• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.32 no.6
• /
• pp.706-712
• /
• 1999

PSD (particle size distribution) for 2,000 mg/$\ell$ natural loess in seawater showed normal distribution cure at 0 minute settling time, accompanying with very large particle distribution range with its mean particle diameter of 31.6 $\mu$m and coencient of variance of $72.6\%$, With elapsed time it showed that the PSD was rapidly changed from normal distribution cure to abnormal distribution curve, steepened the right-hand side of it and its coefficient of variance was getting increased because of rapid settling of large size particles, Cumulative weight distribution showed that 2,000 mg/$\ell$ natural loess in seawater was almost $100\%$ constituted of particles bigger than 20 $\mu$m in diameter. Ratio of $V_s/(D_{bm})^{1/2}$ for loess particles in seawater was increased with increase of particle size in geometrical progression. Almost all loess particles in seawater had Stokes settling velocity not less than 2,255 times of Brownian diffusion coefficient, There was almost to EDL (about 0.4 nm) around natural loess particles in seawater, Thus, there was always LVDW attractive force between loess particles approaching each other in seawater, and almost no EDL repulsive force. Loess particles were not always in the condition of easy floe formation. Concentration of natural loess in seawater increasing from 400 mg/$\ell$ to 10,000 mg/$\ell$, characteristics of the settling was changed from Type I settling (discrete settling) to Type II settling (flocculation settling). PVD (particle volume distribution) showed that natural loess particles in seawater were largely constituted of two types of particles, such as rapidly settling particles and suspended and dispersed particles for a long time. Amount of the latter was much less than that of the former.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.9 no.6
• /
• pp.525-535
• /
• 2004

In this paper, a two-phase DZRCD(Dual Zero Vector Modes RCD) technique is proposed to develope the problem of a conventional two-phase RCD-PWM (Random Centered Distribution PWM) which gives the power spectra of narrow band range in the high modulation index (M). In the proposed DZRCD technique, the zero vector $V_0$ is selected as $V_0$(111) for M$\geqq$0.8. Also, $V_0$ is selected as $V_0$(000) for the modulation indices < 0.8. For the unplementation of the proposed method, a 16-bit micro-controller Cl67 was used and the experiments were conducted with the 1.5kw induction motor under no load condition. The experimental results show that the voltage / current spectra is spread to a wide band range, and the switching noise of motor is reduced by the proposed method compared to the conventional random operation.

• Korean Journal of Environment and Ecology
• /
• v.7 no.2
• /
• pp.187-191
• /
• 1994

A mixed forest community in Tokyusan was studied to determine the adequate plot area of tree stratum for investigating forest community structure. Nineteen nested plots were set up in the studied forest community, and species-area curve and performance curve were established. According to species-area curve, the minimum plot area where a given percentage increase in plot area produced less than the same percentage increase in number of species was 500$m^2$. The minimum plot area where a given percentage increase in plot area produced less than the half of the percentage increase in number of species was 1,000$m^2$. According to performance curve of the importance values of the major species, the minimum plot area where the importance value of the major species was distinguished from each other was 900$m^2$, and the minimum plot area was 500$m^2$ except for a big tree of Pinus densiflora distributed unexpectedly. According to performance curve of species diversity, the minimum plot area was 400$m^2$. Similarity indices between plot area above 900$m^2$ and total plot area were more than 90% and similarity indices between plot area above 400$m^2$ and total plot area were more than 85%. It may be as a conclusion that minimum plot area was generally about 500$m^2$ and in case of requiring more accuracy, minimum plot area was about 1,000$m^2$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2003.10a
• /
• pp.537-541
• /
• 2003

The a-Si:H TFTs using ferroelectric of SrTiO$_3$, as a gate insulator is fabricated on glass. Dielectric characteristics of ferroelectric is better than SiO$_2$, SiN. Ferroelectric increases ON-current, decreases threshold voltage of TFT and also breakdown characteristics. The a-Si:H deposited by PECVD shows absorption band peaks at wavenumber 2,000 $cm^{-1}$ /, 635 $cm^{-1}$ / and 876 $cm^{-1}$ / according to FTIR measurement. Wavenumber 2,000 $cm^{-1}$ /, 635 $cm^{-1}$ / are caused by stretching and rocking mode SiH1. The wavenumber of weaker band, 876 $cm^{-1}$ / is due to SiH$_2$ vibration mode. The a-SiN:H has optical bandgap of 2.61 eV, refractive index of 1.8 - 2.0 and resistivity of 10$^{11}$ - 10$^{15}$ aim respectively. Insulating characteristics of ferroelectric is excellent because dielectric constant of ferroelectric is about 60 - 100 and breakdown strength is over 1 MV/cm. TFT using ferroelectric has channel length of 8 - 20 $\mu$m and channel width of 80 - 200 $\mu$m. And it shows drain current of 3 $\mu$A at 20 gate voltages, Ion/Ioff ratio of 10$^{5}$ - 10$^{6}$ and Vth of 4 - 5 volts.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.4
• /
• pp.339-347
• /
• 2000

An algicidal bacterium, Micrococcus sp. LG-5 against the harmful dinoflagellate, Cochlodinium polykrikoides was isolated. The optimal conditions for the highest algicidal activity of bacterial culture filtrate showed in the range of $20{\~}30^{\circ}C$, at pH 7.0 and $3.0{\%}$ of NaCl concentration. In addition, $IC_(50)(mean of 50{\%} inhibitory concentration)$ of the culture filtrate against C. polykrikoides after incubation of 5 days was $0.482{\%}$. To investigate heat and pH stability of the culture filtrate of Micrococcus sp. LG-5, the culture filtrate ($pore size, 0.1 {\mu}m$) was heated to $121^{\circ}C for 15 min$ and adjusted pH from 2.0 to 10.0. There were no significant changes in algicidal activity by heat treatment and the pH change between pH from 5.0 to 10.0. The algicidal substances produced from Micrococcus sp. LG-5 were mainly detected in the fraction of $10,000{\~}1,000$ MWCO (molecular weight cut-off). The culture filtrate of Micrococous sp. LG-5 showed antimicrobial activity against Enterococcus faecalis, Escheiichia coli, Uebsiella pneunioniae and Vibrio altinolyticus, but did not show against Pseudomonas aeminosa, P. Buorescens, Salmonella typhi, Staphylococcus aureus, V. cholerae and V parahaemolyicus. The culture filtrate of Micrococcus sp. LG-5 was examined against 16 phytoplankton species and showed the algicidal activity against Ajexandzium tuarense, Eutreptiella Drnnastin, Gymnodinium catenatum, G. mikimotoi, G. sanguineum, eyodinium impuaicum, Heterocapsa triquetra, Heterosipa akashiwo, Prorocentrum micans and Pyraminonas sp.. However no algicidal effects of Micrococcus sp. LG-5 were observed against Chlamydomonas sp., Cylindrotheoa closterium, P. mininum, P. triestimum, Pseudonieschia sp. and Sczipuiella trochoidea. On the other hand, algicidal activity on the tested marinelivefood was not detected except for Isochrysis galbana. In addition, physiological responses of cultured olive flounder (Paralichthys oliraceus) exposed to $1 and 10{\%}$ of the culture filtrate of Micrococcus sp. LG-5 were measured. There were no clear changes in AST, GGT, creatinine, urea, total cholesterol, total protein, albumine, $Mg^(+2), Ca^(+2), Na^+, K^+, and Cl^-$. These results indicate that olive flounders were not affected when they were exposed to the culture filtrate of Micrococcus sp. LG-5.

• 전기의세계
• /
• v.16 no.1
• /
• pp.65-67
• /
• 1967

최근 전력수요의 급속한 증가는 전력기기 생산업체의 실력을 Test 할 절호의 기회를 만들어 주었다. 한영공업의 변압기는 송배전용, 또는 공업용으로 널리 쓰이는 용량 500-30,000kVA, 전압 154KV이하의 내철형을 표준품으로 제작하고 있다. 이런 정도의 용량의 변압기로서는 구조가 간단한 내철형이 중량도 가볍고, 표준화가 용이하며, 충격절연내력도 표준절연내력 자체가 그리 크지 않은데다, 구조상 내부전위진동 주기도 짧으므로 충분히 이것에 견디는 강도를 갖인것을 경제적으로 제조가능하다. 한영공업의 내철형변압기는 과거 80년 이상의 경험을 가진 세계적 제작업자인 Westinghouse의 기술지도와 엄선한 외국자재로서 고도의 신뢰성을 갖는 전력용변압기를 공급하게 된것이다.

• Pediatric Infection and Vaccine
• /
• v.18 no.1
• /
• pp.61-67
• /
• 2011

Purpose : This study was performed to investigate the epidemiologic characteristics of human bocavirus (HBoV)-associated lower respiratory tract infections (LRTIs) in children. Methods : Nasopharyngeal aspirate samples were obtained from 658 children who had been hospitalized for LRTIs in Seoul National University (SNU) Children's Hospital and SNU Bundang Hospital from March 2000 to September 2005. Multiplex RT-PCR was performed to detect 11 respiratory viruses including respiratory syncytial virus, adenovirus, rhinovirus, parainfluenza viruses 1 and 3, influenza viruses A and B, human metapneumovirus, HBoV, human coronavirus (HCoV) OC43/ 229E, and HCoV-NL63. Clinical data were reviewed retrospectively. Results : Overall, respiratory viruses were detected in 325 (49.4%) among 658 patients. HBoV was detected in 62 cases (9.4%) and was responsible for 19.1% of virus-positive cases. HBoV was prevalent among infants and young children aged from 3 months to 5 years with the mean age of 25.3 months. Co-detection of HBoV and other respiratory viruses was observed in 37.1% which is significantly higher than average co-detection rate (12.3%) among overall virus-positive cases (P=0.000). HBoV was identified mainly in late spring and early summer from May to July. Conclusion : This study describes epidemiologic features of HBoV in Korean children compared with those associated with other respiratory viruses. HBoV was prevalent among LRTIs in childhood, especially in late spring and early summer season in Korea.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.25 no.4
• /
• pp.701-707
• /
• 1996

Xylanase(EC. 3. 2. 1. 8) was purified approximately 10.2 fold from Aspergillus niger SFN-416 by a sequential process of ammonium sulfate fractionation, Sephadex G-100 gel filtration and DEAE-Sephacel ion exchange chromatography. Molecular weight of the enzyme was approximately 31,000 daltons. The optimum pH and temperature of the enzyme activity were 3.5 and $50^{\circ}C$ respectively. The enzyme activity was enhanced by $Fe^{2+}$ and $Mn^{2+}$, and inhibited by $Hg^{2+}$. The activity was decreased by addition of methanol, ethanol, isopropanol and 1-butanol at a concentration of 10%(v/v).

• Proceedings of the Plant Resources Society of Korea Conference
• /
• 2023.04a
• /
• pp.19-19
• /
• 2023

제비꽃속 34분류군의 61개체를 대상으로 엽록체 DNA 게놈 특이 유전자의 특징을 알아보고자 하였다. 61개체의 엽록체 게놈 전체 길이는 155,535~158,940 bp 로 모두 전형적인 사분할 구조였다. 지역별로는 LSC 지역이 84,826~87,250 bp, SSC 지역이 16,338~18,654 bp, 그리고 IR 지역이 26,029~27,192 bp 였다. 유전자 개수는 131개로 84개 protein coding-gene, 37개 tRNA 유전자, 8개 rRNA유전자, 그리고 2개의 유사유전자인 𝜓rps19, 𝜓ycf1으로 구성되어 있었다. LSC/IRa 경계에 위치한 rps19 유전자 길이는 279 bp로 모든 분류군에서 동일하였으며, 𝜓rps19의 길이는 다양했으나 유전자 개수에는 영향을 미치지 않았다. SSC/IRb 경계에 위치한 ycf1 유전자 길이는 약 5,600 bp 였으나, V. japonica (MZ151699) 1개체에서는 다른 종에 비해 약 1,000 bp 위치에서 발생한 점돌연변이로 인해 종결 코돈이 나타나는 특징을 보였다. 한편 13분류군의 23개체에서는 𝜓ycf1의 길이가 650 bp 정도 짧은 것을 확인하였는데, 이 종류들은 원예종인 V. tricolor (ON262802) 이외에는 모두 줄기가 없는 분류군들로 IR 지역의 확장과 SSC 지역의 수축에 의한 것으로 판단된다. ndhF는 대체로 SSC 지역에 위치하나, V. inconspicua (MZ065354), V. mongolica (MW802534, ON548135), V. yunnanfuensis (MW802541) 등 4개체에서는 IRa/SSC 경계에 위치하면서 유사유전자가 발생하였고, 그 결과 다른 제비꽃 종류에 비해 유전자 개수가 132개로 차이를 보였다. 또한, V. collina (OP271831), V. mirabilis (MH256000), V. tricolor (ON262802) 등 3분류군에서는 SSC 지역이 inversion 되어 엽록체 이성질체가 존재함을 확인하였다. 이상의 결과를 종합하면, 제비 꽃속 엽록체 게놈 61개체의 ycf1, 𝜓ycf1, ndhF, 𝜓ndhF 등은 유전자 길이와 개수 등에 차이를 보이는 것으로 나타났으며, 제비꽃속에서도 엽록체 이성질체가 존재함을 확인할 수 있었다.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.37 no.4
• /
• pp.405-409
• /
• 2008

This study was performed to investigate the physiological activities of Viola mandshurica. Antioxidant activity was evaluated by measuring total phenolic contents, reducing power, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, 2,2'-azino-di-2-ethyl-benzthiazoline sulphonate (ABTS) radical scavenging activity while anti-diabetic activity was measured by inhibition activities on ${\alpha}$-amylase and ${\alpha}$-glucosidase. V. mandshurica extracts were prepared by extracting with four different solvents (methanol, ethanol, acetone, and water). The methanol extract showed the highest total phenol content (34.49 mg/g gallic acid equivalents) among the extracts. The water extract showed the highest reducing power (0.454) at the concentration of $1,000{\mu}g$/mL. The acetone extract showed the most potent radical scavenging activity. DPPH and ABTS radical scavenging activity of the acetone extract at the concentration of $1,000{\mu}g$/mL were 21.13% and 43.53%, respectively. The inhibitory activity of acetone extracts against ${\alpha}$-amylase and ${\alpha}$-glucosidase showed more than 100% at the concentration of $1,000{\mu}g$/mL. The results indicate that V. mandshurica might have potential antioxidant and anti-diabetic activities.