An experimental analysis on the turnover time of railway freight transportation based on the impact strength of factors

Based on the factors impact strength model(FISM), we studied on calculation formulas of influence strength and key elements of FISM, and analyzed the turnover time of railway freight transportation of China. The results show that wagon transfer time is the most critical factor among the three subjective factors of wagons turnover time. The FISM based analysis of wagon transfer time show that the wagon turnover time is significantly correlated with transit time with resorting. Among the seven factors of detention time of transit time with resorting, the time of waiting to departing, converging, and waiting to break-up are key factors, while the time of make-up, break-up, arrival and departure are general factors. We carried out one empirical research based on the data of Baoji East Railway Station in 2015. The results of empirical research and FISM are consistent completely.

The effect of polymer type on electric breakdown strength on a nanosecond time scale

Based on the concepts of fast polarization, effective electric field and electron impact ionization criterion, the effect of polymer type on electric breakdown strength （EBD） on a nanosecond time scale is investigated, and a formula that qualitatively characterizes the relation between the electric breakdown strength and the polymer type is derived. According to this formula, it is found that the electric breakdown strength decreases with an increase in the effective relative dielectric constants of the polymers. By calculating the effective relative dielectric constants for different types of polymers, the theoretical relation for the electric breakdown strengths of common polymers is predicted. To verify the prediction, the polymers of PE （polyethylene）, PTFE （polytetrafluoroethelene）, PMMA （organic glass） and Nylon are tested with a nanosecond-pulse generator. The experimental result shows EBD （PTFE） 〉 EBD （PMMA） 〉 EBD （Nylon） 〉 EBD （PE）. This result is consistent with the theoretical prediction.

RHEOLOGICAL BEHAVIOUR FOR AN ANHYDRITE SPECIMEN AND DETERMINATION OF ITS LONG TIME STRENGTH

Based on the method of torsional creep, the creep laws of ananhydrite specimen are studied in this paper. When a shearing stressapplied to the specimen is less than a value, only the primary stagetakes place. How- ever, when the shearing stress is more than anothervalue, all the three stages of a creep curve, i. e. primary, steady-state and accelerated are exhibited.

Effect of infiltrating time on interfacial reaction and properties of tungsten particles reinforced Zr-based bulk metallic glass composites

The tungsten particles reinforced Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit 1 alloy) bulk metallic glass composites (BMGCs) were prepared by the melt infiltrating casting method with the infiltrating time of 1, 5 and 10 min, respectively. The changes of interfacial reaction and compression properties of the bulk metallic glass composites with different infiltrating times were studied. Results show that with the increase of infiltrating time, tiny nanocrystals are generated at the interfacial boundary of tungsten particles and the amorphous matrix, and the size of tiny crystals increases with the infiltrating time. When the infiltrating time is 10 min, polygonal crystals with a larger size are also generated within the amorphous matrix. The compressive strength of the composites also increases with the infiltrating time. When the infiltrating time is 10 min, the compressive strength of the composite reaches 2,030 MPa and the compression strain is 44%. The fracture morphology of the composite materials is in a vein-like pattern and the melting phenomenon is found on the fracture surface. In addition, the density of the shear bands during the compressive tests of the composite materials increases with the infiltrating time.

Influence of some rock strength properties on jaw crusher performance in granite quarry

The influence of rock strength properties on Jaw Crusher performance was carried out to determine the effect of rock strength on crushing time and grain size distribution of the rocks.Investigation was conducted on four different rock samples namely marble,dolomite,limestone and granite which were representatively selected from fragmented lumps in quarries.Unconfined compressive strength and Point load tests were carried out on each rock sample as well as crushing time and size analysis.The results of the strength parameters of each sample were correlated with the crushing time and the grain size distribution of the rock types.The results of the strength tests show that granite has the highest mean value of 101.67 MPa for Unconfined Compressive Strength(UCS) test,6.43 MPa for Point Load test while dolomite has the least mean value of 30.56 MPa for UCS test and 0.95 MPa for Point Load test.According to the International Society for Rock Mechanic(ISRM) standard,the granite rock sample may be classified as having very high strength and dolomite rock sample,low strength.Also,the granite rock has the highest crushing time(21.0 s) and dolomite rock has the least value(5.0 s).Based on the results of the investigation,it was found out that there is a great influence of strength properties on crushing time of rock types.

Reliability of the Ultimate Strength of Ship Stiffened Panel Subjected to Random Corrosion Degradation

Attentions have been increasingly paid to the influence of the corrosion on the ultimate strength of ship structures. In consideration of the random characteristics of the corrosion of ship structures, the method for the ultimate strength analysis of the ship stiffened panel structure subjected to random corrosion degradation is presented. According to the measured corrosion data of the bulk carriers, the distribution characteristics of the corrosion data for the stiffened panel on the midship deck are analyzed, and a random corrosion model is established. The ultimate strength of the corroded stiffened panel is calculated by lhe nonlinear finite element analysis. The statistical descriptions of the ultimate strength of the corroded stiffened panel are defined through the Monte Carlo simulations. A formula is proposed on the ultimate strength reduction of the stiffened panel as a function of the corrosion volume. The reliability analysis of the ultimate strength of the corroded deck stiffened panel is performed. It shows that both the corrosion data of the deck stiffened panel and the ultimate strength of the random corroded deck stiffened panel follow the log-normal distribution. The ultimate stress ratio of the stiffened panel is inversely proportional to the corrosion volume ratio.

A review of nuclear magnetic resonance(NMR) technology applied in the characterization of polymer gels for petroleum reservoir conformance control

Polymer gel systems have been widely applied to control excessive water and improve oil recovery(IOR)in petroleum reservoirs.They are usually divided into two main types,in-situ cross-linked polymer gels,and pre-formed polymer gels.In recent years,nuclear magnetic resonance(NMR) technology has been gradually applied to the research of polymer gel systems due to its unique analysis advantages.This paper is intent to review these works systematically.For in-situ cross-linked polymer gel systems,NMR can be used to characterize the chemical structure changes of the polymer,the cross-linker,and the auxiliary agent in the formulation of the polymer gel systems.Moreover,the gelation time and the gel strength of the in-situ cross-linked polymer gel systems can also be measured by NMR.For pre-formed polymer gels,NMR can be employed to detect the chemical structure of the designed products.Last,the NMR method can evaluate the plugging,water control,and oil improvement performance of the polymer gels in porous media without using dopants.This review can help readers build a more systematic understanding of the application of NMR technology in polymer gel systems for IOR and help re searchers to more deeply study the performance of polymer gel systems.

Experimental study on remodeling strength of granular materials under different loads and lengths of time

Remodeled clay and sand rock specimens were prepared by designing lateral confinement and water drainage experiments based on the stress exerted on granular materials in a waste dump.An in situ test was conducted in an internal waste dump;the physical and mechanical parameters of the remodeled rock mass dumped at different time and depths were measured.Based on statistics,regression analysis was performed with regard to the shearing stress parameters acquired from the two tests.Other factors,such as remodeling pressure(burial depth),remodeling time(amount of time since waste was dumped),and the corresponding functional relationship,were determined.Analysis indicates that the cohesion of the remodeled clay and its remodeling pressure are correlated by a quadratic function but are not correlated with remodeling time length.In situ experimental results indicate that the shear strength of reshaped granular materials in the internal dump is positively correlated with burial depth but poorly correlated with time length.Cohesion Cand burial depth H follow a quadratic function,specifically for a short time since waste has been dumped.As revealed by both in situ and laboratory experiments,the remodeling strength of granular materials varies in a certain pattern.The consistency of such materials verifies the reliability of the remodeling experimental program.

Stochastic synchronization for time-varying complex dynamical networks

This paper studies the stochastic synchronization problem for time-varying complex dynamical networks. This model is totally different from some existing network models. Based on the Lyapunov stability theory, inequality techniques, and the properties of the Weiner process, some controllers and adaptive laws are designed to ensure achieving stochastic synchronization of a complex dynamical network model. A sufficient synchronization condition is given to ensure that the proposed network model is mean-square stable. Theoretical analysis and numerical simulation fully verify the main results.

Network-based structure optimization method of the anti-aircraft system

The anti-aircraft system plays an irreplaceable role in modern combat. An anti-aircraft system consists of various types of functional entities interacting to destroy the hostile aircraft moving in high speed. The connecting structure of combat entities in it is of great importance for supporting the normal process of the system. In this paper, we explore the optimizing strategy of the structure of the anti-aircraft network by establishing extra communication channels between the combat entities.Firstly, the thought of combat network model(CNM) is borrowed to model the anti-aircraft system as a heterogeneous network. Secondly, the optimization objectives are determined as the survivability and the accuracy of the system. To specify these objectives, the information chain and accuracy chain are constructed based on CNM. The causal strength(CAST) logic and influence network(IN) are introduced to illustrate the establishment of the accuracy chain. Thirdly, the optimization constraints are discussed and set in three aspects: time, connection feasibility and budget. The time constraint network(TCN) is introduced to construct the timing chain and help to detect the timing consistency. Then, the process of the multi-objective optimization of the structure of the anti-aircraft system is designed.Finally, a simulation is conducted to prove the effectiveness and feasibility of the proposed method. Non-dominated sorting based genetic algorithm-Ⅱ(NSGA2) is used to solve the multiobjective optimization problem and two other algorithms including non-dominated sorting based genetic algorithm-Ⅲ(NSGA3)and strength Pareto evolutionary algorithm-Ⅱ(SPEA2) are employed as comparisons. The deciders and system builders can make the anti-aircraft system improved in the survivability and accuracy in the combat reality.

Preparation for Retarding and High Early Strength Concrete

The primary objective of this research was to determine optimum dosage of mixing concrete containing plasticizers and fly ash, consistent with desirable structural grade concrete properties. Factorial tests were also conducted to investigate the four main factors： water-cementing materials ratio, water content, content of superplasticizers （SP） and fly ash content. It was found that the requirement for setting time played the dominant role in shrinkage and anti-cracking, and fly ash played a critical role in workability and reducing heat of hydration but showed insignificant effects on slump, early strength and initial setting time of concrete.

Optimization of the Annealing Parameters for Improved Tensile Properties in Cold Drawn 0.12 wt% C Steel

Drawn low carbon steel is characterized by brittle fracture. These defects are associated with the poor ductility and high strain hardening due to the cold work. There is a need therefore to determine optimum heat treatment parameters that could ensure improved toughness and ductility. Determining the optimum annealing parameters ensures valued recrystallization and also minimizes grain growth that could be detrimental to the resulting product. 40% and 55% cold drawn steels were annealed at temperatures 500℃ to 650℃ at intervals of 50℃ and soaked for 10 to 60 minutes at interval of 10 minutes to identify the temperature range and soaking time where optimum combination of properties could be obtained. Tensile test and impact toughness experiments were done to determine the required properties of the steel. Polynomial regression analysis was used to fit the properties relationship with soaking time and temperatures and the classical optimization technique was used to determine the minimum soaking time and temperature required for improved properties of the steel. Annealing treatment at 588℃ for 11 minutes at grain size of 44.7 mm can be considered to be the optimum annealing treatment for the 40% cold drawn 0.12 wt% C steel and 539℃ for 17 minutes at grain size of 19.5 mm for the 55% cold drawn 0.12 wt% C steel.

Laboratory creep tests for time-dependent properties of a marble in Jinping Ⅱ hydropower station

In order to investigate the time-dependent behaviors of deep hard rocks in the diversion tunnel of Jinping II hydropower station, uniaxial creep tests were carried out by using the triaxial testing machine RC-2000. The axial compressive load was applied step by step and each creep stage was kept for over several days. Test results show that： （1） The lateral deformation of rock specimens is 2-3 times the axial compressive deformation and accelerates drastically before damage, which may be employed as an indicator to predict the excavation-induced instability of rocks. （2） The resultant deformation changes from compression to expansion when the Poisson＇s ratio is larger than 0.5, indicating the starting point of damage. （3） In the step-loading stages, the Poisson＇s ratio approximately remains constant; under constantly imposed load, the Poisson＇s ratio changes with elapsed time, growing continuously before the specimen is damaged. （4） When the applied load reaches a certain threshold value, the rock deteriorates with time, and the strength of rocks approximately has a negative exponent relation with time. （5） The failure modes of the deep marble are different in long- and short-term loading conditions. Under the condition of short-term loading, the specimen presents a mode of tensile failure; while under the condition of long-term loading, the specimen presents a mode of shear failure, followed by tensile failure.

Determination of the Compressive Strength of Concrete from Binary Cement and Ternary Aggregates

One of the most active fields of research embraced by many disciplines, including civil engineering, is material reuse. It is known that ceramics wastes from various construction and demolition sites and manufacturing processes are dumped away into the environment, resulting in the pollution that threatens both agriculture and public health. Therefore, the utilization of ceramic waste in construction industries would help to protect the environment from such pollutions. This paper presents the results of an experimental analysis of the effects of partial replacement of coarse aggregates, fine aggregates, and ordinary Portland cement with the ceramic waste, at percentage levels of 0%, 5%, 10%, and 20%;and the assessment of the strength property of the concrete produced with optimum combination of the constituents. Compressive strengths of this concrete were determined at 7, 28, and 56 days of curing using 150 × 150 × 150 mm cube specimens. Test results showed that the compressive strength of the concrete decreased as the content of ceramic waste present in the concrete increased. Thus, concrete produced from the partial replacement of ordinary Portland cement with ground ceramics gave compressive strengths of 16.6 N/mm2 and 13.4 N/mm2 at 5% and 20% replacement levels respectively. Similarly, the compressive strengths of concrete from the partial replacement of sand with fine ceramics were 13.8 N/mm2 and 10.9 N/mm2 for 5% and 20% replacements respectively. For 5% and 20% replacement levels of granite with crushed ceramics in concrete gave a compressive strength of 11.6 N/mm2 and 9.7 N/mm2, respectively. For concrete derived from the partial replacement of stone dust with fine ceramics, the compressive strengths were 19.6 N/mm2 and 18.10 N/mm2 respectively for 5% and 20%. For concrete produced from the partial replacement of bush gravel with crushed ceramics, the compressive strengths obtained were 10.9 N/mm2 and 8.98 N/mm2 respectively for 5% and 20% replacements. Finally, the concrete derived from the optimal combination of binary cement, ternary fine, and coarse aggregate had a compressive strength of 22.20 N/mm2 which is higher than the compressive strength of the control mixture at 18.10 N/mm2. The result of the ANOVA carried out showed that the compressive strength obtained for each partial replacement of different components is statistically significant at 5%, i.e. the change in the compressive strength of the concrete produced is due to the presence of ceramic waste.

The Progress of the Study on the Effect of Vibration Training on Muscle Strength Exercise

Vibration training is more and more extensively applied to the field of strength training. It, as a beneficial supplement to the traditional strength, is able to improve specific strength or the strength of weak positions, for the purpose of achieving the muscle strength development in an all-round way. In this paper, the anatomy, physiology, and biomechanics foundations for vibration training to increase muscle strength are mainly analyzed, and then the principle of vibration training to increase muscle strength is further expounded, and also the increase of muscle strength is discussed from the aspects such as vibration frequency, vibration amplitude, vibration posture, vibration intermittent time, and vibration mode, so as to clarify the domestic and foreign progress of the study on vibration training.

Curing Process of Phenol Formaldehyde Resin for Plywood under Vacuum Conditions

The study characterized the curing behaviors of phenol formaldehyde(PF)resin under different vacuum degrees and explored the properties of 9-ply plywood panels hot-pressed under both vacuum and atmospheric conditions.The changes in core temperature and moisture content of the plywood mats during hot pressing were investigated as well.It was found that the gel times and gel temperatures of PF resin decreased with the increase of vacuum degree using a self-made device.FTIR spectra indicated the degree of polycondensation of hydroxymethyl gradu-ally increased with the increase in temperature.It was also observed that a higher degree of vacuum led to a slower polycondensation reaction rate of PF resin.During different hot-pressing processes,the bonding strengths in the innermost and uppermost gluelines of the vacuum hot-pressed plywood panels were up to 30%–50%higher than their counterparts of conventional hot-pressed products.A less difference in the bonding strengths between these two gluelines was also observed for vacuum hot-pressed products.In addition,the core of vacuum hot-pressed plywood was found to have a greater heating rate and higher temperature at thefinal stage of hot pressing,which was beneficial to cure the PF resin.The results from this study indicate a promising potential of introducing a vacuum during hot pressing to improve the quality and productivity of plywood products and provide a basis for adopting vacuum to hot press wood composites.

Effect of Soaking Time on the Mechanical Properties of Annealed Cold-Drawn Low Carbon Steel

The paper presents the results of investigation on the effect of soaking time on the yield strength, ductility and hardness properties of annealed cold-drawn low carbon steel. The low carbon steel cold-drawn at 40% deformation was annealed at 900 deg Celsius for soaking times of 10, 20, 30, 40, 50 and 60 minutes. Tensile, charpy and Brinnel hardness tests were conducted to determine the yield strengths, tensile strengths, impact strengths, ductility and hardness of the annealed steel with increasing soaking time. The yield strength, tensile strength, hardness and impact strength of the steel showed a continuous drop in value with increasing soaking time up to 60 minutes with a steep drop between 30 and 40 minutes. Ductility values followed the same decreasing trend up to 40 minutes soaking time after which the values started increasing again till 60 minutes soaking time. There was a linear relationship between the tensile strength and hardness of the material for different soaking times. This linear relationship was also observed for yield strength and hardness of the material.

改性磷石膏作水泥缓凝剂的研究

为将磷石膏应用于水泥缓凝剂,采用水洗等方式对磷石膏进行预处理。确定水洗磷石膏的最优用水量和水洗时间。对比研究天然石膏、原状磷石膏和改性磷石膏对硅酸盐水泥凝结时间和强度的影响。通过水化热、XRD和SEM分析改性磷石膏对硅酸盐水泥水化特性的影响机理。结果表明,磷石膏在液固比为4和水洗时间为25 min条件下水洗效果最佳;生石灰单掺以及生石灰和膨润土复掺对磷石膏中可溶性磷和可溶性氟表现出较好的固化效果;水洗改性后磷石膏可有效缩短水泥的凝结时间,提高早期强度,其中生石灰与膨润土按2∶1复掺水洗改性后磷石膏用于硅酸盐水泥,水泥初、终凝时间比使用原状磷石膏时缩短了50%和31%;改性磷石膏制备的水泥早期水化速率正常,水泥固结体结构致密,缺陷较少,早期强度高。

复合型水性丙烯酸树脂乳液的制备和性能

采用低玻璃化转变温度、高分子量的丙烯酸树脂乳液与高玻璃化转变温度、低分子量的丙烯酸树脂分散体混合的方式,制备了无交联剂水性丙烯酸树脂复合乳液,用于彩印包装纸与塑料薄膜的热复合。以丙烯酸、丙烯酸丁酯、苯乙烯、丙烯酸羟乙酯等为原料,采用种子乳液聚合法制备了相对分子质量(1.48~1.84)×10^(5)、玻璃化转变温度(T_(g))﹣20~﹣40℃的丙烯酸酯乳液。以丙烯酸、丙烯酸丁酯、苯乙烯、α-甲基苯乙烯、马来酸单酯等为原料,采用本体聚合法制备了相对分子质量(1.34~1.65)×10^(4)、T_(g) 20~45℃、软化点80~105℃的固体树脂,进一步采用自乳化方法将固体树脂制备成树脂水分散体。考察了不同Tg的丙烯酸酯乳液与水分散体以不同比例混配后的乳液混合体的性能。研究结果表明,T_(g)为﹣27.6℃的丙烯酸酯乳液与Tg为28.2℃固体树脂的分散体以质量比8:2混合后,用于PET膜-黑色印刷纸的热复合,剥离强度达到5.6 N/25 mm,持粘性达270 h,可以充分满足覆膜材料的附着力和耐压纹等性能要求。

AlN基板表面状态对AlN-AMB覆铜板剥离强度影响机理的研究

为了探究AlN基板表面状态对AlN-AMB覆铜板剥离强度影响的机理,对研磨型和即烧型两类AlN基板表面的微观形貌及其制备的AlN-AMB覆铜板界面反应层、断面和断层微观显微结构进行分析。结果表明,即烧型AlN基板表面平整、致密,其制备的AlN-AMB覆铜板界面反应层平整、致密,铜与AlN基板剥离的断层位于基体内部,Cu发生明显塑性变形,剥离强度高达19.053 N/mm。而研磨型AlN基板表面存在微裂纹和碎晶粒,由其制备的AlN-AMB覆铜板界面反应层凹凸不平,且不连续,钎料渗入AlN基板亚表层的微裂纹中,易于诱发应力集中,铜与AlN基板剥离的断层位于AlN基体的亚表层,Cu塑性变形小,剥离强度只有5.789 N/mm。