• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.2
• /
• pp.94-101
• /
• 1989

Transport properties of 2DEG at AlGaAs/GaAs interface such as average electron energy, flight distance, each valley occupancy ratio, average electron velocity for various fields are investigated by MONTE-CARLO method. As the electric field increases, more electrons transit drastically from (000) valley to (000) upper valley. This phenomenon shows the nonstationary effect such as velocity overshoot. The duration of the transient decreases from about 1.4 psec for electric field E = 7KV/cm to about 0.7 psec for 12KV/cm. The average electron velocity during transient transport in 2DEG is about 8 times the steady-state velocity for E = 12KV/cm at room temperature. In comparison with bulk GaAs the peak velocity in the 2DEG is higher than that in even pure bulk GaAs at electric field E = 7 KV/cm. On the basis of the fact that the electrons in the 2DEG have larger peak velocity and shorter transient time of velocity than those in the bulk GaAs, it is suggested that the device with 2DEG may obtain higher mobility than that with bulk GaAs.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.4
• /
• pp.111-121
• /
• 1993

Changes in bed forms and subsequent changes in channel roughness by changes in water discharge are discussed with the field data collected from some alluvial rivers in Korea. This study is limited to the following condition of river flow: (1) Medium size alluvial rivers with their widths of 100 m more or less, (2) Straight and prismatic river reach with no additional causes for energy loss but bed friction, (3) Lower-flow regime with Froude number less than 0.5. Major conclusions obtained from this study can be summarized as follows: (1) For the channels considered in this study, the bed roughness expressed by Manning's n increases from 0.02 for the plane beds with no sediment motion to 0.05 for the dune beds, (2) The roughness coefficient for alluvial channels should not be estimated from Strickler-type equations developed for the fixed beds, (3) The method for determining the channel roughness suggested in the present guideline for river works, River Structure Standard, appears to be lack of generality. More research based on the field data collected in Korea is needed in order to improve the existing methods.

• Korean Journal of Environment and Ecology
• /
• v.15 no.1
• /
• pp.57-68
• /
• 2001

해안지역의 녹화 및 조경용으로 유용한 내염성 식물자원임과 동시에 서식지가 급격히 감소하고 있는 순기비나무를 대상으로 하여 생장특성과 번식방법을 규명하기 위한 연구를 수행하였던 바, 그 결과를 요약하면 다음과 같다. 1. 줄기의 생장형태는 포복줄기와 직립줄기가동시에 생장하고, 5개 주요 군락지에 직립줄기의 길이는 평균 46.6cm 이고, 포복경의 초대 길이는 7.6cm에 달하였다. 2. 종작발아율은 황적색의 무처리 종자와 $GA_3$처리 종자에서 71.0~72.3%로 가장 높았으나, 두 처리군사이에는 발아율의 차이가 없었다. 종피현화를 목적으로 한 황산처리는 오히려 종자의 발아를 억제하였다. 3. 종피 색깔이 황적생인 종자는 흑갈색 종자에 비해 평균 21.1%(13~30%)발아율이 높았다. 실득모율은 30% 미만으로 아주 낮았으나 흑갈색 종자에 비해 황적색 종가자 약 2배 높았다. 또한 $LD_{50}$은 황적색 종자가 흑갈색 종자보다 10~20일 짧았다. 4. 종피 색깔과 화학처리가 같은 조건에서 기건저장한 종자와 노천매장한 종자사이에는 발아율, 식득묘율, $LD_{50}$등의 차이가 없었다. 5. 기건저장한 황적색 종자가 바다모래에서 30.3%의 발아율과 10.1%의 실득모율을 나타냈으나, 갯벌흙에서는 전혀 발아되지 않았다. 6. 삽목번식의 경우 추삽에서 발근육은 녹지삽이 가장 높았고, 다음이 반지숙삽, 숙지삽의 순이었다. 발근율이 가장 높은 것은 NAA 200ppm+sucrose 2%를 처리한 녹지로서 96.7%의 발근율을 나타내었다. 발근수는 전반적으로발근율에 비례하는 경향이었다. 7. 하삽에서 NAA 200ppm+sucrose 2%를 처리한 녹지, 반숙지, 숙지의 토양별 발근율은 vermiculite+ perlite(1:1)와 마사토에서는 81.1~87.8%로 높았고, 모래와 해상에서 48.9~77.8%로 낮았다.

• Childhood Kidney Diseases
• /
• v.1 no.2
• /
• pp.144-150
• /
• 1997

Purpose : The kidney is one of the most common sites of cyst formation. Cystic diseases of the kidney are a diverse group of clinicopathologic entities and variable prognosis. They span a wide range of both age of presentation and severity of the renal disease. And many of them are systemic disorders, sharing similar process of cyst formation in other organs. Recently, development of imaging studies has been contributing widely to the diagnosis of the diseases. Treatment, however, is not established satisfactorily. We performed this study to evaluate the occurrence and treatment of cystic diseases of the kidney. Methods : We reviewed retrospectively the medical records of 44 patients with cystic diseases of the kidney in the Department of Pediatrics, during last 11 years. Results : In the 44 patients with cystic diseases of the kidney, 31 patients(71%) had multicystic dysplastic kidney and 11(35%) of them received nephrectomy due to differentiation from neoplasms or severe abdominal distension. Seven patients(16%) had polycystic kidney disease, and all of them were infantile type. Five patients(11%) were diagnosed as having a simple renal cysts. Progression to renal failure was noted in none of the cases. In 14(32%) out of total 44 patients, the diagnosis was made in neonatal or infantile pelted. Conclusion : The incidence of cystic diseases of the kidney appeared very low, but further investigation on their pathogenesis, classification, and indication of treatment is needed.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.9 no.2
• /
• pp.129-142
• /
• 1976

Optimum doses The optimum dose that may be defined as the dose below the maximum permissible dose, yet would bring about a significant storage life extension at refrigerated temperatures, varied with species of fish as well as with the postirradiation storage temperatures. Thus the dose of 0. 1 Mrad was considered to be optimum for the croaker and yellow corvenia at $0^{\circ}C$, while at $5^{\circ}C$ the dose of 0.2 Mrad would be suitable for both species. The roundnose flounder was more radiosensitive and even at the dose of 0.1 Mrad a slight irradiation odor was detected immediately after the radiation treatment. Such degree of irradiation odor disappeared upon storage, therefore, the dose of 0.1 Mrad was considered to be optimum for the roundnose flounder at both $0^{\circ}\;and\;5^{\circ}C$. Storage life extension The croaker meats irradiated at 0.1 Mrad could be held at $0^{\circ}C$ as long as 5 weeks in good acceptable conditions, while the unirradiated control became unacceptable within 2 weeks-3-4 for extension of storage life at $0^{\circ}C$. At the storage temperature of $5^{\circ}C$, the storage life of 0.2 Mrad irradiated samples was extended from less than one week to 4 weeks--4-5 fold extension. The storage life extension of 0.1 Mrad irradiated yellow corvenia at $0^{\circ}C$ was from less than 2 weeks for the unirradiated to 4 weeks-approximately a-s folds and that of 0.2 Mrad irradiated samples stored at $5^{\circ}C$ was from 5 days to 3 weeks 4-5 folds. The roundnose flounder meats irradiated at 0.1 Mrad could held at $0^{\circ}C$ for 3-4 weeks as compared to less than 1 week for the unirradiated and at $5^{\circ}C$ the storage life could be extended from less than 3 days to up to 3 weeks. Thus the storage life extension by 4-5 folds and by 6-7 folds was possible at $0^{\circ}C\;and\;5^{\circ}C$ storage, respectively. Postirradiation storage microbiology and biochemistry In general 10 fold reduction of initial microflora was realized as a result of irradiating fish samples at 0.1 Mrad. The extent of microflora reduction increased with increasing doses applied, but not proportionately dependent. The microbial growth in the irradiated was severely retarded during the subsequent storage period, lagging far behind that of the irradiated control samples except in the late storage phase, when the levels of microflora of the irradiated either approached to or rose above the levels of the unirradiated. The microbiological changes caused by irradiation was reflected in the pronounced suppression of TVB and TMA accumulation during the storage period. This suggests that irradiation treatment brought about both quantitative and qualitative changes in microflora initially present and it is reasonable to suggest that the microflora removed by irradiation in fact represent most of the flora capable of producing TVB and TMA in normal fish spoilage process.

• Childhood Kidney Diseases
• /
• v.13 no.2
• /
• pp.189-196
• /
• 2009

Purpose : The pathophysiologic mechanism of nephrotic syndrome is not yet known clearly. At least in some cases, certain 'circulating factors' are thought to increase the glomerular protein permeability. Considering the systemic effect of the circulating factor on peritoneal membrane, we evaluated the loss of protein through peritoneal membrane in patients on peritoneal dialysis due to the end stage renal disease (ESRD) caused by steroid resistant nephrotic syndrome (SRNS). Methods : We retrospectively reviewed the medical records of 26 pediatric patients on peritoneal dialysis ensued during the period from 2001 to 2007 at our clinic. Twelve patients had SRNS, while 14 patients had ESRD caused by the congenital anomalies of urinary system. Results : While the other parameters including nPNA indicating the adequacy of protein intake were similar between the two groups, serum albumin was lower in SRNS patients than the non-SRNS patients ($3.7{\pm}0.3$ g/dL vs. $4.0{\pm}0.4$ g/dL, P=0.021). Peritoneal protein loss was higher in SRNS patients than in non-SRNS patients ($3,044.4{\pm}837.6\;mg/m^2$/day vs. $1,791.6{\pm}1,244.0\;mg/m^2$/day, P=0.007). The protein permeability of the peritoneal membrane measured by the ratio of total protein concentration in dialysate to plasma was twice as high in SRNS patients as the non-SRNS ($1.06{\pm}0.46%$ vs. $0.58{\pm}0.43%$, P=0.010). After 1 year, peritoneal protein loss increased in both patient groups, but to a significantly greater degree in non-SRNS patient (P=0.023). Conclusion : The results of our study support the notion that in nephrotic syndrome there are some 'circulating factors' with the systemic effect. Since the greater protein loss through peritoneal membrane in SRNS was confirmed in this study, more meticulous nutritional support and close monitoring on the nutrition are required in these patients.

• Korean Journal of Ecology and Environment
• /
• v.43 no.3
• /
• pp.409-417
• /
• 2010

Present study aimed to investigate morphological and physiological change in the tissues of Carassius auratus after exposure against Pb (lead) with various rearing condition. We measured the level of accumulated heavy metal and analyzed ultrastructure with transmission electron microscopy. The heavy metal, Pb, was accumulated in the gill, bone and integument increased drastically for exposure periods, the 40 days. The accumulation of Pb in the gill showed relatively higher than that in other tissues. And accumulated Pb amounts also were increased with exposure time dependent manner in the gill, bone and integument tissues. Also, specific activities of antioxidation enzymes in all tissue after exposure to Pb were increased in the course of exposure. And the activities of SOD from tissues exposed to Pb were increased 2 folds than those from the unexposed but GPX activities were maintained constant. The increased numbers of mucous cells in gill tissues exposed to Pb were determined and morphological changes, such as clubbing and fusion, were shown secondary lamella. Also, exposure of Pb for 40 days on gills tissues cause membrane damage in mitochondria and nucleus. In kidney tissues, the atrophied glomerulus was observed, and the empty space in Bowman's capsule was expanded. Based on the all results, it is suggested that the exposure to the high level of Pb for long period affect on the morphology of tissues, and change the enzymatic balance in C. auratus.

• Journal of Yeungnam Medical Science
• /
• v.5 no.2
• /
• pp.87-93
• /
• 1988

The diagnosis of OPCA could be made clinically with important aid of brain CT scanning, although the definite and conclusive diagnosis only by postmortem pathological determination. We reviewed, clinically and with brain CT examination, 12 cases of patients with OPCA who were admitted to the Yeungnam University Hospital for a recent 5 years. The result were as following. : 1. The distribution of age is from 49 to 72, mainly 50 to 60. Man is more frequent than women at the 4.5 times. 2. The interval period from Sx. onset to diagnosis is 1 year to 6 years. 3. The usual initial Sxs. were dizziness(58%), ataxia(33%), and other less frequent Sxs. were weakness of low extremities, dysarthria, headache and urinary incontinence. The clinical manifestations at the initial diagnosis were cerebellar disturbance(100%), dysarthria(83%), and increased deep tendon reflexes(58%). 4. The results of brain CT finding are like this : ${\cdot}$ the width of cerebellar sulci is more than 1mm, other 4 cases more than 2mm. ${\cdot}$ the width of cerebellar pontine cistern of the patient if usually 3 to 4mm, other 2 cases extended to the 5mm. ${\cdot}$ the A. P and lateral lengths of 4th. ventricle is 4mm and 4 to 8mm respectively. ${\cdot}$ 6 cases of whole patients show coincidentally cerebral atrophy.

• The Korean Journal of Air & Space Law and Policy
• /
• v.22 no.2
• /
• pp.3-25
• /
• 2007

In 2002 Republic of Korea successfully launched a self-made mined proportion rocket and it is expected that she will be able to have own space launching system by 2010. According to Article 14 of the Space Exploration Promotion Act, a new law should be established to impose the limit of compensation for the damage by space accident. Therefore, The Space Accident Liability Act was passed in Korean Congress on Nov. 22, 2007 and it will be enforced in six months. The purpose of this Act is to provide reparation for the damage of the third parties that a launch causes; and the Commonwealth should be insured against any possible space accidents to pay for such a damage. Here space accident means the damages to our life, body, and properties from the launching of space objects. There should be an actual loss to establish the compensation of Liability Act. Article 2 in Liability Act defines "damage" as follows: the term "damage" means loss of life, personal injury or loss of or damage to property of persons. Physical and material damages are included in the conception of damage. The meaning of a launching includes any test launch and launch for a real arrangement which will ultimately provides a wide range of compensation. Article 4 indicates that absolute liability should be imposed in compensating for damage by space accidents. Article 4 also indicates that a launching party should be absolutely liable to compensate for the damage caused by its space object on the surface of the Earth. In general, liability stands where fault is. But if the activity is ultra-hazardous and causes serious harm, the individual needs to compensate for the damage unlimitedly. Because of the many launchings for the Seattleite launching, a launching organization is obligated to the liability insurance in preparation for the space accidents. According to the Article 6 of Space Accident Liability Act, to be insured for the compensation for damage is obligatory. It says: "In accordance with Article 11 in the Space Exploration Promotion Act, the person who wants to receive an approval f3r launching needs to be insured in compensation for the possible damage by space accidents.

• Korean Journal of Food Science and Technology
• /
• v.4 no.2
• /
• pp.100-105
• /
• 1972

This experiment was conducted to investigate the combined effects of radiation and antiseptics on the keeping qualities of pork sausage, which was treated with potassium sorbate and AF-2(2-(-2-furyl)-3-(5-nitro-2-furyl)-acrylamide), and then followed by gamma radiation of 0.25, 0.5, and 0.75 Mrad. Amounts of treated antiseptics were a quarter, half, and full levels of their maximum permissible concentration. Irradiated and unirradiated sausages were stored for 50 days at $5^{\circ}C\;and\;25^{\circ}C$, and their changes in rancidity, volatile basic nitrogen, bacterial counts, pH, and sensory analysis were examined during the storage period. The results obtained are as follows: 1) Preservative effects of antiseptics were manifested at cold storage; antiseptics treatment of a quarter-level and unirradiation following low-temperature storage showed the same good keeping qualities as the combined treatment of full-level antiseptics and radiation of 0.25 Mrad following high-temperature storage. 2) There did not appear to recognize irradiation-odor, while color and odor were deteriorated intensively by storage temperature. Sausage irradiated with 0.75 Mrad has shown slightly noticeable off-odor at the end of storage at $25^{\circ}C$. 3) The most suitable radiation dose was considered to be 0.5 Mrad, which could extend the storage life about $2{\sim}3$ times longer than untreated.