基于西门子S7-400的造纸漂白工段PLC控制系统

介绍了漂白工段在制浆造纸工业中的重要性,针对漂白工段复杂的工艺特性,给出了基于西门子S7-400控制系统的结构及硬件配置.同时采用多模态控制算法实现对塔温的优化控制.     

基于MEMS的一种微机械滤波器的分析

介绍了一种自由梁微机械滤波器的组成及工作原理,采用连续系统的方法来分析该微机械滤波器的谐振器,推导了其弯曲振动模态下的谐振频率公式——Euler-Bernoulli方程。然后根据MEMS材料的特性和微系统表面微加工原理设计了一种共振频率为70 MHz的微机械滤波器工艺,并利用MEMS专业软件Coventor进行仿真分析,仿真结果与计算结果一致,验证了该工艺设计的可行性。     

声光控开关的电子工艺制作

通过对声光控电子开关的工作原理、电路板设计和制作流程、元器件选择、元器件检测、焊接技巧、制作检测、制作注意事项等方面的介绍,探讨了一个电子产品的开发和制作过程.电子工艺制作经验的探讨,不仅适用于声光控开关的简单电路,同样也适用于复杂电路.     

微电机制造工艺现状及发展动向

微电机行业是技术密集型、资金密集型和劳动密集型行业。微电机制造工序多,工艺装备数量大,加工精度要求高,一些微特电机还有特殊的使用环境要求。分析了当前我国微电机行业制造工艺技术的特点和状况,阐述了今后微电机制造工艺技术的发展趋势和方向。     

Finite element analysis of vent/hand hole designs for corrugated fibreboard boxes

Corrugated fibreboard is an economical and efficient material for fabricating shipping containers that are widely used for the distribution, transportation and storage of goods. Corrugated fibreboard is usually considered to be an orthotropic material because the principal fibre directions, machine direction (MD) and cross‐machine direction (CD), are identical to the fibres in paperboard, which has apparent directional property differences. The purpose of this study is to investigate the principal design parameters of ventilation holes and hand holes in the faces of the shipping container, (corrugated fibreboard boxes), using finite element analysis (FEA). Various designs of ventilation holes were studied with respect to stress distribution and stress level. It was found that the appropriate pattern and location of the ventilation holes were vertical oblong‐shaped and symmetrically positioned within a certain extent of distance to the right and left from the centre of the front and rear faces of the boxes. On the other hand, the appropriate location and pattern of the hand holes were a short distance from the centre to the top of the boxes on both side faces. The appropriate pattern was a modified shape, such as the radius of curvature of both sides in horizontal oblong. The pattern and location of both the ventilation holes and the hand holes determined by the FEA simulation generally agreed well with laboratory experimental results. The decrease in compression strength of the box could be minimized with identical area of the ventilation holes if the length of the major axis of the ventilation hole is less than 1/4 of the depth of the box and the ratio of the minor axis to the major axis is 1/3.5–1/2.5, provided that even‐numbered holes are located symmetrically. Copyright © 2006 John Wiley & son, Ltd.     

油藏工程学的发展现状及认识

80年代初期 ,国内诞生的油藏工程专业 ,在将近 2 0年的时间里 ,获得了飞速的发展。它经历了两个阶段 ,简单定量阶段和精确定量阶段。简单定量方法在现代研究中仍占主要地位。随着数学模型的完善及计算机技术的发展 ,精确定量的方法得到了较大程度的发展。随着油藏开发工作的进一步加深 ,精确定量的方法必将占据主要地位。     

Prediction Equations for Gases in Flexible Modified-Atmosphere Packages of Respiring Produce are Different Than Those for Rigid Packages

Total pressure generally decreases in a sealed rigid package containing respiring produce, whereas total pressure is essentially constant and free volume decreases in a flexible package. We found that predicted O₂, CO₂, and N₂ partial pressures were different for similarly designed (same surface area, thickness, film permeabilities and produce mass) flexible and rigid packages at “quasi steady state” and steady state, respectively. Predicted O₂ and CO₂ partial pressures were slightly higher in a flexible package than in a rigid package and were a function of the film permeability ratio of N₂ to O₂ and of CO₂ to O₂. They also related to the ratio of product CO₂ production rate to O₂ uptake rate, target steady-state O₂ partial pressure, and respiration characteristics. Differences were slight for films such as low-density polyethylene.     

提高锡铁山铅锌矿伴生金银回收率的优化工艺研究

通过锡铁山铅锌矿石中伴生金银的分布规律的研究，论述了伴生金银的回收现状及生产实践，指出了现存的主要问题和今后的主攻方向。     

中福西湖花园钻孔灌注桩质量控制

本文通过工程实例 ,介绍了钻孔灌注桩施工质量控制的成功经验     

Electron-beam irradiation of fresh broccoli heads (Brassica oleracea L. italica)

Broccoli is a popular item in the diet of the US population, commonly found in salads ready-to-eat. The recent recalls of fresh produce due to contamination with Escherichia coli and other pathogens emphasize the need to find effective means to treat minimally processed fresh foods. Our study assessed the effect of ionizing radiation using electron beams on the shelf-life, physicochemical properties, and consumer acceptability of broccoli florets. One-hundred broccoli heads were irradiated at 1, 2, and 3 kGy with a 10 MeV linear accelerator at 22 °C. We monitored pH, color, texture, respiration rate, weight loss, chlorophyll, total carotenoids, and vitamin C of irradiated and non-irradiated samples at 5-day intervals up to 14 days at 4 °C and 95% RH. Fifty consumer panelists scored the samples using a nine-point hedonic scale.Irradiation did not affect color, firmness, pH, and weight loss of the samples. Both irradiated samples and controls showed a slight change in color during storage, though the effect was not dose-dependent. Irradiation affected (P < 0.05) the respiration rates on the first 5 days of storage (higher CO₂ levels) but all samples, including the controls, attained the same equilibrium value. Vitamin C content of all samples decreased (P < 0.05) with storage time. Chlorophyll and total carotenoids content followed the same trend. In terms of overall acceptability, color, odor, and texture, all irradiated samples were highly accepted by the panelists with scores of 5 and above. By the end of shelf-life, only the controls showed significant quality decline (yellow color, off-odor) due to microbial spoilage. In summary, electron-beam treatment up to 3 kGy maintains the overall quality of fresh broccoli.