• 대한의용생체공학회:의공학회지
• /
• 제33권1호
• /
• pp.32-38
• /
• 2012

Recently, several ultrasound imaging techniques for tissue characterization have been developed. Among them, ultrasound elastography is regarded as the most promising modality and has been rapidly developed. One of ultrasound elastography techniques is shear modulus imaging. Normal and cancerous tissues show big difference of shear moduli and they have good image contrast. However shear wave elastography requires more complicated hardware and more computations for image reconstruction algorithm. Therefore new efficient techniques are being developed. In this paper, we have developed a very flexible ultrasound system for elastography experiments. The developed system has capabilities to acquire ultrasound RF data of all channels and generate arbitrary ultrasound pulse sequences. It has a huge amount of memories for RF data acquisition and a simple and flexible pulse generator. We have verified the performance of the system showing conventional B-mode images and preliminary results of elastography. The developed system will be used to verify our own reconstruction algorithm and to develop more efficient elastography techniques.

• 반도체디스플레이기술학회지
• /
• 제22권1호
• /
• pp.33-38
• /
• 2023

As the demand for large flexible displays such as tablet computers continues to rise, there is an increasing need for cost-efficient colorless and optically transparent polyimide film that can meet the desired performance, particularly optical transmittance. In this study, we investigated a detailed procedure for achieving optimal optical transmittance using two different combinations of monomers: 6FDA+BAPB and 6FDA+BPA+TFDB. We employed a design of experiment method to systematically synthesize polymers, allowing for the optimization of optical transmittance. In addition, we were able to achieve uniform thickness in the films by using a doctor blade. By comparing the price and optical transmittance of four different monomer combinations, we obtained fundamental data on the production of polyimide films that can be customized to meet the specific price and performance requirements of manufacturers. This approach enables users to select the most suitable polyimide film based on their desired price and performance parameters while achieving optimal optical transmittance.

• 한국경영과학회:학술대회논문집
• /
• 한국경영과학회 2001년도 추계학술대회 논문집
• /
• pp.269-272
• /
• 2001

In this paper, we presents a systematic methodology for minimizing tardiness and maximizing resource utilization in a multi-plant supply chain. A methodology is represented to a multi-objective mathematical program model. The model offers flexible and efficient multi-plant planning and scheduling. Also, We develope a realistic and flexible planning model using the genetic algorithm to solve the model.

• 산업경영시스템학회지
• /
• 제22권50호
• /
• pp.209-219
• /
• 1999

This paper presents an efficient operational technique of material feeding process, trainning for multi-operations, machine conditions, and role of foreman and material-supplying man, for constructing the flexible assembly cells in the domestic electronic industries. And an practical method for computing the number of economical cells is also presented by the cost-effective model that compares the additional assembly machine requirement with the four reductive effects including WIP/finished goods inventory, the troubles in the assembly line, the opportunity loss for small order quantity, and amounts of production management due to the introduction of cell line. An case study is introduced in for a domestic electronic assembly line at the end.

• Management Science and Financial Engineering
• /
• 제1권1호
• /
• pp.67-90
• /
• 1995

In planning an assembly system, choosing the proper assembly sequence is one of the most important decisions because it significantly affects the costs associated with the assembly process. This paper deals with the selection of assembly sequences in flexible assembly systems. The selection criterion is the minimization of makespan to complete all assembly products. This problem is formulated as a "modified FAS scheduling problem" (MFASSP) and its scheduling procedure is described. The experimental results show that the procedure is very efficient for both quality of solution and computation time.

• 한국경영과학회지
• /
• 제23권4호
• /
• pp.75-86
• /
• 1998

We address the problem of determining the optimal processing times and pallet/fixture allocation in Flexible Manufacturing systems in order to minimize tool cost while meeting throughput targets of multiple part types. The problem is formulated as a nonlinear program superimposed on a closed queueing network of the FMSs under consideration. A numerical example reveals the potential of our approach for significant cost saving. We argue that our model can be Integrated Into the process planning system of an FMS to generate efficient process plans quickly.

• 산업경영시스템학회지
• /
• 제24권67호
• /
• pp.19-26
• /
• 2001

A design issue for a flexible manufacturing system is to find the number of each resource type which assures a given production ratio with a minimal cost. The FMS is modeled as a closed queueing network with a local buffer of limited capacity. An efficient method to determine this optical configuration is presented. The proposed method consists of three steps : 1) determine a lower configuration, 2) derive a heuristic solution, 3) find the optimal solution. The derived heuristic solutions are close to the optical solution.

• Structural Engineering and Mechanics
• /
• 제37권5호
• /
• pp.475-487
• /
• 2011

In a flexible multi-body dynamic system the typical topological optimization method for structures cannot be directly applied, as the stiffness varies with position. In this paper, the topological optimization of the flexible multi-body dynamic system is converted into structural optimization using the equivalent static load method. First, the actual boundary conditions of the control system and the approximate stiffness curve of the mechanism are obtained from a flexible multi-body dynamical simulation. Second, the finite element models are built using the absolute nodal coordination for different positions according to the stiffness curve. For efficiency, the static reanalysis method is utilized to solve these finite element equilibrium equations. Specifically, the finite element equilibrium equations of key points in the stiffness curve are fully solved as the initial solution, and the following equilibrium equations are solved using a reanalysis method with an error controlled epsilon algorithm. In order to identify the efficiency of the elements, a non-dimensional measurement is introduced. Finally, an improved evolutional structural optimization (ESO) method is used to solve the optimization problem. The presented method is applied to the optimal design of a die bonder. The numerical results show that the presented method is practical and efficient when optimizing the design of the mechanism.

• Structural Engineering and Mechanics
• /
• 제13권5호
• /
• pp.465-478
• /
• 2002

This study lays emphasis on the development of efficient analytical models for a multistory structure with wings, including the in-plane deformation of floor slabs. For this purpose, a multistory structure with wings is regarded as the combination of multistory structures with rectangular plan and their junctions. In addition, a multistory structure with a rectangular plan is considered to be an assemblage of two-dimensional frames and floor slabs connecting two adjacent frames at each floor level. This modeling, concept can be easily applied to multistory structures with plans in the shape of L, T, Y, U, H, etc. To represent the in-plane deformation of floor slabs efficiently, a two-dimensional frame and the floor slab connecting two adjacent frames at each floor level are modeled as a stick model with two degrees of freedom per floor and a stiff beam with shear deformations, respectively. Three models are used to investigate the effect of in-plane deformation of the floor slab at the junction of wings on the seismic behavior of structures. Based on the comparison of dynamic analysis results obtained using the proposed models and three-dimensional finite element models, it could be concluded that the proposed models can be used as an efficient tool for an approximate analysis of a multistory structure with wings.

• 한국전자파학회논문지
• /
• 제19권1호
• /
• pp.61-70
• /
• 2008

본 논문에서는 멤스 기술의 하나인 연성 인쇄 회로 기판을 이용하여 임의의 형태로 변형이 가능한 초고주파 멤스 송신기를 제안하였다. 연성 인쇄 회로 기판은 그 무게가 가볍고 두께가 얇아 경량 소형화 모듈을 만드는데 유리한 장점이 있다. 또한, 연성 인쇄 회로 기판은 종이와 같이 유연한 특성을 가지고 있어 평면이 아닌 임의의 곡면 등에 실장할 수 있는 장정을 가지고 있다. 본 논문에서는 근거리 센서 네트워크 구성을 위한 직교 주파수 분할 다중 전송 방식을 위한 선형 무선 송신기를 설계 제작하였다. 송신 모듈의 능동 회로는 전력효율이 높고 선형성이 우수하여 전력 증폭기에 많이 사용되고 있는 InGaP/GaAs HBT 공정을 사용하여 설계 및 제작하였으며, 매칭 회로 및 필터 등의 수동 회로는 연성 인쇄 회로 기판에 직접 집적화 하여 제작하였다. 제작된 멤스 송신기는 EVM 특성을 통하여 시스템 성능을 분석하였다.