A P-vector method was optimized using variational data assimilation technique, with which the vertical structures and seasonal variations of zonal velocities and transports were investigated. The results showed that w...A P-vector method was optimized using variational data assimilation technique, with which the vertical structures and seasonal variations of zonal velocities and transports were investigated. The results showed that westward and eastward flowes occur in the Luzon Strait in the same period in a year. However the net volume transport is westward. In the upper level (0m -500m),the westward flow exits in the middle and south of the Luzon Strait, and the eastward flow exits in the north. There are two centers of westward flow and one center of eastward flow. In the middle of the Luzon Strait, westward and eastward flowes appear alternately in vertical direction. The westward flow strengthens in winter and weakens in summer. The net volume transport is strong in winter (5.53 Sv) but weak in summer (0.29 Sv). Except in summer, the volume transport in the upper level accounts for more than half of the total volume transport (0m bottom). In summer, the net volume transport in the upper level is eastward (1.01 Sv), but westward underneath.展开更多
The article assesses the determinants of farmers＇ decisions to participate in organic farming, eliciting farmers risk preferences and empirically analysing farmer＇s sources of risk and risk management strategies. Th...The article assesses the determinants of farmers＇ decisions to participate in organic farming, eliciting farmers risk preferences and empirically analysing farmer＇s sources of risk and risk management strategies. The ordered probit results indicate that older farmers, who are less risk averse and reside in the sub-ward Ogagwini, Ezigani and Hwayi were more likely to be certified organic. Similarly, the propensity to adopt organic farming is positively correlated to household size, livestock ownership, asset base and tenure security. At higher pay-offs, farmers were intermediate to moderately risk-averse, with little variation according to personal characteristics. In general, price, production and financial risks were perceived as important sources of risk. Seven principal components, explaining 66.13% of the variation were extracted. Socio-economic factors having a significant effect on the various sources of risk were age, gender, education, location, information access and risk taking ability. The dimensions of risk strategies were named as diversification, precautionary savings and social networks. Results provide practical insights for policy changes relevant in motivating the adoption of organic practices, increasing smallholder farmers＇ capacity to manage risk and driving growth in the organic food market.展开更多
This paper is a further investigation of large deviation for partial and random sums of random variables, where {Xn,n ≥ 1} is non-negative independent identically distributed random variables with a common heavy-tail...This paper is a further investigation of large deviation for partial and random sums of random variables, where {Xn,n ≥ 1} is non-negative independent identically distributed random variables with a common heavy-tailed distribution function F on the real line R and finite mean μ∈ R. {N(n),n ≥ 0} is a binomial process with a parameter p ∈ (0,1) and independent of {Xn,n ≥ 1}; {M(n),n ≥ 0} is a Poisson process with intensity λ > 0, Sn = ΣNn i=1 Xi-cM(n). Suppose F ∈ C, we futher extend and improve some large deviation results. These results can apply to certain problems in insurance and finance.展开更多
基金Supported by the Major State Basic Research Program (No. G1999043810) Open Laboratory for Tropical Marine Environmental Dynamics (LED)+2 种基金 South China Sea Institute of Oceanology Chinese Academy of Sciences and the NSFC (No. 40306004).
文摘A P-vector method was optimized using variational data assimilation technique, with which the vertical structures and seasonal variations of zonal velocities and transports were investigated. The results showed that westward and eastward flowes occur in the Luzon Strait in the same period in a year. However the net volume transport is westward. In the upper level (0m -500m),the westward flow exits in the middle and south of the Luzon Strait, and the eastward flow exits in the north. There are two centers of westward flow and one center of eastward flow. In the middle of the Luzon Strait, westward and eastward flowes appear alternately in vertical direction. The westward flow strengthens in winter and weakens in summer. The net volume transport is strong in winter (5.53 Sv) but weak in summer (0.29 Sv). Except in summer, the volume transport in the upper level accounts for more than half of the total volume transport (0m bottom). In summer, the net volume transport in the upper level is eastward (1.01 Sv), but westward underneath.
文摘The article assesses the determinants of farmers＇ decisions to participate in organic farming, eliciting farmers risk preferences and empirically analysing farmer＇s sources of risk and risk management strategies. The ordered probit results indicate that older farmers, who are less risk averse and reside in the sub-ward Ogagwini, Ezigani and Hwayi were more likely to be certified organic. Similarly, the propensity to adopt organic farming is positively correlated to household size, livestock ownership, asset base and tenure security. At higher pay-offs, farmers were intermediate to moderately risk-averse, with little variation according to personal characteristics. In general, price, production and financial risks were perceived as important sources of risk. Seven principal components, explaining 66.13% of the variation were extracted. Socio-economic factors having a significant effect on the various sources of risk were age, gender, education, location, information access and risk taking ability. The dimensions of risk strategies were named as diversification, precautionary savings and social networks. Results provide practical insights for policy changes relevant in motivating the adoption of organic practices, increasing smallholder farmers＇ capacity to manage risk and driving growth in the organic food market.
文摘This paper is a further investigation of large deviation for partial and random sums of random variables, where {Xn,n ≥ 1} is non-negative independent identically distributed random variables with a common heavy-tailed distribution function F on the real line R and finite mean μ∈ R. {N(n),n ≥ 0} is a binomial process with a parameter p ∈ (0,1) and independent of {Xn,n ≥ 1}; {M(n),n ≥ 0} is a Poisson process with intensity λ > 0, Sn = ΣNn i=1 Xi-cM(n). Suppose F ∈ C, we futher extend and improve some large deviation results. These results can apply to certain problems in insurance and finance.
