• 반도체디스플레이기술학회지
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• 제16권3호
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• pp.31-35
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• 2017

We have fabricated flexible and stretchable pressure sensors using silver nanowires (AgNWs) and analyzed their electric responses. AgNWs are spray coated directly onto uncured polydimethylsiloxane (PDMS) such that AgNWs penetrate into the uncured PDMS, enhancing the adhesion properties of AgNWs. However, the single-layered AgNW sensor exhibits unstable electric response and low pressure sensitivity. To tackle it, we have coated a conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) onto the AgNW layer. Such a hybrid bilayer sensor ensures a stable electric response because the over-coating layer of PEDOT:PSS effectively suppresses the protrusion of AgNWs from PDMS during release. To enhance the sensitivity further, we have also fabricated a stacked bilayer AgNW sensor. However, its electric response varies depending sensitively on the initial overlap pressure.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.159-166
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• 2022

The assembly of the micron-sized Si/CNT/carbon composite wrapped with graphene (SCG composite) is designed and synthesized via a spray drying process. The spherical SCG composite exhibits a high discharge capacity of 1789 mAh g^-1 with an initial coulombic efficiency of 84 %. Moreover, the porous architecture of SCG composite is beneficial for enhancing cycling stability and rate capability. In practice, a blended electrode consisting of spherical SCG composite and natural graphite with a reversible capacity of ~500 mAh g^-1, shows a stable cycle performance with high cycling efficiencies (> 99.5%) during 100 cycles. These superior electrochemical performance are mainly attributed to the robust design and structural stability of the SCG composite during charge and discharge process. It appears that despite the fracture of micro-sized Si particles during repeated cycling, the electrical contact of Si particles can be maintained within the SCG composite by suppressing the direct contact of Si particles with electrolytes.

• 한국분무공학회지
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• 제28권4호
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• pp.169-175
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• 2023

Multi-injection scheme is being applied to GDI combustion to reduce PM and PN emission to meet the EU7 regulation. However, very short injection duration encounters the ballistic injection region, which injection quantity does not increase linearly with injection duration when applying multi-injection. In this study, numerical studies were conducted to reveal the cause of ballistic injection and the effect of design parameters on ballistic region using 1-D simulation, AMESim. Injection rate and injection quantity were compared with experiment to validate the established model, which showed the accuracy with 10% error. The model revealed that the tendency of ballistic region coincides with the needle motion behavior, which means that parameters at the upper part of needle such as electro-magnetic force, needle spring force and needle friction force have dominant effect on ballistic injection. To figure out the effect of electro-magnetic and needle friction force on ballistic, those parameters were varied to plus and minus 10% with model. The result showed that those parameters clearly changed the ballistic region characteristics, however, the impact became insignificant for outside of ballistic region, which means that the ballistic injection is mainly influenced by initial motion of injector needle.

• 한국분무공학회지
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• 제29권3호
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• pp.147-154
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• 2024

This study explores the rate of injection (ROI) and injection quantities of a solenoid-type high-pressure injector under varying conditions by integrating experimental methods with machine learning (ML) techniques. Experimental data for fuel injection were obtained using a Zeuch-based HDA Moehwald injection rate measurement system, which served as the foundation for developing a machine learning model. An artificial neural network (ANN) was employed to predict the ROI, ensuring accurate representation of injection behaviors and patterns. The present study examines the impact of ambient conditions, including chamber temperature, chamber pressure, and injection pressure, on the transient profiles of the ROI, quasi-steady ROI, and injection duration. Results indicate that increasing the injection pressure significantly increases ROI, with chamber pressure affecting its initial rising peak. However, the chamber temperature effect on ROI is minimal. The trained ANN model, incorporating three input conditions, accurately reflected experimental measurements and demonstrated expected trends and patterns. This model facilitates the prediction of various ROI profiles without the need for additional experiments, significantly reducing the cost and time required for developing injection control systems in next-generation aero-engine combustors.

• 한국근적외분광분석학회:학술대회논문집
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• 한국근적외분광분석학회 2001년도 NIR-2001
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• pp.1126-1126
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• 2001

The paper presented here is the initial part of a larger study, in which it was determined which quality parameters in cheese powder could already be predicted by NIR at an early stage in the process and which could only be predicted at the final stages of the process. This initial study was performed in order to establish the levels and nature of variation within and between batches such that the subsequent data collection could be tackled optimally. The perspectives evolved into more than was originally planned and revealed some interesting uses of NIR-technology. Cheese powder production starts as a batch process, where waste cheese from other dairies is melted down in a vat. The process then turns into a continual process as the vat is emptied and the melted cheese is then filtered, homogenized, pasteurized and finally spray dried. Between each batch the powder is to a greater or lesser degree a mixture of 2 batches. This paper is divided into 2 aspects, one regarding the optimization of sampling time and the other is a study of process dynamics. Optimizing sampling time This initial study included 9 powder samples from 9 different batches produced during one day. The raw materials for the batches were chosen with the aim of creating a relatively high level of variation in the data. The total of 81 samples were taken out at regular intervals and spectra were collected on a NIR-systems 6500 instrument. The subsequent reduction of the data by PCA to score values shows the power of NIR as a tool to determine not only when samples are representative of a certain batch, but also which batches are stable enough to include in a further study. Studying process dynamics To take this experiment a step further 1 of the 81 samples were sent to the laboratory for further analyses. The samples were chosen on the criteria that they covered the spectral variation in the dataset. These samples were analysed for 4 chemical components and 5 physical attributes, which are essential for describing the quality of the product. The latent structure of the 7 samples, using the chemical and physical variables, is totally comparable to the latent structure of the NIR spectra. This outcome makes it possible to describe the dynamics of one day's production both chemically and physically with relatively little resources. Additionally it raises the question as to whether reference values are needed, as the latent structure of the NIR-spectra appears to be sufficient in providing information on the quality of the product. To be able to use NIR in this way would require defining quality limits in the principal component space as opposed to each of the reference values. The potential of NIR applied in an explorative fashion with batch processes opens a whole new gateway for the use of this technology. This study explains yet again after so many years in the field “why I'm crazy about NIR!”.

• 한국자기학회지
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• 제5권6호
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• pp.937-946
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• 1995

본 연구에서는 NiCuZn Ferrite 제조공정의 제어를 위하여 제조공정 변수에 따른 NiCuZn Ferrite의 물성 및 자기적특성의 변화를 검토하여, 겉보기밀도(bulk density)와 초기투자율의 관계를 명확하게 하는 것을 목적으로 하였다. $700^{\circ}C$에서 3시간 하소 한 NiCuZn Ferrite를 약 60시간 볼밀링하여 약 $0.5\mu\textrm{m}$ 입자크기로 분쇄한 후 분무 건조하여 과립화하였다. 본 연구에서는 (1)NiCuZn Ferrite 과립의 크기와 성형압력 변화와 (2)일정한 성형조건에서 소성온도의 변화에 따른 성형체 및 소성체의 물성측정, 그리고 자기적 특성을 검토하였다. NiCuZn Ferrite의 green density는 과립의 크기보다는 성형압력에 더 의존하였으며, 과립의 크기가 $150\mu\textrm{m}$ 이하 일 때 성형압력이 증가 함에 따라 green density는 $2.484\;g/cm^{3}$에서 $3.002\;g/cm^{3}$로 크게 증가하 였다. NiCuZn Ferrite의 bulk density는 소성온도에 의하여 거의 직선적으로 $3.470\;g/cm^{3}$에서 $4.754\;g/cm^{3}$로 증가하였다. 성형압력 변화 및 소성온도 변화에 따른 NiCuZn Ferrite 초기투자율과 겉보기밀도 관계를 비교 검토한 결과, NiCuZn Ferrite의 초기투자율($\mu_{i}$)과 겉보기밀도($\rho$)의 관계를 $\mu_{i}=a+b_{\rho}+c_{\rho}^2$와 같이 실험식으로 표현할 수 있었다.

• Asian-Australasian Journal of Animal Sciences
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• 제13권11호
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• pp.1576-1583
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• 2000

Three experiments were conducted to determine the nutritional value of wheat gluten (WG) and spray-dried porcine plasma (SDPP) in diets for nursery pigs. In Exp. 1, 120 weanling pigs (5.7 kg avg initial BW) were used in a 35-d growth assay. Treatments for d 0 to 14 were: 1) dried skim milk (DSM)-dried whey-SBM based control; 2) WG to replace the protein from DSM; 3) SDPP; and 4) WG-SDPP (50:50 blend on a protein basis) to replace the protein from DSM. From d 14 to 35, all pigs were fed a common corn-SBM-whey-based diet. For d 0 to 14, there were no differences in ADG, ADFI, and gain/feed (p>0.11). However, for d 14 to 35, pigs fed diets with WG had greater gain/feed than those fed SDPP (p<0.05), and pigs fed diets with the WG-SDPP blend had greater ADG than pigs fed diets with WG or SDPP alone (p<0.07). In a second experiment, 60 weanling pigs (5.1 kg avg initial BW) were used in a 28-d growth assay. All pigs were fed the WG-SDPP diet fed in Exp. 1 for d 0 to 14, and changed to experimental diets for d 14 to 28. Treatments were: 1) the whey-SBM-based diet used for d 14 to 28 in Exp. 1; or 2) a whey-SBM based diet with 3% added SDPP. There were no differences in ADG, ADFI, gain/feed, or apparent digestibilities of DM and N among treatments for d 14 to 28 or overall (p>0.14). In a third experiment, 150 weanling pigs (5.6 kg avg initial BW) were used in a 32-d growth assay to determine the optimal blend of WG and SDPP for use after weaning. The SDPP was added as 8% of the control diet, and WG was substituted on a protein basis to yield the desired SDPP:WG blends. Treatments were (d 0 to 14): 1) SDPP; 2) 75% SDPP and 25% WG; 3) 50% SDPP and 50% WG; 4) 25% SDPP and 75% WG; and 5) WG. As in Exp. 1, all pigs were switched to a common corn-SBM-whey-based diet for d 14 to 32. For d 0 to 14, ADG and ADFI increased as replacement of the SDPP was increased up to 50% and decreased when more of the SDPP was removed from the diet (quadratic effects, p<0.004 and 0.02, respectively). Apparent digestibilities of DM and N (at d 13) were not affected by treatments (p>0.18). For d 14 to 32, treatments did not affect ADG (p>0.2), although there were quadratic responses in ADFI (p<0.04), with pigs fed the 50:50 blend suggested the greatest intake of feed. For the overall experimental period (d 0 to 32), ADG, ADFI, and gain/feed increased as WG was used to replace as much as 50% of the SDPP (quadratic effects p<0.04, 0.02, and 0.06, respectively). In conclusion, WG can successfully replace up to 50% of the SDPP in a complex nursery diet, when SDPP is included at the 8% level. There is no advantage to keeping SDPP in the diet after Phase I (d 0 to 14).

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.422.1-422.1
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• 2016

Graphene quantum dots (GQDs), a new kind of carbon-based photo luminescent nanomaterial from chemically modified graphene oxide (CMGO) or chemically modified graphene (CMG), has attracted extensive research attention in the last few years due to its outstanding chemical, optical and electrical properties. To further extended its potential applications as optoelectronic devices, solar cells, bio and bio-sensors and so on, intensive research efforts have been devoted to the CMG. However, the CMG, a suspension of aqueous, have problematic since they are prone to agglomeration after drying a solvent. In this study, we synthesized the GQDs from graphite and deposited on silicon substrate by kinetic spray. The photo luminescent properties of deposited GQD films were analyzed and compared with initial GQDs suspension. In addition, its carbon properties were investigated with GQDs solution properties. The properties of deposited GQD films by kinetic spray were similar to that of the GQDs suspension in water. We could provide a pathway for silicon-based silicon based device applications. Finally, the well-adjusted GQD films with photo luminescence effects will show Energy-Down-Shift layer effects on silicon solar cells. The GQD layers deposited at nozzle scan speeds of 40, 30, 20, and 10 mm/s were evaluated after they were used to fabricate crystalline-silicon solar cells; the results indicate that GQDs play an important role in increasing the optical absorptivity of the cells. The short-circuit current density (Jsc) was enhanced by about 2.94 % (0.9 mA/cm2) at 30 mm/s. Compared to a reference device without a GQD energy-down-shift layer, the PCE of p-type silicon solar cells was improved by 2.7% (0.4 percentage points).

• 한국응용과학기술학회지
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• 제33권3호
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• pp.593-598
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• 2016

본 연구에서는 유연성을 갖는 전극 제조를 위해 환원된 그래핀 옥사이드/단일벽 탄소나노튜브 복합체를 금이 코팅된 PET 기판 위에 스프레이 코팅하였다. 제조된 플렉시블한 전극의 전기 용량 값은 1 M의 황산 전해질과 $100mVs^{-1}$ 의 주사속도에서 $82Fg^{-1}$ 으로 측정 되었으며, 이 용량 값은 500 번의 굽힘 시험 후에 $38Fg^{-1}$ 로 감소되는 현상을 확인 하였다. 또한, 이러한 결과는 정전류 충방전과 전기화학 임피던스법을 포함한 전기화학적 분석 결과와도 부합하는 결과를 나타내었다. 유연성을 갖는 환원된 그래핀 옥사이드/단일벽 탄소나노튜브 복합체 전극은 500회의 반복적인 굽힘 시험 후에도 대략 50%의 초기 전기 용량 값을 유지 할 수 있었으며, 이러한 여러 가지 전기화학적 특성을 고려하여 볼 때 미래 개발 가능한 플렉시블한 에너지 저장 매체로써의 적용이 가능 하다는 점을 확인 할 수 있었다.

• 전기화학회지
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• 제15권2호
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• pp.67-73
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• 2012

본 연구에서는 습식분쇄, 구형화 분무건조 및 열처리 공정을 통해 구형의 $LiMn_{2-x}M_xO_4$(M = Al, Mg, B) 스피넬계 양극소재를 합성하고, 이의 전기화학적 성능을 평가하였다. $MnO_2$ (Tosoh, 91.94%), $Li_2CO_3$ (SQM, 97%), $MgCO_3$ (Aldrich, 99%), $Al(OH)_3$ (Aldrich, 99%) 및 $B_2O_3$ (Aldrich, 99%)를 원료로 사용하였으며, 분무건조공정에서 전구체의 구형화도 증가를 위해 PAAH 바인더를 첨가하였다. 200~500 nm 크기로 분쇄된 혼합 슬러리 용액으로부터 분무건조법을 통해 구형의 전구체를 제조하고, 이를 다양한 조건에서 열처리하여 최종 스피넬계 $LiMn_{2-x}M_xO_4$ (M = Al, Mg, B) 양극소재를 제조하였다. 제조된 구형의 $LiMn_{2-x}M_xO_4$ (M = Al, Mg, B) 양극재료는 이종원소 치환량, 특히 Boron 치환량에 따라 입자 표면 및 내부의 치밀도가 변화하는 것을 확인할 수 있었으며, 치밀도가 증가함에 따라 소재의 출력특성이 향상되었으며, 최적 조성의 양극소재는 상온 5 C 용량이 0.2 C 용량 대비 90% 이상이 됨을 확인하였다. 또한 표면의 치밀도도 증가함에 따라 $60^{\circ}C$ 고온 충방전 조건에서 수명특성이 향상되어 500회 사이클 이후에도 초기용량의 80% 이상을 유지하였다.