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      • KCI등재

        RESEARCH ON THE ELECTRO-HYDRAULIC VARIABLE VALVE ACTUATION SYSTEM BASED ON A THREE-WAY PROPORTIONAL REDUCING VALVE

        J.-R. LIU,B. JIN,Y.-J. XIE,Y. CHEN,Z.-T. WENG 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.1

        As the internal combustion engine moves into the 21st century, fully flexible valve actuation systems are being proposed as an enabling technology for advanced internal combustion engine concepts. Electro-hydraulic valve actuator systems are being considered as a potential variable valve technology. Compared to the servo control system, the system using a proportional valve has the advantages of low price, high anti-pollution ability and high reliability. Our research focuses on exploring the dynamic characteristic of the electro-hydraulic variable valve system, which is based on three-way proportional reducing valve. In this paper, the structure and working principles of the system are described. The dynamic mathematical model of the system is derived. From the analysis of a linearized model and dynamic simulation, it is demonstrated that the system will be stable only if the proportional reducing valve has a positive opening. Some structural factors that affect the system’s dynamic characteristics, such as input signal, the stiffness of the return spring and the pre-tightening force of the return spring, are studied using AMESim. The experimental results coincide with the theoretical and simulated analyses. Further study shows that the dynamic response can be improved effectively by adopting closed-loop control of valve lift. As the internal combustion engine moves into the 21st century, fully flexible valve actuation systems are being proposed as an enabling technology for advanced internal combustion engine concepts. Electro-hydraulic valve actuator systems are being considered as a potential variable valve technology. Compared to the servo control system, the system using a proportional valve has the advantages of low price, high anti-pollution ability and high reliability. Our research focuses on exploring the dynamic characteristic of the electro-hydraulic variable valve system, which is based on three-way proportional reducing valve. In this paper, the structure and working principles of the system are described. The dynamic mathematical model of the system is derived. From the analysis of a linearized model and dynamic simulation, it is demonstrated that the system will be stable only if the proportional reducing valve has a positive opening. Some structural factors that affect the system’s dynamic characteristics, such as input signal, the stiffness of the return spring and the pre-tightening force of the return spring, are studied using AMESim. The experimental results coincide with the theoretical and simulated analyses. Further study shows that the dynamic response can be improved effectively by adopting closed-loop control of valve lift.

      • KCI등재

        The Posterior Cranial Vertical Line: A Novel Radiographic Marker for Classifying Global Sagittal Alignment

        Paul J. Park,Fthimnir M. Hassan,Xavier E. Ferrer,Cole Morrissette,Nathan J. Lee,Meghan Cerpa,Zeeshan M. Sardar,Michael P. Kelly,Stephane Bourret,Kazuhiro Hasegawa,Hee-Kit Wong,Gabriel Liu,Hwee Weng De 대한척추신경외과학회 2023 Neurospine Vol.20 No.3

        Objective: To define a novel radiographic measurement, the posterior cranial vertical line (PCVL), in an asymptomatic adult population to better understand global sagittal alignment. Methods: We performed a multicenter retrospective review of prospectively collected radiographic data on asymptomatic volunteers aged 20–79. The PCVL is a vertical plumb line drawn from the posterior-most aspect of the occiput. The horizontal distances of the PCVL to the thoracic apex (TA), posterior sagittal vertical line (PSVL, posterosuperior endplate of S1), femoral head center, and tibial plafond were measured. Classification was either grade 1 (PCVL posterior to TA and PSVL), grade 2 (PCVL anterior to TA and posterior to PSVL), or grade 3 (PCVL anterior to TA and PSVL). Results: Three hundred thirty-four asymptomatic patients were evaluated with a mean age of 41 years. Eighty-three percent of subjects were PCVL grade 1, 15% were grade 2, and 3% were grade 3. Increasing PCVL grade was associated with increased age (p < 0.001), C7–S1 sagittal vertical axis (SVA) (p < 0.001), C2–7 SVA (p < 0.001). Additionally, it was associated with decreased SS (p = 0.045), increased PT (p < 0.001), and increased knee flexion (p < 0.001). Conclusion: The PCVL is a radiographic marker of global sagittal alignment that is simple to implement and interpret. Increasing PCVL grade was significantly associated with expected changes and compensatory mechanisms in the aging population. Most importantly, it incorporates cervical alignment parameters such as C2–7 SVA. The PCVL defines global sagittal alignment in adult volunteers and naturally distributes into 3 grades, with only 3% being grade 3 where the PCVL lies anterior to the TA and PSVL.

      • SCIESCOPUSKCI등재

        Deletion of the Lmna Gene Induces Growth Delay and Serum Biochemical Changes in C57BL/6 Mice

        Ruan, J.,Liu, X.G.,Zheng, H.L.,Li, J.B.,Xiong, X.D.,Zhang, C.L.,Luo, C.Y.,Zhou, Z.J.,Shi, Q.,Weng, Y.G. Asian Australasian Association of Animal Productio 2014 Animal Bioscience Vol.27 No.1

        The A-type lamin deficient mouse line ($Lmna^{-/-}$) has become one of the most frequently used models for providing insights into many different aspects of A-type lamin function. To elucidate the function of Lmna in the growth and metabolism of mice, tissue growth and blood biochemistry were monitored in Lmna-deficient mice, heterozygous ($Lmna^{+/-}$) and wide-type ($Lmna^{+/+}$) backcrossed to C57BL/6 background. At 4 weeks after birth, the weight of various organs of the $Lmna^{-/-}$, $Lmna^{+/-}$ and $Lmna^{+/+}$ mice was measured. A panel of biochemical analyses consisting of 15 serological tests was examined. The results showed that Lmna deficient mice had significantly decreased body weight and increased the ratio of organ to body weight in most of tissues. Compared with $Lmna^{+/+}$ and $Lmna^{+/-}$ mice, $Lmna^{-/-}$ mice exhibited lower levels of ALP (alkaline phosphatase), Chol (cholesterol), CR (creatinine), GLU (glucose), HDL (high-density lipoprotein cholesterol) and higher levels of ALT (alanine aminotransferase) (p<0.05). $Lmna^{-/-}$ mice displayed higher AST (aspartate aminotransferase) values and lower LDL (lowdensity lipoprotein cholesterol), CK-MB (creatine kinase-MB) levels than $Lmna^{+/+}$ mice (p<0.05). There were no significant differences among the three groups of mice with respect to BUN (blood urea nitrogen), CK (creatine kinase), Cyc C (cystatin C), TP (total protein), TG (triacylglycerols) and UA (uric acid) levels (p>0.05). These changes of serological parameters may provide an experimental basis for the elucidation of Lmna gene functions.

      • KCI우수등재
      • KCI등재

        Hepatocyte organoids and cell transplantation: What the future holds

        Peng Weng Chuan,Kraaier Lianne J.,Kluiver Thomas A. 생화학분자생물학회 2021 Experimental and molecular medicine Vol.53 No.-

        Historically, primary hepatocytes have been difficult to expand or maintain in vitro. In this review, we will focus on recent advances in establishing hepatocyte organoids and their potential applications in regenerative medicine. First, we provide a background on the renewal of hepatocytes in the homeostatic as well as the injured liver. Next, we describe strategies for establishing primary hepatocyte organoids derived from either adult or fetal liver based on insights from signaling pathways regulating hepatocyte renewal in vivo. The characteristics of these organoids will be described herein. Notably, hepatocyte organoids can adopt either a proliferative or a metabolic state, depending on the culture conditions. Furthermore, the metabolic gene expression profile can be modulated based on the principles that govern liver zonation. Finally, we discuss the suitability of cell replacement therapy to treat different types of liver diseases and the current state of cell transplantation of in vitro-expanded hepatocytes in mouse models. In addition, we provide insights into how the regenerative microenvironment in the injured host liver may facilitate donor hepatocyte repopulation. In summary, transplantation of in vitro-expanded hepatocytes holds great potential for large-scale clinical application to treat liver diseases.

      • KCI우수등재

        Association between Obesity and Length of COVID-19 Hospitalization: Unexpected Insights from the American Heart Association National COVID-19 Registry

        William J. Collins,Andrew Y. Chang,Yingjie Weng,Alex Dahlen,Connor G. O'Brien,Jason Hom,Neera Ahuja,Fatima Rodriguez,Nidhi Rohatgi 대한비만학회 2022 Journal of obesity & metabolic syndrome Vol.31 No.3

        Background: The mechanism for possible association between obesity and poor clinical outcomes from Coronavirus Disease 2019 (COVID-19) remains unclear. Methods: We analyzed 22,915 adult COVID-19 patients hospitalized from March 2020 to April 2021 to non-intensive care using the American Heart Association National COVID Registry. A multivariable Poisson model adjusted for age, sex, medical history, admission respiratory status, hospitalization characteristics, and laboratory findings was used to calculate length of stay (LOS) as a function of body mass index (BMI). We similarly analyzed 5,327 patients admitted to intensive care for comparison. Results: Relative to normal BMI subjects, overweight, class I obese, and class II obese patients had approximately half-day reductions in LOS (–0.469 days, P<0.01; –0.480 days, P<0.01; –0.578 days, P<0.01, respectively). Conclusion: The model identified a dose-dependent, inverse relationship between BMI category and LOS for COVID-19, which was not seen when the model was applied to critically ill patients.

      • KCI등재후보

        Choice of dispersants for the nano-apatite filler of polylactide-matrix composite biomaterial

        C. Deng,J. Weng,Q.Y. Cheng,S.B. Zhou,X. Lu,J.X. Wan,S.X. Qu,B. Feng,X.H. Li 한국물리학회 2007 Current Applied Physics Vol.7 No.6

        The aim of this study is to compare de-aggregative ability of common organic dispersants for the acicular nano-apatite crystallite withmain composition of calcium hydroxyapatite (HA) as a ller of composite containing polylactide (PLA) matrix. Firstly, the acicularnano-apatite powders with an average length of 70120 nm were synthesized based on traditional chemical co-precipitation andfreeze-drying techniques. Common organic dispersants including tetrahydrofuran, acetone, chloroform,N,N-dimethyl formamideiments showed that nano-apatite suspension dispersed by DMF and ethanol presented homogeneous and stable colloid after vigorly stir-red for 24 h and then kept still for same time, respectively. Results of particle measurements and viscosity measurement illuminated that alarge number of the nano-apatite particles with an average dimension of 297.86 nm and viscosity of 0.8872 cP in DMF suspension couldbe dispersed up to 91.28 nm by the DMF dispersant and the DMF dispersant could minimize agglomeration between the apatite ultra-furan, acetone and ethanol, when the nano-apatite/PLA composite biomaterials were prepared.

      • SCIESCOPUSKCI등재

        Dietary Glutamine Supplementation Enhances Weaned Pigs Mitogen-Induced Lymphocyte Proliferation

        Lee, D.N.,Weng, C.F.,Cheng, Y.H.,Kuo, T.Y.,Wu, J.F.,Yen, H.T Asian Australasian Association of Animal Productio 2003 Animal Bioscience Vol.16 No.8

        Two experiments involving 92 crossbred, 21 day old weaned pigs were used to evaluate the effect of glutamine supplement in a dietary or culture medium on lymphocyte proliferation. In Exp. 1, 88 pigs were fed diets supplemented with 0, 0.5, 1.0, or 1.5% glutamine for 28 days. Lymphocytes were prepared from peripheral blood mononuclear cells (PBMC), ileal Peyer's patches (PP), the mesenteric lymph node (MLN), and the spleen in each dietary supplement group on days 7, 14, or 28 postweaning. Lymphocytes were cultured at $37^{\circ}C$ for 72 h in a RPMI-1640 medium with or without mitogen-stimulated, and pulsed with 3Hthymidine for an additional 18 h. The stimulation index of PBMC proliferation in 1.0% dietary glutamine supplement group and both of the MLN and splenocytes proliferation in 1.5% dietary glutamine supplement group was significantly (p<0.05) increased at 14 days postweaning. In Exp. 2, four weaned pigs were fed a basal diet for 14 days. The 3H-thymidine incorporation of PBMC, PP, and MLN cells, incubated with 0.125 to 0.25 mM glutamine in culture medium were markedly enhanced with Con A-stimulated, however, the splenocyte proliferation was not affected in the addition of glutamine medium. These observations suggest that dietary glutamine supplement might enhance the lymphocyte proliferation of weaned pigs.

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