• 한국철도학회논문집
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• 제11권3호
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• pp.317-325
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• 2008

최근 연구결과 레일연마 및 장대레일화로 누적통과톤수에 의한 레일교체기준의 연장이 가능한 것으로 보고되었다. 본 연구에서는 현재 도시철도에서 사용 중인 대표 궤도구조에 대해 실운행 열차하중에 의한 궤도의 동적 응답을 분석하여 현 궤도의 상태평가를 하였으며 궤도의 상태 변화에 따른 레일의 부담력을 검토하였다. 또한, 측정된 응력파형을 Rainflow Count Method를 이용하여 응력히스토그램을 작성하고 등가응력을 상정하여 신규 레일 용접부의 S-N 선도에 적용함으로써 노후레일의 누적피로손상도 및 휨 피로수명을 산정하였다. 최종적으로 본 연구에서는 궤도구조 및 상태를 고려한 레일교체기준의 개정을 제안하고자 하였다.

• Molecules and Cells
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• 제19권1호
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• pp.74-80
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• 2005

Stress is known to inhibit granule cell proliferation in the hippocampus. However, recent studies suggest that the commonly used dose of bromodeoxyuridine (BrdU) is insufficient to label all fractions of granule cells. Furthermore, stress-induced changes in BrdU availability may influence the labeling of newly born cells. To investigate whether changes in BrdU availability affect measurements of stress-induced granule cell proliferation, granule cell proliferation was assessed using injection of high doses of BrdU before and after restraint stress lasting 1 h. In addition, to determine whether stress-induced changes in plasma corticosterone levels were influenced by the BrdU, time-dependent changes in plasma corticosterone levels over 2 h after BrdU injection were compared with total accumulated plasma corticosterone levels [as determined by areas under the curve (AUC)]. Restraint stress significantly reduced the numbers of BrdU-labeled cells and clusters in the granule cell layer (GCL) of rats that received BrdU after stress, and decreases of similar magnitude were observed when the rats were given BrdU before stress. BrdU injection enhanced the stress-induced plasma corticosterone response, but there was no difference between the mean AUCs of plasma corticosterone levels of animals injected with BrdU before or after stress. These observations suggest that restraint stress decreases granule cell proliferation, and that this may be influenced by the extent and duration of plasma corticosterone increases rather than by changes in the availability of BrdU.

• 대한한의학회지
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• 제19권2호
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• pp.228-243
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• 1998

This study was undertaken to evaluate the effect of Sunghyangchungisan (SHCS) on the regulation of vascular tone. Vascular rings isolated from rabbit carotid artery were myographed isometrically in isolated organ baths and the effect of SHCS on contractile activities were determined. SHCS relaxed the arterial rings which were pre-contracted by phenylephrine(PE). The responses to SHCS were partially dose-dependent at concentrations lower than 0.5 mg/ml. When SHCS was applied prior to the exposure to PE, it inhibited the PE-induced contraction by a similar magnitude which was comparable to the relaxation of pre-contracted arterial rings. Washout of SHCS after observing its relaxant effect resulted in a full recovery of PE-induced contractions, indicating that the action mechanism is reversible. The observation that SHCS did not change the $ED_{50}$ of PE on its dose-response curve ruled out the possible interaction of SHCS and ${\alpha}-receptor$. The relaxant effect of SHCS was not affected by removal of endothelium, and pretreatment of the arterial rings with methylene blue or nitro-L-arginine. This results suggest that the action of SHCS is not mediated by endothelium nor soluble guanylate cyclase. SHCS relaxed high $K^{+}-induced$ contractions as well, whereas it failed to relax phorbol ester-induced contractions. When contraction was induced by additive application of $Ca^{2+}$ in arterial rings which were pre-depolarized by high $K^+$ in a $Ca^{2+}-free$ solution, the relaxant effect of SHCS was attenuated by increasing the $Ca^{2+}$ concentration. SHCS, when applied to the arterial rings pre-contracted by PE and then relaxed by nifedipine, a $Ca^{2+}$ channel blocker, did not show additive relaxation. From above results, it is suggested that SHCS relax PE-induced contraction of rabbit carotid artery in an endothelium-independent manner, and inhibition of $Ca^{2+}$ influx may contribute to the underling mechanism.

• 한방재활의학과학회지
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• 제18권4호
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• pp.13-24
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• 2008

Objectives : The purpose of this study was to investigate the effect of Poncirus Trifoliata(PT) on improvement of fecal impaction in spinal cord injured(SCI) rats. Methods : Fifteen adult Sprague-Dawley female rats were used weighing 200~250 g. A complete spinal cord transection was performed surgically at the T10 cord level. Experimental groups were assigned into 3 groups: Control(n=5), SCI+vehicle(n=5) and SCI+PT(n=5). PT was administered 100mg/kg in 0.5ml every 24 hours from 1st operation day to 7th day. We measured the body weight and food intake as well as the number and the weight of fecal pellet every morning. After 1 week of operation, whole colon was divided into proximal and distal segments under anesthesia. Each segment of colon was mounted with longitudinal direction in a organ bath. We measured spontaneous contraction and compared the area under the curve in each segments. Enhanced responses were observed by acetylcholine($10^{-6}M$), 40 mM KCl solution, L-NAME($10^{-4}M$). Results : The fecal number and weights were significantly higher in the group of SCI+PT than SCI+vehicle group(p<0.05). In organ bath study, area under the curves of the spontaneous contraction in SCI+vehicle and SCI+PT groups were significantly increased compared to control group. Contractility of distal colon in response to acetylcholine or KCl in SCI+vehicle group was significantly decreased compared to other groups(p<0.05). Conclusions : These results suggest that PT might be useful to promote bowel emptying in spinal cord injured rats.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2008년도 추계학술대회 논문집
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• pp.349-354
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• 2008

2008년 8월 우리나라는 온실효과로 인한 기후변화 대응 역량을 강화하고, 에너지의 안정적 공급과 효율화 체계를 구축하기 위한 방안으로 '제1차 국가에너지기본계획'을 발표하였다. 이에 따르면 우리나라는 세계 10위의 에너지다소비 국가이자, 그 중 97% 이상을 해외 수입에 의존하는 나라로서 신재생에너지설비의 중요성이 크게 부각되고 있다. 본 논문은 일반적인 건물의 난방설비로 이용되고 있는 가스와 유류설비를 지열히트펌프로 대체함으로서, 전력계통의 부하율을 향상시키는 방안을 제시하였으며, 이에 따른 에너지비용 절감과 온실가스의 감축방안을 정량적으로 제시하였다.

• Structural Engineering and Mechanics
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• 제75권6호
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• pp.675-684
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• 2020

An innovative retrofit method using pre-stressed steel strips and externally-bonded steel plates was presented in this paper. With the aim of exploring the seismic performance of the retrofitted RC interior joints, four 1/2-scale retrofitted joint specimens together with one control specimen were designed and subjected to constant axial compression and cyclic loading, with the main test parameters being the volume of steel strips and the existence of externally-bonded steel plates. The damage mechanism, force-displacement hysteretic response, force-displacement envelop curve, energy dissipation and displacement ductility ratio were analyzed to investigate the cyclic behavior of the retrofitted joints. The test results indicated that all the test specimens suffered a typical shear failure at the joint core, and the application of externally-bonded steel plates and that of pre-stressed steel strips could effectively increase the lateral capacity and deformability of the deficient RC interior joints, respectively. The best cyclic behavior could be found in the deficient RC interior joint retrofitted using both externally-bonded steel plates and pre-stressed steel strips due to the increased lateral capacity, displacement ductility and energy dissipation. Finally, based on the test results and the softened strut and tie model, a theoretical model for determining the shear capacity of the retrofitted specimens was proposed and validated.

• 한국자기학회지
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• 제14권6호
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• pp.232-235
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• 2004

아날로그 형태의 신호를 전송하기에 적합한 특성을 보이는 선형 GMR(giant magnetoresistance) 아이솔레이터를 모델링하여 입력전류에 따른 출력전압과 전류를 조사하였다. GMR 아이솔레이터를 자기적 부분과 전기적 부분으로 나누고 선택된 스핀밸브 소자의 MR(magnetoresistance) 결과를 대입하여 출력전압을 구할 수 있는 순서도를 설정하였다. 자기적 모델링으로는 평판 코일의 3차원 모델을 FEM방법으로 해석하여 입력전류에 의해 생성되는 자장의 세기를 구하였으며, 여기에서 자기코어층이 있는 경우 50% 이상 더 커지는 결과를 얻었다. 그리고 아이솔레이터의 출력전압파형을 계산한 결과 입력 코일 전류에 따른 궤환 코일 전류가 $I_{out}$ = $I_{in}$ -5 mA의 선형함수와 비교시 평균 $\pm$0.25 mA 이내의 차이로 근사한 값으로 계산되었다. 또한 입력되는 코일 전류가 구형파일 때, 출력전압의 반응시간과 파형을 계산하였으며, 이때 최저전압에서 최대 전압까지 상승 및 하강하는 시간은 연산증폭 기의 slew rate가 0.3 V/${\mu}\textrm{s}$ 일 때, 최저전압에서 최대 전압까지 상승 및 하강하는 시간은 6 ${\mu}\textrm{s}$였다.

• Earthquakes and Structures
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• 제8권3호
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• pp.485-509
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• 2015

This paper presents the experimental results obtained by applying frequency-domain structural health monitoring techniques to assess the damage suffered on a special type of damper called Web Plastifying Damper (WPD). The WPD is a hysteretic type energy dissipator recently developed for the passive control of structures subjected to earthquakes. It consists of several I-section steel segments connected in parallel. The energy is dissipated through plastic deformations of the web of the I-sections, which constitute the dissipative parts of the damper. WPDs were subjected to successive histories of dynamically-imposed cyclic deformations of increasing magnitude with the shaking table of the University of Granada. To assess the damage to the web of the I-section steel segments after each history of loading, a new damage index called Area Index of Damage (AID) was obtained from simple vibration tests. The vibration signals were acquired by means of piezoelectric sensors attached on the I-sections, and non-parametric statistical methods were applied to calculate AID in terms of changes in frequency response functions. The damage index AID was correlated with another energy-based damage index -ID- which past research has proven to accurately characterize the level of mechanical damage. The ID is rooted in the decomposition of the load-displacement curve experienced by the damper into the so-called skeleton and Bauschinger parts. ID predicts the level of damage and the proximity to failure of the damper accurately, but it requires costly instrumentation. The experiments reported in this paper demonstrate a good correlation between AID and ID in a realistic seismic loading scenario consisting of dynamically applied arbitrary cyclic loads. Based on this correlation, it is possible to estimate ID indirectly from the AID, which calls for much simpler and less expensive instrumentation.

• Structural Engineering and Mechanics
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• 제39권1호
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• pp.125-145
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• 2011

Pushover analysis has gained significant popularity as an analytical tool for realistic determination of the inelastic behaviour of RC structures. Though significant work has been done to evaluate the demands realistically, the evaluation of capacity and realistic failure modes has taken a back seat. In order to throw light on the inelastic behaviour and capacity evaluation for the RC framed structures, a 3D Reinforced concrete frame structure was tested under monotonically increasing lateral pushover loads, in a parabolic pattern, till failure. The structure consisted of three storeys and had 2 bays along the two orthogonal directions. The structure was gradually pushed in small increments of load and the corresponding displacements were monitored continuously, leading to a pushover curve for the structure as a result of the test along with other relevant information such as strains on reinforcement bars at critical locations, failure modes etc. The major failure modes were observed as flexural failure of beams and columns, torsional failure of transverse beams and joint shear failure. The analysis of the structure was by considering all these failure modes. In order to have a comparison, the analysis was performed as three different cases. In one case, only the flexural hinges were modelled for critical locations in beams and columns; in second the torsional hinges for transverse beams were included in the analysis and in the third case, joint shear hinges were also included in the analysis. It is shown that modelling and capturing all the failure modes is practically possible and such an analysis can provide the realistic insight into the behaviour of the structure.

• 한국자원식물학회지
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• 제21권5호
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• pp.357-361
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• 2008

고품질의 곰취, 곤달비 및 한대리곰취를 지속적으로 생산할 수 있는 임간재배기술을 개발하고자 횡성군 둔내면의 산채마을 임간재배지에 생육중인 세 식물종의 광합성을 특성을 조사 비교하였다. 광도에 따른 곰취류의 광합성율의 평균은 광도가 높아질수록 높아지는 경향을 보였다. 광도에 따른 곰취의 광합성율의 평균은 광도가 높아질수록 높아지다가 1,600 PPFD에서 최대치인 $21.1{\mu}mol\;CO_{2}m^{-2}s^{-1}$를 보이고 2,000 PPFD에서는 낮아졌다. 한대리곰취가 $27.39({\mu}mol\;CO_{2}m^{-2}s^{-1})$로 가장 높은 광합성율을 보였고, 곰취, 곤달비 순으로 낮아졌다. 5월 27일 측정에서 모두 식물종간 통계적 유의차가 인정되었으며 광합성율은 한대리곰취, 곰취, 곤달비 순이었고, 6월 21일 측정 광합성율은 한대리금취, 곤달비, 곰취순이었다. 횡성군 둔내면 산채마을과 같은 해발고가 낮은 지역에서는 곰취나 곤달비 보다는 한대리곰취의 임판재배가 적합할 것이라 사료된다.