• 수산해양기술연구
• /
• 제35권4호
• /
• pp.435-447
• /
• 1999

It is main objective of this approach to present a method to analyse stochastic design sensitivity for problems of structural dynamics with randomness in design parameters. A combination of the adjoint variable approach and the second order perturbation method is used in the finite element approach. An alternative form of the constant functional that holds for all times is introduced to consider the time response of dynamic sensitivity. The terminal problem of the adjoint system is solved using equivalent homogeneous equations excited by initial velocities. The numerical procedures are shown to be much more efficient when based on the fold superposition method: the generalized co-ordinates are normalized and the correlated random variables are transformed to uncorrelated variables, whereas the secularities are eliminated by the fast Fourier transform of complex valued sequences. Numerical algorithms have been worked out and proved to be accurate and efficient : they can be readily adapted to fit into the existing finite element codes whose element derivative matrices can be explicitly generated. The numerical results of two cases -2 dimensional portal frame for the comparison with reference and 3-dimensional frame structure - for the deterministic sensitivity analysis are presented.

• International Journal of Oral Biology
• /
• 제30권2호
• /
• pp.65-69
• /
• 2005

Periodontitis is a multi-microbial disease and the comparison of a series of periodontopathogenic and non-periodontopathogenic bacteria in terms of microbe-host interaction may provide clues to understand the microbial etiology of the disease better. When we deal with twenty different bacterial species in a study, the first technical issue is how to measure the accurate concentration and use the same number of bacterial cells. We measured bacterial concentration by enumerating bacteria stained with SYTOX green for constant time using a flow cytometer and compared the results with those obtained by plate counting. Concentrations calculated by two different methods were very close. Therefore, flow cytometric counting allowed the rapid analysis of live/dead bacteria, offering the advantage of turbidity measurement and that of colony counting together.

• 소성∙가공
• /
• 제16권2호
• /
• pp.138-143
• /
• 2007

Superplastic forming/diffusion bonding (SPF/DB) processes were analyzed using a 3-D rigid visco-plastic finite element method. A constant-triangular element based on membrane approximation and an incremental theory of plasticity are employed for the formulation. The coulomb friction law is used for interface friction between tool and material. Pressure-time relationship for a given optimal strain rate is calculated by stress and pressure values at the previous iteration step. In order to improve the contact searching, hierarchical search algorithm has been applied and implemented into the code. Various geometries including sandwich panel and 3 sheet shape for 3-D SPF/DB model are analyzed using the developed program. The validity fer the analysis is verified by comparison between analysis and results in the literature.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2011년도 제42회 하계학술대회
• /
• pp.1386-1387
• /
• 2011

Maximum power point tracking(MPPT) techniques are used in photovoltaic systems to maximize the PV array output power by tracking continuously the maximum power point which depends on panels temperature and on irradiance conditions. In this paper, the controller of the stand-alone PV system applicable to various fields are designed. The improved P&O MPPT and traditional P&O MPPT method was applied. This improved algorithm consists of a constant perturbation with an step control which will make easier the controller PV power data acquisition process. This strategy of control has, in first time, been validated by PSIM simulations. After, been field test. The experimental results show that the improved P&O method increased the PV output power compare to traditional P&O method.

• Journal of Applied Biological Chemistry
• /
• 제58권4호
• /
• pp.295-301
• /
• 2015

Five phenylpropanoids (1-5), a benzofuran neolignan (6), two 8-O-4'-neolignans (7-8), and five tetrahydrofuran lignans (9-13) were isolated from a methanol extract of Myristica fragrans seeds. The structures of 1-13 were determined by $^1H$- and $^{13}C$-NMR spectroscopic data analyses and a comparison with the literature data. Compound 3 was isolated for the first time from this plant. All the isolated compounds were evaluated for their inhibitory activity against tyrosinase. Among them, safrole (1) showed significant inhibitions against both the monophenolase ($IC_{50}=32.11{\mu}M$) and diphenolase ($IC_{50}=27.32{\mu}M$) activities of tyrosinase. The kinetic analysis shows that safrole (1) is competitive inhibitors for both monophenolase and diphenolase. The apparent inhibition constant ($K_i$) for safrole (1) binding with free enzyme was determined to be 16.05 and $13.66{\mu}M$ for monophenolase and diphenolase, respectively.

• 오토저널
• /
• 제3권2호
• /
• pp.34-42
• /
• 1981

The feasibility of using fluidic components for improving certain performance characteristics of the suspension systems for tracked vehicle is investigated. This study describes three variable damping systems for which the damping coefficients are function of relative velocity and absolute a of the vehicle body. Through the comparison analysis between constant damping coefficient damper and each of variable dampers. the followings were found: (1)Fluidic Diode Damper gave less accelerations, (2)Both Fluidic Diode Damper and Relative Velocity Damper gave the less time for which the wheel is off the ground, (3) At low vehicle velocity Fluidic Diode Damper gave low energy dissipation rate, while at high vehicle velocity Turbulence Accelerometer Damper gave low energy dissipation rate.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
• /
• pp.47-47
• /
• 2003

Analytical formulae are presented to approximate the evolution of the semi major axis, the maneuver time, and the final mass fraction for low thrust orbital transfers with circular initial orbit, circular target orbit, and constant thrust directed either always along or always opposite the velocity vector. For comparison, the associated results for high-thrust transfers, i.e. the two-impulse Hohmann transfer, are summarized. All results are implemented in a computer code designed to analyze planar planetary and interplanetary space missions. This implementation yields fast and reasonably accurate approximations to trajectory performance boundaries. Consequently, the approach can provide trajectory analysis for each spacecraft configuration during the conceptual space mission design phase. As an example, a mission from Low-Earth Orbit (LEO) to Jupiter's moon Europa is analyzed.

• International Journal of Air-Conditioning and Refrigeration
• /
• 제9권1호
• /
• pp.65-70
• /
• 2001

During the summer season, it is very hot and humid in Korea. So the humidity is an important factor regarding the environmental control function of building envelops. The purpose of this research is to measure and analyze the characteristics of such environmental factors as relative humidity, dry bulb temperature and air velocity varies both in the clay and cement envelop structures using granite dome models during the summer time. The interior relative humidity of the clay model is constant regardless of exterior humidity although a little range of variation is shown in comparison to the cement model.

• International Journal of Human Ecology
• /
• 제13권1호
• /
• pp.89-103
• /
• 2012

Using a life course framework, we compare and contrast the processes of acculturation for first- and second-generation Korean immigrant fathers in the United States. In-depth life history interviews were conducted with 20 first-generation and 15 second-generation fathers in the Midwest. With a modified grounded theory approach of constant comparison, we first explored how these fathers developed their identities in the midst of cultural and social transitions. These men's identity construction was shaped by socio-economic statuses and accessibility to cultural resources, with a marked shift over time toward integration of Korean and American identities. We then examined how these identities informed the men's socialization of their children, and the children's socialization of their parents.

• 동력기계공학회지
• /
• 제14권6호
• /
• pp.5-12
• /
• 2010

In this study, an analysis of evaporative diesel spray and an usefulness of a general-purpose program, ANSYS CFX release 11.0, are investigated through the comparison and investigation of the experimental results carried out under an evaporative field, in which there is phase transition, by an exciplex fluorescence method and the results analyzed by the CFX program. The diesel fuel called n-Tridecane, $C_{13}H_{28}$, is injected from a single-hole nozzle (l/d=1.0mm/0.2mm) into a constant volume chamber under a high temperature and pressure. In the same condition as the experimental condition, the analysis was carried out. Both results of the spray tip penetration were almost coincident at each time. The results have validated the usefulness of this analysis. As a result, if the ambient pressure is high, the spray tip penetration will be shortened and move toward the nozzle exit.