• Korean Journal of Geomatics
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• 제5권1호
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• pp.1-6
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• 2005

When merging various datasets the perennial problem of relative weighting arises. In case of two datasets an iterative algorithm has been developed recently that allows the rigorous determination of optimal variance components of type repro-BIQUUE even for large amounts of data, along with the estimation of the joint parameters. Here we shall present this new algorithm, and show its versatility in an example that will entail the merging of two regional geoid estimates (derived from EGM 96 and CHAMP) in terms of certain series expansions which have been proven previously to belong to the most efficient ones (e.g., wavelets, Hardy's multi-quadrics, etc.). Future attempts will be devoted to the sequential merging of altimeter and tide gauge data.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2005년도 가을 학술발표논문집 Vol.32 No.2 (2)
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• pp.796-798
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• 2005

본 연구에서는 엔트로피 이론을 사용하여 ICA(Independent Component Analysis) 점수함수를 생성하는 새로운 밀도추정자(Density Estimator)를 제안한다. 원 신호에 대한 밀도함수의 추정은 적당한 점수함수를 생성하기 위해 필요하고, 미분 가능한 밀도함수인 커널을 이용한 밀도추정법(Kernel Density Estimation)을 이용하여 점수함수를 생성하였다. 보다 빠른 점수함수의 생성을 위해서 식의 형태를 convolution 형태로 표현하였으며, ICA 학습을 위해서 결합엔트로피를 최대화(Joint Entropy Maximization)하는 방향으로 커널의 폭을 학습하였다. 이를 위해서 기울기 강하법(Gradient descent method)를 사용하였으며, 이러한 제약 사항은 새로운 밀도 추정자를 설계하기 위한 기본적인 개념을 나타낸다. 실험결과, 커널의 폭을 담당하는 smoothing parameters들이 일정한 값으로 학습함을 알 수 있었다.

• Journal of the Korean Data and Information Science Society
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• 제28권2호
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• pp.421-433
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• 2017

The CTE (conditional tail expectation) is a useful risk management measure for a diversified investment portfolio that can be generally estimated by using a transformed univariate distribution. Hong et al. (2016) proposed a multivariate CTE based on multivariate quantile vectors, and explored its characteristics for multivariate normal distributions. Since most real financial data is not distributed symmetrically, it is problematic to apply the CTE to normal distributions. In order to obtain a multivariate CTE for various kinds of joint distributions, distribution fitting methods using copula functions are proposed in this work. Among the many copula functions, the Clayton, Frank, and Gumbel functions are considered, and the multivariate CTEs are obtained by using their generator functions and parameters. These CTEs are compared with CTEs obtained using other distribution functions. The characteristics of the multivariate CTEs are discussed, as are the properties of the distribution functions and their corresponding accuracy. Finally, conclusions are derived and presented with illustrative examples.

• 접착 및 계면
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• 제21권1호
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• pp.1-5
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• 2020

Heated tool joining is a popular method for joining parts made from plastics and composite materials. The method is commonly known as butt fusion in the plastic pipe industry and this paper provides a short introduction to the basics of producing a good butt fusion joint. The function of each of the essential parts of the butt fusion equipment is described followed by a presentation of the important parameters of the bonding process in reference to a well-established interfacial pressure versus time curve. The butt fusion procedure is then outlined with good practices that detail the preparation of equipment and pipes to be joined as well as the fusion joining process.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1614-1625
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• 2006

This paper presents the kinematics and workspace optimization of the two different 2-DOF (Degrees-of-Freedom) planar parallel mechanisms: one (called 2-RPR mechanism) with translational actuators and the other (called 2-RRR mechanism) with rotational ones. First of all, the inverse kinematics and Jacobian matrix for each mechanism are derived analytically. Then, the workspace including the output-space and the joint-space is systematically analyzed in order to determine the geometric parameters and the operating range of the actuators. Finally, the kinematic optimization of the mechanisms is performed in consideration of their dexterity and rigidity. It is expected that the optimization results can be effectively used as a basic material for the applications of the presented mechanisms to more industrial fields.

• Computers and Concrete
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• 제11권4호
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• pp.351-364
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• 2013

This paper presents results from an analytical investigation of the behavior of steel reinforced concrete circular column sections with additional Glass Fiber Reinforced Polymers (GFRP) bars. The primary application of this composite section is to relocate the plastic hinge region from the column-footing joint where repair is difficult and expensive. Mainly, the study focuses on the development of the full nominal moment-axial load (M-P) interaction diagrams for hybrid concrete sections, reinforced with steel bars as primary reinforcement, and GFRP as auxiliary control bars. A large parametric study of circular steel reinforced concrete members were undertaken using a purpose-built MATLAB(c) code. The parameters considered were amount, location, dimensions and mechanical properties of steel, GFRP and concrete. The results indicate that the plastic hinge was indeed shifted to a less critical and congested region, thus facilitating cost-effective repair. Moreover, the reinforced concrete steel-GFRP section exhibited high strength and good ductility.

• 한국운동역학회지
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• 제20권1호
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• pp.67-73
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• 2010

The purpose of this study was to compare the differences in kinematic and kinetic parameters of the ankle and knee joint according to three landing direction(central, left, right). Fifteen collegiate male athletes(age: $22.7{\pm}3.5$ years, height: $174.9{\pm}7.1\;cm$, weight: $69.4{\pm}6.7\;kg$) with the right leg as dominant were chosen. The subjects performed series of drop landings in three directions. In terms of the three different landing directions, plantar flexion was the greatest during the central drop landings. For each initial contact of the landing direction, plantar flexion of the ankle was greatest at the central drop landing, inversion of the ankle was greatest at the right landing and valgus of the knee was greatest at the left drop landing. Regarding the peak force, the greatest was at the 1st peak force during the central drop landing. For the time-span of the 2nd peak force and the 2-1 peak force, both right sides resulted as the greatest. Therefore, with the appropriate training in landing techniques and developing neuromuscular training for proprioception by taking the injury mechanisms on ankle and knee during drop landings into account, it will assist in preventing such injuries.

• Steel and Composite Structures
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• 제18권6호
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• pp.1391-1404
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• 2015

A radially retractable roof structure based on the concept of the hybrid grid shell is proposed in this paper. The single-layer steel trusses of the radially foldable bar structure are diagonally stiffened by cables, which leads to a single-layer lattice shell with triangular mesh. Then comparison between the static behavior between the retractable hybrid grid shell and the corresponding foldable bar shell with quadrangular mesh is discussed. Moreover, the effects of different structural parameters, such as the rise-to-span ratio, the bar cross section area and the pre-stress of the cables, on the structural behaviors are investigated. The results show that prestressed cables can strengthen the foldable bar shell with quadrangular mesh. Higher structural stiffness is anticipated by introducing cables into the hybrid system. When the rise-span ratio is equal to 0.2, where the joint displacement reaches the minimal value, the structure shape of the hyrbid grid shell approaches the reasonable arch axis. The increase of the section of steel bars contributes a lot to the integrity stiffness of the structure. Increasing cable sections would enhance the structure stiffness, but it contributes little to axial forces in structural members. And the level of cable prestress has slight influence on the joint displacements and member forces.

• 대한족부족관절학회지
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• 제9권1호
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• pp.69-73
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• 2005

Purpose: The purpose of our report was to evaluate the result of operative treatment of hallux valgus in old age patients. Materials and Methods: We studied about the clinical & radiologic results of the 31 patients over 55 years old, who had operative treatment of hallux valgus. Clinical evaluation, such as pain, activity limitation, footwear requirement, 1st metatarsophalangeal joint motion, and callosity, was done using AOFAS scale and preoperative and postoperative radiologic parameters, such as hallux valgus angle, intermetatarsal angle, tibial sesamoid position, 1st metatarsal shortening, were evaluated by conventional methods. Results: Objectively, according to AOFAS, the score improved from average of 57.8 to 71.5 postoperatively. The range of motion of first metatarsophalangeal joint was decreased from average of 60.7 to 56.8 degrees. Radiologically, the hallux valgus angle improved from average of 35 to 6.5 degrees and the first intermetatarsal angle improved from average of 14.2 to 4.4 degrees. The position of sesamoid was collected from an average of grade 3.6 to grade 2.2. Conclusion: The combination of proximal metatarsal osteotomy, distal soft tissue procedure and Akin osteotomy may yield rather satisfactory clinacal result in severe elderly hallux valgus patients with massive degenerative change and poor soft tissue condition.

• 터널과지하공간
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• 제27권1호
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• pp.58-68
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• 2017

광학기술의 발달로 LIDAR장비들은 사양이 급속도로 발전하여 현재 암반의 정보들을 효과적으로 얻어 낼 정도의 정밀성과 정확성을 확보하고 있고 현장 활용이 용이하도록 경량화 및 보급화가 이루어진 상황이다. 본 연구에서는 넓은 영역의 암반 사면을 대상으로 LIDAR를 이용하여 절리면 거칠기를 측정하는 방법의 적용성에 대하여 고찰해 보았다. 점 간격에 따른 네 가지 거칠기 변수와 JRC와의 상관관계를 회귀 분석하였으며 LIDAR를 이용하여 삼차원 삼각망을 구성하고 면 구조인 패치를 검출하여 암반 사면 절리면의 거칠기를 산정하는 연구를 수행하였다. 실내시험을 통하여 네 가지 거칠기 파라미터와 JRC의 회귀식을 제시하였으며, 네 가지 파라미터 모두 점 간격이 커질수록 거칠기 파라미터 값의 감소를 보이며, 더 큰 거칠기를 갖는 시료에서 더 큰 감소폭을 보임을 알 수 있었다. 현장에서 LIDAR 스캔을 통하여 $R_s$ 파라미터와 점 간격을 고려한 거칠기를 산정하는 알고리즘을 제시하였으며 실제 거칠기 측정 결과보다 다소 과대평가 되는 경향이 있음을 확인하였다.