Effect of strain rate on the compressive deformation behaviors of lotus-type porous copper

Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10-3–2400 s-1 with the compressive direction parallel to the pores. A GLEEBLE-1500 thermal-mechanical simulation system and a split Hopkinson pressure bar (SHPB) were used to investigate the effect of strain rate on the compressive deformation behaviors of lotus-type porous copper. The influence mechanism of strain rate was also analyzed by the strain-controlling method and by high-speed photography. The results indicated that the stress-strain curves of lotus-typed porous copper consist of a linear elastic stage, a plateau stage, and a densification stage at various strain rates. At low strain rate (< 1.0 s-1), the strain rate had little influence on the stress-strain curves; but when the strain rate exceeded 1.0 s-1, it was observed to strongly affect the plateau stage, showing obvious strain-rate-hardening characteristics. Strain rate also influenced the densification initial strain. The densification initial strain at high strain rate was less than that at low strain rate. No visible inhomogeneous deformation caused by shockwaves was observed in lotus-type porous copper during high-strain-rate deformation. However, at high strain rate, the bending deformation characteristics of the pore walls obviously differed from those at low strain rate, which was the main mechanism by which the plateau stress exhibited strain-rate sensitivity when the strain rate exceeded a certain value and exhibited less densification initial strain at high strain rate.     

Influence of the Indonesian Throughflow on the upwelling off the east coast of South Java

A wave-tide-circulation coupled model is used to simulate upwelling off the south coast of Java, Indone- sia. The results show that the vertical velocity off East Java is stronger than other parts in this area. The strongest vertical velocity is located approximately at 80 m depth. The annual averaged values of upwelling are 2.3 × 10-6 and 1.06 × 10-5 m/s for south of West Java and south of East Java, respectively. The vertical velocity from the model shows that upwelling off West Java has seasonal variability, while it is quite steady and strong off East Java. Additional numerical experiments show that the wind is not the dominant factor for the steady upwelling off the southern part of East Java. It is then hypothesized that the Indonesian Throughflow （ITF） may be responsible for the upwelling. To test this hypothesis, two scenarios are implemented, both of which block the outflow of the ITF. Sensitive study shows that the ITF plays a key role in the formation of East Java upwelling. The effect of the ITF can account for about 55 %-65 % of the upwelling.     

Research and design of the main equipments and structure of Xiangjiaba shiplift

The type of pinion and rack vertical shiplifts has been developed in recent a couple of years in the construction of dams. But the design methods and methodologies have rarely been discussed in literature. The Xiangjiaba shiplift is the second shiplift of this type following the Three Gorges shiplift. Being aimed at the technological rationality of the design in synthetically considering security, economy and applicability, this paper presents the research results of some vital issues relating the design of the Xiangjiaba shiplift, including the determination of design water depth of ship chamber based on fluid numeral computation and physical model test, the optimum design of general layout of main equipments and the civil structure of the Xiangjiaba shiplift, the finite element method （FEM） analysis of stress, vibration modes and the buckling of ship chamber, antiseismic research and the design of structures and mechanisms of the shiplift and the optimum design of driving mechanisms. This research provides the theoretical basis for the design of the Xiangjiaba shiplift. The design principles and research methods are valuable for the design of the same type of shiplifts.     

Recent progress in studies layer in rock on the nano-sized particle shear planes

Since the 1990s, an ultramicro-particle texture in nano- or micron-sized scale has been continually found in shear planes of various rocks, and recently further progress was made in generic physical mechanisms. In this article, the characteristics of the nano-sized particle layer in rock shear planes （including widespread distribution, layering texture, non-linear genetic mechanism, and multiple functions） on an ultra micro-scale were briefly introduced and more information was obtained by analyzing cases from home and abroad. Our findings suggest that （1） there is a paragenetic relationship between the development of shear frictional- viscous and the formation of nano-sized particles, and （2） in the shear movement, partitioning, segregating, and layering in rocks are initiated by the sliding motion of the nano-sized particle layer. Moreover, the plastic rheology of rocks is essentially the movement of ultra-micro-sized particles （nano-size and micro-size）, and the nano-sized particle layer in rock shear planes is characterized by some particular physical and chemical effects.     

On the Functions of Euphemism in Social Communication

In the process of social linguistic communication, due to the different circumstances and conditions, people can not express certain things clearly in a direct way when they come across something painful, unpleasant, disgusted and even embarrassing. Instead, they have to use some vague, implicit, mild and euphemistic expressions, so as to achieve the purpose of expressing feelings and exchanging ideas and thoughts in an appropriate and light atmosphere. This paper tries to deal with the application of euphemisms in various fields, thereby reveal some main functions of euphemism, i.e. avoidance function, politeness function, gloss-over function and disguise function.     

Reliability analysis on bolt support structure of coal roadway under the influence of mining

Based on the features of the serious deformation of coal roadway, many random variables of the mechanics of the surrounding rocks and the influence of mining, the reliability analysis model of the support structure of coal roadway under the influence of mining is established, and the calculating formulas of reliability of the support structure is obtained with the engineering structure reliability theory. And the reliability is calculated based on the method of Monte Carlo to the coal roadway which is exampled on the influence of mining or not. The relationship between support parameters and reliability, the mining influence coefficients and reliability is established, which provides theory foundations for the design of the coal roadway bolt support.     

Development of the Zinc-air Power Battery on Electric Bikes in China

Electric bicycles powered by lead-acid batteries have developed very fast for several years in China. Because the inconvenience caused by the service performance and the inconsistency to the environmental protection policy of the lead-acid battery, the zinc-air power battery was proposed to solve the problem in this paper. The advantage and the feasibility of developing zinc-air power batteries in China have been illustrated in the paper. And, it is represented that development of electric bicycles powered by the zinc-air power battery also can accelerate this kind of battery＇s development in other electric vehicles, which is favorable to economic development and environmental protection.     

Effects of elevation on spring phenological sensitivity to temperature in Tibetan Plateau grasslands

Vegetation phenology is an important indicator of climate change impacts on the seasonal dynamics of the biosphere. However, little is known about the influence of elevation on spring phenological sensitivity to temperature in an alpine ecosystem. Based on remotely sensed land surface phenology and temperature data from 2001 to 2010, this study investigated the rate of spring phenological change of the Tibetan Plateau （TP） grasslands in response to interannual temperature variations at different elevations. Results suggest that spring phenology in the TP grasslands exhibits a stronger response to changes in temperature at higher elevations than at lower ones. In particular, spring phenology advanced by 1-2 days in response to a 1 ℃ increase in May average temperature at elevations from 3,000 to 3,500 m, while the rate was up to 8-9 days/℃ at 5,000-5,500 m. Analysis using accumulated growing degree days （AGDD） from January 1 through May 31 showed the same general trend with increased elevation associated with increased sensitivity （as measured by phenological change per unit of AGDD change）. Such temperature sensitivity gradients in the TP grasslands could be partly explained by the growth efficiency hypothesis which suggests that vegetation adapted to colder climates likely requires less heat energy for the onset of growing season and vice versa in warmer climates. Furthermore, accumulated growing degree days from January 1 to the greenup date were found to decrease with increasing elevations, which provided evidence to support the applicability of the growth efficiency hypothesis in an alpine grassland ecosystem.     

An observational study of snow aging and the seasonal variation of snow albedo by using data from Col de Porte,France

An 18-year long （1993-2011） comprehensive dataset of snow and meteorological variables from Col de Porte, France is used to analyze the variation of shortwave broadband albedo with elapsed time after snowfalls （snow aging） during each snow season. The effects of air temperature, snow surface temperature and snow depth on snow albedo are investigated. An index based on the accumulation of air temperature over several consecutive days with daily mean higher than 2.5 ℃ is proposed to divide each snow-covered period into a dry and the following wet snow season when this index reaches 18 ℃. The results indicate that snow surface albedo decreases exponentially with time in both dry and wet snow seasons. Snow albedo reduction with snow aging is small at low surface temperature and the reduction rate increases with the rise of surface temperature. However, the reduction rate is widely scattered within the observed range of temperature, implying a loose relationship between snow albedo and snow surface temperature. Snow albedo in wet snow season is generally smaller and decreases faster than in dry snow season. For Col de Porte site, snow depths to effectively mask the underlying surface are 21 and 33 cm in dry and wet snow season respectively.     

Observations of thermospheric vector wind over Yellow River Station during auroral substorm events

Strong disturbances associated with auroral substorms originate from the ionosphere-magnetosphere owing to the effects of the solar wind, and the wind field in the ionosphere is related to such substorm activity. Here, we describe the analysis of four auroral substorm events, for which we employed an all-sky Fabry-Perot interferometer to observe the two-dimensional horizontal wind field and combined the results with data from an all-sky charge-coupled device imager, a fluxgate magnetometer installed at Yellow River Station, and the Super Dual Auroral Radar Network. The results demonstrate that, during auroral substorms, the vector wind field is related closely to variations in the ion drift and geomagnetic field. Moreover, we observed a changing wind field of approximately 300 rn/s in response to variations in the electric and magnetic fields （likely caused by ion drag） and a disturbance of about 200 m/s that we attribute to the interaction of Joule heating and ion drag.     

Study on the resistance spot welding technology of 22MnMoB hot stamping quenched steel

In this paper, the spot welding technology of a new kind of 22MnMoB hot stamping quenched steel sheet was systematically studied by power frequency spot welder. Through a series of technology and test experiments, we have obtained the optimal spot welding technological parameter condition. According to the results, the relations among spot welding technological parameter, welding nugget, mechanical property and fracture mode were discussed. The effects of all the welding parameters such as welding current, welding time and electrode force on the quality of joint can be boiled down to one thing--the diameter of welding nugget. The experimental results showed that welding nugget diameter determines the mechanical property of spot welding joint and the relation between welding nugget diameter and the mechanical property of joint presents a kind of linear mathematic representation. There are two typical fracture models of 22MnMoB hot stamping quenched steel sheet, i.e., interracial fracture and nugget pullout. Other than mild steel or normal high strength steel, in the shearing tensile test, hot stamping quenched steel has a great tendency to fail in interfacial mode due to the effects of high strength matrix structure, welding soft zone and the porosity level of fusion zone.     

The Simple Analysis on Motivation and Attitude in Tertiary College Students' English Study

In psycholinguistics, motivation and attitude have much effect on students＇ English study. Because there are different individuals among students, different students have different study motivations and attitudes. Directed against these individuals in tertiary colleges, we formulate different methods to help students study English well.     

Anomalous top-quark coupling effects in rare B and K decays

The Large Hadron Collider at CERN is performing direct searches for top-quark anomalous flavor-changing neutral current （FCNC） processes. However, these processes may be correlated closely with the low-energy rare B and K meson decays. In this paper, we review the anomalous top-quark coupling effects in these low-energy flavor transitions, summarize the flavor constraints and discuss their implications for direct detection of top-FCNC processes at the Large Hadron Collider.     

4 K high frequency pulse tube cryocooler used for terahertz space application

Terahertz(THz) frequency region, defined from0.1 to 10 THz, is an important frequency band for radio astronomy and atmospheric science. As NbN Superconductor-Insulator-Superconductor(SIS) mixers used for terahertz detection, which are studied by the Purple Mountain Observatory(PMO), Chinese Academy of Sciences(CAS), work at 8–10 K, and require condition of micro vibrations, its astronomical observation in aerospace is limited by suitable refrigeration method. 4 K high frequency pulse tube cryocooler developed by Key Laboratory of Space Energy Conversion Technologies(SECT), Technical Institute of Physics and Chemistry(TIPC), CAS, offers an opportunity for the application of SIS mixers. This article introduces the progress of the two-stage high frequency pulse tube cryocooler researched by TIPC. The cryocooler has reached a no load temperature of 4.5 K which is the lowest temperature for this kind of cryocooler reported so far. The successful coupling between the THz component and the high frequency pulse tube cryocooler lays a solid foundation for space detection in the terahertz band.     

Significant isostatic imbalance near the seismic gap between the M8.0 Wenchuan and M7.0 Lushan earthquakes

A gravity network with 302 observation points has been established in the western Sichuan Foreland Basin （SFB） to explore Bouguer gravity anomalies （BGAs）. Our observational results reveal that the BGAs are negative as a whole, with a maximum value of -220 mGal （10^-5m s^-2） at the northwest region of the study area. The real Moho depths beneath the SFB revealed by BGA data change smoothly from 39.5 km in the southeast to 43.7 km in the northwest of the monitoring region. However, the isostatic ones deduced from Airy isostatic model and topographical data vary approximately 39.5-42.0 km. The maximum differences of 2.7 km between the real and isostatic Moho depths are found near the seismic gap between the M8.0 Wenchuan and M7.0 Lushan earthquakes, where the crust is in the greatest isostatic imbalance of the monitoring region. Analysis of the isostatic state indicates that the deep dynamic environment near the seismic gap between these two earthquakes indicates an M ≥ 7.0 earthquake in the future. This study indicates that we can use isostasy as a potential approach to study the dynamic process of crustal material movement and to analyze regional potential seismic risks.     

Response of the East Asian summer monsoon to large volcanic eruptions during the last millennium

The responses of the East Asian summer monsoon （EASM） to large volcanic eruptions were analyzed using a millennial simulation with the FGOALS-gl climate system model. The model was driven by both natural （solar irradiance, volcanic eruptions） and anthro- pogenic （greenhouse gases, sulfate aerosols） forcing agents. The results showed cooling anomalies after large volcanic eruptions almost on a global scale. The cooling over the continental region is stronger than that over the ocean. The precipitation generally decreases in the tropical and subtropical regions in the first summer after large volcanic eruptions. Cooling with amplitudes up to -0.3 ℃ is seen over eastern China in the first summer after large volcanic eruptions. The East Asian continent is dominated by northeasterly wind anomalies and the corresponding summer rainfall exhibits a coherent reduction over the whole of eastern China. An analysis of the surface heat flux suggested the reduction in summer precipitation over eastern China can be attributed to a decrease of moisture vapor over the tropical oceans, and the weakening of the EASM may be attributed to the reduced land-sea thermal contrast after large volcanic eruptions.     

Study of front bumper process on the basis of hot stamping

The fitting method is used for obtaining the constitutive relation of ultra-high strength steel in this paper. At the same time, the forming limit of material is researched under different de/brmation conditions. Through experiments, the paper obtains stress-strain curve under different deformation temperatures and strain rates. On the basis of experimental data, the constitutive relation model is established which can reflect the de- fomlation capacity of ultra-high strength steel during process of hot stamping. Combining with finite element simulation results of hot stamping by the commercial software AUTOFORM, transfer path of load and matching law of strength, the paper determines the design criteria and forming process requirements of parts manufactured by hot stamping. Through setting different process parameters, such as punch velocity and friction coefficient, and blank shape, the paper finds that process parameters and blank shape have an essential effect on the quality of parts.     

The two-body hadronic decays of Bc meson in the perturbative QCD approach： a short review

Along with the running of Large Hadron Collider （LHC） located at CERN in November 2009, a large number of data samples of Bc meson have been collected and some hadronic Bc decay modes have been measured by the LHC experiments. In view of the special and important roles of Bc meson decays playing in the heavy flavor sector, we here give a short review on the status of two body hadronic decays Bc→M1M2 at both experimental and theoretical aspects. For the theoretical progresses, specifically, we will show lots of theoretical studies on two body hadronic Bc decays involving pseudoscalar, vector, scalar, axial-vector, even tensor meson（s） in the final states by employing the perturbative QCD （pQCD） factorization approach. We will present a general analysis about the two- body hadronic decays of the heavy Bc meson and also provide some expectations for the future developments.     

Changes in plant diversity on the Chinese Loess Plateau since the Last Glacial Maximum

Changes in biodiversity during periods of glo- bal warming are of broad public concern. To study the effect of the warming process on the ecosystem, we carried out pollen analyses on samples from seven selected sections at Qingyang, Ningxian, Yangling, Binxian, Baoji, Yanshi, and Lingbao on the Chinese Loess Plateau in order systematically to evaluate changes in plant diversity since the Last Glacial Maximum （LGM）. The plant richness indices （Simpson＇s diversity index and rarefaction analysis） indicated that the plant diversity of each section increased during the process of warming from the LGM to the Holocene Optimum, especially at Baoji and Lingbao. These results are consistent with many long-timescale geological records, which show that warming can increase biodiversity; therefore, the popular viewpoint that warming leads to biodiversity loss or species extinction needs to be re-examined.     

Higher sea surface temperature in the northern South China Sea during the natural warm periods of late Holocene than recent decades

The large-scale syntheses of global mean temperatures in IPCC fourth report suggested that the Northern Hemisphere temperature in the second half of the 20th century was likely the highest in at least the past 1,300 years and the 1990s was likely the warmest decade. However, this remains debated and the controversy is centered on whether temperatures during the recent half century were higher than those during the Medieval Cli- mate Anomaly （MCA, AD 800-1300） and the Roman Warm Period （RWP, BC 200-AD 400）, the most recent two natural warm periods of the late Holocene. Here the high resolution sea surface temperatures （SSTs） of two time windows around AD 990 （±40） and AD 50 （±40）, which located in the MCA and RWP respectively, were reconstructed by the Sr/Ca ratio and 6180 of Tradacna gigas shells from the northern South China Sea. The resultssuggested that the mean SSTs around AD 990 （±40） and AD 50 （＋40） were 28.1 ℃ and 28.7 ℃, 0.8 ℃ and 1.4 ℃ higher than that during AD 199±2005, respectively. These records, together with the tree ring, lake sediment and literature records from the eastern China and northwest China, imply that the temperatures in recent decades do not seem to exceed the natural changes in MCA, at least in eastern Asia from northwest China to northern SCS.