This paper investigates the effective capacity of a point-to-point ultra-reliable low latency communication(URLLC)transmission over multiple parallel sub-channels at finite blocklength(FBL)with imperfect channel state...This paper investigates the effective capacity of a point-to-point ultra-reliable low latency communication(URLLC)transmission over multiple parallel sub-channels at finite blocklength(FBL)with imperfect channel state information(CSI).Based on reasonable assumptions and approximations,we derive the effective capacity as a function of the pilot length,decoding error probability,transmit power and the sub-channel number.Then we reveal significant impact of the above parameters on the effective capacity.A closed-form lower bound of the effective capacity is derived and an alternating optimization based algorithm is proposed to find the optimal pilot length and decoding error probability.Simulation results validate our theoretical analysis and show that the closedform lower bound is very tight.In addition,through the simulations of the optimized effective capacity,insights for pilot length and decoding error probability optimization are provided to evaluate the optimal parameters in realistic systems.展开更多
This paper was designed to verify the influence of phosphate on water-holding capacity (WHC) and texture of emulsiontype sausage prepared with pre-rigor meat, ageing meat or frozen meat. Pre-rigor pork, ageing pork ...This paper was designed to verify the influence of phosphate on water-holding capacity (WHC) and texture of emulsiontype sausage prepared with pre-rigor meat, ageing meat or frozen meat. Pre-rigor pork, ageing pork and frozen pork were pre-blended with five levels of phosphate and made into emulsion-type sausage. The yield, hardness and total expressible fluid (TEF) were measured with texture profile analysis machine and pressiometer when emulsion-type sausage was produced. Meanwhile, hardness and purge loss (PL) were measured during 30 d storage. As emusion-type sausage made by pre-rigor meat, higher yield and relatively stable hardness could be found. It indicated that increasing of phosphate level caused an alleviatable effects in increasing of hardness when emulsion-type sausage made by pre-rigor meat, but opposite effects made by ageing meat or frozen meat. The distribution of PL of emulsion-type sausage was found to be affected by phosphate addition. Significant decrease of PL could not be obtained by increasing of phosphate level during storage. Pre-rigor meat improved WHC and texture of emulsion-type sausage. Problem of WHC and texture of emulsiontype sausage during storage could not be resolved by single use of phosphate at relatively higher level (3%) of NaCl.展开更多
In this paper,the transmission performances are studied in cognitive radio networks with primary user emulator and relay existence.In the proposed network,the users include primary users,secondary users and primary us...In this paper,the transmission performances are studied in cognitive radio networks with primary user emulator and relay existence.In the proposed network,the users include primary users,secondary users and primary user emulators.The decreasing access priority of the users are primary users,primary user emulators and secondary users.Different user access to the network results in different transmission effects.We impose interference power constraints on the secondary users to protect the primary users from being interfered.We also adopt the transmission mechanism that transits among more than one secondary transmitters,secondary receivers and relays.The transition models of the transmission states are proposed to describe the transmission mechanism.To investigate the transmission performances,the theory of effective capacity is adopted.The transmission performances in terms of effective capacity are expressed and demonstrated under different transmission policies.The overall effective capacity,as the overall data traffic in the cognitive radio network,is calculated.Besides,the overall effective capacity is demonstrated under different transmission strategies.The results show the greedy transmission strategy outperforms the rest of the transmission 8 policies in the overall effective capacity.For a larger number of the users,the effective capacity converges to a certain value.展开更多
In this paper, the performance of multichannel transmission in cognitive radio is studied. Both QoS constraints and interference limitations are considered. The activities of the primary users (PU)s are initially dete...In this paper, the performance of multichannel transmission in cognitive radio is studied. Both QoS constraints and interference limitations are considered. The activities of the primary users (PU)s are initially detected by cognitive users (CU)s who perform sensing process over multiple channels. They transmit in a single channel at variable power and rates depending on the channel sensing decisions and the fading environment. The cognitive operation is modeled as a state transition model in which all possible scenarios are studied. The QoS constraint of the cognitive users is investigated through statistical analysis. Analytical form for the effective capacity of the cognitive radio channel is found. Optimal power allocation and optimal channel selection criterion are obtained. Impact of several parameters on the transmission performance, as channel sensing parameters, number of available channels, fading and other, are identified through numerical example.展开更多
For Peer-to-Peer (P2P) streaming services in mobile networks, the selection of appropriate neighbour peers from candidate peers with demanding data is an important approach to improve Quality-of-Service (QoS). This pa...For Peer-to-Peer (P2P) streaming services in mobile networks, the selection of appropriate neighbour peers from candidate peers with demanding data is an important approach to improve Quality-of-Service (QoS). This paper proposes a novel Effective Capacity Peer Selection (ECPS) scheme based on effective capacity. In the ECPS scheme, the neighbour peer selection problem was modeled using the Multiple Attribute Decision Making (MADM) theory, which considered multiple factors of candidate peers, including Signal to Interference and Noise Ratio (SINR), residency time, power level, security, moving speed, and effective capacity. This model could increase the suitability of ECPS for wireless mobile environments. Then, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was used to solve the MADM problem and identify the preferred neighbour peers. Simulation results show that the ECPS scheme can improve the network throughput, reduce packet delay by about 82%, and almost double the packet delivery ratio of the mobile P2P streaming service.展开更多
Oil is extremely crucial to the development of the modern economy. It is important to forecast the oil supply capacity due to its scarcity and non-renewability. This paper attempts to forecast and analyze thirty-five ...Oil is extremely crucial to the development of the modern economy. It is important to forecast the oil supply capacity due to its scarcity and non-renewability. This paper attempts to forecast and analyze thirty-five current and potential net oil-exporting countries. Integrating both qualitative and quantitative methods, the oil production and consumption are predicted based on historical data, so that the world net oil-exporting capacity can be obtained. The results show that the "roof effect" of the world net oil-exporting capacity may appear before 2030. Unconventional oil will play an important role in the future world oil market. The competition and cooperation relationships between OPEC and non-OPEC will last for a long time.展开更多
To understand the effect of the doping amount of Cu^2+ on the structure and reactivity of SnO2 in NOx-SCR with NH3, a series of Sn-Cu-O binary oxide catalysts with different Sn/Cu ratios have been prepared and thoroug...To understand the effect of the doping amount of Cu^2+ on the structure and reactivity of SnO2 in NOx-SCR with NH3, a series of Sn-Cu-O binary oxide catalysts with different Sn/Cu ratios have been prepared and thoroughly characterized. Using the XRD extrapolation method, the SnO2 lattice capacity for Cu^2+ cations is determined at 0.10 g Cu O per g of SnO2, equaling a Sn/Cu molar ratio of 84/16. Therefore, in a tetragonal rutile SnO2 lattice, only a maximum of 16% of the Sn4+ cations can be replaced by Cu^2+ to form a stable solid solution structure. If the Cu content is higher, Cu O will form on the catalyst surface, which has a negative effect on the reaction performance. For samples in a pure solid solution phase, the number of surface defects increase with increasing Cu content until it reaches the lattice capacity, as confirmed by Raman spectroscopy. As a result, the amounts of both active oxygen species and acidic sites on the surface, which critically determine the reaction performance, also increase and reach the maximum level for the catalyst with a Cu content close to the lattice capacity. A distinct lattice capacity threshold effect on the structure and reactivity of Sn-Cu binary oxide catalysts has been observed. A Sn-Cu catalyst with the best reaction performance can be obtained by doping the SnO2 matrix with the lattice capacity amount of Cu^2+.展开更多
Recent experimental and theoretical studies show that energy efficiency, which measures the amount of infor- mation processed by a neuron with per unit of energy consumption, plays an important role in the evolution o...Recent experimental and theoretical studies show that energy efficiency, which measures the amount of infor- mation processed by a neuron with per unit of energy consumption, plays an important role in the evolution of neural systems. Here we calculate the information rates and energy efficieneies of the Hodgkin-Huxley (HH) neuron model at different temperatures in a noisy environment. It is found that both the information rate and energy efficiency are maximized by certain temperatures. Though the information rate and energy efficiency cannot be maximized simultaneously, the neuron holds a high information processing capacity at the tempera- ture corresponding to the maximal energy efficiency. Our results support the idea that the energy efficiency is a selective pressure that influences the evolution of nervous systems.展开更多
In this article,comparative research on residents' effect perception,participation capacity and willingness on Pro-poor Tourism( PPT) is given based on the questionnaire carried out in Wulong County and Fengjie Co...In this article,comparative research on residents' effect perception,participation capacity and willingness on Pro-poor Tourism( PPT) is given based on the questionnaire carried out in Wulong County and Fengjie County in Three Gorges Area,Chongqing,China. Some technologies,such as SPSS 13. 0,ANOVA and T-test are applied to analyze the data and results show Wulong residents' perception behavior is better than that of Fengjie residents. Moreover,the residents with different demographic characteristics have different participation behavior.Finally,multiple regression analysis is applied to identify the key factors influencing residents' perception behavior,that is participation willingness and positive economic effect perception,positive social and cultural effect perception and participation capacity.展开更多
This study identifies the carrying state and value of Tibet’s resource and environmental carrying capacity.A new theoretical framework is proposed for exploring the resource and environmental carrying capacity based ...This study identifies the carrying state and value of Tibet’s resource and environmental carrying capacity.A new theoretical framework is proposed for exploring the resource and environmental carrying capacity based on two perspectives of“growth limit”and“stability of Human-Earth relationship system”.On this basis,an ideal growth model that accords with the“short board”effect is established to predict the population limitation.Analytical results show that the holistic state of resource and environmental carrying capacity in Tibet is in jeopardy.From 2010 to 2016,Tibet’s carrying state continued to decline,moreover,the negative forces still overwhelm the positive forces.Although the resource reserves still have room for more population,the environmental capacity and ecological capacity have been overloaded.Meanwhile,the Human-Earth relationship system is in an unstable stage.Three scenarios that respond to different socioeconomic developments are implemented to predict the population limitation of resource and environmental carrying capacity in Tibet;thus,authors argue that Tibet should keep its population size within 4 million around 2025.This research will provide reference for sustainable development and resources and environmental conservation in Tibet.展开更多
Cell discontinuous transmission(Cell DTx)is a key technology to mitigate inter-cell interference(ICI)in ultra-dense networks(UDNs).The aim of this work is to understand the impact of Cell DTx on physical-layer sum rat...Cell discontinuous transmission(Cell DTx)is a key technology to mitigate inter-cell interference(ICI)in ultra-dense networks(UDNs).The aim of this work is to understand the impact of Cell DTx on physical-layer sum rates of SBSs and link-layer quality-of-service(QoS)performance in multiuser UDNs.In this work,we develop a cross-layer framework for capacity analysis in multiuser UDNs with Cell DTx.In particular,we first extend the traditional one-dimensional effective capacity model to a new multidimensional effective capacity model to derive the sum rate and the effective capacity.Moreover,we propose a new iterative bisection search algorithm that is capable of approximating QoS performance.The convergence of this new algorithm to a unique QoS exponent vector is later proved.Finally,we apply this framework to the round-robin and the max-C/I scheduling policies.Simulation results show that our framework is accurate in approximating 1)queue length distribution,2)delay distribution and 3)sum rates under the above two scheduling policies,and further show that with the Cell DTx,systems have approximately 30% higher sum rate and 35% smaller average delay than those in full-buffer scenarios.展开更多
Methodologies have been developed for calculating cutoffs of reservoir intervals with production capacity (RIPC) and reservoir intervals with accumulation capacity (RIAC) according to the types of pore throat stru...Methodologies have been developed for calculating cutoffs of reservoir intervals with production capacity (RIPC) and reservoir intervals with accumulation capacity (RIAC) according to the types of pore throat structures and dynamic force by using data from petrophysical analysis, production tests and mercury injection. The data are from clastic reservoirs in the third member (Es3) and the fourth member (Es4) of the Shahejie Formation in the Shengtuo area on the North Slope of the Dongying Sag, Jiyang Depression, China. The method of calculating cutoffs of RIPC is summarized as follows: 1) determination of permeability cutoffs of RIPC; 2) classification of types of pore-throat structures according to mercury injection data and then relating porosity to permeability and determining the relationship between porosity and permeability according to each type of pore-throat structure; and 3) calculating porosity cutoffs of RIPC using established correlation between porosity and permeability according to the type of pore throat structure. The method of calculating cutoffs of RIAC includes: 1) establishing a functional relationship between oil-water interracial tension and formation temperature; 2) calculating limiting values of maximum connected pore-throat radii according to formation temperature and dynamic forces of each reservoir interval; 3) correlating permeability with maximum connected pore-throat radius and then obtaining permeability cutoffs of RIAC; and 4) calculating porosity cutoffs on the basis of permeability cutoffs according to specific correlations, suitable for the type of porethroat structure. The results of this study show that porosity and permeability cutoffs of clastic reservoirs decrease with depth. For a fixed permeability cutoff, the porosity cutoff of R1PC varies because the type of pore throat is different. At a fixed temperature, porosity and permeability cutoffs of RIAC decrease as dynamic force increases. For a fixed permeability cutoff of effective hydrocarbon accumulation, the porosity cutoff also varies with different types of pore throat.展开更多
Suspensions of a latosol with a clay concentration of 30 g kg^(-1) wereprepared from electrodialyzed clay fractions, less than 2 μm in diameter, five nitrate solutionswith a concentration of 1 X 10^(04)/z mol L^(-1),...Suspensions of a latosol with a clay concentration of 30 g kg^(-1) wereprepared from electrodialyzed clay fractions, less than 2 μm in diameter, five nitrate solutionswith a concentration of 1 X 10^(04)/z mol L^(-1), where z is the valence, and five sodium saltsolutions with a concentration of 3.3 X 10^(-5)/2 mol L^(-1). The direct current (DC) electricalconductivities (ECs) of the colloidal suspensions were measured at a constant temperature of 25 ℃,using a newly established method of measuring the Wien effect in soil suspensions at field strengthsranging from 13.5 to 150 kV cm^(-1), to determine their electrical conductivity-field strengthrelationships and to infer the order of the bonding strength (retaining force) between soilparticles and various ions. The measurements with the latosol suspensions in NaNO_3, KNO_3,Ca(NO_3)_2, Mg(NO_3)_2 and Zn(NO_3)_2 solutions resulted in increments of the suspension ECs, ΔECs,of 7.9, 5.0, 7.1, 7.0 and 5.8 μS cm^(-1), respectively, when the applied field strength increasedfrom 14.5 to 142 kV cm^(-1). As for the suspensions in NaNO_3, NaCl, Na_2SO_4, Na_3PO_4 andNa_3AsO_4 solutions, the ΔECs were 6.2, 5.3, 4.1, 4.0 and 3.7μS cm^(-1), respectively, when theapplied field strength increased from 13.5 to 90 kV cm^(-1). Thus, it can be deduced that theretaining forces of the clay fraction of the latosol for the cations were in the descending orderK^+ > Zn^(2+) > Mg^(2+) ≥ Ca^(2+) > Na^+, and for the anions in the descending order H_2AsO_4^- >H_2PO_4^-≥ SO_4^(2-) > Cl^- > NO_3~ -.展开更多
The influence of earthquake forces on ultimate bearing capacity of foundations on sloping ground was studied. A solution to seismic ultimate bearing capacity of strip footings on slope was obtained by utilizing pseudo...The influence of earthquake forces on ultimate bearing capacity of foundations on sloping ground was studied. A solution to seismic ultimate bearing capacity of strip footings on slope was obtained by utilizing pseudo-static analysis method and taking the effect of intermediate principal stress into consideration. Based on limit equilibrium theory, the formulae for computing static bearing capacity factors, Nq, Nc, Nγ, and dynamic bearing capacity factors, Nqd, Ned, Nγd, which are associated with surcharge, cohesion and self-weight of soils respectively, were presented. A great number of analysis calculations were carried out to obtain the relationship curves of the static and dynamic bearing capacity factors versus various calculation parameters. The curves can serve as the practical engineering design. The calculation results also show that when the values of horizontal and vertical seismic coefficients are 0.2, the dynamic bearing capacity factors Nqd, Ned and Nγd, in which the effects of intermediate principal stress are taken into consideration, increase by 4%-42%, 3%-27% and 34%-57%, respectively.展开更多
Fish skin collagen hydrolysates (FSCH) were prepared from walleye pollock (Theragra chalcogramrna) using a mixture of enzymes, namely trypsin and flavourzyme. The degree of hydrolysis of the skin collagen was 27.3...Fish skin collagen hydrolysates (FSCH) were prepared from walleye pollock (Theragra chalcogramrna) using a mixture of enzymes, namely trypsin and flavourzyme. The degree of hydrolysis of the skin collagen was 27.3%. FSCH was mainly composed of low-molecular-weight peptides and the relative proportion of 〈1000Da fraction was 70.6%. Free radical and oxygen species scavenging activities of FSCH were investigated in four model systems, including diphenylpicrylhy-drazyl radical (DPPH), superoxide anion radical, hydroxyl radical and hydrogen peroxide model, and compared with that of a native antioxidant, reduced glutathione (GSH). FSCH was also evaluated by water-absorbing and water-holding capacity. The results showed that FSCH was able to scavenge free radical and oxygen species significantly and to enhance water-absorbing and water-holding capacity remarkably. Therefore FSCH may have potential applications in the medicine and food industries.展开更多
Magnesium hydride has attracted great attention because of its high theoretical capacity and outstanding reversibility, nevertheless, its practical applications have been restricted by the disadvantages of the sluggis...Magnesium hydride has attracted great attention because of its high theoretical capacity and outstanding reversibility, nevertheless, its practical applications have been restricted by the disadvantages of the sluggish kinetics and high thermodynamic stability. In this work, an unexpected high reversible hydrogen capacity over 8.0 wt% has been achieved from MgH2 metal hydride composited with small amounts of LiBH4 and Li3AlH6 complex hydrides, which begins to release hydrogen at 276 ℃ and then completely dehydrogenates at 360 ℃. The dehydrogenated MgH2+LiBH4/Li3AlH6 composite can fully reabsorb hydrogen below 300 ℃ with an excellent cycling stability. The composite exhibits a significant reduction of dehydrogenation activation energy from 279.7 kJ/mol(primitive MgH2) to 139.3 kJ/mol(MgH2+LiBH4/Li3AlH6),as well as a remarkable reduction of dehydrogenation enthalpy change from 75.1 k J/mol H2(primitive MgH2) to 62.8 kJ/mol H2(MgH2+LiBH4/Li3AlH6). The additives of LiBH4 and Li3AlH6 not only enhance the cycling hydrogen capacity, but also simultaneously improve the reversible de/rehydrogenation kinetics, as well as the dehydrogenation thermodynamics. This notable improvement on the hydrogen absorption/desorption behaviors of the MgH2+LiBH4/Li3AlH6 composite could be attributed to the dehydrogenated products including Li3Mg7, Mg17Al12 and MgAlB4, which play a key role on reducing the dehydrogenation activation energy and increasing diffusion rate of hydrogen. Meanwhile, the LiBH4 and Li3AlH6 effectively destabilize MgH2 with a remarkable reduction on dehydrogenation enthalpy change in terms of thermodynamics. In particular, the Li3Mg7, Mg17Al12 and MgAlB4 phases can reversibly transform into MgH2, Li3AlH6 and LiBH4 after rehydrogenation, which contribute to maintain a high cycling capacity.This constructing strategy can further promote the development of high reversible capacity Mg-based materials with suitable de/rehydrogenation properties.展开更多
Magnetic entropy change (△SM) and refrigerant capacity (RC) of Ce6Ni2Si3-type Gd6Co1.67Si2.5Geo.5 compounds have been investigated. The Gd6Col.67Si2.5Geo.5 undergoes a reversible second-order phase transition at ...Magnetic entropy change (△SM) and refrigerant capacity (RC) of Ce6Ni2Si3-type Gd6Co1.67Si2.5Geo.5 compounds have been investigated. The Gd6Col.67Si2.5Geo.5 undergoes a reversible second-order phase transition at the Curie temperature Tc = 296 K. The high saturation magnetization leads to a large ASM and the maximal value of △SM is found to be 5.9 J/kg. K around TC for a field change of 0-5 T. A broad distribution of the △SM peak is observed and the full width at half maximum of the △SM peak is about 101 K under a magnetic field of 5 T. The large RC is found around TC and its value is 424 J/kg.展开更多
capacity and creativity tendencies among Chinese baccalaureate nursing students.Design:Cross-sectional study design.Methods:A convenient sample of 445 baccalaureate nursing students were surveyed in two universities i...capacity and creativity tendencies among Chinese baccalaureate nursing students.Design:Cross-sectional study design.Methods:A convenient sample of 445 baccalaureate nursing students were surveyed in two universities in Tianjin,China.Students completed a questionnaire that included their demographic information,Achievement Motivation Scale,Meta-Learning Capacity Questionnaire,and Creativity Tendencies Scale.Pearson correlation was performed to test the correlation among achievement motivation,meta-learning capacity and creativity tendencies.Hierarchical linear regression analyses were performed to explore the mediating role of meta-learning capacity.Results:The participants had moderate levels of achievement motivation(mean score 2.383±0.240)and meta-learning capacity(mean score 1.505±0.241)and a medium-high level of creativity tendency(mean score 1.841±0.288).Creativity tendencies was significantly associated with both achievement motivation and meta-learning capacity(both P<0.01).Furthermore,meta-learning capacity mediated the relationship between achievement motivation and high creativity tendencies.Conclusion:The study hypotheses were supported.Higher achievement motivation,and meta-learning capacity can increase creativity tendencies of baccalaureate nursing students,and meta-learning capacity was found to mediate the relationship between achievement motivation and creativity tendencies.Nursing educators should pay attention to the positive role of meta-learning capacity in nursing students’learning,and make them more confident when they finish their studies.展开更多
基金supported by the National Natural Science Foundation of China under grant 61941106。
文摘This paper investigates the effective capacity of a point-to-point ultra-reliable low latency communication(URLLC)transmission over multiple parallel sub-channels at finite blocklength(FBL)with imperfect channel state information(CSI).Based on reasonable assumptions and approximations,we derive the effective capacity as a function of the pilot length,decoding error probability,transmit power and the sub-channel number.Then we reveal significant impact of the above parameters on the effective capacity.A closed-form lower bound of the effective capacity is derived and an alternating optimization based algorithm is proposed to find the optimal pilot length and decoding error probability.Simulation results validate our theoretical analysis and show that the closedform lower bound is very tight.In addition,through the simulations of the optimized effective capacity,insights for pilot length and decoding error probability optimization are provided to evaluate the optimal parameters in realistic systems.
基金supported by the Key Technology R&D Program of China during the 11th Five-Year PlanPeriod (2006BAD05A15)
文摘This paper was designed to verify the influence of phosphate on water-holding capacity (WHC) and texture of emulsiontype sausage prepared with pre-rigor meat, ageing meat or frozen meat. Pre-rigor pork, ageing pork and frozen pork were pre-blended with five levels of phosphate and made into emulsion-type sausage. The yield, hardness and total expressible fluid (TEF) were measured with texture profile analysis machine and pressiometer when emulsion-type sausage was produced. Meanwhile, hardness and purge loss (PL) were measured during 30 d storage. As emusion-type sausage made by pre-rigor meat, higher yield and relatively stable hardness could be found. It indicated that increasing of phosphate level caused an alleviatable effects in increasing of hardness when emulsion-type sausage made by pre-rigor meat, but opposite effects made by ageing meat or frozen meat. The distribution of PL of emulsion-type sausage was found to be affected by phosphate addition. Significant decrease of PL could not be obtained by increasing of phosphate level during storage. Pre-rigor meat improved WHC and texture of emulsion-type sausage. Problem of WHC and texture of emulsiontype sausage during storage could not be resolved by single use of phosphate at relatively higher level (3%) of NaCl.
基金supported by National Natural Science Foundation of China(No.61379016)
文摘In this paper,the transmission performances are studied in cognitive radio networks with primary user emulator and relay existence.In the proposed network,the users include primary users,secondary users and primary user emulators.The decreasing access priority of the users are primary users,primary user emulators and secondary users.Different user access to the network results in different transmission effects.We impose interference power constraints on the secondary users to protect the primary users from being interfered.We also adopt the transmission mechanism that transits among more than one secondary transmitters,secondary receivers and relays.The transition models of the transmission states are proposed to describe the transmission mechanism.To investigate the transmission performances,the theory of effective capacity is adopted.The transmission performances in terms of effective capacity are expressed and demonstrated under different transmission policies.The overall effective capacity,as the overall data traffic in the cognitive radio network,is calculated.Besides,the overall effective capacity is demonstrated under different transmission strategies.The results show the greedy transmission strategy outperforms the rest of the transmission 8 policies in the overall effective capacity.For a larger number of the users,the effective capacity converges to a certain value.
文摘In this paper, the performance of multichannel transmission in cognitive radio is studied. Both QoS constraints and interference limitations are considered. The activities of the primary users (PU)s are initially detected by cognitive users (CU)s who perform sensing process over multiple channels. They transmit in a single channel at variable power and rates depending on the channel sensing decisions and the fading environment. The cognitive operation is modeled as a state transition model in which all possible scenarios are studied. The QoS constraint of the cognitive users is investigated through statistical analysis. Analytical form for the effective capacity of the cognitive radio channel is found. Optimal power allocation and optimal channel selection criterion are obtained. Impact of several parameters on the transmission performance, as channel sensing parameters, number of available channels, fading and other, are identified through numerical example.
基金supported in part by the National Natural Science Foundation of China under Grant No. 60902047the Fundamental Research Funds for the Central Universities under Grant No. BUPT2013RC0111
文摘For Peer-to-Peer (P2P) streaming services in mobile networks, the selection of appropriate neighbour peers from candidate peers with demanding data is an important approach to improve Quality-of-Service (QoS). This paper proposes a novel Effective Capacity Peer Selection (ECPS) scheme based on effective capacity. In the ECPS scheme, the neighbour peer selection problem was modeled using the Multiple Attribute Decision Making (MADM) theory, which considered multiple factors of candidate peers, including Signal to Interference and Noise Ratio (SINR), residency time, power level, security, moving speed, and effective capacity. This model could increase the suitability of ECPS for wireless mobile environments. Then, the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was used to solve the MADM problem and identify the preferred neighbour peers. Simulation results show that the ECPS scheme can improve the network throughput, reduce packet delay by about 82%, and almost double the packet delivery ratio of the mobile P2P streaming service.
基金support from Key Projects of Philosophy and Social Sciences Research of Ministry of Education(09JZD0038)
文摘Oil is extremely crucial to the development of the modern economy. It is important to forecast the oil supply capacity due to its scarcity and non-renewability. This paper attempts to forecast and analyze thirty-five current and potential net oil-exporting countries. Integrating both qualitative and quantitative methods, the oil production and consumption are predicted based on historical data, so that the world net oil-exporting capacity can be obtained. The results show that the "roof effect" of the world net oil-exporting capacity may appear before 2030. Unconventional oil will play an important role in the future world oil market. The competition and cooperation relationships between OPEC and non-OPEC will last for a long time.
文摘To understand the effect of the doping amount of Cu^2+ on the structure and reactivity of SnO2 in NOx-SCR with NH3, a series of Sn-Cu-O binary oxide catalysts with different Sn/Cu ratios have been prepared and thoroughly characterized. Using the XRD extrapolation method, the SnO2 lattice capacity for Cu^2+ cations is determined at 0.10 g Cu O per g of SnO2, equaling a Sn/Cu molar ratio of 84/16. Therefore, in a tetragonal rutile SnO2 lattice, only a maximum of 16% of the Sn4+ cations can be replaced by Cu^2+ to form a stable solid solution structure. If the Cu content is higher, Cu O will form on the catalyst surface, which has a negative effect on the reaction performance. For samples in a pure solid solution phase, the number of surface defects increase with increasing Cu content until it reaches the lattice capacity, as confirmed by Raman spectroscopy. As a result, the amounts of both active oxygen species and acidic sites on the surface, which critically determine the reaction performance, also increase and reach the maximum level for the catalyst with a Cu content close to the lattice capacity. A distinct lattice capacity threshold effect on the structure and reactivity of Sn-Cu binary oxide catalysts has been observed. A Sn-Cu catalyst with the best reaction performance can be obtained by doping the SnO2 matrix with the lattice capacity amount of Cu^2+.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11105062,11275003,11265014 and 11275084the Fundamental Research Funds for the Central Universities under Grant No LZUJBKY-2015-119
文摘Recent experimental and theoretical studies show that energy efficiency, which measures the amount of infor- mation processed by a neuron with per unit of energy consumption, plays an important role in the evolution of neural systems. Here we calculate the information rates and energy efficieneies of the Hodgkin-Huxley (HH) neuron model at different temperatures in a noisy environment. It is found that both the information rate and energy efficiency are maximized by certain temperatures. Though the information rate and energy efficiency cannot be maximized simultaneously, the neuron holds a high information processing capacity at the tempera- ture corresponding to the maximal energy efficiency. Our results support the idea that the energy efficiency is a selective pressure that influences the evolution of nervous systems.
基金Supported by Chongqing Social Science Planning Project(2012BS44)Special Funds of Central Universities Basic Research Funds under Southwest University(SWU1309219)
文摘In this article,comparative research on residents' effect perception,participation capacity and willingness on Pro-poor Tourism( PPT) is given based on the questionnaire carried out in Wulong County and Fengjie County in Three Gorges Area,Chongqing,China. Some technologies,such as SPSS 13. 0,ANOVA and T-test are applied to analyze the data and results show Wulong residents' perception behavior is better than that of Fengjie residents. Moreover,the residents with different demographic characteristics have different participation behavior.Finally,multiple regression analysis is applied to identify the key factors influencing residents' perception behavior,that is participation willingness and positive economic effect perception,positive social and cultural effect perception and participation capacity.
基金supported by the Specific Project of National Key Research and Development Program of China (Grants No.2016YFC0503506)the Strategy Priority Research Program of Chinese Academy of Sciences (Grants No. XDA20010103)
文摘This study identifies the carrying state and value of Tibet’s resource and environmental carrying capacity.A new theoretical framework is proposed for exploring the resource and environmental carrying capacity based on two perspectives of“growth limit”and“stability of Human-Earth relationship system”.On this basis,an ideal growth model that accords with the“short board”effect is established to predict the population limitation.Analytical results show that the holistic state of resource and environmental carrying capacity in Tibet is in jeopardy.From 2010 to 2016,Tibet’s carrying state continued to decline,moreover,the negative forces still overwhelm the positive forces.Although the resource reserves still have room for more population,the environmental capacity and ecological capacity have been overloaded.Meanwhile,the Human-Earth relationship system is in an unstable stage.Three scenarios that respond to different socioeconomic developments are implemented to predict the population limitation of resource and environmental carrying capacity in Tibet;thus,authors argue that Tibet should keep its population size within 4 million around 2025.This research will provide reference for sustainable development and resources and environmental conservation in Tibet.
文摘Cell discontinuous transmission(Cell DTx)is a key technology to mitigate inter-cell interference(ICI)in ultra-dense networks(UDNs).The aim of this work is to understand the impact of Cell DTx on physical-layer sum rates of SBSs and link-layer quality-of-service(QoS)performance in multiuser UDNs.In this work,we develop a cross-layer framework for capacity analysis in multiuser UDNs with Cell DTx.In particular,we first extend the traditional one-dimensional effective capacity model to a new multidimensional effective capacity model to derive the sum rate and the effective capacity.Moreover,we propose a new iterative bisection search algorithm that is capable of approximating QoS performance.The convergence of this new algorithm to a unique QoS exponent vector is later proved.Finally,we apply this framework to the round-robin and the max-C/I scheduling policies.Simulation results show that our framework is accurate in approximating 1)queue length distribution,2)delay distribution and 3)sum rates under the above two scheduling policies,and further show that with the Cell DTx,systems have approximately 30% higher sum rate and 35% smaller average delay than those in full-buffer scenarios.
基金co-funded by National Natura Science Foundation of China (Grant No. 41102058 Gran No. U1262203)+4 种基金the National Science and Technology Special Grant (No. 2011ZX05006-003)Shandong Natura Science Foundation (Grant No. ZR2011DQ017)the Fundamental Research Funds for the Central Universities (No. 12CX04001A No. 13CX02035A No. 13CX02036A)
文摘Methodologies have been developed for calculating cutoffs of reservoir intervals with production capacity (RIPC) and reservoir intervals with accumulation capacity (RIAC) according to the types of pore throat structures and dynamic force by using data from petrophysical analysis, production tests and mercury injection. The data are from clastic reservoirs in the third member (Es3) and the fourth member (Es4) of the Shahejie Formation in the Shengtuo area on the North Slope of the Dongying Sag, Jiyang Depression, China. The method of calculating cutoffs of RIPC is summarized as follows: 1) determination of permeability cutoffs of RIPC; 2) classification of types of pore-throat structures according to mercury injection data and then relating porosity to permeability and determining the relationship between porosity and permeability according to each type of pore-throat structure; and 3) calculating porosity cutoffs of RIPC using established correlation between porosity and permeability according to the type of pore throat structure. The method of calculating cutoffs of RIAC includes: 1) establishing a functional relationship between oil-water interracial tension and formation temperature; 2) calculating limiting values of maximum connected pore-throat radii according to formation temperature and dynamic forces of each reservoir interval; 3) correlating permeability with maximum connected pore-throat radius and then obtaining permeability cutoffs of RIAC; and 4) calculating porosity cutoffs on the basis of permeability cutoffs according to specific correlations, suitable for the type of porethroat structure. The results of this study show that porosity and permeability cutoffs of clastic reservoirs decrease with depth. For a fixed permeability cutoff, the porosity cutoff of R1PC varies because the type of pore throat is different. At a fixed temperature, porosity and permeability cutoffs of RIAC decrease as dynamic force increases. For a fixed permeability cutoff of effective hydrocarbon accumulation, the porosity cutoff also varies with different types of pore throat.
基金Project supported by the National Natural Science Foundation of China (Nos. 49771046 and 49831005) the Center for International Cooperation, Ministry of Foreign Affairs, State of Israel.
文摘Suspensions of a latosol with a clay concentration of 30 g kg^(-1) wereprepared from electrodialyzed clay fractions, less than 2 μm in diameter, five nitrate solutionswith a concentration of 1 X 10^(04)/z mol L^(-1), where z is the valence, and five sodium saltsolutions with a concentration of 3.3 X 10^(-5)/2 mol L^(-1). The direct current (DC) electricalconductivities (ECs) of the colloidal suspensions were measured at a constant temperature of 25 ℃,using a newly established method of measuring the Wien effect in soil suspensions at field strengthsranging from 13.5 to 150 kV cm^(-1), to determine their electrical conductivity-field strengthrelationships and to infer the order of the bonding strength (retaining force) between soilparticles and various ions. The measurements with the latosol suspensions in NaNO_3, KNO_3,Ca(NO_3)_2, Mg(NO_3)_2 and Zn(NO_3)_2 solutions resulted in increments of the suspension ECs, ΔECs,of 7.9, 5.0, 7.1, 7.0 and 5.8 μS cm^(-1), respectively, when the applied field strength increasedfrom 14.5 to 142 kV cm^(-1). As for the suspensions in NaNO_3, NaCl, Na_2SO_4, Na_3PO_4 andNa_3AsO_4 solutions, the ΔECs were 6.2, 5.3, 4.1, 4.0 and 3.7μS cm^(-1), respectively, when theapplied field strength increased from 13.5 to 90 kV cm^(-1). Thus, it can be deduced that theretaining forces of the clay fraction of the latosol for the cations were in the descending orderK^+ > Zn^(2+) > Mg^(2+) ≥ Ca^(2+) > Na^+, and for the anions in the descending order H_2AsO_4^- >H_2PO_4^-≥ SO_4^(2-) > Cl^- > NO_3~ -.
基金Project (05GK3024) supported by the Program of Hunan Provincial Science and Technology
文摘The influence of earthquake forces on ultimate bearing capacity of foundations on sloping ground was studied. A solution to seismic ultimate bearing capacity of strip footings on slope was obtained by utilizing pseudo-static analysis method and taking the effect of intermediate principal stress into consideration. Based on limit equilibrium theory, the formulae for computing static bearing capacity factors, Nq, Nc, Nγ, and dynamic bearing capacity factors, Nqd, Ned, Nγd, which are associated with surcharge, cohesion and self-weight of soils respectively, were presented. A great number of analysis calculations were carried out to obtain the relationship curves of the static and dynamic bearing capacity factors versus various calculation parameters. The curves can serve as the practical engineering design. The calculation results also show that when the values of horizontal and vertical seismic coefficients are 0.2, the dynamic bearing capacity factors Nqd, Ned and Nγd, in which the effects of intermediate principal stress are taken into consideration, increase by 4%-42%, 3%-27% and 34%-57%, respectively.
基金supported by the High Technology Research and Development Program of China (No. 2006AA09Z438)the National Natural Science Foundation of China (No. 30871943).
文摘Fish skin collagen hydrolysates (FSCH) were prepared from walleye pollock (Theragra chalcogramrna) using a mixture of enzymes, namely trypsin and flavourzyme. The degree of hydrolysis of the skin collagen was 27.3%. FSCH was mainly composed of low-molecular-weight peptides and the relative proportion of 〈1000Da fraction was 70.6%. Free radical and oxygen species scavenging activities of FSCH were investigated in four model systems, including diphenylpicrylhy-drazyl radical (DPPH), superoxide anion radical, hydroxyl radical and hydrogen peroxide model, and compared with that of a native antioxidant, reduced glutathione (GSH). FSCH was also evaluated by water-absorbing and water-holding capacity. The results showed that FSCH was able to scavenge free radical and oxygen species significantly and to enhance water-absorbing and water-holding capacity remarkably. Therefore FSCH may have potential applications in the medicine and food industries.
基金the financial supports for this research from the National Basic Research Program of China(2019YFB1505103)the National Natural Science Foundation of China(51571179 and 51671173)the Open Fund of the Guangdong Provincial Key Laboratory of Advance Energy Storage Materials。
文摘Magnesium hydride has attracted great attention because of its high theoretical capacity and outstanding reversibility, nevertheless, its practical applications have been restricted by the disadvantages of the sluggish kinetics and high thermodynamic stability. In this work, an unexpected high reversible hydrogen capacity over 8.0 wt% has been achieved from MgH2 metal hydride composited with small amounts of LiBH4 and Li3AlH6 complex hydrides, which begins to release hydrogen at 276 ℃ and then completely dehydrogenates at 360 ℃. The dehydrogenated MgH2+LiBH4/Li3AlH6 composite can fully reabsorb hydrogen below 300 ℃ with an excellent cycling stability. The composite exhibits a significant reduction of dehydrogenation activation energy from 279.7 kJ/mol(primitive MgH2) to 139.3 kJ/mol(MgH2+LiBH4/Li3AlH6),as well as a remarkable reduction of dehydrogenation enthalpy change from 75.1 k J/mol H2(primitive MgH2) to 62.8 kJ/mol H2(MgH2+LiBH4/Li3AlH6). The additives of LiBH4 and Li3AlH6 not only enhance the cycling hydrogen capacity, but also simultaneously improve the reversible de/rehydrogenation kinetics, as well as the dehydrogenation thermodynamics. This notable improvement on the hydrogen absorption/desorption behaviors of the MgH2+LiBH4/Li3AlH6 composite could be attributed to the dehydrogenated products including Li3Mg7, Mg17Al12 and MgAlB4, which play a key role on reducing the dehydrogenation activation energy and increasing diffusion rate of hydrogen. Meanwhile, the LiBH4 and Li3AlH6 effectively destabilize MgH2 with a remarkable reduction on dehydrogenation enthalpy change in terms of thermodynamics. In particular, the Li3Mg7, Mg17Al12 and MgAlB4 phases can reversibly transform into MgH2, Li3AlH6 and LiBH4 after rehydrogenation, which contribute to maintain a high cycling capacity.This constructing strategy can further promote the development of high reversible capacity Mg-based materials with suitable de/rehydrogenation properties.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11004204 and 51001114), the Knowledge Inno- vation Project of the Chinese Academy of Sciences, and the National Basic Research Program of China (Grant No. 2006CB601101).
文摘Magnetic entropy change (△SM) and refrigerant capacity (RC) of Ce6Ni2Si3-type Gd6Co1.67Si2.5Geo.5 compounds have been investigated. The Gd6Col.67Si2.5Geo.5 undergoes a reversible second-order phase transition at the Curie temperature Tc = 296 K. The high saturation magnetization leads to a large ASM and the maximal value of △SM is found to be 5.9 J/kg. K around TC for a field change of 0-5 T. A broad distribution of the △SM peak is observed and the full width at half maximum of the △SM peak is about 101 K under a magnetic field of 5 T. The large RC is found around TC and its value is 424 J/kg.
文摘capacity and creativity tendencies among Chinese baccalaureate nursing students.Design:Cross-sectional study design.Methods:A convenient sample of 445 baccalaureate nursing students were surveyed in two universities in Tianjin,China.Students completed a questionnaire that included their demographic information,Achievement Motivation Scale,Meta-Learning Capacity Questionnaire,and Creativity Tendencies Scale.Pearson correlation was performed to test the correlation among achievement motivation,meta-learning capacity and creativity tendencies.Hierarchical linear regression analyses were performed to explore the mediating role of meta-learning capacity.Results:The participants had moderate levels of achievement motivation(mean score 2.383±0.240)and meta-learning capacity(mean score 1.505±0.241)and a medium-high level of creativity tendency(mean score 1.841±0.288).Creativity tendencies was significantly associated with both achievement motivation and meta-learning capacity(both P<0.01).Furthermore,meta-learning capacity mediated the relationship between achievement motivation and high creativity tendencies.Conclusion:The study hypotheses were supported.Higher achievement motivation,and meta-learning capacity can increase creativity tendencies of baccalaureate nursing students,and meta-learning capacity was found to mediate the relationship between achievement motivation and creativity tendencies.Nursing educators should pay attention to the positive role of meta-learning capacity in nursing students’learning,and make them more confident when they finish their studies.