• 한국생산제조학회지
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• 제19권6호
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• pp.889-894
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• 2010

Conventional shrink-fit tool holders have positive features, such as high accuracy, high strength, high stiffness and low sensitivity to centrifugal forces, but they require heavy investments for heating and cooling equipment. Generally the heating equipment has to heat the tool holder up to $200{\sim}300^{\circ}C$ for tool changes. This paper introduces a novel shrink-fit tool holder that is able to unclamp a tool at $40{\sim}50^{\circ}C$. This feature makes it possible to switch between the clamped and unclamped states by using a simple device, which has lower power, smaller size and lower cost than the heating equipment of the conventional shrink-fit tool holders. The proposed shrink-fit tool holder is able to expand its tool hole by using the shape memory alloys which are integrated in the tool holder body. Performances of the SMA shrink-fit tool holder were evaluated experimentally. The experimental results confirm that the proposed tool holder is feasible in aspects of clamping/unclamping operations, clamping force and repeatability of tool setup.

• 대한안전경영과학회지
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• 제11권1호
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• pp.43-49
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• 2009

This study set three kinds of situation and observed the various states such as carbonization by experimenting damages by fire of electric iron. The results of this study are as follows: The fire did not occurred when the unpowered iron over mattress and cotton shirts was com busted completely by external flame because the temperature of surface of soleplate and mattress did not reach the minimum ignition energy and when the powered electric iron over mattress and cotton shirts was left for an hour with its temperature dial set to high because the temperature of combustibles did not reach the minimum ignition energy. The fire occurred when the electric iron in which the outer box, bi-metal switch, and temperature fuse were removed over mattress and cotton shirts was powered by through heater terminal, and then the electric iron, mattress, and cotton shirts were combusted by the fallen combustibles because the temperature of combustibles reached to the minimum ignition energy with the help of active transfer of heat.

• BMB Reports
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• 제38권3호
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• pp.266-274
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• 2005

High temperature requirement A (HtrA) and its homologues constitute the HtrA familiy proteins, a group of heat shock-induced serine proteases. Bacterial HtrA proteins perform crucial functions with regard to protein quality control in the periplasmic space, functioning as both molecular chaperones and proteases. In contrast to other bacterial quality control proteins, including ClpXP, ClpAP, and HslUV, HtrA proteins contain no regulatory components or ATP binding domains. Thus, they are commonly referred to as ATP-independent chaperone proteases. Whereas the function of ATP-dependent chaperone-proteases is regulated by ATP hydrolysis, HtrA exhibits a PDZ domain and a temperature-dependent switch mechanism, which effects the change in its function from molecular chaperone to protease. This mechanism is also related to substrate recognition and the fine control of its function. Structural and biochemical analyses of the three HtrA proteins, DegP, DegQ, and DegS, have provided us with clues as to the functional regulation of HtrA proteins, as well as their roles in protein quality control at atomic scales. The objective of this brief review is to discuss some of the recent studies which have been conducted regarding the structure and function of these HtrA proteins, and to compare their roles in the context of protein quality control.

• 한국기계가공학회지
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• 제13권6호
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• pp.46-53
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• 2014

An automatic grease lubricator provides an adequate amount of fresh grease constantly to any type of rotating machine to minimize friction heat and reduce friction loss. This study seeks to develop an automatic grease lubricator by means of rapid prototyping with a gear-driven mechanism and a controlled operation time. The ultimate design is to lubricate an adequate amount of grease by a simple dip-switch clicking mechanism according to an advanced set cycle. The backlash of the gear was minimized to increase the power, and to increase the power of the mechanism, the binding frequency and the thickness of the coil were changed. To control the rotation cycles of the main shaft according to certain set numbers, different resistances and chips were used in the design of the circuit which controls the electrical signals via a pulse. A digital mock-up was analyzed and the rapid prototyping (RP) trial products were tested with a PCB circuit and grease. An evaluation of the outlet capacity of RP trial products was conducted, as the friction caused by the outlet on the wall surface was an important factor in the operation of the equipment. Finally, a finishing process was applied to decrease the roughness of a surface to a comparable level to test the performance of the product.

• 한국의류산업학회지
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• 제15권2호
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• pp.231-239
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• 2013

This research developed a smart girdle for adult women in their 20's that has an inserted carbon weaving heater to help with relief from coldness and abdominal disease through the thermal insulation effect. A pocket of powernet fabric was attached to the inside of the girdle for the easy insertion and separation of the heating device, while the heating device was fixed to a mesh material by cotton yarn and was wrapped with elastic lining material to prevent the mechanical devices from being exposed. A set of 3 hooks was attached to the center of the back of the heating device in consideration of convenience and mobility. Whereas the switch was inserted into around the right waistband, and the battery into the inner pocket around the waist, to integrate the heating device with the girdle. The satisfaction and usability of the fabricated smart girdle was verified by having research participants wear it to evaluate the appearance change caused by the device, the inconvenience of wearing/unwearing, mobility, and the satisfactory functionality of the device. As a result, the grand mean was evaluated to be high, with appearance (4.19), mobility (4.17), and functionality (4.51) being higher than 4.00; which indicates that the heat generation function of the smart girdle is effective. It may be said that such collection and analysis of data that reflect users' opinions have value and significance in that they can be grafted onto future research on new technology as well as they contribute to taking a step forward in the rapidly increasing research of smart clothing, with the new-type clothing equipped with new function.

• 한국자기공명학회논문지
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• 제19권3호
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• pp.99-105
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• 2015

Hsp33 is a prokaryotic molecular chaperon that exerts a holdase activity upon response to an oxidative stress at raised temperature. In particular, intramolecular disulfide bond formation between the four conserved cysteines that bind a zinc ion in reduced state is known to be critically associated with the redox sensing. Here we report the backbone NMR assignment results of the half-oxidized Hsp33, where only two of the four cysteines form an intramolecular disulfide bond. Almost all of the resolved peaks could be unambiguously assigned, although the total assignments extent reached just about 50%. Majority of the missing assignments could be attributed to a significant spectral collapse, largely due to the oxidation-induced unfolding of the C-terminal redox-switch domain. These results support two previous suggestions: conformational change in the first oxidation step is localized mainly in the C-terminal zinc-binding domain, and the half-oxidized form would be still inactive. However, some additional regions appeared to be potentially changed from the reduced state, which suggest that the half-oxidized conformation would be an intermediate state that is more labile to heat and/or further oxidation.

• 한국정밀공학회지
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• 제23권2호
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• pp.199-206
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• 2006

Automatic grease lubricator is equipment that provides adequate amount of fresh grease constantly to the shaft and the bearings of machines. It minimizes the friction heat and reduces the friction loss of machines to the least. This research is to develop automatic grease lubricator by gear driven mechanism with controlled operation time. The ultimate design of this equipment is to lubricate an adequate amount of grease by a simple switch clicking according to the advanced set cycle. The backlash of the gear was minimized to increase the output power. To increase the power of gear mechanism, the binding frequency and the thickness of the coil were changed. To control the rotating cycles of the main shaft according to its set numbers, different resistance and chips were used to design the circuit to controls electrical signals with pulse. The body of the lubricator was analyzed by stress analysis with different constructed angle. The stress analysis for differing loading pressures applied to the exterior body of grease lubricator due to the setup angle, was found that the maximum stress was distributed over the outlet part where the grease lubricator suddenly narrowed contracts. Digital mock-up was analyzed and the rapid prototyping(RP) trial products were tested with PCB circuit and grease. The evaluation of the outlet capacity for RP trial products was conducted, because the friction caused by the outlet on the wall surface was an important factor in the operation of the equipment. Finally, the finishing process was applied to decrease the roughness of the surface to a comparable level and was able to test the performance examination for the product.

• 한국건설관리학회논문집
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• 제23권1호
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• pp.73-82
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• 2022

국내 지정폐기물 중 하나인 폐페인트는 현재 전량 소각 방법으로 처리되고 있으며, 다른 폐기물에 비해 재활용도 거의 이루어지지 않고 있어, 자원이 부족한 우리나라에 엄청난 자원의 손실뿐 아니라 소각으로 인한 에너지원의 낭비, 그리고 소각 시 발생하는 대기오염 등의 환경문제도 유발하고 있다. 이를 위해 본 연구에서는 기존의 폐페인트의 소각처리법을 탈피하여, 온도 조절에 의한 증발·응축, 열분해를 통해 전처리 조작하는 방법으로 전환하고, 이때 발생하는 잔재물을 활용하여 일정한 형상(과립형 및 분말형)으로 성형한 후 이를 대체에너지 열원으로 재활용할 수 있는 친환경(지속가능한) 폐페인트 처리프로세스를 제시하고자 한다. 폐페인트를 처리하는 새로운 방법과 재활용하는 기술개발이 이루어지고 보급된다면 환경적·경제적 면에서 그 효과가 클 것으로 기대한다.

• 생명과학회지
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• 제20권12호
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• pp.1777-1783
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• 2010

식물체는 대사과정의 부산물로서 또는 생물학적으로 피해를 줄 수 있는 다양한 종류의 외부 스트레스에 직면했을 활성산소(Reactive Oxygen Species, ROS)를 생산한다. 이러한 oxidative 스트레스로부터 자신들을 보호하기 위하여 식물세포들은 다양한 종류의 항산화 단백질들을 보유하고 있다. 하지만 이들의 작용기작은 여전히 자세히 밝혀지지 않았다. Peroxiredoxins (Prxs)은 식물체에 광범위하게 존재하는 thiol-을 함유한 항산화 단백질로 N-말단에 존재하는 cysteine 잔기를 이용하여 hydrogen peroxide를 환원한다. 이러한 과정에서 peroxiredoxins의 활성부위인 cysteine 잔기는 선택적으로 cysteine sulfinic acid로 산화됨으로써 peroxidase activity의 불활성화를 일으킨다. 이러한 산화과정은 비가역적으로 일어난다. 최근 발견된 진핵생물들에 잘 보존된 sulphiredoxin (Srx1)이라 불리는 단백질은 cysteine-sulphinic acid를 환원시키는 기능을 지닌다. 본 논문에서는 애기장대에 존재하는 Prxs와 Srx의 기능에 대하여 서술할 예정이다.

• 감성과학
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• 제21권2호
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• pp.137-144
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• 2018

본 연구에서는 가변 통기성 스마트 의류의 제작을 위해 필요한 형상기억합금 액추에이터의 작동 조건을 파악하였다. 의복의 개방, 폐쇄와 같은 양방향 작동 시 형태 변형 시에만 전력을 소모하는 저전력 소모 액추에이터 개발을 위해 복수 채널의 일방향 형상기억합금을 이용하여 스위치로 작동되는 액추에이터를 설계하였으며 가장 효율적으로 작동할 수 있는 와이어의 직경과 전압인가 단위시간을 도출하였다. 선행연구 결과 도출된 양방향 작동이 가능한 일방향 형상기억합금의 직경 범위 내에서 Arduino 스위치를 제작하여 3.7V 전압인가 시 변화량을 분석한 결과 $0.4{\Phi}$의 액추에이터가 가장 적합한 것으로 나타났다. $0.4{\Phi}$ 형상기억합금와이어를 사용한 양방향작동 액추에이터의 개방, 폐쇄에 필요한 최적전압인가 시간을 도출하기 위해 액추에이터의 최대개방, 최소폐쇄 도달 전압인가 시간으로부터 50ms씩 감소, 증가 시키며 냉각 후 액추에이터의 내경을 비교하는 방식으로 측정한 결과 개방 동작에 필요한 최적 전압인가 단위시간은 4,100ms로 나타났다. 각 채널간의 발열에 의한 간섭을 최소화하기 위한 양방향간 작동 시 필요 딜레이 분석을 위해 상온에서 형상기억합금에 최적 전압입가 시간인 4.1초 동안 전원을 공급하고 가열 후 냉각까지의 과정을 열화상카메라로 촬영하여 형상기억합금 와이의 온도가 냉각시의 상변태온 이하로 하강하는 시점을 파악한 결과, 액추에이터의 양방향간 작동 딜레이는 1.8초 이상이 확보되어야 함을 파악할 수 있었다.