• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.331-334
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• 2000

The organic electroluminescent(EL) device has gathered much interest because of its large potential in materials and simple device fabrication. We fabricated EL devices which have a blended single emitting layer containg poly(Nvinylcarbazole)[PVK] and poly(3-dodecylthiophene)[P3DoDT]. The molar ratio between P3DoDT and PVK changed with 1:0, 2:1 and 1:1. To improve the external quantum efficiency of EL devices, we applied insulating layer, LiF layer between polymer emitting layer and AI electrode. All of the devices emit orange-red light and it's can be explained that the energy transfer occurs from PVK to P3DoDT. Within the molar ratio 1:0, 2:1 and 1:1, the energy transfer was not saturated, which results in the not appearance of PVK emission in the blue region. In the voltage-current and voltage-light power characteristics of devices applied LiF layer, current and light power drastically increased with increasing with applied voltage. In the consequence of the result, the light power of the device have a molar ratio 1:1 with LiF layer was about 10 times larger than that of the device without PVK at 6V.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(1)
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• pp.482-484
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• 2005

• 한국초지조사료학회지
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• 제16권1호
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• pp.27-38
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• 1996

This study was conducted to evaluate the potential of Festulolium braunii(Festuca pratensis Huds. $\times$ Loliurn mulrijZorum Lam.)as forge sources. The experiment was arranged in a split plot design with four replications from Feb. 1995. to Jan. 1996 at Hohenheim university. Main plots consisted of three forage species, Festulolirtrn braunii(Paulita), Lolium multiJomm(Lemtla), and Secale cereale(Halo) and subplots consisted of three maturity, boot, heading, and anthesis. The growth characteristics, DM yields, nutritive value, N and energy balance were observed. The heading date of Festulolium braunii was about two days earlier than that of Loliunz mrtltiflorum, farthermore Fesrulolium braunii retained higher leaf weight ratio(LWR) than other species. Festulolium brarrnii failed to show any significant differences in grass length, number of tillers, LAI, CGR, and DM accumulation when harvested at the same stage of maturity as compare with Loliurn mulriiflorutn or Setale cerede, bur the content of CP, OMD, and mineral elements and NEL value of Festulolium braunii compare to othes were slightly increased(P<0.05), while the content of NDF, ADF, and lignin decreased(P<0.05). The yield of CP was greater for Festulolium braunii than for Lolium multfimm and yields of DOM and NEL per unit area(ha) for Festulolium braunii were greater than for other species(P<0.05). The equivalent or higher DM production and nutritive value are obtained when Festulolium braunii are cut during the period from boot to anthesis stages, therefor DM intake, preference, and N and energy balance were also higher for Festulolirtm braunii compare to for other species. It could be suggested that Lolium multrfirum would be a more suitable substitute to Festuloliron braunii without decreasing forage production and quality, but the substitutive effect of Secale cereale would be difficult because of the maor differences in growth type and period compare to Fesrulolium braunii. From above the results of this experiment it appears that Festulolium braunii have a potential to provide forage sources. but funher research is needed to ascertain their potential under the climate of Korea.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.297.2-297.2
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• 2013

Scavenging electricity from wasteful energy resources is currently an important issue and piezoelectric nanogenerators (NGs) based on zinc oxide (ZnO) are promising energy harvesters that can be adapted to various portable, wearable, self-powered electronic devices. Although ZnO has several advantages for NGs, the piezoelectric semiconductor material ZnO generate an intrinsic piezoelectric potential of a few volts as a result of its mechanical deformation. As grown, ZnO is usually n-type, a property that was historically ascribed to native defects. Oxygen vacancies (Vo) that work as donors exist in ZnO thin film and usually screen some parts of the piezoelectric potential. Consequently, the ZnO NGs' piezoelectric power cannot reach to its theoretical value, and thus decreasing the effect from Vo is essential. In the present study, c-axis oriented insulator-like sputtered ZnO thin films were grown in various temperatures to fabricate an optimized nanogenerator (NGs). The purity and crystalinity of ZnO were investigated with photoluminescence (PL). Moreover, by introducing a p-type polymer usually used in organic solar cell, it was discussed how piezoelectric passivation effect works in ZnO thin films having different types of defects. Prepared ZnO thin films have both Zn vacancies (accepter like) and oxygen vacancies (donor like). It generates output voltage 20 time lager than n-type dominant semiconducting ZnO thin film without p-type polymer conjugating. The enhancement is due to the internal accepter like point defects, zinc vacancies (VZn). When the more VZn concentration increases, the more chances to prevent piezoelectric potential screening effects are occurred, consequently, the output voltage is enhanced. Moreover, by passivating remained effective oxygen vacancies by p-type polymers, we demonstrated further power enhancement.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3405-3410
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• 2011

We have investigated the cytotoxic potential of tellurium (Te) nanowires in BALB/3T3 fibroblast cells. Te nanowires were synthesized through an aqueous phase surfactant assisted method. Toxicological experiments, such as analysis of morphological changes, MTT assay, DAPI staining, and estimation of intracellular reactive oxygen species, were carried out to reveal the cytotoxic effects of Te nanowires. Te nanowires were found to be cytotoxic at all concentrations tested, in a dose-dependent manner. The UV/Vis spectra of Te nanowires suspended in a culture medium showed drastic changes and disappearance of two broad absorption peaks. The physicochemical properties such as, surface charge, size, and shape of Te nanowires were found to be altered during exposure of cells, due to the instability and agglomeration of nanowires in the culture medium. These results suggest that the chemical components of the DMEM medium significantly affect the stability of Te nanowires. In addition, TEM images revealed that necrosis was the basic pattern of cell death, which might stem from the formation of toxic moieties of tellurium, released from nanowire structures, in the bioenvironment. These observations thus suggest that Te nanomaterials may pose potential risks to environmental and human health.

• Asian-Australasian Journal of Animal Sciences
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• 제15권6호
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• pp.800-805
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• 2002

Two experiments were conducted to compare digestibility of 12 diets in sheep, red and fallow deer. No differences (p>0.05) between sheep, red and fallow deer in digestibility of dry matter, organic matter and digestible energy content for all diets were found except for the sorghum diet and medic hay. Sheep and fallow deer digested the sorghum diet better than red deer. An in vitro study showed that sheep had a lower in vitro dry matter digestibility and digestible energy content than both red and fallow deer, with a significant interaction between animal species and feed ingredient. Deer digested straws and hays better (p<0.05) than sheep. In vitro digestibility was lower (p<0.05) than in vivo digestibility, but significantly correlated with in vivo digestibility for red and fallow deer. The in vitro method for digestibility estimation has potential as a rapid feed evaluation system for deer, but needs further validation.

• Nuclear Engineering and Technology
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• 제53권4호
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• pp.1284-1288
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• 2021

In this work, we propose and design a GaN-based diode with a p-doped GaN (p-GaN) multi-well structure for high efficiency betavoltaic (BV) cells. The short-circuit current density (J_SC) and opencircuit voltage (V_OC) of the devices were investigated with variations of parameters such as the doping concentration, height, width of the p-GaN well region, well-to-well gap, and number of well regions. The J_SC of the device was significantly improved by a wider depletion area, which was obtained by applying the multi-well structure. The optimized device achieved a higher output power density by 8.6% than that of the conventional diode due to the enhancement of J_SC. The proposed device structure showed a high potential for a high efficiency BV cell candidate.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.284-284
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• 2012

본 연구에서는 다이오드 소자의 온도 증가에 따른 C-V 특성을 분석하였다. 180 kHz 주파수 조건에서 온도는 300 K에서 450 K까지 50 K 간격으로 가변하였다. 측정 결과 reverse bias 영역에서는 커패시턴스의 온도 의존성이 없었으나, forward bias 영역에서는 온도가 증가함에 따라 동일 전압에서의 커패시턴스가 증가하였다. 이로부터 온도가 증가 할수록 소자가 반전(inversion) 상태에서 축적(accumulation) 상태로 빨리 전환함을 확인하였으며, 1/C2-V 그래프로부터 온도 증가에 따른 전위장벽(Built-in potential, Vbi) 감소를 확인하였다. 전위장벽은 0.63 V에서 0.31 V로 온도 상승에 따라 약 0.1 V씩 감소하였다. 이는 energy band diagram에서 p-type 영역과 n-type 영역의 energy band 차가 감소해 공핍층 영역의 폭이 좁아짐을 의미한다. 공핍층의 두께 감소로 다이오드 전류의 급격한 증가뿐 아니라 위에서 언급한 바와 같은 C-V 특성을 보였다. 이번 연구에서는 기존의 보편화 된 I-V 측정을 통한 다이오드 소자 분석과는 달리 온도 변화에 따른 C-V 분석을 통해 소자 내부의 전위 장벽 및 공핍층 폭 감소에 따른 소자 특성 변화를 분석하였다.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.89-94
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• 2011

The mechanism of the cycloaddition reaction of forming germanic bis-heterocyclic compound between singlet dimethylgermylene carbene and acetone has been investigated with CCSD(T)//B3LYP/6-$31G^*$ method. From the potential energy profile, it can be predicted that, this reaction has one dominant channel. The presented rule of this dominant channel is that the two reactants firstly form a four-membered ring carbene (RC4) through the [2+2] cycloaddition reaction. Due to $sp^2$ hybridization of carbene C atom in RC4, RC4 further combines with acetone to form a reactant complexe (RC5). Due to the further $sp^3$ hybridization of carbene C atom in RC4, RC5 isomerizes to a germanic bisheterocyclic compound (P6) via the transition state (TS5).

• Structural Engineering and Mechanics
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• 제78권1호
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• pp.31-39
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• 2021

To investigate numerically the effect of all parameters on the outcome of an aircraft impact into robust engineering structures like nuclear power plant containments is a tedious task. In order to reduce the problem to a manageable size, we propose a single dimensionless parameter, the damage potential, to characterize the main features of the impact. The damage potential, which is the ratio of the initial kinetic energy of the aircraft to the work required to crush it, enables us to find the crucial parameter settings that need to be modelled numerically in detail. We show in this paper that the damage potential is indeed the most important parameter of the impact that determines the time-dependent reaction force when either finite element (FE) modelling or the Riera model is applied. We find that parameters that do not alter the damage potential, like elasticity of the target, are of secondary importance and if parameters are altered in a way that the damage potential remains the same then the course of the impact remains similar. We show, however, that the maximum value of the reaction force can be higher in case of elastic targets than in case of rigid targets due to the vibration of the target. The difference between the Riera and FE model results is also found to depend on the damage potential.