Theory and Practice of Rolling Metal Powders

The theoretical and technological fundamentals are considered for rolling metal powders. The equipment and production schemes for rolling powders is described as well as unit for feeding powder between rolls for the case of manufacturing two-layer strips. The main technological schemes for production copper rollings are presented.     

Evaluation of an educational program for asthma control in adults

We have developed a 6-month educational plan associated with outpatient follow-up and special clinical care for asthmatic patients in a deprived population, with serious socioeconomic problems and a very low level of education. The objective was to determine the effects of the program on clinical asthma outcomes, lung function, and quality of life. Forty patients were enrolled in the program with a regular schedule of outpatient visits, and 31 finished the 6-month intervention, which included information about asthma, instruction in appropriate use of medication, training in metered-dose inhaler technique, how to identify and control asthma triggers, how to use symptom diary cards, and how to recognize early signs of deterioration. Patients included 8 males and 23 females, 47.8 +/- 16.5 years old, with 77.4% elementary school education and 22.6% illiterate, and an average monthly income of around $450. After the 6-month program there was a significant change in asthma control with a reduction in asthma emergency visits and hospitalization, reduction of score symptoms, and improvement in quality of life. Based on the results, educational programs are recommended and should be adapted to the socioeconomic and cultural characteristics of the target population.     

A new VME-based high voltage power supply for large photomultiplier systems

We describe a new high voltage power supply, developed for the leadglass calorimeter of the WA98 experiment at CERN. The high voltage is produced for each of the 10 080 photomultiplier tubes of the detector individually, by the same number of active bases with on-board Greinacher voltage multipliers. The full VME-based HV controller system, which addresses each base via bus cables once per second, is miniaturized and fits into a single VME crate. The main advantages of this approach are the low heat dissipation, the considerably reduced amount of cabling and cost, as well as the high stability and low noise of the system.     

Viscosity and thermal conductivity of alkali metal vapors at temperatures up to 2000 K

New experimental data were obtained on transport coefficients of alkali metals in gaseous phase at high temperatures and within the pressure range from about 10 to about 100 kPa: lithium—thermal conductivity, T= 1400–1800 K, and viscosity, T=1600–2000 K; sodium-viscosity, T= 1100–1500 K; and cesiumviscosity, T=900–1250 K. Viscosity of the alkali metal vapors has been measured using a stationary-technique viscometer with an annular gap. Thermal conductivity was measured by the method of the nonstationary monotonous heating. Experimental data were used as a basis for computing effective atomatom and atom-molecule collision cross section, the values obtained from data on viscosity being in good agreement with those derived from thermal conductivity data. In the case of lithium, the atom-atom cross sections yielded by experiments are fairly consistent with the results of calculations with exact formulae of kinetic theory on the basis of quantum-mechanical potential curves for atom-atom interactions. This has enabled the authors to compile consistent tables of viscosities and thermal conductivities for lithium in a gaseous phase within the temperature range from 800 to 2500 K and pressures from 0.5 to 800 kPa, including the saturation curve.     

Control of a multilevel frequency converter of a power-efficient electric drive

The paper is devoted to an investigation of the control algorithms of a high-voltage electric drive, the converting part of which is represented by the well-known multilevel Series Connected H-Bridge Voltage Source Converter (SCHB VSC) topology. The control algorithm in the framework of the method forming a Space Vector Pulse-Width Modulation (SPWM) is based on the known principle of choosing the three nearest vectors on the voltage diagram of the converter and calculation of the durations of their switching per modulation cycle. A technique that is the same for all converters of creation of a switching algorithm of power valves based on this principle was proposed. The technique uses the principle of a “centered” SPWM with minimization of switching component of the losses in IGBT inverters of the converter cells. The technique of uniform distribution of the switching load by the cells in the phases of the converter and the method of estimation of the power efficient of a high-voltage electric drive and comparison of SPWM based on the results of the computer modeling were proposed. Results of the integrated simulating and modeling test of a 17-level SCHB VSC composed of a high-voltage variable-frequency electric drive, showing a decrease in the total power losses in the power modules of the converter with a modulator of the developed structure of the space-vector PWM by 43–46% compared to the traditional algorithm of sinusoidal PWM, were obtained.     

Rapid Total Synthesis of DARPin pE59 and Barnase

We report the convergent total synthesis of two proteins: DARPin pE59 and Bacillus amyloliquefaciens RNase (Barnase). Leveraging our recently developed fast‐flow peptide‐synthesis platform, we rapidly explored numerous conditions for the assembly of long polypeptides, and were able to mitigate common side reactions, including deletion and aspartimide products. We report general strategies for improving the synthetic quality of difficult peptide sequences with our system. High‐quality protein fragments produced under optimal synthetic conditions were subjected to convergent native chemical ligation, which afforded native full‐length proteins after a final desulfurization step. Both DARPin and Barnase were folded and found to be as active as their recombinant analogues.     

Numerical simulation of burning front propagation

In the context of a numerical experiment, it is shown that the switching wave described by the reaction-diffusion equation can be delayed at a medium inhomogeneity with a thickness Δ and amplitude Δβ for a finite time τ = τ(Δβ, Δ) up to a complete stop at it (τ = ∞). Critical values Δβ _c and Δ _c corresponding to the autowave stop are found. The similarity laws \(\tau \sim (\Delta _c - \Delta )^{ - \gamma _\Delta } \) and \(\tau \sim (\Delta \beta _c - \Delta \beta )^{ - \gamma _\beta } \) are established, and the critical indices and are found. The similarity law is established for critical values of amplitude and width of the inhomogeneity corresponding to the autowave stop Δβ _c ～ Δ _c ^-δ where δ ≈ 1.     

Dynamic precipitation during cyclic deformation of an underaged Al-Cu alloy

The cyclic deformation behavior of Al-4Cu alloy containing shear-resistant particles was investigated systematically as a function of precipitate state. Pronounced cyclic hardening was observed in the under aged Al-4Cu-0.05Sn (wt.%) alloy strained under various imposed plastic strain amplitudes at room temperature. Such cyclic hardening is absent from the longer aging treatments. Microstructural characterization reveals that the pronounced cyclic hardening of the under aged alloy is due to the dynamic precipitation of GP zones. The dynamic precipitation occurs during all the cyclic loading process and only at the peak stress, where the hardening increment from dynamic precipitation saturates, does strain localization occur which is soon followed by failure of the material. The dynamic precipitation of GP zones has a positive effect on the low cycle fatigue performance of this alloy, and can significantly elevate the strength of this alloy without loss in ductility. Experiments performed to test the dependence of the cyclic hardening on plastic strain amplitude and strain-rate illustrate a relatively strain-rate independent and strain amplitude dependent behavior. Such kinetic behavior is approximately consistent with that expected if the GP zone formation is controlled by the vacancies production process during plastic deformation.