皮带运输机接头连接的探讨

为了向市场提供合格的煤质,选煤厂在矿井生产中扮演着重要的洗选角色,而皮带运输机又是选煤厂中最重要的运输设备,因此皮带机保持稳定正常的运行极其重要。皮带接头质量的好坏直接关系到输煤系统能否正常稳定的生产,皮带接头的连接有多种方式,本文对此进行相应的分析探讨。

DNA纳米结构自装配的语言能力分析(英文)

文中研究了DNA分子杂交的内在计算能力.一方面,文中基于Winfree先前关于线性分子自装配仅能产生正则语言工作的基础上,进一步扩展证明了线性自装配通过杂交分别表示左、右线性派生的线性分子,也能产生线性语言.另一方面,文中定义了一种新的通过上下文无关语言通过自装配产生线性语言的方法,即证明了等价于上下文无关语言的特定序列集能通过1-,2-,3-粘头分子的混合自装配产生线性语言,同时,这是对Winfree关于树状纳米结构自装配等价于上下文无关语言理论的一个较好的补充.

Crk adaptor protein-induced phosphorylation of Gab1 on tyrosine 307 via Src is important for organization of focal adhesions and enhanced cell migration

Upon growth factor stimulation, the scaffold protein, Gabl, is tyrosine phosphorylated and subsequently the adaptor protein, Crk, transmits signals from Gabl. We have previously shown that Crk overexpression, which is detectable in various human cancers, induces tyrosine phosphorylation of Gabl without extracellular stimuli. In the present study, the underlying mechanisms were further investigated. Mutational analyses of CrkII demonstrated that the SH2 domain, but not the SH3（N） or the regulatory Y221 residue of CrkII, is critical for the induction of Gabl- Y307 phosphorylation. SH2 mutation of CrkII also decreased the interaction with Gabl. In GST pull-down assay, Crk-SH2 bound to wild-type Gahl, whereas Crk-SH3（N） interacted with the Gabl mutant, which lacks the clus- tered tyrosine region （residues 242-410）. Tyrosine phosphorylation of Gabl was induced by all Crk family proteins, but not other SH2-containing signalling adaptors. Src-family kinase inhibitor, PP2, abrogates Crk-induced tyrosine phosphorylations of Gabl. Y307 phosphorylation was undetectable in fibroblasts lacking Src, Yes, and Fyn, even upon overexpression of Crk, whereas cells lacking only Yes and Fyn still contained Gabl with phosphorylated Y307. Furthermore, Crk induced the phosphorylation of Src-Y416; accordingly the interaction between Crk and Csk was increased. The Gabl-Y307F mutant failed to localize near the plasma membrane even upon HGF stimulation and decreased cell migration. Moreover, Gabl-Y307F disturbed the localization of Crk, FAK, and paxillin, which are the typical components of focal adhesions. Taken together, these results indicate that Crk facilitates tyrosine phosphory- lation of Gabl-Y307 through Src, contributing to the organization of focal adhesions and enhanced cell migration, thereby possibly promoting human cancer development.

有限元分析在头罩粘接强度校核中的应用

通过对头罩粘接接头建立有限元仿真模型,分析了静态载荷、动态载荷、温差导致的热载荷、疲劳载荷四种工况下胶层产生的应力和应变,结合胶黏剂本身的特性,对粘接接头的安全性能进行评估,对轨道交通车辆部件粘接接头安全设计具有重要意义。

电动轮卡车电阻栅防烧毁保护装置

针对目前矿内使用的MT5500卡车存在B2、B3接触器触头粘死经常引起电栅烧毁的问题,在分析其故障原因的基础上,加装PLC弥补了原系统程序上的不足,解决了电阻栅烧毁的问题。

Influences of diffusion bonding process parameters on bond characteristics of Mg-Cu dissimilar joints

In many circumstances,dissimilar metals have to be bonded together and the resulting joint interfaces must typically sustain mechanical and/or electrical forces without failure,which is not possible by fusion welding processes.The melting points of magnesium(Mg)and copper(Cu)have a significant difference(nearly 400℃)and this may lead to a large difference in the microstructure and joint performance of Mg-Cu joints.However,diffusion bonding can be used to join these alloys without much difficulty.This work analyses the effect of parameters on diffusion layer thickness,hardness and strength of magnesium-copper dissimilar joints.The experiments were conducted using three-factor,five-level,central composite rotatable design matrix.Empirical relationships were developed to predict diffusion layer thickness,hardness and strength using response surface methodology.It is found that bonding temperature has predominant effect on bond characteristics.Joints fabricated at a bonding temperature of 450℃, bonding pressure of 12 MPa and bonding time of 30 min exhibited maximum shear strength and bonding strength of 66 and 81 MPa, respectively.

Evaluation of Adhesive Joints for Combined Load Test-Fixtures

Abstract： In a test-fixture that the authors were using, steel tabs adhesively bonded to an aluminum panel debonded before the design load on the real test panel was fully applied. Therefore, studying behavior of adhesive joints for joining dissimilar materials was deemed to be necessary. To determine the failure load responsible for debonding of adhesive joints of two dissimilar materials, stress distributions in adhesive joints as obtained by a nonlinear finite element model of the test-fixture were studied under a gradually increasing compression-shear load. It was observed that in-plane stresses were responsible for the debonding of the steel tabs. To achieve a better understanding of adhesive joints of dissimilar materials, finite element models of adhesive lap joints and ADCB （asymmetric double cantilever beam） were studied, under loadings similar to the loading faced by the test-fixture. The analysis was performed using ABAQUS, a commercially available software, and the cohesive zone modeling was used to study the debonding growth.

Investigations of Physical and Chemical Characteristics of Masonry Stones and Bricks during Building Cleaning： Part 1. Physical Testing

This series of study focused on analysing and assessing the changes of the physical and chemical characteristics of the surfaces of the masonrystones and bricks during the sandblasting cleaning process by conducting various physical and chemical tests. Seven masonry stones and bricks were adopted, including yellow sandstone, red sandstone, limestone, marble, granite, white clay brick and yellow clay brick. The physical testing included evaluating the cleaning degree, determining the Vickers hardness, and detecting the water absorption. Using a digital imaging analysis method, the greyscale and cleanness were introduced to quantitatively assess the effectiveness of masonry building cleaning and confirmed to be useful and appropriate. The cleanness analysis, together with the hardness and water absorption tests showed that a masonry stone or a brick with a higher cleaning degree corresponded to a brighter and harder stone surface. In general, the physical properties were found to vary largely during the building cleaning.

Intraductal papillary neoplasm of the bile duct in liver cirrhosis with hepatocellular carcinoma

A case of intraductal papillary neoplasm of the bile duct (IPNB) arising in a patient with hepatitis B-related liver cirrhosis with hepatocellular carcinoma (HCC) is reported. A 76-year-old man was admitted to our hospital with recurrent HCC. Laboratory data showed that levels of carcinoembryonic antigen and carbohydrate antigen 19-9 were elevated. He died of progressive hepatic failure. At autopsy,in addition to HCCs,an intraductal papillary proliferation of malignant cholangiocytes with fibrovascular cores was found in the dilated large bile ducts in the left lobe,and this papillary carcinoma was associated with an invasive mucinous carcinoma (invasive IPNB). Interestingly,extensive intraductal spread of the cholangiocarcinoma was found from the reactive bile ductular level to the interlobular bile ducts and septal bile ducts and to the large bile ducts in the left lobe. Neural cell adhesion molecule,a hepatic progenitor cell marker,was detected in IPNB cells. It seems possible in this case that hepatic progenitor cells located in reactive bile ductules in liver cirrhosis may have been responsible for the development of the cholangiocarcinoma and HCC,and that the former could have spread in the intrahepatic bile ducts and eventually formed grossly visible IPNB.

钢铝异质无铆钉粘铆复合连接胶层厚度分布

为了研究粘铆复合接头的胶层厚度对接头的成形质量和服役性能的影响,建立了无铆钉粘铆成形有限元模型,并通过实验验证有限元模型的有效性。利用有限元模型分析了接头成形后胶层的分布规律及接头成形过程中胶层的变化趋势,研究胶层厚度对接头成形的影响。结果表明:胶层厚度从接头底部中心到自锁处呈先增大后减小的趋势,其中底部圆角处胶层厚度最大;铆接过程中胶层厚度随冲头行程增加而变化;胶层厚度影响接头的自锁值与颈厚值。

Adhesive bonding of composite aircraft structures:Challenges and recent developments

In this review paper,the challenges and some recent developments of adhesive bonding technology in composite aircraft structures are discussed.The durability of bonded joints is defined and presented for parameters that may influence bonding quality.Presented is also,a numerical design approach for composite joining profiles used to realize adhesive bonding.It is shown that environmental ageing and pre-bond contamination of bonding surfaces may degrade significantly fracture toughness of bonded joints.Moreover,it is obvious that additional research is needed in order to design joining profiles that will enable load transfer through shearing of the bondline.These findings,together with the limited capabilities of existing non-destructive testing techniques,can partially explain the confined use of adhesive bonding in primary composite aircraft structural parts.

Analysis of flow and heat transfer characteristics of micro-pin fin heat sink using silver nanofluids

Silver nanofluids with three different volume fractions are prepared by a one-step chemical reduction method(Ultra-sound-assisted Membrane Reaction(UAMR)).The convective heat transfer and friction characteristics of silver nanofluid in micro-pin fin heat sink are investigated experimentally.The results indicate that the pressure drops of nanofluids with different volume fractions have little difference.Compared to the base fluid(polyvinylpyrrolidone(PVP) solution),the pressure drop of nanofluids increases slightly at the same volume flow rate.When the flow rate is small,the increment is not obvious.The in-troduction of surfactant increases the fluid viscosity,so the pressure drops of nanofluids are larger than those of pure water,under the same flow rate.However,the maximum difference is no more than 10%.The volume fraction of silver nanoparticles significantly affects the convection heat transfer coefficient of micro-pin fin heat sink.The presence of nanoparticles improves significantly the heat transfer performance.However,high viscosity of the nanofluids hinders the heat transfer strengthening effect of nanofluids.In the present work,when the volume fraction of silver particles reaches to 0.012%,the thermal resistance of nanofluid gradually becomes lower than that of deionized water,which indicates the integrated heat transfer enhancement of nanofluids.

Study on the mechanical behavior of adhesive interface by digital image correlation

The shear modulus of the adhesive layer and the failure mode of adhesive structure on single lap joint specimens under tensile tests are investigated in this paper.The aluminum-aluminum adherends are bonded by two different adhesives:polydimethylsiloxane (PDMS) and epoxy.The full deformation fields are measured using the digital image correlation (DIC) method with the images on the middle part of the adhesive layer recorded by a high resolution microscope.Then,the shear modulus values of the two adhesives are calculated with a simple pure shear strain model.A numerical model is proposed to simulate the single lap joint structure under tensile load in comparison with the experimental results.The results show that this method can successfully estimate the shear modulus of the adhesive layer.The failure behavior of epoxy adhesive/adherend interface is also analyzed and discussed.