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Optimization of Soldering Process of Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.7Cu-1.6Bi-0.2In Alloys for Solar Combiner Junction Box Module (태양광 접속함 정션박스 모듈 적용을 위한 Sn-3.0Ag-0.5Cu 및 Sn-1.0Ag-0.7Cu-1.6Bi-0.2In 솔더링의 공정최적화)

  • Lee, Byung-Suk;Oh, Chul-Min;Kwak, Hyun;Kim, Tae-Woo;Yun, Heui-Bog;Yoon, Jeong-Won
    • Journal of the Microelectronics and Packaging Society
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    • v.25 no.3
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    • pp.13-19
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    • 2018
  • The soldering property of Pb-containing solder(Sn-Pb) and Pb-free solders(Sn-3.0Ag-0.5Cu and Sn-1.0Ag-0.7Cu-1.6Bi-0.2In) for solar combiner box module was compared. The solar combiner box module was composed of voltage and current detecting modules, diode modules, and other modules. In this study, solder paste printability, printing shape inspection, solder joint property, X-ray inspection, and shear force measurements were conducted. For optimization of Pb-free soldering process, step 1 and 2 were divided. In the step 1 process, the printability of Pb-containing and Pb-free solder alloys were estimated by using printing inspector. Then, the relationship between void percentages and shear force has been estimated. Overall, the property of Pb-containing solder was better than two Pb-free solders. In the step 2 process, the property of reflow soldering for the Pb-free solders was evaluated with different reflow peak temperatures. As the peak temperature of the reflow process gradually increased, the void percentage decreased by 2 to 4%, but the shear force did not significantly depend on the reflow peak temperature by a deviation of about 0.5 kgf. Among different surface finishes on PCB, ENIG surface finish was better than OSP and Pb-free solder surface finishes in terms of shear force. In the thermal shock reliability test of the solar combiner box module with a Pb-free solder and OSP surface finish, the change rate of electrical property of the module was almost unchanged within a 0.3% range and the module had a relatively good electrical property after 500 thermal shock cycles.

Poststructural Curriculum and Topic-centered Framework of The New Science Curriculum (후기 구조주의 교육과정과 새 과학과 교육과정의 주제 중심 내용 구성)

  • Kwak, Young-Sun;Lee, Yang-Rak
    • Journal of the Korean earth science society
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    • v.28 no.2
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    • pp.169-178
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    • 2007
  • In this research we diagnosed the actual status of the 7th National science elective curriculum and suggested a way to select and organize the content of the new science elective curriculum. The first science education reform was grounded in the structuralism where the structure of discipline was valued above everything else. On the other hand, the second science education reform suggested alternative interpretations of students' opportunity to learn, putting a brake on the structuralist thinking. According to the survey result, the majority of the science elective courses are in need for revision because the contents are overcrowded, too difficult in light of students' learning readiness, failed to draw students' interest in science, and are overlapped and repeated among the 10th grade science, high school science I and II. In particular, Earth Science II and physics II are the most unfavorable courses among students. Thus, we recommended a fundamental change be made in the new curriculum in addition to the optimization of the content. In this paper, we suggested 'topic-centered content organization' for the science elective course I, i.e., Physics I, Chemistry I, Biology I and Earth Science I that is designed for both science track and non-science track students. Since curriculum provides students with an 'opportunity to learn', a curriculum study should focus on what the 'opportunity to learn' is that students ought to be offered. Based on the result of this study, we recommended one way to select and organize the content of high school elective curriculum.

극성 (0001) 및 반극성 (11-22) n-ZnO/p-GaN 이종접합 발광 다이오드의 광전 특성 분석에 대한 연구

  • Choe, Nak-Jeong;Lee, Jae-Hwan;Han, Sang-Hyeon;Son, Hyo-Su;Lee, Seong-Nam
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.310-310
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    • 2014
  • ZnO박막은 넓은 밴드갭 (3.37 eV), 높은 여기 결합 에너지 (60 meV)를 가지는 육방정계 우르자이트(hexagonal wurtzite) 결정구조를 가지는 II-VI족 화합물 반도체로, 가시광선 영역에서의 높은 광학적 투과도 특성과 자외선 파장에서 발광이 가능한 장점을 가진다. 최근, ZnO박막 성장 기술이 상당히 발전하였지만, 아직까지도 p-형 ZnO박막 성장 기술은 충분히 발전하지 못하여 ZnO의 동종접합 LED는 아직 상용화되지 않고 있는 실정이다. 따라서, 많은 연구 그룹에서 p-GaN, p-SiC, p-diamond, p-Si 등과 같은 p-type 물질 위에 n-type ZnO를 성장시킨 이종접합 다이오드가 연구되고 있다. 특히, p-GaN의 경우 ZnO와의 격자 불일치 정도가 1.8 % 정도로 작다는 장점이 있어 많은 연구가 이루어 지고 있다. 일반적으로 c-축을 기반으로 한 극성ZnO 발광다이오드에서는 자발 분극과 압전 분극 현상에 의해 밴드 휨 현상이 발생하고, 이로 인해 전자와 정공의 공간적 분리가 발생하게 되어 발광 재결합 효율이 제한되고 있다는 문제가 발생한다. 따라서, 본 연구에서는 극성 (0001) 및 비극성 (10-10) n-ZnO/p-GaN 발광다이오드의 성장 및 발광 소자의 전기 및 광학적 특성에 대한 비교 연구를 진행하였다. 금속유기 화학증착법을 이용하여 c-면과 m-면 위에 각각 극성 (0001) 및 반극성 (11-22) GaN박막을 $2.0{\mu}m$ 성장시킨 후 Mg 도핑을 한 p-GaN을 $0.4{\mu}m$ 성장시켜 각각 극성 (0001) 및 반극성 (11-22) p-GaN템플릿을 준비하였다. 이후, N2분위기 $700^{\circ}C$에서 3분동안 열처리를 통하여 Mg 도펀트를 활성화시킨 후 원자층 증착법을 이용하여 동시에 극성 및 반극성 p-GaN의 위에 n-ZnO를 $0.11{\mu}m$ 성장시켜 이종접합구조의 발광소자를 형성하였다. 이때, 극성 (0001) p-GaN 위에는 극성의 n-ZnO 박막이 성장되는 반면, 반극성 (11-22) p-GaN 위에는 비극성 (10-10) n-ZnO 박막이 성장됨을 HR-XRD로 확인하였다. 극성 (0001) n-ZnO/p-GaN이종접합 발광다이오드의 전계 발광 스펙트럼에서는 430 nm 와 550 nm의 두 피크가 동시에 관찰되었다. 430 nm 대역의 파장은 p-GaN의 깊은 준위에서 발광하는 것으로 판단되며, 550 nm 피크 영역은 ZnO의 깊은 준위에서 발광되는 것으로 판단된다. 특히, 10 mA 이하의 저전류 주입시 550 nm의 피크는 430 nm 영역보다 더 큰 발광세기를 나타내고 있다. 하지만, 10 mA 이상의 전류주입 하에서는 550 nm의 영역보다 430 nm의 발광세기가 더욱 증가하는 것을 확인할 수 있었다. 이것은 ZnO의 밴드갭이 3.37 eV로 GaN의 밴드갭인 3.4 eV다 작기 때문에 우선적으로 ZnO의 깊은 준위에서 발광하는 550 nm가 더욱 우세하지만, 지속적으로 전류주입 증가에 따른 캐리어 증가시 n-ZnO에서 p-GaN로 전자가 넘어가며 p-GaN의 깊은 준위인 430 nm에서의 피크가 우세해지는 것으로 판단된다. 반면에, 비극성 (10-10) n-ZnO/반극성 (11-22) p-GaN 구조의 이종접합 발광다이오드로 전계 발광 스펙트럼에서는 극성 (0001) n-ZnO/p-GaN에 비하여 매우 낮은 전계 발광 세기를 나타내고 있다. 이는, 극성 n-ZnO/p-GaN에 비하여 비극성 n-ZnO/반극성 p-GaN의 결정성이 상대적으로 낮기 때문으로 판단된다. 또한, 20 mA 영역에서도 510 nm의 깊은 준위와 430 nm의 발광이 관찰되었다. 동일한 20 mA하에서 두 피크의 발광세기를 비교하면 430 nm의 영역은 극성 n-ZnO/p-GaN에 비하여 매우 낮은 값을 나타내고 있다. 이는 반극성 (11-22) p-GaN의 경우 극성 (0001) p-GaN에 비하여 우수한 p-형 특성에 기인한 것으로 판단된다.

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Synthesis of Methanol from Carbon Dioxide (I). Study on Cu / ZnO Catalyst System (이산화탄소에 의한 메탄올 합성 (제 1 보). Cu / ZnO 촉매계 연구)

  • Sung Yun Cho;Ki Won Jun;Dae Chul Park;Kyu Wan Lee
    • Journal of the Korean Chemical Society
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    • v.33 no.5
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    • pp.558-567
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    • 1989
  • The synthesis of methanol from carbon dioxide and hydrogen was studied for various compositions of Cu/ZnO catalyst system. Effect of the composition ratio of CuO and ZnO on the catalytic activity in the above reaction and the relationship between the activity and the characteristics of the catalysts were explained from the result of surface area measurements, SEM, XRD, and XPS. The major products of the reaction were methanol and carbon monoxide. The selectivity to methanol increased with increase of the copper oxide content in the catalyst up to CuO: ZnO = 30:70 weight ratio, and decreased rapidly when the content is above 70%. SEM and BET measurements, indicate that this point corresponds to the increasing point of the catalyst crystallite size and the decreasing point of the surface area. As to the Cu/Cu + Zn atomic ratio, the surface concentration of copper measured by XPS decreased remarkably when the copper oxide content in catalyst was higher than 50%. All the unreduced catalysts had almost same binding energy of Cu(2P3) level, but the binding energy for $Cu(2P^3)$ level of reduced catalysts was lowered than that of calcined catalysts. The surface copper species which was in the maximum amount when the CuO:ZnO composition in the catalyst was 30:70, existed as zero valent copper. This result agreed with the experimental result that the highest rate of methanol formation was observed when the CuO content in the catalyst was 30%. It was postulated that these reduced catalysts performed with a relatively strong basicity because the formation rate of acetone was higher than that of propylene in isopropanol decomposition as measured in a pulse type reactor.

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A new diagnostic method for diabetic neuropathy using $TcpO_2$ ($TcpO_2$ 이용한 당뇨병성 신경병증 환자의 조기진단)

  • Hong, Hyun-Ki;Kim, Sung-Woo;Nam, Ki-Chang;Cha, Eun-Jong;Kim, Deok-Won
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.44 no.3
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    • pp.1-8
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    • 2007
  • PDiabetic neuropathy is one of the most common diabetes related complications including diabetic nephropathy and retinopahty. In clinical practices, nerve conduction velocity (NCV) has been used as a standard method for diagnosing diabetic neuropathy. However, it applies maximum current of 100mA to nerves causing stress and pain to patients. In this study, as a non-invasive method, $TcpO_2$ was utilized to investigate the difference and relationship between $TcpO_2$ and $SpO_2$ of normal and diabetic neuropathy subjects. In addition, a new method of diagnosing diabetic neuropathy using $TcpO_2$ is suggested. 50 normal subjects and 50 diabetic patients with neuropathy diagnosed by NCV participated in this study. Parameters used in this study were $TcpO_2$, $TcpCO_2$, and $SpO_2$. As a result of the $TcpO_2$ measurements, statistical significances were found from $TcpO_2$ of hands and feet from normal and patients group(p<0.01). $SpO_2$ measured from index finger of normal and patient groups showed no statistical significance(p>0.05). On the other hand, $SpO_2$ measured from great toes of normal and patient groups showed statistical significance(p<0.01). Correlation coefficient between $SpO_2$ of finger and $TcpO_2$ of hand was 0.400 (p<0.01) and $SpO_2$ of toe and $TcpO_2$ of foot was 0.471(p<0.01). Both correlation values were statistically significant. Sensitivities and specificities of the $TcpO_2$ method were found to be 66 % and 92 %, respectively. If the suggested $TcpO_2$ method is used periodically, prevention and early diagnosis of diabetic neuropathy would be possible.

Mechanical Property Evaluation of Dielectric Thin Films for Flexible Displays using Organic Nano-Support-Layer (유기 나노 보강층을 활용한 유연 디스플레이용 절연막의 기계적 물성 평가)

  • Oh, Seung Jin;Ma, Boo Soo;Yang, Chanhee;Song, Myoung;Kim, Taek-Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.28 no.3
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    • pp.33-38
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    • 2021
  • Recently, rollable and foldable displays are attracting great attention in the flexible display market due to their excellent form factor. To predict and prevent the mechanical failure of the display panels, it is essential to accurately understand the mechanical properties of brittle SiNx thin films, which have been used as an insulating film in flexible displays. In this study, tensile properties of the ~130 nm- and ~320 nm-thick SiNx thin films were successfully measured by coating a ~190 nm-thick organic nano-support-layer (PMMA, PS, P3HT) on the fragile SiNx thin films and stretching the films as a bilayer state. Young's modulus values of the ~130 nm and ~320 nm SiNx thin films fabricated through the controlled chamber pressure and deposition power (A: 1250 mTorr, 450 W/B: 1000 mTorr, 600 W/C: 750 mTorr, 700 W) were calculated as A: 76.6±3.5, B: 85.8±4.6, C: 117.4±6.5 GPa and A: 100.1±12.9, B: 117.9±9.7, C: 159.6 GPa, respectively. As a result, Young's modulus of ~320 nm SiNx thin films fabricated through the same deposition condition increased compared to the ~130 nm SiNx thin films. The tensile testing method using the organic nano-support-layer was effective in the precise measurement of the mechanical properties of the brittle thin films. The method developed in this study can contribute to the robust design of the rollable and foldable displays by enabling quantitative measurement of mechanical properties of fragile thin films for flexible displays.

Characteristics of Flue Gas Using Direct Combustion of VOC and Ammonia (휘발성 유기 화합물 및 암모니아 직접 연소를 통한 배기가스 특성)

  • Kim, JongSu;Choi, SeukCheun;Jeong, SooHwa;Mock, ChinSung;Kim, DooBoem
    • Clean Technology
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    • v.28 no.2
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    • pp.131-137
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    • 2022
  • The semiconductor process currently emits various by-products and unused gases. Emissions containing pollutants are generally classified into categories such as organic, acid, alkali, thermal, and cabinet exhaust. They are discharged after treatment in an atmospheric prevention facility suitable for each exhaust type. The main components of organic exhaust are volatile organic compounds (VOC), which is a generic term for oxygen-containing hydrocarbons, sulfur-containing hydrocarbons, and volatile hydrocarbons, while the main components of alkali exhaust include ammonia and tetramethylammonium hydroxide. The purpose of this study was to determine the combustion characteristics and analyze the NOX reduction rate by maintaining a direct combustion and temperature to process organic and alkaline exhaust gases simultaneously. Acetone, isopropyl alcohol (IPA), and propylene glycol methyl ether acetate (PGMEA) were used as VOCs and ammonia was used as an alkali exhaust material. Independent and VOC-ammonia mixture combustion tests were conducted for each material. The combustion tests for the VOCs confirmed that complete combustion occurred at an equivalence ratio of 1.4. In the ammonia combustion test, the NOX concentration decreased at a lower equivalence ratio. In the co-combustion of VOC and ammonia, NO was dominant in the NOX emission while NO2 was detected at approximately 10 ppm. Overall, the concentration of nitrogen oxide decreased due to the activation of the oxidation reaction as the reaction temperature increased. On the other hand, the concentration of carbon dioxide increased. Flameless combustion with an electric heat source achieved successful combustion of VOC and ammonia. This technology is expected to have advantages in cost and compactness compared to existing organic and alkaline treatment systems applied separately.

A Study on Industries's Leading at the Stock Market in Korea - Gradual Diffusion of Information and Cross-Asset Return Predictability- (산업의 주식시장 선행성에 관한 실증분석 - 자산간 수익률 예측 가능성 -)

  • Kim Jong-Kwon
    • Proceedings of the Safety Management and Science Conference
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    • 2004.11a
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    • pp.355-380
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    • 2004
  • I test the hypothesis that the gradual diffusion of information across asset markets leads to cross-asset return predictability in Korea. Using thirty-six industry portfolios and the broad market index as our test assets, I establish several key results. First, a number of industries such as semiconductor, electronics, metal, and petroleum lead the stock market by up to one month. In contrast, the market, which is widely followed, only leads a few industries. Importantly, an industry's ability to lead the market is correlated with its propensity to forecast various indicators of economic activity such as industrial production growth. Consistent with our hypothesis, these findings indicate that the market reacts with a delay to information in industry returns about its fundamentals because information diffuses only gradually across asset markets. Traditional theories of asset pricing assume that investors have unlimited information-processing capacity. However, this assumption does not hold for many traders, even the most sophisticated ones. Many economists recognize that investors are better characterized as being only boundedly rational(see Shiller(2000), Sims(2201)). Even from casual observation, few traders can pay attention to all sources of information much less understand their impact on the prices of assets that they trade. Indeed, a large literature in psychology documents the extent to which even attention is a precious cognitive resource(see, eg., Kahneman(1973), Nisbett and Ross(1980), Fiske and Taylor(1991)). A number of papers have explored the implications of limited information- processing capacity for asset prices. I will review this literature in Section II. For instance, Merton(1987) develops a static model of multiple stocks in which investors only have information about a limited number of stocks and only trade those that they have information about. Related models of limited market participation include brennan(1975) and Allen and Gale(1994). As a result, stocks that are less recognized by investors have a smaller investor base(neglected stocks) and trade at a greater discount because of limited risk sharing. More recently, Hong and Stein(1999) develop a dynamic model of a single asset in which information gradually diffuses across the investment public and investors are unable to perform the rational expectations trick of extracting information from prices. Hong and Stein(1999). My hypothesis is that the gradual diffusion of information across asset markets leads to cross-asset return predictability. This hypothesis relies on two key assumptions. The first is that valuable information that originates in one asset reaches investors in other markets only with a lag, i.e. news travels slowly across markets. The second assumption is that because of limited information-processing capacity, many (though not necessarily all) investors may not pay attention or be able to extract the information from the asset prices of markets that they do not participate in. These two assumptions taken together leads to cross-asset return predictability. My hypothesis would appear to be a very plausible one for a few reasons. To begin with, as pointed out by Merton(1987) and the subsequent literature on segmented markets and limited market participation, few investors trade all assets. Put another way, limited participation is a pervasive feature of financial markets. Indeed, even among equity money managers, there is specialization along industries such as sector or market timing funds. Some reasons for this limited market participation include tax, regulatory or liquidity constraints. More plausibly, investors have to specialize because they have their hands full trying to understand the markets that they do participate in

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Manufacturing and Functional Properties of Soymilk prepared with Korean and Chinese Soybeans (국내산 및 중국산 대두의 두유 제조 및 기능적 특성)

  • Jeon, Ki-Suk;Park, Shin-In
    • Culinary science and hospitality research
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    • v.21 no.3
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    • pp.68-79
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    • 2015
  • The purpose of this study is to provide preliminary information relating to the applicability of Chinese soybean as functional food material. This study compared the manufacturing characteristics, phenolic compounds contents, and antioxidative activities of soymilk prepared with Korean(Jinpumkong) and Chinese Heinong 48) soybean. Antioxidative activities were measured by in vitro models such as 1,1-diphenyl-2-crylhydrazyl DPPH) radical scavenging activity, and 2,2'-azino-bis(3-ethylbenzothiazoline-6-ulfonic acid ABTS) radical scavenging activity. The physicochemical properties(solid contents, pH, and color) and suspension stability of soymilk were not significantly different between the types of raw soybean. Total phenolic and flavonoid contents of soymilk prepared with Chinese cultivar($20.71{\pm}0.34GAE\;mg/g\;dw$ and $6.31{\pm}0.11QE\;mg/g\;dw$, respectively) were significantly higher than those of soymilk prepared with Korean cultivar $^{***}p<.001$ and $^{**}p<0.01$, respectively). Total tannin content of soymilk prepared with Korean cultivar($2.29{\pm}.22TAE\;mg/g\;dw$) was significantly higher than that of soymilk prepared with Chinese cultivar($^{***}p<0.01$). The electron donating ability(EDA) of soymilk was significantly increased in a dose dependent manner(p<0.05); the soymilk prepared with Chinese cultivar showed significantly higher EDA on the concentration of 2.5 mg/mL(p<0.01) and 10.0 mg/mL(p<0.05) than that of soymilk prepared with Korean cultivar. The antioxidative activities of soymilk were significantly increased in a dose dependent manner on ABTS radical scavenging(p<0.05), and there was no significant difference between the types of raw soybean. These results suggest that Chinese soybean, which contains plenty of phenolic compounds and has superior antioxidant activity, may have great potential as a raw material for functional beverage preparation.

The Clinical and Genetic Characteristics of Three Korean Patients with Glycogen Storage Disease Type V (McArdle Disease) (세 명의 대한민국 제 V형 당원축적근육병(McArdle 병) 환자들의 유전학적 및 임상적 특성 보고)

  • Lee, Sunghee;Kang, Eungu;Kim, Yoonmyung;Lee, Beom Hee;Kim, Gu Hwan;Yoo, Han Wook
    • Journal of The Korean Society of Inherited Metabolic disease
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    • v.16 no.2
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    • pp.93-101
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    • 2016
  • Purpose: McArdle disease, glycogen storage disease type V (GSD V), is one of the most common adolescent-onset glycogen storage diseases. It is caused by recessive mutations in PYGM encoding myophosphorylase, which is critical to glycogen metabolism. Since only a few korean patients have been reported, we will observe the clinical and genetic features of three korean patients with McArdle disease. Methods: We retrospectively reviewed the medical records of three patients with genetically confirmed McArdle disease, including the results of forearm ischemic exercise test, electromyogram, nerve conduction velocity, muscle biopsy, and PYGM analysis in peripheral leukocytes. Results: All three cases were males and their age of symptom onset was 12, 5, 14 years old, respectively. A high basal level of serum creatine kinase was noted in all three patients. They experienced the recurrent episodes of rhabdomyolysis, but second wind phenomenon was not definite. In muscle biopsy, subsarcolemmal space vacuoles including periodic acid schiff stained materials were found in two patients, while no evidence of glycogen storage disease was found in the other. A total of five different mutations, $p.Arg50^*$, p.Trp798Arg, $p.Arg50^*$, p.Glu779del, $p.Asp511Thrfs^*28$ and p.Phe710del, were found in three patients. Avoidance of isometric exercise, aerobic exercise and glucose intake before each exercise were recommended for all patients. Conclusion: The three Korean patients with McArdle disease showed the typical manifestations of the condition. The most mutations were private. Therefore, identification of more cases with long-term follow-up will be required to understand the clinical and genetic features of this disease among Korean population.

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