5W@77K气体轴承斯特林制冷机研究

气体轴承斯特林制冷机是相同制冷量中体积最小、重量最轻、效率最高及寿命最长的制冷机。对于小型化的5W@77K型气体轴承斯特林制冷机,以其独特的优势,在高温超导、低温制冷与深空探测等领域,赢得了广泛的需求。因此,基于redich线性电机形式,运用气体轴承支撑技术和高效回热器技术,国内首次研制成功了小型化气体轴承斯特林制冷机,为我国的低温制冷领域的发展提供坚实的基础。     

Laser emission of 2,2″-dimethylparaterphenyl at 77 K

Dye laser emission of 2,2-dimethylparaterphenyl at 77 K down to 208.5 nm is reported.     

77K下高温超导带材电磁各项异性多样性研究

在高温超导装置的设计过程中,超导材料临界电流的电磁各向异性参数是关键基础数据,也是进行优化设计的依据。文中对国内外5家高温超导生产商的8款高温超导带材在77K下的电磁各项异性情况进行了测试,通过对比分析发现并总结了这些高温超导带材电磁各向异性的多样性。基于文中的研究结果,在高温超导磁体设计过程中需要对所选型号、所用批次的高温超导带材进行全面的电磁各项异性测试,以确保设计的可靠性。     

C77N+异构体的稳定性和电子光谱研究

用INDO系列方法对C78(C2V)的等电子体C77N+的所有21种可能异构体进行系统的理论研究.研究结果表明,最稳定异构体是由C78(C2V)沿Y方向椭球短轴所穿过的C(78)-C(73)键上的原子C(78)被N+取代所形成,椭球长轴附近的原子被取代所形成的异构体能量较低,取代位置附近易成为进一步反应的中心.用INDO/SCI方法计算了C77N+电子光谱,表明其吸收峰与C78(C2V)相比发生红移,对特征吸收峰进行了理论指认,讨论吸收峰红移的原因.     

77K时蒽在乙醇刚性玻璃体中的吸收光谱

有关蒽的光谱研究已有许多报导,但至今这方面工作仍相当活跃,因为有些问题尚未搞清,有待进一步研究。在线型稠环芳香族化合物中,环数为1和2的苯和荼的最低受激单态为~1L_b态,第二受激单态为~1L_a态。理论计算和实验结果已证实了这个结论。然而,理论计算表明,环数为3的蒽的最低受激单态应为~1L_a态,第二受激单态应为~1L_b态,恰巧与前者颠倒过来。遗憾的是人们至今尚未在实验上确定蒽的~1L_b态的存在。为此,本文测量了77K     

77 GHz车载毫米波中远距雷达天线阵列设计

为了在雷达中实现对中距和长距的探测,首先研究并实现了针对中长距雷达探测需求的天线及其组阵形式,然后通过雷达方程得出天线阵列所需的增益与组阵方式,设计了高增益窄波束和低增益宽波束形式的毫米波雷达天线阵列,最后的仿真和测试结果表明,该中长距雷达天线阵列能够满足77 GHz车载毫米波雷达对中距大角度和长距小角度的视野范围探测需求。     

邮票上的物理学史(77)--生物物理学

生物物理学是生物学和物理学之间的边缘学科,它用物理学的概念和方法研究生物各层次的结构与功能的关系,以及生命活动的物理过程和物理化学过程.它的研究范围很广泛,历史上,像对生物发光(萤火虫)现象的研究,伽凡尼对肌肉的电学性质的研究,托马斯*杨对眼睛的几何光学性质的研究,亥姆霍兹把能量守恒定律应用于生物系统等,都可以归到生物物理学.我们不在这里追溯这些历史,只结合邮票上的资料就20世纪40年代以来的新进展作一简述,以便从中看到物理学和物理学家对生物学发展所起的重要作用.     

纳米Ni在77 K温度下压缩行为的研究

利用低温力学测试系统研究了电化学沉积纳米Ni在77 K温度下的压缩行为. 室温下纳米Ni 的屈服强度为 2.0 GPa, 77 K温度下的屈服强度为3.0 GPa, 压缩变形量则由室温的10%左右下降到5%. 借助应变速率敏感指数、激活体积、扫描电子显微和高分辨透射电子显微分析, 对纳米Ni的塑性变形机制进行了表征. 研究表明, 在77 K温度下的塑性变形主要是由晶界-位错协调变形主导, 晶界本征位错弓出后无阻碍地在晶粒内无位错区运动, 直至在相对晶界发生类似切割林位错行为. 同时分析了弓出位错的残留位错部分在协调塑性变形时起到的增加应变相容性和减小应力集中的作用. 利用晶界-位错协调机制和残留位错运动与温度及缺陷的相关性揭示了纳米Ni室温和77 K温度压缩性能差异的内在原因. 关键词： 塑性变形 强度 位错     

用于77—300K固体粉末比热测量的绝热量热器

本文描述了一个用于77—300K测量固体粉末比热的绝热量热器,经标准样品苯甲酸的校验,结果为:装置的准确度达到0.65％,测量精度优于1％.用此装置测量;国产绝热材料——膨胀珍珠岩粉末在77—300K温区内的比热.     

高压Ni77P23非晶合金自由体积变化的同步辐射研究

利用同步辐射高能X光散射的方法,研究了室温下非晶合金Ni77P23的自由体积的变化所引起的压缩行为的变化规律,通过傅里叶变换得到不同压力下的径向分布函数,并由此获得了不同压力下,该非晶合金的配位数、近邻原子间距等原子构型的结构信息. 研究表明,至直30.5GPa压力,Ni77P23合金仍保持稳定的非晶结构,根据Bridgman方程通过拟合数据,得到状态方程为 -ΔV/V0=0.08606P-3.2×10-4P2+5.7×10-6P3.     

Compression Behaviour of Ni77P23 Amorphous Alloy up to 30.5 GPa

The compression behaviour of Ni77P23 amorphous alloy is investigated at room temperature in a diamond-anvil cell instrument using in-situ high pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state is determined by fitting the experimental data according to the Birch-Murnaghan equation. It is found that the structure of Ni77P23 amorphous alloy is stable under pressures up to 30.5 GPa. Within the pressure range from zero to the experimental one, the pressure-induced structural relaxation is reversible.     

Untersuchung der γ-Strahlung bei Einfang thermischer Neutronen in Se77 mit der Summen-Koinzidenz-Methode

Two-step cascades of neutron captureγ-rays of Se⁷⁷(n,γ) Se⁷⁸ were studied. The employed sum-coincidence method restricts the involved levels facilitating the analysis of the observed spectra. Some new cascades were found and the relative intensities were determined.     

ESR study on radiation chemical processes in polyvinyl alcohol films at 77°k

Abstract

Trapped electrons (e_t ^?) were detected in irradiated PVA films at 77°K. Yield of e_t ^? was decreased as evaporating water from the films, indicating that water molecules contribute to construct pre-existing traps in the polymer. The radical produced at 77°K was identified as a precursor of the radical produced at room temperature.     

Nuclear spin effect on recombination of H₃⁺ ions with electrons at 77 K

Utilizing different ratios of para to ortho H? in normal and para enriched hydrogen, we varied the population of para-H?? in an H?? dominated plasma at 77 K. Absorption spectroscopy was used to measure the densities of the two lowest rotational states of H??. Monitoring plasma decays at different populations of para-H?? allowed us to determine the rate coefficients for binary recombination of para-H?? and ortho-H?? ions: (p)α(bin)(77 K) = (1.9 ± 0.4) × 10?? cm3 s?1 and (o)α(bin)(77 K) = (0.2 ± 0.2) × 10?? cm3 s?1.     

Raman Spectra Concentrational Dependence of Naphthalene - Cyclohexane and Naphthalene-Methanol Solutions Frozen at 77° K

The concentrational dependence of Raman spectra of frozen at 77°K naphthalene solutions in cyclohexane and in methanol is studied. An increase in the naphthalene Raman line intensity is observed for the naphthalene-cyclohexane system in a concentrational range in which a quasilinear fluorescence spectrum is recorded.     

Generation of an ultrashort optical pulse by four-wave Raman mixing in deuterium cooled at 77 K

When a 100-fs Ti:sapphire laser is focused into molecular deuterium cooled at 77 K, rotational stimulated Raman emission is generated based on four-wave Raman mixing. By phase locking the emission lines, the laser pulsewidth was reduced to 40 fs, when a nearly transform-limited pulse was utilized as a fundamental laser. The pulsewidth was further reduced to 20 fs, when a positively chirped pulse was employed. Computer simulation suggests that the Raman emission is strongly chirped and a train of pulses with lower intensities are formed when a chirp pulse is used as a fundamental laser. PACS 42.65.Dr; 42.55.Ye; 42.50-p