Air-side thermal hydraulic performance of multi-louvered fin aluminum heat exchangers

An experimental study on the air-side heat transfer and pressure drop characteristics for multi-louvered fin and flat tube heat exchangers has been performed. For 45 heat exchangers with different louver angles (15–29°), fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm), a series of tests were conducted for the air-side Reynolds numbers of 100–600, at a constant tube-side water flow rate of 0.32 m³/h. The inlet temperatures of the air and water for heat exchangers were 21 and 45°C, respectively. The air-side thermal performance data were analyzed using effectiveness-NTU method for cross-flow heat exchanger with both fluid unmixed conditions. The heat transfer coefficient and pressure drop data for heat exchangers with different geometrical configurations were reported in terms of Colburn j-factor and Fanning friction factor f, as functions of Reynolds number based on louver pitch. The general correlations for j and f factors are developed and compared to other correlations. The f correlation indicates that the flow depth is one of the important parameters for the pressure drop.     

Influence and mechanism of dissolved oxygen on the performance of Ammonia-Oxidation Microbial Fuel Cell

Based on inorganic fuel, an Ammonia-Oxidation Microbial Fuel Cell (AO-MFC) had been developed, and the influence and mechanism of dissolved oxygen (DO) on the performance of nitrification and electricity generation were investigated. The results showed that the maximum conversion percentage of ammonium–nitrogen (NH₄⁺–N) was 99.7%. The output voltage and the power density were 98.5 ± 1.41 mV and 9.70 ± 0.27 mW m⁻² in the stable phase of electricity generation. In the AO-MFC, the electrons originated from ammonia and flowed to ammonia monooxygenase (AMO, which catalyzes the conversion of ammonia to hydroxylamine), Cyt aa₃ oxidase (which catalyzes the reduction of oxygen) and electrode, which were used for triggering ammonia oxidation, synthesizing ATP and generating electricity. Molecular oxygen played a key role in the electron distribution among these three acceptors. DO concentration too high (>6.45 mg L⁻¹) or too low (<0.5 mg L⁻¹) could exert a great negative influence on the performance of electricity generation.     

基于分布式协调系统的并行频繁模式增长算法的优化

频繁模式挖掘可以发现数据中频繁出现的模式,是关联规则挖掘的重要步骤。并行频繁模式算法将其应用到并行环境中,以对海量数据进行挖掘。在Apachc软件基金会的Mahout项目实现的基础上,对计数和排序阶段以及算法的执行顺序提出了新的优化策略。优化后的设计将计数信息存储在分布式协调系统上,充分地利用了分布式协调系统的高可用性、适宜存储元数据信息的特点。该设计减小了小文件在分布式文件系统(HDFS)上的开销,同时保留了其优点,还能使计数过程和排序过程并行执行,减小了计算节点的内存开销。对比了文件系统I/O的开销,并分析了实现设计中的难点,为未来的工作打下了基础。     

中国传统装饰艺术在数字绘画艺术中应用初探

数字绘画技术主要应用在商业插画、科普插画、少儿插画、游戏人物及场景设定等方面,其中又是在动画与游戏中应用最广,让数字绘画艺术更好地为我国的文化创意产业服务,向世界展示出具有本民族特色的文化艺术产品,中国的传统装饰艺术将是其取之不尽的艺术宝库。     

Analyzing the performance and fairness of BitTorrent-like networks using a general fluid model

In this paper, a general fluid model is developed to study the performance and fairness of BitTorrent-like networks. The fluid model incorporates two important features previously isolated from system performance models, user settings with multiple groups and inter-group data exchange induced by the choking algorithm. Our numerical results point out some key parameters of performance, such as the staying time of seeders. Generally, selfish behavior does not receive equal performance degradation, and in some scenarios users have strong incentives of free-riding. We also find content delivery can be greatly deterred when malicious free-riders are overwhelming.     

两种准在线装箱算法

在装箱问题中，下次填充法（NF）由于其在线特性，而被广泛应用。然而这种算法由于按照物件到达先后顺序来填充，资源利用率比较低。该文根据计算机通信网络中的实际应用，在NF算法基础上添加了置换功能，提出两种新的算法：最后物件置换算法和每个物件置换算法。由于物件被置换后，可能会被填充到后续箱内，因此称之为准在线算法。通过平均分析发现，这两种算法性能比NF算法有较大提高，类似于智能NF算法的性能。     

基于RBF代理模型的袋式除尘器清灰性能优化设计

针对袋式除尘器清灰系统性能优化设计中非线性和多参数耦合的问题,提出基于RBF代理模型的袋式除尘器清灰性能优化方法。以数值模拟为基础获取优化目标响应值。采用拉丁超立方试验设计控制清灰参数的设计空间,根据得到的试验数据建立清灰参数与响应值之间的RBF代理模型,并在此基础上采用遗传算法进行优化,得到距袋底1m处侧壁压力峰值最大的清灰参数组合。优化结果表明:距袋底1m处侧壁压力峰值由1.099kPa上升至2.294kPa,实现了对清灰性能的优化设计。     

Experimental study of a solar desalination pond as second stage in proposed zero discharge desalination process

This work represents the efficiency of a solar desalination pond as a second stage of proposed zero discharge desalination processes to reach fresh water and also concentrated brine from the effluent wastewater of the desalination unit of Mobin petrochemical complex. So a solar desalination pond is constructed after a pretreatment unit to concentrate the softened wastewater to about 20 wt%. The concentrated wastewater is as a suited feed for a forced circulation crystallizer. During one year, the effects of major parameters such as ambient temperature and solar insolation rate are investigated, experimentally. specific gravity in each layer of concentrated brine wastewater is evaluated. Also, evaporation rates are calculated theoretically and are verified by experimental data. Theoretical values predict evaporation rate accurately. Results show good agreement with experimental data. According to results, maximum evaporation rate is 5 l/m² day when the insolation rate is about 24,602 kJ/m² day Solar energy absorption factor on June is max. Also, experimental results show the best proposed time to gain highest thermal energy is on spring therefore performance efficiency of solar desalination pond promote on spring comparing with the other months. Extracted data for specific gravity prove the bottom of solar desalination pond, layer 1, is best zone for energy saving and energy utilization.Also, theoretical values of evaporation rate are calculated according to measured temperatures and related mass conservation equation. Comparison between theoretical and experimental values shows dusty weather, humidity and wind velocity affects on heat transfer coefficients approximately. So, deviations between theoretical data and measured values can be explained. Results show good agreements with experimental data.     

浅析数字媒体艺术的技术特征

数字媒体艺术是一个以技术为基础平台,艺术为上层建筑,两者相结合的新兴学科。此门学科在创作方式、传播途径以及展示效果上,都呈现出与传统艺术不同的新特点。在创作和运用过程中,应该把握好数字媒体的技术特征,才能处理好数字媒体中技术和艺术的关系,充分发掘数字媒体的艺术价值。     

The early design model for prediction of energy and cost performance of building design options

In order to encourage the use of computer modelling in building environmental analysis, it is necessary to provide a model developed from the designer's point of view. Detailed simulation models require a high degree of expertise and familiarity, further, there is also a need for detailed information not available in the early stages of the design process. Simplified models play an important role in the early stages of a design to achieve an integrated design: firstly, they are easy to use and, secondly, they require information easily available at the start of a design. In the Early Design Model (EDM) the solar gain utilisation factor has been determined as a continuous function of thermal mass. The differences between the annual energy predictions of EDM and SERI-RES ranges from 0.1% to 4.6% for time constants ranging from 378 to 2.52 hours. The differences between the two sets of predictions on monthly basis ranges from m 3.6% to m 6.48% (EDM's predictions being larger) during the heating season, and from +2.86% to a maximum of +51% (EDM's predictions being smaller) in the remaining part of the year. In addition to energy predictions, EDM incorporates a facility which gives cost indications.