• 한국물환경학회지
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• 제29권4호
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• pp.523-530
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• 2013

This study has been carried out to clarify the characteristics of discharge and pollutant loading according to flow conditions at jiseok stream watershed (JSW). A flow rate and pollutant load in the study watershed were estimated by equation of stage-discharge and discharge-loads rating curve. By using the methods above, I've evaluated the water quality (WQ) of the JSW if it is satisfied with the standard target. I've collected the data of BOD and T-P from the JSW every 8 days for the duration of 12 months. And then, I've schematized the data upon the load duration curve and the results showed me that the WQ of JSW was satisfied with the standard target. I've also collected the same data every each day for the duration of 12 months from JSW and have schematized the data again. And the results showed that it also was satisfied with the standard target. To be concluded, I've determined that point pollution sources of JSW gives more significant impacts to the WQ than non-point pollution sources of JSW and hence, as time goes, point pollution sources will keep depriciating the WQ of JSW. Therefore, further efforts will be required to JSW to maintain the WQ.

• 한국수산과학회지
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• 제3권3호
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• pp.154-160
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• 1970

우리나라 서해안의 참조기를 대상으로 1967년 6월부터 1968년 5월 사이의 자료에서 체장, 체중 및 인문(鱗紋)조사를 실시하며 다음의 결과를 얻었다. 1. 윤문은 연 1회 형성되고, 형성 시기는 $4\~7$월로, Bae(1960)가 발표한 산란기와 일치되고 있다. 2. 윤군(輪群)별 각 윤경(輪徑)적 평균 성장률은 0.73이었다. 3. 체장(total length)과 인경(鱗徑)과의 관계는 직선 회귀로, 그 관계식은 다음과 같다. L=61.350R+50.184 4. 체중과 체장(total length)과의 관계는 지수 곡선으로 다음과 같다. $$W=4.298L^{3.227}\times10^{-3}$$ 5. Walford의 정차도에 의하여 산출된 이론적인 최대 체강은 346.9mm이었고, 그 관계식은 다음과 같다. $$L_{n+1}=0.6866L_n+10.8730$$ 6. 연령과 체장(total length)과의 관계를 von Bertalanffy의 성장 방정식에 적응시킨 결과 다음과 같았다. $$L_t=346.9(1-e^{-0.376(t+0.609)})$$

• 한국물환경학회지
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• 제29권5호
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• pp.648-655
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• 2013

Nonpoint source pollution characteristics of recreation park was investigated. Runoff ratio of recreation park ranged 23-57%, which was lower than other urban area since impervious area was less than 37%. The average BOD, COD, TOC, SS, T-N, T-P, were 14.09, 32.86, 12.19, 121.51, 7.78 and 0.72 mg/L, respectively. First flush of recreation park was analyzed by normalized cumulative load - volume curve and mass first flush ratio(MFFn), MFF10 for BOD, COD, SS, T-P, T-N, TOC were 2.90, 1.59, 2.15, 2.74, 2.60, and 1.59, respectively. Observed data showed that 62% of pollutant could be removed by storaging 5 mm rainfall-runoff and even 3 mm depth could store up to 50% of pollutant in runoff.

• Investigative Magnetic Resonance Imaging
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• 제21권1호
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• pp.9-19
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• 2017

Background: Normalized cerebral blood volume (nCBV) can be measured using manual or semiautomatic segmentation method. However, the difference in diagnostic performance on brain tumor differentiation between differently measured nCBV has not been evaluated. Purpose: To compare the diagnostic performance of manually obtained nCBV to that of semiautomatically obtained nCBV on glioblastoma (GBM) and primary central nervous system lymphoma (PCNSL) differentiation. Materials and Methods: Histopathologically confirmed forty GBM and eleven PCNSL patients underwent 3T MR imaging with dynamic susceptibility contrast-enhanced perfusion MR imaging before any treatment or biopsy. Based on the contrast-enhanced T1-weighted imaging, the mean nCBV (mCBV) was measured using the manual method (manual mCBV), random regions of interest (ROIs) placement by the observer, or the semiautomatic segmentation method (semiautomatic mCBV). The volume of enhancing portion of the tumor was also measured during semiautomatic segmentation process. T-test, ROC curve analysis, Fisher's exact test and multivariate regression analysis were performed to compare the value and evaluate the diagnostic performance of each parameter. Results: GBM showed a higher enhancing volume (P = 0.0307), a higher manual mCBV (P = 0.018) and a higher semiautomatic mCBV (P = 0.0111) than that of the PCNSL. Semiautomatic mCBV had the highest value (0.815) for the area under the curve (AUC), however, the AUCs of the three parameters were not significantly different from each other. The semiautomatic mCBV was the best independent predictor for the GBM and PCNSL differential diagnosis according to the stepwise multiple regression analysis. Conclusion: We found that the semiautomatic mCBV could be a better predictor than the manual mCBV for the GBM and PCNSL differentiation. We believe that the semiautomatic segmentation method can contribute to the advancement of perfusion based brain tumor evaluation.

• Advances in Traditional Medicine
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• 제7권1호
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• pp.41-45
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• 2007

The roots of the plant Korean ginseng have been extensively used in the traditional Chinese herbal medicine. The effects of chronic administration of Korean ginseng extract (KGE) were investigated on two different anxiety models: the elevated T-maze (for inhibitory avoidance and escape measurements) and the open field test (OFT). Diazepam (1 mg/kg), KGE (10, 30 and 100 mg/kg) were administered orally for 15 days. On the 14th day, mice were previously exposed for 30 min to one of the open arms of the T-maze, 24 h before the test. On 15th day, mice had two exposures to the enclosed and open arm of the elevated T-maze followed by exposure to the open field apparatus. The number of line crossings in the apparatus was used to assess locomotor changes. Cumulative Concentration Response Curve of 5-HT was plotted using rat fundus which were pre-treated in a similar way. Treatment with Diazepam (1 mg/kg) and KGE (10, 30 and 100 mg/kg) significantly (P < 0.05) impaired inhibitory avoidance performance but did not impair escape latency. In OFT, diazepam facilitated locomotion as compared to vehicle and other treatment groups. KGE at any of the selected doses did not impair locomotion. Concentration response curve of 5-HT was shifted towards the right with suppression of maxima in rats treated with KGE. The results suggest that KGE exerts anxiolytic like behaviour in a specific subset of defensive behaviour, particularly those related to generalized anxiety disorder.

• 대한조선학회논문집
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• 제47권1호
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• pp.67-75
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• 2010

Submarine and deep sea diving structures are generally designed based on their ultimate strength. Fatigue strength at welded joint must be also taken into account because working stress is increased due to the increasing of diving depth and using high yield steel. The pressure hulls of submarine are subjected to fluctuating compressive loading. But in addition to the calculated stresses, high residual tensile stresses at welded part have to be considered. The state of stress level of pressure hull is tensile at surface and compressive at deep diving depth. This paper presents the results of an experimental investigation on the crack initiation and growth at the weld toe of T welded joints of HY-100 steel plate under constant amplitude loading. It is also investigated the phenomenon of the fatigue failure and test methods. Fatigue tests have been using real scaled local structural models of full penetration T-welded joint, which is a part of the cylindrical shell structures reinforced by ring stiffeners. Several load ratios under constant amplitude loading are considered in the tests. Crack initiation and growth characteristics are examined based on the beach marks of the cracked section of the test specimens. A design stress-life curve including the design formula is suggested according to tested data.

• 한국물환경학회지
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• 제37권4호
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• pp.249-262
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• 2021

This study investigated the pollution characteristics of the main pollution zone in the Hwangguji watershed and the influence of the tributary on the main stream. The characteristics of the main pollution zone, including, the water quality index (WQI), stream rating, load duration curve (LDC), delivery load density (DLD), and contribution of the tributary to the mainstream, were evaluated by time-series visual heatmap. The WQI of the mainstream of Hwangguji was lowered to the poor (IV) level from the inflow point of Suwon stream (SW) and the LDC excess rate in the T-P was higher than that of BOD₅, especially for the wet season, suggesting that management of non-point source with T-P is preferred. The contribution (%) of the tributaries in the upstream section of Hwangguji watershed were BOD₅ 14.54%, TOC 15.67%, T-N 5.43%, and T-P 6.97%. In particular, the Suwon sewage treatment plant located in the mainstream showed a high contribution of BOD₅ (64.40%) and T-P (53.54%), respectively, due to the high discharge rate (6.019 m³/sec). Meanwhile, Sammi and Gal stream have a large impact on the mainstream with high DLD and poor WQI. Thus, both streams were considered as pollution hot spots. These results provide useful basic data for preparing more effective water quality improvement and management plans in the watershed.

• 한국압력기기공학회 논문집
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• 제10권1호
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• pp.100-106
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• 2014

There is a growing need to introduce advanced pressure vessel steels with higher strength and toughness for the optimizatiooCn of the design and construction of longer life and larger capacity nuclear power plants. SA508 Gr.4N Ni-Cr-Mo low alloy steels have superior strength and fracture toughness, compared to SA508 Gr.3 Mn-Mo-Ni low alloy steel. Therefore, the application of SA508 Gr.4N low alloy steel could be considered to satisfy the strength and toughness required in advanced nuclear power plants. The purpose of this study is to characterize the microstructure and mechanical properties of SA508 Gr.4N low alloy steels. 1 ton ingot of SA508 Gr.4N model alloy was fabricated by vacuum induction melting followed by forging, quenching, and tempering. The predominant microstructure of the SA508 Gr.4N model alloy is tempered martensite having small packet and fine Cr-rich carbides. The yield strength at room temperature was 540MPa, and it was decreased with an increase of test temperature while DSA phenomenon occurred at around $288^{\circ}C$. Overall transition property of SA508 Gr.4N model alloy was much better than SA508 Gr.3 low alloy steel. The index temperature, $T_{41J}$, of SA508 Gr.4N model alloy was $-132^{\circ}C$ in Charpy impact tests, and reference nil-ductility transition temperature, $RT_{NDT}$ of $-105^{\circ}C$ was obtained from drop weight tests. From the fracture toughness tests performed in accordance with the ASTM standard E1921 Master curve method, the reference temperature, $T_0$ was $-147^{\circ}C$, which was improved more than $60^{\circ}C$ compared to SA508 Gr.3 low alloy steels.

• 대한화학회지
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• 제8권4호
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• pp.142-146
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• 1964

The author proposed an equation of fading rate, expressed as ${\Delta}E$=${\Delta}E_{1{\infty}}({{1-e^{-k}}_1}^t)+k_2t$, where ${\Delta}E$=fading of dye (colour difference of N.B.S. unit), ${\Delta}E_{1{\infty}}$=extremity value of fading of molecularly dispersed dye, $k_1$, $k_2$=constants, t=exposure (hours). The validity of above equation, which is connected with the state of dye in fibre, was confirmed by experimental in a range of 2-3 colour fading in grey scale value for assessing change in colour visually, except the case of increasing the fading rate with the time resulted from the break-down of dye particles through the heat effect of light; it was also discussed about possiblity of evaluating of fastness to light of dye in early stage.

• 한국해양공학회지
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• 제23권2호
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• pp.74-80
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• 2009

Surface hardening treatments, such as using the high-frequency induction hardening method, are widely used to increase the fatigue life and prevent the failure of materials by locally increasing the surface hardness. This method, in particular, brings an improvement in static strength by compressive residual surface stress due to the hardening. In this study, the mechanical properties of high-frequency induction hardened SCM440 steel were investigated. These results were also compared with those for base metal and a Q/T (tempering after quenching) treatment specimen. The test results showed that partially high-frequency induction hardened SCM440 steel specimens were more improved in static strength, surface hardness, fatigue limit, and anti-wear than the base metal and Q/T treatment specimens. In particular, the fatigue limit of the high-frequency induction hardened SCM440 steel increased by more than about 52% compared to that of base metal and by about 25% compared to that of the Q/T specimen.