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Cost Optimization in SIS Model of Worm Infection
Jonghyun Kim,Sridhar Radhakrishnan,Jongsoo Jang 한국전자통신연구원 2006 ETRI Journal Vol.28 No.5
Recently, there has been a constant barrage of worms over the Internet. Besides threatening network security, these worms create an enormous economic burden in terms of loss of productivity not only for the victim hosts, but also for other hosts, as these worms create unnecessary network traffic. Further, measures taken to filter these worms at the router level incur additional network delays because of the extra burden placed on the routers. To develop appropriate tools for thwarting the quick spread of worms, researchers are trying to understand the behavior of worm propagation with the aid of epidemiological models. In this study, we present an optimization model that takes into account infection and treatment costs. Using this model we can determine the level of treatment to be applied for a given rate of infection spread.
Holographic fluorescence microscopy with incoherent digital holographic adaptive optics
Jang, Changwon,Kim, Jonghyun,Clark, David C.,Lee, Seungjae,Lee, Byoungho,Kim, Myung K. SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS 2015 JOURNAL OF BIOMEDICAL OPTICS Vol.20 No.11
<P>Introduction of adaptive optics technology into astronomy and ophthalmology has made great contributions in these fields, allowing one to recover images blurred by atmospheric turbulence or aberrations of the eye. Similar adaptive optics improvement in microscopic imaging is also of interest to researchers using various techniques. Current technology of adaptive optics typically contains three key elements: a wavefront sensor, wavefront corrector, and controller. These hardware elements tend to be bulky, expensive, and limited in resolution, involving, for example, lenslet arrays for sensing or multiactuator deformable mirrors for correcting. We have previously introduced an alternate approach based on unique capabilities of digital holography, namely direct access to the phase profile of an optical field and the ability to numerically manipulate the phase profile. We have also demonstrated that direct access and compensation of the phase profile are possible not only with conventional coherent digital holography, but also with a new type of digital holography using incoherent light: selfinterference incoherent digital holography (SIDH). The SIDH generates a complex?i.e., amplitude plus phase?hologram from one or several interferograms acquired with incoherent light, such as LEDs, lamps, sunlight, or fluorescence. The complex point spread function can be measured using guide star illumination and it allows deterministic deconvolution of the full-field image. We present experimental demonstration of aberration compensation in holographic fluorescence microscopy using SIDH. Adaptive optics by SIDH provides new tools for improved cellular fluorescence microscopy through intact tissue layers or other types of aberrant media.</P>
Jonghyun Sung,Jongwook Choi,Kum Whang,Sung Min Cho,Jong Yeon Kim,Seung Jin Lee,Yeon gyu Jang 대한신경손상학회 2023 Korean Journal of Neurotrauma Vol.19 No.3
This study investigated the change in the number of patients with head trauma according to the trauma mechanism among severely injured patients transferred to the emergency department of Wonju Severance Christian Hospital before and during the coronavirus disease 2019 (COVID-19) pandemic.
Retinal 3D : augmented reality near-eye display via pupil-tracked light field projection on retina
Jang, Changwon,Bang, Kiseung,Moon, Seokil,Kim, Jonghyun,Lee, Seungjae,Lee, Byoungho Association for Computing Machinery 2017 ACM transactions on graphics Vol. No.
<P>We introduce an augmented reality near-eye display dubbed 'Retinal 3D.' Key features of the proposed display system are as follows: Focus cues are provided by generating the pupil-tracked light field that can be directly projected onto the retina. Generated focus cues are valid over a large depth range since laser beams are shaped for a large depth of field (DOF). Pupil-tracked light field generation significantly reduces the needed information/computation load. Also, it provides 'dynamic eye-box' which can be a break-through that overcome the drawbacks of retinal projection-type displays. For implementation, we utilized a holographic optical element (HOE) as an image combiner, which allowed high transparency with a thin structure. Compared with current augmented reality displays, the proposed system shows competitive performances of a large field of view (FOV), high transparency, high contrast, high resolution, as well as focus cues in a large depth range. Two prototypes are presented along with experimental results and assessments. Analysis on the DOF of light rays and validity of focus cue generation are presented as well. Combination of pupil tracking and advanced near-eye display technique opens new possibilities of the future augmented reality.</P>
Development and application of chip calorimeter as an X-ray detector
Jonghyun Kim,Sung Min Nam,Heejun Jang,Jae-Pil Chung,Jin Sung Kim,Byoung-Chul Kim,Kook Jin Chun,Wonhee Lee 한국물리학회 2020 Current Applied Physics Vol.20 No.2
Radiotherapy for cancer patients requires accurate measurement of the absorbed dose of radiation in a treatment planning step. Various types of radiation detectors are currently utilized for dose measurement. Among them, calorimeters are known to be the most precise detector for measuring absorbed dose, but their on-site application is limited by the large size of the equipment. We developed a miniaturized chip calorimeter for application as a radiation detector. The calorimetric radiation detector was built using micro/nano fabrication techniques, and consists of an SU-8 photoresist absorber and high-sensitivity vanadium oxide (VOx) thermistors. The thermistors had a temperature resolution of 135 μK, and the calorimeter showed a thermal conductance of 11 μW/K. The detector was irradiated with various X-ray dose rates from a linear accelerator, and the absorbed dose to SU-8 was measured. The detector responses showed high linearity with dose rates, demonstrating the feasibility of the radiation detector for practical uses.
( Jonghyun Choi ),( Yongwoo Jang ),( Haedong Kim ),( Jungwon Wee ),( Sinyoung Cho ),( Woo Sung Son ),( Sung Min Kim ),( Young Duk Yang ) 생화학분자생물학회(구 한국생화학분자생물학회) 2018 BMB Reports Vol.51 No.5
Anoctamin 1 (ANO1) is an anion channel that is activated by changes in cytosolic Ca<sup>2+</sup> concentration and noxious heat. Although the critical roles of ANO1 have been elucidated in various cell types, the control of its gating mechanisms by Ca<sup>2+</sup> and heat remain more elusive. To investigate critical amino acid residues for modulation of Ca<sup>2+</sup> and heat sensing, we constructed a randomized mutant library for ANO1. Among 695 random mutants, reduced Ca<sup>2+</sup> sensitivity was observed in two mutants (mutant 84 and 87). Consequently, the E143A mutant showed reduced sensitivity to Ca<sup>2+</sup> but not to high temperatures, whereas the E705V mutant exhibited reduced sensitivity to both Ca<sup>2+</sup> and noxious heat. These results suggest that the glutamic acids (E) at 143 and 705 residues in ANO1 are critical for modulation of Ca<sup>2+</sup> and/or heat responses. Furthermore, these findings help to provide a better understanding of the Ca<sup>2+</sup>-mediated activation and heat-sensing mechanism of ANO1. [BMB Reports 2018; 51(5): 236-241]
Optimal Control of Filtering Treatment for Internet Worm
Jonghyun Kim,Jungchan Na,Jongsoo Jang 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
The task of detection and prevention of worms has become more difficult on our existing computing infrastructure. However, controlling the spread of worms in computer networks has recently become one of the most important issues. One possible way to control the spread of computer worms/viruses is to require routers to monitor the Internet traffic, but the measures taken to filtering these worms at the router level incur additional network delay because of extra burden placed on the routers. Further, the infected hosts add to the delays on the Internet as they generate traffic. In this paper, we investigate the effect of controlling the spread of computer worms on network delays. A model is presented that can be used to determine the adequate level of control on the total network delay ? the delay caused by worms and the delay caused by controlling worm propagation.