Effects of some factors on the thermal-dissipation characteristics of high-power LED packages

Ji, Peng Fei,Moon, Cheol-Hee The Korean Infomation Display Society 2012 Journal of information display Vol.13 No.1

Decreasing the thermal resistance is the critical issue for high-brightness light-emitting diodes. In this paper, the effects of some design factors, such as chip size (24 and 35 mil), substrate material (AlN and high-temperature co-fired ceramic), and die-attach material (Ag epoxy and PbSn solder), on the thermal-dissipation characteristics were investigated. Using the thermal transient method, the temperature sensitivity parameter, $R_{th}$ (thermal resistance), and junction temperature were estimated. The 35-mil chip showed better thermal dissipation, leading to lower thermal resistance and lower junction temperature, owing to its smaller heat source density compared with that of the 24-mil chip. By adopting an AlN substrate and a PbSn solder, which have higher thermal conductivity, the thermal resistance of the 24-mil chip can be decreased and can be made the same as that of the 35-mil chip.

De novo malignancy after liver transplantation

Peng Ji Gao,Jie Gao,Zhao Li,Zhi Ping Hu,Ji Ye Zhu 대한외과학회 2015 Annals of Surgical Treatment and Research(ASRT) Vol.88 No.4

Purpose: The aim of this study is to evaluate the incidence of de novo malignancy after liver transplantation (LT) and compare with those among the general Chinese population. Methods: A total of 466 patients who had a minimum follow-up time of 6 months were enrolled in the study. All data of medical records and follow up were retrospectively reviewed. Results: The incidence rate of de novo malignancy was 3.0% (14 in 466 patients). The median elapsed time from transplant to the diagnosis of de novo malignancy was 42 months (range, 6 to 106 months). The cumulative risk for development of de novo malignancy was 1.6%, 2.7%, and 8.2% at 3, 5 and 10 years after LT, respectively. The patients were all male. The types of de novo tumors included digestive system tumor (8 in 14), lung cancer (2 in 14), urologic neoplasm (2 in 14), and hematologic malignant tumor (2 in 14). Over a mean follow-up of 24 months after diagnosis of de novo malignancy, 7 patients (50.0%) died; the overall 5-year patient survival rate was 54.5%. The relative risk of malignancy following LT was 9.5 folds higher than the general Chinese population. Conclusion: The relative risk of malignancy following LT was much higher than the general Chinese population. Digestive system tumor is the most common type of de novo malignancy after LT in China.

Angle-tolerant linear variable color filter based on a tapered etalon

Ji, Peng,Park, Chul-Soon,Gao, Song,Lee, Sang-Shin,Choi, Duk-Yong The Optical Society 2017 Optics express Vol.25 No.3

Effects of some factors on the thermal-dissipation characteristics of high-power LED packages

Peng Fei Ji,문철희 한국정보디스플레이학회 2012 Journal of information display Vol.13 No.1

Decreasing the thermal resistance is the critical issue for high-brightness light-emitting diodes. In this paper, the effects of some design factors, such as chip size (24 and 35 mil), substrate material (AlN and high-temperature co-fired ceramic), and dieattach material (Ag epoxy and PbSn solder), on the thermal-dissipation characteristics were investigated. Using the thermal transient method, the temperature sensitivity parameter, Rth (thermal resistance), and junction temperature were estimated. The 35-mil chip showed better thermal dissipation, leading to lower thermal resistance and lower junction temperature, owing to its smaller heat source density compared with that of the 24-mil chip. By adopting an AlN substrate and a PbSn solder,which have higher thermal conductivity, the thermal resistance of the 24-mil chip can be decreased and can be made the same as that of the 35-mil chip.

Analyses of Flavonoid-biosynthesis Gene Expression in the Flowers of Major Lily Cultivars

Ji Peng Liu,Young Sook Ryu,Byung Joon Ahn 한국원예학회 2014 한국원예학회 학술발표요지 Vol.2014 No.5

Determination of geometry-induced positional distortion of ultrafast laser-inscribed circuits in a cylindrical optical fiber

Ji, Peng,Lee, Sang-Shin,Im, Young-Eun,Choi, Younghee The Optical Society 2019 Optics letters Vol.44 No.3

Guidance Laws against Towed Decoy Based on Adaptive Back-stepping Sliding Mode and Anti-saturation Methods

Ji-Peng Dong,Jing-Guang Sun,Yong Guo,Shen-Min Song 제어·로봇·시스템학회 2018 International Journal of Control, Automation, and Vol.16 No.4

In order to meet the needs of high-precision guidance for missile-guided maneuvering targets in the presence of towed bait interference, this paper proposes a new guidance strategy based on heading angle method and parallel approaching method. Its main idea: a suitable angle is determined by heading angle method which of the missile trajectory is above that of the towing bait. Meanwhile, the accurate interception of missiles to targets is guaranteed by parallel approaching method. Firstly, system models of missile and target with towed decoy are established. Then, considering unknown bounded system disturbances, a controller is given based on sliding mode, back-stepping method. Furthermore, to solve the input saturation problem, an anti-saturation controller is given using adaptive and back-stepping sliding mode methods. Finally, strict proofs of the two controllers are given using Lyapunov stability theory, and simulations are carried out to verify the effectiveness of the two controllers.

Microstructure of Antarctic Krill (Euphausia suberba) Cuticle

Yuanhuai Peng,Wei Ji,Hongwu Ji 한국해양과학기술원 2022 Ocean science journal Vol.57 No.2

In this study, the microstructure of Antarctic krill cuticle was deeply investigated using scanning electron microscope (SEM). The krill cuticles were treated with clean water, dilute hydrochloric acid solution and dilute sodium hydroxide solution to remove the adhesive substances, inorganic salts and protein, respectively. The organic substances were removed by sintering the cuticle in a muffle furnace to obtain the inorganic salts. The resulting cuticle of Antarctic krill was then observed under SEM and it was found that the cuticle has a hierarchical structure in which the α-crystal chitin fibers, with chitin spheres, extended from the pore canals, thus shaping layers; multiple stacked layers formed the three-dimensional structure; the inorganic salts were sparsely distributed in the cuticle; protein was wrapped around the surfaces of the chitin fiber bundles and the crystals of inorganic salts. These structural investigations revealed the interrelation among the main components of Antarctic krill cuticle. This study and following studies will be helpful in understanding the relationship between the forms of fluorine in Antarctic krill cuticle and its structural changes during postmortem storage.

The American Cockroach Peptide Periplanetasin-2 Blocks Clostridium Difficile Toxin A-Induced Cell Damage and Inflammation in the Gut

( Ji Hong ),( Peng Zhang ),( I Na Yoon ),( Jae Sam Hwang ),( Jin Ku Kang ),( Ho Kim ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.4

Clostridium difficile, which causes pseudomembranous colitis, releases toxin A and toxin B. These toxins are considered to be the main causative agents for the disease pathogenesis, and their expression is associated with a marked increase of apoptosis in mucosal epithelial cells. Colonic epithelial cells are believed to form a physical barrier between the lumen and the submucosa, and abnormally increased mucosal epithelial cell apoptosis is considered to be an initial step in gut inflammation responses. Therefore, one approach to treating pseudomembranous colitis would be to develop agents that block the mucosal epithelial cell apoptosis caused by toxin A, thus restoring barrier function and curing inflammatory responses in the gut. We recently isolated an antimicrobial peptide, Periplanetasin-2 (Peri-2, YPCKLNLKLGKVPFH) from the American cockroach, whose extracts have shown great potential for clinical use. Here, we assessed whether Peri-2 could inhibit the cell toxicity and inflammation caused by C. difficile toxin A. Indeed, in human colonocyte HT29 cells, Peri-2 inhibited the toxin A-induced decrease in cell proliferation and ameliorated the cell apoptosis induced by this toxin. Moreover, in the toxin A-induced mouse enteritis model, Peri-2 blocked the mucosal disruption and inflammatory response caused by toxin A. These results suggest that the American cockroach peptide Peri-2 could be a possible drug candidate for addressing the pseudomembranous colitis caused by C. difficile toxin A.

Improved PSO Research for Solving the Inverse Problem of Parabolic Equation

Peng Yamian,Ji Nan,Zhang Huancheng 보안공학연구지원센터 2016 International Journal of Database Theory and Appli Vol.9 No.12

Parameter identification problem has important research background and research value, has become in recent years inverse problem of heat conduction of top priority. This paper studies the Parabolic Equation Inverse Problems of parameter identification problem, and applies PSO to solve research. Firstly, this paper establishes the model of the inverse problem of partial differential equations. The content and classification of the inverse problem of partial differential equations are explained. Frequently, the construction and solution of the finite difference method for parabolic equations are studied, and two stable schemes for one dimensional parabolic equation are given. And two numerical simulations were given. Partial differential equation discretization was with difference quotient instead of partial derivative. The partial differential equations with initial boundary value problem into algebraic equations, and then solving the resulting algebraic equations. Then, the basic principles of PSO and its improved algorithms are studied and compared. Particle swarm optimization algorithm program implementation. Finally, the Parabolic Equation Inverse Problems of particle swarm optimization algorithm performed three simulations. We use a set of basis functions gradually approaching the true solution, selection of initial value. The reaction is converted into direct problem question, then use difference method Solution of the direct problem. The solution of the problem with the additional conditions has being compared. The reaction optimization problem is transformed into the final particle swarm optimization algorithm to solve. Verify the Parabolic Equation Inverse Problems of particle swarm optimization algorithm correctness and applicability.