Motion of a body sliding on a rough horizontal plane and supported at three points

The problem on the motion of a heavy solid body supported by a rough horizontal plane at three points (“tripod” [1]) is considered. The contacts at the support points are assumed unilateral and subject to the laws of dry friction. The dynamics of the possible motions of such a body under the action of forces of gravity and dry friction is studied.     

强迫振动方法确定黏弹性细棒的复杨氏模量

提出了一种方法--强迫纵振动法(该计算方法不同于以前的梁振动法)来确定黏弹性样品细棒的杨氏模量。在室温下,对长度分别为108 mm,100 mm,90 mm,83.5 mm,80 mm,74.5 mm,70 mm的聚碳酸酯细棒,实验测试得到了棒两端的振幅比与激励频率之间的关系曲线,并由曲线的3 dB带宽计算得到损耗因子,进一步得到棒的储能和耗能杨氏模量。依照这种方法,只要能得到足够多的数据,用最小二乘算法,可得到在感兴趣的频段内该材料相应的杨氏模量随频率变化的曲线。若测试频率步长减小到5 Hz,则测试最大误差可小于6%。与现有测试方法相比较,本方法计算简单,物理意义清晰。     

The equivalent nonlinearity for a nonlinear system with dither

Given a single loop nonlinear control system. The problem of constructing a dither signal in order to obtain a desired equivalent nonlinearity is considered. It is assumed that the nonlinearity may be described by a kth order polynomial. For this case it is shown that in general k different levels for the dither signal are necessary.     

Parametric interaction and backward wave oscillation in stimulated compton scattering

Stimulated Compton-Raman scattering and free electron lasers are formulated as parametric (four-photon) or three-wave interaction processes. Manley-Rowe relations and depletable pump equations are derived for both free electron lasers and optical klystron schemes. A process of backward wave oscillation is predicted when a pump radiation field is back scattered off a codirectionally propagating e beam with frequency down conversion. A practicable experiment in the optical regime is proposed to demonstrate this effect.     

Light-dependent Oxygen Consumption in Bacteriochlorophyll-Serine-treated Melanoma Tumors: On-line Determination Using a Tissue-inserted Oxygen Microsensor

Successful application of anticancer therapy, and especially photodynamic therapy (PDT) mediated by type II (PDTII) processes, depends on the oxygen content within the tumor before, during and after treatment. The high consumption of oxygen during type II PDT imposes constraints on therapy strategies. Although rates of oxygen consumption and repletion during PDTII were suggested by theoretical studies, direct measurements have not been reported. Application of a novel oxygen sensor allowed continuous and direct in situ measurements (up to a depth of 8–9 mm from the tumor surface and for several hours) of temporal variations in the oxygen partial pressure (pO₂) during PDT. Highly pigmented M2R mouse melanoma tumors implanted in CD1 nude mice were treated with bacteriochlorophyll-serine (Bchl-Ser; a new photodynamic reagent) and were subjected to fractionated illumination (700 < λ. < 900 nm) at a fluence rate of 12 mW cm^-2. This illumination led to total oxygen depletion with an average consumption rate of 7.2 uAf(O₂) s^-1. Spontaneous reoxygenation (at an average rate of 2.5 µM(O₂)/s) was observed during the following dark period. These rates are in good agreement with theoretical considerations (Foster et al., Radiat. Res. 126, 296,1991 and Henning et al, Radiat. Res. 142, 221, 1995). The observed patterns of oxygen consumption and recovery during prolonged periods of light/dark cycles were interpreted in terms of vasculature damage and sensitizer clearance. The presented data support the previously suggested advantages of fractionated illumination for type II photodynamic processes.     

Interfacial characterization of chemical solution‐deposited thin films of PbSe on GaAs(100)

The microstructure and composition of the interfacial layer between chemically deposited PbSe and GaAs substrates were studied using high‐resolution transmission electron microscopy (HRTEM), Auger electron spectroscopy (AES), x‐ray photoelectron spectroscopy (XPS) and energy‐filtered TEM. The thickness of the interfacial layer varied significantly from direct contact of the film with the substrate to 5 nm in the thickest regions. The results established the presence of a discontinuous, amorphous intermediate layer of Ga₂O₃ at the PbSe/GaAs interface. Copyright © 2008 John Wiley & Sons, Ltd.     

On Optimal Rotation of a Rigid Body by Applying Internal Forces

Doklady Mathematics - The article describes results obtained for the problem of maximum rotation of a rigid body in a given time interval by moving an internal mass. The mass moves by applying a...     

Model for cost estimation in a finite-capacity stochastic environment based on shop floor optimization combined with simulation

In recent years several researchers suggested cost estimation models that consider limited capacity. These researchers ignored the stochastic nature of the shop floor. This paper presents a cost estimation model that takes into account the stochastic environment. It is based on marginal analysis – the difference between the total cost without the new order and the total cost with the new order. The proposed model is based on the integration of simulation and optimization. Data generated by the simulation is inserted into the optimization procedure that finds good feasible solutions quickly. A significant advantage of the proposed stochastic cost estimation over an existing deterministic approach is shown. A computational study is performed to test different factors affecting the proposed model.     

Determination of complex Young’s modulus of viscoelastic bars using forced longitudinal vibration of slender rods

A method to identify complex Young’s modulus of viscoelastic materials using forced longitudinal vibration of slender rods is proposed.The method differs from the beam one.Experimental tests were carried out at room temperature with different lengths in 108 mm, 100 mm,90 mm,83.5 mm,80 mm.74.5 mm,70 mm for the polycarbonate bars,and the curves of ratios A₂/A₁ between two ends of a viscoelastic bar versus frequencies are obtained, furthermore,the corresponding 3 dB bandwidth and the storage and loss modulus can be calculated.Sufficient number of obtained complex Young’s modulus at different frequency allows us to calculate other ones using the least square method.If the step of the tested frequency is 5 Hz,the maximum error of results can be less than 6%.By comparison with the measurement methods which the previous literature mentioned,this new method simplifies the calculation,and the physical meaning appears apparently and clearly.