Browsing by Author "Cheng, Chieh-Jen"

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A Scalable High-Performance Virus Detection Processor Against a Large Pattern Set for Embedded Network Security
(2012-05-01)
Cheng, Chieh-Jen
;
Wang, Chao-Ching
;
Ku, Wei-Chun
;
Chen, Tien-Fu
;
Wang, Jinn-Shyan
Contemporary network security applications generally require the ability to perform powerful pattern matching to protect against attacks such as viruses and spam. Traditional hardware solutions are intended for firewall routers. However, the solutions in the literature for firewalls are not scalable, and they do not address the difficulty of an antivirus with an ever-larger pattern set. The goal of this work is to provide a systematic virus detection hardware solution for network security for embedded systems. Instead of placing entire matching patterns on a chip, our solution is a two-phase dictionary-based antivirus processor that works by condensing as much of the important filtering information as possible onto a chip and infrequently accessing off-chip data to make the matching mechanism scalable to large pattern sets. In the first stage, the filtering engine can filter out more than 93.1% of data as safe, using a merged shift table. Only 6.9% or less of potentially unsafe data must be precisely checked in the second stage by the exact-matching engine from off-chip memory. To reduce the impact of the memory gap, we also propose three enhancement algorithms to improve performance: 1) a skipping algorithm; 2) a cache method; and 3) a prefetching mechanism.
Design of aspheric lens to collimate and uniform irradiance of a light source with Lambertian angular distribution
(2006-01-01)
Cheng, Chieh-Jen
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A design of aspheric lens is proposed to collimate a light source of Lambertian angular distribution and generate homogenous irradiance. Two numerical solutions were calculated. One used even orders of general aspheres to describe the aspheric surfaces and the performance was evaluated by commercial optical software package Tracepro. Both of high numerical aperture (NA) of 0.79 and good RMS uniformity within 95% of designed area in the second surface of lens could be obtained. The reverse of this lens would be used in focusing and the simulated point spread function (PSF) is almost diffraction-limited. The other fitted both of aspheric surface with radial spline surface and the performance was evaluated by commercial optical software package OSLO. With the radial spline surface representation, the aspheric lens has a higher NA of 0.9; meanwhile, the uniformity was still good enough and PSF is also near diffraction-limited.
Design of aspheric lens to collimate and uniform irradiance of a light source with Lambertian angular distribution - art. no. 63422F
(2006)
Cheng, Chieh-Jen
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
A design of aspheric lens is proposed to collimate a light source of Lambertian angular distribution and generate homogenous irradiance. Two numerical solutions were calculated. One used even orders of general aspheres to describe the aspheric surfaces and the performance was evaluated by commercial optical software package Tracepro. Both of high numerical aperture (NA) of 0.79 and good RMS uniformity within 95% of designed area in the second surface of lens could be obtained. The reverse of this lens would be used in focusing and the simulated point spread function (PSF) is almost diffraction-limited. The other fitted both of aspheric surface with radial spline surface and the performance was evaluated by commercial optical software package OSLO. With the radial spline surface representation, the aspheric lens has a higher NA of 0.9; meanwhile, the uniformity was still good enough and PSF is also near diffraction-limited.
Gut microbiome changes in overweight male adults following bowel preparation
(2018-12-31)
Chen, Hui-Mei
;
Chen, Chung-Chu
;
Chen, Chien-Chi
;
Wang, Shen-Chih
;
Wang, Chun-Lin
BackgroundHuman gut microbiome has an essential role in human health and disease. Although the major dominant microbiota within individuals have been reported, the change of gut microbiome caused by external factors, such as antibiotic use and bowel cleansing, remains unclear. We conducted this study to investigate the change of gut microbiome in overweight male adults after bowel preparation, where none of the participants had been diagnosed with any systemic diseases.MethodsA total of 20 overweight, male Taiwanese adults were recruited, and all participants were omnivorous. The participants provided fecal samples and blood samples at three time points: prior to bowel preparation, 7days after colonoscopy, and 28days after colonoscopy. The microbiota composition in fecal samples was analyzed using 16S ribosome RNA gene amplicon sequencing.ResultsOur results demonstrated that the relative abundance of the most dominant bacteria hardly changed from prior to bowel preparation to 28days after colonoscopy. Using the ratio of Prevotella to the sum of Prevotella and Bacteroides in the fecal samples at baseline, the participants were separated into two groups. The fecal samples of the Type 1 group was Bacteroides-dominant, and that of the Type 2 group was Prevotella-dominant with a noticeable presence Bacteroides. Bulleidia appears more in the Type 1 fecal samples, while Akkermensia appears more in the Type 2 fecal samples. Of each type, the gut microbial diversity differed slightly among the three collection times. Additionally, the Type 2 fecal microbiota was temporarily susceptible to bowel cleansing. Predictive functional analysis of microbial community reveals that their activities for the mineral absorption metabolism and arachidonic acid metabolism differed significantly between the two types. Depending on their fecal type, the variance of triglycerides and C-reactive protein also differed between the two types of participants.ConclusionsDepending upon the fecal type, the microbial diversity and the predictive functional modules of microbial community differed significantly after bowel preparation. In addition, blood biochemical markers presented somewhat associated with fecal type. Therefore, our results might provide some insights as to how knowledge of the microbial community could be used to promote health through personalized clinical treatment.
Quasi Bessel beam by Billet's N-split lens
(2010-12-15)
Cheng, Chieh-Jen
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
This study utilizes the focal property of a classical Billets split lens to create more focal points by splitting the lens This approach distributes the focal points circularly on the focal plane This study explores the characteristics of beam propagation and analytically derives the asymptotic characteristics of beam propagation based on the stationary phase approximation and the moment-free Filon-type method Results show that the unique Billets N-split lens can generate a quasi Bessel beam if the number of splitting N is large enough e g N >= 24 This study also explores the diffraction efficiency of corresponding quasi Bessel beam and the influence of aperture size The potential advantage of proposed split lens approach is that unlike the classical means of annular aperture this simple lens approach allows a much larger throughput in creating the Bessel beam and hence the Bessel beam could have more optical energy (C) 2010 Elsevier B V All rights reserved
Symmetry property of a generalized Billet's N-split lens
(2010-10-01)
Cheng, Chieh-Jen
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
This study examines the diffraction properties of a generalized split N-sector lens originating from Billet's split bi-sector lens. The intensity distributions vary dramatically as the number of split sectors increases, and especially compared with those of the classical Billet's split lens. Nevertheless, the type of lens splitting selected causes the interference pattern of equidistant straight lines in the original Billet's lens to form an N-fold angularly distributed pattern with an angle difference of 2 pi/N. For an odd number of splitting N, there is an additional angle shift of pi/N for the azimuthally distributed patterns of equidistant straight lines. In other words, there are two kinds of symmetry even for simple splitting operations. On the other hand, the peak intensity distribution in the central portion resembles a concentric-circle-like pattern, when N is large as a result of N-beam interference. (C) 2010 Elsevier B.V. All rights reserved.
Symmetry property of a generalized Billet's N-split lens
(2010-10-01)
Cheng, Chieh-Jen
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
This study examines the diffraction properties of a generalized split N-sector lens originating from Billet's split bi-sector lens. The intensity distributions vary dramatically as the number of split sectors increases, and especially compared with those of the classical Billet's split lens. Nevertheless, the type of lens splitting selected causes the interference pattern of equidistant straight lines in the original Billet's lens to form an N-fold angularly distributed pattern with an angle difference of 2 pi/N. For an odd number of splitting N, there is an additional angle shift of pi/N for the azimuthally distributed patterns of equidistant straight lines. In other words, there are two kinds of symmetry even for simple splitting operations. On the other hand, the peak intensity distribution in the central portion resembles a concentric-circle-like pattern, when N is large as a result of N-beam interference. (C) 2010 Elsevier B.V. All rights reserved.