Product design for strong cover glass

Strength is one of the most important properties of cover glass. In this study, fracture analysis is used to classify the breakage mode of cover glass into four typical modes. Moreover, the mechanism and evaluation method of each mode are investigated. Consequently, a chemical strengthening design with high compressive stress (CS) and low center tension (CT) is obtained. In addition, processing design is determined to be an important factor. Fining of edge processing and surface polishing after chemical strengthening are shown to enhance the edge and surface strength, respectively.     

Dynamics behavior of flat glass panels under impact conditions: Experiments and numerical modeling

Response of brittle plate‐like structures such as glass panels to impact loads has been the subject of many research studies. Different compositions of glass are used in wide variety of applications in daily life. Of interest in this study are the glass panels that are used in consumer electronics devices such as mobile phones, tablets, and televisions that help to protect the displays from every day wear and tear. Therefore, the requirement of this glass to resist scratches, drop impacts, and bumps from everyday use leads to the importance of investigation of the glass response under dynamic impact loading. Ball drop test is a widely accepted test for impact reliability in the industry. The test specifies the impact energy threshold as a qualification and prediction metric. Use of energy as the key parameter in impact testing is limited, because it does not account for the time spent in contact during the impact event. This study attempts to establish a reliable metric for impact testing based on a momentum change. The deformation and the strain of the glass will be obtained by the digital image correlation system, while the rebound velocity will be measured with the high‐speed cameras. The global and local measurements are conducted to verify the accuracy of the experimental results. Finite element analysis is conducted using ABAQUS to provide a comprehensive understanding of the dynamic response of the glass. Constitutive relationship for a tape, a hyperelastic material, is developed in this study. Good correlation in deflection time history is obtained between the measurements and predictions.     

A study of 3D cover glass design that improves handheld device drop reliability

Cover glass in commercial handheld devices is now evolving from flat (2D) to curved (3D) shapes. For example, some commercial devices have utilized sled‐shape cover glass, 1 which partially covers long edges of the device. According to the patents published by key handheld manufacturers, 2 , 3 we can expect more variety of 3D shaped cover glass for handheld devices in the market. In this study, we have focused on the reliability of 3D cover glass when it is dropped to a rigid surface. The key parameters under study are the corner/edge bend radius and angle of the cover glass, which determines the 3D shape of the cover glass. To achieve this goal, we developed a finite element model to simulate the drop 4 - 13 of a handheld device with 3D‐shaped glass. The model uses explicit algorithm to simulate the high speed impact on the device during the drop test. The glass performance was evaluated based on contact force between the glass and the ground and maximum principal stress in the glass. We showed that to avoid severe damage because of first impact between the glass and the ground, the bend angle of 3D glass has to be in the range between 0 and 45°. For drop angles of 45° and higher, with the proposed glass bend angle, the impact can be taken over by the edge of the back cover of the device. In addition, we showed that optimum glass bend radius is in the range of 3.8 mm and larger. This is required to reduce stress in glass because of impact. The approach and conclusions from the current study can serve as a general guideline to improve the 3D cover glass reliability of a handheld device.     

A 2-approximation NC algorithm for connected vertex cover and tree cover

The connected vertex cover problem is a variant of the vertex cover problem, in which a vertex cover is additional required to induce a connected subgraph in a given connected graph. The problem is known to be NP-hard and to be at least as hard to approximate as the vertex cover problem is. While several 2-approximation NC algorithms are known for vertex cover, whether unweighted or weighted, no parallel algorithm with guaranteed approximation is known for connected vertex cover. Moreover, converting the existing sequential 2-approximation algorithms for connected vertex cover to parallel ones results in RNC algorithms of rather high complexity at best.In this paper we present a 2-approximation NC (and RNC) algorithm for connected vertex cover (and tree cover). The NC algorithm runs in O(log²n) time using O(Δ²(m+n)/logn) processors on an EREW-PRAM, while the RNC algorithm runs in O(logn) expected time using O(m+n) processors on a CRCW-PRAM, when a given graph has n vertices and m edges with maximum vertex degree of Δ.     

Mechanism design for set cover games with selfish element agents

In this article, we study the set cover games when the elements are selfish agents, each of which has a privately known valuation of receiving the service from the sets, i.e., being covered by some set. Each set is assumed to have a fixed cost. We develop several approximately efficient strategyproof mechanisms that decide, after soliciting the declared bids by all elements, which elements will be covered, which sets will provide the coverage to these selected elements, and how much each element will be charged. For single-cover set cover games, we present a mechanism that is at least -efficient, i.e., the total valuation of all selected elements is at least fraction of the total valuation produced by any mechanism. Here, d_max is the maximum size of the sets. For multi-cover set cover games, we present a budget-balanced strategyproof mechanism that is -efficient under reasonable assumptions. Here, H_n is the harmonic function. For the set cover games when both sets and elements are selfish agents, we show that a cross-monotonic payment-sharing scheme does not necessarily induce a strategyproof mechanism.     

Refined memorization for vertex cover

Memorization is a technique which allows to speed up exponential recursive algorithms at the cost of an exponential space complexity. This technique already leads to the currently fastest algorithm for fixed-parameter vertex cover, whose time complexity is O(k^1.2832k^1.5+kn), where n is the number of nodes and k is the size of the vertex cover. Via a refined use of memorization, we obtain an O(k^1.2759k^1.5+kn) algorithm for the same problem. We moreover show how to further reduce the complexity to O(k^1.2745k⁴+kn).     

Parameterized algorithm for eternal vertex cover

In this paper we initiate the study of a “dynamic” variant of the classical Vertex Cover problem, the Eternal Vertex Cover problem introduced by Klostermeyer and Mynhardt, from the perspective of parameterized algorithms. This problem consists in placing a minimum number of guards on the vertices of a graph such that these guards can protect the graph from any sequence of attacks on its edges. In response to an attack, each guard is allowed either to stay in his vertex, or to move to a neighboring vertex. However, at least one guard has to fix the attacked edge by moving along it. The other guards may move to reconfigure and prepare for the next attack. Thus at every step the vertices occupied by guards form a vertex cover. We show that the problem admits a kernel of size k⁴(k+1)+2k, which shows that the problem is fixed parameter tractable when parameterized by the number of available guards k. Finally, we also provide an algorithm with running time O(²O(k²)+nm) for Eternal Vertex Cover, where n is the number of vertices and m the number of edges of the input graph. In passing we also observe that Eternal Vertex Cover is NP-hard, yet it has a polynomial time 2-approximation algorithm.     

逻辑函数无冗余覆盖选择问题

逻辑函数的最小化算法可以分为两大步骤,产生本源蕴涵项和在这些蕴涵项中选择一个最小覆盖。提出一个适于大变量输入输出逻辑函数的实质项与相对冗余项的识别和选择近似最小覆盖的算法。Benchmark例题测试表明,算法具有理想的处理效果。     

On the parameterized vertex cover problem for graphs with perfect matching

A vertex cover of an n-vertex graph with perfect matching contains at least n/2 vertices.In this paper,we study the parameterized complexity of the problem vc-pm*that decides if a given graph with perfect matching has a vertex cover of size bounded by n/2+k.We first present an algorithm of running time O*(4k)for a variation of the vertex cover problem on K¨onig graphs with perfect matching.This algorithm combined with the iterative compression technique leads to an algorithm of running time O*(9k)for the problem vc-pm*.Our result improves the previous best algorithm of running time O*(15k)for the vc-pm*problem,which reduces the problem to the almost 2-sat problem and solves the latter by Razgon and O’Sullivan’s recent algorithm.     

Dasymetric modelling of small-area population distribution using land cover and light emissions data

Despite the improvements made in census procedures over recent decades, the availability of detailed population data is limited. For many applications, including environmental and health analyses, methods are therefore needed to model population distribution at the small-area level. With the development of GIS and remote sensing techniques, the ability to develop such models has greatly improved. This paper describes a GIS-based approach using remotely sensed land cover and nighttime light emissions data to model population distribution at the land parcel level across the European Union. Light emission data from the DMSP satellites were first resampled and modelled using kriging and inverse distance weighting methods to provide a 200-m resolution light emissions map. This was then matched to CORINE land cover classes across the EU. Regression methods were used to derive models of relationships between census population counts (at NUTS 5 level) and land cover area and light emissions. Models were developed at both national and EU scale, using a range of different modelling strategies. Model performance, as indicated by the regression statistics, was seen to be good, with R² typically in the order of 0.8-0.9 and SEE ca. 4000 people. In southern countries, especially, incorporation of light emissions data was found to improve model performance considerably compared to models based only on land cover data. More detailed post hoc validation in Great Britain, using independent data on population at census tract (enumeration district and output area) and postcode level, for 1991 and 2001, showed that models gave good predictions of population at the 1 km level (R² > 0.9), but were less reliable at resolutions below ca. 500 m. Impending enhancements in the available land cover and light emissions data are expected to improve the capability of this modelling approach in the future.     

Approximation algorithm for weighted weak vertex cover

The problem of efficiently monitoring the network flow is regarded as the problem to find out the minimum weighted weak vertex cover set for a given graph G = (V, E). In this paper, we give an approximation algorithm to solve it, which has the approximation ratio ln d 1, where d is the maximum degree of the vertex in graph G, and improve the previous work.     

浮法玻璃带缺陷自动检测技术研究

玻璃缺陷自动检测已成为提高玻璃质量的重要技术之一,它在检测出不合格玻璃产品的同时,还能将缺陷信息传递给玻璃生产的各个流程,再对各个环节加以改进。为能够生产出高质量的玻璃和准确地获取玻璃缺陷信息,提出了一种基于光栅的玻璃缺陷检测和三值化的处理方法,不但能够检测出微小缺陷,还能有效地检测出玻璃的波筋缺陷。     

Simulation of tin penetration process in the surface layer of soda-lime-silica float glass

Based on the analysis of tin penetration mechanism in the float glass process, the oxidation model of stannous ion is constructed considering the oxygen activity and the redox reaction in the glass surface layer. The calculation of stannous ion’s oxidation rate makes it possible to predict both stannous and stannic ion’s concentrations independently. And it is also the necessary precondition for the numerical verification of tin penetration mechanism. Coupled diffusion simulation method is established to si...     

A parallel algorithm for approximating the minimum cycle cover

We address the problem of approximating aminimum cycle cover in parallel. We give the first efficient parallel algorithm for finding an approximation to aminimum cycle cover. Our algorithm finds a cycle cover whose size is within a factor of 0(1 +n logn/(m + n) of the minimum-sized cover usingO(log² n) time on (m + n)/logn processors.Research supported by ONR Grant N00014-88-K-0243 and DARPA Grant N00039-88-C0113 at Harvard University.Research supported by a graduate fellowship from GE. Additional support provided by Air Force Contract AFOSR-86-0078, and by an NSF PYI awarded to David Shmoys, with matching funds from IBM, Sun Microsystems, and UPS.     

覆盖层材料对触觉传感器空间分辨率的影响

通过有限元计算 ,分析了弹性覆盖层材料对触觉传感器空间分辨率的影响 ,给出了一些覆盖层材料的选择准则。     

地下综合管廊井盖检测报警系统设计

基于STC89C58RD+单片机,设计了一种地下综合管廊井盖报警系统。该系统采用nRF24L01无线通信和RS-485通信方式,通过主机设定并发送指定从机授权码,工作人员用遥控器向指定从机井盖发送相应授权码,则该从机井盖可以被合法打开;如果从机井盖被非法打开,井盖打开时触发行程开关,产生报警信号并发送到主机,主机显示被非法打开井盖编号,此时工作人员便可采取相应措施。试验测试结果表明：系统响应速度快,传输距离远,传输信号稳定,操作简单,安全性能高。     

A note on ‘Algorithms for connected set cover problem and fault-tolerant connected set cover problem’

A flaw in the greedy approximation algorithm proposed by Zhang et al. (2009) [1] for the minimum connected set cover problem is corrected, and a stronger result on the approximation ratio of the modified greedy algorithm is established. The results are now consistent with the existing results on the connected dominating set problem which is a special case of the minimum connected set cover problem.     

PTAS for connected vertex cover in unit disk graphs

This paper gives the first polynomial time approximation scheme for the connected vertex cover problem in unit disk graphs.     

一种新的商覆盖立方体生成算法

提出一种的新的商覆盖立方体生成算法GroupDFS,将待计算的基本表先依据各维属性进行Group By运算,再对得到的结果集采用DFS算法计算其上界集,所得结果即为原待计算基本表的商覆盖立方体。GroupDFS算法结合了2^N算法和DFS算法的优点,相对于DFS算法缩短了计算所需的时间。采用weather数据集进行的实验结果表明,采用GroupDFS计算商覆盖立方体所需时间仅为采用DFS算法时的45%。     

Subexponential algorithms for partial cover problems

Partial Cover problems are optimization versions of fundamental and well-studied problems like Vertex Cover and Dominating Set. Here one is interested in covering (or dominating) the maximum number of edges (or vertices) using a given number k of vertices, rather than covering all edges (or vertices). In general graphs, these problems are hard for parameterized complexity classes when parameterized by k. It was recently shown by Amini et al. (2008) [1] that Partial Vertex Cover and Partial Dominating Set are fixed parameter tractable on large classes of sparse graphs, namely H-minor-free graphs, which include planar graphs and graphs of bounded genus. In particular, it was shown that on planar graphs both problems can be solved in time ²O(k)nO(1).During the last decade there has been an extensive study on parameterized subexponential algorithms. In particular, it was shown that the classical Vertex Cover and Dominating Set problems can be solved in subexponential time on H-minor-free graphs. The techniques developed to obtain subexponential algorithms for classical problems do not apply to partial cover problems. It was left as an open problem by Amini et al. (2008) [1] whether there is a subexponential algorithm for Partial Vertex Cover and Partial Dominating Set. In this paper, we answer the question affirmatively by solving both problems in time not only on planar graphs but also on much larger classes of graphs, namely, apex-minor-free graphs. Compared to previously known algorithms for these problems our algorithms are significantly faster and simpler.