• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.23-23
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• 2009

GaN-based nitride semiconductors have attracted considerable attention in high-brightness light-emitting-diodes (LEDs) and laser diodes (LDs) covering from green to ultraviolet spectral range. LED and LD heterostructures are usually grown on (0001)-$Al_2O_3$. The large lattice mismatch between $Al_2O_3$ substrates and the GaN layers leads to a high density of defects(dislocations and stacking faults). Moreover, Ga and N atoms are arranged along the polar [0001] crystallographic direction, which leads to spontaneous polarization. In addition, in the InGaN/GaN MQWs heterostructures, stress applied along the same axis can also give rise to piezoelectric polarization. The total polarization, which is the sum of spontaneous and piezoelectric polarizations, is aligned along the [0001] direction of the wurtzite heterostructures. The change in the total polarization across the heterolayers results in high interface charge densities and spatial separation of the electron and hole wave functions, redshifting the photoluminescence peak and decreasing the peak intensity. The effect of polarization charges in the GaN-based heterostructures can be eliminated by growing along the non-polar [$11\bar{2}0$] (a-axis) or [$1\bar{1}00$] (m-axis) orientation instead of thecommonly used polar [0001] (c-axis). For non-polar GaN growth on non-polar substrates, the GaN films have high density of planar defects (basal stacking fault BSFs, prismatic stacking fault PSFs), because the SFs are formed on the basal plane (c-plane) due to their low formation energy. A significant reduction in defect density was recently achieved by applying blocking layer such as SiN, AlN, and AlGaN in non-polar GaN. In this work, we were performed systematic studies of the defects in the nonpolar GaN by conventional and high-resolution transmission electron microscopy.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.1
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• pp.27-48
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• 1984

This study is conserned with the optimization of reinforced concrete frames using limit state design theory. Formulations of the optimal design for reinforced concrete frame based on the limit state theory turn out to be the nonlinear programming problems which have to deal with the required steel area, the width and effective height of the beam and column section and the moment reduction factor as the design variables. The objective function is formulated as the total construction cost which considers the costs of steel, concrete and forming for the reinforced concrete frames, and the basic constraints are imposed upon both ultimate and serviciability limit state concepts. Also, the stress blocks assumpted in CP110 and Hognestad et al. theory are applied to analysis an ultimate resistant section force for the ultimate limit state and only the criteria of CP110 are used for serviciability limit state. The optimized technique which is applied to solve the nonlinear programming problems for the optimization of reinforced concrete frames is SUMT utilizing the modified Newton-Raphson method. This algorithm is used to test for the two reinforced concrete frames, and then is compared and analysized with the numerical results of reference(10) to examine its convergence, applicability and stability under the same conditions. The results of this study are discussed about the economy comparision of the optimal values for CP110 and Hognestad et al., and the applicability, stability, convergence and validity of this algorithm used herein through the numerical analyses.

• Ecology and Resilient Infrastructure
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• v.3 no.1
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• pp.46-53
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• 2016

This study was conducted to analyze the effect of the different land covers of an urban park (Hyowon park) in downtown Suwon on the urban thermal variations during a hot summer. The effect of the air temperature reduction in the urban park was 4.4%-4.5% for the downtown residence (Maetan-dong). This value was about 0.8% lower than that of the outskirts residence (Sanggwanggyo-dong). The daily mean temperature, daily maximum temperature, summer day and heat wave frequency were measured under the different land covers (cement-block, grass, pine-grass, shading area and mixed forest) showed these values generally decreased under natural land cover types. Daily minimum temperature and tropical night frequency didn't seem to correlate with the land cover types. Means of thermal comfort indices (wet bulb globe temperature, heat index and discomfort index) in the shading area, mixed forest and the pine-grass types were lower than those of cement block and grass types. However the levels of those indices were equal to 'very high' or 'caution' levels in the afternoon (13:00-15:00). In the morning (06:00-08:00), thermal comfort indices of the urban park didn't correlate with land cover types. Therefore, to reduce heat stress and to improve the thermal comfort in urban parks, an increase in the area of natural land cover such as grass, forest and open spaces is required.

• Ecology and Resilient Infrastructure
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• v.3 no.3
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• pp.207-211
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• 2016

This study focuses on the categorization of the phenomenon of vegetative recruitment on riparian channels, so called, the phenomenon from "white river" to "green river", and proposes for the corresponding research direction. According to the literature review and research outputs obtained from the authors' previous research performed in Korea within a limited scope, the necessary and sufficient conditions for the recruitment and retrogression of riparian vegetation may be the mechanical disturbance (riverbed tractive stress), soil moisture (groundwater level, topography, composition of riverbed material, precipitation etc.), period of submergence, extreme weather, and nutrient inflow. In this study, two categories, one for the reduction in spring flood due to the change in spring precipitation pattern in unregulated rivers and the other for the increase in nutrient inflow into streams, both of which were partially proved, have been added in the categorization of the vegetative recruitment and retrogression on the riparian channels. In order to scientifically investigate further the phenomenon of the riparian vegetative recruitment and retrogression and develop the working riparian vegetative models, it is necessary to conduct a systematic nationwide survey on the "white to green" rivers, establishment of the categorization of the vegetation recruitment and retrogression based on the proof of those hypotheses and detailed categorization, development of the working mathematical models for the dynamic riparian vegetative recruitment and retrogression, and adaptive management for the river changes.

• Journal of Life Science
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• v.26 no.5
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• pp.592-602
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• 2016

This study investigated the muscular dystrophin levels in freely moving Australian cattle mainly fed grass, freely moving Korean cattle fed mainly a grain diet, and Korean cattle fed a grain diet but housed in a relatively limited space of a cow house. The total skeletal muscle specimens of 244 cattle were collected and immediately fixed in 10% neutral formalin. The same area was biopsied from the cattle in both countries. The findings showed that fatty infiltration is highly correlated with membrane-associated protein degradation in skeletal muscle, and that among several membrane-associated proteins, dystrophin showed the most significant reduction in expression in the cattle with fatty infiltration. Similarly, CD36 was more highly expressed in the cattle with fatty infiltration of skeletal muscle. Various breeding factors, such as oxidative stress; the presence of oxidized lipids in the diet; and environmental factors such as exercise, temperature and amount of time spent, may have critical effects on the degradation of normal cytoskeleton proteins, which are required for maintaining normal skeletal muscle architecture. Among the sarcolemma membrane-associated proteins, dystrophin is the most sensitive membrane protein that is involved muscular dystrophy and muscular degeneration. Thus, the present findings may be useful for studies on muscular dystrophy in humans or the pathogenesis of muscular diseases in animal models.

• The Journal of Internal Korean Medicine
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• v.39 no.1
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• pp.84-96
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• 2018

Objective: This is aprospective clinical case study that includes the administration of Ahnjeonbaekho-tang (AJBHT) to patients who have suffered from Graves' disease for the 8 weeks of the clinical research. Methods: Without administration of an antithyroid drug, AJBHT was administered 3 times a day for 8 weeks. In Case 1, AJBHT without modification was administered and in Case 2, in accordance with the patients' symptoms, a dose of Gypsum Fibrosum was increased by 4g from the beginning of week 2, and further increased by 16 g, for a total of 20 g between week 6 and week 8. Body mass index (BMI), thyroid function test (TFT), thyroid autoantibody test, complete blood cell count (CBC), and blood chemistry (BC) tests were conducted at an interval of 4 weeks, for a total of 3 times during the study. The clinical manifestations, a spectrum of symptoms of the patients, was observed by Wayne's Index, Euro-QOL-5 Dimension (EQ-5D), and Perceived Stress Scale (PSS). Results: In both cases, an acceptable significance of reduction of value in T3, fT4, Thyroid stimulating antibody (TSAb) and Thyroid stimulating hormone receptor antibody (TSH-R-Ab) was observed. After treatment, in TFT, T3 decreased by 31.66%, fT4 decreased by 32.82% in Case 1, and T3 decreased by 43.42%, and fT4 decreased by 37.32% in Case 2. In the thyroid autoantibody test, TSAb decreased by 7.59%, and TSH-R-Ab decreased by 53.19% in Case 1, and TSAb decreased by 33.45%, TSH-R-Ab decreased by at least 7.75% in Case 2. Besides this, there was a decreasing trend of Wayne's index, and a loss of typical symptoms of hyperthyroidism also declared the efficacy. Conclusion: From these results, AJBHT is very effective in the regulation of TFT and improving the symptoms of hyperthyroidism, and is also expected to be an effective alternative to antithyroid drugs for patients who have side effects or drug intolerance.

• Biomolecules & Therapeutics
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• v.23 no.2
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• pp.180-188
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• 2015

This study investigated the possible effects and molecular mechanisms of diallyl disulfide (DADS) against cyclophosphamide (CP)-induced hemorrhagic cystitis (HC) in rats. Inflammation response was assessed by histopathology and serum cytokines levels. We determined the protein expressions of nuclear transcription factor kappa-B (NF-${\kappa}B$), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and tumor necrosis factor-${\alpha}$ (TNF-${\alpha}$), oxidative stress, urinary nitrite-nitrate, malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Finally, we studied the involvement of mitogen-activated protein kinases (MAPKs) signaling in the protective effects of DADS against CP-induced HC. CP treatment caused a HC which was evidenced by an increase in histopathological changes, proinflammatory cytokines levels, urinary nitrite-nitrate level, and the protein expression of NF-${\kappa}B$, COX-2, iNOS, TNF-${\alpha}$, p-c-Jun N-terminal kinase (JNK), and p-extracellular signal regulated kinase (ERK). The significant decreases in glutathione content and glutathione-S-transferase and glutathione reductase activities, and the significant increase in MDA content and urinary MDA and 8-OHdG levels indicated that CP-induced bladder injury was mediated through oxidative DNA damage. In contrast, DADS pretreatment attenuated CP-induced HC, including histopathological lesion, serum cytokines levels, oxidative damage, and urinary oxidative DNA damage. DADS also caused significantly decreased the protein expressions of NF-${\kappa}B$, COX-2, iNOS, TNF-${\alpha}$, p-JNK, and p-ERK. These results indicate that DADS prevents CP-induced HC and that the protective effects of DADS may be due to its ability to regulate proinflammatory cytokines production by inhibition of NF-${\kappa}B$ and MAPKs expressions, and its potent anti-oxidative capability through reduction of oxidative DNA damage in the bladder.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.121-123
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• 2002

The design of an air seat cushion for preventing decubitus ulcer includes many design factors such as the even distribution of interface pressure, the minimization of mean and peak interface pressure values, and the reduction of interface shear force and pressure gradient. It involves the anatomic condition of plegia's buttock as well as air pressure in air cells of cushion. As a result, a suitable design of the cushion satisfying the all requirements is a difficult problem. Therefore, an appropriate and effective numerical tool to develop an air cushion orthosis is required. The purpose of the present study was to develop an air seat cushion orthosis having optimized air cells for evenly distributed interface pressure between the buttock and cushion surface. For the purpose, an advanced finite element (FE) model for the design of air cushion was developed. Since the interface pressure and shear force behavior, as well as stress analyses were primary concern, a FE air cell model was developed and verified by the experiments. Then, the interactions of two cells were checked. Also, the human part of the developed numerical model includes every material property and geometry related to buttock and femoral parts. For construction of dimension data of buttock and femoral parts, CT scans were performed. A commercial FE program was employed for the simulation representing the seating process on the orthosis. Then, sensitive analyses were performed with varying design parameters. A set of optimal design parameters was found satisfying the design criteria of the orthosis. The results were utilized to produce a prototype of the orthosis. Experimentally, the buttock interface pressure distributions from the optimized and previous ones were compared. The new seat orthosis showed a significantly improved interface pressure characteristics compared to the most popular one in the market. The new orthosis will be used for the development of the AI(artificial intelligent) controlled seat orthosis fur prevention of decubitus ulcer fur various plegic patients and the elderly.

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2002.04a
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• pp.69-75
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• 2002

Sterols play two major roles in plants: a bulk component in biological membranes and precursors of plant steroid hormones. Physiological effects of plant steroids, brassinosteroids (BRs), include cell elongation, cell division, stress tolerance, and senescence acceleration. Arabidopsis mutants that carry genetic defects in BR biosynthesis or its signaling display characteristic phenotypes, such as short robust inflorescences, dark-green round leaves, and sterility. Currently there are more than 100 dwarf mutants representing 7 genetic loci in Arabidopsis. Mutants of 6 loci, dwf1/dim1/cbb1, cpd/dwf3, dwf4, dwf5, det2/dwf6, dwf7 are rescued by exogenous application of BRs, whereas bri1/dwf2 shares phenotypes with the above 6 loci but are resistant to BRs. These suggest that the 6 loci are defective in BR biosynthesis, and the one locus is in BR signaling. Biochemical analyses, such as intermediate feeding tests, examining the levels of endogenous BR, and molecular cloning of the genes revealed that dwf7, dwf5, and dwf1 are defective in the three consecutive steps of sterol biosynthesis, from episterol to campesterol via 5-dehydroepisterol. Similarly, det2/dwf6, dwf4, and cpd/dwf3 were shown to be blocked in $D^4$ reduction, 22a-hydroxylation, and 23 a-hydroxylation, respectively. A signaling mutant bri1/dwf2 carries mutations in a Leucine-rich repeat receptor kinase. Interestingly, the bri1 mutant was shown to accumulate significant amount of BRs, suggesting that signaling and biosynthesis are dynamically coupled in Arabidopsis. Thus It is likely that transgenic plants over-expressing the rate-limiting step enzyme DWF4 as well as blocking its use by BRI1 could dramatically increase the biosynthetic yield of BRs. When applied industrially, BRs will boost new sector of plant biotechnology because of its potential use as a precursor of human steroid hormones, a novel lead compound for cholesterol-lowering effects, and a various application in plant protection.

• Journal of Chest Surgery
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• v.20 no.1
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• pp.112-127
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• 1987

Myasthenia gravis is a neuromuscular transmission function disorder characterized by fatigue and weakness of voluntary muscles. This muscular weakness is intensified by activity and stress, and improved by the use of anticholinesterase compounds. It was initially described by Erb in 1879 and later named myasthenia gravis by Jolly in 1895. Although the pathogenesis is Known to be an autoimmune related reduction in the number of available acetylcholine receptors at neuromuscular junctions, the role of thymus in myasthenia gravis is still unclear and under investigation. Thymectomy in the management of myasthenia gravis has become increasingly important since Dr. Blalock observed in 1939 that some patients with thymic tumors and myasthenia gravis improved following thymectomy. A clinical study of 102 cases of myasthenia gravis was performed at Yonsei University College of Medicine. Seoul, Korea from Jan. 1976 to Jun. 1986. In order to determine which factors are of prognostic significance, attention is focused upon pre-operative patient evaluation, problems in operative and post-operative care, and long-term follow-up observations. The results were as follows: 1. The sex distribution was 67 females and 35 males, the mean age of onset was 28.95*1.69 years, and the maximal incidence occurred between 21 and 40 years of age [56 cases: 54.9%]. 2. Clinical manifestations of ocular symptoms were seen to 70 patients [68.6%] extremities weakness in 33 [32.3%], bulbar weakness in 29 [28.4%], and dyspnea in 13 [12.7%]. 3. Study cases more than two thirds were classified as mild types [MG 1 and MG 11A] and 6 cases as grave [MG 1V] based on the modified Osserman`s classification system, 4. Thymectomy was performed in 19 cases which presented in severe myasthenia symptoms and showed no improvement with cholinergic drugs. Histologic examination of the excised thymus glands revealed no abnormalities in 4 cases, thymic hyperplasia in 5, benign thymoma in 5, and malignant thymoma in 5. 5. Immediate post-operative complications included 2 cases of pneumothorax which were treated by tube thoracostomies, there was no operative mortality. 6. The response to cholinergic drugs in 36 cases younger than 20 years old and in 27 cases older than 40 years was relatively poor, while that in 35 cases between the ages of 21 and 40 years old was good. 7. Thirty of 39 cases in groups IIB, III & IV improved markedly with medical or surgical management while only 16 of 59 cases in the mild groups [I and IIA] improved, almost all surgical cases improved in all categories. 8. There were 5 deaths. occurring between 7 months and 3 years 3 months of treatment of myasthenia gravis. The causes of death were myasthenic crisis in 2 cases, respiratory failure due to candidiasis & radiation pneumonitis in one case, cerebral hemorrhage due to high blood pressure in two case.