Response of pile embedded in stochastic ground media

This paper reports a study on the response variability of piles in ground media which is uncertain and is assumed to be one-dimensional stochastic field along the depth. For such problems, no general solutions can be obtained in an analytical form. Accordingly, approximations need to be introduced. In this study, a stochastic analysis based on the Galerkin method and the first-order approximation is proposed for estimating the response variability of a single pile embedded in stochastic ground media. The horizontal force is assumed to be applied from a superstructure in a deterministic manner. Numerical examples are presented to show the usefulness of this method with regard to the number of trial functions, and the spatial correlation property of the ground media. In addition, comparison is made using two different modelings, random variable modeling and stochastic field modeling for the stochastic ground media. Finally, the correlation-free upper bounds of response variation are proposed for the practical purpose.     

Selective silicon epitaxy by photo-chemical vapor deposition at a very low temperature of 160°C

We have grown epitaxial Si films by the photo-chemical vapor deposition (photo-CVD) technique with SiH₄ and H₂ at a very low-temperature of 160°C. Epitaxial films were grown on silicon substrates, while amorphous-like films were deposited on glass substrates. Furthermore, it was found from the atomic hydrogen etching which was produced by photo-dissociation of hydrogen that the etching rate of amorphous silicon was much higher than that of crystal silicon. By using these selectively, we have demonstrated selective epitaxial growth of silicon by the photo-CVD technique followed by the atomic hydrogen photo-etching. Furthermore, heavily phosphorus-doped silicon films (>1 × 10²¹ cm¹⁻³) were also selectively grown by this novel technique.     

Carbonyl reduction of timiperone in human liver cytosol

PURPOSE: The purpose of this study was to assess the acute effects of methylene blue, an inhibitor of nitric oxide synthesis, on hemodynamics and gas exchange in patients with refractory septic shock in a prospective clinical trial at medical and surgical intensive care units in a tertiary university hospital. PATIENTS AND METHODS: Prospective, sequential study of 10 consecutive patients admitted with severe septic shock of diverse causes and unable to achieve an adequate arterial pressure despite the use of at least two vasoactive drugs. Six of them also developed acute lung injury. All received 1 mg/kg intravenous bolus of methylene blue. Hemodynamic and respiratory parameters were measured at baseline and at 30, 60, 120, and 180 minutes after the bolus injection. RESULTS: Systolic, diastolic, mean arterial blood pressure, and systemic vascular resistance increased significantly in all patients, whereas no significant changes were observed in cardiac output, oxygen consumption, or oxygen extraction ratio. Gas exchange remained unaffected in patients with acute lung injury. CONCLUSIONS: Methylene blue had an acute vasopressor effect in patients with refractory septic shock, and it was not deleterious on respiratory function.     

Effect of Tableting Pressure and Geometrical Factor of Tablet on Dehydration Kinetics of Theophyline Monohydrate Tablets

The effect of compression pressure and geometrical factors (thickness and diameter) of tablet on the dehydration kinetics of theophylline monohydrate tablets was studied using an infrared water-content measuring instrument. The dehydration rate of 2 cm diameter tablets decreased with increase in tabletting pressure. The dehydration rates of tablets also depended on tablet shape. The 2 cm diameter tablets (thin tablets) dehydrated faster than 1 cm diameter tablets (thick tablets). Dehydration of the powder bed (loosely packed tablets) and 2 cm tablets compressed at 49 MPa followed the two-dimensional phase boundary equation, and that of 2 cm diameter tablets compressed at 98 MPa and 196 MPa (thin tablets) followed the three-dimensional phase boundary equation. Dehydration of 1 cm diameter tablets compressed at 98 MPa (thick tablets) followed the one-dimensional diffusion equation. It seems that the dehydration of the tablet was controlled by the porosity and the surface area of the tablet. Therefore, tablet thickness and tabletting pressure are important factors affecting the dehydration mechanism.     

Analysis and performance improvement of motor speed control system with nonlinear friction

Solid friction in machine elements is one of the dominant nonlinearities affecting the control accuracy of servo drive systems. Many schemes, including feedforward control, observer-based control and repetitive learning control have been proposed to compensate for nonlinear friction. These schemes show superior performance compared to that of the conventional P- and/or PI-controller; however, friction model errors and bandwidth restriction of the observer cause compensation errors, thus decreasing control accuracy. This paper presents a new control algorithm for performance improvement of a motor speed control system having nonlinear friction. By analyzing characteristics of conventional compensation control schemes during velocity reversal, the relation between control parameters and control accuracy is examined so as to explore problems with each scheme. Based on these analyses, a new feedforward control algorithm is proposed. The proposed algorithm is verified by analyses of control characteristics and experiments using a prototype. Experimental results show the superior performance improvement of the proposed algorithm.     

Thermohydraulic characteristics of coolant gas flow through a control rod channel in a very high temperature gas cooled reactor

A calculation code was developed to evaluate the thermohydraulic performance of a coolant flow through a control rod channel in a very high temperature gas cooled reactor (VHTR) and a high temperature engineering test reactor (HTTR). A one-dimensional flow network model was employed in the present calculation code. The calculated results agreed well with the experimental ones on the flow rate distribution and the total pressure loss in an isothermal coolant flow. The thermohydraulic characteristics of the HTTR control rod channel were evaluated by the code under various conditions, including the normal operating conditions of a HTTR.