• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.12
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• pp.1193-1199
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• 2012

A cup burner experiment was performed to investigate the effect of the oxidizer velocity and concentration on flame instability near extinction. Heptane was used as a fuel and air diluted by nitrogen and carbon dioxide was used in the oxidizer stream. Two types of flame instabilities at the flame base and at axial downstream were observed near extinction. The instability at the flame base could be characterized by cell, swing, and rotation modes, and the cell mode changed to the rotation mode through the swing mode as the oxidizer velocity increased. To assess the parameters for the flame instability, the initial mixture strengths, Lewis number, and adiabatic flame temperature were investigated under each condition. The Lewis number might be the most important among them, but it is impossible to generalize because of the insufficient number of cases. Furthermore, the axial periodic flickering motion disappeared at low and high oxidizer velocities near extinction. This resulted from the fact that low oxidizer velocity induced evaporated fuel velocity below the critical velocity and high velocity made the reacting fuel velocity comparable.

• Proceedings of the Membrane Society of Korea Conference
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• 2003.11a
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• pp.154-154
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• 2003

세계의 특허동향을 분석해 보면 수처리용 MF/UF 분리막의 제조 및 응용에 관한 연구개발이 매우 활발하게 진행되어져 왔음을 알 수 있다. 또한 다국적 기업들의 적극적인 마케팅과 분리막 공법의 우수한 처리효율이 인정되면서 90년대 후반부터는 수십만톤/일 규모의 징수처리 및 하수고도처리 분야에까지 MF/UF 분리막이 괄목할만한 수요의 증대를 보이고 있으며 이러한 추세는 앞으로도 더욱 확대될 것으로 전망이 되고 있다. 고분자재료를 이용하여 MF/UF 분리막을 제조하는 방법으로는 보편적으로 첫째, 고분자를 용매에 녹인 후 용매와 비 용매간의 상호교환을 유도하여 분리막을 제조하는 상전이법(Phase Inversion). 둘째, 고분자를 고온에서 희석제와 melt-blending 한 후 가해진 열을 제거하면서 상분리를 일으켜 다공성을 부여하는 열유도 상분리법(TIPS, Thermally Induced Phase Separation). 셋째, 결정성 고분자를 용융, 압출 및 냉각하여 결정화도가 매우 높은 전구체를 제조한 후 연신에 의해 비결정 영역을 개열시켜 기공을 형성하는 연신법(Stretching process)이 있다. 이 중 물성이 매우 우수한 폴리올레핀계 결정성 고분자를 이용하여 분리막을 제조할 수 있는 방법은 열유도 상분리법 및 연신법에 제한된다. 본 연구 발표에서는 세계적으로도 극소수의 기업들만이 보유하고 있으며 고도로 축적된 노하우를 필요로 하는 열유도 상분리법 및 연신법에 의하여 폴리프로필렌 및 폴리에틸렌 중공사막을 제조하는 방법과 이 두 가지 방법에 의해서 제조된 중공사막의 구조, 물성 및 수투과 성능 그리고 KMS 중공 사막의 응용사례를 통한 실제 운전특성 등을 소개하고자 한다.좋은 결과를 가져다 주는 술식으로 판단되었다.결과를 이용하여 향후 전개될 홈 네트워크 서비스 및 관련시장의 발전 방향을 전망해 보고 이에 따른 기업이나 정부차원의 대응전략을 파악하고자 한다.육구에서는 큰 변화를 나타내고 있지 않았다(p<0.05). 운동과 비운동시킨 참돔의 지질 함량의 변화는 운동시킨 참돔은 운동으로 인한 에너지 소비로 인하여 함량이 유의적으로 감소했으며(r=-0.35), 비운동사육구에서는 절식으로 인하여 지질함량이 감소하였다(r=-0.38). 파괴강도와 가장 밀접한 영향을 가지는 콜라겐은 운동과 비운동 모두 사육기간동안 큰 변화는 보이지 않았다. 초기의 파괴강도값은 1.45±0.02kg(운동사육구), 1.36±0.18kg(비운동사육구)이였으며 사육기간동안 운동사육구는 파괴강도값이 증가한 반면, 비운동수조에서는 참돔의 파괴강도는 사육기간동안 큰 유의차가 없었다. 각 성분간의 상관도를 살펴보면, 수분함량과 파괴강도는 상관성을 가졌으며, 지질함량과 파괴강도도 같은 경향은 나타내었다. 운동기간동안의 파괴강도와 콜라겐 사이에는 상관성의 거의 없었다. 이는 운동기간에 따른 파괴강도의 증가가 콜라겐의 함량의 증가보다는 지질함량의 감소와 수분함량의 증가와 같은 성분과의 상관성이 크다고 판단된다. 다음으로는, 운동횟수에 의한 영향으로써 운동시간을 1일 6시간으로 설정하여, 운동횟수를 결정하기 위하여 오전, 오후에 각 3시간씩 운동시키는 방법과 오전부터 6시간동안 운동시키는 두 방법을 이용하여 품질을 비교하였다. 각 조건에 따라 운동시킨 참돔의 수분함량을 나타낸 것으로, 2회(오전 3시간, 오후 3시간)에 나누어서 운동시키기 위한 육의 수분함량은 73.37±2.02%를 나타냈으며, 1회(6시간 운동)

• Resources Recycling
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• v.28 no.3
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• pp.15-20
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• 2019

The recovery of struvite using nitrogen and phosphorus in wastewaters is useful for prevention of eutrophication and use as fertilizer, but there are theoretical and technical issues to be resolved. Through the detailed literature review, this study discusses the possible reasonable prediction of struvite formation reaction by setting a feasible reaction equation with some theoretical considerations. In a technical aspect, the purity of struvite in solid precipitates can be promoted by excluding Ca in an effective way. As for the struvite reaction prediction issue, selection of proper equilibrium reaction as well as its reaction equilibrium coefficient is significant in the neutral and basic pH regions. The equilibrium reaction agrees well with the experimental batch test results. Considering the charge balance of the ions, the pH drop along struvite formation in a diluted solution can be predicted. Also, improvement of struvite purity through elimination of Ca can be expected by providing a highly concentrated ${NH_4}^+-N$ relative to ${HPO_4}^{2-}-P$ because ${NH_4}^+$ can enhance the thermodynamic driving force toward favorable struvite formation. Even though the phosphate reacts rapidly with Ca to form a solid precipitate, the thermodynamic driving force due to the high ${NH_4}^+$ activity can dissociate the phosphate-calcium precipitates and produce struvite.

• Journal of Internet Computing and Services
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• v.22 no.2
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• pp.123-131
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• 2021

The Fourth Industrial Revolution was triggered by data-driven digital technologies such as AI and big data. There is a rapid movement to expand the scope of data utilization to the privacy area, which was considered only a protected area. Through the revision of the Data 3 Act, laws and systems were established that allow personal information to be freely transferred and utilized under their consent. But, it will be necessary to support the platform that encompasses the entire process from collecting personal information to managing and utilizing it. In this paper, we propose a platform model that can be applied to building mydata ecosystem using personal information. It describes the six essential functional requirements for building MyData platforms and the procedures and methods for implementing them. The six proposed essential features describe consent, sharing/downloading/ receipt of data, data collection and utilization, user authentication, API gateway, and platform services. We also illustrate the case of applying the MyData platform model to real-world, underprivileged mobility support services.

• Korean Journal of Ichthyology
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• v.34 no.3
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• pp.208-217
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• 2022

We wanted to develop a real-time PCR assay capable of detecting Liobagrus obesus in environmental DNA (eDNA) extracted from freshwater samples using a pair of species-specific primers and probe for the endangered fish, L. obesus. The species-specific primers and probe were designed in consideration of single nucleotide polymorphisms between 65 species of freshwater fish living in the Republic of Korea within the cytochrome b (cytb) gene of mitochondrial DNA. The species-specific primers and probe, in the real-time PCR assay, showed high specificity as only the L. obesus genomic DNA (gDNA) was found to be positive in the specificity verification using 65 species gDNA of freshwater fish in the Republic of Korea. In addition, in the detection limit analysis using the serial dilution concentrations of L. obesus gDNA, it was found that it was possible to detect up to 0.2 pg, showing high sensitivity. Afterwards, using the species-specific primers and probe, real-time PCR assay was performed on freshwater samples obtained from 8 stations in the mid-upper basin of Geum River. As a result, the cytb gene of L. obesus was detected in total 5 stations including all 3 stations where this species was collected at the time of field survey. Therefore, the species-specific primers and probe developed in present study, and the real-time PCR assay using them, can accurately detect the cytb gene of L. obesus from eDNA samples, which can be utilized to monitor the existing habitats of this species and to discover potential new habitats.

• Information Systems Review
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• v.19 no.4
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• pp.87-110
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• 2017

Analyzing and finding the risk factors in information technology (IT) projects have been discussed because risk management is an important issue in IT project management. This study obtained the risk factor checklists with priorities, analyzed the causal relationship of risk factors, and determined their influences on IT project management. However, only few studies systematically classified IT project risk factors in terms of risk exposure. These studies considered both the probability of occurrence and the degree of risk simultaneously. The present study determined 53 IT project risk factors on the basis of literature and expert group discussions. Additionally, this study presented clustering analysis based on the data of 140 project managers. The IT project risk factor classification framework was divided into four areas (HIHF, HILF, LIHF, and LILF). The present results can be used to help IT project managers establish effective risk management strategies and reduce IT project failures. This study also provides academic implication because it considers both the probability of occurrence and the degree of influence of risk factors.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.2
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• pp.19-25
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• 2002

Ternary $xSrO-yB_2O_3-0.1Al_2O_3$ and $xSrO-yB_2O_3-0.1SiO_2$ glasses were prepared as a function of R(${\equiv}x/y$). The fraction of four-coordinated brans ($N_4$), symmetric three-coordinated barons ($N_{3S}$), and asymmetric three-coordinated barons ($N_{3A}$) were determined quantitatively to study the structures of these glasses by $^{11}B$ NMR. The values of $Q_{cc}$ and ${\eta}$ for $BO_3$ unit in the glasses were 2.74MHz and 0.22, those for $BO_3{^-}$ unit were 2.54MHz and 0.55, and those for $BO_4$ unit 0.60~0.75MHz and 0.00, respectively. The structure of SrBAl glass at $R_{1st}$ consisted of tetraborate ($[B_8O_{13}]^{-2}$) units and 1st-modified diborate ($[B_2Al_2O_7]^{-2}$) units, and those for the glass at $R_{max}$consisted of diborate ($[B_4O_7]^{-2}$) units, metaborate ($[BO_2^{-1}]$), 1st-modified diborate units, and 2nd-modified diborate ($[B_2Al_2O_8]^{-4}$) units. Due to the oxygens introduced from the strontium oxide. $AlO_4$ units were preferably formed rather than $BO_4$ units. And, the structure of SrBSi glasses in the region $R{\leq}0.5$ could be viewed as binary $SrO-B_2O_3$ glasses structure diluted by silicate oxide: therefore, the Si atoms of the glasses did not contributed to the change the configuration around the boron atoms. The silicate oxide was formed the $SiO_4{^-}$ units rather than the $BO_3{^-}$ units by the oxygens introduced from the storntium oxide in the region of $R{\geq}R_{max}$, and structure of those glass at $R_{max}$ consisted of diborate units, metaborate units loose $BO_4([BO_2]^{-1})$, and $SiO_4{^-}([SiO_{2.5}]^{-1})$ units.

• Journal of the Korean Chemical Society
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• v.42 no.6
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• pp.618-628
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• 1998

Pure CaO, Mn-doped CaO, Mn/CaO, and K/CaO catalysts were prepared and tested as catalysts for the oxidative coupling of methane in the temperature range of 600 to 800$^{\circ}C$ to investigate the effects of Mn- and K-addition on the catalytic activity of calcium oxide. To characterize the catalysts, X-ray powder diffraction(XRD), XPS, SEM, DSC, and TG analyses were performed. The catalytic reaction was carried out in a single-pass flow reactor using on-line gas chromatography system. Normalized reaction conditions were generally $p(CH_4)/p(O_2)=250$ Torr/50 Torr, total feed flow rate=30 mL/min, and 1 atm of total pressure with He being used as diluent gas. Among the catalysts tested, 6.3 mol% Mn-doped CaO catalyst showed the best $C_2$ yield of 8.0% with a selectivity of 43.2% at 775$^{\circ}C$. The $C_2$ selectivity increased on lightly doped CaO catalysts, while decreased on heavily doped CaO([Mn] > 6.3 mol%) catalysts. 6 wt.% Mn/CaO and 6 wt.% K/CaO catalysts showed the $C_2$ selectivities of 13.2% and 30.9%, respectively, for the reaction. Electrical conductivities of CaO and Mn-doped CaO were measured in the temperature range of 500 to 1000$^{\circ}C$ at Po2's of $10^{-3}\; to\;10^{-1}\;atm.$ The electrical conductivity was decreased with Mn-doping and increased with increasing $P0_2$in the range of $10^{-3}\;to\;10^{-1}\;atm,$ indicating the specimens to be p-type semiconductors. It was suggested that the interstitial oxygen ions formed near the surface can activate methane and the formation of interstitial oxygen ions was discussed on the basis of solid-state chemistry.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.1
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• pp.102-107
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• 2012

Purpose : Because of the rapid physical decay of the short half-lived radionuclide, counting of event for image is very limited. In this reason, long scan duration is applied for more accurate quantitative analysis in the relatively low sensitive examination. The aim of this study was to evaluate the difference according to scan duration and investigate the resonable scan duration using the radionuclide of 11C and 18F in PET scan. Materials and Methods : 1994-NEMA Phantom was filled with 11C of $30.08{\pm}4.22MBq$ and 18F of $40.08{\pm}8.29MBq$ diluted with distilled water. Dynamic images were acquired 20frames/1minute and static image was acquired for 20minutes with 11C. And dynamic images were acquired 20frames/2.5minutes and static image was acquired for 50minutes with 18F. All of data were applied with same reconstruction method and time decay correction. Region of interest (ROI) was set on the image, maximum radioactivity concentration (maxRC, kBq/mL) was compared. We compared maxRC with acquired dynamic image which was summed one bye one to increase the total scan duration. Results : maxRC over time of 11C was $3.85{\pm}0.45{\sim}5.15{\pm}0.50kBq/mL$ in dynamic image, and static image was $2.15{\pm}0.26kBq/mL$. In case of 18F, the maxRC was $9.09{\pm}0.42{\sim}9.48{\pm}0.31kBq/mL$ in dynamic image and $7.24{\pm}0.14kBq/mL$ in static. In summed image of 11C, as total scan duration was increased to 5, 10, 15, 20minutes, the maxRC were $2.47{\pm}0.4$, $2.22{\pm}0.37$, $2.08{\pm}0.42$, $1.95{\pm}0.55kBq/mL$ respectively. In case of 18F, the total scan duration was increased to 12.5, 25, 37.5, and 50minutes, the maxRC were $7.89{\pm}0.27$, $7.61{\pm}0.23$, $7.36{\pm}0.21$, $7.31{\pm}0.23kBq/mL$. Conclusion : As elapsed time was increased after completion of injection, the maxRC was increased by 33% and 4% in dynamic study of 11C and 18F respectively. Also the total scan duration was increased, the maxRC was reduced by 50% and 20% in summed image of 11C and 18F respectively. The percentage difference of each result is more larger in study using relatively shorter half-lived radionuclide. It appears that the accuracy of decay correction declined not only increment of scan duration but also increment of elapsed time from a starting point of acquisition. In study using 18F, there was no big difference so it's not necessary to consider error of quantitative evaluation according to elapsed time. It's recommended to apply additional decay correction method considering decay correction the error concerning elapsed time or to set the scan duration of static image less than 5minutes corresponding 25% of half life in study using shorter half-lived radionuclide as 11C.

• Economic and Environmental Geology
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• v.38 no.6 s.175
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• pp.643-656
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• 2005

The East Sea, a marginal sea or back-arc basin, consists of Japan Basin, Yamato Basin, and Ulleung Basin and is surrounded by the Pacific Plate and Philippine Sea Plate. Ulleung Basin locates in the southwestern part of the East Sea and shows the depth of 1,500 m in average and 2,500 m in maximum, connecting to the Japan Basin along 2,000 m contour. The slope of the seafloor is greater in the western side of the basin than in the southern and the eastern side. The crustal thickness of the Ulleung Basin from the OBS tends to get thicker toward the north and the west side and the sediment thickness of the Ulleung Basin is getting thicker toward the southeast side and reaches up to 12 km. The crustal type of the Ulleung Basin was variously suggested as like as a rifted continental crust, an extended continental crust, and an incipient oceanic trust. The origin of the crustal formation and the Ulleung Basin, however, is still controversial. Based on the bathymetry and gravtiy anomaly data for this study, the axis of the Ulleung Basin shows that the basin develops along the axis trending NW-SE direction and reveals a general symmetry of the bathymetry. And also the free-air gravity anomalies show a very similar pattern to the bathymetry of the basin. The sediment thickness is relatively thicker in the southeastern side of the basin than in the northwestern side. Although the crustal age of the Ulleung Basin is supposed to be younger than them of the Japan Basin and the Yamato Basin, the free-air gravity anomalies of the Ulleung Basin ranging -40 to 50 mGals are lower than the other basins, which suggests that the densities of crust and sediment of the Ulleng Basin are lower than the Japan Basin and the Yamato Basin.