• International Journal of CAD/CAM
• /
• 제4권1호
• /
• pp.47-53
• /
• 2004

The subdivision surface is the limit of recursively refined polyhedral mesh. It is quite intuitive that the multi-resolution feature can be utilized to simplify generation of NC (Numerical Control) tool paths for rough machining. In this paper, a new method of parallel NC tool path generation for subdivision surfaces is presented. The basic idea of the method includes two steps: first, extending G-Buffer to a strip buffer (called S-Buffer) by dividing the working area into strips to generate NC tool paths for objects of large size; second, generating NC tool paths by parallel implementation of S-Buffer based on MPI (Message Passing Interface). Moreover, the recursion depth of the surface can be estimated for a user-specified error tolerance, so we substitute the polyhedral mesh for the limit surface during rough machining. Furthermore, we exploit the locality of S-Buffer and develop a dynamic division and load-balanced strategy to effectively parallelize S-Buffer.

• 한국멀티미디어학회논문지
• /
• 제17권9호
• /
• pp.1084-1091
• /
• 2014

When demand for transmitting multimedia data increases, network congestion is more likely to occur and users will suffer high loss rate as well as high delay. In order to enhance quality-of-service (QoS) of video multicasting, we need to raise transmission reliability and reduce end-to-end delay. This paper proposes a routing mechanism for a OpenFlow-based small-scale network in order to multicast video reliably with low delay. In our method, multipath routing will be applied to Multiple Description (MD) Coded video to exploit its multi-description property. Through performance evaluation, our method shows improvement on loss rate, delay and video distortion.

• ETRI Journal
• /
• 제24권1호
• /
• pp.23-30
• /
• 2002

MPEG-7 Visual Standard specifies a set of descriptors that can be used to measure similarity in images or video. Among them, the Edge Histogram Descriptor describes edge distribution with a histogram based on local edge distribution in an image. Since the Edge Histogram Descriptor recommended for the MPEG-7 standard represents only local edge distribution in the image, the matching performance for image retrieval may not be satisfactory. This paper proposes the use of global and semi-local edge histograms generated directly from the local histogram bins to increase the matching performance. Then, the global, semi-global, and local histograms of images are combined to measure the image similarity and are compared with the MPEG-7 descriptor of the local-only histogram. Since we exploit the absolute location of the edge in the image as well as its global composition, the proposed matching method can retrieve semantically similar images. Experiments on MPEG-7 test images show that the proposed method yields better retrieval performance by an amount of 0.04 in ANMRR, which shows a significant difference in visual inspection.

• Journal of Computing Science and Engineering
• /
• 제2권1호
• /
• pp.98-108
• /
• 2008

Terrain reconstruction from images is an ill-posed, yet commonly desired Structure from Motion task when compositing visual effects into live-action photography. These surfaces are required for choreography of a scene, casting physically accurate shadows of CG elements, and occlusions. We present a novel framework for generating the geometry of landscapes from extremely noisy point cloud datasets obtained via limited resolution techniques, particularly optical flow based vision algorithms applied to live-action video plates. Our contribution is a new statistical approach to remove erroneous tracks ('outliers') by employing a unique combination of well established techniques-including Gaussian Mixture Models (GMMs) for robust parameter estimation and Radial Basis Functions (REFs) for scattered data interpolation-to exploit the natural constraints of this problem. Our algorithm offsets the tremendously laborious task of modeling these landscapes by hand, automatically generating a visually consistent, camera position dependent, thin-shell surface mesh within seconds for a typical tracking shot.

• 전기학회논문지
• /
• 제57권6호
• /
• pp.1069-1074
• /
• 2008

This paper presents an efficient architecture for $2^n$-point DCT algorithm. The proposed approach makes use of the fact that, in most DCT applications, the scaling operation in the DCT unit can be eliminated and combined with the scaling operation in the quantizer unit. This important property is efficiently exploited with the CORDIC(COordinate Rotation DIgital Computer) algorithm to produce a regular architecture suitable for VLSI implementation. Although there have been several attempts to exploit CORDIC algorithm in developing DCT architectures, the proposed approach provides the most efficient way for scaled DCT applications by completely eliminating the scale factor compensation.

• 한국통신학회논문지
• /
• 제21권1호
• /
• pp.144-154
• /
• 1996

Proposed numerous algorithms for the policing function have mainly focused on their performances. Besides their performance evaluation, however, the VLSI-implementation of these algorithms is worth consideration as well. Although, no algorithms for the policing function have been standardized up to now, ITU-T I.371 suggests two examples of algorithms, the Virtual Scheduling Algorithm (VSA) and the Continuous State Leaky Bucket algorithm. In this paper, we suggest the architecture of a policing device implementing the VSA among various algorithms for the peak cell rate policing and discuss some issues on the implementation. We also present how to select the policing modes of the two devices used to realize various policing schemes and show the experimental results obtained under four different peak cell rate values to confirm that the device performs the policing function satisfactorily. We exploit the priority encoder to run the algorithm in parallel instead of sequentially, which reduces the operation time to a great extent.

• 대한수학교육학회지:수학교육학연구
• /
• 제8권1호
• /
• pp.137-144
• /
• 1998

A common geoboard puzzel serves as the point of departure for an investigation that lends itself to whole-group discussion with a class of prospective secondary school teachers. Students are provided with opportunities to devise and carry out problem-solving strategies (called 'heuristics' by Polya); exploit inerrelationships among geometry, arithmetic and algebra; formulate generalizations and conjectures; plan and execute an computational project; construct mathematical arguments to establish theorems; and find counter-examples to dispose of a false conjecture. In recent tears, Eugene F. Krause wrote two papers having the same title except for the numeral In that papers he arrives at an theorem about the sizes of squares with lattice point vertices in the coordinate plane, In this paper we follow a different path genearlization to coordinate 3-space

• 한국CDE학회논문집
• /
• 제15권2호
• /
• pp.106-114
• /
• 2010

The swept volume, the region of a moving object, is applied in many fields such as valid paths for motions of tools, visualization in robot paths and interference tests for parts assembling or disjointing. The shape of a swept volume depends on an generators computed with normal vectors of an object and velocity vectors of a motion. Although free-from surfaces are widely used to represent geometric models in CAD, computing the generators for a free-form object is a formidable task. Previous approaches exploit the closed form expressions of generators but limited to planer or quadric faces. In this paper, we propose the algorithm to compute swept volumes generated by free-form objects in screw motions. For the algorithm a tracing method is applied to the computation of generators. It considers curvatures of surfaces of an object to increase the computational accuracy. We implemented our algorithm in the CATIA V.5 environment to test the validity of our algorithm and to generate examples.

• 한국정보처리학회논문지
• /
• 제5권4호
• /
• pp.883-891
• /
• 1998

본 논문에서는 원소오토마타 모델의 시뮬레이션에서 SIMD형 병렬성을 이용하는 방법을 제안한다. 제안된 방법에서는 SIMD 병렬성을 이용하여 시뮬레이션에 사용되는 컴퓨터 내에 들어 있는 ALU의 이용도를 높이고 시뮬레이션 시간을 줄인다. 그래서 몇 개의 원소들을 결합하여 하나의 표준 크기의 컴퓨터 단어로 만들고 그 원소들의 상태를 동시에 변환시킨다. 제안된 시뮬레이션 방법의 성능을 보이기 위하여, 본 논문에서는 두 가지 원소오토마타 모델을 세 가지 하드웨어 환경에서 시뮬레이션 하였다. 실험결과로부터, 모든 경우에서 시뮬레이션 속도가 매우 크게 향상되었다. 특히 최상의 경우에는 제안된 시뮬레이션 방법에 의한 속도 향상이 20배에 달하는 경우도 있었다.

• 대한화장품학회지
• /
• 제28권2호
• /
• pp.55-57
• /
• 2002

The fabrication, characterization and manipulation of nanosystems brings together physics, chemistry, materials science and biology in an unprecedented way, Phenomena occurring in such systems are fundamental to the workings of electronic devices, but also to living organisms. The ability to fabricate nanostructures is essential in the further development of functional devices that incorporate nanoscale features. Even more essential is the ability to introduce a wide range of chemical and materials flexibility into these structures to build up more complex nanostructures that can ultimately rival biological nanosystems. In this respect, polymers are potentially ideal nanoscale building blocks because of their length scale, well-defined architecture, controlled synthesis, ease of processing and wide range of chemical functionality that can be incorporated. In this presentation, we will look at a number of promising polymer-based nanofabrication strategies that have been developed recently, with an emphasis on those techniques that incorporate nanostructured polymers into devices and that exploit intrinsic polymer properties.