Temperature distribution of fluids in a two-section two-phase closed thermosyphon wellbore

Compared with a conventional single section two-phase closed thermosyphon （TPCT） wellbore, a two-section TPCT wellbore has better heat transfer performance, which may improve the temperature distribution of fluid in wellbores, increase the temperature of fluid in wellheads and even more effectively reduce the failure rate of conventional TPCT wellbores. Heat transfer performance of two-section TPCT wellbores is affected by working medium, combination mode and oil flow rate. Different working media are introduced into the upper and lower TPCTs, which may achieve a better match between the working medium and the temperature field in the wellbores. Interdependence exists between the combination mode and the flow rate of the oil, which affects the heat transfer performance of a two-section TPCT wellbore. The experimental results show that a two-section TPCT wellbore, with equal upper and lower TPCTs respectively filled with Freon and methanol, has the best heat transfer performance when the oil flow rate is 200 L/h.     

微裂缝研究进展、意义及发展趋势

近年来随着非常规油气的开发,微裂缝对于油气勘探开发的意义日益突显。国内外学者围绕不同储层中微裂缝的定义、分类、成因、主控因素及预测方法等方面进行了广泛而深刻的探讨。总结认为:定义微裂缝长度的上限值为50 mm,开度的上限值在不同储层中有所差异。基于成因的分类方案优于其他分类方案且目前应用最广。不同岩石中的微裂缝均是构造作用、成岩作用和异常高压作用等单因素或多因素叠合作用下形成的。不同类型的微裂缝主控因素差异较大,且不同储层中同一类型的微裂缝主控因素也有所差异。微裂缝的预测目前仍处于早期探索阶段,现有方法存在准确性和可靠性差、对资料要求高和成本高等方面的问题。基于分形和压汞曲线等的定量化分析技术是微裂缝定量化表征的主要手段。微裂缝的研究对于宏观裂缝的预测、沉积成岩演化的恢复以及油气开发具有重要意义。不同储层中微裂缝的对比、微裂缝与沉积和成岩的关系、微裂缝预测与定量化研究、不同成因微裂缝与孔隙空间的组合关系以及不同成因微裂缝对储层渗透率的贡献是下一步微裂缝研究的重点。     

提高虚拟车削仿真质量的工件建模方法

根据车削加工工件的几何外形和成形特点 ,提出了包含加工误差信息的回转体类工件半剖轮廓多边形建模方法和记录、组织加工误差信息的刀具轨迹法。在虚拟加工中 ,刀具扫描体被简化表示为刀具扫描体轮廓多边形 ,简化了仿真计算。同时还对加工过程仿真和反映加工误差的已加工表面形貌的构建等关键问题进行了研究。该建模方法在VMIS虚拟加工与检测系统中获得了应用     

MPEG标准中的音频编码与应用

MPEG系列标准是计算机多媒体应用比较广泛的国际标准之一,音频编码是这标准中的重要内容.近年来人们对压缩音频数据的研究已经取得了很大的进展,本文对几种MPEG音频编码标准进行了较为详细的分析和比较,并简要介绍了它们主要的应用.     

Microclimatic modeling of the urban thermal environment of Singapore to mitigate urban heat island

This study investigates the urban heat island effect in Singapore and examines the key factors causing this effect. The possibilities of improving heat extraction rate by optimizing air flow in selected hot spots were explored. The effect of building geometry, façade materials and the location of air-conditioning condensers on the outdoor air temperature was explored using computational fluid dynamics (CFD) simulations. It was found that at very low wind speeds, the effect of façade materials and their colours was very significant and the temperature at the middle of a narrow canyon increased up to 2.5 °C with the façade material having lower albedo. It was also found that strategically placing a few high-rise towers will enhance the air flow inside the canyon thereby reducing the air temperature. Adopting an optimum H/W ratio for the canyons increased the velocity by up to 35% and reduced the corresponding temperature by up to 0.7 °C.     

Efficient routing for IP subnet VLAN over Ethernet

Existing IP routing algorithms have been developed mainly for non‐VLAN networks. For these routing algorithms to work, an end station must be attached to its associated network. The introduction of VLAN has, however, allowed the physical location of the end station to be changed from time to time. Therefore, some extra mechanism is required to support routing in VLAN environment. Existing approaches have some drawbacks in terms of inefficiency in traffic forwarding and switch software complexity. In this paper, a simple and efficient method for routing over IP subnet VLAN in Ethernet is proposed. This method has been implemented in hardware and found to work correctly. Various measurements and analyses have been performed to verify the efficiency of this protocol. Copyright © 2002 John Wiley & Sons, Ltd.     

利用环形调制器产生与解调过调幅信号

采用开关函数分析方法,利用二极管环形调制器电路产生与解调过调幅信号,导出实现的过调幅信号与解调输出信号表达式;由此,可将过调幅信号的产生与解调方法扩展到微波频段.     

谈广州城市化发展下家具建材商业中心的演化

本文通过对广州珠江新城关居中心，即将搬迁到东圃花花世界中心商场继续发展的阐述，说明了广州城市化发展下，家具建材商业中心的演化过程，提出城市化发展下，家具建材商业中心新的发展方向以及对人们新生活模式的影响。     

Using 10 Gb/s remodulation DPSK signal in self-restored colorless WDM-PON system

In this investigation, we propose and experimentally demonstrate the remodulation technique using DPSK format in both downlink and uplink traffics with high extinction ratio (ER) in colorless WDM-PON; together with a simple self-restored architecture against fiber fault. Error free operation was achieved in a 20-km-reach 10-Gb/s WDM-PON without dispersion compensation. Comparison with other wavelength remodulation schemes for WDM-PONs is also performed, showing the proposed scheme can be a potential candidate for next generation wavelength reuse WDM-PONs. In addition, the performance of self-protection has also been discussed and analyzed.     

Probabilistic simulation for developing likelihood distribution of engineering project cost

Inaccurate early project cost estimates can eliminate investment benefits. This study focuses on assisting estimators who are attempting to enhance the accuracy and reliability of engineering project cost in the pre-conceptual stage. This aim has recently garnered the attention of the transportation communities. Data from the Texas Department of Transportation (TxDOT) were utilized to develop an alternative approach that aids decision makers in terms of probability and confidence level. The proposed procedure comprises heuristic and practical simulation models that can be employed to calculate the probabilistic costs of highway bridge replacement projects. The simulation models utilize independent, correlated, and Latin Hypercube sampling approaches that incorporate major work items, roll-up work items, and project-level engineering contingencies. Cumulative distribution functions (CDFs) are then developed as a user-friendly chart for decision makers and these CDFs can be used to assess project risks during the pre-conceptual stage. Trial runs using these estimating procedures generate reliable pre-conceptual estimates. Additionally, these procedures can be extended to other project types along with programming techniques for developing an engineering project cost decision support system.