考虑车辆高速和低速耐撞性的多目标优化设计

<正>面高速耐撞性设计,需确保车内乘员的人身安全,使车内乘员的人身伤害降到最低;正面低速耐撞性设计,要求尽量减少车辆在碰撞中的损伤,使车辆具有良好的碰撞损伤修复经济性。本文根据上述特点,将车辆的正面高速耐撞性与正面低速耐撞性相结合,并且考虑车身部件的轻量化,提出了一种优化设计方法。该方法将保险杠、吸能盒内外板以及前纵梁内外板五个部件厚度作为优化设计变量,在正面低速碰撞中,以前纵梁吸收的碰撞总能量作为其是否发生较大变形的依据,利用代理模型和遗传算法进行了优化计算。最后,将该方法应用在某一车型的耐撞性设计中。     

14N pulsed nuclear quadrupole resonance. 3. Effect of a pulse train. Optimal conditions for data averaging

The calculations developed in this paper aim at determining the optimal conditions of a NQR experiment when a transition is monitored by means of a pulse train with pulses of identical duration and signal acquisition after each pulse; coherences are assumed to vanish by effective transverse relaxation prior to every new pulse. These calculations demonstrate that, as in NMR, a steady state is effectively reached for any value of the recycle time. However, by contrast with NMR, it is shown that, for optimal data averaging under steady state conditions, the recycle time T can be kept as low as possible (the only limitation is the acquisition time). Nutation curves (signal amplitude versus pulse length) calculated in the steady state case are shown to depend strongly on the ratio T/T ₁ (T ₁: longitudinal relaxation time). The signal growth as a function of T/T ₁under averaging of the first transients has been evaluated as well as the number of pulses necessary for reaching a steady state.     

两台联动转镜式高速相机像漂移分析

 讨论了两台联动转镜式高速相机像漂移的各种原因，从理论和实验对相机像漂移的影响因素进行了分析，比如磁电式传感器、材料、制作工艺、装配精度及操作不当等。并针对这些影响因素，提出了解决像漂移的技术措施，通过实验证明了改进效果。     

Single- and dual-wavelength pulse train generation in frequency-modulated Er–Yb lasers up to 20 GHz

In this paper we present recent results obtained on the generation of ultra-high repetition rate optical pulse trains at 1.5 μm in asynchronously frequency-modulated Er–Yb : glass lasers. Nearly transform-limited pulse trains at either single or dual carrier wavelength with repetition rates up to 20 GHz are generated by means of an external fiber Bragg grating. These pulse trains are of great potential interest for soliton-based optical transmission systems.     

Spatiotemporal Aspects of Prolactin-Induced Calcium Signaling

We have examined the spatiotemporal aspects of PRL-induced Ca²⁺ signals using high-speed fluo-3 confocal imaging. We found that PRL stimulated Ca²⁺ entry and intracellular Ca²⁺ mobilization. Ca²⁺ influx was seen as a peripheral increase in [Ca²⁺]_i without amplification in the nucleus region. Intracellular Ca²⁺ mobilization was seen as a propagating intracellular calcium wave with a strong amplification in the nuclear region. The amplitude of PRL-induced Ca²⁺ increases would be sufficient to stimulate cell proliferation. Furthermore, PRL induced an increase in [³H]thymidine incorporation. These data suggest that PRL would be able to induce mitogenesis through a Ca²⁺-dependent pathway.     

深埋隧道地震动力响应的复反应分析

采用高速摄影技术对定常来流中ＮＡＣＡ４４１２翼的不稳定的空泡流形态特征进行了水洞试验研究．试验结果揭示了由于空泡形态断裂而产生的低频脉动现象．这一现象在跨空泡流（Ｔｒａｎｓ－ｃａｖｉｔａｔｉｎｇｆｌｏｗ）情况下尤为明显，常使空泡长度和厚度在大幅范围内拟周期地变动，其频率特性比较稳定，有别于空泡末端局部泡团脱落而产生的脉动     

Mathematical expression of pressure gradient in the flow of spherical capsules less dense than water

This study yielded a mathematical expression to calculate the pressure gradient (ΔP/L)_m of the flow of a spherical capsule train. An experimental investigation was carried out to determine pressure drops of two-phase mixture flow of spherical ice capsules and water inside the pipelines of cooling systems. Instead of ice capsules, spherical capsules made of polypropylene material whose density (870 kg/m³) is similar to that of ice were used in the experiments. Flow behavior of the spherical capsules, 0.08 m outer diameter, was observed in the measuring section inside plexiglass pipes, 0.1 m inner diameter (ID) and 6 m in length; pressure drops were measured on the 4 m section. The investigation was carried out in the 1.2 × 10⁴ < Re < 1.5 × 10⁵ range and under transport concentration (C_tr) by 5–30%. Dimensionless numbers of the physical event were found out by conducting a dimensional analysis, so that mixture density was expressed in terms of specific gravity and in situ concentration. After arriving at certain conclusions based on the relevant experimental findings and observations, empirical and mathematical models which can be used for calculation of the pressure gradient were developed. Comparison of the mathematical model with the experimental findings revealed that pressure drop values deviated by 2.7% on average for 2.5 × 10⁴ < Re < 1.5 × 10⁵.     

爆炸成型弹丸的试验研究

本文主要介绍了在炸药爆炸驱动下形成EFP的装药结构设计，并对爆炸形成EFP过程进行了必要的光测和电测，得到EFP运动过程的分幅照片，EFP速度－距离曲线。对钢板叠靶及混凝土靶进行了模拟实验，并对破坏效果进行了分析与讨论。     

方管在高速撞击下的能量吸收能力

本文报导了速度约为100m/sec的子弹高速撞击铝合金方管的实验,表明在这种撞击条件下仍与准静态实验中一样,方管仍呈现“开裂与卷曲”的变形破坏模式,并证实了在高速碰撞下方管仍是一种极好的能量吸收装置.理论分析表明,在这种撞击条件下惯性力仍是不重要的;计入了应变率效应之后,理论预计的方管承载能力与实验符合良好.