• Tuberculosis and Respiratory Diseases
• /
• v.50 no.2
• /
• pp.236-244
• /
• 2001

Background : Most current research using prognostic scoring systems in critically ill patients have focused on prediction using the first intensive care unit (ICU) day data or daily updated data. Usually the mean ICU length of stay in Korea is longer than in the western world. Consequently, a more cost-effective and practical prognostic parameter is required. The principal aim of this study was to assess the prognostic value of the seventh day(7th day : the average mean ICU length of stay) APACHE III score in a medical intensive care unit. Methods : 241 medical ICU patients from July 1997 to April 1998 were enrolled. The 1st and 7th scores were measured by using the APACHE III scoring system and compared between survivors and non-survivors. Logistic regression analysis was performed to determine the relationship between the $1^{st}$ and $7^{th}$ APACHE III scores and the mortality risk. Results : 1 )The mean length of stay in the ICU was $10.3{\pm}13.8$ days. 2)The mean $1^{st}$ and $7^{th}$ day APACHE III scores were $59.7{\pm}30.9$ and $37.9{\pm}27.7$. 3) The mean $1^{st}$ day APACHE III score was significantly lower in survivors than in non- survivors($49.9{\pm}23.8$ vs $86.3{\pm}32.3$, P<0.0001). 4)The mean $7^{th}$ day APACHE III score was significantly lower in survivors than in non- survivors($30.1{\pm}18.5$ vs $80.1{\pm}30.4$, P<0.0001). 5)The odds ratios among the $1^{st}$ and $7^{th}$ day APACHE III scores and the mortality rate were 1.0507 and 1.0779 respectively. Conclusion : These results suggest that the seventh day APACHE III score is as useful in predicting the outcome as is such like the first day APACHE III score. Therefore, in comparison to the daily APACHE III score, measuring the $1^{st}$ and $7^{th}$ day APACHE III scores are also useful for predicting the prognosis of critically ill patients in terms of cost-effectiveness. It is suggested that the $7^{th}$ day APACHE III score is useful for predicting the clinical outcome.

• Korean Chemical Engineering Research
• /
• v.58 no.1
• /
• pp.84-91
• /
• 2020

The efficiency of the synthetic magnesium silicate used in basic polyols and edible oil purification is evaluated by its purification ability and filtration rate and is affected by the particle size and surface area of magnesium silicate. In this study, it was investigated the change on the particle size of magnesium silicate was influenced by the reaction temperature, injection rate, injection order (Si, Mg) and Mg/Si reaction mole ratio. The synthesized magnesium silicate was compared and analyzed for the synthesis, grinding, and refining processes. In the synthesis process, the reaction temperature and feed rate did not affect the average particle size change of magnesium silicate, while the reaction molar ratio of Mg / Si and the order of injection acted as main factors for the change of average particle size. The average particle size of magnesium silicate increased by 8.7 ㎛ from 54.4 ㎛ to 63.1 ㎛ at Mg injection when Mg molar ratio increased from 0.125 to 0.500, and increased by about 4.8 ㎛ from 47.3 ㎛ to 52.1 ㎛ at Si injection. The average particle size according to the order of injection was 59.1 ㎛ for Mg injection and 48.4 ㎛ for Si injection and the difference was shown 10.7 ㎛, therefore the filtration rate was about 2 times faster under the condition of Mg injection. That is, as the particle size increases, the filtration time is shortened and washing filtration rate can be increased to improve the productivity of magnesium silicate. The cake form of separated magnesium silicate after filtration becomes a solid through drying process and is used as powdery adsorbent through the grinding process. As the physical strength of the dried magnesium silicate increased, the average particle size of the powder increased and it was confirmed that this strength was affected by the reaction molar ratio. As the reaction molar ratio of Mg / Si increased, the physical strength of magnesium silicate decreased and the average particle size after grinding decreased by about 40% compared to the average particle size after synthesis. This reduction of strength resulted in an improvement of the refining ability due to the decrease of the average particle size and the increase of the amount of fine particle after the pulverization, but it resulted in the decrease of the purification filtration rate. While the molar ratio of Mg/Si was increased from 0.125 to 0.5 at Mg injection, the refining ability increased about 1.3 times, but the purification filtration rate decreased about 1.5 times. Therefore, in order to improve the productivity of magnesium silicate, the reaction molar ratio of Mg / Si should be increased, but in order to increase the purification filtration rate of the polyol, the reaction molar ratio should be decreased. In the synthesis parameters of magnesium silicate, the order of injection and the reaction molar ratio of Mg / Si are important factors affecting the changes in average particle size after synthesis and the changes of particle size after grinding due to the changes of compressive strength, therefore the synthetic parameter is an important thing that determines productivity and refining capacity.

• Clean Technology
• /
• v.26 no.2
• /
• pp.145-150
• /
• 2020

Nitrous oxide (N₂O) is one of the six greenhouse gases, and it is essential to reduce N₂O by showing a global warming potential (GWP) equivalent to 310 times that of carbon dioxide (CO₂). Selective catalytic reduction (SCR) is a technology that converts ammonia into harmless N₂ and H₂O by using ammonia as a reducing agent to remove NOx, one of the air pollutants; the process also produces high denitrification efficiency. In this study, the Fe-BEA catalyst was steam-treated at 100 ℃ for 2 h before Fe ion exchange in the fixed bed reactor in order to investigate the effect of the steam-treated Fe-BEA catalyst on the NH₃-SCR reaction. NH₃-SCR reaction test of synthesized catalysts was performed at WHSV = 180 h^-1, 370 to 400 ℃ in the fixed bed reactor. The Fe-BEA(100) catalyst steam-treated at 100 ℃ showed a somewhat higher activity than the Fe-BEA catalyst at 370 to 390 ℃. The catalysts were characterized by BET, ICP, NH₃-TPD, H₂-TPR, and ²⁷Al MAS NMR in order to determine the cause affecting NH₃-SCR activity. The H₂-TPR result confirmed that the Fe-BEA(100) catalyst had a higher reduction of isolated Fe³⁺ than the Fe-BEA catalyst, and that the steam treatment increased the amount of isolated Fe³⁺ as an active species, thus increasing the activity.

• Clean Technology
• /
• v.26 no.2
• /
• pp.102-108
• /
• 2020

In recent years, packed column has been widely used in separation processes, such as absorption, desorption, distillation, and extraction, in the petrochemical, fine chemistry, and environmental industries. Packed column is used as a contacting facility for gas-liquid and liquid-liquid systems filled with random packed materials in the column. Packed column has various advantages such as low pressure drop, economical efficiency, thermally sensitive liquids, easy repairing restoration, and noxious gas treatment. The performance of a packed column is highly dependent on the maintenance of good gas and liquid distribution throughout a packed bed; thus, this is an important consideration in a design of packed column. In this study, hydraulic pressure drop, hold-up as a function of liquid load, and mass transfer in the air, air/water, and air-NH₃/water systems were studied to find the geometrical characteristic for raschig super-ring experiment dry pressure drop. Based on the results, design factors and operating conditions to handle noxious gases were obtained. The dry pressure drop of the random packing raschig super-ring was linearly increased as a function of gas capacity factor with various liquid loads in the Air/Water system. This result is lower than that of 35 mm Pall-ring, which is most commonly used in the industrial field. Also, it can be found that the hydraulic pressure drop of raschig super-ring is consistently increased by gas capacity factor with various liquid loads. When gas capacity factor with various liquid loads is increased from 1.855 to 2.323 kg^-1/2 m^-1/2 S^-1, hydraulic pressure drop increases around 17%. Finally, the liquid hold-up related to packing volume, which is a parameter of specific liquid load depending on gas capacity factor, shows consistent increase by around 3.84 kg^-1/2 m^-1/2 S^-1 of the gas capacity factor. However, liquid hold-up significantly increases above it.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.425-426
• /
• 2013

IIIN계 물질 기반의 광 반도체는 직접 천이형 넓은 밴드갭 구조를 갖고 있기 때문에 적외선부터 가시광선 및 자외선까지를 포함한 폭 넓은 발광파장 조절이 가능하여 조명 및 디스플레이 관련 차세대 광원으로 많은 관심을 받고 있다. 일반적인 청색 및 녹색 발광영역의 활성층으로는 InGaN/GaN 다중양자우물구조를 사용하고 있으나, 장파장의 녹색 발광을 얻기 위해서는 인듐의 함유량이 증가하여야 한다. 하지만, 인듐의 함유량이 증가함에 따라서 InGaN/GaN 다중양자우물 구조내에서 인듐의 편석현상의 발생이 용이하게 되어 계면 특성을 저하할 뿐 아니라, 비발광 센터를 증가하여 발광 효율을 급격히 감소시키는 원인이 되고 있다. 또한, InGaN과 GaN의 큰 성장온도의 차이에 따라 800도 부근의 저온 영역에서 성장된 InGaN층이 1,000도 이상의 고온 영역에서 GaN층이 성장시 InGaN층의 열화 현상이 급격히 발생되고 있다. 이를 억제하기 위해서 금속유기화학증착법의 성장 변수 최적화, 응력제어, 도핑 등의 편석 억제기술 및 보호층이 사용되고 있다. 본 연구에서는 인듐함유량이 증가된 녹색 InGaN/GaN 다중양자우물구조에서 InGaN 우물층 상하부에 도입된 GaN 보호층에 따라 발생되는 양자우물구조의 광학 및 결정학적 특성 분석을 통해 GaN 보호층의 역할을 분석하고자 한다. 본 연구에서는 금속유기화학증착장치를 이용하여 사파이어 기판위에 GaN 템플릿을 성장하고, n-형 GaN, InGaN/GaN 다중양자우물구조 및 p-형 층을 성장하였다. 앞선 언급하였듯이, InGaN/GaN 다중양자우물구조내에 GaN 보호층의 역할을 규명하기 위하여 샘플 A의 경우는 보호층이 전혀 없는 구조이고, 샘플 B의 경우는 InGaN 우물층의 상단부에만, 샘플 C의 경우에는 우물층 상부 및 하단부 모두에 약 2.0 nm 두께의 GaN 보호층을 형성하였다. 이 보호층의 유무에 따른 다중양자우물구조의 계면 특성을 확인하기 위한 X-선 회절을 이용하였고, 광학적 특성을 확인하고 상온 포토루미네선스법을 이용하여 녹색 발광 파장의 변화 및 발광세기를 관찰하였다. 우선적으로, 상온 포토루미네선스법을 이용하여 각 샘플의 발광특성을 확인한 바 상하부 모두에 GaN 보호층이 존재하는 샘플 C의 경우 약 510 nm 부근에서 발광이 관찰되었지만, 상단부에 GaN 보호층이 존재하는 샘플 B는 약 495 nm영역에 발광이 확인되었다. 특히, 전혀 보호층이 존재하지 않는 샘플 A의 경우 약 440 nm에서 발광하는 현상을 관찰하였다. 이는 우물층 상단부 및 하단부에 존재하는 GaN 보호층이 In의 확산을 억제하는 것으로 판단된다. 또한, 발광파장 및 세기를 확인한 바, 보호층의 존재하지 않을수록 단파장화가 발생함에도 불구하고 발광세기는 급격히 약해지는 것으로 보아 계면특성이 저하되어 비발광센터가 증가되는 것으로 판단된다. 이를 구조적으로 확인하기 위하여 X-선 회절법을 통한 ${\omega}$/$2{\Theta}$ 스캔의 결과는 In의 0차 피크가 GaN 보호층이 없을 경우 GaN의 피크 방향으로 이동하는 것으로 보아 GaN 보호층은 우물층 성장 후 GaN 장벽층을 성장하기 위해 온도를 증가시키는 과정에서 In의 확산되는 것으로 판단된다. 또한, 하부 GaN 보호층의 경우 GaN 장벽층 성장 후 온도를 감소시키는 과정에서 성장되므로, 우물층으로부터 In의 탈착현상이 아닌 장벽층과의 상호 확산으로 판단된다. 또한, 계면특성을 확인하기 위해 InGaN의 X-선 위성 피크를 확인한 바 샘플 A의 경우 매우 넓고 약한 피크가 관찰된 반면, 보호층이 존재하는 샘플 B와 C의 경우 강하고 얇은 피크가 확인되었다. 이는 GaN 보호층의 도입으로 인해 계면특성이 향상되는 것으로 판단된다. 따라서, 우리는 InGaN/GaN 다중양자우물구조에서 GaN 보호층은 상부의 열화 억제 뿐아니라, 하부의 장벽층 및 우물층 사이의 상호확산을 억제하는 GaN 보호층의 도입을 통하여 우수한 계면 특성 및 비발광센터의 억제를 얻을 수 있을 것으로 생각되며, 이는 향후 GaN계 발광다이오드의 전계 발광특성을 증가하여 우수한 발광소자를 개발할 수 있을 것으로 기대된다.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.14 no.3
• /
• pp.108-118
• /
• 2012

To investigate the responses of yellow poplar (Liriodendron tulipifera L.) seedlings to the interactive effects of the elevated atmospheric $CO_2$ level and nitrogen addition, we measured biomass, photosynthetic pigments, photosynthesis, and the contents of nitrogen (N) and carbon (C) from the seedlings after 16 weeks of the treatments. Yellow poplar seedlings were grown under the ambient ($400{\mu}mol\;mol^{-1}$) and the elevated (560 and $720{\mu}mol\;mol^{-1}$) CO2 concentratoins with three different N addition levels (1.2, 2.4, and $3.6g\;kg^{-1}$) in the Open Top Chambers (OTC). The dry weight of the seedlings enhanced with the increased N levels under the elevated $CO_2$ concentrations and the increment of the dry weight differed among the different N levels. Photosynthetic pigment content of the yellow poplar leaves also increased with the increase of the $CO_2$ concentration levels. The effects of the N levels on the photosynthetic pigment content, however, were significantly different among the $CO_2$ levels. Photosynthetic rates were affected by the levels of $CO_2$ and N concentrations. Stomatal conductance and transpiration rates increased with increasing $CO_2$ concentration. The carboxylation efficiency of the seedlings without N addition increased under the higher $CO_2$ concentrations whereas that with N addition decreased under the elevated $CO_2$ concentrations. Nitrogen and carbon uptake in leaf, stem, and root increased with the elevated $CO_2$ concentration level and N addition. In conclusion, under the elevated $CO_2$ concentrations, physiological characteristics and carbon uptake of the yellow poplar seedling were improved and increased with N addition.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.40 no.5
• /
• pp.673-681
• /
• 2011

We investigated the effects of an ethanol extract of Eriobotrya japonica Lindl. (loquat) leaves (EJ) on the lipid metabolism of serum, liver, and adipose tissue, and antioxidative activity in rats fed a fat/cholesterol diet for four weeks. Male Sprague-Dawley rats weighing 207 g were divided into 4 groups: a normal diet group (N), a high-fat/high-cholesterol diet group (HFC), a high-fat/high-cholesterol diet group administered 200 mg/kg day EJ (HFC-EJL), and a high-fat/high-cholesterol diet group administered 400 mg/kg/day EJ (HFC-EJH). The serum ALT and AST activities of the EJ groups were lower than those of HFC group, but there was no significant change in serum ALP or LDH activities. The serum total and LDL-cholesterol, atherogenic index, and cardiac risk factor tended to be decreased in the EJ groups compared to the HFC group, while the serum HDL-cholesterol decreased in the HFC group and increased only minimally in the EJ groups. The total cholesterol in liver and mesenteric adipose tissues was lower in the EJ groups than in the HFC group. Triglycerides in the mesenteric and epididymal adipose tissues were lower in the EJ groups than in the HFC group. The liver GSH levels of the EJ groups were significantly lower than the HFC group. The liver TBARS content was significantly lower in the EJ groups than in the HFC group. These results suggest that EJ ethanol extract may improve the lipid metabolism of serum, liver, and adipose tissue and prevent oxidative stress by stimulating antioxidative systems in rats fed a high-fat/high-cholesterol diet.

• Journal of the Korean Geophysical Society
• /
• v.3 no.2
• /
• pp.99-112
• /
• 2000

The Iksan Jurassic Granite shows relatively less fractures and homogeneous rock fabrics, and is one of the most popular stone materials for architectures and sculptures. Almost mutually perpendicular rift, grain, and halfway in the Iksan Jurassic Granite are well known to quarrymen based on its splitting directions, and therefore it should exhibit orthorhombic symmetry. Theoretically, there are 9 independent elastic stiffness coefficients $(C_{1111},\;C_{2222},\;C_{3333},\;C_{2323},\;C_{1313},\;C_{1212},\;C_{1122},\;C_{2233},\;and\;C_{1133})$ for orthorhombic anisotropy. In order to characterize the static and dynamic elastic properties of the Iksan Jurassic Granite, triaxial strains under uniaxial compressive stresses and ultrasonic velocities of elastic waves in three different polarizations are measured. Both experiments are carried out with six directional core samples from massive rock body. Using the results of experiments and the densities measured independently, the static and dynamic elastic coefficients are computed by simple mathematical manipulation derived from the governing equations for general anisotropic media. The static elastic coefficients increase ar uniaxial compressive stress rises. Among those, the static elastic coefficients at uniaxial compressive stress of a 24.5 MPa appear to be similar to the dynamic elastic coefficients under ambient condition. Although some deviations are observed, the preferred orientations of microcracks appear to be parallel or subparallel to the rift, the grain, and the hardway from microscopic observation of thin sections. This indicates that the preferred orientations of microcracks cause the elastic anisotropy of the Iksan Jurassic Granite. The results are to be applied to the effective use of the Iksan Jurassic Granite as stone materials, and can be used for the non-destructive safety test.

• Journal of Korea Water Resources Association
• /
• v.46 no.4
• /
• pp.401-412
• /
• 2013

Water footprint of a product and service is the volume of freshwater used to produce the product, measured in the life cycle or over the full supply chain. Since water footprint assessment helps us to understand how human activities and products relate to water scarcity and pollution, it can contribute to seek a sustainable way of water use in the consumption perspective. For the introduction of WFP scheme, it is indispensable to construct water inventory/accounting for the assessment, but there is no database in Korea to cover all industry sectors. Therefore, the aim of the study is to develop water footprint inventory within a nation at 403 industrial sectors using Input-Output Analysis. Water uses in the agricultural sector account for 79% of total water, and industrial sector have higher indirect water at most sectors, which is accounting for 82%. Most of the crop water is consumptive and direct water except rice. The greatest water use in the agricultural sectors is in rice paddy followed by aquaculture and fruit production, but the greatest water use intensity was not in the rice. The greatest water use intensity was 103,263 $m^3$/million KRW for other inedible crop production, which was attributed to the low economic value of the product with great water consumption in the cultivation. The next was timber tract followed by iron ores, raw timber, aquaculture, water supply and miscellaneous cereals like corn and other edible crops in terms of total water use intensity. In holistic view, water management considering indirect water in the industrial sector, i.e. supply chain management in the whole life cycle, is important to increase water use efficiency, since more than 56% of total water was indirect water by humanity. It is expected that the water use intensity data can be used for a water inventory to estimate water footprint of a product for the introduction of water footprint scheme in Korea.

• Korean journal of food and cookery science
• /
• v.27 no.5
• /
• pp.599-610
• /
• 2011

This study was performed to investigate the effect of water extracts from Namhae special crops (NSC) on improved serum lipid composition using rats fed a 1% cholesterol diet for 4 weeks. Male Wister rats (200-210 g) were divided into six groups: Normal cholesterol diet group (Normal), 1% cholesterol diet group (Control), 1% cholesterol and NSC water extract powder supplemented groups, including, turmeric (Tu-EP), cactus (Ba-EP), aloe vera (Al-EP) and asparagus (As-EP). No significant differences were observed for food intake or body weight gain between the control and experimental groups. However, food efficiency ratio (FER) was the lowest in the As-EP group. The serum levels of total cholesterol and triglycerides in the NSC water powder extract supplement groups were lower than those in the control group. The serum high density lipoprotein (HDL)-cholesterol content in the Tu-EP group was higher than that in the other experimental groups. Very low density lipoprotein (VLDL)-cholesterol content in the As-EP group was similar to that in normal group. Furthermore, the VLDL content in the Al-EP group was lower than that in the normal group. Serum antioxidant activity by TBARS level and DPPH radical scavenging were significantly higher in the Ba-EP group than that in the control group. Hepatic total cholesterol and lipid content in the Al-EP group decreased significantly compared to that in the control group. These results suggest that the NSC water extract may reduce serum cholesterol and prevent oxidative stress by stimulating antioxidative systems in rats fed a 1% cholesterol diet.