溅镀C轴倾斜的压电膜和切变波谐振器

作者对溅镀的压电膜能否应用于甚高频至微波频率的声波器件进行了研究。本文介绍了切变波谐振器用的C轴倾斜的氧化锌(ZnO)和氮化铝(AlN)膜的生长及特性。文中计算了某些膜的切变波激动的定向关系。这些膜在C轴取向与表面法线成大约45°时,可能激励出接近于纯的切变波。在其他角度,则只能激励准切变波和准纵向波。 C轴对膜法线倾斜方向合适的ZnO或AlN膜,是在配有辅助阳极的反应式直流面磁控管溅镀系统中生长的。这类膜可用扫描式电子显微镜(SEM)和体声波器件测量法进行鉴定。自Si基片法线倾斜的C轴晶粒柱形结构可在扫描式电子显微镜中清楚地看到。C轴倾斜角达45°,厚度达10微米的薄膜已经制做成功。在P~+Si基片上溅镀上ZnO和AlN可以制成复合谐振器。这类谐振器的Q值在200兆赫到500兆赫基频谐振范围内大约为5000。特别令人感兴趣的是可以对谐振频率进行温度补偿。在ZnO/Si和AlN/Si的复合结构上已制造出室温下串联谐振频率的绝对温度系数小于1×10~6/℃的谐振器。ZnO和AlN晶片谐振器的温度系数已测出为-36.2×10~-6/℃和-25×10~-6/℃。这表明P~+Si基片在切变膜时的温度系数大约是+9×10~6/℃、     

SBS改性再生型木塑复合材料及其耐水性能

为了充分利用城市固体废弃物中的各项资源，本项工作将固体废弃物中的高密度聚乙烯（HDPE）回收后与废弃的木纤维、苯乙烯-丁二烯-苯乙烯（SBS）进行复合，成功地制备出SBS／再生型木塑复合材料，并进行了力学性能测试和水煮试验。结果表明，SBS的加入使木塑复合材料的冲击韧性得到显著改善，同时，复合材料的弯曲强度和弯曲模量没有明显的影响，表明SBS可以作为木塑复合材料的增韧剂。SBS／木塑复合材料经过8周、60℃的水煮后，复合材料的吸水率和厚度膨胀率均有所增加，弯曲模量和冲击韧性分别平均下降14．4％、10．8％。水煮试验初期复合材料的弯曲强度逐渐降低，然后又逐渐增大，第8周后弯曲强度增加的幅度约10％。木塑复合材料的冲击破坏模式以界面脱粘为主，而加入SBS后，复合材料的破坏以纤维断裂和基体断裂为主。     

降阶脉冲发动机的点火控制逻辑

本文研究脉冲发动机在战术导弹,特别是空空导弹上的应用.因为其飞行任务要求对能量消耗作仔细地监控.一般的中程空空导弹使用助推-主发动机作为动力.除了接近交会之外,发射时导弹雷达导引头并不知道目标.一般的中程空空导弹使用比例导航或者在终段制导使用改进的比例导航,同时为了使导弹在较高的高度飞行以减小阻力,在中段附加了预编程的     

耐用防热方案的验证试验

为了给未来空间运载系统表面提供耐用的热防护,正在研制三种新型防热系统(TPS):钛合金多层壁、超级合金蜂窝和新的碳-碳多支柱结构。该文介绍这些方案的验证试验(热、振动、噪声、存放环境、雷击、气动热)。初步试验结果表明三种防热方案,可以在2300°F以下表面温度范围内使用。     

飞机高锁螺栓孔边缺陷阵列远场涡流传感器仿真与试验

飞机高锁螺栓孔边隐藏缺陷的检测是航空无损检测领域中的难点,远场涡流检测技术不受集肤效应影响,对飞机高锁螺栓紧固件孔边隐藏缺陷检测具有极大优势。针对飞机高锁螺栓紧固件孔边缺陷的检测,设计研发了放置式阵列远场涡流传感器,建立了高锁螺栓孔边隐藏缺陷检测三维模型,优化了检测线圈中心与高锁螺栓中心放置距离,研究了阵列相邻通道间磁场薄弱区缺陷信号衰减趋势,采用阵列放置式的检测方式研究了不同尺寸缺陷检测信号特征。仿真与试验结果表明：检测线圈中心与高锁螺栓中心距离11 mm时检测灵敏度最佳;相邻通道间磁场薄弱区检测信号存在一定程度上的衰减,优化后的探头可检测埋深为4 mm、长×宽×深为5 mm×0.2 mm×2 mm的紧固件孔边隐藏缺陷,且随缺陷长度增大检测信号幅值呈上升趋势。     

Adaptational changes in the neural control of cardiorespiratory function in a confined environment: the CNEC#3 experiment

The goal of the study was to characterize the changes in neurovegetative control of the circulation, attending the presumed physiological and psychological stress originated by the isolation and confinement typical of the living condition of space stations, as simulated in a ground based unit, using time and frequency domain analysis. As a secondary goal we sought to verify the implementation of real time data acquisition, for off line spectral analisys of R-R interval, systolic arterial pressure (by Finapres) and respiration (by PVF2 piezoelectric sensors).

We addressed the cardiorespiratory and neurovegetative responses to standardized, simple Stressors (active standing, dynamic and static handgrip) on the EXEMSI 92 crew, before, during and after the isolation period.

On average the appropriate excitatory responses (to stand, dynamic and static handgrip) were elicited also in isolation and confinement.

Active standing and small masses muscular exercises are easy to be performed in a confined and isolated environment and provide a valuable tool for investigating the adaptational changes in neural control mechanisms.

The possibility there exists of using this time and frequency domain approach to monitor the level of performance and well being of the space crew in (quasi) real time.     

Effect on the cardiac function of repeated LBNP during a 1-month head down tilt

Cardiovascular assessment by ultrasound methods was performed during two long duration (1 month) Head Down Tilt (HDT) on 6 healthy volunteers. On a first 1 month HDT session, 3 of the 6 subjects (A, B, C) had daily several lower body negative pressure tests (LBNP), whereas the 3 subjects remaining (D, E, F) rested without LBNP. On a second 1 month HDT session subjects D, E, and F had daily LBNP tests and the A, B and C subjects did not. The cardiac function was assessed by Echocardiography, (B mode, TM mode). On all the "6 non LBNP" subjects the left ventricule diastolic volume (LVDV), the stroke volume (SV) and the cardiac output (CO) increase (+10%, -15%) after HDT then decrease and remain inferior (-5%, -5%) or equal to the basal value during the HDT. Immediately after the end of the HDT the heart rate (HR) increase (+10%, +30%) whereas the cardiac parameters decrease weakly (-5%, -10%) and normalize after 3 days of recovery. On the "6 LBNP" subjects the LVDV, SV and CO increase (+10%, 15%) after 1 h HDT as in the previous group then decrease but remain superior (+5%, +15%) or equal to the basal value. After the HDT session, the HR is markedly increased (+20%, +40%) the LVDV and SV decrease (-15%, -20%) whereas the CO increases or decreases depending on the amplitude of the HR variations. These parameters do not completely normalize after 3 day's recovery. Repeated LBNP sessions have a significant effect on the cardiovascular function as it maintains all cardiac parameters above the basal value. The LBNP manoeuvre can be considered as an efficient countermeasure to prevent cardiac disadaptation induced by HDT position and probably microgravity.     

HMX复合推进剂燃烧模型计算

本文建立了一个描述 HMX 复合推进剂燃烧特性的模型。该模型基于以下几个重要概念:1.氧化剂和粘合剂具有不同的表面温度;2.能处理由三种不同粒度级配的氧化剂,3.取时间平均方法来计算推进剂燃速,而不取大多数 BDP 类模型所用的空间平均计算燃速的方法,时间平均方法之要点是考虑了氧化剂的点火延迟时间;4.根据修正的 Burke—Sehumann 扩散火     

火箭发动机聚氨酯包复层配方

本发明叙述制造固体推进剂发动机用的聚氨酯配方,着重叙述火箭发动机燃烧室即壳体的完全固化包复层。由于种种原因,固体推进剂发动机需要有包复层,使发动机壳体具有不透气性;在壳体与推进剂之间形成一层绝热薄膜;并作为壳体与推进剂之间增强推进剂粘结的中间层。业已