Inhibition of premixed and nonpremixed flames with phosphorus-containing compounds

The inhibition/extinction of various flames—premixed stoichiometric C₃H₈/air, nonpremixed counterflow CH₄/O₂/N₂, and nonpremixed coflow n-heptane/air cup-burner flames doped with a number of phosphorus-containing compounds (PCCs)—has been investigated experimentally. More than 20 PCCs (organic phosphates, phosphonates, phosphates) and their fluorinated derivatives were studied. All PCCs exhibited similar dependencies in burning velocities, extinction strain rates, and extinction volume fractions of CO₂ upon PCC loading in the range of mole fractions of 0–7000 ppm within an experimental deviation of ± 5%. This confirms that the inhibition effectiveness of the PCCs is influenced by the phosphorus content in the PCC molecule rather than by the structure of the molecule. The burning velocity of a stoichiometric C₃H₈/air mixture and the extinction strain rate of a nonpremixed counterflow CH₄/O₂/N₂ flame doped with trimethylphosphate were calculated. Satisfactory agreement between experimental and modeling results confirms the conclusion that the reactions of phosphorus oxyacids with radicals are responsible for flame inhibition.     

The Weight-Bearing Rate on the Paretic Limb of Cerebrovascular Hemiplegic Patients Necessary for an Independent Obstacle Negotiation Gait

Purpose: The obstacle negotiation gait (ONG) is a fundamental activity of daily living. In cerebrovascular hemiplegic patients (stroke patients), the weight-bearing rate (WBR) on the paretic limb necessary for an independent ONG was studied. Methods: One hundred and seventeen stroke patients were involved. The patients'' average age at the time of the study was 67 years, and the average time from stroke onset was 102 days. There were 68 men and 49 women. Seventy patients were right hemiplegics, and 47 were left hemiplegics. The correlations between ONG and age, sex, body mass index (BMI), time from stroke onset, muscle strength of both the paretic and non-paretic limbs, Brunnstrom stage of the lower limbs, deep sensation, and the WBR on both the paretic and non-paretic limbs were studied. Patients who could perform ONG independently and safely were categorized as the independent group (IG), and those who needed observation or any assistance were categorized as the dependent group (DG). Results: The BMI, muscle strength of both the paretic and non-paretic limbs, Brunnstrom stage of the lower limbs, deep sensation and the WBR for both the paretic and non-paretic limbs were significantly different between the IG and DG groups. In particular, the WBR on the paretic limb was found to correlate significantly with the ONG, and a WBR value of 80.5% on the paretic limb gave a clear cut-off value. Conclusion: Although multiple factors influenced the ONG of stroke patients, the WBR on the paretic limb was the most influential.     

Competition Between Self-birth and Catalyzed Death in Aggregation Growth with Catalysis Injection

We propose two irreversible aggregation growth models of aggregates of two distinct species (A and B) to study the interactions between virus aggregates and medicine efficacy aggregates in the virus-medicine cooperative evolution system. The A-species aggregates evolve driven by self monomer birth andB-species aggregate-catalyzed monomer death in model I and by self birth, catalyzed death, and self monomer exchange reactions in model II, while the catalyst B-species aggregates are assumed to be injected into the system sustainedly or at a periodic time-dependent rate. The kinetic behaviors of the A-species aggregates are investigated by the rate equation approach based on the mean-field theory with the self birth rate kernel I_A(K)=Ik, catalyzed death rate kernel J_AB(k)=Jk and self exchange rate kernel K_A(k,l)=Kkl. The kinetic behaviors of the A-species aggregates are mainly dominated by the competition between the two effects of the self birth (with the effective rate I) and the catalyzed death (with the effective rate JB₀), while the effects of the self exchanges of the A-species aggregates which appear in an effectiverate KA₀ play important roles in the cases of I>JB₀ and I=JB₀. The evolution behaviors of the total mass M^A(t)₁ and the total aggregate number M^A(t)₀ are obtained, and the aggregate size distribution a_k(t) of species A is found toapproach a generalized scaling form in the case of I ≧ JB₀ and a special modified scaling form in the case of I0. The periodical evolution of the B-monomers concentration plays an exponential form of the periodic modulation.     

A prototype of a high rating MRPC

Six-gap resistive plate chamber (MRPC) prototypes with semiconductive glass electrodes (bulk resistivity～1010.cm) were studied for suitability in time-of-flight (TOF) applications at high rates. These studies were performed using a continuous electron beam of 800 MeV at IHEP and an X-ray machine. Time resolutions of about 100 ps and efficiencies larger than 90% were obtained for flux densities up to 28 kHz/cm2.     

Effect of unfolding on the thickness of the hydration layer of a protein

Properties of water in the hydration layer around a protein is intimately correlated with its function. A knowledge of the thickness of the hydration layer is important to understand its role in guiding the folding-unfolding of the protein. We have performed atomistic molecular dynamics simulations of the folded native and a partially unfolded molten globule structure of the villin headpiece subdomain or HP-36 in aqueous solution to estimate the effect of unfolding on the thickness of hydration layer around different segments of the protein. In particular, several dynamic properties of water around different segments of the folded native and the unfolded structure have been calculated by varying the thickness of the hydration layers. It is found that unfolding of a segment of the protein is correlated with the dynamics of water around it, i.e., within the first hydration layer. The effect of unfolding on water properties has been found to diminish when water molecules present beyond the first hydration layer were included in the calculations.      

227-W output all-fiberized Tm-doped fiber laser at 1908 nm

In this paper, we report that a diode-pumped thulium-doped double clad silica fiber laser can provide powers of up to 227 W at 1908 nm, corresponding to a slope efficiency of 54.3%, and an optical-to-optical efficiency of 51.2%. The output power, to the best of our knowledge, is the highest output at 1908 nm. The beam quality M2 factor is about 1.56. Also discussed in this paper is the dependence of the laser performance on fiber length.     

The randomly fluctuating impurity strength initiated excitation in doped quantum dots

We investigate the excitation behavior of a repulsive impurity doped quantum dot under the influence of randomly fluctuating dopant potential. We have considered Gaussian impurity centers doped at different locations. The investigation reveals the interplay between dopant location and dopant’s spatial stretch in modulating the excitation pattern. Maximization in the excitation rate has been observed as a function of fluctuating dopant strength owing to the conflict between opposing influences that promote and hinder excitation.     

High repetition rate laser pulses amplified by Nd/Cr:YAG ceramic amplifier under CW arc-lamp-light pumping

Laser pulses with high repetitive rate generated from a Q-switch microchip Nd:YAG oscillator were amplified by Active mirror composed of Nd/Cr:YAG ceramic pumped by CW arc-lamp. The laser pulses were amplified, and saturation of averaged output laser power was observed. Repetitive ratio of injected laser pulses was changed from 20 to 100 kHz. Averaged output laser power and gain were measured, and gain coefficient and power-extraction efficiency were evaluated. Output laser power was calculated and compared to experimentally measured one, and the calculated results are consistent with the experimental ones. For amplification of laser pulses with high repetitive ratio, this laser material can realize very high laser gain with low pumping power density and high optical-optical conversion efficiency under CW-lamp-light pumping.     

波导耦合纳米光栅结构的光学滤波和角分辨调谐特性

利用干涉光刻技术制备了波导耦合纳米光栅结构,系统研究了其波导共振模式的角分辨调谐特性及其对光栅参数、入射光偏振特性的依赖关系,并作了相应的理论模拟.特别研究了光栅周期和厚度对波导共振模式角分辨调谐速率的影响.实验结果对于器件进一步应用于滤波、生物传感技术具有重要的指导意义. 关键词： 波导耦合光栅 干涉光刻 角分辨 调谐速率     

纳米晶磁芯恒定磁化速率磁性能参数

设计加工了一套可用于测量环形磁芯在8～12 T/s恒定磁化速率下脉冲性能的实验平台,该实验装置主要包括脉冲形成网络、放电开关、匹配负载及被测磁芯。基于该平台对国产的铁基纳米晶磁芯的磁化曲线进行了测试,得到了铁基纳米晶磁芯在200～300 ns范围内的损耗和非饱和脉冲导磁率。实验结果表明:铁基纳米晶磁芯的相对脉冲导磁率随着磁感应增量增大及工作脉宽减小而减小,磁芯损耗则逐渐增大。