3×35m连续钢-混组合梁桥施工期受力性能的分析

为了解连续钢-混组合梁桥在施工架设过程当中钢主梁顶底板和桥面板钢筋的受力状态,检验设计的合理性,选取(3×35+3×35)m的连续钢板组合梁桥为研究对象,在施工阶段,通过在边跨3L/8位置和墩顶位置布置应力传感器来测量钢主梁顶底板的应力,在墩顶、距墩顶0.15L和边跨3L/8位置埋设应力传感器测量桥面板钢筋应力;并在成桥阶段对该桥进行了荷载试验。建立(3×35+3×35)m连续钢板组合梁桥有限元模型,获取桥梁在不同施工阶段的理论应力值。结果表明:施工阶段墩顶负弯矩钢主梁最大拉应力为91.9MPa,小于理论计算值,边跨桥面板钢筋最大压应力为30.9MPa,大于理论计算值;在等效设计荷载作用下,该桥试验跨的强度和刚度满足设计要求,结构处于弹性工作状态。     

焦散线法确定应力强度因子的一种简便方法

通过测定焦散线上点的坐标及初始曲线半径，得到了焦散线法确定应力强度因子的一种简便方法。以有机玻璃为例，在不同裂纹、不同载荷的条件下，确定了试件的应力强度因子，并将所得结果与Ｐ．Ｓ．Ｔｈｅｏｃａｒｉｓ方法得到的结果一起与相应的理论计算值相比较。     

基于有限元的薄木刨切机机架分析与设计

为了缓解我国天然优质森林资源短缺的现状,提高珍贵木材的利用率,刨切机的加工效率与稳定性尤为重要。本文对刨切机进行了整体设计,采用双面刨刀纵向同时进给、工件固定的刨切方式,减少了机器的占地面积,提高了刨切的效率和精度。对刨切机机架进行了详细分析与设计,采用焊接工艺及螺栓连接以保证机架有较好的结构工艺性、足够的强度、较高的抗振性。通过有限元分析理论节点模型中的单元节点力与节点位移的关系,进而分析出整体的应力与变形量,将Solidworks中的机架三维模型导入ANSYS,并根据该机器的加工过程,进行静力学分析,应力与变形量均满足许用条件,为机架的设计提供了强有力的理论基础,进而最终确保设计满足要求。本文的设计为珍贵原木的开发利用及产业化生产提供了技术支持,可产生较好的经济效益。     

强度为Weibull分布，应力为其他分布的可靠度求解

运用应力-强度相干理论，推导出强度为Weibull分布，应力为其他分布时可靠度求解表达式，并应用专用数学软件Mathematica实现了数值的求解。文中给出若干求解实例，求解的过程简便、直观，有利于工程可靠性设计与分析借鉴。     

黄麻纤维增强混凝土的抗压和抗折性能研究

在混凝土中添加黄麻纤维,以增强混凝土的抗压和抗折性能。通过测定纤维增强混凝土的抗压和抗折强度,并与素混凝土进行对比,进而研究黄麻纤维的长度和掺量对混凝土的增强作用。结果表明:黄麻纤维长度为30mm,掺量为0.5～0.6kg/m3时,对混凝土的抗压及抗折强度增强作用最为显著。     

混合办公废纸纤维素酶脱墨的工艺研究

采用四种不同纤维素酶制剂进行混合办公废纸酶法脱墨实验，对脱墨浆性能和脱墨效果进行综合评价。从既能提高脱墨率，又尽可能保持物理强度方面考虑，在本实验条件下，同时存在内切酶、外切酶与木聚糖酶且FPA／CMCase值为0．0292的纤维素酶比较适合办公废纸酶法脱墨，其脱墨率最高，为82．3%；裂断长仅比对照样低0．8％，成纸强度好；最佳脱墨条件：加酶量：1．0IU／g(CMCase)，温度：50—55℃，pH值，5．0—5．5，时间：30—45min；浆浓5．0—5．5%。     

可靠性设计的全概率法─-机械可靠性设计方法的新突破

依据应力-强度干涉理论，推导出5大类型统计分布及各种不同应力、强度组合下可靠度计算的表达式，并运用数值积分方法给出可靠度的高精度解。通过建立可视化操作平台，使机械可靠性设计变得非常容易。同时，本研究使机械可靠性设计的全概率法在精确度上取得了突破性进展。     

孤岛工作面窄煤柱临空巷道动压影响下围岩控制技术研究

孤岛工作面由于高应力存在,容易造成巷道、工作面大变形等问题。以山西晋煤集团翼城晟泰青洼煤业2102工作面为工程背景,为解决青洼煤业生产接续的问题,拟采用水力压裂技术对青洼煤业2103工作面运输顺槽进行切顶卸压,通过FLAC3D软件模拟不同切顶高度情况下对煤柱及巷道围岩的影响,选出合理的切顶高度;并分析2102工作面新掘进风顺槽在新提出的支护方案下巷道的围岩变形情况,验证方案的合理性。通过方案的实施和监测,证明切顶卸压可切断采空区顶板与留巷顶板间的应力传递,削弱采空区侧上覆岩层对2102工作面进风顺槽产生的附加应力,达到控制巷道变形以及维护其稳定性的目的。     

高速铣削淬硬H13钢表面粗糙度及残余应力实验研究

为了获得淬硬H13模具钢在高速铣削后的高质量表面,基于单因素实验设计法,采用TiAlN涂层硬质合金立铣刀对其进行高速铣削实验。通过使用NPFLEX白光干涉仪和PROTO-X射线衍射仪对加工后工件表面粗糙度、表面形貌以及表面残余应力进行测试,同时分析了切削速度、每齿进给量和轴向切深对测试结果的影响规律。研究结果表明:当切削速度为150 m/min时,表面粗糙度R_a值最小;当每齿进给量为0. 06 mm/z时,R_a值最佳;而当轴向切深为0. 06 mm时,R_a值最大。随着切削速度的增大,表面残余压应力呈现先减小后增大再减小的变化趋势,随着每齿进给量的增加,表面残余压应力变化并不显著,而随着轴向切深的增加,表面残余压应力增大;最大表面残余压应力和最小表面粗糙度的组合并不在相同的切削参数下获得。     

基于ANSYS软件对压力容器开孔接管区的应力与疲劳分析

文章利用ANSYS有限元软件对压力容器开孔接管区进行应力分析,获得了开孔接管区的应力强度分布图,得到最大应力发生在筒体最高位置与接管的连接处,最大应力强度值为247.478 MPa。然后利用ANSYS进行疲劳寿命分析,将有限元方法与疲劳寿命分析理论相结合,得到累积使用系数均小于1,即开孔接管部位满足疲劳强度的要求,因此该容器是安全的。通过此次分析再次证明了ANSYS软件为压力容器实际工程应用中提供了可靠的、高效的理论依据。图4表3参11     

Reliable identification of grapevine rootstock varieties using RAPD PCR on woody samples

Since grapevine ( Vitis spp .) rootstock material is being traded increasingly as disbudded woody material a lack of distinctive morphological features on such material necessitates an alternative and reliable means of identification. Methods described here were developed for rapid and efficient extraction of DNA from woody samples rich in phenolic compounds and polysaccharides, and for subsequent identification of varieties by RAPD PCR. Using these methods, and with the application of only one selected RAPD primer, we were able to differentiate sixteen rootstock varieties, including the seven varieties most commonly used in Germany. Problems commonly encountered with reproducibility of RAPD patterns were avoided by choosing primers with a dinucleotide sequence and a high G/C content that allowed a rather high annealing temperature of 45°C. Methods described here should also be useful for other horticultural crops, especially those with woody tissues rich in phenolic compounds and polysaccharides.     

An internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics

An internet website (http://cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-ofcharge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.     

Aroma characterization of various apricot varieties using headspace–solid phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The characterization of the aromatic profile of several apricot cultivars with molecular tracers in order to obtain objective data concerning the aromatic quality of this fruit was undertaken using headspace–solid phase microextraction (HS–SPME). Six apricot cultivars were selected according to their organoleptic characteristics: Iranien, Orangered, Goldrich, Hargrand, Rouge du Roussillon and A4025. The aromatic intensity of these varieties measured by HS–SPME–Olfactometry were defined and classified according to the presence and the intensity of grassy, fruity and apricot like notes. In the six varieties, 23 common volatile compounds were identified by HS–SPME–GC–MS. Finally, 10 compounds, ethyl acetate, hexyl acetate, limonene, β-cyclocitral, γ-decalactone, 6-methyl-5-hepten-2-one, linalool, β-ionone, menthone and (E)-hexen-2-al were recognized by HS–SPME–GC–O as responsible of the aromatic notes involved in apricot aroma and considered as molecular tracers of apricot aromatic quality which could be utilized to discriminate apricot varieties.     

Tests of potential functional barriers for laminated multilayer food packages. Part I: Low molecular weight permeants

The advent of the functional barrier concept in food packaging has brought with it a requirement for fast tests of permeation through potential barrier materials. In such tests it would be convenient for both foodstuffs and materials below the functional barrier (sub-barrier materials) to be represented by standard simulants. By means of inverse gas chromatography, liquid paraffin spiked with appropriate permeants was considered as a potential simulant of sub-barrier materials based on polypropylene (PP) or similar polyolefins. Experiments were performed to characterize the kinetics of the permeation of low molecular weight model permeants (octene, toluene and isopropanol) from liquid paraffin, through a surrogate potential functional barrier (25 μm-thick oriented PP) into the food simulants olive oil and 3% (w/v) acetic acid. These permeation results were interpreted in terms of three permeation kinetic models regarding the solubility of a particular model permeant in the post-barrier medium (i.e. the food simulant). The results obtained justify the development and evaluation of liquid sub-barrier simulants that would allow flexible yet rigorous testing of new laminated multilayer packaging materials.     

Analysis of benzo[a]pyrene in spiked fatty foods by second derivative synchronous spectrofluorimetry after microwave-assisted treatment of samples

A simple, rapid and inexpensive method has been developed for the determination of benzo[a     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. II: Certification study

This paper describes the second part of a project undertaken to develop certified mussel reference materials for paralytic shellfish poisoning toxins. In the first part two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin and decarbamoyl-saxitoxin in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the certification exercise. Fifteen laboratories participated in this certification study and were asked to measure saxitoxin and decarbamoyl-saxitoxin in rehydrated lyophilized mussel material and in a saxitoxin-enriched mussel material. The participants were allowed to use a method of their choice but with an extraction procedure to be strictly followed. The study included extra experiments to verify the detection limits for both saxitoxin and decarbamoyl-saxitoxin. Most participants (13 of 15) were able to meet all the criteria set for the certification study. Results for saxitoxin.2HCl yielded a certified mass fraction of <0.07 mg/kg in the rehydrated lyophilized mussels. Results obtained for decarbamoyl-saxitoxin.2HCl yielded a certified mass fraction of 1.59+/-0.20 mg/kg. The results for saxitoxin.2HCl in enriched blank mussel yielded a certified mass fraction of 0.48 +/- 0.06 mg/kg. These certified reference materials for paralytic shellfish poisoning toxins in lyophilized mussel material are the first available for laboratories to test their method for accuracy and performance.     

Announcing a new international peer-reviewed journal:Food Science and Human Wellness now accepting manuscript submission in English

<正>We are pleased to announce the launch of a new international peer-reviewed journal-Food Science and Human Wellness,ISSN 2213-4530,which is an open access journal,produced and hosted by Elsevier B.V.on behalf of Beijing Academy of Food Sciences.Food Science and Human Wellness is an international peer-reviewed English journal that provides a forum for the dissemination of the     

Chinese CTP Market

According to Printing and Printing Equipment Industries Association of China（PEIAC）＇s statistics to the plate manufucturer in China, in 2013, the actual offset plate production has reached 346 million square meters in China. Among them, the CTP production volume was 245 million square meters, up by 11% than that of last year; the total sales of the CTP plate was 239 million square meters, up by 13%.     

Preparatory Work of Print China 2015 is Going Smoothly

正Held at Guangdong Modern International Exhibition Center,Print China 2015 will cover 7exhibition halls,besides the original Hall No.3,4,5,6,7,the newly built F zone of Hall 3 will be used too.The total area will be140,000 square meters.Hall 3:Offset and large printing equipment,package printing equipment,post press