薄板镁合金激光焊接专用焊枪的设计

介绍了薄板镬合金激光焊接专用焊枪的设计.该焊枪在焊接过程中可有效地得到冷却,也可在焊接区域形成保护气体氛围,从而可获得优良的焊接接头,且焊接重复性好.     

汽车制造企业生产成本管理研究

介绍了制造业生产成本管理的一种基本模型,它由3个相互制约、相互影响的体系组成,即生产成本的控制体系、现场管理体系和质量保证体系.通过对国内某汽车制造企业的生产成本和生产现场的研究,总结了一套生产成本管理的模式,并且探讨了生产成本管理在汽车制造业中的应用.     

浇注型耐热聚氨酯树脂材料的合成及性能

以二异氰酸酯(4,4’-二苯甲烷二异氰酸酯MDI;4,4’-二环己基甲烷二异氰酸酯Hl2MDI),聚醚多元醇(PPG),小分子交联扩链剂,催化剂及助剂合成了一系列耐热聚氨酯树脂材料。用FT-IR表征了结构,用X射线衍射分析了微观结构,用DSC,TGA对其热稳定性进行了分析测试,对力学性能也进行了测试。结果表明,合成的聚氨酯材料具有高耐热性和卓越的力学性能。     

魅力型领导与团队学习:团队目标明确度的缓冲效应

本研究采用分组回归方法,以89支学生研究项目团队作为研究对象,考查魅力型领导与团队学习间的影响关系;并检验了团队目标的明确程度对魅力型领导和团队学习间关系所起的缓冲效应.结果表明,魅力型领导有助于团队学习;另一方面,当团队目标相对明确时,魅力型领导对团队学习的积极影响效应才较为显著;而当团队目标相对不明确时,魅力型领导...     

Collaborative Design of Hollow Nanocubes,In Situ Cross‐Linked Binder,and Amorphous Void@SiOx@C as a Three‐Pronged Strategy for Ultrastable Lithium Storage

Although silicon‐based materials are ideal candidate anodes for high energy density lithium‐ion batteries, the large volumetric expansion seriously damages the integrity of the electrodes and impedes commercial processes. Reasonable electrode design based on adjustable structures of silicon and strong binders prepared by a facile method is still a great challenge. Herein, a three‐pronged collaborative strategy via hollow nanocubes, amorphous Void@SiO_x@C, and in situ cross‐linked polyacrylic acid and d ‐sorbitol 3D network binder (c‐PAA‐DS) is adopted to maintain structural/electrode integrality and stability. The all‐integrated c‐PAA‐DS/Void@SiO_x@C electrode delivers excellent mechanical property, which is attributed to ductility of the c‐PAA‐DS binder and high adhesion energy between Void@SiO_x@C and c‐PAA‐DS calculated by density functional theory. Benefiting from the synergistic effect of accommodation of the hollow structure, protection of outer carbon shell, amorphous Void@SiO_x@C, and strong adhesive c‐PAA‐DS binder, c‐PAA‐DS/Void@SiO_x@C shows excellent electrochemical performance. Long cycling stability with a reversible capacity of 696 mAh g^?1 is obtained, as well as tiny capacity decay after 500 cycles at 0.5 A g^?1 and high‐rate performance. The prelithiated Void@SiO_x@C||LiNi_0.5Co_0.2Mn_0.3O₂ (NCM523) full cell is also assembled and shows a reversible capacity of 157 mAh g^?1 at 0.5 C, delivering an excellent capacity retention of 94% after 160 cycles.     

松软煤层中螺旋钻进技术应用

对松软煤层中螺旋钻进技术进行了介绍,并对其输煤原理及钻进工艺规程参数进行理论分析,利用此技术在新元煤矿松软煤层钻进成孔取得较好的效果。     

一种改进的Wu-Manber多关键字匹配算法

针对Wu-Manber算法在处理公共子后缀模式情况下的不足,该文提出了一种基于非空公共子后缀模式的处理算法。该算法把有非空公共子后缀的模式汇集在一起,进一步减小了next链表的平均长度。在匹配过程中减少了字符比较的次数,从而提高算法的运行效率。该文对搜狗实验室给出的相关文档进行全文检索实验,并和原Wu-Manber算法、孙晓山等提出的改进算法进行比较。实验结果表明,该文提出的改进算法有效地减少了匹配过程中字符比较的次数,从而提高匹配的速度和效率。     

冬青树叶表面的红外光谱特征

用红外衰减全反射技术(ATR)研究了各生长期和不同环境中冬青树叶表面的红外光谱特征.当用黑色塑料袋套在冬青枝条上48 h后,树叶表面的水分有所增加,其它成分变化甚微.当用透明塑料袋套在枝条上48 h后,树叶表面酯类物质的特征峰1 730、1 682 cm-1增加,且峰强度相当.当冬青叶片与甲苯气体接触48 h后,叶片反面酯类物质的特征峰(1 730、1 168、1 039 cm-1)有所减少.同样,叶片正面的酯类物质(1 730、1 168、1 039 cm-1)也有所减少.扫描电镜能谱也证实了叶片反面酯类物质确有减少.     

新兴本科院校理工科学生词汇学习策略调查

对新兴本科院校理工科158名学生的词汇学习观念和策略使用情况的调查表明:新兴本科院校理工科学生普遍认为词汇学习很重要,赞成边用边学;但采用的策略少于其他名校和历史悠久的本科院校的学生;其中使用频率较高的策略只有选择性注意、查词典、猜测和自我激励策略;好生与差生的词汇学习观念和策略使用存在很大的差异。     

Occurrence and characteristics of Vibrio vulnificus in retail marine shrimp in China

Vibrio vulnificus is a gram-negative bacterium that naturally occurs in estuarine waters and marine environment. Consumption of seafood contaminated with V. vulnificus or exposure to the contaminated water causes septicemia, gastroenteritis or wound infections in humans. This study aimed at identifying the prevalence of V. vulnificus in shrimps in Chinese seafood market. From June to September 2009, 239 samples encompassing six shrimp species were collected from ten cities in China. To quantify the prevalence and the levels of V. vulnificus in shrimps, the most probable number (MPN) method was used combining with the polymerase chain reaction (PCR) which was used to classify the isolates by detecting V. vulnificus hemolysin gene (vvhA). One hundred and forty out of 239 samples were positive for V. vulnificus, with the geometric mean level at 153.3 MPN/g. The prevalence and levels of V. vulnificus in shrimps varied in different geographic areas, with the values for the samples in the South cities (179.6 MPN/g) remarkably higher than that in the North cities (7.6 MPN/g). In addition, we found that 61.7% (79/128) of the V. vulnificus positive samples contained C-type (Clinical) strains and 8 contained E-type (Environmental) strains. The antimicrobial susceptibility of the isolates to 12 antibiotics was tested as well. Most of the 169 isolates remained susceptible to the majority of antimicrobials tested, whereas some strains tend to be less sensitive to amikacin, ampicillin, tetracycline and gentamicin. In conclusion, V. vulnificus is commonly found in retail marine shrimp in Chinese seafood market, and most of the shrimp samples contained C-type strains, which may pose a potential threat to human health.