柴油抗蜡分散剂的工业应用

柴油抗蜡分散剂PDN -3 0 2 3应用试验表明 ,抗蜡分散剂能有效改变蜡结晶的形状及尺寸 ,抑制蜡结晶的生长 ,有助于蜡晶体在柴油中分布得更均匀。     

Synthesis and properties of PDMS modified waterborne polyurethane–acrylic hybrid emulsion by solvent-free method

A new type of polysiloxane modified polyurethane–acrylic hybrid emulsion was synthesized by solvent-free method and the polysiloxane was introduced into the soft segment of polyurethane chains using dihydroxybutyl-terminated polydimethylsiloxane (PDMS). The formed film from the hybrid emulsion could provide obviously higher water-resistance property. The preparation technologies such as the content of carboxy group and acrylic monomer, the rate and the time of emulsification were discussed systematically. The chain structure and the particle size were confirmed by the analysis of Fourier transform infrared spectroscopy and transmission electron microscopy, respectively. The effect of PDMS content on the water resistance and the mechanical property were investigated by absorbed water ratio, water contact angle and dynamic mechanical measurement.     

Particle distribution and interfacial reactions of Al–7%Si–10%B<Subscript>4</Subscript>C die casting composite

Aluminum–boron carbide particle reinforced composite is an advanced material which can be used in applications such as neutron-shielding components, aircraft, and aerospace structures. In the microstructural characterization of an Al–7%Si–10%B₄C die casting, attention is particularly focused on particle distribution and interface reaction products between B₄C particles and the aluminum matrix. The quantitative analysis results show that, in a cross-section of the cast part, more particles concentrate in the center and fewer particles are present in the wall regions. Moreover, some particle segregation bands have been observed. The mechanisms of the particle migration are proposed to describe the phenomenon. However, the average particle fraction in any cross-section of the cast part is almost the same. A barrier layer consisting of several sublayers was detected on the surface of B₄C particles. Using electron diffraction in selected areas, it is found that these sublayers are composed of Al₃BC crystals, TiB₂ crystals, Si crystals, and coarse stick-shaped TiB₂ particles. In addition, it is observed that Si plays an important role in the formation of a dense barrier layer. The barrier layer can limit B₄C decomposition and improve B₄C stability in the aluminum melt.     

An empirical investigation of bias and variance in time series forecasting: modeling considerations and error evaluation

Bias and variance play an important role in understanding the fundamental issue of learning and generalization in neural network modeling. Several studies on bias and variance effects have been published in classification and regression related research of neural networks. However, little research has been done in this area for time-series modeling and forecasting. We consider modeling issues related to understanding error components given the common practices associated with neural-network time-series forecasting. We point out the key difference between classification and time-series problems in consideration of the bias-plus-variance decomposition. A Monte Carlo study on the role of bias and variance in neural networks time-series forecasting is conducted. We find that both input lag structure and hidden nodes are important in contributing to the overall forecasting performance. The results also suggest that overspecification of input nodes in neural network modeling does not impact the model bias, but has significant effect on the model variance. Methods such as neural ensembles that focus on reducing the model variance, therefore, can be valuable and effective in time-series forecasting modeling.     

导数火焰原子吸收法对调味品中锌的测定

将微量脉冲进样技术和导数火焰原子吸收法结合，建立了测定调味品中锌含量的新方法。该方法的检出限为0．013μg／mL，精密度4．46％，回收率96．67～113．33。     

两相管流工艺计算软件的研制

利用流体力学理论 ,结合目前国内外最新的两相流理论和实验研究成果 ,在描述气液两相流水力计算、热力计算和流型判断的数学物理模型基础上 ,研制出适用于海洋、沙漠、丘陵地区原油与伴生气、凝析天然气与凝液输送工艺的一套新的计算模拟软件TFTCS。介绍TFTCS软件的结构、功能、适用范围。用该软件对锦州 2 0 - 2海底湿天然气管道进行模拟计算 ,并与管线生产数据进行对比 ,用国外同类软件PIPEPHASE进行验算。实例计算分析表明 ,该软件功能完善 ,操作方便 ,计算结果可靠 ,能满足油气混输管道的设计计算和生产管理的需要     

水吸收-催化燃烧技术处理PET聚酯废气的中试研究

应用水吸收—催化燃烧技术处理PET聚酯生产中排放的含乙二醇、2—甲基—1，3—二氧戊环、乙醛等废气。水吸收可以有效脱除高沸点的乙二醇，通过对乙醛的吸收、解吸作用使废气的总烃浓度得到均匀化处理；采用Pt／Pd／CeO2蜂窝状催化剂，在反应器床层空速40000h^-1，人口温度250℃，人口总烃浓度3522—5666μL/L的条件下，反应器出口总烃浓度54—84μL/L，乙醛浓度3—11μL/L，总烃去除率达到97．6％一98．9％，净化后气体符合国家排放标准。     

Flow efficiency in multi-louvered fins

The paper studies the effect of Reynolds number, fin pitch, louver thickness, and louver angle on flow efficiency in multi-louvered fins. Results show that flow efficiency is strongly dependent on geometrical parameters, especially at low Reynolds numbers. Flow efficiency increases with Reynolds number and louver angle, while decreasing with fin pitch and thickness ratio. A characteristic flow efficiency length scale ratio is identified based on geometrical and first-order hydrodynamic effects, which together with numerical results is used to develop a general correlation for flow efficiency. Comparisons show that the correlation represents more than 95% of numerical predictions within a 10% error band, and 80% of predictions within a 5% error band over a wide range of geometrical and hydrodynamic conditions.