Reuse of Ti6Al4V Powder and Its Impact on Surface Tension,Melt Pool Behavior and Mechanical Properties of Additively Manufactured Components

The quality and characteristics of a powder in powder bed fusion processes play a vital role in the quality of additively manufactured components. Its characteristics may influence the process in various ways. This paper presents an investigation highlighting the influence of powder deterioration on the stability of a molten pool in a laser beam powder bed fusion (LB-PBF, selective laser melting) process and its consequences to the physical properties of the alloy, porosity of 3D-printed components and their mechanical properties. The intention in this was to understand powder reuse as a factor playing a role in the formation of porosity in 3D-printed components. Ti6Al4V (15 μm–45 μm) was used as a base material in the form of a fresh powder and a degraded one (reused 12 times). Alloy degradation is described by possible changes in the shape of particles, particle size distribution, chemical composition, surface tension, density and viscosity of the melt. An approach of 3D printing singular lines was applied in order to study the behavior of a molten pool at varying powder bed depths. Single-track cross-sections (STCSs) were described with shape parameters and compared. Furthermore, the influence of the molten pool stability on the final density and mechanical properties of a material was discussed. Electromagnetic levitation (EML) was used to measure surface tension and the density of the melt using pieces of printed samples. It was found that the powder degradation influences the mechanical properties of a printed material by destabilizing the pool of molten metal during printing operation by facilitating the axial flow on the melt along the melt track axis. Additionally, the observed axial flow was found to facilitate a localized lack of fusion between concurrent layers. It was also found that the surface tension and density of the melt are only impacted marginally or not at all by increased oxygen content, yet a difference in the temperature dependence of the surface tension was observed.     

Influence of Polypropylene,Glass and Steel Fiber on the Thermal Properties of Concrete

The variety of approaches to tackle climate change reflects the size of this global problem. No technology will act as a panacea to cure the greenhouse gas emissions problem, but new building materials with byproducts or even wastes have the potential to play a major role in reducing the environmental impacts of the building sector. In this study, three potential solutions of concrete with dispersed reinforcement in the form of recycled fibers (polypropylene, glass and steel) were examined. The aim is to present a detailed analysis of the thermal properties of new building materials in an experimental approach. Concrete mixtures were prepared according to a new, laboratory-calculated recipe containing granite aggregate, a polycarboxylate-based deflocculant, Portland cement (52.5 MPa) and fibers. This experimental work involved three different contents of each fiber (0.5%, 0.75% and 1.0 wt.%), and all tests were carried after the complete curing cycle of concrete (28 days).     

Anévrismes intracrâniens et sclérose tubéreuse de Bourneville : une association rare

Introduction

Tuberous sclerosis is an autosomal dominant inherited phakomatosis. It is associated with a wide variety of central nervous system abnormalities, but intracranial aneurysms are rare.

Case report

We report a 34-year-old patient fulfilling the diagnostic criteria of tuberous sclerosis in association with intracranial aneurysm.

Discussion

This association has been reported in only 17 other cases of tuberous sclerosis. We discuss the etiopathogenic mechanisms, preferential localizations and the various therapeutic propositions.     

透析器血室容积检测方法的探讨

目的 探讨不同检测方法对透析器血室容积(TCV)检测值的影响.方法 对60支可重复使用的透析器(低通量透析器和高通量透析器各30支),按检测方法不同分为传统检测组、改良检测组和复用机检测组3组各20支,分别采用传统检测法、改良检测法和复用机检测法对透析器使用前、后行TCV检测,并对结果进行比较.结果 传统检测组、改良检测组和复用机检测组测量6LR透析器和17 R透析器TCV基础值分别为(100.10±0.25)ml、(100.13±0.50)ml、(102.00±1.41)ml和(113.67±1.30)ml、(118.67±1.30)ml、(119.93±1.77)ml;对重复使用后6LR透析器和17 R透析器进行TCV检测,检测值分别为(95.20±7.76)ml、(96.20±7.22)ml、(102.80±4.26)ml和(100.00±11.48)ml、(114.35±3.31)ml、(117.07±2.96)ml;改良检测组与传统检测组对重复使用高通量透析器TCV检测值的比较差异显著.结论 采用改良检测法对重复使用高通量透析器进行TCV检测,能提高TCV检测值的准确性.     

Status of dialyser reuse in Korea

BACKGROUND AND AIM: Dialyser reuse treatments in Korea were first practised at a facility in 1985. Until 1999, there was only one facility practising dialyser reuse treatments, but the reuse practice has gradually increased since 1999. The purpose of this study was to gather and analyse the current (April 2002) dialyser reuse treatment data in Korea. METHOD AND RESULTS: Data was collected via a questionnaire sent to the each hospital that reuses the dialyser, and we received a response from 26 out of 29 facilities (89.7%). Twenty-nine facilities comprised 7.7% (29 of 376) of the total nationwide haemodialysis facilities in Korea. The percentage of patients on dialyser reuse treatments was 6.2% (1234 of 20,010). All facilities used an automated reuse processing technique for dialyser reuse and 22 facilities used a peracetic acid mixture (PAM) without hypochlorite. There was one facility that used the heated citric acid method. Eighty per cent of facilities used only high flux membranes (Kuf > or = 20 mL/h per mmHg) and 12% of the facilities used both high and low flux membranes. The average number of the reuse treatments was 15-fold (range 10-22) and the average of the maximum number of reuse treatments was 20-fold (range 10-50). CONCLUSION: Although dialyser reuse treatments are not a common practice in Korea, the reuse programs are steadily increasing. Strict quality control and further regulations regarding the reuse program should be promptly enacted to provide a better quality of haemodialysis treatment for patients in Korea.     

消毒技术在中水回用中的应用

阐述了中水回用工程中几种常见的消毒技术,对消毒技术发展方向进行了论述.     

Survival and Mortality in 3,701 Pacemaker Patients: Arguments in Favor of Pacemaker Reuse

This study analyzed the results of 3,701 patients implanted with cardiac pacemakers at the Centre Chirurgical du Val d'Or between 1976 and 1981. Two pacemaker populations were compared; those having a new pacemaker and (hose implanted with a reused pacemaker. There were no statistically significant differences between the two groups, either in terms of indications for implantation or in terms of actuarial survival of patients. In addition, there was no significant change in survival of the pulse generator. The reutilization of pacemakers appeared to be in no way detrimental to patients.     

复用滤器对联机血液透析滤过溶质清除率及安全性的影响

目的 研究复用滤器对联机血液透析滤过溶质清除率、安全性及氧化应激指标的影响。方法 8例稳定的维持性透析患者分别接受初用和复用滤器的后稀释联机血液透析滤过治疗。测定透析开始后20 min和整个治疗时间的透析液侧及血液侧溶质清除率。全血培养法测定透前、透后、透析开始后20 min滤器前后细胞因子产生量。高效液相色谱法测定透前、透后血浆及透析液中总抗坏血酸、脱氢抗坏血酸和维生素E含量。结果 两组透析开始后20 min及总治疗时间内透析液侧及血液侧小分子物质清除率相似,但复用组β2-微球蛋白(β2-m)吸附清除率明显低于初用组,透析液侧清除率则显著高于初用组。复用组透析液白蛋白含量明显高于初用组,两组透前、透后维生素E水平无显著改变,但透后总抗坏血酸水平均明显下降,其中复用组透析后脱氢抗坏血酸/总抗坏血酸比例较透前明显下降。全血培养法显示,两组彼此之间及透前、透后及透析开始后20 min滤器前后细胞因子产生量差异均无显著性意义。初用组及复用组透析中临床症状以及透析后体温无明显差异。结论复用滤器不影响联机血液透析滤过的溶质清除率,但可增加白蛋白丢失;虽然复用滤器对血液炎症因子产生细胞的激活程度与初用组相似,但有增加氧化应激的危险。     

再生口腔检查器械取代一次性口腔诊疗盘的可行性临床验证及实施

目的探讨再生口腔检查器械取代一次性口腔诊疗盘的可行性及实用性,以减少使用一次性口腔诊疗盘所导致的资源浪费和环境污染。方法收集相关信息及数据并进行成本核算,从多方面对再生口腔检查器械取代一次性口腔诊疗盘的可行性进行论证。结果再生口腔检查器械成本为1.15元/套。2005年7月—2006年4月共使用再生口腔检查器械37815套,减少医疗垃圾2 366斤,节约垃圾处置等费用6 884元。结论再生口腔检查器械取代一次性口腔诊疗盘可节约成本与资源,减少环境污染,有其可行性与实用性。