Synthesis and Characterization of Novel Biodegradable Poly (butylene succinate-co-triethylene glycol succinate)Copolymers

Novel biodegradable aliphatic polyesters,poly(butylene succinate-co-triethylene glycol succinate)(P(BS-co-TEGS))and poly(butylene succinate)(PBS),were synthesized through a two-step procedure of esterification and polycondensation with succinic acid and1,4-butanediol/triethylene glycol as raw materials as well as tetrabutyl titanate and diphenylphosphinic acid as the co-catalysts.The chemical structure and molecular weight of the copolymers were characterized by 1~H nuclear magnetic resonance(~1H NMR)and gel permeation chromatography(GPC),respectively.In addition,thermal properties,crystal structure and mechanical properties were also analyzed with various techniques.P(BS-co-TEGS)exhibited more excellent mechanical properties than PBS,especially in elongation at break.Meanwhile,the crystal structure and thermal stability of the P(BS-co-TEGS)have hardly changed.The crystallinity of P(BS-co-TEGS)was lower than that of PBS and decreased with the increase of mole ratio of triethylene glycol.With the increase of TEGS unit molar composition,the melting point(T_m),crystallization temperatures(T_c)and heat of fusion(ΔH_m)of P(BS-co-TEGS)decreased,while glass transition temperature(T_g)increased.     

20Cr11MoVNbNB钢的蠕变性能与组织的关系

研究了20Cr11MoVNbNB钢550—650℃的蠕变性能及组织的变化,发现在550℃,蠕变应力>180MPa时,过渡蠕变应变和蠕变时间的ε_β-ι~(1/3)关系中,呈现前期斜率β_1大于后期β_2的两段线性关系;550℃稳态蠕变速率可用■=Aσ~nexp(-Q_c/RT)来表示,其中n=4.7,Aexp(-Q_c/RT)=5.37×10_(-16);550—650℃的表观蠕变激活能Q_c=430kJ/mol,其值远大于基体Fe原子的自扩散激活能;发现在蠕变过程中,随蠕变应力和蠕变时间增加,沉淀相的总量和其中的Cr,Mo,V含量增加,Fe和Nb含量则下降。     

RELATIONSHIP BETWEEN CREEP PROPERTIES AND STRUCTURE OF STEEL 20Cr11MoVNbNB

Studies were made of the creep properties and structure change of steet 20Cr11MoVNbNB at550-650℃.It is found that at 550℃ when creep stress>180 MPa there exists linear rela-tion with two different slopes β_1 and β-2 between transitional creep strain ε_β and creeptime t~(1/3),and β_1(in initiol period)>β_2(in later period).The Creep rate of stable stage at550℃ can be expressed by =Aσ exp(-Q_ /RT),where,n=4.7.A exp(-Q_ /RT)=5.37×10~(-16).Apparent creep activation energy Q_ =430 kJ/mol at 550-650℃,which ismuch higher than the self-diffusion activation energy of atoms for matrix Fe.In creepprocess,as the creep stress and time increase,the total weight of precipitated phases and rela-tive weight of Cr,Mo and V increase,but those of Fe and Nb decrease in precipitated phases,     

群机器人多目标搜索中的合作协同和竞争协同

群机器人进行多目标搜索时,通过任务分工形成多个子群,各子群分别针对一个意向目标协同搜索,故围绕子群协同中存在的合作关系和竞争关系提出控制策略.为进行合作协同,建立子群发言人的动态遴选机制,不同子群的发言人进行通信,交换所属各子群的最优信息,引导本子群的搜索行为;为进行竞争协同,引入承包机制,按子群的优势地位高低决定是承包还是放弃对某些目标的搜索.两类协同控制的仿真结果表明,合作协同扩大了机器人的感知范围,竞争协同降低了空间冲突机率.二者综合作用,明显提高了群机器人的搜索效率.     

An elastic net-based hybrid hypothesis method for compressed video sensing

Multimedia Tools and Applications - Compressed Sensing, an emerging framework for signal processing, can be used in image and video application, especially when available resources at the...     

急冷废热锅炉扁集箱堵板焊接的新工艺

对大庆乙烯石化总厂急冷废热锅炉扁集箱堵板焊接时存在的未熔合问题进行了分析,认为扁集箱和堵板之间壁厚差异,以及受到铁水重力影响,是造成靠扁集箱侧单面夹沟的主要原因.经采用扁集箱侧手工堆焊坡口的焊接方法,焊口背面成型良好,扁集箱侧熔合良好,超声波检验合格,保证了焊接质量,满足了安装施工要求.     

大型转换桁架预拼装工艺

工厂预拼装目的在于检验构件工厂加工能否保证现场拼装、安装的质量要求,确保下道工序的正常运转和安装质量达到规范、设计要求,满足现场一次拼装和吊装成功率,减少现场拼装和安装的误差.本文介绍了某大型转换桁架预拼装方案与工艺,可供同类大型工程参考.     

铜电解添加剂的作用机理及生产实践

随着现代工业的发展,对阴极铜质量的要求更加严格,但阴极铜质量的优劣,取决于它们的组织结构和杂质含量,若要获得优质阴极铜,必须严格控制好各项技术条件.添加剂就是一项主要的控制因素,实践证明,加入适量添加剂,是获得结构致密、表面光滑、杂质含量少的优质阴极铜的有效措施.     

磷酸二氢铝对高铬耐火泥浆性能的影响

选用工业级电熔氧化铬粉、氧化铬绿以及α-A l2O3细粉等为原料,以磷酸二氢铝(w(P2O5)≥65%,w(A l2O3)≥17%)作为高铬泥浆的结合剂,研究了磷酸二氢铝加入量对不同系列(电熔氧化铬粉和氧化铬绿的加入量不同)泥浆加水量、粘结时间和粘结强度的影响,并对磷酸二氢铝的作用机理进行了分析。结果表明,随着磷酸二氢铝加入量的增大,泥浆的加水量降低,粘结时间延长,粘结强度提高。