• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.244.1-244.1
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• 2013

The p-type GaN which act as a hole injection layer in GaN-based LEDs has fundamental problems. The first one arises from the difficulty in growing a highly doped p-GaN (with a carrier concentration exceeding ~1018 $cm^{-3}$). And the second one is the absence of appropriate metals or conducting oxides having a work function that is larger than that of p-type GaN (7.5 eV). Moreover, the LED efficiency is decreases gradually as the injection current increases (the so-called 'efficiency droop' phenomenon). The efficiency droop phenomenon in InGaN quantum wells (QWs) has been a large obstacle that has hindered high-efficiency operation at high current density. In this study, we introduce the new approaches to improve the light-output power of LEDs by using graphene oxide sheets. Graphene oxide has many functional groups such as the oxygen epoxide, the hydroxyl, and the carboxyl groups. Due to nature of such functional groups, graphene oxide possess a lot of hole carriers. If graphene oxide combine with LED top surface, graphene oxide may supply hole carriers to p-type GaN layer which has relatively low free carrier concentration less than electron concentration in n-type GaN layer. To prove the enhancement factor of graphene oxide coated LEDs, we have investigated electrical and optical properties by using ultra-violet photo-excited spectroscopy, confocal scanning electroluminescence microscopy.

• 한국약용작물학회지
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• 제26권4호
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• pp.317-327
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• 2018

Background: The root of Angelica gigas Nakai is used as a traditional herbal medicine in Korea for the treatment of many diseases. However, the poor water solubility of the active components in A. gigas Nakai is a major obstacle to its bioavailability. Methods and Results: This work aimed at enhancing the solubility of the active compounds of A. gigas Nakai by a chemical (using a surfactant) and physical (hot melt extrusion, HME) crosslinking method. Fourier transform infrared spectroscopy revealed multiple peaks in the case of the extrudate solids, attributable to new functional groups including carboxylic acid, alkynes, and benzene derivatives. Differential scanning calorimetry analysis showed that the extrudate soilid had a lower glass transition temperature ($T_g$) and enthalpy (${\Delta}H$) ($T_g:43^{\circ}C$, ${\Delta}H$ : < 6 J/g) as compared to the non-extrudate ($T_g:68.5^{\circ}C$, ${\Delta}H:123.2$) formulations. X-ray powder diffraction analysis revealed the amorphization of crystalline materials in the extrudate solid. In addition, enhanced solubility (53%), nanonization (403 nm), and a higher amount of extracted phenolic compounds were achieved in the extrudate solid than in the non-extrudate (solubility : 36%, nanonization : 1,499 nm) formulation. Among the different extrudates, acetic acid and span 80 mediated formulations showed superior extractions efficiency. Conclusions: HME successfully enhanced the production of amorphous nano dispersions of phenolic compound including decursin from extrudate solid formulations.

• 지역사회간호학회지
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• 제29권4호
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• pp.467-475
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• 2018

Purpose: The purpose of this study is to investigate adherence to the clean intermittent catheterization (CIC) and influencing factors on the adherence following a customized intensive education program (CIEP). Methods: This work is a retrospective descriptive study. The subjects were 226 emptying failure patients who learned in a CIEP from January 2012 to July 2014. The program developed in 2011 and consisted of 1) customized theoretical education; based on the results of urologic tests, underlying disease, or surgery of the patients, 2) hands-on practice until the trainees were able to master the techniques, 3) questions about the process of catheterization and what he/she needs to know. 4) at follow-up, the survey about adherence and barrier to CIC. Clinical characteristics; the level of satisfaction, understanding, and self-confidence; the barrier in medical records were reviewed. Results: The short-term adherence rate (median 22 days) is 87.6% and the long-term adherence rate (median 112 days) is 50.4%. The biggest obstacle is time management. The levels of satisfaction, understanding, and self-confidence are very high. The variable of Income is the only factor that has influence on adherence. Conclusion: Despite the CIEP, the adherence rate is relatively low. In addition to the education, emotional and psychological supports and regular follow-up are needed to improve long-term adherence.

• Smart Structures and Systems
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• 제29권3호
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• pp.499-512
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• 2022

This work proposes a novel contactless vibration damping and thermal isolation tripod platform based on Superconducting Magnetic Levitation (SML). This prototype is suitable for cryogenic environments, where classical passive, semi active and active vibration isolation techniques may present tribological problems due to the low temperatures and/or cannot guarantee an enough thermal isolation. The levitating platform consists of a Superconducting Magnetic Levitation (SML) with inherent passive static stabilization. In addition, the use of Operational Modal Analysis (OMA) technique is proposed to characterize the transmissibility function from the baseplate to the platform. The OMA is based on the Stochastic Subspace Identification (SSI) by using the Expectation Maximization (EM) algorithm. This paper contributes to the use of SSI-EM for SML applications by proposing a step-by-step experimental methodology to process the measured data, which are obtained with different unknown excitations: ambient excitation and impulse excitation. Thus, the performance of SSI-EM for SML applications can be improved, providing a good estimation of the natural frequency and damping ratio without any controlled excitation, which is the main obstacle to use an experimental modal analysis in cryogenic environments. The dynamic response of the 510 g levitating platform has been characterized by means of OMA in a cryogenic, 77 K, and high vacuum, 1E-5 mbar, environment. The measured vertical and radial stiffness are 9872.4 N/m and 21329 N/m, respectively, whilst the measured vertical and radial damping values are 0.5278 Nm/s and 0.8938 Nm/s. The first natural frequency in vertical direction has been identified to be 27.39 Hz, whilst a value of 40.26 Hz was identified for the radial direction. The determined damping values for both modes are 0.46% and 0.53%, respectively.

• 한국기계가공학회지
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• 제21권4호
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• pp.114-130
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• 2022

The purpose of this study was to investigate the possibility of increasing the efficiency of disaster relief rescue operations through collaboration among multiple aerial and ground robots. The robots create 2.5D maps, which are merged into a 2.5D map. The 2.5D map can be handled by a low-specification controller of an aerial robot and is suitable for ground robot navigation. For localization of the aerial robot, a six-degree-of-freedom pose recognition method using VIO was applied. To build a 2.5D map, an image conversion technique was employed. In addition, to merge 2.5D maps, an image similarity calculation technique based on the features on a wall was used. Localization and navigation were performed using a ground robot to evaluate the reliability of the 2.5D map. As a result, it was possible to estimate the location with an average and standard error of less than 0.3 m for the place where the 2.5D map was normally built, and there were only four collisions for the obstacle with the smallest volume. Based on the 2.5D map building and map merging system for the aerial robot used in this study, it is expected that disaster response work efficiency can be improved by combining the advantages of heterogeneous robots.

• Smart Structures and Systems
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• 제31권5호
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• pp.485-500
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• 2023

Machine learning-based structural health monitoring (ML-based SHM) methods are researched extensively in the recent decade due to the availability of advanced information and sensing technology. ML methods are well-known for their pattern recognition capability for complex problems. However, the main obstacle of ML-based SHM is that it often requires pre-collected historical data for model training. In most actual scenarios, damage presence can be detected using the unsupervised learning method through anomaly detection, but to further identify the damage types would require prior knowledge or historical events as references. This creates the cold-start problem, especially for new and unobserved structures. Modal-based methods identify damages based on the changes in the structural global properties but often require dense measurements for accurate results. Therefore, a two-stage hybrid modal-machine learning damage detection scheme is proposed. The first stage detects damage presence using Principal Component Analysis-Frequency Response Function (PCA-FRF) in an unsupervised manner, whereas the second stage further identifies the damage. To solve the cold-start problem, mode shape assessment using the first mode is initiated when no trained model is available yet in the second stage. The damage identified by the modal-based method would be stored for future training. This work highlights the performance of the scheme in alleviating the cold-start issue as it transitions through different phases, starting from zero damage sample available. Results showed that single and multiple damages can be identified at an acceptable accuracy level even when training samples are limited.

• Journal of Microbiology and Biotechnology
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• 제33권10호
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• pp.1384-1389
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• 2023

This work aimed to evaluate the feasibility of biohydrogen production from Barley Straw and Miscanthus. The primary obstacle in plant biomass decomposition is the recalcitrance of the biomass itself. Plant cell walls consist of cellulose, hemicellulose, and lignin, which make the plant robust to decomposition. However, the hyperthermophilic bacterium, Caldicellulosiruptor bescii, can efficiently utilize lignocellulosic feedstocks (Barley Straw and Miscanthus) for energy production, and C. bescii can now be metabolically engineered or isolated to produce more hydrogen and other biochemicals. In the present study, two strains, C. bescii JWCB001 (wild-type) and JWCB018 (ΔpyrFA Δldh ΔcbeI), were tested for their ability to increase hydrogen production from Barley Straw and Miscanthus. The JWCB018 resulted in a redirection of carbon and electron (carried by NADH) flow from lactate production to acetate and hydrogen production. JWCB018 produced ~54% and 63% more acetate and hydrogen from Barley Straw, respectively than its wild-type counterpart, JWCB001. Also, 25% more hydrogen from Miscanthus was obtained by the JWCB018 strain with 33% more acetate relative to JWCB001. It was supported that the engineered C. bescii, such as the JWCB018, can be a parental strain to get more hydrogen and other biochemicals from various biomass.

• 한국안전학회지
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• 제39권1호
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• pp.41-54
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• 2024

Efforts to reduce on-site safety incidents have expanded, leading to active research in this domain. However, a systematic analysis to improve the utility of technology is lacking. In this study, we conducted a survey on the various institutional and technical improvement measures to promote the application of smart construction safety technology over three years after the implementation of the "Smart Safety Equipment Support Project." The results showed that financial constraint was the primary obstacle in the adoption of this innovation. Fostering a flexible environment in the utilization of management fees and financial support of projects was determined to aid in the extensive application of the technology. Ensuring cost efficiency and user-friendliness were principally necessary for technical enhancements in the smart construction safety technology. Technologies, such as VR/AR safety education, real-time location tracking, wearable devices, and innovation on streamlining safety-related work efficiency, had been anticipated to contribute to on-site safety. Operating a smart safety control center was expected to be beneficial in the systematic securing of data and reduction of safety blind spots. Effective methods had been suggested to overcome the barriers that hindered the development and application of smart construction safety technology. This study facilitates in the technological improvements in this field.

• 한국사회복지학
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• 제65권4호
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• pp.61-88
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• 2013

이 연구는 아동학대 예방과 개입의 큰 축을 담당하는 병원 학대피해아동보호팀의 아동학대 사망사건 개입경험을 탐색할 목적으로 수행되었다. 이를 위하여 전국적으로 등록된 62개 병원 학대피해아동보호팀과 접촉하였고, 최종적으로 아동학대 사망사건을 경험한 5개 병원 학대피해아동보호팀 구성원들(의료사회복지사와 의사)과의 인터뷰를 통해 자료를 수집하였다. 수집된 자료를 질적연구방법을 사용하여 분석한 결과, 팀의 개입에도 불구하고, 학대 피해 아동이 매우 위중한 상태에서 병원에 도착했거나, 보호자의 거짓말이나 치료 거부로 인한 치료적 대응의 지연 때문에, 아동의 사망 진행을 막기 어려웠던 것으로 나타났다. 그럼에도 학대피해아동보호팀의 의심과 개입을 통해 사망 원인이 학대임을 밝혀낸 것은 팀 활동의 의미 있는 성과로 간주되었다. 이 과정에서 신고의무자 역할에 대한 인식 부족과 부담은 의료진의 적극적인 개입을 막는 장애물이며, 개입을 지속하기 위해서는 학대 인과관계 규명에 필요한 증거자료의 확보가 중요하다는 점이 확인되었다. 이러한 연구 결과를 토대로 학대 상황에 대한 조기 발견과 증거 확보 조치, 사망 원인 규명을 위한 실천적 및 정책적 방안에 대해 제언하였다.

• 한국산학기술학회논문지
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• 제12권7호
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• pp.3258-3266
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• 2011

본 연구의 목적은 IT 부문 여성기업인을 대상으로 여성기업인이 일과 가족을 병행하면서 기업의 성과를 향상시키는데 기여할 수 있는 요인을 찾아내며, 이들 요인과 여성기업 성과간의 관련성을 실증연구를 통해 규명하는 것이다. 이를 위해, 본 연구에서는 여성기업의 창업 및 성장, 여성의 일-가족 갈등 관리전략 등에 관한 문헌을 고찰하여, 외부자원(배우자자원, 시간자원, 직원의 신뢰, 재정적 자원), 일가족 역할 중심성 (일 중심, 가정 중심, 일가족 이중 중심), 역할조정전략(가족역할감소, 일역감소, 일가족 역할공유)을 여성기업 성과의 주요 결정요인으로 도출하였다. 본 연구의 자료는 IT부문 여성기업인을 대상으로 수행한 설문조사를 통해 수집한 유효 설문 111개이다. 본 연구에서 제시한 연구모형을 검증하기 위하여 다섯 개의 가설을 설정하고, 이를 실증 분석 한 결과는 다음과 같다. 외부자원 중 배우자자원은 모든 역할조정전략과 관련성이 없는 것으로 나타난 반면에 재정적 자원은 일가족 역할 공유전략에 유의미한 수준에서 영향을 미치는 것으로 나타났다. 시간 및 직원자원은 공유전략과 관련성이 없는 것으로 밝혀졌지만 가족역할 감소전략과는 유의미한 관련성이 있는 것으로 나타났다. 일가족 역할 중심에서는 일가족 역할 이중 중심성이 일가족 역할공유전략과 관련성이 있는 것으로 나타났다. 마지막으로 외부자원, 일가족 역할 이중 중심성, 그리고 일가족역할공유전략이 여성기업의 성과에 영향을 주지 않는 것으로 나타났다. 이는 여성기업인이 사업성장과 매출 증대에 있어서 가족역할을 감소하고 일 역할을 중심에 두고 있는 것을 의미하며, 여성기업인의 사업성과에 여전히 가족역할 수행이 갈등요인이 되고 있음을 시사하고 있다.