谈“双头蜗杆车削”的技能训练

本文针对“双头蜗杆车削”实习课题的教学实践以及训练中出现的问题进行分析,提出了有利于提高学生技能训练水平的方法。

独立董事和监事会:替代抑或互补?——基于公司风险的治理效率检验

以公司风险为切入点,以1999—2012年我国2 375家上市公司19 469个年度观测值为研究样本,检验独立董事和监事会的治理效率,并通过交互效应考察二者之间的关系,研究发现:(1)导入独立董事制度前监事会治理效率微弱,导入独立董事制度后监事会治理效率有了明显改善,说明从国家宏观层面看,引入独立董事制度,增加了治理监督的制度供给,优化了制度结构,获得了制度竞争带来的红利。(2)勤勉履职的独立董事有利于降低公司风险,表明在我国公司治理结构中设立独立董事具有经济合理性。(3)独立董事和监事会两者之间是一种替代关系,而非互补关系,说明从公司微观层面看,独立董事和监事会存在职能冲突,并不利于降低公司风险。采用独立董事和监事会"双头"监督模式难以从根本解决我国上市公司治理监督的有效性问题,最佳的选择是,允许独立董事制度和监事会制度同时并存、共同竞争,许可公司根据自身情况选择合适的内部监督模式。

东亚经济格局的变动及其对两岸经贸关系的影响

20世纪90年代以来,东亚经济格局发生重大变化,由日本″单极″变成了中日″双头″。这一变化导致两岸经济从单方面的依赖到互相依赖;在贸易平衡、外汇储备等方面台湾对祖国大陆更加依赖;台商投资从短期经营到本土化经营;两岸产业分工从产业间发展到产业内、产品内;两岸从企业间一般技术合作到行业组织间标准方面的合作。

改进农村审计模式新思路

我国农村现行审计模式面临协调机制差、国家审计不到位和乡镇经管站内部审计独立性差的问题。文章基于现有文献中审计模式的梳理和评述,提出改进的农村审计模式新思路以及该模式运行的保障机制。

Effect of welding current on morphology and microstructure of Al alloy T-joint in double-pulsed MIG welding

The effect of current on the morphology of Al alloy T-joint in double-pulsed metal inert gas（DP-MIG） welding process was investigated by simulation and experiment.A three-dimensional finite element model and the DP-MIG heat source of double-ellipsoidal volumetric model were developed to simulate the temperature and stress fields under different welding conditions.The macro-morphology and microstructure of welding joints at the corresponding currents were observed in the experiment.The results show that the best condition is at an average current of 90 A and current difference of 40 A,when the maximum temperature is 200 °C higher than the fusion points,with the temperature difference of about 100 °C and stress change of 10 MPa between thermal pulse and thermal base.Under these conditions,Al alloy T-joint with proper fusion condition has smooth fish-scale welding appearance and finer microstructure.Furthermore,the thermal curves and stress distribution in the experiment are consistent with those in the simulation,verifying the precision of the welding simulation.

高职院校教师党支部书记双带头人培育实践与探索

近年来,在党和国家的高度关注与重视下,高职院校不断建立、发展教师党支部书记工作室,使得“双带头人”培育的重要性得到显著提高。这就需要高职院校的教师开展全新的教学方法,教师对自身的工作方式进行实践,对教学方法进行探索。基于此,本文主要对党支部书记“双带头人”培育的关键点进行分析,对“双带头人”培育的实践进行相关分析。

Formation, microstructure and mechanical properties of double-sided laser beam welded Ti-6Al-4V T-joint

The T-joints of Ti?6Al?4V alloy were manufactured by double-sided synchronized laser beam welding with the homologous filler wire. The formation, microstructure and mechanical properties of welded joints as well as the correlations of each other were investigated. The results indicate that the quality of weld seams is good without defects such as discontinuity, beading, visible cracks or porosity, which is linked to the steady molten pool behavior and droplet transition. The morphologies of the heat affected zone (HAZ) located on the skin and stringer are disparate. The microstructure of the HAZ and fusion zone (FZ) is mainly comprised of acicular martensiticα′ phases. The microhardness of the HAZ and FZ is higher than that of the base metal (BM) and reaches a maximum value at the HAZ near FZ on the stringer. The tensile specimens along the skin and stringer fractured at the BM with ductile fracture surfaces.

A new probe for atmospheric electric field mill

A new probe for atmospheric electric field mill is introduced.It consists of three parts：signal acquisition circuit for atmospheric electric field,preamplifier circuit and phase sensitive detection circuit.The signal acquisition circuit adopts the double-stator structure to form differential input circuit,thus double-precision is obtained.Preamplifier circuit is made of current-to-voltage （I-V） conversion circuit,differential amplifier circtuit and secondary amplifying circuit.The polarity of electric field is obtained via phase sensitive detection circuit.Simulation results are obtained using Multisim,and the feasibility of the designed probe is verified.

Design methods of headed studs for composite decks of through steel bridges in high-speed railway

Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure,mechanical characteristics and transmission routes of deck loads.The simplified calculation models were brought out for the stud design of the longitudinal girders and transverse girders in the composite floor system of Nanjing Dashengguan Yangtze River Bridge (NDB).Studs were designed and arranged by taking the middle panel of 336 m main span for example.The results show that under deck loads,the longitudinal girders in the composite floor system of through steel bridges are in tension-bending state,longitudinal shear force on the interface is caused by both longitudinal force of "The first mechanical system" and vertical bending of "The second mechanical system",and studs can be arranged with equal space in terms of the shear force in range of 0.2d (where d is the panel length) on the top ends.Transverse girders in steel longitudinal and transverse girders-concrete slab composite deck are in compound-bending state,and out-of-plane bending has to be taken into account in the stud design.In orthotropic integral steel deck-concrete slab composite deck,out-of-plane bending of transverse girders is very small so that it can be neglected,and studs on the orthotropic integral steel deck can be arranged according to the structural requirements.The above design methods and simplified calculation models have been applied in the stud design of NDB.

Pricing decision of green supply chain under the game competition of duopolistic retailers

In order to evaluate the impact of green production introduced by the manufacturer and study the competitive strategy between two retailers,four strategic models among diverse retailers,i.e.,Cournot,Stackelberg and two cases of collusion,are constructed.The optimal decision is obtained by the game theory and numerical analysis.The results indicate that the manufacturer's marginal profitability is no less than that of the two retailers.However,due to the manufacturer's green cost,the downstream profitability of the supply chain may exceed the upstream manufacturer's profitability.The retailers'Cournot behavior causes the manufacturer to acquire the highest profitability and set the highest green level.However,there is an opposite result in collusion.Two retailers will choose Cournot pricing when the consumer's green sensitivity is higher than a threshold.When consumers are more sensitive to the price difference of products,retailers prefer collusion,and then choose the Stackelberg behavior.Manufacturers'profitability will increase as competition among retailers intensifies.Proper competition allows two duopolistic retailers to acquire a higher profitability.

Numerical simulation of cyclic behavior of double sand lenses and corresponding liquefaction-induced soil settlement

A two-dimensional numerical model was used to explain the liquefaction mechanism of double sand lenses and the corresponding soil deformation due to the cyclic loading. Moreover, in order to investigate the influences of the soil characteristics and input loading data a parametric study was carried out on the essential parameters affecting the soil settlement, and so the variation of these parameters with the corresponding displacements was mainly examined. At last, the results obtained from the numerical analyses of double sand lenses and a continuous sand layer with similar characteristics were compared with those of an estimating method proposed by ISHIHARA and YOSHIMINE. The comparisons show that the settlements due to liquefaction of the continuous sand layer in both numerical and the estimating method are in a good agreement with and are obviously greater than those of double sand lenses.

A Double Shot Noise Process and Its Application in Insurance

The authors consider a compound Cox model of insurance risk with the additional economic assumption of a positive interest rate. As the authors note a duality result relating a compound Cox model of insurance risk with a positive interest rate and a double shot noise process, the authors analyze a double shot noise process systematically for its theoretical distributional properties, based on the piecewise deterministic Markov process theory, and the martingale methodology. The authors also obtain the moments of aggregate accumulated/discounted claims where the claim arrival process follows a Cox process with shot noise intensity. Removing the parameters in a double shot noise process gradually, the authors show that it becomes a compound Cox process with shot noise intensity, a single shot noise process and a compound Poisson process. Numerical comparisons are shown between the moments （i.e. means and variances） of a compound Poisson model and their counterparts of a compound Cox model with/without considering a positive interest rate. For that purpose, the authors assume that claim sizes and primary event sizes follow an exponential distribution, respectively.

Effect of pin penetration depth on double-sided friction stir welded joints of AA6061-T913 alloy

Friction stir welding (FSW) of aluminum alloys is currently utilized in several modern industries. The joints must have sufficient elastic?plastic response and formability levels similar to that of the base metal. In this work, double-sided FSW of AA6061 sheet was compared with its conventional single-sided one. An adjustable tool with different pin lengths (50%?95% of the sheet thickness) was used to perform the double-sided welds. Macro- and micro-structures, strength, and hardness of the joints were investigated to determine the optimum pin penetration depth. The best results were obtained for a double-sided joint made by a pin length equal to 65% of the sheet thickness, which showed an increase of 41% in the ultimate tensile strength compared with the single-sided joint.

Clinical Application of Double-hand Needling Manipulation

Double-hand manipulation is a needling technique, with which No. 30 filiform needles of various lengths are selected and inserted into the affected part of the body in opposite directions or symmetrically upward-downward, rightward- leftward, anteriorly-posteriorly to the point, followed by needle twirling with both hands. When the two opposite needle tips are twirled to a certain degree, the soreness, warm, numbness, and distending needling sensation tends be connected in a line, forming a rather strong needling sensation. After such manipulation for some time, the needles are retained for 30 min., during which the needle manipulation is given 3-5 times at intervals. This needling treatment is given once daily. The author of this article has adopted this manipulation method in the acupuncture treatment of various diseases with quite satisfactory results. Some of the sample cases are listed as follows.

Impacts of trade-in program on duopoly competition with product quality differentiation and secondhand market

Considering the existence of the secondhand market and the implementation of trade-in program,the competition models between two manufacturers who produce the same products at various qualities are developed by the Nash game,and the impacts of the trade-in program from the perspectives of the demands,profits,marginal profits of manufacturers and the net costs of consumers are investigated.It finds that the trade-in program has different impacts when it is implemented by different manufacturers.When the low-quality manufacturer implements the program,it is always beneficial to himself and consumers but harmful to the high-quality manufacturer.However,when the program is implemented by the high-quality manufacturer,it can be beneficial to the low-quality manufacturer as well as to the implementer but harmful to consumers if the transaction cost of the consumer selling the used product in the secondhand market is low enough.Furthermore,with the increase in transaction cost,it also becomes harmful to the low-quality manufacturer and beneficial to consumers,which is the same as in the case that the low-quality manufacturer implements the trade-in program.The impacts of related parameters on the demands,marginal profits of manufacturers and the net costs of consumers are also analyzed.

Seismic Behavior of Confined RC ColumnComposite Beam Joints

In order to evaluate the seismic behavior of confined RC column-composite beam joints, five interior joints were tested under low cyclic reversed load. The weakening extent of flanges, the number of studs, and whether to reinforce weakened flanges were used as parameters in designing these five joints. Failure characteristics, hysteretic curves, skeleton curves, ductility, energy dissipation, strength degradation, and stiffness degradation were analyzed. The test results revealed that the steel beam flanges in the joints were equivalent to the tie rod. Weakened flanges resulted in poor seismic behavior; however, the seismic behavior could be improved by increasing studs and reinforcing weakened flanges. The joint steel plate hoops, equivalent to stirrups, did not yield when the maximum load was reached, but yielded when the failure load was reached for the joints with shear failure. Increasing stud-type joints and reinforcing flange-type joints ensured good seismic behavior and met project requirements. Based on the experimental results, the failure mechanism of the joints was discussed, and the shear capacity equations of the joints was presented.

Effect of reverse dual rotation process on properties of friction stir welding of AA7075 to AISI304

The friction stir lap welding of AISI304 stainless steel to AA7075 aluminium alloy was investigated using the conventional friction stir welding (C-FSW) and the reverse dual rotation friction stir welding (DR-FSW) processes. In order to reduce the heat input, a dual rotation tool with a lower shoulder rotating speed was used. The results showed that both processes provide welds with excellent appearance and free of internal defects. The use of the DR-FSW process with the tool shoulder rotating reversely at low speed results in larger grain refinement in the nugget and less change in the microstructure of the aluminium alloy than using the C-FSW. The use of DR-FSW process at low speed of rotation allows to reduce the amount of intermetallic compounds in the welding interface, but does not prevent their formation. Although DR-FSW welding exhibits tensile strength superior to that achieved with the conventional process (C-FSW), both exhibit brittle behaviour with fracture at the weld interface.

A two-phase tabu search approach to scheduling optimization in container terminals

An optimization model for scheduling of quay cranes (QCs) and yard trailers was proposed to improve the overall efficiency of container terminals. To implement this model, a two-phase tabu search algorithm was designed. In the QCs scheduling phase of the algorithm, a search was performed to determine a good QC unloading operation order. For each QC unloading operation order generated during the QC's scheduling phase, another search was run to obtain a good yard trailer routing for the given QC's unloading order. Using this information, the time required for the operation was estimated, then the time of return to availability of the units was fed back to the QC scheduler. Numerical tests show that the two-phase Tabu Search algorithm searches the solution space efficiently, decreases the empty distance yard trailers must travel, decreases the number of trailers needed, and thereby reduces time and costs and improves the integration and reliability of container terminal operation systems.

Plate reinforced square hollow section X-joints subjected to in-plane moment

The static test of 13 square hollow section(SHS) X-joints with different β and different types of plate reinforcement under in-plane moment in brace was carried out. Experimental test schemes, failure modes of specimens, moment-vertical displacement curves, moment-deformation of the chord, and strain strength distribution curves were presented. The effect of β and plate reinforcement types on in-plane flexural property of SHS X-joints was studied. Results show that punching shear of chord face disappears, brace material fracture appears and concave and convex deformation of chord decrease when either collar plates or doubler plates were welded on chord face. Moment-vertical displacement curves of all specimens have obvious elastic, elastic-plastic and plastic stages. As β increases, the in-plane flexural ultimate capacity and initial stiffness of joints of the same plate reinforcement type increase, but ductility of joints decreases. With the same β, the in-plane flexural initial stiffness and ultimate capacity of doubler plate reinforced joints, collar plate reinforced joints, and unreinforced joints decrease progressively. Thickness of reinforcement plate has no obvious effect on in-plane flexural initial stiffness and ultimate capacity of joints. As thickness of reinforcement plate increases, the ductility of reinforced X-joints decreases. The concave and convex deformation of every specimen has good symmetry;as β increases, the yield and ultimate deformation of chord decrease.