To more accurately answer the questions “who will feed China?” and “whether Chinese people can feed themselves?”, we proposed a concept of agricultural support capacity, defined as the population that can be fed b...To more accurately answer the questions “who will feed China?” and “whether Chinese people can feed themselves?”, we proposed a concept of agricultural support capacity, defined as the population that can be fed by energy, protein and fat from food, respectively, according to nutritional intake standards. In this study, we established models to measure this, based on analysis of China’s agricultural support capacity and how this changes under self-sufficiency and open conditions, in addition to the degrees of external dependence. Our results show that, since 2007, even without foreign resources, the energy, protein, superior protein and fat obtained from domestic agriculture had been able to feed the Chinese. However, the use of foreign resources increased and strengthened China’s agricultural support capacity, in addition to improving food diversity, optimizing nutrition, assisting in the regulation of food surplus and deficiency, and providing feed for the animal breeding industry. For the past decade, China’s degree of external dependence on energy from cereals has been relatively low, however, the degrees external dependence on superior protein and fat has increased steadily at a certain rate and have been over the national food security warning level. Therefore, China still has great demand for agricultural products from other regions of the world.展开更多
The distortion of GDP and foreign trade data has exaggerated China＇s foreign trade dependence degree and external imbalance degree. The distortion of GDP is mainly caused by the difference between the exchange rate m...The distortion of GDP and foreign trade data has exaggerated China＇s foreign trade dependence degree and external imbalance degree. The distortion of GDP is mainly caused by the difference between the exchange rate method and purchasing power parity （PPP） estimation. The distortion of trade data includes double counting of customs statistics as well as the discrepancy between the international trade flows of goods and of capital caused by the ownership issue. The re-estimation of China＇s trade dependence degree and external imbalance degree reveals that according to official statistics, in 2007 the dependence degree of China＇s foreign trade decreased to 31.59 percent from 68.02 percent and its imbalance degree decreased to 2.11 percent from 10.13 percent. Therefore, it is utterly groundless to accuse China of ＂manipulating the exchange rate.＂展开更多
This paper considers a class of ratio-dependent Holling-Taner model with infinite delay and prey harvest, which is of periodic coefficients. By means of the coincidence degree theory, a set of sufficient conditions fo...This paper considers a class of ratio-dependent Holling-Taner model with infinite delay and prey harvest, which is of periodic coefficients. By means of the coincidence degree theory, a set of sufficient conditions for the existence of at least two positive periodic solutions of this model is established.展开更多
A delayed semi-ratio-dependent predator-prey system in a periodic environment is investigated in this paper.By using a continuation theorem based on Gaines and Mawhin's coincidence degree,the global existence of p...A delayed semi-ratio-dependent predator-prey system in a periodic environment is investigated in this paper.By using a continuation theorem based on Gaines and Mawhin's coincidence degree,the global existence of positive periodic solution is studied.A set of easily verifiable sufficient conditions are obtained.展开更多
We study a non-autonomous ratio-dependent predator-prey model with exploited terms. This model is of periodic coefficients, which incorporates the periodicity of the varying environment. By means of the coincidence de...We study a non-autonomous ratio-dependent predator-prey model with exploited terms. This model is of periodic coefficients, which incorporates the periodicity of the varying environment. By means of the coincidence degree theory, we establish sufficient conditions for the existence of at least four positive periodic solutions of this model.展开更多
In order to supply better accordance for mod eling and simulation of complex networks, a new degree dependence entropy （DDE） descriptor is proposed to describe the degree dependence relationship and corre sponding c...In order to supply better accordance for mod eling and simulation of complex networks, a new degree dependence entropy （DDE） descriptor is proposed to describe the degree dependence relationship and corre sponding characteristic in this paper. First of all, degrees of vertices and the shortest path lengths between all pairs of ,ertices are computed. Then the degree dependence matrices under different shortest path lengths are con structed. At last the DDEs are extracted from the degree dependence matrices. Simulation results show that the DDE descriptor can reflect the complexity of degree dependence relationship in complex networks; high DDE indicates complex degree dependence relationship; low DDE indicates the opposite one. The DDE can be seen as a quantitative statistical characteristic, which is meaningful for networked modeling and simulation.展开更多
With k_8/k_(16), the ratio of the hydrolytic rate-constants of p-nitrophenyl octanoate (C8) to hexadecanoate (C16), as the indicator of the degree of aggregation, the linear dependence of the deg- ree of aggregation o...With k_8/k_(16), the ratio of the hydrolytic rate-constants of p-nitrophenyl octanoate (C8) to hexadecanoate (C16), as the indicator of the degree of aggregation, the linear dependence of the deg- ree of aggregation on solvent aggregating power (SAgP) has been established in five aquiorgano sol- vents, each within a certain range of volume fraction ( values) of the organic cosolvent. The mea- ning of this linearity has been discussed.展开更多
文摘To more accurately answer the questions “who will feed China?” and “whether Chinese people can feed themselves?”, we proposed a concept of agricultural support capacity, defined as the population that can be fed by energy, protein and fat from food, respectively, according to nutritional intake standards. In this study, we established models to measure this, based on analysis of China’s agricultural support capacity and how this changes under self-sufficiency and open conditions, in addition to the degrees of external dependence. Our results show that, since 2007, even without foreign resources, the energy, protein, superior protein and fat obtained from domestic agriculture had been able to feed the Chinese. However, the use of foreign resources increased and strengthened China’s agricultural support capacity, in addition to improving food diversity, optimizing nutrition, assisting in the regulation of food surplus and deficiency, and providing feed for the animal breeding industry. For the past decade, China’s degree of external dependence on energy from cereals has been relatively low, however, the degrees external dependence on superior protein and fat has increased steadily at a certain rate and have been over the national food security warning level. Therefore, China still has great demand for agricultural products from other regions of the world.
基金supported by the National Natural Science Foundation of China(Grant No.70810107020)National Social Science Fund of China(Grant No.11CJL038)
文摘The distortion of GDP and foreign trade data has exaggerated China＇s foreign trade dependence degree and external imbalance degree. The distortion of GDP is mainly caused by the difference between the exchange rate method and purchasing power parity （PPP） estimation. The distortion of trade data includes double counting of customs statistics as well as the discrepancy between the international trade flows of goods and of capital caused by the ownership issue. The re-estimation of China＇s trade dependence degree and external imbalance degree reveals that according to official statistics, in 2007 the dependence degree of China＇s foreign trade decreased to 31.59 percent from 68.02 percent and its imbalance degree decreased to 2.11 percent from 10.13 percent. Therefore, it is utterly groundless to accuse China of ＂manipulating the exchange rate.＂
文摘This paper considers a class of ratio-dependent Holling-Taner model with infinite delay and prey harvest, which is of periodic coefficients. By means of the coincidence degree theory, a set of sufficient conditions for the existence of at least two positive periodic solutions of this model is established.
文摘A delayed semi-ratio-dependent predator-prey system in a periodic environment is investigated in this paper.By using a continuation theorem based on Gaines and Mawhin's coincidence degree,the global existence of positive periodic solution is studied.A set of easily verifiable sufficient conditions are obtained.
基金Supported by the China Postdoctoral Science Foundation (20060400267)
文摘We study a non-autonomous ratio-dependent predator-prey model with exploited terms. This model is of periodic coefficients, which incorporates the periodicity of the varying environment. By means of the coincidence degree theory, we establish sufficient conditions for the existence of at least four positive periodic solutions of this model.
基金supported by the National Natural Science Foundation of China(Grants Nos.61174156,61273189,71073172,61174035,61203140)
文摘In order to supply better accordance for mod eling and simulation of complex networks, a new degree dependence entropy （DDE） descriptor is proposed to describe the degree dependence relationship and corre sponding characteristic in this paper. First of all, degrees of vertices and the shortest path lengths between all pairs of ,ertices are computed. Then the degree dependence matrices under different shortest path lengths are con structed. At last the DDEs are extracted from the degree dependence matrices. Simulation results show that the DDE descriptor can reflect the complexity of degree dependence relationship in complex networks; high DDE indicates complex degree dependence relationship; low DDE indicates the opposite one. The DDE can be seen as a quantitative statistical characteristic, which is meaningful for networked modeling and simulation.
基金Project supported by the National Natural Science Foundation of China.
文摘With k_8/k_(16), the ratio of the hydrolytic rate-constants of p-nitrophenyl octanoate (C8) to hexadecanoate (C16), as the indicator of the degree of aggregation, the linear dependence of the deg- ree of aggregation on solvent aggregating power (SAgP) has been established in five aquiorgano sol- vents, each within a certain range of volume fraction ( values) of the organic cosolvent. The mea- ning of this linearity has been discussed.
文摘目的探索美沙酮维持治疗(methadone maintenance treatment,MMT)对海洛因依赖(heroin dependence,HD)患者大脑拓扑特性度中心性(degree centrality,DC)的影响及其与心理行为学的相关性。材料与方法回顾性分析2016年1月至2017年12月于西安市灞桥区美沙酮门诊招募的41名正在接受MMT的HD患者,采集静息态功能磁共振成像(functional magnetic resonance imaging,fMRI)数据,评估稽延性戒断症状与渴求评分,纵向随访一年。对影像数据进行DC分析,并采用配对样本t检验进行纵向比较,差异脑区与心理学指标进行相关分析。结果HD患者入组时与MMT一年后稽延性戒断症状评分差异存在统计学意义(Z=3.004,P=0.003),渴求评分差异无统计学意义(Z=0.872,P=0.383)。与基线相比,HD患者经过MMT一年后,双侧丘脑、尾状核、壳核与左侧苍白球的DC降低;右侧舌回与距状回的DC值升高(Gaussian random field校正,单体素水平P<0.001,团块体素水平P<0.01,团块体素>95)。双侧尾状核及左侧苍白球DC值与戒断症状呈负相关性(r=-0.417,P=0.030;r=-0.392,P=0.043;r=-0.383,P=0.049),双侧壳核及左侧苍白球DC值的变化量与渴求的变化量呈正相关性(r=0.410,P=0.008;r=0.332,P=0.034;r=0.395,P=0.011)。结论美沙酮可能通过降低HD患者纹状体在成瘾奖赏脑网络中的中心性,从而调节HD患者戒毒后的稽延性戒断症状与心理渴求;同时可能抑制了冲动性,增强了视觉核心脑区的活动。该研究结果可以为美沙酮对HD患者治疗的神经机制提供影像学依据。
