• 한국전산구조공학회논문집
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• 제30권3호
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• pp.239-248
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• 2017

솔레노이드 밸브는 구조에 따라 스풀 밸브와 포핏 밸브로 구분된다. 구조가 단순하고 오염에 민감한 스풀 밸브에 대하여 연구가 많이 진행되고 있는 반면 오염에 덜 민감하고 장시간 작동에 용이한 포핏 밸브는 구조가 복잡하여 여전히 많은 연구가 필요하다. 포핏 밸브를 설계하기 위해서 고려해야 하는 사항으로 포핏의 직경, 포핏의 각도, 디스크의 지름, 스프링 강성, 스프링 예하중, 유로 구조 등 다양한 설계변수가 있다. 기존 연구에서는 설계변수를 한가지로 선정하여 연구가 진행되었고, 설계변수가 포핏 밸브의 유동특성에 미치는 영향에 대한 연구가 부족하다. 본 논문에서는 3/2Way 솔레노이드 밸브용 포핏 밸브의 설계변수 변화에 따른 유동특성의 변화를 분석하였다. 포핏 밸브의 설계변수 선정은 선행연구된 사례와 초기모델해석결과를 참고하여 진행하였다. 그리고 설계변수에 따른 최대압력, 최소압력, 압력강하의 영향을 평균분석(ANOM)을 사용하여 살펴보았다. 향후 3/2Way 솔레노이드 밸브용 포핏 밸브를 설계할 때 주효과를 파악하여 설계변수 선정에 사용하면 효율적인 설계변수 선정이 가능할 것으로 예상된다.

• 자원환경지질
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• 제34권1호
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• pp.133-146
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• 2001

옥천대 중부 충주-수안보 일원에 분포하는 황강리층을 대상으로 대자율 비등방성을 측정하고 야외 지질구조 자료들을 수입하였다. 그 결과, 연구지역의 북동부와 남서부 지역은 변성과 변형사가 서로 달랐음이 드러났다. 황강리층에는 야외에서 구별되는 두 종류의 벽개, 즉 점판벽개($S_1$)와 파랑벽개($S_2$)가 발달하고 있으나 $S_1$면은 연구지역의 북동부에서 뚜렷이 관찰되는 반면, 남서부에서는 $S_2$면의 발달이 절대적으로 우세하다. 등온잔류자기 강도, 제적 총 대자율 그리고 비등방성의 정도는 모두 남서부에 비해 북동부 지역에서 훨씬 높은 값을 보이고 있으며 남서쪽으로 갈수록 이들 값들이 현저히 감소하여 남서부 지역에 이르러서는 일관되게 매우 낮은 값을 보여준다. 또한, 대자율 비등방체의 형태도 북동부 지역에서 자기적 엽리구조가 우세하며 남서쪽으로 갈수록 선구조 영역으로 점진적으로 변화되어 남서부 지역에 이르러서는 일관되게 구에 가까운 형태를 이룬다. 이러한 사실들은 모두 북동부에 비해 남서부에서 보다 강한 후기 변성과 변형이 있었음을 지시하는 것이다. 한편, 북동부 지역에서 얻어진 대자율 비등방 타원체의 주축들($k_1$, $k_2$, $k_3$)의 분포 양상을 근거하면, 연구지역 황강리층은 세 번의 변형사건($D_1$, $D_2$, $D_3$)을 겪은 것으로 해석된다. 북서-남동방향의 압축력에 의해서 북동-남서방향의 $S_1$면이 형성되고 이 엽리면을 따라 순수 전단작용이 발생하여 황강리층을 편평화시킨 동축 변형사건($D_1$)이 제일 먼저 있었으며, 이후 $S_2$면을 따라 북서향의 충상단층과 좌수향의 연성 혹은 준 연성의 단순 전단작용이 일어나 기존의 변형타원체의 주축들이 차별적으로 회전되는 비동축 변형사건($D_2$)이 있었고, 마지막으로는 북동방향의 수평축을 가진 요굴습곡을 형성시킨 변형사건($D_3$)이 있었다. 남서부 지역에서는 비등방 타원체의 모든 주축들이 분산되어 있으며 야외에서 $S_2$면이 우세하게 관찰되고 북동부에 비해 IRM강도, 체적 총대자율 그리고 대자율 비등방성 정도 등이 한결같이 매우 낮다. 이러한 점들은 북동부에 비해 강한 후기 변형 혹은 변성 과정에서 자성광물의 배열이 분산되었거나 강한 $D_2$변형으로 $D_1$변형타원체가 중첩되어 역변형된 결과이거나 혹은 이 두가지가 복합된 결과로 해석된다.

• The Plant Pathology Journal
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• 제15권4호
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• pp.210-216
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• 1999

TREGRO, a computer simulation model of individual tree growth, was applied to estimate ozone ($\textrm{O}_3$) effects on aspen(Populus tremuloides) growth under ambient and 1.7 times ambient $\textrm{O}_3$ of Seoul in 1996. The three highest $\textrm{O}_3$ (Kuui-dong, Ssangmun-dong, Sungsoo-dong) and the two lowest $\textrm{O}_3$ sites (Mapo-dong, Namgajwa-dong) were evaluated. The current ambient $\textrm{O}_3$ did not affect aspen growth compared to simulation without $\textrm{O}_3$. The only effect was 6.6 percent of total assimilated carbonloss at Ssangmun-dong where the level of $\textrm{O}_3$ was greatest among the 21 sites examined. Decrease as much as 50 percent of total carbon gain was calculated at 1.7 times ambient $\textrm{O}_3$ of the three highest sites. The carbon loss by $\textrm{O}_3$ came from biomass of tissues and total nonstructural cabron (TNC) such as starch and sugar. The most sensitive fraction was TNC and the next was root biomass. Foliage mass was not affected by $\textrm{O}_3$. Structural biomass loss was at best 1 to 3 percent at 1.7 times ambient $\textrm{O}_3$ at the two lowest sites. The daily carbon simulation was affected by $\textrm{O}_3$ mainly during Growth Period 4 (Jul. 21-Oct. 26). Correlations between site, dose, and the simulated responses of aspen (tissue biomass, TNC, respiration, and senescence) ranged from -0.703 to -0.973 depending on the plant responses. The ozone effects on poplar in Seoul are not severe currently, but are probably measurable at Ssangmun-dong. However, severe $\textrm{O}_3$ effects on biomass would occur if $\textrm{O}_3$ levels increase to 1.7 times ambient $\textrm{O}_3$ in Seoul. In addition, v could weaken the trees thus increasing susceptibility to pathogens or insects.

• Structural Engineering and Mechanics
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• 제16권6호
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• pp.749-769
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• 2003

The structural deterioration of concrete structures due to reinforcement corrosion is a major worldwide problem. Service life of the age-degraded concrete structures is governed by the protective action provided by the cover concrete against the susceptibility of the reinforcement to the corrosive environment. The corrosion of steel would result in the various corrosion products, which depending on the level of the oxidation may have much greater volume than the original iron that gets consumed by the process of corrosion. This volume expansion would be responsible for exerting the expansive radial pressure at the steel-concrete interface resulting in the development of hoop tensile stresses in the surrounding cover concrete. Once the maximum hoop tensile stress exceeds the tensile strength of the concrete, cracking of cover concrete would take place. The cracking begins at the steel-concrete interface and propagates outwards and eventually resulting in the through cracking of the cover concrete. The cover cracking would indicate the loss of the service life for the corrosion-affected structures. In the present paper, analytical models have been developed considering the residual strength of the cracked concrete and the stiffness provided by the combination of the reinforcement and expansive corrosion products. The problem is modeled as a boundary value problem and the governing equations are expressed in terms of the radial displacement. The analytical solutions are presented considering a simple 2-zone model for the cover concrete viz. cracked or uncracked. A sensitivity analysis has also been carried out to show the influence of the various parameters of the proposed models. The time to cover cracking is found to be function of initial material properties of the cover concrete and reinforcement plus corrosion products combine, type of rust products, rate of corrosion and the residual strength of the cover concrete. The calculated cracking times are correlated against the published experimental and analytical reference data.

• 한국전산구조공학회논문집
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• 제30권2호
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• pp.179-184
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• 2017

적외선 유도 무기의 급속한 발달로 인해 현대 장갑 차량의 생존성은 크게 위협 받고 있다. 따라서 적외선 신호를 줄여 탐지가능성을 줄이는 것이 지상 장갑 차량의 생존성 향상을 위해 반드시 필요하다. 이러한 목적으로 본 연구는 수치해석을 사용해 차량 적외선 신호의 시간 및 탐지 위치별 특성을 분석하였다. 그 결과 가장 낮은 대비복사강도를 보이는 방사율이 시간 및 탐지 위치별로 상이하며 적외선 신호를 효과적으로 저감하기 위해서는 차량 부위별로 다른 방사율을 갖는 제어 구조를 적용해야 할 것이다.

• Advances in nano research
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• 제16권3호
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• pp.231-249
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• 2024

When the amplitude of the vibrations is equivalent to that clearance, the vibrations for small amplitudes will really be significantly nonlinear. Nonlinearities will not be significant for amplitudes that are rather modest. Finally, nonlinearities will become crucial once again for big amplitudes. Therefore, the concrete panel system may experience a big amplitude in this work as a result of the high temperature. Based on the 3D modeling of the shell theory, the current work shows the influences of the von Kármán strain-displacement kinematic nonlinearity on the constitutive laws of the structure. The system's governing Equations in the nonlinear form are solved using Kronecker and Hadamard products, the discretization of Equations on the space domain, and Duffing-type Equations. Thermo-elasticity Equations. are used to represent the system's temperature. The harmonic solution technique for the displacement domain and the multiple-scale approach for the time domain are both covered in the section on solution procedures for solving nonlinear Equations. An effective data-driven solution is often utilized to predict how different systems would behave. The number of hidden layers and the learning rate are two hyperparameters for the network that are often chosen manually when required. Additionally, the data-driven method is offered for addressing the nonlinear vibration issue in order to reduce the computing cost of the current study. The conclusions of the present study may be validated by contrasting them with those of data-driven solutions and other published articles. The findings show that certain physical and geometrical characteristics have a significant effect on the existing concrete panel structure's susceptibility to temperature change and GPL weight fraction. For building construction industries, several useful recommendations for improving the thermo-mechanics' behavior of structural concrete panels are presented.

• 대한화학회지
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• 제20권1호
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• pp.35-42
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• 1976

사면체 구조를 갖는 철(III)-옥살산 착화합물 5개와 팔면체 구조를 갖는 착화합물을 3개를 합성한 후 화학분석과 적외선스펙트럼을 이용하여 이들 착이온의 구조에 관하여 연구하였다. 이들중 $[FeC_2O_4Br_2]^-,$ $[FeC_2O_4(NCS)_4]^{3-}$ 및 $[Fe_2(C_2O_4)_3Cl_4]^{4-}$등의 3개의 피리딘염은 아직 보고되지 않은 새로운 착물이며, 특히 이합체로 생각되는 착물 $(PyH)_4[Fe_2(C_2O_4)_3Cl_4]$는 광화학 반응성이 아주 큼을 알 수 있었다. 이들 여러 철(III)-옥살산 착물의 물전기전도도와 자기화율에 관한 측정결과도 함께 보고하였다.

• Clinical and Experimental Pediatrics
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• 제51권10호
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• pp.1031-1037
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• 2008

Macrolide antimicrobial agents including erythromycin, roxithromycin, clarithromycin, and azithromycin are commonly used in the treatment of respiratory tract infections in children. Newer macrolides that have structural modifications of older drug erythromycin show improved change in the spectrum of activity, dosing, and administration. However, recent studies reported that increasing use of macrolide antibiotics is the main force driving the development of macrolide resistance in streptococci. In particular, azithromycin use is more likely to select for macrolide resistance with Streptococcus pneumoniae than is clarithromycin use, a possible reflection of its much longer half life. Recently, erythromycin resistance rates of S. pneumoniae and Streptococcus pyogenes are rapidly increasing in Korea. Two main mechanisms of acquired macrolide resistance have been described, altered binding site on the bacterial ribosome encoded by the ermB gene and active macrolide efflux pump encoded by the mef gene. Relationship between the susceptibility of S. pneumoniae and the response to macrolides has been shown in studies of acute otitis media, but less clear in cases of pneumonia. This article reviews the spectrum of activity, pharmacokinetic properties, mechanisms of action and resistance, and clinical implication of resistance on the treatment of respiratory tract infections in children.

• Journal of Microbiology and Biotechnology
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• 제28권3호
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• pp.381-390
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• 2018

We have previously derived a novel antimicrobial peptide, LPcin-YK3(YK3), based on lactophoricin and have successfully studied and reported on the relationship between its structure and function. In this study, antimicrobial peptides with improved antimicrobial activity, less cytotoxicity, and shorter length were devised and characterized on the basis of YK3, and named YK5, YK8, and YK11. The peptide design was based on a variety of knowledge, and a total of nine analog peptides consisted of one to three amino acid substitutions and C-terminal deletions. In detail, tryptophan substitution improved the membrane perturbation, lysine substitution increased the net charge, and excessive amphipathicity decreased. The analog peptides were examined for structural characteristics through spectroscopic analytical techniques, and antimicrobial susceptibility tests were used to confirm their activity and safety. We expect that these studies will provide a platform for systematic engineering of new antibiotic peptides and generate libraries of various antibiotic peptides.

• 대한간호학회지
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• 제44권5호
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• pp.525-533
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• 2014

Purpose: This study was done to propose and test a predictive model that would explain and predict fall prevention behaviors in postmenopausal women. The health belief model was the theoretical basis to aid development of a nursing intervention fall prevention program. Methods: Data for 421 postmenopausal women were selected from an original data set using a survey design. The structural equation model was tested for 3 constructs: modifying factors, expectation factors, and threat factors. Expectation factors were measured as relative perceived benefit (perceived benefit minus perceived barrier), self-efficacy, and health motivation; threat factors, as perceived susceptibility (fear of falling) and perceived severity (avoiding activity for fear of falling); and modifying factors: level of education and knowledge about fall prevention. Data were analyzed using SPSS Windows and AMOS program. Results: Mean age was 55.7 years (range 45-64), and 19.7% had experienced a fall within the past year. Fall prevention behaviors were explained by expectation and threat factors indicating significant direct effects. Mediating effect of health beliefs was significant in the relationship between modifying factors and fall prevention behaviors. The proposed model explained 33% of the variance. Conclusion: Results indicate that fall prevention education should include knowledge, expectation, and threat factors based on health belief model.