Optimal Control Policy of M/G/1 Queueing System with Delayed Randomized Multiple Vacations Under the Modified Min(N,D)-Policy Control

Based on the number of customers and the server’s workload,this paper proposes a modified Min(N,D)-policy and discusses an M/G/1 queueing model with delayed randomized multiple vacations under such a policy.Applying the well-known stochastic decomposition property of the steady-state queue size,the probability generating function of the steady-state queue length distribution is obtained.Moreover,the explicit expressions of the expected queue length and the additional queue length distribution are derived by some algebraic manipulations.Finally,employing the renewal reward theorem,the explicit expression of the long-run expected cost per unit time is given.Furthermore,we analyze the optimal policy for economizing the expected cost and compare the optimal Min(N,D)-policy with the optimal N-policy and the optimal D-policy by using numerical examples.

An assessment of China's joint prevention and control policy on sulfur dioxide emissions reduction:A spatial econometric analysis

Sulfur dioxide(SO_(2))is a typical pollutant that affects human health,climate,and environmental and ecological conditions.China has been experiencing high concentrations of SO_(2),particularly in urban areas,since the 1990s.In 2010,a"joint prevention and control"(JPC)policy was issued to address air pollution problems and strengthen the regulation of SO_(2)emissions.This study aimed to describe the mitigation effects of this policy on SO_(2)emissions in 116 Chinese cities from 2003 to 2017.We applied global and local Moran's I indices to confirm the presence of significant spatial autocorrelation in SO_(2)emissions and constructed four spatial models to assess the effect of the JPC policy in reducing SO_(2)emissions and its transmission mechanism.We found that the policy decreased SO_(2)emissions by 1.89×10^(4)tons,S0_(2)intensity by 1.70 tons per km^(2),and S0_(2)per capita of 158.49 tons per 10,000 people in each city,on average,all of which are significant changes.The empirical results also show that population growth,economic structure,and environmental protection significantly decrease SO_(2)emissions.Finally,we recommended policies to encourage regional cooperation under the JPC policy,with the aim of promoting furtherreductions in SO_(2)emissions.

Simulation-based optimization of control policy on multi-echelon inventory system for fresh agricultural products

As fresh agricultural products are perishable and vulnerable,reducing inventory cost is a strategic target for supply chain enterprises.How to design a reliable multi-echelon inventory control policy is still a great challenge.Therefore,the inventory cost of a three-level fresh agricultural products inventory system was firstly mathematically analyzed.Then,the simulation-based optimization model of the multi-echelon inventory system for fresh agricultural products was proposed by using the Flexsim simulation software and the improved particle swarm optimization algorithm.Finally,the multi-echelon inventory system is simulated based on a large number of survey data.Simulation results demonstrate that the proposed simulation-based optimization model of multi-echelon inventory system for fresh agricultural products can provide decision-making and technical support for the formulation of inventory control policy,and also it shows that the modeling of system simulation is an effective method to solve the problem of complex system.

Response surface modeling-based source contribution analysis and VOC emission control policy assessment in a typical ozone-polluted urban Shunde,China

To develop a sound ozone（O_3） pollution control strategy,it is important to well understand and characterize the source contribution due to the complex chemical and physical formation processes of O_3.Using the ＂Shunde＂ city as a pilot summer case study,we apply an innovative response surface modeling（RSM） methodology based on the Community Multi-Scale Air Quality（CMAQ） modeling simulations to identify the O_3 regime and provide dynamic analysis of the precursor contributions to effectively assess the O_3 impacts of volatile organic compound（VOC） control strategy.Our results show that Shunde is a typical VOC-limited urban O_3 polluted city.The ＂Jiangmen＂ city,as the main upper wind area during July 2014,its VOCs and nitrogen oxides（NO_x） emissions make up the largest contribution（9.06%）.On the contrary,the contribution from local（Shunde） emission is lowest（6.35%） among the seven neighbor regions.The local VOCs industrial source emission has the largest contribution comparing to other precursor emission sectors in Shunde.The results of dynamic source contribution analysis further show that the local NO_x control could slightly increase the ground O_3 under low（10.00%） and medium（40.00%）reduction ratios,while it could start to turn positive to decrease ground O_3 under the high NO_x abatement ratio（75.00%）.The real-time assessment of O_3 impacts from VOCs control strategies in Pearl River Delta（PRD） shows that the joint regional VOCs emission control policy will effectively reduce the ground O_3 concentration in Shunde.

A Study of China’s Air Pollution Prevention and Control Policy Framework from a Policy Instrument Perspective

Environmental pollution caused by rapid economic development like that seen in China over the past twenty years poses various threats to human health. People have started to place much more of an emphasis on environmental security, working to find a balance between sustainability and economic growth. In recent years, air pollution has emerged as a highly discussed topic of social and environmental relevance in China, due in part to persistent smog that affects everyday life and causes serious harm to human health. Although air pollution is normally associated with human activity, is can be caused by natural processes such as eruptions and forest fires, but is always characterized by the release of certain substances into the atmosphere which, when present in certain concentrations or for given durations, can harm human health, daily life, productivity, and other aspects. In humans, it mainly affects the respiratory system, notably the lungs, as well as the immune system. A series of studies both in China and overseas have shown, in certain cases, even low concentrations of air pollution can pose a great threat to human health. In this study, we conducted an analysis of air quality policies, focusing on the 2018 revision of the People’s Republic of China’s Law on the Prevention and Control of Air Pollution(LPCAP). We utilized the content analysis method and Strauss and Corbin’s grounded theory to construct a policy framework, demarcate analysis units, code and classify policy texts, determine descriptive statistics, and analyze dimensional interactions. We used two dimensions(basic policy instruments classified as demand-, supply-, and environment-side;and air carrying capacity) to quantify and analyze the LPCAP, which enabled us to analyze the deficiencies and conflicts within policy instruments. The results show a higher utilization frequency of environment-side policy instruments, particularly regulation management and strategic measures. This reflects efforts by the government to create a favorable environment for improving air quality. Additionally, supply-side policy instruments are used far less frequently than environment-side policy instruments. Air quality legal policies and pollution control measures mainly consist of environment-side policy instruments;ecological thinking and air quality policies that are based mainly on supply-side and environment-side policy instruments;and social coordination policies that mainly use environment-side policy instruments. Based on the results of this study, we recommend an increase in the number of supply-and demand-side policy instruments, particularly the latter which includes promoting ecological thinking amongst citizens, to optimize and improve air pollution prevention and control policies.

The Effect of Family Size on Children＇s Education： Evidence from the Fertility Control Policy in China

Empirical research on the effect of family size on child education is complicated by the endogeneity of family size. This study exploits plausibly exogenous changes in family size caused by China＇s population control policy to estimate the causal relationship between family size and child education outcomes. The results show that, compared to an only child, a person with an additional sibling will have an approximate seventeen percentage points lower likelihood of completing middle school in China. Separate regressions across individual characteristics reveal that much of this negative effect appears to be driven by the cohorts born in earlier years after the policy, and children with the highest birth order within a family.

Analysis of a multi-component system with double threshold control policy

This paper investigates a multi-component repairable system with double threshold control policy.The system is composed of n identical and independent components which operate simultaneously at the beginning,and it is down when the number of operating components decreases to k−1(k≤n).When the number of failed components is less than the value L,the repairman repairs them with a low repair rate.The high repair rate is activated as soon as L failed components present,and continues until the number of failed components drops to the value N−1.Applying the matrix analytical method,the Laplace transform technique and the properties of the phase type distribution,various performance measures including the availability,the rate of occurrence of failures,and the reliability are derived in transient and stationary regimes.Further,numerical examples are reported to show the behaviour of the system.

A policy and technical measures for controlling soil and water loss in the Loess Plateau of China

Loess Plateau is the most serious region of soil and water loss in China and the world. The sediment carried into the Yellow River amounts to 1.6 billion tons every year. This paper reviews the factors and reasons for erosion in this area, and puts forward a comprehensive controlling policy on the basis of the principles of ecology and practise of Chinese scientists for 40 years. In conformity with the policy, a number of technical measures for controlling soil and water loss are suggested.

Analysis on the Effect of Beijing＇s Traffic Control Policies

With the rapid development of economy and motorization, the traffic congestion and environmental problems have become more and more serious day by day in Beijing. Therefore, traffic control policies have been gradually adopted by Beijing municipal government since 2008, so as to ease traffic and environmental problems. In this paper, the background and current situation of Beijing to implement traffic control policies are introduced, and also this measure is analyzed and evaluated from traffic effect, environmental effect, motor vehicle development, urban road development, public transport development, and balance between supply and demand, etc. Finally, related conclusions are drawn up as follows： an induced traffic volume will be generated by traffic control policies, and the effect of the traffic control will be erased by the natural growth rate of motor vehicles in three years; public traffic service should be improved for better making traffic control policies; the traffic congestion and environmental problems are alleviated by traffic control policies in the short term, but can＇t be fundamentally solved in the long run; traffic control policies should cooperate with other traffic demand management policies for reducing demands, and traffic condition should be optimized in both time and space, so that the traffic congestion and environmental problems will be fundamentally solved.

Group Decision-Making Method of Entry Policy During a Pandemic

Omicron,the new mutant coronavirus,has spread rapidly globally,attracting close attention from different stakeholders worldwide.The complex and constantly changing epidemic situation has had a new impact on the world.Therefore,this paper focuses on the characteristics of the rapid spread of the COVID-19 variant strain.Generally,epidemic prevention experts conduct preliminary screening as part of the existing epidemic plan database according to the current local situation,after which they sort the alternatives deemed more suitable for the situation.Then the decision-makers identify the most divergent expert group,plan for consultation and adjustments,and finally obtain the plan with the smallest divergence.This article aims to integrate the experts'opinions with the method of minimizing the differences,which can maximize the expert consensus and help organize the schemes that best meet the epidemic situation.The experts'negotiation and iteration of the differences in the initial plan align with the current complex and dynamic epidemic situation and are of great significance to the rapid formulation of plans to achieve effective prevention and control.

Agent based automated trust negotiation model

To enhance the practicability of the trust negotiation system, an agent based automated trust negotiation model （ABAM） is proposed. The ABAM introduces an agent to keep the negotiation process with no human intervention. Meanwhile, the ABAM specifies the format of a meta access control policy, and adopts credentials with flexible format to meet the requirements of access control policies instead of disclosing the whole contents of a certificate. Furthermore, the ABAM uses asymmetric functions with a high security intensity to encrypt the transmitting message, which can prevent information from being attacked. Finally, the ABAM presents a new negotiation protocol to guide the negotiation process. A use case is studied to illuminate that the ABAM is sound and reasonable. Compared with the existing work, the intelligence, privacy and negotiation efficiency are improved in the ABAM.

Progress in the Prevention and Treatment of AIDS Associated with Tuberculosis

Epidemiological studies have shown that infection with the human immunodeficiency virus(HIV) is an influential risk factor for infection with Mycobacterium tuberculosis(MTb),the rapid progression of the initial infection to active tuberculosis(TB),and the reactivation of latent TB infection.MTb infection is also one of the most common opportunistic infections in people with HIV,including AIDS patients receiving anti-retroviral therapy.Given the prevalence of HIV infection,the incidence of TB infection,which had begun to decline,is facing a severe situation.HIV associated with TB exerts an immense burden on the public health-care system,especially in countries with high incidences of HIV infection.Therefore,the global policies for the prevention and control of TB should be revised.Moreover,an increased investment in TB control has to be guaranteed.The purpose of this review is to summarize the recent progress in the prevention,treatment,and control of HIV and TB co-infection.

A review and evaluation of nonroad diesel mobile machinery emission control in China

China’s emission control for nonroad diesel mobile machinery(NDMM)must deal with a fast increase in stock as well as regulations that are two decades behind those for on-road vehicles.This study provides the first large-scale review and evaluation of China’s NDMM policies,along with emission measurements and an investigation on diesel fuel quality.The sulfur contents of the investigated diesel declined from 430 ppm(median value)in 2011 to6-8 ppm during the 2017-2018 period.The emission control of NO_(x)and PM greatly improved with the shift from the China II to China IV standards,as demonstrated by engine tests and field NO_(x)measurements.However,the NO_(x)emission factors for non-type-approved engines were approximately twice the limits of the China II standards.Emission compliance based on bench tests was not sufficient to control actual emissions because the field-measured NO_(x)emission factors of all machinery ranged from 24%to 225%greater than the respective emission limits for the engines.These circumstances adversely affected the effectiveness of the regulations and policies for China’s emission control of NDMM.Nevertheless,the policies on new and in-use NDMM,as well as diesel fuel quality,prevented NO_(x)and PM emissions amounting to 4.4 Tg and 297.8 Gg during the period 2008-2017,respectively.The emission management strategy contributed to enhancing the international competitiveness of China’s NDMM industries by promoting advanced technologies.For effective NDMM emission control in the future,portable testing and noncontact remote supervision should be strengthened;also,the issue of noncompliant diesel should be addressed through rigorous control measures and financial penalties.

Evaluating cost and benefit of air pollution control policies in China:A systematic review

China has put great efforts into air pollution control over the past years and recently committed to its most ambitious climate target.Cost and benefit analysis has been widely used to evaluate the control policies in terms of past performance,future reduction potential,and direct and indirect impacts.To understand the cost and benefit analysis for air pollution control in China,we conducted a bibliometric review of more than 100 studies published over the past two decades,including the current research progress,most commonly adopted methods,and core findings.The control target in cost and benefit analysis has shifted in three stages,from individual and primary pollution control,moving to joint prevention of multiple and secondary pollutants,and then towards synergistic control of air pollution and carbon.With the expansion of the research scope,the integrated assessment model has gradually demonstrated the necessity for long-term ex-anti policy simulation,especially for dealing with complex factors.To ensure long-term air quality,climate,public health,and sustainable economic development,substantial evidence from published studies has suggested that China needs to continue its efforts in the upstream adjustment of the energy system and industrial structure with multi-regional and-sector collaboration.This cost and benefit review paper provides decision-makers with the fundamental information and knowledge gaps in air pollution control strategies in China,and direction for facing future challenges.

Understanding Globalization. The Inter-Parliamentary Union From the Late Nineteenth to Early Twentieth Century

The Inter-Parliamentary Union was formed in 1889, gathering, initially, 38 British and French parliamentarians. The IPU （guided, from 1901 up to 1908, by Fredreric Passy and William Randall Cremer）, was to support and reinforce the objective of extending arbitration as a ＇peaceful tool＇ for resolving the dispute between states. The aftermath of the First World War marked a decisive step forward in the development of a strong liberal internationalist milieux which promoted a peaceful order based on the international rule of law. This paper summarizes some issues of ongoing research and it focuses on two key topics： the rise of parliamentary control of foreign policy and the making of ＇parliamentary diplomacy＇. Besides, it tried to elucidate, from another point of view, the political building of ＇transnational and peaceful politics＇ aimed at the growth of peaceful and ＇progressive＇ social relations among States and how the ＇peaceful politics＇ are subjects that engage the complexity and the deep-rooted issues of State facing to the ＇first globalization＇ and the ＇end of century crisis＇.

The Determination of the Optimal Buffer Size Based on the Control Point Policy

The failure prone production systems are examined. For the hybrid systems, the failure of machines is unavoidable. By introduced the idea of purchasing extra capacity to the system, a so-call blockage hedging point is obtained. Meanwhile, a near-optimal method is presented to determine the optimal buffer sizes. The continuous flow model of the unreliable manufacturing systems is considered and the control point policy is involved in. Numerical results not only testify the method and show us its application but also to some extent show the impact of the machines＇ failure rate on the optimal buffer size.

Product Form Solution of a Queuing-Inventory System with Lost Sales and Server Vacation

In this study,the authors consider an M/M/1 queuing system with attached inventory under an(s,S)control policy.The server takes multiple vacations whenever the inventory is depleted.It is assumed that the lead time and the vacation time follow exponential distributions.The authors formulate the model as a quasi-birth-and-dearth(QBD)process and derive the stability condition of the system.Then,the stationary distribution in product form for the joint process of the queue length,the inventory level,and the server’s status is obtained.Furthermore,the conditional distributions of the inventory level when the server is on and operational,and when it is off due to a vacation,are derived.Using the stationary distribution,the authors obtain some performance measures of the system.The authors investigate analytically the effect of the server’s vacation on the performance measures.Finally,several numerical examples are presented to investigate the effects of some parameters on the performance measures,the optimal policy,and the optimal cost.

燃烧源氨排放对灰霾期间北京大气铵的重要贡献

Aerosol ammonium(NH_(4)^(+)),mainly produced from the reactions of ammonia(NH_(3))with acids in the atmosphere,has significant impacts on air pollution,radiative forcing,and human health.Understanding the source and formation mechanism of NH_(4)^(+)can provide scientific insights into air quality improvements.However,the sources of NH_(3)in urban areas are not well understood,and few studies focus on NH_(3)/NH_(4)^(+)at different heights within the atmospheric boundary layer,which hinders a comprehensive understanding of aerosol NH_(4)^(+).In this study,we perform both field observation and modeling studies(the Community Multiscale Air Quality,CMAQ)to investigate regional NH_(3)emission sources and vertically resolved NH_(4)^(+)formation mechanisms during the winter in Beijing.Both stable nitrogen isotope analyses and CMAQ model suggest that combustion-related NH_(3)emissions,including fossil fuel sources,NH_(3)slip,and biomass burning,are important sources of aerosol NH_(4)^(+)with more than 60%contribution occurring on heavily polluted days.In contrast,volatilization-related NH_(3)sources(livestock breeding,N-fertilizer application,and human waste)are dominant on clean days.Combustion-related NH_(3)is mostly local from Beijing,and biomass burning is likely an important NH_(3)source(~15%–20%)that was previously overlooked.More effective control strategies such as the two-product(e.g.,reducing both SO_(2)and NH_(3))control policy should be considered to improve air quality.

The impact of the COVID-19 prevention and economic interventions on express delivery industry:Evidence from China

As a fundamental logistics service,the express delivery(ED)industry provides production and consumption activities to maintain efficient supply chain operations.It plays an important role in promoting industrial development and maintaining daily life and consumption.This study examined the effects of COVID-19 on the ED industry using ED package delivery data from 31 provinces(autonomous regions and municipalities)in China.Using a difference-in-differences method,the COVID-19 outbreak was found to have a positive effect and epidemic prevention and control(EPC)policies were found to have negative effects on the development of the ED industry.In addition to EPC policies,the Chinese government has implemented other short-term economic interventions(SEI),such as the resumption of work and production(RWP),policies to balance economic growth,and epidemic prevention.This study divided the pandemic period into three stages to analyze the different impacts of EPC and SEI policy changes on the ED industry.The RWP policies adopted during the pandemic positively impacted the volume and income of packages delivered to the ED industry.The conclusions of this study are significant for the ED industry in addressing public health emergencies and for the Chinese government to formulate EPC and SEI policies during epidemic periods.

Emerging contaminant control:From science to action

Since the concept of emerging contaminants(ECs)was first proposed in 2001,the global scientific research of ECs has developed rapidly.In the past decades,great progress has been achieved in the scientific research of ECs in China,including the establishment of EC analysis method system,the evaluation of the pollution status,pollution characteristics and environmental risk of ECs in typical regions of China,and establishment of EC control technology system.Continuous progress in scientific research of ECs promoted China’s action on EC control.It is planned that the environmental risk of ECs will be generally controlled by 2035 in China.Priority ECs should be screened for environmental management.Although great efforts have been made,the EC control in China still faces tremendous challenges.It is necessary to bridge the gap between scientific research and decision-making management.Based on the science and technology study,various measures such as engineering,policy management and public participation should be combinedly adopted for EC control.