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식품 접촉 모사 환경에서 식품유사용매의 LDPE-나노 TiO<sub>2</sub> 복합필름 재질특성 영향 평가
이우석,최재천,박세종,김미경,고성혁,Lee, Wooseok,Choi, Jae Chun,Park, Se-jong,Kim, MeeKyung,Ko, Seonghyuk 한국포장학회 2017 한국포장학회지 Vol.23 No.3
The effect of food simulants on properties and light barrier function of LDPE-nano $TiO_2$ composite film has been investigated. LDPE-nano $TiO_2$ composite films were prepared with 5.0wt% $TiO_2$ content by melt-extrusion. To simulate food contact environment, according to KFDA standards and specifications for food utensils, containers and packages, food simulants were selected with deionized water, 50% ethanol, 4% acetic acid and n-heptane and composite films were immersed in each food simulant at $70^{\circ}C$, 30 min except n-heptane ($25^{\circ}C$, 60 min). A variety of material properties, including crystallinity, chemical bonds, surface morphology, mechanical, oxygen barrier and optical properties, of LDPE-nano $TiO_2$ composite film were examined with and without the food simulants treatment. As a result, under regulated migration condition, LDPE-nano $TiO_2$ composite showed extremely stable in all properties tested in the study in contact with food simulants indicating that $TiO_2$ nanoparticles are physicochemically stable and quite compatible with LDPE. Results enable us to anticipate migration of $TiO_2$ will probably not occur. To evaluate influence of migration of $TiO_2$ on food stuffs, their color, pH and acidity were observed as well.
LDPE-나노 TiO<sub>2</sub> 복합 필름의 기능성 및 재질안정성 평가
이우석,고성혁,Lee, Wooseok,Ko, Seonghyuk 한국포장학회 2017 한국포장학회지 Vol.23 No.2
In this work, the effects of nano $TiO_2$ on functionality and stability of low density polyethylene (LDPE) composite films were investigated for food packaging application. LDPE-nano $TiO_2$ composite films were prepared with various $TiO_2$ contents (0, 0.5, 1.0, 3.0 and 5.0wt%) by melt-extrusion and their basic properties such as crystallinity, chemical bonds and surface morphology were examined by XRD, FTIR and SEM. Ultraviolet (UV) light barrier property of as-prepared LDPE-nano $TiO_2$ composite films was also studied and the presence of nano $TiO_2$ resulted in significant improvement of UV light barrier compared to the pure LDPE film. To evaluate influence of nano $TiO_2$ on LDPE properties required as packaging material, thermal, mechanical, gas barrier and optical properties of LDPE-nano $TiO_2$ composite films were characterized with various analytical techniques including TGA, UTM, OTR, WVTR and UV-vis spectroscopy. As a result, except optical property of LDPE, no significant effects were found in other properties. Opacity of pure LDPE was greatly increased with increasing concentration of nano $TiO_2$.
LDPE-나노 ZnO 복합필름의 기능성 및 재질안정성 평가
이우석,고성혁,Lee, Wooseok,Ko, Seonghyuk 한국포장학회 2018 한국포장학회지 Vol.24 No.1
In this work, nano ZnO was introduced into low density poly ethylene (LDPE) composites films with various contents (0, 0.5, 1.0, 3.0 and 5.0 wt%) by melt-extrusion. Their basic properties such as crystallinity, chemical bonds and surface morphology were examined by XRD, FTIR and SEM. XRD patterns and FTIR peaks intensity were increased in proportion to the ZnO contents. SEM images showed well dispersed nano ZnO in LDPE composite films. Antimicrobial functionality of LDPE-nano ZnO composite films was also studied and the presence of nano ZnO resulted in significant improvement of antimicrobial functionality compared to the pure LDPE film. To evaluate influence of nano ZnO on LDPE properties required as packaging material, thermal, mechanical, gas barrier and optical properties of LDPE-nano ZnO composite films were characterized with various analytical techniques including TGA, UTM, OTR, WVTR and UV-Vis spectroscopy. As a result, except optical and mechanical properties of LDPE, no significant effects were found in other properties. Opacity of pure LDPE was greatly increased with increasing concentration of nano ZnO and tensile strength was also improved at 0.5wt% ZnO content.
이우석,최정욱,송혁환,고성혁,Lee, Wooseok,Choi, Jungwook,Song, Hyuk-Hwan,Ko, Seonghyuk 한국포장학회 2020 한국포장학회지 Vol.26 No.3
As HMR (home meal replacement) food market grows rapidly, a new packaging with more HMR specialized functions is highly required to promote consumers' convenience. A susceptor is defined as a material generating heat by absorbing electromagnetic energy such typically as radiofrequency or microwave radiation. In microwave cooking, susceptors are made of conductive metal thin film deposited on paper or plastic sheet and have generally been used to help crispen or brown foods by converting microwave energy into heat. This mini review article deals with current status of microwave susceptor packaging including commercial products, technical theory, types of susceptor and a test method for heating performance.
Enhance Charge Cycle Efficiency of Lead-acid Battery using Solar Power System
Wooseok Lee(이우석),Hanmil Park(박한밀),Eunsonn Justin Shin(신은수) 적정기술학회 2018 적정기술학회지(Journal of Appropriate Technology) Vol.4 No.2
In developing countries, many areas are not supplied with electricity due to lack of electric power infrastructure, and many others are suffering from unstable power quality and frequent power outages. As an alternative, power supply using renewable energy, such as solar, wind, and small hydro power, is being activated. Among these, the most widely used source is photovoltaic power generation system, which is easy to install and maintain. In developed countries where power supply is smooth, grid connected photovoltaic systems that use conventional electricity together are generally used for the purpose of reducing electricity bill. However, in developing countries, because conventional electricity supply is unstable, independent solar power generation systems using batteries are mainly used. Among these, a solar panel is a semi-permanent product that can be used for more than 20 years, whereas a typical battery is a consumable with a maximum life span of less than five years, accounting for most maintenance cost of solar power systems. In addition, in the case of a lead storage cell, which is readily available in developing countries and therefore is most widely used, lifespan has been drastically reduced depending on environmental conditions such as pre-charge method, temperature, and humidity, which frequently makes it replaced in six months. For these reasons, management methods to extend lifespan of lead storage cell have become an important research topic. In this study, a voltage level was set as a measure value to identify and manage the characteristics of charging and discharging of lead storage batteries, and standardized discharge curves were created using LED lamps that consume the most stable power. Based on this, the discharging characteristics for different kinds of DC and AC products were identified. Also, the proper isolation voltage level to extend the battery lifespan was verified. The study will be used to design an optimized solar power system along with the further study on charging efficiency of solar power systems in developing countries.
GaN-HEMT를 이용한 X-대역 이단 전력증폭기 설계
이우석(Wooseok Lee),이휘섭(Hwiseob Lee),박승국(Seungkuk Park),임원섭(Wonseob Lim),한재경(Jaekyoung Han),박광근(Kwanggun Park),양영구(Youngoo Yang) 한국전자파학회 2016 한국전자파학회논문지 Vol.27 No.1
본 논문에서는 GaN-HEMT를 이용하여 X-대역에서 동작하는 이단으로 구성된 전력증폭기를 설계 및 제작하였다. 높은 전력 이득을 얻기 위해 간단한 구조의 중간 단 정합 네트워크를 통해 이단으로 구성하였다. 3D EM 시뮬레이션을 통하여 본드와이어 인덕턴스와 기생 캐패시턴스를 예측하였다. 본드와이어 인덕턴스를 줄임으로써 정합 네트워크의 Q(quality-factor)를 최소화하여 대역 특성을 향상시켰다. 제작된 전력증폭기는 40 V의 동작 전압을 인가하였으며, 8.1~8.5GHz에서 16 dB 이상의 전력 이득, 42.5 dBm 이상의 출력 전력, 35 % 이상의 효율 특성을 나타냈다. This paper presents an X-band two-stage power amplifier using GaN-HEMT. Two-stage structure was adopted to take its high gain and simple inter-stage matching network. Based on a 3D EM simulation, the bond-wire inductance and the parasitic capacitance were predicted. By reducing bond-wire inductance, Q of the matching network is decreased and the bandwidth is improved. The implemented two-stage PA shows a power gain of more than 16 dB, saturated output power of more than 42.5 dBm, and a efficiency of more than 35 % in frequency range of 8.1~8.5 GHz with an operating voltage of 40 V.
정적 분석 경보 사이의 종속 관계를 이용한 대표 경보 찾기
이우석(Wooseok Lee),김유일(Youil Kim),이광근(Kwangkeun Yi) 한국정보과학회 2011 한국정보과학회 학술발표논문집 Vol.38 No.1C
오류 정적 분석기가 출력하는 분석 경보 사이의 종속 관계를 안전하게 계산하여, 분석 경보들을 무리짓는 짓고, 대표 경보들만을 출력하는 기법을 소개한다. 경보 1이 가짜 경보일 때 경보 2도 항상 가짜 경보가 된다면, 경보 1을 살펴 가짜 경보임을 안 경우에 경보 2를 살펴볼 필요가 없다. 따라서, 경보 2는 경보 1에 종속적이라고 말할 수 있다. 버퍼 오버런 분석기의 분석 경보 보고서를 개선하기 위해 이러한 기법을 적용한 결과, 여러 개의 오픈 소스 소프트웨어들의 분석 후에 보고되는 경보의 수를 평균 60% 줄일 수 있었다. 종속 관계 계산을 위해 소요되는 추가적인 분석 시간은 평균 20% 이다. 제안하는 기법은 요약 해석에 기반을 둔 모든 정적 분석기에 적용할 수 있으며, 실제 오류일 가능성이 높은 경보를 먼저 보여주는 통계적인 기법들과 독립적으로 사용될 수 있다.