Enhanced crystallization of poly(L‐lactide‐co‐ε‐caprolactone) in the presence of water

Poly(L ‐lactide‐co‐ε‐caprolactone) [P(LLA‐CL)], which is used in biodegradable biomedical materials such as drug‐delivery systems, surgical sutures, orthopedics, and scaffolds for tissue engineering, has been reported to crystallize upon storage in a dry state even at room temperature; this results in rapid changes in the mechanical properties. In biomedical applications, P(LLA‐CL) is used in the presence of water. This study investigated the effects of water on the crystallization of P(LLA‐CL) at 37°C in phosphate buffered solution, which was anticipated to alter its mechanical properties and hydrolytic degradation behavior. Surprisingly, the crystallinity of P(LLA‐CL) in the presence of water rapidly increased in 6–12 h and then slowly increased up to 120 h. The period of time for the initial rapid crystallization increase in the presence of water was much shorter than that in the absence of water. The obtained information would be useful for the selection, preparation, and use of P(LLA‐CL) in various biomedical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Design of steel frames for specified seismic member ductility via inverse eigenmode formulation

A new direct method of ductility design is presented for planar moment-resisting steel frames such that a set of member stiffnesses and the corresponding member strengths of a frame with realistic cross-sectional proportions are found for a specified distribution of member ductility factors under design major earthquakes. An inverse method of stiffness design is developed such that every predominant member-end strain in a frame under design earthquakes estimated on the basis of lowest eigenvibration would coincide with the specified value. A concept called ‘a set of similar cross-sections’ is introduced to make it possible to obtain a set of members with realistic cross-sectional proportions. It is then shown that this inverse formulation for specified predominant member-end strains is quite useful for developing a direct stiffness design method for specified mean maximum member-end strains under design earthquakes. It is further demonstrated that, if a frame is designed elastically for specified ductility factors based on a new concept of a ‘virtually elastic frame’ even under design major earthquakes, then the so-designed frame exhibits the desired response ductility characteristics specified for inelastic frames. Several design examples are presented to illustrate the usefulness of this design method and time history response analyses are performed to demonstrate the validity and accuracy of this design method.     

Generation II knee bracing for severe medial compartment osteoarthritis of the knee

OBJECTIVE: The tolerability of clonazepam in geropsychiatric inpatients was examined in patients with and without a diagnosis of dementia. DESIGN: Forward-looking retrospective study comprising consecutive patients placed on clonazepam. SETTING: A geropsychiatry unit of a large Veterans Affairs Medical Center. PATIENTS: All geropsychiatry inpatients placed on clonazepam over a 21-month period of time. MEASURE: Mini-Mental State Examination, Brief Psychiatric Rating Scale, Cohen-Mansfield Agitation Inventory and the Rating Scale for Side Effects were performed at admission and discharge as part of an ongoing database. RESULTS: Twenty-four geropsychiatric inpatients were treated with clonazepam (mean dose of 1.2 mg for a minimum of 2 weeks) during the 21 months studies. About one half of the patients had a primary diagnosis of dementia and the remainder had a diagnosis of an affective or psychotic disorder. Two of these patients were discontinued because they had responded to the acute need for clonazepam and a third patient was discontinued because of the development of sedation and confusion. For the remaining 21 patients, scores improved significantly on the Brief Psychiatric Rating Scale (p = 0.017), the Cohen-Mansfield Agitation Inventory (p = 0.011), the Rating Scale for Side Effects (0.004) and the Global Assessment of Functioning (p < 0.000), with no differences in amount of improvement between demented and non-demented patient groups. Scores on the Mini-Mental State Examination remained unchanged. CONCLUSIONS: Clonazepam shows promise as a benzodiazepine with good tolerability in the elderly.     

A control design of robotics using the genetic algorithm

This paper presents a new and practical method for a control design of a robotic system. In general, actuators in robotic systems are set with gears whose characteristics are elastic. Since a state feedback-type digital controller is usually used for such a robotic system, the design of the feedback gain of the controller is important, because undesirable vibrations or an overshoot in responses occur for high gains. Therefore the desired response, the output of a reference model, is designed first, and the feedback gains are determined so that the response will coincide with the desired response, which is an optimization problem. The gradient method works to some extent, but it takes a long time to get a satisfactory result. Thus we applied the genetic algorithm (GA) to this nonlinear optimization problem, which gave the very first convergence. The gains obtained have many useful applications. The results of a simulation are also given. This work was presented, in part, at the International Symposium on Artificial Life and Robotics, Oita, Japan, February 18–20, 1996     

A study on the swelling of a sintered nickel hydroxide electrode

The swelling and blistering of a sintered nickel hydroxide electrode, which usually determine the life of the electrode, have been found to be dependent on the the change in the density of the active material during charge and discharge. In particular, the swelling after cycling has been related to the degree of formation of -NiOOH. The largest swelling, as represented by an increase in the thickness of the electrode, occurs when -NiOOH changes to -NiOOH during charging rather than discharging. Addition of cadmium, zinc and magnesium is effective in preventing the formation of -NiOOH. In particular, the swelling can be almost completely prevented by addition of cobalt and cadmium together, even with overcharging at the 1 C rate.     

H∞ control approach to a magnetic levitation system by 4-point attraction with nonlinear characteristics

An H_∞ control system design for a magnetic levitation system by 4 points attraction is presented. In the levitation system, a vehicle which runs as the secondary in a reluctance-type linear motor is levitated by four pairs of attraction forces and guided by two pairs of attraction forces. Because it has contactlessness, in the field of semiconductor products, its application is favorable for ultraclean environments in microscopic processing. In the control system design, the influence of both disturbances and uncertainties in the model is considered. The main disturbances stem from the position sensors. The uncertainties are divided into electromagnetic and mechanical ones: the former are due to the gain change in the current amplifier, the influence of leakage flux and linearization error in the magnetic circuit, and the latter are due to the changes of the mass and the moment of inertia of the vehicle. Therefore, the designed controller is indispensable to guarantee robustness of this system for both stability and performance. The controller design is based on the standard H_∞-optimal control problem. As the novel features in this paper, the low sensitivity and the robust stability for this system design is obtained. Further, there are two-poles on jω-axis in the controlled model, and an integrator is included in the controller so that equivalently there are three poles on the jω-axis in the model. Finally, several experiments, comparisons and simulations are carried out to verify the low sensitivity and robustness of the designed control system.