对蜗轮转角的变化率和蜗轮角速度.最后具体分析了离合器结构参数、蜗轮转角和电机转速对线控离合器接合性能的影响,为进一步进行线控离合器控制策略研究奠定基础.

  1. Hydrodynamic and geomorphic controls on the morphology of an island ecosystem in the Vembanad Lake, West Coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Laluraj, C.M.; Gopinath, G.; DineshKumar, P.K.; Balachandran, K.K.

    is controlled by the productivity of the overlying water column. The evolution of this island is believed to be due to fluvial inputs from Muvattupuzha River. The braid shape of the island is attributed to the high-energy flow along the wedge of the estuary...

  2. Hydrodynamics and black holes

    CERN Document Server

    Oz, Yaron

    2015-01-01

    This chapter describes how the AdS/CFT correspondence (the Holographic Principle) relates field theory hydrodynamics to perturbations of black hole (brane) gravitational backgrounds. The hydrodynamics framework is first presented from the field theory point of view, after which the dual gravitational description is outlined, first for relativistic fluids and then for the nonrelativistic case. Further details of the fluid/gravity correspondence are then discussed, including the bulk geometry and the dynamics of the black hole horizon.

  3. Clutch transmitting torque estimation during AMT vehicle starting based on Kalman iflter%基于Kalman滤波的AMT车辆起步时离合器传递扭矩估计

    Institute of Scientific and Technical Information of China (English)

    邬学斌; 张欣; 陈宏伟

    2015-01-01

    A power train dynamics model was built for an automatic manual transmission (AMT) vehicle to realize the transmitting torque direct control of the automatic clutch. The discrete state space model for estimating the clutch transmitting torque was derived. The state vector was constituted by the engine rotation speed and the clutch transmitting torque. The Kalman ifltering algorithm was used to estimate the clutch transmitting torque, to estimate clutch transmitting torque for vehicle starting process, and to analyze estimation errors by comparing the estimated and simulated values of the clutch torque. Impact of the sample time (5-25 ms) on clutch torque estimation errors was explored. The results show that the torque estimation error increases with the increase of sampling time; the lower limit of torque estimation accuracy is 7.5% at sampling time 10 ms. Therefore, the algorithm show sufifcient accuracy.%为了实现自动离合器传递扭矩的直接控制,以自动手动变速器(AMT)车辆为研究对象,建立了车辆动力传动系统动力学模型。以发动机转速和离合器传递扭矩为元素构建状态向量,推导离散状态空间模型,设计了基于离散Kalman滤波的离合器传递扭矩估计算法,对车辆起步过程中的离合器扭矩进行了估计,通过与仿真设定值对比,对扭矩估计误差进行了分析。研究了采样周期变化(5~25 ms内)对离合器扭矩估计的影响。结果表明,扭矩估计误差随采样周期的增加而增大,在采样周期为10 ms时,扭矩估计精度下限为7.5%,所以该算法具有足够的精确性。

  4. Kinetically driven self-assembly of a binary solute mixture with controlled phase separation via electro-hydrodynamic flow of corona discharge.

    Science.gov (United States)

    Jung, Hee Joon; Huh, June; Park, Cheolmin

    2012-10-21

    This feature article describes a new and facile process to fabricate a variety of thin films of non-volatile binary solute mixtures suitable for high performance organic electronic devices via electro-hydrodynamic flow of conventional corona discharge. Both Corona Discharge Coating (CDC) and a modified version of CDC, Scanning Corona Discharge Coating (SCDC), are based on utilizing directional electric flow, known as corona wind, of the charged uni-polar particles generated by corona discharge between a metallic needle and a bottom plate under a high electric field (5-10 kV cm(-1)). The electric flow rapidly spreads out the binary mixture solution on the bottom plate and subsequently forms a smooth and flat thin film in a large area within a few seconds. In the case of SCDC, the static movement of the bottom electrode on which a binary mixture solution is placed provides further control of thin film formation, giving rise to a film highly uniform over a large area. Interesting phase separation behaviors were observed including nanometer scale phase separation of a polymer-polymer binary mixture and vertical phase separation of a polymer-organic semiconductor mixture. Core-shell type phase separation of either polymer-polymer or polymer-colloidal nanoparticle binary mixtures was also developed with a periodically patterned microstructure when the relative location of the corona wind was controlled to a binary solution droplet on a substrate. We also demonstrate potential applications of thin functional films with controlled microstructures by corona coating to various organic electronic devices such as electroluminescent diodes, field effect transistors and non-volatile polymer memories.

  5. Exploring patterns of variation in clutch size-density reaction norms in a wild passerine bird

    NARCIS (Netherlands)

    Nicolaus, M.; Brommer, J. E.; Ubels, R.; Tinbergen, J. M.; Dingemanse, N. J.

    2013-01-01

    Negative density dependence of clutch size is a ubiquitous characteristic of avian populations and is partly due to within-individual phenotypic plasticity. Yet, very little is known about the extent to which individuals differ in their degree of phenotypic plasticity, whether such variation has a g

  6. Wheeled Vehicle Clutches, Transmissions, and Transfers. Military Curriculum Materials for Vocational and Technical Education.

    Science.gov (United States)

    Army Ordnance Center and School, Aberdeen Proving Ground, MD.

    This course is one of several subcourses that make up the entire Army correspondence course on wheeled vehicle maintenance. The subcourse is designed to provide the student with information about the operation, malfunction diagnosis, maintenance, and repair of wheeled vehicle clutches, transmissions, and transfer cases. It provides the basic…

  7. Calculation of the magnetic field in the active zone of a hysteresis clutch

    Science.gov (United States)

    Ermilov, M. A.; Glukhov, O. M.

    1977-01-01

    The initial distribution of magnetic induction in the armature stationary was calculated relative to the polar system of a hysteresis clutch. Using several assumptions, the problem is reduced to calculating the static magnetic field in the ferromagnetic plate with finite and continuous magnetic permeability placed in the air gap between two identical, parallel semiconductors with rack fixed relative to the tooth or slot position.

  8. Clutch size and parental effort in the Great Tit Parus major

    NARCIS (Netherlands)

    Verhulst, S.; Tinbergen, J.M.

    1997-01-01

    We experimentally reduced clutch size of Great Tits Parus major to investigate the effects on parental care (including Daily Energy Expenditure, DEE, measured with doubly labelled water), and the relationship between DEE and the residual reproductive value. The length of a working day was not affect

  9. Clutch size and parental effort in the Great Tit Parus major

    NARCIS (Netherlands)

    Verhulst, S.; Tinbergen, J.M.

    1997-01-01

    We experimentally reduced clutch size of Great Tits Parus major to investigate the effects on parental care (including Daily Energy Expenditure, DEE, measured with doubly labelled water), and the relationship between DEE and the residual reproductive Value. The length of a working day was not affect

  10. Factors influencing offspring traits in the oviparous multi-clutched lizard, Calotes versicolor (Agamidae)

    Indian Academy of Sciences (India)

    Rajkumar S Radder; Bhagyashri A Shanbhag

    2004-03-01

    The determinants of offspring size and number in the tropical oviparous multi-clutched lizard, Calotes versicolor, were examined using both univariate and multivariate (path) analyses. In C. versicolor maternal snout-vent length (SVL) and body condition influence clutch mass and clutch size but have no significant influence on offspring size. The positive effect of maternal SVL and body condition on offspring number is counterbalanced by a negative effect of breeding time on egg mass. In fact, breeding time directly influences the offspring body mass and condition through variation in the egg mass. There is a trade-off between offspring mass and condition with offspring number, and breeding time influences both. Offspring hatched from the eggs of early (May–June) or mid (July–August) breeding periods invariably show lower mass and condition than those hatched from the eggs of late breeding season (September–October). Yet, there is no variation in offspring SVL among early, mid and late clutches. Thus, in C. versicolor offspring SVL is optimized while body mass and condition are not optimized.

  11. New tractors with dual-clutch transmission; Neue Traktoren mit Doppelkupplungsgetriebe

    Energy Technology Data Exchange (ETDEWEB)

    Fuchs, Andreas

    2012-04-15

    John Deere unveiled its new 6R series of tractors at Agritechnica 2011. The tractors will be offered in the course of 2012 with a dual-clutch transmission. Further innovations include a higher engine output and a higher lifting capacity. (orig.)

  12. Nesting phenology and clutch characteristics of captive Siamese crocodiles (Crocodylus siamensis) in Cambodia.

    Science.gov (United States)

    Platt, Steven G; Monyrath, Vuthy; Sovannara, Heng; Kheng, Long; Rainwater, Thomas R

    2012-01-01

    The Siamese crocodile (Crocodylus siamensis) is considered one of the least studied and most critically endangered crocodilians in the world. Although few wild populations remain, more than 700,000 C. siamensis are held on commercial crocodile farms in Southeast Asia. Despite conservation concerns, many aspects of C. siamensis life history remain poorly known, particularly with regards to its reproductive biology. We studied nesting phenology, clutch characteristics, and other aspects of C. siamensis reproductive biology on crocodile farms in Cambodia during 2000 and 2001. Oviposition among captive crocodiles began in February and continued into early June. The mean (±1 SD) oviposition date based on pooled data from 2000 and 2001 was 5 April ± 24 days. Mean oviposition date differed significantly between 2000 and 2001, possibly as a result of annual variability among nesting cues. The mean incubation period was 72 ± 3 days and eggs hatched from 5 May to 18 August. Mean clutch size (25.0 ± 8.8 eggs; n = 183) differed significantly between years, possibly resulting from the >2.5-fold increase in sample size during 2001. There was no correlation between clutch size and oviposition date during either 2000 or 2001. A single female produced two clutches during 2001, complimenting previous reports of double-clutching among C. siamensis. The mean length and width of 515 eggs were 78.2 ± 4.9 and 48.1 ± 2.5 mm, respectively; mean egg mass was 90.8 ± 16.5 g (n = 471). One unpipped egg contained a set of twins.

  13. A kinetic clutch governs religation by type IB topoisomerases and determines camptothecin sensitivity.

    Science.gov (United States)

    Seol, Yeonee; Zhang, Hongliang; Pommier, Yves; Neuman, Keir C

    2012-10-02

    Type IB topoisomerases (Top1Bs) relax excessive DNA supercoiling associated with replication and transcription by catalyzing a transient nick in one strand to permit controlled rotation of the DNA about the intact strand. The natural compound camptothecin (CPT) and the cancer chemotherapeutics derived from it, irinotecan and topotecan, are highly specific inhibitors of human nuclear Top1B (nTop1). Previous work on vaccinia Top1B led to an elegant model that describes a straightforward dependence of rotation and religation on the torque caused by supercoiling. Here, we used a single-molecule DNA supercoil relaxation assay to measure the torque dependence of nTop1 and its inhibition by CPT. For comparison, we also examined mitochondrial Top1B and an N-terminal deletion mutant of nTop1. Despite substantial sequence homology in their core domains, nTop1 and mitochondrial Top1B exhibit dramatic differences in sensitivity to torque and CPT, with the N-terminal deletion mutant of nTop1 showing intermediate characteristics. In particular, nTop1 displays nearly torque-independent religation probability, distinguishing it from other Top1B enzymes studied to date. Kinetic modeling reveals a hitherto unobserved torque-independent transition linking the DNA rotation and religation phases of the enzymatic cycle. The parameters of this transition determine the torque sensitivity of religation and the efficiency of CPT binding. This "kinetic clutch" mechanism explains the molecular basis of CPT sensitivity and more generally provides a framework with which to interpret Top1B activity and inhibition.

  14. Complex interactions among temporal variables affect the plasticity of clutch size in a multi-brooded bird.

    Science.gov (United States)

    Westneat, David F; Stewart, Ian R K; Hatch, Margret I

    2009-05-01

    Phenotypic plasticity is a widespread phenomenon and may have important influences on evolutionary processes. Multidimensional plasticity, in which multiple environmental variables affect a phenotype, is especially interesting if there are interactions among these variables. We used a long-term data set from House Sparrows (Passer domesticus), a multi-brooded passerine bird, to test several predictions from life-history theory regarding the shape of optimal reaction norms for clutch size. The best-fit model for variation in clutch size included three temporal variables (the order of attempt within a season, the date of those attempts, and the age of the female). Clutch size was also sensitive to the quadratics of date and female age, both of which had negative coefficients. Finally, we found that the relationship between date and clutch size became more negative as attempt order increased. These results suggest that female sparrows have a multidimensional reaction norm for clutch size that matches predictions of life-history theory but also implicates more complexity than can be captured by any single model. Analysis of the sources of variation in reaction norm height and slope was complicated by the additional environmental dimensions. We found significant individual variation in mean clutch size in all analyses, indicating that individuals differed in the height of their clutch size reaction norm. By contrast, we found no evidence of significant individual heterogeneity in the slopes of several dimensions. We assess the possible mechanisms producing this reaction norm and discuss their implications for understanding complex plasticity.

  15. Graphite Form and Failure of Clutch%石墨形态与汽车离合器失效断裂

    Institute of Scientific and Technical Information of China (English)

    哈胜男; 任颂赞

    2011-01-01

    By means of SEM and metallography microscope, the failure clutch platen were analyzed. The results show that improper control of numbers and area distribution of E type graphite may cause platen earlier crack.%应用扫描电镜、金相显微镜等多种手段,分析了离合器压盘失效的原因,发现E型石墨的数量、分布的区域控制不当会导致压盘早期断裂失效。

  16. Hydrodynamic controls on respiration in the Amazon River and the importance of particle interactions on organic matter decomposition

    Science.gov (United States)

    Ward, N. D.; Sawakuchi, H. O.; Bianchi, T. S.; Gagne-Maynard, W.; Neu, V.; da Silva, D. F.; Diniz, J. E. D. M.; de Matos Valerio, A.; Cunha, A. C.; Brito, D. C.; da Silva, R.; Krusche, A. V.; Richey, J. E.; Keil, R. G.

    2016-12-01

    Microbial decomposition of terrestrial and aquatic organic matter (OM) drives an evasive CO2gas flux from the world's inland waters comparable to the amount of anthropogenic carbon absorbed by the terrestrial biosphere. However, the physical factors regulating aquatic respiration rates are not well understood and traditional respiration experiments have not satisfactorily represented the turbulent conditions that microbes experience in large rivers. We hypothesize that interactions between the OM/microbes associated with particles and their free-living/dissolved counterparts such as exoenzyme activity, cometabolism, and priming effects are a critical factor controlling respiration rates. River velocity is directly linked to the abundance of particles that remain suspended, and as such, should regulate respiration accordingly. This study examines the influence of river velocity on aquatic respiration based on experiments performed in the lower Amazon River with stationary and rotating incubation chambers equipped with integrated O2 probes to monitor O2 drawdown in real-time. For all experiments performed there was a robust positive correlation between the rate at which chambers were spun and the measured respiration rate (r2 values ranged from 0.76 to 1.00). This relationship was then used to normalize respiration rates to instantaneous measurements of river velocity across each river channel. Whereas average respiration rates measured in traditional BOD bottles could only account for 12 ± 7% of the annual average CO2 outgassing rate measured along the lower Amazon River mainstem, respiration rates based on chambers spinning at 0.22 m s-1, 0.66 m s-1, and velocity-normalized calculations could account for 64 ± 22%, 104 ± 36%, and 130 ± 62% of the CO2 outgassing rate, respectively (average river velocity along the lower Amazon River was 0.98 ± 0.42 m s-1). During each sampling campaign there was a positive correlation with river velocity and in situ CO2

  17. The efficiency of a new hydrodynamic cavitation pilot system on Artemia salina cysts and natural population of copepods and bacteria under controlled mesocosm conditions.

    Science.gov (United States)

    Cvetković, Martina; Grego, Mateja; Turk, Valentina

    2016-04-15

    A study of the efficiency of hydrodynamic cavitation and separation was carried out to evaluate an innovative, environmentally safe and acceptable system for ballast water treatment for reducing the risk of introducing non-native species worldwide. Mesocosm experiments were performed to assess the morphological changes and viability of zooplankton (copepods), Artemia salina cysts, and the growth potential of marine bacteria after the hydrodynamic cavitation treatment with a different number of cycles. Our preliminary results confirmed the significant efficiency of the treatment since more than 98% of the copepods and A. salina cysts were damaged, in comparison with the initial population. The efficiency increased with the number of the hydrodynamic cavitation cycles, or in combination with a separation technique for cysts. There was also a significant decrease in bacterial abundance and growth rate, compared to the initial number and growth potential.

  18. Anisotropic hydrodynamics -- basic concepts

    CERN Document Server

    Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael

    2013-01-01

    Due to the rapid longitudinal expansion of the quark-gluon plasma created in relativistic heavy ion collisions, potentially large local rest frame momentum-space anisotropies are generated. The magnitude of these momentum-space anisotropies can be so large as to violate the central assumption of canonical viscous hydrodynamical treatments which linearize around an isotropic background. In order to better describe the early-time dynamics of the quark gluon plasma, one can consider instead expanding around a locally anisotropic background which results in a dynamical framework called anisotropic hydrodynamics. In this proceedings contribution we review the basic concepts of the anisotropic hydrodynamics framework presenting viewpoints from both the phenomenological and microscopic points of view.

  19. CALIBRATED HYDRODYNAMIC MODEL

    Directory of Open Access Journals (Sweden)

    Sezar Gülbaz

    2015-01-01

    Full Text Available The land development and increase in urbanization in a watershed affect water quantityand water quality. On one hand, urbanization provokes the adjustment of geomorphicstructure of the streams, ultimately raises peak flow rate which causes flood; on theother hand, it diminishes water quality which results in an increase in Total SuspendedSolid (TSS. Consequently, sediment accumulation in downstream of urban areas isobserved which is not preferred for longer life of dams. In order to overcome thesediment accumulation problem in dams, the amount of TSS in streams and inwatersheds should be taken under control. Low Impact Development (LID is a BestManagement Practice (BMP which may be used for this purpose. It is a land planningand engineering design method which is applied in managing storm water runoff inorder to reduce flooding as well as simultaneously improve water quality. LID includestechniques to predict suspended solid loads in surface runoff generated over imperviousurban surfaces. In this study, the impact of LID-BMPs on surface runoff and TSS isinvestigated by employing a calibrated hydrodynamic model for Sazlidere Watershedwhich is located in Istanbul, Turkey. For this purpose, a calibrated hydrodynamicmodel was developed by using Environmental Protection Agency Storm WaterManagement Model (EPA SWMM. For model calibration and validation, we set up arain gauge and a flow meter into the field and obtain rainfall and flow rate data. Andthen, we select several LID types such as retention basins, vegetative swales andpermeable pavement and we obtain their influence on peak flow rate and pollutantbuildup and washoff for TSS. Consequently, we observe the possible effects ofLID on surface runoff and TSS in Sazlidere Watershed.

  20. Dispersive hydrodynamics: Preface

    Science.gov (United States)

    Biondini, G.; El, G. A.; Hoefer, M. A.; Miller, P. D.

    2016-10-01

    This Special Issue on Dispersive Hydrodynamics is dedicated to the memory and work of G.B. Whitham who was one of the pioneers in this field of physical applied mathematics. Some of the papers appearing here are related to work reported on at the workshop "Dispersive Hydrodynamics: The Mathematics of Dispersive Shock Waves and Applications" held in May 2015 at the Banff International Research Station. This Preface provides a broad overview of the field and summaries of the various contributions to the Special Issue, placing them in a unified context.

  1. Hydrodynamics of slip wedge and optimization of surface slip property

    Institute of Scientific and Technical Information of China (English)

    MA GuoJun; WU ChengWei; ZHOU Ping

    2007-01-01

    The hydrodynamic load support generated by a slip wedge of a slider bearing was studied. The surface slip property was optimized so that a maximum hydrodynamic load support could be obtained. A multi-linearity method was given for the slip control equation of two-dimensional (2-D) wall slip. We investigated 2-D wall slip and the hydrodynamics of a finite length bearing with any values of the surface limiting shear stress. It was found that the hydrodynamic effect of the slip wedge is greater than the traditional geometrical convergent-wedge. Even though the geometrical gap is a parallel or divergent sliding gap, the slip wedge still gives rise to a very big hydrodynamic pressure. The optimized slip wedge can give rise to a hydrodynamic load support as high as 2.5 times of what the geometrical convergent-wedge can produce. Wall slip usually gives a small surface friction.

  2. An innovative multi-gap clutch based on magneto-rheological fluids and electrodynamic effects: magnetic design and experimental characterization

    Science.gov (United States)

    Rizzo, R.

    2017-01-01

    In this paper an innovative multi-gap magnetorheological clutch is described. It is inspired by a device previously developed by the author’s research group and contains a novel solution based on electrodynamic effects, capable to considerably improve the transmissible torque during the engagement phase. Since this (transient) phase is characterized by a non-zero angular speed between the two clutch shafts, the rotation of a permanent magnets system, used to excite the fluid, induces eddy currents on some conductive material strategically positioned in the device. As a consequence, an electromagnetic torque is produced which is added to the torque transmitted by the magnetorheological fluid only. Once the clutch is completely engaged and the relative speed between the two shafts is zero, the electrodynamic effects vanish and the device operates like a conventional magnetorheological clutch. The system is investigated and designed by means a 3D FEM model and the performance of the device is experimentally validated on a prototype.

  3. Smoothed Particle Hydrodynamic Simulator

    Energy Technology Data Exchange (ETDEWEB)

    2016-10-05

    This code is a highly modular framework for developing smoothed particle hydrodynamic (SPH) simulations running on parallel platforms. The compartmentalization of the code allows for rapid development of new SPH applications and modifications of existing algorithms. The compartmentalization also allows changes in one part of the code used by many applications to instantly be made available to all applications.

  4. Hydrodynamic aspect of caves

    Directory of Open Access Journals (Sweden)

    Franci Gabrovsek

    2008-01-01

    Full Text Available From a hydrological point of view, active caves are a series of connected conduits which drain water through an aquifer. Water tends to choose the easiest way through the system but different geological and morphological barriers act as flow restrictions. The number and characteristics of restrictions depends on the particular speleogenetic environment, which is a function of geological, geomorphological, climatological and hydrological settings. Such a variety and heterogeneity of underground systems has presented a challenge for human understanding for many centuries. Access to many underground passages, theoretical knowledge and recent methods (modeling, water pressure-resistant dataloggers, precise sensors etc. give us the opportunity to get better insight into the hydrodynamic aspect of caves. In our work we tried to approach underground hydrodynamics from both theoretical and practical points of view. We present some theoretical background of open surface and pressurized flow in underground rivers and present results of some possible scenarios. Moreover, two case studies from the Ljubljanica river basin are presented in more detail: the cave system between Planinsko polje and Ljubljansko barje, and the cave system between Bloško polje and Cerkniško polje. The approach and methodology in each case is somewhat different, as the aims were different at the beginning of exploration. However, they both deal with temporal and spatial hydrodynamics of underground waters. In the case of Bloško polje-Cerkniško polje system we also explain the feedback loop between hydrodynamics and Holocene speleogenesis.

  5. Multigenerational response to artificial selection for biased clutch sex ratios in Tigriopus californicus populations.

    Science.gov (United States)

    Alexander, H J; Richardson, J M L; Anholt, B R

    2014-09-01

    Polygenic sex determination (PSD) is relatively rare and theoretically evolutionary unstable, yet has been reported across a range of taxa. Evidence for multilocus PSD is provided by (i) large between-family variance in sex ratio, (ii) paternal and maternal effects on family sex ratio and (iii) response to selection for family sex ratio. This study tests the polygenic hypothesis of sex determination in the harpacticoid copepod Tigriopus californicus using the criterion of response to selection. We report the first multigenerational quantitative evidence that clutch sex ratio responds to artificial selection in both directions (selection for male- and female-biased families) and in multiple populations of T. californicus. In the five of six lines that showed a response to selection, realized heritability estimated by multigenerational analysis ranged from 0.24 to 0.58. Divergence of clutch sex ratio between selection lines is rapid, with response to selection detectable within the first four generations of selection.

  6. Clutch and egg size variation, and productivity of the House Sparrow (Passer domesticus): effects of temperature, rainfall, and humidity

    OpenAIRE

    ASLAN, Aziz; Yavuz, Mustafa

    2010-01-01

    This study was conducted on the campus of the regional department of the forestry service, encompassing 2.25 ha in Antalya city center. The area has gardens and is surrounded by trees, providing nesting and feeding opportunities for many songbird species. The study aimed to determine clutch and egg size variation, breeding success, and productivity of the House Sparrow (Passer domesticus), in terms of clutch size and breeding attempts, and to evaluate variation in temperature, rainfall, and h...

  7. Hydrodynamics of the Dirac spectrum

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yizhuang, E-mail: yizhuang.liu@stonybrook.edu [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Warchoł, Piotr, E-mail: piotr.warchol@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, PL-30348 Krakow (Poland); Zahed, Ismail, E-mail: ismail.zahed@stonybrook.edu [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)

    2016-02-10

    We discuss a hydrodynamical description of the eigenvalues of the Dirac spectrum in even dimensions in the vacuum and in the large N (volume) limit. The linearized hydrodynamics supports sound waves. The hydrodynamical relaxation of the eigenvalues is captured by a hydrodynamical (tunneling) minimum configuration which follows from a pertinent form of Euler equation. The relaxation from a phase of unbroken chiral symmetry to a phase of broken chiral symmetry occurs over a time set by the speed of sound.

  8. DESIGN OF A COMPACT DUAL-PURPOSE STARTING CLUTCH IN THE DRIVE OF A PROTOTYPE VEHICLE

    Directory of Open Access Journals (Sweden)

    Ján PETRÓCI

    2016-06-01

    Full Text Available Initially, the development of a dual-purpose clutch was based on racing experiences and application requirements, as well as the results from testing the new power unit in the existing prototype vehicle. In order to achieve the highest possible driving range of the prototype vehicle, it has been necessary to eliminate the maximum possible losses and drive in unnecessary components. The design aimed to achieve simple access, reliability and low weight.

  9. Condition-dependent clutch desertion in Great Tit (Parus major) females subjected to human disturbance

    OpenAIRE

    Dubiec, Anna

    2011-01-01

    Abstract Nest desertion behaviour in relation to body condition and timing of breeding was studied in Great Tit (Parus major) females during two breeding seasons. Desertion, most likely unintentionally provoked by catching females during the incubation period, occurred at a very high rate with 41.2 and 25.6% of deserted first clutches in the two study years. The association between desertion probability, body condition (index calculated as residuals from the regression of body mass...

  10. Different temperature and cooling patterns at the blunt and sharp egg poles reflect the arrangement of eggs in an avian clutch.

    Directory of Open Access Journals (Sweden)

    Miroslav E Šálek

    Full Text Available Incubation is an energetically demanding process during which birds apply heat to their eggs to ensure embryonic development. Parent behaviours such as egg turning and exchanging the outer and central eggs in the nest cup affect the amount of heat lost to the environment from individual eggs. Little is known, however, about whether and how egg surface temperature and cooling rates vary among the different areas of an egg and how the arrangement of eggs within the clutch influences heat loss. We performed laboratory (using Japanese quail eggs and field (with northern lapwing eggs experiments using infrared imaging to assess the temperature and cooling patterns of heated eggs and clutches. We found that (i the sharp poles of individual quail eggs warmed to a higher egg surface temperature than did the blunt poles, resulting in faster cooling at the sharp poles compared to the blunt poles; (ii both quail and lapwing clutches with the sharp poles oriented towards the clutch centre (arranged clutches maintained higher temperatures over the central part of the clutch than occurred in those clutches where most of the sharp egg poles were oriented towards the exterior (scattered clutches; and (iii the arranged clutches of both quail and lapwing showed slower cooling rates at both the inner and outer clutch positions than did the respective parts of scattered clutches. Our results demonstrate that egg surface temperature and cooling rates differ between the sharp and blunt poles of the egg and that the orientation of individual eggs within the nest cup can significantly affect cooling of the clutch as a whole. We suggest that birds can arrange their eggs within the nest cup to optimise thermoregulation of the clutch.

  11. Infanticide and within-clutch competition select for reproductive synchrony in a cooperative bird.

    Science.gov (United States)

    Riehl, Christina

    2016-08-01

    Reproduction among members of social animal groups is often highly synchronized, but neither the selective advantages nor the proximate causes of synchrony are fully understood. Here I investigate the evolution of hatching synchrony in the Greater Ani (Crotophaga major), a communally nesting bird in which several unrelated females contribute eggs to a large, shared clutch. Hatching synchrony is variable, ranging from complete synchrony to moderate asynchrony, and is determined by the onset of incubation of the communal clutch. Data from a 10-year field study indicate that individual reproductive success is highest in synchronous groups, and that nestlings that hatch in the middle of the hatching sequence are most likely to survive. Nestling mortality is high in asynchronous clutches because early-hatching nestlings are more likely to be killed by adult group members, whereas late-hatching nestlings are more likely to starve due competition with their older nest-mates. Therefore, the timing of hatching appears to be under stabilizing selection from infanticide and resource competition acting in concert. These results provide empirical support for models predicting that synchrony may evolve as an adaptive counter-strategy to infanticide, and they highlight the importance of competition in shaping the timing of reproduction in social groups.

  12. Engagement characteristics of a friction pad for commercial vehicle clutch system

    Indian Academy of Sciences (India)

    Aravind Vadiraj

    2010-10-01

    A commercially available sintered friction pad is coupled with a standard gray cast iron pressure plate (FG 250 grade) and tested in a clutch dynamometer for understanding the engagement characteristics and thereby predicting the useful life in number of engagements. Results show that sintered friction pad has a very stable range of friction coefficient (0·43–0·61) even after 5000 engagement cycles. The torque transmitted ranges from 350 to 400 N during one engagement cycle. The energy dissipation and mass loss of friction materials linearly increases with increasing sliding distance. A correlation is derived based on energy dissipation and mass loss in terms of total number of useful or available engagements before replacement or repair of friction pad or clutch pressure plate. Both the pressure plate and clutch disc with the sintered friction pad was tested in a 49 tons load capacity vehicle on a test track. Both sintered friction pad and pressure plate showed scoring marks along the sliding direction. Friction pad showed dense cracks along the top edge. Microscopic features of worn sintered friction pads show silica particle providing the required wear resistance for the pads. Pressure plate showed transfer layer of oxides and carbon with less scoring marks due to short duration vehicle level trials.

  13. Hydrodynamic simulations with the Godunov SPH

    CERN Document Server

    Murante, Giuseppe; Brunino, Riccardo; Cha, Suneg-Hoon

    2011-01-01

    We present results based on an implementation of the Godunov Smoothed Particle Hydrodynamics (GSPH), originally developed by Inutsuka (2002), in the GADGET-3 hydrodynamic code. We first review the derivation of the GSPH discretization of the equations of moment and energy conservation, starting from the convolution of these equations with the interpolating kernel. The two most important aspects of the numerical implementation of these equations are (a) the appearance of fluid velocity and pressure obtained from the solution of the Riemann problem between each pair of particles, and (b the absence of an artificial viscosity term. We carry out three different controlled hydrodynamical three-dimensional tests, namely the Sod shock tube, the development of Kelvin-Helmholtz instabilities in a shear flow test, and the "blob" test describing the evolution of a cold cloud moving against a hot wind. The results of our tests confirm and extend in a number of aspects those recently obtained by Cha (2010): (i) GSPH provi...

  14. Scalability of Hydrodynamic Simulations

    CERN Document Server

    Tang, Shikui

    2009-01-01

    Many hydrodynamic processes can be studied in a way that is scalable over a vastly relevant physical parameter space. We systematically examine this scalability, which has so far only briefly discussed in astrophysical literature. We show how the scalability is limited by various constraints imposed by physical processes and initial conditions. Using supernova remnants in different environments and evolutionary phases as application examples, we demonstrate the use of the scaling as a powerful tool to explore the interdependence among relevant parameters, based on a minimum set of simulations. In particular, we devise a scaling scheme that can be used to adaptively generate numerous seed remnants and plant them into 3D hydrodynamic simulations of the supernova-dominated interstellar medium.

  15. Relativistic Hydrodynamics with Wavelets

    CERN Document Server

    DeBuhr, Jackson; Anderson, Matthew; Neilsen, David; Hirschmann, Eric W

    2015-01-01

    Methods to solve the relativistic hydrodynamic equations are a key computational kernel in a large number of astrophysics simulations and are crucial to understanding the electromagnetic signals that originate from the merger of astrophysical compact objects. Because of the many physical length scales present when simulating such mergers, these methods must be highly adaptive and capable of automatically resolving numerous localized features and instabilities that emerge throughout the computational domain across many temporal scales. While this has been historically accomplished with adaptive mesh refinement (AMR) based methods, alternatives based on wavelet bases and the wavelet transformation have recently achieved significant success in adaptive representation for advanced engineering applications. This work presents a new method for the integration of the relativistic hydrodynamic equations using iterated interpolating wavelets and introduces a highly adaptive implementation for multidimensional simulati...

  16. Burst Mechanisms in Hydrodynamics

    CERN Document Server

    Knobloch, E

    1999-01-01

    Different mechanisms believed to be responsible for the generation of bursts in hydrodynamical systems are reviewed and a new mechanism capable of generating regular or irregular bursts of large dynamic range near threshold is described. The new mechanism is present in the interaction between oscillatory modes of odd and even parity in systems of large but finite aspect ratio, and provides an explanation for the bursting behavior observed in binary fluid convection. Additional applications of the new mechanism are proposed.

  17. Relativistic cosmological hydrodynamics

    CERN Document Server

    Hwang, J

    1997-01-01

    We investigate the relativistic cosmological hydrodynamic perturbations. We present the general large scale solutions of the perturbation variables valid for the general sign of three space curvature, the cosmological constant, and generally evolving background equation of state. The large scale evolution is characterized by a conserved gauge invariant quantity which is the same as a perturbed potential (or three-space curvature) in the comoving gauge.

  18. Hydrodynamics of insect spermatozoa

    Science.gov (United States)

    Pak, On Shun; Lauga, Eric

    2010-11-01

    Microorganism motility plays important roles in many biological processes including reproduction. Many microorganisms propel themselves by propagating traveling waves along their flagella. Depending on the species, propagation of planar waves (e.g. Ceratium) and helical waves (e.g. Trichomonas) were observed in eukaryotic flagellar motion, and hydrodynamic models for both were proposed in the past. However, the motility of insect spermatozoa remains largely unexplored. An interesting morphological feature of such cells, first observed in Tenebrio molitor and Bacillus rossius, is the double helical deformation pattern along the flagella, which is characterized by the presence of two superimposed helical flagellar waves (one with a large amplitude and low frequency, and the other with a small amplitude and high frequency). Here we present the first hydrodynamic investigation of the locomotion of insect spermatozoa. The swimming kinematics, trajectories and hydrodynamic efficiency of the swimmer are computed based on the prescribed double helical deformation pattern. We then compare our theoretical predictions with experimental measurements, and explore the dependence of the swimming performance on the geometric and dynamical parameters.

  19. 干式双离合器和作动器设计实例%Design Examples of the Dry Twin Clutch and Actuation

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    最近一种设计方案是在平行轴齿轮箱(PSG)中采用干式双离合器,它将在有限的安装空间内,装入双离合器(twin clutch)、飞轮(flywheel)、离合器释放装置(clutch release system)和离合器作动器(clutch actuator)。

  20. A phylogenetic analysis of egg size, clutch size, spawning mode, adult body size, and latitude in reef fishes

    Science.gov (United States)

    Kasimatis, Katja; Riginos, Cynthia

    2016-06-01

    Theoretical treatments of egg size in fishes suggest that constraints on reproductive output should create trade-offs between the size and number of eggs produced per spawn. For marine reef fishes, the observation of distinct reproductive care strategies (demersal guarding, egg scattering, and pelagic spawning) has additionally prompted speculation that these strategies reflect alternative fitness optima with selection on egg size differing by reproductive mode and perhaps latitude. Here, we aggregate data from 278 reef fish species and test whether clutch size, reproductive care, adult body size, and latitudinal bands (i.e., tropical, subtropical, and temperate) predict egg size, using a statistically unified framework that accounts for phylogenetic correlations among traits. We find no inverse relationship between species egg size and clutch size, but rather that egg size differs by reproductive mode (mean volume for demersal eggs = 1.22 mm3, scattered eggs = 0.18 mm3, pelagic eggs = 0.52 mm3) and that clutch size is strongly correlated with adult body size. Larger eggs were found in temperate species compared with tropical species in both demersal guarders and pelagic spawners, but this difference was not strong when accounting for phylogenetic correlations, suggesting that differences in species composition underlies regional differences in egg size. In summary, demersal guarders are generally small fishes with small clutch sizes that produce large eggs. Pelagic spawners and egg scatterers are variable in adult and clutch size. Although pelagic spawned eggs are variable in size, those of scatterers are consistently small.

  1. Egg clutch patterning in Lestes virens (Odonata, Lestidae) with evolutionary emphasis on endophytic oviposition in lestid dragonflies.

    Science.gov (United States)

    Matushkina, Natalia A; Buy, Denis; Lambret, Philippe

    2016-12-01

    Egg deposition within plants is one of the most widely distributed and ancient behaviors in Odonata. The resulting clutch consists of eggs placed in peculiar pattern that can be a characteristic for certain groups of Odonata. Despite their importance for paleontological and evolutionary research, data on egg-clutch positioning are missing or insufficient for most species. Here, patterning of egg clutches in Lestes virens was measured and described in detail for the first time. The female usually produces a linear row of single eggs directed at an angle rightward or leftward to the longitudinal axis of plant substrate. Less often eggs are arranged in egg-sets consisting of up to 4 eggs. Apparently, the female insect follows the rigid behavior stereotypes during oviposition and is unable to easily switch to the alternate stereotypical behavior of single egg deposition or production of multiegg sets. Based on a literature review and original data, egg clutch patterning of European Lestidae is overlaid on preexisting phylogenies. The resulting evolutionary scenario of egg-clutch patterning can be considered in the framework of egg-laying behavior in Lestidae.

  2. Foundations of radiation hydrodynamics

    CERN Document Server

    Mihalas, Dimitri

    1999-01-01

    Radiation hydrodynamics is a broad subject that cuts across many disciplines in physics and astronomy: fluid dynamics, thermodynamics, statistical mechanics, kinetic theory, and radiative transfer, among others. The theory developed in this book by two specialists in the field can be applied to the study of such diverse astrophysical phenomena as stellar winds, supernova explosions, and the initial phases of cosmic expansion, as well as the physics of laser fusion and reentry vehicles. As such, it provides students with the basic tools for research on radiating flows.Largely self-contained,

  3. Hydrodynamics of slip wedge and optimization of surface slip property

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The hydrodynamic load support generated by a slip wedge of a slider bearing was studied. The surface slip property was optimized so that a maximum hydrodynamic load support could be obtained. A multi-linearity method was given for the slip control equation of two-dimensional (2-D) wall slip. We investigated 2-D wall slip and the hydrodynamics of a finite length bearing with any values of the surface limiting shear stress. It was found that the hydrodynamic effect of the slip wedge is greater than the traditional geometrical convergent-wedge. Even though the geo- metrical gap is a parallel or divergent sliding gap, the slip wedge still gives rise to a very big hydrodynamic pressure. The optimized slip wedge can give rise to a hy- drodynamic load support as high as 2.5 times of what the geometrical conver- gent-wedge can produce. Wall slip usually gives a small surface friction.

  4. Optimization of Submarine Hydrodynamic Coefficients Based on Immune Genetic Algorithm

    Institute of Scientific and Technical Information of China (English)

    HU Kun; XU Yi-fan

    2010-01-01

    Aiming at the demand for optimization of hydrodynamic coefficients in submarine's motion equations, an adaptive weight immune genetic algorithm was proposed to optimize hydrodynamic coefficients in motion equations. Some hydrody-namic coefficients of high sensitivity to control and maneuver were chosen as the optimization objects in the algorithm. By using adaptive weight method to determine the weight and target function, the multi-objective optimization could be transla-ted into single-objective optimization. For a certain kind of submarine, three typical maneuvers were chosen to be the objects of study: overshoot maneuver in horizontal plane, overshoot maneuver in vertical plane and turning circle maneuver in horizontal plane. From the results of computer simulations using primal hydrodynamic coefficient and optimized hydrody-namic coefficient, the efficiency of proposed method is proved.

  5. Hydrodynamics of evaporating sessile drops

    CERN Document Server

    Barash, L Yu

    2010-01-01

    Several dynamical stages of the Marangoni convection of an evaporating sessile drop are obtained. We jointly take into account the hydrodynamics of an evaporating sessile drop, effects of the thermal conduction in the drop and the diffusion of vapor in air. The stages are characterized by different number of vortices in the drop and the spatial location of vortices. During the early stage the array of vortices arises near a surface of the drop and induces a non-monotonic spatial distribution of the temperature over the drop surface. The number of near-surface vortices in the drop is controlled by the Marangoni cell size, which is calculated similar to that given by Pearson for flat fluid layers. The number of vortices quickly decreases with time, resulting in three bulk vortices in the intermediate stage. The vortex structure finally evolves into the single convection vortex in the drop, existing during about 1/2 of the evaporation time.

  6. Performance Investigation of A Mix Wind Turbine Using A Clutch Mechanism At Low Wind Speed Condition

    Science.gov (United States)

    Jamanun, M. J.; Misaran, M. S.; Rahman, M.; Muzammil, W. K.

    2017-07-01

    Wind energy is one of the methods that generates energy from sustainable resources. This technology has gained prominence in this era because it produces no harmful product to the society. There is two fundamental type of wind turbine are generally used this day which is Horizontal axis wind turbine (HAWT) and Vertical axis wind turbine (VAWT). The VAWT technology is more preferable compare to HAWT because it gives better efficiency and cost effectiveness as a whole. However, VAWT is known to have distinct disadvantage compared to HAWT; self-start ability and efficiency at low wind speed condition. Different solution has been proposed to solve these issues which includes custom design blades, variable angle of attack mechanism and mix wind turbine. A new type of clutch device was successfully developed in UMS to be used in a mix Savonius-Darrieus wind turbine configuration. The clutch system which barely audible when in operation compared to a ratchet clutch system interconnects the Savonius and Darrieus rotor; allowing the turbine to self-start at low wind speed condition as opposed to a standalone Darrieus turbine. The Savonius height were varied at three different size in order to understand the effect of the Savonius rotor to the mix wind turbine performance. The experimental result shows that the fabricated Savonius rotor show that the height of the Savonius rotor affecting the RPM for the turbine. The swept area (SA), aspect ratio (AR) and tip speed ratio (TSR) also calculated in this paper. The highest RPM recorded in this study is 90 RPM for Savonius rotor 0.22-meter height at 2.75 m/s. The Savonius rotor 0.22-meter also give the highest TSR for each range of speed from 0.75 m/s, 1.75 m/s and 2.75 m/s where it gives 1.03 TSR, 0.76 TSR, and 0.55 TSR.

  7. Asbestos-induced lung disease in small-scale clutch manufacturing workers

    Science.gov (United States)

    Gothi, Dipti; Gahlot, Tanushree; Sah, Ram B.; Saxena, Mayank; Ojha, U. C.; Verma, Anand K.; Spalgais, Sonam

    2016-01-01

    Background: The crocidolite variety of asbestos is banned. However, chrysotile, which is not prohibited, is still used in developing countries in making products such as clutch plate. Fourteen workers from a small-scale clutch plate-manufacturing factory were analyzed for asbestos-induced lung disease as one of their colleagues had expired due to asbestosis. Aims: This study was conducted to evaluate the awareness of workers, the prevalence and type of asbestos-induced lung disease, and the sensitivity and specificity of diffusion test. Materials and Methods: History, examination, chest radiograph, spirometry with diffusion, and high resolution computed tomography (HRCT) thorax was performed in all the workers. The diagnosis of asbestos-induced lung disease was suspected on the basis of HRCT. This was subsequently confirmed on transbronchial lung biopsy (TBLB). Results: None of the workers had detailed information about asbestos and its ill effects. Eleven out of 14 (71.42%) workers had asbestos-induced lung disease. All 11 had small airway disease (SAD). Three had SAD alone, 6 had additional interstitial lung disease (ILD), and 2 patients had additional ILD and chronic obstructive pulmonary disease. Sensitivity and specificity of residual volume (RV) or total lung capacity (TLC) for detecting SAD was 90% and 100%, respectively, and that of diffusion capacity of lung for carbon monoxide (DLCO) for detecting ILD was 100%. Conclusion: The awareness about asbestos in small-scale clutch-plate manufacturing industry is poor. The usage of chrysotile should be strictly regulated as morbidity and mortality is high. DLCO and RV/TLC are sensitive and specific in detecting nonmalignant asbestos induced lung disease.

  8. Model for adhesion clutch explains biphasic relationship between actin flow and traction at the cell leading edge

    Science.gov (United States)

    Craig, Erin M.; Stricker, Jonathan; Gardel, Margaret; Mogilner, Alex

    2015-05-01

    Cell motility relies on the continuous reorganization of a dynamic actin-myosin-adhesion network at the leading edge of the cell, in order to generate protrusion at the leading edge and traction between the cell and its external environment. We analyze experimentally measured spatial distributions of actin flow, traction force, myosin density, and adhesion density in control and pharmacologically perturbed epithelial cells in order to develop a mechanical model of the actin-adhesion-myosin self-organization at the leading edge. A model in which the F-actin network is treated as a viscous gel, and adhesion clutch engagement is strengthened by myosin but weakened by actin flow, can explain the measured molecular distributions and correctly predict the spatial distributions of the actin flow and traction stress. We test the model by comparing its predictions with measurements of the actin flow and traction stress in cells with fast and slow actin polymerization rates. The model predicts how the location of the lamellipodium-lamellum boundary depends on the actin viscosity and adhesion strength. The model further predicts that the location of the lamellipodium-lamellum boundary is not very sensitive to the level of myosin contraction.

  9. Model for adhesion clutch explains biphasic relationship between actin flow and traction at the cell leading edge

    Science.gov (United States)

    Craig, Erin M.; Stricker, Jonathan; Gardel, Margaret L.; Mogilner, Alex

    2015-01-01

    Cell motility relies on the continuous reorganization of a dynamic actin-myosin-adhesion network at the leading edge of the cell, in order to generate protrusion at the leading edge and traction between the cell and its external environment. We analyze experimentally measured spatial distributions of actin flow, traction force, myosin density, and adhesion density in control and pharmacologically perturbed epithelial cells in order to develop a mechanical model of the actin-adhesion-myosin self-organization at the leading edge. A model in which the F-actin network is treated as a viscous gel, and adhesion clutch engagement is strengthened by myosin but weakened by actin flow, can explain the measured molecular distributions and correctly predict the spatial distributions of the actin flow and traction stress. We test the model by comparing its predictions with measurements of the actin flow and traction stress in cells with fast and slow actin polymerization rates. The model predicts how the location of the lamellipodium-lamellum boundary depends on the actin viscosity and adhesion strength. The model further predicts that the location of the lamellipodium-lamellum boundary is not very sensitive to the level of myosin contraction. PMID:25969948

  10. Molecular hydrodynamics from memory kernels

    CERN Document Server

    Lesnicki, Dominika; Carof, Antoine; Rotenberg, Benjamin

    2016-01-01

    The memory kernel for a tagged particle in a fluid, computed from molecular dynamics simulations, decays algebraically as $t^{-3/2}$. We show how the hydrodynamic Basset-Boussinesq force naturally emerges from this long-time tail and generalize the concept of hydrodynamic added mass. This mass term is negative in the present case of a molecular solute, at odds with incompressible hydrodynamics predictions. We finally discuss the various contributions to the friction, the associated time scales and the cross-over between the molecular and hydrodynamic regimes upon increasing the solute radius.

  11. Morphological diversity and evolution of egg and clutch structure in amphibians

    Science.gov (United States)

    Altig, Ronald; McDiarmid, Roy W.

    2007-01-01

    The first part of this synthesis summarizes the morphology of the jelly layers surrounding an amphibian ovum. We propose a standard terminology and discuss the evolution of jelly layers. The second part reviews the morphological diversity and arrangement of deposited eggs?the ovipositional mode; we recognize 5 morphological classes including 14 modes. We discuss some of the oviductal, ovipositional, and postovipositional events that contribute to these morphologies. We have incorporated data from taxa from throughout the world but recognize that other types will be discovered that may modify understanding of these modes. Finally, we discuss the evolutionary context of the diversity of clutch structure and present a first estimate of its evolution.

  12. Hydrodynamics of pronuclear migration

    Science.gov (United States)

    Nazockdast, Ehssan; Needleman, Daniel; Shelley, Michael

    2014-11-01

    Microtubule (MT) filaments play a key role in many processes involved in cell devision including spindle formation, chromosome segregation, and pronuclear positioning. We present a direct numerical technique to simulate MT dynamics in such processes. Our method includes hydrodynamically mediated interactions between MTs and other cytoskeletal objects, using singularity methods for Stokes flow. Long-ranged many-body hydrodynamic interactions are computed using a highly efficient and scalable fast multipole method, enabling the simulation of thousands of MTs. Our simulation method also takes into account the flexibility of MTs using Euler-Bernoulli beam theory as well as their dynamic instability. Using this technique, we simulate pronuclear migration in single-celled Caenorhabditis elegans embryos. Two different positioning mechanisms, based on the interactions of MTs with the motor proteins and the cell cortex, are explored: cytoplasmic pulling and cortical pushing. We find that although the pronuclear complex migrates towards the center of the cell in both models, the generated cytoplasmic flows are fundamentally different. This suggest that cytoplasmic flow visualization during pronuclear migration can be utilized to differentiate between the two mechanisms.

  13. Hydrodynamic dispersion within porous biofilms

    KAUST Repository

    Davit, Y.

    2013-01-23

    Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher\\'s equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels\\' network; (2) the solute\\'s diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport. © 2013 American Physical Society.

  14. Design optimization of clutch housing mold by fluid flow and solidification simulation

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Seyedeh Maryam; Utlu, Zafer [Istanbul Aydin Univ., Istanbul (Turkmenistan)

    2016-06-15

    Aluminum die casting is so complex where flow momentum is critical matter in the mould filling process due the high velocity of the liquid metal. Actually, in complex parts the exact calculation of mould filling performance with using experimental knowledge is almost impossible. Aluminum die castings play a definitive role in the manufacturing of lightweight automobile bodies. Hence it is more essential today that these castings be produced with the high quality methods. In this condition the simulation is becoming more important in the designing procedure. This saves time and reduces the cost of the casting system design, which is an advantage of using simulation programs. Also, economical utilization of materials can be obtained when the quantity of test castings is decreased. This paper describes the advantages of the clutch housing die casting mold simulations to achieve better casting system design in High pressure die castings (HPDC). Filling analysis is used to determine the size and location of the gate as well as proper runner system design for ensuring a complete and balanced filling of the clutch housing part.

  15. Multiple mating and clutch size in invertebrate brooders versus pregnant vertebrates.

    Science.gov (United States)

    Avise, John C; Tatarenkov, Andrey; Liu, Jin-Xian

    2011-07-12

    We summarize the genetic literature on polygamy rates and sire numbers per clutch in invertebrate animals that brood their offspring and then compare findings with analogous data previously compiled for vertebrate species displaying viviparity or other pregnancy-like syndromes. As deduced from molecular parentage analyses of several thousand broods from more than 100 "pregnant" species, invertebrate brooders had significantly higher mean incidences of multiple mating than pregnant vertebrates, a finding generally consistent with the postulate that clutch size constrains successful mate numbers in species with extended parental care. However, we uncovered no significant correlation in invertebrates between brood size and genetically deduced rates of multiple mating by the incubating sex. Instead, in embryo-gestating animals otherwise as different as mammals and mollusks, polygamy rates and histograms of successful mates per brooder proved to be strikingly similar. Most previous studies have sought to understand why gestating parents have so many mates and such high incidences of successful multiple mating; an alternative perspective based on logistical constraints turns the issue on its head by asking why mate numbers and polygamy rates are much lower than they theoretically could be, given the parentage-resolving power of molecular markers and the huge sizes of many invertebrate broods.

  16. Comparison of the incidence of sibling cannibalism between male-killing Spiroplasma infected and uninfected clutches of a predatory ladybird beetle, Harmonia axyridis (Coleoptera: Coccinellidae)

    NARCIS (Netherlands)

    Nakamura, K.; Miura, K.; Jong, de P.W.; Ueno, H.

    2006-01-01

    The incidence of sibling cannibalism in clutches of Harmonia axyridis infected by the male-killing Spiroplasma was compared with that in uninfected clutches, and the way in which fitness compensation was realized by sibling cannibalism was investigated. Primarily the rate of sibling cannibalism was

  17. Density dependence of avian clutch size in resident and migrant species: is there a constraint on the predictability of competitor density?

    NARCIS (Netherlands)

    Both, C.

    2000-01-01

    The presence of density dependence of clutch size is tested in 57 long-term population studies of 10 passerine bird species. In about half of the studies of tit species Parus spp. density dependence of clutch size was found, while none was found in studies of two flycatcher species Ficedula spp. One

  18. Comparison of the incidence of sibling cannibalism between male-killing Spiroplasma infected and uninfected clutches of a predatory ladybird beetle, Harmonia axyridis (Coleoptera: Coccinellidae)

    NARCIS (Netherlands)

    Nakamura, K.; Miura, K.; Jong, de P.W.; Ueno, H.

    2006-01-01

    The incidence of sibling cannibalism in clutches of Harmonia axyridis infected by the male-killing Spiroplasma was compared with that in uninfected clutches, and the way in which fitness compensation was realized by sibling cannibalism was investigated. Primarily the rate of sibling cannibalism was

  19. No experimental evidence for local competition in the nestling phase as a driving force for density-dependent avian clutch size

    NARCIS (Netherlands)

    Nicolaus, Marion; Both, Christiaan; Ubels, Richard; Edelaar, Pim; Tinbergen, Joost M.; Butler, Simon

    2009-01-01

    In birds, local competition for food between pairs during the nestling phase may affect nestling growth and survival. A decrease in clutch size with an increase in breeding density could be an adaptive response to this competition. To investigate whether breeding density causally affected the clutch

  20. Produced water re-injection in a non-fresh water aquifer with geochemical reaction, hydrodynamic molecular dispersion and adsorption kinetics controlling: model development and numerical simulation

    Science.gov (United States)

    Obe, Ibidapo; Fashanu, T. A.; Idialu, Peter O.; Akintola, Tope O.; Abhulimen, Kingsley E.

    2017-06-01

    An improved produced water reinjection (PWRI) model that incorporates filtration, geochemical reaction, molecular transport, and mass adsorption kinetics was developed to predict cake deposition and injectivity performance in hydrocarbon aquifers in Nigeria oil fields. Thus, the improved PWRI model considered contributions of geochemical reaction, adsorption kinetics, and hydrodynamic molecular dispersion mechanism to alter the injectivity and deposition of suspended solids on aquifer wall resulting in cake formation in pores during PWRI and transport of active constituents in hydrocarbon reservoirs. The injectivity decline and cake deposition for specific case studies of hydrocarbon aquifers in Nigeria oil fields were characterized with respect to its well geometry, lithology, and calibrations data and simulated in COMSOL multiphysics software environment. The PWRI model was validated by comparisons to assessments of previous field studies based on data and results supplied by operator and regulator. The results of simulation showed that PWRI performance was altered because of temporal variations and declinations of permeability, injectivity, and cake precipitation, which were observed to be dependent on active adsorption and geochemical reaction kinetics coupled with filtration scheme and molecular dispersion. From the observed results and findings, transition time t r to cake nucleation and growth were dependent on aquifer constituents, well capacity, filtration coefficients, particle-to-grain size ratio, water quality, and more importantly, particle-to-grain adsorption kinetics. Thus, the results showed that injectivity decline and permeability damage were direct contributions of geochemical reaction, hydrodynamic molecular diffusion, and adsorption kinetics to the internal filtration mechanism, which are largely dependent on the initial conditions of concentration of active constituents of produced water and aquifer capacity.

  1. Produced water re-injection in a non-fresh water aquifer with geochemical reaction, hydrodynamic molecular dispersion and adsorption kinetics controlling: model development and numerical simulation

    Science.gov (United States)

    Obe, Ibidapo; Fashanu, T. A.; Idialu, Peter O.; Akintola, Tope O.; Abhulimen, Kingsley E.

    2016-12-01

    An improved produced water reinjection (PWRI) model that incorporates filtration, geochemical reaction, molecular transport, and mass adsorption kinetics was developed to predict cake deposition and injectivity performance in hydrocarbon aquifers in Nigeria oil fields. Thus, the improved PWRI model considered contributions of geochemical reaction, adsorption kinetics, and hydrodynamic molecular dispersion mechanism to alter the injectivity and deposition of suspended solids on aquifer wall resulting in cake formation in pores during PWRI and transport of active constituents in hydrocarbon reservoirs. The injectivity decline and cake deposition for specific case studies of hydrocarbon aquifers in Nigeria oil fields were characterized with respect to its well geometry, lithology, and calibrations data and simulated in COMSOL multiphysics software environment. The PWRI model was validated by comparisons to assessments of previous field studies based on data and results supplied by operator and regulator. The results of simulation showed that PWRI performance was altered because of temporal variations and declinations of permeability, injectivity, and cake precipitation, which were observed to be dependent on active adsorption and geochemical reaction kinetics coupled with filtration scheme and molecular dispersion. From the observed results and findings, transition time t r to cake nucleation and growth were dependent on aquifer constituents, well capacity, filtration coefficients, particle-to-grain size ratio, water quality, and more importantly, particle-to-grain adsorption kinetics. Thus, the results showed that injectivity decline and permeability damage were direct contributions of geochemical reaction, hydrodynamic molecular diffusion, and adsorption kinetics to the internal filtration mechanism, which are largely dependent on the initial conditions of concentration of active constituents of produced water and aquifer capacity.

  2. Fluctuations in Relativistic Causal Hydrodynamics

    CERN Document Server

    Kumar, Avdhesh; Mishra, Ananta P

    2013-01-01

    The formalism to calculate the hydrodynamics fluctuation using the quasi-stationary fluctuation theory of Onsager to the relativistic Navier-Stokes hydrodynamics is already known. In this work we calculate hydrodynamic fluctuations in relativistic causal theory of Muller, Israel and Stewart and other related causal hydrodynamic theories. We show that expressions for the Onsager coefficients and the correlation functions have form similar to the ones obtained by using Navier-Stokes equation. However, temporal evolution of the correlation functions obtained using MIS and the other causal theories can be significantly different than the correlation functions obtained using the Navier-Stokes equation. Finally, as an illustrative example, we explicitly plot the correlation functions obtained using the causal-hydrodynamics theories and compare them with correlation functions obtained by earlier authors using the expanding boost-invariant (Bjorken) flows.

  3. Gradient expansion for anisotropic hydrodynamics

    CERN Document Server

    Florkowski, Wojciech; Spaliński, Michał

    2016-01-01

    We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of non-hydrodynamic modes.

  4. Lifshitz Superfluid Hydrodynamics

    CERN Document Server

    Chapman, Shira; Oz, Yaron

    2014-01-01

    We construct the first order hydrodynamics of quantum critical points with Lifshitz scaling and a spontaneously broken symmetry. The fluid is described by a combination of two flows, a normal component that carries entropy and a super-flow which has zero viscosity and carries no entropy. We analyze the new transport effects allowed by the lack of boost invariance and constrain them by the local second law of thermodynamics. Imposing time-reversal invariance, we find eight new parity even transport coefficients. The formulation is applicable, in general, to any superfluid/superconductor with an explicit breaking of boost symmetry, in particular to high $T_c$ superconductors. We discuss possible experimental signatures.

  5. Hydrodynamics of Ship Propellers

    DEFF Research Database (Denmark)

    Breslin, John P.; Andersen, Poul

    This book deals with flows over propellers operating behind ships, and the hydrodynamic forces and moments which the propeller generates on the shaft and on the ship hull.The first part of the text is devoted to fundamentals of the flow about hydrofoil sections (with and without cavitation......) and about wings. It then treats propellers in uniform flow, first via advanced actuator disc modelling, and then using lifting-line theory. Pragmatic guidance is given for design and evaluation of performance, including the use of computer modelling.The second part covers the development of unsteady forces...... arising from operation in non-uniform hull wakes. First, by a number of simplifications, various aspects of the problem are dealt with separately until the full problem of a non-cavitating, wide-bladed propeller in a wake is treated by a new and completely developed theory. Next, the complicated problem...

  6. Hydrodynamics of sediment threshold

    Science.gov (United States)

    Ali, Sk Zeeshan; Dey, Subhasish

    2016-07-01

    A novel hydrodynamic model for the threshold of cohesionless sediment particle motion under a steady unidirectional streamflow is presented. The hydrodynamic forces (drag and lift) acting on a solitary sediment particle resting over a closely packed bed formed by the identical sediment particles are the primary motivating forces. The drag force comprises of the form drag and form induced drag. The lift force includes the Saffman lift, Magnus lift, centrifugal lift, and turbulent lift. The points of action of the force system are appropriately obtained, for the first time, from the basics of micro-mechanics. The sediment threshold is envisioned as the rolling mode, which is the plausible mode to initiate a particle motion on the bed. The moment balance of the force system on the solitary particle about the pivoting point of rolling yields the governing equation. The conditions of sediment threshold under the hydraulically smooth, transitional, and rough flow regimes are examined. The effects of velocity fluctuations are addressed by applying the statistical theory of turbulence. This study shows that for a hindrance coefficient of 0.3, the threshold curve (threshold Shields parameter versus shear Reynolds number) has an excellent agreement with the experimental data of uniform sediments. However, most of the experimental data are bounded by the upper and lower limiting threshold curves, corresponding to the hindrance coefficients of 0.2 and 0.4, respectively. The threshold curve of this study is compared with those of previous researchers. The present model also agrees satisfactorily with the experimental data of nonuniform sediments.

  7. 干式离合器摩擦片表面温度测量与分析%Research on temperature measurement of dry clutch plate based on wireless technology

    Institute of Scientific and Technical Information of China (English)

    熊玉杰; 席军强; 翟涌; 项俊男

    2016-01-01

    离合器摩擦片表面温度是离合器传递转矩最直接的影响因素,对修正离合器参数、优化离合器控制具有重要意义。为了解决离合器摩擦片表面工作温度难以测量这一技术难题,在研究影响离合器摩擦片表面温度的主要因素时,通过设计离合器摩擦片表面温度无线采集系统,得到了不同工况下摩擦片表面温度沿径向和周向变化的数据,然后在仿真软件ANSYS中建立了摩擦片有限元模型,并进行热分析,仿真结果与试验数据显示:摩擦片表面温度主要沿径向变化,滑磨产生的热流量是导致摩擦片温升的主要因素,通过修正对流换热系数能提高摩擦片温度的计算精度,将仿真结果与试验数据的误差降低在3.75%以内,而热辐射对于摩擦片温度的影响可以忽略不计。通过对摩擦片温度场变化规律和温度影响因素的分析,对于离合器结构设计、离合器温度模型优化以及离合器控制具有参考价值。%Clutch temperature is a key factor affecting the performance of the clutch and it is of great significance to establish the model of clutch temperature for the correction of parameters and the opti-mization of clutch control. To measure the friction surface temperature and to analyze the influencing factors of temperature, a temperature acquisition system was designed based on the wireless trans-mission technology which can collect the surface temperature under different radius, circumferential and working conditions. Then, the finite element model of friction disc was created by ANSYS. The experimental date and simulation results show that heat flux is a major factor leading to temperature rise, the simulation accuracy can be improved by correcting convection heat transfer coefficient, and the error can be reduced about 3. 75%, and the influence of thermal radiation on temperature can be ignored. By analyzing the change rule of temperature

  8. 连续管滚筒排管液压离合器的研制与应用%Development and Application of Hydraulic Clutch for CT Level Wing

    Institute of Scientific and Technical Information of China (English)

    吴大飞; 张三坡; 马曾林; 祝克强

    2012-01-01

    The friction disk of the overrunning clutch for the CT level wing on the reel of the existing CT unit will be subject to abrasion. A frequent manual regulation of the clutch gland nut is required in order to recover the contact pressure of friction disk. But the field regulation is inconvenient and it increases the risk of operation. Therefore, a hydraulic clutch was developed. The clutch adopts a two-segment design whose dimensions can be completely exchanged with those of the original jackshaft assembly. The lubrication of the whole clutch can be achieved. The service life of the clutch friction disk and bearing can be lengthened. The whole CT level wing adopts hydraulic operation and interlocking control, which is characterized by quick response and safe and reliable operation. Several friction disks are used to transmit torque jointly, reducing the force of a single friction disk. The field test and application show that the clutch is convenient in control, with large transmission torque and smooth and reliable operation. It satisfies the requirement of CT handling on the reel.%现有连续管作业机滚筒排管机构超越摩擦离合器的摩擦片容易磨损,经常需要人工调节离合器上的压紧螺母以恢复摩擦片上的接触压力,但现场调节很不方便,增大了作业的危险性。为此,研制了连续管滚筒排管液压离合器。该离合器采用两段式设计,其设计尺寸与原中间轴总成可完全互换;可实现离合器的整体润滑,延长离合器摩擦片和轴承的使用寿命;整个排管系统采用液压操作,互锁控制,响应速度快,运行安全可靠,既可减轻操作人员的劳动强度,又可提高现场作业安全性;由多块摩擦片共同传递力矩,减小了单块摩擦片的受力,手动排管时摩擦片之间无接触压力,不会产生滑动摩擦作用,大大延长了摩擦片的寿命。现场试验及应用结果表明,连续管滚筒排管液

  9. 控制动作下带缆遥控水下机器人的水动力特性%Hydrodynamic Characteristics of Tethered Underwater Robot Under Control Manipulations

    Institute of Scientific and Technical Information of China (English)

    吴家鸣; 崔寅; 邓威; 伍力; 马志权

    2012-01-01

    首先利用模糊神经网络算法构建了基于完整的带缆遥控水下机器人水动力数学模型的控制器,对水下机器人多自由度上的轨迹和姿态进行控制;然后,针对传统螺旋桨推进力分析方法中的缺陷,引入神经网络相关理论并结合计算流体方法对推进力和转速之间的相互关系进行辨识和换算;在此基础上构建了一个完整的、包括模糊神经控制器、机器人水动力数学模型以及推进力和转速换算模块的带缆遥控水下机器人控制系统;最后,在考虑系统各部分间相互影响的前提下进行了水动力特性的整体分析和计算.数值计算结果表明,所建立的控制系统可以对带缆遥控水下机器人进行有效的轨迹和姿态控制,文中方法可以从整体的角度分析一定控制动作下水下机器人的水动力响应.%A controller based on an integrated hydrodynamic model of the tethered underwater robot is constructed with the help of FNN ( Fuzzy Neural Network) algorithm and is used to control the trajectory and attitude of the robot in multiple degrees of freedom. Then, in order to remedy the disadvantages of the traditional method of analyzing propeller propulsion, a new method combining the theory of neural network and the computational fluid dynamics technique is proposed for the conversion between the propulsion and the rotating speed. Moreover, an integrated control system, which consists of a FNN controller, a robotic hydrodynamic model and a conversion module of propulsion and rotating speed, is presented for the tethered underwater robot. Finally, the hydrodynamic characteristics of the robot are globally analyzed and calculated by taking into consideration the interaction among different parts of the robot. Numerical simulation results indicate that the proposed system effectively controls the trajectory and attitude of the tethered underwater robot, and that it helps to globally calculate the

  10. Recent development of hydrodynamic modeling

    Science.gov (United States)

    Hirano, Tetsufumi

    2014-09-01

    In this talk, I give an overview of recent development in hydrodynamic modeling of high-energy nuclear collisions. First, I briefly discuss about current situation of hydrodynamic modeling by showing results from the integrated dynamical approach in which Monte-Carlo calculation of initial conditions, quark-gluon fluid dynamics and hadronic cascading are combined. In particular, I focus on rescattering effects of strange hadrons on final observables. Next I highlight three topics in recent development in hydrodynamic modeling. These include (1) medium response to jet propagation in di-jet asymmetric events, (2) causal hydrodynamic fluctuation and its application to Bjorken expansion and (3) chiral magnetic wave from anomalous hydrodynamic simulations. (1) Recent CMS data suggest the existence of QGP response to propagation of jets. To investigate this phenomenon, we solve hydrodynamic equations with source term which exhibits deposition of energy and momentum from jets. We find a large number of low momentum particles are emitted at large angle from jet axis. This gives a novel interpretation of the CMS data. (2) It has been claimed that a matter created even in p-p/p-A collisions may behave like a fluid. However, fluctuation effects would be important in such a small system. We formulate relativistic fluctuating hydrodynamics and apply it to Bjorken expansion. We found the final multiplicity fluctuates around the mean value even if initial condition is fixed. This effect is relatively important in peripheral A-A collisions and p-p/p-A collisions. (3) Anomalous transport of the quark-gluon fluid is predicted when extremely high magnetic field is applied. We investigate this possibility by solving anomalous hydrodynamic equations. We found the difference of the elliptic flow parameter between positive and negative particles appears due to the chiral magnetic wave. Finally, I provide some personal perspective of hydrodynamic modeling of high energy nuclear collisions

  11. Hydrodynamics Research on Amphibious Vehicle Systems:Modeling Theory

    Institute of Scientific and Technical Information of China (English)

    JU Nai-jun

    2006-01-01

    For completing the hydrodynamics software development and the engineering application research on the amphibious vehicle systems, hydrodynamic modeling theory of the amphibious vehicle systems is elaborated, which includes to build up the dynamic system model of amphibious vehicle motion on water, gun tracking-aiming-firing, bullet hit and armored check-target, gunner operating control, and the simulation computed model of time domain for random sea wave.

  12. Differential deposition of antimicrobial proteins in blue tit (Cyanistes caeruleus) clutches by laying order and male attractiveness

    NARCIS (Netherlands)

    D'Alba, Liliana; Shawkey, Matthew D.; Korsten, Peter; Vedder, Oscar; Kingma, Sjouke A.; Komdeur, Jan; Beissinger, Steven R.; Alba, Liliana D’; Graves, J.

    Female birds can influence offspring fitness by varying the relative quantities of egg components they deposit within and between clutches. Antimicrobial proteins (lysozyme, ovotransferrin, and avidin) are significant components of the avian albumen and likely aid in defense of embryos from

  13. The influence of competition between foragers on clutch size decisions in an insect parasitoid with scramble larval competition

    NARCIS (Netherlands)

    Visser, M.E.

    1996-01-01

    The effect of competition between ovipositing females on their clutch size decisions is studied in animals that lay their eggs in discrete units of larval food (hosts). In such species the effect of competition depends on the form of the larval competition within such units. In insect parasitoids, t

  14. The influence of competition between foragers on clutch size decisions in an insect parasitoid with scramble larval competition

    NARCIS (Netherlands)

    Visser, M.E.

    1996-01-01

    The effect of competition between ovipositing females on their clutch size decisions is studied in animals that lay their eggs in discrete units of larval food (hosts). In such species the effect of competition depends on the form of the larval competition within such units. In insect parasitoids,

  15. Special Relativistic Hydrodynamics with Gravitation

    Science.gov (United States)

    Hwang, Jai-chan; Noh, Hyerim

    2016-12-01

    Special relativistic hydrodynamics with weak gravity has hitherto been unknown in the literature. Whether such an asymmetric combination is possible has been unclear. Here, the hydrodynamic equations with Poisson-type gravity, considering fully relativistic velocity and pressure under the weak gravity and the action-at-a-distance limit, are consistently derived from Einstein’s theory of general relativity. An analysis is made in the maximal slicing, where the Poisson’s equation becomes much simpler than our previous study in the zero-shear gauge. Also presented is the hydrodynamic equations in the first post-Newtonian approximation, now under the general hypersurface condition. Our formulation includes the anisotropic stress.

  16. Special relativistic hydrodynamics with gravitation

    CERN Document Server

    Hwang, Jai-chan

    2016-01-01

    The special relativistic hydrodynamics with weak gravity is hitherto unknown in the literature. Whether such an asymmetric combination is possible was unclear. Here, the hydrodynamic equations with Poisson-type gravity considering fully relativistic velocity and pressure under the weak gravity and the action-at-a-distance limit are consistently derived from Einstein's general relativity. Analysis is made in the maximal slicing where the Poisson's equation becomes much simpler than our previous study in the zero-shear gauge. Also presented is the hydrodynamic equations in the first post-Newtonian approximation, now under the {\\it general} hypersurface condition. Our formulation includes the anisotropic stress.

  17. Bosonization and quantum hydrodynamics

    Indian Academy of Sciences (India)

    Girish S Setlur

    2006-03-01

    It is shown that it is possible to bosonize fermions in any number of dimensions using the hydrodynamic variables, namely the velocity potential and density. The slow part of the Fermi field is defined irrespective of dimensionality and the commutators of this field with currents and densities are exponentiated using the velocity potential as conjugate to the density. An action in terms of these canonical bosonic variables is proposed that reproduces the correct current and density correlations. This formalism in one dimension is shown to be equivalent to the Tomonaga-Luttinger approach as it leads to the same propagator and exponents. We compute the one-particle properties of a spinless homogeneous Fermi system in two spatial dimensions with long-range gauge interactions and highlight the metal-insulator transition in the system. A general formula for the generating function of density correlations is derived that is valid beyond the random phase approximation. Finally, we write down a formula for the annihilation operator in momentum space directly in terms of number conserving products of Fermi fields.

  18. Engineering Hydrodynamic AUV Hulls

    Science.gov (United States)

    Allen, J.

    2016-12-01

    AUV stands for autonomous underwater vehicle. AUVs are used in oceanography and are similar to gliders. MBARIs AUVs as well as other AUVs map the ocean floor which is very important. They also measure physical characteristics of the water, such as temperature and salinity. My science fair project for 4th grade was a STEM activity in which I built and tested 3 different AUV bodies. I wanted to find out which design was the most hydrodynamic. I tested three different lengths of AUV hulls to see which AUV would glide the farthest. The first was 6 inches. The second was 12 inches and the third was 18 inches. I used clay for the nosecone and cut a ruler into two and made it the fin. Each AUV used the same nosecone and fin. I tested all three designs in a pool. I used biomimicry to create my hypothesis. When I was researching I found that long slim animals swim fastest. So, my hypothesis is the longer AUV will glide farthest. In the end I was right. The longer AUV did glide the farthest.

  19. Electro-hydrodynamics near Hydrophobic Surfaces

    CERN Document Server

    Maduar, S R; Lobaskin, V; Vinogradova, O I

    2014-01-01

    We show that the dynamics of the electrostatic diffuse layer at the slippery hydrophobic surface depends strongly on the mobility of surface charges. For a hydrophobic surface with immobile charges the fluid transport is considerably amplified by the existence of a hydrodynamic slippage. In contrast, near the hydrophobic surface with mobile adsorbed charges it is also controlled by an additional electric force, which increases the shear stress at the slipping interface. To account for this we formulate electro-hydrodynamic boundary conditions at the slipping interface, which are applied to quantify electro-osmotic flows. Our theoretical predictions are fully supported by dissipative particle dynamics simulations with explicit charges. These results lead to a new general concept of zeta-potential of hydrophobic surfaces.

  20. Filling the gaps of dinosaur eggshell phylogeny: Late Jurassic Theropod clutch with embryos from Portugal.

    Science.gov (United States)

    Araújo, Ricardo; Castanhinha, Rui; Martins, Rui M S; Mateus, Octávio; Hendrickx, Christophe; Beckmann, F; Schell, N; Alves, L C

    2013-01-01

    The non-avian saurischians that have associated eggshells and embryos are represented only by the sauropodomorph Massospondylus and Coelurosauria (derived theropods), thus missing the basal theropod representatives. We report a dinosaur clutch containing several crushed eggs and embryonic material ascribed to the megalosaurid theropod Torvosaurus. It represents the first associated eggshells and embryos of megalosauroids, thus filling an important phylogenetic gap between two distantly related groups of saurischians. These fossils represent the only unequivocal basal theropod embryos found to date. The assemblage was found in early Tithonian fluvial overbank deposits of the Lourinhã Formation in West Portugal. The morphological, microstructural and chemical characterization results of the eggshell fragments indicate very mild diagenesis. Furthermore, these fossils allow unambiguous association of basal theropod osteology with a specific and unique new eggshell morphology.

  1. A force transmission system based on a tulip-shaped electrostatic clutch for haptic display devices

    Science.gov (United States)

    Sasaki, Hikaru; Shikida, Mitsuhiro; Sato, Kazuo

    2006-12-01

    This paper describes a novel type of force transmission system for haptic display devices. The system consists of an array of end-effecter elements, a force/displacement transmitter and a single actuator producing a large force/displacement. It has tulip-shaped electrostatic clutch devices to distribute the force/displacement from the actuator among the individual end effecters. The specifications of three components were determined to stimulate touched human fingers. The components were fabricated by using micro-electromechanical systems and conventional machining technologies, and finally they were assembled by hand. The performance of the assembled transmission system was experimentally examined and it was confirmed that each projection in the arrayed end effecters could be moved individually. The actuator in a system whose total size was only 3.0 cm × 3.0 cm × 4.0 cm produced a 600 mN force and displaced individual array elements by 18 µm.

  2. Effect of one-way clutch on the nonlinear vibration of belt-drive systems with a continuous belt model

    Science.gov (United States)

    Ding, Hu; Zu, Jean W.

    2013-11-01

    This study focuses on the nonlinear steady-state response of a belt-drive system with a one-way clutch. A dynamic model is established to describe the rotations of the driving pulley, the driven pulley, and the accessory shaft. Moreover, the model considers the transverse vibration of the translating belt spans for the first time in belt-drive systems coupled with a one-way clutch. The excitation of the belt-drive system is derived from periodic fluctuation of the driving pulley. In automotive systems, this kind of fluctuation is induced by the engine firing harmonic pulsations. The derived coupled discrete-continuous nonlinear equations consist of integro-partial-differential equations and piece-wise ordinary differential equations. Using the Galerkin truncation, a set of nonlinear ordinary differential equations is obtained from the integro-partial-differential equations. Applying the Runge-Kutta time discretization, the time histories of the dynamic response are numerically solved for the driven pulley and the accessory shaft and the translating belt spans. The resonance areas of the coupled belt-drive system are determined using the frequency sweep. The effects of the one-way clutch on the belt-drive system are studied by comparing the frequency-response curves of the translating belt with and without one-way clutch device. Furthermore, the results of 2-term and 4-term Galerkin truncation are compared to determine the numerical convergence. Moreover, parametric studies are conducted to understand the effects of the system parameters on the nonlinear steady-state response. It is concluded that one-way clutch not only decreases the resonance amplitude of the driven pulley and shaft's rotational vibration, but also reduces the resonance region of the belt's transverse vibration.

  3. Is there a weekend bias in clutch-initiation dates from citizen science? Implications for studies of avian breeding phenology

    Science.gov (United States)

    Cooper, Caren B.

    2014-09-01

    Accurate phenology data, such as the timing of migration and reproduction, is important for understanding how climate change influences birds. Given contradictory findings among localized studies regarding mismatches in timing of reproduction and peak food supply, broader-scale information is needed to understand how whole species respond to environmental change. Citizen science—participation of the public in genuine research—increases the geographic scale of research. Recent studies, however, showed weekend bias in reported first-arrival dates for migratory songbirds in databases created by citizen-science projects. I investigated whether weekend bias existed for clutch-initiation dates for common species in US citizen-science projects. Participants visited nests on Saturdays more frequently than other days. When participants visited nests during the laying stage, biased timing of visits did not translate into bias in estimated clutch-initiation dates, based on back-dating with the assumption of one egg laid per day. Participants, however, only visited nests during the laying stage for 25 % of attempts of cup-nesting species and 58 % of attempts in nest boxes. In some years, in lieu of visit data, participants provided their own estimates of clutch-initiation dates and were asked "did you visit the nest during the laying period?" Those participants who answered the question provided estimates of clutch-initiation dates with no day-of-week bias, irrespective of their answer. Those who did not answer the question were more likely to estimate clutch initiation on a Saturday. Data from citizen-science projects are useful in phenological studies when temporal biases can be checked and corrected through protocols and/or analytical methods.

  4. Reciprocal relations in dissipationless hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Melnikovsky, L. A., E-mail: leva@kapitza.ras.ru [Russian Academy of Sciences, Kapitza Institute for Physical Problems (Russian Federation)

    2014-12-15

    Hidden symmetry in dissipationless terms of arbitrary hydrodynamics equations is recognized. We demonstrate that all fluxes are generated by a single function and derive conventional Euler equations using the proposed formalism.

  5. Relativistic Hydrodynamics on Graphic Cards

    CERN Document Server

    Gerhard, Jochen; Bleicher, Marcus

    2012-01-01

    We show how to accelerate relativistic hydrodynamics simulations using graphic cards (graphic processing units, GPUs). These improvements are of highest relevance e.g. to the field of high-energetic nucleus-nucleus collisions at RHIC and LHC where (ideal and dissipative) relativistic hydrodynamics is used to calculate the evolution of hot and dense QCD matter. The results reported here are based on the Sharp And Smooth Transport Algorithm (SHASTA), which is employed in many hydrodynamical models and hybrid simulation packages, e.g. the Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). We have redesigned the SHASTA using the OpenCL computing framework to work on accelerators like graphic processing units (GPUs) as well as on multi-core processors. With the redesign of the algorithm the hydrodynamic calculations have been accelerated by a factor 160 allowing for event-by-event calculations and better statistics in hybrid calculations.

  6. Gradient expansion for anisotropic hydrodynamics

    Science.gov (United States)

    Florkowski, Wojciech; Ryblewski, Radoslaw; Spaliński, Michał

    2016-12-01

    We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of nonhydrodynamic modes.

  7. Modelling and simulation of a dual-clutch transmission vehicle to analyse the effect of pump selection on fuel economy

    Science.gov (United States)

    Ahlawat, R.; Fathy, H. K.; Lee, B.; Stein, J. L.; Jung, D.

    2010-07-01

    Positive displacement pumps are used in automotive transmissions to provide pressurised fluid to various hydraulic components in the transmission and also lubricate the mechanical components. The output flow of these pumps increases with pump/transmission speed, almost linearly, but the transmission flow requirements often saturate at higher speeds, resulting in excess flow capacity that must be wasted by allowing it to drain back to the sump. This represents a parasitic loss in the transmission leading to a loss in fuel economy. To overcome this issue, variable displacement pumps have been used in the transmission, where the output flow can be reduced by controlling the displacement of the pump. The use of these pumps in automatic transmissions has resulted in better fuel economy as compared with some types of fixed displacement pumps. However, the literature does not fully explore the benefits of variable displacement pumps to a specific type of transmission namely, dual-clutch transmission (DCT), which has different pressure and flow requirements from an epicyclic gear train. This paper presents an analysis of the effect of pump selection on fuel economy in a five-speed DCT of a commercial vehicle. Models of the engine, transmission, and vehicle are developed along with the models of two different types of pumps: a fixed displacement gerotor pump and a variable displacement vane pump. The models are then parameterised using experimental data, and the fuel economy of the vehicle is simulated on a standard driving cycle. The results suggest that the fuel economy benefit obtained by the use of the variable displacement pump in DCTs is comparable to the benefit previously shown for these pumps in automatic transmissions.

  8. Ecology and reproductive patterns of the agamid lizard Japalura swinhonis on an east Asian island, with comments on the small clutch sizes of island lizards.

    Science.gov (United States)

    Huang, Wen-San

    2007-02-01

    I describe the habitat use, diet, and the male and female reproductive cycles of Japalura swinhonis, an oviparous agamid lizard inhabiting Orchid Island, a tropical island off the southeastern coast of Taiwan. Ninety percent of lizards (n=126) were observed on tree trunks or at the forest edge. The diet of J. swinhonis on Orchid Island consisted mostly of hymenopterans (53.33%) and orthopterans (16.67%). The mean snout-vent length (SVL) of adult males was 74.58 (n=89) and that of females was 69.31 (n=37) mm. Females exhibited a long vitellogenic period from November to February, with parturition occurring from March to October. The onset of vitellogenesis did not correlate with the mass of the female fat bodies. Females produced two to five eggs per clutch, and clutch size was not correlated with SVL. Two clutches were recorded during a single year in some individuals. Clutch size in J. swinhonis was compared with that in other Japalura species. Clutch sizes of Japalura species are larger in mainland China than on insular Taiwan. Clutch size is also mainly affected by environmental constraints, and smaller clutch sizes are probably affected by predators on Orchid Island.

  9. An introduction to astrophysical hydrodynamics

    CERN Document Server

    Shore, Steven N

    1992-01-01

    This book is an introduction to astrophysical hydrodynamics for both astronomy and physics students. It provides a comprehensive and unified view of the general problems associated with fluids in a cosmic context, with a discussion of fluid dynamics and plasma physics. It is the only book on hydrodynamics that addresses the astrophysical context. Researchers and students will find this work to be an exceptional reference. Contents include chapters on irrotational and rotational flows, turbulence, magnetohydrodynamics, and instabilities.

  10. Slurry bubble column hydrodynamics

    Science.gov (United States)

    Rados, Novica

    Slurry bubble column reactors are presently used for a wide range of reactions in both chemical and biochemical industry. The successful design and scale up of slurry bubble column reactors require a complete understanding of multiphase fluid dynamics, i.e. phase mixing, heat and mass transport characteristics. The primary objective of this thesis is to improve presently limited understanding of the gas-liquid-solid slurry bubble column hydrodynamics. The effect of superficial gas velocity (8 to 45 cm/s), pressure (0.1 to 1.0 MPa) and solids loading (20 and 35 wt.%) on the time-averaged solids velocity and turbulent parameter profiles has been studied using Computer Automated Radioactive Particle Tracking (CARPT). To accomplish this, CARPT technique has been significantly improved for the measurements in highly attenuating systems, such as high pressure, high solids loading stainless steel slurry bubble column. At a similar set of operational conditions time-averaged gas and solids holdup profiles have been evaluated using the developed Computed Tomography (CT)/Overall gas holdup procedure. This procedure is based on the combination of the CT scans and the overall gas holdup measurements. The procedure assumes constant solids loading in the radial direction and axially invariant cross-sectionally averaged gas holdup. The obtained experimental holdup, velocity and turbulent parameters data are correlated and compared with the existing low superficial gas velocities and atmospheric pressure CARPT/CT gas-liquid and gas-liquid-solid slurry data. The obtained solids axial velocity radial profiles are compared with the predictions of the one dimensional (1-D) liquid/slurry recirculation phenomenological model. The obtained solids loading axial profiles are compared with the predictions of the Sedimentation and Dispersion Model (SDM). The overall gas holdup values, gas holdup radial profiles, solids loading axial profiles, solids axial velocity radial profiles and solids

  11. Morphologic and hydrodynamic controls on the occurrence of tidal bundles in an open-coast macrotidal environment, northern Gyeonggi Bay, west coast of Korea

    Science.gov (United States)

    Choi, Kyungsik; Kim, Do Hyeong

    2016-06-01

    Tidal dunes with well-defined rhythmic tidal bundles are documented from the lower intertidal zone of an open-coast macrotidal environment in Gyeonggi Bay, Korea. Based on combined morphologic, sedimentologic and hydrodynamic datasets, this study aims to characterize the factors that govern the temporal and spatial variability of tidal bundles in a non-barred, unconfined macrotidal environment. The tidal dunes are flood-asymmetric and of longer wavelength (10-20 m) with small ebb caps on the upper bank, and symmetric to slightly ebb-asymmetric and of shorter wavelength (5-10 m) with larger ebb caps on the lower bank. The upper-bank dunes are characterized by more steeply dipping flood-directed planar cross-beds and thinner mud drapes than the lower-bank dunes. Each tidal bundle consists of a single mud drape that is stratified to cross-stratified, rich in silt and very fine sand. It overlies ebb-directed ripples and represents dynamic mud deposition during the ebb tidal phase. The presence of strong rotary currents (up to 0.25 m/s) and low suspended-sediment concentration of flood currents prevent deposition of mud drapes during the high-tide slack-water period. The distinct asymmetry in the water elevation at which the velocity peaks during the ebb and flood phases results in the preferential preservation of flood-directed cross-beds in the lower intertidal zone, where the ebb current - although stronger than the flood currents - is of shorter duration and hence unable to reverse the dune profile. The pronounced time-velocity asymmetry at the higher elevation combined with the distinct velocity peak asymmetry leads to a better preservation of hierarchical tidal cycles in the upper-bank dunes. The present study suggests that the persistent occurrence of single, stratified to cross-stratified mud drapes, which reflect dynamic mud deposition during the ebb phase, and the dominance of flood-directed cross-beds are diagnostic features of tidal bundles in the intertidal

  12. The hydrodynamics of colloidal gelation.

    Science.gov (United States)

    Varga, Zsigmond; Wang, Gang; Swan, James

    2015-12-14

    Colloidal gels are formed during arrested phase separation. Sub-micron, mutually attractive particles aggregate to form a system spanning network with high interfacial area, far from equilibrium. Models for microstructural evolution during colloidal gelation have often struggled to match experimental results with long standing questions regarding the role of hydrodynamic interactions. In nearly all models, these interactions are neglected entirely. In the present work, we report simulations of gelation with and without hydrodynamic interactions between the suspended particles executed in HOOMD-blue. The disparities between these simulations are striking and mirror the experimental-theoretical mismatch in the literature. The hydrodynamic simulations agree with experimental observations, however. We explore a simple model of the competing transport processes in gelation that anticipates these disparities, and conclude that hydrodynamic forces are essential. Near the gel boundary, there exists a competition between compaction of individual aggregates which suppresses gelation and coagulation of aggregates which enhances it. The time scale for compaction is mildly slowed by hydrodynamic interactions, while the time scale for coagulation is greatly accelerated. This enhancement to coagulation leads to a shift in the gel boundary to lower strengths of attraction and lower particle concentrations when compared to models that neglect hydrodynamic interactions. Away from the gel boundary, differences in the nearest neighbor distribution and fractal dimension persist within gels produced by both simulation methods. This result necessitates a fundamental rethinking of how dynamic, discrete element models for gelation kinetics are developed as well as how collective hydrodynamic interactions influence the arrest of attractive colloidal dispersions.

  13. Recent progress in anisotropic hydrodynamics

    CERN Document Server

    Strickland, Michael

    2016-01-01

    The quark-gluon plasma created in a relativistic heavy-ion collisions possesses a sizable pressure anisotropy in the local rest frame at very early times after the initial nuclear impact and this anisotropy only slowly relaxes as the system evolves. In a kinetic theory picture, this translates into the existence of sizable momentum-space anisotropies in the underlying partonic distribution functions, . In such cases, it is better to reorganize the hydrodynamical expansion by taking into account momentum-space anisotropies at leading-order in the expansion instead of as a perturbative correction to an isotropic distribution. The resulting anisotropic hydrodynamics framework has been shown to more accurately describe the dynamics of rapidly expanding systems such as the quark-gluon plasma. In this proceedings contribution, I review the basic ideas of anisotropic hydrodynamics, recent progress, and present a few preliminary phenomenological predictions for identified particle spectra and elliptic flow.

  14. Numerical Hydrodynamics in Special Relativity

    Directory of Open Access Journals (Sweden)

    Martí José Maria

    2003-01-01

    Full Text Available This review is concerned with a discussion of numerical methods for the solution of the equations of special relativistic hydrodynamics (SRHD. Particular emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods in SRHD. Results of a set of demanding test bench simulations obtained with different numerical SRHD methods are compared. Three applications (astrophysical jets, gamma-ray bursts and heavy ion collisions of relativistic flows are discussed. An evaluation of various SRHD methods is presented, and future developments in SRHD are analyzed involving extension to general relativistic hydrodynamics and relativistic magneto-hydrodynamics. The review further provides FORTRAN programs to compute the exact solution of a 1D relativistic Riemann problem with zero and nonzero tangential velocities, and to simulate 1D relativistic flows in Cartesian Eulerian coordinates using the exact SRHD Riemann solver and PPM reconstruction.

  15. Comparative hydrodynamics of bacterial polymorphism

    CERN Document Server

    Spagnolie, Saverio E

    2011-01-01

    Most bacteria swim through fluids by rotating helical flagella which can take one of twelve distinct polymorphic shapes. The most common helical waveform is the "normal" form, used during forward swimming runs. To shed light on the prevalence of the normal form in locomotion, we gather all available experimental measurements of the various polymorphic forms and compute their intrinsic hydrodynamic efficiencies. The normal helical form is found to be the most hydrodynamically efficient of the twelve polymorphic forms by a significant margin - a conclusion valid for both the peritrichous and polar flagellar families, and robust to a change in the effective flagellum diameter or length. The hydrodynamic optimality of the normal polymorph suggests that, although energetic costs of locomotion are small for bacteria, fluid mechanical forces may have played a significant role in the evolution of the flagellum.

  16. Quantum Plasmas An Hydrodynamic Approach

    CERN Document Server

    Haas, Fernando

    2011-01-01

    This book provides an overview of the basic concepts and new methods in the emerging scientific area known as quantum plasmas. In the near future, quantum effects in plasmas will be unavoidable, particularly in high density scenarios such as those in the next-generation intense laser-solid density plasma experiment or in compact astrophysics objects. Currently, plasmas are in the forefront of many intriguing questions around the transition from microscopic to macroscopic modeling of charged particle systems. Quantum Plasmas: an Hydrodynamic Approach is devoted to the quantum hydrodynamic model paradigm, which, unlike straight quantum kinetic theory, is much more amenable to investigate the nonlinear realm of quantum plasmas. The reader will have a step-by-step construction of the quantum hydrodynamic method applied to plasmas. The book is intended for specialists in classical plasma physics interested in methods of quantum plasma theory, as well as scientists interested in common aspects of two major areas of...

  17. HYDRODYNAMIC INTERACTIONS BETWEEN TWO BODIES

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    On the basis of model tests, potential flow theory, and viscous Computational Fluid Dynamics (CFD) method, the hydrodynamic interactions between two underwater bodies were investigated to determine the influencing factors, changing rule, interaction mechanism, and appropriate methods describing them. Some special phenomena were discovered in two series of near-wall interaction experiments. The mathematical model and predicting methods were presented for interacting forces near wall, and the calculation results agreed well with the experimental ones. From the comparisons among numerical results with respect to nonviscosity, numerical results with respect to viscosity, and measured results, data on the influence of viscosity on hydrodynamic interactions were obtained. For hydrodynamic interaction related to multi-body unsteady motions with six degrees of freedom that is difficult to simulate in tests, numerical predictions of unsteady interacting forces were given.

  18. Hydrodynamic shocks in microroller suspensions

    Science.gov (United States)

    Delmotte, Blaise; Driscoll, Michelle; Chaikin, Paul; Donev, Aleksandar

    2017-09-01

    We combine experiments, large-scale simulations, and continuum models to study the emergence of coherent structures in a suspension of magnetically driven microrollers sedimented near a floor. Collective hydrodynamic effects are predominant in this system, leading to strong density-velocity coupling. We characterize a uniform suspension and show that density waves propagate freely in all directions in a dispersive fashion. When sharp density gradients are introduced in the suspension, we observe the formation of a shock. Unlike Burgers' shocklike structures observed in other active and driven confined hydrodynamic systems, the shock front in our system has a well-defined finite width and moves rapidly compared to the mean suspension velocity. We introduce a continuum model demonstrating that the finite width of the front is due to far-field nonlocal hydrodynamic interactions and governed by a geometric parameter, the average particle height above the floor.

  19. Numerical Hydrodynamics in Special Relativity.

    Science.gov (United States)

    Martí, José Maria; Müller, Ewald

    2003-01-01

    This review is concerned with a discussion of numerical methods for the solution of the equations of special relativistic hydrodynamics (SRHD). Particular emphasis is put on a comprehensive review of the application of high-resolution shock-capturing methods in SRHD. Results of a set of demanding test bench simulations obtained with different numerical SRHD methods are compared. Three applications (astrophysical jets, gamma-ray bursts and heavy ion collisions) of relativistic flows are discussed. An evaluation of various SRHD methods is presented, and future developments in SRHD are analyzed involving extension to general relativistic hydrodynamics and relativistic magneto-hydrodynamics. The review further provides FORTRAN programs to compute the exact solution of a 1D relativistic Riemann problem with zero and nonzero tangential velocities, and to simulate 1D relativistic flows in Cartesian Eulerian coordinates using the exact SRHD Riemann solver and PPM reconstruction.

  20. Comprehensive design and optimization of an electric vehicle powertrain equipped with a two-speed dual-clutch transmission

    Directory of Open Access Journals (Sweden)

    Yu Wang

    2017-01-01

    Full Text Available This article develops a systematic model to study electric vehicle powertrain system efficiency by combining a detailed model of two-speed dual-clutch transmission system efficiency losses with an electric vehicle powertrain system model. In this model, the design factors including selection of the electric machine, gear ratios’ change, multi-plate wet clutch design, and gear shift schedule design are considered. Meanwhile, the application of detailed model for drag torque losses in the gearbox is discussed. Furthermore, the proposed model, developed with the MATLAB/Simulink platform, is applied to optimize/maximize the efficiency of the electric vehicle powertrain system using genetic algorithms. The optimization results demonstrate that the optimal results are different between simulations via New Europe Drive Cycle and Urban Dynamometer Driving Schedule, and comprehensive design and optimization of the powertrain system are necessary.

  1. On the correlation between the shape of eggs and their quantity in the clutches of Grass snake Natrix natrix (Linnaeus, 1758

    Directory of Open Access Journals (Sweden)

    Klenina Anastasia Alexandrovna

    2014-12-01

    Full Text Available Positive correlation between the quantity of eggs in clutch of the grass snake and their diameter as well as negative correlation between quantity of eggs and their length and between the diameter of eggs and their length was revealed. It was determined that the more the quantity of eggs in the clutch, the more they are rounded, that was explained by their deformation in accumulating in the oviduct.

  2. Hydrodynamics of soft active matter

    Science.gov (United States)

    Marchetti, M. C.; Joanny, J. F.; Ramaswamy, S.; Liverpool, T. B.; Prost, J.; Rao, Madan; Simha, R. Aditi

    2013-07-01

    This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: biofilaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semimicroscopic to phenomenological. In particular, first considered are “dry” systems, defined as those where momentum is not conserved due to friction with a substrate or an embedding porous medium. The differences and similarities between two types of orientationally ordered states, the nematic and the polar, are clarified. Next, the active hydrodynamics of suspensions or “wet” systems is discussed and the relation with and difference from the dry case, as well as various large-scale instabilities of these nonequilibrium states of matter, are highlighted. Further highlighted are various large-scale instabilities of these nonequilibrium states of matter. Various semimicroscopic derivations of the continuum theory are discussed and connected, highlighting the unifying and generic nature of the continuum model. Throughout the review, the experimental relevance of these theories for describing bacterial swarms and suspensions, the cytoskeleton of living cells, and vibrated granular material is discussed. Promising extensions toward greater realism in specific contexts from cell biology to animal behavior are suggested, and remarks are given on some exotic active-matter analogs. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized.

  3. Anisotropic hydrodynamics: Motivation and methodology

    Energy Technology Data Exchange (ETDEWEB)

    Strickland, Michael

    2014-06-15

    In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can be made around an anisotropic background, and the resulting dynamical framework has been dubbed “anisotropic hydrodynamics”. I also discuss expectations for the degree of momentum-space anisotropy of the quark–gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches.

  4. Hydrodynamics of oceans and atmospheres

    CERN Document Server

    Eckart, Carl

    1960-01-01

    Hydrodynamics of Oceans and Atmospheres is a systematic account of the hydrodynamics of oceans and atmospheres. Topics covered range from the thermodynamic functions of an ideal gas and the thermodynamic coefficients for water to steady motions, the isothermal atmosphere, the thermocline, and the thermosphere. Perturbation equations, field equations, residual equations, and a general theory of rays are also presented. This book is comprised of 17 chapters and begins with an introduction to the basic equations and their solutions, with the aim of illustrating the laws of dynamics. The nonlinear

  5. Abnormal pressures as hydrodynamic phenomena

    Science.gov (United States)

    Neuzil, C.E.

    1995-01-01

    So-called abnormal pressures, subsurface fluid pressures significantly higher or lower than hydrostatic, have excited speculation about their origin since subsurface exploration first encountered them. Two distinct conceptual models for abnormal pressures have gained currency among earth scientists. The static model sees abnormal pressures generally as relict features preserved by a virtual absence of fluid flow over geologic time. The hydrodynamic model instead envisions abnormal pressures as phenomena in which flow usually plays an important role. This paper develops the theoretical framework for abnormal pressures as hydrodynamic phenomena, shows that it explains the manifold occurrences of abnormal pressures, and examines the implications of this approach. -from Author

  6. A clutch integrated electric motor; Le moteur electrique s'integre a l'embrayage

    Energy Technology Data Exchange (ETDEWEB)

    Dumas, A.

    2006-01-01

    The German car-fitter Luk has developed an alternator-starter directly integrated inside the gear-box. This solution is based on the double-clutch gear-box principle. The alternator-motor allows to use the stop and start function but also the energy recovery and battery charging function during braking. This system allows to save between 14 and 18% of fuel and 10% more in urban use. Short paper. (J.S.)

  7. Brood reduction via intra-clutch variation in testosterone--an experimental test in the great tit.

    Directory of Open Access Journals (Sweden)

    Katarzyna Podlas

    Full Text Available In birds, yolk androgen concentrations in eggs can increase or decrease over the laying sequence and common hypotheses hold that this serves to favour the competitive ability of either first- or last-hatched chicks depending on the prevailing conditions, and thus promote brood reduction or maintenance of original brood size respectively. Intra-clutch variation of testosterone can shift relative competitive ability of siblings and hence competitive dynamics. In a natural population of great tits, we experimentally investigated the effects and function of maternal testosterone on offspring phenotype in relation to the laying position of the egg in a context of hatching asynchrony. To this end, we created three types of clutches where either the first three or the last three eggs of a clutch were injected with testosterone (T dissolved in sesame oil, and the remaining eggs with sesame oil only, or where all eggs of a clutch were injected with sesame oil. Increased levels of yolk T in the last-laid eggs resulted in the last-hatched chicks being significantly lighter and smaller than their siblings, while increased levels of T in the first-laid eggs had no direct effect on the first-hatched chicks, but an indirect negative effect on their siblings. Our results suggest that females can potentially adjust offspring phenotype by modulating, over the laying sequence, the amounts of T deposited in the eggs. These results are in contradiction, however, with current hypotheses and previous findings, which suggest that under good conditions higher levels of maternally derived T in the last-laid eggs should mitigate the negative effects of hatching asynchrony.

  8. Relationships of maternal body size and morphology with egg and clutch size in the diamondback terrapin, Malaclemys terrapin (Testudines: Emydidae)

    Science.gov (United States)

    Kern, Maximilian M.; Guzy, Jacquelyn C.; Lovich, Jeffrey E.; Gibbons, J. Whitfield; Dorcas, Michael E.

    2016-01-01

    Because resources are finite, female animals face trade-offs between the size and number of offspring they are able to produce during a single reproductive event. Optimal egg size (OES) theory predicts that any increase in resources allocated to reproduction should increase clutch size with minimal effects on egg size. Variations of OES predict that egg size should be optimized, although not necessarily constant across a population, because optimality is contingent on maternal phenotypes, such as body size and morphology, and recent environmental conditions. We examined the relationships among body size variables (pelvic aperture width, caudal gap height, and plastron length), clutch size, and egg width of diamondback terrapins from separate but proximate populations at Kiawah Island and Edisto Island, South Carolina. We found that terrapins do not meet some of the predictions of OES theory. Both populations exhibited greater variation in egg size among clutches than within, suggesting an absence of optimization except as it may relate to phenotype/habitat matching. We found that egg size appeared to be constrained by more than just pelvic aperture width in Kiawah terrapins but not in the Edisto population. Terrapins at Edisto appeared to exhibit osteokinesis in the caudal region of their shells, which may aid in the oviposition of large eggs.

  9. A Study of Structural Stress Technique for Fracture Prediction of an Auto-Mobile Clutch Snap-Ring

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ju Hee [Korea Military Academy, Seoul (Korea, Republic of); Myeong, Man Sik [Samsung Display, Suwon (Korea, Republic of); Oh, Chang Sik [KINS, Daejeon (Korea, Republic of); Kim, Yun Jae [Korea Univ., Sejong (Korea, Republic of)

    2016-02-15

    The endurance reliability assessment of a highly complex mechanism is generally predicted by the fatigue life based on simple stress analysis. This study discusses various fatigue life assessment techniques for an automobile clutch snap ring. Finite element analyses were conducted to determine the structural stress on the snap ring. Structural stress that is insensitive in regards to the mesh size and type definition is presented in this study. The structural stress definition is consistent with elementary structural mechanics theory and provides an effective measure of a stress state that pertains to fatigue behavior of welded joints in the form of both membrane and bending components. Numerical procedures for both solid models and shell or plate element models are presented to demonstrate the mesh-size insensitivity when extracting the structural stress parameters. Conventional finite element models can be used with the structural stress calculations as a post-processing procedure. The two major implications from this research were: (a) structural stresses pertaining to fatigue behavior can be consistently calculated in a mesh-insensitive manner regardless of the types of finite element models; and (b) by comparing with the clutch snap-ring fatigue test data, we should predict the fatigue fractures of an automobile clutch snap ring using this method.

  10. 离合器从动盘平行度检测系统%Clutch Driven Plate Parallelism Detection System

    Institute of Scientific and Technical Information of China (English)

    于伟; 李国欣

    2014-01-01

    Clutch is an indispensable component in automobile mechanical transmission, the clutch driven plate as an important part, its quality directly affects whether the clutch can work normally. So, its parallelism needs measuring after driven plate assembly. From the viewpoint of engineering practice, this paper discusses the method of testing the platen parallelism by using the displacement sensor and the method of data processing, develops the experiment test system with industrial computer as the core and verifies the feasibility and testing accuracy of the testing method through the system.%离合器是汽车机械传动中不可缺少的组成部件,作为离合器重要组成部分的从动盘,其质量好坏直接影响离合器能否正常工作。所以,在从动盘总成之后需要进行平行度测量。本文从工程实践的角度出发,探讨了采用位移传感器对从动盘平行度进行检测的方法以及数据处理的方法,开发了以工控机为核心的实验检测系统,并通过该系统验证了检测方法的可行性和检测精度。

  11. A novel design procedure for tractor clutch fingers by using optimization and response surface methods

    Energy Technology Data Exchange (ETDEWEB)

    Dogan, Oguz; Karpat, Fatih; Yuce, Celalettin; Kaya, Necmettin; Yavuz, Nurettin [Uludag University, Gorukle (Turkmenistan); Sen, Hasan [Valeo A. S., Bursa (Turkmenistan)

    2016-06-15

    This paper presents a methodology for re-designing a failed tractor transmission component subjected to cyclic loading. Unlike other vehicles, tractors cope with tough working conditions. Thus, it is necessary to re-design components by using modern optimization techniques. To extend their service life, we present a design methodology for a failed tractor clutch power take-off finger. The finger was completely re-designed using topology and shape optimization approach. Stress-life based fatigue analyses were performed. Shape optimization and response surface methodology were conducted to obtain optimum dimensions of the finger. Two design parameters were selected for the design of experiment method and 15 cases were analyzed. By using design of the experiment method, three responses were obtained: Maximum stresses, mass, and displacement depending on the selected the design parameters. After solving the optimization problem, we achieved a maximum stress and mass reduction of 14% and 6%, respectively. The stiffness was improved up to 31.6% compared to the initial design.

  12. Assessment of circumferential cracks in hypereutectic Al-Si clutch housings

    Directory of Open Access Journals (Sweden)

    M. Haghshenas

    2017-04-01

    Full Text Available As in situ natural composites with silicon phase acting as the reinforcing phase, Al-Si alloys are among most commonly used aluminum alloys in automotive applications (i.e. engine component. Silicon contributes to the strength of Al-Si alloys through load transfer from the Al matrix to the hard (rigid Si phase in the microstructure (load-carrying capacity. Casting parameters (i.e. solidification rate, elemental segregation, secondary dendrite spacing… as well as the size and distribution of the microstructural constituents in Al-Si alloys (i.e. morphology of Si particles, intermetallic compounds, secondary dendrite spacing contribute directly to the mechanical response and failure (or fracture behavior of the alloy within the service. In hyper-eutectic Al-Si alloys (i.e. B390.0, distribution of coarse pre-eutectic Si particle mainly contribute to stress concentration, crack initiation and propagation during the actual service condition. In the present paper, the parameters contribution to the formation of the circumferential cracks in clutch housings made of die cast hyper-eutectics B390.0 Al-Si alloys are assessed through optical microscopy and scanning electron microscopy. Casting variable, cooling rate, their effect on the cracks as well some of the possible causes are also discussed in detail.

  13. Failure analysis of wear of main clutch separating ring of heavy vehicles

    Institute of Scientific and Technical Information of China (English)

    SUN Xiao-long; LI Xiao-yan; ZHU You-li; XU Bin-shi

    2005-01-01

    The severe wear of separating ring is considered to be a main reason which leads to the improper declutch of the main clutch of heavy vehicles. The wear mechanism of the separating ring is not well understood. Scanning electron microscopy and transmission electron microscopy were employed to analyze the surface features and dislocation characteristics of the separating ring. The typical features of furrows and rolled tongue-like metal were found on the surface of separating ring by scanning electron microscopy observation, which can be considered as a major indi cation of the grain-abrasion. A zone of high density dislocation was noted on the subsurface of the separating ring by transmission electron microscopy observation, which implies the contribution of the severe impact on the surface of the separating ring in the wear process. The influences of the structure of the separating ring, the service condition and the in-service stress distribution on the wear behavior, were also analyzed. The results show that the failure of separating ring results from the impact wear and grain-abrasion together with the plastic deformation.

  14. Hydrodynamics of a quark droplet

    DEFF Research Database (Denmark)

    Bjerrum-Bohr, Johan J.; Mishustin, Igor N.; Døssing, Thomas

    2012-01-01

    We present a simple model of a multi-quark droplet evolution based on the hydrodynamical description. This model includes collective expansion of the droplet, effects of the vacuum pressure and surface tension. The hadron emission from the droplet is described following Weisskopf's statistical...

  15. Numerical Hydrodynamics in General Relativity

    Directory of Open Access Journals (Sweden)

    Font José A.

    2003-01-01

    Full Text Available The current status of numerical solutions for the equations of ideal general relativistic hydrodynamics is reviewed. With respect to an earlier version of the article, the present update provides additional information on numerical schemes, and extends the discussion of astrophysical simulations in general relativistic hydrodynamics. Different formulations of the equations are presented, with special mention of conservative and hyperbolic formulations well-adapted to advanced numerical methods. A large sample of available numerical schemes is discussed, paying particular attention to solution procedures based on schemes exploiting the characteristic structure of the equations through linearized Riemann solvers. A comprehensive summary of astrophysical simulations in strong gravitational fields is presented. These include gravitational collapse, accretion onto black holes, and hydrodynamical evolutions of neutron stars. The material contained in these sections highlights the numerical challenges of various representative simulations. It also follows, to some extent, the chronological development of the field, concerning advances on the formulation of the gravitational field and hydrodynamic equations and the numerical methodology designed to solve them.

  16. Anomalous hydrodynamics in two dimensions

    Indian Academy of Sciences (India)

    Rabin Banerjee

    2016-02-01

    A new approach is presented to discuss two-dimensional hydrodynamics with gauge and gravitational anomalies. Exact constitutive relations for the stress tensor and charge current are obtained. Also, a connection between response parameters and anomaly coefficients is discussed. These are new results which, in the absence of the gauge sector, reproduce the results found by the gradient expansion approach.

  17. Hydrodynamic Noise and Surface Compliance.

    Science.gov (United States)

    1982-09-08

    Lighthill, 3,4 Ffowcs-Wiiliams, 5-7 and Morse and Ingard .8 Ffowcs-Williams’ 7 excellent review identifies five distinctly different theoretical...Williams, "Hydrodynamic Noise," Annual Review of Fluid Mechanics (Annual Reviews, Palo Alto, CA), vol. 1, 1969, pp. 197-222. 8. P. Morse and K. V. Ingard

  18. Hydrodynamic slip in silicon nanochannels

    Science.gov (United States)

    Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

    2016-03-01

    Equilibrium and nonequilibrium molecular dynamics simulations were performed to better understand the hydrodynamic behavior of water flowing through silicon nanochannels. The water-silicon interaction potential was calibrated by means of size-independent molecular dynamics simulations of silicon wettability. The wettability of silicon was found to be dependent on the strength of the water-silicon interaction and the structure of the underlying surface. As a result, the anisotropy was found to be an important factor in the wettability of these types of crystalline solids. Using this premise as a fundamental starting point, the hydrodynamic slip in nanoconfined water was characterized using both equilibrium and nonequilibrium calculations of the slip length under low shear rate operating conditions. As was the case for the wettability analysis, the hydrodynamic slip was found to be dependent on the wetted solid surface atomic structure. Additionally, the interfacial water liquid structure was the most significant parameter to describe the hydrodynamic boundary condition. The calibration of the water-silicon interaction potential performed by matching the experimental contact angle of silicon led to the verification of the no-slip condition, experimentally reported for silicon nanochannels at low shear rates.

  19. Hydrodynamic sensing does not facilitate active drag reduction in the golden shiner (Notemigonus crysoleucas)

    NARCIS (Netherlands)

    McHenry, M. J.; Michel, K. B.; Stewart, W.; Mueller, U. K.

    2010-01-01

    The lateral line system detects water flow, which allows fish to orient their swimming with respect to hydrodynamic cues. However, it is unclear whether this sense plays a role in the control of propulsion. Hydrodynamic theory suggests that fish could reduce drag by coordinating the motion of the

  20. Design and Analysis of the Gemini Chain System in Dual Clutch Transmission of Automobile

    Institute of Scientific and Technical Information of China (English)

    CHENG Yabing; GUO Haitao; FU Zhenming; WAN Nen; LI Lei; WANG Yang

    2015-01-01

    Chain drive system is widely used in the conditions of high-speed, overload, variable speed and load. Many studies are focused on the meshing theory and wear characteristics of chain drive system, but system design, analysis, and noise characteristics of the chain drive system are weak. System design and noise characteristic are studied for a new type Gemini chain of dual-clutch automatic transmission. Based on the meshing theory of silent chain, the design parameters of the Gemini chain system are calculated and the mathematical models and dynamic analysis models of the Gemini chain system are established. Dynamic characteristics of the Gemini chain system is simulated and the contact force of plate and pin, plate and sprockets, the chain tension forces, the transmission error and the stress of plates and pins are analyzed. According to the simulation results of the Gemini chain system, the noise experiment about system is carried out. The noise values are tested at different speed and load and spectral characteristics are analyzed. The results of simulation and experimental show that the contact forces of plate and pin, plate and sprockets are smaller than the allowable stress values, the chain tension force is less than ultimate tension and transmission error is limited in 1.2%. The noise values can meet the requirements of industrial design, and it is proved that the design and analysis method of the Gemini chain system is scientific and feasible. The design and test system is built from analysis to test of Gemini chain system. This research presented will provide a corresponding theoretical guidance for the design and dynamic characteristics and noise characteristics of chain drive system.

  1. Design and analysis of the Gemini chain system in dual clutch transmission of automobile

    Science.gov (United States)

    Cheng, Yabing; Guo, Haitao; Fu, Zhenming; Wan, Nen; Li, Lei; Wang, Yang

    2015-01-01

    Chain drive system is widely used in the conditions of high-speed, overload, variable speed and load. Many studies are focused on the meshing theory and wear characteristics of chain drive system, but system design, analysis, and noise characteristics of the chain drive system are weak. System design and noise characteristic are studied for a new type Gemini chain of dual-clutch automatic transmission. Based on the meshing theory of silent chain, the design parameters of the Gemini chain system are calculated and the mathematical models and dynamic analysis models of the Gemini chain system are established. Dynamic characteristics of the Gemini chain system is simulated and the contact force of plate and pin, plate and sprockets, the chain tension forces, the transmission error and the stress of plates and pins are analyzed. According to the simulation results of the Gemini chain system, the noise experiment about system is carried out. The noise values are tested at different speed and load and spectral characteristics are analyzed. The results of simulation and experimental show that the contact forces of plate and pin, plate and sprockets are smaller than the allowable stress values, the chain tension force is less than ultimate tension and transmission error is limited in 1.2%. The noise values can meet the requirements of industrial design, and it is proved that the design and analysis method of the Gemini chain system is scientific and feasible. The design and test system is built from analysis to test of Gemini chain system. This research presented will provide a corresponding theoretical guidance for the design and dynamic characteristics and noise characteristics of chain drive system.

  2. Conformational Manipulation of DNA in Nanochannels Using Hydrodynamics

    CERN Document Server

    He, Qihao; Carrivain, Pascal; Viero, Yannick; Lacroix, Joris; Blatché, Charline; Daran, Emmanuelle; Victor, Jean-Marc; Bancaud, Aurélien

    2014-01-01

    The control over DNA elongation in nanofluidic devices holds great potential for large-scale genomic analysis. So far, the manipulation of DNA in nanochannels has been mostly carried out with electrophoresis and seldom with hydrodynamics, although the physics of soft matter in nanoscale flows has raised considerable interest over the past decade. In this report the migration of DNA is studied in nanochannels of lateral dimension spanning 100 to 500 nm using both actuation principles. We show that the relaxation kinetics are 3-fold slowed down and the extension increases up to 3-fold using hydrodynamics. We propose a model to account for the onset in elongation with the flow, which assumes that DNA response is determined by the shear-driven lift forces mediated by the proximity of the channels' walls. Overall, we suggest that hydrodynamic actuation allows for an improved manipulation of DNA in nanochannels.

  3. Hydrodynamic, neotectonic and climatic control of the evolution of a barrier beach in the microtidal environment of the NE Ionian Sea (eastern Mediterranean)

    Science.gov (United States)

    Poulos, Serafim E.; Ghionis, George; Verykiou, Efthymia; Roussakis, Grigoris; Sakellariou, Dimitrios; Karditsa, Aikaterini; Alexandrakis, George; Petrakis, Stelios; Sifnioti, Dafni; Panagiotopoulos, Ioannis P.; Andris, Periklis; Georgiou, Panos

    2015-02-01

    The existence of barrier beaches is crucial, as they act as a buffer zone to the associated wetlands, whilst they are sensitive to climate change. The present study offers an insight into the processes controlling the formation and evolution of the Gyra barrier beach (NW coast of the island of Lefkada) in the microtidal, tectonically very active Ionian Sea under the influence of regional climate change and human interference. Such investigations are sparse in the literature. Existing information regarding regional geology, sediment availability and human intervention is combined with the collection of geophysical data, field observations and simulations of nearshore hydro- and sediment dynamics, analysis of climatic variations with respect to offshore wind/wave patterns (including storminess), in situ measurements of recent morphometric changes (2006-2008) and historical shoreline changes (since the 1960s). The recent formation and evolution (mostly under retreat) of the Gyra barrier beach is shown to be the combined result of the regional seismotectonic setting, relative increase of sea level, coastal sediment transport patterns, as well as human impact (negative) on primarily terrestrial sediment influxes. The current erosional trend of the barrier beach is associated with a shift in the wind and wave direction (from SW to NW) of extreme storm events in the Ionian Sea since the 1980s. The regional climatic variations of the last decades are well correlated with the trend of the North Atlantic Oscillation.

  4. Brain vascular and hydrodynamic physiology

    Science.gov (United States)

    Tasker, Robert C.

    2013-01-01

    Protecting the brain in vulnerable infants undergoing surgery is a central aspect of perioperative care. Understanding the link between blood flow, oxygen delivery and oxygen consumption leads to a more informed approach to bedside care. In some cases, we need to consider how high can we let the partial pressure of carbon dioxide go before we have concerns about risk of increased cerebral blood volume and change in intracranial hydrodynamics? Alternatively, in almost all such cases, we have to address the question of how low can we let the blood pressure drop before we should be concerned about brain perfusion? This review, provides a basic understanding of brain bioenergetics, hemodynamics, hydrodynamics, autoregulation and vascular homeostasis to changes in blood gases that is fundamental to our thinking about bedside care and monitoring. PMID:24331089

  5. Hydrodynamic interactions in two dimensions

    Science.gov (United States)

    di Leonardo, R.; Keen, S.; Ianni, F.; Leach, J.; Padgett, M. J.; Ruocco, G.

    2008-09-01

    We measure hydrodynamic interactions between colloidal particles confined in a thin sheet of fluid. The reduced dimensionality, compared to a bulk fluid, increases dramatically the range of couplings. Using optical tweezers we force a two body system along the eigenmodes of the mobility tensor and find that eigenmobilities change logarithmically with particle separation. At a hundred radii distance, the mobilities for rigid and relative motions differ by a factor of 2, whereas in bulk fluids, they would be practically indistinguishable. A two dimensional counterpart of Oseen hydrodynamic tensor quantitatively reproduces the observed behavior, once the relevant boundary conditions are recognized. These results highlight the importance of dimensionality for transport and interactions in colloidal systems and proteins in biological membranes.

  6. Algorithm refinement for fluctuating hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Sarah A.; Bell, John B.; Garcia, Alejandro L.

    2007-07-03

    This paper introduces an adaptive mesh and algorithmrefinement method for fluctuating hydrodynamics. This particle-continuumhybrid simulates the dynamics of a compressible fluid with thermalfluctuations. The particle algorithm is direct simulation Monte Carlo(DSMC), a molecular-level scheme based on the Boltzmann equation. Thecontinuum algorithm is based on the Landau-Lifshitz Navier-Stokes (LLNS)equations, which incorporate thermal fluctuations into macroscopichydrodynamics by using stochastic fluxes. It uses a recently-developedsolver for LLNS, based on third-order Runge-Kutta. We present numericaltests of systems in and out of equilibrium, including time-dependentsystems, and demonstrate dynamic adaptive refinement by the computationof a moving shock wave. Mean system behavior and second moment statisticsof our simulations match theoretical values and benchmarks well. We findthat particular attention should be paid to the spectrum of the flux atthe interface between the particle and continuum methods, specificallyfor the non-hydrodynamic (kinetic) time scales.

  7. Hydrodynamics from Landau initial conditions

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Abhisek [University of Tennessee, Knoxville (UTK); Gerhard, Jochen [Frankfurt Institute for Advanced Studies (FIAS), Germany; Torrieri, Giorgio [Universidade Estadual de Campinas, Instituto de Física " Gleb Wataghin" (IFGW), Sao Paulo, Brazil; Read jr, Kenneth F. [University of Tennessee (UTK) and Oak Ridge National Laboratory (ORNL); Wong, Cheuk-Yin [ORNL

    2015-01-01

    We investigate ideal hydrodynamic evolution, with Landau initial conditions, both in a semi-analytical 1+1D approach and in a numerical code incorporating event-by-event variation with many events and transverse density inhomogeneities. The object of the calculation is to test how fast would a Landau initial condition transition to a commonly used boost-invariant expansion. We show that the transition to boost-invariant flow occurs too late for realistic setups, with corrections of O (20 - 30%) expected at freezeout for most scenarios. Moreover, the deviation from boost-invariance is correlated with both transverse flow and elliptic flow, with the more highly transversely flowing regions also showing the most violation of boost invariance. Therefore, if longitudinal flow is not fully developed at the early stages of heavy ion collisions, 2+1 dimensional hydrodynamics is inadequate to extract transport coefficients of the quark-gluon plasma. Based on [1, 2

  8. Non-boost-invariant dissipative hydrodynamics

    CERN Document Server

    Florkowski, Wojciech; Strickland, Michael; Tinti, Leonardo

    2016-01-01

    The one-dimensional non-boost-invariant evolution of the quark-gluon plasma, presumably produced during the early stages of heavy-ion collisions, is analyzed within the frameworks of viscous and anisotropic hydrodynamics. We neglect transverse dynamics and assume homogeneous conditions in the transverse plane but, differently from Bjorken expansion, we relax longitudinal boost invariance in order to study the rapidity dependence of various hydrodynamical observables. We compare the results obtained using several formulations of second-order viscous hydrodynamics with a recent approach to anisotropic hydrodynamics, which treats the large initial pressure anisotropy in a non-perturbative fashion. The results obtained with second-order viscous hydrodynamics depend on the particular choice of the second-order terms included, which suggests that the latter should be included in the most complete way. The results of anisotropic hydrodynamics and viscous hydrodynamics agree for the central hot part of the system, ho...

  9. Hydrodynamics of catheter biofilm formation

    CERN Document Server

    Sotolongo-Costa, Oscar; Rodriguez-Perez, Daniel; Martinez-Escobar, Sergio; Fernandez-Barbero, Antonio

    2009-01-01

    A hydrodynamic model is proposed to describe one of the most critical problems in intensive medical care units: the formation of biofilms inside central venous catheters. The incorporation of approximate solutions for the flow-limited diffusion equation leads to the conclusion that biofilms grow on the internal catheter wall due to the counter-stream diffusion of blood through a very thin layer close to the wall. This biological deposition is the first necessary step for the subsequent bacteria colonization.

  10. Soliton propagation in relativistic hydrodynamics

    CERN Document Server

    Fogaça, D A; 10.1016/j.nuclphysa.2007.03.104

    2013-01-01

    We study the conditions for the formation and propagation of Korteweg-de Vries (KdV) solitons in nuclear matter. In a previous work we have derived a KdV equation from Euler and continuity equations in non-relativistic hydrodynamics. In the present contribution we extend our formalism to relativistic fluids. We present results for a given equation of state, which is based on quantum hadrodynamics (QHD).

  11. Hydrodynamic Evolution of GRB Afterglow

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    We investigate the dynamics of a relativistic fireball which decelerates as it sweeps up ambient matter. Not only the radiative and adiabatic cases, but also the realistic intermediate cases are calculated. We perform numerical calcula-tion for various ambient media and sizes of beaming expansion, and find that the deceleration radius R0 may play an important role for the hydrodynamic evolution of GRB afterglow.

  12. Recent progress in anisotropic hydrodynamics

    Directory of Open Access Journals (Sweden)

    Strickland Michael

    2017-01-01

    Full Text Available The quark-gluon plasma created in a relativistic heavy-ion collisions possesses a sizable pressure anisotropy in the local rest frame at very early times after the initial nuclear impact and this anisotropy only slowly relaxes as the system evolves. In a kinetic theory picture, this translates into the existence of sizable momentum-space anisotropies in the underlying partonic distribution functions, 〈 pL2〉 ≪ 〈 pT2〉. In such cases, it is better to reorganize the hydrodynamical expansion by taking into account momentum-space anisotropies at leading-order in the expansion instead of as a perturbative correction to an isotropic distribution. The resulting anisotropic hydrodynamics framework has been shown to more accurately describe the dynamics of rapidly expanding systems such as the quark-gluon plasma. In this proceedings contribution, I review the basic ideas of anisotropic hydrodynamics, recent progress, and present a few preliminary phenomenological predictions for identified particle spectra and elliptic flow.

  13. Particle Mesh Hydrodynamics for Astrophysics Simulations

    Science.gov (United States)

    Chatelain, Philippe; Cottet, Georges-Henri; Koumoutsakos, Petros

    We present a particle method for the simulation of three dimensional compressible hydrodynamics based on a hybrid Particle-Mesh discretization of the governing equations. The method is rooted on the regularization of particle locations as in remeshed Smoothed Particle Hydrodynamics (rSPH). The rSPH method was recently introduced to remedy problems associated with the distortion of computational elements in SPH, by periodically re-initializing the particle positions and by using high order interpolation kernels. In the PMH formulation, the particles solely handle the convective part of the compressible Euler equations. The particle quantities are then interpolated onto a mesh, where the pressure terms are computed. PMH, like SPH, is free of the convection CFL condition while at the same time it is more efficient as derivatives are computed on a mesh rather than particle-particle interactions. PMH does not detract from the adaptive character of SPH and allows for control of its accuracy. We present simulations of a benchmark astrophysics problem demonstrating the capabilities of this approach.

  14. Does polyandry really pay off? The effects of multiple mating and number of fathers on morphological traits and survival in clutches of nesting green turtles at Tortuguero.

    Science.gov (United States)

    Alfaro-Núñez, Alonzo; Jensen, Michael P; Abreu-Grobois, F Alberto

    2015-01-01

    Despite the long debate of whether or not multiple mating benefits the offspring, studies still show contradictory results. Multiple mating takes time and energy. Thus, if females fertilize their eggs with a single mating, why to mate more than once? We investigated and inferred paternal identity and number of sires in 12 clutches (240 hatchlings) of green turtles (Chelonia mydas) nests at Tortuguero, Costa Rica. Paternal alleles were inferred through comparison of maternal and hatchling genotypes, and indicated multiple paternity in at least 11 of the clutches (92%). The inferred average number of fathers was three (ranging from 1 to 5). Moreover, regression analyses were used to investigate for correlation of inferred clutch paternity with morphological traits of hatchlings fitness (emergence success, length, weight and crawling speed), the size of the mother, and an environmental variable (incubation temperature). We suggest and propose two different comparative approaches for evaluating morphological traits and clutch paternity, in order to infer greater offspring survival. First, clutches coded by the exact number of fathers and second by the exact paternal contribution (fathers who gives greater proportion of the offspring per nest). We found significant differences (P 0.05) for any of the traits. We conclude that multiple paternity does not provide any extra benefit in the morphological fitness traits or the survival of the offspring, when analysed following the proposed comparative statistical methods.

  15. Does polyandry really pay off? The effects of multiple mating and number of fathers on morphological traits and survival in clutches of nesting green turtles at Tortuguero

    Directory of Open Access Journals (Sweden)

    Alonzo Alfaro-Núñez

    2015-04-01

    Full Text Available Despite the long debate of whether or not multiple mating benefits the offspring, studies still show contradictory results. Multiple mating takes time and energy. Thus, if females fertilize their eggs with a single mating, why to mate more than once? We investigated and inferred paternal identity and number of sires in 12 clutches (240 hatchlings of green turtles (Chelonia mydas nests at Tortuguero, Costa Rica. Paternal alleles were inferred through comparison of maternal and hatchling genotypes, and indicated multiple paternity in at least 11 of the clutches (92%. The inferred average number of fathers was three (ranging from 1 to 5. Moreover, regression analyses were used to investigate for correlation of inferred clutch paternity with morphological traits of hatchlings fitness (emergence success, length, weight and crawling speed, the size of the mother, and an environmental variable (incubation temperature. We suggest and propose two different comparative approaches for evaluating morphological traits and clutch paternity, in order to infer greater offspring survival. First, clutches coded by the exact number of fathers and second by the exact paternal contribution (fathers who gives greater proportion of the offspring per nest. We found significant differences (P 0.05 for any of the traits. We conclude that multiple paternity does not provide any extra benefit in the morphological fitness traits or the survival of the offspring, when analysed following the proposed comparative statistical methods.

  16. Two-Dimensional Hydrodynamic Modeling and Analysis of the Proposed Channel Modifications and Grade Control Structure on the Blue River near Byram's Ford Industrial Park, Kansas City, Missouri

    Science.gov (United States)

    Huizinga, Richard J.

    2007-01-01

    The Blue River Channel Modification project being implemented by the U.S. Army Corps of Engineers (USACE) is intended to provide flood protection within the Blue River valley in the Kansas City, Mo., metropolitan area. In the latest phase of the project, concerns have arisen about preserving the Civil War historic area of Byram's Ford and the associated Big Blue Battlefield while providing flood protection for the Byram's Ford Industrial Park. In 1996, the USACE used a physical model built at the Waterways Experiment Station (WES) in Vicksburg, Miss., to examine the feasibility of a proposed grade control structure (GCS) that would be placed downstream from the historic river crossing of Byram's Ford to provide a subtle transition of flow from the natural channel to the modified channel. The U.S. Geological Survey (USGS), in cooperation with the USACE, modified an existing two-dimensional finite element surface-water model of the river between 63d Street and Blue Parkway (the 'original model'), used the modified model to simulate the existing (as of 2006) unimproved channel and the proposed channel modifications and GCS, and analyzed the results from the simulations and those from the WES physical model. Modifications were made to the original model to create a model that represents existing (2006) conditions between the north end of Swope Park immediately upstream from 63d Street and the upstream limit of channel improvement on the Blue River (the 'model of existing conditions'). The model of existing conditions was calibrated to two measured floods. The model of existing conditions also was modified to create a model that represents conditions along the same reach of the Blue River with proposed channel modifications and the proposed GCS (the 'model of proposed conditions'). The models of existing conditions and proposed conditions were used to simulate the 30-, 50-, and 100-year recurrence floods. The discharge from the calibration flood of May 15, 1990, also

  17. Gear ratio optimization and shift control of 2-speed I-AMT in electric vehicle

    Science.gov (United States)

    Gao, Bingzhao; Liang, Qiong; Xiang, Yu; Guo, Lulu; Chen, Hong

    2015-01-01

    Connecting a 2-speed transmission with the drive motor improves the dynamic and economic performance of electric passenger vehicles. A novel 2-speed I-AMT (Inverse Automated Manual Transmission) is studied, and the dry clutch is located at the rear of the transmission so that the traction interruption of traditional AMT can be cancelled. After the gear ratios are optimized using Dynamic Programming, gear shift control is addressed, and smooth shift process without torque hole is achieved through feed-forward and feed-back control of the clutch and the motor. Finally the proposed electric vehicle (EV) is compared with an EV with fixed-ratio gear box, and it is shown that the 2-speed AMT with a rear-mounted dry clutch has much better performance in terms of acceleration time, maximum speed and energy economy. The effect of clutch friction loss during shifting on the energy efficiency of the whole driving range is analyzed as well.

  18. Variation in levels of reactive oxygen species is explained by maternal identity, sex and body-size-corrected clutch size in a lizard

    Science.gov (United States)

    Olsson, Mats; Wilson, Mark; Uller, Tobias; Mott, Beth; Isaksson, Caroline

    2009-01-01

    Many organisms show differences between males and females in growth rate and crucial life history parameters, such as longevity. Considering this, we may expect levels of toxic metabolic by-products of the respiratory chain, such as reactive oxygen species (ROS), to vary with age and sex. Here, we analyse ROS levels in female Australian painted dragon lizards ( Ctenophorus pictus) and their offspring using fluorescent probes and flow cytometry. Basal level of four ROS species (singlet oxygen, peroxynitrite, superoxide and H2O2) measured with a combined marker, and superoxide measured specifically, varied significantly among families but not between the sexes. When blood cells from offspring were chemically encouraged to accelerate the electron transport chain by mitochondrial uncoupling, net superoxide levels were three times higher in daughters than sons (resulting in levels outside of the normal ROS range) and varied among mothers depending on offspring sex (significant interaction between maternal identity and offspring sex). In offspring, there were depressive effects on ROS of size-controlled relative clutch size, which relies directly on circulating levels of vitellogenin, a confirmed antioxidant in some species. Thus, levels of reactive oxygen species varies among females, offspring and in relation to reproductive investment in a manner that makes its regulatory processes likely targets of selection.

  19. Entropy-limited hydrodynamics: a novel approach to relativistic hydrodynamics

    Science.gov (United States)

    Guercilena, Federico; Radice, David; Rezzolla, Luciano

    2017-07-01

    We present entropy-limited hydrodynamics (ELH): a new approach for the computation of numerical fluxes arising in the discretization of hyperbolic equations in conservation form. ELH is based on the hybridisation of an unfiltered high-order scheme with the first-order Lax-Friedrichs method. The activation of the low-order part of the scheme is driven by a measure of the locally generated entropy inspired by the artificial-viscosity method proposed by Guermond et al. (J. Comput. Phys. 230(11):4248-4267, 2011, doi: 10.1016/j.jcp.2010.11.043). Here, we present ELH in the context of high-order finite-differencing methods and of the equations of general-relativistic hydrodynamics. We study the performance of ELH in a series of classical astrophysical tests in general relativity involving isolated, rotating and nonrotating neutron stars, and including a case of gravitational collapse to black hole. We present a detailed comparison of ELH with the fifth-order monotonicity preserving method MP5 (Suresh and Huynh in J. Comput. Phys. 136(1):83-99, 1997, doi: 10.1006/jcph.1997.5745), one of the most common high-order schemes currently employed in numerical-relativity simulations. We find that ELH achieves comparable and, in many of the cases studied here, better accuracy than more traditional methods at a fraction of the computational cost (up to {˜}50% speedup). Given its accuracy and its simplicity of implementation, ELH is a promising framework for the development of new special- and general-relativistic hydrodynamics codes well adapted for massively parallel supercomputers.

  20. Drag torque prediction model of wet multi-disk shifting clutch%湿式多片换档离合器带排转矩的预测模型

    Institute of Scientific and Technical Information of China (English)

    张志刚; 周晓军; 李永军; 沈路; 杨富春

    2011-01-01

    为了研究湿式多片换档离合器带排转矩的形成机理,建立湿式离合器的带排转矩预测模型.根据黏性流体力学中层流理论的Navier-Stokes方程,考虑到分离间隙中冷却润滑油膜的离心惯性作用,推导油膜的径向速度模型.通过对径向速度的仿真分析,揭示离心惯性力会使油膜产生收缩的现象.为了描述这一现象引入等效外径的概念,利用油膜的表面张力作用求出等效外径.将等效外径应用于牛顿内摩擦定律推导新的预测模型,通过试验数据和传统模型验证了新模型的正确性和有效性.%A new prediction model was presented to predict the drag torque of a disengaged wet clutch in order to analyze the formation mechanism of drag torque of wet multi-disk shifting clutch. A radial velocity model of the oil film was deduced according to the Navier-Stokes equation based on laminar flow of viscosity hydrodynamics and considering the centrifugal effect of cooling and lubricating oil film in clearance. Then the radial velocity was analyzed. Results showed that the centrifugal force caused the shrinking of oil film. The equivalent outer radius was introduced to describe the phenomenon, and was resolved by utilizing the effect of surface tension of oil film. A new model was derived by combining the equivalent outer radius with the Newton inner friction law. The correctness and effectiveness of the new model were verified by test data and traditional model.

  1. A Novel Torque Coordination Control Strategy of a Single-Shaft Parallel Hybrid Electric Vehicle Based on Model Predictive Control

    Directory of Open Access Journals (Sweden)

    Jing Sun

    2015-01-01

    Full Text Available The torque coordination control during mode transition is a very important task for hybrid electric vehicle (HEV with a clutch serving as the key enabling actuator element. Poor coordination will deteriorate the drivability of the driver and lead to excessive wearing to the clutch friction plates. In this paper, a novel torque coordination control strategy for a single-shaft parallel hybrid electric vehicle is presented to coordinate the motor torque, engine torque, and clutch torque so that the seamless mode switching can be achieved. Different to the existing model predictive control (MPC methods, only one model predictive controller is needed and the clutch torque is taken as an optimized variable rather than a known parameter. Furthermore, the successful idea of model reference control (MRC is also used for reference to generate the set-point signal required by MPC. The parameter sensitivity is studied for better performance of the proposed model predictive controller. The simulation results validate that the proposed novel torque coordination control strategy has less vehicle jerk, less torque interruption, and smaller clutch frictional losses, compared with the baseline method. In addition, the sensitivity and adaptiveness of the proposed novel torque coordination control strategy are evaluated.

  2. Constructing stable 3D hydrodynamical models of giant stars

    Science.gov (United States)

    Ohlmann, Sebastian T.; Röpke, Friedrich K.; Pakmor, Rüdiger; Springel, Volker

    2017-02-01

    Hydrodynamical simulations of stellar interactions require stable models of stars as initial conditions. Such initial models, however, are difficult to construct for giant stars because of the wide range in spatial scales of the hydrostatic equilibrium and in dynamical timescales between the core and the envelope of the giant. They are needed for, e.g., modeling the common envelope phase where a giant envelope encompasses both the giant core and a companion star. Here, we present a new method of approximating and reconstructing giant profiles from a stellar evolution code to produce stable models for multi-dimensional hydrodynamical simulations. We determine typical stellar stratification profiles with the one-dimensional stellar evolution code mesa. After an appropriate mapping, hydrodynamical simulations are conducted using the moving-mesh code arepo. The giant profiles are approximated by replacing the core of the giant with a point mass and by constructing a suitable continuation of the profile to the center. Different reconstruction methods are tested that can specifically control the convective behaviour of the model. After mapping to a grid, a relaxation procedure that includes damping of spurious velocities yields stable models in three-dimensional hydrodynamical simulations. Initially convectively stable configurations lead to stable hydrodynamical models while for stratifications that are convectively unstable in the stellar evolution code, simulations recover the convective behaviour of the initial model and show large convective plumes with Mach numbers up to 0.8. Examples are shown for a 2 M⊙ red giant and a 0.67 M⊙ asymptotic giant branch star. A detailed analysis shows that the improved method reliably provides stable models of giant envelopes that can be used as initial conditions for subsequent hydrodynamical simulations of stellar interactions involving giant stars.

  3. Hydrodynamic Flow Control in Marine Mammals

    Science.gov (United States)

    2008-05-06

    propulsive thrust pro- duction is confined to oscillations of the caudal hydrofoil (Lighthill 1969; Webb 1975). The propul- sive hydrofoils of cetaceans...propulsive efficiency, considered the flukes as rigid hydrofoils (Parry 1949; Wu 1971; Lighthill 1975; Chopra and Kambe 1977; Fish 1993a, 1993b; 1998a; Liu...vertebrae of the skeleton (Long et al. 1997; Fish 1998b). As the angle of attack is increased, lift will increase faster than the drag for a hydrofoil

  4. 双离合器自动变速器故障诊断与处理%Fault Diagnosis and Treatment of Double Clutch Automatic Transmission

    Institute of Scientific and Technical Information of China (English)

    陈麒

    2013-01-01

    以双离合器自动变速器的空转故障为研究现象,经诊断分析得出离合器温度传感器超温是故障原因,为今后双离合器自动变速器的故障诊断、检修等提供了理论依据。%Taking idle motion of double clutch automatic transmission as research object , it was concluded that overtemperature of clutch temperature transmitter was fault origin by diagnosis and analysis , which provides theoretical reference for fault diagnosis , examination and repair of double clutch automatic transmission in further .

  5. The integrin-ligand interaction regulates adhesion and migration through a molecular clutch.

    Directory of Open Access Journals (Sweden)

    Lingfeng Chen

    Full Text Available Adhesive and migratory behavior can be cell type, integrin, and substrate dependent. We have compared integrin and substrate differences using three integrin receptors: α5β1, α6β1, and αLβ2 expressed in a common cell type, CHO.B2 cells, which lack integrin α subunits, as well as in different cell types that express one or more of these integrins. We find that CHO.B2 cells expressing either α6β1 or αLβ2 integrins migrate and protrude faster and are more directionally persistent on laminin or ICAM-1, respectively, than CHO.B2 cells expressing α5β1 on fibronectin. Despite rapid adhesion maturation and the presence of large adhesions in both the α6β1- and αLβ2-expressing cells, they display robust tyrosine phosphorylation. In addition, whereas myosin II regulates adhesion maturation and turnover, protrusion rates, and polarity in cells migrating on fibronectin, surprisingly, it does not have comparable effects in cells expressing α6β1 or αLβ2. This apparent difference in the integration of myosin II activity, adhesion, and migration arises from alterations in the ligand-integrin-actin linkage (molecular clutch. The elongated adhesions in the protrusions of the α6β1-expressing cells on laminin or the αLβ2-expressing cells on ICAM-1 display a novel, rapid retrograde flux of integrin; this was largely absent in the large adhesions in protrusions of α5β1-expressing cells on fibronectin. Furthermore, the force these adhesions exert on the substrate in protrusive regions is reduced compared to similar regions in α5-expressing cells, and the adhesion strength is reduced. This suggests that intracellular forces are not efficiently transferred from actomyosin to the substratum due to altered adhesion strength, that is, avidity, affinity, or the ligand-integrin-actin interaction. Finally, we show that the migration of fast migrating leukocytes on fibronectin or ICAM-1 is also largely independent of myosin II; however, their

  6. Annual Report: Hydrodynamics and Radiative Hydrodynamics with Astrophysical Applications

    Energy Technology Data Exchange (ETDEWEB)

    R. Paul Drake

    2005-12-01

    We report the ongoing work of our group in hydrodynamics and radiative hydrodynamics with astrophysical applications. During the period of the existing grant, we have carried out two types of experiments at the Omega laser. One set of experiments has studied radiatively collapsing shocks, obtaining high-quality scaling data using a backlit pinhole and obtaining the first (ever, anywhere) Thomson-scattering data from a radiative shock. Other experiments have studied the deeply nonlinear development of the Rayleigh-Taylor (RT) instability from complex initial conditions, obtaining the first (ever, anywhere) dual-axis radiographic data using backlit pinholes and ungated detectors. All these experiments have applications to astrophysics, discussed in the corresponding papers either in print or in preparation. We also have obtained preliminary radiographs of experimental targets using our x-ray source. The targets for the experiments have been assembled at Michigan, where we also prepare many of the simple components. The above activities, in addition to a variety of data analysis and design projects, provide good experience for graduate and undergraduates students. In the process of doing this research we have built a research group that uses such work to train junior scientists.

  7. Galaxy clusters as hydrodynamics laboratories

    Science.gov (United States)

    Roediger, Elke; Sheardown, Alexander; Fish, Thomas; ZuHone, John; Hunt, Matthew; Su, Yuanyuan; Kraft, Ralph P.; Nulsen, Paul; Forman, William R.; Churazov, Eugene; Randall, Scott W.; Jones, Christine; Machacek, Marie E.

    2017-08-01

    The intra-cluster medium (ICM) of galaxy clusters shows a wealth of hydrodynamical features that trace the growth of clusters via the infall of galaxies or smaller subclusters. Such hydrodynamical features include the wakes of the infalling objects as well as the interfaces between the host cluster’s ICM and the atmosphere of the infalling object. Furthermore, the cluster dynamics can be traced by merger shocks, bow shocks, and sloshing motions of the ICM.The characteristics of these dynamical features, e.g., the direction, length, brightness, and temperature of the galaxies' or subclusters' gas tails varies significantly between different objects. This could be due to either dynamical conditions or ICM transport coefficients such as viscosity and thermal conductivity. For example, the cool long gas tails of of some infalling galaxies and groups have been attributed to a substantial ICM viscosity suppressing mixing of the stripped galaxy or group gas with the hotter ambient ICM.Using hydrodynamical simulations of minor mergers we show, however, that these features can be explained naturally by the dynamical conditions of each particular galaxy or group infall. Specifically, we identify observable features to distinguish the first and second infall of a galaxy or group into its host cluster as well as characteristics during apocentre passage. Comparing our simulations with observations, we can explain several puzzling observations such as the long and cold tail of M86 in Virgo and the very long and tangentially oriented tail of the group LEDA 87445 in Hydra A.Using our simulations, we also assess the validity of the stagnation pressure method that is widely used to determine an infalling galaxy's velocity. We show that near pericentre passage the method gives reasonable results, but near apocentre it is not easily applicable.

  8. Intra-clutch ratio of yolk progesterone level changes with laying date in rockhopper penguins: a strategy to influence brood reduction?

    Directory of Open Access Journals (Sweden)

    Maud Poisbleau

    Full Text Available Hatching asynchrony in avian species generally leads to a size hierarchy among siblings, favouring the first-hatched chicks. Maternally deposited hormones affect the embryo and chick's physiology and behaviour. It has been observed that progesterone, a hormone present at higher levels than other steroid hormones in egg yolks, is negatively related to body mass in embryos, chicks and adults. A differential within-clutch progesterone deposition could therefore be linked to the size hierarchy between siblings and to the resulting brood reduction. We tested whether yolk progesterone levels differed between eggs according to future parental ability to feed the entire clutch in wild rockhopper penguins Eudyptes chrysocome. This species presents a unique reversed egg-size dimorphism and hatching asynchrony, with the larger second-laid egg (B-egg hatching before the smaller first-laid egg (A-egg. Yolk progesterone levels increased only slightly with female body mass at laying. However, intra-clutch ratios were not related to female body mass. On the other hand, yolk progesterone levels increased significantly with the date of laying onset for A-eggs while they decreased for B-eggs. Early clutches therefore had proportionally more progesterone in the B-egg compared to the A-egg while late clutches had proportionally less progesterone in the B-egg. We propose that females could strategically regulate yolk progesterone deposition within clutches according to the expected food availability during chick growth, an adaptive strategy to adjust brood reduction to conditions. We also discuss these results, relating to yolk progesterone, in the broader context of other yolk steroids.

  9. Hydrodynamic characteristics of UASB bioreactors.

    Science.gov (United States)

    John, Siby; Tare, Vinod

    2011-10-01

    The hydrodynamic characteristics of UASB bioreactors operated under different organic loading and hydraulic loading rates were studied, using three laboratory scale models treating concocted sucrose wastewater. Residence time distribution (RTD) analysis using dispersion model and tanks-in-series model was directed towards the characterization of the fluid flow pattern in the reactors and correlation of the hydraulic regime with the biomass content and biogas production. Empty bed reactors followed a plug flow pattern and the flow pattern changed to a large dispersion mixing with biomass and gas production. Effect of increase in gas production on the overall hydraulics was insignificant.

  10. Disruptive Innovation in Numerical Hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Waltz, Jacob I. [Los Alamos National Laboratory

    2012-09-06

    We propose the research and development of a high-fidelity hydrodynamic algorithm for tetrahedral meshes that will lead to a disruptive innovation in the numerical modeling of Laboratory problems. Our proposed innovation has the potential to reduce turnaround time by orders of magnitude relative to Advanced Simulation and Computing (ASC) codes; reduce simulation setup costs by millions of dollars per year; and effectively leverage Graphics Processing Unit (GPU) and future Exascale computing hardware. If successful, this work will lead to a dramatic leap forward in the Laboratory's quest for a predictive simulation capability.

  11. Turbulence Models of Hydrodynamic Lubrication

    Institute of Scientific and Technical Information of China (English)

    张直明; 王小静; 孙美丽

    2003-01-01

    The main theoretical turbulence models for application to hydrodynamic lubrication problems were briefly reviewed, and the course of their development and their fundamentals were explained. Predictions by these models on flow fields in turbulent Couette flows and shear-induced countercurrent flows were compared to existing measurements, and Zhang & Zhang' s combined k-ε model was shown to have surpassingly satisfactory results. The method of application of this combined k-ε model to high speed journal bearings and annular seals was summarized, and the predicted results were shown to be satisfactory by comparisons with existing experiments of journal bearings and annular seals.

  12. Sandbar-regulated hydrodynamic influences on river hydrochemistry at Mengabang Telipot River, Peninsular Malaysia.

    Science.gov (United States)

    Koh, Mei Kee; Sathiamurthy, Edlic; Suratman, Suhaimi; Tahir, Norhayati Mohd

    2012-12-01

    Influences of river hydrodynamic behaviours on hydrochemistry (salinity, pH, dissolved oxygen saturations and dissolved phosphorus) were evaluated through high spatial and temporal resolution study of a sandbar-regulated coastal river. River hydrodynamic during sandbar-closed event was characterized by minor dependency on tidal fluctuations, very gradual increase of water level and continual low flow velocity. These hydrodynamic behaviours established a hydrochemistry equilibrium, in which water properties generally were characterized by virtual absence of horizontal gradients while vertical stratifications were significant. In addition, the river was in high trophic status as algae blooms were visible. Conversely, river hydrodynamic in sandbar-opened event was tidal-controlled and showed higher flow velocity. Horizontal gradients of water properties became significant while vertically more homogenised and with lower trophic status. In essence, this study reveals that estuarine sandbar directly regulates river hydrodynamic behaviours which in turn influences river hydrochemistry.

  13. Highly-anisotropic hydrodynamics for central collisions

    CERN Document Server

    Ryblewski, Radoslaw

    2016-01-01

    The framework of leading-order anisotropic hydrodynamics is supplemented with realistic equation of state and self-consistent freeze-out prescription. The model is applied to central proton-nucleus collisions. The results are compared to those obtained within standard Israel-Stewart second-order viscous hydrodynamics. It is shown that the resulting hadron spectra are highly-sensitive to the hydrodynamic approach that has been used.

  14. Simulacioni model višelamelastih frikcionih sklopova / Simulation model of multiple plate friction clutches and brakes

    Directory of Open Access Journals (Sweden)

    Aleksandar Grkić

    2009-01-01

    Full Text Available Višelamelasti frikcioni sklopovi koriste se za promenu stepena prenosa u planetarnim menjačkim prenosnicima motornih vozila. Razvijeni simulacioni model frikcione spojnice i kočnice omogućava simulaciju rada menjačkog prenosnika pri promeni stepena prenosa. Primenom razvijenog modela moguće je na bazi simulacije analizirati prelazni proces pri promeni stepena prenosa i obezbediti identifikaciju relevantnih parametara bez izrade većeg broja fizičkih prototipova. Na taj način obezbeđuje se smanjenje troškova i skraćenje procesa razvoja novih prenosnika snage, uz poboljšanje upotrebnog kvaliteta. Simulacioni model može da se koristi i pri razvoju upravljačkog sistema menjačkog prenosnika za definisanje potrebnih karakteristika njegovih komponenata. / Multiple plate friction clutches and brakes are used for gear shifting within planetary gear trains of motor vehicles. The developed simulation model of the friction clutch and brake enables the simulation and the analysis of the planetary gear train transitional processes during gear shifting and provides identification of relevant parameters without making numerous physical prototypes. Costs are thus reduced and time for developing new gear trains shortened, while the product quality is increased. The simulation model can be use additionally in developing steering systems of planetary gear trains for defining characteristics of their components.

  15. Orchestration of avian reproductive effort: an integration of the ultimate and proximate bases for flexibility in clutch size, incubation behaviour, and yolk androgen deposition.

    Science.gov (United States)

    Sockman, Keith W; Sharp, Peter J; Schwabl, Hubert

    2006-11-01

    How much effort to expend in any one bout of reproduction is among the most important decisions made by an individual that breeds more than once. According to life-history theory, reproduction is costly, and individuals that invest too much in a given reproductive bout pay with reduced reproductive output in the future. Likewise, investing too little does not maximize reproductive potential. Because reproductive effort relative to output can vary with predictable and unpredictable challenges and opportunities, no single level of reproductive effort maximizes fitness. This leads to the prediction that individuals possessing behavioural mechanisms to buffer challenges and take advantage of opportunities would incur fitness benefits. Here, we review evidence in birds, primarily of altricial species, for the presence of at least two such mechanisms and evidence for and against the seasonal coordination of these mechanisms through seasonal changes in plasma concentrations of the pituitary hormone prolactin. First, the seasonal decline in clutch size of most bird species may partially offset a predictable seasonal decline in the reproductive value of offspring. Second, establishing a developmental sibling-hierarchy among offspring may hedge against unpredictable changes in resource availability and offspring viability or quality, and minimize energy expenditure in raising a brood. The hierarchy may be a product, in part, of the timing of incubation onset relative to clutch completion and the rate of yolk androgen deposition during the laying cycle. Because clutch size should influence the effects of both these traits on the developmental hierarchy, we predicted and describe evidence in some species that females adjust the timing of incubation onset and rate of yolk androgen deposition to match clutch size. Studies on domesticated precocial species reveal an inhibitory effect of the pituitary hormone prolactin on egg laying, suggesting a possible hormonal basis for the

  16. Some open questions in hydrodynamics

    CERN Document Server

    Dyndal, Mateusz

    2014-01-01

    When speaking of unsolved problems in physics, this is surprising at first glance to discuss the case of fluid mechanics. However, there are many deep open questions that come with the theory of fluid mechanics. In this paper, we discuss some of them that we classify in two categories, the long term behavior of solutions of equations of hydrodynamics and the definition of initial (boundary) conditions. The first set of questions come with the non-relativistic theory based on the Navier-Stokes equations. Starting from smooth initial conditions, the purpose is to understand if solutions of Navier-Stokes equations remain smooth with the time evolution. Existence for just a finite time would imply the evolution of finite time singularities, which would have a major influence on the development of turbulent phenomena. The second set of questions come with the relativistic theory of hydrodynamics. There is an accumulating evidence that this theory may be relevant for the description of the medium created in high en...

  17. High Efficiency Hydrodynamic DNA Fragmentation in a Bubbling System

    Science.gov (United States)

    Li, Lanhui; Jin, Mingliang; Sun, Chenglong; Wang, Xiaoxue; Xie, Shuting; Zhou, Guofu; van den Berg, Albert; Eijkel, Jan C. T.; Shui, Lingling

    2017-01-01

    DNA fragmentation down to a precise fragment size is important for biomedical applications, disease determination, gene therapy and shotgun sequencing. In this work, a cheap, easy to operate and high efficiency DNA fragmentation method is demonstrated based on hydrodynamic shearing in a bubbling system. We expect that hydrodynamic forces generated during the bubbling process shear the DNA molecules, extending and breaking them at the points where shearing forces are larger than the strength of the phosphate backbone. Factors of applied pressure, bubbling time and temperature have been investigated. Genomic DNA could be fragmented down to controllable 1-10 Kbp fragment lengths with a yield of 75.30-91.60%. We demonstrate that the ends of the genomic DNAs generated from hydrodynamic shearing can be ligated by T4 ligase and the fragmented DNAs can be used as templates for polymerase chain reaction. Therefore, in the bubbling system, DNAs could be hydrodynamically sheared to achieve smaller pieces in dsDNAs available for further processes. It could potentially serve as a DNA sample pretreatment technique in the future.

  18. Relativistic Hydrodynamics for Heavy-Ion Collisions

    Science.gov (United States)

    Ollitrault, Jean-Yves

    2008-01-01

    Relativistic hydrodynamics is essential to our current understanding of nucleus-nucleus collisions at ultrarelativistic energies (current experiments at the Relativistic Heavy Ion Collider, forthcoming experiments at the CERN Large Hadron Collider). This is an introduction to relativistic hydrodynamics for graduate students. It includes a detailed…

  19. Hydrodynamic models of a Cepheid atmosphere

    Science.gov (United States)

    Karp, A. H.

    1975-01-01

    Instead of computing a large number of coarsely zoned hydrodynamic models covering the entire atmospheric instability strip, the author computed a single model as well as computer limitations allow. The implicit hydrodynamic code of Kutter and Sparks was modified to include radiative transfer effects in optically thin zones.

  20. Hydrodynamic correlation functions in nematic liquid crystals

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Carle, D.; Laidlaw, W.G.

    1976-01-01

    The result, recently discovered by Forster, that the strength factors of the nonpropagating modes in certain hydrodynamic correlation functions in nematic liquid crystals are not fully determined by the hydrodynamic matrix is reconsidered. Using time reversal and space inversion symmetry one finds t

  1. Hydrodynamic Overview at Hot Quarks 2016

    CERN Document Server

    Noronha-Hostler, Jacquelyn

    2016-01-01

    This presents an overview of relativistic hydrodynamic modeling in heavy-ion collisions prepared for Hot Quarks 2016, at South Padre Island, TX, USA. The influence of the initial state and viscosity on various experimental observables are discussed. Specific problems that arise in the hydrodynamical modeling at the Beam Energy Scan are briefly discussed.

  2. Measurement of the hydrodynamic resistance of microdroplets.

    Science.gov (United States)

    Jakiela, Slawomir

    2016-10-07

    Here, we demonstrate a novel method of measurement which determines precisely the hydrodynamic resistance of a droplet flowing through a channel. The obtained results show that the hydrodynamic resistance of a droplet in a microchannel achieves its maximum for lengths of the droplet ranging from 3w to 4w and that interactions between beads in a train exist.

  3. Hydrodynamic correlation functions in nematic liquid crystals

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Carle, D.; Laidlaw, W.G.

    1976-01-01

    The result, recently discovered by Forster, that the strength factors of the nonpropagating modes in certain hydrodynamic correlation functions in nematic liquid crystals are not fully determined by the hydrodynamic matrix is reconsidered. Using time reversal and space inversion symmetry one finds t

  4. Quasiparticle anisotropic hydrodynamics for central collisions

    CERN Document Server

    Alqahtani, Mubarak; Strickland, Michael

    2016-01-01

    We use quasiparticle anisotropic hydrodynamics to study an azimuthally-symmetric boost-invariant quark-gluon plasma including the effects of both shear and bulk viscosities. In quasiparticle anisotropic hydrodynamics, a single finite-temperature quasiparticle mass is introduced and fit to the lattice data in order to implement a realistic equation of state. We compare results obtained using the quasiparticle method with the standard method of imposing the equation of state in anisotropic hydrodynamics and viscous hydrodynamics. Using these three methods, we extract the primordial particle spectra, total number of charged particles, and average transverse momentum for various values of the shear viscosity to entropy density ratio eta/s. We find that the three methods agree well for small shear viscosity to entropy density ratio, eta/s, but differ at large eta/s. We find, in particular, that when using standard viscous hydrodynamics, the bulk-viscous correction can drive the primordial particle spectra negative...

  5. Hydrodynamic Approaches in Relativistic Heavy Ion Reactions

    CERN Document Server

    de Souza, Rafael Derradi; Kodama, Takeshi

    2016-01-01

    We review several facets of the hydrodynamic description of the relativistic heavy ion collisions, starting from the historical motivation to the present understandings of the observed collective aspects of experimental data, especially those of the most recent RHIC and LHC results. In this report, we particularly focus on the conceptual questions and the physical foundations of the validity of the hydrodynamic approach itself. We also discuss recent efforts to clarify some of the points in this direction, such as the various forms of derivations of relativistic hydrodynamics together with the limitations intrinsic to the traditional approaches, variational approaches, known analytic solutions for special cases, and several new theoretical developments. Throughout this review, we stress the role of course-graining procedure in the hydrodynamic description and discuss its relation with the physical observables through the analysis of a hydrodynamic mapping of a microscopic transport model. Several questions to...

  6. Hydrodynamics research of wastewater treatment bioreactors

    Institute of Scientific and Technical Information of China (English)

    REN Nan-qi; ZHANG Bing; ZHOU Xue-fei

    2009-01-01

    To optimize the design and improve the performance of wastewater treatment bioreactors, the review concerning the hydrodynamics explored by theoretical equations, process experiments, modeling of the hydrody-namics and flow field measurement is presented. Results of different kinds of experiments show that the hydro-dynamic characteristics can affect sludge characteristics, mass transfer and reactor performance significantly. A-long with the development of theoretical equations, turbulence models including large eddy simulation models and Reynolds-averaged Navier-Stokes (RANS) models are widely used at present. Standard and modified k-ε models are the most widely used eddy viscosity turbulence models for simulating flows in bioreactors. Numericalsimulation of hydrodynamics is proved to be efficient for optimizing design and operation. The development of measurement techniques with high accuracy and low intrusion enables the flow filed in the bioreactors to be transparent. Integration of both numerical simulation and experimental measurement can describe the hydrody-namics very well.

  7. Hydrodynamic Nambu Brackets derived by Geometric Constraints

    CERN Document Server

    Blender, Richard

    2015-01-01

    A geometric approach to derive the Nambu brackets for ideal two-dimensional (2D) hydrodynamics is suggested. The derivation is based on two-forms with vanishing integrals in a periodic domain, and with resulting dynamics constrained by an orthogonality condition. As a result, 2D hydrodynamics with vorticity as dynamic variable emerges as a generic model, with conservation laws which can be interpreted as enstrophy and energy functionals. Generalized forms like surface quasi-geostrophy and fractional Poisson equations for the stream-function are also included as results from the derivation. The formalism is extended to a hydrodynamic system coupled to a second degree of freedom, with the Rayleigh-B\\'{e}nard convection as an example. This system is reformulated in terms of constitutive conservation laws with two additive brackets which represent individual processes: a first representing inviscid 2D hydrodynamics, and a second representing the coupling between hydrodynamics and thermodynamics. The results can b...

  8. Decoherent Histories and Hydrodynamic Equations

    CERN Document Server

    Halliwell, J J

    1998-01-01

    For a system consisting of a large collection of particles, a set of variables that will generally become effectively classical are the local densities (number, momentum, energy). That is, in the context of the decoherent histories approach to quantum theory, it is expected that histories of these variables will be approximately decoherent, and that their probabilites will be strongly peaked about hydrodynamic equations. This possibility is explored for the case of the diffusion of the number density of a dilute concentration of foreign particles in a fluid. It is shown that, for certain physically reasonable initial states, the probabilities for histories of number density are strongly peaked about evolution according to the diffusion equation. Decoherence of these histories is also shown for a class of initial states which includes non-trivial superpositions of number density. Histories of phase space densities are also discussed. The case of histories of number, momentum and energy density for more general...

  9. Hydrodynamic stability and stellar oscillations

    Indian Academy of Sciences (India)

    H M Antia

    2011-07-01

    Chandrasekhar’s monograph on Hydrodynamic and hydromagnetic stability, published in 1961, is a standard reference on linear stability theory. It gives a detailed account of stability of fluid flow in a variety of circumstances, including convection, stability of Couette flow, Rayleigh–Taylor instability, Kelvin–Helmholtz instability as well as the Jean’s instability for star formation. In most cases he has extended these studies to include effects of rotation and magnetic field. In a later paper he has given a variational formulation for equations of non-radial stellar oscillations. This forms the basis for helioseismic inversion techniques as well as extension to include the effect of rotation, magnetic field and other large-scale flows using a perturbation treatment.

  10. Integration of quantum hydrodynamical equation

    Science.gov (United States)

    Ulyanova, Vera G.; Sanin, Andrey L.

    2007-04-01

    Quantum hydrodynamics equations describing the dynamics of quantum fluid are a subject of this report (QFD).These equations can be used to decide the wide class of problem. But there are the calculated difficulties for the equations, which take place for nonlinear hyperbolic systems. In this connection, It is necessary to impose the additional restrictions which assure the existence and unique of solutions. As test sample, we use the free wave packet and study its behavior at the different initial and boundary conditions. The calculations of wave packet propagation cause in numerical algorithm the division. In numerical algorithm at the calculations of wave packet propagation, there arises the problem of division by zero. To overcome this problem we have to sew together discrete numerical and analytical continuous solutions on the boundary. We demonstrate here for the free wave packet that the numerical solution corresponds to the analytical solution.

  11. Particle hydrodynamics with tessellation techniques

    CERN Document Server

    Hess, S

    2009-01-01

    Lagrangian smoothed particle hydrodynamics (SPH) is a well-established approach to model fluids in astrophysical problems, thanks to its geometric flexibility and ability to automatically adjust the spatial resolution to the clumping of matter. However, a number of recent studies have emphasized inaccuracies of SPH in the treatment of fluid instabilities. The origin of these numerical problems can be traced back to spurious surface effects across contact discontinuities, and to SPH's inherent prevention of mixing at the particle level. We here investigate a new fluid particle model where the density estimate is carried out with the help of an auxiliary mesh constructed as the Voronoi tessellation of the simulation particles instead of an adaptive smoothing kernel. This Voronoi-based approach improves the ability of the scheme to represent sharp contact discontinuities. We show that this eliminates spurious surface tension effects present in SPH and that play a role in suppressing certain fluid instabilities. ...

  12. Nonstandard Gaits in Unsteady Hydrodynamics

    Science.gov (United States)

    Fairchild, Michael; Rowley, Clarence

    2016-11-01

    Marine biology has long inspired the design and engineering of underwater vehicles. The literature examining the kinematics and dynamics of fishes, ranging from undulatory anguilliform swimmers to oscillatory ostraciiform ones, is vast. Past numerical studies of these organisms have principally focused on gaits characterized by sinusoidal pitching and heaving motions. It is conceivable that more sophisticated gaits could perform better in some respects, for example as measured by thrust generation or by cost of transport. This work uses an unsteady boundary-element method to numerically investigate the hydrodynamics and propulsive efficiency of high-Reynolds-number swimmers whose gaits are encoded by Fourier series or by Jacobi elliptic functions. Numerical results are presented with an emphasis on identifying particular wake structures and modes of motion that are associated with optimal swimming. This work was supported by the Office of Naval Research through MURI Grant N00014-14-1-0533.

  13. Introduction to Magneto-Hydrodynamics

    Science.gov (United States)

    Pelletier, Guy

    Magneto-Hydrodynamics (hereafter MHD) describes plasmas on large scales and more generally electrically conducting fluids. This description does not discriminate between the various fluids that constitute the medium. In laboratory, it allows to globally describe a plasma machine, for instance a toroidal nuclear fusion reactor like a Tokamak. In astrophysics it plays an essential role in the description of cosmic objects and their environments, as well as the media, such as the interstellar or the intergalactic medium. A set of phenomena are specific to MHD description. Some of them will be presented in this lecture such as the tension effect, confinement, magnetic diffusivity, magnetic field freezing, Alfvén waves, magneto-sonic waves, reconnection. A celebrated phenomenon of MHD will not be introduced in this brief lecture, namely the dynamo effect.

  14. The hydrodynamics of dolphin drafting

    Directory of Open Access Journals (Sweden)

    Weihs Daniel

    2004-05-01

    Full Text Available Abstract Background Drafting in cetaceans is defined as the transfer of forces between individuals without actual physical contact between them. This behavior has long been surmised to explain how young dolphin calves keep up with their rapidly moving mothers. It has recently been observed that a significant number of calves become permanently separated from their mothers during chases by tuna vessels. A study of the hydrodynamics of drafting, initiated in the hope of understanding the mechanisms causing the separation of mothers and calves during fishing-related activities, is reported here. Results Quantitative results are shown for the forces and moments around a pair of unequally sized dolphin-like slender bodies. These include two major effects. First, the so-called Bernoulli suction, which stems from the fact that the local pressure drops in areas of high speed, results in an attractive force between mother and calf. Second is the displacement effect, in which the motion of the mother causes the water in front to move forwards and radially outwards, and water behind the body to move forwards to replace the animal's mass. Thus, the calf can gain a 'free ride' in the forward-moving areas. Utilizing these effects, the neonate can gain up to 90% of the thrust needed to move alongside the mother at speeds of up to 2.4 m/sec. A comparison with observations of eastern spinner dolphins (Stenella longirostris is presented, showing savings of up to 60% in the thrust that calves require if they are to keep up with their mothers. Conclusions A theoretical analysis, backed by observations of free-swimming dolphin schools, indicates that hydrodynamic interactions with mothers play an important role in enabling dolphin calves to keep up with rapidly moving adult school members.

  15. Evolutionary genetics of life-history traits in a structured environment : Understanding variation in clutch size and laying date in great tits (Parus major)

    NARCIS (Netherlands)

    Postma, Erik

    2005-01-01

    Understanding variation in clutch size and laying date in great tits (Parus major) Some of the key questions evolutionary biology aims to answer are how genetic variation is being maintained in traits that are closely related to fitness, how populations are adapted to their environment, and, if thei

  16. Evolutionary genetics of life-history traits in a structured environment. Understanding variation in clutch size and laying date in great tits (Parus major)

    NARCIS (Netherlands)

    Postma, E.

    2005-01-01

    Understanding variation in clutch size and laying date in great tits (Parus major) Some of the key questions evolutionary biology aims to answer are how genetic variation is being maintained in traits that are closely related to fitness, how populations are adapted to their environment, and, if thei

  17. Evaluation of asbestos exposure within the automotive repair industry: a study involving removal of asbestos-containing body sealants and drive clutch replacement.

    Science.gov (United States)

    Blake, Charles L; Dotson, G Scott; Harbison, Raymond D

    2008-12-01

    Two independent assessments were performed of airborne asbestos concentrations generated during automotive repair work on vintage vehicles . The first involved removal of asbestos-containing seam sealant, and the second involved servicing of a drive clutch. Despite the relatively high concentrations (5.6-28%) of chrysotile fibers detected within bulk samples of seam sealant, the average asbestos concentration for personal breathing zone (PBZ) samples during seam sealant removal was 0.006 f/cc (fibers/cubic centimeter of air). Many other air samples contained asbestos at or below the analytical limit of detection (LOD). Pneumatic chiseling of the sealant material during removal resulted in 69% of area air samples containing asbestos. Use of this impact tool liberated more asbestos than hand scraping. Asbestos fibers were only detected in air samples collected during the installation of a replacement clutch. The highest asbestos corrected airborne fiber concentration observed during clutch installation was 0.0028 f/cc. This value is approximately 100 times lower than Occupational Safety and Health Administration's (OSHA) permissible exposure limit (PEL) of 0.1f/cc. The airborne asbestos concentrations observed during the servicing of vintage vehicles with asbestos-containing seam sealant and clutches are comparable to levels reported for repair work involving brake components and gaskets.

  18. Dynamics and stability of rigid rotors levitated by passive cylinder-magnet bearings and driven/supported axially by pointwise contact clutch

    DEFF Research Database (Denmark)

    Andersen, Søren Bøgh; Enemark, Søren; Santos, Ilmar

    2013-01-01

    A stable rotor—supported laterally by passive magnetic bearings and longitudinally by magnetic forces and a clutch—loses suddenly its contact to the clutch and executes abruptly longitudinal movements away from its original equilibrium position as a result of small increases in angular velocity. ...

  19. The hydrodynamics analysis for the underwater robot with a spherical hull

    Science.gov (United States)

    Lan, Xiaojuan; Sun, Hanxu; Jia, Qingxuan

    2009-05-01

    The underwater spherical robot has a spherical pressure hull which contains power modules, sensors, and so on. It lacks robot arms or end effectors but is highly maneuverable, for the simplest symmetrical geometry is the sphere. This paper analyzes the spherical robot's hydrodynamic model with CFD software, concludes the spherical robot's hydrodynamic characteristics, and compares these characteristics with the hydrodynamic model of another underwater robot which has a streamlined hull. The effect of sphere hydraulic resistance on the control of the robot is analyzed with some examples.

  20. Hydrodynamic Self-Assembly of Topographical Patterns on Soft Materials

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Satish [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-01-06

    The objective of this project is to use theoretical tools to explore fundamentally new ways of creating and controlling surface topography on soft materials (e.g., polymeric liquids, gels, colloidal suspensions) that make use of principles from hydrodynamics and self-assembly. Surface topography is known to have a significant impact on the optical, adhesive, and wetting properties of materials, so improved fundamental understanding of how to create and control it will help enable the tailoring of these properties to desired specifications. Self-assembly is the spontaneous organization of an ordered structure, and hydrodynamics often plays an important role in the self-assembly of soft materials. This research supported through this project has led to the discovery of a number of novel phenomena that are described in published journal articles. In this way, the research significantly adds to the fundamental understanding of the topics investigated.

  1. Record length, mass, and clutch size in the nonindigenous Burmese Python, Python bivittatus Kuhl 1820 (Squamata: Pythonidae), in Florida

    Science.gov (United States)

    Krysko, Kenneth L.; Hart, Kristen M.; Smith, Brian J.; Selby, Thomas H.; Cherkiss, Michael S.; Coutu, Nicholas T.; Reichart, Rebecca M.; Nuñez, Leroy P.; Mazzotti, Frank J.; Snow, Ray W.

    2012-01-01

    The Burmese Python, Python bivittatus Kuhl 1820 (Squamata: Pythonidae), is indigenous to northern India,east to southern China, and south to Vietnam and a few islands in Indonesia (Barker and Barker 2008, Reed and Rodda 2009). This species has been introduced since at least 1979 in southern Florida, USA, where it likely began reproducing and became established during the 1980s (Meshaka et al. 2000, Snowet al. 2007b,Kraus 2009, Krysko et al. 2011, Willson et al. 2011). Python bivittatus has been documented in Florida consuming a variety of mammals and birds, and the American Alligator(Alligator mississippiensis) (Snowet al. 2007a, 2007b; Harvey et al. 2008; Rochford et al. 2010b; Holbrook and Chesnes 2011), many of which are protected species. Herein, we provide details on two of the largest known wild P. bivittatus in Florida to date, including current records on length,mass,clutch size, and diet.

  2. Research on Hydrodynamics Model Test for Deepsea Open-Framed Remotely Operated Vehicle

    Institute of Scientific and Technical Information of China (English)

    FAN Shi-bo; LIAN Lian; REN Ping

    2012-01-01

    This paper presents the features of newly designed hydrodynamics test for the scaled model of 4500 m deepsea open-framed remotely operated vehicle (ROV),which is being researched and developed by Shanghai Jiao Tong University.Accurate hydrodynamics coefficients measurement and spatial modeling of ROV are significant for the maneuverability and control algorithm.The scaled model of ROV was constructed by 1∶ 1.6.Hydrodynamics coefficients were measured through VPMM and LAHPMM towing test.And dynamics model was derived as a set of equations,describing nonlinear and coupled 5-DOF spatial motions.Rotation control motion was simulated to verify spatial model proposed.Research and application of hydrodynamics coefficients are expected to enable ROV to overcome uncertainty and disturbances of deepsea environment,and accomplish some more challengeable and practical missions.

  3. Electronic 4-wheel drive control device

    Science.gov (United States)

    Hayato, S.; Takanori, S.; Shigeru, H.; Tatsunori, S.

    1984-01-01

    The internal rotation torque generated during operation of a 4-wheel drive vehicle is reduced using a control device whose clutch is attached to one part of the rear-wheel drive shaft. One torque sensor senses the drive torque associated with the rear wheel drive shaft. A second sensor senses the drive torque associated with the front wheel drive shaft. Revolution count sensors sense the revolutions of each drive shaft. By means of a microcomputer, the engagement of the clutch is changed to insure that the ratio of the torque sensors remains constant.

  4. Experimental Investigation on The Electromagnetic Clutch Water pump and Pneumatic Compressor for Improving the Efficiency of an Engine

    Science.gov (United States)

    Kumarasubramanian, R.; Xavier, Goldwin; Nishanthi, W. Mary; Rajasekar, R.

    2017-05-01

    Considering the fuel crises today many work and research were conducted to reduce the fuel consumption of the internal combustion engine. The fuel consumption of an internal combustion engine can be relatively reduced by use of the electromagnetic clutch water pump and pneumatic compressor. Normally in an engine, the water pump is driven by the crankshaft, with an aid of belt, for the circulation of the water for the cooling process. The circulation of coolant is resisted by the thermostat valve, while the temperature inside the coolant jacket of the engine is below 375K the thermostat is closed only above 375K it tends to open. But water pump run continuously even when thermostat is closed. In pneumatic braking system, pneumatic or air compressor purpose is to compress the air and stored into the storage tank for the brake operation. When the air pressure of the storage tanks gets increases above its storage capacity pressure is regulated by governor, by passing them to atmosphere. Such unnecessary work of this water pump and air compressor can be minimized by use of the electromagnetic clutch water pump and air compressor. The European Driving Cycle is used to evaluate the performance of this water pump and air compressor when used in an engine. The result shows that the fuel economy of the engine while using electromagnetic water pump and pneumatic compressor were improved by 8.0% compared with conventional types which already exist. The application of these electromagnetic water pump and pneumatic compressor are expected to contribute for the improvement of engine performance because of their effect in reduction of the rate of fuel consumption.

  5. Safety assessment of liver-targeted hydrodynamic gene delivery in dogs.

    Directory of Open Access Journals (Sweden)

    Kenya Kamimura

    Full Text Available Evidence in support of safety of a gene delivery procedure is essential toward gene therapy. Previous studies using the hydrodynamics-based procedure primarily focus on gene delivery efficiency or gene function analysis in mice. The current study focuses on an assessment of the safety of computer-controlled and liver-targeted hydrodynamic gene delivery in dogs as the first step toward hydrodynamic gene therapy in clinic. We demonstrate that the impacts of the hydrodynamic procedure were limited in the injected region and the influences were transient. Histological examination and the hepatic microcirculation measurement using reflectance spectrophotometry reveal that the liver-specific impact of the procedure involves a transient expansion of the liver sinusoids. No systemic damage or toxicity was observed. Physiological parameters, including electrocardiogram, heart rate, blood pressure, oxygen saturation, and body temperature, remained in normal ranges during and after hydrodynamic injection. Body weight was also examined to assess the long-term effects of the procedure in animals who underwent 3 hydrodynamic injections in 6 weeks with 2-week time interval in between. Serum biochemistry analysis showed a transient increase in liver enzymes and a few cytokines upon injection. These results demonstrate that image-guided, liver-specific hydrodynamic gene delivery is safe.

  6. Initial conditions for hydrodynamics from weakly coupled pre-equilibrium evolution

    CERN Document Server

    Keegan, Liam; Mazeliauskas, Aleksas; Teaney, Derek

    2016-01-01

    We use effective kinetic theory, accurate at weak coupling, to simulate the pre-equilibrium evolution of transverse energy and flow perturbations in heavy-ion collisions. We provide a Green function which propagates the initial perturbations to the energy-momentum tensor at a time when hydrodynamics becomes applicable. With this map, the complete pre-thermal evolution from saturated nuclei to hydrodynamics can be modelled in a perturbatively controlled way.

  7. Biomimetic shark skin: design, fabrication and hydrodynamic function.

    Science.gov (United States)

    Wen, Li; Weaver, James C; Lauder, George V

    2014-05-15

    Although the functional properties of shark skin have been of considerable interest to both biologists and engineers because of the complex hydrodynamic effects of surface roughness, no study to date has successfully fabricated a flexible biomimetic shark skin that allows detailed study of hydrodynamic function. We present the first study of the design, fabrication and hydrodynamic testing of a synthetic, flexible, shark skin membrane. A three-dimensional (3D) model of shark skin denticles was constructed using micro-CT imaging of the skin of the shortfin mako (Isurus oxyrinchus). Using 3D printing, thousands of rigid synthetic shark denticles were placed on flexible membranes in a controlled, linear-arrayed pattern. This flexible 3D printed shark skin model was then tested in water using a robotic flapping device that allowed us to either hold the models in a stationary position or move them dynamically at their self-propelled swimming speed. Compared with a smooth control model without denticles, the 3D printed shark skin showed increased swimming speed with reduced energy consumption under certain motion programs. For example, at a heave frequency of 1.5 Hz and an amplitude of ± 1 cm, swimming speed increased by 6.6% and the energy cost-of-transport was reduced by 5.9%. In addition, a leading-edge vortex with greater vorticity than the smooth control was generated by the 3D printed shark skin, which may explain the increased swimming speeds. The ability to fabricate synthetic biomimetic shark skin opens up a wide array of possible manipulations of surface roughness parameters, and the ability to examine the hydrodynamic consequences of diverse skin denticle shapes present in different shark species.

  8. A Displayer of Stellar Hydrodynamics Processes

    Science.gov (United States)

    Vigo, José Antonio Escartín; Senz, Domingo García

    The graphics display tool that we present here was originally developed to meet the needs of the Astronomy and Astrophysics group at the UPC (GAA). At present, it is used to display the plots obtained from hydrodynamic simulations using the SPH (smoothed particle hydrodynamics) method. It is, however, a generic program that can be used for other multidimensional hydrodynamic methods. The application combines the most widely used features of other programs (most of them commercial) such as GnuPlot, Surfer, Grapher, IDL, Voxler, etc.

  9. Non abelian hydrodynamics and heavy ion collisions

    Energy Technology Data Exchange (ETDEWEB)

    Calzetta, E. [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Ciudad Universitaria, Buenos Aires 1428 (Argentina)

    2014-01-14

    The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined by the conservation laws of energy momentum and color currents. Therefore it is possible to describe its main features in hydrodynamic terms, the very short color neutralization time notwithstanding. In this lecture we shall give a simple derivation of the hydrodynamics of a color charged fluid, by generalizing the usual derivation of hydrodynamics from kinetic theory to the non abelian case.

  10. Quantum ideal hydrodynamics on the lattice

    CERN Document Server

    Burch, Tommy

    2013-01-01

    After discussing the problem of defining the hydrodynamic limit from microscopic scales, we give an introduction to ideal hydrodynamics in the Lagrange picture, and show that it can be viewed as a field theory, which can be quantized using the usual Feynman sum-over-paths prescription. We then argue that this picture can be connected to the usually neglected thermal microscopic scale in the hydrodynamic expansion. After showing that this expansion is generally non-perturbative, we show how the lattice can be used to understand the impact quantum and thermal fluctuations can have on the fluid behavior.

  11. Non abelian hydrodynamics and heavy ion collisions

    CERN Document Server

    Calzetta, Esteban

    2013-01-01

    The goal of the relativistic heavy ion collisions (RHIC) program is to create a state of matter where color degrees of freedom are deconfined. The dynamics of matter in this state, in spite of the complexities of quantum chromodynamics, is largely determined by the conservation laws of energy momentum and color currents. Therefore it is possible to describe its main features in hydrodynamic terms, the very short color neutralization time notwithstanding. In this lecture we shall give a simple derivation of the hydrodynamics of a color charged fluid, by generalizing the usual derivation of hydrodynamics from kinetic theory to the non abelian case.

  12. Modeling and performance investigation of electromagnetic slip clutch of E-ECHPS%E-ECHPS用电磁转差离合器建模与性能研究

    Institute of Scientific and Technical Information of China (English)

    唐斌; 江浩斌; 耿国庆; 夏磊; 尧骏

    2015-01-01

    In order to solve the problems of single assisted characteristics and high reactive power loss of hydraulic power steering system, a novel electronically controlled hydraulic power steering system based on electromagnetic slip clutch ( E-ECHPS) is proposed for optimal handling and ener-gy saving, which is characterized by the electromagnetic slip clutch ( ESC) . The ESC is a key part of overall system, which is used to adjust steering pump speed to realize on-demand flow output and variable assisted characteristics. For studying ESC’ performance, the model of ESC was built and dynamical characteristics were simulated. In the dynamical characteristics, electromagnetic torque of ESC increases with excited current, and it reaches the maximum when speed difference is 600 r/min. The finite element model of ESC was constructed and the flux density curve was gained.By fast Fourier transform ( FFT) of the flux density curve, proportions of fundamental and harmonic waves were 75. 3% and 24. 7%. Optimization measures of short distance, distributed windings and chute were used, consequently fundamental wave proportion of ESC back electromotive force reached 83. 9%, increased by 11. 4%, which is demonstrated that the measures are benefit to improve the ESC air-gap magnetic field. Finally, the bench test of ESC prototype was carried out including me-chanical characteristics, input-output and input speed-field current characteristics tests. The consis-tency of simulated and experimental results indicated that the model of ESC was correct and precise;the prototype reached the design requirements.%为了解决液压助力转向系统( HPS)助力特性单一、无功损耗高的问题,提出了基于电磁转差离合器( ESC)的兼顾操控与节能的电控液压助力转向系统( E-ECHPS)。 ESC是整个系统的关键部件,为了研究其性能,建立了ESC的数学模型并仿真得到了动力学特性,ESC的电磁转矩在转差为600 r/min时达到最大,并且随着

  13. Smoothed particle hydrodynamics and magnetohydrodynamics

    Science.gov (United States)

    Price, Daniel J.

    2012-02-01

    This paper presents an overview and introduction to smoothed particle hydrodynamics and magnetohydrodynamics in theory and in practice. Firstly, we give a basic grounding in the fundamentals of SPH, showing how the equations of motion and energy can be self-consistently derived from the density estimate. We then show how to interpret these equations using the basic SPH interpolation formulae and highlight the subtle difference in approach between SPH and other particle methods. In doing so, we also critique several 'urban myths' regarding SPH, in particular the idea that one can simply increase the 'neighbour number' more slowly than the total number of particles in order to obtain convergence. We also discuss the origin of numerical instabilities such as the pairing and tensile instabilities. Finally, we give practical advice on how to resolve three of the main issues with SPMHD: removing the tensile instability, formulating dissipative terms for MHD shocks and enforcing the divergence constraint on the particles, and we give the current status of developments in this area. Accompanying the paper is the first public release of the NDSPMHD SPH code, a 1, 2 and 3 dimensional code designed as a testbed for SPH/SPMHD algorithms that can be used to test many of the ideas and used to run all of the numerical examples contained in the paper.

  14. Fluctuating hydrodynamics for ionic liquids

    Science.gov (United States)

    Lazaridis, Konstantinos; Wickham, Logan; Voulgarakis, Nikolaos

    2017-04-01

    We present a mean-field fluctuating hydrodynamics (FHD) method for studying the structural and transport properties of ionic liquids in bulk and near electrified surfaces. The free energy of the system consists of two competing terms: (1) a Landau-Lifshitz functional that models the spontaneous separation of the ionic groups, and (2) the standard mean-field electrostatic interaction between the ions in the liquid. The numerical approach used to solve the resulting FHD-Poisson equations is very efficient and models thermal fluctuations with remarkable accuracy. Such density fluctuations are sufficiently strong to excite the experimentally observed spontaneous formation of liquid nano-domains. Statistical analysis of our simulations provides quantitative information about the properties of ionic liquids, such as the mixing quality, stability, and the size of the nano-domains. Our model, thus, can be adequately parameterized by directly comparing our prediction with experimental measurements and all-atom simulations. Conclusively, this work can serve as a practical mathematical tool for testing various theories and designing more efficient mixtures of ionic liquids.

  15. Hydrodynamic properties of fin whale flippers predict maximum rolling performance.

    Science.gov (United States)

    Segre, Paolo S; Cade, David E; Fish, Frank E; Potvin, Jean; Allen, Ann N; Calambokidis, John; Friedlaender, Ari S; Goldbogen, Jeremy A

    2016-11-01

    Maneuverability is one of the most important and least understood aspects of animal locomotion. The hydrofoil-like flippers of cetaceans are thought to function as control surfaces that effect maneuvers, but quantitative tests of this hypothesis have been lacking. Here, we constructed a simple hydrodynamic model to predict the longitudinal-axis roll performance of fin whales, and we tested its predictions against kinematic data recorded by on-board movement sensors from 27 free-swimming fin whales. We found that for a given swimming speed and roll excursion, the roll velocity of fin whales calculated from our field data agrees well with that predicted by our hydrodynamic model. Although fluke and body torsion may further influence performance, our results indicate that lift generated by the flippers is sufficient to drive most of the longitudinal-axis rolls used by fin whales for feeding and maneuvering.

  16. Hydrodynamic manoeuvrability data of a flatfish type AUV

    DEFF Research Database (Denmark)

    Aage, Christian; Wagner Smitt, Leif

    1994-01-01

    Hydrodynamic manoeuvrability data of the flatfish type autonomous underwater vehicle (AUV) “MARIUS” are presented. “MARIUS” was developed under the EC MAST Programme as a vehicle for seabed inspection and environmental surveys in coastal waters. The AUV has an overall length of 4.5 m and is driven...... by two propellers and four thrusters. The data comprise added mass and inertia coefficients, damping, lift and drag coefficients of the vehicle and its control surfaces, as well as resistance and propulsion characteristics. The hydrodynamic data have been determined by full scale tests, using a towing...... tank equipped with a planar motion mechanism. A few free-sailing tests have been carried out as well. Application of the data and possible improvements of the shape of the vehicle are discussed...

  17. Hydrodynamics of Normal Atomic Gases with Spin-orbit Coupling.

    Science.gov (United States)

    Hou, Yan-Hua; Yu, Zhenhua

    2015-10-20

    Successful realization of spin-orbit coupling in atomic gases by the NIST scheme opens the prospect of studying the effects of spin-orbit coupling on many-body physics in an unprecedentedly controllable way. Here we derive the linearized hydrodynamic equations for the normal atomic gases of the spin-orbit coupling by the NIST scheme with zero detuning. We show that the hydrodynamics of the system crucially depends on the momentum susceptibilities which can be modified by the spin-orbit coupling. We reveal the effects of the spin-orbit coupling on the sound velocities and the dipole mode frequency of the gases by applying our formalism to the ideal Fermi gas. We also discuss the generalization of our results to other situations.

  18. Low torque hydrodynamic lip geometry for rotary seals

    Energy Technology Data Exchange (ETDEWEB)

    Dietle, Lannie L.; Schroeder, John E.

    2015-07-21

    A hydrodynamically lubricating geometry for the generally circular dynamic sealing lip of rotary seals that are employed to partition a lubricant from an environment. The dynamic sealing lip is provided for establishing compressed sealing engagement with a relatively rotatable surface, and for wedging a film of lubricating fluid into the interface between the dynamic sealing lip and the relatively rotatable surface in response to relative rotation that may occur in the clockwise or the counter-clockwise direction. A wave form incorporating an elongated dimple provides the gradual convergence, efficient impingement angle, and gradual interfacial contact pressure rise that are conducive to efficient hydrodynamic wedging. Skewed elevated contact pressure zones produced by compression edge effects provide for controlled lubricant movement within the dynamic sealing interface between the seal and the relatively rotatable surface, producing enhanced lubrication and low running torque.

  19. 3D Kinematics and Hydrodynamic Analysis of Freely Swimming Cetacean

    Science.gov (United States)

    Ren, Yan; Sheinberg, Dustin; Liu, Geng; Dong, Haibo; Fish, Frank; Javed, Joveria

    2015-11-01

    It's widely thought that flexibility and the ability to control flexibility are crucial elements in determining the performance of animal swimming. However, there is a lack of quantification of both span-wise and chord-wise deformation of Cetacean's flukes and associated hydrodynamic performance during actively swimming. To fill this gap, we examined the motion and flexure of both dolphin fluke and orca fluke in steady swimming using a combined experimental and computational approach. It is found that the fluke surface morphing can effectively modulate the flow structures and influence the propulsive performance. Findings from this work are fundamental for understanding key kinematic features of effective Cetacean propulsors, and for quantifying the hydrodynamic force production that naturally occurs during different types of swimming. This work is supported by ONR MURI N00014-14-1-0533 and NSF CBET-1313217.

  20. Nonlinear hydrodynamic corrections to supersonic F-KPP wave fronts

    Science.gov (United States)

    Antoine, C.; Dumazer, G.; Nowakowski, B.; Lemarchand, A.

    2012-03-01

    We study the hydrodynamic corrections to the dynamics and structure of an exothermic chemical wave front of Fisher-Kolmogorov-Petrovskii-Piskunov (F-KPP) type which travels in a one-dimensional gaseous medium. We show in particular that its long time dynamics, cut-off sensitivity and leading edge behavior are almost entirely controlled by the hydrodynamic front speed correction δUh which characterizes the pushed nature of the front. Reducing the problem to an effective comoving heterogeneous F-KPP equation, we determine two analytical expressions for δUh: an accurate one, derived from a variational method, and an approximate one, from which one can assess the δUh sensitivity to the shear viscosity and heat conductivity of the fluid of interest.

  1. Hydrodynamically driven colloidal assembly in dip coating.

    Science.gov (United States)

    Colosqui, Carlos E; Morris, Jeffrey F; Stone, Howard A

    2013-05-01

    We study the hydrodynamics of dip coating from a suspension and report a mechanism for colloidal assembly and pattern formation on smooth substrates. Below a critical withdrawal speed where the coating film is thinner than the particle diameter, capillary forces induced by deformation of the free surface prevent the convective transport of single particles through the meniscus beneath the film. Capillary-induced forces are balanced by hydrodynamic drag only after a minimum number of particles assemble within the meniscus. The particle assembly can thus enter the thin film where it moves at nearly the withdrawal speed and rapidly separates from the next assembly. The interplay between hydrodynamic and capillary forces produces periodic and regular structures below a critical ratio Ca(2/3)/sqrt[Bo] particles in suspension. The hydrodynamically driven assembly documented here is consistent with stripe pattern formations observed experimentally in dip coating.

  2. Adiabatic hydrodynamics: The eightfold way to dissipation

    CERN Document Server

    Haehl, Felix M; Rangamani, Mukund

    2015-01-01

    We provide a complete solution to hydrodynamic transport at all orders in the gradient expansion compatible with the second law constraint. The key new ingredient we introduce is the notion of adiabaticity, which allows us to take hydrodynamics off-shell. Adiabatic fluids are such that off-shell dynamics of the fluid compensates for entropy production. The space of adiabatic fluids is quite rich, and admits a decomposition into seven distinct classes. Together with the dissipative class this establishes the eightfold way of hydrodynamic transport. Furthermore, recent results guarantee that dissipative terms beyond leading order in the gradient expansion are agnostic of the second law. While this completes a transport taxonomy, we go on to argue for a new symmetry principle, an Abelian gauge invariance that guarantees adiabaticity in hydrodynamics. We suggest that this symmetry is the macroscopic manifestation of the microscopic KMS invariance. We demonstrate its utility by explicitly constructing effective ac...

  3. Thermo--hydrodynamics As a Field Theory

    CERN Document Server

    Jezierski, Jacek

    2011-01-01

    The field theoretical description of thermo-hydrodynamics is given. It is based on the duality between the physical space--time and the "material space-time" which we construct here. The material space appearing in a natural way in the canonical formulation of the hydrodynamics is completed with a material time playing role of the field potential for temperature. Both Lagrangian and Hamiltonian formulations, the canonical structure, Poisson bracket, N\\"other theorem and conservation laws are discussed.

  4. Hydrodynamics of bacterial colonies: Phase diagrams

    Science.gov (United States)

    Lega, J.; Passot, T.

    2004-09-01

    We present numerical simulations of a recent hydrodynamic model describing the growth of bacterial colonies on agar plates. We show that this model is able to qualitatively reproduce experimentally observed phase diagrams, which relate a colony shape to the initial quantity of nutrients on the plate and the initial wetness of the agar. We also discuss the principal features resulting from the interplay between hydrodynamic motions and colony growth, as described by our model.

  5. Improvements to SOIL: An Eulerian hydrodynamics code

    Energy Technology Data Exchange (ETDEWEB)

    Davis, C.G.

    1988-04-01

    Possible improvements to SOIL, an Eulerian hydrodynamics code that can do coupled radiation diffusion and strength of materials, are presented in this report. Our research is based on the inspection of other Eulerian codes and theoretical reports on hydrodynamics. Several conclusions from the present study suggest that some improvements are in order, such as second-order advection, adaptive meshes, and speedup of the code by vectorization and/or multitasking. 29 refs., 2 figs.

  6. Relabeling symmetries in hydrodynamics and magnetohydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Padhye, N.; Morrison, P.J.

    1996-04-01

    Lagrangian symmetries and concomitant generalized Bianchi identities associated with the relabeling of fluid elements are found for hydrodynamics and magnetohydrodynamics (MHD). In hydrodynamics relabeling results in Ertel`s theorem of conservation of potential vorticity, while in MHD it yields the conservation of cross helicity. The symmetries of the reduction from Lagrangian (material) to Eulerian variables are used to construct the Casimir invariants of the Hamiltonian formalism.

  7. Hydrodynamic design of the humpback whale flipper.

    Science.gov (United States)

    Fish, F E; Battle, J M

    1995-07-01

    The humpback whale (Megaptera novaeangliae) is reported to use its elongate pectoral flippers during swimming maneuvers. The morphology of the flipper from a 9.02-m whale was evaluated with regard to this hydrodynamic function. The flipper had a wing-like, high aspect ratio planform. Rounded tubercles were regularly interspersed along the flipper's leading edge. The flipper was cut into 71 2.5-cm cross-sections and photographed. Except for sections near the distal tip, flipper sections were symmetrical with no camber. Flipper sections had a blunt, rounded leading edge and a highly tapered trailing edge. Placement of the maximum thickness placement for each cross-section varied from 49% of chord at the tip to 19% at mid-span. Section thickness ratio averaged 0.23 with a range of 0.20-0.28. The humpback whale flipper had a cross-sectional design typical of manufactured aerodynamic foils for lift generation. The morphology and placement of leading edge tubercles suggest that they function as enhanced lift devices to control flow over the flipper and maintain lift at high angles of attack. The morphology of the humpback whale flipper suggests that it is adapted for high maneuverability associated with the whale's unique feeding behavior.

  8. Rotational vibration modeling and optimization design of serpentine belt accessory drive system with one-way clutch%具有单向离合器的多楔带附件驱动系统旋转振动建模及参数优化设计

    Institute of Scientific and Technical Information of China (English)

    张少飞; 上官文斌; 曾祥坤

    2012-01-01

    A mathematical model for nonlinear rotational vibration analysis of a three pulley-serpentine belt accessory drive system (SBADs) with a one-way clutch was established. Gear's method was used to calculate the angle fluctuations of driven pulleys and tensioner arm. Calculation results show that, the dynamic indices of the SBADs, including angle fluctuations of driven pulleys and tensioner arm, tension of each belt span, and slip rate between belt and pulley decrease significantly as compared with those in the case of without the one-way clutch. Then, the dynamic properties of the SBADs were investigated under different spring stiffness of the one-way clutch, and different inertia ratio of the accessory shaft and driven pulley. Moreover, an optimization design model with the spring stiffness of the one-way clutch, and the inertia of the accessory shaft as two optimizing variables was established. In the optimization model, the minima of the angle fluctuation of tensioner arm, the spring torque of one-way clutch, and the slip ratio between belt and driven pulley were taken as objective functions. The optimization results were obtained by using fminimax function in the mat lab software. The analytical results show that the dynamic responses of the SBADs decrease significantly when using the optimization parameters. The methods of modeling, calculation and optimization design are instructive for the vibration control of an engine front end accessory drive (FEAD) system with one-way clutch.%建立有单向离合器装置的三轮-多楔带附件驱动系统的非线性旋转振动数学模型.用Gear数值算法求解从动轮与张紧臂的角度波动.计算结果表明,有单向离合器装置时从动轮与张紧臂的角度波动、各带段的动态张力、带-轮间的滑移率等系统动态特性均明显减小.计算、研究单向离合器弹簧刚度的大小、附件轴与从动轮转动惯量比的大小对系统动态特性的影响.以张

  9. Introduction to thematic section on hydrodynamic studies of mineralization

    Institute of Scientific and Technical Information of China (English)

    Guoxiang Chi; Chunji Xue

    2011-01-01

    Most metallic mineral deposits formed from hydrothermal fluids,and the mineralization processes include both chemical (e.g.,fluid-rock and fluid-fluid interactions) and physical (e.g.,fluid flow) aspects.More attention has been paid to the chemical processes than the physical ones,even though the latter is equally important in controlling the formation of mineral deposits and their localization.Nevertheless,a number of studies have been carried out regarding the hydrodynamics of fluid flow associated with ore mineralization (e.g.,Cathles,1981,1997;Garven and Raffensperger,1997;Cathles and Adams,2005;Cox,2005;Ingebritsen et al.,2006),and it is timely to evaluate our current understanding on this topic and gaps in knowledge to be addressed in further studies.This special section on “Hydrodynamics of mineralization” contains four papers (Chi and Xue,2011;Xue et al.,2011;Zhang et al.,2011;Ju et al.,2011),which summarize the current status of study in the field,and present a few case studies to highlight the importance of hydrodynamics in the research of mineral deposits.

  10. Hydrodynamic interactions in freely suspended liquid crystal films

    Science.gov (United States)

    Kuriabova, Tatiana; Powers, Thomas R.; Qi, Zhiyuan; Goldfain, Aaron; Park, Cheol Soo; Glaser, Matthew A.; Maclennan, Joseph E.; Clark, Noel A.

    2016-11-01

    Hydrodynamic interactions play an important role in biological processes in cellular membranes, a large separation of length scales often allowing such membranes to be treated as continuous, two-dimensional (2D) fluids. We study experimentally and theoretically the hydrodynamic interaction of pairs of inclusions in two-dimensional, fluid smectic liquid crystal films suspended in air. Such smectic membranes are ideal systems for performing controlled experiments as they are mechanically stable, of highly uniform structure, and have well-defined, variable thickness, enabling experimental investigation of the crossover from 2D to 3D hydrodynamics. Our theoretical model generalizes the Levine-MacKintosh theory of point-force response functions and uses a boundary-element approach to calculate the mobility matrix for inclusions of finite extent. We describe in detail the theoretical and computational approach previously outlined in Z. Qi et al., Phys. Rev. Lett. 113, 128304 (2014), 10.1103/PhysRevLett.113.128304 and extend the method to study the mutual mobilities of inclusions with asymmetric shapes. The model predicts well the observed mutual mobilities of pairs of circular inclusions in films and the self-mobility of a circular inclusion in the vicinity of a linear boundary.

  11. Clutch size and breeding success of great tit (Parus major and blue tit (P. caeruleus in the parks of Kharkiv city

    Directory of Open Access Journals (Sweden)

    A. B. Chaplygina

    2014-04-01

    Full Text Available The analysis of clutch size and breeding success of great tits and blue tits is conducted using 115 nests: 92 great tits and 23 blue tits. Nest boxes for small passerine birds were made in 2009–2013 and placed in the city parks in order to improve their ecological condition. Thus, the experimental plots were established in the Central park of culture and recreation named after M. Gorky in the number of 37 nest boxes in the area of about 5 ha; in the territory of Zhuravlevskiy hydropark in the amount of 30 units on two sites on each of 4 ha and 20 units on an area of 2 ha. 20 nest boxes were placed in the forest park along the central motorway of the city. All the nest boxes were placed by the group method (distance between nest boxes was about 10–15 m at height to 3 m, and entrance diameter of 3 cm. The front wall in such nest boxes is taken out, thus facilitating their further verification carried out during the period from the first ten-day period of April till the second ten-day period of July up to ten times. It was shown that the average size of the full clutch for great tits amounted to 8.9 ± 0.35 (n = 61 and for blue tits 9.5 ± 0.33 (n = 12. The great tits has the largest proportion of 10 (33.5% and 9 eggs (16.7% in the clutch. For the blue tits the dominating figure was 10 egg (25.0% in the clutch of Zhuravlevskiy hydropark and 12 eggs (17.5% in the clutch in the Gorky park. We determined high success of reproduction for great tits (85.1% and blue tits (84.0%. On average, per one pair of great tits and blue tits 5.1 ± 0.16 and 8.5 ± 0.38 chicks, respectively, flied the nests. The decreased parameter in breeding success during the existence of an artificial population of great tits was revealed. For example, in Zhuravlevskiy hydropark on average 6.7 ± 0.12 chicks per pair flied the nests during the year of placing the nest boxes. During four years, this value decreased almost by half and amounted to 3.6 ± 0.15 (P < 0.05. For

  12. Analysis and Design of a Permanent Magnet Bi-Stable Electro-Magnetic Clutch Unit for In-Wheel Electric Vehicle Drives

    Directory of Open Access Journals (Sweden)

    Wanli Cai

    2015-06-01

    Full Text Available Clutches have been used in internal combustion vehicles and concentrated electric vehicles (EVs to smoothen impulsion while starting and shifting. This paper proposes a permanent magnet bi-stable electromagnetic clutch unit (PMBECU which is specially introduced into in-wheel EVs to make the rigid connection between hub and wheel more flexible. Firstly, the operation principle of the PMBECU is illustrated. Then, the basic magnetic circuit model is presented and analyzed, followed by optimal design of the main structural parameters by investigating the PM leakage flux coefficient. Further, according to the basic electromagnetic characteristics of the PMBECU, the current pulse supply is put forward, and the minimum pulse width which enables the operation of the PMBECU and its dynamic characteristics are analyzed by an improved finite element method. Finally, a prototype machine is manufactured and tested to validate all the analysis results.

  13. Dynamic analysis of archimedes curved surface wedge PCE clutch%阿基米德曲面楔块的PCE型离合器动力学特性分析

    Institute of Scientific and Technical Information of China (English)

    严宏志; 吴凯; 何明生; 谭援强

    2011-01-01

    根据离合器设计理论,设计了阿基米德曲面楔块的PCE型离合器和单圆弧曲面楔块的PCE型离合器.在对两种PCE型离合器进行三维几何造型基础上,建立其动力学模型,对比分析了阿基米德曲面楔块的PCE型离合器与单圆弧曲面楔块的PCE型离合器的楔合时同、楔入冲击力及稳态楔合力等参数,结果表明阿基米德曲面楔块的PCE型离合器具有楔入迅速、冲击较小、稳态楔合力小的特点,具有较好的综合性能.文中研究为阿基米德曲面楔块的PCE型离合器的设计及应用提供了重要依据.%The Archimedes curved surface wedge PCE clutch and the single arc curved surface wedge PCE clutch were designed according to the theory of clutch design. The dynamic model of two kinds of PCE clutches were established on the basis of their three dimensional geometric models. A comparative analysis was done on the engagement time, impact of engagement, steady state engage ment force and other parameters of the Archimedes curved surface wedge PCE clutch and the single arc curved surface wedge PCE clutch. The results indicate that the Archimedes curved surface wedge PCE clutch has the characteristics as quick engagement, lower impact and low steady state engagement force , which is good in comprehensive property. This study provides an important basis for the Archimedes curved surface wedge PCE clutch design and ap plication.

  14. Asynchronous Electric Motor with Built-in Combined Braking Device Based on Electro-Mechanical Brake and Electro-Magnetic Clutch

    OpenAIRE

    V. V. Solenkov; Brel, V. V.

    2011-01-01

    The paper shows advantages and disadvantages of the known designs of asynchronous motors with electro-mechanical braking device. A new developed and studied asynchronous motor design with built-in combined braking device based on an electro-mechanical brake and an electro-magnetic clutch is given in the paper. The paper describes its advantages and prospects of its usage for electric drives operating in intermittent cycle.

  15. Asynchronous Electric Motor with Built-in Combined Braking Device Based on Electro-Mechanical Brake and Electro-Magnetic Clutch

    Directory of Open Access Journals (Sweden)

    V. V. Solenkov

    2011-01-01

    Full Text Available The paper shows advantages and disadvantages of the known designs of asynchronous motors with electro-mechanical braking device. A new developed and studied asynchronous motor design with built-in combined braking device based on an electro-mechanical brake and an electro-magnetic clutch is given in the paper. The paper describes its advantages and prospects of its usage for electric drives operating in intermittent cycle.

  16. 一种液压夹套式平动离合器的设计和试验研究%The Design and Experiment of a Hydraulic Metal Thin-wall Clutch

    Institute of Scientific and Technical Information of China (English)

    韩旭; 马德森; 赵国平; 童军

    2016-01-01

    该文介绍一种液压夹套式平动离合器,该离合器利用液压夹套金属薄壁段受压应力变形和释放压力后金属薄壁回弹的性能实现离合功能,使用了液压油作为介质对薄壁均匀施压。经过初步结构设计及仿真设计了离合器产品。经过离合器的试验研究,考核了离合器性能,并通过试验研究的结果对仿真参数进行了修正。%This paper introduces a Hydraulic metal thin-wall clutch used in translational motion mechanism. The deformation and spring-back of the metal thin-wall is used for separation and reunion of the clutch. The clutch uses hydraulic oil to impose pressure in whole worked area. The clutch is designed after first structural design and simulation. Through experiment of the clutch, the function of the clutch is tested, and the results of the experiment improve the simulation.

  17. 锥盘摩擦离合器性能优化设计及试验%Optimization Design and Test for the Cone Friction Clutch

    Institute of Scientific and Technical Information of China (English)

    李久武; 吉晓界

    2012-01-01

    锥盘摩擦离合器一般位于电机和动力部件中间,以达到缓冲和传递转矩的目的.如果设计不合理和工艺及试验等方面不够完善,很可能达不到预期效果,还可能引起事故.通过锥盘摩擦离合器优化设计和实际工艺及试验,取得一些经验,对锥盘摩擦离合器推广应用起到一定作用.%The cone friction clutch is generally located between motor and power components, in order to buffer and transfer torsion. If the design is unreasonable, or the processes and tests are not desired, it may not achieve the desired effect, and may cause some accidents. By the cone disk friction clutch design calculations and the actual process and test, the experience is obtained and it' s useful to promote the cone friction clutch.

  18. Variation in egg size and nestling growth rate in relation to clutch size and laying sequence in great tits Parus major

    Institute of Scientific and Technical Information of China (English)

    Yuyan You; Jiang Feng; Haitao Wang; Jilong Wang; Chao Dong; Xunrui Su; Hanmei Sun; Wei Gao

    2009-01-01

    The objectives of this study were to examine (1) optimal clutch size in great tits (Parus major) nesting in nest boxes;(2) variation in egg morphology and nestling growth rate with position in the laying sequence;and (3) hatching asynchrony and nestling survival as determined by infrared nest cameras.We collected data from 73 clutches in artificial nest boxes in the Zuojia Natural Preserve area in Jilin Province,China,in 2005 and 2006,using infrared cameras to match laying order to hatching order for four nests.Egg morphology and growth rate were significantly affected by clutch size and position in the laying order.Overall,egg size and growth rate increased with position in the laying order.In general,it was difficult to detect asynchronous hatching from observations alone,but data from our infrared cameras showed that early-laid eggs tended to hatch before later-laid eggs,leading to hatching asynchrony.However,females invested more into last-laid eggs and nestlings,reducing size asynchrony among the chicks and leading to higher survival rates of nestlings.Our results,therefore,provide support for the "brood survival" hypothesis rather than for the "brood reduction" hypothesis.

  19. Effects of sea ice on breeding numbers and clutch size of a high arctic population of the common eider Somateria mollissima

    Science.gov (United States)

    Mehlum, Fridtjof

    2012-04-01

    The breeding performance of high-arctic bird populations shows large inter-annual variation that may be attributed to environmental variability, such as the timing of snow melt and break-up of the landfast sea ice that surrounds breeding colonies on islands and along coasts. In the Kongsfjorden area (79°N) on Svalbard, the number of breeding pairs and the average egg clutch size vary considerably among years. In this study, data on breeding performance are presented from 15 years in the period 1981-2000. The results showed that early break-up of sea ice in Kongsfjorden resulted in larger numbers of nests and larger average clutch sizes than late break-up. Also, individual islands with early break-up of sea ice in a particular year had more nests and larger clutch sizes compared to other islands surrounded by sea ice during a longer period in spring. Thus, the inter-annual variation in the break-up of sea ice in the fjord has considerable implications for the inter-annual variability of recruitment to the population. The results indicate that the effects of global warming on changes in the sea ice melting regime in coastal regions are important for the reproductive output of island-nesting eiders.

  20. Influence of wall slip on the hydrodynamic behavior of a two-dimensional slider bearing

    Institute of Scientific and Technical Information of China (English)

    G.J.Ma; C.W.Wu; P.Zhou

    2007-01-01

    In the present paper, a multi-linearity method is used to address the nonlinear slip control equation for the hydrodynamic analysis of a two-dimensional (2-D) slip gap flow. Numerical analysis of a finite length slider beating with wall slip shows that the surface limiting shear stress exerts complicated influences on the hydrodynamic behavior of the gap flow. If the slip occurs at either the stationary surface or the moving surface (especially at the stationary surface),there is a transition point in the initial limiting shear stress for the proportional coefficient to affect the hydrodynamic load support in two opposite ways: it increases the hydrody-namic load support at higher initial limiting shear stresses, but decreases the hydrodynamic load support at lower ini-tial limiting shear stresses. If the slip occurs at the moving surface only, no fluid pressure is generated in the case of null initial limiting shear stress. If the slip occurs at both the surfaces with the same slip property, the hydrodynamic load support goes off after a critical sliding speed is reached. A small initial limiting shear stress and a small proportionality coefficient always give rise to a low friction drag.

  1. Numerical Prediction of Hydrodynamic Forces on A Ship Passing Through A Lock

    Institute of Scientific and Technical Information of China (English)

    王宏志; 邹早建

    2014-01-01

    While passing through a lock, a ship usually undergoes a steady forward motion at low speed. Owing to the size restriction of lock chamber, the shallow water and bank effects on the hydrodynamic forces acting on the ship may be remarkable, which may have an adverse effect on navigation safety. However, the complicated hydrodynamics is not yet fully understood. This paper focuses on the hydrodynamic forces acting on a ship passing through a lock. The unsteady viscous flow and hydrodynamic forces are calculated by applying an unsteady RANS code with a RNG k-εturbulence model. User-defined function (UDF) is compiled to define the ship motion. Meanwhile, the grid regeneration is dealt with by using the dynamic mesh method and sliding interface technique. Numerical study is carried out for a bulk carrier ship passing through the Pierre Vandamme Lock in Zeebrugge at the model scale. The proposed method is validated by comparing the numerical results with the data of captive model tests. By analyzing the numerical results obtained at different speeds, water depths and eccentricities, the influences of speed, water depth and eccentricity on the hydrodynamic forces are illustrated. The numerical method proposed in this paper can qualitatively predict the ship-lock hydrodynamic interaction. It can provide certain guidance on the manoeuvring and control of ships passing through a lock.

  2. Hydrodynamic Modeling and Its Application in AUC.

    Science.gov (United States)

    Rocco, Mattia; Byron, Olwyn

    2015-01-01

    The hydrodynamic parameters measured in an AUC experiment, s(20,w) and D(t)(20,w)(0), can be used to gain information on the solution structure of (bio)macromolecules and their assemblies. This entails comparing the measured parameters with those that can be computed from usually "dry" structures by "hydrodynamic modeling." In this chapter, we will first briefly put hydrodynamic modeling in perspective and present the basic physics behind it as implemented in the most commonly used methods. The important "hydration" issue is also touched upon, and the distinction between rigid bodies versus those for which flexibility must be considered in the modeling process is then made. The available hydrodynamic modeling/computation programs, HYDROPRO, BEST, SoMo, AtoB, and Zeno, the latter four all implemented within the US-SOMO suite, are described and their performance evaluated. Finally, some literature examples are presented to illustrate the potential applications of hydrodynamics in the expanding field of multiresolution modeling.

  3. Anisotropic hydrodynamics for conformal Gubser flow

    Energy Technology Data Exchange (ETDEWEB)

    Strickland, Michael; Nopoush, Mohammad [Kent State University, Kent OH 44242 (United States); Ryblewski, Radoslaw [The H. Niewodniczański Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków (Poland)

    2016-12-15

    In this proceedings contribution, we review the exact solution of the anisotropic hydrodynamics equations for a system subject to Gubser flow. For this purpose, we use the leading-order anisotropic hydrodynamics equations which assume that the distribution function is ellipsoidally symmetric in local-rest-frame momentum. We then prove that the SO(3){sub q} symmetry in de Sitter space constrains the anisotropy tensor to be of spheroidal form with only one independent anisotropy parameter remaining. As a consequence, the exact solution reduces to the problem of solving two coupled non-linear differential equations. We show that, in the limit that the relaxation time goes to zero, one obtains Gubser's ideal hydrodynamic solution and, in the limit that the relaxation time goes to infinity, one obtains the exact free streaming solution obtained originally by Denicol et al. For finite relaxation time, we solve the equations numerically and compare to the exact solution of the relaxation-time-approximation Boltzmann equation subject to Gubser flow. Using this as our standard, we find that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches.

  4. Within-clutch variation in offspring sex determined by differences in sire body size: cryptic mate choice in the wild.

    Science.gov (United States)

    Calsbeek, Ryan; Sinervo, Barry

    2004-03-01

    Sexual selection theory predicts that paternal quality should drive female investment in progeny. We tested whether polyandrous female side-blotched lizards, Uta stansburiana, would adjust within-clutch progeny investment according to sire phenotypes. In two different years, polyandrous females selectively used sperm from larger sires to produce sons and used sperm from smaller sires to produce daughters. This cryptic sperm choice had significant effects on progeny survival to maturity that were consistent with sexually antagonistic effects associated with sire body size. Large sires produced sons with high viability and small sires produced daughters with high viability. These results are consistent with our previous findings that alleles for male body size have different fitness effects in male and female progeny. Breeding experiments in the laboratory indicate that results from the wild are more likely due to female choice than biased sperm production by males. Our results demonstrate highly refined gender-specific female choice for sperm and indicate that sire body size may signal the quality of sons or daughters that a sire will produce.

  5. Status and future of hydrodynamical model atmospheres

    CERN Document Server

    Ludwig, H G

    2004-01-01

    Since about 25 years ago work has been dedicated to the development of hydrodynamical model atmospheres for cool stars (of A to T spectral type). Despite their obviously sounder physical foundation in comparison with standard hydrostatic models, their general application has been rather limited. In order to understand why this is, and how to progress, we review the present status of hydrodynamical modelling of cool star atmospheres. The development efforts were and are motivated by the theoretical interest of understanding the dynamical processes operating in stellar atmospheres. To show the observational impact, we discuss examples in the fields of spectroscopy and stellar structure where hydrodynamical modelling provided results on a level qualitatively beyond standard models. We stress present modelling challenges, and highlight presently possible and future observations that would be particularly valuable in the interplay between model validation and interpretation of observables, to eventually widen the ...

  6. First Numerical Simulations of Anomalous Hydrodynamics

    CERN Document Server

    Hongo, Masaru; Hirano, Tetsufumi

    2013-01-01

    Anomalous hydrodynamics is a low-energy effective theory that captures effects of quantum anomalies. We develop a numerical code of anomalous hydrodynamics and apply it to dynamics of heavy-ion collisions, where anomalous transports are expected to occur. This is the first attempt to perform fully non-linear numerical simulations of anomalous hydrodynamics. We discuss implications of the simulations for possible experimental observations of anomalous transport effects. From analyses of the charge-dependent elliptic flow parameters ($v_2^\\pm$) as a function of the net charge asymmetry $A_\\pm$, we quantitatively verify that the linear dependence of $\\Delta v_2 \\equiv v_2^- - v_2^+$ on the net charge asymmetry $A_\\pm$ cannot be regarded as a sensitive signal of anomalous transports, contrary to previous studies. We, however, find that the intercept $\\Delta v_2(A_\\pm=0)$ is sensitive to anomalous transport effects.

  7. Hydrodynamics of a unitary Bose gas

    Science.gov (United States)

    Man, Jay; Fletcher, Richard; Lopes, Raphael; Navon, Nir; Smith, Rob; Hadzibabic, Zoran

    2016-05-01

    In general, normal-phase Bose gases are well described by modelling them as ideal gases. In particular, hydrodynamic flow is usually not observed in the expansion dynamics of normal gases, and is more readily observable in Bose-condensed gases. However, by preparing strongly-interacting clouds, we observe hydrodynamic behaviour in normal-phase Bose gases, including the `maximally' hydrodynamic unitary regime. We avoid the atom losses that often hamper experimental access of this regime by using radio-frequency injection, which switches on interactions much faster than trap or loss timescales. At low phase-space densities, we find excellent agreement with a collisional model based on the Boltzmann equation. At higher phase-space densities our results show a deviation from this model in the vicinity of an Efimov resonance, which cannot be accounted for by measured losses.

  8. Hydrodynamics of the Chiral Dirac Spectrum

    CERN Document Server

    Liu, Yizhuang; Zahed, Ismail

    2016-01-01

    We derive a hydrodynamical description of the eigenvalues of the chiral Dirac spectrum in the vacuum and in the large $N$ (volume) limit. The linearized hydrodynamics supports sound waves. The stochastic relaxation of the eigenvalues is captured by a hydrodynamical instanton configuration which follows from a pertinent form of Euler equation. The relaxation from a phase of localized eigenvalues and unbroken chiral symmetry to a phase of de-localized eigenvalues and broken chiral symmetry occurs over a time set by the speed of sound. We show that the time is $\\Delta \\tau=\\pi\\rho(0)/2\\beta N$ with $\\rho(0)$ the spectral density at zero virtuality and $\\beta=1,2,4$ for the three Dyson ensembles that characterize QCD with different quark representations in the ergodic regime.

  9. Hydrodynamics of bacterial colonies: A model

    Science.gov (United States)

    Lega, J.; Passot, T.

    2003-03-01

    We propose a hydrodynamic model for the evolution of bacterial colonies growing on soft agar plates. This model consists of reaction-diffusion equations for the concentrations of nutrients, water, and bacteria, coupled to a single hydrodynamic equation for the velocity field of the bacteria-water mixture. It captures the dynamics inside the colony as well as on its boundary and allows us to identify a mechanism for collective motion towards fresh nutrients, which, in its modeling aspects, is similar to classical chemotaxis. As shown in numerical simulations, our model reproduces both usual colony shapes and typical hydrodynamic motions, such as the whirls and jets recently observed in wet colonies of Bacillus subtilis. The approach presented here could be extended to different experimental situations and provides a general framework for the use of advection-reaction-diffusion equations in modeling bacterial colonies.

  10. Hydrodynamics, resurgence and trans-asymptotics

    CERN Document Server

    Basar, Gokce

    2015-01-01

    The second-order hydrodynamical description of a homogeneous conformal plasma that undergoes a boost- invariant expansion is given by a single nonlinear ordinary differential equation, whose resurgent asymptotic properties we study, developing further the recent work of Heller and Spalinski [Phys. Rev. Lett. 115, 072501 (2015)]. Resurgence clearly identifies the non-hydrodynamic modes that are exponentially suppressed at late times, analogous to the quasi-normal-modes in gravitational language, organizing these modes in terms of a trans-series expansion. These modes are analogs of instantons in semi-classical expansions, where the damping rate plays the role of the instanton action. We show that this system displays the generic features of resurgence, with explicit quantitative relations between the fluctuations about different orders of these non-hydrodynamic modes. The imaginary part of the trans-series parameter is identified with the Stokes constant, and the real part with the freedom associated with init...

  11. Holography, Hydrodynamization and Heavy-Ion Collisions

    CERN Document Server

    Heller, Michal P

    2016-01-01

    In the course of the past several years holography has emerged as an ab initio tool in exploring strongly-time-dependent phenomena in gauge theories. These lecture notes overview recent developments in this area driven by phenomenological questions concerning applicability of hydrodynamics under extreme conditions occurring in ultrarelativistic heavy-ion collisions at RHIC and LHC. The topics include equilibration time scales, holographic collisions and hydrodynamization from the point of view of the asymptotic character of the hydrodynamic gradient expansion. The emphasis is put on concepts rather than calculational techniques and particular attention is devoted to present these developments in the context of the most recent advances and some of the open problems.

  12. The RAGE radiation-hydrodynamic code

    CERN Document Server

    Gittings, Michael; Clover, Michael; Betlach, Thomas; Byrne, Nelson; Coker, Robert; Dendy, Edward; Hueckstaedt, Robert; New, Kim; Oakes, W Rob; Ranta, Dale; Stefan, Ryan

    2008-01-01

    We describe RAGE, the ``Radiation Adaptive Grid Eulerian'' radiation-hydrodynamics code, including its data structures, its parallelization strategy and performance, its hydrodynamic algorithm(s), its (gray) radiation diffusion algorithm, and some of the considerable amount of verification and validation efforts. The hydrodynamics is a basic Godunov solver, to which we have made significant improvements to increase the advection algorithm's robustness and to converge stiffnesses in the equation of state. Similarly, the radiation transport is a basic gray diffusion, but our treatment of the radiation-material coupling, wherein we converge nonlinearities in a novel manner to allow larger timesteps and more robust behavior, can be applied to any multi-group transport algorithm.

  13. Hydrodynamic dispersion broadening of a sedimentation front

    Science.gov (United States)

    Martin, J.; Rakotomalala, N.; Salin, D.

    1994-10-01

    Hydrodynamic dispersion is responsible for the spreading of the sedimentation front even in a noncolloidal monodisperse suspension. Measurements of the broadening of the top front observed during sedimentation have been used in determining the hydrodynamic dispersion coefficient. Hindered settling has an opposed effect and leads to the self-sharpening of the front. Both effects have to be taken into account simultaneously. This Letter provides a simple, but complete determination of the space and time concentration profile and shows that the final front should consist of a steady-shape profile propagating at constant velocity. With such a solution, the data of Davis et al. [AIChE J. 34, 123 (1988); J. Fluid Mech. 196, 107 (1988)] give hydrodynamic dispersion coefficient five times larger than their former analysis, in agreement with Lee et al. [Phys. Fluids A 4, 2601 (1992)].

  14. Radiation hydrodynamics integrated in the PLUTO code

    Science.gov (United States)

    Kolb, Stefan M.; Stute, Matthias; Kley, Wilhelm; Mignone, Andrea

    2013-11-01

    Aims: The transport of energy through radiation is very important in many astrophysical phenomena. In dynamical problems the time-dependent equations of radiation hydrodynamics have to be solved. We present a newly developed radiation-hydrodynamics module specifically designed for the versatile magnetohydrodynamic (MHD) code PLUTO. Methods: The solver is based on the flux-limited diffusion approximation in the two-temperature approach. All equations are solved in the co-moving frame in the frequency-independent (gray) approximation. The hydrodynamics is solved by the different Godunov schemes implemented in PLUTO, and for the radiation transport we use a fully implicit scheme. The resulting system of linear equations is solved either using the successive over-relaxation (SOR) method (for testing purposes) or using matrix solvers that are available in the PETSc library. We state in detail the methodology and describe several test cases to verify the correctness of our implementation. The solver works in standard coordinate systems, such as Cartesian, cylindrical, and spherical, and also for non-equidistant grids. Results: We present a new radiation-hydrodynamics solver coupled to the MHD-code PLUTO that is a modern, versatile, and efficient new module for treating complex radiation hydrodynamical problems in astrophysics. As test cases, either purely radiative situations, or full radiation-hydrodynamical setups (including radiative shocks and convection in accretion disks) were successfully studied. The new module scales very well on parallel computers using MPI. For problems in star or planet formation, we added the possibility of irradiation by a central source.

  15. 轿车用干式离合器的发展潜力和局限%Potential and limits of the passenger car dry clutch

    Institute of Scientific and Technical Information of China (English)

    MatthiasFischer; SachsAG

    2003-01-01

    比较不同的传动系统可知,在欧洲内燃机和带启动马达的多档圆柱齿轮变速器仍然占据领导地位.在最主要的轻型和中型轿车方面,机械自动变速器的份额将明显增加,因为它们具有减少燃油消耗和排放的潜力和突出的效费比.干式离合器作为一启动和换档元件,在传扭能力安装空间和操纵力等方面进一步发展后将能适应新的要求.而干式离合器特有的优点,如高效率和无阻力矩将继续保持下去,同时成本仍可维持在相对低的水平.在持续打滑时的热容量或热变形问题等缺点可通过增加能耗来解决.在一些不考虑舒适性的工况下,可通过合适的控制策略以避免离合器的过载.%Comparison of different driveline variants shows that the combustion engine and the spur gear multistage transmission, complemented by the starter generator, will remain a leading driveline concept in Europe. In the important sector for compact and medium-size cars, the number of automated manual trans-missions will significantly increase on account of their potential for reduced consumption and emission and their outstanding cost-effectiveness.The dry clutch, as the accessory starting and shifting component, can be adapted to new requirements through developments regarding torque capacity, installation space and operating forces. The specific ad-vantages, such as efficiency and the absence of drag torque, are maintained in this process, with costs re-maining relatively Iow. The disadvantages, such as the thermal capacity under permanent slipping or creep-ing should be avoided in view of the resulting consumption increase. When in certain operating situations this is not possible for reasons of comport, overloading can be avoided by means of appropriate control strategies.

  16. Fish stocking density impacts tank hydrodynamics

    DEFF Research Database (Denmark)

    Rasmussen, Michael R.; Lunger, Angela; Laursen, Jesper;

    2006-01-01

    hydrodynamics was established using in-tank-based Rhodamine WT fluorometry at a flow rate of 0.23 l s-1 (tank exchange rate of 1.9 h-1). With increasing numbers of animals, curvilinear relationships were observed for dispersion coefficients and tank mixing times. Stocking densities of 3, 6, 9 and 12 kg m-3......The effect of stocking density upon the hydrodynamics of a circular tank, configured in a recirculation system, was investigated. Red drums Sciaenops ocellatus of approximately 140 g wet weight, were stocked at five rates varying from 0 to 12 kg m-3. The impact of the presence of fish upon tank...

  17. Bounce-free Spherical Hydrodynamic Implosion

    CERN Document Server

    Kagan, Grigory; Hsu, Scott C; Awe, Thomas J

    2011-01-01

    In a bounce-free spherical hydrodynamic implosion, the post-stagnation hot core plasma does not expand against the imploding flow. Such an implosion scheme has the advantage of improving the dwell time of the burning fuel, resulting in a higher fusion burn-up fraction. The existence of bounce-free spherical implosions is demonstrated by explicitly constructing a family of self-similar solutions to the spherically symmetric ideal hydrodynamic equations. When applied to a specific example of plasma liner driven magneto-inertial fusion, the bounce-free solution is found to produce at least a factor of four improvement in dwell time and fusion energy gain.

  18. Introduction to physics mechanics, hydrodynamics thermodynamics

    CERN Document Server

    Frauenfelder, P

    2013-01-01

    Introduction of Physics: Mechanics , Hydrodynamics, Thermodynamics covers the principles of matter and its motion through space and time, as well as the related concepts of energy and force. This book is composed of eleven chapters, and begins with an introduction to the basic principles of mechanics, hydrodynamics, and thermodynamics. The subsequent chapters deal with the statics of rigid bodies and the dynamics of particles and rigid bodies. These topics are followed by discussions on elasticity, mechanics of fluids, the basic concept of thermodynamic, kinetic theory, and crystal structure o

  19. Supernova hydrodynamics experiments using the Nova laser

    Energy Technology Data Exchange (ETDEWEB)

    Remington, B.A.; Glendinning, S.G.; Estabrook, K.; Wallace, R.J.; Rubenchik, A. [Lawrence Livermore National Lab., CA (United States); Kane, J.; Arnett, D. [Arizona Univ., Tucson, AZ (United States). Stewart Observatory; Drake, R.P. [Michigan Univ., Ann Arbor, MI (United States); McCray, R. [Colorado Univ., Boulder, CO (United States)

    1997-04-01

    We are developing experiments using the Nova laser to investigate two areas of physics relevant to core-collapse supernovae (SN): (1) compressible nonlinear hydrodynamic mixing and (2) radiative shock hydrodynamics. In the former, we are examining the differences between the 2D and 3D evolution of the Rayleigh-Taylor instability, an issue critical to the observables emerging from SN in the first year after exploding. In the latter, we are investigating the evolution of a colliding plasma system relevant to the ejecta-stellar wind interactions of the early stages of SN remnant formation. The experiments and astrophysical implications are discussed.

  20. Broken Lifshitz invariance, spin waves and hydrodynamics

    CERN Document Server

    Roychowdhury, Dibakar

    2016-01-01

    In this paper, based on the basic principles of thermodynamics, we explore the hydrodynamic regime of interacting Lifshitz field theories in the presence of broken rotational invariance. We compute the entropy current and discover new dissipative effects those are consistent with the principle of local entropy production in the fluid. In our analysis, we consider both the parity even as well as the parity odd sector upto first order in the derivative expansion. Finally, we argue that the present construction of the paper could be systematically identified as that of the hydrodynamic description associated with \\textit{spin waves} (away from the domain of quantum criticality) under certain limiting conditions.

  1. Colliding shockwaves and hydrodynamics in extreme conditions

    CERN Document Server

    Chesler, Paul M

    2015-01-01

    Using numerical holography, we study the collision of a planar sheet of energy with a bounded localized distribution of energy. The collision, which mimics proton-nucleus collisions, produces a localized lump of debris with transverse size $R \\sim 1/T_{\\rm eff}$ with $T_{\\rm eff}$ the effective temperature, and has large gradients and large transverse flow. Nevertheless, the post-collision evolution is well-described by viscous hydrodynamics. Our results bolster the notion that debris produced in proton-nucleus collisions may be modeled using hydrodynamics.

  2. Hydrodynamic interactions between nearby slender filaments

    CERN Document Server

    Man, Yi; Lauga, Eric

    2016-01-01

    Cellular biology abound with filaments interacting through fluids, from intracellular microtubules, to rotating flagella and beating cilia. While previous work has demonstrated the complexity of capturing nonlocal hydrodynamic interactions between moving filaments, the problem remains difficult theoretically. We show here that when filaments are closer to each other than their relevant length scale, the integration of hydrodynamic interactions can be approximately carried out analytically. This leads to a set of simplified local equations, illustrated on a simple model of two interacting filaments, which can be used to tackle theoretically a range of problems in biology and physics.

  3. Holography and hydrodynamics in small systems

    Science.gov (United States)

    Chesler, Paul M.

    2016-12-01

    Using holographic duality, we present results for the off-center collision of Gaussian wave packets in strongly coupled N = 4 supersymmetric Yang-Mills theory. The wave packets are thin along the collision axis and superficially at least resemble Lorentz contracted colliding protons. The collision results in the formation of a droplet of liquid of size R ∼ 1 /Teff where Teff is the effective temperature, which is the characteristic microscopic scale in strongly coupled plasma. These results demonstrate the applicability of hydrodynamics to microscopically small systems and bolster the notion that hydrodynamics can be applied to heavy-light ion collisions as well as proton-proton collisions.

  4. Family Planning in the Kestrel (Falco tinnunculus) : The Proximate Control of Covariation of Laying Date and Clutch Size

    NARCIS (Netherlands)

    Meijer, Theo; Daan, Serge; Hall, Michael

    The time in spring when a male kestrel rapidly increases his daily hunting time and his hunting yield, and thereby the amount of food delivered to the female, determines the date when she lays the first egg. Food experiments in free-living and captive kestrels gave a significant advance in laying

  5. Drivability Improvement Control for Vehicle Start-Up Applied to an Automated Manual Transmission

    Directory of Open Access Journals (Sweden)

    Danna Jiang

    2017-01-01

    Full Text Available Drivability is the key factor for the automated manual transmission. It includes fast response to the driver’s demand and the driving comfort. This paper deals with a control methodology applied to an automated manual transmission vehicle for drivability enhancement during vehicle start-up phase. Based on a piecewise model of powertrain, a multiple-model predictive controller (mMPC is designed with the engine speed, clutch disc speed, and wheel speed as the measurable input variables and the engine torque reference and clutch friction torque reference as the controller’s output variables. The model not only includes the clutch dynamic, the flexible shaft dynamic, but also includes the actuators’ delay character. Considering the driver’s intention, a slipping speed trajectory is generated based on the acceleration pedal dynamically. The designed control strategy is verified on a complete powertrain and longitudinal vehicle dynamic model with different driver’s torque demands.

  6. Within clutch co-variation of egg mass and sex in the black-headed gull

    NARCIS (Netherlands)

    Mueller, Wendt; Groothuis, TGG; Eising, CM; Daan, S; Dijkstra, C

    Female birds of several species have control over the production of daughters and sons. However, most studies failed to find a relationship between egg size and sex. This is intriguing as adjustment of egg size would constitute a powerful tool for the female to meet different resource demands of the

  7. Hydrodynamic Forces on Composite Structures

    Science.gov (United States)

    2014-06-01

    tub test rig and a wireless data acquisition system was contained on the carriage Figure 15 Tow tank dimensions, from [18] A Baldor Super-E motor...connected to the carriage assembly by a series of pulleys. The motor is controlled by the Baldor VS1SP AC inverter utilizing Voltage/Hz control...demonstrating a slowdown of the Baldor motor with resistance applied, it was important to gather data on each case of speed. Furthermore, as

  8. Research on the Unsteady Hydrodynamic Characteristics of Vertical Axis Tidal Turbine

    Institute of Scientific and Technical Information of China (English)

    张学伟; 张亮; 王峰; 赵东亚; 庞程燕

    2014-01-01

    The unsteady hydrodynamic characteristics of vertical axis tidal turbine are investigated by numerical simulation based on viscous CFD method. The starting mechanism of the turbine is revealed through analyzing the interaction of its motion and dynamics during starting process. The operating hydrodynamic characteristics of the turbine in wave-current condition are also explored by combining with the linear wave theory. According to possible magnification of the cyclic loads in the maximum power tracking control of vertical axis turbine, a novel torque control strategy is put forward, which can improve the structural characteristics significantly without effecting energy efficiency.

  9. Vortex-Based Aero- and Hydrodynamic Estimation

    Science.gov (United States)

    Hemati, Maziar Sam

    Flow control strategies often require knowledge of unmeasurable quantities, thus presenting a need to reconstruct flow states from measurable ones. In this thesis, the modeling, simulation, and estimator design aspects of flow reconstruction are considered. First, a vortex-based aero- and hydrodynamic estimation paradigm is developed to design a wake sensing algorithm for aircraft formation flight missions. The method assimilates wing distributed pressure measurements with a vortex-based wake model to better predict the state of the flow. The study compares Kalman-type algorithms with particle filtering algorithms, demonstrating that the vortex nonlinearities require particle filters to yield adequate performance. Furthermore, the observability structure of the wake is shown to have a negative impact on filter performance regardless of the algorithm applied. It is demonstrated that relative motions can alleviate the filter divergence issues associated with this observability structure. In addition to estimator development, the dissertation addresses the need for an efficient unsteady multi-body aerodynamics testbed for estimator and controller validation studies. A pure vortex particle implementation of a vortex panel-particle method is developed to satisfy this need. The numerical method is demonstrated on the impulsive startup of a flat plate as well as the impulsive startup of a multi-wing formation. It is clear, from these validation studies, that the method is able to accommodate the unsteady wake effects that arise in formation flight missions. Lastly, successful vortex-based estimation is highly dependent on the reliability of the low-order vortex model used in representing the flow of interest. The present treatise establishes a systematic framework for vortex model improvement, grounded in optimal control theory and the calculus of variations. By minimizing model predicted errors with respect to empirical data, the shortcomings of the baseline vortex model

  10. Cryptic female choice: frogs reduce clutch size when amplexed by undesired males.

    OpenAIRE

    Reyer, H U; Frei, G; Som, C

    1999-01-01

    In species with internal fertilization, females can 'cryptically' choose (e.g. through sperm selection) which individuals sire their offspring, even when their overt preferences for copulatory partners are overrun by male-male competition and sexual coercion. The experiment presented here reveals that control of paternity after copulation has begun is also possible in species with external fertilization. Females of the hybridogenetic Rana essonae-Rana esculenta (LL-LR) waterfrog complex adjus...

  11. A kinetic clutch governs religation by type IB topoisomerases and determines camptothecin sensitivity

    OpenAIRE

    2012-01-01

    Type IB topoisomerases (Top1Bs) relax excessive DNA supercoiling associated with replication and transcription by catalyzing a transient nick in one strand to permit controlled rotation of the DNA about the intact strand. The natural compound camptothecin (CPT) and the cancer chemotherapeutics derived from it, irinotecan and topotecan, are highly specific inhibitors of human nuclear Top1B (nTop1). Previous work on vaccinia Top1B led to an elegant model that describes a straightforward depende...

  12. Development of 3 DOF manipulator using ER fluid clutches for reduction of collision force

    Energy Technology Data Exchange (ETDEWEB)

    Boku, Kazuhiko; Nakamura, Taro [Chuo University, Faculty of Science and Engineering, Department of Precision Mechanics, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551 (Japan)], E-mail: k_boku@bio.mech.chuo-u.ac.jp

    2009-02-01

    Abstract.With robots and users more commonly sharing space such as in the fields of medicine and home automation, the possibility of a physical collision has increased, even though many robots use actuators with high-ratio gear trains to minimize the effects of impact. We developed a 3-DOF manipulator having a smart flexible joint using an ER fluid and a sensor-equipped pneumatic cushion. Results of position control and collision experiments using the manipulator demonstrated its effectiveness.

  13. Development of 3 DOF manipulator using ER fluid clutches for reduction of collision force

    Science.gov (United States)

    Boku, Kazuhiko; Nakamura, Taro

    2009-02-01

    .With robots and users more commonly sharing space such as in the fields of medicine and home automation, the possibility of a physical collision has increased, even though many robots use actuators with high-ratio gear trains to minimize the effects of impact. We developed a 3-DOF manipulator having a smart flexible joint using an ER fluid and a sensor-equipped pneumatic cushion. Results of position control and collision experiments using the manipulator demonstrated its effectiveness.

  14. Hydrodynamics `experiments' on supernovae and on Nova - the laser*

    Science.gov (United States)

    Remington, Bruce A.

    1996-11-01

    To make progress in understanding the complex phenomena of supernovae (SN), one does not have the luxury of setting up clean, well controlled experiments in the universe to test the physics of our models and theories. Consequently, creating a surrogate environment to serve as an experimental astrophysics testbed would be highly beneficial. The existence of highly sophisticated, modern research lasers in the 1-50 kJ class, developed largely as a result of the world-wide effort in inertial confinement fusion, opens a new potential for creating just such an experimental testbed utilizing well-controlled, well-diagnosed laser plasmas. The next generation MJ-class ``superlasers" planned for the U.S. and France offer incentive to invest effort now on gaining experience using current laser facilities to develop genuinely useful laser-plasma astrophysics experiments. I will discuss two areas of physics critical to an understanding of supernovae that are amenable to supporting research on large lasers: nonlinear hydrodynamic instability evolution in 2D and 3D and (2) the radiative shock hydrodynamics of colliding plasmas such as SN ejecta-circumstellar matter interactions. The astrophysical relevance of these areas to supernovae will be developed in a companion talk.^2 *Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48. ^1In collaboration with S. G. Glendinning, J. Kane, J. Castor, A. Rubenchik, J. Colvin, R. P. Drake, R. London, E. Liang, and R. McCray. ^2Roger Chevalier, "The radiative hydrodynamics of supernova shock waves", these proceedings.

  15. Design, implementation, and experimental validation of optimal power split control for hybrid electric trucks

    NARCIS (Netherlands)

    Keulen, T. van; Mullem, D. van; Jager, B. van; Kessels, J.T.B.A.; Steinbuch, M.

    2012-01-01

    Hybrid electric vehicles require an algorithm that controls the power split between the internal combustion engine and electric machine(s), and the opening and closing of the clutch. Optimal control theory is applied to derive a methodology for a real-time optimal-control-based power split

  16. Stabilizing geometry for hydrodynamic rotary seals

    Science.gov (United States)

    Dietle, Lannie L.; Schroeder, John E.

    2010-08-10

    A hydrodynamic sealing assembly including a first component having first and second walls and a peripheral wall defining a seal groove, a second component having a rotatable surface relative to said first component, and a hydrodynamic seal comprising a seal body of generally ring-shaped configuration having a circumference. The seal body includes hydrodynamic and static sealing lips each having a cross-sectional area that substantially vary in time with each other about the circumference. In an uninstalled condition, the seal body has a length defined between first and second seal body ends which varies in time with the hydrodynamic sealing lip cross-sectional area. The first and second ends generally face the first and second walls, respectively. In the uninstalled condition, the first end is angulated relative to the first wall and the second end is angulated relative to the second wall. The seal body has a twist-limiting surface adjacent the static sealing lip. In the uninstalled condition, the twist-limiting surface is angulated relative to the peripheral wall and varies along the circumference. A seal body discontinuity and a first component discontinuity mate to prevent rotation of the seal body relative to the first component.

  17. Hydrodynamic modelling of hydrostatic magnesium extrusion

    NARCIS (Netherlands)

    Moodij, E.; Rooij, de M.B.; Schipper, D.J.

    2006-01-01

    Wilson’s hydrodynamic model of the hydrostatic extrusion process is extended to meet the geometry found on residual billets. The transition from inlet to work zone of the process is not considered sharp as in the model of Wilson but as a rounded edge, modelled by a parabolic function. It is shown th

  18. Hydrodynamic limits of the Vlasov equation

    Energy Technology Data Exchange (ETDEWEB)

    Caprino, S. (Universita' de L' Aquila Coppito (Italy)); Esposito, R.; Marra, R. (Universita' di Roma tor Vergata, Roma (Italy)); Pulvirenti, M. (Universita' di Roma la Sapienza, Roma (Italy))

    1993-01-01

    In the present work, the authors study the Vlasov equation for repulsive forces in the hydrodynamic regime. For initial distributions at zero temperature the limit equations turn out to be the compressible and incompressible Euler equations under suitable space-time scalings. 17 refs.

  19. Microflow Cytometers with Integrated Hydrodynamic Focusing

    Directory of Open Access Journals (Sweden)

    Martin Schmidt

    2013-04-01

    Full Text Available This study demonstrates the suitability of microfluidic structures for high throughput blood cell analysis. The microfluidic chips exploit fully integrated hydrodynamic focusing based on two different concepts: Two-stage cascade focusing and spin focusing (vortex principle. The sample—A suspension of micro particles or blood cells—is injected into a sheath fluid streaming at a substantially higher flow rate, which assures positioning of the particles in the center of the flow channel. Particle velocities of a few m/s are achieved as required for high throughput blood cell analysis. The stability of hydrodynamic particle positioning was evaluated by measuring the pulse heights distributions of fluorescence signals from calibration beads. Quantitative assessment based on coefficient of variation for the fluorescence intensity distributions resulted in a value of about 3% determined for the micro-device exploiting cascade hydrodynamic focusing. For the spin focusing approach similar values were achieved for sample flow rates being 1.5 times lower. Our results indicate that the performances of both variants of hydrodynamic focusing suit for blood cell differentiation and counting. The potential of the micro flow cytometer is demonstrated by detecting immunologically labeled CD3 positive and CD4 positive T-lymphocytes in blood.

  20. Hydrodynamics and Roughness of Irregular Boundaries

    Science.gov (United States)

    2011-01-01

    principle component analysis (PCA) similar to that used by Preston (2009) for ship- mounted multibeam data. Several variables derived from the...complex boundaries as well as characterization of acoustic and optical processes. Turbulent processes at the seabed are at the foundation of littoral...nearshore hydrodynamics, turbulence over rough beds influences optical and acoustic properties. Bed roughness also directly affects acoustic propagation in

  1. Impact of Hydrodynamics on Oral Biofilm Strength

    NARCIS (Netherlands)

    Paramonova, E.; Kalmykowa, O. J.; van der Mei, H. C.; Busscher, H. J.; Sharma, P. K.

    2009-01-01

    Mechanical removal of oral biofilms is ubiquitously accepted as the best way to prevent caries and periodontal diseases. Removal effectiveness strongly depends on biofilm strength. To investigate the influence of hydrodynamics on oral biofilm strength, we grew single- and multi-species biofilms of S

  2. Hydrodynamic erosion process of undisturbed clay

    NARCIS (Netherlands)

    Zhao, G.; Visser, P.J.; Vrijling, J.K.

    2011-01-01

    This paper describes the hydrodynamic erosion process of undisturbed clay due to the turbulent flow, based on theoretical analysis and experimental results. The undisturbed clay has the unique and complicated characteristics of cohesive force among clay particles, which are highly different from dis

  3. Hydrodynamic impact response, a flexible view

    NARCIS (Netherlands)

    Vredeveldt, A.W.; Hoogeland, M.; Janssen, G.Th.M.

    2001-01-01

    The popularity of high-speed craft is steadily increasing. Until now, much attention has been focussed on the hydrodynamic aspects of these craft. The structural design of these vessels is usually considered in a quasi static sense. However, due to the requirement of light ship structures, fast ship

  4. Hydrodynamics: Fluctuating initial conditions and two-particle correlations

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, R.P.G.; Grassi, F. [Instituto de Fisica, Universidade de Sao Paulo (Brazil); Hama, Y., E-mail: hama@fma.if.usp.b [Instituto de Fisica, Universidade de Sao Paulo (Brazil); Qian, W.-L. [Instituto de Fisica, Universidade de Sao Paulo (Brazil)

    2011-03-15

    Event-by-event hydrodynamics (or hydrodynamics with fluctuating initial conditions) has been developed in the past few years. Here we discuss how it may help to understand the various structures observed in two-particle correlations.

  5. Simulation of Helical Flow Hydrodynamics in Meanders and Advection-Turbulent Diffusion Using Smoothed Particle Hydrodynamics

    Science.gov (United States)

    Gusti, T. P.; Hertanti, D. R.; Bahsan, E.; Soeryantono, H.

    2013-12-01

    Particle-based numerical methods, such as Smoothed Particle Hydrodynamics (SPH), may be able to simulate some hydrodynamic and morphodynamic behaviors better than grid-based numerical methods. This study simulates hydrodynamics in meanders and advection and turbulent diffusion in straight river channels using Microsoft Excel and Visual Basic. The simulators generate three-dimensional data for hydrodynamics and one-dimensional data for advection-turbulent diffusion. Fluid at rest, sloshing, and helical flow are simulated in the river meanders. Spill loading and step loading are done to simulate concentration patterns associated with advection-turbulent diffusion. Results indicate that helical flow is formed due to disturbance in morphology and particle velocity in the stream and the number of particles does not have a significant effect on the pattern of advection-turbulent diffusion concentration.

  6. Scaling supernova hydrodynamics to the laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Kane, J.O.

    1999-06-01

    Supernova (SN) 1987A focused attention on the critical role of hydrodynamic instabilities in the evolution of supernovae. To test the modeling of these instabilities, we are developing laboratory experiments of hydrodynamic mixing under conditions relevant to supernovae. Initial results were reported in J. Kane et al., Astrophys. J.478, L75 (1997) The Nova laser is used to shock two-layer targets, producing Richtmyer-Meshkov (RM) and Rayleigh-Taylor (RT) instabilities at the interfaces between the layers, analogous to instabilities seen at the interfaces of SN 1987A. Because the hydrodynamics in the laser experiments at intermediate times (3-40 ns) and in SN 1987A at intermediate times (5 s-10{sup 4} s) are well described by the Euler equations, the hydrodynamics scale between the two regimes. The experiments are modeled using the hydrodynamics codes HYADES and CALE, and the supernova code PROMETHEUS, thus serving as a benchmark for PROMETHEUS. Results of the experiments and simulations are presented. Analysis of the spike and bubble velocities in the experiment using potential flow theory and a modified Ott thin shell theory is presented. A numerical study of 2D vs. 3D differences in instability growth at the O-He and He-H interface of SN 1987A, and the design for analogous laser experiments are presented. We discuss further work to incorporate more features of the SN in the experiments, including spherical geometry, multiple layers and density gradients. Past and ongoing work in laboratory and laser astrophysics is reviewed, including experimental work on supernova remnants (SNRs). A numerical study of RM instability in SNRs is presented.

  7. THE EXPERIMENTAL DIDACTIC STAND FOR DETERMINING THE PARAMETERS OF THE GEAR WITH MAGNETORHEOLOGICAL CLUTCH AND BRAKE

    Directory of Open Access Journals (Sweden)

    Jerzy BAJKOWSKI

    2014-03-01

    Full Text Available In this paper the laboratory stand, designed to be used as a part of the Laboratory of Machine Design and Research which is part of the subject Fundamentals of Machine Design, is presented. Originally the laboratory stand was designed as an element of one of the research projects, and the adopted for didactic purposes. The students have the chance to get familiar with unique type of fluids controlled by the magnetic field and their application in the special purpose devices. The laboratory stand allows to conduct individual measurements of the torque, for different coil currents which generate the magnetic field. In the final report students provide the results with the individual analysis of the system parameters.

  8. Hydrodynamical Modeling of Hydrogen Escape from Rocky Planets

    Science.gov (United States)

    Barringer, Daniel; Zugger, M.; Kasting, J.

    2013-01-01

    Hydrogen escape affects both the composition of primitive atmospheres of terrestrial planets and the planet’s state of oxidation. On Mars, hydrogen escape played a critical role in how long the planet remained in a warm wet state amenable to life. For both solar and extrasolar planets, hydrogen-rich atmospheres are better candidates for originating life by way of Miller-Urey-type prebiotic synthesis. However, calculating the rate of atmospheric hydrogen escape is difficult, for a number of reasons. First, the escape can be controlled either by diffusion through the homopause or by conditions in the upper atmosphere, whichever is slower. Second, both thermal and non-thermal escape mechanisms are typically important. Third, thermal escape itself can be subdivided into Jeans escape (thin upper atmosphere), and hydrodynamic escape, and hydrodynamic escape can be further subdivided into transonic escape and slower subsonic escape, depending on whether the exobase occurs above or below the sonic point. Additionally, the rate of escape for real terrestrial planet atmospheres, which are not 100% hydrogen, depends upon the concentration of infrared coolants, and upon heating and photochemistry driven largely by extreme ultraviolet (EUV) radiation. We have modified an existing 1-D model of hydrodynamic escape (F. Tian et al., JGR, 2008) to work in the high- hydrogen regime. Calculations are underway to determine hydrogen escape rates as a function of atmospheric H2 mixing ratio and the solar EUV flux. We will compare these rates with the estimated upper limit on the escape rate based on diffusion. Initial results for early Earth and Mars will later be extended to rocky exoplanets.

  9. RANS SIMULATION OF HYDROFOIL EFFECTS ON HYDRODYNAMIC COEFFICIENTS OF A PLANING CATAMARAN

    Directory of Open Access Journals (Sweden)

    Amin Najafi

    2016-03-01

    Full Text Available Determination of high-speed crafts’ hydrodynamic coefficients will help to analyze the dynamics of these kinds of vessels and the factors affecting their dynamic stabilities. Also, it can be useful and effective in controlling the vessel instabilities. The main purpose of this study is to determine the coefficients of longitudinal motions of a planing catamaran with and without a hydrofoil using RANS method to evaluate the foil effects on them. Determination of hydrodynamic coefficients by experimental approach is costly, and requires meticulous laboratory equipment; therefore, utilizing numerical methods and developing a virtual laboratory seems highly efficient. In the present study, the numerical results for hydrodynamic coefficients of a high-speed craft are verified against Troesch’s (1992 experimental results. In the following, after determination of hydrodynamic coefficients of a planing catamaran with and without foil, the foil effects on its hydrodynamic coefficients are evaluated. The results indicate that most of the coefficients are frequency independent especially at high frequencies.

  10. Improvement of hemocompatibility for hydrodynamic levitation centrifugal pump by optimizing step bearings.

    Science.gov (United States)

    Kosaka, Ryo; Yada, Toru; Nishida, Masahiro; Maruyama, Osamu; Yamane, Takashi

    2011-01-01

    We have developed a hydrodynamic levitation centrifugal blood pump with a semi-open impeller for a mechanically circulatory assist. The impeller levitated with original hydrodynamic bearings without any complicated control and sensors. However, narrow bearing gap has the potential for causing hemolysis. The purpose of the study is to investigate the geometric configuration of the hydrodynamic step bearing to minimize hemolysis by expansion of the bearing gap. Firstly, we performed the numerical analysis of the step bearing based on Reynolds equation, and measured the actual hydrodynamic force of the step bearing. Secondly, the bearing gap measurement test and the hemolysis test were performed to the blood pumps, whose step length were 0 %, 33 % and 67 % of the vane length respectively. As a result, in the numerical analysis, the hydrodynamic force was the largest, when the step bearing was around 70 %. In the actual evaluation tests, the blood pump having step 67 % obtained the maximum bearing gap, and was able to improve the hemolysis, compared to those having step 0% and 33%. We confirmed that the numerical analysis of the step bearing worked effectively, and the blood pump having step 67 % was suitable configuration to minimize hemolysis, because it realized the largest bearing gap.

  11. Interspecific variation in the relationship between clutch size, laying date and intensity of urbanization in four species of hole-nesting birds.

    Science.gov (United States)

    Vaugoyeau, Marie; Adriaensen, Frank; Artemyev, Alexandr; Bańbura, Jerzy; Barba, Emilio; Biard, Clotilde; Blondel, Jacques; Bouslama, Zihad; Bouvier, Jean-Charles; Camprodon, Jordi; Cecere, Francesco; Charmantier, Anne; Charter, Motti; Cichoń, Mariusz; Cusimano, Camillo; Czeszczewik, Dorota; Demeyrier, Virginie; Doligez, Blandine; Doutrelant, Claire; Dubiec, Anna; Eens, Marcel; Eeva, Tapio; Faivre, Bruno; Ferns, Peter N; Forsman, Jukka T; García-Del-Rey, Eduardo; Goldshtein, Aya; Goodenough, Anne E; Gosler, Andrew G; Grégoire, Arnaud; Gustafsson, Lars; Harnist, Iga; Hartley, Ian R; Heeb, Philipp; Hinsley, Shelley A; Isenmann, Paul; Jacob, Staffan; Juškaitis, Rimvydas; Korpimäki, Erkki; Krams, Indrikis; Laaksonen, Toni; Lambrechts, Marcel M; Leclercq, Bernard; Lehikoinen, Esa; Loukola, Olli; Lundberg, Arne; Mainwaring, Mark C; Mänd, Raivo; Massa, Bruno; Mazgajski, Tomasz D; Merino, Santiago; Mitrus, Cezary; Mönkkönen, Mikko; Morin, Xavier; Nager, Ruedi G; Nilsson, Jan-Åke; Nilsson, Sven G; Norte, Ana C; Orell, Markku; Perret, Philippe; Perrins, Christopher M; Pimentel, Carla S; Pinxten, Rianne; Richner, Heinz; Robles, Hugo; Rytkönen, Seppo; Senar, Juan Carlos; Seppänen, Janne T; Pascoal da Silva, Luis; Slagsvold, Tore; Solonen, Tapio; Sorace, Alberto; Stenning, Martyn J; Tryjanowski, Piotr; von Numers, Mikael; Walankiewicz, Wieslaw; Møller, Anders Pape

    2016-08-01

    The increase in size of human populations in urban and agricultural areas has resulted in considerable habitat conversion globally. Such anthropogenic areas have specific environmental characteristics, which influence the physiology, life history, and population dynamics of plants and animals. For example, the date of bud burst is advanced in urban compared to nearby natural areas. In some birds, breeding success is determined by synchrony between timing of breeding and peak food abundance. Pertinently, caterpillars are an important food source for the nestlings of many bird species, and their abundance is influenced by environmental factors such as temperature and date of bud burst. Higher temperatures and advanced date of bud burst in urban areas could advance peak caterpillar abundance and thus affect breeding phenology of birds. In order to test whether laying date advance and clutch sizes decrease with the intensity of urbanization, we analyzed the timing of breeding and clutch size in relation to intensity of urbanization as a measure of human impact in 199 nest box plots across Europe, North Africa, and the Middle East (i.e., the Western Palearctic) for four species of hole-nesters: blue tits (Cyanistes caeruleus), great tits (Parus major), collared flycatchers (Ficedula albicollis), and pied flycatchers (Ficedula hypoleuca). Meanwhile, we estimated the intensity of urbanization as the density of buildings surrounding study plots measured on orthophotographs. For the four study species, the intensity of urbanization was not correlated with laying date. Clutch size in blue and great tits does not seem affected by the intensity of urbanization, while in collared and pied flycatchers it decreased with increasing intensity of urbanization. This is the first large-scale study showing a species-specific major correlation between intensity of urbanization and the ecology of breeding. The underlying mechanisms for the relationships between life history and

  12. Does polyandry really pay off? The effects ofmultiple mating and number of fathers on morphological traits and survival in clutches of nesting green turtles at Tortuguero

    DEFF Research Database (Denmark)

    Alfaro Nuñez, Luis Alonso; Jensen, Michael P.; Abreu-Grobois, F. Alberto

    2015-01-01

    Despite the long debate of whether or not multiple mating benefits the offspring, studies still show contradictory results. Multiple mating takes time and energy. Thus, if females fertilize their eggs with a single mating, why to mate more than once? We investigated and inferred paternal identity...... of fathers was three (ranging from 1 to 5). Moreover, regression analyses were used to investigate for correlation of inferred clutch paternity with morphological traits of hatchlings fitness (emergence success, length, weight and crawling speed), the size of the mother, and an environmental variable...

  13. Two-dimensional hydrodynamic flow focusing in a microfluidic platform featuring a monolithic integrated glass micronozzle

    Science.gov (United States)

    Liu, Yifan; Shen, Yusheng; Duan, Lian; Yobas, Levent

    2016-10-01

    Two-dimensional hydrodynamic flow focusing is demonstrated through a microfluidic device featuring a monolithic integrated glass micronozzle inside a flow-focusing geometry. Such a coaxial configuration allows simple one-step focusing of a sample fluid stream, jetted from the micronozzle tip, in both in-plane and out-of-plane directions. The width of the focused filament can be precisely controlled and further scaled down to the submicrometer regime to facilitate rapid hydrodynamic mixing. Fluorescence quenching experiments reveal ultra-fast microsecond mixing of the denaturant into the focused filament. This device offers new possibilities to a set of applications such as the study of protein folding kinetics.

  14. Development of Fully Coupled Aeroelastic and Hydrodynamic Models for Offshore Wind Turbines: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Jonkman, J. M.; Sclavounos, P. D.

    2006-01-01

    Aeroelastic simulation tools are routinely used to design and analyze onshore wind turbines, in order to obtain cost effective machines that achieve favorable performance while maintaining structural integrity. These tools employ sophisticated models of wind-inflow; aerodynamic, gravitational, and inertial loading of the rotor, nacelle, and tower; elastic effects within and between components; and mechanical actuation and electrical responses of the generator and of control and protection systems. For offshore wind turbines, additional models of the hydrodynamic loading in regular and irregular seas, the dynamic coupling between the support platform motions and wind turbine motions, and the dynamic characterization of mooring systems for compliant floating platforms are also important. Hydrodynamic loading includes contributions from hydrostatics, wave radiation, and wave scattering, including free surface memory effects. The integration of all of these models into comprehensive simulation tools, capable of modeling the fully coupled aeroelastic and hydrodynamic responses of floating offshore wind turbines, is presented.

  15. Low-frequency 1/f fluctuations in hydrodynamic and magnetohydrodynamic turbulence.

    Science.gov (United States)

    Dmitruk, Pablo; Matthaeus, W H

    2007-09-01

    We investigate the occurrence of 1/f spectra of low-frequency fluctuations in numerical simulations of three-dimensional hydrodynamic and magnetohydrodynamic turbulence driven by a random forcing with a controlled correlation time. A range of one decade of 1/f spectrum is observed when a strong background magnetic field is present. The frequency spectra of individual Fourier modes is also analyzed and it is observed that the 1/f range is present in the largest available wavelength mode for the magnetohydrodynamic simulations with and without a background magnetic field and it is not observed (or is less clear) for the hydrodynamic case. The presence of 1/f spectra of low-frequency fluctuations is also analyzed for two-dimensional magnetohydrodynamic and hydrodynamic turbulence simulations and it is observed in both cases. The origin of these long period fluctuations is discussed.

  16. Impact of cornstalk buffer strip on hillslope soil erosion and its hydrodynamic understanding

    Science.gov (United States)

    Soil erosion is still a serious concern on the Loess Plateau despite extensive soil conservation measures. Cornstalk buffer strip is not well utilized on the Loess Plateau, and there is little information on the hydrodynamic understanding of this soil erosion control practice. A simulated rainfall e...

  17. Non-isothermal diffusion in a binary mixture with smoothed particle hydrodynamics

    NARCIS (Netherlands)

    Thieulot, C; Espanol, P

    2005-01-01

    We explore the possibility of controlling the pattern formation in a purely diffusive binary mixture described by a van der Waals equation of state in non-isothermal situations. Simulations are conducted with a previously formulated thermodynamically consistent smoothed particle hydrodynamics model

  18. A THERMO-ELECTRO-HYDRODYNAMIC MODEL FOR VIBRATION-ELECTROSPINNING PROCESS

    OpenAIRE

    Lan Xu; Liang Wang; Naeem Faraz

    2011-01-01

    In this paper, a thermo-electro-hydrodynamic model of the vibration- electrospinning process is first established. The model can offer in-depth insight into physical understanding of many complex phenomena which can not be fully explained experimentally. It is a powerful tool to controlling over physical characters.

  19. A THERMO-ELECTRO-HYDRODYNAMIC MODEL FOR VIBRATION-ELECTROSPINNING PROCESS

    Directory of Open Access Journals (Sweden)

    Lan Xu

    2011-01-01

    Full Text Available In this paper, a thermo-electro-hydrodynamic model of the vibration- electrospinning process is first established. The model can offer in-depth insight into physical understanding of many complex phenomena which can not be fully explained experimentally. It is a powerful tool to controlling over physical characters.

  20. Non-isothermal diffusion in a binary mixture with smoothed particle hydrodynamics

    NARCIS (Netherlands)

    Thieulot, C; Espanol, P

    2005-01-01

    We explore the possibility of controlling the pattern formation in a purely diffusive binary mixture described by a van der Waals equation of state in non-isothermal situations. Simulations are conducted with a previously formulated thermodynamically consistent smoothed particle hydrodynamics model

  1. Research on Operating Characteristics and Driving Method of High—speed On—off Valve in Clutch Starting%离合起步用高速开关阀工作特性与驱动方法研究

    Institute of Scientific and Technical Information of China (English)

    夏晶晶

    2012-01-01

    In general pulse width modulation (PWM) signal driven,the high - speed on - off solenoid valve opening and closing time are longer,slower reaction, which affected the high-speed on-off solenoid valve control performance. In order to improve the control performance of the high-speed valve,on the basis of the analyses in the operating characteristics of high - speed on - off valve, a multi - hybrid driving method was designed to shorten the opening and closing time,reduce the pressure fluctuations in pressure control to improve the control performance of the valve. In vehicle clutch control,the use of the above method can improve the starting performance,and the engine speed is relatively stable,the driven plate speed increasing trend fluctuation is smaller.%在普通脉宽调制(PWM)信号驱动下,高速开关电磁阀的开启和关闭时间较长,反应慢,影响了高速开关电磁阀的控制性能.为了进一步提高高速开关阀的控制性能,在分析高速开关阀工作特性的基础上,提出了多路混合驱动方法,缩短了高速开关阀的开启和关闭时间,减小了压力控制时的压力波动,改善了高速开关阀的控制性能.在汽车离合器起步控制中,使用该方法很好地改善了汽车的起步性能,发动机转速比较平稳,从动盘转速增加趋势的波动较小.

  2. Effective Hydrodynamic Boundary Conditions for Corrugated Surfaces

    CERN Document Server

    Mongruel, Anne; Asmolov, Evgeny S; Vinogradova, Olga I

    2012-01-01

    We report measurements of the hydrodynamic drag force acting on a smooth sphere falling down under gravity to a plane decorated with microscopic periodic grooves. Both surfaces are lyophilic, so that a liquid (silicone oil) invades the surface texture being in the Wenzel state. A significant decrease in the hydrodynamic resistance force as compared with that predicted for two smooth surfaces is observed. To quantify the effect of roughness we use the effective no-slip boundary condition, which is applied at the imaginary smooth homogeneous isotropic surface located at an intermediate position between top and bottom of grooves. Such an effective condition fully characterizes the force reduction measured with the real surface, and the location of this effective plane is related to geometric parameters of the texture by a simple analytical formula.

  3. Axially symmetric pseudo-Newtonian hydrodynamics code

    CERN Document Server

    Kim, Jinho; Choptuik, Matthew William; Lee, Hyung Mok

    2012-01-01

    We develop a numerical hydrodynamics code using a pseudo-Newtonian formulation that uses the weak field approximation for the geometry, and a generalized source term for the Poisson equation that takes into account relativistic effects. The code was designed to treat moderately relativistic systems such as rapidly rotating neutron stars. The hydrodynamic equations are solved using a finite volume method with High Resolution Shock Capturing (HRSC) techniques. We implement several different slope limiters for second order reconstruction schemes and also investigate higher order reconstructions. We use the method of lines (MoL) to convert the mixed spatial-time partial differential equations into ordinary differential equations (ODEs) that depend only on time. These ODEs are solved using 2nd and 3rd order Runge-Kutta methods. The Poisson equation for the gravitational potential is solved with a multigrid method. In order to confirm the validity of our code, we carry out four different tests including one and two...

  4. Kinetic and hydrodynamic models of chemotactic aggregation

    CERN Document Server

    Chavanis, Pierre-Henri

    2007-01-01

    We derive general kinetic and hydrodynamic models of chemotactic aggregation that describe certain features of the morphogenesis of biological colonies (like bacteria, amoebae, endothelial cells or social insects). Starting from a stochastic model defined in terms of N coupled Langevin equations, we derive a nonlinear mean field Fokker-Planck equation governing the evolution of the distribution function of the system in phase space. By taking the successive moments of this kinetic equation and using a local thermodynamic equilibrium condition, we derive a set of hydrodynamic equations involving a damping term. In the limit of small frictions, we obtain a hyperbolic model describing the formation of network patterns (filaments) and in the limit of strong frictions we obtain a parabolic model which is a generalization of the standard Keller-Segel model describing the formation of clusters (clumps). Our approach connects and generalizes several models introduced in the chemotactic literature. We discuss the anal...

  5. SPHGR: Smoothed-Particle Hydrodynamics Galaxy Reduction

    Science.gov (United States)

    Thompson, Robert

    2015-02-01

    SPHGR (Smoothed-Particle Hydrodynamics Galaxy Reduction) is a python based open-source framework for analyzing smoothed-particle hydrodynamic simulations. Its basic form can run a baryonic group finder to identify galaxies and a halo finder to identify dark matter halos; it can also assign said galaxies to their respective halos, calculate halo & galaxy global properties, and iterate through previous time steps to identify the most-massive progenitors of each halo and galaxy. Data about each individual halo and galaxy is collated and easy to access. SPHGR supports a wide range of simulations types including N-body, full cosmological volumes, and zoom-in runs. Support for multiple SPH code outputs is provided by pyGadgetReader (ascl:1411.001), mainly Gadget (ascl:0003.001) and TIPSY (ascl:1111.015).

  6. Filter-less submicron hydrodynamic size sorting.

    Science.gov (United States)

    Fouet, M; Mader, M-A; Iraïn, S; Yanha, Z; Naillon, A; Cargou, S; Gué, A-M; Joseph, P

    2016-02-21

    We propose a simple microfluidic device able to separate submicron particles (critical size ∼0.1 μm) from a complex sample with no filter (minimum channel dimension being 5 μm) by hydrodynamic filtration. A model taking into account the actual velocity profile and hydrodynamic resistances enables prediction of the chip sorting properties for any geometry. Two design families are studied to obtain (i) small sizes within minutes (low-aspect ratio, two-level chip) and (ii) micron-sized sorting with a μL flow rate (3D architecture based on lamination). We obtain quantitative agreement of sorting performances both with experiments and with numerical solving, and determine the limits of the approach. We therefore demonstrate a passive, filter-less sub-micron size sorting with a simple, robust, and easy to fabricate design.

  7. VH1 Hydrodynamics for Introductory Astronomy

    Science.gov (United States)

    Christian, Wolfgang; Blondin, John

    1997-05-01

    Improvements in personal computer operating systems and hardware now makes it possible to run research grade Fortran simulations on student computers. Unfortunately, many legacy applications do not have a graphical user interface and are sometimes hard coded to a specific problem making them unsuitable for beginning students. A good way to re-purpose such legacy code for undergraduate teaching is to build a graphical front end using a Rapid Application Development, RAD, tool that starts the simulation as a separate thread. This technique is being used with Virginia Hydrodynamics One, VH1, to provide an introduction to computational hydrodynamics. Standard test problems including gravitational collapse of an interstellar cloud, radiation cooling, and formation of shocks are demonstrated using this on Microsoft Windows 95/NT.

  8. Electro-hydrodynamic synchronization of piezoelectric flags

    CERN Document Server

    Xia, Yifan; Michelin, Sebastien

    2016-01-01

    Hydrodynamic coupling of flexible flags in axial flows may profoundly influence their flapping dynamics, in particular driving their synchronization. This work investigates the effect of such coupling on the harvesting efficiency of coupled piezoelectric flags, that convert their periodic deformation into an electrical current. Considering two flags connected to a single output circuit, we investigate using numerical simulations the relative importance of hydrodynamic coupling to electrodynamic coupling of the flags through the output circuit due to the inverse piezoelectric effect. It is shown that electrodynamic coupling is dominant beyond a critical distance, and induces a synchronization of the flags' motion resulting in enhanced energy harvesting performance. We further show that this electrodynamic coupling can be strengthened using resonant harvesting circuits.

  9. Application of hydrodynamics to heavy ion collisions

    Energy Technology Data Exchange (ETDEWEB)

    Felsberger, Lukas

    2014-12-02

    The Bjorken model is a simple tool for making rough predictions of the hydrodynamic evolution of the thermalized matter created in a heavy ion collision. The advantage of the model clearly lies in its simplicity, rather than accuracy. As it is still used for making rough estimations 'by hand', in this thesis, I investigate in which cases the Bjorken model gives useful results and in which it is not recommended. For central collisions, I show which critical size the nuclei should have so that the Bjorken model can be applied. For non-central collisions, I demonstrate that using Glauber initial conditions combined with the Bjorken evolution, leads to reasonable results up to large impact parameters. Finally, I study the case of a non-ideal (viscous) description of the thermalized matter which leads to strongly differing results if first- or second-order hydrodynamics is applied.

  10. Simple Waves in Ideal Radiation Hydrodynamics

    CERN Document Server

    Johnson, Bryan M

    2008-01-01

    In the dynamic diffusion limit of radiation hydrodynamics, advection dominates diffusion; the latter primarily affects small scales and has negligible impact on the large scale flow. The radiation can thus be accurately regarded as an ideal fluid, i.e., radiative diffusion can be neglected along with other forms of dissipation. This viewpoint is applied here to an analysis of simple waves in an ideal radiating fluid. It is shown that much of the hydrodynamic analysis carries over by simply replacing the material sound speed, pressure and index with the values appropriate for a radiating fluid. A complete analysis is performed for a centered rarefaction wave, and expressions are provided for the Riemann invariants and characteristic curves of the one-dimensional system of equations. The analytical solution is checked for consistency against a finite difference numerical integration, and the validity of neglecting the diffusion operator is demonstrated. An interesting physical result is that for a material comp...

  11. Pursuit and Synchronization in Hydrodynamic Dipoles

    CERN Document Server

    Kanso, Eva

    2015-01-01

    We study theoretically the behavior of a class of hydrodynamic dipoles. This study is motivated by recent experiments on synthetic and biological swimmers in microfluidic \\textit{Hele-Shaw} type geometries. Under such confinement, a swimmer's hydrodynamic signature is that of a potential source dipole, and the long-range interactions among swimmers are obtained from the superposition of dipole singularities. Here, we recall the equations governing the positions and orientations of interacting asymmetric swimmers in doubly-periodic domains, and focus on the dynamics of swimmer pairs. We obtain two families of `relative equilibria'-type solutions that correspond to pursuit and synchronization of the two swimmers, respectively. Interestingly, the pursuit mode is stable for large tail swimmers whereas the synchronization mode is stable for large head swimmers. These results have profound implications on the collective behavior reported in several recent studies on populations of confined microswimmers.

  12. Hydrodynamic Electron Flow and Hall Viscosity

    Science.gov (United States)

    Scaffidi, Thomas; Nandi, Nabhanila; Schmidt, Burkhard; Mackenzie, Andrew P.; Moore, Joel E.

    2017-06-01

    In metallic samples of small enough size and sufficiently strong momentum-conserving scattering, the viscosity of the electron gas can become the dominant process governing transport. In this regime, momentum is a long-lived quantity whose evolution is described by an emergent hydrodynamical theory. Furthermore, breaking time-reversal symmetry leads to the appearance of an odd component to the viscosity called the Hall viscosity, which has attracted considerable attention recently due to its quantized nature in gapped systems but still eludes experimental confirmation. Based on microscopic calculations, we discuss how to measure the effects of both the even and odd components of the viscosity using hydrodynamic electronic transport in mesoscopic samples under applied magnetic fields.

  13. Hyperbolic metamaterial lens with hydrodynamic nonlocal response

    DEFF Research Database (Denmark)

    Yan, Wei; Mortensen, N. Asger; Wubs, Martijn

    2013-01-01

    in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we......We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves...... of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens...

  14. Hyperbolic metamaterial lens with hydrodynamic nonlocal response.

    Science.gov (United States)

    Yan, Wei; Mortensen, N Asger; Wubs, Martijn

    2013-06-17

    We investigate the effects of hydrodynamic nonlocal response in hyperbolic metamaterials (HMMs), focusing on the experimentally realizable parameter regime where unit cells are much smaller than an optical wavelength but much larger than the wavelengths of the longitudinal pressure waves of the free-electron plasma in the metal constituents. We derive the nonlocal corrections to the effective material parameters analytically, and illustrate the noticeable nonlocal effects on the dispersion curves numerically. As an application, we find that the focusing characteristics of a HMM lens in the local-response approximation and in the hydrodynamic Drude model can differ considerably. In particular, the optimal frequency for imaging in the nonlocal theory is blueshifted with respect to that in the local theory. Thus, to detect whether nonlocal response is at work in a hyperbolic metamaterial, we propose to measure the near-field distribution of a hyperbolic metamaterial lens.

  15. Low Mach Number Fluctuating Hydrodynamics for Electrolytes

    CERN Document Server

    Péraud, Jean-Philippe; Chaudhri, Anuj; Bell, John B; Donev, Aleksandar; Garcia, Alejandro L

    2016-01-01

    We formulate and study computationally the low Mach number fluctuating hydrodynamic equations for electrolyte solutions. We are interested in studying transport in mixtures of charged species at the mesoscale, down to scales below the Debye length, where thermal fluctuations have a significant impact on the dynamics. Continuing our previous work on fluctuating hydrodynamics of multicomponent mixtures of incompressible isothermal miscible liquids (A. Donev, et al., Physics of Fluids, 27, 3, 2015), we now include the effect of charged species using a quasielectrostatic approximation. Localized charges create an electric field, which in turn provides additional forcing in the mass and momentum equations. Our low Mach number formulation eliminates sound waves from the fully compressible formulation and leads to a more computationally efficient quasi-incompressible formulation. We demonstrate our ability to model saltwater (NaCl) solutions in both equilibrium and nonequilibrium settings. We show that our algorithm...

  16. Hydrodynamics of charge fluctuations and balance functions

    CERN Document Server

    Ling, B; Stephanov, M

    2013-01-01

    We apply stochastic hydrodynamics to the study of charge density fluctuations in QCD matter undergoing Bjorken expansion. We find that the charge density correlations are given by a time integral over the history of the system, with the dominant contribution coming from the QCD crossover region where the change of susceptibility per entropy, chi T/s, is most significant. We study the rapidity and azimuthal angle dependence of the resulting charge balance function using a simple analytic model of heavy-ion collision evolution. Our results are in agreement with experimental measurements, indicating that hydrodynamic fluctuations contribute significantly to the measured charge correlations in high energy heavy-ion collisions. The sensitivity of the balance function to the value of the charge diffusion coefficient D allows us to estimate the typical value of this coefficient in the crossover region to be rather small, of the order of 1/(2pi T), characteristic of a strongly coupled plasma.

  17. Frictionless dispersive hydrodynamics of Stokes flows

    CERN Document Server

    Maiden, Michelle D; Anderson, Dalton V; Schubert, Marika E; Hoefer, Mark A

    2016-01-01

    Effectively frictionless, dispersive flow characterizes superfluids, nonlinear optical diffraction, and geophysical fluid interfaces. Dispersive shock waves (DSWs) and solitons are fundamental nonlinear excitations in these media, but DSW studies to date have been severely constrained by a loss of coherence. Here we report on a novel dispersive hydrodynamics testbed: the effectively frictionless flow of interfacial waves between two high contrast, low Reynolds' number Stokes fluids. This system enables high fidelity observations of large amplitude DSWs, found to agree quantitatively with a nonlinear wave averaging theory. We then report on observations of highly coherent phenomena including DSW backflow, the refraction or absorption of solitons by DSWs, and multi-phase DSW-DSW merger. The complex, coherent, nonlinear mixing of DSWs and solitons observed here are universal features of dissipationless, dispersive hydrodynamic flows.

  18. Hydrodynamic theory of tissue shear flow

    CERN Document Server

    Popović, Marko; Merkel, Matthias; Etournay, Raphaël; Eaton, Suzanne; Jülicher, Frank; Salbreux, Guillaume

    2016-01-01

    We propose a hydrodynamic theory to describe shear flows in developing epithelial tissues. We introduce hydrodynamic fields corresponding to state properties of constituent cells as well as a contribution to overall tissue shear flow due to rearrangements in cell network topology. We then construct a constitutive equation for the shear rate due to topological rearrangements. We identify a novel rheological behaviour resulting from memory effects in the tissue. We show that anisotropic deformation of tissue and cells can arise from two distinct active cellular processes: generation of active stress in the tissue, and actively driven cellular rearrangements. These two active processes result in distinct cellular and tissue shape changes, depending on boundary conditions applied on the tissue. Our findings have consequences for the understanding of tissue morphogenesis during development.

  19. Hydrodynamics of ultra-relativistic bubble walls

    Directory of Open Access Journals (Sweden)

    Leonardo Leitao

    2016-04-01

    Full Text Available In cosmological first-order phase transitions, gravitational waves are generated by the collisions of bubble walls and by the bulk motions caused in the fluid. A sizeable signal may result from fast-moving walls. In this work we study the hydrodynamics associated to the fastest propagation modes, namely, ultra-relativistic detonations and runaway solutions. We compute the energy injected by the phase transition into the fluid and the energy which accumulates in the bubble walls. We provide analytic approximations and fits as functions of the net force acting on the wall, which can be readily evaluated for specific models. We also study the back-reaction of hydrodynamics on the wall motion, and we discuss the extrapolation of the friction force away from the ultra-relativistic limit. We use these results to estimate the gravitational wave signal from detonations and runaway walls.

  20. Chaos in hydrodynamic BL Herculis models

    CERN Document Server

    Smolec, R

    2014-01-01

    We present non-linear, convective, BL Her-type hydrodynamic models that show complex variability characteristic for deterministic chaos. The bifurcation diagram reveals a rich structure, with many phenomena detected for the first time in hydrodynamic models of pulsating stars. The phenomena include not only period doubling cascades en route to chaos (detected in earlier studies) but also periodic windows within chaotic band, type-I and type-III intermittent behaviour, interior crisis bifurcation and others. Such phenomena are known in many textbook chaotic systems, from the simplest discrete logistic map, to more complex systems like Lorenz equations. We discuss the physical relevance of our models. Although except of period doubling such phenomena were not detected in any BL Her star, chaotic variability was claimed in several higher luminosity siblings of BL Her stars - RV Tau variables, and also in longer-period, luminous irregular pulsators. Our models may help to understand these poorly studied stars. Pa...