薄壁玻璃靶丸低温保气性能研究

对薄壁玻璃靶丸在液氮保存状态下保气性能进行了研究。实验结果表明 :在 -1 96℃环境中 ,薄壁靶丸的保气半寿命由常温的 3～ 1 0 d延长到 1 0 0～ 5 0 0 d左右 ,靶丸的表面粗糙度没有明显变化 ,能满足

Microstructure characteristics and corrosion behavior of metal inert gas welded dissimilar joints of 6005A modified by Sc and 5083 alloys

The corrosion behavior and microstructure characteristics of metal inert gas(MIG)welded dissimilar joints of the 6005A alloy modified with Sc(designated as 6005A+Sc)and the 5083 alloy were investigated using corrosion tests and microscopy techniques.Results show that the dissimilar joints exhibit strong stress corrosion cracking(SCC)resistance,maintaining substantial strength during slow strain rate tensile tests.Notably,the heat-affected zone(HAZ)and base metal(BM)on the 6005A+Sc side show superior performance in terms of inter-granular corrosion(IGC)and exfoliation corrosion(EXCO)compared to the corresponding zones on the 5083 side.The lower corrosion resistance of the 5083-BM and the 5083-HAZ can be attributed to the presence of numerous Al_(2)Mg_(3)phases and micro-scaled Al_(6)(Mn,Fe)intermetallics,mainly distributed along the rolling direction.Conversely,the enhanced corrosion resistance of the 6005A+Sc-BM and the 6005A+Sc-HAZ can be attributed to the discontinuously distributed grain boundary precipitates(β-Mg_(2)Si),the smaller grain size,and the reduced corrosive current density.

玉米胚芽面包面团的发酵性能

通过对不同玉米胚芽渣添加量的面包面团发酵体积的试验，分析了玉米胚芽渣添加量对面团保气性和成熟时间的影响。试验结果表明：玉米胚芽渣对面筋结构的影响以及酵母可利用的碳源量的变化直接影响到面团发酵的最大体积和发酵速度，随着胚芽渣添加量的增加，面团发酵后的最大体积减小，发酵时间缩短。当胚芽渣添加量（按质量计）不大于3％时，胚芽面包面团发酵的最大体积与面包专用粉基本相同，但当胚芽渣达到9%时，面团发酵的最大体积减小约18%。

国外流行的食品包装材料

目前国际上流行六种较为热门和有发展前途的食品包装材料。 高温杀菌塑料罐:材料组成PP-EVOH-PP,其特点在于夹层以EVOH为材料,保气性极为良好,保存期与罐头相同,在常温下保存两年,可取代目前的金属罐。此项材料在美国、日本均处于试生产阶段,并有专利。 微波炉、烤箱双用塑料盘:以结晶性PET为材料,可耐高温,用于微波炉及烤箱食品,用后即丢弃。此材料在美国发展快,现在60％家庭使用。

Microstructures and mechanical properties of metal inert-gas arc welded Mg-steel dissimilar joints

The joining of Mg alloy to steel was realized by metal inert-gas arc welding, and the weld thermal cycle characteristics and Mg-steel joints were investigated. The results show that the temperature distribution in the joints is uneven. Mg alloy welds present a fine equiaxed grain structure. There exists a transition layer consisting mainly of AlFe, AlFe3 and Mg（Fe, Al）2O4 phases at Mg/steel interface, and it is the weakest link in Mg？steel joints. The welding heat input and weld Al content have the significant effect on the joint strength. The joint strength increases with increasing the heat input from 1680 J/cm to 2093 J/cm, due to promoting Mg/steel interface reaction. When weld Al content is increased to 6.20%, the joint strength reaches 192 MPa, 80% of Mg alloy base metal strength. It is favorable to select the suitable welding heat input and weld Al content for improving joint strength.

Microstructure analysis and mechanical characteristics of tungsten inert gas and metal inert gas welded AA6082-T6 tubular joint: A comparative study

The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding （TIG） and metal inert gas welding （MIG） processes. The effect of welding processes was analysed based on optical microscopy image, tensile testing, and Vickers micro-hardness measurements. The results showed that the tensile strengths of the TIG-welded joints were better than those of the MIG-welded joints, due to the contribution of fine equiaxed grains formation with narrower spacing arms. In terms of joint efficiency, the TIG process produced more reliable strength, which was about 25% higher compared to the MIG-joint. A significant decay of hardness was recorded in the adjacent of the weld bead zone, shown in both joints, related to phase transformation, induced by high temperatures experienced by material. A very low hardness, which was about 1.08 GPa, was recorded in the MIG-weldcd specimens. The extent of the heat-affected-zone （HAZ） in the MIG-welded joints was slightly wider than those of the TIG-welded specimens, which corresponded with a higher heat input per unit length.

Effect of welding speed on microstructural characteristics and tensile properties of GTA welded AZ31B magnesium alloy

The effect of welding speed on tensile and microstructural characteristics of pulsed current gas tungsten arc welded（PCGTAW） AZ31 B magnesium alloy joints was studied. Five joints were fabricated using different levels of welding speeds（105-145 mm/min）. It was found that the joints fabricated using a welding speed of 135 mm/min yielded superior tensile properties compared to other joints. The formation of fine grains and uniformly distributed precipitates in the fusion zone are the main reasons for the superior tensile properties of these joints.

Effect of protective coal seam mining and gas extraction on gas transport in a coal seam

A gas–solid coupling model involving coal seam deformation,gas diffusion and seepage,gas adsorption and desorption was built to study the gas transport rule under the effect of protective coal seam mining.The research results indicate:(1) The depressurization effect changes the stress state of an overlying coal seam and causes its permeability to increase,thus gas in the protected coal seam will be desorbed and transported under the effect of a gas pressure gradient,which will cause a decrease in gas pressure.(2) Gas pressure can be further decreased by setting out gas extraction boreholes in the overlying coal seam,which can effectively reduce the coal and gas outburst risk.The research is of important engineering significance for studying the gas transport rule in protected coal seam and providing important reference for controlling coal and gas outbursts in deep mining in China.

Influence of welding processes on microstructure, tensile and impact properties of Ti-6Al-4V alloy joints

Titanium alloys have been successfully applied for aerospace, ship and chemical industries because they possess many good characteristics such as high specific strength, superior corrosion resistance and excellent high temperature resistance. Though these alloys show reasonable weldability characteristics, the joint properties are greatly influenced by the welding processes. Weld thermal cycle of the processes will control the weld metal solidification and subsequent phase transformation and resultant microstructure. The welded joints of Ti-6Al-4V alloy were fabricated by gas tungsten arc welding （GTAW）, laser beam welding （LBW） and electron beam welding （EBW） processes. The joints fabricated by EBW process exhibit higher strength compared with the GTAW and LBW joints; but the joints by GTAW process exhibit higher impact toughness compared with the LBW and EBW joints. The resultant tensile and impact properties of the welded joints were correlated with the weld metal microstructures.

Assessment of gas tungsten arc welding thermal cycles on Inconel 718 alloy

Heat moving source models along with transient heat analysis by finite element method were used to determine weld thermal cycles and isothermal sections obtained from the application of a gas tungsten arc welding beads on Inconel 718 plates. Analytical (Rosenthal’s thick plate model) and finite element results show an acceptable approximation with the experimental weld thermal cycles. The isothermal sections determined by numerical simulation show a better approximation with the experimental welding profile for double-ellipse model heat distribution than Gauss model. To analyze the microstructural transformation produced by different cooling rates in the fusion and heat affected zones, Vickers microhardness measurements (profile and mapping representation) were conducted. A hardness decrement for the heat affected zone (~200 HV0.2) and fusion zone (~240 HV0.2) in comparison with base material (~350 HV0.2) was observed. This behavior has been attributed to the heterogeneous solubilization process of the γ″ phase (nickel matrix), which, according to the continuous-cooling-transformation curve, produced the Laves phase,δ and MC transition phases, generating a loss in hardness close to the fusion zone.

Effect of welding processes on AA2219 aluminium alloy joint properties

AA2219 aluminium alloy square butt joints without filler metal addition were fabricated using gas tungsten arc welding （GTAW）, electron beam welding （EBW） and friction stir welding （FSW） processes. The effects of three welding processes on the tensile, fatigue and corrosion behaviour were studied. Microstructure analysis was carried out using optical and electron microscopes. The results show that the FSW joints exhibit superior tensile and fatigue properties compared to EBW and GTAW joints. It is also found that the friction stir welds show lower corrosion resistance than EB and GTA welds. This is mainly due to the presence of finer grains and uniform distribution of strengthening precipitates in the weld metal of FSW joints.

Biodiversity and Climate Change Adaptation in Australia:Strategy and Research Developments

Many countries are developing national strategies and action plans aimed at minimising the negative impacts of climate change on biodiversity.The purpose of this paper is to provide a brief overview not only of strategies and plans that have been developed in Australia,but also of research that has been carried out in Australia by the Commonwealth Scientific and Industrial Research Organisation(CSIRO) Climate Adaptation Flagship to assist the development of future strategies and plans.Major points are summarised from key policy documents such as the National Biodiversity and Climate Change Action Plan 2004-2007,and Australia's Biodiversity Conservation Strategy 2010-2030,as well as the 2009 report on "Australia's Biodiversity and Climate Change".Within the first three years of its existence,the Natural Ecosystems theme in CSIRO Climate Adaptation Flagship has carried out studies analysing impacts and identifying potential adaptations across the whole of Australia's vast terrestrial and marine environments.Techniques used in these studies could be applied easily in other countries and could assist the development of more effective national strategies and adaptation action plans for the conservation of biodiversity under climate change.

Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy TIG-welded joint

Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas(TIG)welded joint were analyzed in detail.In weld zone(WZ),α+θeutectic structure formed at grain boundaries with no precipitates inside the grains.In partially melted zone(PMZ),symbiotic eutectic or divorced eutectic formed at grain boundaries and needle-likeθ′phases appeared in the secondary heated zone.In over aged zone(OAZ),the coarsening and dissolution ofθ′phases occurred and mostθ′phases transformed intoθphases.In general heat affected zone(HAZ),θ′phases coarsened.Factors such as the strengthening phases,the grain size,the Cu content in matrix and the dislocation density can affect the mechanical properties in different regions of the joint.Moreover,a model describing the relationship between mechanical properties of the material and the volume fraction of precipitates,the average diameter of precipitates and the concentration of soluble elements was proposed.

Tracheobronchial Polyflex stents for the management of benign refractory hypopharyngeal strictures

AIM:To describe a modified technique for placement of a tracheobronchial self-expanding plastic stent(SEPS) in patients with benign refractory hypopharyngeal strictures in order to improve dysphagia and allow stricture remodeling.METHODS:A case series of four consecutive patients with complex hypopharyngeal strictures after combinedtherapy for laryngeal cancer,previously submitted to multiple sessions of dilation without lasting improvement,is presented.All patients underwent placement of a small diameter and unflared tracheobronchial SEPS.Main outcome measurements were improvement of dysphagia and avoiding of repeated dilation.RESULTS:The modified introducer system allowed an easy and technically successful deployment of the tracheobronchial Polyflex stent through the stricture.All four patients developed complications related to stent placement.Two patients had stent migration(one proximal and one distal),two patients developed phanryngocutaneous fistulas and all patients with stents in situ for more than 8 wk had hyperplastic tissue growth at the upper end of the stent.Stricture recurrence was observed at 4 wk follow-up after stent removal in all patients CONCLUSION:Although technically feasible,placement of a tracheobronchial SEPS is associated with a high risk of complications.Small diameter stents must be kept in place for longer than 3 mo to allow adequate time for stricture remodeling.

Influence of Different Filling Materials on Stiffness of a New Buffer Bag

A buffer bag mechanism is designed,which can provide axial impact protection under small displacement.The stiffness characteristics of the structure under impact load are studied.The stiffness of the mechanism and the internal pressure change of the buffer bag are compared and analyzed,when the filling materials are liquid and gas respectively.Finally,the influence of initial fluid bag pressure,bulk modulus and shell thickness on the stiffness of the mechanism and the change of bag pressure are studied.The results show that the stiffness of the liquid bag is better than that of the gas bag when the filler is liquid and gas;the liquid bag has obvious pressure rise after the mechanism is subjected to axial force by 300 kN,and the gas bag has almost no pressure rise;the change of bulk modulus,which is1000,1500,2000 and 2500 MPa,has an obvious effect on the liquid bag,and it is positively correlated with the stiffness of the mechanism.The change of gas modulus,which is 28 and 44,has little effect on the stiffness of the mechanism;the thickness of the buffer bag,which is 5,10 and 15 mm,also has an obvious effect on the stiffness.The stiffness of the liquid bag is greater,and the protection for flexible joint is better in the same condition.

Analysis on Policies of Oil and Gas in China

The Government has actively introduced oil and gas policies to promote the sustainable and healthy development of the industry it, 2017. The purposes of such policies are： to accelerate the reform of mineral resource royalties and advance the competitive transfer of mining rights; to promote the reform of the natural gas price, introduce cost supervision on long-distance natural gas pipeline enterprises in the area of gas pipeline transportation, and strengthen the regulation qf the distribution price; to liberalize the import qf crude oil in an orderly manner, increase the allowable volume of non-state trading crude oil imports, strengthen the supervision and periodically pause the approval of the right to use imported crude oil; and to enhance environmental protection.

Comparison of Magnetic Pulse Welding with Other Welding Methods

The paper explains the comparison of magnetic pulse welding method which belongs to non-conventional machining methods with other conventional and non-conventional welding methods which include brazing, explosive welding, ultrasonic welding, tungsten and metal inert gas and roll bonding. Magnetic pulse welding differs completely in technology when compared with conventional welding processes because the process is done with high velocity and without heat or consumable materials. It is better than other methods because it＇s cold process and can be done without any heat affect zone. In addition, there is no need for rework and post welding cleaning and there is no scrap problem. Magnetic pulse welding is a green process used to design and build light structure with high strength to reduce the weight and the energy. Magnetic pulse welding reduces the risk of corrosion by limiting the metallic interaction to just the two metals welded; therefore, it replaces the brazing method. Also, it is better than the explosive welding method because there is no risk of handling the explosive material and there is no noise. The part assembly by magnetic pulse welding is stronger than the parts assembly by tungsten and metal inert gas welding and it is easy to achieve a good aesthetic with high speed. Therefore, using magnetic pulse welding technology will not affect the environment.

Oncologic Trogocytosis Protects Tumour Stromal Cells from γδ Cell Cytotoxicity

Tumours progressively develop chemoresistance and immunoescape abilities thanks to support from their stromal microenvironment. In ovarian carcinomas, for instance, tumour-associated mesenchymal stem cells （TAMC） can transfer multi-drug-resistant proteins to develop metastases. However, since the microenvironment of such carcinomas is frequently infiltrated by both TAMC and γδ T lymphocytes, the consequences of interactions between these cell types were unclear. Here, we report that whilst γδ T lymphocytes were not activated when co-incubated in vitro with TAMC, their cell membranes were trogocytosed by the TAMC. Since TAMC constitutively express a low level of HLA class I, which is increased by trogocytosis of γδ cell-derived HLA class I, the interaction increased the expression of HLA class-I molecules on TAMC. In addition, γδ T lymphocytes are HLA-unrestricted cytolytic cells and their activity is regulated by inhibitory receptors （KIR） for self-HLA class I. Hence, although the lytic activity of γδ T lymphocytes for unrelated target cells was unaffected by trogocytosis, it spared the TAMC. Therefore, interactions between TAMC and cytolytic γδ T cells avoided the killing of these stromal cells due to an active transfer of their protective HLA class-I molecules. These results suggest that trogocytosis contributes to the maintenance of cancer-associated stromal cells.

Designing Trade Rules to Promote Climate Sustainability

Climate sustainability has become a key issue of our time. Measures protecting the environment, however, can have an impact on the competitiveness of domestic firms and on cross-border trade. Therefore, regulatory bodies should enlarge the scope of their policies and treat climate sustainability as global public good; based on such concept trade rules are to be designed in a way that allows a fair balancing between the diverse interests.

Microbial Aspects in Comparing Modified Atmosphere Packaging and Vacuum Packaging on Shelf Life of Fresh Bull Meat

The importance of meat preservation and various reports on different types of packaging, and to compare the effects of modified atmosphere packaging （MAP） and vacuum packaging （VP） on shelf life of flesh bull meat, and microbiological tests on meat together with some chemical and sensory tests was on tight observation. It was an experimental study, 96 samples were randomly packaged in two groups of MAP and VP equally. The package consists of five layers which are Polyvinylidin Chloride （PVDC）, Ethyl Vinyl Alcohol （EVOH）, Poly Ethylene （PE）, Linear Low Density Poly Ethylene （LLDPE）, and poly Amid （PA）, respectively. MAP meat with 700 mL of CO2 per kg of meat. The packaging were made in at-ameh-pars factory and transported in chilled condition to a well prepared refrigerator in National Research Institute of Food Science （NRIFS） of Shahidbeheshti University of Medical Sciences. These samples tested weekly, since first day after packaging, and week 2, 3, 4, 5, 6, 7, and 8. Microbial tests include Total Microbial, Coliform, Lactic Acid Bacteria, Pseudomonas Counts, and Clostridium. Chemical and sensory tests also carried out. Total volatile bases （TVN）, TBA, and pH as chemical analyses and color, odor, and weep as sensory analyses are also added. Results revealed that total microbial count was in standard range within the 6 weeks for VP, and 5 weeks for MAP technique. Other microbial factors including coliforms, lactic acid bacteria are less and somehow in chemical and sensory tests emphasized the microbial figures. recommended for meat packaging. similar pattern to total count, and no clostridia were found. By the way, The results showed that according to our existing facilities, VP is