• Journal of Korean Society of Steel Construction
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• v.23 no.6
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• pp.669-677
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• 2011

The multi-span suspension bridge generally has more than three towers and two main spans. To economically and effectively design a multi-span suspension bridge, the proper stiffness ratio of the center tower to the side tower must be determined. This study was conducted to propose a method of figuring out briefly the structural behavior of the towers in a multi-span suspension bridge. In the equivalent suspension bridge model, the main cable of the multi-span suspension bridge is idealized as an equivalent cable spring, and the external loads of horizontal and vertical forces that were calculated using the tensile forces of the main cable were applied on top of the towers. The equilibrium equations of the equivalent multi-span suspension bridge model were derived and the equations were solved via nonlinear analysis. To verify the proposed method, a sample four-span suspension bridge with a main span length of 3,000 m was analyzed using thefinite element method. The displacements and moment reactions of each tower in the proposed method were compared with the FEM analysis results. Consequently, the results of the analysis of the equivalent suspension bridge model tended to be consistent with the results of the FEM analysis.

• Korean Journal of Microbiology
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• v.39 no.4
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• pp.272-276
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• 2003

Sapgyo Lake is an artificial freshwater reservoir which is located to the midwest of Korea and is the main water reservoir for industry and agriculture of the region. In this study we investigated environmental factors and the change of bacterial community with the influence of surrounding inflow water and the seasonal variation using the molecular ecological approach. Water samples were collected at front of the dike in May and August, 2001. Bacterial genomic DNAs were extracted directly and purified for the amplification of bacterial 16S rDNA. Clone libraries of the 16S rDNA were constructed using pGEM-T easy vector and RFLP analysis was performed to make a group as OTUs with 4 base recognizing enzymes (MspI and HaeIII). The estimated values of richness in August sample was higher than in May. Thirty-three of 153 clones in May and thirty-eight of 131 clones in August were sequenced from forward region of bacterial 16S rDNA for about 600~800 bp. Proteobacteria, Cytophaga, gram positive bacteria and Verrucomicrobia were observed both months. Especially, Planctomyces, cyanobacteria and chloroplast appeared in August when algal bloom occurred. On the whole investigation, Sapgyo lake showed a typical community structure of estuarine and was influenced by heterochthonous organic matters from the surrounding stream.

• Korean Journal of Ichthyology
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• v.35 no.3
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• pp.171-176
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• 2023

The olfactory organ of Carassius auratus and C. cuvieri was compared morphologically and morphometrically using stereomicroscopy and statistical program (SPSS version 18.0). The external morphology of the olfactory organ consists of the open semicircular anterior and posterior nostril, and nasal flap. The internal structure showed the oval rosette consisting of several lamellae arranged radiately. In statistical analysis of standard length (SL), olfactory lamellar number (LN), and SL/LN ratio between two species using independent two sample t-test and Pearson's correlation and coefficient, C. cuvieri is the longer SL than that of C. auratus and C. auratus LN (14~20) is lager than that of C. cuvieri (14~16) (P<0.001) and C. auratus LN/SL ratio (12.7±0.7%) is larger than that of C. cuvieri (8.2±0.6%). These results suggest that i) open semicircular nostrils is functional morphology to offset the boundary layer and ii) the lager LN of smaller C. auratus may be a morphological adaptation to reflect its higher olfactory dependence than C. cuvieri and iii) such interspecific difference in LN and LN/SL ratio could be applied as a new taxonomic trait for identification.

• Journal of Hydrogen and New Energy
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• v.17 no.4
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• pp.379-388
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• 2006

Two mesophilic trickling bed bioreactors filled with two different types of media, hydrophilic- and hydrophobic-cubes, were designed and conducted for hydrogen production under the anaerobic fermentation of sucrose. Each bioreactor consisted of the column packed with polymeric cubes and inoculated with heat-treated sludge obtained from anaerobic digestion tank. A defined medium containing sucrose was fed by the different hydraulic retention time(HRT), and recycle rate. Hydrogen concentrations in gas-phase were constant, averaging 40% of biogas throughout the operation. Hydrogen production rate was increased till $10.5\;L{\cdot}h^{-1}{\cdot}L^{-1}$ of bioreactor when influent sucrose concentrations and recycle rates were varied. At the same time, the hydrogen production rate with hydrophobic media application was higher than its hydrophilic media application. No methane was detected when the reactor was under a normal operation. The major fermentation by-products in the liquid effluent of the both trickling biofilters were acetate, butyrate and lactate. In order to run in the long term operation of both reactor filled with hydrophilic and hydrophobic media, biofilm accumulation on hydrophilic media and biogas produced should be controlled through some process such as periodical backwashing or gas-purging. Four sample were collected from each reactor on the opposite hydrogen production rate, and their bacterial communities were compared by terminal restriction fragment length polymorphism (T-RFLP) analysis of PCR products generated using bacterial 16s rRNA gene primers (8f and 926r). It was expressed a marked difference in bacterial communities of both reactors. The trickling bed bioreactor with hydrophobic media demonstrates the feasibility of the process to produce hydrogen gas. A likely application of this reactor technology can be hydrogen gas recovery from pre-treatment of high carbohydrate-containing wastewaters.

• Journal of agricultural medicine and community health
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• v.35 no.3
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• pp.239-248
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• 2010

Objective: Despite the increasing number of female participation in employment, blue-collar women have been exposed to higher health risk. This study is to describe the prevalence of chronic diseases, health behaviors, and medical service utilization of female blue-collar workers. Methods: Data were derived from the 2001 Korea National Health and Nutrition Survey (KNHANES). The sample was made up of 37,108 male and female participants aged 20 or over selected nation-wide by probability sampling from Korea. This study applied the logistic regression for nominal variables such as disease prevalence and health behaviors and with the regression for continuos variables such as the length and costs of medical services. Results: In general, women's prevalence of chronic illness and uncured rate were significantly higher than male, and especially female blue-collar workers had the highest prevalence, uncured rate, unhealthy status, and perceived stress. However, the medical care cost was the lowest in female blue-collar workers. Conclusions: The findings suggest that female blue-collar workers were more likely to experience health problems, and that despite the highest health risk, health service is not effectively utilized, and health policy maker should take consider of special status of female blue collar workers who are in health inequality.

• Journal of Powder Materials
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• v.9 no.6
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• pp.394-408
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• 2002

Nanostructured high strength metastable Al-, Mg- and Ti-based alloys containing different amorphous, quasicrystalline and nanocrystalline phases are synthesized by non-equilibrium processing techniques. Such alloys can be prepared by quenching from the melt or by powder metallurgy techniques. This paper focuses on one hand on mechanically alloyed and ball milled powders containing different volume fractions of amorphous or nano-(quasi)crystalline phases, consolidated bulk specimens and, on the other hand. on cast specimens containing different constituent phases with different length-scale. As one example. $Mg_{55}Y_{15}Cu_{30}$- based metallic glass matrix composites are produced by mechanical alloying of elemental powder mixtures containing up to 30 vol.% $Y_2O_3$ particles. The comparison with the particle-free metallic glass reveals that the nanosized second phase oxide particles do not significantly affect the glass-forming ability upon mechanical alloying despite some limited particle dissolution. A supercooled liquid region with an extension of about 50 K can be maintained in the presence of the oxides. The distinct viscosity decrease in the supercooled liquid regime allows to consolidate the powders into bulk samples by uniaxial hot pressing. The $Y_2O_3$ additions increase the mechanical strength of the composites compared to the $Mg_{55}Y_{15}Cu_{30}$ metallic glass. The second example deals with Al-Mn-Ce and Al-Cu-Fe composites with quasicrystalline particles as reinforcements, which are prepared by quenching from the melt and by powder metallurgy. $Al_{98-x}Mn_xCe_2$ (x =5,6,7) melt-spun ribbons containing a major quasicrystalline phase coexisting with an Al-matrix on a nanometer scale are pulverized by ball milling. The powders are consolidated by hot extrusion. Grain growth during consolidation causes the formation of a micrometer-scale microstructure. Mechanical alloying of $Al_{63}Cu_{25}Fe_{12}$ leads to single-phase quasicrystalline powders. which are blended with different volume fractions of pure Al-powder and hot extruded forming $Al_{100-x}$$(Al_{0.63}Cu_{0.25}Fe_{0.12})_x$ (x = 40,50,60,80) micrometer-scale composites. Compression test data reveal a high yield strength of ${\sigma}_y{\geq}$700 MPa and a ductility of ${\varepsilon}_{pl}{\geq}$5% for than the Al-Mn-Ce bulk samples. The strength level of the Al-Cu-Fe alloys is ${\sigma}_y{\leq}$550 MPa significantly lower. By the addition of different amounts of aluminum, the mechanical properties can be tuned to a wide range. Finally, a bulk metallic glass-forming Ti-Cu-Ni-Sn alloy with in situ formed composite microstructure prepared by both centrifugal and injection casting presents more than 6% plastic strain under compressive stress at room temperature. The in situ formed composite contains dendritic hcp Ti solid solution precipitates and a few $Ti_3Sn,\;{\beta}$-(Cu, Sn) grains dispersed in a glassy matrix. The composite micro- structure can avoid the development of the highly localized shear bands typical for the room temperature defor-mation of monolithic glasses. Instead, widely developed shear bands with evident protuberance are observed. resulting in significant yielding and homogeneous plastic deformation over the entire sample.

• Journal of the Korean Professional Engineers Association
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• v.20 no.3
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• pp.15-25
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• 1987

Statistical control charts are useful tools to monitor and control the manufacturing processes and are widely used in most Korean industries. Many Korean companies, however, do not always obtain desired results from the traditional control charts by Shewhart such as the X-chart, X-chart, X-chart, etc. This is partly because the quality charterstics of the process are not distributed normally but are skewed due to the intermittent production, small lot size, etc. In Shewhart X-chart, which is the most widely used one in Korea, such skewed distributions make the plots to be inclined below or above the central line or outside the control limits although no assignable causes can be found. To overcome such shortcomings in nonnormally distributed processes, a distribution-free type of confidence interval can be used, which should be based on order statistics. This thesis is concerned with the design of control chart based on a sample median which is easy to use in practical situation and therefore properties for nonnormal distributions may be easily analyzed. Control limits and central lines are given for tile more famous nonnormal distributions, such as Gamma, Beta, Lognormal, Weibull, Pareto, Truncated-normal distributions. Robustness of the proposed median control chart is compared with that of the X-chart, the former tends to be superior to the latter as the probability distribution of the process becomes more skewed. The average run length to detect the assignable cause is also compared when the process has a Normal or a Gamma distribution for which the properties of X are easy to verify, the proposed chart is slightly worse than the X-chart for the normally distributed product but much better for Gamma-distributed products. Average Run Lengths of the other distributions are also computed. To use the proposed control chart, the probability distribution of the process should be known or estimated. If it is not possible, the results of comparison of the robustness force us to use the proposed median control chart based on a normal distribution. To estimate the distribution of the process, Sturge's formula is used to graph the histogram and the method of probability plotting, $X^2$-goodness of fit test and Kolmogorov-Smirnov test, are discussed with real case examples. A comparison of the propose4 median chart and the X chart was also performed with these examples and the median chart turned out to be superior to the X-chart.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.6
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• pp.717-723
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• 2007

Statement of problem. Unreasonable distal cantilevered implant-supported prosthesis can mask functional problems of reconstruction temporarily, but it can cause serious strain and stress around its supported implant and surrounding alveolar bone. Purpose. The purpose of this study was to evaluate strain of implants supporting distal cantilevered fixed prosthesis with two different cantilevered length under distal cantilevered static load. Material and methods. A partially edentulous mandibular test model was fabricated with auto-polymerizing resin (POLYUROCK; Metalor technologies, Stuttgart, Swiss) and artificial denture teeth (Endura; Shofu inc., Kyoto, Japan). Two implants-supported 5-unit screw-retained cantilevered fixed prosthesis was made using standard methods with Type III gold alloy (Harmony C&B55; Ivoclar-vivadent, Liechtenstein, Germany) for superstructure and reinforced hard resin (Tescera; Ivoclar-vivadent, Liechtenstein, Germany) for occlusal material. Two strain gauges (KFG-1-120-C1-11L1M2R; KYOWA electronic instruments, Tokyo, Japan) were then attached to the mesial and the distal surface of each standard abutment with adhesive (M-bond 200; Tokuyama, Tokyo, Japan). Total four strain gauges were attached to test model and connected to dynamic signal conditioning strain amplifier (CTA1000; Curiotech inc., Paju, Korea). The stepped $20{\sim}100$ N in 25 N increments, cantilevered static load 8mm apart (Group I) or 16mm apart (Group II), were applied using digital push-pull gauge (Push-Pull Scale & Digital Force Gauge, Axis inc., Seoul, Korea). Each step was performed ten times and every strain signal was monitored and recorded. Results. In case of Group I, the strain values were surveyed by $80.7{\sim}353.8{\mu}m$ in Ch1, $7.5{\sim}47.9{\mu}m/m$ in Ch2, $45.7{\sim}278.6{\mu}m/m$ in Ch3 and $-212.2{\sim}718.7{\mu}m/m$ in Ch4 depending on increasing cantilevered static load. On the other hand, the strain values of Group II were surveyed by $149.9{\sim}612.8{\mu}m/m$ in Ch1, $26.0{\sim}168.5{\mu}m/m$ in Ch2, $114.3{\sim}632.3{\mu}m/m$ in Ch3, and $-323.2{\sim}-894.7{\mu}m/m$ in Ch4. Conclusion. A comparative statistical analysis using paired sample t-test about Group I Vs Group II under distal cantilevered load shows that there are statistical significant differences for all 4 channels (P<0.05).

• Journal of the Korean Society of Food Science and Nutrition
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• v.46 no.3
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• pp.374-380
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• 2017

Image analysis and k-mean clustering were conducted to develop a grading system of dried sea cucumber (SC) based on rehydration rate. The SC images were obtained by taking pictures in a box under controlled light conditions. The region of interest was extracted to depict the shape of the SC in a 2D graph, and those 2D shapes were rendered to build a 3D model. The results from the image analysis provided the morphological features of the SC, including length, width, surface area, and volume, to obtain the parameters of the k-mean clustering weight. The k-mean clustering classified the SC samples into three different grades. Each SC sample was rehydrated at $30^{\circ}C$ for 40 h. During rehydration, the flux of each grade was analyzed. Our study demonstrates that the mass transfer rate of SC increased as the surface area increased, and the grade of SC was classified based on rehydration rate. This study suggests that the optimal rehydration process for SC can be achieved by applying a suitable grading system.

• Korean Journal of Medicinal Crop Science
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• v.13 no.3
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• pp.114-117
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• 2005

Orostachys japonicus, called Wasong as herbal medicine and a short day plant, should be artificially kept in long daylength to control anthesis of its florets. The study was done to clarify the effect of daylength (10, 13, 16 hours a day) on growth, morphological characters, and flowering. The treatments were done on August 25 and afterward samples were taken every 2 weeks. Growth, morphological and flowering related characters were measured from each sample. With longer daylength plant height and inflorescence length were increased but number of leaves including bracts and stem diameter were decreased. Leaves and bracts, stem, root, shoot and total dry weights were increased with longer daylength from late September while floret dry weight showed reverse result. Florets formed were the greatest in daylength of 10 hours during September but the least during the other period. Anthesis of the florets was observed only in daylength of 10 hours during October and all the plants from the treatment were flowered.