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Formation, Propagation and Reflection of 1D Normal shocks in Riemann shock Tube

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Applied Mathematics 2022年第3期13卷 295-323页

作者： Karan s. surana Jacob K. Kendall Celso h. Carranza Mechanical Engineering University of Kansas Lawrence USA

The purpose of this paper is to consider 1D Riemann shock tube to investigate the formation and propagation of compression waves leading to formation, propagation and reflection of 1D normal shocks using simplified mathematical models commonly used in the published work as well as using complete mathematical models based on Conservation and Balance Laws (CBL) of classical continuum mechanics and constitutive theories for compressible viscous medium derived using entropy inequality and representation theorem. This work is aimed at resolving compression waves, the shock structure, shock formation, propagation and reflection of fully formed shocks. Evolutions obtained from the mathematical models always satisfy differentiability requirements in space and time dictated by the highest order of the derivatives of the dependent variables in the mathematical models investigated. All solutions reported in this paper including boundary conditions and initial conditions are always analytic. solutions of the mathematical models are obtained using the space-time finite element method in which the space-time integral forms are space-time variationally consistent ensuring unconditionally stable computations during the entire evolution. solution for a space-time strip or slab is calculated and is time marched upon convergence to obtain complete evolution for the desired space-time domain, thus ensuring time accurate evolutions. The space-time local approximation over a space-time element of a space-time strip or slab is p-version hierarchical with higher-order global differentiability in space and time, i.e., we consider scalar product approximation spaces in which k = (ksub>1sub>, ksub>2sub>) are the order of the space in space and time and p = (psub>1sub>, psub>2sub>) are p-levels of the approximations in space and time. Model problem studies are presented for different mathematical models and are compared with solutions obtained from the complete mathematical model b

关键词： Compression Wave 1D Normal shock Riemann shock Tube space-Time

Insights into kinetic inhibition effects of MEG,PVP,and L-tyrosine aqueous solutions on natural gas hydrate formation

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Petroleum science 2021年第2期18卷 495-508页

作者： Amir saberi Abdolmohammad Alamdari Ali Rasoolzadeh Amir h.Mohammadi Department of Natural Gas Engineering School of Chemical and Petroleum EngineeringShiraz UniversityShiraz71345Iran Department of Process Engineering National Iranian Gas Company(NIGC)South Pars Gas Complex(SPGC)Phases 4&5Bushehr75391/311Iran Discipline of Chemical Engineering School of EngineeringUniversity of KwaZulu-NatalHoward College CampusKing George V AvenueDurban4041South Africa

It is necessary to understand all the prerequisites, which result in gas hydrate formation for safe design and control of a variety of processes in petroleum industry. Thermodynamic hydrate inhibitors (ThIs) are normally used to preclude gas hydrate formation by shifting hydrate stability region to lower temperatures and higher pressures. sometimes, it is difficult to avoid hydrate formation and hydrates will form anyway. In this situation, kinetic hydrate inhibitors (KhIs) can be used to postpone formation of gas hydrates by retarding hydrate nucleation and growth rate. In this study, two kinetic parameters including natural gas hydrate formation induction time and the rate of gas consumption were experimentally investigated in the presence of monoethylene glycol (MEG), L-tyrosine, and polyvinylpyrrolidone (PVP) at various concentrations in aqueous solutions. since hydrate formation is a stochastic phenomenon, the repeatability of each kinetic parameter was evaluated several times and the average values for the hydrate formation induction times and the rates of gas consumption are reported. The results indicate that from the view point of hydrate formation induction time, 2 wt% PVP and 20 wt% MEG aqueous solutions have the highest values and are the best choices. It is also interpreted from the results that from the view point of the rate of gas consumption, 20 wt% MEG aqueous solution yields the lowest value and is the best choice. Finally, it is concluded that the combination of PVP and MEG in an aqueous solution has a simultaneous synergistic impact on natural gas hydrate formation induction time and the rate of gas consumption. Furthermore, a semi-empirical model based on chemical kinetic theory is applied to evaluate the hydrate formation induction time data. A good agreement between the experimental and calculated hydrate formation induction time data is observed.

关键词： Gas hydrate Clathrate hydrate Natural gas Kinetic hydrate inhibitor(KhI) Induction time Kinetics

Axial Breakthrough in Athens： Religious Topography and Transformation

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Fudan Journal of the humanities and social sciences 2016年第4期9卷 577-588页

作者： h. A. shapiro Department of Classics Johns Hopkins University Baltimore MD 21218 USA

Axial Age theory posits that there should be major transformations in Greece （as elsewhere） in the middle of the first millennium BCE. One could point to the creation of the world＇s first democracy in Athens in the years around 508. Equally important, and not unrelated to the democracy, was a re-conceptualizing of the role of religion and worship in society, for which Athens provides especially striking archeological evidence. The physical setting for religious expression changed markedly around the end of the sixth century, especially at Athens. The Agora was filled with cults, temples, and shrines of gods and heroes, laid out along with the establishment of the democracy and adapted to the changing political and social needs of the community. Conversely, the Acropolis, which had been strictly the domain of the goddess Athena, takes on a more civic character in the late sixth century with a radical change in the nature of votives dedicated to her. Thus, in the Greek version of axial breakthrough, religion is not set aside or diluted, but put in the service of a new political order.

关键词： Archaic and classical Greece Athens Acropolis - Agora Cults -Temples Democracy

Is the global sea surface temperature rise accelerating?

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Geodesy and Geodynamics 2018年第6期9卷 432-438页

作者： h.Baki Iz Division of Geodetic science School of Earth Sciences The Ohio State University Columbus OH 43210 USA

This is an exploratory investigation to search for the presence of an acceleration in global sea surface temperature rise, which is essential to identify anthropogenic contributions to the climate change during the 20 th century. A weighted statistical model with an acceleration parameter was built progressively to reconstruct the variations in the global sea surface temperature data considering statistically significant confounders and autoregressive disturbances in the process. From the preliminary residual analysis of a weighted regression model, emerged a parsimonious model with first order autoregressive disturbances with a deterministic trend, acceleration and periodicity of 69 yr and its 138 yr subharmonic. The final model solution, selected from 29 alternative combinations of the model parameters using Mallows' s Cp metric, revealed a statistically significant deterministic trend, 0.40 ± 0.03C/c(p he global sea surface temperature variations. The combined yearly trend and acceleration in global sea surface temperature as predicted by the model,exhibit a strong correlation with the yearly increase in the global CO^2 concentrations observed during the 20th century.

关键词： Climate change First order autoregressive model Global sea surface temperature Global sea surface temperature acceleration Global CO^2 concentration

hydrogeology of Eastern Niger Delta: A Review

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Journal of Water Resource and Protection 2020年第9期12卷 741-777页

作者： T. K. s. Abam h. O. Nwankwoala Institute of Geosciences and space Technology Rivers State University Port Harcourt Nigeria Department of Geology Faculty of Science University of Port Harcourt Port Harcourt Nigeria

This paper characterizes the aquifer system of the Niger Delta for sustainable development of the groundwater resource. The heavy-dependence on groundwater in the region and the fears of its unsustainability triggered by the weak regulations, pollution, increasing user population and industrialization coupled with the present limited knowledge of the true geological condition prevailing within the groundwater domain of the Niger Delta are the considerations that compelled this review study. The hydraulic properties of the region’s aquifers are discussed. The Niger Delta is characterized by a complex multilayered aquifer system hosted in the Benin Formation with the main body of fresh water, with increasing occurrence of intercalating clay units towards the coast. Lithological analysis indicates the prevalence of unconsolidated sand and sandy gravels in the aquiferous horizons, presenting them as pervious and prolific aquifers. Reported hydrochemical data gathered from wells drilled suggest that the quality of groundwater in the Niger Delta is considered generally very good and compares favorably with WhO standards for drinking water. however, relatively high iron/manganese and chloride values are localized in time and space. In the coastal areas however, seawater intrusion has been identified as one of the major influences on hydrochemistry of groundwater in the shallow unconfined aquifers. Regional groundwater flow direction is from north to south. Changes in groundwater flow directions which occur at some places generally serve localized discharge areas. The resultant flow path eventually joins and feeds the major regional north-south flow direction. The increasing pressure on groundwater, the need for urgent attention and the absence of strong institutions and regulations have made the management of groundwater resources in the region a difficult task. Therefore, future ground water resources development in the Niger Delta requires adequate observational data, in

关键词： hydrogeology Groundwater quality saline Water Intrusion Aquifer Water Table Niger Delta

Preparative Fractionation of Feruloyl Oligosaccharides Produced by Combinatorial Enzyme Digestion of Arabinoxylan

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Advances in Enzyme Research 2024年第3期12卷 35-43页

作者： Dominic W. s. Wong sarah Batt William h. Orts Western Regional Research Center USDA-ARS Albany CA USA

Pretreated wheat insoluble arabinoxylan was converted to oligosaccharides of structural variants using combinatorial enzyme approach. The digestive products were separated by preparative scale chromatographic Amberlite XAD-2 column. Fractions containing feruloyl oligosaccharides (FOs) were isolated, pooled, freeze-dried, and demonstrated to possess antimicrobial activity. The FOs suppressed cell growth of the test organism ATCC 8739 E. coli with a MIC value of 0.028% (w/v, 35˚C, 24 hr). The antimicrobial action was observed exceeding 72 hr of culture incubation. The FOs product could be a useful source of prebiotics or preservatives. The present results further confirm the science and application of the concept of combinatorial enzyme technique.

关键词： Format Wheat Insoluble Arabinoxylan Feruloyl Oligosaccharide Combinatorial Enzyme Digestion

Entrapment of DNA topoisomerase-DNA complexes by nucleotide/nucleoside analogs

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Cancer Drug Resistance 2019年第4期2卷 994-1001页

作者： William h.Gmeiner Department of Cancer Biology Wake Forest School of MedicineWinston-SalemNC 27157USA

Topoisomerases are well-validated targets for cancer chemotherapy and DNA topoisomerase 1(Top1)is the sole target of the camptothecin(CPT)class of anticancer *** the last 20 years,multiple studies have shown Top1 activity is modulated by non-native DNA structures and this can lead to trapping of Top1 cleavage complexes(Top1cc)and conversion to DNA double strand *** the perturbations to DNA structure that generate Top1cc are nucleoside analogs that are incorporated into genomic DNA during replication including cytarabine,gemcitabine,and 5-fluoro-2’-deoxyuridine(FdU).We review the literature summarizing the role of Top1cc in mediating the DNA damaging and cytotoxic activities of nucleoside *** also summarize studies demonstrating distinct differences between Top1cc induced by nucleoside analogs and CPTs,particularly with regard to DNA ***,these studies demonstrate that,while Top1 is a common target for both Top1 poisons such as CPT and nucleoside analogs such as FdU,these agents are not *** recent years,studies have shown that Top1 poisons and nucleoside analogs together with other anti-cancer drugs such as cisplatin cause replication stress and the DNA repair pathways that modulate the cytotoxic activities of these compounds are being *** present an overview of this evolving literature,which has implications for how targeting of Top1 with nucleoside analogs can be used more effectively for cancer treatment.

关键词： DNA topoisomerase 1 cancer chemotherapy cytarabine gemcitabine fluoropyrimidine

On a New Extension of the Zero-Divisor Graph

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Algebra Colloquium 2020年第3期27卷 469-476页

作者： A.Cherrabi h.Essannouni E.Jabbouri A.Ouadfel Laboratory of Mathematics Computing and Applications-Information Security(LabMia-SI)Faculty of SciencesMohammed V University in RabatRabatMorocco

In this paper,we introduce a new graph whose vertices are the non-zero zerodivisors of a commutativc ring R、and for distincts elements x and y in the set Z(R)^(*)of the non-zero zero-divisors of R,x and y are adjacent if and only if xy=0 or x+y∈Z(R).We present some properties and examples of this graph,and we study its relationship with the zero-divisor graph and with a subgraph of the total graph of a commutative ring.

关键词： finite commutative ring graph diameter girth

Equilibrium state of axially symmetric electric solar wind sail at arbitrary sail angles

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Chinese Journal of Aeronautics 2024年第11期37卷 232-241页

作者： Chonggang DU Zheng h.ZhU Changqing WANG Aijun LI Tuanjie LI school of Mechano-Electronic Engineering Xidian UniversityXi’an 710071China Department of Mechanical Engineering York UniversityOntario M3J 1P3Canada school of Automation Northwestern Polytechnical UniversityXi’an 710129China

This paper studies the equilibrium state and trajectory dynamics of an axially symmetric Electric solar wind sail(E-sail)at arbitrary sail *** E-sail is assumed operating in a heliocentric-ecliptic orbit at approximately one astronomic unit(au)from the sun,and experiencing various dynamic disturbances like solar wind pressure,tether tension oscillations,and centrifugal *** study derives analytical expressions for the E-sail's equilibrium state and its maximal coning angle under small coning angle ***,an improved propulsion model is developed for the E-sail in this equilibrium *** assess the precision of these formulations,a high-fidelity E-sail dynamic model is constructed using the nodal position finite element method,where the tethers are modeled as two-noded tensile elements and the central spacecraft and remote units are simplified as lumped *** thorough parametric analyses,this paper conclusively demonstrates that the operation of the E-sail at the equilibrium state can be achieved in accordance with the derived analytical prediction of the equilibrium ***,the improved propulsion model is employed in trajectory analyses for a mission to reach the solar system's *** study provides valuable insights and findings and foundation for the practical application and further advancement of the E-sail technology.

关键词： Electric solar wind sail Extremely flexible system Multi-body dynamics harmonic motion Maximum coning angle Equilibrium configuration Improved propulsion model high-fidelity modeling