http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
OPTIMIZATION RESEARCH FOR A HIGH PRESSURE COMMON RAIL DIESEL ENGINE BASED ON SIMULATION
Y. LIU,Y.-T. ZHANG,T. QIU,X. DING,Q. XIONG 한국자동차공학회 2010 International journal of automotive technology Vol.11 No.5
ABSTRACT−A TP (Temperature Phase) model is presented to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature is the most important parameter in the TP model. For the lower branch (when temperature T < 850 K) of the S-shaped curve (auto-ignition phase), a 6-step ad-hoc model with adjusted rate constants of nheptane is used, referred to steady state assumption. Steady state assumption is based on the observation that, due to very fast chemical processes in combustion problems, many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. For the middle branch (850 K ≤ T < 1100 K) of the S-shaped curve, a 4-step model is used to calculate the unstable phase. For the upper branch (T≥1100 K) of the S-shaped curve, onestep model is used because the one-step model has widely been used in descriptions of flame stability where it essentially serves as a model that produces a thin flame with strong temperature sensitivity. When zone temperature T<1500 K, only the soot precursors –PAHs (Polycyclic aromatic hydrocarbons) is created and there is no soot emission. When zone temperature T≥1500 K, PAHs and soot source terms (particle inception, surface growth, oxidation, coagulation) are calculated. The TP model is then applied in multidimensional simulations to carry out optimizing, which reduces experiment cost. The results of cylinder pressures, the corresponding heat release rates, NOx and soot with variation of injection time at constant rail pressure, variation of EGR-rate at constant rail pressure and variation of rail pressure at constant EGR-rate between simulation and experimental data are analyzed. The results indicate that the TP model can carry out optimization and CFD (computational fluid dynamics) and can be a tool to calculate for a high-pressure common rail diesel engine.
Activation of antiferromagnetic domain switching in exchange-coupled Fe/CoO/MgO(001) systems
Li, Q.,Chen, G.,Ma, T. P.,Zhu, J.,N'Diaye, A. T.,Sun, L.,Gu, T.,Huo, Y.,Liang, J. H.,Li, R. W.,Won, C.,Ding, H. F.,Qiu, Z. Q.,Wu, Y. Z. American Physical Society 2015 Physical review. B, Condensed matter and materials Vol.91 No.13
Qiu, Binbin,Yang, Qingchuan,Yan, Junjie,li, Gen,Revankar, Shripad T. Elsevier 2017 Experimental thermal and fluid science Vol.88 No.-
<P><B>Abstract</B></P> <P>The propagation characteristics of pressure oscillation in direct contact condensation with low mass flux steam jet have been investigated experimentally. Steam is injected into subcooled water at one atmosphere pressure with steam mass flux and water temperature range of 186–272kg/(m<SUP>2</SUP> s) and 293–343K. The pressure oscillation propagates in the form of wave with stable dominant frequency, however the wave intensity attenuates with the increasing distance from the oscillation source. The root mean square of pressure wave <I>p</I> <SUB>rms</SUB> attenuates rapidly with the increasing dimensionless radial distance from the nozzle exit. At about dimensionless radial distance <I>R</I> =100, the <I>p</I> <SUB>rms</SUB> is attenuated by about 90%. Although the dominant frequency of the pressure oscillation is constant during the propagation, after <I>R</I> =100, there will be not enough energy for the pressure oscillation to resonate with relevant equipment. A correlation equation to calculate the root mean square of pressure oscillation along the radial distance is given. The prediction errors are within ±30% compared with the experimental data.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The pressure oscillation propagates in the form of wave. </LI> <LI> In the propagation process, the frequency remains the same but the intensity attenuates. </LI> <LI> A correlation to calculate the <I>p</I> <SUB>rms</SUB> along the radial distance is given. </LI> <LI> At about R=100, the <I>p</I> <SUB>rms</SUB> is attenuated by about 90% and most of the energy is dissipated. </LI> </UL> </P>
Temporal Variation of Intertidal Seagrass in Southern China (2008–2014)
Guanglong Qiu,Frederick T. Short,Hangqing Fan,Guohua Liu 한국해양과학기술원 2017 Ocean science journal Vol.52 No.3
Understanding the temporal dynamics of seagrasses and the major influences on seagrass growth is critical for seagrass habitat conservation and administration. However, little work has been done regarding these issues in southern China. To examine inter-annual and seasonal variations of the intertidal Halophila ovalis community in southern China, we conducted quarterly sampling using the SeagrassNet methodology and assessed environmental conditions as well as direct anthropogenic impacts on the seagrass meadow from July 2008 to October 2014. Our study demonstrated strong inter-annual and seasonal dynamics of the intertidal seagrass meadow in the study area. Generally, the community performed best (highest seagrass cover, leaf area, shoot density, total biomass) in summer and worst in spring among the 4 seasons. The temporal variations in the seagrass community attributes (e.g. above-ground biomass) were significantly affected by precipitation, atmospheric visibility, and salinity, while leaf width was significantly negatively correlated with temperature, atmospheric visibility and salinity. Temperature was a major factor influencing the seagrass community (both macroalgae and seagrass), with temperature data showing an inverse relationship between seagrass and macroalgae. The above-ground: below-ground biomass ratio and leaf width of H. ovalis were the most sensitive plant parameters monitored when assessing environmental interactions. Human physical disturbances did not have a significant effect on seagrass dynamics in the study area. We concluded that long-term monitoring (like SeagrassNet) is valuable in understanding the relationship between environmental variables and seagrasses.
Jiang, H.,Yu, T.,Liu, S. S.,Qiu, Y. J.,Li, B. B. 한국지능정보시스템학회 2022 한국지능정보시스템학회 학술대회논문집 Vol.2022 No.6
This study employed the Difference in Difference (DID) model and the bibliometrics method with aim to novel corona virus disease (COVID-19) pandemic. This study conducted a comparative analysis based on the number of publications, co-authorship, and institutional collaborations on telemedicine literature research in China before and after the outbreak of COVID-19 (October 2017 to March 2022). The quantity, classification, and research focus of Chinese telemedicine literature was also compared based on data before the outbreak (October 2017 to December 2019) and after the outbreak (January 2020 to March 2022).The results show that the number of articles published by Chinese scholars on telemedicine research have soared after the outbreak of COVID-19, with significant emergence in the trend of co-authorship and institutional collaboration. The research hotspots focused on artificial intelligence, Wise Information Technology of Med (WITMED), and public hospitals, extending from the pre-pandemic topics including teleconsultation, internet+, and hierarchical medical system.