The calculation method of potential evapotranspiration(PET) was improved by adopting a more reliable PET estimate based on the Penman-Monteith equation into the standardized precipitation evapotranspiration index(SPEI...The calculation method of potential evapotranspiration(PET) was improved by adopting a more reliable PET estimate based on the Penman-Monteith equation into the standardized precipitation evapotranspiration index(SPEI) in this study(SPEI PM). This improvement increased the applicability of SPEI in North China Plain(NCP). The historic meteorological data during 1962–2011 were used to calculate SPEI PM. The detrended yields of maize from Hebei, Henan, Shandong, Beijing, and Tianjin provinces/cities of NCP were obtained by linear sliding average method. Then regression analysis was made to study the relationships between detrended yields and SPEI values. Different time scales were applied, and thus SPEI PM was mentioned as SPEI PMk-j(k=time scale, 1, 2, 3, 4,…, 24 mon; j=month, 1, 2, 3,..., 12), among which SPEI PM3-8 reflected the water condition from June to August, a period of heavy precipitation and vigorous growth of maize in NCP. SPEI PM3-8 was highly correlated with detrended yield in this region, which can effectively evaluate the effect of drought on maize yield. Additionally, this relationship becomes more significant in recent 20 yr. The regression model based on the SPEI series explained 64.8% of the variability of the annual detrended yield in Beijing, 45.2% in Henan, 58.6% in Shandong, and 54.6% in Hebei. Moreover, when SPEI PM3-8 is in the range of –0.6 to 1.1, –0.9 to 0.8 and –0.8 to 2.3, the detrended yield increases in Shandong, Henan and Beijing. The yield increasing range was during normal water condition in Shandong and Henan, where precipitation was abundant. It indicated that the field management matched well with local water condition and thus allowed stable and high yield. Maize yield increase in these two provinces in the future can be realized by further improving water use efficiency and enhancing the stress resistance as well as yield stability. In Hebei and Beijing, the precipitation is less and thus the normal water condition cannot meet the high yield target. Increasing of water input and improving water use efficiency are both strategies for future yield increase. As global climate change became stronger and yield demands increased, the relationship between drought and maize yield became much closer in NCP too. The research of drought monitoring method and strategies for yield increase should be enhanced in the future, so as to provide strong supports for food security and agricultural sustainable development in China.展开更多
我们在中子星的内部在阶段转变，状态(曙光女神) 的方程，和相应集体半径的关系上学习模型参数的影响。数字分析证明重核子的联合常数在阶段上有细微影响转变和曙光女神，而是对粒子部分的明显的影响当袋子常数 B 和联合经常的 g 在阶...我们在中子星的内部在阶段转变，状态(曙光女神) 的方程，和相应集体半径的关系上学习模型参数的影响。数字分析证明重核子的联合常数在阶段上有细微影响转变和曙光女神，而是对粒子部分的明显的影响当袋子常数 B 和联合经常的 g 在阶段转变， EOS，和集体半径的关系上有重要影响时。我们发现那两个袋子常数 B 和联合的经常的 g 玩在对在混血儿的夸克之间的相互作用的描述的一样的角色担任主角。使用袋子常数计算的最大的团与试验性的数据决定了(从 175 ～ 200 兆电子伏) 在 1.4 ～的间隔的下降 1.7 太阳的质量。相应半径在结果与中子星的观察价值一致的 9.3 和 12 km.These 之间。第三个家庭的存在的可能性被讨论。第三个家庭的察觉可以在中子星内为阶段转变提供签名。展开更多
The uneven distribution of solar radiation is one of the main reasons for the variations in the yield gap between different regions in China and other countries of the world.In this study,different solar radiation lev...The uneven distribution of solar radiation is one of the main reasons for the variations in the yield gap between different regions in China and other countries of the world.In this study,different solar radiation levels were created by shading and the yield gaps induced by those levels were analyzed by measuring the aboveground and underground growth of maize.The experiments were conducted in Qitai,Xinjiang,China,in 2018 and 2019.The maize cultivars Xianyu 335 (XY335)and Zhengdan 958 (ZD958) were used with planting density of 12×10^(4) plants ha^(–1) under either high solar radiation (HSR)or low solar radiation (LSR,70%of HSR).The results showed that variation in the solar radiation resulted in a yield gap and different cultivars behaved differently.The yield gaps of XY335 and ZD958 were 8.9 and 5.8 t ha^(–1) induced by the decreased total intercepted photosynthetically active radiation (TIPAR) of 323.1 and 403.9 MJ m^(–2) from emergence to the maturity stage,respectively.The average yield of XY335 was higher than that of ZD958 under HSR,while the average yield of ZD958 was higher than that of XY335 under LSR.The light intercepted by the canopy and the photosynthetic rates both decreased with decreasing solar radiation.The aboveground dry matter decreased by 11.1% at silking and 21% at maturity,and the dry matter of vegetative organs and reproductive organs decreased by 9.8 and 20.9%at silking and by 12.1 and 25.5% at physiological maturity,respectively.Compared to the HSR,the root weights of XY335 and ZD958 decreased by 54.6 and 45.5%,respectively,in the 0–60 cm soil layer under LSR at silking stage.The aboveground and underground growth responses to different solar radiation levels explained the difference in yield gap.Selecting suitable cultivars can increase maize yield and reduce the yield gaps induced by variation of the solar radiation levels in different regions or under climate change.展开更多
Yield gap exists because the current attained actual grain yield cannot yet achieve the estimated yield potential. Chinese high yield maize belt has a wide span from east to west which results in different solar radia...Yield gap exists because the current attained actual grain yield cannot yet achieve the estimated yield potential. Chinese high yield maize belt has a wide span from east to west which results in different solar radiations between different regions and thus different grain yields. We used multi-site experimental data, surveyed farmer yield data, the highest recorded yield data in the literatures, and simulations with Hybrid-Maize Model to assess the yield gap and tried to reduce the yield gap by matching the solar radiation and plant density. The maize belt was divided into five regions from east to west according to distribution of accumulated solar radiation. The results showed that there were more than 5.8 Mg ha^(–1) yield gaps between surveyed farmer yield and the yield potential in different regions of China from east to west, which just achieved less than 65% of the yield potential. By analyzing the multi-site density experimental data, we found that the accumulated solar radiation was significantly correlated to optimum plant density which is the density with the highest yield in the multi-site density experiment(y=0.09895 x–32.49, P<0.01), according to which the optimum plant densities in different regions from east to west were calculated. It showed that the optimum plant density could be increased by 60.0, 55.2, 47.3, 84.8, and 59.6% compared to the actual density, the grain yield could be increased by 20.2, 18.3, 10.9, 18.1, and 15.3% through increasing plant density, which could reduce the yield gaps of 33.7, 23.0, 13.4, 17.3, and 10.4% in R(region)-1, R-2, R-3, R-4, and R-5, respectively. This study indicates that matching maize plant density and solar radiation is an effective approach to reduce yield gaps in different regions of China.展开更多
In the relativistic mean field approximation,the relativistic energy losses of the nucleon direct Urca processes are studied in the degenerate baryon matter of neutron stars.We investigate the effects of hyperon degre...In the relativistic mean field approximation,the relativistic energy losses of the nucleon direct Urca processes are studied in the degenerate baryon matter of neutron stars.We investigate the effects of hyperon degrees of freedom and the isovector scalar interaction which is considered by exchangingδmeson on the nucleon direct Urca processes in neutron star matter.The results indicate that the existence of hyperons decreases the abundance of protons and leptons and can sharply suppress the neutrino emissivity of the nucleon direct Urca processes,while it has only a little influence on the neutrino luminosity for a fixed neutron star whetherδmesons appear in a neutron star or not.However,the presence ofδmesons can result in obvious growth in the neutrino emissivity and luminosity which will speed up the cooling rate for the nonsuperfluid neutron star.展开更多
We investigate the influence of the energy gap(Δ)of the color-flavor locked(CFL)quark phase on the bulk properties of hybrid stars.The relativistic mean field model is used for hadronic matter and the MIT bag model f...We investigate the influence of the energy gap(Δ)of the color-flavor locked(CFL)quark phase on the bulk properties of hybrid stars.The relativistic mean field model is used for hadronic matter and the MIT bag model for CFL quark matter.In our calculation results,we find that with the increase of the CFL energy gap there exists a transition behavior,which goes from the hadron star range through the transition range into the CFL quark star range.The observation data of PRS J1614-2230 are in the hadron star range(withΔ<40MeV).We also find that with hyperons the equation of state(EOS)for the hybrid star matter with the CFL quark matter core has a small change,which can be disregarded.展开更多
Within the framework of the relativistic mean field theory,we investigate the ^(1)S_(0) superfluidity (SF) of A hyperons in neutron star (NS) matter including σ^(*) and φ mesons.The energy gap of ∧ hyperons is calc...Within the framework of the relativistic mean field theory,we investigate the ^(1)S_(0) superfluidity (SF) of A hyperons in neutron star (NS) matter including σ^(*) and φ mesons.The energy gap of ∧ hyperons is calculated with the Nijmegen one-boson-exchange potentials for a (∧∧) pair. The parameter set we use is in line with the recent experimental data △B_(∧∧) ~ 1.01 ± 0.20_+0.18-0.11 MeV.It is found that with σ^(*) and φ mesons the pairing energy gap △F of ∧ hyperons and the corresponding SF critical temperature T_(C∧) are suppressed.In addition the NS mass range of ∧ hyperon SF is enlarged obviously.展开更多
In the relativistic mean field approximation,the relativistic energy losses of the direct Urca processes with nucleons(N-DURCA)and hyperons(Y-DURCA)are studied in the degenerate baryon matter of neutron stars.We inves...In the relativistic mean field approximation,the relativistic energy losses of the direct Urca processes with nucleons(N-DURCA)and hyperons(Y-DURCA)are studied in the degenerate baryon matter of neutron stars.We investigate the effects of hyperon degrees of freedom and the Y-DURCA processes on the N-DURCA processes,and the total neutrino emissivity of neutron star matter.The results show that the existence of hyperons decreases the abundance of protons and leptons,and can sharply suppress the neutrino emissivity of the N-DURCA processes.展开更多
A new effect of self-consistency in the relativistic Hartree-Fock(HF)approximation suggested previously is con firmed by a renormalized calculation with the on-shell renormalization conditions.Two self-consistency sch...A new effect of self-consistency in the relativistic Hartree-Fock(HF)approximation suggested previously is con firmed by a renormalized calculation with the on-shell renormalization conditions.Two self-consistency schemes,ne requiring self-consistency in the HF potential(scheme P)and the other in the baryon propagator(scheme BP),are studied.It is pointed out that the on-shell renormalization conditions make the self-consistency require-ment in scheme P automatically satisfied.Our calculated results show that scheme P is a good approximation to scheme BP for the calculation of the baryon propagator and the self-consistency in scheme BP diminishes the continuum part of the spectral representation for the baryon propagator,while scheme P yields a baryon propagator which is the same as the HF result contributed by the single particle part of the above spectral representation alone.Further,it is demonstrated that the region of validity of the quasi-particle approximationmay depend on the renormalization conditions.展开更多
We investigate the nucleon superfluidity in the^(1)S_(0)channel in neutron star matter using the relativistic mean field theory and the BCS theory.We discuss particularly the influence of the isovector scalar interact...We investigate the nucleon superfluidity in the^(1)S_(0)channel in neutron star matter using the relativistic mean field theory and the BCS theory.We discuss particularly the influence of the isovector scalar interaction which is considered by exchangingδmeson on the nucleon superfluidity.It is found that theδmeson leads to a growth of the nucleon^(1)S_(0)pairing energy gaps in a middle density range of the existing nucleon superfluidity.In addition,when the densityρB>0.36 fm^(-3),the proton^(1)S_(0)pairing energy gap obviously decreases.The density range of the proton^(1)S_(0)superfluidity is narrowed due to the presence ofδmesons.In our results,theδmeson not only changes the EOS and bulk properties but also changes the cooling properties of neutron stars.展开更多
基金supported by the Chinese National Public Scientific Research (201203031)the Chinese National Corn Industry Technology System (CARS-02-26)the Chinese Postdoctoral Science Foundation Project funded on the surface (2013M 541092)
文摘The calculation method of potential evapotranspiration(PET) was improved by adopting a more reliable PET estimate based on the Penman-Monteith equation into the standardized precipitation evapotranspiration index(SPEI) in this study(SPEI PM). This improvement increased the applicability of SPEI in North China Plain(NCP). The historic meteorological data during 1962–2011 were used to calculate SPEI PM. The detrended yields of maize from Hebei, Henan, Shandong, Beijing, and Tianjin provinces/cities of NCP were obtained by linear sliding average method. Then regression analysis was made to study the relationships between detrended yields and SPEI values. Different time scales were applied, and thus SPEI PM was mentioned as SPEI PMk-j(k=time scale, 1, 2, 3, 4,…, 24 mon; j=month, 1, 2, 3,..., 12), among which SPEI PM3-8 reflected the water condition from June to August, a period of heavy precipitation and vigorous growth of maize in NCP. SPEI PM3-8 was highly correlated with detrended yield in this region, which can effectively evaluate the effect of drought on maize yield. Additionally, this relationship becomes more significant in recent 20 yr. The regression model based on the SPEI series explained 64.8% of the variability of the annual detrended yield in Beijing, 45.2% in Henan, 58.6% in Shandong, and 54.6% in Hebei. Moreover, when SPEI PM3-8 is in the range of –0.6 to 1.1, –0.9 to 0.8 and –0.8 to 2.3, the detrended yield increases in Shandong, Henan and Beijing. The yield increasing range was during normal water condition in Shandong and Henan, where precipitation was abundant. It indicated that the field management matched well with local water condition and thus allowed stable and high yield. Maize yield increase in these two provinces in the future can be realized by further improving water use efficiency and enhancing the stress resistance as well as yield stability. In Hebei and Beijing, the precipitation is less and thus the normal water condition cannot meet the high yield target. Increasing of water input and improving water use efficiency are both strategies for future yield increase. As global climate change became stronger and yield demands increased, the relationship between drought and maize yield became much closer in NCP too. The research of drought monitoring method and strategies for yield increase should be enhanced in the future, so as to provide strong supports for food security and agricultural sustainable development in China.
基金The project supported by National Natural Science Foundation of China under Grant Nos. 10047001 and 10275029, the State Key Basic Reserch Development Program under Grant No, G2000-0774-07, and the CAS Knowledge Innovation Project under Grant No. KJCX2-N11
文摘我们在中子星的内部在阶段转变，状态(曙光女神) 的方程，和相应集体半径的关系上学习模型参数的影响。数字分析证明重核子的联合常数在阶段上有细微影响转变和曙光女神，而是对粒子部分的明显的影响当袋子常数 B 和联合经常的 g 在阶段转变， EOS，和集体半径的关系上有重要影响时。我们发现那两个袋子常数 B 和联合的经常的 g 玩在对在混血儿的夸克之间的相互作用的描述的一样的角色担任主角。使用袋子常数计算的最大的团与试验性的数据决定了(从 175 ～ 200 兆电子伏) 在 1.4 ～的间隔的下降 1.7 太阳的质量。相应半径在结果与中子星的观察价值一致的 9.3 和 12 km.These 之间。第三个家庭的存在的可能性被讨论。第三个家庭的察觉可以在中子星内为阶段转变提供签名。
基金financially supported by the National Key Research and Development Program of China(2016YFD0300110,2016YFD0300101)the National Natural Science Foundation of China(31871558)the National Basic Research Program of China(973 Program,2015CB150401)。
文摘The uneven distribution of solar radiation is one of the main reasons for the variations in the yield gap between different regions in China and other countries of the world.In this study,different solar radiation levels were created by shading and the yield gaps induced by those levels were analyzed by measuring the aboveground and underground growth of maize.The experiments were conducted in Qitai,Xinjiang,China,in 2018 and 2019.The maize cultivars Xianyu 335 (XY335)and Zhengdan 958 (ZD958) were used with planting density of 12×10^(4) plants ha^(–1) under either high solar radiation (HSR)or low solar radiation (LSR,70%of HSR).The results showed that variation in the solar radiation resulted in a yield gap and different cultivars behaved differently.The yield gaps of XY335 and ZD958 were 8.9 and 5.8 t ha^(–1) induced by the decreased total intercepted photosynthetically active radiation (TIPAR) of 323.1 and 403.9 MJ m^(–2) from emergence to the maturity stage,respectively.The average yield of XY335 was higher than that of ZD958 under HSR,while the average yield of ZD958 was higher than that of XY335 under LSR.The light intercepted by the canopy and the photosynthetic rates both decreased with decreasing solar radiation.The aboveground dry matter decreased by 11.1% at silking and 21% at maturity,and the dry matter of vegetative organs and reproductive organs decreased by 9.8 and 20.9%at silking and by 12.1 and 25.5% at physiological maturity,respectively.Compared to the HSR,the root weights of XY335 and ZD958 decreased by 54.6 and 45.5%,respectively,in the 0–60 cm soil layer under LSR at silking stage.The aboveground and underground growth responses to different solar radiation levels explained the difference in yield gap.Selecting suitable cultivars can increase maize yield and reduce the yield gaps induced by variation of the solar radiation levels in different regions or under climate change.
基金supported by the National Key Research and Development Program of China(2016YFD0300110,2016YFD0300101)the National Natural Science Foundation of China(31871558)the National Basic Research Program of China(973 Program,2015CB150401)。
文摘Yield gap exists because the current attained actual grain yield cannot yet achieve the estimated yield potential. Chinese high yield maize belt has a wide span from east to west which results in different solar radiations between different regions and thus different grain yields. We used multi-site experimental data, surveyed farmer yield data, the highest recorded yield data in the literatures, and simulations with Hybrid-Maize Model to assess the yield gap and tried to reduce the yield gap by matching the solar radiation and plant density. The maize belt was divided into five regions from east to west according to distribution of accumulated solar radiation. The results showed that there were more than 5.8 Mg ha^(–1) yield gaps between surveyed farmer yield and the yield potential in different regions of China from east to west, which just achieved less than 65% of the yield potential. By analyzing the multi-site density experimental data, we found that the accumulated solar radiation was significantly correlated to optimum plant density which is the density with the highest yield in the multi-site density experiment(y=0.09895 x–32.49, P<0.01), according to which the optimum plant densities in different regions from east to west were calculated. It showed that the optimum plant density could be increased by 60.0, 55.2, 47.3, 84.8, and 59.6% compared to the actual density, the grain yield could be increased by 20.2, 18.3, 10.9, 18.1, and 15.3% through increasing plant density, which could reduce the yield gaps of 33.7, 23.0, 13.4, 17.3, and 10.4% in R(region)-1, R-2, R-3, R-4, and R-5, respectively. This study indicates that matching maize plant density and solar radiation is an effective approach to reduce yield gaps in different regions of China.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11075063,11073033,11247312 and 11103047.
文摘In the relativistic mean field approximation,the relativistic energy losses of the nucleon direct Urca processes are studied in the degenerate baryon matter of neutron stars.We investigate the effects of hyperon degrees of freedom and the isovector scalar interaction which is considered by exchangingδmeson on the nucleon direct Urca processes in neutron star matter.The results indicate that the existence of hyperons decreases the abundance of protons and leptons and can sharply suppress the neutrino emissivity of the nucleon direct Urca processes,while it has only a little influence on the neutrino luminosity for a fixed neutron star whetherδmesons appear in a neutron star or not.However,the presence ofδmesons can result in obvious growth in the neutrino emissivity and luminosity which will speed up the cooling rate for the nonsuperfluid neutron star.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10675024,11075063 and 11265009the National Found for Fostering Talents of Basic Science under Grant No J1103202.
文摘We investigate the influence of the energy gap(Δ)of the color-flavor locked(CFL)quark phase on the bulk properties of hybrid stars.The relativistic mean field model is used for hadronic matter and the MIT bag model for CFL quark matter.In our calculation results,we find that with the increase of the CFL energy gap there exists a transition behavior,which goes from the hadron star range through the transition range into the CFL quark star range.The observation data of PRS J1614-2230 are in the hadron star range(withΔ<40MeV).We also find that with hyperons the equation of state(EOS)for the hybrid star matter with the CFL quark matter core has a small change,which can be disregarded.
基金Supported by the National Natural Science Foundation of China under Grants Nos 10675024 and 11075063the National Fundamental Fund Project in Subsidy Funds of Personnel Training J0730311.
文摘Within the framework of the relativistic mean field theory,we investigate the ^(1)S_(0) superfluidity (SF) of A hyperons in neutron star (NS) matter including σ^(*) and φ mesons.The energy gap of ∧ hyperons is calculated with the Nijmegen one-boson-exchange potentials for a (∧∧) pair. The parameter set we use is in line with the recent experimental data △B_(∧∧) ~ 1.01 ± 0.20_+0.18-0.11 MeV.It is found that with σ^(*) and φ mesons the pairing energy gap △F of ∧ hyperons and the corresponding SF critical temperature T_(C∧) are suppressed.In addition the NS mass range of ∧ hyperon SF is enlarged obviously.
基金by the National Natural Science Foundation of China under Grant Nos 10675024 and 11075063the National Fundamental Project for Subsidy Funds of Personnel Training J0730311.
文摘In the relativistic mean field approximation,the relativistic energy losses of the direct Urca processes with nucleons(N-DURCA)and hyperons(Y-DURCA)are studied in the degenerate baryon matter of neutron stars.We investigate the effects of hyperon degrees of freedom and the Y-DURCA processes on the N-DURCA processes,and the total neutrino emissivity of neutron star matter.The results show that the existence of hyperons decreases the abundance of protons and leptons,and can sharply suppress the neutrino emissivity of the N-DURCA processes.
基金Supported in part by the National Natural Science Foundation of China under Grant No.19875022the Foundation of Education Ministry(197018304)Center of Theoretical Nuclear Physics,National Laboratory of Heavy Ion Accelerator in Lanzhou.
文摘A new effect of self-consistency in the relativistic Hartree-Fock(HF)approximation suggested previously is con firmed by a renormalized calculation with the on-shell renormalization conditions.Two self-consistency schemes,ne requiring self-consistency in the HF potential(scheme P)and the other in the baryon propagator(scheme BP),are studied.It is pointed out that the on-shell renormalization conditions make the self-consistency require-ment in scheme P automatically satisfied.Our calculated results show that scheme P is a good approximation to scheme BP for the calculation of the baryon propagator and the self-consistency in scheme BP diminishes the continuum part of the spectral representation for the baryon propagator,while scheme P yields a baryon propagator which is the same as the HF result contributed by the single particle part of the above spectral representation alone.Further,it is demonstrated that the region of validity of the quasi-particle approximationmay depend on the renormalization conditions.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11075063,11073033,11247312 and 11103047.
文摘We investigate the nucleon superfluidity in the^(1)S_(0)channel in neutron star matter using the relativistic mean field theory and the BCS theory.We discuss particularly the influence of the isovector scalar interaction which is considered by exchangingδmeson on the nucleon superfluidity.It is found that theδmeson leads to a growth of the nucleon^(1)S_(0)pairing energy gaps in a middle density range of the existing nucleon superfluidity.In addition,when the densityρB>0.36 fm^(-3),the proton^(1)S_(0)pairing energy gap obviously decreases.The density range of the proton^(1)S_(0)superfluidity is narrowed due to the presence ofδmesons.In our results,theδmeson not only changes the EOS and bulk properties but also changes the cooling properties of neutron stars.
