• Smart Structures and Systems
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• 제24권6호
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• pp.793-802
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• 2019

The centrifuge model test is usually used for two-dimensional deformation and instability study of the soil slopes. As a typical loose slope, the municipal solid waste (MSW) landfill is easy to slide with large deformation, under high water levels or large earthquakes. A series of centrifuge model tests of landfill slide induced by rising water level and earthquake were carried out. The particle image velocimetry (PIV), laser displacement transducer (LDT) and marker tracer (MT) methods were used to measure the deformation of the landfill under different centrifugal accelerations, water levels and earthquake magnitudes. The PIV method realized the observation of continuous deformation of the landfill model, and its results were consistent with those by LDT, which had higher precision than the MT method. The deformation of the landfill was mainly vertically downward and increased linearly with the rising centrifugal acceleration. When the water level rose, the horizontal deformation of the landfill developed gradually due to the seepage, and a global slide surface formed when the critical water level was reached. The seismic deformation of the landfill was mainly vertical at a low water level, but significant horizontal deformation occurred under a high water level. The results of the tests and analyses verified the applicability of PIV in the two-dimensional deformation measurement in the centrifuge model tests of the MSW landfill, and provide an important basis for revealing the instability mechanism of landfills under extreme hydraulic and seismic conditions.

• 소성∙가공
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• 제17권8호
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• pp.643-648
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• 2008

Ultra-thin sheet metal forming techniques are required in precision forming of miniaturized and integrated products. In order to manufacture a good quality and low cost ultra-thin sheet metal products, a highly precise high-speed press is needed. The precision of a press is related with its vibration characteristics during pressing operation. This study evaluated the vibration characteristics of a proposed press design using computer simulation. The analysis compares the static deformation characteristics of the slide and the slide motion for the metal forming of an ultra-thin sheet of thickness less than 0.1mm. Further, in order to minimize the vibrations during high speed pressing operation, revolution balances of the eccentric shaft and the balance weight device is also considered. Finally, modal analysis is used to characterize the natural frequency of vibration of the press.

• 대한인간공학회지
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• 제33권2호
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• pp.155-165
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• 2014

Objective: The aim of this study is to develop an office chair enabling to keep working at reclined sitting posture. Background: Sedentary workers are supposed to change the posture frequently during long hours of sitting. A reclined sitting position has been recommended to reduce disc pressure. But slumped sitting posture caused by the buttock sliding forward without any adjustment of back reclining is commonly observed. The worker seems to have tendency to change the sitting posture maintaining working condition. We assumed the reason to be their hands movement away from the working space when tilting backward. Method: Slide mechanism allowing seat to move forward was designed to maintain the hand position in working space during reclining. A prototype was manufactured and tilting motion was analyzed using motion capture system. Four experiment chairs were tested including the manufactured prototype chair and three other commercial chairs. Results: A backward movements of the hand position were 13.0mm, 101.7mm, 156.1mm and 139.3mm at the prototype chair, compared to chair B, chair C and chair D, respectively. And the movement was remarkably small at the prototype chair. Conclusion: The developed seat sliding chair allows back tilting maintaining hand position at working space. We expect the user tilting back more often than normal tilting chair during seated work. But further investigation is required to figure out the effectiveness of the developed chair using prolonged working hours. Application: The developed office chair directly affects commercialization.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.167-174
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• 1999

A Land slide in Granitic Gneiss weathered soil was stabilized successfully with soil nailing using 929mm steel bar. To understand the behavior of load transfer between soil and nail, in-situ pdl-out tests were carried out. The strains of steel bars were measured using strain gauges during pull-out tests. Forces-strain data from laboratory tension tests on steel bar and grouted steel bar were examined to compare with those of the pull-out tests. Comparisons were made between the pull-out test results and laboratory test result to understand load transfer mechanism.

• 소성∙가공
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• 제22권1호
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• pp.42-47
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• 2013

The bicycle is one of the most important eco-friendly transport methods which can mitigate global warming. The portability of a bike on public transportation systems is essential for the wide spread use of bicycles by people in urban environments. In this study, a lightweight urban folding bike was developed with careful consideration of the association with public transport. A folding frame using a moving slide link mechanism made from AL6061 is proposed. Numerical analysis was conducted to evaluate structural safety of the bike in both vertical and pedal loading tests. The proposed urban folding bicycle weights only 10kg and summation of its width, length, and height in the folded configuration is under 158cm.

• 산업기술연구
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• 제19권
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• pp.15-23
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• 1999

Active damping system is generally used for the vibration suppression and precise motion control for the flexible structure. This application can be easily found on the space structure and driving mechanism of optical storage devices. Although a control system using the flexible structure has many advantages over using rigid mechanism in driving energy saving, system weights, and etc., more complex and precise control strategies are required. A position control system using flexible structure and the concept of active damper is designed and manufactured, which is driven by slide DC motor and moving coil motor located at the tip of the flexible beam. Dynamic characteristics of this system are investigated by analytic and experimental ways. By the comparison of those two results, a nominal reference model for this system is proposed.

• 소성∙가공
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• 제6권6호
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• pp.471-481
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• 1997

This paper is concerned with the kinematic analysis of several linkage drives for mechanical presses. Load and velocity characteristics of conventional presses are illustrated and a design of new drive for a mechanical press is represented. In this regard, a crank-slider mechanism with arc crank-pin guide is introduced and compared with other linkage drives. Kinematic performances are analyzed in respect of load capacity, slide velocity characteristics using a developed SS-Plot program. The new linkage drive turns out to be effective in terms of load and velocity characteristics, and productivity.

• Design & Manufacturing
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• 제2권4호
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• pp.11-15
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• 2008

In the sheet metal forming using a high speed press machine, driving device, such as crank, link, and knuckle mechanism, has to be designed in consideration of impact at a moment when press die contact with material, because the impact affects a dimensional accuracy of products and a life span of press die. In this study, dynamic analysis was performed using numerical simulation in order to verify the impact reduction effect for proposed double knuckle mechanism by estimating rolling and pitching moment of slide.

• Structural Engineering and Mechanics
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• 제86권4호
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• pp.573-587
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• 2023

A conventional tuned mass damper (TMD) provides a passive control option to suppress the structures' wind- or earthquake-induced vibrations. However, excessive displacements of the TMD raise concerns in the practical implementation. Therefore, this study proposes a novel TMD designed for and deployed on a high-rise sightseeing tower. The device consists of an integrated two-way slide rail mount and an eddy current damper (ECD) with a stroke control mechanism. This stroke control mechanism allows the damping coefficient to automatically increase when the stroke reaches a predetermined value, preventing excessive damper displacements during large earthquakes. The corresponding two-stage damping parameters are designed with a variable-thickness copper plate to enable the TMD stroke within a specified range. Thus, this study discusses the detailed design schemes of the device components in TMD. The designed two-stage damping parameters are also numerically verified, and the structural responses with/without the TMD are compared. As seen in the results, the proposed TMD yields effective control authority to limit the acceleration response within a comfort level. In addition, this TMD resolves the spatial availability for the damper movement in high-rise buildings by the controllable damping mechanism.

• Journal of Biosystems Engineering
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• 제23권3호
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• pp.259-270
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• 1998

An automatic seedling transplanter, employed an innovative plug-seedling feeder was developed by improving the problems of conversational feeding and transplanting mechanisms. With conventional methods, missing and damage rates of seedling were high for long seedlings over 20cm and also breaking seed-bed was frequently observed. Thus, a pushout-bucket slide-hopper type trandsplanter was devised and tested. Test results of picking and transferring accuracies of the developed transplanter are as follows : A prototype transplanter performed with 1.5% of missing rate. The deviations of horizontal feed ranged from -0.3mm to 2.8mm and averaged 0.673mm for the 128-hoe test tray : and ranged from -lmm to ＋3mm and averaged 0.785mm for the 200-hole test tray. The deviations could decrease with precise manufacturing and lightening the mechanism. The maximum and deviations of vertical feed were -2.3mm and + 1mm, respectively, for the 128-hole test tray ; and were ＋3mm and ＋2.5mm, respectively, for the 200-hole test tray. The missing rate, seeding bruise rate and seed-bed damage rate were esitmate to be 1.3％, 0.4% and 3.5％, respectively, with the developed automatic transplanter.