Coupled Conduction-convective Heat Transfer in the Louvered Fin Heat Exchanger

The heat transfer process in the louvered fin heat exchanger is analyzed,and the corresponding physical and mathematical models on the coupled conduction-convective heat transfer for the louver fin geometry are proposed.The control volume-based finite element method(CVFEM) is employed to solve numerically the problem.The computed(results) reveal the flow structure and heat transfer in the geometry in detail.Compared with the empirical correlation of heat transfer and friction coefficients previously proposed,the computed results show better consistency with the experimental results.     

THE EQUATION OF STBING IN THE EXTERNAL FIELDS

The classical equations of string in the external fields deduced with Kaluza's method. A solution of the equations for uniform magnetic field is got by means of differential geometry technlqde.     

基于OpenCV的Android手机植物叶片几何参数测量系统

通过Android 手机对植物叶片图像进行处理以测量其长、宽、周长、面积等几何参数,避免其他测量方法的缺点,提高数据采集效率。首先,获取含有已知尺寸矩形框的叶片图像。然后,对图像进行校正以消除倾斜失真。在校正阶段,采用了更为鲁棒的特征点检测法代替可能出现错误结果的Hough 变换法来处理矩形框,得到其4 个角点。根据求得的角点与标准图像的角点对图像进行映射得到校正图像。最后,处理校正图像计算叶片几何参数。参数计算提出以叶片轮廓为基础的方法,所有参数均通过对轮廓的处理求出,提高了计算效率。此外,基于轮廓求面积不需要对叶片进行形态学处理消除空隙及不连续,还可避免统计像素方法中将噪声像素误认为叶片造成的计算不精确。在求叶片长、宽时,给出了2 种方法供用户根据叶片实际形状选择。另外,在编程方面,采用了OpenCV-Android-SDK,大幅提高了图像处理速度。结果表明,精确度测试中,对打印出的规则图形几何参数测量的结果误差均在2%以内;而实际叶片的测量结果中长、宽的误差在2%以内,周长误差小于4%,面积误差低于3%。耗时测试中,相同图像处理算法采用OpenCV后,处理速度明显提升;对多部不同配置手机的测试中,处理1 幅分辨率为2448×3264 的叶片图像的耗时均在3 s 以内。另外,对于同一叶片图像,不同手机测量的结果完全一致。实验表明,该系统不仅操作简单、速度快、通用性强,而且对叶片几何参数的测量精确度也较高。     

Practical Method of Form-finding of Semi-rigid Structures

Based on the discussion of the simulation for the cable prestress, the rigidity theory was used to identify the geometrical dimensions of semi-rigid structures in zero state. When the structural geometry in initial state is given, the geometrical dimension in zero state is determined by the initial prestress distribution. The contribution-matrix method is firstly applied to get the initial lack of fit. However, the influencing factor of initial lack of fit on the displacement of control point is linear superposition, that is, the structural response is linear, and it is irreconcilable with the geometry nonlinear of semi-rigid structure. In order to reduce the error of nonlinear structural response, the influencing factor in the contribution-matrix method is revised, and modified contribution-matrix method is put forward. Programs by ANSYS parameter design language APDL are worked out for the form-finding analysis of beam-string structure of a practical project. The numerical results show that the modified contribution-matrix method reduces the errors of the assumption of structural linear response. And it can be applied to the form-finding of semi-rigid structures with small stiffness.     

Designing Complex Shapes with NURBS

This article discusses the designing method of complex shapes with NURBS. The general design process of curve and surface is put forward in this paper,and the correspondent mathematical expressions and computational method are also presented. Because of the superior feature of NURBS, these methods are very suitable for constructing different kinds of shapes,and easy to use in engineering applications. Finally,the authors summarize various kinds of method of geometry design, based on NURBS.     

Numerical Method for Load Bearing Capacity of High Strength Steel Columns at Elevated Temperature

In order to make fire resistance design of high strength steel columns in building structures, the numerical calculation method on load bearing capacity of high strength steel columns at elevated temperature was investigated. By taking the mechanical property of high strength steel at elevated temperature into consideration, extension was made on the inverse calculation segment length method and the program to compute the load bearing capacity of high strength steel columns at elevated temperature was performed. The program was adopted to compute the load bearing capacity. The results obtained by the program and the finite element analysis were compared and good agreement had been found. The influence of magnitude, distribution mode of residual stress and initial geometry imperfection on ultimate load bearing capacity was analyzed by employing the program. It is shown that the extended method can be is shown used to calculate the load bearing capacity of high strength steel columns at elevated temperature; the magnitude and distribution mode of residual stress had little influence but the geometry imperfection have significant influence on ultimate load bearing capacity.     

Analysis of Heat Transfer and Optimal Parameters of Multi-louvered Fin Condenser

The authors conduct the experimental study and optimal computing for the condenser of automobile air conditioner. The especially the properties of heat transfer and flow at the side of air when using shutter fin. The authors the influence of several combinations of fin's geometry parameter to heat transfer and flow resistance. The maximal heat transfer is used as a criterion relation to select the fin's geometry parameters in the same facing air area of condenser. Furthermore, a program is designed to conduct optimal computing, and the computing results are basically consistent with experimental results. It shows that the optimal method is reasonable and the results can be applied to engineering practice.     

Numerical simulation of the internal dynamic excitation of a spiral bevel gear transmission

A 3-D geometry model and a static/dynamic finite element (FE) model of a spiral bevel gear transmission are established. Using ANSYS software, the mesh stiffness excitation of a tooth pair is calculated via the static contact FE method. Using LS     

Short- Line Match Casting Technique for Precast Segmental Construction

The precast segmental construction technique is widely used in the viaduct structures for both vehicular and light rail systems.The present paper highlights the application of short-line match casting technique in fabricating the precast segments for 75m span continuous approach structures of Sutong bridge project.It discusses the functional specifications of the segment mould and its geometry control method.     

Defects detection in the inner surface of pipes based on inverse heat conduction problem

It is a typical ill posed inverse heat conduction problem to estimate the geometry boundary of the inner surface of pipe by the temperature of outer surface. With the establishment of a two dimensional steady model for pipe with irregular inner surface, the inverse problem is transformed into a direct problem and an optimization problem. Based on the temperature at the outer surface obtained from the infrared thermography and the variation of the object function, the conjugate gradient method (CGM) is introduced into the geometry problem. With the numerical analysis of three typical defects, the effects of the measurement errors, choice of the initial value, boundary conditions and number of discrete temperature points are discussed and the proposed methodology is approved.     

A Non-Euclidean Geometry Electronic Drawing-board

The concept and method of adding a projection plane to AUTO CAD drawing-board and drawing non-Euclidean geometry graph on the board are discussed. The correlative application software is programmed. The analysis of the working angle of complicate shows that developing the new type cutters are rapidly and accurately with this software.     

Method to Determine the Intersection of Two Arbitrary Solid Polygon With Node Operation

The method to polygon' intersection is applied in computational geometry, computer graphics, GIS, evaluation of geo-hazards and civil engineering. Based on the node state of polygon, the authors propose the method and algorithm of polygon' intersection, the key to which is node operation. This method's concept is simple; and it is easy to computer program's implementation. It avoids to singular problem of Boolean Operation, and is easy to solve the problem of overlapping side and sides intersecting in node of polygon. For the arbitrary way of intersecting of arbitrary solid polygon, this method is accurate and general.     

Dynamic Modeling and Analysis for a Humanoid Robot

To resolve the kinematics modeling and dynamics modeling of a humanoid robot with complicated machine, a modeling method based on the conventional mechanism combined with neural network is presented. First the kinematics formulas are deduced by analyzing its geometry structure. Second, the dynamics models are built up with Lagrange-Euler method combined with the define of interactive force among all parts of the humanoid robot. The interactive force is realized by neural network method. Finally, the true robot parameters are applied to the model. The simulation results show the validity of the modeling. So, the method is practical and available.     

苹果果实几何造型及可视化研究

提出了一种苹果果实几何造型的方法。采用Bézier曲线拟合苹果果实的轮廓,通过加入表征品种特征的扰动函数来控制果实表面的果棱。模型可控参数少且具有明确的生物学意义,易于与农业知识结合。针对苹果果实品种繁多、表面颜色丰富的特点,除了采用纹理映射方法绘制苹果表面外,还提出了基于颜色表的表面颜色随机填充法。实验结果表明该方法能够模拟多种苹果品种果实的外观特征,具有较好的真实感效果。     

基于最小阈值法的棉花幼苗识别研究

 面对纯机械式分苗机构经常出现的漏分和多分的问题,本文提出使用基于最小阈值法的图像识别技术对棉花幼苗进行识别和分离。使用了HSV颜色空间内与光照条件无关的H值将RGB真彩色图像转化为灰度图像,以提高图像处理的实时性。基于最小值阈值法,提出一种能够有效地将处于复杂背景下的棉花幼苗茎部图像提取的方法,使用棉花幼苗茎部图像的面积和长宽比等几何信息能有效识别棉花幼苗,并得到棉花幼苗茎部的重心坐标。本文的研究证明了用图像处理中的最小阈值法识别棉花幼苗是可行的。     

蒲公英-夏枯草-野菊花复合饮料的研制

以蒲公英、夏枯草、野菊花为原料,研究蒲公英、夏枯草、野菊花复合饮料的加工工艺,探究复合饮料的稳定效果。通过正交试验、感官评价等获得蒲公英、夏枯草、野菊花的最佳比例和复合饮料成品各配料比例、稳定性等的最佳配方。采用硝酸铝分光光度法（芦丁标准品）、苯酚硫酸法、折光计法、微生物检测国家标准等进行其质量测定。获得该饮品的最佳配方为：蒲公英汁2%、夏枯草汁55%、野菊花汁43%、白砂糖12%、柠檬酸0.16%。该复合饮料总黄酮含量为0.89 mg/mL,总多糖含量为95.45 mg/mL,可溶性固形物为8.6%,pH 3.30(25℃)。     

农业信息网站服务质量评价指标优化研究

提高农业信息网站服务质量是有效解决农业信息化发展瓶颈的方法之一。科学的网站服务质量评价,可以提高用户获取信息的效率,同时网站设计者通过了解影响其服务质量的主要因素,可以优化网站资源配置。笔者参考服务质量管理的有关原理和已有的指标设计方法,构建了一个农业信息网站服务质量评价通用模型,利用R型系统聚类法探索描述性指标项优化问题,以避免指标项之间存在的相关、重复情况,最后以40个茶叶信息网为实验对象进行数据采集与分析,构建农业信息网站服务质量评价影响因素的多元回归模型,得出在信息服务系统构建过程中影响信息服务质量的重要因素。     

安新县地下水多组分含量分析及水质评价

为了查明安新县地下水水化学特征以及水质现状,选取45组地下水,采用仪器分析和容量分析相结合的方式进行测定,综合运用描述性数理统计和三元相图,分析安新县地下水的主要离子特征,并运用综合评价法对地下水质量予以评价。结果表明:（1）该区域地下水偏弱碱性,水化学类型主要以HCO₃-Na型为主。（2）pH和偏硅酸在空间上变异最低(CV<30%);K⁺和NO₃^-的空间变异性最高(CV>100%);其余指标的空间变异中等(CV:30%~100%)。（3）影响本区地下水环境质量的指标主要为TDS、SO₄^2-、F^-和总硬度。（4）水质评价结果显示该区地下水水质总体状况较好,多为Ⅲ类水,研究成果对了解安新县地下水水质现状具有重要意义。     

三维轴对称功能梯度材料瞬态热传导问题的自然单元法

为了更有效地求解三维轴对称功能梯度材料瞬态热传导问题,对无网格自然单元法应用于此类问题进行了研究,并发展了相应的计算方法。基于几何形状和边界条件的轴对称性,三维的轴对称问题可降为二维平面问题。为了简化本质边界条件的施加,轴对称面上的温度场采用自然邻近插值进行离散。功能梯度材料特性的变化由高斯点的材料参数进行模拟。时间域上,采用传统的两点差分法进行离散求解,进而得到瞬态温度场的响应。数值算例结果表明,提出的方法是行之有效的,理论及方法不仅拓展了自然单元法的应用范围,而且对三维轴对称瞬态热传导分析具有普遍意义。     

Non-linear finite element analysis based on the spatial catenary cables

According to the elastic catenary theory,this paper derives the spatial catenary cable element from the exact analytical expression,which is used for finite element analysis of the structure.It deduces the precise expression of two-node cable element tangent stiffness matrix and the tension of cable end.The equivalent node load of cable element is expressed by the total load algorithm,and the non-linear equation is solved by double Newdon-rapson method.The proposed non-linear semi-analytical finite element method based on spatial catenary cable element can take full account of the impact of non-linear geometry.The initial configuration and the internal forces on any directional spatial loads can be solved.The example shows that the calculation method is accurate and effective.