Algorithm for 2D irregular-shaped nesting problem based on the NFP algorithm and lowest-gravity-center principle

INTRODUCTION 2D irregular-shaped nesting problem is the problem of finding an efficient arrangement for pieces in a containing region without overlapping (Fig.1), and is aimed at maximizing use of material. Nesting problem is of great interest to garment, paper, ship building, and sheet metal industries since small improvement of layout can lead to large savings in material. Many effective solutions have been pro- posed for the case when pieces and containing region are both rectangular. …     

A new extension algorithm for cubic B-splines based on minimal strain energy

INTRODUCTION B-spline curves and surfaces have been widely used in Computer Graphics (CG) and Computer Aided Design (CAD) (Hoschek and Lasser, 1993; Piegl and Tiller, 1997). Many practical algorithms, such as those for position and derivatives evaluation, knot insertion, knot deletion and degree elevation, are usually implemented in a CAD system that uses B-spline as a shape design tool. In curve and surface design, a given B-spline curve or surface usually needs to be extended in …     

Algorithm for 2D irregular-shaped nesting problem based on the NFP algorithm and lowest-gravity-center princlple

The nesting problem involves arranging pieces on a plate to maximize use of material. A new scheme for 2D irregular-shaped nesting problem is proposed. The new scheme is based on the NFP （No Fit Polygon） algorithm and a new placement principle for pieces. The novel placement principle is to place a piece to the position with lowest gravity center based on NFP. In addition, genetic algorithm （GA） is adopted to find an efficient nesting sequence. The proposed scheme can deal with pieces with arbitrary rotation and containing region with holes, and achieves competitive results in experiment on benchmark datasets.     

A new algorithm for computing the convex hull of a planar point set

When the edges of a convex polygon are traversed along one direction,the interior of the convex polygon is always on the same side of the edges. Based on this characteristic of convex polygons,a new algorithm for computing the convex hull of a simple polygon is proposed in this paper,which is then extended to a new algorithm for computing the convex hull of a planar point set. First,the extreme points of the planar point set are found,and the subsets of point candidate for vertex of the convex hull between extreme points are obtained. Then,the ordered convex hull point sequences between extreme points are constructed separately and concatenated by removing redundant extreme points to get the convex hull. The time complexity of the new planar convex hull algorithm is O(nlogh) ,which is equal to the time complexity of the best output-sensitive planar convex hull algorithms. Compared with the algorithm having the same complexity,the new algorithm is much faster.     

A new fast algorithm for computing the distance between two disjoint convex polygons based on Voronoi diagram

INTRODUCTION To compute the minimum distance between two convex polygons or polyhedrons is often a main step of many applications, such as collision detection (Choi et al., 2006; Li et al., 2003), path planning. In order to reduce the time complexity of the algorithm as much as possible, the convex property must be applied fully. Edelsbrunner (1985) proposed an algorithm for computing the minimum distance between two dis- joint convex polygons. The algorithm takes O(logm logn) time, and …     

A power divider based on a new kind of composite right/left-handed transmission line （CRLH TL） unit

A new power divider, composed of a novel composite right/left-handed （CRLH） transmission line （TL） unit, is proposed. The properties of the power divider based on four CRLH TL unit cells are investigated theoretically. By adjusting the parameters of the capacitors and the inductors, the power divider shows perfectly symmetric power division at 5.13 GHz, return loss up to -24 dB, with the transmitted power being close to 3.1 dB. The phenomena are demonstrated by simulation results. Being compact in size and low-cost, the proposed power divider is very suitable for microwave and millimeter wave integrated circuits.     

Does a formal wiki event contribute to the formation of a network of practice? A social capital perspective on the potential for informal learning

Informal learning in blended and online settings plays an increasingly important role in the continuous professional development of individuals. Yet, how do individuals engage into these types of activities? We argue that social capital theory can provide valuable insights into how people behave and decide to take part in (in)formal learning. Using social network analysis, we provide empirical evidence on an informal learning activity, where participants collaboratively created knowledge on wiki sites on a predefined set of topics. Our results show that there are three types of active participants in these types of informal learning activities, namely leaders, collaborators and lone editors. These findings provide valuable insights for other, similar activities that aim at enhancing the professional development of individuals.     

Science Letters:Demonstration of a new biosensing concept for immunodiagnostic applications based on change in surface conductance of antibodies after biomolecular interactions

Electrical conductivity in biomolecules and other large polymeric systems has become an important topic of current research. Schlag et al.(2000a; 2000b) demonstrated that charge migration in proteins is highly efficient although the mechanistic origin is still debated and largely unknown even though various models have been proposed by Weinkauf et al.(1995; 1996; 1997). According to them, the charge transfer between amino acids takes place by hole hopping between local sites of lowest ionizati…     

‘Building Schools for the Future’: reflections on a new social architecture

The Labour Government launched the ‘Building Schools for the Future’ programme (BSF) in February 2003 with the aim of refurbishing or rebuilding all secondary schools in England over a 15‐year period, with an anticipated budget of £45 billion. In this article, we locate BSF in a wider public policy context which has already had important implications in other sectors of public provision. The local improvement finance trusts (LIFTs) initiative within the National Health Service (NHS) is of particular relevance to this discussion both because it reflects contemporary developments within New Public Management and because it also reveals new ways of extending and developing the private finance initiative (PFI) approach to public provision. We shall also consider the purposes and ‘delivery’ mechanisms of BSF and identify some of the key commentaries which have been provided by parliamentary reports and other evaluations. Although still in the early stages of its implementation, the BSF is of such significance for the future shape and form of educational provision that it is important to begin the process of considering possible directions and dimensions for a research agenda which will provide a secure empirical and analytical foundation on which to base discussion.     

GAJA： 3D CAD methodology for developing a parametric system for the automatic （re）modeling of the cutting components of compound washer dies

For the designing of cutting-dies is a complex and experience-based process, it is poorly supported by conventional 3D CAD software. Thus, the majority of design activities, including the (re)modeling of those cutting die-components that are directly responsible for performing shaping operations on a sheet-metal stamping part, traditionally still need to be carried-out repetitively, separately, and manually by the designer. To eliminate some of these drawbacks and upgrade the capabilities of conventional 3D CAD software, this paper proposes a new methodology for the development of a parametric system capable of automatically performing a (re)modeling process of compound washer dies’ cutting-components. The presented methodology integrates CATIA V5 built-in modules, including Part Design, Assembly Design and Knowledge Advisor, publication mechanism, and compound cutting die-design knowledge. The system developed by this methodology represents an ‘intelligent’ assembly template composed of two modules GAJA1 and GAJA2, respectively. GAJA1 is responsible for the direct input of the die-design problem regarding the shape, dimensions and material of the stamping part, its extraction in the form of geometric features, and the transferring of relevant design parameters and features to the module GAJA2. GAJA2 interprets the current values for the input parameters and automatically performs the modeling process of cutting die-components, using die-design knowledge and the company’s internal design and manufacturing standards. Experimental results show that this system significantly shortens the modeling-time for cutting the die-components, improves the modeling-quality, and enables the training of inexperienced designers.     

基于遗传算法的二维排样问题求解新策略

针对采用自然编码的遗传算法在排样问题（CSP）过程中初始群体设置和交叉变异操作过于复杂的缺点,采用了顺序编码（Grefenstette编码）作为遗传算法编码方案,并对排样问题进行求解。采用这种遗传算法策略对CSP试算的结果表明,该策略利于排样问题的求解,算法操作简单,可推广应用到制造业及其他规划领域的排样规划中。     

基于BP算法的多层感知器网络原理及程序实现

针对已有的三层感知器工作原理,通过增加多个隐层的方法,将其扩展成为基于BP算法的多层感知器网络;利用单、双极性Sigmoid函数的性质和多元函数的偏导数求导法则,推导出了多层感知器网络工作原理,并且给出BP算法的编程步骤;最后的实例证明了本文算法的有效性.     

基于一个新核函数的半定规划的内点算法的复杂性分析

Interior-point methods （IPMs） for linear optimization （LO） and semidefinite optimization （SDO） have become a hot area in mathematical programming in the last decades. In this paper, a new kernel function with simple algebraic expression is proposed. Based on this kernel function, a primal-dual interior-point methods （IPMs） for semidefinite optimization （SDO） is designed. And the iteration complexity of the algorithm as O（n^3/4 log n/ε） with large-updates is established. The resulting bound is better than the classical kernel function, with its iteration complexity O（n log n/ε） in large-updates case.     

核心素养导向的幼儿古筝启蒙教育探析

核心素养源于三维目标,却高于三维目标,它更能体现以人为本的教育理念。在幼儿古筝启蒙教育阶段,应避免传统的以知识(读谱识谱等)、技法技巧为重点而忽视幼儿为本的教育理念,着重培养幼儿现在和将来所必有的关键能力、情感态度。即在幼儿已有经验的基础上,通过感性认识、潜意识培养幼儿想象力、创造力及审美情趣。     

基于生态问题下的新型城镇化建设对策思考

新型城镇化建设的主要目标,就是保障新型农村、城镇以及中小城市的统筹协调,进而实现生态化、集约化的城乡和谐发展模式。本文对基于生态问题下的新型城镇化建设对策进行了探究。     

基于能量密度的地图线性要素提取改进算法

在地理图形中,线性特性目标的能量密度与背景图像的能量密度不同,根据这一特性,分析了基于能量密度对线性目标识别算法的不足,提出基于多个模板搜索目标算法,不同的模板应用不同的规则以及自适应的算法,通过仿真实验,该算法能较好地识别出地理图像的目标要素.