从学科细分角度分析,材料力学(mechanics of materials)属于固体力学范畴,它的主要研究对象是棒状材料(如梁、轴、杆等),旨在揭示材料在不同外力作用下发生形变的规律,以及材料应变、强度、刚度、稳定性等各类参数的极限,以此确保材料...从学科细分角度分析,材料力学(mechanics of materials)属于固体力学范畴,它的主要研究对象是棒状材料(如梁、轴、杆等),旨在揭示材料在不同外力作用下发生形变的规律,以及材料应变、强度、刚度、稳定性等各类参数的极限,以此确保材料投入应用之后的安全性。简言之,材料力学在现实中是一门探索单体构件、机械部件、工程零件等承载力的学科,实践过程中需要将具有简单结构的材料转化成一维杆件,这就涉及到从具象到抽象的过程一一对于材料力学实践主体而言,这是一个基于现实需求的"提出问题"过程,即将真实的材料对象抽象成力学模型,然后在此基础上建立数学模型,翻入导入测量结果对数学模型进行完善——当材料力学对应的数学模型达到一定精读之后,就可以节约大量实验成本,提高材料利用的实效性和安全性,因此材料力学中应用数学模型是非常重要性的。展开更多
Centrifugal forces are commonly created when ships turn, which may cause a ship to capsize in a critical situation. A mathematical model has been developed to optimize the stability coefficients for ship, with the aim...Centrifugal forces are commonly created when ships turn, which may cause a ship to capsize in a critical situation. A mathematical model has been developed to optimize the stability coefficients for ship, with the aim to prevent capsizing and to increase ship maneuverability in high-speed water craft. This model can be used to develop algorithms for control system improvement. The mathematical model presented in this paper optimized the use of multipurpose hydrofoils to reduce heeling and the trimming moment, maintaining an upright ship’s position and lessening the resistance via transverse force. Conventionally, the trimming and heeling of a ship are controlled using ballast water;however, under variable sea conditions it is sometimes difficult to control a ship’s motion using ballast water. In this case, a hydrofoil would be more stable and maneuverable than a ballast tank controlled vessel. A movable hydrofoil could theoretically be adapted from moveable aerofoil technology. This study proves the merit of further investigation into this possibility.展开更多
Mathematical models of propellers were created that investigate the influence of periodic boundary conditions on predictions of a propeller's performance.Thrust and torque coefficients corresponding to different a...Mathematical models of propellers were created that investigate the influence of periodic boundary conditions on predictions of a propeller's performance.Thrust and torque coefficients corresponding to different advance coefficients of DTMB 4119, 4382, and 4384 propellers were calculated.The pressure coefficient distribution of the DTMB 4119 propeller at different sections was also physically tested.Comparisons indicated good agreement between the results of experiments and the simulation.It showed that the periodic boundary condition can be used to rationally predict the open water performance of a propeller.By analyzing the three established modes for the computation, it was shown that using the spline curve method to divide the grids can meet the calculation's demands for precision better than using the rake cutting method.展开更多
Small water-plane area twin-hull（SWATH） has drawn the attention of many researchers due to its good sea-keeping ability.In this paper,MMG＇s idea of separation was used to perform SWATH movement modeling and simulat...Small water-plane area twin-hull（SWATH） has drawn the attention of many researchers due to its good sea-keeping ability.In this paper,MMG＇s idea of separation was used to perform SWATH movement modeling and simulation;respectively the forces and moment of SWATH were divided into bare hull,propeller,rudder at the fluid hydrodynamics,etc.Wake coefficient at the propellers which reduces thrust coefficient,and rudder mutual interference forces among the hull and propeller,for the calculation of SWATH,were all considered.The fourth-order Runge-Kutta method of integration was used by solving differential equations,in order to get SWATH＇s movement states.As an example,a turning test at full speed and full starboard rudder of ‘Seagull＇ craft is shown.The simulation results show the SWATH＇s regular pattern and trend of motion.It verifies the correctness of the mathematical model of the turning movement.The SWATH＇s mathematical model is applied to marine simulator in order to train the pilots or seamen,or safety assessment for ocean engineering project.Lastly,the full mission navigation simulating system（FMNSS） was determined to be a successful virtual reality technology application sample in the field of navigation simulation.展开更多
In this study, we propose the use of the Degree of Alignment(DOA) in engineering applications for evaluating the precision of and identifying the transfer alignment on a moving base. First, we derive the statistical f...In this study, we propose the use of the Degree of Alignment(DOA) in engineering applications for evaluating the precision of and identifying the transfer alignment on a moving base. First, we derive the statistical formula on the basis of estimations. Next, we design a scheme for evaluating the transfer alignment on a moving base, for which the attitude error cannot be directly measured. Then, we build a mathematic estimation model and discuss Fixed Point Smoothing(FPS), Returns to Scale(RTS), Inverted Sequence Recursive Estimation(ISRE), and Kalman filter estimation methods, which can be used when evaluating alignment accuracy. Our theoretical calculations and simulated analyses show that the DOA reflects not only the alignment time and accuracy but also differences in the maneuver schemes, and is suitable for use as an integrated evaluation index. Furthermore, all four of these algorithms can be used to identify the transfer alignment and evaluate its accuracy. We recommend RTS in particular for engineering applications. Generalized DOAs should be calculated according to the tactical requirements.展开更多
On the basis of the essential connotation of the training effect on human resource development and the basic principles of setting up a index system, the evaluation index system of the training effect on human resourc...On the basis of the essential connotation of the training effect on human resource development and the basic principles of setting up a index system, the evaluation index system of the training effect on human resource development in enterprises has been established. It evaluates the training effect on human resource development with the method of fuzzy comprehensive evaluation and achieves better results. It also provides a scientific, practical and quantitative method for the systematic analysis and comprehensive evaluation of the training effect on human resource development.展开更多
文摘从学科细分角度分析,材料力学(mechanics of materials)属于固体力学范畴,它的主要研究对象是棒状材料(如梁、轴、杆等),旨在揭示材料在不同外力作用下发生形变的规律,以及材料应变、强度、刚度、稳定性等各类参数的极限,以此确保材料投入应用之后的安全性。简言之,材料力学在现实中是一门探索单体构件、机械部件、工程零件等承载力的学科,实践过程中需要将具有简单结构的材料转化成一维杆件,这就涉及到从具象到抽象的过程一一对于材料力学实践主体而言,这是一个基于现实需求的"提出问题"过程,即将真实的材料对象抽象成力学模型,然后在此基础上建立数学模型,翻入导入测量结果对数学模型进行完善——当材料力学对应的数学模型达到一定精读之后,就可以节约大量实验成本,提高材料利用的实效性和安全性,因此材料力学中应用数学模型是非常重要性的。
文摘Centrifugal forces are commonly created when ships turn, which may cause a ship to capsize in a critical situation. A mathematical model has been developed to optimize the stability coefficients for ship, with the aim to prevent capsizing and to increase ship maneuverability in high-speed water craft. This model can be used to develop algorithms for control system improvement. The mathematical model presented in this paper optimized the use of multipurpose hydrofoils to reduce heeling and the trimming moment, maintaining an upright ship’s position and lessening the resistance via transverse force. Conventionally, the trimming and heeling of a ship are controlled using ballast water;however, under variable sea conditions it is sometimes difficult to control a ship’s motion using ballast water. In this case, a hydrofoil would be more stable and maneuverable than a ballast tank controlled vessel. A movable hydrofoil could theoretically be adapted from moveable aerofoil technology. This study proves the merit of further investigation into this possibility.
基金Supported by the National Natural Science Foundation of China under Grant No.10702016
文摘Mathematical models of propellers were created that investigate the influence of periodic boundary conditions on predictions of a propeller's performance.Thrust and torque coefficients corresponding to different advance coefficients of DTMB 4119, 4382, and 4384 propellers were calculated.The pressure coefficient distribution of the DTMB 4119 propeller at different sections was also physically tested.Comparisons indicated good agreement between the results of experiments and the simulation.It showed that the periodic boundary condition can be used to rationally predict the open water performance of a propeller.By analyzing the three established modes for the computation, it was shown that using the spline curve method to divide the grids can meet the calculation's demands for precision better than using the rake cutting method.
基金Supported by the National Nature Science Foundation of China under Grant No.51109020 the National Key Project for Basic Research“973”（2009CB320805）
文摘Small water-plane area twin-hull（SWATH） has drawn the attention of many researchers due to its good sea-keeping ability.In this paper,MMG＇s idea of separation was used to perform SWATH movement modeling and simulation;respectively the forces and moment of SWATH were divided into bare hull,propeller,rudder at the fluid hydrodynamics,etc.Wake coefficient at the propellers which reduces thrust coefficient,and rudder mutual interference forces among the hull and propeller,for the calculation of SWATH,were all considered.The fourth-order Runge-Kutta method of integration was used by solving differential equations,in order to get SWATH＇s movement states.As an example,a turning test at full speed and full starboard rudder of ‘Seagull＇ craft is shown.The simulation results show the SWATH＇s regular pattern and trend of motion.It verifies the correctness of the mathematical model of the turning movement.The SWATH＇s mathematical model is applied to marine simulator in order to train the pilots or seamen,or safety assessment for ocean engineering project.Lastly,the full mission navigation simulating system（FMNSS） was determined to be a successful virtual reality technology application sample in the field of navigation simulation.
基金Supported by the National Natural Science Foundation of China （61633008）, the National Natural Science Foundation of China （61203225）, the Natural Science Foundation of Heilongjiang Province of China（QC2014C069）, the Special fund for the Central Universities （HEUCF160401）, and Provincial Postdoctoral Scientific Research Foundation （LBH-Q 15032）.
文摘In this study, we propose the use of the Degree of Alignment(DOA) in engineering applications for evaluating the precision of and identifying the transfer alignment on a moving base. First, we derive the statistical formula on the basis of estimations. Next, we design a scheme for evaluating the transfer alignment on a moving base, for which the attitude error cannot be directly measured. Then, we build a mathematic estimation model and discuss Fixed Point Smoothing(FPS), Returns to Scale(RTS), Inverted Sequence Recursive Estimation(ISRE), and Kalman filter estimation methods, which can be used when evaluating alignment accuracy. Our theoretical calculations and simulated analyses show that the DOA reflects not only the alignment time and accuracy but also differences in the maneuver schemes, and is suitable for use as an integrated evaluation index. Furthermore, all four of these algorithms can be used to identify the transfer alignment and evaluate its accuracy. We recommend RTS in particular for engineering applications. Generalized DOAs should be calculated according to the tactical requirements.
文摘On the basis of the essential connotation of the training effect on human resource development and the basic principles of setting up a index system, the evaluation index system of the training effect on human resource development in enterprises has been established. It evaluates the training effect on human resource development with the method of fuzzy comprehensive evaluation and achieves better results. It also provides a scientific, practical and quantitative method for the systematic analysis and comprehensive evaluation of the training effect on human resource development.
