Investigation on the pinch point position in heat exchangers

The pinch point is important for analyzing heat transfer in thermodynamic cycles.With the aim to reveal the importance of determining the accurate pinch point,the research on the pinch point position is carried out by theoretical method.The results show that the pinch point position depends on the parameters of the heat transfer fluids and the major fluid properties.In most cases,the pinch point locates at the bubble point for the evaporator and the dew point for the condenser.However,the pinch point shifts to the supercooled liquid state in the near critical conditions for the evaporator.Similarly,it shifts to the superheated vapor state with the condensing temperature approaching the critical temperature for the condenser.It even can shift to the working fluid entrance of the evaporator or the supercritical heater when the heat source fluid temperature is very high compared with the absorbing heat temperature.A wrong position for the pinch point may generate serious mistake.In brief,the pinch point should be founded by the iterative method in all conditions rather than taking for granted.     

Synthesis of a non-integer periodic function generator of a four-bar mechanism using a Haar wavelet

In this study, a synthesis method for a non-integer periodic function generator of a four-bar mechanism using a Haar wavelet is presented. Using wavelet theory, the mathematical model for the output of a four-bar mechanism is established. Next, the characteristics of the four-bar mechanism output variable are described by the wavelet feature parameters; the relationship of the wavelet feature parameters between the output and its translation or dilation is also investigated. Based on this finding, three numerical atlas databases comprising of 203,500 groups of basic dimensional types of planar four-bar mechanisms, 148,995 groups of basic dimensional types of spherical four-bar mechanism and 11,175 groups of basic dimensional types of planar slider–crank mechanism are compiled. According to the internal relationship between the wavelet feature parameters, the sizes of the objective mechanism can be obtained using fuzzy recognition. Based on a genetic algorithm, optimization of the link parameters can be realized. Three examples are presented to demonstrate the efficacy and practicality of the proposed theory.     

Ball milling improves extractability and antioxidant properties of the active constituents of mushroom Inonotus obliquus powders

Inonotus obliquus has been used as a folk remedy for a long time. An improved method using fine grinding by ball mill was investigated, and the main chemical components and physicochemical properties of Inonotus obliquus powders were analysed. The Inonotus obliquus fine grinding powders were prepared by pulverising the coarse powder with planetary ball mill for different time. The results showed that the yields of polysaccharides increased from 41.08 mg g^?1 (coarse powder) to 319.62 mg g^?1, and the yields of polyphenols were also increased fourfold in ball‐milled powders as compared to the untreated one. Ball‐milled powders showed higher values in the bulk density, angles of repose and slide, water solubility index and swelling capacity (P < 0.05), but lower values in the water‐holding capacity and oil‐holding capacity. The shape and surface morphology of the powders were changed after ball mill treatment. The antioxidant properties of the extracts from ball‐milled powders were significantly improved (P < 0.05). The results will be helpful for the application of Inonotus obliquus in food and pharmaceutical industries.     

The use of genetic programming for the construction of a financial management model in an enterprise

The fast development in China’s economy has caused the rapid expansion of the domestic market. Since many economists do not have optimistic views regarding the bubble economy of China, it is necessary for Taiwanese businessmen to understand in-depth the business operational performance and financial situation of enterprises in China, so as to reduce the risk of a potential investment. In this article, data from the China Economic Research Database (CCER), the financial database of financial corporations are collected for analysis to investigate the business operation and management performance and financial characteristic of enterprises in China. In this article, grey relational analysis is applied first in order to investigate the business operational performance of 600 enterprises in China. Afterwards, a more recent clustering technique is used to divide, based on financial characteristic, enterprises in China into two groups. Finally, three models, namely genetic programming, Back-Propagation Neural Network and Logistic Regression are adopted to construct an Enterprise Operational Performance model and an Enterprise Finance Characteristic model, respectively. Based on the results found, it can be concluded that genetic programming yielded the best classification and forecast performance, compared to the other three techniques.     

Preparation and properties of polyimide solvent‐resistant nanofiltration membrane obtained by a two‐step method

This study investigated the preparation of polyimide solvent‐resistant nanofiltration membranes by a two‐step method (casting the membrane first and then crosslinking by the thermal imidization method). The influences of polymer concentration, thickness of membranes, temperature of the imidization, phase inversion time and thermal imidization procedure were studied. The membranes with the highest rejection rate of Fast Green FCF (molecular weight 808.86 g mol^?1) were prepared in the following conditions: polymer concentration 13 wt%, phase inversion time 1 h, membrane thickness 150 µm and thermal imidization procedure 200 °C for 2.5 h, 250 °C for 2 h and 300 °C for 2 h in a vacuum environment; the heating rate was 5 °C min^?1. The membrane was stable in most of the solvents tested and the fluxes of some common solvents were equal to or higher than a number of commercial solvent‐resistant nanofiltration membranes. A much higher rejection of dyes in water than in methanol was observed in the filtration experiments and a new way to explain it was developed. Copyright © 2011 Society of Chemical Industry     

提高晶闸管di/dt能力的研究

从di/dt损坏机制、定量公式入手,分析了国内外有关di/dt的著作、文章,研究了提高晶闸管器件di/dt能力的各种有效方法,给出了一个常规新设计及其研究成果。     

乙炔/甲烷预混燃烧合成碳纳米管的试验研究

采用乙炔和甲烷的混合气作为燃料,利用涂覆硝酸镍的铜基板,进行合成碳纳米管的试验研究。对于制备出的碳纳米材料的微观形貌采用扫描电镜(SEM)和透射电镜(TEM)进行了表征,分析了不同燃料对火焰合成的影响,并研究了硝酸镍催化剂的浓度对合成碳纳米管的影响。研究结果表明:利用两种混合气体预混燃烧能够成功合成出质量较好的多壁碳纳米管;采用浓度为0.01mol/L的硝酸镍催化剂无法合成出碳纳米管,只有碳纳米纤维等纳米材料。硝酸镍催化剂浓度为0.1和1.0mol/L时能合成形态和结构都较理想的碳纳米管。     

家具卖场体验式设计浅析

体验经济是一种全新的经济形态,它的提出展示了经济社会发展的方向,孕育着消费方式及生产方式的重大变革,适应体验经济的快慢将成为企业竞争胜负的关键。本论文通过对体验的商业价值剖析,体验设计过程解析,及家具行业外体验设计案例分析,得出体验设计的必要性和可行性,从而探索一条家具卖场可行性的体验设计之路。