• Journal of Educational Research in Mathematics
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• v.20 no.1
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• pp.85-102
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• 2010

Linear programming(LP) is useful for finding the best way in a given condition for some list of requirements represented as linear equations. This study analysed LP in mathematics contexts and LP in school mathematics contexts, considered learning process of LP from an epistemological point of view, and explored a hypothetical learning trajectory of LP. The differences between mathematics contexts and school mathematics contexts are whether they considered that the convex polytope $\Omega$ is feasible/infeasible or bounded/unbounded or not, and whether they prove the theorem that the optimum is always attained at a vertex of the polyhedronor not. And there is a possibility that students could not understand what is maximum and minimum of a linear function when the domain of the function is limited. By considering these three aspects, we constructed hypothetical learning trajectory consisted of 4 steps. The first step is to see a given linear expression as linear function, the second step is to partition a given domain by straight lines, the third step is to construct the conception of y-intercept by relating lines and the range of k, and the forth step is to identify whether there exists the optimum in a given domain or not.

• Journal of Nutrition and Health
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• v.21 no.4
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• pp.242-252
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• 1988

In vivo effects of leucine on skeletal muscle protein synthesis in fed and I-day food deprived young rats were examined. Animals assigned to leucine group were given a single i.p. injection of 80 or 160flmoles of leucine while control group animals were saline sham injected. The rate of protein synthesis was measured by the amount of $^{14}\textrm{C} incorporated into muscle protein after a single injection of $^{14}\textrm{C}-tyrosine, IO$\mu$ Ci/l00g B.W. Examined muscles were two different types of hind limb muscles. the oxidative solues and the glycolytic EDL and plantaris. Administered leucine elevated the concentration of free leucine in soleus muscles by 4-6.8 times the normal level. A massive dose of leucine, 160 flmoles, stimulated protein synthesis in the EDL and plantaris by 24 %, 29 % respectively of straved rats. The soleus of I-day food deprived rats and both types of muscles in fed rats did not respond to the injected leucine. The synthesis rate of the EDL and plantaris was supressed to one-half of the normal while the soleus that was not stimulated by leucine maintained a relatively normal rate, 78 %, of protein synthesis after I-day of food deprivation. Thus, in vivo stimulatory effect of leucine appears to be not a general phenomenon but to be related to the degree of catabolic condition developed by stress such as food deprivation. Although anabolic effects of leucine observed in this study was limited, any applicability of this special property of leucine to human subjects for the purpose of protein sparing in skeletal muscles remains to be examined.

• Journal of Korean Society of Steel Construction
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• v.30 no.2
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• pp.115-126
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• 2018

Internationally representative steel design standards have forbidden or limited the application of high-strength steels to tubular joints, partly because of concerns about their unique material characteristics such as high yield ratio. Most of design standards stipulate that for steels whose yield strengths exceed 355 or 360 MPa, the strength equations cannot be utilized or strength reduction factor below 1.0 should be multiplied. However, the mechanical background behind these limitations is not clear. Experimental testing of high-strength steel CHS (circular hollow section) X-joints recently conducted by the authors also clearly indicated that the current limitations might be unduly conservative. As a continuing work, extensive, test-validated numerical analyses were made to investigate the behavior of high-strength steel CHS X-joint under axial compression. Three steel grades covering ordinary to very high strength steels were considered in the analysis. Again it was found that the high strength penalty to the joint strength in current standards is too severe and needs to be relaxed. The high-strength steel joints under the effects of chord stress generally showed higher strength than the ordinary steel joints and their strengths were conservatively predicted by current standards. It is also emphasized that current format of the CHS X-joint strength equation does not reflect observed behavior and needs to be recast.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.2 no.2
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• pp.78-86
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• 1997

To clarify the phytoplankton blooms in Lake Shihwa after the construction of a dyke, a study on the environmental factors, the distribution of chlorophyll-a, phytoplankton standing stocks, dominant species and primary productivity was carried out in Lake Shihwa and adjacent coastal areas from October, 1995 to August, 1996. Lake Shihwa is brackish water with mixing of freshwater from tributaries and the remaining salt water at the bottom. The dense phytoplankton bloom of average value of 168.6 ${\mu}gChl-a\;l^{-1}$ have occurred throughout the year in Lake Shihwa which is eutrophicated by the large input of nutrients from inflowing 5 tributaries and Shihwa Industrial Complex. The major organisms of algal bloom in Lake Shihwa were diatoms, Cyclotella atomus, Nitzschia sp. and Chaetoceros sp. in autumn and winter, and dinoflagellate Prorocentrum minimum and Chrysophyceae in spring and summer. The autumn and winter diatom blooms were limited by the depletion of silicate in the lake. Diatom blooms have occurred in the coastal areas adjacent to Shihwa lake from winter to summer due to the inflow of nutrient rich-water from Lake Shihwa. The primary productivities in the Lake Shihwa ranged from 2,653 mgC $m^{-2}\;day^{-1}$ to 9,505 mgC $m^{-2}\;day^{-1}$ with an average of 3,972 mgC $m^{-2}\;day^{-1}$. However, most of the high primary production was limited to the shallow euphotic zone due to the inhibition of light penetration. The primary productivities during autumn and winter were limited by the depletion of silicate. Lack of photosynthesis and the decomposition of falling organic matter under the middle of water column accelerated the depletion of dissolved oxygen in the bottom layer.

• The Korean Journal of Food And Nutrition
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• v.15 no.3
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• pp.228-234
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• 2002

In this paper, we proposed a preparation of Jeung- pyun (Korean fermented steamed rice cake with sour taste and spongy texture) using fuzzy theory. Before this preparation was introduced, it thoroughly analyzed the existing data of Jeung-pyun preparation with sensory evaluation and instrumental measurement. It defined a membership auction of Fuzzy set by analyzed three sorts of data on Jeung-pyun. And it established the Fuzzy model using the quantity of materials as input, such as rice, flour, wheat flour and fermentation time, and the sensory test scores as output, such as grain, softness, sourness, chewiness, overall quality, pH value and volume, respectively. We got the results that the Fuzzy model was accord with the conventional method with sensory evaluation. And the validity of this method is shown through the computer simulation of the test data. Therefore, the proposed method by Fuzzy model will apply to make Jeung-pyun without sensory evaluation. This study will contribute to develop standard preparation for korean foods and expert system of preparation using computer system.

• Journal of the Korea Society for Simulation
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• v.24 no.3
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• pp.37-44
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• 2015

A queueing system with 2 parallel workstations is common in the field. Typically, the workstations have different features in terms of the inter arrival times of customers and the service times for the customers. Computer simulation study on the optimal server allocation for parallel heterogeneous queueing systems with fixed number of identical servers is presented in this paper. The queueing system is optimized with respect to minimizing the weighted system time of the customers served by 2 parallel workstations. The system time formula for the M/M/c systems in Kendall's notation is known. Thus, we first compute the optimal allocation for parallel M/M/c systems, comparing the results with those from the computer simulation experiments, and have the same results. The CETI rule is devised through optimizing M/M/c cases, which allocates the servers based on Close or Equal Traffic Intensities between workstations. Traffic intensity is defined as the arrival rate divided by the service rate times the number of servers. The CETI rule is shown to work for M/G/c, G/M/c queueing systems by numerous computer simulation experiments, even if the rule cannot be proven analytically. However, the CETI rule is shown not to work for some of G/G/c systems.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.847-855
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• 2004

The criterion or specification on fatigue design has been generally based on fatigue strength curve derived by tests on specimens with varying thickness (10-30mm). Making the plate thicker, however, also decreases fatigue strength. It has been noted from the test results and the results of the analysis by fracture mechanics that the effect of thickness cannot be bypassed. From the several fatigue strength curves of specimen tests, modification of fatigue strength on plate thickness has been proposed. In this study, fatigue tests on SM520C-TMC were carried out, and the effects of thickness were evaluated. Finally, in consideration of the thickness, the modification of fatigue strength was derived. Comparing the results of this paper with those of previous studies, an outline of the behavior obtained is similar to previous ones, but the rate of decrease is smaller.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.4 no.2
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• pp.249-255
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• 2001

Methylmalonic acidemia is a rare congenital autosomal recessive metabolic disease. It is caused by blocking in the pathways of isoleucine, valine, threonine, methionine, cholesterol and odd-chain fatty acids to succinyl CoA, resulting in the increase of L-methylmalonyl CoA and methylmalonic acid. In most cases, there are symptoms such as recurrent vomitings, lethargy and laboratory abnormalities including metabolic acidosis and hyperammonemia from the neonatal period. We had a 6-month-old infant with methylmalonyl acidemia who presented with recurrent vomiting episodes since 3 months of age, failure to thrive and developmental delay. The laboratory findings showed hyperammoninemia and ketotic metabolic acidosis. Plasma amino acid analysis showed nonspecific finding. Urine organic acid ananysis by gas chromatography and mass spectrometry detected large amount of methylmalonic acid excreted in the urine. We restrained the supply of protein in the amount of 1~1.5 g/kg of body weight a day using leucine, isoleucine and valine-r-estrained milk and administered vitamine $B_{12}$, in the amount of 1mg per day. During the follow-up in the outpatient clinic, He could control his head and showed increased muscle strength.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.643-653
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• 2007

The ultimate bending strength and flexural ductility performance of longitudinally stiffened plate girders fabricated with mild steel were investigated utilizing nonlinear incremental finite element analysis. AASHTO LRFD (2002) design specifications were reviewed for possible application of longitudinally stiffened plate girders as compact sections. In order to investigate compact section requirements for plate girders with longitudinal stiffeners in webs, a number of full-scale plate girders were modeled and analyzed up to the collapse under pure bending condition. It was found that the slenderness of sub panel of the webs, the stiffness of longitudinal stiffeners, and the slenderness of compression flanges are key parameters governing the flexural ductility of the plate girders. It was also found from finite element analysis that longitudinally stiffened plate girder sections can satisfy compact section requirements both in full plastic moment capacity and flexural ductility requirement. New design equations have been proposed for longitudinally stiffened plate girders to be treated as compact sections.

• Journal of Nutrition and Health
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• v.16 no.4
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• pp.263-272
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• 1983

Effects of dietary protein qualify, energy restriction, and subsequent rehabilitation were studied in the weanling rats. Rats were devided into the six experimental diet groups. Rats in AC (casein- containing diet ), AS (soyprotein-containing diet), and AG(gluten-containing diet) group consumed their diets ad libitum, and rats in PC, PS, PG groups were pair-fed in 60% of the of amounts eaten by corresponding rats in the AC, AS, AG groups, respectively. After 3 weeks of nutritional restriction, all rats were switched to the AC diet for 14 days. At the end of restriction period, body weight, weight gain, food intake, and FER were higher in casein- fed rats than other groups of rats. The differences were, however, disappeared with rehabilitation diet, except body weights which were not fully recovered until the end of experiment. The weights of liver, gastrocnemius muscle, kidney, small intestine, spleen, and lung were the highest in the casein group, and the lowest in gluten group at the end of restriction period. The recovery with rehabilitation diet were differ in different organs. The muscle and liver seemed to be the most affected organs by dietary protein quality and energy restriction. There were no differences in brain weights among the experimental groups during the restriction period, however, after 2 weeks of rehabilitation, rats in AC group showed lower brain weight compared to AC and AS groups, and the brain weight of PC group was lower than AC group. Protein contents in liver and muscle showed the same trends as their weights. Gluten-fed rats showed low serum protein concentration, but recovered fully with rehabilitation diet for 3 days.