• 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.

• 한국석유지질학회:학술대회논문집
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• 대한자원환경지질학회/한국석유지질학회/한국암석학회 2000년도 추계공동학술발표회 초록집
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• pp.42-42
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• 2000

• 원예과학기술지
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• 제19권3호
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• pp.325-328
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• 2001

종자(種子) 파종에 의한 토마토 실생묘(實生苗)를 대체하고 반드시 제거(除去)해야하는 측지(側枝)를 이용한 삽목묘(揷木苗)를 다량생산(多量生産)하여 종자수입을 대체하고 공정육묘의 가능성을 검토하기 위하여 본(本) 시험(試驗)을 수행(遂行)하였다. 처리는 관행 삽목상과 배지용량 23mL인 트레이 128구부터 300mL 용량의 직경 8cm 비닐폿트를 이용하여 삽목하였다. 그리고 배지의 조성은 훈탄단용과 훈탄과 펄라이트, 훈탄과 피트모스, 펄라이트와 피트모스를 혼용하여 이용하였다. 토마토 삽목묘(揷木苗)의 생육량(生育量)은 배지용량(培地容量)이 120mL 이상으로 증가되어도 크게 영향을 받지 않았다. 그러나 배지 용량이 감소되어 플러그 수가 증가되면 묘(苗)의 생육은 저하되었으나 23mL 용량의 128구 플러그 트레이에서도 정상적인 묘(苗)가 생산되었다. 배지용량이 감소되면 지상부보다 지하부중이 크게 감소되었다. 토마토 측지삽목묘(側枝揷木苗)의 생육은 방울토마토 뻬뻬가 완숙토마토 모모타로 품종보다 양호하고 T/R율이 높았으며, 발근율(發根率)도 뻬뻬 품종은 100%였으나 모모타로는 90% 수준(水準)이었다. 배지용량과 배지종류에 관계없이 삽목후(揷木後) 15-20일경에 정식 가능한 묘가 생산되었다. 삽목 육묘용(育苗用) 배지(培地)의 조성이 발근(發根)과 근발달(根發達)에 미치는 영향은 처리간(處理間)에 유의차(有意差)가 인정되지 않았다.

• 한국습지학회지
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• 제3권1호
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• pp.75-89
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• 2001

Constructed wetlands were typically cost less to build and operate, and require less energy than standard mechanical treatment technology but they have similar performance to centralized wastewater treatment plants. Therefore, they were constructed especially many in rural areas, where are small villages but not industries. Accordingly, plantless column tests were performed to investigate the possibility on using zeolite as a filter medium of constructed wetland for the wastewater treatment. $COD_{cr}$ removal efficiency was 94.63% at hydraulic load $314L/m^2{\cdot}d$ and filtering hight 100cm filled with a zeolite mixture. This zeolite mixture consisted of 1 : 1 by volume of a zeolite in the diameter range of 0.5 to 1mm to a zeolite in the diameter range of 1 to 3mm. According, hydraulic load $314L/m^2{\cdot}d$ was considered as optimal. Three zeolite mixture were used to determine the optimal mixing ratio by volume of a zeolite(A) in the diameter range of 0.5 to 1mm to a zeolite(B) in the diameter range of 1 to 3mm diameter. 1 : 3, 1 : 1 and only B in A to B by volume were tested at hydraulic load $314L/m^2{\cdot}d$ and filtering hight 100cm. $COD_{cr}$ removal efficiency was more than 89% at mixing ratios of 1 : 3 and 1 : 1 in A to B. Removal efficiency was lower at the column filled with only B. Removal efficiency was better at filter medium filled with mixing ratio 1 : 1 in A to B than with the other mixing ratios. Thus, it was found that the mixture of mixing ratio 1 : 1 in A to B was appropriate for filter medium of constructed wetland. Removal efficiency was higher in down-flow than in up-flow, and $COD_{cr}$ and BOD were removed best in 20cm filter height near feeding area.

• 한국자동차공학회논문집
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• 제17권1호
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• pp.154-161
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• 2009

This study is a part of project of urea-SCR system development for an in-use medium duty diesel engine. This study shows the effect of ammonia oxidation catalyst and SCR volume on $NO_X$ reduction performance. When AOC(Ammonia Oxidation Catalyst) is not used, the urea injection should be controlled accurately to prevent $NH_3$ slip. However, it is found that the accurate $NH_3$ slip control is not easy without AOC in real engine operating conditions, because $NH_3$ and $NO_X$ reaction characteristics change with many factors such as exhaust gas temperature and $NH_3$ absorbance on SCR. SCR volume is also one of important design parameters. This study shows that $NO_X$ reduction efficiency increases with increase of SCR volume especially at high space velocity and low exhaust gas temperature conditions. Additionally, this paper shows the emissions of EURO-2 medium duty diesel engine can be improved to the level of EURO-5 with a DPF and urea-SCR system.

• 대한수학회보
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• 제34권3호
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• pp.335-350
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• 1997

In this article, a scattering problem in a nonhomogeneous medium is formulated as an integral equation which contains boundary and volume integrals. The integral equation is solved for sufficiently small $$\mid$$\mid$1-p$\mid$$\mid$,$\mid$$\mid${k_i}^2-k^2$\mid$$\mid$\;and\;$\mid$$\mid${\nabla}p$\mid$$\mid$$ where $k,\;k_i$ and p the wave numbers and the density respectively.

• 한국식품조리과학회지
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• 제16권4호
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• pp.316-320
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• 2000

This study was carried out to standardize the recipe of Gaeseong-Juak. The formation and quality of the Juak were investigated under different treatment conditions. 1. The high ratio of medium flour(20%) in the flour mixture resulted in poor swelling. 2. The flour mixture with 10% strong flour showed higher volume of Gaeseong-Juak compared with the 10% mixture of medium flour, but the score of sensory evaluation was low. 3. The addition of Makkoli in the dough did not give significant difference in the formation of Juak, but the sensory score was low. 4. The deep-frying temperature in the range of 150$\^{C}$ to 170$\^{C}$ allowed the greatest swelling of Gaeseong-Juak, but the highest quality score was obtained at 160$\^{C}$ treatment. Overall, the best preparation condition of Gaeseong-Juak was that the mixture of waxy rice flour with 10% medium flour was kneaded with Makkoli and fried at 160$\^{C}$.

• Wind and Structures
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• 제24권3호
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• pp.267-285
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• 2017

This paper addresses vibration and instability of embedded functionally graded (FG)-carbon nanotubes (CNTs)-reinforced pipes conveying viscous fluid. The surrounding elastic medium is modeled by temperature-dependent orthotropic Pasternak medium. Flugge shell model is applied for mathematical modeling of structure. Based on energy method and Hamilton's principal, the motion equations are derived. Differential quadrature method (GDQM) is applied for obtaining the frequency and critical fluid velocity of system. The effects of different parameters such as volume percent of CNTs, elastic medium, boundary condition and geometrical parameters are discussed.

• Steel and Composite Structures
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• 제27권4호
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• pp.465-477
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• 2018

In this research, vibration and smart control analysis of a concrete foundation reinforced by $SiO_2$ nanoparticles and covered by piezoelectric layer on soil medium is investigated. The soil medium is simulated with spring constants and the Mori-Tanaka low is used for obtaining the material properties of nano-composite structure and considering agglomeration effects. With considering first order shear deformation theory, the total potential energy of system is calculated and by means of Hamilton's principle in three displacement directions and electric potential, the six coupled equilibrium equations are obtained. Also, based an analytical method, the frequency of system is calculated. The effects of applied voltage, volume percent and agglomeration of $SiO_2$ nanoparticles, soil medium and geometrical parameters of structure are shown on the frequency of system. Results show that with applying negative voltage, the frequency of structure is increased.

• 한국미생물·생명공학회지
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• 제25권3호
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• pp.277-285
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• 1997

Kluyveromyces marxianus var. marxianus isolated as an inulin-assimilating microorganism produces inulin fructotransferase (inulaseII) which catalyses the conversion of inulin into di-D-fructofuranose 1, 2' : 2, 3' dianhydrde (DFAIII). The DFA produced by the organism was isolated by using active carbon column, and identified as DFAIII by high performance liguid chromatography. The culture medium giving maximum inulaseII production was found to consist of 1% sucrose and 0.75% yeast nitrogen base (YNB). The inulasell production was induced by inulin or sucrose as a carbon source and increased by addition of YNB as a nitrogen source. Optimal initial pH of the culture medium, culture temperature and medium volume for the enzyme production were pH 4.7, 30$\circ$C and 140 ml, respectively. Under the optimal conditions described above, the enzyme activity in the culture supematant reached 4.2 units/ml after cultivation for 36 h. The DFAIII was accumulated at 13.25 mg/ml after 48 h of culture in the Jerusalem artichoke tuber medium.