• 한국추진공학회지
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• 제4권4호
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• pp.50-58
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• 2000

본 연구에서는 RDX가 함유된 HTPB/AP/Al 추진제내에 Ag선을 단선 삽입하여 RDX 함량(0~20%)에 따른 추진제 연소속도와 Ag선 0.15mm를 삽입하였을 때 금속선과 인접한 추진제의 연소속도($r_w$)의 변화를 살펴보았고, RDX 10%가 함유된 추진제를 대상으로 금속선 3종(Ag, Cu, Ni-Cr선)을 직경(0.1~0.6mm)별로 $r_w$/$r_{sb}$와 압력지수(n)의 변화를 고찰하였다. 금속선을 삽입한 RDX를 함유한 니트라민계 추진제의 경우 직경이 0.1 mm인 Ag선을 삽입하였을 때 연소속도 증가비가 압력 1000psia에서 5.94배로 RDX를 함유하지 않은 HTPB/AP추진제의 경우에 비해 약 16.4% 크게 나타났으며, 그 이유는 니트라민계 추진제의 자연발화온도가 상대적으로 낮기 때문이라 판단된다. 또한 금속선의 물리적 성질인 열확산 계수, 녹는점, 직경, 추진제의 열역학 특성치인 연소기체 불꽃온도, 추진제의 자연발화 온도와 연소속도가 $r_w$에 영향을 주는 인자로 고려하여 무차원해석에 의한 실험식을 도출한 결과($r_{wc}$-$r_{we}$)/$r_{we}$ 절대값의 표준편차는 6.11%로 기존의 3개의 무차원군을 사용한 경우의 표준편차보다 17.5% 작아짐을 알 수 있었다.

• 한국대기환경학회지
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• 제20권5호
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• pp.697-711
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• 2004

Severe haze, mist, and fog phenomena occurred in the central part of Korea during 15~25 May 2003 resulted in poor visibility and air quality. When these phenomena occurred, Korean peninsula was under the effects of anticyclone. The atmosphere was stable, and wind speed was so weak. Under this meteorological conditions, air quality was worse and worse. The characteristics of aerosol in Seoul, Incheon, and Gosan (Jeju) during this period are investigated from the $PM_{10}$. TSP concentrations and aerosol number concentrations. Concentrations of $PM_{10}$ and TSP measured at KMA increased upto 176 and 230 J.${\mu}g/m^3$ on 22 May 2003, respectively. Aerosol number concentrations of size range from 0.82 to 6.06 ${\mu}m$ increased in Seoul on 17, 19, and 21~24 May 2003, and the concentrations of $NO_2$ and $SO_2$had maximum value of 0.165 ppm at Gwanak Mt. and 0.036 ppm at Guro-dong on 23 May 2003, respectively. Result from analysis on heavy metal elements showed high concentrations of Zn, Pb, Cr, Ni, Cu, and Cd during 20~24 May 2003. This event is examined by comprehensive analyses of synoptic weather conditions, satellite images, concentrations of suspended particles and air pollutants, and heavy metal elements.

• Journal of Nutrition and Health
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• 제6권3호
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• pp.17-20
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• 1973

Quantitative analysis was achieved by gas-liquid chromatographic method (GLC) with a single column system of OV-17 for 16 of free amino acids in Korean green tea and the contents of mineral in it was determined by atomic absorption flame emission. The results are summarized as follows: 1) Korean green tea contained Mn 1% or over out of the total ash content and $0.05{\sim}0.20%$ in the water extraction, as the major mineral. 2) Ba, Cr, Ni, Pb and V were analyzed also by small quantities relatively and Co, Tin and Ywere not detected in the water extraction. 3) GLC indicated the presence of 16 components in free ammo acids. 4) The quantities of free amino acids in Korean green tea were determined $2.96{\sim}6.61%$ Alanine, $1.01{\sim}l.89mg%$ Glycine, $2.07{\sim}7.81mg%$ Valine, $1.27{\sim}8.76mg%$ Leucine and Isoleucine, $94.31{\sim}316.27mg%$ Threonine, $9.10{\sim}39.91mg%$ Serine, $2.18{\sim}36.76mg%$ Hydroxyproline, $2.72{\sim}5.90mg%$ Proline, $39.64{\sim}70.02mg%$ Aspartic Acid, $25.93{\sim}101.28mg%$ Glutamic Acid and Lysine, $8.32{\sim}18.30mg%$ Phenylalanine and Tyrosine in trace amount. 5) The total free amino acid contents in Korean green tea ranged from 207.24mg% to 516.06mg% and Moo-Deoung tea contained outstandingly high, 516 mg% or over.

• 한국연초학회지
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• 제20권1호
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• pp.5-12
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• 1998

Pot experiment was conducted to investigate the effects of fly ash on growth responses and on accumulation of the heavy metals in soil. Two kinds of fly ash, anthracite and bituminous coal, were treated with different levels of 0, 0.4, 0.8, and 1.2 kg/pot(20L). Tobacco growth was better by application of fly ash than that by the control. However, the early stage of growth by application of bituminous coal, 1.2 kg/pot, was decreased due to the boron toxicity occurred by fly ash. Generally, tobacco yield was significantly increased with applying fly ash, showing the highest yield at 1.2 kg/pot for anthracite and at 0.8 kg/pot for bituminous coal. The content of total nitrogen in leaves was higher with fly ash than that of the control, while the content of calcium in leaves was low, Contents of heavy metal and the other minerals were not significantly different between the control and the treatment of fly ash. Soil pH after experiment was linearly increased with application level of fly ash, indicating that the application of bituminous coal was more effective than that of anthracite. Contents of available phosphate, exchangeable $Ca^{2+}$+ and $Mg^{2+}$ in soil were increased by application of fly ash, especially with bituminous coal. Contents of Cu, Cr, and Ni were increased with application level of bituminous coati even if the contents were still lower than critical levels for farming land. The other heavy metals were similar between the control and the application of fly ash.

• 대한치과보철학회지
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• 제29권2호
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• pp.85-101
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• 1991

The purpose of this study was to determine the optimum range of laser energy density to the enamel surface of permanent incisors when they are irradiated with the pulsed Nd : YAG laser, Laser impacts on each experimental group were made at energy density of $20\sim50J/cm^2$ by 20 pulses of the pulse width 1.2 msec. The author investigated the enamel surface with the sunning electron microscope(SEM) and the surface roughness tester, and measured the shear bond strength between electrolytically etched Ni-Cr-Be alloy casting and composite resin. The obtained results were as follows: 1. The surface roughness of enamel after laser irradiation showed the significant difference level from the energy density $40J/cm^2(P<0.05)$. 2. The mean shear bond strength of etched-metal resin-bonded specimens were $154.23{\pm}33.30kg/cm^2$ at unlased enamel surface and $195.72{\pm}29.56kg/cm^2$ at lased energy density $30J/cm^2$, and showed a significant difference(P<0.05). 8. SEM photographs showed the irregular microcracks and the structural changes of lased enamel surface. 4. SEM photographs of the fracture surface after testing the shear bond strength showed the aspect of interfacial fracture between bonding agent and composite resin at the metal sides.

• Journal of the korean society of oceanography
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• 제35권4호
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• pp.179-191
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• 2000

Both acid-leached and residual Pb in surface sediments of the Yellow Sea are analyzed in order to explain the spatial distribution of Pb contents and to determine a major controlling factor of its geographical distribution. Leached and residual Pb contents in surface sediments, which may have a different origin, show mirrored geographical distribution. Sediments with high residual Pb ( ${\sim}$20 ${\mu}$g/g; northeastern sand) contain low leached Pb (6-8 ${\mu}$g/g) while sediments with high leached Pb ( ${\sim}$20 ${\mu}$g/g; central mud) contain low residual Pb. As a result, total Pb shows little variation spatially. The mirrored distribution of both species also leads the grain-size dependence of Pb contents to be unclear although the grain-size dependence of other trace metals (Cr, Co, Ni etc.) has been well reported in this shelf. High leached Pb contents (>15 ${\mu}$g/g) were also observed in sediments off the Changjiang River mouth and off the Kyunggi Bay where they can be interpreted as the results of diagenetic accumulation and anthropogenic pollution, respectively. Residual Pb enriched in sands of the northeastern area might be from K-feldspar, which in turn allows the suggestion that northeastern sands may have originated from coastal erosion of granitic landmass or directly from nearby rivers.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.147-147
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• 2011

High crystalline nonpolar a-plane (11-20) nitride light emitting diodes (LEDs) have been fabricated on r-plane (1-102) sapphire substrates by metalorganic chemical-vapor deposition (MOCVD). The multi-quantum wells (MQWs) active region is consists of 4 periods the nonpolar a-plane InGaN/GaN(a-InGaN/GaN) on a high quality a-plane GaN (a-GaN) template grown by using the multibuffer layer technique. The full widths at half maximum (FWHMs) of x-ray rocking curve (XRC) obtained from phiscan of the specimen that was grown up to nonpolar a-plane GaN LED layers with double crystal x-ray diffraction. The FWHM values were decreased down to 477 arc sec for $0^{\circ}$ and 505 arc sec for $-90^{\circ}$, respectively. After fabricating a conventional lateral LED chip which size was $300{\times}600{\mu}m^2$, we measured the optical output power by on-wafer measurements. N-electrode was made with Cr/Au contact, and ITO on p-GaN was formed with Ohmic contact using Ni/Au followed by inductively coupled plasma etching for mesa isolation. The optical output power of 1.08 mW was obtained at drive current of 20 mA with the peak emission wavelength of 502 nm.

• Corrosion Science and Technology
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• 제20권4호
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• pp.210-229
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• 2021

To safely operate domestic nuclear power plants approaching the end of their design life, the material degradation management strategy of the components is important. Among studies conducted to improve the soundness of nuclear reactor components, research methods for understanding the degradation of reactor internals and preparing management strategies were surveyed. Since the IGSCC (Intergranular Stress Corrosion Cracking) initiation and propagation process is associated with metal dissolution at the crack tip, crack initiation sensitivity was decreased in the hydrogenated water with decreased crack sensitivity but occurrence of small surface cracks increased. A stress of 50 to 55% of the yield strength of the irradiated materials was required to cause IASCC (Irradiation Assisted Stress Corrosion Cracking) failure at the end of the reactor operating life. In the threshold-stress analysis, IASCC cracks were not expected to occur until the end of life at a stress of less than 62% of the investigated yield strength, and the IASCC critical dose was determined to be 4 dpa (Displacement Per Atom). The stainless steel surface oxide was composed of an internal Cr-rich spinel oxide and an external Fe and Ni-rich oxide, regardless of the dose and applied strain level.

• 자원환경지질
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• 제31권2호
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• pp.111-125
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• 1998

Dispersion, migration and enrichment of environmental toxic elements from the Samkwang Au-Ag mine area were investigated based upon major, minor and rare earth element geochemistry. The Samkwang mine area composed mainly of Precambrian granitic gneiss. The mine had been mined for gold and silver, but closed in 1996. According to the X-ray powder diffraction, mineral composition of stream sediments and soils were partly variable mineralogy, which are composed of quartz, orthoclase, plagioclase, amphibole, muscovite, biotite and chlorite, respectively. Major element variations of the host granitic gneiss, stream sediments and soils of mining and non-mining drainage, indicate that those compositions are decrese $Al_2O_3$, $Fe_2O_3$, MgO, $TiO_2$, $P_2O_5$ and LOI with increasing $SiO_2$ respectively. Average compositional ranges (ppm) of minor and/or environmental toxic elements within those samples are revealed as As=<2-4500, Cd=<1-24, Cu=6-117, Sb=1-29, Pb=17-1377 and Zn=32-938, which are extremely high concentrations of sediments from the mining drainage (As=2006, Cd=l1, Cu=71, Pb=587 and Zn=481 ppm, respectively) than concentrations of the other samples and host granitic gneiss. Major elements (average enrichment index=6.53) in all samples are mostly enriched, excepting $SiO_2$, $Na_2O$ and $K_2O$, normalized by composition of host granitic gneiss. Rare earth element (average enrichment index=2.34) are enriched with the sediments from the mining drainage. Minor and/or environmental toxic elements within all samples on the basis of host rock were strongly enriched of all elements (especially As, Br, Cu, Pb and Zn), excepting Ba, Cr, Rb and Sr. Average enrichment index of trace elements in all samples is 15.55 (sediments of mining drainage=37.33). Potentially toxic elements (As, Cd, Cr, Cu, Ni, Pb, and Zn) of the samples revealed that average enrichment index is 46.10 (sediments of mining drainage=80.20, sediments of nonmining drainage=5.35, sediments of confluent drainage=20.22, subsurface soils of mining drainage=7.97 and subsurface soils of non-mining drainage=4.15). Sediments and soils of highly concentrated toxic elements are contained some pyrite, arsenopyrite, sphalerite, galena and goethite.

• 한국식품위생안전성학회지
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• 제25권4호
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• pp.367-375
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• 2010

이 연구는 통영항 내의 해수와 저질의 특성과 주변횟집의 수질의 품질 특성에 대하여 2008년 6월부터 2009년 5월까지 월 1회 조사를 실시하였으며 그 결과는 다음과 같다. 통영항의 해양수온은 평균 $17.4{\pm}5.77^{\circ}C$, 투명도 평균 $1.9{\pm}0.46$ m, 부유물질 $36.7{\pm}5.00$ mg/L, COD $2.36{\pm}0.80$ mg/L, DO $6.67{\pm}1.54$ mg/L, 염분농도 $32.3{\pm}0.64$‰를 각각 나타내었다. 아질산 질소는 $0.010{\pm}0.005$ mg/L, 질산 질소 $0.050{\pm}0.011$ mg/L, 암모니아 질소 $0.030{\pm}0.007$ mg/L, 인산 인 $0.050{\pm}0.006$ mg/L로 각각 나타났으며, TBT는 검출한계 이하로 검출되었다. 통영항 해수 중의 total coliform은 조사기간 중 < 1.8~22,000 MPN/100 mL 범위에 기하학적 평균값이 164.9 MPN/100 mL이었고 230 MPN/l00 mL을 초과하는 비율은 39.6%를 나타내었다. fecal coliform은 < 1.8~7,900 MPN/100 mL 범위에 기하학적평균값은 33.7 MPN/100 mL, 43 MPN/100 mL을 초과하는 비율은 47.9%로 조사되었다. total coliform에 대한 fecal coliform 검출 비율은 69.2%로 나타났다. 통영항 해수 중의 비브리오는 6월부터 11월에 240주가 검출되었으며, V. alginolyticus가 82주로 34.2%를 차지하여 가장 많이 검출되었고, 그 밖에 parahaemolyticus가 13.8%, V. culnificus 10.0%, V. cholerae non-O1이 0%, V. mimicus 12.5%가 검출되었다. 저질 특성은 함수율이 $56.63{\pm}5.51$ %, 강열감량 $9.20{\pm}1.36$%, COD $7.64{\pm}1.13$ mg/g, AVS $0.07{\pm}0.02$mg/g으로 다른 해역에 비하여 다소 높게 나타났다. 중금속의 함량은 카드뮴(Cd)은 $0.10{\pm}0.05$, 구리(Cu) $4.79{\pm}8.20$, 비소(As) $1.95{\pm}0.17$, 수은(Hg) $0.10{\pm}0.07$, 납은 불검출, 6가크롬은 ($Cr^{6+}$) $0.34{\pm}0.12$, 아연 (Zn) $125.33{\pm}16.40$, 니켈(Ni) $16.34{\pm}1.93$ mg/kg을 나타내었다. 통영항 주변 횟집의 total coliform 및 fecal coliform은 횟집에 따라서 다소 차이가 있었지만 여름철에 주로 검출되었으며, 여름철 집중관리가 요구되었다.