复杂环境61m高双曲线冷却塔拆除爆破

为成功拆除复杂环境下1座61 m高的冷却塔,根据其周边环境及结构特点,采用定向倒塌方案.首先采用机械方法开设定向窗和减荷槽,随后对19对人字柱进行爆破,使用毫秒延时爆破技术,控制单段起爆药量,成功完成拆除爆破.对拆除爆破后冷却塔的倒塌情况进行分析,冷却塔按照设计方向倒塌,解体完全,爆破振动以及触地振动控制在合理范围之内...     

复杂环境61 m高双曲线冷却塔拆除爆破

为成功拆除复杂环境下1座61 m高的冷却塔,根据其周边环境及结构特点,采用定向倒塌方案。首先采用机械方法开设定向窗和减荷槽,随后对19对人字柱进行爆破,使用毫秒延时爆破技术,控制单段起爆药量,成功完成拆除爆破。对拆除爆破后冷却塔的倒塌情况进行分析,冷却塔按照设计方向倒塌,解体完全,爆破振动以及触地振动控制在合理范围之内。爆破后周边民房、办公室等设施未损坏,证明本次拆除爆破效果良好,达到了预期效果,可为类似工程提供参考。     

隧道全断面开挖光面爆破设计

介绍了军都山隧道开挖施工中所采用的全断面光面爆破快速施工技术。根据隧道围岩硬度大、节理裂隙发育等地质情况,在施工现场进行了掏槽孔不同深度的装药试验,对隧道开挖的爆破参数、炮孔布置、装药结构和起爆网路进行了分析和设计,提出了保证隧道开挖成型质量和提高循环进尺的施工方案与措施,确保了军都山隧道全断面开挖爆破取得圆满成功,可供类似工程参考。     

Thermophysical property measurements on molten semiconductors using 10-s microgravity in a drop shaft

The effectiveness of 10-s microgravity on thermophysical property measurements on molten materials, such as molten semiconductors, is discussed. The thermal conductivity of molten InSb was successfully measured under microgravity conditions on board the German sounding rocket TEXUS and in a drop shaft in Hokkaido, Japan. Surface tension measurements using an oscillating drop method was attempted in low gravity using a parabolic flight of the NASA KC-135 aircraft. Combined levitation and microgravity, which can provide a contamination-free and undercooled condition. is recommended as a novel approach to obtain missing thermophysical property data on undercooled melts of semiconductors.Paper presented at the Fourth International Workshop on Subsecond Thermophysics, June 27–29. 1995. Köln, Germany.     

复杂环境90m高双曲线冷却塔拆除爆破

针对复杂环境1座90 m高冷却塔的周边环境及结构特点,采用爆破手段进行拆除。采用复合型切口的定向倒塌方案,首先采用机械方法开设定向窗和减荷槽,再对21对人字立柱进行爆破。由于泵房和更衣室等建(构)物距离被爆冷却塔过近,采用开挖减振沟和铺设减振垫层的方式减小爆破振动和触地振动。爆破结果表明,爆破参数选取合理,冷却塔按照设计方向倒塌,解体完全。爆破后泵房等设施未损坏,达到了预期效果,可为类似工程提供参考。     

复杂环境90 m高双曲线冷却塔拆除爆破

针对复杂环境1座90 m高冷却塔的周边环境及结构特点,采用爆破手段进行拆除.采用复合型切口的定向倒塌方案,首先采用机械方法开设定向窗和减荷槽,再对21对人字立柱进行爆破.由于泵房和更衣室等建(构)物距离被爆冷却塔过近,采用开挖减振沟和铺设减振垫层的方式减小爆破振动和触地振动.爆破结果表明,爆破参数选取合理,冷却塔按照设...     

61m高双曲线冷却塔爆破拆除失败原因分析

针对爆破拆除双曲线冷却塔易出现后坐或爆后立而不倒等险情,结合61m高双曲线冷却塔爆破拆除失败的原因,从方案设计以及现场施工等方面进行分析,指出冷却塔的支撑部位属于点支撑,其承压能力有限,设计时不但要充分考虑爆破切口的展长满足冷却塔失稳要求,还要保证爆破切口有合理的高度,使其在失稳状态下重心能够发生明显偏移,形成足够的倾覆力矩;同时强调在施工中,因切口部位预开一定数量的定向窗能够破坏塔体的刚度,对于塔体爆后顺利倒塌起到非常重要作用。精心设计,精细化施工是确保冷却塔拆除爆破成功的关键,分析结果可为今后类似爆破工程提供参考依据。     

冷却塔供冷的应用和分析

本文介绍了冷却塔供冷的原理、系统形式和设计计算，模拟分析了冷却塔供冷在我国不同气候分区的使用情况，对冷却塔供冷的可行性及经济性进行了分析，对冷却塔供冷系统设计时应该注意的问题进行了归纳总结。     

两座100m高薄壁结构冷却塔控制爆破拆除

根据冷却塔高、质量大、壁厚薄以及周围环境复杂等特点,制定了安全可靠的爆破方案。通过采用高卸荷槽复式切口爆破拆除技术,选择合适的爆破参数,采取合理的预处理措施和相应的安全防护措施,对两座100m高薄壁结构冷却塔成功实施了控制爆破拆除。降低了冷却塔爆破振动效应,实现了冷却塔爆破拆除精准定向。振动测试结果显示,冷却塔爆破拆除产生的振动速度均在安全允许范围内,证实了振动控制措施的有效性和实用性,可为同类爆破拆除工程提供参考。     

两座100m高薄壁结构冷却塔控制爆破拆除

根据冷却塔高、质量大、壁厚薄以及周围环境复杂等特点,制定了安全可靠的爆破方案。通过采用高卸荷槽复式切口爆破拆除技术,选择合适的爆破参数,采取合理的预处理措施和相应的安全防护措施,对两座100m高薄壁结构冷却塔成功实施了控制爆破拆除。降低了冷却塔爆破振动效应,实现了冷却塔爆破拆除精准定向。振动测试结果显示,冷却塔爆破拆除产生的振动速度均在安全允许范围内,证实了振动控制措施的有效性和实用性,可为同类爆破拆除工程提供参考。     

利用冷却塔供冷技术的初探

介绍了冷却塔水侧免费供冷的工作原理，主要系统形式及系统设计中应注意的几个问题，通过工程经济性比较，阐明冷却塔水侧免费供冷节能经济的优越性。     

Development of refractory ohmic contact materials for gallium arsenide compound semiconductors

Recent strong demands for optoelectronic communication and portable telephones have encouraged engineers to develop optoelectronic devices, microwave devices, and high-speed devices using hetero-structural GaAs-based compound semiconductors. Although the GaAs crystal growth techniques had reached a level to control the compositional stoichiometry and crystal defects on a nearly atomic scale by the advanced techniques such as molecular beam epitaxy and metal organic chemical vapor deposition techniques, development of ohmic contact materials (which play a key role to inject external electric current from the metals to the semiconductors) was still on a trial-and-error basis.Our research efforts have been focused to develop low resistance, refractory ohmic contact materials to n-type GaAs using the deposition and annealing techniques, and it was found the growth of homo-or hetero-epitaxial intermediate semiconductor layers (ISL) on the GaAs surface was essential for the low resistance ohmic contact formation. In this paper, two typical examples of ohmic contact materials developed by forming ISL were given. The one was refractory NiGe-based ohmic contact material, which was developed by forming the homo-epitaxial ISL doped heavily with donors. This heavily doped ISL was discovered to be formed through the regrowth mechanism of GaAs layers at the NiGe/GaAs interfaces during annealing at elevated temperatures. To reduce the contact resistance further down to a value required by the device designers, an addition of small amounts of third elements to NiGe, which have strong binding energy with Ga, was found to be essential. These third elements contributed to increase the carrier concentration in ISL. The low resistance ohmic contact materials developed by forming homo-epitaxial ISL were Ni/M/Ge where a slash ‘/’ denotes the deposition sequence and M is an extremely thin (∼5 nm) layer of Au, Ag, Pd, Pt or In. The other was refractory In_xGa_1−xAs-based ohmic contact materials which were developed by forming the hetero-epitaxial ISL with low Schottky barrier to the contacting metals by growing the In_xGa_1−xAs layers on the GaAs substrate by sputter-depositing In_xGa_1−xAs targets and subsequently annealing at elevated temperatures. To reduce the contact resistance, it was found that this In_xGa_1−xAs (ISL) layer had to have In compositional gradient normal to the GaAs surface: the In concentration being rich at the metal/In_xGa_1−xAs interface and poor close to the In_xGa_1−xAs/GaAs interface. This concentration graded ISL reduced both the barrier heights at the metal/ISL and ISL/GaAs interfaces and reduced the contact resistance. The ohmic contact materials developed by forming hetero-epitaxial ISL was In_0.7Ga_0.3As/Ni/WN₂/W. These contact materials formed refractory compounds at the interfaces, which was also found to be essential to improve thermal stability of ohmic contacts used in the GaAs devices.     

Micro-explosion of a water-in-hexadecane compound drop

The micro-explosion of a water-in-oil compound drop, without emulsification, was investigated experimentally. The compound drop, composed of a water core encased by an n-hexadecane shell, was suspended and heated to micro-explosion. The heating process and the micro-explosion behavior were recorded by a high-speed video system, and the temperature history of the compound drop was measured under three ambient temperatures, namely 320°C, 400°C and 500°C. The behaviors of the micro-explosion were grouped into three modes, namely direct explosion, partial explosion, and swelling, according to the outcomes of micro-explosion recorded by the high-speed video camera. At an ambient temperature of 400°C or 500°C, the micro-explosion onset time was observed to increase with the micro-explosion temperature; but this trend was not as obvious for the ambient temperature of 320°C. The intensity, judged from the production of secondary drops, of the micro-explosion rose as the micro-explosion time lengthened because the accumulation of thermal energy within the oversaturated water core drop grew to a higher extent.     

Role of drop superheating in the nonsteady drop cooling of a high-temperature wall

The influence of superheating and explosive boiling of a contact layer of drops on the heat transfer in drop cooling of a wall at a temperature exceeding the temperature of achievable heating of the liquid is considered.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 1, pp. 128–136, July, 1986.     

The oscillation spectrum of a compound drop

Under microgravity conditions the equilibrium shape of a compound drop, consisting of two immiscible mutually wetting liquids, is given by a spherical liquid core, encapsulated by the second liquid phase. Due to energy considerations, the outer liquid is the one with the lower (vapour-liquid) surface tension. The oscillation spectrum of such a compound drop corresponds to that of two coupled oscillators, one being driven by the surface tension, while the other is due to the interfacial (liquid-liquid) tension between the two immiscible liquids. Therefore, in principle, the values of both, the surface and the interfacial tension, can be derived from the frequencies of the coupled oscillations. In this paper, an analytic expression is presented, relating the frequency spectrum to the surface and interfacial tension, respectively. In addition, the concept for technical realisation using electromagnetic levitation and copper-cobalt as a model system, is discussed.     

Characterisation of vacancy-like defects in III–V compound semiconductors using positron annihilation technique

Single crystals of GaP and InSb were irradiated by 3 MeV electrons at 20 K to a total dose of 4 × 10¹⁸ e ⁻/cm². Isochronal annealing in the temperature region 77–650 K followed the irradiation. In GaP, the positron lifetime measurement indicated the presence of irradiation-induced vacancies in the Ga-sublattice. The vacancies disappeared at two stages observed in temperature ranges 200–300 and 450–550 K. In InSb the positron lifetime was found to increase by 8 ps compared to that in as-grown crystals (i.e. 282±2 ps) after irradiation. The increase indicated the presence of irradiation-induced defects; the crystal was found to recover until 350 K with a sharp annealing stage at 250–350 K.     

冷却塔供冷系统设计中应该注意的问题

针对冷却塔供冷系统中的供冷形式的选择、供水温度的选择、切换温度的确定、冷水温度的控制以及冷却水泵与系统的匹配等问题进行讨论。     

中央空调冬季冷却塔供冷节能实践

对于全年供冷的中央空调系统,冬季采用冷却塔代替冷水机组为空调供冷水,是非常理想的节能措施之一。本文根据不同工程实践,分析了不同冷却水系统的可行方案及注意事项,可供设计及管理人员参考。     

导热塑料管在冷却塔中应用的可行性分析

从力学、耐热、传热及经济性等方面对冷却塔中导热塑料管替代铜管的可行性进行介绍和分析。指出冷却塔中采用导热塑料管能够大大降低耗铜量。     

Mathematical modeling of heat and mass transfer in transpiration cooling of water droplets in a cooling tower

Mathematical modeling of the processes of heat and mass transfer in transpiration cooling of water droplets is carried out. In a self-consistent approximation the variation of the temperature and density of the water vapor in the vapor-air mixture of a flowing droplet as it falls in the water distributing space of a cooling tower is taken into account.Academic Scientific Complex A. V. Luikov Institute of Heat and Mass Transfer, Academy of Sciences of Belarris Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 64, No. 2, pp. 154–159, February, 1993.