Velopharyngeal aerodynamics of /m/ and /p/ in tracheoesophageal speech

The purpose of this study was to compare oral pressure (P_o), nasal airflow (V_n), and velopharyngeal (VP) orifice area estimates from 12 tracheoesophageal (TE) and 12 laryngeal speakers as they produced /p/ and /m/ in syllable series. The findings were as follows: (1) TE speakers produced greater P_o than the laryngeal speakers; (2) for /p/, TE speakers generated V_n, and VP orifice area estimates comparable with, or less than, the laryngeal speakers; and (3) for /m/, TE speakers had V_n and VP orifice area estimates greater than the laryngeal speakers. The elevated P_o could be the result of several factors such as high source driving pressures and vocal tract volume changes postlaryngectomy. Attempts at more precise articulation, and subsequently less coarticulation, by the TE speakers may explain the V_n and VP orifice area estimates for /p/ and /m/. TE speakers may be limiting the oral-nasal cavity coupling for /p/ (smaller VP gap, less V_n) in an attempt to produce a very precise oral /p/. For /m/, TE speakers may be attempting to overtly mark the consonant as a nasal (greater V_n, larger VP gap). Further studies are needed to confirm/refute the explanations postulated here regarding the VP aerodynamic differences that were identified.     

EAST低温系统已研制氦透平膨胀机测试分析

EAST氦低温系统是EAST( Experimental Advanced Super-conducting Tokamak)先进超导托卡马克实验装置重要子系统之一;4 台氦透平膨胀机又是EAST氦低温系统的核心部件.文中主要对已研制出的1台氦透平膨胀机的结构、调试过程与调试结果等进行一些分析,还给出了氦透平的启动过程...     

Ab initio potential energy curve for the helium atom pair and thermophysical properties of dilute helium gas. I. Helium–helium interatomic potential

A helium–helium interatomic potential energy curve was determined from quantum-mechanical ab initio calculations. Very large atom-centred basis sets including a newly developed d-aug-cc-pV8Z basis set supplemented with bond functions and ab initio methods up to full CI were applied. The aug-cc-pV7Z basis set of Gdanitz (J. Chem. Phys. 113, 5145 (2000)) was modified to be more consistent with the aug-cc-pV5Z and aug-cc-pV6Z basis sets. The diagonal Born–Oppenheimer corrections as well as corrections for relativistic effects were also calculated. A new analytical representation of the interatomic potential energy was fitted to the ab initio calculated values. In a following paper this potential model will be used in the framework of quantum-statistical mechanics and of the corresponding kinetic theory to calculate the most important thermophysical properties of helium governed by two-body and three-body interactions.     

一种低温气体分离回收方法研究

介绍了一种适合于分离氦气中微量Kr、Xe、H2及其同位素的方法。对比了不同分离方法的特点,并最终采用低温分凝法来分离混合气体。设计了分离的流程及温度、压力等物理参数,通过分析和计算,确定了在合适温度下,可以分离提取出混合气体中的杂质气体,实现最终尾气中杂质气体所要求的浓度指标。并得出最终混合气体杂质浓度只与进气压力和冷冻温度有关的结论。     

冷冻靶制备用低温氦气循环系统

常温高压渗透充气、低温冷却的冷冻靶球,需要20K以下的低温循环氦气,用于冷却高压渗透室和低温恒温腔。本套系统采用GM制冷机为冷源,采用专用氦压缩机为循环泵,设计高效率的回热式换热器,实现末端的20K以下低温氦气,通过低温氦气冷却终端部件,实现了20K的低温恒温环境和渗透室的冷却。     

氦透平膨胀机叶轮(理想气体)S_2流面流场计算

为保证核聚变装置EAST(Experimental Advanced Super-conducting Tokamak)氦低温系统的稳定运行,其核心部件氦透平膨胀机必须满足制冷量的要求;因此有必要用流线曲率法对低温氦透平膨胀机T2叶轮流场进行计算。经过计算得出T2叶轮子午面流场,同时也对叶轮性能进行分析,结果完全满足要求。     

Helium Droplets: An Apparatus to Study Ultra Cold Chemistry

A new pulsed helium nano droplets machine has been constructed. The droplets were gener-ated by expansion of the pure helium through the cryogenic valve attached to a closed-cycle cryostat. The mean size of helium droplets can be controlled between 103 and 105 helium atoms by tuning the backing pressure (10-40 bar) and temperature (10-30 K). Compared with the continuous-flow beam source, the density of droplet is at least one order of magni-tude higher, which offers the opportunity to combine the system with the commercial pulsed laser to study chemical reactions inside of the superfluid helium at ultra-low temperature. The performance for the system has been checked by studying the photodissociation of CH₃I doped droplets at 252 nm with the velocity map imaging technique. The photofragments, CH₃, were detected by (2+1) resonance enhanced multiphoton ionization. The speed and angular distributions derived from resulting images show clear evidence of the relaxation effect by the surrounding helium atoms. The pulsed helium droplets depletion spectroscopy was also demonstrated. The depletion spectrum of benzene doped helium droplets indicatesthat less than 3% depletion can be observed with the newly constructed apparatus.     

温度对fcc铁中氦行为的影响研究

温度对fcc铁中的氦行为具有重要的影响,编写了居于fcc晶格的面向对象动力学蒙特卡罗程序（Object Kinetic Monte Carlo）,采用该程序结合分子动力学（MD）方法对fcc铁中的氦行为进行多尺度模拟,研究了温度对fcc铁中氦行为的影响,给出了不同温度退火过程中氦行为的原子细节。模拟结果表明引入一定量的非热平衡空位可以使模拟结果与文献实验结果有非常好的吻合;室温至1073K,温度对氦行为影响可以分为四个阶段：第一阶段,298-473K,正电子长寿命随退火温度增加略有减少,这主要由于非热平衡空位浓度降低;第二阶段,473-673K,正电子长寿命随退火温度增加而增加,主要由于晶粒内平均氦泡尺寸增加;第三阶段,673-873K,正电子长寿命随退火温度增加而迅速减少,主要是由于氦泡的平均尺寸减小和晶粒内的空位浓度降低;第四阶段,873-1073K,正电子长寿命随退火温度增加而迅速增加,与晶粒内氦泡的平均尺寸变大,且空位浓度随温度的增加而指数增加有关。     

美国物理化学家朗缪尔在中日2国讲学概况

欧文·朗缪尔是1932年诺贝尔化学奖得主。1934年,朗缪尔受邀前往日本和中国北平学术演讲,与我国物理学家、化学家进行座谈。他的精彩演讲给我国学者留下了深刻的印象。依据朗缪尔文集等文献和当时报刊的报道,力图重现朗缪尔中日讲学之盛况。     

氦气对MPCVD沉积金刚石的影响

为了确定添加氦气对微波等离子体化学气相沉积(MPCVD)金刚石膜的影响,采用发射光谱法(OES)在线诊断了CH₄-H₂-He等离子体的发射光谱特性,研究了He对等离子体内基团空间分布的影响;并利用扫描电子显微镜(SEM)和拉曼(Raman)光谱对不同He体积分数下沉积出的金刚石膜进行了表征。结果表明：随着He体积分数的增加,等离子体内H_α, H_β, H_γ, CH和C₂基团的谱线强度均呈上升趋势,其中H_α基团的谱线强度增加最大。光谱空间诊断发现He的加入导致等离子体中各基团的空间分布均匀性变差,造成沉积出的金刚石膜厚度极不均匀。沉积速率测试表明,He的加入导致碳源基团相对浓度增加,有利于提高薄膜的沉积速率,当He体积分数由0 vol.%增加至4.7 vol.%时,沉积速率提高了24%。SEM测试结果表明,随着He体积分数的增加,金刚石膜表面形貌由(111)晶面取向向晶面取向混杂转变,孪晶生长明显。高He(4.7 vol.%)体积分数下由于C₂基团的相对浓度较高,导致二次形核密度增加。此外,由于基片台受到等离子体的刻蚀和溅射作用,导致薄膜沉积过程中引入了金属杂质原子。二次形核和杂质原子的存在使得孪晶大量的产生,薄膜呈现出压应力。