In order to apply overbooking idea in Chinese railway freight industry to improve revenue, a Markov decision process(dynamic programming) model for railway freight reservation was formulated and the overbooking limit ...In order to apply overbooking idea in Chinese railway freight industry to improve revenue, a Markov decision process(dynamic programming) model for railway freight reservation was formulated and the overbooking limit level was proposed as a control policy. However, computing the dynamic programming treatment needs six nested loops and this will be burdensome for real-world problems. To break through the calculation limit, the properties of value function were analyzed and the overbooking protection level was proposed to reduce the calculating quantity. The simulation experiments show that the overbooking protection level for the lower-fare class is higher than that for the higher-fare class, so the overbooking strategy is nested by fare class. Besides, by analyzing the influence on the overbooking strategy of freight arrival probability and cancellation probability, the proposed approach is efficient and also has a good application prospect in reality. Also, compared with the existing reservation(FCFS), the overbooking strategy performs better in the fields of vacancy reduction and revenue improvement.展开更多
Trichobezoar is a rare intriguing disorder in which swallowed hairs accumulates in the stomach. Being indigestible and slippery, it could not be propulsed and becomes entrapped within the stomach. Large amounts can th...Trichobezoar is a rare intriguing disorder in which swallowed hairs accumulates in the stomach. Being indigestible and slippery, it could not be propulsed and becomes entrapped within the stomach. Large amounts can thus accumulate over the years forming a hair ball. Rapunzel syndrome is a variant where hair accumulation reaches the small gut and beyond in some cases. Although the syndrome has been known for many years, only 24 cases have been reported in the literature and the discovery of a new case is always surprising. In this report, we present two cases discovered within a period of three months. One of them was pregnant and had small bowel intussusception and perforation, a very rare combination. We hereby add two more cases to the literature. To our knowledge, this is the first report on two cases of Rapunzel syndrome, the diagnosis of which demands a high index of suspicion.展开更多
The California least tern （Sternula antillarum browni） is an endangered species. The two largest colonies of this bird species in the San Francisco Bay, California, USA, are located 23 km apart at Alameda Point and ...The California least tern （Sternula antillarum browni） is an endangered species. The two largest colonies of this bird species in the San Francisco Bay, California, USA, are located 23 km apart at Alameda Point and Hayward Regional Shoreline. The Alameda Point colony, on the former Naval Air Station, Alameda, has grown at an average rate of 9.2% per year since its discovery in 1976 and has a nesting density ranging from 1-153 nests per ha. Long-term breeding success at Alameda has averaged 0.86 fledglings per breeding pair. Least tems began appearing in 2003, at an island in Hayward enhanced with substrate mediums and social attraction devices. Successful breeding attempts have been observed at the Hayward colony since 2006. The Hayward colony has grown at an average rate of 51.5% per year, has a nesting density ranging from 33-333 nests per ha and long-term breeding success average of 0.87 fledglings per breeding pair. Dropped fish have been collected from both colonies, and silversides （family Atherinopsidae） are the dominant prey. Alameda terns forage on a greater variety of species than the Hayward terns. The regression results indicate the importance of Northern anchovy （Engraulis mordax） to the breeding success of the Alameda colony.展开更多
The paper extends the Adle and Dumas's simple regression approach of foreign currency hedging to the case of exposure to multiple foreign currencies and provides extension methodology.
基金Project(2010QZZD021)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2015F024)supported by China Railway Science and Technology Research Development Program
文摘In order to apply overbooking idea in Chinese railway freight industry to improve revenue, a Markov decision process(dynamic programming) model for railway freight reservation was formulated and the overbooking limit level was proposed as a control policy. However, computing the dynamic programming treatment needs six nested loops and this will be burdensome for real-world problems. To break through the calculation limit, the properties of value function were analyzed and the overbooking protection level was proposed to reduce the calculating quantity. The simulation experiments show that the overbooking protection level for the lower-fare class is higher than that for the higher-fare class, so the overbooking strategy is nested by fare class. Besides, by analyzing the influence on the overbooking strategy of freight arrival probability and cancellation probability, the proposed approach is efficient and also has a good application prospect in reality. Also, compared with the existing reservation(FCFS), the overbooking strategy performs better in the fields of vacancy reduction and revenue improvement.
文摘Trichobezoar is a rare intriguing disorder in which swallowed hairs accumulates in the stomach. Being indigestible and slippery, it could not be propulsed and becomes entrapped within the stomach. Large amounts can thus accumulate over the years forming a hair ball. Rapunzel syndrome is a variant where hair accumulation reaches the small gut and beyond in some cases. Although the syndrome has been known for many years, only 24 cases have been reported in the literature and the discovery of a new case is always surprising. In this report, we present two cases discovered within a period of three months. One of them was pregnant and had small bowel intussusception and perforation, a very rare combination. We hereby add two more cases to the literature. To our knowledge, this is the first report on two cases of Rapunzel syndrome, the diagnosis of which demands a high index of suspicion.
文摘The California least tern （Sternula antillarum browni） is an endangered species. The two largest colonies of this bird species in the San Francisco Bay, California, USA, are located 23 km apart at Alameda Point and Hayward Regional Shoreline. The Alameda Point colony, on the former Naval Air Station, Alameda, has grown at an average rate of 9.2% per year since its discovery in 1976 and has a nesting density ranging from 1-153 nests per ha. Long-term breeding success at Alameda has averaged 0.86 fledglings per breeding pair. Least tems began appearing in 2003, at an island in Hayward enhanced with substrate mediums and social attraction devices. Successful breeding attempts have been observed at the Hayward colony since 2006. The Hayward colony has grown at an average rate of 51.5% per year, has a nesting density ranging from 33-333 nests per ha and long-term breeding success average of 0.87 fledglings per breeding pair. Dropped fish have been collected from both colonies, and silversides （family Atherinopsidae） are the dominant prey. Alameda terns forage on a greater variety of species than the Hayward terns. The regression results indicate the importance of Northern anchovy （Engraulis mordax） to the breeding success of the Alameda colony.
文摘The paper extends the Adle and Dumas's simple regression approach of foreign currency hedging to the case of exposure to multiple foreign currencies and provides extension methodology.
