恒温恒湿系统最佳除霜时刻控制的研究

针对于恒温恒湿系统的除霜最佳时刻的研究,本文提出了在户外温湿度恒定,室内温湿度变化状况下,当蒸发器表面上所结的霜的面积达到蒸发器总换热面积的75%时,利用此时的冷凝压力与蒸发压力的比值作为对机组除霜指令发出的基准.经实验的验证此方法还是可行的,能够运用于实际的工业恒温恒湿机组的最佳除霜时刻控制.     

恒温恒湿机在结霜工况下运行的实验研究

对在结霜工况下工作的恒温恒湿机进行了分析研究.根据被控环境对温湿度的更低要求,在制冷系统中增加了热气除霜功能,设计了适合于结霜工况的直接蒸发表冷器和供除霜过程储存排液的气液分离器,调整了普通机型的控制逻辑关系.经实验表明:设计可满足使用要求.     

恒温恒湿空调系统的节能优化设计

分析了目前采用恒温恒湿空调系统的设计方法,针对该类系统空气处理过程中通常采用的再热方式进行优化设计。计算结果表明,采用优化设计的空气处理方式能明显降低空调系统能耗。同时,对将高效节能的变制冷剂流量空调系统应用于恒温恒湿领域存在的问题进行了分析,并提出一种在不同分区采用不同系统的方式。     

论质检机构一体化恒温恒湿实验室建设方案

结合质检机构恒温恒湿实验室使用、设计要求,概括介绍了一体化恒温恒湿实验室建设方案,包括其工程组成及其特点。     

恒温恒湿空调系统全年运行控制

结合焓湿图分析了空调系统全年恒温恒湿空气处理过程,分别给出了小型和中大型精密恒温恒湿空调系统的控制系统图．并介绍了相应的全年运行控制方法。     

HVI恒温恒湿实验室验收测试方法研究

探讨了HVI恒温恒湿实验室在质量验收中如何引用规范、测试标准器的选用、测试方法以及测试结果的数据处理等,以确定一个更适宜的测试方法实现对恒温恒湿实验室的验收。HVI实验室属高精度恒温恒湿实验室,其建设的技术含量很高,难度较大,不同的测试方法可能会有不同的测试结果,适宜的验收方法是建设质量评估的关键。     

高精度恒温恒湿洁净室的控制设计

本文以一个实际的高精度恒温恒湿洁净室为例,在对其房间气流组织进行分析的基础上,优化了空气处理系统。系统采用了一套合理的控制方法,在满足洁净室所需高级别洁净度的同时,使洁净室的温湿度也分别达到了±０－１ ℃、±５ ％ 的设计要求,并大幅度降低了制冷机组的成本和运行费用。     

恒温恒湿空调房间的解耦控制方案

采用机制分析和实验分析相结合的方法，建立恒温恒湿空调系统的数学模型，推导四输入、四输出的传递函数矩阵，采用前馈补偿法设计解耦补偿器，使恒温恒湿空调系统的传递函数矩阵变换为对角矩阵，从而解除各个控制回路之间的耦合，并通过仿真进行验证。结果表明，该解耦控制器在恒温恒湿空调系统中的应用效果较好，改善和提高系统的品质和性能。     

S7-200可编程控制器在精密恒温恒湿空调机组上的应用

本文介绍了西门子S7-200系列可编程控制器在我公司精密恒温恒湿空调机组系统上的具体应用,着重讨论其控制系统的设计、数据采集、监测及其控制功能的实现,以及S7-200在精密恒温恒湿空调机组分布式监控系统中的设计.     

自动控制在空调工程中的应用（5）

本文介绍一个洁净室的恒温恒湿室空调工程及其温度、湿度、风量和静压的自动控制原理.在该工程中尽管对室内相对湿度的控制精度较严,但由于采用了新的空气处理方式,取消了再热,避免了冷热抵消,从而展示了一个恒温恒湿型空调系统的节能设计范例.     

Degradable and bioresorbable polymers in surgery and in pharmacology: beliefs and facts

The number of articles dealing with degradable polymers and macromolecules is increasing rapidly and the number of proposed compounds as well. However, not all have a high potential for effective applications. This contribution examines first the criteria to be taken into account when commercialisation of polymeric compounds and devices aimed at helping the body for a limited period of time, i.e. the healing time, is the main goal. What is really known is tentatively analysed by considering some of the candidates present in literature confronted to the targeted potential applications. Tentative comments are made on what should be done to qualify a candidate. Last but not least, trends in the search for polymers to be exploited in presently attracting areas such as bioresorbable stents, hydrogels to deliver bioactive macromolecules like proteins and polynucleotides or polyelectrolytes to temporarily complex charged biomacromolecules like proteins or genes are considered.     

Improvements in medical care and technology and reductions in traffic-related fatalities in Great Britain

Great Britain has one of the lowest levels of traffic-related fatalities in the industrialized world with a current total of about 3500 fatalities per year. Large reductions have occurred over the last 20-30 years and the government has targets of achieving another 40% reduction by 2010. This paper analyzes some of the factors that have been statistically significant in helping to achieve those reductions with a focus on improvements in medical care and technology. Using a cross-sectional time-series of regional data a fixed effects negative binomial (NB) model is estimated which includes three proxies of medical care and technology changes. These are the average length of inpatient stay in the hospital, the per-capita level of National Health Service (NHS) staff, and number of people per-capita waiting for hospital treatment. All are statistically significant with the expected sign showing that improvements in medical technology have reduced total fatalities with less of an impact from changes in medical care. Other variables are also found to be significant, including the percent of elderly people in the population, per-capita expenditure on alcohol, motorway capacity, and average vehicle age. The latter shows a surprisingly unexpected effect, with more older vehicles in a region leading to fewer fatalities. Models evaluating effects on serious and slight injuries are also estimated and serve to confirm the expected effects of medical care and technology.     

Non-uniformity in braking in coaching and freight stock in Indian Railways and associated causes

Non-uniform braking of wheel sets in locomotives and coaches/wagons can have disastrous consequences e.g. from wheel locking leading to derailments or thermal cracking, particularly under emergency braking conditions. Currently, while rigorous testing is used to characterize brake block characteristics and brake application time, no methods exist to determine the “variability” in braking across the different wheel sets, e.g. from differences in brake block characteristics, brake rigging, and performance of distributor valves. In this work, temperature rise in railway wheels is used to gauge normalized heat input coming in to wheels from braking. Two sets of field trial data are used to investigate variability of braking: (i) continuous rim temperature data for locomotive wheels and (ii) one time measurement of wheel rim temperatures of all wheels. The data is used to pin point the causes for non-uniformity in braking and to characterize the extent of non-uniformity. Non-uniformity in braking is found to be particularly severe in freight trains as compared to passenger trains. Faulty distributor valves are seen to result in maximum braking effort on wheels that is as high as seven times that of average braking effort in freight trains.