两体碰撞与牛顿第二定律

在现有的碰撞理论的基础上 ,导出了一个适用于一般两体问题相互作用力求解的关系式 ;将该式与牛顿第二定律作了比较 ,认为第二定律是两体间的作用力在特定条件下该式的简化形式 ,该式在形式上与李映华教授在《牛顿力学述评》

FEM for Stability Analysis Against Overturning of Portal Water Injection Sheet Pile

Portal water injection sheet pile (PWISP), as a retaining wall, appeared in seashore engineering in 2000. Although there have been many systematic methods addressing the issue, there are very few focusing on the new structure because of the difficulties in defining the earth pressure between the two piles. A new method is proposed in this paper to obtain the earth pressure between the PWISPs. Stability analysis against overturning follows as a consequence. Using Finite Element Analysis (FEA) software ANSYS, both the nonlinear characteristics of the soil and those of the contact elements are taken into account to obtain the earth pressure distribution on the contact surface. Based on the results of the FEA, Rankin’s theory and the slip plane theory, the formula of the earth pressure on the inner surfaces between the piles is given. Assuming the PWISP as the analysis object and the earth pressure as an outside force acting upon it, the equation of stability against overturning of the PWISP is presented. Finally, some parameters are discussed about the stability of the PWISP against overturning, such as the embedded depth of the front pile, the distance between the two rows of piles, the internal friction angle and the cohesion of the earth. The results show that the increase of the cohesion and the internal friction angle will decrease the distance and the embedded depth, and therefore enhance the stability against overturning. Specifically, when the distance is 1/3-2/3 of the maximal excavation depth, the two rows of piles give the best performance in stability.

Approach for electrodynamic force for compensation in low voltage circuit breaker WP 630-1.2 type

Undesirable repulsive force between contact members due to both a current path shrink near a real contact area and/or so-called pinch effect is particularly onerous for power switch applications, and results in either contact floating or bouncing which are associated with an electric arc following contact welding. This problem is of great importance for any circuit breaker especially for compact low voltage vacuum circuit breakers. To avoid contact floating at closure and during any inrush current under short circuit conditions, the electrodynamic repulsive force can be employed successfully if we use a special compensation system flexibly combined with the contact itself. However to select and design the compensation system properly, its efficiency has to be known. This paper presents an approach to obtain the electrodynamic force value depending on different shaped (rectangular, square, circle and arch) copper plates used in the compensator by using ANSYS for current values 40 kA RMS. Curve-fitting was done according to the calculating results, the optimization designing of compensation unit is based on them.

Effect of Different Fertilization Practices on Yield of a Wheat-Maize Rotation and Soil Fertility

A 15-year field experiment was carried out in Henan Province, China, to study the effects of different fertilization practices on yield of a wheat-maize rotation. Fertilizers tested contained N alone (N), N plus P (NP) or plus P and K (NPK), all with or without manure (M). Different long-term fertilization practices affected the yields under the rotation system of wheat and maize differently and the effects on yields was in a general trend of MNPK＞MNP＞MN＞NPK＞NP＞M＞N＞the control. The average contribution rate of soil fertility to the highest yield was 37.9%, and the rest 62.1% came from fertilizer applications. The yield effects of the chemical fertilizers were in the order of N＞P＞K and were increased by application of manure.Balanced fertilization with multielement chemical fertilizers and manure can be effective in maintaining growth in agricultural production. Combined application of chemical fertilizer and organic manure also increased the content of soil organic matter.

Orbital Ordering Induced by Direct Coulomb Repulsion

We consider the covalence characters of the 3d electron with the eg orbital freedoms and put forward a new mechanism of the orbital ordering （00） based on the direct coulomb repulsion in this article. The results show that the orbital-orbital interaction （OO-I） between the adjacent ions in 180-degree configuration is dominated by the superexchange energy accompanied by a weak orbital-spin coupling, and the OO-I in 90-degree configuration is monitored by the oxygen on-site coulomb repulsion. The ferro-OO is the stable ground state for the one-dimensional chain in the case of the 90-degree configuration.

Corn Leaf Water Retention as Affected by OrganicFertilizations and Effective Microbes Applications

Effects of organic fertilizers and effective microbes on leaf water retention of sweet corn (Zea mays L. cv.Honey-Bantam) were studied. Sweet corns were grown with organic or chemical fertilizers with or without effective microbes (EM). A water retention curve was obtained by drying the excised leaves under a light of 500 μmol (m2·s)-1. The curve shows two distinct phases. The initial steep slope indicates the water loss speed by stomatal transpiration (Est) and the gentle slope of the second phase indicates water loss speed by cuticular transpiration (Ecu). Both Est and Ecu were lower for leaves of plants grown with organic materials than for those with chemical fertilizers. Addition of EM to both organic and chemical fertilizers decreased Est but showed no effect on Ecu. The water retention ability of the excised leaves was proportional to photosynthetic maintenance ability under soil water deficit conditions as well as the solute concentration in leaves. The results suggested that organic fertilization and EM application increased water stress resistance both under in situ conditions and in excised leaves of sweet corn plants.

Effects of working parameters on gasoline engine exergy balance

To improve the energy utilization efficiency of internal combustion （IC） engine, exergy analysis was conducted on a passenger car gasoline engine. According to the thermodynamic theory of IC engine, in-cylinder exergy balance model was built. The working processes of gasoline engine were simulated by using the GT-power. In this way, the required parameters were calculated and then gasoline engine exergy balance was obtained by programming on computer. On this basis, the influences of various parameters on exergy balance were analyzed. Results show that, the proportions of various forms of exergy in gasoline engine from high to low are irreversible loss, effective work, exhaust gas exergy and heat transfer exergy. Effective exergy proportion fluctuates with cylinder volumetric efficiency at full load, while it always increases with break mean effective pressure （BMEP） at part load. Exhaust gas exergy proportion is more sensitive to speed, and it increases with speed increasing except at the highest speed. The lower proportion of heat transfer exergy appears at high speed and high load. Irreversible loss is mainly influenced by load. At part load, higher BMEP results in lower proportion of irreversible loss; at full load, the proportion of irreversible loss changes little except at the highest speed.

Three Dimension Finite Element Analysis of the Influence Factors of Stress Responses in the Roadbed and Ground under a Moving Load

Focusing on the vibration of the roadbed and ground induced by high-speed train load, a three dimensional finite element model which includes the roadbed and horizontal layered site is established to study how the site conditions, the load moving speed and the depth of the soil element influence the soil element stress response. Based on a track-subsoil analytical model in which the rail is simulated as an Euler-Bernoulli beam resting on Winkler foundation in the vertical plane, the reaction force between the sleeper and roadbed excited by a single axle is presented, and then that is exerted on relevant elements to simulate the moving load. The dynamic response in the roadbed and subsoil excited by a single axle moving load is computed based on the parallel computing platform of the ABAQUS finite element software, and the stress time-history, stress path and curves of the principal stress axes rotation of the soil element under the track are presented. The results show that： the soil element stress path is an apple-shaped curve in the horizontal shear stress τd versus the stress difference （σsh - σch ）/2 coordinate system; the principal stress axes rotate 180° for the soil element under the load moving line during the load running, and the stress state changes from the pure shear to triaxial shear and then back to the pure shear again. The element dynamic stress increases as the moving load speed increases, which increases sharply when the load speed approaches the Rayleigh wave velocity of soil layer; the site conditions and the soil element depth affect the soil element stress path significantly.

Study on mechanism of circumferential cracks in cold-region tunnels

There exists frost damage in cold-region tunnels. The circumferential cracks affect the function of tunnels. Using three-dimensional finite element method, the authors analyzed the mechanism of circumferential cracks in cold-region tunnels It is proved that the internal thermal stress in lining exceeds the tensile strength of concrete, which is the direct cause for circumferential cracks occurring. The laws of thermal stress in lining induced by parameters such as temperature drop, horizontal drag coefficient and length of lining are analyzed. The conclusions are valuable to the design and construction of cold-region tunnels considering the thermal stress.

Design and energy absorption enhancement of vehicle hull under high dynamic loads

V-shape hulls are widely used in peacekeeping efforts such as demining vehicles in order to deflect the blast energy and reduce the effects of mine blast. Blast resistant design and energy absorption enhancement of V-shape plates were carried out using finite element analysis package ABAQUS. Various geometries of V-shape plates with and without interlayer of materials like Al-foams and honeycomb were employed to analyze their effects on the deformation of the plate and applied stresses and strains. The results obtained show that application of metallic foams leads to better response of the plate and consequently results in more energy dissipation, less dame to vehicle and enhances crew survivability.

Gap Equations and Effective Potentials at Finite Temperature and Chemical Potential in D—Dimensional Four—Fermion Models

We have proven the general relations between the gap equations obeyed by dynamical fermion mass and thecorresponding effective potentials at finite temperature and chemical potential in D-dimensional four-fermion interactionmodels. This gives an easy approach to get effective potentials directly from the gap equations. We find out explicitexpressions for the effective potentials at zero temperature in the cases of D = 2,3, and 4 for practical use.

Interactions Mode of Amphoteric Molecules with Ordered Phospholipid Membrane

Aim To explore interaction mode between amphoteric molecules with the orderedphospholipid membrane. Methods Membrane interactions were determined by immobilized artificialmembrane (IAM) chromatography and solutes' hydrophobicity was measured by n-octanol/buffer system.Results The ampholytes, similar to bases, generally exhibited higher membrane affinity than expectedfrom their hydrophobicity, resulting from the attractive polar interaction with phospholipidmembrane. Furthermore, the strength of additional polar interaction with membrane (Δlg k_(IAM)) wasthen calculated. The Δlg k_(IAM) values were far greater for bases and ampholytes ranging from0.50 - 1.39, than those for acids and neutrals with the scope from - 0.55 - 0.44. ConclusionConsidering the microspecies distribution of amphoteric molecules, it was assumed that not onlyneutral and positive but also zwitterionic microspecies are capable of partitioning into orderedamphoteric lipid membrane with complementarily conformational and energetically favorableinteractions.

THE FACILITATING EFFECT OF TRANSLATION ON EFL (ENGLISH AS A FOREIGN LANGUAGE)WRITINGⅡ:WRITERS' ATTENTION PATTERNS

This study is undertaken to find out writers' attention patterns in these two different writing methods (the direct method and the translation-based method) during the writing process through the think-aloud method and EFL learners' perception of the advantages and disadvantages of those two writing methods.The results show that the subjects' attention patterns in the direct method and in the translation-based method are quite different and the differences are mainly embodied in the linguistic level attention and personal comment.As far as the subjects are concerned,writing directly in English is easier and faster than writing through translation,and the direct writing method often helps them learn English language and forces them to focus on English expression.In contrast,for the translation-based writing method,the subjects as a whole relate that they have a wide range of vocabulary and expressions,have a greater number of ideas,and can think through ideas clearly.

A new class of HIV-1 inhibitors and the target identification via proteomic profiling

Anti-HIV screening with the MT-4/MTT assay on a focused library of structurally diverse natural products has led to the discovery of a group of steroids with potent activities, which include four new ergostane-type steroids, named amotsterols A-D （1-4）, together with two known analogs. Among them, the most potent amotsterol D （4） exhibited anti-HIV activity against wild- type and some clinically relevant multidrug resistant HIV-I strains. Subsequent studies on its target identification through a proteomic approach found that compound 4 might target PKM2, a rate limiting enzyme ofglycolysis, in host cells to restrict HIV replication. The docking model of compound 4 to PKM2 showed that the two hydroxyl groups of 4 form hydrogen bonds with the two parallel Y390 in each subunit of PKM2 separately, and the ring C of 4 is sandwiched between the two parallel aromatic rings ofF26. The identified hit compound may have the potential to be further developed as a novel anti-HIVagent. These results demonstrated that an integrated approach, which combines new chemical structures and phenotypic screening with a proteomic approach, could not only identify novel HIV-1 inhibitors, but also elucidate the unknown targets of compound interactions in antiviral drug discovery.

Preliminary studies on the basic factors of bionics

The bionic consciousness,idea,and practice opened a unique path for the progress of mankind,the development of the society,and the innovation of science and technology from the subconscious bionic activities of the ancient humans to the significant bionic designs in modern engineering.Nowadays,driven by the practical demand of human beings,bionics becomes an important factor for the sustainable development of technology.A lot of new and outstanding innovations have been produced through the effective interactions between bionics,technology,and demand.The stronger the interactions,the greater the innovation success would be.In this article,the basic factors such as the connotation,characteristics,and interactions of bionic demands,bionic models,bionic simulations,and bionic products were explained,which are the indispensable basic knowledge for improving the ability of innovation especially for the original one,realizing the design and innovation of new technology and manufacturing for better bionic products.

The instability of an elastic planet with a liquid core

Considering a spherical planet with a liquid core surrounded by a solid shell,we developed a quasi-static model to investigate the deformation of the double-layered planet with self-gravity and obtained the boundary value problem about radial equilibrium,which is solved by the numerical methods.The effects of governing parameters about geometry,density and bulk modulus on the deformation of the planet with self-gravity were discussed.In addition,we also developed the incremental equation theory to investigate the stability of the double-layered planet under its own gravity.It is concluded that instability is more likely to occur on the planet with smaller liquid cores when the outer radius and density of the planets are constant.Although we only study special double-layered planets,these methods can be conveniently extended to complex multi-layered planets.

Effect of Transverse Correlation Function on the Thermodynamic Quantities of Ferromagnetic Systems

The effect of transverse correlation between spins on the thermodynamic properties of ferromagnetic systems is investigated in details. Qualitatively, at finite temperature the transverse correlation reflects the short-range interaction between spins, so that lowers the internal energy and consequently raises the free energy. It also means the introduction o[ some ordering, and hence lowers the entropy. It is depressed by the field which forces the spins to turn to the field direction, so that it decreases with the field when temperature is fixed. The low-temperature expansion of the energy shows that the inclusion of the transverse correlation at least partly considers the interaction between spin waves.

3D-FEM modeling of the microscopic stress field of forsterite aggregate under hydrostatic pressure:Significance of the crystal orientation

Three Dimensional Finite Element Method(3D-FEM)has been used to model the deviatoric stress field in a forsterite aggregate with a sandwich geometry:two forsterite cubes aligned in the same crystallographic orientation(the"breads")sandwich a third forsterite cube(the"filling"),which might have an identical or different crystallographic orientation.The results show that there is no von Mises stress in the forsterite sandwich if the sandwiching and sandwiched forsterite cubes are aligned in the same crystallographic orientation.If the crystallographic orientations are different,however,von Mises stress and heterogeneous stress distribution occur both along the boundary and in the forsterite cubes.For the investigated P-T conditions(up to 6.4GPa and 500°C),the resulted deviatoric stress is much lower than the yield strength of forsterite,so that higher P,higher T,or other means to create higher deviatoric stress is necessary,in order to constrain the yielding behavior of forsterite.

Advances in environmental behaviors and effects of dissolved organic matter in aquatic ecosystems

Dissolved organic matter(DOM) is a group of compounds that have complex chemical structures and multiple interactions with their surrounding materials. More than one trillion tons of DOM are stocked in the world's aquatic ecosystems. DOM is a very important part of aquatic ecosystem productivity and plays a crucial role in global carbon cycling. DOM has rich environmental behaviors and effects such as influencing the bioavailability of contaminants, serving as an important inducer of reactive oxygen species(ROS), and protecting aquatic organisms from the harm of dangerous ultraviolet radiation. There have been many systematic studies on the composition, structure, and sources of DOM because such studies are much easier to conduct than studies on the environmental behaviors and effects of DOM. Due to many factors, the research systems of DOM's environmental behaviors and effects are still being developed and have become a hotspot of environmental science. This review paper focuses on some critical progress, problems, and trends of DOM's environmental behaviors and effects in aquatic ecosystems, including mutual exchange mechanisms between DOM and particulate organic matter(POM) with influencing factors, photochemical behaviors of DOM especially inducing ROS, binding interactions between DOM and anthropogenic organic contaminants(AOC), interactions between DOM and microorganisms, effects of DOM on pollutants' bioavailability, ecotoxicity, and ecological risks. Hopefully, this paper will contribute to a more systematic understanding of the DOM environmental behaviors and effects and to promoting further relevant studies.