• Journal of Mechanical Science and Technology
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• v.15 no.8
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• pp.1090-1096
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• 2001

In this paper, new methods for efficiently solving linear acceleration equations of multibody dynamic simulation exploiting sparsity for real-time simulation are presented. The coefficient matrix of the equations tends to have a large number of zero entries according to the relative joint coordinate numbering. By adequate joint coordinate numbering, the matrix has minimum off-diagonal terms and a block pattern of non-zero entries and can be solved efficiently. The proposed methods, using sparse Cholesky method and recursive block mass matrix method, take advantages of both the special structure and the sparsity of the coefficient matrix to reduce computation time. The first method solves the η$\times$η sparse coefficient matrix for the accelerations, where η denotes the number of relative coordinates. In the second method, for vehicle dynamic simulation, simple manipulations bring the original problem of dimension η$\times$η to an equivalent problem of dimension 6$\times$6 to be solved for the accelerations of a vehicle chassis. For vehicle dynamic simulation, the proposed solution methods are proved to be more efficient than the classical approaches using reduced Lagrangian multiplier method. With the methods computation time for real-time vehicle dynamic simulation can be reduced up to 14 per cent compared to the classical approach.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.4
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• pp.427-434
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• 2000

In tradition, there have been two kinds of drying methods, which are sun drying and artificial drying. The sun drying method which has been adopted traditionally has been replaced by the hot-air drying method which is one of the most general methods of artificial drying, with its simple drying system, low initial cost of drying plant, and easy operating method. But the hot-air drying method has some defects; (1) much energy loss happens due to the discharge of hot air during the drying process, (2) control of drying rate is not easy on account of changing relative humidity of inlet air for uniform hot air temperature, (3) high temperature of foods in drying process brings about the production of low-grade drying products. Vacuum drying takes advantage of energy saving and mass production because it reduces the drying time by increasing the drying rate under low temperature condition. The aim of this paper is to develop the low temperature vacum dryer, with low initial investments and operating costs, easy operating method and trouble-free operation.

• Genomics & Informatics
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• v.20 no.2
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• pp.16.1-16.12
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• 2022

Various methodologies for the genetic analysis of longitudinal data have been proposed and applied to data from large-scale genome-wide association studies (GWAS) to identify single nucleotide polymorphisms (SNPs) associated with traits of interest and to detect SNP-time interactions. We recently proposed a grid-based Bayesian mixed model for longitudinal genetic data and showed that our Bayesian method increased the statistical power compared to the corresponding univariate method and well detected SNP-time interactions. In this paper, we further analyze longitudinal obesity-related traits such as body mass index, hip circumference, waist circumference, and waist-hip ratio from Korea Association Resource data to evaluate the proposed Bayesian method. We first conducted GWAS analyses of cross-sectional traits and combined the results of GWAS analyses through a meta-analysis based on a trajectory model and a random-effects model. We then applied our Bayesian method to a subset of SNPs selected by meta-analysis to further discover SNPs associated with traits of interest and SNP-time interactions. The proposed Bayesian method identified several novel SNPs associated with longitudinal obesity-related traits, and almost 25% of the identified SNPs had significant p-values for SNP-time interactions.

• Journal of Environmental Health Sciences
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• v.22 no.2
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• pp.10-18
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• 1996

Experiments were carried out to find the possibility of an economic production of single cell protein(SCP) in mixed culture by Cellulomonas sp. KL-6 and a second organism. The second organism, strain LI-10, was isolated from the large intestines of a mouse. 1. When these strains were mixed, cell growth and carboxymethyl cellulase (CMCase) activity were increased to about 63% and 161%, respectively compared with that of single culture of strain KL-6. We found the mixed culture as a proper method of degradation of cellulose in our study. 2. Strain LI-10 was identified as E. coli. 3. This strain produced trace amounts of cellobiose, but glucose was not found in detectable amounts in the filter paper(FP) medium. 4. $CaCO_3$ injected in the medium at the ratio of 0.1% not only enhanced cell growth but also was effective as an acid neutralizing agent. 5. When this organism was cultured under the optimal medium (glucose 0.1%, $NH_4Cl$ 0.1%, yeast extract 2.0%, $KH_2PO_4$ 0.1%, KCl 0.05%, pH 7.2 and a temperature 30$\circ$C) for 5 days, a cell mass produced 1.18 g/l. The results showed the increase of cell mass up to 300% compared to 0.28 g/l produced in CMC medium.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.568-572
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• 2001

An industrial vibratory conveyor system is devised for large-scale feeding by the low-power, using natural frequency of the system. The important thing in this system is to determine the natural frequency and to drive by it. The purpose of this study is to build up reliance on the system with changing of element parameters for vibration characteristics of balancing type vibratory conveyor by using F.E.M. modeling. For investigating the natural frequency, modal testing is performed by using impact hammer, accelerometer and LMS/Vibration Analysis System. Experimental results are compared with F.E.M results. The results of the comparisons within the errors of less than 2 percent can verify the reliability of the F.E.M. analysis of the system. Also we can verify that the characteristics of natural frequency have linearly decreased(-6%) as adding the mass($50{\sim}600kg$). We can find that controlling driving frequency is necessary for triggering the natural frequency, but natural frequency is less affected by adding the mass on the balancing weight.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.5
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• pp.408-415
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• 2011

Advanced tanks in the future combat system are expected to have the trends of large caliber, high explosive shell and light weight for destructive power and improvement in mobility. Their guns are required to have longer barrels to meet increased muzzle exit velocities. However, as the length of the barrel is extended, the vibrations induced by the breech forces in fire and the terrain lead to increased muzzle pointing errors. Therefore, the fire-induced and terrain-induced vibrations must be attenuated. A method to reduce these vibrations without the significant increase of the gun mass is to use the forward thermal shroud as part of a tuned mass damper. In this study, the dynamically-tuned-shroud using this shroud and leaf springs is introduced and its effectiveness on the vibration attenuations of the barrel are verified. The parametric studies on the stiffness of these leaf springs are performed and the analytical results are verified using the experimental model of the dynamically-tuned-shroud.

• Journal of Ecology and Environment
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• v.31 no.1
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• pp.75-81
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• 2008

Rates of molecular evolution are known to vary widely among taxonomic groups. A number of studies, examining various taxonomic groups, have indicated that body size is negatively and clutch size is positively correlated with the rates of nucleotide substitutions among vertebrate species. Generally, either smaller body mass or larger clutch size is associated with shorter generation times and higher metabolic rates. However, this generality is subject to ongoing debate, and large-scale comparative studies of species below the Order level are lacking. In this study, phylogenetically independent methods were used to test for relationships between rates of the mitochondrial cytochrome b evolution and a range of life history traits, such as body mass and clutch size in the Order Galliformes. This analysis included data from 67 species of Galliformes birds and 2 outgroup species in Anseriformes. In contrast to previous studies, taxa were limited to within-Order level, not to Class or higher. I found no evidence to support an effect of life history traits on the rate of molecular evolution within the Galliformes. These results suggest that such relationship may be too weak to be observed in comparisons of closely related species or may not be a general pattern that is applicable to all nucleotide sequences or all taxonomic groups.

• Earthquakes and Structures
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• v.18 no.1
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• pp.1-14
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• 2020

The vehicle-bridge interaction (VBI) analysis might be cumbersome and computationally expensive in bridge engineering due to the necessity of solving large number of coupled system of equations. However, VBI analysis can provide valuable insights into the dynamic behavior of highway bridges under specific loading conditions. Hence, this paper presents a numerical study on the dynamic behavior of a conventional highway bridge under strong near-field and far-field earthquake motions considering the VBI effects. A recursive substructuring method, which enables solving bridge and vehicle equations of motion separately and suitable to be adapted to general purpose finite element softwares, was used. A thorough analysis that provides valuable information about the effect of various traffic conditions, vehicle velocity, road roughness and effect of soil conditions under far-field and near-field strong earthquake motions has been presented. A real-life concrete highway bridge was chosen for numerical demonstrations. In addition, sprung mass models of vehicles consist of conventional truck and car models were created using physical and dynamic properties adopted from literature. Various scenarios, of which the results may help to highlight the different aspects of the dynamic response of concrete highway bridges under strong earthquakes, have been considered.

• Journal of ILASS-Korea
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• v.17 no.3
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• pp.140-145
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• 2012

Recent common-rail injector of a diesel engine needs more smaller nozzle hole to meet the stringent emission regulation. But, small nozzle hole diameter can cause nozzle coking which is occurred due to the deposits of post-combustion products. Nozzle coking has a negative effect on the performance of fuel injector because it obstructs the fuel flow inside a nozzle hole. In this study DFSS (Design for six sigma) method was applied to find the effect of nozzle design parameter on nozzle coking. Total 9 injector samples were chosen and tested at diesel engine. The results show that nozzle hole diameter and K-factor have more effect on nozzle coking than A-mass and hole length. Large hole diameter and A-mass, small hole length and K-factor give more positive performance on nozzle coking in these experimental conditions. But, a performance about nozzle coking and exhaust gas emission shows the opposite tendency. Further study is needed to find the relation between nozzle coking and emission characteristic for the optimization of injector nozzle design.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.141.2-141.2
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• 2012

We present photometric solutions of the 26,212 eclipsing binaries discovered in the LMC by Graczyk et al. (2011). They published that 70 percent of a total are detached systems. Another 25 and 5 percent are semi-detached and contact binaries, respectively. We discovered that 21 percent of 26,121 eclipsing binary stars are eccentric orbit systems. The binary star distribution in the LMC is different from those of the Galactic center direction (Bade window). It is very interesting that there are only 5 of 357 (2 percent) stars have eccentric orbit in the Galactic Center (Kang 2011). We selected the light curve of 18,274 detached systems. Then we estimated the fundamental parameters on the basis of their photometric solutions and the semi-major-axis (a) assuming the distance modulus to the LMC~18.50. We compared the estimated fundamental parameters with an empirical mass-luminosity relation and consistency between mass-radius relation base on stellar evolution model in the low metallicity (Z=0.008) by Bertelli et al. (2009). This method allows for independent determine of the fundamental parameters of the eclipsing binaries in the LMC without the radial velocity curves.