Evaluation of Leak Detectors for Flammable Refrigerants (AHRTI #9014)

As the HVAC&R industry is moving towards low-GWP refrigerants, many flammable working fluids are being considered. While these refrigerants perform quite well in terms of capacity and efficiency, the widespread use of flammable fluids will require changes to the way systems are designed and manufactured to address new safety codes and guidelines related to building design, HVAC&R installation and service requirements. This paper presents the results of a recently completed AHRTI study aimed at exploring the suitability of different leak detectors when exposed to A2L refrigerants. The sensing principles investigated include NDIR, micromachined membranes, MOS, and thermal conductivity-based sensors. R32 was used as the test fluid. An experimental facility to investigate sensor response to a step change in concentration has been designed and put into service. In order to evaluate sensor response to more realistic refrigerant release scenarios, research has also been conducted to address time-varying concentration profiles that would be encountered, for example, during release in a machinery room or residential setting. The paper also presents modeling results in which experimental step change responses were used to perform sensor characterization. This data can then be used to accurately predict the performance of the same sensor when exposed to a realistic, time-varying concentration

Research on EPQ Model Based on Random Defective Rate

In the real economic life, it is inevitable that a lot of phenomena will happen, such as damage in transportation and machine failure, which may generate a certain percentage of defective products in the process of logistics and production. Especially in the production process, the stoppage on the production line often brings about defective products. To provide mathematical models that more closely conform to actual inventories and respond to the factors that contribute to inventory costs, based on the classical EPQ model, this paper develops an EPQ model for defective items with a certain price relative to the defective level. And this paper also considers the issue that defective items are sold at a lower price which depends on the degree of product defects. A mathematical model is developed and numerical examples are provided to illustrate the solution procedure. The research will enrich researches and it has important practical significance

Clinical reports: the care of elderly patients with diabetic heel ulcer

目的  评价老年糖尿病足跟溃疡的临床护理效果。方法  选择我院整合门诊收治的老年糖尿病足跟溃疡患者6例，采用创面处理、适宜的抗菌敷料、减压技术和全身支持治疗，观察治疗护理效果。结果  6例足跟溃疡全部愈合，创面愈合时间为63～448天，159±62.56天。结论  创面减压、活性炭纤维含银敷料的应用及全身治疗能够促进糖尿病患者足跟溃疡的愈合。Objective: To evaluate the effect of clinical nursing in the elderly with diabetic heel ulcer. Methods: 6 elderly patients with diabetic heel ulcer admitted to our hospital integration outpatient were recruited. All of these patients accepted wound treatment, appropriate antimicrobial dressing, decompression technology and systemic support treatment. Results: All 6 cases of heel ulcer has healed, wound healing time was 63~448d, (159 ± 62.56)d. Conclusion: The application of wound decompression, a silver-containing activated carbon fiber dressing and systemic treatment can promote the healing of diabetic heel ulcer