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Focusing through turbid media by polarization modulation.
Park, Jongchan,Park, Jung-Hoon,Yu, Hyeonseung,Park, YongKeun Optical Society of America 2015 Optics letters Vol.40 No.8
<P>We demonstrate that polarization modulation of an illumination beam can effectively control the spatial profile of the light transmitted through turbid media. Since the transmitted electric fields are completely mingled in turbid media, polarization states of an illumination beam can be used effectively to control the propagation of light through turbid media. Numerical simulations were performed which agree with experimental results obtained using a commercial in-plane switching liquid crystal display for modulating the input polarization states.</P>
Scattering Optical Elements: Stand-Alone Optical Elements Exploiting Multiple Light Scattering
Park, Jongchan,Cho, Joong-Yeon,Park, Chunghyun,Lee, KyeoReh,Lee, Heon,Cho, Yong-Hoon,Park, YongKeun American Chemical Society 2016 ACS NANO Vol.10 No.7
<P>Optical design and fabrication techniques are crucial for making optical elements. From conventional lenses to diffractive optical elements and to recent metasurfaces, various types of optical elements have been proposed to manipulate light where optical materials are fabricated into desired structures. Here, we propose a scattering optical element (SOE) that exploits multiple light scattering and wavefront shaping. Instead of fabricating optical materials, the SOE consists of a disordered medium and a photopolymer-based wavefront recorder, with shapes impinging on light on demand. With the proposed stand-alone SOEs, we experimentally demonstrate control of various properties of light, including intensity, polarization, spectral frequency, and near field. Due to the tremendous freedom brought about by disordered media, the proposed approach will provide unexplored routes to manipulate arbitrary optical fields in stand-alone optical elements.</P>
Park, Jongchan,Yu, Hyeonseung,Park, Jung-Hoon,Park, YongKeun Optical Society of America 2014 Optics express Vol.22 No.20
<P>We present measurements of the full Jones matrix of individual pixels in a liquid-crystal display (LCD) panel. Employing a polarization-sensitive digital holographic microscopy based on Mach-Zehnder interferometry, the complex amplitudes of the light passing through individual LCD pixels are precisely measured with respect to orthogonal bases of polarization states, from which the full Jones matrix components of individual pixels are obtained. We also measure the changes in the Jones matrix of individual LCD pixels with respect to an applied bias. In addition, the complex optical responses of a LCD panel with respect to arbitrary polarization states of incident light were characterized from the measured Jones matrix.</P>
박종찬(Jongchan Park),박민철(Minchul Park),전제성(Jesung Jeon),정상국(Sangguk Jeong),박경한(Kyunghan Park),이송(Song Lee) 한국지반환경공학회 2014 한국지반환경공학회논문집 Vol.15 No.7
소일 시멘트 혼합토의 역학적 성질을 파악할 수 있는 인자로서는 일축압축강도로 기존 연구사례에서 제시되었다. 본 연구에서는 저소성실트를 이용한 시멘트 혼합토의 일축압축강도 시험을 통해 실트함수비, 재령일, 시멘트 함유율에 대한 역학적 변화를 분석하였으며, Abrams가 제안한 B계수에 대한 변화를 기존연구사례와 비교?분석 및 시멘트 혼합토의 일축압축강도 예측식도 제안하였다. 상수 B계수값은 토질의 특성 및 재령일 등에 따라 변화였으며, B계수 변화의 적정성 여부를 일축압축강도로 분석한 결과 변수형태의 고려가 적정한 것으로 나타났다. Abrams 방정식을 적용하고 재령일, 시멘트 함유율과 재령일을 고려한 저소성실트 혼합토의 일축압축강도 예측식을 제안하였다. For analysis of mechanics properties of soil cement, unconfined compressive strength has been proposed by existing case studies. In this study, mechanical changes with water content of silt, curing time and cement content were analyzed through unconfined compressive strength test. In addition, the changes for B factor by Abrams were compared with existing case studies after the prediction equations could be proposed about the unconfined compressive strength of admixed cement soil. Especially, the B constant factor was changed with soil characteristics and curing time. For analysis results of appropriateness status and unconfined compressive strength, consideration of variable form was titrated. The prediction equations at low plasticity silt admixed using the uniaxial compressive strength with applying Abrams’s equation and considering cement content, curing time is proposed.
전기자동차 소음저감을 위한 구동모터 하우징의 동특성 평가
박종찬(Jongchan Park),박승용(Seungyong Park),조현규(Hyun-kyu Cho),박윤수(Yunsu Park) 한국소음진동공학회 2012 한국소음진동공학회 학술대회논문집 Vol.2012 No.10
Assessment of the dynamics properties, like damping, dynamic stiffness and resonance sharpness is essential for the development of a robust system, specifically for the reduction of a traction motor noise. A practical method for identifying dynamic characteristics of a traction motor hosing for an electric vehicle is proposed. Assembling using interference fit of the components of the motor is attributed to the main cause of strong nonlinearity. It is well known that nonlinearity of a structure makes it difficult to assess damping properties or dynamic characteristics of the system. This research presents a practical damping or dynamic stiffness identifying procedures for a nonlinear system according to the boundary condition between assembled components. Based on the simple idea that impact forces of modal tests are highly affected on the condition of the hammer tip, Auto Power Spectrum of the impact forces are used to assess the assembling condition and dynamic characteristics of the system, especially, damping of the system.
Privacy Protection Policy in Mongolia
Jongchan Park 동중앙아시아경상학회 2004 동중앙아시아연구 Vol.13 No.-
The objective of this paper is to evaluate the level of concern on the privacy protection in Mongolia. Most of the people think the level of concern on privacy protection in Mongolia must be poor since the information infrastructure has started being built recently. We can see the level of concern on privacy protection indirectly by checking whether respective web sites have the statement on privacy protection in their home pages. Therefore, I selected 179 Mongolian web sites and evaluated those sites whether the sites satisfy the 14 principles of the OECD Guidelines which has been the foundation for the various countries' privacy laws and regulations or not. The results of the analysis have found that the level of privacy protection in Mogolia is very poor. Only 2.8%(5 out of 179 web sites) of the Mongolian web sites have been posting "the Privacy Policy" in their home pages. Even those five web sites did not follow the 14 items of the OECD Guidelines satisfactorily. Especially, none of the five web sites which have the privacy policy includes the statement on the children's privacy protection in the privacy policy. These result on the children's privacy protection in Mongolian web sites is not the problem of Mongolia alone. Many countries in the world also neglect in protecting children's online privacy. In conclusion, considering the results of this paper, I suggest that Mongolian government should request and regulate Mongolian web sites more actively to post the privacy policy in their home pages as a first step to increase the level of concern on privacy protection. Eventually, the privacy protection legislation should be made and implemented to enforce the privacy protection overall. The limitation of this research is the following: the choice of web sites, which were surveyed for this project, is not statistically significant nor is it representative of all online services in Mongolia. Also, the survey for the web sites has been done in August 2002. Hence, I expect the percentage of the web sites which is posting the privacy policy in the home pages must have increased in Mongolia as of 2004. I hope somebody does the new research to find out the recent development and the increase in the level of concern on the privacy protection in Mongolia.