• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.186-186
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• 2012

This report investigates a new synthetic route and the size-dependent optical and electrical properties of PbS nanocrystal quantum dots (NQDs) in diameters ranging between 1.5 and 6 nm. Particularly we synthesize ultra-small sized PbS NQDs having extreme quantum confinement with 1.5~2.9 nm in diameter (2.58~1.5 eV in first exciton energy) for the first time by adjusting growth temperature and growth time. In this region, the Stokes shift increases as decreasing size, which is testimony to the highly quantum confinement effect of ultra-small sized PbS NQDs. To find out the electrical properties, we fabricate self-assembled films of PbS NQDs using layer by layer (LBL) spin-coating method and replacing the original ligands with oleic acid to short ligands with 1, 2-ethandithiol (EDT) in the course. The use of capping ligands (EDT) allows us to achieve effective electrical transport in the arrays of solution processed PbS NQDs. These high-quality films apply to Schottky solar cell made in an glass/ITO/PbS/LiF/Al structure and thin-film transistor varying the PbS NQDs diameter 1.5~6 nm. We achieve the highest open-circuit voltage (＜0.6 V) in Schottky solar cell ever using PbS NQDs with first exciton energy 2.58 eV.

• Bulletin of the Korean Chemical Society
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• 제23권5호
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• pp.741-744
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• 2002

Single phase of multicomponent oxide ZrTiO4 film could be prepared through surface sol-gel route simply by coating the mixture of 100 mM zirconium butoxide and titanium butoxide on $Pt/Ti/SiO_2Si(100)$ substrate, following pyro lysis at $450^{\circ}C$, and annealing it at 770 $^{\circ}C.$ The dielectric constant of the film was reduced as the film thickness decreased due to of the interfacial effects caused by layer/electrode and a few voids inside the multilayer. However, the dielectric property was independent of applied dc bias sweeps voltage (-2 to +2 V).The dielectric constant of bulk film, 31.9, estimated using series-connected capacitor model was independent of film thickness and frequency in the measurement range, but theoretical interfacial thickness, ti, was dependent on the frequency. It reached a saturated ti value, $6.9{\AA}$, at high frequency by extraction of some capacitance component formed at low frequency range. The dielectric constant of bulk ZrTiO4 pellet-shaped material was 33.7 and very stable with frequency promising as good applicable devices.

• Archives of Pharmacal Research
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• 제26권12호
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• pp.1102-1108
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• 2003

We studied the effects of phytolaccosides, saponins from Phytolacca americana, on the intestinal absorption of heparin in vitro and in vivo. The absorption enhancing activity of these compounds (phytolaccosides B, $D_2$, E, F, G and I) was determined by changes in transepithelial electrical resistance (TEER) and the transport amount of heparin disaccharide, the major repeating unit of heparin, across Caco-2 cell monolayers. With the exception of phytolaccoside G, all of them decreased TEER values and increased the permeability in a dose-dependent and time-dependent manner. In vitro, phytolaccosides B,$D_2$, and E showed significant absorption enhancing activities, while effects by phytolaccoside F and I were mild. In vivo, phytolaccoside E increased the activated partial thromboplastin time (APTT) and thrombin time, indicating that phytolaccoside E modulated the transport of heparin in intestinal route. Our results suggest that a series of phytolaccosides from Phytolacca americana can be applied as pharmaceutical excipients to improve the permeability of macromolecules and hydrophilic drugs having difficulty in absorption across the intestinal epithelium.

• Archives of Pharmacal Research
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• 제25권1호
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• pp.86-92
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• 2002

The enhancement of paracellular transport of heparin disaccharide using several absorption enhancers across Caco-2 cell monolayers was tested . The cytotoxicity of these enhancers was also examined. The enhancing effects by Quillaja saponin, diponin glycyrrhizinate, $18{\beta}-glycyrrhetinic$ acid, sodium caprate and taurine were determined by changes in transepithelial electrical resistance (TEER) and the amount of heparin disaccharide transported across Caco-2 cell monolayers. Among the absorption enhancers, $18{\beta}-glycyrrhetinic$ acid arid taurine decreased TEER and increased the permeability of heparin disaccharide in a dose-dependent and time-dependent manner with little or negligible cytotoxicity. Our results indicate that these absorption enhancers can widen the tight junction, which is a dominant paracellular absorption route of hydrophilic compounds . It is highly possible that these absorption enhancers can be applied as pharmaceutical excipients to improve the transport of macromolecules and hydrophilic drugs having difficulty in permeability across the intestinal epithelium.

• Bulletin of the Korean Chemical Society
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• 제26권8호
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• pp.1214-1218
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• 2005

Ti-HMS samples in which titanium species exist in various forms of isolated tetrahedral state, finely dispersed $TiO_2$ cluster, and some in extra-framework anatase phase were prepared via a direct synthesis route using dodecylamine (DDS) as a structure directing agent by systematically varying the titanium loadings between 2 and 50 mol% Ti/(Ti+Si) in substrate composition. Physicochemical properties of the materials were evaluated using XRD, SEM/TEM, N2 adsorption, UV-vis and XANES spectroscopies. Catalytic properties of Ti-HMS in cyclohexene and 2,6-di-tert-butyl phenol (2,6-DTBP) oxidation using aqueous $H_2O_2$, and vapor phase photocatalytic degradation of acetaldehyde were evaluated. High $H_2O_2$ selectivity was obtained in cyclohexene oxidation, and cyclohexene conversion was found primarily dependent on the amount of tetrahedrally coordinated Ti sites. For bulky 2,6-DTBP oxidation and photocatalytic oxidation of acetaldehyde, on the other hand, conversions were found dependent on the total amount of Ti sites and maintaining an uniform mesoporous structure in the catalysts was not critical for efficient catalysis.

• 한국콘텐츠학회논문지
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• 제13권9호
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• pp.193-203
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• 2013

본 연구는 재가요양서비스 부양가족의 가족스트레스와 가족탄력성이 어떤 경로를 통해 가족적응에 영향을 미치는지를 살펴보기 위하여 광주 전남 재가요양서비스 노인의 부양가족 203명을 대상으로 설문 조사를 실시하였다. 연구결과 재가요양서비스 부양가족의 가족스트레스는 가족적응에 직접적인 영향을 미치지 않고 가족탄력요인 중 의사소통을 통하여 간접적으로 영향을 미치는 것으로 나타났다. 이러한 연구 결과를 바탕으로 보면 가족탄력성은 스트레스 보다 가족적응에 영향을 미치기 때문에 가족적응력을 향상시키기 위해서는 가족스트레스를 감소시키는 기존의 결점시각에 초점을 맞추기보다 가족탄력성의 강점관점으로 전환이 이루어져야 함을 제안한다.

• 대한토목학회논문집
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• 제35권6호
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• pp.1309-1320
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• 2015

본 연구는 시내버스 서비스 수준을 의미하는 노선별 차량 운행대수의 영향을 미치는 운행여건과 상관성 분석에 관한 연구이다. 분석방법은 회귀분석방법을 적용하였으며, 분석대상은 울산시 2013년 기준 98개 노선으로 한정하였다. 상관성분석을 위한 모형 도출을 위해 먼저 상관분석을 실시하여 종속변수인 운행대수와 독립변수인 운행거리, 운송수입금, 운송원가간의 관계를 분석한 결과, 아주 높은 유의수분에서 상관성이 있는 것으로 확인되었다. 회귀분석은 모형을 3가지 유형으로 구분하여 실시하였으며, 그 결과는 다음과 같다. 첫 번째 울산시 98개 버스노선 전체를 대상으로 도출한 모형은 Y(운행대수)=$-4.532+0.00002877*X_1$(운송수입금)인데, 이 의미는 운행대수 1대 증차를 위한 필요조건은 1일 승객 수가 140명 정도 증가하여야 시행할 수 있다는 점을 알려준다. 두 번째는 일반형, 좌석형, 중형으로 구분되는 버스 운행형태별 모형은 일반형의 경우 Y(운행대수)=$-10.954+0.00004283*X_1$(운송수입금), 일반형 시내버스를 1대 증차하기 위해서는 1일 승객 수가 약 153명 정도 증가되어야 시행할 수 있음을 보여주며, 중형의 모형은 Y(운행대수)=$-0.859+0.00001438*X_1$(운송수입금)인데, 이 의미는 1일 승객 수가 약 52명 정도 증가되어야 시행 가능함을 보여준다. 세 번째는 버스노선 운행체계별 모형 분석의 경우, 공동배차제의 경우 Y(운송대수)=$-4.786+0.00003028*X_1$(운송수입금)인데, 이 의미는 운행대수 1대 증차를 위한 필요조건은 1일 승객 수가 약 140명 정도 증가해야만 시행할 수 있으며, 개별노선제의 경우 Y(운행대수)=$-2.339+0.00002030*X_1$(운송수입금)인데, 이 의미는 운행대수 1대 증차를 위한 필요조건은 1일 승객수가 약 140명 정도 증가되어야 시행할 수 있음을 보여준다. 따라서 버스노선 운영체계별로 모형을 도출하여 운영체계가 시내버스 노선별 차량 운행대수에 미치는 영향을 분석한 결과, 두 가지 운영체계 모두 차량 증차를 위한 추진할 경우, 1일 승객 수가 140명 정도는 확보되어야 한다는 공통적인 결론에 도달되었으며, 노선운영체계 특성에 따른 노선별 차량 운영대수 차이는 거의 없는 것으로 분석되었다.

• 한국토양비료학회지
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• 제47권2호
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• pp.80-84
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• 2014

Phosphorus (P) is an essential nutrient for all living organisms. P is mostly obtained from mined rock phosphate. However, existing rock phosphate reserves could be exhausted in the next 50-100 years. As Korea is totally dependent on imported rock phosphate, we should seek for solution to overcome the P depletion by efficient use and recycling. For this, this study suggested a P flow model to identify the location and flow route of P in urban area based on traditional material flow analysis. The type of P entering the urban areas are fertilizer, food and feed. Each type of P is used in agriculture, human consumption and animal husbandry. After going through each process, P is moved to waste management facilities within food waste, excreta and sewage. Some portion of P in waste are buried, incinerated and discharged, which can be reservoir of P in the future.

• 대한교통학회지
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• 제14권3호
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• pp.27-44
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• 1996

The purpose of the thesis is providing a new formulation for the transit assignment problem. The existing models dealing with the transit assignment problem don't consider the congestion effects due to the insufficient capacity of transit vehicles. Besides, these models don't provide solutions satisfying the Wardrop's user equilibrium conditions. The congestion effects are considered to be concentrated at the transit stops. For the transit lines, the waiting times at the transit stops are dependent on the passenger flows. The new model suggests the route section cost function analogous to the link performance function of the auto assignment to reflect the congestion effects in congested transit network. With the asymmetric cost function, the variational inequality programming is used to obtain the solutions satisfying Wardrop's condition. The diagonalization algorithm is introduced to solve this model. Finally, the results are compared with those of EMME/2.

• 한국분말재료학회지
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• 제24권3호
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• pp.229-234
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• 2017

We report on a simple and robust route to the spontaneous assembly of well-ordered magnetic nanoparticle superstructures by irreversible evaporation of a sessile single droplet of a mixture of a ferrofluid (FF) and a nonmagnetic fluid (NF). The resulting assembled superstructures are seen to form well-packed, vertically arranged columns with diameters of $5{\sim}0.7{\mu}m$, interparticle spacings of $9{\sim}2{\mu}m$, and heights of $1.3{\sim}3{\mu}m$ The assembled superstructures are strongly dependent on both the magnitude of magnetic field and the mixing ratio of the mixture. As the magnitude of the externally applied magnetic field and the mixing ratio of the mixture increase gradually, the size and interspacing of the magnetic nanoparticle aggregations decrease. Without an externally applied magnetic field, featureless patterns are observed for the ${\gamma}-Fe_3O_4$ nanoparticle aggregations. The proposed approach may lead to a versatile, cost-effective, fast, and scalable fabrication process based on the field-induced self-assembly of magnetic nanoparticles.