Simulation and Design Considerations on Transverse Connection of Prestressed Concrete T-girder Bridge

Chen Chen,Caiqian Yang,Yong Pan,Honglei Zhang,Hans De Backer 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.4

In this paper, the structural performance of the prestressed concrete T-girder bridge with a newly proposed diaphragm transverse connections (DTCs) have been investigated. The DTCs are composed of diagonal braces and horizontal brace, and the braces are structural steel with square cross section. A series of simulations have been carried out to study the eff ectiveness of the proposed DTCs on enhancing the transverse connection of the prestressed concrete T-girder bridge. Load Model 1 in accordance with Eurocode 1 is considered in the simulations, which consists of tandem system and uniformly distributed loads (UDL system). The Von Mises stress of the DTCs has been checked and corresponding steel grade has been given. The force on the surface between the T-girder bridge and the proposed DTCs has been studied and detailed connection design has been given for both new bridge construction and existing bridge retrofi tting. The simulation results show that the maximum defl ection arises when the deck is fully loaded with the UDL system and with lane 1 centrally located on exterior girder, and the tandem systems are applied at midspan simultaneously. It is revealed that with the proposed DTCs installed at midspan, the maximum defl ection of the prestressed concrete T-girder bridge reduces 12.8% in the most unfavorable load case. In all the discussed load cases, the Von Mises stress of the proposed DTCs is within the reasonable range and can be borne by normal steel material. Additionally, connection methods have been given for the DTCs’ application to new bridge and existing bridge. For the use of chemical anchor in existing bridge, the concrete and prestress tendons should be checked in case of any additional damage during the installing of the DTCs.

A Secondary Resonance Soft Switching Half Bridge DC-DC Converter with an Inductive Output Filter

Zhang-yong Chen,Yong Chen 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6

In this paper, a secondary resonance half-bridge dc-dc converter with an inductive output filter is presented. The primary side of such a converter utilizes asymmetric pulse width modulation (APWM) to achieve zero-voltage switching (ZVS) of the switches, and clamps the voltage of the switch to the input voltage. In addition, zero current switching (ZCS) of the output diode is achieved by a half-wave rectifier circuit with a filter inductor and a resonant branch in the secondary side of the proposed converter. Thus, the switching losses and diode reverse-recovery losses are eliminated, and the performance of the converter can be improved. Furthermore, an inductive output filter exists in the converter reduce the output current ripple. The operational principle, performance analysis and design equation of this converter are given in this paper. The analysis results show that the output diode voltage stress is independent of the duty cycle, and that the voltage gain is almost linear, similar to that of the isolation Buck-type converter. Finally, a 200V~380V input, 24V/2A output experimental prototype is built to verify the theoretical analysis.

Reduction of Brain Infarct Size and Extracellular Glutamate Accumulation by Dihydrokinate in Spontaneously Hypertensive Rat after Transient Forebrain Ischemia

Yong Hua Zhang,Yong Cai Li,Zheng Hua Cai,Yang Chen 대한신경외과학회 2004 Journal of Korean neurosurgical society Vol.36 No.4

Objective : Using bilateral carotid artery occlusion, controlled hypotension and in vivo microdialysis, we evaluate the changes in extracellular concentrations of the excitatory amino acids(EAA) glutamate and aspartate in the striatum of ischemic Wistar-Kyoto rats(WKY) and spontaneously hypertensive rats (SHR), as well as the resulting changes of infarct volume and neurological deficit scores. Methods : During 30 minutes of ischemia, microdialysate concentrations of glutamate and aspartate were measured in the presence of infusion of artificial cerebrospinal fluid(aCSF) or the dihydrokinate (DHK, the GLT-1 selective nontransportable inhibitor)-containing aCSF respectively. And infarct volume of neurological deficit were measured for each groups using triphenyltetrazolium chloride(TTC) staining and neurological deficit function tests. Results : In control aCSF infusing WKY group, glutamate and aspartate concentrations increased 36-fold and 14- fold increase to baseline, respectively, and returned to baseline values on reperfusion; while in control aCSF infusing SHR group, glutamate and aspartate increased 51-fold and 25-fold increase respectively. DHK (10nM) significantly attenuated EAA increases in both experimental WKY group and SHR group compared with control (glutamate peak for WKY, 7.09±1.04 versus control, 18.48±1.87 pmol/ul; for SHR, 18.90±1.54 versus control, 40.64±2.38 pmol/ul). There is a significant improving with neurological deficit score in DHK application groups both in WKY and SHR, which was also convinced by comparison of infarct volume between experimental DHK infusing group and control. Conclusion : Our results suggest that the astrocytic glutamate transporter contributes significantly to EAA release in the early phase of ischemia and inhibition of excessive glutamate release by DHK may contribute to effective treatment in ischemia-induced brain damage.

EMI Noise Source Reduction of Single-Ended Isolated Converters Using Secondary Resonance Technique

Zhang-yong Chen,Yong Chen,Qiang Chen,Wei Jiang,Rongqiang Zhong 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.2

Aiming at the problems of large dv/dt and di/dt in traditional single-ended converters and high electromagnetic interference (EMI) noise levels, a single-ended isolated converter using the secondary resonance technique is proposed in this paper. In the proposed converter, the voltage stress of the main power switch can be reduced and the voltage across the output diode is clamped to the output voltage when compared to the conventional flyback converter. In addition, the peak current stress through the main power switch can be decreased and zero current switching (ZCS) of the output diode can be achieved through the resonance technique. Moreover, the EMI noise coupling path and an equivalent model of the proposed converter topology are presented through the operational principle of the proposed converter. Analysis results indicate that the common mode (CM) EMI noise and the differential mode (DM) EMI noise of such a converter are deduced since the frequency spectra of the equivalent controlled voltage sources and controlled current source are decreased when compared with the traditional flyback converter. Furthermore, appropriate parameter selection of the resonant circuit network can increase the equivalent impedance in the EMI coupling path in the low frequency range, which further reduces the common mode interference. Finally, a simulation model and a 60W experimental prototype of the proposed converter are built and tested. Experimental results verify the theoretical analysis.

Effect of acidified milk feeding on the intake, average daily gain and fecal microbiological diversity of Holstein dairy calves

Chen Yong,Gao Yan,Yin Shuxin,Zhang Shuai,Wang Lu,Qu Yongli 아세아·태평양축산학회 2020 Animal Bioscience Vol.33 No.8

Objective: To evaluate the effect of feeding acidified milk on the growth and fecal microbial diversity of dairy calves. Methods: Twenty healthy 3-day-old female Holstein calves with similar body weights were selected and randomly divided into two groups. One group was fed pasteurized milk (PM, Control), while the other was fed acidified milk (AM) ad libitum until weaned (day 60). The experiment lasted until day 180. Results: There was no difference in the nutritional components between PM and AM. The numbers of Escherichia coli and total bacteria in AM were lower than in PM. At 31 to 40 and 41 to 50 days of age, the milk intake of calves fed AM was higher than that of calves fed PM (p<0.05), and the solid feed intake of calves fed AM was higher than that of calves fed PM at 61 to 90 days (p<0.05). The average daily gain of calves fed AM was also higher than that of calves fed PM at 31 to 60, 61 to 180, and 7 to 180 days (p<0.05). The calves fed AM tended to have a lower diarrhea rate than those fed PM (p = 0.059). Bacteroides had the highest abundance in the feces of calves fed AM on day 50, while Ruminococcaceae_UCG_005 had the highest abundance in the feces of calves fed AM on day 90 and calves fed PM on days 50 and 90. At the taxonomic level, the linear discriminant analysis scores of 27 microorganisms in the feces of calves fed AM and PM on days 50 and 90 were higher than 4.0. Conclusion: Feeding AM increased calf average daily gain and affected fecal bacterial diversity.

ANTI-PERIODIC SOLUTIONS FOR HIGHER-ORDER NONLINEAR ORDINARY DIFFERENTIAL EQUATIONS

Chen, Tai Yong,Liu, Wen Bin,Zhang, Jian Jun,Zhang, Hui Xing Korean Mathematical Society 2010 대한수학회지 Vol.47 No.3

In this paper, the existence of anti-periodic solutions for higher-order nonlinear ordinary differential equations is studied by using degree theory and some known results are improved to some extent.

ZVT Series Capacitor Interleaved Buck Converter with High Step-Down Conversion Ratio

Zhang-yong Chen,Yong Chen,Wei Jiang,Tiesheng Yan 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.4

Voltage step-down converters are very popular in distributed power systems, voltage regular modules, electric vehicles, etc. However, a high step-down voltage ratio is required in many applications to prevent the traditional buck converter fromoperating at extreme duty cycles. In this paper, a series capacitor interleaved buck converter with a soft switching technique isproposed. The DC voltage ratio of the proposed converter is half that of the traditional buck converter and the voltage stressacross the one main switch and the diodes is reduced. Moreover, by paralleling the series connected auxiliary switch and theauxiliary inductor with the main inductor, zero voltage transition (ZVT) of the main switches can be obtained without increasingthe voltage or current stress of the main power switches. In addition, zero current turned-on and zero current switching (ZCS) ofthe auxiliary switches can be achieved. Furthermore, owing to the presence of the auxiliary inductor, the turned-off rate of theoutput diodes can be limited and the reverse-recovery switching losses of the diodes can be reduced. Thus, the efficiency of theproposed converter can be improved. The DC voltage gain ratio, soft switching conditions and a design guideline for the criticalparameters are given in this paper. A loss analysis of the proposed converter is shown to demonstrate its advantages overtraditional converter topologies. Finally, experimental results obtained from a 100V/10V prototype are presented to verify theanalysis of the proposed converter.

A Secondary Resonance Soft Switching Half Bridge DC-DC Converter with an Inductive Output Filter

Chen, Zhang-yong,Chen, Yong The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6

In this paper, a secondary resonance half-bridge dc-dc converter with an inductive output filter is presented. The primary side of such a converter utilizes asymmetric pulse width modulation (APWM) to achieve zero-voltage switching (ZVS) of the switches, and clamps the voltage of the switch to the input voltage. In addition, zero current switching (ZCS) of the output diode is achieved by a half-wave rectifier circuit with a filter inductor and a resonant branch in the secondary side of the proposed converter. Thus, the switching losses and diode reverse-recovery losses are eliminated, and the performance of the converter can be improved. Furthermore, an inductive output filter exists in the converter reduce the output current ripple. The operational principle, performance analysis and design equation of this converter are given in this paper. The analysis results show that the output diode voltage stress is independent of the duty cycle, and that the voltage gain is almost linear, similar to that of the isolation Buck-type converter. Finally, a 200V~380V input, 24V/2A output experimental prototype is built to verify the theoretical analysis.

Effect of the Oxygen Flux Ratio on the Structural and the Optical Properties of Silver-oxide Films Deposited by Using the Direct-current Reactive Magnetron Sputtering Method

Xiao-Yong Gao,Hong-Liang Feng,Zeng-Yuan Zhang,Jiao-Min Ma,Meng-Ke Zhao,Chao Chen,Jin-Hua Gu,Shi-E Yang,Yong-Sheng Chen,Jing-Xiao Lu 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.2

Using values of the oxygen flux ratio (OFR = [O2]/[Ar]) ranging from 0 to 0.5, authors deposited a series of silver-oxide (Ag_xO) films on glass substrates by direct-current reactive magnetron sputtering (DC sputtering) at a substrate temperature of 150 ℃. The effect of the OFR on the film’s structural and optical properties was systematically investigated by using X-ray diffractometry, scanning electron microscopy and spectrophotometry. The Ag_xO films deposited clearly show an evolution of the film’s phase structure from the biphased (Ag + Ag_2O) structure to the biphased (AgO + Ag_2O) structure and then to the single-phased (Ag_2O) structure as value of the OFR increases. Accordingly, the film’s surface morphology, related to the film’s crystalline structure, clearly changes from a loose and porous surface structure to a compact surface structure and then to a pyramid-like surface structure with increasing value of the OFR. The novel porous structure may be attributed to the interruption of the silver’s growth course by the AgO on the film’s surface. Notably, a single-phased Ag_2O film is deposited by DC-sputtering at OFR = 0.5 due to the dual effects of thermal decomposition of the AgO phase and a combination reaction of AgO and Ag to Ag_2O. The oscillations both in the film’s reflectivity and transmissivity spectra are strengthened with increasing OFR, indicating an evolution from the metallic behavior of the biphased (Ag + Ag_2O) film to the dielectric behavior of the biphased (Ag_2O + AgO) film and the single-phased Ag2O film. The fitted optical absorption edges of the Ag_2O and the Ag_xO films deposited at values of the OFR of 0.5 and 0.33 are approximately 2.43 eV and 2.34 eV, respectively. The absorption edges are closely related to the direct interband transitions.

Unilateral ureteral obstruction causes gut microbial dysbiosis and metabolome disorders contributing to tubulointerstitial fibrosis

Lin Chen,Dan-Qian Chen,Jing-Ru Liu,Jun Zhang,Nosratola D. Vaziri,Shougang Zhuang,Hua Chen,Ya-Long Feng,Yan Guo,Ying-Yong Zhao 생화학분자생물학회 2019 Experimental and molecular medicine Vol.51 No.-

Chronic kidney disease (CKD) increases the risk and prevalence of cardiovascular disease (CVD) morbidity and mortality. Recent studies have revealed marked changes in the composition of the microbiome and the metabolome and their potential influence in renal disease and CVD via the accumulation of microbial-derived uremic toxins. However, the effect of unilateral ureteral obstruction (UUO) on the gut microbiome and circulating metabolites is unknown. Male Sprague-Dawley rats were randomized to UUO and sham-operated control groups. Renal histology, colonic microbiota, and plasma metabolites were examined two weeks later. We employed 16S rRNA sequence and untargeted metabolomic analyses to explore the changes in colonic microbiota and plasma metabolites and their relationship with tubulointerstitial fibrosis (TIF). The UUO rats exhibited tubular atrophy and dilatation, interstitial fibrosis and inflammatory cell infiltration in the obstructed kidney. UUO rats showed significant colonic enrichment and depletion of genera. Significant differences were identified in 219 plasma metabolites involved in lipid, amino acid, and bile acid metabolism, which were consistent with gut microbiota-related metabolism. Interestingly, tryptophan and its metabolites kynurenine, 5-hydroxytryptophan and 5-hydroxytryptamine levels, which were linked with TIF, correlated with nine specific genera. Plasma tryptophan level was positively correlated with Clostridium IV, Turicibacter, Pseudomonas and Lactobacillales, and negatively correlated with Oscillibacter, Blautia, and Intestinimonas, which possess the genes encoding tryptophan synthase (K16187), indoleamine 2,3-dioxygenase (K00463) and tryptophan 2,3-dioxygenase (K00453) and their corresponding enzymes (EC:1.13.11.52 and EC:1.13.11.11) that exacerbate TIF. In conclusion, UUO results in profound changes in the gut microbiome and circulating metabolites, events that contribute to the pathogenesis of inflammation and TIF.