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Capital Structure of Start-ups: Evidence on Non-accounting Characteristics
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作者 Marika Miettinen Markku Virtanen 《Journal of Modern Accounting and Auditing》 2013年第7期889-907,共19页
Research is scarce on non-financial characteristics, including owner characteristics and their influences on capital structure in the establishment phase. The objective of this study is to examine the factors affectin... Research is scarce on non-financial characteristics, including owner characteristics and their influences on capital structure in the establishment phase. The objective of this study is to examine the factors affecting firms' availability of external finance, utilizing a sample of Finnish start-up micro firms. The overall purpose is not to produce a comprehensive model for capital structure, but to illustrate the importance of non-accounting characteristics in explaining the attractiveness of the new venture from the lender's point of view. The results show that a founder who has prior work experience from the same sector and has little or no personal financial property seems to have higher leverage. After splitting the data into survived and failed firms, lenders viewed work experience positively only in the sample of failed firms. In addition, limited liability companies, firms located in bigger cities, and firms with good demand evaluated by the lender have a lower level of leverage. 展开更多
关键词 capital structure FINANCING start-ups micro firms
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The Role of Venture Capital in Supporting the Development Process of Innovative Start-Ups:Evidence From the Italian Market
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作者 Anna Gervasoni Francesco Bollazzi Andrea Odille Bosio 《Management Studies》 2018年第6期484-501,共18页
This research paper investigates the role of Italian venture capital in supporting innovative start-ups in their early-stage process,which is usually focused on the creation of a new product or the development of a ne... This research paper investigates the role of Italian venture capital in supporting innovative start-ups in their early-stage process,which is usually focused on the creation of a new product or the development of a new service.The aim of the study is to observe and assess the key economic features of innovative start-ups funded at the beginning of the early-stage by venture capital funds and thereafter analyze the level of development of target companies at four years since the capital injection.The sample of deals created to describe this dynamic process is composed by investments realized between 1996 and 2012 and,in this way,according to the chosen methodology,it is representative of Italian venture capital role and contribution in the years from 1996 to 2016.The authors used for their empirical study a proprietary database,Venture Capital Monitor—VeMTM.Through the analysis of collected data,the paper describes the strategic importance of venture capital investments in early-stage opportunities both for target companies and the Italian socio-economic environment,and finds aggregate values of reference to quantitatively define the socio-economic outcome of this kind of operations.A final further contribution is provided by comparing the present results to the ones of two previous studies conducted by the authors. 展开更多
关键词 VENTURE capital start-up early stage Italy ITALIAN MARKET economic impact development PROCESS
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Readiness of financial resilience in start-ups 被引量:1
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作者 Aswathy Sreenivasan M.Suresh 《Journal of Safety Science and Resilience》 EI CSCD 2023年第3期241-252,共12页
Financial resilience refers to a start-up's capacity to anticipate,plan for,respond to,and adapt to gradual change and abrupt unforeseen shocks to survive and thrive by enacting appropriate economic policies to de... Financial resilience refers to a start-up's capacity to anticipate,plan for,respond to,and adapt to gradual change and abrupt unforeseen shocks to survive and thrive by enacting appropriate economic policies to decrease budget deficits.Economic history tells us that more companies fail to emerge from a downturn than go into or during it.Many studies have been done on financial resilience in many dimensions,but no one has studied start-ups’organizational readiness for financial resilience.This gap inspires the current research,which uses the Total Interpretive Structural Modelling(TISM)approach to identify financial resilience factors and analyze hierarchical interrelationships start-ups’organizational readiness factors for financial resilience.This article aims to identify,assess,and categorize start-up organizational preparation elements for financial resilience.The result shows that the first importance should be given to digital financial innovation,liquidity planning,going concern consideration,financial strategy of CFOs,and cyberthreats.Managers of start-ups can utilize the findings of this study to prepare for financial resilience professionally.In a fast-paced environment,start-ups may use financial resilience to gain a competitive edge. 展开更多
关键词 Financial resilience READINESS start-ups Lender management Business continuity plan Digital financial innovation
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Numerical study of plasmas start-up by electron cyclotron waves in NCST spherical tokamak and CN-H1 stellarator
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作者 刘亿卓行 郑平卫 +4 位作者 龚学余 尹岚 陈小昌 钟翊君 杨文军 《Plasma Science and Technology》 SCIE EI CAS CSCD 2024年第7期12-22,共11页
According to the physics of tokamak start-up,this study constructs a zero-dimensional(0D)model applicable to electron cyclotron(EC)wave assisted start-up in NCST spherical torus(spherical tokamak)and CN-H1 stellarator... According to the physics of tokamak start-up,this study constructs a zero-dimensional(0D)model applicable to electron cyclotron(EC)wave assisted start-up in NCST spherical torus(spherical tokamak)and CN-H1 stellarators.Using the constructed 0D model,the results obtained in this study under the same conditions are compared and validated against reference results for pure hydrogen plasma start-up in tokamak.The results are in good agreement,especially regarding electron temperature,ion temperature and plasma current.In the presence of finite Ohmic electric field in the spherical tokamak,a study on the EC wave assisted start-up of the NCST plasma at frequency of 28 GHz is conducted.The impact of the vertical magnetic field B_(v)on EC wave assisted start-up,the relationship between EC wave injection power P_(inj),Ohmic electric field E,and initial hydrogen atom density n_(H0)are explored separately.It is found that under conditions of Ohmic electric field lower than ITER(~0.3 V m^(-1)),EC wave can expand the operational space to achieve better plasma parameters.Simulating the process of28 GHz EC wave start-up in the CN-H1 stellarator plasma,the plasma current in the zerodimensional model is replaced with the current in the poloidal coil of the stellarator.Plasma startup can be successfully achieved at injection powers in the hundreds of kilowatts range,resulting in electron densities on the order of 10^(17)-10^(18)m^(-3). 展开更多
关键词 spherical torus STELLARATOR electron cyclotron wave start-up 0D model
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Numerical Simulation of a Two-Phase Flow with Low Permeability anda Start-Up Pressure Gradient 被引量:1
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作者 Xuanyu Dong Jingyao Yang 《Fluid Dynamics & Materials Processing》 EI 2023年第1期175-185,共11页
A new numerical model for low-permeability reservoirs is developed.The model incorporates the nonlinear characteristics of oil-water two-phase flows while taking into account the initiation pressure gradient.Related n... A new numerical model for low-permeability reservoirs is developed.The model incorporates the nonlinear characteristics of oil-water two-phase flows while taking into account the initiation pressure gradient.Related numerical solutions are obtained using a finite difference method.The correctness of the method is demonstrated using a two-dimensional inhomogeneous low permeability example.Then,the differences in the cumulative oil and water production are investigated for different starting water saturations.It is shown that when the initial water saturation grows,the water content of the block continues to rise and the cumulative oil production gradually decreases. 展开更多
关键词 Low-permeability reservoirs two-phase flow water cut start-up pressure gradient non-darcy flow
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Dynamic interaction between clustered liquid propellant rocket engines under their asynchronous start-ups
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作者 Sergey I.Dolgopolov Olexiy D.Nikolayev Nataliia V.Khoriak 《Propulsion and Power Research》 SCIE 2021年第4期347-359,共13页
A nonlinear mathematical model of the low-frequency dynamics of the clustered multi-engine rocket propulsion system has been developed and the computations of the engine transient processes during the start-ups of the... A nonlinear mathematical model of the low-frequency dynamics of the clustered multi-engine rocket propulsion system has been developed and the computations of the engine transient processes during the start-ups of the four-engine propulsion system with a shared feed system have been made applied.Based on propulsion system start-up modeling the influence of the connectivity of engines in a cluster on the starting characteristics of individual engines is shown.In particular,an advanced nonlinear mathematical model of the pump cavitation phenomena is a distinctive feature of the mathematical model.The computation results showed that the asynchronous engines start-ups during rocket lift-off lead to severely nonlinear engine transients and clustered engine thrust misbalance.The influence of the rocket engines asynchronous start-ups on the clustered feed system transients depends on many factors,mainly on from the clustered feed system low-frequency dynamics,the magnitude of the disturbance and the phase difference between disturbances acting on different branches of the feed system.The deep lingering dips in the flow rate and pressure transients are possible due to the nonlinear dynamic interaction of the engines.In case of great pressure dips at the pump inlet(up to the pressure of saturated vapors during significant periods of start-up time)the cavitation breakdowns of the pumps of one or more engines from the cluster are possible.This can disrupt the operation of the entire propulsion system and leads to the failure of the launch vehicle mission. 展开更多
关键词 Liquid propellant rocket engine Clustered engine thrust misbalance Nonlinear mathematical model start-up transient Pump cavitation model Low-frequency processes start-up sequence Shared feed system
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Dynamic evaluation of a scaled-down heat pipe-cooled system during start-up/shut-down processes using a hardware-in-the-loop test approach
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作者 Jiao‑Long Deng Tian‑Shi Wang +3 位作者 En‑Ping Zhu Shuo Yuan Xiao‑Jing Liu Xiang Chai 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2023年第11期174-198,共25页
Micro-mobile heat pipe-cooled nuclear power plants are promising candidates for distributed energy resource power genera-tors and can be flexibly deployed in remote places to meet increasing electric power demands.How... Micro-mobile heat pipe-cooled nuclear power plants are promising candidates for distributed energy resource power genera-tors and can be flexibly deployed in remote places to meet increasing electric power demands.However,previous steady-state simulations and experiments have deviated significantly from actual micronuclear system operations.Hence,a transient analysis is required for performance optimization and safety assessment.In this study,a hardware-in-the-loop(HIL)approach was used to investigate the dynamic behavior of scaled-down heat pipe-cooled systems.The real-time features of the HIL architecture were interpreted and validated,and an optimal time step of 500 ms was selected for the thermal transient.The power transient was modeled using point kinetic equations,and a scaled-down thermal prototype was set up to avoid mod-eling unpredictable heat transfer behaviors and feeding temperature samples into the main program running on a desktop PC.A series of dynamic test results showed significant power and temperature oscillations during the transient process,owing to the inconsistency of the rapid nuclear reaction rate and large thermal inertia.The proposed HIL approach is stable and effective for further studying of the dynamic characteristics and control optimization of solid-state small nuclear-powered systems at an early prototyping stage. 展开更多
关键词 Micro-heat pipe-cooled nuclear reactor HARDWARE-IN-THE-LOOP Dynamic evaluation start-up/shut-down processes
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Analysis on the Problems in Start-up and Debugging of Two 600 MW Generating Units in Yangzhou No.2 Thermal Power Plant
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作者 蒯狄正 《Electricity》 2001年第2期11-15,共5页
The problems including excessive flow of attemperating water for boiler, failure of butterfly valve at the outlet of circulating water pump, burnt-out of thyristor for excitation regulator, load variation rate of CCS ... The problems including excessive flow of attemperating water for boiler, failure of butterfly valve at the outlet of circulating water pump, burnt-out of thyristor for excitation regulator, load variation rate of CCS not complying with the contract target, etc. occurred during start-up and debugging of two 600 MW generating units in Yangzhou No.2 Thermal Power Plant. Through analysis on these problems. the remedial measures were put forward, to which can be referred for similar units. 展开更多
关键词 start-up and debugging problems analysis remedial measures 600 MW generating unit
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Start-up of anaerobic ammonia oxidation bioreactor with nitrifying activated sludge 被引量:26
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作者 ZHENGPing LINFeng-mei +1 位作者 HUBao-lan CHENJian-song 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2004年第1期13-16,共4页
The anaerobic ammonia oxidation(Anammox) bioreactor was successfully started up with the nitrifying activated sludge. After anaerobically operated for 105 d, the bioreactor reached a good performance with removal perc... The anaerobic ammonia oxidation(Anammox) bioreactor was successfully started up with the nitrifying activated sludge. After anaerobically operated for 105 d, the bioreactor reached a good performance with removal percentage of both ammonia and nitrite higher than 95% and volumetric total nitrogen removal as high as 149.55 mmol/(L·d). The soft padding made an important contribution to the high efficiency and stability because it held a large amount of biomass in the bioreactor. 展开更多
关键词 Anammox bioreactor nitrifying activated sludge start-up
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A method to refine the start-up scheme of compression and refrigeration systems in ethylene plants via dynamic simulation 被引量:2
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作者 Shengfu Zhang Yongchen Zhao +2 位作者 Tong Qiu Guang Song Jinsong Zhao 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2016年第8期1007-1012,共6页
Starting the cracking gas compressor and precooling the refrigeration system are keys to start-up of an ethylene plant and accounts for up to 50% of the total start-up time and plant flare emissions. Premature feeding... Starting the cracking gas compressor and precooling the refrigeration system are keys to start-up of an ethylene plant and accounts for up to 50% of the total start-up time and plant flare emissions. Premature feeding of cracking furnaces can be avoided if the cracking gas compressor is started and the refrigeration system is precooled in advance using mixed gas as the start-up working medium(SWM). Start-up scenario with mixed gas as SWM could significantly reduce the emission loss and shorten the precooling time. Research shows that making appropriate start-up scheme is important not only to ensure operational safety and feasibility, but also to reduce energy consumption. In this paper, a method is proposed to select suitable start-up operational parameters of compression and refrigeration system with sufficient safe operating ranges and short precooling time. The complex interrelation among key parameters of start-up is analyzed. It is found that higher energy consumption, especially for super high-pressure steam(SS), can promote operational safety and shorten the precooling time during start-up.Based on steady-state and dynamic simulation, appropriate operating parameter ranges are determined with reasonable SS consumption. A real case study demonstrates that an appropriate start-up scheme will optimize the operation. 展开更多
关键词 start-up ETHYLENE PLANT start-up working MEDIUM MIXED gas RUN Compression system
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The exact solution of Stokes' second problem including start-up process with fractional element 被引量:3
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作者 Kaixin Hu Keqin Zhu 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2009年第5期577-582,共6页
The start-up process of Stokes' second problem of a viscoelastic material with fractional element is studied. The fluid above an infinite flat plane is set in motion by a sudden acceleration of the plate to steady os... The start-up process of Stokes' second problem of a viscoelastic material with fractional element is studied. The fluid above an infinite flat plane is set in motion by a sudden acceleration of the plate to steady oscillation. Exact solutions are obtained by using Laplace transform and Fourier transform. It is found that the relationship between the first peak value and the one of equal-amplitude oscillations depends on the distance from the plate. The amplitude decreases for increasing frequency and increasing distance. 展开更多
关键词 Stokes' second problem start-up process Fractional element Laplace transform Fourier transform
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The start-up of biohydrogen-producing process by bioaugmentation in the EGSB reactor 被引量:5
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作者 王相晶 Ren Nanqi +1 位作者 Xiang Wensheng Guo Wanqian 《High Technology Letters》 EI CAS 2006年第3期328-332,共5页
Expanded granular sludge bed (EGSB) reactor and bioaugmentation were employed to investigate biohydrogen production with molasses wastewater. The start-up experiments consisted of two stages. In the first stage (0 ... Expanded granular sludge bed (EGSB) reactor and bioaugmentation were employed to investigate biohydrogen production with molasses wastewater. The start-up experiments consisted of two stages. In the first stage (0 - 24d) seeded with activated sludge, the butyric acid type-fermentation formed when the initial expanding rate, organic loading rate (OLR), the initial redox potential (ORP) and hydraulic retention time (HRT) were 10%, 10.0 kg COD/(m^3·d), -215 mV and 6.7 h, respectively. At the beginning of the second stage on day 25, the novel hydrogen-producing fermentative bacterial strain B49 (AF481148 in EMBL) were inoculated into the reactor under the condition of OLR 16. 0 kg COD/(m^3·d), ORP and HRT about - 139 mV and 6.7 h, respectively, and then the reaction system transformed to ethanol-type fermentation gradually with the increase in OLR. When OLR, ORP and HRT were about 94.3 kg COD/(m^3·d), -250 mV and 1.7 h, respectively, the system achieved the maximum hydrogen-producing rate of 282.6 mL H2/L reactor·h and hydrogen percentage of 51% -53% in the biogas. 展开更多
关键词 start-up biohydrogen production BIOAUGMENTATION hydrogen-producing bacterial strain B49 EGSB reactor
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Start-up and Performance of a Novel Reactor----Jet Biogas Inter-loop Anaerobic Fluidized Bed 被引量:2
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作者 邓志毅 韦朝海 周秀峰 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2008年第1期143-150,共8页
A novel anaerobic reactor, jet biogas inter-loop anaerobic fluidized bed (JBILAFB), was designed and constructed. The start-up and performance of the reactor was investigated in the Process. of .artificial glucose w... A novel anaerobic reactor, jet biogas inter-loop anaerobic fluidized bed (JBILAFB), was designed and constructed. The start-up and performance of the reactor was investigated in the Process. of .artificial glucose wastewater treatment. With the wastewater recycle ratio of 2.5 : 1, the recycled wastewater with biogas could mix sludge and wastewater in the JBILAFB reactor completely. The start-up of the JBILAFB reactor could be completed in less than 70 d through maintenance of hydraulic retention time (HR^I") and stepwise increase of feed total organic carbon (TOC) concentration. After the start-up, with the volumetric TOC loadings of 14.3 kg·m ^-3·d^-1, the TOC removal ratio, the effluent pH, and the volatile fatty acids (VFA)/alkalinity of the JBILAFB reactor were more than 80%, close to 7.0 and less than 0.4, respectively. Moreover, CH4 was produced at more than 70% of the theoretical value, The reactor exhibited high stability under the condition of high volumetric TOC loading. Sludge granules in the JBILAFB reactor were developed during the start-up and their sizes were enlarged with the stepwise increase of volumetric TOC loadings from 0.8 kg.m^-3.d ^-1 to 14.3 kg.m^-3.d^-1. Granules, an offwhite color and a similar spherical shape, were mainly comprised of global-like bacteria. These had good methanogenic activity and settleability, which were formed probably through adhesion of the bacteria. Some inorganic metal compounds such as Fe, Ca, Mg, Al, etc. were advantageous to the formation of the granules. 展开更多
关键词 anaerobic reactor jet biogas inter-loop anaerobic fluidized bed wastewater treatment start-up granule sludge
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Experimental research on characteristic of start-up pressure wave propagation in gelled crude oil by large-scale flow loop 被引量:1
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作者 崔秀国 艾慕阳 +2 位作者 姜保良 霍连风 张立新 《Journal of Central South University》 SCIE EI CAS 2008年第S1期467-470,共4页
In order to research start-up pressure wave propagation mechanism and determine pressure wave speed in gelled crude oil pipelines accurately,experiment of Large-scale flow loop was carried out.In the experiment,start-... In order to research start-up pressure wave propagation mechanism and determine pressure wave speed in gelled crude oil pipelines accurately,experiment of Large-scale flow loop was carried out.In the experiment,start-up pressure wave speeds under various operation conditions were measured,and effects of correlative factors on pressure wave were analyzed.The experimental and theoretical analysis shows that thermal shrinkage and structural properties of gelled crude oils are key factors influencing on start-up pressure wave propagation.The quantitative analysis for these effects can be done by using volume expansion coefficient and structural property parameter of gelled crude oil.A new calculation model of pressure wave speed was developed on the basis of Large-scale flow loop experiment and theoretical analysis. 展开更多
关键词 gelled CRUDE oil start-up pressure wave PROPAGATION CHARACTERISTIC lager-scale FLOW LOOP
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Start-up and contaminants removal characteristics of aerobic granules-membrane bioreactor at low temperature 被引量:1
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作者 王硕 于水利 +2 位作者 时文歆 王玉兰 衣雪松 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2012年第1期67-70,共4页
In order to understand the effect of low temperature on the formation process of aerobic granules and contaminants removal characteristics,the aerobic granules-membrane bioreactor (AGS-MBR) has been started up and ope... In order to understand the effect of low temperature on the formation process of aerobic granules and contaminants removal characteristics,the aerobic granules-membrane bioreactor (AGS-MBR) has been started up and operated at low temperature using the carbon resource of sodium acetate. Aerobic granules cultivated in AGS-MBR possess smooth surface and compact structure in morphology as well as better settling property and higher biomass after 38 days. The average parameters of aerobic granules are: diameter 3. 1 mm,wet density 1. 041 g/mL,sludge volume index 42. 35 mL/g and settling velocity 20. 6 - 45. 2 cm/min. During the start-up of AGS-MBR,the respectively average contaminants removal efficiencies at low temperature are 91. 9% for chemical oxygen demand (COD) ,89. 2% for NH4 + -N and 86. 3% for PO43- -P,and the overgrowth of filamentous bacteria has been well controlled. In addition,the hollow fiber microfiltration (MF) membrane fouling is light and the regime membrane layer is capable of enhancing membrane filtration as well as the average growth of trans-membrane pressure (TMP) is 1. 07 kPa/d. Compared with the conventional cultivation of aerobic granules,the sludge granulation time significantly decreases from 73 days to 38 days by the application of microfiltration membrane at low temperature. 展开更多
关键词 Aerobic Granules-Membrane Bioreactor (AGS-MBR) Low Temperature start-up CONTAMINANTS Removal MICROFILTRATION (MF) Trans-Membrane Pressure (TMP)
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Study on durability of Pt supported on graphitized carbon under simulated start-up/shut-down conditions for polymer electrolyte membrane fuel cells 被引量:2
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作者 Won Suk Jung 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2018年第1期326-334,共9页
The primary issue for the commercialization of proton exchange membrane fuel cell(PEMFC) is the carbon corrosion of support under start-up/shut-down conditions. In this study, we employ the nanostructured graphitize... The primary issue for the commercialization of proton exchange membrane fuel cell(PEMFC) is the carbon corrosion of support under start-up/shut-down conditions. In this study, we employ the nanostructured graphitized carbon induced by heat-treatment. The degree of graphitization starts to increase between 900 and 1300 ℃ as evidenced by the change of specific surface area, interlayer spacing, and ID/IG value. Pt nanoparticles are deposited on fresh carbon black(Pt/CB) and carbon heat-treated at 1700 ℃(Pt/HCB17) with similar particle size and distribution. Electrochemical characterization demonstrates that the Pt/HCB17 shows higher activity than the Pt/CB due to the inefficient microporous structure of amorphous carbon for the oxygen reduction reaction. An accelerating potential cycle between 1.0 and 1.5 V for the carbon corrosion is applied to examine durability at a single cell under the practical start-up/shutdown conditions. The Pt/HCB17 catalyst shows remarkable durability after 3000 potential cycles. The Pt/HCB17 catalyst exhibits a peak power density gain of 3%, while the Pt/CB catalyst shows 65% loss of the initial peak power density. As well, electrochemical surface area and mass activity of Pt/HCB17 catalyst are even more stable than those of the Pt/CB catalyst. Consequently, the high degree of graphitization is essential for the durability of fuel cells in practical start-up/shut-down conditions due to enhancing the strong interaction of Pt and π-bonds in graphitized carbon. 展开更多
关键词 Polymer electrolyte membrane fuel ceils Membrane electrolyte assembly Carbon corrosion start-up/shut-down Durability
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START-UP AND DYNAMIC PROCESSES SIMULATION OF A DISTILLATION COLUMN
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作者 宋海华 余国琮 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 1995年第3期13-23,共11页
A new dynamic non-equilibrium mixing-pool model for simulating start-up and dynamic re-sponse of a distillation column is reported.The proposed model is established on the basis ofconsidering the two dimensional flow/... A new dynamic non-equilibrium mixing-pool model for simulating start-up and dynamic re-sponse of a distillation column is reported.The proposed model is established on the basis ofconsidering the two dimensional flow/mixing behavior of actual trays in a distillation column.Com-parison is made among the computed results of the start-up time and the dynamic response time bythe proposed and five other typical models.It is found that the computed time for both dynamicprocesses is longer by the model which considers any flow/mixing pattern than by the model withoutsuch concern.The inertia effect of flow/mixing seems to be important and can not be ignored inmodeling the transient process of distillation.The proposed model,which is believed to be suitableto large column,seems somewhat useful in predicting industrial distillation dynamics. 展开更多
关键词 DISTILLATION SIMULATION start-up dynamic process three dimensional NON-EQUILIBRIUM mixing-pool model
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New Start-up Method for a Closed-Cycle Compression System with Gas Bearings and Its Characteristics
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作者 Huaqi Lian Hong Wu +1 位作者 Yulong Li Chengjun Rong 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2020年第6期118-133,共16页
Gas bearings,which have the advantages of low frictional resistance and power loss,high rotational speed and high temperature operation,and long life,are more suitable than are traditional liquid lubricated bearings b... Gas bearings,which have the advantages of low frictional resistance and power loss,high rotational speed and high temperature operation,and long life,are more suitable than are traditional liquid lubricated bearings because of their high precision,high rotational speed,and special condition support.However,the problem of starting a closed-cycle compression system with gas bearings still needs to be solved for practical application.Thus,a new start-up method for a closed-cycle compression system with aerostatic gas bearings is proposed in this paper.Further,this paper presents a numerical simulation and experimental investigation of the method’s feasibility and characteristics during the start-up process when the gas tank’s initial pressure is fixed.The results show that the gas tank volume is approximately directly proportional to the start-up time allowable,and a gas tank volume sufficiently small,which not only ensures the feasibility of start-up,but also affects other components only slightly,can be obtained.A perfect combination of radial and axial loads also can be achieved to make the start-up time allowable as long as possible.R134a is a better choice for the working medium than is air,as the start-up time allowable is longer,which leads to a smaller gas tank.This research proposes a new start-up method for a closed-cycle compression system with aerostatic gas bearings which has sufficient load capacity to support system during the start-up method. 展开更多
关键词 Gas bearing start-up method Gas tank start-up time allowable
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Start-up phase plasma discharge design of a tokamak via control parameterization method
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作者 郭珊 许珂 +2 位作者 许超 任志刚 肖炳甲 《Chinese Physics B》 SCIE EI CAS CSCD 2015年第3期248-254,共7页
The tokamak start-up is a very important phase during the process to obtain a suitable equalizing plasma, and its governing model can be described as a set of nonlinear ordinary differential equations(ODEs). In this... The tokamak start-up is a very important phase during the process to obtain a suitable equalizing plasma, and its governing model can be described as a set of nonlinear ordinary differential equations(ODEs). In this paper, we first estimate the parameters in the original model and set up an accurate model to express how the variables change during the start-up phase, especially how the plasma current changes with respect to time and the loop voltage. Then, we apply the control parameterization method to obtain an approximate optimal parameters selection problem for the loop voltage design to achieve a desired plasma current target. Computational optimal control techniques such as the variational method and the costate method are employed to solve the problem, respectively. Finally, numerical simulations are performed and the results obtained via different methods are compared. Our numerical parameterization method and optimization procedure turn out to be effective. 展开更多
关键词 TOKAMAK start-up optimal control variational method
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Evaluation of Inocula and Packing Material for Acceleration of Start-Up in Biofilters
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作者 Li Chao Zhao Dongfeng +3 位作者 Mu Guiqin Song Xiangning Zhang Tingting Liu Jun 《China Petroleum Processing & Petrochemical Technology》 SCIE CAS 2019年第2期67-75,共9页
Several strategies with different combination of inocula and packing material were investigated to obtain the optimal start-up time and elimination capacity (EC) in toluene biofiltration. The inocula contained the act... Several strategies with different combination of inocula and packing material were investigated to obtain the optimal start-up time and elimination capacity (EC) in toluene biofiltration. The inocula contained the activated sludge and toluene degrading bacteria, and the packing material consisted of different mixing ratios of peat and wood chips. A final toluene load of 21.2 g/(m3·h) was attained step by step in four parallel biofilters. A shortest start-up time of 15 days and a highest EC of 17.0 g/(m3·h) were observed in the biofilter B-4, which was inoculated with a special microbial consortium consisting of three strains of toluene degrading bacteria and was packed with the mixture of peat and wood chips at a ratio of 80:20 (w/w). These results indicated that inoculating pre-acclimatized microbes dramatically shortened the start-up time, and such a composition of packing material could maintain an appropriate environment (with the bed porosity and water content equating to 0.45 and 1.96, respectively) for the growth of dominant toluene degrading bacteria in the biofilter. 展开更多
关键词 ACCELERATION of start-up BIOFILTER INOCULA PACKING material
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