Analysis of cross-flow jet-type singlet oxygen generator

A cross-flow jet-type singlet oxygen generator has been developed, tested and analyzed in order to characterize the dependence of output performance on major input parameters. A thermal-balance model, which can predict O/sub 2/(/sup 1//spl Delta/) yield, gas temperature, and gas residence time, is proposed, and the resultant theoretical results are compared to the experimental data. Combined with computational fluid dynamics-based gas residence-time analysis, the model provides good agreement with the measured value of the O/sub 2/(/sup 1//spl Delta/) yield and the gas temperature. The surface chemistry model was applied to the measured Cl/sub 2/ utilization data, and was found to be inconsistent in the regime of high Cl/sub 2/ loading on the basic hydrogen peroxide jet, indicating that depletion of HO/sub 2//sup -/ is taking place.     

小型单重态氧发生器中氯气利用率的测量

在一台为化学氧碘激光器而研制的小型射流式单重态氧发生器上建立了一套氯气利用率测量系统;从实验和理论两方面详细研究了光源线宽、气流温度、水气含量、气流组分对紫外吸光光度法测量氯气利用率的影响;测量结果和误差分析表明,在良好设计的实验中,氯气利用率的相对测量误差约为2%,主要来源于光电倍增管(PMT)的噪音.最后,提出了减少测量误差和扩大氯气利用率测量量程的方法.我们的工作将有助于更加准确地和精确地测量化学氧碘激光系统中的单重态氧发生器的氯气利用率.     

Power optimization of small-scale chemical oxygen-iodine laser withjet-type singlet oxygen generator

Studies of power optimization of a 5-cm gain length chemical oxygen-iodine laser (COIL) energized by a jet-type singlet oxygen generator (JSOG) are presented. For 10 mmol/s of Cl₂ flow rate, output power of 132 W with chemical efficiency of 14.5% was obtained without a water vapor trap, 163 W and 18% were achieved when coholed (173 K). He was introduced downstream of the JSOG; under these conditions, the small-signal gain was estimated to be 0.32% cm^-1 . 190 W and 10.5% were obtained for 20 mmol/s of CI₂ flow rate. Replacing He by N₂ as a buffer gas resulted in a 13% power decrease only. The main key for increasing the chemical efficiency of a COIL without a water vapor trap for a given iodine-oxygen mixing system is found to be high oxygen pressure and low water vapor pressure inside the reaction zone of the JSOG. The last goal was achieved by optimizing the composition and temperature of the basic hydrogen-peroxide solution (BHP). The experimental results are discussed and related to the composition and flow conditions of the gaseous reactants and of the BHP     

Role of singlet oxygen in formation of nanoporous silicon

The effect of singlet oxygen on the formation of nanoporous silicon in the case of photoelectrochemical etching of p-Si is studied. Pulsed electrolysis was used to discriminate between chemical and electrochemical processes. The pulsed etching of silicon was accompanied by pulsed illumination coinciding either with current pulses or with zero-current periods. An analysis of the results obtained demonstrated that, as the number of silicon nanocrystals increases under illumination, singlet oxygen starts to be generated from molecular oxygen dissolved in the electrolyte. This process leads to oxidation of the surface of silicon nanocrystallites and to a change in its passivation.     

酞菁类光敏剂单重态氧量子产额的激光诱导ESR研究

本文应用激光诱导ESR波谱法研究酞菁类光敏剂的光动力反应动力学过程,对几种酞菁的单重态氧(~1O_2)相对量子产额进行了测定比较。     

Parametric study of an efficient supersonic chemical oxygen-iodinelaser/jet generator system operating without buffer gas

A detailed experimental study of an efficient supersonic chemical oxygen-iodine laser is presented. The laser is energized by a jet-type singlet oxygen generator, operated without primary buffer gas and applies simple nozzle geometry and transonic mixing of iodine and oxygen. Output power of 190 W with chemical efficiency of 18% was obtained in a 5-cm gain length for Cl₂ flow rate of 11.8 mmole/s. The power is studied as a function of the distance between the optical axis and the supersonic nozzle exit plane, the molar flow rates of various reagents, the basic hydrogen peroxide solution and gas pressures in the generator, the type of the secondary buffer gas (N₂ or He) and the stagnation temperature of the gas. It is found that the power under the present operation conditions is almost unaffected by water vapor in the medium. The role of buffer gas under different conditions is discussed     

Detection of singlet oxygen in photoexcited porous silicon nanocrystals by photoluminescence measurements

Luminescence of gas-phase singlet oxygen optically sensitized by microporous silicon at room temperature is detected for the first time. At the same time, a photoinduced increase in the photoluminescence intensity of defects at the sample surface in oxygen atmosphere is observed. It is shown that mechanical grinding of porous silicon layers yields a decrease in the amount of photogenerated singlet oxygen.     

Experimental study on a novel polarization state generator

Duetothe spoilageinduced bythe polarization-relatedeffects (PRE) in high-speed(≥10 Gb/s/channel) opti-cal fiber communication systems ,it is necessary to in-vestigate the effect of PRE on optical components andentire transmission systems .In general , PR…     

Photosensitized generation of singlet oxygen in powders and aqueous suspensions of silicon nanocrystals

The photoluminescence spectra and kinetics in powders and aqueous suspensions produced from porous silicon layers are studied. The systematic features of photosensitized generation of singlet oxygen by silicon nanocrystals in the samples are established. The dependence of the efficiency of generation of singlet oxygen on the pressure of molecular oxygen is analyzed. It is concluded that the generation can be described on the basis of concepts of energy transfer from photoexcited silicon nanocrystals to oxygen molecules adsorbed at the nanocrystal surface to the concentration described by Langmuir’s adsorption model. The processes limiting the efficiency of photosensitized generation of singlet oxygen in the systems are discussed.     

The crucial role of singlet oxygen in the formation of photoluminescence from nanoporous silicon

It is shown that nanoporous silicon electrochemically fabricated on p-type silicon (1–4 Ω cm) in complete darkness exhibits nearly no photoluminescence in the visible spectral range. Photoluminescence properties appear upon irradiation of a porous silicon layer with white light in a water-alcohol solution of HF. The effect is accounted for by the action of the singlet form of molecular oxygen, generated when dissolved oxygen comes in contact with a porous silicon layer under illumination.     

Observations of a bistable twisted nematic liquid-crystal effect

In nematic liquid-crystal layers with a π/2 twist, reverse twist disclination lines occur which can be pinned by surface features and moved by electric fields. We consider these effects as the basis of a bistable matrix display. The optical transmission through twisted regions of opposite chirality is analyzed using a Poincaré sphere construction.     

Parametric study of depressed inner cladding single-mode fibers

A parametric study on the depressed inner cladding (DIC) single-mode fibers shows the influence of the inner-cladding diameter on the effective cutoff wavelengths of the first two modes, determining a practical transmission window. The set of curves that is obtained can be considered universal, at least for a value of the inner-cladding/core index differences ratio close to 0.5. The behavior of the effective cutoff wavelengths is explained by studying the effective index of the modes and the fundamental mode diameter, this explanation being confirmed by a bending and microbending sensitivity test. It appears that DIC fibers optimized for long-range transmission should have an inner cladding to core diameter ratio greater than 3 and a relative depth of the inner cladding smaller than 0.5.     

Parametric study of a constant E/N pumped high-power KrF* laser

The application of a novel constant voltage excitation technique has led to the production of volume glow discharges in a scalable multiatmosphere rare gas halide laser. Such discharges are obtained using a high-voltage discharge circuit which optimizes energy transfer from the power conditioning system into the load, up to the voltage limit of the system components. A detailed parametric study has been carried out for KrF* at pressures up to 6 atm and output energies in excess of 0.6 J were obtained from an active volume of 0.18 l.     

Rotation of a waveform generator

A recently suggested oscillator model which generates two triangular waves in quadrature is transformed by rotation to a new model that generates two trapezoidal waves also in quadrature. In the phase plane the limit cycle of the first oscillator model is in a form of a square standing on its edge, the limit cycle of the latter is a square lying on its side.     

Analysis of a PRSA generator

The pseudorandom sequence of arrays (PRSA) and a method to generate it was reported earlier by the authors. This paper presents another method to generate a PRSA. The mathematical recursion describing the PRSA and some of its properties are discussed.     

Parametric study of the crosspolarisation efficiency of parabolic reflectors

The crosspolarisation efficiency of a reflector antenna is the ratio between the peak crosspolarisation from the complete antenna to that from the feed. The results of a parametric study into this factor for parabolic reflectors fed by a mathematical model of a common class of feeds are presented, and it is concluded that the efficiency is typically ?4 to ?6 dB.     

Parametric study of the CuBr laser with hydrogen additives

A systematic investigation of the electric parameters of the CuBr laser plasma during the excitation pulse in their correlation to the laser output characteristics is presented. Based on the electric parameters, the temporal course is calculated of the electron density during the discharge. The authors offer a simple mechanism which generally explains how the hydrogen occurred in the copper vapor laser. The mechanism consists of shielding copper ionization by the process of electron detachment from negative hydrogen ions     

Parametric study of warpage in printed wiring board assemblies

Out-of-plane displacement (warpage) causes mis-registration, delamination, possibly solder joint opening(s), and other printed wiring board assembly (PWBA) failures during surface-mount assembly processes and life-span operations. Many material, geometry, and process related parameters contribute to the warpage of a PWBA. The objective of this paper is to investigate these parametric effects on PWBA warpage. Based on the parametric study, the identified material, geometry, and process parameters can then be optimized to achieve the most reliable product. In this paper, a PWBA test vehicle consisting of a four-layer PWB and a surface-mount ball grid array package is studied. Its warpage during infrared reflow is measured by the shadow moire/spl acute/ method to validate finite-element results. The validated modeling results are used for parametric study. In the parametric study, Taguchi and full-factorial design of experiments (DOE) are adopted to systematically vary parameters that are of interest. After running experiments based on DOE, analysis of variance is employed to identify the influential parameters. Thereafter, the warpage data is regressed with respect to the identified influential parameters. According to the regression model, the influential parameters can be optimized within practical range to achieve the least warped design.     

一种正弦信号发生器的设计

设计一个以单片机和FPGA为核心,基于DDS AD9851的正弦信号发生器,能在100 Hz-15 MHz频率范围可调.通过AGC、幅度控制、调制电路、功率放大等模块实现AM、FM、ASK、FSK、PSK多种调制功能.同时FPGA实现直接频率合成技术,产生基波信号,控制AD9851产生载波信号.用户通过按键选择系统输出调制方式,操作简单.     

AC strength of a pattern generator

The AC strength of a pattern generator is the fraction of the exhaustive two-pattern count that it can apply to the logic given sufficient time. It is a measure that allows assessing how well a pattern generator can serve in applying AC test vectors to the logic. Generators with high AC strengths tend to perform better than generators with low AC strengths.Special generators with high AC strengths can be designed with a considerable penalty of hardware overhead. An alternative to designing special pattern generators that can serve well during AC test is to separate the inputs of the logic fed by the generator, so that no two inputs belonging to the same output cone in the logic are connected to adjacent stages of the generator. This input separation will facilitate an effective AC test, and will not suffer from the high overhead that the special generators suffer from.This paper introduces the notion of the AC strength of a pattern generator and proposes the input separation scheme that will allow an efficient AC test to be performed on the logic.