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文章速递Optimal Allocation of a Hybrid Wind Energy-Fuel Cell System Using Different Optimization Techniques in the Egyptian Distribution Network 认领
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作者 Adel A. Abou El-Ela Sohir M. Allam Nermine K. Shehata 《能源与动力工程(英文)》 2021年第1期17-40,共24页
This paper presents an optimal proposed allocating procedure for hybrid wind energy combined with proton exchange membrane fuel cell (WE/PEMFC) system to improve the operation performance of the electrical distributio... This paper presents an optimal proposed allocating procedure for hybrid wind energy combined with proton exchange membrane fuel cell (WE/PEMFC) system to improve the operation performance of the electrical distribution system (EDS). Egypt has an excellent wind regime with wind speeds of about 10 m/s at many areas. The disadvantage of wind energy is its seasonal variations. So, if wind power is to supply a significant portion of the demand, either backup power or electrical energy storage (EES) system is needed to ensure that loads will be supplied in reliable way. So, the hybrid WE/PEMFC system is designed to completely supply a part of the Egyptian distribution system, in attempt to isolate it from the grid. However, the optimal allocation of the hybrid units is obtained, in order to enhance their benefits in the distribution networks. The critical buses that are necessary to install the hybrid WE/ PEMFC system, are chosen using sensitivity analysis. Then, the binary Crow search algorithm (BCSA), discrete Jaya algorithm (DJA) and binary particle swarm optimization (BPSO) techniques are proposed to determine the optimal operation of power systems using single and multi-objective functions (SOF/MOF). Then, the results of the three optimization techniques are compared with each other. Three sensitivity factors are employed in this paper, which are voltage sensitivity factor (VSF), active losses sensitivity factor (ALSF) and reactive losses sensitivity factor (RLSF). The effects of the sensitivity factors (SFs) on the SOF/MOF are studied. The improvement of voltage profile and minimizing active and reactive power losses of the EDS are considered as objective functions. Backward/forward sweep (BFS) method is used for the load flow calculations. The system load demand is predicted up to year 2022 for Mersi-Matrouh City as a part of Egyptian distribution network, and the design of the hybrid WE/PEMFC system is applied. The PEMFC system is designed considering simplified mathematical expressions. The economics of operation of both WE and PEMFC system are also presented. The results prove the capability of the proposed procedure to find the optimal allocation for the hybrid WE/PEMFC system to improve the system voltage profile and to minimize both active and reactive power losses for the EDS of Mersi-Matrough City. 展开更多
关键词 Wind Energy System Proton Exchange Membrane Fuel Cell Binary Crow Search Algorithm Discrete Jaya Algorithm Binary Particle Swarm Optimization Technique
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Exertional heat illness risk factors and physiological responses of youth football players 认领
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作者 Susan W.Yeargin John J.Dickinson +3 位作者 Dawn M.Emerson Jessica Koller Toni M.Torres-McGehee Zachary Y.Kerr 《运动与健康科学(英文)》 SCIE 2021年第1期91-98,共8页
Objective:To determine which intrinsic and extrinsic exertional heat illness(EHI)risk factors exist in youth American football players and observe perceptual and physiological responses of players during events(games ... Objective:To determine which intrinsic and extrinsic exertional heat illness(EHI)risk factors exist in youth American football players and observe perceptual and physiological responses of players during events(games and practices).Methods:Cross-sectional cohort study observing 63 youth football players,varying in position.Independent variables were league(weightrestricted(WR,n=27)and age-restricted(AR,n=36))and event type.Dependent variables were anthropometrics,work-to-rest ratio,and wet bulb globe temperature.Descriptive variables included preparticipation examination and uniform configuration.A subset of 16 players participated in physiological variables(heart rate and gastrointestinal temperature).Data collection occurred on 7 AR and 8 WR nonconsecutive practices and the first 3 games of the season.Results:Mean values for anthropometric variables were higher(p<0.05)in the AR league than the WR league.Work time(χ^2(1,111)=4.232;p=0.039)and rest time(χ^2(1,111)=43.41;p<0.001)were significantly greater for games,but ratios were significantly higher for practices(χ^2(1,111)=40.62;p<0.001).The majority of events(77%)observed were in black and red flag wet bulb globe temperature risk categories.A total of 57%of the players had a preparticipation examination,and up to 82%of events observed were in full uniforms.Individual gastrointestinal temperature and heart rate responses ranged widely and no players reached critical thresholds.Conclusion:Extrinsic(disproportionate work ratios,environmental conditions)and intrinsic(higher body mass index)EHI risk factors exist in youth football.Certain risk factors may be influenced by event and league type.National youth football organizations need to create thorough guidelines that address EHI risk factors for local leagues to adopt. 展开更多
关键词 Adolescents ANTHROPOMETRICS Core temperature Heat exchange PEDIATRIC Wet bulb globe temperature
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Model Building and Anisotropy of PrFeB Permanent Magnetic Materials 认领
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作者 Min Liu Xuehui Cai +2 位作者 Weiping Gong Yajie Li Lixia Cheng 《材料科学与应用期刊(英文)》 2020年第11期757-766,共10页
This paper considers that the crystal grains of HDDR Pr2Fe14B permanent magnetic material are cubic, the size is 0.3 μm, and the crystal grains are in simple cubic accumulation. It is considered that there are bounda... This paper considers that the crystal grains of HDDR Pr2Fe14B permanent magnetic material are cubic, the size is 0.3 μm, and the crystal grains are in simple cubic accumulation. It is considered that there are boundary phases between grains. It is assumed that the boundary phases are non-magnetic phases with the thickness of d, and evenly distributed between grains. The anisotropy expression of single grain boundary is given considering structure defect and intergranular exchange coupling interaction. Based on micro-magnetic simulation calculation, the variation of the average anisotropy of a single grain with the structural defects and boundary phases was calculated. The results show that when the thickness of structural defects is constant, the average anisotropy of a single grain decreases with increasing of grain boundary phase thickness, and while the thickness of grain boundary phase is constant, it also decreases with increasing of structural defect thickness. 展开更多
关键词 Structural Defects Boundary Phases Exchange Coupling Interactions ANISOTROPY
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Levels of Selected Essential and Non-Essential Metals in the Soil and Ginger (<i>Zingiber officinale</i>) Cultivated in Wolaita Zone, Ethiopia 认领
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作者 Fekadu Thomas Kaba Mesfin Bibiso Doda Camerun Kastro Kanido 《农业化学和环境(英文)》 2020年第4期276-298,共23页
Ginger (<i><span>Zingiber officinale</span></i><span>) is an important spice and medicinal plant used in different parts of the world. The objective of current study was to determine the ... Ginger (<i><span>Zingiber officinale</span></i><span>) is an important spice and medicinal plant used in different parts of the world. The objective of current study was to determine the level of essential and non-essential metals in ginger and its correlation with concentration of metals in the supporting soil. The level of K, Na, Ca, Mg, Mn, Fe, Zn, Cu, Co, Cd and Pb in soil and ginger cultivated in the selected districts of Wolaita zone, Southern Ethiopia were determined using flame atomic absorption spectrometry. A 0.5 g ginger sample was digested using a mixture of 4 ml HNO</span><sub><span style="vertical-align:sub;">3</span></sub><span> and 1.5 ml HClO</span><sub><span style="vertical-align:sub;">4</span></sub><span> at 210°</span><span>C</span><span> for 150 min</span><span>utes, and a 0.5 g soil sample was digested employing a mixture of 6 ml aqua-regia and 1 ml H</span><sub><span style="vertical-align:sub;">2</span></sub><span>O</span><sub><span style="vertical-align:sub;">2</span></sub><span> at 280°</span><span>C</span><span> for 150 minutes. The metal</span><span> concentrations range in dry weight basis for ginger samples is decreasing in the order: K (1691 </span><span>-</span><span> 3487 mg/kg) > Mg (701 </span><span>-</span><span> 1583 mg/kg) > Ca (862 </span><span>-</span><span> 1476 mg/kg) > Na (398 </span><span>-</span><span> 776 mg/kg) > Mn (325 </span><span>-</span><span> 672 mg/kg) > Fe (6.14 </span><span>-</span><span> 11.92 mg/kg) > Zn (5.30 </span><span>-</span><span> 10.09 mg/kg) > (0.12 </span><span>-</span><span> 0.23 mg/kg) for Pb. The concentration of Cd, Cu and Co in ginger samples were below the limit of detection. The results revealed that ginger has the ability to accumulate relatively higher amounts of K and Mg among the determined essential metals. The soil samples have been found to be acidic pH, sandy clay loam in texture, a very low electrical conductivity and moderate level of (CEC, organic carbon, available phosphorus and total nitrogen). Although, a positive correlatio 展开更多
关键词 Essential Metals Flame Atomic Absorption Spectroscopy GINGER Non-Essential Metals SOIL Organic Carbon Total Nitrogen Cation Exchange Capacity Organic Matter
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Effects of Heat Exchange Tube Structural Parameters on Performance of Vehicle Radiator 认领
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作者 Zeyan Liu Xilei Kong +3 位作者 Xiaobiao Han Hui Liu Quanzhen Wang Zhenling Wang 《电力能源(英文)》 2020年第9期1-7,共7页
In order to improve the performance of vehicle radiators, a two-dimensional heat transfer steady-state model of the radiator was set up. The influence of the structural parameters (axial ratio) of the heat exchange tu... In order to improve the performance of vehicle radiators, a two-dimensional heat transfer steady-state model of the radiator was set up. The influence of the structural parameters (axial ratio) of the heat exchange tube on the windward side on the heat transfer performance of the radiator was studied. With the increase of the axial ratio of the heat exchange tube on the windward side, the heat exchange capacity of the heat exchange tube surface slightly decreases. The heat exchange area increases significantly, which increases the total heat exchange of the radiator and improves the heat transfer performance of the radiator. When the axial ratio increases from 1.0 to 2.0, the average surface heat transfer capacity decreases from 5664.16</span><span style="font-family:""> </span><span style="font-family:Verdana;">W/m<sup>2</sup> to 5623.57</span><span style="font-family:""> </span><span style="font-family:Verdana;">W/m<sup>2</sup>. 展开更多
关键词 Vehicle Radiator Heat Transfer Performance Heat Exchange Tube Structure Parameters Axial Ratio
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Experimental Analysis of Influencing Factors on Heat Exchange Efficiency of Cast-in Place Energy Piles 认领
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作者 陈智 肖彧 +2 位作者 肖衡林 阙梦珂 孙洋 《东华大学学报:英文版》 EI CAS 2020年第1期66-73,共8页
The energy pile is a kind of building energy-saving technology using shallow geothermal energy,and its heat exchange performance is an important factor affecting its development.In this study,heat exchange tests were ... The energy pile is a kind of building energy-saving technology using shallow geothermal energy,and its heat exchange performance is an important factor affecting its development.In this study,heat exchange tests were carried out on three full-size cast-in place energy piles,and the influence of various factors on the heat exchange amount and the heat exchange rate was analyzed.The following conclusions are drawn:(1)the heat exchange rate of the cast-in place energy pile is greatly affected by the inlet water temperature;(2)increasing the pile length can increase the heat exchange amount,but has little effect on improving the heat exchange rate;(3)the increase in the heat exchange amount by heat exchange pipes in series is not significant,and therefore the parallel-type heat exchange pipes should be considered in practical engineering;(4)the appropriate circulating water flow velocity gives the best heat exchange efficiency. 展开更多
关键词 energy PILE CAST-IN PLACE HEAT EXCHANGE AMOUNT HEAT EXCHANGE rate
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Carbon dioxide fluxes of tundra vegetation communities on an esker top in the low-Arctic 认领
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作者 Peter M.LAFLEUR A.Brett CAMPEAU Sohee KANG 《极地科学进展:英文版》 CSCD 2020年第3期167-177,共11页
Previous studies have shown that carbon dioxide fluxes vary considerably among Arctic environments and it is important to assess these differences in order to develop our understanding of the role of Arctic tundra in ... Previous studies have shown that carbon dioxide fluxes vary considerably among Arctic environments and it is important to assess these differences in order to develop our understanding of the role of Arctic tundra in the global carbon cycle. Although many previous studies have examined tundra carbon dioxide fluxes, few have concentrated on elevated terrain(hills and ridge tops) that is exposed to harsh environmental conditions resulting in sparse vegetation cover and seemingly low productivity. In this study we measured carbon dioxide(CO2) exchange of four common tundra communities on the crest of an esker located in the central Canadian low-Arctic. The objectives were to quantify and compare CO2 fluxes from these communities, investigate responses to environmental variables and qualitatively compare fluxes with those from similar communities growing in less harsh lowland tundra environments. Measurements made during July and August 2010 show there was little difference in net ecosystem exchange(NEE) and gross ecosystem production(GEP) among the three deciduous shrub communities, Arctous alpina, Betula glandulosa and Vaccinium uliginosum, with means ranging from -4.09 to -6.57 μmol·m^-2·s^-1 and -7.92 to -9.24 μmol·m^-2·s^-1, respectively. Empetrum nigrum communities had significantly smaller mean NEE and GEP(-1.74 and -4.08 μmol·m^-2·s^-1, respectively). Ecosystem respiration(ER) was similar for all communities(2.56 to 3.03 μmol·m^-2·s^-1), except the B. glandulosa community which had a larger mean flux(4.66 μmol·m^-2·s^-1). Overall, fluxes for these esker-top communities were near the upper range of fluxes reported for other tundra communities. ER was related to soil temperature in all of the communities. Only B. glandulosa GEP and ER showed sensitivity to a persistent decline in soil moisture throughout the study. These findings may have important implications for how esker tops would be treated in construction of regional carbon budgets and for predicting the impacts of climate change on Arctic 展开更多
关键词 tundra carbon exchange net ecosystem exchange gross ecosystem productivity ecosystem respiration low-Arctic esker top xerophytes
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Study at Two Dimensions of Thermal Transfer through a Fibers Panel Subjected to Climatic Constraints in Dynamic Frequency Regulations Established 认领
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作者 Mohamed Sidya Ould Brahim Issa Diagne +7 位作者 Mamadou Babacar Ndiaye Youssou Traore Seydou Faye Cheikh Thiam Pape Touty Traore Ablaye Fame Sokhna Khadidiatou Ben Thiam Gregoire Sissoko 《能源与动力工程(英文)》 2020年第5期135-142,共8页
From resolution of two-dimensional equation of heat in dynamic frequency regime, we have plotted evolution curves of temperature according to depth of material or in lateral direction. They will allow us to evaluate t... From resolution of two-dimensional equation of heat in dynamic frequency regime, we have plotted evolution curves of temperature according to depth of material or in lateral direction. They will allow us to evaluate thermal behavior of towed material. Aim of study is to use fibers as a thermal insulating material by proposing a method for determining effective thermal insulation layer in dynamic frequency regime. 展开更多
关键词 Thermal Transfer Heat Exchange COEFFICIENT Frequency Dynamic REGIME Fibers
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Preliminary Study on the Magnetic Properties of GeMn Nanocolumn/Ge Multilayers 认领
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作者 Thi Giang Le Minh Tuan Dau 《材料科学与应用期刊(英文)》 2020年第7期441-449,共9页
Ge<sub>0.94</sub>Mn<sub>0.06</sub> nanocolumn thin film is a unique phase of GeMn diluted magnetic semiconductors (DMS) which exhibit Curie temperature (TC) > 400 K. The multilayers of Ge<... Ge<sub>0.94</sub>Mn<sub>0.06</sub> nanocolumn thin film is a unique phase of GeMn diluted magnetic semiconductors (DMS) which exhibit Curie temperature (TC) > 400 K. The multilayers of Ge<sub>0.94</sub>Mn<sub>0.06</sub> nanocolumns separated by nano-scaled spacers represent great interests for spintronic applications, such as spin valves or giant magneto-resistance (GMR) multilayers. In this article, we present the results obtained from the preliminary study on the exchange coupling in two types of GeMn nanocolumn/Ge multilayers. All the samples have been grown using molecular beam epitaxy (MBE). The superconducting quantum interference device (SQUID) magnetometer has been used to determine the magnetic properties of the samples. In the multilayer system Ge/[Ge<sub>0.94</sub>Mn<sub>0.06</sub>(40 nm)/Ge(d nm)]9/Ge<sub>0.94</sub>Mn<sub>0.06</sub>(40 nm)/Ge, no exchange coupling can be observed. Inversely, exchange coupling between the layers exists and depends on the thickness of the Ge spacers for the GeMn nanocolumns/Ge multilayer spin valve systems. The exchange coupling in the nanocolumns multilayer systems has been shown to be complex due to the leakage field induced by neighboring nanocolumns and the magnetic anisotropy of nanocolumns. 展开更多
关键词 MULTILAYERS Ferromagnetic Semiconductor GeMn Nanocolumns Exchange Coupling Thin Film
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Experimental Evaluation of Parameterized Nonlinear MPC Applied to PEM Fuel Cell 认领
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作者 Cédric Damour Dominique Grondin +2 位作者 Michel Benne Brigitte Grondin-Perez Jean-Pierre Chabriat 《工程(英文)(1947-3931)》 2020年第2期99-116,共18页
This paper proposes a parameterized nonlinear model-based predictive control (NMPC) strategy to tackle the oxygen excess ratio regulation challenge of a proton exchange membrane fuel cell. In practice, the most challe... This paper proposes a parameterized nonlinear model-based predictive control (NMPC) strategy to tackle the oxygen excess ratio regulation challenge of a proton exchange membrane fuel cell. In practice, the most challenging part regarding NMPC strategies remains the on-line implementation. In fact, NMPC strategies, at least in their basic form, involve heavy computation to solve the optimization problem. In this work, a specific parameterization of control actions has been designed to address this limitation and achieve on-line implementation. To assess the effectiveness and relevance of the proposed strategy, the controller has been implemented on-line, experimentally validated on a real fuel cell and compared to the built-in controller. Performance of the parameterized NMPC controller in terms of setpoint tracking accuracy, disturbances rejection and computational cost, have tested under several control scenarios. Experimental results have shown the excellent tracking capability, disturbances rejection ability and low computational cost of the NMPC controller, regardless of the operating conditions. Moreover, compared to the built-in controller the proposed strategy has demonstrated better disturbances rejection capability. Overall, the proposed parameterized NMPC controller appears as an excellent candidate to address the oxygen excess ratio regulation issue. 展开更多
关键词 CONTROL Application Parameterized NONLINEAR Model PREDICTIVE CONTROL PROTON Exchange MEMBRANE Fuel Cell
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Volatility Modelling of Global Financial Crises Effects on the Nigerian Banks 认领
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作者 Maruf A. Raheem Timothy K. Samson 《统计学期刊(英文)》 2020年第2期303-324,共22页
The most appropriate heteroskedastic models for predicting volatility of daily stocks prices of 10 major Nigerian banks are proposed. The banks are Access, United Bank for Africa (UBA), Guaranty Trust, Skye, Diamond, ... The most appropriate heteroskedastic models for predicting volatility of daily stocks prices of 10 major Nigerian banks are proposed. The banks are Access, United Bank for Africa (UBA), Guaranty Trust, Skye, Diamond, Fidelity, Sterling,?Union, ETI and Zenith banks;and these are examined from 2004 to 2014.?The models employed are Autoregressive Conditional Heteroscedastic (ARCH(1)), Generalized Autoregressive Conditional Heteroscedastic (GARCH(1, 1)),?Exponential Generalized Autoregressive Conditional Heteroscedastic?(EGARCH(1, 1))?and Glosten, Jagananthan and Runkle-Generalized Autoregressive Conditional Heteroscedastic?(GJR-GARCH(1, 1)). The results show that all the?bank returns are highly leptokurtic, significantly skewed and thus non-normal across the four periods except for Fidelity bank during financial crises;findings similar to those of other global markets. Also noticed is the strong evidence for the presence of heteroscedasticity, and that volatility persistence during crisis?is?higher than before the crisis across the 10 banks, with that of UBA taking the lead, about 11 times higher during the crisis. The same with persistence?levels in volatility, which were relatively higher during financial crises across the ten banks compared to before the crises.?Findings further indicate that Asymmetric GARCH models outperformed the symmetric GARCH models, especially during the financial crises and post the crises. Thus with these findings, one could generally conclude that Nigerian banks’?returns are volatility persistent during and after the crises, and are characterized by leverage effects of negative and positive shocks during these periods. 展开更多
关键词 GLOBAL Financial CRISIS Leverage Effect NIGERIAN Stock Exchange VOLATILITY Clustering PERSISTENCE
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Online Vaccine Information in a Knowledge Exchange Social Website (KESW) 认领
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作者 Fiona Gorman Desa Yadegarians +2 位作者 Linda Meng Nicholas Gorman Esther Johnston 《预防医学期刊(英文)》 2020年第6期151-167,共17页
<strong>Background:</strong> The potential for misinformation on usercontrolled Knowledge Exchange Social Websites (KESWs) is concerning since it can actively influence Internet users’ knowledge, attitude... <strong>Background:</strong> The potential for misinformation on usercontrolled Knowledge Exchange Social Websites (KESWs) is concerning since it can actively influence Internet users’ knowledge, attitudes, and behaviors related to childhood vaccinations. <strong>Objective:</strong> The present study examines the accuracy and predictors of health information posted to a Knowledge Exchange Social Website (KESW). <strong>Methods:</strong> A sample of 480 answers to childhood vaccination questions were retrieved and rated for accuracy. Multiple logistic regression modeling was used to examine whether answer characteristics (best answer, professional background, statistical information, source disclosure, online link, word count, vaccine stance, and tone) predict accuracy. <strong>Results:</strong> Overall, only 56.2% of the posted answers were rated as “accurate.” Accuracy varied by topics with between 52.8% - 64.3% being rated as accurate. When Yahoo Answers’ “best answers” were examined, only 49.2% rated as accurate compared to 57.7% of all other answers, a finding attributed to widespread nominations of vaccine misinformation as “best answers” for questions addressing the side effects of vaccines. For all other types of questions, “best answers” were more likely to be accurate. Regression modeling revealed that discussions of personal choices regarding childhood vaccinations predicted the accuracy of posted answers, with those who mentioned vaccinating their own children proving more likely to communicate accurate vaccine information, and those expressing vaccine hesitancy proving more likely to share factually inaccurate statements about vaccines. <strong>Conclusion:</strong> The high prevalence of misinformation on KESWs suggests that these websites may serve as a vector for spreading vaccine misperceptions. Further research is needed to assess the impact of various KESWs and to develop effective, coordinated responses by public health agencies. 展开更多
关键词 Online Health Information Childhood Vaccines IMMUNIZATIONS Infectious Diseases Accuracy Knowledge Exchange Social Websites
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The Radioactive <sup>45</sup>Ca Cannot Be Used for Adequate Estimation of the Functional Activity of <sup>40</sup>Ca Ions in Cells and Organisms 认领
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作者 Anna Nikoghosyan Lilia Narinyan +1 位作者 Armenuhi Heqimyan Sinerik Ayrapetyan 《生物物理学期刊(英文)》 2020年第1期13-26,共14页
Previously we have shown that nM ouabain-induced activation of cAMP-dependent Na/Ca exchange in reverse (R) mode in cell membrane has age-dependent weakening hydration effect on heart muscle and brain tissues and such... Previously we have shown that nM ouabain-induced activation of cAMP-dependent Na/Ca exchange in reverse (R) mode in cell membrane has age-dependent weakening hydration effect on heart muscle and brain tissues and such Na/Ca exchange is characterized by quantum mechanical sensitivity. As in biological experiments radioactive 45Ca is used for the study of cold 40Ca exchange in cells and organisms, in the present work, the age-dependent effect of physiological solution (PS) containing either 40Ca or 45Ca on tissue hydration in different experimental conditions was studied in order to evaluate the bioequivalence of these two forms of Ca. The obtained data indicate that the intraperitoneal injections of 40Ca PS and 45Ca PS leading to activation of RNa/40Ca and RNa/45Ca exchanges, respectively, have different age-dependent effects on heart muscle and brain tissue hydration. As in myocyte membrane, the Na/Ca exchange is more expressed than in neuronal membrane, the age-dependent heart muscle hydration is more sensitive to quantum properties of Ca than brain tissue hydration. The [45Ca]i, in contrary to [40Ca]i, has age-dependent weakening and stabilizing effect on tissue hydration and makes the latter insensitive to ouabain. The obtained data bring us to a strong conclusion that RNa/Ca exchange has quantum mechanical properties and in biological experiments radioactive 45Ca cannot be used for adequate estimation of the functional activity of 40Ca ions in cells and organisms. 展开更多
关键词 Rat Brain Heart Muscle 45Ca Na/Ca Exchange OUABAIN
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Net Ecosystem CO2 Flux and Effect Factors in Peatland Ecosystem of Central China 认领
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作者 Ihab Alfadhel Jiwen Ge Sakinatu Issaka 《地球科学和环境保护期刊(英文)》 2020年第8期95-106,共12页
Peatland ecosystems play an important role in the global carbon cycle because they act as a pool or sink for the carbon cycle. However, the relationship between seasonality effect factors and net ecosystem CO<sub&g... Peatland ecosystems play an important role in the global carbon cycle because they act as a pool or sink for the carbon cycle. However, the relationship between seasonality effect factors and net ecosystem CO<sub>2</sub> exchange (NEE) remains to be clarified, particularly for the non-growing season. Here, based on the eddy covariance technique, NEE in the peatland ecosystem of Central China was examined to measure two years’ (2016 and 2017) accumulation of carbon dioxide emissions with contrasting seasonal distribution of environmental factors. Our results demonstrate the cumulative net ecosystem CO<sub>2</sub> emissions during the study period was in the first non-growing season 2.94 ± 4.83 μmolCO<sub>2</sub> m<sup><span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">-</span>2<span style="white-space:nowrap;">.</span></sup>s<sup><span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">-</span>1</sup> with the lowest values in the same year in first growing season was <span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">-</span>2.79 ± 4.92 μmolCO<sub>2</sub> m<sup><span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">-</span>2</sup><span style="font-family:" font-size:13.3333px;white-space:normal;"=""><span style="white-space:nowrap;"><sup>.</sup></span></span>s<sup><span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#ffffff;"="">-</span>1</sup>. The results indicate the effect of seasonal variations of NEE can be directly reflected in daily and seasonal variations in growth and respiration of peatland ecosystem by environmental parameters over different growing stages. 展开更多
关键词 Dajiuhu Peatland Ecosystem Respiration Eddy Covariance Gross Primary Product Net Ecosystem CO2 Exchange
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Phosphorus release from vivianite and hydroxyapatite by organic and inorganic compounds 认领
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作者 Stella GYPSER Dirk FREESE 《土壤圈:英文版》 SCIE CAS CSCD 2020年第2期190-200,共11页
Based on recent mining rates and the exhaustion of global phosphorus(P)reserves,there is a need to mobilize P already stored in soils,and its recovery from secondary resources such as Ca-and Fe-phosphates is important... Based on recent mining rates and the exhaustion of global phosphorus(P)reserves,there is a need to mobilize P already stored in soils,and its recovery from secondary resources such as Ca-and Fe-phosphates is important.The Ca-phosphate hydroxyapatite forms a good fertilizer source,while vivianite is formed in waterlogged soils and sediments.During sludge treatment,the formation of vivianite has been identified,being mainly Fe-phosphate.Long-term P release from both hydroxyapatite and vivianite was studied using different inorganic(CaCl2 and CaSO4)and organic(citric and humic acid)reagents during batch experiments.Reagents CaCl2 and CaSO4 represent the soil solution,while citric and humic acids as organic constituents affect P availability in the rhizosphere and during the process of humification.Additionally,the flow-through reactor(FTR)technique with an infinite sink was used to study the long-term P release kinetics.The cumulative P release was higher by organic acids than by inorganic compounds.The cumulative P release rates were higher in the FTR with CaCl2 as compared to the batch technique.The infinite sink application caused a continuously high concentration gradient between the solid and liquid phases,leading to higher desorption rates as compared to the batch technique.The predominant amount of the total P released over time was available for a short term.While inorganic anion exchange occurred at easily available binding sites,organic acids affected the more heavily available binding sites,which could be embedded within the mineral structure.The results showed that organic compounds,especially citric acid,play a superior role as compared to the inorganic constituents of the soil solution during the recovery of already stored P from the tertiary phosphates vivianite and hydroxyapatite. 展开更多
关键词 ANION EXCHANGE batch technique citric ACID FLOW-THROUGH reactor HUMIC ACID ligand EXCHANGE phosphate phosphorus recovery
The Quantum-Mechanical Sensitive Na/K Pump Is a Key Mechanism for the Metabolic Control of Neuronal Membrane Function 认领
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作者 Sinerik Ayrapetyan? 《生物物理学期刊(英文)》 2020年第2期59-83,共25页
At present, there are relevant scientific materials on the cellular and molecular mechanisms of electrogenic Na/K pump function and structure, as well as on the potential- and ligand-activated ionic channels in the me... At present, there are relevant scientific materials on the cellular and molecular mechanisms of electrogenic Na/K pump function and structure, as well as on the potential- and ligand-activated ionic channels in the membrane. However, the role of electrogenic Na/K pump in regulation of semipermeable properties of cell membrane has not been elucidated yet, which is due to the fact that our knowledge about the biophysical properties of cell membrane is based on the conductive membrane theory of Hodgkin-Huxley-Katz, which is developed on internally perfused squid axon and lacks intracellular metabolism. Thus, the accumulated abundance of data on the role of G-proteins-dependent intracellular signaling system in regulation of Na/K pump activity and biophysical properties of cell membrane presumes fundamental revision of some statements of membrane theory. The aim of the present review is to briefly demonstrate our and literature data on cell hydration-induced auto-regulation of Na/K pump as well as on its role in metabolic control of semipermeable properties and excitability of neuronal membrane, which are omitted in the study of internally perfused squid axon. 展开更多
关键词 Na/K PUMP HYDRATION IONIC Channel Membrane Na/Ca Exchange Cyclic NUCLEOTIDES
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Political Economy Factors Shaping News Culture of Hyperlocal News Website www.ippodhu.com 认领
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作者 Aquil Ahmad Khan 《社交网络(英文)》 2020年第3期39-51,共13页
In contemporary media ecosystem, media content is not only produced by employees rather it is also produced by its users in the form of curating stories, writing feedback, engaging in online discussions and at the sam... In contemporary media ecosystem, media content is not only produced by employees rather it is also produced by its users in the form of curating stories, writing feedback, engaging in online discussions and at the same time disseminating the content through their personal online profiles. Keeping these views in mind, this paper critically examines the political economy of <em>Ippodhu</em> (Tamil Nadu based news website), a hyperlocal news application, in terms of digital labour, audience as participatory commodities and audience as producers, which Alvin Toffler terms as prosumer. Further, this paper explores how social media, analytics, or other analytical tools create value or anti-value for <em>Ippodhu</em>. The qualitative data obtained through in-depth interview reveals that readers/audiences of <em>Ippodhu</em> are commodified in two ways, first they consume the content of the website by spending their time, which will be sold to the advertisers and secondly by creating free content either in the writing stories, uploading photographs or even in the form of comment which will be consumed by other readers/audiences which result in the chain of production of values. 展开更多
关键词 Political Economy Hyperlocal News Website Use Value Exchange Value Prosumer Audience Commodity Immaterial Labour
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Research Progress on the Separation of Alkaloids from Chinese Medicines by Column Chromatography 认领
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作者 Yaqin He Zhaozeng Chen +1 位作者 Haibin Qu Xingchu Gong 《化学工程与科学期刊(英文)》 2020年第4期358-377,共20页
Alkaloids have a variety of bioactivities and great development value in the fields of pharmaceuticals, cosmetics and health food. Column chromatography is a common method for preparing alkaloids. In this paper, the r... Alkaloids have a variety of bioactivities and great development value in the fields of pharmaceuticals, cosmetics and health food. Column chromatography is a common method for preparing alkaloids. In this paper, the research status of the separation and purification of alkaloids from Chinese medicines by column chromatography is reviewed, and the factors that influence the refining of alkaloids via a macroporous adsorption resin, ion exchange resin and silica gel are summarized. The thermodynamic and kinetic modeling methods for the static adsorption of adsorbents are also reviewed in this paper. It is suggested that the modeling method of the column chromatography process be deeply studied to establish a more stringent quality control method for sampling liquid and to strengthen the online detection of the chromatography process to improve the refining effect of alkaloids. 展开更多
关键词 ALKALOID Column Chromatography Ion Exchange Resin Macroporous Adsorbent Resin Model Silica Gel
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A Short-Term Stock Exchange Prediction Model Using Box-Jenkins Approach 认领
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作者 Paul Boye Yao Yevenyo Ziggah 《应用数学与应用物理(英文)》 2020年第5期766-779,共14页
This paper developed a short-term stock exchange prediction model using the Box-Jenkins approach. In this study, monthly data from Ghana Stock Exchange market report that spans from March 2013 to February 2018 were us... This paper developed a short-term stock exchange prediction model using the Box-Jenkins approach. In this study, monthly data from Ghana Stock Exchange market report that spans from March 2013 to February 2018 were used to develop the model. ARIMA (0, 2, 1) model was fitted to the data based on the Bayesian Information Criterion (BIC) for model selection. Diagnostic checks showed that the residuals of the fitted model were uncorrelated. The developed model was used for forecasting for a period of six months. The trend of the forecasted values showed a significant increase in the Ghana Stock Exchange performance for the next six months. 展开更多
关键词 ARIMA BAYESIAN Information CRITERION Ghana STOCK Exchange Perfor-mance Indicator
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Morphological Characteristics of Cambodia Mekong Delta and Tonle Sap Lake and Its Response to River-Lake Water Exchange Pattern 认领
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作者 Zhaoming Xu Changwen Li +4 位作者 Anqiang Li Zhongqiong You Wei Yao Yongsheng Chen Liyao Huang 《水资源与保护(英文)》 2020年第4期275-302,共28页
Tonle Sap Lake is the largest river-connected lake, buffer area and ecological zone of Mekong River, which plays a huge role in dispelling flood peak and compensating water, and the conservation of biological diversit... Tonle Sap Lake is the largest river-connected lake, buffer area and ecological zone of Mekong River, which plays a huge role in dispelling flood peak and compensating water, and the conservation of biological diversity. The river-lake relationship between Mekong River and Tonle Sap Lake is unique and has always been a major focus in the international community. The land terrain and under-water topography were used to analyze the morphological characteristics of Cambodia Mekong Delta and Tonle Sap Lake. Long series of hydrological data of river-lake controlling stations were used to analyze the water level variation characteristics and water volume exchange pattern between Mekong River and Tonle Sap Lake, and the response relationship to river-lake morphological characteristics were also researched. The results show that: Cambodia Mekong Delta and Tonle Sap Lake Area is low-lying and flat with gentle channel gradient and water surface gradient, making the relationship between water level and area (or volume) smooth. The channel storage capacity of Mekong River and Tonle Sap River is not enough compared to the inflow, so vast flooding plain is extremely prone to be inundated, making the flood relationships between the left and right banks become very complicated. Tonle Sap Lake is a seasonal freshwater lake with water flowing in and flowing out, and the timing and intensity of water exchange with Mekong River are closely related to the water flow resistance at the exit section of Tonle Sap Lake and the cross-sectional area of Tonle Sap River, which can be reflected by the river-lake water level difference and the water level of Tonle Sap River. Affected by the river-lake morphological characteristics, the water exchange intensity between Mekong River and Tonle Sap Lake is great. Tonle Sap Lake not only stores 14.4% of flood volume (39.7 billion m3) from the Mekong River every year, but also supplies 29.7% of dry water (69.4 billion m3) to the Mekong River. Influenced by the adjustment of the floodplain, the water l 展开更多
关键词 Tonle Sap LAKE Mekong RIVER Morphological Characteristic River-Lake RELATIONSHIP Water EXCHANGE PATTERN RESPONSE RELATIONSHIP
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