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排序方式: 共有1419条查询结果,搜索用时 15 毫秒
111.
介绍了目前较流行的两种查询系统的开发平台模式-客户机/服务器(C/S)和浏览器/服务器模式(B/S),引出了动态网页的概念,通过对几种动态网页技术的比较,提出了运用微软公司的ASP开发动态,交互的基于Web的话费查询系统,并通过简单的实例,介绍了ASP和Oracle数据库集成的方法。 相似文献
112.
在ASP中使用ADO对象访问数据库存储过程 总被引:1,自引:0,他引:1
陈丹 《广西师范学院学报(自然科学版)》2002,19(2):42-46
该文介绍了ASP的功能及数据库中存储过程的作用,通过实例,较详细地阐述了在ASP中调用存储过程的方法。 相似文献
113.
114.
利用超声波从废触媒中回收活性炭的研究 总被引:10,自引:1,他引:10
合成醋酸乙烯的触媒为载有醋酸锌的活性碳,目前工业生产过程中产生的废触媒大量堆积于某些工厂附近,造成环境问题。由于这种载体活性碳具有丰富的微孔,用重复煮沸的方法清洗醋酸锌后再活化回收的活性碳质量达不到中国林业部的标准。本文用功率超声来处理这种废触媒,用正交表安排实验,试验了作用时间、声能大小、温度、体系固液比、外加搅拌等条件的影响。结果表明,所提供的声能大小是洗脱醋酸锌的关键因素,另外,机械搅拌有利于物料的均匀分散,也是一个重要因素.在声强为0.3W/cm2,频率为27kHz的超声条件下,当固液比为1:2时,只需在室温的水中超声处理15min,回收大部分醋酸锌后所得的活性碳在650℃下活化0.5h后,产品便可达到中国林业部标准LY216—79的要求。由于这种方法操作简单,便于生产自动控制,可望成为一种再生利用废资源的好方法。通过对比了冷水浸提、沸水清洗和超声清洗等几种方法所得活性碳的DTA,TG曲线,初步认为超声处理的特效性可归因于声毛细效应。 相似文献
115.
本文提出了一个描述扭曲向列型(TN)液晶显示器件电光特性的简化模型。根据模型,可以很容易地计算出各类参数液晶显示器件的电光特性。理论计算与实验数据符合的很好。因此该模型可用于有源矩阵(Active Matix)液晶显示系统的模拟程序。 相似文献
116.
合成CFC-12替代物HFC-134a的CrF_3/AlF_3催化剂研究(Ⅴ)──CrF_3与AlF_3的相互作用 总被引:1,自引:0,他引:1
由于氟氯烃(CFCs)对大气臭氧层的破坏作用,使得开发CFCs无污染替代品的研究成为热门课题[1~4].氢氟烃(HFCs,如HFC-134a)是CFCs的理想替代物.在氟氯交换合成HFC-134a的反应中,AlF3基催化剂的活性、稳定性明显优于CrF... 相似文献
117.
陈鹤琴关于幼儿心理特点和幼儿智力开发思想述略 总被引:3,自引:0,他引:3
陈鹤琴认为,科学育儿首先要了解幼儿、研究幼儿;针对幼儿好动的心理特点,游戏、音乐等活动是“发展幼儿智力的钥匙”,感觉训练是幼儿认识环境的基础,是幼儿智力开发的重要环节;在教育活动中开发幼儿智力,应注意掌握刺激的原则、联念的原则、动作的原则及开发幼儿智力的具体作法。陈鹤琴先生关于幼儿心理特点和幼儿智力开发的思想,充分体现了他的“活教育”的主张。 相似文献
118.
The implementation of clean energy techniques, including clean hydrogen generation, use of solar-driven photovoltaic hybrid systems, photochemical heat generation as well as thermoelectric conversion, is crucial for the sustainable development of our society. Among these promising techniques, electrocatalysis has received significant attention for its ability to facilitate clean energy conversion because it promotes a higher rate of reaction and efficiency for the associated chemical transformations. Noble-metal-based electrocatalysts typically show high activity for electrochemical conversion processes. However, their scarcity and high cost limit their applications in electrocatalytic devices. To overcome this limitation, binary catalysts prepared by alloying with transition metals can be used. However, optimization of the activity of the binary catalysts is considerably limited because of the presence of the miscibility gap in the phase diagram of binary alloys. The activity of binary electrocatalysts can be attributed to the adsorption energy of molecules and intermediates on the surface. High-entropy alloys (HEAs), which consist of diverse elements in a single NP, typically exhibit better physical and/or chemical properties than their single-element counterparts, because of their tunable composition and inherent surface complexity. Further, HEAs can improve the performance of binary electrocatalysts because they exhibit a near-continuous distribution of adsorption energy. Recently, HEAs have gained considerable attention for their application in electrocatalytic reactions. This review summarizes recent research advances in HEA nanostructures and their application in the field of electrocatalysis. First, we introduce the concept, structure, and four core effects of HEAs. We believe that this part will provide the basic information about HEAs. Next, we discuss the reported top-down and bottom-up synthesis strategies, emphasizing on the carbothermal shock method, nanodroplet-mediated electrodeposition, fast moving bed pyrolysis, polyol process, and dealloying. Other methods such as combinatorial co-sputtering, ultrashort-pulsed laser ablation, ultrasonication-assisted wet chemistry, and scanning-probe block copolymer lithography are also highlighted. Among these methods, wet chemistry has been reported to be effective for the formation of nano-scale HEAs because it facilitates the concurrent reduction of all metal precursors to form solid-solution alloys. Next, we present the theoretical investigation of HEA nanocatalysts, including their thermodynamics, kinetic stability, and adsorption energy tuning for optimizing their catalytic activity and selectivity. To elucidate the structure–property relationship in HEAs, we summarize the research progress related to electrocatalytic reactions promoted by HEA nanocatalysts, including the oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, methanol oxidation reaction, and CO2 reduction reaction. Finally, we discuss the challenges and various strategies toward the development of HEAs. 相似文献
119.
Alexander I. Nosich Elena I. Smotrova Svetlana V. Boriskina Trevor M. Benson Phillip Sewell 《Optical and Quantum Electronics》2007,39(15):1253-1272
Research into microdisk lasers demonstrates new achievements both in the technology and in the associated physical effects
and applications. Melting and rounding of the disk edge boosts the Q-factors due to improved surface smoothness. In-plane
cavity shape is widely used as a design instrument. Optimal shaping of pumped area lowers the threshold power. Photonic molecules
made of several microdisks as “photonic atoms” show lasing at several closely spaced frequencies. A microdisk with a single
quantum dot as an active region is considered as the most promising system for realisation of a single photon emitter necessary
for quantum computing. These new effects and devices can be simulated with accurate numerical techniques, developed recently
for “warm-cavity” linear modelling, that are able to bring a new vision of the physics of lasing. 相似文献
120.
An experimental implementation of a global sound equalization method in a rectangular room using active control is described in this paper. The main purpose of the work has been to provide experimental evidence that sound can be equalized in a continuous three-dimensional region, the listening zone, which occupies a considerable part of the complete volume of the room. The equalization method, based on the simulation of a progressive plane wave, was implemented in a room with inner dimensions of 2.70 m × 2.74 m × 2.40 m. With this method, the sound was reproduced by a matrix of 4 × 5 loudspeakers in one of the walls. After traveling through the room, the sound wave was absorbed on the opposite wall, which had a similar arrangement of loudspeakers, by means of active control. A set of 40 digital FIR filters was used to modify the original input signal before it was fed to the loudspeakers, one filter for each transducer. The optimal arrangement of the loudspeakers and the maximum frequency that can be equalized is analyzed theoretically in this paper. The presented experimental results show that sound equalization was possible from 10 Hz to approximately 425 Hz in the listening zone. A flat frequency response with deviations within ±5 decibels from the desired value was achieved. A higher demanding performance with deviations within ±1.5 decibels from a flat frequency response was attained in the interval between 20 Hz and 280 Hz. At the same time, the impulse response was quite well approximated to a delayed delta function in the listening zone. Examples of the spatial distribution of the sound field are also shown. 相似文献