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101.
Chunshan Zheng Baiquan Lin Mehmet S.Kizil Saiied M.Aminossadati He Li Zhongwei Chen 《矿业科学技术学报(英文版)》2018,28(4):701-705
Hydraulic slotting in a gas drainage borehole is an effective method of enhancing gas drainage performance. However, it frequently occurs that a large amount of slotting products(mainly the coal slurry and gas) intensely spurt out of the borehole during the slotting, which adversely affects the slotting efficiency. Despite extensive previous investigations on the mechanism and prevention-device design of the spurt during ordinary borehole drilling, a very few studies has focused on the spurt in the slotting process. The slotting spurt is mainly caused by two reasons: the coal and gas outburst in the borehole and the borehole deslagging blockage. This paper focuses on the second reason, and investigates the hydraulic deslagging flow patterns in the annular space between the drill pipe and borehole wall.Results show that there are six deslagging flow patterns when the drill pipe is still: pure slurry flow, pure gas flow, bubble flow, intermittent flow, layering flow and annular flow. When the drill pipe rotates, each of those six flow patterns changes due to the Taylor vortex effect. Outcomes of this study could help to better understand the slotting-spurt mechanism and provide guidance on the anti-spurt strategies through eliminating the borehole deslagging blockage. 相似文献
102.
Mehmet Salih Mami? 《International Journal of Electrical Power & Energy Systems》2011,33(7):1256-1261
A non-iterative algorithm based on nodal equation formulation is proposed for transient simulation of nonlinear and time-varying elements. Terminal equations of inductors and capacitors are transformed into algebraic equations using the trapezoidal rule of integration by treating all nonlinear elements as linear and nodal equations are formulated as a set of algebraic equations. LU factorization is used for the solution of nodal equations. Variation of system elements is represented by renewing the nodal conductance matrix at each time step of the solution accordingly. In the first illustrative example, a nonlinear oscillator circuit is considered. In the second, the transient response of a transmission line with a surge arrester is computed by including the corona effects and in the third, a time-dependent primary arc model of a faulty transmission line is examined. Obtained results are compared with those obtained using EMTP and state-space method. Change of simulation time with respect to the step length of the numerical integration is also investigated. 相似文献
103.
Formation of chlorination by-products in waters with low SUVA--correlations with SUVA and differential UV spectroscopy 总被引:4,自引:0,他引:4
The formation of THMs and HAAs after chlorination of bulk water fractions of low-SUVA (specific UV absorbance) surface waters was investigated, and the applicability of SUVA and differential UV spectroscopy for monitoring THMs and HAAs in such waters was evaluated. Samples from two reservoirs were fractionated employing XAD-8, XAD-4, MIEX resin and granular activated carbon adsorption. A total of 83 bulk water NOM fractions (i.e., the remaining solutions after contact with the adsorbent or resin at various doses) were obtained and chlorinated. The majority of NOM in both waters was found to have average molecular weights <2000 Da and SUVA values <2L/mg Cm, indicating that NOM in the tested waters contained dominantly lower molecular weight fractions and low aromaticity. SUVA did not correlate well with the formation and speciation of THMs and HAAs, suggesting that SUVA does not capture the reactive sites on NOM moieties responsible for DBP formation in low-SUVA waters. Similarly, no correlations were found among THMs/HAAs formations and differential UV spectroscopy, indicating the formation of DBPs independent of destruction in UV-absorbing sites. In all fractions, concentrations of THMs were higher than those of HAAs. Chlorinated DBP species were dominant over brominated ones due to low bromide concentrations. The results overall suggested that low- or non-UV-absorbing NOM moieties play important roles in the formation of DBPs in waters with low SUVA, low DOC and low bromide levels. 相似文献
104.
Mehmet Ayvaz Safiye İpek Ayvaz İbrahim Aydin 《International Journal of Hydrogen Energy》2018,43(44):20271-20283
Consumption of the fossil fuels causes greenhouse gas effect and environmental pollution, which are two basic problems of our age. As a result of this problem, clean and renewable alternative energy sources are beginning to replace fossil fuels. Nowadays, the use of hydrogen energy, which is one of the clean energy, is increasing in transportation and industrial areas. Increasing of hydrogen energy usage, scientists are attempting to solve the many safety problems (such as fire, burst, impact and hydrogen embrittlement) that can occur during the storage and consumption of hydrogen energy. In this study, during the event of fire, the safety of metallic Type I pressure hydrogen storage tanks is investigated by using a novel approach. In this new approach, the mechanical strength drops of the tank materials that is related with temperature rising are added to the safety calculations. In the study, 6061 T6 aluminum and SS 316L stainless steel alloys were used as hydrogen tank material. The safety of hydrogen tanks modelled using these alloys was investigated under different temperature conditions (22, 100, 200 and 300 °C) and internal pressure (15, 20 and 25 MPa). 相似文献
105.
106.
The Internet not only facilitates our daily activities, such as communication, entertainment and shopping but also serves as the enabling technology for many critical services, including finance, manufacturing, healthcare and transportation. On the other hand, a wide spectrum of attacks targets its communication infrastructure to disable or disrupt the network connectivity and traffic flow until recovery processes take place. Attacking all autonomous systems (ASes) in the Internet is typically beyond the capability of an adversary. Therefore, targeting a small number of ASes which results in the highest impact is the best strategy for attackers. Similarly, it is important for network practitioners to identify, fortify and secure those critical ASes to mitigate the impact of the attacks. In this study we introduce an intuitive and effective measure, IP address spatial path stress centrality, to assess and identify the critical ASes in the Internet. We compare IP address spatial path stress centrality to the three well-known and widely used centrality measures, namely customer-cone size, node degree and betweenness. We demonstrate that the proposed measure incorporates business relations and IP address spaces to achieve a better measure for identifying the critical ASes in the Internet. 相似文献
107.
Scientometrics - A novel hashing algorithm is applied to match two prominent and important bibliographic databases at the paper level. In the literature, such tasks have been studied and conducted... 相似文献
108.
109.
The wave energy potential is directly proportional to the wave period and second power of wave height averaged over a suitable time period. The wave height and period have temporal and spatial stochastic variations. It is the main purpose of this paper to derive the most general wave energy formulation by considering simultaneously the temporal variations both in the wave height and period. The correction factor is derived explicitly in terms of cross-correlation and the coefficients of variation. The application of the methodology is performed for wave measurement stations located in the Pacific Ocean off the west coast of the US. 相似文献
110.
Modelling and boundary control for the Burgers equation is studied in this paper. Modelling has been done via processing of numerical observations through proper orthogonal decomposition (POD) with Galerkin projection. This results in a set of spatial basis functions together with a set of ordinary differential equations (ODEs) describing the temporal evolution. Since the dynamics described by the Burgers equation are non-linear, the corresponding reduced-order dynamics turn out to be non-linear. The presented analysis explains how the free boundary condition appears as a control input in the ODEs and how controller design can be accomplished. The issues of control system synthesis are discussed from the point of practicality, performance and robustness. The numerical results obtained are in good compliance with the theoretical claims. A comparison of various different approaches is presented. 相似文献