Generation of Gas Discharge Plasma by an Arc Source with a Cold Hollow Cathode

The results from a study of an arc plasma source with a cold hollow cathode are presented. The source generates plasma with a density of ∼10¹⁰ cm⁻³ in a volume of ∼0.2 m³ at discharge currents of up to 150 A, an arc discharge operating voltage of 30–40 V, and a low pressure of 0.1–1 Pa. The motion of the cathode spot in the crossed electric and magnetic fields inside the hollow cathode and the cathode’s special design make it possible to eliminate almost completely the penetration of the sputtered cathode material into the working vacuum chamber.__________Translated from Pribory i Tekhnika Eksperimenta, No. 3, 2005, pp. 62–66.Original Russian Text Copyright © 2005 by Schanin, Koval, Akhmadeev.     

Research on Marine Boiler＇s Pressurized Combustion and Heat Transfer

The effect of pressure on combustion and heat transfer is analyzed. The research is based on the basic combustion and heat transfer theorem. A correction for the heat calculation method for pressurized furnace is made on the basis of the normal pressure case. The correction takes the effect of pressurizing into account. The results show that the correction is reasonable and the method is applicable to combustion and heat transfer of the marine supercharged boiler.     

Modelling the FEBEX THM experiment using a state surface approach

Buffer materials being considered as engineered barriers in nuclear fuel waste (NFW) disposal systems possess a pronounced nonlinear behaviour in the unsaturated state. In order to simulate such non-linear responses,the authors adopted an incrementally nonlinear poro-elastic approach where the coefficients of the governing equations are assumed to be functions of suction and the void ratio. These functions are in turn developed from a state-surface equation obtained from suction-controlled oedometric tests. In this paper we show the derivation of the governing equations of the poro-elastic model. A finite element computer code, FRACON, was developed by the authors to numerically solve the above equations. We first use the code to simulate laboratory tests to characterize the swelling properties of a typical bentonite. That same bentonite was used in the FEBEX in-situ heater experiment, conducted at the Grimsel site, Switzerland. The FRACON code was also used to perform blind predictions of the FEBEX heater experiment. It is shown that the model correctly predicts drying of the bentonite near the heaters and re-saturation near the rock interface. The evolution of temperature and the heater thermal output were also reasonably well predicted by the model. The trends in the total stresses developed in the bentonite were correctly predicted; the absolute values however were underestimated probably due to the omission of pore pressure build-up in the rock mass.     

Standby power system VRLA battery reserve life estimation scheme

This paper presents a valve-regulated lead acid (VRLA) battery reserve life estimation scheme. The scheme is adaptive in both type and frequency of involvement. The scheme is based on capacity trending with the support of a number of state-of-health (SOH) indicators. These SOH indicators include accumulated thermal stress, float voltage, and indicators acquired from the start-of-discharge (coup de fouet) region. An implementation test case is given, indicating that the scheme is capable of providing an accurate estimation of reserve life long before the end of life. Furthermore, the estimation accuracy improves as the end of battery life approaches.     

Performance of natural‐fiber–plastic composites under stress for outdoor applications: Effect of moisture,temperature, and ultraviolet light exposure

The effects of moisture, temperature, and ultraviolet (UV) light on performance of natural‐fiber–plastic composites (NFPC) were assessed. We conducted short‐term tests in the laboratory and long‐term tests under natural exposure and measured changes in mechanical properties and color in samples of the composite. Chemical changes of the composite's materials were measured by X‐ray photoelectron spectroscopy to elucidate the mechanisms of chemical transformations on the material surface. Relative humidity highly affected the modulus of rupture (MOR) and the modulus of elasticity (MOE), and had a greater effect than temperature and UV exposure on performance of the composite. The lightness of the composite was increased by the UV effect in the short‐ and the long‐term tests. The X‐ray photoelectron spectroscopy (XPS) analysis suggested that the composite was protected by the UV absorber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2570–2577, 2006     

Synthesis, characterization and devitrification behaviour of an yttrium containing boroaluminate glass

The glass forming region in the B₂O₃-Al₂O₃-Y₂O₃ composition diagram has been determined by a melting and quenching procedure at temperatures up to 1800°C. Different physical characteristics (density, coefficient of thermal expansion, glass transition and crystallization peak temperatures) have been determined for a 35B₂O₃-40Al₂O₃-25Y₂O₃ glass composition (in mol.%). By using a predictive model and some NMR structural data, different elastic moduli (Young's modulus, bulk modulus, shear modulus and Poisson's ratio) have been calculated. The devitrification behaviour has also been studied. Internal crystallization is the dominant mechanism and a new (Y, Al)BO₃ ternary phase has been characterized by X-ray powder diffraction. The temperature and time nucleation dependence have been determined from DTA experiments as well as the crystallization kinetics (i.e. the Avrami exponent and the activation energy for crystal growth).     

An Experimental Investigation into the Feed Rate Capacity of Rotary Valve and Blow Tank Feeders

Industry widely uses rotary valves and blow tanks for the pneumatic conveying of products, each having their pros and cons depending on the specific application. This article shows the differing results obtained when low-velocity conveying a product through a common pipeline using both a drop-through rotary valve and a bottom-discharge blow tank feeder. A number of issues arise in the rotary valve system, the main one being rotary valve air leakage. A blow tank system, on the other hand, does not leak, as it is an enclosed system. The experimental results show dramatic differences in product throughput. Further exploration leads to a novel modification being made to the rotary valve system in an attempt to increase its capacity. The result of this modification shows a slight increase in output tonnage, but still significantly less than that obtained from the blow tank.     

The radiative recombination coefficient and the internal quantum yield of electroluminescence in silicon

The results of the analysis of variations in the radiative recombination coefficient with varying doping level and concentration of excess electron-hole pairs are reported. It is shown that, along with the effect of narrowing of the band gap calculated in the many-electron approximation, the effect of screening of the Coulomb interaction responsible for the decrease in the excition binding energy should be taken into account. Both effects produce similar trends and decrease the radiative recombination coefficient with increasing levels of doping or injection. The contributions of excitonic radiative recombination and band-to-band radiative recombination to the total radiative recombination coefficient are separated from each other. It is shown that, in the region of room temperature, both contributions are comparable, while at liquid-nitrogen temperature, the excitonic component dominates over the band-to-band component. The results obtained by refined calculations of the limiting value of the internal quantum yield of electroluminescence for the silicon diodes and p-i-n structures are presented. It is shown that the internal quantum yield of electroluminescence can be as high as 14%. However, this values sharply decreases with increasing surface recombination rate and decreasing lifetime of excess charge carriers in the bulk.     

A Low-Power CMOS Linear-in-Decibel Variable Gain Amplifier With Programmable Bandwidth and Stable Group Delay

This brief presents a new circuit architecture for linear-in-decibel, constant-bandwidth variable gain amplifier (VGA). To obtain high linearity under low-voltage operation, this VGA is a closed-loop structure. In loop amplifier design, two techniques are applied: first, the loop amplifier is given finite input impedance. This arrangement keeps the VGA bandwidth constant under different gain setting. Second, a current-buffered compensation is applied for loop stability. Compared to the Miller compensation, this method achieves wider bandwidth. The prototype chip using 0.18-mum CMOS technology demonstrates that -10- to 20-dB gain and 0.5- to 30-MHz bandwidth can be programmed independently. The group delay difference within 30-dB gain control range is smaller than 1%. The total circuit dissipates 1.35 mA from a 1.8-V supply     

64-Mb/s data transmission beyond the relaxation oscillation frequency using monolithically integrated two laterally coupled diode lasers

In this letter, we demonstrate the possibility of using two monolithically integrated laterally coupled diode lasers for data transmission beyond the intrinsic relaxation oscillation frequency of semiconductor lasers. The resonance of the lateral modes of such structure provides a peak in the small signal modulation response of the device above the relaxation oscillation frequency of the intrinsic emitters that is studied in terms of relative intensity noise and phase noise to characterize this new, simple, and compact device. Optical transmission of a 64-Mb/s pseudorandom bit sequence signal using a microwave carrier over this resonance peak of the lateral modes above the relaxation oscillation is demonstrated for the first time to our knowledge.