Along with the economic development and the acceleration of urbanization,urban construction land expands rapidly in China,and has resulted in a series of socio-economic problems.This article summarized the major point...Along with the economic development and the acceleration of urbanization,urban construction land expands rapidly in China,and has resulted in a series of socio-economic problems.This article summarized the major points of controlling the unchecked and rash expansion of construction land in the academic circle,and analyzed the problems of regulating the expansion of construction land from three aspects.First,this article analyzed the relationships between socio-economic development and urbanization from the historical viewpoints,and pointed out that the expansion of construction land is a historical phenomenon which will be surely appeared in the development of human race.Second,the authors utilized two-sector model to analyze the importance of urbanization in the socio-economic development from the academic angles.At last,the authors utilize four-quadrant model and bidrent curve model to analyze the influence that brought by the strict control of construction land expansion.Through analysis,this article drew some conclusions.First,the expansion of construction land is a phenomenon which will surely appear in the social development.It is impossible to accomplish the national modernization on the basis of dualistic structure between urban and rural areas.Second,under the function of rent gradient gap,strict control of construction land expansion will not only obtain the anticipated effects,but also cause a series of socio-economic problems,such as land-levying contradiction,the appearance of limited property right house,and being dependant on lease instead of expropriation.Third,unreasonable policies and governmental behaviors are the roots of the unchecked and rash expansion of urban construction land.Based on these conclusions,this article proposed that three transformations should be realized to regulate the unchecked and rash expansion of construction land:transfers from quantity regulation to quality regulation,from direct regulation to indirect regulation,and from single-measure regulation to multi-measures regulation.展开更多
Expansive soils in Saudi Arabia have received wide attention in recent decades, following the rapid urbanization of rural and agricultural parts of the country. Tayma expansive shale inflicted serious damages to light...Expansive soils in Saudi Arabia have received wide attention in recent decades, following the rapid urbanization of rural and agricultural parts of the country. Tayma expansive shale inflicted serious damages to light structures, roads and boundary walls. This research is aimed at studying the engineering characteristics of the shale at this area including the basic geotechnical parameters as well as swelling behavior under oedometric loading conditions. The engineering properties were determined and compared to the local and international characterization charts. Mineralogy study using x-ray diffraction was conducted to investigate clay minerals present. The swell percent and the swelling pressure of the shale were investigated for samples prepared at different initial moisture contents and various dry densities. A close-up view of damages caused by the expansive shale in the town is highlighted and measures to reduce the risk of potential swelling distress for future constructions are presented.展开更多
There has been a great deal of research on the driving force of aviation network.Moreover, the research methods and perspectives are also varied.This article mainly studies the driving force of aviation network,the in...There has been a great deal of research on the driving force of aviation network.Moreover, the research methods and perspectives are also varied.This article mainly studies the driving force of aviation network,the influencing factors of main driving force are analyzed.The driving force analysis of different airport and route is carried out respectively.The results can better reveal the connection mechanism of solid routes.Because the sample space of the hub airport and the trunk airport is too small,the conclusions are not sufficiently illustrative,therefore, this article studies only the branch airports.The conclusions are compared with the results of the comprehensive analysis,and we see if the conclusions are the same or similar.展开更多
This paper reports the practicability of using coffee residues to remove widely used basic dyes like MB （Methylene Blue） from wastewaters. The effect of different batch system parameters, namely stirring speed, pH, ...This paper reports the practicability of using coffee residues to remove widely used basic dyes like MB （Methylene Blue） from wastewaters. The effect of different batch system parameters, namely stirring speed, pH, initial dye concentration and contact time were studied. Moreover, in continuous fixed-bed column systems, the effects of parameters such as bed-depth, flow rate and initial dye concentration were examined. The experimental batch systems data were simulated using （a） Freundlich, Langmuir and Sips isotherm models and （b） 1st order, 2nd order, and intra-particle kinetic models. The results revealed that the MB is fairly adsorbed on coffee residues. This process could be a low cost technique for the removal of basic dyes from aqueous systems.展开更多
This study proposes an efficient indirect approach for general nonlinear dynamic optimization problems without path constraints. The approach incorporates the virtues both from indirect and direct methods: it solves t...This study proposes an efficient indirect approach for general nonlinear dynamic optimization problems without path constraints. The approach incorporates the virtues both from indirect and direct methods: it solves the optimality conditions like the traditional indirect methods do, but uses a discretization technique inspired from direct methods. Compared with other indirect approaches, the proposed approach has two main advantages: (1) the discretized optimization problem only employs unconstrained nonlinear programming (NLP) algorithms such as BFGS (Broyden-Fletcher-Goldfarb-Shanno), rather than constrained NLP algorithms, therefore the computational efficiency is increased; (2) the relationship between the number of the discretized time intervals and the integration error of the four-step Adams predictor-corrector algorithm is established, thus the minimal number of time intervals that under desired integration tolerance can be estimated. The classic batch reactor problem is tested and compared in detail with literature reports, and the results reveal the effectiveness of the proposed approach. Dealing with path constraints requires extra techniques, and will be studied in the second paper.展开更多
The DArk Matter Particle Explorer(DAMPE)is well suitable for searching for monochromatic and sharpγ-ray structures in the GeV-TeV range thanks to its unprecedented high energy resolution.In this work,we search forγ-...The DArk Matter Particle Explorer(DAMPE)is well suitable for searching for monochromatic and sharpγ-ray structures in the GeV-TeV range thanks to its unprecedented high energy resolution.In this work,we search forγ-ray line structures using five years of DAMPE data.To improve the sensitivity,we develop two types of dedicated data sets(including the BgoOnly data which is the first time to be used in the data analysis for the calorimeter-based gamma-ray observatories)and adopt the signal-to-noise ratio optimized regions of interest(ROIs)for different DM density profiles.No line signals or candidates are found between 10 and 300 GeV in the Galaxy.The constraints on the velocity-averaged cross section for xx→γγand the decay lifetime for x→γv,both at 95%confidence level,have been calculated and the systematic uncertainties have been taken into account.Comparing to the previous Fermi-LAT results,though DAMPE has an acceptance smaller by a factor of~10,similar constraints on the DM parameters are achieved and below 100 GeV the lower limits on the decay lifetime are even stronger by a factor of a few.Our results demonstrate the potential of high-energy-resolution observations on dark matter detection.展开更多
The theoretical model of docking impact dynamics based on flexible cone is presented according to Foppl-von Karman＇s non-linear differential equations and Hertz contact theory. Finite diflerence technique is used to ...The theoretical model of docking impact dynamics based on flexible cone is presented according to Foppl-von Karman＇s non-linear differential equations and Hertz contact theory. Finite diflerence technique is used to solve this theoretical model. Results of the theoretical model show good agreement with the experimental and ANSYS/LS-DYNA simulation results. In ad- dition, the influence of flexible cone parameters on impact process is discussed based on theoretical model systemically.展开更多
Cosmic rays(CR)play an important role in space weather-related studies.Their temporal variability,both of a quasi-periodic character as well as an irregular one,has been studied from ground-based direct measurements,a...Cosmic rays(CR)play an important role in space weather-related studies.Their temporal variability,both of a quasi-periodic character as well as an irregular one,has been studied from ground-based direct measurements,as well as from cosmogenic nuclides,over a long time.We attempt to describe the current knowledge of selected quasi-periodicities in CR flux in the energy range above the atmospheric threshold,from direct measurements.The power spectrum density(PSD)of the CR time series as measured by neutron monitors(NMs)and by muon detectors has a rather complicated character.Along with the shape(slope)of the PSD,knowledge of the contribution of quasi-periodic variations(q-per)to the CR signal is of importance for the modulation,as well as for checking the links of CR to space weather,and/or to space climate effects.The rotation of the Earth and solar rotation cause two types of mechanisms behind the certain q-per observed in secondary CR on the Earth’s surface.Solar activity and solar magnetic field cyclicities contribute to the q-per signals in CR if studied over a longer time.The complexity of the spatial structure of the interplanetary magnetic field(IMF)and its evolution within the heliosphere,in addition to the changes in the geomagnetic field,cause variability in contributions of the q-per in CR.Wavelet spectra are useful tools for checking the fine structure of q-per and their temporal behaviour.Over a long time NMs and muon telescopes provide information about q-per in CR.展开更多
基金founded by the National S&T Pillar Program (Grant no.2007BAC15B03)the Project for Knowledge Innovation Program of CAS (Grant no.066U0111SZ)
文摘Along with the economic development and the acceleration of urbanization,urban construction land expands rapidly in China,and has resulted in a series of socio-economic problems.This article summarized the major points of controlling the unchecked and rash expansion of construction land in the academic circle,and analyzed the problems of regulating the expansion of construction land from three aspects.First,this article analyzed the relationships between socio-economic development and urbanization from the historical viewpoints,and pointed out that the expansion of construction land is a historical phenomenon which will be surely appeared in the development of human race.Second,the authors utilized two-sector model to analyze the importance of urbanization in the socio-economic development from the academic angles.At last,the authors utilize four-quadrant model and bidrent curve model to analyze the influence that brought by the strict control of construction land expansion.Through analysis,this article drew some conclusions.First,the expansion of construction land is a phenomenon which will surely appear in the social development.It is impossible to accomplish the national modernization on the basis of dualistic structure between urban and rural areas.Second,under the function of rent gradient gap,strict control of construction land expansion will not only obtain the anticipated effects,but also cause a series of socio-economic problems,such as land-levying contradiction,the appearance of limited property right house,and being dependant on lease instead of expropriation.Third,unreasonable policies and governmental behaviors are the roots of the unchecked and rash expansion of urban construction land.Based on these conclusions,this article proposed that three transformations should be realized to regulate the unchecked and rash expansion of construction land:transfers from quantity regulation to quality regulation,from direct regulation to indirect regulation,and from single-measure regulation to multi-measures regulation.
文摘Expansive soils in Saudi Arabia have received wide attention in recent decades, following the rapid urbanization of rural and agricultural parts of the country. Tayma expansive shale inflicted serious damages to light structures, roads and boundary walls. This research is aimed at studying the engineering characteristics of the shale at this area including the basic geotechnical parameters as well as swelling behavior under oedometric loading conditions. The engineering properties were determined and compared to the local and international characterization charts. Mineralogy study using x-ray diffraction was conducted to investigate clay minerals present. The swell percent and the swelling pressure of the shale were investigated for samples prepared at different initial moisture contents and various dry densities. A close-up view of damages caused by the expansive shale in the town is highlighted and measures to reduce the risk of potential swelling distress for future constructions are presented.
文摘There has been a great deal of research on the driving force of aviation network.Moreover, the research methods and perspectives are also varied.This article mainly studies the driving force of aviation network,the influencing factors of main driving force are analyzed.The driving force analysis of different airport and route is carried out respectively.The results can better reveal the connection mechanism of solid routes.Because the sample space of the hub airport and the trunk airport is too small,the conclusions are not sufficiently illustrative,therefore, this article studies only the branch airports.The conclusions are compared with the results of the comprehensive analysis,and we see if the conclusions are the same or similar.
文摘This paper reports the practicability of using coffee residues to remove widely used basic dyes like MB （Methylene Blue） from wastewaters. The effect of different batch system parameters, namely stirring speed, pH, initial dye concentration and contact time were studied. Moreover, in continuous fixed-bed column systems, the effects of parameters such as bed-depth, flow rate and initial dye concentration were examined. The experimental batch systems data were simulated using （a） Freundlich, Langmuir and Sips isotherm models and （b） 1st order, 2nd order, and intra-particle kinetic models. The results revealed that the MB is fairly adsorbed on coffee residues. This process could be a low cost technique for the removal of basic dyes from aqueous systems.
基金Supported by the National Natural Science Foundation of China (U1162130)the National High Technology Research and Development Program of China (2006AA05Z226)the Outstanding Youth Science Foundation,Zhejiang Province (R4100133)
文摘This study proposes an efficient indirect approach for general nonlinear dynamic optimization problems without path constraints. The approach incorporates the virtues both from indirect and direct methods: it solves the optimality conditions like the traditional indirect methods do, but uses a discretization technique inspired from direct methods. Compared with other indirect approaches, the proposed approach has two main advantages: (1) the discretized optimization problem only employs unconstrained nonlinear programming (NLP) algorithms such as BFGS (Broyden-Fletcher-Goldfarb-Shanno), rather than constrained NLP algorithms, therefore the computational efficiency is increased; (2) the relationship between the number of the discretized time intervals and the integration error of the four-step Adams predictor-corrector algorithm is established, thus the minimal number of time intervals that under desired integration tolerance can be estimated. The classic batch reactor problem is tested and compared in detail with literature reports, and the results reveal the effectiveness of the proposed approach. Dealing with path constraints requires extra techniques, and will be studied in the second paper.
基金the Strategic Priority Science and Technology Projects in Space Science of Chinese Academy of Sciencessupported in part by the National Key Research and Development Program of China(2016YFA0400200)+6 种基金the National Natural Science Foundation of China(U1738210,U1738206,11921003,12003074,U1738205,U1738207,U1738208,12022302,11773086,12003069,11903084,11622327,and U1738123)the Scientific Instrument Developing Project of the Chinese Academy of Sciences(GJJSTD20210009)the Key Research Program of the Chinese Academy of Sciences(ZDRW-KT-2019-5)the Youth Innovation Promotion Association CAS,the Natural Science Foundation of Jiangsu Province(BK20201107)the Entrepreneurship and Innovation Program of Jiangsu Provincethe Swiss National Science Foundation(SNSF),Switzerlandthe National Institute for Nuclear Physics(INFN),Italy。
文摘The DArk Matter Particle Explorer(DAMPE)is well suitable for searching for monochromatic and sharpγ-ray structures in the GeV-TeV range thanks to its unprecedented high energy resolution.In this work,we search forγ-ray line structures using five years of DAMPE data.To improve the sensitivity,we develop two types of dedicated data sets(including the BgoOnly data which is the first time to be used in the data analysis for the calorimeter-based gamma-ray observatories)and adopt the signal-to-noise ratio optimized regions of interest(ROIs)for different DM density profiles.No line signals or candidates are found between 10 and 300 GeV in the Galaxy.The constraints on the velocity-averaged cross section for xx→γγand the decay lifetime for x→γv,both at 95%confidence level,have been calculated and the systematic uncertainties have been taken into account.Comparing to the previous Fermi-LAT results,though DAMPE has an acceptance smaller by a factor of~10,similar constraints on the DM parameters are achieved and below 100 GeV the lower limits on the decay lifetime are even stronger by a factor of a few.Our results demonstrate the potential of high-energy-resolution observations on dark matter detection.
基金supported by the National Natural Science Foundation of China(Grant Nos.91216201 and 51205403)
文摘The theoretical model of docking impact dynamics based on flexible cone is presented according to Foppl-von Karman＇s non-linear differential equations and Hertz contact theory. Finite diflerence technique is used to solve this theoretical model. Results of the theoretical model show good agreement with the experimental and ANSYS/LS-DYNA simulation results. In ad- dition, the influence of flexible cone parameters on impact process is discussed based on theoretical model systemically.
基金Project VEGA 2/0040/13 for supportKuwait for supporting project HS-13-01
文摘Cosmic rays(CR)play an important role in space weather-related studies.Their temporal variability,both of a quasi-periodic character as well as an irregular one,has been studied from ground-based direct measurements,as well as from cosmogenic nuclides,over a long time.We attempt to describe the current knowledge of selected quasi-periodicities in CR flux in the energy range above the atmospheric threshold,from direct measurements.The power spectrum density(PSD)of the CR time series as measured by neutron monitors(NMs)and by muon detectors has a rather complicated character.Along with the shape(slope)of the PSD,knowledge of the contribution of quasi-periodic variations(q-per)to the CR signal is of importance for the modulation,as well as for checking the links of CR to space weather,and/or to space climate effects.The rotation of the Earth and solar rotation cause two types of mechanisms behind the certain q-per observed in secondary CR on the Earth’s surface.Solar activity and solar magnetic field cyclicities contribute to the q-per signals in CR if studied over a longer time.The complexity of the spatial structure of the interplanetary magnetic field(IMF)and its evolution within the heliosphere,in addition to the changes in the geomagnetic field,cause variability in contributions of the q-per in CR.Wavelet spectra are useful tools for checking the fine structure of q-per and their temporal behaviour.Over a long time NMs and muon telescopes provide information about q-per in CR.
