Unsteadiness in non-transferred dc arc plasma generators

Non-transferred dc arc plasma generators are widely used in materials processing. They are generally considered steadily-operating devises. However, unsteady phenomena do exist in them, and may cause non-ideal effects in processes which require high controllability and reproducibility. These unsteady phenomena can cause parameter fluctuations in the arc and the plasma jet, some of which have been studied in recent years. Several types and mechanisms of these phenomena have been identified. This paper reviews the research progress in this specific area, hoping to present a more complete picture of this subject

Research on Influence of CEO Characteristic on Working Capital Policy of Listed Companies

营运资本政策是现代公司财务管理中的重要内容，它与股利政策、负债政策、资本投资政策等共称为四大财务政策，在公司理财中具有举足轻重的地位。企业的资产中，营运资本占有相当比重，是整体财务结构的重要组成部分。营运资本与诸多财务指标密切相关，对企业的生存与发展、企业利润增长、风险控制以及价值创造都起着重要的作用。资金紧缺是国内企业普遍面临的问题，反映企业资金流动状况的营运资本管理是企业财务管理的当务之急。 与营运资本管理的重要地位相对应，对营运资本管理的研究也理应在财务理论研究中占据重要的位置。然而传统的理论多从公司层面出发研究营运资本政策的相关问题，而忽视了人即财务政策制定者自身的异质性对营运资本政...Working capital policy is an important content in modern company's financial management. Working capital policy, dividend policy, debt policy and capital investment policy are known as the four major financial policies. It plays an important role in financial management of a company. In enterprise assets, working capital takes a large proportion and is an important part in overall financial struct...学位：管理学硕士院系专业：管理学院_财务学学号：3212010115058

Wear Resistance of Cast Iron Remelted by Non-Transferred Laminar Plasma Jet

对在大气压条件下用非转移弧层流等离子体射流熔凝强化处理的W-Mo-Cu铸铁表面,采用光学显微镜、显微硬度计、磨损试验机、扫描电镜等,观察和测试了熔凝试样的表面层组织、硬度、耐磨性和磨损形貌.结果表明,熔凝后铸铁表面为初晶渗碳体和莱氏体组成的过共晶组织,硬度和耐磨性有了明显的提高

Perioperative Preventive Use of Antibiotics in Orthopedic Patients

目的:了解2008年我院骨科围术期预防性应用抗菌药物的情况,并评价其用药合理性。方法:利用我院“军卫一号系统“查阅2008年1~12月骨科围手术期的3 229份病历,对其中预防性应用抗菌药物的品种、联合用药、用药疗程、用药时机和手术类型等进行统计分析。结果:我院骨科围手术期患者的抗菌药物总使用率为96.72%(3 123例);手术类型Ⅰ类切口2 468例(76.43%)、Ⅱ类切口404例(12.51%)、Ⅲ类切口357例(11.06%);预防性应用抗菌药物开始时机:术前2 H内给药的444例,占14.28%,术后1~3 H给药2 426例,占78.03%,术后预防性持续用药时间3天内有964例(31.00%),3~7天1 719例(57.61%)。抗菌药物用药方式:单用、二联和三联分别为2 861例(91.61%)、260例(8.33%)和2例(0.06%);以单用为主,主要品种为头孢菌素(77.91%)、氟喹诺酮类(14.61%)及其他(7.48%)。结论:骨外科围术期抗菌药物的预防性应用基本合理,但用药种类较多,用药时间较长,需加强对抗菌药物的应用管理,按规范要求使用,提高合理用药水平。OBJECTIVE: To investigate the status quo and rationality of the perioperative use of antibiotics in orthopedic patients of our hospital.METHODS: A total of 3 229 perioperative medical records of orthopedic patients retrieved by Army No.1 System between Jan.and Dec.in 2008 were analyzed statistically in respect of the category of antibiotics,combined use of antibiotics,courses of treatment,application time and surgery types etc.RESULTS: 96.72%(3 123 patients) received antibiotics perioperatively.76.43%(2 468) patients had type I incision,12.51%(404) type II and 11.06%(357) type III.444(14.28%) received antibiotics 2h prior surgery and 2 425(78.03%) within 1 to 3 hours postoperatively;964(31.00%) received antibiotics for 3 consecutive days and 1 719(57.61%) for 3 to 7 days.2 861(91.61%) received one kind of antibiotics,and 260(8.33%) received two kinds and 2(0.06%) three kinds of antibiotics in combination.The main categories administered were cephalosporins(77.91%),quinolones(14.61%) and others(7.48%).CONCLUSION: The preventive use of antibiotics in orthopedic patients is rational on the whole.But the category and of antibiotics applied is on the high side and the medication duration of which is long.It is urgent to tighten control on the management in the application of antibiotics to ensure standard use of antibiotics and improve the level of rational use of antibiotics

高等教育自学考试制度改革的成就与展望

高等教育自学考试制度自创建以来经历了规模扩张与转型发展两个阶段,为我国经济、社会的现代化建设提供了巨大的人才与智力支持,已经成为我国高等教育的重要组成部分,为我国教育改革与创新作出了重要贡献。展望未来,自学考试制度发展应坚持以质量意识为核心,确立非学历考试的价值、功能与地位,坚持服务意识,重视理论研究与实证研究,把自学考试教育制度融入终身教育体系中

长汀时期的厦门大学与西南联大之比较

长汀时期的厦门大学与西南联大,是抗战时期坚持在后方培养人才的两所著名高校。两校在许多方面有相似之处,都在艰难的历史条件下创造出安定而自由的学术环境,都汇集了一批学术大师和优秀学生,培养出大量的杰出人才。但两校校长的教育理念同中有异,两校也有各自的办学特色。比较和探讨两校之异同及其得失,有助于深化抗战时期的中国高等教育研究,对当前的大学改革也有重要启迪

应用型人才培养的历史探源

应用型人才是大学人才培养的一种类型。中世纪大学以应用学科为主,其课程和教学内容充满实用性,毕业生主要从事非学术性、研究性工作,大学的主要任务是培养和训练专业性应用型人才;中国近代第一所高等学校福建船政学堂,实行厂校一体的办学体制,目标是培养造船与驾驶人才,毕业生多成为我国船政事业的骨干,其人才培养过程符合近代高等教育分系科、专业培养应用型人才的特点

小功率氮电弧推力器的性能

采用自然辐射冷却结构的小功率电弧推力器,实现了以氮气为推进剂的长时间稳定运行。采用间接测力方法得到推力,利用铜镜反射法拍摄喉道处的放电状态,结合测量的弧电压、弧电流和气流量数据以及导出的比冲和推力效率,对推力器运行性能和放电特性进行了研究。结果显示:在气流量为100~700 mL/min,输入功率为35~55W的条件下,最大推力约为24 mN,最大比冲接近175 s,当弧电流为80~120 mA范围内变化时,弧电压变化范围为420~520V,并且弧电压随气流量的增加呈现出先下降后上升的趋势

丁苯酞软胶囊联合阿托伐他汀钙片治疗脑梗死的效果

目的观察丁苯酞软胶囊联合阿托伐他汀钙片治疗脑梗死的临床疗效。方法选取福建中医药大学附属人民医院2015年1月～2018年6月收治的脑梗死患者186例,随机分为A、B、C组,每组各62例。A组给予丁苯酞软胶囊治疗,B组给予阿托伐他汀钙片治疗,C组给予丁苯酞软胶囊联合阿托伐他汀钙片治疗。采用美国国立卫生研究院卒中量表(NIHSS)评价患者的神经功能缺损情况,采用Barthel指数评定量表评价患者日常生活能力,采用经颅多普勒超声测量缺血区域脑血流量。治疗1个月后,观察比较3组患者的NIHSS评分、Barthel指数、缺血区域脑血流量及临床总有效率。结果 3组患者治疗后的NIHSS评分、Barthel指数和缺血区脑血流量比较,差异均有统计学意义(F=6.48、5.78、15.69,P<0.05)。3组患者治疗后的NIHSS评分均低于治疗前(t=2.523,P<0.05;t=3.016,P<0.05;t=2.642,P<0.05),Barthel指数均高于治疗前(t=2.232,P<0.05;t=2.694,P<0.05;t=2.086,P<0.05),缺血区脑血流量均高于治疗前(t=5.962,P<0.05;t=4.672,P<0.05;t=5.214,P<0.05)。治疗后,C组NIHSS评分低于A、B组(均P<0.05),Barthel指数和缺血区脑血流量均明显高于A、B组(均P<0.05)。C组治疗总有效率为82.26%,高于A、B组的58.06%、53.23%(χ~2=5.342,P<0.05;χ~2=4.163,P<0.05)。结论丁苯酞软胶囊联合阿托伐他汀钙片能有效治疗脑梗死

Modeling study to compare the flow and heat transfer characteristics of low-power hydrogen, nitrogen and argon arc-heated thrusters

A modelling study is performed to compare the plasma °ow and heat transfer char- acteristics of low-power arc-heated thrusters (arcjets) for three di®erent propellants: hydrogen, nitrogen and argon. The all-speed SIMPLE algorithm is employed to solve the governing equa- tions, which take into account the e®ects of compressibility, Lorentz force and Joule heating, as well as the temperature- and pressure-dependence of the gas properties. The temperature, veloc- ity and Mach number distributions calculated within the thruster nozzle obtained with di®erent propellant gases are compared for the same thruster structure, dimensions, inlet-gas stagnant pressure and arc currents. The temperature distributions in the solid region of the anode-nozzle wall are also given. It is found that the °ow and energy conversion processes in the thruster nozzle show many similar features for all three propellants. For example, the propellant is heated mainly in the near-cathode and constrictor region, with the highest plasma temperature appear- ing near the cathode tip; the °ow transition from the subsonic to supersonic regime occurs within the constrictor region; the highest axial velocity appears inside the nozzle; and most of the input propellant °ows towards the thruster exit through the cooler gas region near the anode-nozzle wall. However, since the properties of hydrogen, nitrogen and argon, especially their molecular weights, speci¯c enthalpies and thermal conductivities, are di®erent, there are appreciable di®er- ences in arcjet performance. For example, compared to the other two propellants, the hydrogen arcjet thruster shows a higher plasma temperature in the arc region, and higher axial velocity but lower temperature at the thruster exit. Correspondingly, the hydrogen arcjet thruster has the highest speci¯c impulse and arc voltage for the same inlet stagnant pressure and arc current. The predictions of the modelling are compared favourably with available experimental results