This paper investigates an optimal investment strategy on consumption and portfolio problem, in which the investor must withdraw funds continuously at a given rate. By analyzing the evolving process of wealth, we give...This paper investigates an optimal investment strategy on consumption and portfolio problem, in which the investor must withdraw funds continuously at a given rate. By analyzing the evolving process of wealth, we give the definition of safe-region for investment. Moreover, in order to obtain the target wealth as quickly as possible, using Bellman dynamic programming principle, we get the optimal investment strategy and corresponding necessary expected time. At last we give some numerical computations for a set of different parameters.展开更多
The Chinese automotive indus-try has a history of nearly 50 years with the vehicle population up to 15 million by now. With sustainable national economic boom and growth of personal income, more and more private cars ...The Chinese automotive indus-try has a history of nearly 50 years with the vehicle population up to 15 million by now. With sustainable national economic boom and growth of personal income, more and more private cars will appear in China. It is predicated that the private car will keep a stable growing trend in the future. And along with the de-velopment of the automotive indus-try and increase of the vehicle parc, environment pollution展开更多
Objectives:Papua New Guinea(PNG)has among the highest rates of sexually transmitted infections(STIs)globally and is committed to reducing their incidence.The Syphilis Interventions Towards Elimination(SITE)model was u...Objectives:Papua New Guinea(PNG)has among the highest rates of sexually transmitted infections(STIs)globally and is committed to reducing their incidence.The Syphilis Interventions Towards Elimination(SITE)model was used to explore the expected impact and cost of alternative syphilis intervention scale-up scenarios.Methods:SITE is a dynamical model of syphilis transmission among adults 15-49 years.Individuals are divided into nine groups based on sexual behaviour and into six stages of infection.The model was calibrated to PNG using data from routine surveillance,biobehavioural surveys,research studies and program records.Inputs included syphilis prevalence,risk behaviours,intervention coverage and service delivery unit costs.Scenarios compared different interventions(clinical treatment,contact tracing,syphilis screening,and condom promotion)for incidence and cost per infection averted over 2021-2030.Results:Increasing treatment coverage of symptomatic primary/secondary-stage syphilis cases from 25-35%in 2020 to 60%from 2023 onwards reduced estimated incidence over 2021-2030 by 55%,compared to a scenario assuming constant coverage at 2019-2020 levels.The introduction of contact tracing in 2020,assuming 0.4 contacts per symptomatic person treated,reduced incidence over 2021-2030 by 10%.Increasing screening coverage by 20-30 percentage points from the 2019-2020 level reduced incidence over 2021-2030 by 3e16%depending on the target population.Scaling-up clinical,symptom-driven treatment and contact tracing had the lowest cost per infection averted,followed by condom promotion and periodic screening of female sex workers and men who have sex with men.Conclusions:PNG could considerably reduce its syphilis burden by scaling-up clinical treatment and contact tracing alongside targeted behavioural risk reduction interventions.SITE is a useful tool countries can apply to inform national STI programming and resource allocation.展开更多
文摘This paper investigates an optimal investment strategy on consumption and portfolio problem, in which the investor must withdraw funds continuously at a given rate. By analyzing the evolving process of wealth, we give the definition of safe-region for investment. Moreover, in order to obtain the target wealth as quickly as possible, using Bellman dynamic programming principle, we get the optimal investment strategy and corresponding necessary expected time. At last we give some numerical computations for a set of different parameters.
文摘The Chinese automotive indus-try has a history of nearly 50 years with the vehicle population up to 15 million by now. With sustainable national economic boom and growth of personal income, more and more private cars will appear in China. It is predicated that the private car will keep a stable growing trend in the future. And along with the de-velopment of the automotive indus-try and increase of the vehicle parc, environment pollution
基金Financial support for this work was provided by the World Health Organization(WHO)PNG Country Office.
文摘Objectives:Papua New Guinea(PNG)has among the highest rates of sexually transmitted infections(STIs)globally and is committed to reducing their incidence.The Syphilis Interventions Towards Elimination(SITE)model was used to explore the expected impact and cost of alternative syphilis intervention scale-up scenarios.Methods:SITE is a dynamical model of syphilis transmission among adults 15-49 years.Individuals are divided into nine groups based on sexual behaviour and into six stages of infection.The model was calibrated to PNG using data from routine surveillance,biobehavioural surveys,research studies and program records.Inputs included syphilis prevalence,risk behaviours,intervention coverage and service delivery unit costs.Scenarios compared different interventions(clinical treatment,contact tracing,syphilis screening,and condom promotion)for incidence and cost per infection averted over 2021-2030.Results:Increasing treatment coverage of symptomatic primary/secondary-stage syphilis cases from 25-35%in 2020 to 60%from 2023 onwards reduced estimated incidence over 2021-2030 by 55%,compared to a scenario assuming constant coverage at 2019-2020 levels.The introduction of contact tracing in 2020,assuming 0.4 contacts per symptomatic person treated,reduced incidence over 2021-2030 by 10%.Increasing screening coverage by 20-30 percentage points from the 2019-2020 level reduced incidence over 2021-2030 by 3e16%depending on the target population.Scaling-up clinical,symptom-driven treatment and contact tracing had the lowest cost per infection averted,followed by condom promotion and periodic screening of female sex workers and men who have sex with men.Conclusions:PNG could considerably reduce its syphilis burden by scaling-up clinical treatment and contact tracing alongside targeted behavioural risk reduction interventions.SITE is a useful tool countries can apply to inform national STI programming and resource allocation.
