• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.04a
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• pp.282-286
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• 1995

일반적으로 관성계 내의 물체에 대한 동적특성의 파악을 위해서는 속도, 가속도 및 각속도, 각가속도에 대한 정보를 필요로 하며 자이로는 이중에서 각속도를 측정하는 장치이다. 운동하는 질량에 회전각속도가 인가될 때 발생되는 코리올리힘을 측정하여 회전각속도를 검출하는 개념의 각속도 센서인 진동자이로는 성능이 회전형 자이로에 비해 떨어지나 구조가 간단하고 소형이며 대량생산이 가능한 장점이 있다. 진동자이로의 효시로는 1950년 영국의 Sperry Gyroscope Company의 "Gyroton"이며, 전자기력을 이용한 가진과 측정이 그 특징으로서 실험실 조건에서 지구의 자전속도를 측정할 수 있었다. 그후 1960년대에 General Electric에서 "VYRO"라는 모델을 개발했는데 압전소자를 이용하여 가진과 측정을 하는 방법이 사용되었다. 1980년대에 Watson Ind., Soderkvist등은 센서자체가 압전물질로 만들어진 자이로를 실험하였고 1990년도에 들어서는 진동자이로의 원리를 마이크로 머시닝 기술과 연계시켜서 소형 경량화와 대량생산을 목표로 연구가 일부 진행되고 있다. 현재 제품화되어 실제 응용되고 있는 예로는 무라다사의 삼각프리즘 형태의 자이로, 토킨사의 원통형 자이로 등이 있으며 이러한 자이로는 캠코더 화면의 안정화 장치에 주로 사용되고 있다. 본 논문에서는 압전소자의 압전, 전왜 방정식으로 출발하여 자이로헤드의 동적 거동을 해석하였다. 진동자이로는 물체의 공진주파수에서의 진동현상을 이용하며, 두 방향의 고유진동수를 일치시켜야 하는 등의 설계조건이 있다. 이러한 조건을 만족하도록 사각보 구조를 기본으로 하여 새로운 형태의 자이로헤드를 고안하였다. 자이로헤드의 구동회로를 설계, 해석하고 각속도를 측정할 수 있는 검출회로를 설계하여 설계된 진동자이로의 동적 특성을 확인하고 보정회로를 이용하여 사용 주파수 영역을 넓혔다.이용하여 사용 주파수 영역을 넓혔다.러한 강이성들이 보장되는 제어이론들 중 H$_{\infty}$ 제어이론이 많이 연구/응용 되고 있다. 특히 공칭 플랜트 모델과 함께 사용되는 플랜트 모델과 함께 사용되는 플랜트 불확실성 모델은 직접적으로 성능 및 안정도에 영향을 미치므로 주의 깊게 선정해야 한다. 방법의 실질적인 적용에는 어려움이 있다. 본 연구에서는 기존의 방법들의 단점을 극복할 수 있는 새로운 회귀적 모우드 변수 규명 방법을 개발하였다. 이는 Fassois와 Lee가 ARMAX모델의 계수를 효율적으로 추정하기 위하여 개발한 뱉치방법인 Suboptimum Maximum Likelihood 방법[5]를 기초로 하여 개발하였다. 개발된 방법의 장점은 응답 신호에 유색잡음이 존재하여도 모우드 변수들을 항상 정확하게 구할 수 있으며, 또한 알고리즘의 안정성이 보장된 것이다.. 여기서는 실험실 수준의 평 판모델을 제작하고 실제 현장에서 이루어질 수 있는 진동제어 구조물에 대 한 동적실험 및 FRS를 수행하는 과정과 동일하게 따름으로써 실제 발생할 수 있는 오차나 error를 실험실내의 차원에서 파악하여 진동원을 있는 구조 물에 대한 진동제어기술을 보유하고자 한다. 이용한 해마의 부피측정은 해마경화증 환자의 진단에 있어 육안적인 MR 진단이 어려운 제한된 경우에만 실제적 도움을 줄 수 있는 보조적인 방법으로 생각된다.ofile whereas relaxivity at high field is not affected by τS. On the other hand, the change in τV does not affect low field profile but strongly in fluences on both inflection fie이 and the maximum relaxivity value. The results shows a fluences on both inflection field and the

• Composites Research
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• v.31 no.4
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• pp.133-138
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• 2018

Polymer foams were used to fill the void in the structure in addition to flame retardant and heat insulation. Polymer foams such as polyurethane, polyisocyanurate, poly(vinyl chloride), polyethylene terephthalate were used to weight lighting materials. In this study, epoxy foam was used to improve mechanical properties of polymer foam. Acid anhydride type hardener reacts with polyol. Using this phenomenon, if blowing agent was added into epoxy resin using acid anhydride type hardener, formation and compressive properties of epoxy foam was studied. Formation of polymer foam was compared with type of blowing agent and concentration of blowing agent via compressive test. As these results, optimized condition of epoxy foam was found and epoxy foam had better compressive property than other polymer foam.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.10
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• pp.983-989
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• 2017

This paper presents the bearing strength for laminates in advanced composite materials in bolted joints. Bolted single lap joint tests were experimentally investigated with respect to stabilized and unstabilized lap joints. Stabilized bolted single lap joints refer to joints with out-of-plane rotational constraints. Unstabilized bolted single lap joints refer to joints with absence of out-of-plane deflection constraints. The bearing strength values of laminates in the bolted joint showed that the percentages of ply angle for 0, 45, -45, and 90 degrees were not affected. The bearing strength value in the unstabilized bolted joint was smaller than the bearing strength value in the stabilized bolted joint because of the influence of the out-of-plane behavior. The composite material studied in this paper is a carbon/epoxy unidirectional (UD) tape prepreg cured at $177^{\circ}C(350^{\circ}F)$. In the laminate reference system, the standard angles of 0, 45, -45, and 90 degrees were used for ply orientation within the laminate. A total of 112 bolted single lap joint tests were conducted on specimens from eight distinct laminates. The ASTM-D-5961M standards were adhered to for the stabilized and unstabilized bolted single lap joint tests.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.574-580
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• 2020

An inorganic binder is eco-friendly because it can be cured at low temperatures and does not emit harmful gases. In addition, related research is progressing rapidly owing to the small defects in the core. On the other hand, inorganic binders based on silicates (SiO₂-Na₂O) have unique absorbent properties. This results in the absorption of moisture from the air and the weakening of the bonding force. In particular, the castings used in cast steel require high-strength properties because of the higher temperatures than aluminum castings. In this study, waxes containing ester groups were selected to improve the absorption of moisture of inorganic binders. The inorganic binder was characterized by X-ray fluorescence and thermogravimetric analysis-differential thermal analysis. The inorganic binder core strength was then evaluated. In the case of an inorganic binder containing wax, the water resistance increased to 216 N/㎠, confirming the up to 55% improvement in strength. Excellent casting characteristics were confirmed through steel castings.

• Journal of the Korean Society of Food Science and Nutrition
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• v.35 no.4
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• pp.499-506
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• 2006

Response surface methodology was used to investigate the cookie manufacturing process with black rice flour. A three- variable, three-level central composite design was employed where the independent variables were the amount of black rice flour ($0{\sim}20%$), baking time ($10{\sim}14 min$), and sugar type (sucrose, aspartame and oligosaccarides). pHs of dough and cookie tended to increase with the addition of black rice flour. Moisture content of dough slightly increased with tile addition of black rice flour but nearly affected by baking time. Spread factor increased with the addition of black rice flour and it was more evident in the samples prepared with sucrose. L*-value decreased but a*-value increased significantly with the addition of black rice flour. Generally the amount of black rice flour in the sample did not affect the textural characteristics of cookie. As the amount of black rice and baking time increased, sensory flavor became stronger. Sensory sweetness as well as hardness increased but sensory color became darker with the addition of black rice flour. In addition, the response surface models developed in this study for most of physicochemical and sensory characteristics of black rice cookie were adequate.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.1
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• pp.74-80
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• 2009

This study analysis the fundamental properties of temperature-dependence corresponding the change of curing temperature classified by the replacement ratio of BS, and the results are summarized as following. As the properties of flow, plain satisfied with the target slump, and as the replacement ratio of BS increased, the flow increased, but the air content slightly decreased. The time of set delayed as the replacement ratio of BS increased, but the curing temperature $35^{\circ}C$, even with 80% BS replaced concrete, the time of set was faster than $5^{\circ}C$, $20^{\circ}C$ plain, so the temperature-dependence was much greater. The compressive strength was decreased as the replacement ratio of BS increased, especially as the curing temperature lower, the compressive strength was lower comparatively. Also as the age increased, the plain developed more strength, therefore it show the temperature-dependence is much larger.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.2
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• pp.331-337
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• 2001

The effect of Phellinus linteus methanol extract on the lipid metabolism in the liver of rat was investigated in this study. Rats were randomly divided into 6 groups including the control, $CCl_4$and high fat group plus sub-groups with Phellinus linteus methanol extract administration. Methanol extracts of Phellinus linteus were fed 50mg/kg B.W daily via drinking water. A 1.2mL of $CCl_4/kg$ body weight was administered by oral intubation twice a week for total six times. The administration of $CCl_4$ increased total cholesterol, TG, LDL and LDL-phospholipid. However, the level of liver cholesterol and triglycerides were significantly decreased while HDL-cholesterol was increased by the extract feeding. The activities of GOT, GPT, AP and LDH were greatly enhanced by the extract feeding. Electronmicrograph showed that $CCl_4$ treatment deteriorated the structure of cytoplasmic matrix with its uneven distribution. However, the extract treatment reconstituted the damaged cytoplasm and stimulated mitochondriagenesis. From these results, it was suggested that Phellinus linteus can help to recover the damaged liver function and further may help to prevent senescence diseases such as fatty liver, hypertension and hyperlipidemia.

• Journal of Conservation Science
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• v.27 no.3
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• pp.301-312
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• 2011

Epoxy resin has superior durability and adhesive strength and proper physical strength so that it is used to diversity materials for multi-purposes. However epoxy resin is hardly removed after hardening specially once it is applied to artefacts, it is difficult to remove them under re-conservation. This paper is an experimental study on removing epoxy resin applied to iron objects using Nd:YAG laser cleaning system. Tests conducted in this study investigated how increasing laser energy and pulses would give effect on samples. The samples were prepared in a way that epoxy resin, itself pure and one which was mixed with pigment and they were applied to iron coupons and corroded iron coupons respectively. As a result of experiment, pure epoxy resin applied to corroded iron coupons was ablated at high laser energy but epoxy resin applied to iron coupons and mixing with pigment were not ablated but discolored and bubbled due to laser-induced heat generation. Results of FT-IR showed no component alteration of shifted resins and no residues on the surfaces ablated by laser irradiation. From SEM-EDS for removed surfaces, the debris from epoxy resin and melting iron was observed. Therefore, this study demonstrated the possibilities and limitations for laser cleaning to remove epoxy resin from iron objects.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.573-580
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• 2009

This paper presents the mix composition, production method, and curing condition applied to the extruded ECC(Engineered Cementitious Composite) panel which are able to exhibit multiple cracking and potential pseudo strain-hardening behavior. In addition to the production technique of extruded ECC panel, the effect of fiber distribution characteristics, which are uniquely created by applying extrusion process, on the flexural behavior of the panel is also focussed. In order to demonstrate fiber distribution, a series of experiments and analyses, including image processing/analysis and micro-mechanical analysis, was performed. The optimum mix composition of extruded ECC panel was determined in terms of water matrix ratio, the amount of cement, ECC powder, and silica powder. It was found that flexural behavior of extruded ECC panel was highly affected by the slight difference in mix composition of ECC panel. This is mainly because the difference in mix composition results in the change of micro-mechanical properties as well as fiber distribution characteristics, represented by fiber dispersion and orientation. In terms of the average fiber orientation, the fiber distribution was found to be similar to the assumption of two dimensional random distribution, irrespective of mix composition. In contrast, the probability density function for fiber orientation was measured to be quite different depending on the mix composition.

• Korean Journal of Food Science and Technology
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• v.48 no.6
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• pp.565-568
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• 2016

This study was conducted to soften the tough texture of retorted beef in storage by increasing the water holding capacity (WHC) after pretreatment involving soaking and blanching in a phosphate solution. The yield of pretreated beef, based on weight as an indirect indicator of WHC, soaked in 0.35% (w/w) complex phosphates for 1 h, increased by 5-10%, in contrast to the untreated control in which the rib and shank was heated at $100^{\circ}C$ for 5-40 min. Additionally, strength of mechanical toughness in the fore rump and rib after phosphate curing at $115^{\circ}C$ for 30 min and blanching at $100^{\circ}C$ for 2 min were significantly decreased to 1.3 and $1.4kg_f$ (p<0.05) as compared to 2.0 and $1.8kg_f$ in the control, respectively. During storage of retorted beef for 30 days at $10^{\circ}C$, rib and shank pretreated with 0.35% complex phosphates exhibited a highly soft texture as compared to that of untreated beef. The softening of pretreated beef was based on the increased WHC due to complex phosphates.