An optimal dynamic output feedback controller for a flexible spacecraft

The design of a low-order dynamic output feedback controller for a flexible spacecraft is carried out using modified linear quadratic Gaussian (LQG) theory. The necessary conditions for optimization are given. The linear equations governing a flexible spacecraft with a central rigid body and two sun-tracking solar panels are presented. The parameters of the Solar Electric Propulsion Spacecraft (SEPS) are selected for analysis and simulation. The optimal gains for the dynamic controller are estimated using an iterative algorithm. The sequential procedure which assures convergence is selected. The initial gains which stabilize the system are chosen on the basis of the principle of a PD controller. A third-order controller for pitch, roll and yaw axes of the 18th-order system, which includes sensor and actuator dynamics, is designed. Numerical simulations carried out to ascertain the performance of the controller show the performance to be satisfactory.     

胫,股骨内压与膝关节疼痛关系的研究和治疗方法探讨

作者对膝关节痛和休息痛病人21例做了股、胫骨内压和关节镜检查,其均值股骨髁0.143±0.01kPa,16例(76.19％)超过对照组0.130kPa(P<0.01);胫骨髁0.180±0.022kPa,18例(85.7％),超过对照组0.105kPa。同时测量膝关节腔内压21例。均值为0.135±0.035kPa,18例(85.7％)高于对照组0.120kPa。认为骨内压增高是引起膝关节痛的原因。本文还就膝关节特发性骨内高压症的临床表现、镜下特点、个体临界骨内压和治疗方法进行了探讨。     

Reconstruction of plantar defects

Plantar defects are a challenge for the plastic surgeon; from 1984–1995 59 operations were performed in 57 patients. The radial forearm flap and the latissimus dorsi (LD) flaps were mainly used depending on the amount of tissue loss. Local flaps such as dorsalis pedis and instep flaps were used for smaller defects. The radial forearm flap is ideal in terms of thickness and stability for the sole but limited in its size. The LD flap is a safe procedure especially for severe injuries and osteitis, but has the disadvantage of being bulky and debulking procedures are frequently performed. For nerve reconstruction deep sensibility seems to be sufficient in order to obtain stable postoperative results. In this report the different operative methods are evaluated. Since 1991, the patients were monitored with static and dynamic foot pressure measurements and gait analysis to assess the postoperative result and prevent pressure ulcers, scar irritation and hyperkeratosis. Preoperative investigations may contribute to an optimal schedule for planning and stabilization of the operative regimen.     

Detection of Human Heart Rate in Exercises State

作者介绍了一种动态心率检测电路，它能准确、可靠地检出在运动状态下的人体心率。电路采用两种检测技术，一种为双时值ＱＲＳ波检测法，另一种为光电脉搏检测法。     

Patello-femoral complications associated with total knee arthroplasty

The patello-femoral articulation accounts for a significant number of the complications that occur after total knee replacements and which require re-operation. These include problems with stability, component wear, fracture, loosening, and osteonecrosis. With careful attention to prosthetic design and surgical technique, these complications can be minimized. Guest Lecture presented at the 26th meeting of the Japanese Society for Replacement Arthroplasty in Tokyo on February 2, 1996     

Proteoglycan fragments in knee joint fluid after exercise

The concentration of cartilage proteoglycan fragments in knee joint fluid was measured before and after one event of physical exercise in 33 healthy athletes. Nine athletes ran on a treadmill for 60 min, 16 ran on road for 80 min and 8 played one soccer game (90 min). Before exercise, the levels of proteoglycan fragments in the athlete joint fluid were lower than in a previously analyzed reference group. After exercise, the concentration of proteoglycan fragments increased in all of the 7 athletes that could be directly compared before and after exercise. This increased concentration of proteoglycan fragments in the joint fluid could be an effect of mechanical loading of the cartilage in combination with a possible high turn-over rate of the cartilage matrix in the athletes.     

Comparison of the biomechanical effect of posterior condylar offset and kinematics between posterior cruciate-retaining and posterior-stabilized total knee arthroplasty

Background

The effect of the changes in the femoral posterior condylar offset (PCO) on anterior–posterior (AP) translation and internal–external (IE) rotation in cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA) remains unknown. The purpose of this study was to compare the kinematics in CR and PS TKA with respect to the difference in prosthetic design and PCO change through a computational simulation.

On the role of static and dynamic visual afferent information in goal-directed aiming movements

Movement planning has been shown to be optimized when the participant is permitted to see his or her hand resting on the starting base prior to movement initiation. However, this proposition is opposed by contradictory results. In the present study, we wanted to determine whether these conflicting results were caused by procedural differences. The results showed that seeing one's hand on the starting base did not result in more accurate aiming movement than when this information was not available. However, lower aiming errors were found when one was asked to foveate the starting base and then the target prior to movement initiation, but only when no dynamic visual information was available during movement. When an aiming movement was performed while one's hand was visible in visual periphery, foveating the starting base or not prior to movement initiation did not modify aiming accuracy. These results suggest that gazing at the starting base and then at the target provides an eye-based representation of the movement to be performed that can be used by the CNS to plan a manual aiming movement. Information for better planning of the direction – but not the extent – dimension of an upcoming movement can also be derived from dynamic visual information available in peripheral vision. Electronic Publication     

Physiological effects of dynamic work on a bicycle ergometer combined with different types of static contraction

Summary The effects on heart rate, oxygen uptake, and pulmonary ventilation of muscular exercises, including both dynamic contractions, either simple or combined, were studied in 4 male subjects, aged 21 to 23 years. The dynamic work consisted in cycling on an ergometric bicycle at three power levels: 40, 80, and 100 W. The static work consisted in pushing against, pulling and holding with the arms a 6, 9, 12, or 18 kg load. The physiological effects are expressed as cardiac cost (HR), oxygen cost (VO₂) and ventilation cost (V). The physiological cost of the combined work increases according to the cycling power and to the isometric load developed. A statistical analysis shows that the costs of combined work are not different from the sum of the costs of the static and dynamic contractions measured separately. Thus, the physiological responses to the combinations investigated are of an additive type.