非正弦时域正交调制性能分析及仿真

给出基于时限椭圆球面波函数的非正弦时域正交调制解调的数学模型,从理论上推导调制信号的频带利用率、功率谱特性以及AWGN信道下的差错性能,给出功率谱及误码率的数学表达式,进行仿真并与理论推导结果进行比较,验证理论推导的正确性,为通信系统设计和应用提供理论和实验依据。     

Dynamic analysis of evaporator characteristics

An analysis of the dynamic characteristics in an evaporator was numerically performed for control and design of the refrigeration and air conditioning systems. The important factors, such as refrigerant flow rate, inlet enthalpy, inlet air velocity and air temperature, are incorporated with this analysis. An evaporator is modeled for the dynamic characteristics analysis separated into three regions which are the two-phase region, the saturated vapor region and the superheated vapor region. The basic equations of each region were derived in the continuity, heat energy equilibrium and heat transfer equations. The transfer functions of the dynamic characteristics were obtained by the linearization and Laplace transformation. The dynamic response characteristics were evaluated on the Bode diagram with the frequecy response method. These results may be used for the analysis of the dynamic characteristics and design in the total system.     

浅说英语中的"oxymoron"

本文简要介绍了矛盾修辞法的几种修辞功能，即比喻格，夸张格，含蓄格和移就格，说明此修辞法的使用可增强感染力和表现力。     

产品功能化的物性转向及设计思维研究

针对现代工业产品"即用即弃"的现实困境,拟从设计哲学视阈出发,分析科学主导下的现代主义数理功能和后现代主义表意形式,揭示二者功、能化本质是造成当前困境的根源。为此,通过对现象学的物性思想解读,明确该思想具有摆脱当前困境的意义。在此基础上,以现代工业生产模式为基础,展开物性化产品设计原则的思维建构。围绕生存世界为核心,生命意义为起点,用者参与和多元衍生的辅助思维让功、能在空间中展开。最终使产品和人能向着持久共存的方向发展。     

On the dynamics of ball end milling: modeling of cutting forces and stability analysis

This paper presents a dynamic force model and a stability analysis for ball end milling. The concept of the equivalent orthogonal cutting conditions, applied to modeling of the mechanics of ball end milling, is extended to include the dynamics of cutting forces. The tool is divided into very thin slices and the cutting force applied to each slice is calculated and summed for all the teeth engaged. To calculate the instantaneous chip thickness of each tooth slice, the method of regenerative chip load calculation which accounts for the effects of both the surface undulations and the instantaneous deflection is used. To include the effect of the interference of the flank face of the tool with the finished surface of the work, the plowing force is also considered in the developed model. Experimental cutting forces are obtained using a five-axis milling machine with a rotary dynamometer. The developed dynamic model is capable of generating force and torque patterns with very good agreement with the experimental data. Stability of the ball end milling in the semi-finishing operation of die cavities is also studied in this paper. The tangential and radial forces predicted by the method of equivalent orthogonal condition are fitted by the equations F_t = K_t(Z)bh_av and F_r = K_r(Z)F_t, where b is the depth of cut and h_av is the average chip thickness along the cutting edge and Z is the tool axis coordinate. The polynomial functions K_t(Z) and K_r(Z) are the cutting force constants. The interdependency of the axial and radial depths of cut in ball end milling results in an iterative solution of the characteristic equation for the critical width of cut and spindle speed. In addition, due to different cutting characteristics of the cutting edge at different heights of the ball nose, stability lobes are represented by surfaces. Comparison of the time domain simulation for the shoulder removal process in die cavity machining with the analytical predictions shows that the proposed method is capable of accurate prediction of the stability lobes.     

超宽带通信脉冲波形的分析与仿真

首先介绍一种回转椭球波函数(Prolate Spheroidal Wave Functions,PSWF),主要阐述了PSWF的相关概念、特性及其近似求解算法,然后阐述应用PSWF脉冲基来组合设计UWB脉冲波形的算法。如果要求陷波点有干扰抑制,可以对该点左右两侧的频段分别求对应的频域波形,再做相应线性变换,使陷波点的频域值为0,然后对两个脉冲的时域波形做同样的变换,即得所求脉冲波形,最后通过仿真验证了算法的有效性。     

Identification of damage on a substructure with measured frequency response functions

Recently the authors tried to find damage position only using measured frequency response functions. According to their work, it seems that the algorithm is very practical since it needs only measured frequency responses while other methods require exact analytic model. But when applying the method to a real structure, it requires lots of experiment. The authors, in this time, propose a method to reduce its experimental load by detecting damage within a substructure. This method searches damages not within an entire structure but within substructures. In addition, damage severity was treated in this paper since it is worthy to know damage severity. Optimization technique is used to estimate damage level using measured responses and damage model. Two test examples, a plate and a jointed structure, are chosen to verify the suggesting method.     

Understanding the formative stage of technological innovation system development: The case of natural gas as an automotive fuel

This study contributes to insights into mechanisms that influence the successes and failures of emerging energy technologies. It is assumed that for an emerging technology to fruitfully develop, it should be fostered by a Technological Innovation System (TIS), which is the network of actors, institutions and technologies in which it is embedded. For an emerging technology a TIS has yet to be built up. This research focuses on the dynamics of this build-up process by mapping the development of seven key activities: so-called system functions. The main contribution revolves around the notion of cumulative causation, or the phenomenon that the build-up of a TIS accelerates due to system functions reinforcing each other over time. As an empirical basis, an analysis is provided of the historical development of the TIS around automotive natural gas technology in the Netherlands (1970–2007). The results show that this TIS undergoes a gradual build-up in the 1970s, followed by a breakdown in the 1980s and, again, a build-up from 2000 to 2007. It is shown that underlying these trends are different forms of cumulative causation, here called motors of innovation. The study provides strategic insights for practitioners that aspire to support such motors of innovation.     

Inversion Of A Generalized Vandermonde Matrix

In this paper the author gives an explicit closed form expression for the $n\times n$ inverse matrix $(V_{G}^{(k)})^{-1}(n)$ of the $n\times n$ Vandermonde matrix $V_{G}^{(k)}(n)$ by using the elementary symmetric functions. Symbolic and numerical results are presented.     

IMPROVED DEM-CFD MODEL AND VALIDATION： A CONICAL-BASE SPOUTED BED SIMULATION STUDY

An improved and efficient DEM-CFD approach is developed for spouted beds. A nonlinear Discrete Element Method (DEM), with a concept of spring, dash-pot and friction slider, is used for tracing the movement of each individual particle. The gas flow is described by a set of reorganized governing equations. Two phases are coupled through contributions due to effects of porosity, viscosity and drag. All equations are solved with the commercial package Fluent with an implementation of User Defined Functions (UDF). To validate the improved model, a two-dimensional conical-base spouted bed is chosen as a case study. An unstructured mesh system is adopted instead of regular grid system. The simulation also takes the Saffman force and Magnus effect into account. The calculation results show good agreement with the experimental observations which are taken from the literature.