Earticle

본 연구에서는 female adult mesh (FASH) 팬텀으로부터 획득한 CT 영상에 FNLM 알고리즘을 적용하여 유사도를 분석하고자 한다. 먼저, GATE (geant4 application for tomographic emission) 프로그램을 이용하여 FASH의 전신 CT 스캔 데이터를 모델링한 뒤 그 데이터로부터 MATLAB 프로그램을 통해 442 × 256 사이즈의 CT axial 영상을 획득하였다. 그리고 획득한 원본 이미지에 표준편차 0.002를 가지는 가우시안 노이즈를 부가함으로서 Noisy 이미지를 획득한 뒤 그 이미지에 fast non-local means (FNLM) 알고리즘을 가중치 조절 인자 h를 0.05로 적용하였다. 본 연구에서는 유사도를 평가하기 위하여 평균 제곱근 편차 (Root Mean Square Error, RMSE)와 최대 신호 대 잡음비 (Peak Signal-to-noise ratio, PSNR)를 사용하였다. 원본이미지와 FNLM 알고리즘이 적용된 영상과의 유사도를 평가 한 결과, 원본이미지와 노이즈 이미지의 유사도에 비하여 RMSE 수치는 1.45배 향상되었으며, PSNR 수치는 1.04배 향상되었다. 결론적으로 FNLM 알고리즘은 영상을 복원하는데 효과가 있음이 증명되었다.

In this study, we analyzed the similarity about image applied fast non-local means (FNLM) algorithm to CT images obtained from the female adult mesh (FASH) phantom. First, full-body CT scan data of the FASH was modeled using the genant4 application for tomographic emission (GATE) program, and from that data, a 442 × 256 CT axial image was obtained through the MATLAB program. Subsequently, a noisy image was obtained by adding Gaussian noise with a standard deviation of 0.002 to the acquired original image and the FNLM algorithm which has 0.05 weight was applied to the image. In this study, root mean square error (RMSE) and peak signal-to-noise ratio (PSNR) were used to evaluate the similarity. As a result of evaluating the similarity between the original image and the image with FNLM algorithm, the RMSE level was 1.45 times and PSNR level was 1.04 times higher than the noisy image. In conclusion, we demonstrated that the FNLM algorithm can restore efficiently the noisy images.

최근 BIM (Building Information Modeling)과 AR (Augmented Reality)을 결합한 실시간 시각화 기술이 건설관리 의사 결정 및 처리 효율성을 높이는 데 도움이 된다는 것을 보여주기 위한 다양한 연구가 활발히 진행되고 있다. 그러나, 대용량 BIM 데이터는 AR에 적용할 경우 데이터 전송 문제, 이미지 단절, 영상 끊김 등과 같은 다양한 문제가 발생함으로 3차원(3D) 모델의 메쉬 최적화를 통해 시각화의 효율성을 향상시켜야 한다. 대부분의 기존 메쉬 경량화 방법은 복잡하고 경계가 많은 3D 모델의 메쉬를 적절하게 처리할 수 없다. 이에 본 연구에서는 고성능 AR 시각화를 위해 BIM 데이터를 재구성하기 위한 k-최근접이웃(KNN) 분류 프레임워크 기반 메쉬 경량화 알고리즘을 제안하였다. 제안 알고리즘은 선정된 BIM 모델을 삼각형 중심 개념 기반의 Unity C# 코드로 경량화하였고 모델의 데이터 세트를 활용하여 정점 사이의 거리를 정의할 수 있는 KNN로 분류되었다. 그 결과 전체 모델과 각 구조의 경량화 메쉬 점 및 삼각형 개수가 각각 약 56 % 및 약 42 % 감소됨을 확인할 수 있었다. 결과적으로, 원본 모델과 비교했을 때 경량화한 모델은 시각적인 요소 및 정보 손실이 없었고, 따라서, AR 기기 활용 시 고성능 시각화를 향상시킬 수 있을 것으로 기대된다.

Various studies are being actively conducted to show that the real-time visualization technology that combines BIM (Building Information Modeling) and AR (Augmented Reality) helps to increase construction management decision-making and processing efficiency. However, when large-capacity BIM data is projected into AR, there are various limitations such as data transmission and connection problems and the image cut-off issue. To improve the high efficiency of visualizing, a mesh optimization algorithm based on the k-nearest neighbors (KNN) classification framework to reconstruct BIM data is proposed in place of existing mesh optimization methods that are complicated and cannot adequately handle meshes with numerous boundaries of the 3D models. In the proposed algorithm, our target BIM model is optimized with the Unity C# code based on triangle centroid concepts and classified using the KNN. As a result, the algorithm can check the number of mesh vertices and triangles before and after optimization of the entire model and each structure. In addition, it is able to optimize the mesh vertices of the original model by approximately 56 % and the triangles by about 42 %. Moreover, compared to the original model, the optimized model shows no visual differences in the model elements and information, meaning that high-performance visualization can be expected when using AR devices.

노드들 간의 설치비용과 트래픽 요구량이 주어졌을 때, 이 조건을 만족하는 메쉬망을 설계하는 주요 고려사항으로는 설계시간, 비용, 지연, 신뢰성등 여러 가지가 있으며, 일반적으로 설계시간을 줄이고, 비용은 작게, 지연은 적게, 신뢰성이 높은 메쉬망을 설계하여야 한다. 설계시간에 대한 문제는 Aaron Kershenbaum이 제안한 MENTOR (mesh network topology optimization and routing) 알고리즘에 의해 최소화를 이루는데 성공하였지만 비용, 지연, 신뢰성에는 여전히 문제가 남아있다. 본 논문에서는 MENTOR의 설계시간의 장점을 유지하면서 다른 성능인자들을 만족시킬 수 있는 새로운 망설계 알고리즘을 제안하고자 한다. 제안된 알고리즘의 설계결과는 MENTOR 알고리즘의 성능인자들보다 개선되었음을 보여주었다.

We consider the problems that consist of designing time, establishment cost, delay time and reliability in designing a mesh network when given link costs and traffic requirements between nodes. Designing time, establishment cost and delay time are less, reliability is higher in designing a mesh network. One of the problems designing time is solved by mesh network topology optimization and routing (MENTOR) algorithm that Aaron Kershenbaum propose, but the others remain. In this paper we propose a new mesh network design algorithm with small computational complexity that the others are solved. The result of the proposed algorithm is better than MENTOR's in total establishment cost, delay time and reliability.

본 논문에서는 가상 공간에서 객체와의 상호 작용을 위한 빠른 충돌 감지 방법을 제안하였다. 먼저 메쉬 그룹화 단계에서는, 전체 공간을 일정한 크기의 소공간들로 분할하고, 각각의 소공간에 속하는 메쉬들에 대하여 이들을 모두 포함하는 최소의 기본 입체도형(육면체 혹은 구)의 위치와 크기를 정함으로써 그룹화한다. 충돌 검출 단계에서는, HIP(Haptic Interface Point)가 어떤 그룹을 대표하는 입체도형 내부에 들어 있는지를 검사하여 특정 입체도형과의 충돌이 확인되면 해당 그룹의 메쉬들만을 대상으로 실제 충돌이 일어난 메쉬를 찾는다. 본 논문에서 제안한 방법을 적용한 경우와 적용하지 않은 경우의 연산시간을 측정 및 비교함으로써 제안한 알고리즘의 효용성을 확인하였다.

In this paper, we propose a fast collision detection method for interacting with objects in virtual space. First, in the mesh grouping step, the entire space is divided into small spaces of a predetermined size, and the positions and sizes of the smallest basic stereoscopic shapes (cube or sphere) including all of the meshes belonging to each small space are determined. In the collision detection step, it is checked whether a haptic interface point (HIP) is included in a three-dimensional figure representing a group. When a collision with a specific three-dimensional figure is confirmed, searching is performed only for the meshes in the group to find a mesh on which a possible real collision with HIP occurred. The effectiveness of the proposed algorithm is verified by measuring and comparing the computation time of the proposed method with and without the proposed method.

Wireless Mesh Networks (WMNs) have emerged as one of the new hot topics in wireless communications. WMNs have been suggested for use in situations in which some or all of the users are mobile or are located in inaccessible environments. Unconstrained transmission in a WMN may lead to the time overlap of two or more packet receptions, called collisions or interferences, resulting in damaged useless packets at the destination. There are two types of collisions; primary collision, due to the transmission of the stations which can hear each other, and hidden terminal collision, when stations outside the hearing range of each other transmit to the same receiving stations. For a WMN, direct collisions can be minimized by short propagation and carrier sense times. Thus, in this paper we only consider hidden terminal collision while neglecting direct collisions. To reduce or eliminate hidden terminal collision, code division multiple access (CDMA) protocols have been introduced. The collision-free property is guaranteed by the use of spread spectrum communication techniques and the proper assignment of orthogonal codes. Such codes share the fixed channel capacity allocated to the network in the design stage. Thus, it is very important to minimize the number of codes while achieving a proper transmission quality level in CDMA WMNs. In this paper, an efficient heuristic code assignment algorithm for eliminating hidden terminal collision in CDMA WMNs with general topology.

Remote protein homology detection is a problem of detecting evolutionary relationship between proteins at low sequence similarity level. Among several problems in remote protein homology detection include the questions of determining which combination of multiple alignment and classification techniques is the best as well as the misalignment of protein sequences during the alignment process. Therefore, this paper deals with remote protein homology detection via assessing the impact of using structural information on protein multiple alignments over sequence information. This paper further presents the best combinations of multiple alignment and classification programs to be chosen. This paper also improves the quality of the multiple alignments via integration of a refinement algorithm. The framework of this paper began with datasets preparation on datasets from SCOP version 1.73, followed by multiple alignments of the protein sequences using CLUSTALW, MAFFT, ProbCons and T-Coffee for sequence-based multiple alignments and 3DCoffee, MAMMOTH-mult, MUSTANG and PROMALS3D for structural-based multiple alignments. Next, a refinement algorithm was applied on the protein sequences to reduce misalignments. Lastly, the aligned protein sequences were classified using the pHMMs generative classifier such as HMMER and SAM and also SVMs discriminative classifier such as SVM-Fold and SVM-Struct. The performances of assessed programs were evaluated using ROC, Precision and Recall tests. The result from this paper shows that the combination of refined SVM-Struct and PROMALS3D performs the best against other programs, which suggests that this combination is the best for RPHD. This paper also shows that the use of the refinement algorithm increases the performance of the multiple alignments programs by at least 4%.

In order to improve serious signal interference and energy consumption of wire mesh backbone network due to omni-directional antenna communication mechanism, a topology control optimization algorithm in wireless mesh backbone networks based on directional antenna is proposed. At first, this algorithm used Delaunay graph model to quickly find gateway node by position information of network nodes. Then, in view of the relationship between network transmission distance and the node degrees, it optimizes the network topology structure and lines. In order to improve the transmission rate of wireless mesh network and solve new interference and energy loss problem after adjusting Delaunay graph to achieve a gateway deployment of wireless mesh network using directional antenna, the algorithm reduces wireless links that the transmission distance is too long and energy consumption is higher, and defines the upper limit of the number of directional antenna on routing nodes. The simulation results show that this algorithm can minimize the number of gateway and the shorten network transmission distance from route node to gateway node. This algorithm can effectively decrease the deployment cost and interference by using less antennas and promote the network performance at the same time.

Despite the great success in smoothing of triangular mesh, the classical methods mostly require human interactions. In order to reduce the parameter settings, an adaptive and anisotropic smoothing algorithm for removing noise and preserving features of triangular mesh model was proposed. First calculate the expected normal vector of the model triangles, the expected normal vector should be an accurate representation of the desired movement direction and be similar to the original surface normal vector, and then we compute the value of the offset value. We develop an adaptive coefficient scheme which can avoid the parameter settings to obtain the coefficient value for each vertex. Finally, we updated every vertex’s position of the model by formula. Experimental results show that the algorithm can be adaptive to preserve sharp features and avoid shrinkages by comparing with classical methods.

The majority of recent embedded systems are based on MPSoCs (Multi-Processors System on Chip) architectures. The topologies and the interconnections inside multi processors almost adopt NoCs (Networks on Chip) whose topology and task scheduling algorithm have a direct impact on its performances. In this paper, by using static data flow, a task scheduling algorithm which would automatically assign the application tasks onto different processors is proposed based on complex network. The goal of our algorithm is to replace the static data flow subnetwork by a single dynamic data flow actor such that the global performance in terms of latency and throughput is optimized. Through complex network, it greatly enhances the power of our algorithm in terms of avoiding deadlock, saving energy and providing for integration with more general models of computation. Experimental results show up to 60% performance improvement for real-world examples.

In this paper, we propose a simplified pollution adaptive mesh generation algorithm using singular elements. The algorithm based on the element pollution error indicator concentrate on boundary nodes. The automatic mesh generation method is followed by either a node-relocation or a node-insertion method. The boundary node relocation phase is introduced to reduce pollution error estimates without increasing the boundary nodes. The node insertion phase greatly improves the error and the factor with the cost of increasing the node numbers. It is shown that the suggested r-h version algorithm combined with singular elements converges more quickly than the conventional one.

Objective: Quadric Error Metrics (QEM) algorithm can simplify complex 3D models. However, for its simple error metrics, QEM is not suitable to simplify medical model that contains many minute detail features. We need to develop a new algorithm because we are often interested in these features. Methods: Based on QEM, We classify the vertex into seven classes. Different class has different cost of collapse. In our algorithm, collapse usually occurs with the lowest cost during simplification, thus minute feature can be preserved as possible. We also introduce the average of correlative triangles' area to estimate the volume change during the simplification. Results: We test our algorithm on several complex medical models and find that our improved algorithm is effective and fast. Conclusion: To simplify a complex medical model, we want to preserve the minute feature during simplification. By classifying the vertexes, we develop an improved algorithm based on QEM. The testing results shows that our algorithm not only maintains the high efficiency of QEM algorithm, but also meets the high requirements of medical image processing on fidelity and mesh quality. (Journal of Korean Society of Medical Informatics 13-2, 165-169, 2007)

A combined procedure for two-dimensional Delaunay mesh generation algorithm and an adaptive remeshing technique with higher-order compressible flow solver is presented. A pseudo-code procedure is described for the adaptive remeshing technique. The flux-difference splitting scheme with a modified multidimensional dissipation for high-speed compressible flow analysis on unstructured meshes is proposed. The scheme eliminates nonphysical flow solutions such as the spurious bump of the carbuncle phenomenon observed from the bow shock of the flow over a blunt body and the oscillation in the odd-even grid perturbation in a straight duct for the Quirk's odd-even decoupling test. The proposed scheme is further extended to achieve higher-order spatial and temporal solution accuracy. The performance of the combined procedure is evaluated on unstructured triangular meshes by solving several steady-state and transient high-speed compressible flow problems.

A new mesh reconstruction scheme for approximating a surface from a set of unorganized 3D points is proposed. The proposed method, called a shrink-wrapped boundary face (SWBF) algorithm, produces the final surface by iteratively shrinking the initial mesh generated from the definition of the boundary faces. SWBF surmounts the genus-0 spherical topology restriction of previous shrink-wrapping-based mesh generation techniques and can be applied to any type of surface topology. Furthermore, SWBF is significantly faster than a related algorithm of Jeong and others, as SWBF requires only a local nearest-point-search in the shrinking process. Our experiments show that SWBF is very robust and efficient for surface reconstruction from an unorganized point cloud.

In this paper, we consider a group mobility model to formulate a clustering mechanism called Dual Coalescent Energy-Efficient Algorithm (DCEE) which is scalable, distributed and energy-efficient for wireless mesh network. The differences of the network nodes will be distinguished to exploit heterogeneity of the network. Furthermore, a topology control, that is, adjusting the transmission range to further reduce power consumption will be integrated with the cluster formation to improve network lifetime and connectivity. Along with network lifetime and power consumption, clusterhead changes will be measured as a performance metric to evaluate the. effectiveness and robustness of the algorithm.

This article presents a new global-local hybrid coarse-mesh finite difference (HCMFD) method for efficient parallel calculation of pin-by-pin heterogeneous core analysis. In the HCMFD method, the one-node coarse-mesh finite difference (CMFD) scheme is combined with a nodal expansion method (NEM)-based two-node CMFD method in a nonlinear way. In the global-local HCMFD algorithm, the global problem is a coarse-mesh eigenvalue problem, whereas the local problems are fixed source problems with boundary conditions of incoming partial current, and they can be solved in parallel. The global problem is formulated by one-node CMFD, in which two correction factors on an interface are introduced to preserve both the surface-average flux and the net current. Meanwhile, for accurate and efficient pin-wise core analysis, the local problem is solved by the conventional NEM-based two-node CMFD method. We investigated the numerical characteristics of the HCMFD method for a few benchmark problems and compared them with the conventional two-node NEM-based CMFD algorithm. In this study, the HCMFD algorithm was also parallelized with the OpenMP parallel interface, and its numerical performances were evaluated for several benchmarks.

This paper presents two sequential advanced split and merge algorithms and a parallel image segmentation algorithm based on them. First, the two advanced methods are obtained from the combination of edge detection and classic split and merge to solve the inherent problems of the classical method. Besides, the parallel image segmentation algorithm on mesh-connected MIMD system considers three types in the merge stage to reduce the communication overhead between processors, such as intraprocessor merge, interprocessor with boundary merge, and interprocessor without boundary merge. Finally , we prove that the proposed algorithms achieve the improved performance by implementing them.

We present a monolithic semi-implicit algorithm for solving fluid-structure interaction problem at small structural displacements. The algorithm uses one global mesh for the fluid-structure domain obtained by gluing the fluid and structure meshes which are matching on the interface. The continuity of velocity at the interface is automatically satisfied and the continuity of stress does not appear explicitly in the global weak form due to the action and reaction principle. At each time step, we have to solve a monolithic system of unknowns velocity and pressure defined on the global fluid-structure domain. Numerical results are presented.

This paper investigates the problem of protecting multicast sessions in mesh wavelength-division multiplexing (WDM) networks against single link failures, for example, a fiber cut in optical networks. First, we study the two characteristics of multicast sessions in mesh WDM networks with sparse light splitter configuration. Traditionally, a multicast tree does not contain any circles, and the first characteristic is that a multicast tree has better performance if it contains some circles. Note that a multicast tree has several branches. If a path is added between the leave nodes on different branches, the segment between them on the multicast tree is protected. Based the two characteristics, the survivable multicast sessions routing problem is formulated into an Integer Linear Programming (ILP). Then, a heuristic algorithm, named the adaptive shared segment protection (ASSP) algorithm, is proposed for multicast sessions. The ASSP algorithm need not previously identify the segments for a multicast tree. The segments are determined during the algorithm process. Comparisons are made between the ASSP and two other reported schemes, link disjoint trees (LDT) and shared disjoint paths (SDP), in terms of blocking probability and resource cost on CERNET and USNET topologies. Simulations show that the ASSP algorithm has better performance than other existing schemes.