• 한국한의학연구원논문집
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• 제10권2호
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• pp.79-92
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• 2004

Objectives : This experiments were performed to determine the effect of OYakSoonGi-San extract on hypertension in spontaneous hypertensive rat and norepinephrine-induced arterial contraction in rabbit. Methods : In order to define the effect of OYakSoonGi-San extract on contracted rabbit carotid arterial strips, transverse strips with intact or damaged endothelium were used for the experiment using organ bath. To analyze the mechanism of OYakSoonGi-San extract-induced relaxation, OYakSoonGi-San extract infused into contracted arterial strips induced by norepinephrine after treatment of indomethacin, $N{\omega}-nitro-L-arginine$, methylene blue or tetraethylammonium chloride. Results : Blood pressure was significantly decreased five days after administration of OYakSoonGi-San extract. The relaxation effect of OYakSoonGi-San extract was dependent on the presence of endothelium, showing that OYakSoonGi-San extract-induced relaxation was not observed in the strips without endothelium. Also OYakSoonGi-San extract-induced relaxation was significantly inhibited in arterial strips which were contracted by high $K^+$. OYakSoonGi-San extract-indeced relaxation was significantly inhibited by the pre-treatment of $N{\omega}-nitro-L-arginine$ or methylene blue, but it was not observed in the strips pre-treated with indomethacin or tetraethylammonium chloride. When additive application of $Ca^{2+}$ in arterial strips which were pre-contracted by norepinephrine in a $Ca^{2+}$-free solution, arterial contraction was increased. But contractile response to $Ca^{2+}$ was attenuated by pre-treatment of OYakSoonGi-San extract. Conclusions : These results demonstrated that OYakSoonGi-San could be applied effectively to hypertension and may inhibit agonist-induced contraction through an decrease influx of extra-cellular $Ca^{2+}$ by the formation of nitric oxide in the vascular endothelial cells.

• 한국도로학회논문집
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• 제9권4호
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• pp.65-74
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• 2007

노면요철포장은 1950년대 처음 설치된 후 사고감소효과에 대하여 여러 가지 연구가 있어왔다. 대부분의 연구에서 주로 졸음과 부주의 사고를 예방하는 것으로 알려져 있다. 본 논문에서는 고속도로 377개소에서 4년 동안 수집한 교통사고를 바탕으로 노면요철포장 설치 전 후에 사고감소원인과 환경을 분석하였다. 분석결과 노면요철포장 설치 전 후 교통사고를 비교할 때 -200건/2년(-32.3%) 감소하여, 노면요철포장 설치시 사고감소 효과가 있는 것으로 나타났다. 세부교통사고 원인분석결과 노면요철포장 설치효과가 유의하다고 할 수 있는 교통사고원인 항목을 제시할 수 있었다. 졸음, 과속, 주시태만, 부주의, 차량결함, 안전거리 미확보 교통사고감소가 유의하였다. A, B, C 등급 사고의 경우 교통사고감소가 유의하였다. 기상 상태 원인분석결과 맑음, 비, 흐림 기상상태에서 노면요철포장으로 인한 교통사고감소가 유의하였다. 본 논문 결과는 그동안 졸음 혹은 부주의 교통사고우려에 대응하도록 한 기존 노면요철포장 설치기준보다 원인인자를 명확히 하고 확장하여 고속도로 교통사고감소에 기여할 것으로 생각된다.

• Structural Engineering and Mechanics
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• 제55권6호
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• pp.1139-1155
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• 2015

In this study, a new retrofitting method for improving the seismic performance of reinforced concrete column was presented, in which prestressed steel strips were utilized as retrofitting stuff to confine the reinforced concrete column transversely. In order to figure out the seismic performance of concrete column specimen retrofitted by such prestressed steel strips methods, a series of quasi-static tests of five retrofitted specimens and two unconfined column specimen which acted as control specimens were conducted. Based on the test results, the seismic performance including the failure modes, hysteresis performance, ductility performance, energy dissipation and stiffness degradation of all these specimens were fully investigated and analyzed. And furthermore the influences of some key parameters such as the axial force ratios, shear span ratios and steel strips spacing on seismic performance of those retrofitted reinforced concrete column specimens were also studied. It was shown that the prestressed steel strips provided large transverse confining effect on reinforced concrete column specimens, which resulted in improving the shearing bearing capacity, ductility performance, deformation capacity and energy dissipation performance of retrofitted specimens effectively. In comparison to the specimen which was retrofitted by the carbon fiber reinforced plastics (CFRP) strips method, the seismic performance of the specimens retrofitted by the prestressed steel strips was a bit better, and with much less cost both in material and labor. From this research results, it can be concluded that this new retrofitting method is really useful and has significant advantages both in saving money and time over some other retrofitting methods.

• 한국콘텐츠학회논문지
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• 제18권12호
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• pp.102-107
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• 2018

건강 상식과 우스갯소리를 섞어서 그린 만화를 재미있게 본 사람은 건강 상식을 한 번 더 생각하면서 따르게 된다. 교신저자는 의사로서 건강 상식을 담은 4칸 만화(제목: 몸 지킬 박사)를 그렸고, 이것을 중앙일간지에 27편 연재하였다. 이 연구의 목적은 교신저자의 경험을 낱낱이 알려서, 다른 전문가도 자기 분야의 상식을 만화로 알리는 데 도움 주는 것이었다. 그림을 그리기에 앞서 글을 썼으며, 글을 쓰는 원칙은 다음과 같았다. 첫째, 실제로 따를 만한 건강 상식을 담아서 만화를 이롭게 만들었다. 둘째, 건강 상식을 논리적으로 풀이해서 만화를 쉽게 만들었다. 셋째, 건강 상식과 관련된 우스갯소리를 담아서 만화를 재미있게 만들었다. 교신저자가 겪은 바에 따르면, 전문가가 직접 그리는 것에 장점이 있었다. 전문 지식이 있으면 만화를 잘 그릴 수 있다는 생각을 가지고, 다른 분야(법률, 건축 등)의 전문가도 만화를 그리기 바란다.

• 한국구조물진단유지관리공학회 논문집
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• 제26권6호
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• pp.256-262
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• 2022

본 연구의 목적은 실험을 통하여 FRP를 이용한 철근콘크리트 부재의 표면매립 전단보강 효과를 규명하는 것이다. 연구목적을 달성하기 위하여, 3개의 철근콘크리트 T형 보를 제작하고 이중 두 개의 보에 대해서 표면매립 보강방법으로 FRP를 전단보강한 뒤 실험을 통하여 보강효과를 규명하였다. 실험에서 두 가지의 전단보강방법을 고려하였는데, 첫째 충분한 매립길이를 가진 표면매립 (NSM) 보강, 둘째 다소 짧은 표면매립길이를 가지지만 추가의 표면부착 (EB) 보강을 한 경우이다. 연구결과, FRP strip을 이용한 표면매립길이를 플랜지 하부까지 길게 확보할 경우에는 충분한 전단보강효과가 발휘되는 것으로 나타났다. 반면에 충분한 매립길이가 확보되지 않은 경우에는 FRP sheet로 추가 보강하더라도 전단보강효과가 나타나지 않는 것으로 나타났다.

• Steel and Composite Structures
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• 제44권6호
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• pp.845-865
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• 2022

In this study, the performance of shear deficient reinforced concrete (RC) beams with rectangular cross-sections, which were externally bonded reinforced (EBR) with high strength CFRP and GFRP strips composite along shear spans, has been experimentally and analytically investigated under vertical load. In the study, the minimum CFRP and GFRP strips width over spacing were considered. The shear beam with turned end to a bending beam was investigated by applying different composite strips. Therefore various arising in each of strength, ductility, rigidity, and energy dissipation capacity were obtained. A total of 12 small-scaled experimental programs have been performed. Beam dimensions have been taken as 100×150×1000 mm. Four beams have been tested as unstrengthened samples. This paper focuses on the effect of minimum CFRP and GFRP strip width on behaviours of RC beams shear-strengthened with full-wrapping, U-wrapping, and U-wrapping+longitudinal bonding strips. Strengthened beams showed significant increments for flexural ductility, energy dissipation, and inelastic performance. The full wrapping strips applied against shear failure have increased the load-carrying capacity of samples 53%-63% interval rate. Although full wrapping is the best strengthening choice, the U-wrapping and U-wrapping+longitudinal strips of both CFRP and GFRP bonding increased the shear capacity by 53%~75% compared to the S2 sample. In terms of ductility, the best result has been obtained by the type of strengthening where the S5 beam was completely GFRP wrapped. The experimental results were also compared with the analytically given by ACI440.2R-17, TBEC-2019 and FIB-2001. Especially in U-wrapped beams, the estimation of FIB was determined to be 81%. The estimates of the other codes are far from meeting the experimental results; therefore, essential improvements should be applied to the codes, especially regarding CFRP and GFRP deformation and approaches for longitudinal strip connections. According to the test results, it is suggested that GFRP, which is at least as effective but cheaper than CFRP, may be preferred for strengthening applications.

• Structural Engineering and Mechanics
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• 제84권3호
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• pp.345-360
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• 2022

In this paper, the impact on seismic performance of an economical effective technique for retrofitting reinforced concrete (RC) columns using high-strength steel strips under high axial compression ratios was presented. The experimental program included a series of cyclic loading tests on one nonretrofitted control specimen and three retrofitted specimens. The effects of the axial compression ratio and spacing of the steel strips on the cyclic behavior of the specimens were studied. Based on the test results, the failure modes, hysteretic characteristics, strength and stiffness degradation, displacement ductility, and energy dissipation capacity of the specimens were analyzed in-depth. The analysis showed that the transverse confinement provided by the high-strength steel strips could effectively delay and restrain diagonal crack development and improve the failure mode, which was flexural-shear failure controlled by flexural failure with better ductility. The specimens retrofitted using high-strength steel strips showed more satisfactory seismic performance than the control specimen. The seismic performance and deformation capacity of the retrofitted RC columns increased with decreasing axial compression ratio and steel strip spacing. Based on the test results, a hysteretic model for RC columns that considers the transverse confinement of high-strength steel strips was then established. The hysteretic model showed good agreement with the experimental results, which verified the effectiveness of the proposed hysteretic model. Therefore, the aforementioned analysis can be used for the design of retrofitted RC columns.

• The Korean Journal of Physiology
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• 제23권2호
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• pp.277-289
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• 1989

The effects of noradrenaline on the contractile and electrical activities were investigated using the circular muscle strips with intact mucosa prepared from the antrum and fundus of guinea-pig stomach. Electrical responses of circular muscle cells were recorded using glass capillary microelectrodes filled with 3 M KCI. All experiments were performed in tris-buffered Tyrode solution which was aerated with 100% $O_2\;and\;kept\;at\;35^{\circ}C$. The results obtained were as follows: 1) The spontaneous contractions recorded from the antral and fundic circular muscle strips with intact mucosa were suppressed dose-dependently by the application of noradrenaline, whereas those recorded from the mucosa-free strips were potentiated in a dose-dependent manner. 2) The inhibitory influences on the contractile activities in the normal intact strips were developed via both ${\alpha}-adrenoceptors\;and\;{\beta}-adrenoceptors$, while the excitatory influences in the mucosa-free strips resulted from the strong excitatory effect via ${\alpha}-adrenoceptors$ and the weak inhibitory effect via ${\beta}-adrenoceptors$. 3) Noradrenaline produced hyperpolarization of membrane potential, and increased the amplitude and the maximum rate of rise of slow waves in the mucosa-free strips of antral and fundic circular muscle. 4) Apamin blocked the appearance of the component of initial suppression of spontaneous phasic contractions observed in the mucosa-free strips of antral circular muscle after the application of noradrenaline. 5) The inhibitory influences on the contractile activities in the normal strips with intact mucosa remained unaffected even in the strip with separate mucosa, in which mucosa and muscle layer were mechanically disconnected . From the above results, following conclusions could be made. (1) There are no regional differences between the effects of noradrenaline on the antral circular muscle and those on the fundic circular muscle. (2) Excitatory responses to noradrenaline observed in the mucosa-free strip result from the dominant ${\alpha}-excitatory$ and tile weak ${\beta}-inhibitory$ action of noradrenaline. (3) Inhibitory responses to noradrenaline in the normal strips with intact mucosa develop via both ${\alpha}-inhibitory\;and\;{\beta}-inhibitory$ actions.

• Journal of Biosystems Engineering
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• 제43권3호
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• pp.237-246
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• 2018

Purpose: This study (a) investigated the effect of microwave power intensity and sample thickness on microwave drying characteristics of radish strips, and (b) determined the best-fit drying model for describing experimental drying data, effective moisture diffusivity ($D_{eff}$), and activation energy ($E_a$) for all drying conditions. Methods: A domestic microwave oven was modified for microwave drying and equipped with a small fan installed on the left upper side for removing water vapor during the drying process. Radishes were cut into two fixed-size strip shapes (6 and 9 mm in thickness). For drying experiments, the applied microwave power intensities ranged from 180 to 630 W at intervals of 90 W. Six drying models were evaluated to delineate the experimental drying curves of both radish strip samples. The effective moisture diffusivity ($D_{eff}$) was determined from Fick's diffusion method, and the Arrhenius equation was applied to calculate the activation energy ($E_a$). Results: The drying time was profoundly decreased as the microwave power intensity was increased regardless of the thickness of the radish strips; however, the drying rate of thicker strips was faster than that of the thinner strips up to a certain moisture content of the strip samples. The majority of the applied drying models were suitable to describe the drying characteristics of the radish strips for all drying conditions. Among the drying models, based on the model indices, the best model was the Page model. The range of estimated $D_{eff}$ for both strip samples was from $2.907{\times}10^{-9}$ to $1.215{\times}10^{-8}m^2/s$. $E_a$ for the 6- and 9-mm strips was 3.537 and 3.179 W/g, respectively. Conclusions: The microwave drying characteristics varied depending on the microwave power intensity and the thickness of the strips. In order to produce high-quality dried radish strips, the microwave power intensity should be lower than 180 W.

• International Journal of Concrete Structures and Materials
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• 제8권2호
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• pp.117-128
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• 2014

Numerous investigations of RC beams strengthened in shear with externally-bonded (EB) fibre-reinforced polymer (FRP) sheets, plates and strips have been successfully conducted in recent years. These valuable studies have highlighted a number of influencing parameters that are not captured by the design guidelines. The objective of this study was: (1) to highlight experimentally and analytically the influential parameters on the shear contribution of FRP to RC beams strengthened in shear using EB FRP sheets and strips; and (2) to develop a set of transparent, coherent, and evolutionary design equations to calculate the shear resistance of RC beams strengthened in shear. In the experimental part of this study, 12 tests were performed on 4,520-mm-long T-beams. The specimens were strengthened in shear using carbon FRP (CFRP) strips and sheets. The test variables were: (1) the presence or absence of internal transverse-steel reinforcement; (2) use of FRP sheets versus FRP strips; and (3) the axial rigidity of the EB FRP reinforcement. In the analytical part of this study, new design equations were proposed to consider the effect of transverse-steel in addition to other influential parameters on the shear contribution of FRP. The accuracy of the proposed equations has been verified in this study by predicting the FRP shear contribution of experimentally tested RC beams.