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임재혁,Jean-Baptiste Charpentier,손동우 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.3
In this work, the coefficients of thermal expansion (CTEs) of fibers in composite materials that contain microstructures are numericallyevaluated using a lamina-scale cost function with quasi-analytical gradients. To consider the effects of fiber arrangements and local defects,such as interface debonding and voids, a variety of representative volume elements are modeled with a number of finite elementmeshes. Then, the CTEs of fibers are evaluated by minimizing a lamina-scale cost function that represents the difference between themeasured CTEs and the computed CTEs by means of a computational homogenization scheme for the composite lamina. The descentdirection of the cost function is obtained using quasi-analytical gradients that take partial derivatives from prediction models, such as theSchapery model and Hashin model defined in an explicit manner, which accelerates the minimization procedure. To verify the performanceof the proposed scheme in terms of accuracy and efficiency, the CTEs of constituents calculated using the proposed scheme in aunidirectional composite lamina are compared with experimental values reported in the literature. Furthermore, the convergence behaviorof the proposed scheme with quasi-analytical gradients is also investigated and compared with other minimization methods.
Lymphopenia following pancreaticoduodenectomy is associated with pancreatic fistula formation
Joshua T. Cohen,Kevin P. Charpentier,Thomas J. Miner,William G. Cioffi,Rachel E. Beard 한국간담췌외과학회 2021 Annals of hepato-biliary-pancreatic surgery Vol.25 No.2
Backgrounds/Aims: Post-operative pancreatic fistulas (POPF) are a major source of morbidity following pancreaticoduodenectomy (PD). This study aims to investigate if persistent lymphopenia, a known marker of sepsis, can act as an additional marker of POPF with clinical implications that could help direct drain management. Methods: A retrospective chart review of all patients who underwent PD in a single hospital network from 2008 to 2018. Persistent lymphopenia was defined as lymphopenia beyond post-operative day #3. Results: Of the 201 patients who underwent PD during the study period 161 patients had relevant laboratory data, 81 of whom had persistent lymphopenia. 17 patients with persistent lymphopenia went on to develop a POPF, compared to 7 patients without. Persistent lymphopenia had a negative predictive value of 91.3%. Multivariate analysis revealed only persistent lymphopenia as being independently associated with POPF (HR 2.57, 95% CI 1.07-6.643, p=0.039). Patients with persistent lymphopenia were more likely to have a complication requiring intervention (56.8% vs 35.0%, p<0.001). Conclusions: Persistent lymphopenia is a readily available early marker of POPF that holds the potential to identify clinically relevant POPF in patients where no surgical drain is present, and to act as an adjunct of drain amylase helping to guide drain management.
Modeling Chagas Disease at Population Level to Explain Venezuela’s Real Data
Gilberto Gonza´lez-Parra,Benito M. Chen-Charpentier,Moises Bermu´dez 질병관리본부 2015 Osong Public Health and Research Persptectives Vol.6 No.5
Objectives: In this paper we present an age-structured epidemiological model for Chagas disease. This model includes the interactions between human and vector populations that transmit Chagas disease. Methods: The human population is divided into age groups since the proportion of infected individuals in this population changes with age as shown by real prevalence data. Moreover, the age-structured model allows more accurate information regarding the prevalence, which can help to design more specific control programs. We apply this proposed model to data from the country of Venezuela for two periods, 1961-1971, and 1961-1991 taking into account real demographic data for these periods. Results: Numerical computer simulations are presented to show the suitability of the age-structured model to explain the real data regarding prevalence of Chagas disease in each of the age groups. In addition, a numerical simulation varying the death rate of the vector is done to illustrate prevention and control strategies against Chagas disease. Conclusion: The proposed model can be used to determine the effect of control strategies in different age groups.
1kHz 이하 구조기인 소음예측을 위한 트림바디 모델의 개발과 적용
유지우(Ji Woo Yoo),채기상(Ki-Sang Chae),A. Charpentier,임종윤(Jong Yun Lim) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.10
Vehicle CAE models for NVH predictions are largely developed in two schemes. One is FE models generally used for below 200 Hz problems such as booming noise, and the other is SEA models for high frequencies of more than 1 kHz, representatively related to sound packages. HMC has tried to develop a CAE model for 200-1000 Hz, so-called mid-frequency region, and this paper is one of the corresponding results. The CAE model is developed based on an FE model, and then FE elements at some areas are substituted with SEA elements to reduce DOFs. SEA panels are described by modal density, radiation efficiency, stiffness and damping characteristics that are found from some numerical assessments. Sound packages are modeled similarly as a conventional SEA model. The CAE model developed in this manner, the hybrid model, was compared to experimental results. Predicted pressure and vibrational velo city generally show a good agreement. The developed CAE model and related technology are successfully being used in vehicle development process.
Mangoni, Matteo E.,Traboulsie, Achraf,Leoni, Anne-Laure,Couette, Brigitte,Marger, Laurine,Le Quang, Khai,Kupfer, Elodie,Cohen-Solal, Anne,Vilar, José,Shin, Hee-Sup,Escande, Denis,Charpentier, Fl Ovid Technologies Wolters Kluwer -American Heart A 2006 Circulation research Vol.98 No.11
<P>The generation of the mammalian heartbeat is a complex and vital function requiring multiple and coordinated ionic channel activities. The functional role of low-voltage activated (LVA) T-type calcium channels in the pacemaker activity of the sinoatrial node (SAN) is, to date, unresolved. Here we show that disruption of the gene coding for CaV3.1/alpha1G T-type calcium channels (cacna1g) abolishes T-type calcium current (I(Ca,T)) in isolated cells from the SAN and the atrioventricular node without affecting the L-type Ca2+ current (I(Ca,L)). By using telemetric electrocardiograms on unrestrained mice and intracardiac recordings, we find that cacna1g inactivation causes bradycardia and delays atrioventricular conduction without affecting the excitability of the right atrium. Consistently, no I(Ca,T) was detected in right atrium myocytes in both wild-type and CaV3.1(-/-) mice. Furthermore, inactivation of cacna1g significantly slowed the intrinsic in vivo heart rate, prolonged the SAN recovery time, and slowed pacemaker activity of individual SAN cells through a reduction of the slope of the diastolic depolarization. Our results demonstrate that CaV3.1/T-type Ca2+ channels contribute to SAN pacemaker activity and atrioventricular conduction.</P>