• Journal of the Korean Society of Propulsion Engineers
• /
• v.10 no.1
• /
• pp.44-53
• /
• 2006

In this study, the non-destructive computed tomography was adopted to observe the density profile of the needle-punched Carbon/Carbon(C/C) composites nozzle throat. The density profile of C/C was evaluated within ${\pm}0.01g/cm^3$ with 98.74% confidence when the correction of the image and high signal-to-noise ratio were achieved by the optimization of the beam hardening, the electrical noise and the scattered X-ray. The density variation of C/C with the computed tomography was in good agreement with the results obtained by the water immersion method and the observation with scanning electron microscope.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
• /
• 2003.10a
• /
• pp.185.1-185
• /
• 2003

최근 세계적으로 편의식품의 소비가 증가하면서 과채류의 신선도를 유지시킴과 동시에 편리하게 조리에 이용할 수 있는 최소가공식품(minimally processed foods)의 시장이 확대되고 있다. 그러나, 기개발된 최소가공 과채류는 미생물학적 안전성 및 색 변화 등의 문제점을 수반하여 이 부분을 보완할 수 있는 기술개발이 시급한 실정이다. 따라서 본 연구는 감마선을 이용하여 미생물학적 안전성 및 저장성을 향상시킨 최소가공식품 개발의 일환으로, 김치를 모델식품으로 원료배추의 최소가공식품을 개발하기 위해 미생물학적, 이화학적 품질특성을 조사하였다. 절단한 배추의 염농도가 3%가 되도록 절임 및 함기포장 하고, 0~2 kGy의 선량으로 감마선 조사한 후 4$^{\circ}C$에서 3주 동안 저장, 분석하였다. 비조사구의 경우 총균수, coliform Salmonella spp., lactic acid bacteria 등이 모두 7 log cycle 수준을 보였으며, 감마선 조사시 2-5 log cycle 이상 감소하는 것으로 나타났다. 또한 색도, 물성 등은 감마선 조사에 의해 비조사구와의 유의적인 차이를 보이지 않았으며, 감마선 조사시 절임배추의 발효현상에 의해 나타나는 pH 저하를 억제할 수 있어 저장성을 향상시킬 수 있는 것으로 나타났다. 결론적으로 감마선 조사를 이용한 최소가공 절임배추의 개발시 미생물학적 안전성을 보장하면서, 이화학적 특성이 저하되지 않고 저장성을 향상시킨 최소가공식품을 개발할 수 있었다.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
• /
• 2003.10a
• /
• pp.165.2-166
• /
• 2003

최소 가공 수박의 가공과 유통 중 품질 열화에 있어 가장 중요한 문제는 과육의 조직연화이다. 따라서 본 연구에서는 세포 분리를 제한하고 과실 조직의 경도를 유지시키는데 효과가 있는 것으로 알려져 있는 칼슘제제 중 calcium chloride, calcium lactate, CaO를 처리하여, 최소 가공 수박에서 조직연화로 발생되는 품질저하 억제에 가장 효과적인 칼슘제제를 알아보고자 하였다. 수박의 과육부위를 2cm의 정육면체 형태로 절단한 후, 0.5% calcium chloride, 0.5% calcium lactate, 0.05% CaO용액에 3분 동안 침지시켰다. 그리고 fan을 이용하여 상온에서 30분 동안 draining한 다음 PP tray에 담아 PP film로 sealing하고 $10^{\circ}C$에서 일주일간 저장하며 품질변화를 살펴보았다. 호흡특성은 0.05% CaO 및 0.5% calcium chloride용액을 처리한 구가 호흡률이 가장 낮게 나타났다. 가용성고형분은 처리 직후 처리구의 함량이 무처리구에 비해 다소 낮아지는 경향을 보였으나, 저장기간 중 0.5% calcium chloride 용액처리구는 다른 처리구에 비하여 큰 함량 변화 없이 당도가 일정 수준으로 유지되었다. pH 변화는 0.5% calcium chloride용액 처리구에서 변화가 가장 작았으며, 경도변화 역시 저장 초기값과 비교하였을 때보다 감소가 적게 일어나 다른 처리구에 비하여 연화 저해에 효과가 있는 것으로 확인되었다. 따라서 최소가공 수박에 대해 칼슘제제 중 calcium chloride용액 처리가 품질유지에 가장 효과적임을 알 수 있었다.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2009.11a
• /
• pp.177-177
• /
• 2009

사용후 핵연료의 건식처리 시 핵연료 다발을 절단하여 voloxidation 즉 휘발산화처리를 하면 고온에 의해 분리가 가능한 핵분열생성물의 분리와 우라늄의 산화에 의한 부피팽창으로 핵연료가 쪼개져서 입도가 작아지고 또한 핵연료가 피복재에서 쉽게 박리되게 된다. 그 결과 폐기물 처리 시에 발열핵종으로 폐기물의 저준위화시에 분리가 요망되는 Cs-137이 분리되는 장점이 있어 습식 재처리에 있어서도 바람직하다. 건식처리에 있어서는 voloxidation 으로 처리된 피복재에는 금속 지르코늄에 불순물로 함유된 우라늄의 의한 방사화 생성물과 피복재 표변에 부착/침투한 방사화 생성물이 방사능을 갖게 된다. 이러한 부착된 TRU 잔류물은 통상 1% 미만으로 알파핵종의 방사능이 원자로에서 배출시에는 고준위 기준치의 약 100배 수준이었다가 30년 냉각후에는 약 1/10 수준으로 저준위화 된다. 지르코늄 금속중에 불순물로 함유된 우라늄의 방사화로 생기는 방사능은 고준위 기준치의 10% 를 넘지 않아서 피복재의 저준위화시에 고려할 필요가 없다. 발생열은 방출시에 고준위 기준치의 약 30 배 수준에서 5년 냉각후에는 기준치 미만이 되며 30년후에는 1/8000 정도로 저준위화 된다. 사용후 핵연료를 습시처리시에 발생하는 고준위 폐기물 중 약 1/4 가 피복재 (hull) 임을 고려하면 피복재의 저준위화는 사용후 연료의 건식처리에 있어서도 필수적인 과정이다. 특히 미국의 고준위 폐기물 처분장 Yucca Mt.의 포기와 우리의 고준위 폐기불 처분장이 공론화되는 싯점에서 저준위화는 매우 필요한 기술이다. 피복재는 방사성 물질의 침투두께가 0.01mm 미만이 대부분으로 저준위화에는 표면제염에 의한 저준위화가 주로 연구되어왔다. 표면제염에 의한 저준화는 이온 빔, laser에 의한 방법, dry ice 분사에 의한 방법이 시도되었다. 염소기체를 이용하여 지르코늄의 산화막을 제거하고자 하였으나 이 산화막이 안정적이어서 표변의 연마, 아크릴 칼의 사용, 표면을 눌러서 처리하는 등 전처리하여서 염소기체 반응에 의한 표면제거 실험이 가장 효과적임이 실험적 결과이었다. 이러한 전처리로 방사능을 1/100 수준으로 낮춘다고 하더라도 지르코늄 금속중에 불순물로 함유된 우라늄의 방사화에 의해 중저준위 폐기물의 범주에서 벗어나지 않으므로 재활용에는 제한이 있다. 또한 전처리(표면제염)하여 분리되는 고준위는 다른 고준위 염폐기물과 함께 처리하여 발열 핵종을 제거하면 중저준위화가 가능하다. 저준위화 된 hull폐기물에는 지르코늄 금속에 불순물로서 함유되어있는 우라늄에 의한 방사능을 갖는데 이들의 제거나 분리는 지르코늄 합금 피복재 원료물질에 불순물로 함유하는 우라늄의 함량을 낮추는 것과 유사한 문제이다. 현재까지 지르코늄합금 피복재에 우라늄이 불순물로 함유된 것을 사용함으로 원자로내에서 방사화되어서 방사능을 갖게 되는 것은 피할 수가 없다. 따라서 저준위화 처리된 피복재는 장기 보관으로 방사능을 감쇠시켜서 재활용하도록 한다. 처리 방법으로는 초고압 압축저장, 시멘트 고화, 합성암석에 의한 고화법 등으로 장기간 보관 후에 금속으로서 재활용한다.

• Archives of design research
• /
• v.17 no.1
• /
• pp.383-392
• /
• 2004

The power tools is the product using working power generated by electric motor. Many companies are manufacturing numerous devices. Main features of tools are included various assembled products, small, light and solid and durable enough to match several standards. Fundamental requirements for the product is excellent performance and convenience for use. The quality of them depends on the equipped motor'(s) capability, accuracy of gear and endurance against worn-out. By adapting the state-of-the-art parts, they could be used in the place from home to heavy industry broadly. They can be classified electronic drills, grinders, saws and sanders families for the household appliances. For industrial tools, bore drill, grinder, polisher, and driver drill are classified as special and high priced group. This study presents the strategy of power tool development of BOSCH, BLACK&DECKER and KEYANG. Their products were analyzed in terms of product line and product mix concept. Then they are examined by design elements, such as color, shape and material for housing. As an analysis method, the image scale parameter and criteria were applied to each company's product.

• Sleep Medicine and Psychophysiology
• /
• v.6 no.1
• /
• pp.52-60
• /
• 1999

Objectives: With the object of finding the appropriate conditions and algorithms for dimensional analysis of human EEG, we calculated correlation dimensions in the various condition of sampling rate and data aquisition time and improved the computation algorithm by taking advantage of bit operation instead of log operation. Methods: EEG signals from 13 scalp lead of a man were digitized with A-D converter under the condition of 12 bit resolution and 1000 Hertz of sampling rate during 32 seconds. From the original data, we made 15 time series data which have different sampling rate of 62.5, 125, 250, 500, 1000 hertz and data acqusition time of 10, 20, 30 second, respectively. New algorithm to shorten the calculation time using bit operation and the Least Trimmed Squares(LTS) estimator to get the optimal slope was applied to these data. Results: The values of the correlation dimension showed the increasing pattern as the data acquisition time becomes longer. The data with sampling rate of 62.5 Hz showed the highest value of correlation dimension regardless of sampling time but the correlation dimension at other sampling rates revealed similar values. The computation with bit operation instead of log operation had a statistically significant effect of shortening of calculation time and LTS method estimated more stably the slope of correlation dimension than the Least Squares estimator. Conclusion: The bit operation and LTS methods were successfully utilized to time-saving and efficient calculation of correlation dimension. In addition, time series of 20-sec length with sampling rate of 125 Hz was adequate to estimate the dimensional complexity of human EEG.

• Journal of Ginseng Research
• /
• v.27 no.3
• /
• pp.146-150
• /
• 2003

This study was carried out to obtain basic information on breeding using PCR-aided RFLP technology which can identify the variation inter- and intra-species of ginseng in the level of DNA. It was intended to investigate banding pattern on psbA and rbeL genes of chloroplast DNA in ginseng after treating with restriction enzymes. To isolate psbA and rbcL genes of chloroplast, both psbA-N, psbA-C primer and rbcL-N, PX-1 primer were used. As a result, 1,008 bp band of psbA gene and 1,336 bp band of rbcL gene were appeared, which was optimal and expected molecular weight. In addition, primers to isolate atpB, rpoB, trnL, and trnF genes were used, resulting in the expected 1366, 900, 1500 and 1008 bp bands. Genes of psbA and rbcL isolated by PCR were cut by restriction enzymes, Sau3A, TaqI, AluI, HaeIII, and RFLP pattern was investigated. KG line and other species of ginseng were cut by TaqI treatment, and bands were located in 800 bp. The treatment treated by AluI also showed the same 800 bp band in KG line and other species. In HaeIII treatment, 500 bp of faint bands were shown in case of KG line, whereas any bands were not observed in other species. All chloroplast genes formed bands by PCR amplification. However, it was not evident to distinguish intra-or inter-species of ginseng after restriction enzyme treatment. Therefore, more restriction enzyme treatment or sequence comparison method should be considered for further experiment.

• The Journal of Engineering Geology
• /
• v.26 no.4
• /
• pp.447-460
• /
• 2016

Samples of Hangdeung granite and Berea sandstone containing sliding planes were prepared by saw-cutting and polishing using #100 or #600 grinding powders. Their basic friction angles were then measured directly in direct shear tests and triaxial compression tests, and also in tilt tests, which measure the angles indirectly. Although the angles measured by the direct methods were generally accurate, those measured along certain planes were greatly different from the others depending on the condition of the plane. The tilt tests yielded similar angles regardless of the sliding plane condition or the rock type; however, the error range was relatively wide. Sliding planes polished by the grinding powders yielded more accurate results than those cut by the saw and tested without polishing, as polishing ensured consistent conditions among all the planes. Sliding planes polished using #100 grinding powder yielded better results than polishing with #600 grinding powder. Therefore, the basic friction angles measured along the sliding planes polished using #100 grinding powder, as obtained in direct shear and triaxial compression tests, were the most reliable. The angle could also be measured satisfactorily by tilt testing along sliding planes polished with #100 grinding powder.

• Journal of Korea Water Resources Association
• /
• v.49 no.4
• /
• pp.275-282
• /
• 2016

The objective of this study is to propose a new method to determine the drought event and the design drought severity. In order to define a drought event from precipitation data, theory of run was applied with the cumulative rainfall deficit. When we have a large amount of rainfall over the threshold level, in this study, we compare with the previous cumulative rainfall deficit to determine whether the drought is relieved or not. The recurrence characteristics of the drought severity on the specific duration was analyzed by the conditional bivariate copula function and confidence intervals were estimated to quantify uncertainties. The methodology was applied to Seoul station with the historical dataset (1909~2015). It was observed that the past droughts considered as extreme hydrological events had from 10 to 50 years of return period. On the other hand, the current on-going drought event started from 2013 showed the significantly higher return period. It is expected that the result of this study may be utilized as the reliable criteria based on the concept of return period for the drought contingency plan.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.6C
• /
• pp.251-258
• /
• 2011

Steel pipe piles have been used as various deep foundation materials for a long time. Recent increase in steel material cost has made engineers reluctant in using it even with its good quality and ease of construction. Therefore when constructing with steel pipe pile, the decision to reuse the excessive pile length that is cut off from the designed pile head elevation after pile driving can be cost saving. This has caused many constructors to reuse the pile leftovers with new piles, but the absence of quantitative structural capacity behaviors of steel pipe pile after pile driving or appropriate countermeasures and standards in reusing steel pipe pile has resulted in wrong applications, pile structural integrity problems, inappropriate limitation of reusable pile length, etc. The structural performance analysis between a new pile and a pile that has undergone working state and ultimate state stress level during pile driving was performed in this research by means of comparing the results between the dynamic pile load test, tensile load test, charpy energy test and fatigue test for high strength steel of $440N/mm^2$ yield strength. Test results show that under working load conditions the yield strength variation is less than 2% and for ultimate load conditions the variation is less than 5% for maximum total blow count of 3000. The results have been statistically analyzed to check the sensitivity of each factors involved. From the test results, reusability of steel pipe pile lies not in the main pipe yield strength deviation but in the reduction of absorb energy, strength changes and quality control at the welded section, shape deformation and local buckling during pile driving.