Low thermal drift in highly sensitive doped channel Al0.3Ga0.7As/GaAs/In0.2Ga0.8As micro-Hall element

Micro-Hall sensors with high sensitivity, low noise, and high thermal stability, 5 μm square, are fabricated using pseudomorphic Al_0.3Ga_0.7As/GaAs/In _y Ga_1-y As (0.2 ≤ y ≤ 0.3) heterostructures with Si-doped channels. The structures were optimized for thermal stability using a calculation of the self-consistent solution of Schrödinger-Poisson equations and Fermi-Dirac statistics in Hartree approximation. The optimized structure based on a Si-δ-doped 144 Å In_0.2Ga_0.8As quantum well embedded into uniformly doped GaAs channel showed thermal drifts of only 90 ppm·K^?1 in current drive mode and 192 ppm K^?1 in voltage drive mode. The measurements of the absolute magnetic sensitivity and the low frequency noise were done. The micro-Hall sensor, optimized for thermal drift, is able to resolve the magnetic field of 438 nT.     

Numerical analysis and synthesis of 2D quasi-optical reflectors and beam waveguides based on an integral-equation approach with Nystrom's discretization

Considered is the beam wave guidance and scattering by 2D quasi-optical reflectors modeling the components of beam waveguides. The incident field is taken as the complex-source-point field to simulate a finite-width beam generated by a small-aperture source. A numerical solution is obtained from the coupled singular integral equations (SIEs) for the surface currents on reflectors, discretized by using the recently introduced Nystrom-type quadrature formulas. This analysis is applied to study what effect the edge illumination has on the performance of a chain of confocal elliptic reflectors. We also develop a semianalytical approach for shaped reflector synthesis after a prescribed near-field pattern. Here a new point is the use of auxiliary SIEs of the same type as in the scattering analysis problem, however, for the gradient of the objective function. Sample results are presented for the synthesis of a reflector-type beam splitter.     

D'Alembert's Solution in Thermoelasticity—Impact of a Rod Against a Heated Barrier: Part I. A Case of Uncoupled Strain and Temperature Fields

The problem of impact of a thermoelastic rod against a heated rigid barrier is considered, in so doing lateral surfaces and free end of the rod are heat insulated, while there is either free heat exchange between the rod and the rigid obstacle within contacting end or ideal thermal contact, as a particular case. The rod's thermoelastic behavior is described by the Green–Naghdi theory of thermoelasticity. D'Alembert's method, which is based on the analytical solution of equations of the hyperbolic type describing the dynamic behavior of the thermoelastic rod, is used as the method of solution. This solution involves four arbitrary functions which are determined from the initial and boundary conditions and are piecewise constant functions. The procedure developed enables one to analyze the influence of thermoelastic parameters on the values to be found, as well as to investigate numerically the longitudinal coordinate dependence of the desired functions at each fixed instant of the time beginning from the moment of the rod's collision with the barrier up to the moment of its rebound. The case of uncoupled stress and temperature fields is examined in the first part of the paper, while the case of coupling thermoelasticity is considered in detail in the companion paper. It has been shown that the possibility for generating the reflected thermal wave from the incident elastic wave at the free rod's end is unavailable in the case of the uncoupled strain and temperature fields, and that the rod's rebound may occur either at the moment of arrival at the contact place of the reflected elastic wave from the incident thermal wave or at the time when the reflected elastic wave from the incident elastic wave reaches the contact point.     

Application of Thermodynamic and Kinetic Model for Converter Steelmaking to Optimize Manganese Yield in Crude Steel

A thermodynamic and kinetic model of the converter steelmaking process was developed allowing the analysis of the influence of the technological parameters, such as the amount and addition time of a charge material on the chemical composition of the crude steel. The process of the manganese ore addition to the converter to increase the final content of manganese in the crude steel was simulated. The optimal technological parameters for the enhancement of manganese yield were determined.     

Barkhausen criterion for pulse oscillators

This work presents the study of the conditions for forming periodic oscillations of non-sinusoidal pulse waveforms in oscillatory systems consisting of a linear frequency-dependent circuit and an active nonlinear element. Based on Barkhausen stability criterion, an application under the frequencies of all harmonics of output oscillations is discussed.     

Protective Effect of Water-Soluble C60 Fullerene Nanoparticles on the Ischemia-Reperfusion Injury of the Muscle Soleus in Rats

The biomechanical parameters of muscle soleus contraction in rats and their blood biochemical indicators after the intramuscular administration of water-soluble C₆₀ fullerene at doses of 0.5, 1, and 2 mg/kg 1 h before the onset of muscle ischemia were investigated. In particular, changes in the contraction force of the ischemic muscle soleus, the integrated power of the muscle, the time to achieve the maximum force response, the dynamics of fatigue processes, and the parameters of the transition from dentate to smooth tetanus, levels of creatinine, creatine kinase, lactate and lactate dehydrogenase, and parameters of prooxidant–antioxidant balance (thiobarbituric acid reactive substances, hydrogen peroxide, and reduced glutathione and catalase) were analyzed. The positive therapeutic changes in the studied biomechanical and biochemical markers were revealed, which indicate the possibility of using water-soluble C₆₀ fullerenes as effective prophylactic nanoagents to reduce the severity of pathological conditions of the muscular system caused by ischemic damage to skeletal muscles.     

基于穴位点体温差别的药效监测系统设计

设计了一种通过检测生物活性点与皮肤完整区域之间温度差来监测药物疗效并优化心理疾病治疗的系统。该系统通过实时监控服药计量,以及时调整药量,从而提高治疗的有效性。系统采用两电极 Foll方法结合中该地形解剖参考点找到生物活性点,通过 DS18B20测量温度,利用 ATmega 32单片机对温度进行处理并实时显示温度差,进而通过温度差反应药效。本文数据证实了温差指标 BAP C7、Gi4与评估心理疾病严重程度的神经尺度之间的相关性。实验结果表明,温度差指标能够作为衡量药效的标准,通过监测温度差可以有效实现心理疾病药效的监测。     

Dy(III) sorption from water solutions by mesoporous silicas functionalized with phosphonic acid groups

The sorption properties towards dysprosium(III) ions of three samples of mesoporous silicas functionalized with phosphonic groups????Si(CH₂)₂P(O)(OH)₂ were studied. It was found that for the sample synthesized by spray-drying using OTAB as a template both sorption and desorption rate of Dy³⁺ ions is high, due to the defined porosity of the sorbent. Sorption of Dy³⁺ ions by bridged silsesquioxane xerogels with disordered structure is significantly hindered by diffusion processes, due to the chaotic packing of globules. Using a model for the chemical reactions, the composition of dysprosium(III) complexes with surface phosphonic groups were determined, and their formation constants were calculated. It was shown that xerogels with higher surface concentration of ligand groups (L), can form complexes DyL₃ and DyL₄ ^?. Meanwhile, the sample synthesized by spray-drying method forms only DyL₂ ⁺ and DyL₃ complexes. For this sample, complexes DyL₃ are more stable than for xerogels. So, mesoporous silica derived by spray-drying method, with defined spatial porosity and relatively low surface concentration complexation groups, is characterized by the best sorption properties towards dysprosium(III) (adsorption and desorption kinetics, the value of the static sorption capacity).     

Shape Memory Behavior of [111]-Oriented NiTi Single Crystals After Stress-Assisted Aging

The shape memory behavior of [111]-oriented Ni_(51)Ti_(49) (at.%) single crystals was investigated after stressassisted aging at 500 °C for 1.5 h under a compressive stress of-150 MPa.It was found that a single family of Ni_4Ti_3 precipitates with two crystallographically equivalent variants was formed after aging under compressive stress.Stressassisted aging resulted in tensile two-way shape memory effect strain of 1.56% under-5 MPa.Thermal cycling under-600 MPa resulted in a transformation strain of-2.15%,while the subsequent thermal cycling under-5 MPa resulted in a tensile two-way shape memory effect strain of 2.2%.     

The effect of silica content on microstructure and mechanical properties of calcia-stabilized tetragonal zirconia polycrystalline ceramic

The present study was aimed at investigating the effect of silica impurities on structure and mechanical properties of zirconia ceramics, stabilized in tetragonal phase by addition of 6.5?mol% calcia. The effect of silica was studied in 0–5?mol% silica concentration range. It was shown that notable increase in fracture toughness (from 7.5?MPa?m^0.5 to 12.5?MPa?m^0.5) as well as limited rise in hardness (from 12?GPa to 13?GPa) can be achieved by addition of ~ 2.5?mol% of SiO2. It was shown that further increase in SiO₂ concentration above 3.75?mol% results in destabilization of tetragonal phase and degradation of mechanical properties. It is suggested that silica reacts with calcia resulting in formation of amorphous calcium silicate, decreasing calcia content in zirconia matrix, and facilitates sintering and grain growth, resulting in lower stability of tetragonal phase.