• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.205-214
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• 2012

Crack widths play an important role in the serviceability limit state. When crack widths are controlled sufficiently, the reinforcement corrosion can be reduced using only existing concrete cover thickness due to low permeability in the region of finely distributed hair-cracks. Thus, the knowledge about the tensile crack opening is essential in designing more durable concrete structures. Therefore, numerous researches related to the topic have been performed. Nevertheless accurate measurement of a crack width is not a simple task due to several reasons such as unknown potential crack formation location and crack opening damaging strain gages. In order to overcome these difficulties and measure precise crack widths, a displacement measurement system was developed using digital image correlation. Accuracy calibration tests gave an average measurement error of 0.069 pixels and a standard deviation of 0.050 pixels. Direct tensile test was performed using ultra high performance concrete specimens. Crack widths at both notched and unnotched locations were measured and compared with clip-in gages at various loading steps to obtain crack opening profile. Tensile deformation characteristics of concrete were well visualized using displacement vectors and full-field displacement contour maps. The proposed technique made it possible to measure crack widths at arbitrary locations, which is difficult with conventional gages such as clip-in gages or displacement transducers.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.203-203
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• 2019

도시화로 인한 불투수면의 증가는 물순환 왜곡, 비점오염원 발생 및 수생태계 건상성 훼손 등을 야기시키며, 이를 해결하기 위하여 다양한 LID 기법을 적용하고 있다. 일반적으로 LID 내 적용 되는 여재들은 무기성여재로 중량이 크고 미세공극의 부재로 물리화학적 및 생물학적 저감기능이 제한적이다. 따라서 본 연구에서는 중량성이 낮은 생물폐자원을 선정하여 LID 시설 적용성평가를 수행하고자 한다. 생물폐자원은 발생량, 경량성 및 용이성을 고려하여 꼬막껍질(CS)과 호두껍질(WS)을 선정하였다. 생물폐자원의 산화부식을 고려하여 무기성 여재인 화산석과 혼합하여 Bioretention 시설에 적용하였으며, 여재 혼합비율에 따라 총 3가지의 Case 로 구성하였다. 식생은 구절초와 꽃댕강나무를 식재하였으며, 여재의 물리적 특성 분석을 위하여 적용 전과 후의 SEM(Scanning Electronic Microscope)을 수행하였다. 모니터링은 도로퇴적물 100g과 물 110L를 제조하여 인공강우유출수를 이용하여 수행하였으며, $0.0003{\sim}0.007m^3/sec$의 유속으로 주입하였다. 시설의 유입 및 유출부에서 유량 측정 및 수질 시료를 채취하였으며, 채취된 시료는 수질오염공정 시험법에 준하여 입자상 물질, 유기물, 영양물질 및 중금속 등을 분석하였다. Bioretention 시설의 모니터링 결과를 이용하여 물수지 및 TSS 저감 효율을 산정하였으며. 물수지 분석결과 시설의 저류율은 Case 1(soil) > Case 3(WS+RV) > Case 2(CS+RV) 순으로 나타났다. 시설 내 공극률이 가장 낮았던 Case 1에서 저류율이 약 55%로 가장 높게 것으로 분석되었다. Case 3(WS+RV)은 Case 2(WS+RV)와 시설 내 공극률이 유사함에도 불구하고 저류율이 약 10% 높은 것으로 분석되었다. 오염물질 저감효율 분석 결과, TSS와 TP의 제거효율은 모든 Case에서 약 75% 이상으로 높게 나타났으며, COD의 경우 모래를 적용한 Case 1에 비해 생물폐자원인 꼬막껍질과 호두껍질을 적용한 Case에서 약 1.3배 이상 높게 나타났다. 호두껍질과 꼬막껍질의 SEM 분석 결과 표면에 다공성이 형성되어 있는 것으로 조사되었다. 이는 여과 및 저류기작으로 인한 물순환 효과증대와 다공성과 돌기사이로 인한 입자상의 물질 여과 및 흡착으로 인하여 오염물질의 제거효율이 증대 된 것으로 평가된다. LID시설 내 생물폐자원과 무기성여재를 적절히 배합하여 복합여재로 조성할 경우 침하현상을 방지할 뿐만 아니라 저류 및 침투기능 향상과 미생물의 서식환경을 제공하기에 물순환 회복 및 비점오염물질 저감에 기여할 것으로 평가된다.

• Journal of the Mineralogical Society of Korea
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• v.5 no.2
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• pp.109-121
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• 1992

For the purpose of mineralogical and chemical study on the topazes from various localities of world(Brzail, China, India, Nigeria and Sri Lanka), electron microprobe analysis(EPMA), neutron activation analysis(NAA), X-ray diffractometry, Raman spectroscopy, etch test, scanning electron microscopy, refractive index, specific gravity, fluid inclusion were performed. The chemical composition in topaz was discussed along with its physical and structural properties. Variations in the unit-cell dimension and physical properties of topaz were found to have a close relations in the unit-cell dimension and physical properties of topaz were found to have a close relationship with extent of substitution of $OH^-\;for\;F^-$. According to neutron activation analyses, the trace elements had no effects on the physical properties of topaz. Raman spectra showed that the peaks of topaz were different in intensity from one locality to another. Etching defects in topaz includes negative crystal defect o point-bottom pit(India, Nigeria) and net work defect of curl-bottom pit(Brazil, China). Fluid inclusions in topaz may be classiffied into liquid $CO_2$-bearing inclusion, gaseous inclusion, halite, sylvite-bearing inclusion and liquid inclusion. The results of this study can be useful to devising artificial coloring methods for topaz with different mineralogical compositions.

• Journal of Gastric Cancer
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• v.5 no.1
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• pp.1-9
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• 2005

Purpose: The debate is still on-going as to whether a transthoracic esophagectomy (TTE) or a transhiatal esophagectomy(THE) is the proper treatment for patients with cardia and esophageal cancers. This study tries to demonstrate and assess the efficacy and the validity of both surgeries. Materials and Methods: In a retrospective study, data from 52 cases of patients with esophageal and/or cardia cancer who received a surgical operation during the last decade were analyzed. Results: A TTE was done in 20 cases and a THE in 32 cases. The average times for the operations were 558.0 min for a TTE and 451.7 min for a THE (P>0.05). The estimated blood loss was 1,825.0 ml in a TTE and 1459.4 ml in a THE (P>0.05). The amounts of transfusion during the operations were 3.9 units in a TTE and 2.6 units in a THE (P<0.05). Post-operative complications occurred in 15 cases of TTE and 23 cases of THE. The average length of stay in the hospital was 25.6 days for a TTE and 20.6 days for a THE. The 5-year survival rate was $10\%$ for TTE patients and $28\%$ for THE patients (P>0.05). Conclusion: For most factors, including morbidity and mortality, there was no statistically significant difference between a TTE and a THE. However, a THE is expected to be more convenient, leading to a shorter operative duration, a shorter post-operative hospitalization and lesser amounts of hemorrhage and transfusion. Hence, the THE may be a more valid or efficient surgical method for those patients with cardia and esophagus cancer who require a resection of the esophagus. (J Korean Gastric Cancer Assoc 2005;5:1-9)

• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.3-10
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• 2005

The purpose of this study is to investigate the properties of composite systems using polymer cement and epoxy resins for waterproofing and anti-corrosion to concrete structures such as water supply facilities and sewage-works. For the waterproofing and anti-corrosion of concrete structures, there can be required various properties such as absorption capacity and water permeability, adhesion and tensile strength, hair crack-resistance, impact-resistance, repeated low and high temperature test and chemical resistance, soundness for drinking water, soundness for drinking water and etc. In this study these engineering properties of composite systems using polymer-modified mortar and epoxy resins were examined and could be confirmed to satisfy the guidelines of KS. Especially, it was turn out that the adhesion properties was excellent and high crack-resistance up to 1.49 mm will be perform.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.6
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• pp.635-642
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• 2011

It is well known that conventional welding techniques can result in welding defects due to the large groove angle of the weld. In this context, the narrow gap welding (NGW) technique is applied in the nuclear industry because of its inherent merits such as the reduction in welding time and the shrinkage of the weld, and the small deformation of the weld resulting from the small groove angle and welding bead width. In this paper, the distribution of welding residual stress and deformation behavior of the ER308L weld due to NGW are predicted through nonlinear two-dimensional finite element analysis, in which the actual NGW process is simulated in detail. In particular, the effects of the shape of weld, i.e., the width of the weld and the shape of the welding groove, on the residual stress are investigated. The present results can be used to assess the integrity of defective nuclear components and to improve the welding process.

• Journal of Radiation Protection and Research
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• v.14 no.2
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• pp.10-17
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• 1989

A study for the assessment of dose given by outdoor radon to respiratory system has been carried out by making use of radon-cups containing CR-39 plastic track detectors. Detection efficiencies were determined by irradiation of the radon-cups in a standard radon chamber of known concentration. Thus determined detection factors of CR-39 plastic track detector in bare, open cup and filtered cup geometry are found to be 0.273, 0.0813 and 0.0371 $trmm^{-2}$/(37$Bqm^{-3}{\cdot}d$), respectively, which are chemically etched in 30% NaOH solution of $70^{\circ}C$ for 220 minutes. The outdoor radon concentrations measured at Taejeon(Chungnam National University) from May 1988 to March 1989 are in the range of 27.4 - 135.8 Bq/$m^3$(0.74 - 3.67pCi/l)by open cup and 16.7 - 143.9 Bq/$m^3$(0.45 - 3.89 pCi/l) by filtered cup, which yield overall annual average value of outdoor radon concentration of $70.8Bq/m^3$(1.91 pCi/l). Corresponding effective dose equivalent rate to respiratory system of ICRP standard man is assessed to be 520 nSv /h.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.35 no.4
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• pp.438-444
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• 2002

The purpose of this study is screening of microfloras involved in hydrolysis of sea tangle (Laminaria japonica) and sea mustard ( Undaria pinnatifida), This is a part of studies on the hydrolysis of seaweed using microorganisms. General process is difficult to extract of the useful constituent parts as intercellular mucilage, storage polysaccharide and mineral from seafood. It was screening to thirty-three microflora samples as destructed of tissue in sea tangle and sea mustard to about two hundred microflora samples from mountain, rice field, dry field, sea, seaside and fish market etc. in the neighborhood of Yeosu. Sufficient results of the naked eye observation were obtained at eight microflora samples as a feces of bull, a decayed pine tree, a soil of dry field, the mud of the banks in a rice Held, the water of a ditch in a rice Held, the weed of the banks in a rice field, the water in a rice field and leaved in the air, And the value of chemical analysis of the sample is much better in comparison with control. Accordingly, the hydrolysis of seaweed using microorganisms in the inside of these microflora samples can possibility.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.2
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• pp.89-96
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• 2009

As increasing the number of digital control devices installed on aircrafts and their transmission speed, various digital data buses have been introduced to provide reliable and high-speed characteristics. These characteristics of avionics data bus are highly related on the fault-tolerant performance which can make minimize jitter and loss during data transfer. In this paper, we concerned about a new traffic shaping scheme for increasing the reliability of Avionics Full Duplex Switched Ethernet (AFDX) systems based on ARINC 664 standard. We note that the conventional AFDX with a single regulator per virtual link system may produce aggregated traffics as the number of virtual links increasing. The aggregated traffic results in large jitters among frames. To remedy for the jitter and loss of data, we propose a dual regulator scheme for the AFDX system. The purpose of the additional regulator is to additionally regulate aggregated traffics from a number of per virtual link regulators. Using NS-2 simulator, we show that the proposed scheme provides a better performance than the single regulator one. It is worthwhile note that the proposed AFDX with Dual Regulator scheme can be employed to not only aircraft networks but other QoS sensitive networks for robot and industrial control systems.

• Proceedings of the KSCN Conference
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• 2003.11a
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• pp.1083-1084
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• 2003

사회생활 양식이 점차 복잡해지고 생활전반의 조직이 고도화됨에 따라 대규모 급식의 필요성이 점점 증가되고 있다. 그 동안 단체급식은 자체적으로 운영하는 경우가 많았으나, 최근 들어 위탁운영의 효율성에 대한 인식이 높아짐에 따라 위탁 운영률이 크게 높아지고 있다. 현재까지 대학급식에 관한 연구는 대학식당의 이용실태, 대학 식단의 만족도 평가, 대학급식 메뉴 관리 및 운영 등을 조사한 연구는 많았으나 운영형태에 따른 식단 분석 연구는 미흡한 실정이다. 이에 본 연구에는 서울 시내 일부 대학교의 구내에 있는 5개 식당 23가지 식단에 대하여 직영급식과 위탁급식으로 나누어 학생들에게 제공되는 메뉴를 영양가면과 다양성 면에서 평가하고, 제공된 메뉴를 학생들이 실제 섭취하는 실태를 조사하여 섭취한 식단의 영양가와 음식의 종류를 분석하였다. 본 조사에서 이용한 식단은 총 23가지였고, 그 중에서 직영급식 13가지, 위탁급식 10가지였다. 제공된 상용식단형태는 직영급식은$\ulcorner$밥+국+반찬2+김치1$\lrcorner$, 위탁급식은 $\ulcorner$한그릇+국+반찬1+김치1$\lrcorner$이었으며, 우리나라 전통의 기본패턴을 갖추고 있었다. 제공된 식단 중 한끼 영양소 함량을 평가해본 결과 여자의 경우 1/3 영양권장량을 제공하였으나, 남자의 경우는 부족하였다. 제공되는 식단의 음식군별 제공열량을 살펴보면 밥은 평균 399㎉, 한그릇음식은 425㎉로 한 그릇음식의 경우가 높은 열량을 제공하고 있었다. 반찬의 경우 1가지로부터 얻는 열량은 평균 107㎉였으며 김치의 경우는 9.84 ㎉였다. 직영급식과 위탁급식으로 나누어 살펴보면 한 그릇음식, 반찬, 김치의 제공열량이 위탁급식에서 약간 높은 경향을 보였다. 대상자의 음식의 평균 가짓수는 직영 5.5가지, 위탁 4.3가지였으며, 음식 및 반찬 가짓수가 증가할수록 섭취열량이 증가하였다. 대상자들의 섭취한 식단의 한끼당 섭취한 영양소 함량은 직영급식 524㎉, 위탁급식 494㎉였고, 단백질, 지질, 인, 철, 비타민A, 나이아신 등이 유의적으로 직영급식에서 높았다(p<0.001) 섭취한 식단의 영양소 함량은 인과 비타민C를 제외한 모든 영양소에서 권장량에 미달되었다. 섭취한 식단의 영양소적정섭취비는 대부분 0.4-0.9의 값을 보였고, 평균적정섭취비도 직영, 위탁 모두 0.68로 낮은 값을 보였다. 영양소 밀도의 경우 절대적 섭취에서 직영급식이 대부분의 영양소를 많이 섭취하고 있는 것과는 달리 위탁급식에서 철분의 밀도가 유의적으로 높았다(p<0.01). 총 대상자들이 식단에서 섭취한 열량을 살펴보면, 주식류의 경우 밥은 298㎉, 한 그릇음식은 386㎉로 한 그릇음식이 많은 열량을 제공하고 있었다. 반찬의 경우는 1가지로부터 얻는 열량은 78㎉, 김치는 8㎉였다. 이상의 결과로 볼 때, 제공량은 직영급식에서 많았으나 영양밀도 면에서는 큰 차이가 없는 것으로 보아 위탁급식의 제공량을 늘린다면 급식운영형태별 두 식단의 질적 차이가 크게 줄어들 것으로 보인다. 그러나 두 급식 형태 모두 제공식단의 영양소 함량은 다른 지역이나 연령에 비해 부족한 것으로 나타나 아침 결식 및 불규칙한 식사 등 영양상태가 좋지 못한 대학생들에게 교내 식당에서 질 높은 식사를 제공해야 할 것이다. 또한 식단 작성 시 학생들의 메뉴 기호도를 충분히 반영시키고 다양한 메뉴를 제공하는데 한계가 있다면 주.부식 외에 다양한 후식제공을 통하여 학교 급식에 대한 질을 향상시키는 노력을 해야 할 것이다.