• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 지반공학 공동 학술발표회
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• pp.117-128
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• 2005

Korea is affected by typhoon 2-3 times a year, and 50${\sim}$60 % of annual rainfall is concentrated during summer with heavy daily precipitation. Recently such natural conditions cause many of failures or damages of reservoirs and embankments. Overflow by heavy flood is the main cause that results 54.2 % of total embankment failures with damages of spillway, outlet channel and stilling basin. Since damages by overflow are triggered by scour of soils nearby the structures, use of proper backfill materials with great resistance against erosion should be considered and application of suitable construction method to protect erosion may be adopted. Most failures of levee are caused by piping along the surface of cross-structure underneath levee. Such failures may be protected by deep consideration of piping at the stage of design and good quality control during construction. Sufficient magnitude of spillway and outlet channel is the ideal way to prevent failures by the flood. For existing structures, remodeling with reinforcement to protect against flood with review of required storage of dam should be considered.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2001년도 추계학술대회 논문집
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• pp.286-289
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• 2001

This paper deals with the procedures of effective mid-term Operation Planning establishment for painting shop in shipbuilding. and develop prototype system. In general, the block painting process consists of two stages such as blasting operation for surface preparation and painting operation for paint application for blocks. Weather condition is a potent Influence on those operations. The procedures consists of four steps, Load analysis, Generate alternative simulation plan. Implementation of Allocation automation module and Compare result of each simulation plan. Explain of each step. as follows, 1.step, Load analysis measure amount of assigned workload and manhour. 2.step, simulation scheme include alterable control variable such as overtime, weather. Auto allocating module carry out feasibility of simulation plan. 3.step, Allocation automation module are composed of three algorithms, as followings: - the block allocation algorithm that determines the number of blocks to be processed each day, - the team allocation algorithm that allocates blocks to worker groups. - the block arrangement algorithm that arrange blocks in blasting and painting cells. Since the block arrangement algorithm is conducted simultaneously with the team allocation algorithm, the total structure of the operating algorithms is considered to have two phases: first, daily load balancing with capacity limit and second, team allocation considering arrangement each day 4 step, Comparing result of each simulation plan. and select best simulation plan.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.914-920
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• 2002

Nonlinear flow-induced vibration characteristics of a generic missile wing (or control surface) are investigated in this study. The wing model has freeplay structural nonlinearity at its pitch axis. Nonlinear aerodynamic flows with unsteady shock waves are considered in the transonic flow region. To practically consider the effects of freeplay structural nonlinearity, the fictitious mass method (FMM) is applied to structural vibration analysis based on a finite element method (FEM). A computational fluid dynamics (CFD) technique is used for computing the nonlinear unsteady aerodynamics of all-movable wings. The aerodynamic analysis is based on the efficient transonic small-disturbance aerodynamic equations of motion using the potential-flow theory. To solve the nonlinear aeroelastic governing equations including the freeplay effect, a modal-based computational structural dynamic (CSD) analysis technique based on fictitious mass method (FMM) is used in time-domain. In addition, CSD and unsteady CFD techniques are simultaneously coupled to give accurate computational results. Various aeroelastic computations have been performed for a generic missile wing model. Linear and nonlinear aeroelastic computations have been conducted and the characteristics of flow-induced vibration are introduced.

• 오토저널
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• 제14권5호
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• pp.69-82
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• 1992

Vibration of intake menifold is important as it could worsen the noise levels radiated from surface itself and support bracket, and it eventually leads to the failures of a Throttle Position Sensor and an Idle Air Control Valve. In this study, structural modification method is proposed to reduce structural vibration of an intake manifold system. At first, vibration problems are identified through tests on a running engine. Then modal data acquired by modal testing and finite element analysis are helpful to understand vibration mechanism of the system, and used as the design guide when structural modifications are attempted. After the system model is validated by comparison of the modal data obtained from analysis and experiment, iterative calculations are performed to find optimized structure of the system by finite element analysis. As a result, a newly designed plenum bracket is suggested in such a way that the intake manifold is stiffened, and that design of the support bracket is suggested in such a way that the intake manifold is stiffened, and that design of the support bracket is changed in terms of bolting position, thickness, shape, and minimum weight increase. Finally, it is shown that a new design achieves a significant reduction of vibration of an intake manifold system and it is confirmed by tests on a running engine.

• Design & Manufacturing
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• 제7권1호
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• pp.28-33
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• 2013

During the cold forming, due to high working pressure acting on the die surface, failure mechanics must be considered before die design. One of the main reasons of die failure in industrial application of metal forming technologies is wear. The mechanisms of wear are consisted of adhesion, abrasion, erosion and so on. Die wear affects the tolerances of formed parts, metal flow, and costs of process. The only way to control these failures is to develop a prediction method on die wear suitable in the design state in order to optimize the process. The wear system is used to analyse 'operating variables' and 'system structure'. In this study, with AISI D2, AISI 1020, AISI 304SS materials, a series of the wear experiments of pin-on-disk type to obtain the wear coefficients from Archard's wear model and the upsetting processes are carried out to observe the wear phenomenon during the cold forming process. The analysis of upsetting processes are performed by the rigid-plastic finite element method. The result of the analysis is used to investigate the die wear the processes, and the analysis simulated die wear profiles are compared with the experimental measured die wear profiles.

• Wind and Structures
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• 제7권4호
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• pp.215-234
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• 2004

The tuned liquid damper (TLD) is increasingly being used as an economical and effective vibration absorber. It consists of a water tank having the fundamental sloshing fluid frequency tuned to the natural frequency of the structure. In order to perform efficiently, the TLD must possess a certain amount of inherent damping. This can be achieved by placing screens inside the tank. The current study experimentally investigates the behaviour of a TLD equipped with damping screens. A series of shake table tests are conducted in order to assess the effect of the screens on the free surface motion, the base shear forces and the amount of energy dissipated. The variation of these parameters with the level of excitation is also studied. Finally, an amplitude dependent equivalent tuned mass damper (TMD), representing the TLD, is determined based on the experimental results. The dynamic characteristics of this equivalent TMD, in terms of mass, stiffness and damping parameters are determined by energy equivalence. The above parameters are expressed in terms of the base excitation amplitude. The parameters are compared to those obtained using linear small amplitude wave theory. The validity of this nonlinear model is examined in the companion paper.

• 한국분무공학회지
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• 제12권2호
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• pp.86-93
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• 2007

There is a growing interest to develop an eco-friendly air cleaner with high performance through a remanufacturing process. Two kinds of polyurethane filter media, a coarse (Filter-A) and a fine filter media (Filer-B), are used in this study to protect a vehicle engine from airborne particles. In order to improve the collection performance of the filters (Filter-A, Filter-B), an oil coating technology on the filter surface was introduced. As a result, inertial force is a dominant collection mechanism for a dry filter media, so that collection efficiency increases with increasing filtration velocity. However, intra-structure change of an oil-coated filter media influences on the collection mechanism, which shows a non-linear collection efficiency curve in terms of filtration velocity. The result shows that the developed filter media are eco-friendly and effective to protect a vehicle engine from airborne particles especially at low filtration velocity.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.494-504
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• 2008

Successful design, construction and maintenance of NATM tunnel demands prediction, control, stability estimation and monitoring of surface settlement, gradient and ground displacement with high accuracy. Back analysis using measured data and forward analysis have been and are indispensable tools to achieve this goal. Sakurai provided the hazard warning levels for assessing the stability of tunnels using the relation of critical strain and apparent Young's modulus. This paper performed the estimation of tunnel stability on construction. Firstly, the apparent Young's modulus concept and back analysis method is introduced for the assessment of tunnel safety during excavation a brief framework. Secondly, this paper deals with case study using "Apparent Young's modulus" and "Back analysis" for the purpose of estimating the stability of NATM tunnel in Korea. Finally, a general method that can be estimated the tunnel stability discussed by a flow chart.

• 한국세라믹학회지
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• 제26권1호
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• pp.59-66
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• 1989

Single crystals of the superconducting Y-Ba-Cu oxide were grown by a flux technique. Stoichiometric mixture with excess BaO and CuOcontent was melted at 130$0^{\circ}C$, followed by fast cooling to 108$0^{\circ}C$ to prevent crystallizing of CuO. It was then reheated to 110$0^{\circ}C$ followed by being held at this temperature to control the number of nuclei, and cooled by 5$^{\circ}C$/hr to 80$0^{\circ}C$. This procedure was repeated with various compositions and crystals were obtained in cavity. Molten solution was seperated to two parts : the upper part of almost CuO and the rest of different composition. Appropriate composition of flux was 30mol% BaO and 70mol% CuO due to the seperation of molten solution. Single crystals have the habit of thin plate with good developed (001) crystal face, XRD, EDAX and single crystal X-ray investigations were carried out. The grown crystals have tetragonal structure with the lattice parameters a=b=3.84$\AA$, c=11.7$\AA$, and the space group P4/mmm. The crystal surface were observed by SEM.

• 한국전기전자재료학회논문지
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• 제26권9호
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• pp.686-689
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• 2013

The carbon nanowall (CNW) is a carbon-based nanomaterials and it was constructed with vertical structure graphenes and it has the highest surface density among carbon-based nanostructures. In this study, we have checked the growth properties of CNW according to the substrate angle. Microwave plasma enhanced chemical vapor deposition (PECVD) system was used to grow CNW on Si substrate with methane ($CH_4$) and hydrogen ($H_2$) gases. And, we have changed the substrate angle from $0^{\circ}$ to $90^{\circ}$ in steps of $30^{\circ}$. The planar and vertical conditions of the grown CNWs according to the substrate angle were characterized by a field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). In case of the growth angle increases, our experimental results showed that the length of the CNW was shortened and the content of carbon component was decreased.