• Tunnel and Underground Space
• /
• v.23 no.6
• /
• pp.480-492
• /
• 2013

After the introduction of geothermal power generation technology based on engineering reservoir creation that can be applied on non-volcanic region, industrial need for studies on the efficient and economic execution of costly deep-depth drilling work becomes manifest increasingly. However, since it is very difficult to predict duration and cost of boring work with acceptable reliability because of many uncertain events during the execution, efficient and organized work management for drilling is not easily achievable. Especially, the round trip that discretely occurs because of the abrasion of bit takes more time as the depth goes deeper and it has a great impact on the work performance. Therefore, a technology that can simulate the occurrence timing and depth of round trip in advance and therefore optimize them is essentially required. This study divided the abrasion state of bit into eight steps for simulation cases and developed a forecast algorithm, i.e., TOSA which can analyze the depth and timing of round trip occurrence. A methodology that can divide a unit section for simulation has been suggested; while the Bourgoyne and Young model has been used for the forecast of drilling rates and bit abrasion extent by section. Lastly, the designed algorithm has been systemized for the convenience of the user.

• Journal of the Korean Society of Radiology
• /
• v.14 no.4
• /
• pp.375-383
• /
• 2020

This study aimed to propose a methodology for quantitatively analyzing problems resulting from the performance and combination of the ionization chamber when using an automatic exposure control (AEC) and to optimize the performance of the digital radiography (DR). In the experimental method, the X-ray quality of the parameters used for the examination of the abdomen and pelvis was evaluated by percentage average error (PAE) and half value layer (HVL). Then, the stability of the radiation output and the image quality were analyzed by calculating the entrance surface dose (ESD) and entropy when the three ionization chambers were combined. As a result, all of the X-ray quality of the digital radiography used in the experiment showed a percentage average error and a half value layer in the normal range. The entrance surface dose increased in proportion to the combination of chambers, and entropy increased in proportion to the combination of ionization chambers except when three chambers were combined. In conclusion, analysis using entrance surface dose and entropy was found to be a useful method for evaluating the performance and combination problems of the ionization chamber, and the optimal performance of the digital radiography can be maintained when two or less ionization chambers are combined.

• The Korean Journal of Food And Nutrition
• /
• v.25 no.2
• /
• pp.407-412
• /
• 2012

Wild grass is edible, and it grows in the mountains or field areas. Wild grass has diverse biological effects, such as antiobesity, anti-cancer, antioxidant activities and immune stimulation. Currently, many studies are aimed at enhancing the efficacy of medicinal foods on biological activity using a bioconversion technology, including the fermentation process. In this study, the quality characteristics and antioxidative activity of the fermented wild grass was investigated. The antioxidant activity of fermented wild grass was assessed by various radical scavenging assays using DPPH(2,2-diphenyl-1-picrylhydrazyl), FRAP(ferric ion reducing antioxidant power), reducing power, and ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)). Moisture contents of the fermented wild grass is $49.6{\pm}0.06%$. Contents of crude ash, crude protein, and crude fat were $0.65{\pm}0.01$, $0.65{\pm}0.04$, and $3.3{\pm}0.59%$, respectively. Moreover, fermented wild grass showed that the hunter's color values were 80.36(lightnees), 11.47(redness), and 44.53(yellowness), respectively. Total phenolic contents of the fermented wild grass was $1,185{\pm}159{\mu}g$ GAE(gallic acid equivalent)/g. The antioxidative activities of the fermented wild grass were significantly increased in a dose dependent manner. In addition, fermented wild grass did not show any cytotoxicity up to 500 ${\mu}g/m{\ell}$. However, the anti-adipogenic effect of the fermented wild grass extract was barely detectable. This antioxidant potential is partly due to the phenolic compounds that are present in the fermented wild grass extracts.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.46 no.2
• /
• pp.185-194
• /
• 2020

This study was conducted to find out the optimal extraction conditions to obtain extracts with a high content of ginsenosides and antioxidant activity using the ginseng berry. After extraction by stirring, ultrasound and microwave method using 70% ethanol and distilled water as solvents, the results of considering the content of ginsenoside Re and Rb1, total polyphenol content, antioxidant activity, and whether it is an environmentally friendly manufacturing method, it was confirmed that the microwave method using distilled water is good method of extraction. The optimization of extraction conditions for microwave method were made by response surface methodology (RSM). Microwave power (50 ~ 200 W, X1), solvent and ginseng berry ratio (5 ~ 20 times, X2) and the extraction time (30 ~ 120 s, X3) were used as independent variables. The model showed a good fit having a determination coefficient of the regression equation of 0.9 or more and a p-value less than 0.05. Estimated conditions for the maximized extraction of ginsenoside contents and total polyphenols were 200 w in microwave power, 20 times in solvent and ginseng berry ratio, and 90 s in extraction time. Predicted values at the optimum conditions were total polyphenols of 6.23 mg GAE/g, ginsenoside Re of 17.69 mg/g, and ginsenoside Rb1 of 16.01 mg/g. In the verification of the actual measurement the obtained values showed 6.33 mg GAE/g, 17.79 mg/g, and 15.59 mg/g, respectively, in good agreement with predicted values.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.559-559
• /
• 2013

KSTAR (Korea Superconducting Tokamak Advanced Research) 장치는 차세대 에너지원 중의 하나인 핵융합로를 위한 과학기술 기반을 마련하기 위해 개발된 중형급 토카막 실험장치로서 토카막 운전 영역의 확장과 안정성 확보, 정상상태 운전 도달을 위한 방법 연구, 최적화된 플라즈마 상태와 연속 운전 실현 등을 주요 목표로 하고 있다. 이를 위해 핵융합 반응에 의한 점화조건과 가까운 상태로 플라즈마를 가열해주어야 하며, 토카막 장치의 저항가열 이외에도 외부에서 추가 가열이 반드시 필요하다. 중성 입자빔 입사 장치는 현재 토카막에서 사용되고 있는 가열장치 중 가장 신뢰성있는 추가 가열 장치라 할 수 있으며 한국 원자력연구원에서는 1997년부터 KSTAR 토카막 실험 장치에 사용될 중성 입자빔 입사 장치를 개발해왔었다. 중성빔 입사 장치는 크게 이온원, 진공함, 열량계, 진공 펌프, 중성화 장치, 이온덤프와 전자석으로 이루어져 있으며, 이중 이온원은 중성빔의 성능을 좌우하는 핵심적인 장치라 할 수 있다. 최근 한국원자력연구원에서는 2 MW 중성 입자빔 입사장치용 이온원 개발을 완료하여 KSTAR 토카막 장치에 설치하였으며, 2013년 현재 KSTAR에는 총 두 개의 이온원이 장착되어 최대 약 3 MW 이상의 중수소 중성 입자빔을 입사하여 KSTAR 토카막 실험의 H-mode 달성과 운전 시나리오 연구에 많은 기여를 하고 있다. 한국원자력연구원에서 최초로 개발된 이온원은 미국 TFTR 장치에서 사용되었던 US LPIS (Long Pulse Ion Source)를 기본으로 하여 국내 개발을 수행하였다. 이 온원은 크게 플라즈마를 발생시키는 플라즈마 발생부와 발생된 이온을 인출 및 가속시키는 가속부로 구성되는데, 개발과정에서 가장 먼저 KSTAR의 장주기 운전에 적합하도록 플라즈마 방전부와 가속부의 냉각회로를 요구되는 열부하에 맞게 설계 수정하였다. 그 후 플라즈마 방전부는 방전 시간과 안정성, 플라즈마 밀도의 균일도, 정격 운전, 방전 효율 등을 고려하여 수정 보완하며 개발을 진행하여왔다. 가속부의 경우 국내 제작기술의 한계를 극복하기 위해 빔 인출그리드를 TFTR의 US LPIS 모델의 슬릿형 그리드 타입에서 원형 인출구 타입으로 변경하였으며, 이후 가속 전극의 고전압 내전력 문제, 빔 인출 전류와 전력, 인출 빔의 광학적 질(quality), 빔 인출 시간 동안의 안정성 등을 위해 그리드의 크기와 간격, 모양 등을 변경하여 개발을 수 행하여 왔다. 이 논문은 한국원자력연구원에서 개발이 진행되어 왔던 이온원들을 시간적으로 되짚어 보면서 현재까지의 성과와 문제점, 그리고 앞으로의 개발 방향에 대해 논의하고자 한다.

• Korean Chemical Engineering Research
• /
• v.56 no.5
• /
• pp.655-662
• /
• 2018

To respond effectively to climate change following the launch of the new climate system, the government is seeking to expand the use of distributed power resources. Among them, the district heating system centered on Combined Heat and Power (CHP) is accepted as the most realistic alternative. On the other hand, the government recently announced the change of energy paradigm focusing on eco-friendly power generation from the base power generation through $8^{th}$ Basic Plan for Long-term Electricity Supply and Demand(BPE). In this study, we analyzed the quantitative effects of profit and loss on the CHP operating business by changing patterns of the heat production, caused by the change of energy paradigm. To do this, the power market long-term simulation was carried out according to the $7^{th}$ and $8^{th}$ BPE respectively, using the commercialized power market integrated analysis program. In addition, the CHP operating model is organized to calculate the power and heat production level for each CHP operation mode by utilizing the operating performance of 830MW class CHP in Seoul metropolitan area. Based on this, the operation optimization is performed for realizing the maximum operating profit and loss during the life-cycle of CHP through the commercialized integrated energy optimization program. As a result, it can be seen that the change of the energy paradigm of the government increased the level of the ordered power supply by Korean Power Exchange(KPX), decreased the cost of the heat production, and increased the operating contribution margin by 90.9 billion won for the 30 years.

• Journal of the Korean Geotechnical Society
• /
• v.34 no.5
• /
• pp.19-35
• /
• 2018

The necessity of predicting the spatial information of the site-specific seismic response, which is essential information for the comprehensive earthquake disaster countermeasures, is increasing for the mid-west urban areas where the earthquake-induced damages can be increased due to frequent occurrence of mid-scale earthquake such as 2016 Gyeongju Earthquake and 2017 Pohang Earthquake. Especially, researches on strategic securing of site survey datasets and understanding the site-specific site response characteristics were conducted for Gyeonggi-do, South Korea. In this study, a GIS-based framework for site-specific assessment of site response and induced vulnerable area in Gyeonggi-do, South Korea was proposed. Geo-Data based on GIS platform was constructed for regional estimation of geotechnical characteristics by collecting borehole and land coverage datasets. And the geo-spatial grid information was developed for deriving spatial distribution of geotechnical layer and site response parameters based on the optimization of the geostatistical interpolation method. Accordingly, base information for Improving earthquake preparedness measures was derived as seismic zonation map with administrative sub-units considering the quantitative site effect of Gyeonggi-do.

• Korean Journal of Remote Sensing
• /
• v.18 no.4
• /
• pp.209-220
• /
• 2002

We carried out studies on SAR image intensity and interferometric phase over oyster sea farms. Strong backscattering was observed in amplitude images, and that was considered as a radar signal double bouncing from horizontal bars. These sea farming structures are not visible in satellite optical images except IKONOS image, so that it demonstrates the value of radar remote sensing as an effective tool in support of sea farm detection. The intensity of the image is sensitive to system parameters including wavelength, polarization, and look direction, but does not correlate to tide height. We found that the strongest backscattering can be obtained by L-band HH-polarization with a look direction perpendicular to the horizontal bar. We also succeeded in generating 21 coherent JERS-1 SAR interferometric pairs over the oyster farms. The general trend of the fringe rate of the interferometric phases appeared to be governed by altitude of ambiguity. The general trend was modeled by an inverse function and removed to have a residual phase. The residual phase showed a linear relation with the tide height. The results demonstrate for the first time that SAR can possibly be used to estimate sea level. However, the r.m.s. error of a regression line is 11.7 cm, and that is so far too large to make reliable assessments of sea level in practical applications. Further studies is required to improve the accuracy specifically using multi-polarization SAR data.

• Korean Chemical Engineering Research
• /
• v.59 no.3
• /
• pp.417-428
• /
• 2021

The combustion characteristics of anthracite, which follow a complex process with low reactivity, must be considered through the dynamic behavior of circulating fluidized bed (CFB) boilers. In this study, computational fluid dynamics (CFD) simulation was performed to analyze the combustion characteristics of anthracite in a pilot scale 0.1 MW_th Oxy-fuel circulating fluidized bed (Oxy-CFB) boiler. The 0.1MW_th Oxy-CFB boiler is composed of combustor (0.15 m l.D., 10 m High), cyclone, return leg, and so on. To perform CFD analysis, a 3D simulation model reactor was designed and used. The anthracite used in the experiment has an average particle size of 1,070 ㎛ and a density of 2,326 kg/m³. The flow pattern of gas-solids inside the reactor according to the change of combustion environment from air combustion to oxygen combustion was investigated. At this time, it was found that the temperature distribution in air combustion and oxygen combustion showed a similar pattern, but the pressure distribution was lower in oxygen combustion. addition, since it has a higher CO₂ concentration in oxygen combustion than in air combustion, it can be expected that carbon dioxide capture will take place actively. As a result, it was confirmed that this study can contribute to the optimized design and operation of a circulating fluidized bed reactor using anthracite.

• Economic and Environmental Geology
• /
• v.53 no.6
• /
• pp.703-713
• /
• 2020

In many geological fields, including hydrogeology, it is of great importance to determine the heterogeneity of the subsurface media. This study briefly introduces the concept and theory of the method that can estimate the hydraulic properties of the media constituting the aquifer, which was recently introduced by Park (2020). After the introduction, the method was applied to the synthetic aquifer to demonstrate the practicality, from which various implications were drawn. The introduced technique uses a global optimization technique called the covariance matrix adaptation evolution strategy (CMA-ES). Conceptually, it is a methodology to characterize the aquifer heterogeneity by assimilating the groundwater level time-series data due to the imposed hydraulic stress. As a result of applying the developed technique to estimate the hydraulic conductivity of a hypothetical aquifer, it was confirmed that a total of 40000 unknown values were estimated in an affordable computational time. In addition, the results of the estimates showed a close numerical and structural similarity to the reference hydraulic conductivity field, confirming that the quality of the estimation by the proposed method is high. In this study, the developed method was applied to a limited case, but it is expected that it can be applied to a wider variety of cases through additional development of the method. The development technique has the potential to be applied not only to the field of hydrogeology, but also to various fields of geology and geophysics. Further development of the method is currently underway.