• Journal of the Korean Society for Marine Environment & Energy
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• v.7 no.1
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• pp.42-46
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• 2004

Deep Ocean Water (DOW) is formed within restricted area including polar sea (high latitude) by cooling of surface seawater and globally circulating in the state of isolation from surface seawater. Although it is not as obvious as estuaries mixing, brine ground water is mixture of recirculated seawater and ground water. Seawater having high osmotic pressure infiltrates into an aquifer which is connected to the sea. In order to clarify the characteristics of deep ocean water and brine ground water, we investigated their origins, chemical compositions, water qualities and resources stabilities. While concentrations of stable isotopes (/sup 18/O and ²H) in seawater is 0‰, those in brine ground water is on meteoric water line or shifted toward oxygen line. It means that origin of brine ground water is different than that of deep ocean water. The ions dissolved in seawater (Na, Ca, Mg, K) are present in constant proportions to each other and to the total salt content of seawater. However deviations in ion proportions have been observed in some brine ground water. Some causes of these exception to the rule of constant proportions are due to many chemical reactions between periphery soil and ground water. While DOW has a large quantity of functional trace metals and biological affinity relative to brine ground water, DOW has relatively small amount of harmful bacteria and artificial pollutants.

• Analytical Science and Technology
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• v.7 no.3
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• pp.339-347
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• 1994

A multicolumn system consisted of two valve(10-port and 6-port valve)-three column (28% DC 200, SP 1700 and Chromosorb 102 column) was developed. Nine natural gas components composed of $N_2$, $CH_4$, $CO_2$, $C_2H_6$, $C_3H_8$, $i-C_4H_{10}$, $n-C_4H_{10}$, $i-C_5H_{12}$ 및 $n-C_5H_{12}$ completed all the baseline separation within 18 minutes. The accuracy and the precision of this system was tested. The retention times and the peak areas were determined with a repeatability between 0.02 and 0.16%, and less than 1%, respectively. Calibration curves for natural-gas components were plotted by the partial pressure injection method of pure gases, and good linear relationships for each component were presented. By using these calibration curves the accuracy of the multicolumn system compaired with that of the single column system for a certified standard gas of natural gas. As a result, relative error in the single and the multicolumn system was less than 0.5% and 0.04%, respectively. The result of application of this system in the analysis of importing LNG composition showed that the heating values calculated by the multicolum system were estimated lower compared with those calculated by the single column system and consequently, the importing price of LNG was able to be cut down.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.5
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• pp.615-622
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• 2020

Frangible bullets, which are shredded after impact on a target, reduce the possibility of both ricochet and unexpected injury in shooting training and in mission acts in dams, nuclear power plants, and cultural properties. Reducing the levels of hazardous materials in shooting ranges, such as lead, has become an important agenda for the government and environmental groups. In this study, the shape of a frangible bullet was designed for efficient shredding, and the safety and reliability were confirmed by actual firing under different process conditions. In addition, the physical characteristics, such as compaction pressure, density, and frangibility of each process, were compared by analyzing the microstructure of the sintered frangible bullet. The experiment revealed the smallest fragmentation after impact on the target under the following conditions: Cu-Sn 85:15; sintering temperature, 600℃; sintering time, one hour. Further development of the process conditions and experimental methods will contribute to the performance and environmental improvement of a frangible bullet.

• Journal of the Korean Magnetics Society
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• v.1 no.2
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• pp.60-68
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• 1991

In compacting the melt-spun $Nd_{14}Fe_{76}Co_{4}B_{6}$ and $Nd_{10.5}Fe_{79}Co_{2}Zr_{15}B_{7}$ magnetic powders. the difference in composition induces a different behavior of closed packing rate as a function of aspect ratio of the powders. The $Nd_{10.5}Fe_{79}Co_{2}Zr_{1.5}B_{7}$ alloy having a low Co/Fe ratio (low density) shows the better green density to have an enhanced closed packing rate. An empirical power equation relating the green density with the compacting pressure was obtained such as ${\phi}(g/cm^{2})=5.2~5.6{\times}P^{0.045~0.065}(ton/cm^{2})$. The $Nd_{14}Fe_{76}Co_{4}B_{6}$ alloy having a high Nd/Fe ratio possesses much finer grain size(50~60 nm) than that of $Nd_{10.5}Fe_{79}Co_{2}Zr_{1.5}B_{7}$ alloy and shows the higher coercivity($iH_{c}=14~15kOe$). The higher Nd/Fe ratio in the melt-spun Nd-Fe-Co-B alloy, where the domain wall pinning mechanism was found to be predominant, assists the formation of Nd-rich grain boundary phase acting as a pinning site. The grain boundary ranges over $12~16\;{\AA}$ thick in the Nd-Fe-Co-B alloy while it ranges over $8~12\;{\AA}$ thick in the Nd-Fe-Co-Zr-B alloy.

• Journal of Life Science
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• v.19 no.10
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• pp.1403-1409
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• 2009

The purpose of this study was to compare Obesity Age (OA) and chronological age, to calculate Obesity Age (OA), which gauges the state of obesity, and to analyze presented factors of obesity using expectant factors on middle-aged obese women. The subjects were one hundred twenty seven middle-aged obese women ($49.6\pm7.3$ yr, BMI $29.41\pm2.9$, fat $36.8\pm4.6%$) who participated in different weight loss programs three times. The body composition, physical fitness, blood pressure and blood were measured before the weight loss programs. Informed consent was obtained from all subjects before enrollment in the study. The regression equation is as follows: (1) OAS (Obesity Age Score)=$0.106*X_1+0.035*X_2+0.048*X_3+0.041*X_4+0.003*X_5-0.037*X_6-10.667$ ($X_1$: BMI, $X_2$: weight, $X_3$: %fat, $X_4$: WC, $X_5$: TG, $X_6$: $VO_{2max}$), (2) OA (Obesity Age)=7.3*OAS+49.6*(-1), (3) Z (correction factor)=(CA-49.6)(1-0.03), (4) OAc (corrected Obesity Age)=1.03*CA-7.3*OAS+1.47. The comparison of corrected Obesity Age (OAc) and chronological age did not have any differences, and the average of the OAc was close to chronological age. The correlation coefficient between the OAc and chronological age was r=0.724 (p<0.05). The equation can be utilized for middle-aged obese women, because it could evaluate the obesity-related factors by including BMI, body weight, %fat, waist circumference, triglycerides and $VO_{2max}$.

• Journal of the Korean Electrochemical Society
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• v.15 no.3
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• pp.181-189
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• 2012

We developed a new high-yield synthesis method of free-standing germanium nanocrystals (Ge NCs) by means of the gas-phase photolysis of tetramethyl germanium in a closed reactor using an Nd-YAG pulsed laser. Size control (5-100 nm) can be simply achieved using a quenching gas. The $Ge_{1-x}Si_x$ NCs were synthesized by the photolysis of a tetramethyl silicon gas mixture and their composition was controlled by the partial pressure of precursors. The as-grown NCs are sheathed with thin (1-2 nm) carbon layers, and well dispersed to form a stable colloidal solution. Both Ge NC and Ge-RGO hybrids exhibit excellent cycling performance and high capacity of the lithium ion battery (800 and 1100 mAh/g after 50 cycles, respectively) as promising anode materials for the development of high-performance lithium batteries. This novel synthesis method of Ge NCs is expected to contribute to expand their applications in high-performance energy conversion systems.

• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.637-642
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• 1993

Changes in the physicochemical characteristics and triglyceride molecular species of corn oil under the following condition of hydrogenation; temperature $180^{\circ}C,\;H_{2}$, pressure $2.0{\pm}0.3bar$, the amount of Ni catalyst 0.048%(Ni/oil by wt.) and agitation speed 300 rpm. The rate of hydrogenation, expressed as the reduction rate of the iodine value with respect to time, is first order and high (K>0.01). When the reduction rate of the iodine value was 39.9%, hydrogenation time was 30 min, 18:1 was highest(77.06%), thereafter that was decreased and 18:0 increased. In the triglyceride composition, OLL, LLL were reduced markedly in 10 min, thereafter reduced slightly. And PLO, PLL, OLO were eliminated in first 30 min. On the other hand, POO, PLS(CN52) and OOO, SLO(CN54) were increased sharply, and then that showed little change. The melting point(MP) of hydrogenated corn oil were $27.8^{\circ}C\;and\;44.1^{\circ}C$ after 20 min and 60 min, respectively. Trans isomer content increased to 46.8% during 40 mins of hydrogenation and then decreased insignificantly. The solid fat content were linearly increased with hydrogenation time. Accordingly, it is confirmed that this condition of hydrogenation was selective, preferential elimination of polyunsaturated fatty acid went stepwise and trans isomer was formed promotedly. These results suggest that fat modification techniques can be used for practical application.

• Journal of the Korean Chemical Society
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• v.37 no.11
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• pp.923-928
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• 1993

The series of solid solutions in the $Sr_{1+x}Ho_{1-x}FeO_{4-y}$ (x = 0.00, 0.25, 0.50, 0.75 and 1.00) systems with $K_2NiF_4$ type structure have been prepared at 1550$^{\circ}$C under an atmospheric air pressure. The X-ray powder diffraction spectra of these samples assign that the crystallographic phases are tetragonal system over the whole x range. The lattice volume was increased with increasing the substitution amount of the $Sr^{2+}$ ion. The mole ratio of the $Fe^{4+}$ ion to total iron ions or ${\tau}$ value has been determined by Mohr salt titration of the sample and then the y value was calculated from x and ${\tau}$ values. The ${\tau}$ and y values have been increased with x values. The nonstoichiometric chemical formula are formulated from the general formula of $Sr_{1+x}Ho_{1-x}Fe^3_{1-}\;^+_{\tau}Fe_{\tau}^{4+}O_{4-y}$ replaced by x,${\tau}$ and y values. Mossbauer spectra show the mixed valence state and coordination state of $Fe^{3+}\;and\;Fe^{4+}$ ions. It is found out that the magnetic property of the samples is paramagnetic at room temperature. Electrical conductivity varied within the semiconductivity range of 1.0 to 1 ${\times}\;10^{-9}{\Omega}^{-1}cm^{-1}$. Activation energy of the electrical conductivity was decreased with the $\tau$ value. The conduction mechanism should be explained by the hopping model of the conduction electrons between the valence states of $Fe^{3+}\;and\;Fe^{4+}$ ions.

• Journal of Adhesion and Interface
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• v.21 no.3
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• pp.101-106
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• 2020

In this study, epoxy-modified acrylate was synthesized. The synthesized acrylate was added to the composition for sheet molding compound (SMC) in the range of 5 phr to 15 phr. The prepared SMC prepreg was molded at high temperature and pressure to produce a glass fiber reinforced composite. Physical properties such as tensile and impact strength of the composite were measured, respectively. Experimental data show that the composite with 5 phr of synthesized acrylate has 20% improved tensile strength and 12% improved impact strength than that of the reference sample.

• Journal of Plant Biology
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• v.13 no.1
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• pp.33-46
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• 1970

Pinus densiflora stands are common secondary forest communities on infertile soils in Korea. The stands are results of long severe past biotic pressure such as cutting, burning and grazing. These could be regarded as biotic climax in Korea. Because of their prevalent occurrence, relatively simple species and age composition, and their domestic economic importance, study of their distributional patterns may give some basic knowledge for better utilization of land resources in Korea. To detect distributional patterns and interspecific associations ten pine stands, each of which was homogenious with respect to topography and physiognomy, were subjectively selected from pine stands in Kyunggi Province near Seoul in 1969 and were made object of this study. Four contiguous systematic samples of count for trees, shrubs and seedlings from belt transects were collected from homogeneous areas within ten natural pine stands. The belt transect was 64m or 128m in length, and 1m, 2m or 4m in width. Basic units within the transect ranged from 64 to 256. The data from the contiguous transects were analysed in terms of multiple split-plot experiment. Departure from randomness of stem distribution, i.e., pattern, was tested in terms of variance mean ratio. For the detection of association between species, correlation coefficient was calculated for different block sizes. The values of ${\gamma}$ were tested by the usual t-test. Fine trees within one of the stands showed significant regular distribution through out the blocks. Within other eight stands pines were randomly distributed at basic unit with 4$\times$4m, 2$\times$2m, 2$\times$1m and 1$\times$1m. One significantly clumped distribution at basic unit 2$\times$2m, however, was observed from one of the pine stands. These randomly distributed groups were themselves significantly regularly distributed throughout the blocks for four pine stands. For the other four pine stands, in addition to the random distribution at the basie unit(the primary random group), randomly distributed groups with 32m dimension(the secondary random groups) were also observed. Both the primary and the secondary random groups were significantly regularly distributed at the rest of blocks. Pine seedlings were not distributed randomly thoughout the blocks. Within three of the ten stands they were contagiously distributed. Important shrub species underneath pines such as Querus serrata, Q. acutissima, Leapedeza intermedia, Rhododendron Yedoense var. poukhanenae, Juniperus utilis, Rhododendron mucronulatum var. ciliatum shnwed consistently similar distributional pattern with the pine at each stand. The shrub species pairs; Rhododendron Yedoense var. poukhanenae/Quercus serrata, Rhododendron mucronulatum var. ciliatum/Lespedeza intermedia were significantly negatively associated from 1m to 4m dimensional block sizes but became significantly positively associated from 8m sized blocks on. On the other hand the shrub species pairs; Lespedeza intermedia/Robinia Pseudoacacia, and Lespedeza bicolor var, japonica/Lespedeza intermedia were also significnalty negatively associated from 1m to 8m sized blocks but became significantly positively associated from 16m sized blocks on. The associational pattern between Rhododendron mucronul tun var. poukhanenae and Lespedeza intermedia was not consistent throughout the stands. In some stands negative associations were observed throughout the blocks except NS 32. From these observatons micro-edaphic variation within the pine stands seems not to be great enough to cause distributinal difference of pine trees within the ten pine stands. Among each species and pine seedings, however, the edaphic variation within the pine stands may be great enought to cause distributional variation.