型式学之外——磨制石器的研究应当加强

自四十年代后期安志敏先生发表《殷墟之石刀》一文以来,史前生产工具特别是磨制石器的专题研究有了长足的进步。从石刀、石斧、石铲、石锛到石镰、石犁、石凿、石楔等等,几乎每一种有一定数量的古代石制生产工具都引起人们重视并已有专文发表。这无疑极大地丰富了我们对于史前人类生产生活方式的认识,功不可没。但是,总的看来,除了个别文章从力学的或民族志类比的角度,对石器的功能及制作方式做过一些推论之外。

英语课型式学案有利于提高学生的综合素能

一、学案的提出 近年来，随着素质教育的日益高涨，“学案”迅速出现在英语教学中。布鲁诺的发现学习理论强调学生的学习是一个主动发现的过程：现代教学论认为，学生的能力不是单纯的“教”就能培养出来的。

从传统的考古学中走出来

考古学在20世纪60年代发生了革命,芝加哥大学的W·F·利比博士发明了用放射性碳素测定过去的有机质遗物年代的方法,经过对埃及的独木舟年代的验证,证明用这种方法确定考古遗物是切实可行的.这种方法得到了被授于诺贝尔奖的崇高荣誉,同时也使考古学自身发生了很大的变化.传统的考古学是通过对人类制作、使用的各种遗物的分型分式、排队比较来确定其早晚的相对年代的,与此相比。

A Tentative Probe into Task-based Mode of Translation Teaching

By analyzing the traditional model of E-C （English-Chinese） translation teaching, this paper points out the shortcomings of this old model, and presents a brand-new task-based approach to E-C translation teaching which takes contrastive linguistics as a base and threads with the concept of text translation.

Mathe matical model and calculation for heat transfer during condensation on surfaces of corrugated plates

A mathematical model was established for condensation on surfaces of verticalcorrugated plates based on the mechanism of heat transfer enhancement to thin down the liquid filmdue to surface tension effect between corrugated plate surfaces and liquid films. The relative heattransfer coefficients of condensation on corrugation plates were calculated in contrast withequivalent vertical plane ones. The heat transfer enhancement effects for the main geometricparameters such as pitch, height, corrugation angle, tilt angle, and fillet radii of corrugationswere analyzed to guide the optimization of corrugation structure for application. A two-scalecorrugation is suggested, which can compromise both the enhanced heat transfer effect and adequatecross section area for flows, and it makes the heat transfer coefficient 1 to 2 times more than thatof an equivalent plane one.

MATHEMATICAL MODEL FOR ACCESS MODE OF CONTENTION-COLLISION CANCELLATION IN A STAR LAN

I type system model of CCCAM(Contention-Collision Cancellation Access Mode) is studied through mathematical modelling and simulation. There are two innovations: (1) in the process of mathematical modelling, the instance of 'serving customers unsuccessfully' is taken into account; (2) the time at which customers depart after having been served successfully are chosen to be the embedded point, thereby 'free period' is introduced reasonably. So the mathematical modelling and analysis result in this paper are significant for application of wire star LAN and wireless star LAN.

Modeling and Optimization of the Steam Turbine Network of an Ethylene Plant

In this paper,we developed a hybrid model for the steam turbines of a utility system,which combines an improved neural network model with the thermodynamic model.Then,a nonlinear programming(NLP) model of the steam turbine network is formulated by utilizing the developed steam turbine models to minimize the total steam cost for the whole steam turbine network.Finally,this model is applied to optimize the steam turbine network of an ethylene plant.The obtained results demonstrate that this hybrid model can accurately estimate and evaluate the performance of steam turbines,and the significant cost savings can be made by optimizing the steam turbine network operation at no capital cost.

A Novel Exponential Kinetic Model for Casein Tryptic Hydrolysis to Prepare Active Peptides

The kinetics of casein tryptic hydrolysis to prepare activepeptides was investigated. Taking into account the reaction mechanismincluding single substrate hydrolysis, irreversible enzymeinactivation, and substrate inhibition, a set of exponentialequations was established to characterize the enzymatic hydrolysiscurves. The verification was carried out by a series of experimentalresults and indicated that the average regressive error was less than5/100. According to the proposed kinetic model, the kinetic constantsand thermodynamic constants of the reaction system were alsocalculated.

Study on the Grey Polynomial Geometric Programming

In the model of geometric programming, values of parameters cannot be gotten owing to data fluctuation and incompletion. But reasonable bounds of these parameters can be attained. This is to say, parameters of this model can be regarded as interval grey numbers. When the model contains grey numbers, it is hard for common programming method to solve them. By combining the common programming model with the grey system theory, and using some analysis strategies, a model of grey polynomial geometric programming, a model of θ positioned geometric programming and their quasi-optimum solution or optimum solution are put forward. At the same time, we also developed an algorithm for the problem. This approach brings a new way for the application research of geometric programming. An example at the end of this paper shows the rationality and feasibility of the algorithm.

Recent Study of Drag Embedment Plate Anchors in China

Experimental and theoretical studies of drag embedment plate anchors recently carried out in Tianjin University are summarized in this research paper, which involve a series of important topics relevant to the study of drag anchors. The techniques for measuring the trajectory and movement direction of drag anchors in soils, the techniques for measuring the moving embedment point and reverse eatenary shape of the embedded drag line, the penetration mechanism and kinematic behavior of drag anchors, the ultimate embedment depth of drag anchors, the movement direction of the anchor with an arbitrary fluke section, the reverse catenary properties of the embedded drag line, the interaetional properties between drag anchor and installation line, the kinematic model of drag anchors in seabed soils, and the analytical method for predicting the anchor trajectory in soils will all be examined. The present work remarkably reduces the uncertainties in design and analysis of drag embedment plate anchors, and is beneficial to improving the application of this new type of drag anchor in offshore engineering.

Recent Advances in Studies on Formation Mechanism of Subtropical Mode Water and Its Climate Features in North Pacific

Mode Water’, as a product of air-sea interaction, influences the thermal structure and circulation pattern in upper layer ocean and consequently affects the variations of climate. In this paper the recent research results about the subtropi-cal Mode Water in the North Pacific are overiewed. A detailed description of the three kinds of Mode Water in the subtropical North Pacific and some comparisons of their similarities and differences are introduced. Some science problems that need further exploration have been raised.

A distributed dynamic mesh model of a helical gear pair with tooth profile errors

A dynamic model of a helical gear rotor system is proposed.Firstly,a generally distributed dynamic model of a helical gear pair with tooth profile errors is developed.The gear mesh is represented by a pair of cylinders connected by a series of springs and the stiffness of each spring is equal to the effective mesh stiffness.Combining the gear dynamic model with the rotor-bearing system model,the gear-rotor-bearing dynamic model is developed.Then three cases are presented to analyze the dynamic responses of gear systems.The results reveal that the gear dynamic model is effective and advanced for general gear systems,narrow-faced gear,wide-faced gear and gear with tooth profile errors.Finally,the responses of an example helical gear system are also studied to demonstrate the influence of the lead crown reliefs and misalignments.The results show that both of the lead crown relief and misalignment soften the gear mesh stiffness and the responses of the gear system increase with the increasing lead crown reliefs and misalignments.

Design and dynamic analysis of the micro-suspended monorail

A 20 degree of the freedom model of the micro-suspended monorail is established to analyze a new type of the vehicle system named micro-suspended monorail.The formula of the tire is established by using the magic formula.Through the modal analysis of the vehicle,the modes of the vehicle are obtained,and resonance has little effect on the vehicle.When the vehicle moves in a right turn curve,it yaws in the clockwise direction.Under the action of the guidewheel(stable wheel)force,the front bogie yaws clockwise but the rear one yaws counterclockwise.Moreover,the two bogies and the car body roll during the curve passing process of the vehicle.When the vehicle speed is high enough,the left drive wheel will derail and the anti-overturning moments are provided by the stable wheels.Then,the car body yaws in the counterclockwise direction when it moves out of the curve.In the simulation of the vehicle passing the curve,the clearance between the guide wheel and rail surface will lead to a fatal impact on the bogie.At the same time,the dynamic response of the vehicle under the crosswind is tested.The vehicle will not overturn due to the crosswind.Finally,the collision of adjacent vehicles is analyzed.The results show that there is an intermittent collision force between two vehicles due to the vehicle's non synchronous pitch motion.

Modeling and simulation of a mini AUV in spatial motion

Accurate modeling and simulation of autonomous underwater vehicle （AUV） is essential for autonomous control and maneuverability research. In this paper, a mini AUV- ＂MAUV-Ⅱ＂ was researched and the nonlinear mathematic model of the AUV in spatial motion was derived based on momentum theorem. The forces acting on AUV were resolved to several modules which were expressed in matrix form. Based on the motion model and combined with virtual reality technology, a motion simulation system was constructed. Considering the characteristic of ＂MAUV-Ⅱ ＂, the heading control and depth control were simulated by adopting S-surface control method. A long distance traveling simulation experiment based on target planning was also done. The simulation results show that the ＂MAUV-Ⅱ＂ has good spatial maneuverability, and verify the feasibility and reliability of control software.

Perceptual Models of Art students and Its Enlightenment on English Teaching

Art students, as a whole, have a variety of learning style of sensory receivers. The Variety of learning styles requires the variety of teaching strategies. The analysis of learners＇ learning styles is one of the factors on which the design of learning strategies should be based. Matching teaching strategies and mismatching strategies are chosen intentionally according to the teaching contents, the teaching goals, and the learner＇s learning styles. Matching teaching strategies can reach the best result of teaching and learning. On the contrary, mismatching strategies can remedy the disadvantages caused by learning styles and be helpful for the development of learning styles.

Calculation of Thermodynamic Parameters for Freundlichand Temkin Isotherm Models

Derivation of the Freundlich and Temkin isotherm models from the kinetic adsorption/desorpt ion equations was carried out to calculate their thermodynamic equilibrium constants. The calculation formulae ofthree thermodynamic parameters, the standard molar Gibbs free energy change, the standard molar enthalpy change and the standard molar entropy change, of isothermal adsorption processes for Freundlich andTemkin isotherm models were deduced according to the relationship between the thermodynamic equilibriumconstats and the temperature.

Kinematic Analysis and Trajectory Planning of J-Groove Welding Robot

This paper introduces the complexity and particularity of tube-sphere intersection weld(J-groove weld) and establishes the mathematical model of tube-sphere intersection trajectory.Based on the characteristics of J-groove welds,the computational process of welding gun orientation is first simplified.Then the kinematic algorithm of a welding robot is obtained according to screw theory and exponential product formula.Finally,Solidworks and SimMechanics are employed to simulate the kinematics of the welding robot,which proves the feasibility of the kinematic algorithm.

Orthogonal moment based texture segmentation

Texture segmentation is a necessary step to identify the surface or an object in an image. We present a Legendre moment based segmentation algorithm. The Legendre moments in small local windows of the image are computed first and a nonlinear transducer is used to map the moments to texture features and these features are used to construct feature vectors used as input data. Then an RBF neural network is used to perform segmentation. A k-mean algorithm is used to train the hidden layers of the RBF neural network. The training of the output layer is the supervised algorithm based on LMS. The algorithm has been successfully used to segment a number of gray level texture images. Compared with the geometric moment-based texture segmentation, we can reduce the error rates using orthogonal moments.

Adsorption Behavior of Methyl Orange onto Modified Ultrafine Coal Powder

The adsorption of methyl orange onto ultrafine coal powder （UCP） and modified ultrafine coal powder （MUCP） from aqueous solutions were studied, in which the influence of contact time, dosage, temperature, pH, and methyl orange concentration in the solution were investigated. The adsorption kinetics of methyl orange by UCP and MUCP can be described by the Lagergren first-order and pseudo second-order kinetic models, respectively. The adsorption isotherms of methyl orange onto MUCP at 303, 313 and 323 K follow the Freundlich and Langmuir isotherm equation. Values of △G^0 for methyl orange adsorption onto MUCP are -22.55, -23.10 and -23.79 kJ·mol^-1 at 303, 313, and 323 K, respectively. The values of △H^0 and △S^0 are -3.74 kJ· mol^-1 and 61.99 J·mol^-1, respectively. The adsorption process is spontaneous and exothermic.

Hydrodynamic Performance of Multiple-Row Slotted Breakwaters

This study examines the hydrodynamic performance of multiple-row vertical slotted breakwaters. We developed a mathematical model based on an eigenfunction expansion method and a least squares technique for Stokes second-order waves. The numerical results obtained for limiting cases of double-row and triple-row walls are in good agreement with results of previous studies and experimental results. Comparisons with experimental measurements of the reflection, transmission, and dissipation coefficients （CR, Cr, and CE） for double-row walls show that the proposed mathematical model adequately reproduces most of the important features. We found that for double-row walls, the CR increases with increasing wave number, kd, and with a decreasing permeable wall part, din. The Cr follows the opposite trend. The CE slowly increases with an increasing kd for lower kd values, reaches a maximum, and then decreases again. In addition, an increasing porosity of dm would significantly decrease the CR while increasing the Cr. At lower values of kd, a decreasing porosity increases the CE, but for high values of kd, a decreasing porosity reduces the Ce. The numerical results indicate that, for triple-row walls, the effect of the arrangement of the chamber widths on hydrodynamic characteristics is not significant, except when kd〈0.5 Double-row slotted breakwaters may exhibit a good wave-absorbing performance at kd〉0.5, where by the horizontal wave force may be smaller than that of a single wall. On the other hand, the difference between double-row and triple-row vertical slotted breakwaters is marginal.