• 한국정밀공학회지
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• 제20권7호
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• pp.233-240
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• 2003

Recently, the world are preparing for new revolution, called as If (Information Technology), NT (Nano-Technology), and BT (Bio-Technology). NT can be applied to various fields such as semiconductor-micro technology. Ultra precision processing is required for NT in the field of mechanical engineering. Recently, together with radical advancement of electronic and photonics industry, necessity of ultra precision processing is on the increase for the manufacture of various kernel parts. Therefore, in this paper, stability of ultra precision cutting unit is investigated, this unit is the kernel unit in ultra precision processing machine. According to alteration of shape and material about hinge, stability investigation is performed. In this paper, hinge shapes of micro stage in UPCU(Ultra Precision Cutting Unit) are designed as two types, where, hinge shapes are composed of round and rectangularity. Elasticity and strength are analyzed about micro stage, according to hinge shapes, by FE analysis. Micro stage in ultra precision processing machine has to keep hinge shape under cutting condition with 3-component force (cutting component, axial component, radial component) and to reduce modification against cutting force. Then we investigated its elasticity and its strength against these conditions. Material of micro stage is generally used to duralumin with small thermal deformation. But, stability of micro stage is investigated, according to elasticity and strength due to various materials, by FE analysis. Where, Used materials are composed of aluminum of low strength and cooper of medium strength and spring steel of high strength. Through this stability investigation, trial and error is reduced in design and manufacture, at the same time, we are accumulated foundation data for unit control.

• 소음진동
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• 제5권4호
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• pp.515-524
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• 1995

Tubes in heat exchanger of fuel rods in reactor core are supported at intemediate point by support p0lates or springs. Current practice is, in case of heat exchanger, to allow clearance between tube and support plate for design and manufacturing consideration. And in case of fuel rod the clearance in support point can be generated due to the support spring force relaxation. Flow-induced vibration of a tube can cause it to impact or rub against support plate or against adjacent tubes and can result in fretting-wear. The tube-to- support dynamic interaction is used to relate experimental wear data from single-span test rigs to real multi-span heat exchanger configurations. The dynamic interaction cna be measured during experimental wear tests. However, the dynamic interaction is difficult to measure in real heat exchangers and, therefore, analytical techniques are required to estimate this interaction. This paper describels the nonlinear impact model of DAGS(Dynamic Analysis of Gapped Structure) code which simulates the tube response to external sinusodial or step excitation and predicts tube motion and tube-to-support dynamic interaction. Three experimental measurements-two single span rods excited by sinusodial force and a two span rod impacted by a steel ball are compared from the simulation nonlinear model of DAGS code. The simulation results from DAGS code are in good agreement with measurements. Therefore, the developed model of DAGS code is good analytical tool for estimating tube-to-support dynamic interaction in real heat exchangers.

• 한국자동차공학회논문집
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• 제16권1호
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• pp.86-92
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• 2008

Recently, the use of tubes in the manufacturing of the automobile parts has increased and therefore many automotive manufactures have tried to use hydro-forming technology. The hydro-forming technology may cause many advantages to automotive applications in terms of better structural integrity of the parts, lower cost from fewer part count, material saving, weight reduction, lower spring-back, improved strength and durability and design flexibility. In this study, the whole process of front engine cradle (or front sub-frame) parts development by tube hydro-forming using steel material having tensile strength of 440MPa grade is presented. At the part design stage, it requires feasibility study and process design aided by CAE (Computer Aided Design) to confirm hydro-formability in details. Effects of parameters such as internal pressure, axial feeding and geometry shape on automotive sub-frame by hydro-forming process were carefully investigated. Overall possibility of hydro-formable sub-frame parts could be examined by cross sectional analyses. Moreover, it is essential to ensure the formability of tube material on every forming step such as pre-bending, preforming and hydro-forming. At the die design stage, all the components of prototyping tools are designed and interference with press is examined from the point of geometry and thinning.

• 대한한의학회지
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• 제22권2호
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• pp.109-119
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• 2001

Objective : There are many reports that acupuncture has thermoregulatory effects on human and animals. To investigate the effect and mechanism of antipyretic action of acupuncture, we observed the body temperature and cytokine expressions in the hypothalamus of rats. Methods : Lipopolysaccharide (LPS, i.p., 2.5mg/kg) was injected to conscious rats (Sprague-Dawley, male, n=4l) to cause hyperthermia and simple needling (stainless steel, 0.25 mm o.d., 5 mm insertion for 10 sec with no manipulation) was performed bilaterally with the measurement of rectal temperature. Next, we sacrificed rats to remove brain and determined the level of mRNA for interleukin-6 (IL-6), $interleukin-1{\beta}{\;}(IL-1{\beta})$, interleukin-2 (IL-2) and $interferon-{\gamma}{\;}(IFN-{\gamma})$ in the hypothalamus by using reverse transcriptase-polymerase chain reaction (RT-PCR). Resul1s : Needling on forepaw (acupoint HT8) and needling on hindpaw (acupoint BL66 and acupoint LR2) significantly inhibited LPS-induced fever of rats (P<0.01, 10 min after treatment respectively), but same treatment on proximal tail (non-acupoint) did not cause any change on fever. The levels of IL-6 and $IL-1{\beta}$ mRNA in the hypothalamus was significantly enhanced by LPS-injection, while the level of IL-6 and $IL-1{\beta}$ mRNA was markedly reduced after treatment on BL66 (P<0.01). Treatment on forepaw reduced it slightly, but not significantly. Equivalent stimulation on proximal tail did not cause any changes. Conclusions : Our results indicate that acupuncture stimulation on various body parts has differential thermoregulatory effects on LPS-induced fever of rats with site-specificity. And, we suggest that its antipyretic action might be accompanied with the suppression of hypothalamic production of pro-inflammatory cytokine of immune system, IL-6 and $IL-1{\beta}$.

• 대한기관식도과학회:학술대회논문집
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• 대한기관식도과학회 1982년도 제16차 학술대회연제순서 및 초록
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• pp.8.1-8
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• 1982

기도 이물은 이비인후와 영역에서 중요한 위치를 차지하고 있는 질환으로서, 타 질환에 비하여 그리 드문 것은 아니며 지금까지 국내외에서 많은 보고가 있어왔다. 기도 이물은 때로는 순식간에 생명을 위협하거나 중증의 합병증을 초래하기도 하며, 이물의 종류와 형태도 다양할 뿐 아니라 그 개재부위도 달라서 이물적출은 항상 낙관을 불허하는 것으로 수술적 방법을 요할때도 있다. 저자들은 최근에, 이물이 자연 객출된 1예와 기관지경술로 성공한 4예 및 외과적 수술로 제거한 2 예를 경험하였기에 문헌적 고찰과 함께 보고하는 바이다.

• 한국환경과학회지
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• 제21권5호
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• pp.597-603
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• 2012

Non-thermal plasma processing using a dielectric barrier discharge (DBD) has been investigated as an alternative method for the degradation of non-biodegradable organic compounds in wastewater. The active species such as OH radical, produced by the electrical discharge may play an important role in degrading organic compound in water. The degradation of N, N-Dimethyl-4-nitrosoaniline (RNO) was investigated as an indicator of the generation of OH radical. The DBD plasma reactor of this study consisted of a plasma reactor, recycling pump, power supply and reservoir. The effect of diameter of external reactor (15 ~ 40 mm), width of ground electrode (2.5 ~ 30 cm), shape (pipe, spring) and material (copper, stainless steel and titanium) of ground electrode, water circulation rate (3.1 ~ 54.8 cm/s), air flow rate (0.5 ~ 3.0 L/min) and ratio of packing material (0 ~ 100 %) were evaluated. The experimental results showed that shape and materials of ground were not influenced the RNO degradation. Optimum diameter of external reactor, water circulation rate and air flow rate for RNO degradation were 30 mm, 25.4 cm/s and 4 L/min, respectively. Ground electrode length to get the maximum RNO degradation was 30 cm, which was same as reactor length. Filling up of glass beads decreased the RNO degradation. Among the experimented parameters, air flow rate was most important parameters which are influenced the decomposition of RNO.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.377-379
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• 2007

To reduce the chattering errors of reed switch sensors used for automatic remote measurement of water supply system, a reed switch sensor was analyzed and improved. The operation of reed switch sensors can be described as a mechanical contact by approximation of permanent magnet piece to generate an electrical pulse. The reed switch sensors are used in measurement application by detecting the rotational or translational displacement. To apply for flow measurement devices, the reed switch sensors should keep high reliability. They are applied for the electronic digital type of water flow meters. The reed switch sensor is just installed simply on the mechanical type flow meter. A small magnet is attached on a pointer of the water meter counter rotor. Inside the reed sensor, two steel leaf springs make mechanical contact and apart as rotation of flow meter counter. The counting electrical contact pulses can be converted as the water flow amount. The MCU sends the digital flow rate data to the server using the wireless communication network. But it occurs data difference or errors by chattering noise. The reed switch sensor contains chattering error by it self at the force equivalent position. The vibrations such as passing car near to the switch sensor installed location. In order to reduce chattering error, most system uses just software methods for example using filter and also statistical calibration methods. The chattering errors were reduced by changing leaf spring structure using mechanical hysteresis characteristics.

• 한국산림과학회지
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• 제26권1호
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• pp.7-12
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• 1975

고래(古來)로부터 채취(採取)하여 약용(藥用)으로 음용(飮用)하여 왔고 단풍나무류(類)중 산림(山林)에 축적(蓄積)에 가장 큰 고로쇠나무(Acer mono Max.)의 수액(樹液)의 당도(糖度)는 평균(平均) $2.6^{\circ}-3.3^{\circ}Brix$로 감류자원(甘類資源)으로 개발(開發)이 가능(可能)한 범위이고 색도지수(色度指數)는 $15.3^{\circ}Brix$(10시간농축(時間濃縮))에서 2.69, 표준(標準)물엿은 3.380으로 심(甚)한 착색(着色)을 하였다. 알코올 추출물(抽出物)은 담황색(淡黃色)을 나타냈으며 흡특성(吸特性)은 파장(波長)(${\lambda}_{max}$) 350 nm, 1,000 nm, 1,170 nm, 1460 nm 및 1900 nm에서 흡광최대(吸光最大)를 나타냈다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.820-824
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• 2010

본 연구는 소형 하이브리드 로켓의 제작 및 발사를 통해 하이브리드 발사체의 기초 발사기술을 확보하는 것이다. 연료로는 HDPE, 산화제는 $LN_2O$를 적용하였으며, 알루미늄 외형재질의 설계 총 무게 12.5 kg, 외경 114 mm, 전장 1.8 m의 소형 하이브리드 로켓을 설계하였다. 로켓의 목표고도는 500 m로 설정하였고, 목표 추력 50 kgf와 연소시간 2.5 초의 연료 그레인 및 인젝터를 설계 및 제작하였다. 발사 후 실시간 압력 및 속도 등의 데이터를 수집하기 위한 데이터 획득장치와 로켓의 안정적인 회수를 위한 스프링-모터를 이용한 사출장치를 제작 탑재하였다. 로켓의 발사는 성공적으로 수행되었으나, 로켓 중량의 증가 및 추력의 부족으로 설계 최고 고도에는 로켓이 미치지 못했고, 로켓의 비행 궤도를 분석하였다.

• Steel and Composite Structures
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• 제25권2호
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• pp.141-155
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• 2017

This paper presents an investigation into the magneto-thermo-mechanical vibration and damping of a viscoelastic functionally graded-carbon nanotubes (FG-CNTs)-reinforced curved microbeam based on Timoshenko beam and strain gradient theories. The structure is surrounded by a viscoelastic medium which is simulated with spring, damper and shear elements. The effective temperature-dependent material properties of the CNTs-reinforced composite beam are obtained using the extended rule of mixture. The structure is assumed to be subjected to a longitudinal magnetic field. The governing equations of motion are derived using Hamilton's principle and solved by employing differential quadrature method (DQM). The effect of various parameter like volume percent and distribution type of CNTs, temperature change, magnetic field, boundary conditions, material length scale parameter, central angle, viscoelastic medium and structural damping on the vibration and damping behaviors of the nanocomposite curved microbeam is examined. The results show that with increasing volume percent of CNTs and considering magnetic field, material length scale parameter and viscoelastic medium, the frequency of the system increases and critically damped situation occurs at higher values of damper constant. In addition, the structure with FGX distribution type of CNTs has the highest stiffness. It is also observed that increasing temperature, structural damping and central angle of curved microbeam decreases the frequency of the system.