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81.
建设方自行招标与专职代理机构招标的比较 总被引:1,自引:0,他引:1
通过对水利工程建设方自行招标与专职招标代理机构招标两种招标形式的对比,对我国现阶段推行的委托专职招标代理机构进行招标的必要性作进一步说明。 相似文献
82.
目的探讨和评价儿童先天性心脏病心血管造影技术.方法11 045例儿童先天性心脏病患者做了心血管造影检查,采用的设备包括早期的快速换片心血管造影设备,电影心血管造影设备和数字减影心血管造影设备.使用了不同的心血管造影技术.结果用快速换片心血管造影设备和常规正侧位投照时的儿童先天性心脏病心血管造影诊断符合率为80.5%,用电影心血管造影设备和轴位成角投照技术时的造影诊断符合率为90.0%,采用数字减影心血管造影设备,轴位成角投照技术和非离子型对比剂时的造影诊断符合率为96.5%.结论对于儿童先天性心脏病心血管 相似文献
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84.
A model of a human neural knowledge processing system is presented that suggests the following. First, an entity in the outside world lends to be locally encoded in neural networks so that the conceptual information structure is mirrored in its physical implementation. Second, the knowledge of problem solving is implemented in a quite implicit way in the internal structure of the neural network (a functional group of associated hidden neurons and their connections to entity neurons) not in individual neurons or connections. Third, the knowledge system is organized and implemented in a modular fashion in neural networks according to the local specialization of problem solving where a module of neural network implements an inter-related group of knowledge such as a schema, and different modules have similar processing mechanisms, but differ in their input and output patterns. A neural network module can be tuned just as a schema structure can be adapted for changing environments. Three experiments were conducted to try to validate the suggested cognitive engineering based knowledge structure in neural networks through computer simulation. The experiments, which were based on a task of modulo arithmetic, provided some insights into the plausibility of the suggested model of a neural knowledge processing system. 相似文献
85.
基于GPRS的闸门监控系统设计 总被引:3,自引:3,他引:0
利用通用分组无线电业务(GPRS)通信技术、可编程逻辑控制器(PLC)和RS-485总线设计了稳定、经济的分布式闸门监控系统。该系统采用Internet/数字数据网(DDN)和GPRS Modem方式接入无线通信网络,并根据闸门监控系统的运行特点,采用GPRS实时通信与短信服务(SMS)通信相结合的方式,不仅保证了系统通信的稳定性和平衡性,且优化了系统的运行成本。最后,对基于GPRS的闸门监控系统的经济性和适用性进行了讨论。 相似文献
86.
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88.
通过对启闭机关键部件卷筒的受力分析,研制出一种新的单吊点、双驱动、超大容量、高扬程启闭机.从理论上分析了它的整体工作性能.所依托工程的使用情况表明,该机达到了设计要求. 相似文献
89.
Power-handling capability for RF filters 总被引:1,自引:0,他引:1
Ming Yu 《Microwave Magazine, IEEE》2007,8(5):88-97
A simplified method for evaluating the power-handling capability inside an RF filter has been introduced based on the general cross-coupled prototype network theory, modern EM modeling techniques, and well-established breakdown threshold analysis. The electrical field strength and voltages evaluated using either the single-cavity resonator (eigen mode) model or simply the prototype model have been presented and compared against the direct EM computation of the complete filter structure. Close agreement has been found between the full EM modeling and the scaling of a single resonator or even prototype network analysis only. This procedure is expected to simplify the multipaction and ionization breakdown analysis of filters and filter-based diplexers and multiplexers. The method presented is general and is applicable to all filter types that can be described in a circuit model. Practical issues such as the multicarrier operation, sharp edge condition, design margin, and prevention techniques are also covered. 相似文献
90.
Huiping Hu Qiyuan Chen Zhoulan Yin Pingmin Zhang Lusheng Ye 《Metallurgical and Materials Transactions A》2003,34(13):793-797
The thermal decompositions of mechanically activated and nonactivated galenas were studied by thermogravimetry analysis (TGA)
at the heating rate of 10 K min−1 in argon. Results indicate that the initial temperature of thermal decomposition (abbreviated as T
di) in the TGA curves for different galenas decreases gradually with increased grinding time. The specific granulometric surface
area (S
G), the structural disorder, and the content of elemental sulfur of mechanically activated galenas were analyzed by an X-ray
diffraction (XRD) laser particle-size analyzer, XRD analysis, and the gravimetric method, respectively, which shows that the
specific granulometric surface area of mechanically activated galenas remains almost constant after a certain grinding time,
but the lattice distortions (ε) rise, the crystallite sizes (D) decrease, and the elemental sulfur contents of mechanically activated galenas increase with increased grinding time. The
results imply that the decrease of the initial temperature of thermal decomposition in the TGA curves for mechanically activated
galenas is mainly caused by the increase of lattice distortions, and the formation of new dangling bonds resulted from the
production of elemental sulfur of mechanically activated galenas with increased grinding time. Finally, the differences in
the thermal-decomposition reactivity between nonactivated and mechanically activated galenas were also discussed. 相似文献