Resource planning is becoming an increasingly important and timely problem for cloud users.As more Web services are moved to the cloud,minimizing network usage is often a key driver of cost control.Most existing appro...Resource planning is becoming an increasingly important and timely problem for cloud users.As more Web services are moved to the cloud,minimizing network usage is often a key driver of cost control.Most existing approaches focus on resources such as CPU,memory,and disk I/O.In particular,CPU receives the most attention from researchers,but the bandwidth is somehow neglected.It is challenging to predict the network throughput of modem Web services,due to the factors of diverse and complex response,evolving Web services,and complex network transportation.In this paper,we propose a methodology of what-if analysis,named Log2Sim,to plan the bandwidth resource of Web services.Log2Sim uses a lightweight workload model to describe user behavior,an automated mining approach to obtain characteristics of workloads and responses from massive Web logs,and traffic-aware simulations to predict the impact on the bandwidth consumption and the response time in changing contexts.We use a real-life Web system and a classic benchmark to evaluate Log2Sim in multiple scenarios.The evaluation result shows that Log2Sim has good performance in the prediction of bandwidth consumption.The average relative error is 2%for the benchmark and 8% for the real-life system.As for the response time,Log2Sim cannot produce accurate predictions for every single service request,but the simulation results always show similar trends on average response time with the increase of workloads in different changing contexts.It can provide sufficient information for the system administrator in proactive bandwidth planning.展开更多
The multistage queue model was developed for a situation where parallel and unrelated queues exist at the first stage only. These queues merged into single queues at the remaining stages. The parallel queues offer ser...The multistage queue model was developed for a situation where parallel and unrelated queues exist at the first stage only. These queues merged into single queues at the remaining stages. The parallel queues offer services that are different from one another and customers arrive to join the queue that offer services that they need. The mathematical model was developed assuming an M/M/1 queue system and the measures of effectiveness were derived. The model was applied to solve the problem of customer congestion in a restaurant in the city of Ibadan, Nigeria that serves three different local delicacies. The three local delicacies constitute three different queues at the first stage. The second stage consists of only one queue which is for purchase of drinks and the third stage which is the last stage is for payment. Every customer in the restaurant passes through the three stages. Utilization factors for the five queues were determined and found to range from 70% to 97%. The average time spent by customers in the system was found to be 543.04 minutes. A simulation study using what-if scenario analysis was performed to determine the optimum service configuration for the system. The optimum configuration reduced average time for customers in the system from 543.04 minutes to 13.47 minutes without hiring new servers.展开更多
There are many techniques for hazard identification and are divided into shortcut,standard and advanced techniques.Among these,HAZOP and What-If techniques are mostly engaged by practitioners in the chemical process i...There are many techniques for hazard identification and are divided into shortcut,standard and advanced techniques.Among these,HAZOP and What-If techniques are mostly engaged by practitioners in the chemical process industry.Both of these have certain advantages and limitations,i.e.,HAZOP is structured,and what-if covers broad range of scenarios.There is no hazard identification method,which can cover a broad range of scenarios and is structured in nature.For this purpose,a new technique namely integrated hazard identification(IHI)is proposed in this article that integrates HAZOP and What-If.The methodology is demonstrated via hazard identification study of urea synthesis section.Risk ranking is used to sort out the worst-case scenario.This worst-case scenario is further studied in detail for quantification that is performed using the ALOHA software.This quantification has assisted to detect ammonia concentrations in nearby control room and surroundings for worst-case scenario.It is revealed that if ammonia pump is not stopped within 10 minutes,concentration inside and outside the control room may reach to 384 ppm and 2630 ppm,compared to 1100 ppm(AEGL-3).Thus the proposed method would be easy,time saving and covers more details and would be handy for practicing engineers working in different chemical process industries.展开更多
基金This work was supported by the National Key Research and Development Program of China(2018YFB1003302)the National Natural Science Foundation of China(Grant No.61472241).
文摘Resource planning is becoming an increasingly important and timely problem for cloud users.As more Web services are moved to the cloud,minimizing network usage is often a key driver of cost control.Most existing approaches focus on resources such as CPU,memory,and disk I/O.In particular,CPU receives the most attention from researchers,but the bandwidth is somehow neglected.It is challenging to predict the network throughput of modem Web services,due to the factors of diverse and complex response,evolving Web services,and complex network transportation.In this paper,we propose a methodology of what-if analysis,named Log2Sim,to plan the bandwidth resource of Web services.Log2Sim uses a lightweight workload model to describe user behavior,an automated mining approach to obtain characteristics of workloads and responses from massive Web logs,and traffic-aware simulations to predict the impact on the bandwidth consumption and the response time in changing contexts.We use a real-life Web system and a classic benchmark to evaluate Log2Sim in multiple scenarios.The evaluation result shows that Log2Sim has good performance in the prediction of bandwidth consumption.The average relative error is 2%for the benchmark and 8% for the real-life system.As for the response time,Log2Sim cannot produce accurate predictions for every single service request,but the simulation results always show similar trends on average response time with the increase of workloads in different changing contexts.It can provide sufficient information for the system administrator in proactive bandwidth planning.
文摘The multistage queue model was developed for a situation where parallel and unrelated queues exist at the first stage only. These queues merged into single queues at the remaining stages. The parallel queues offer services that are different from one another and customers arrive to join the queue that offer services that they need. The mathematical model was developed assuming an M/M/1 queue system and the measures of effectiveness were derived. The model was applied to solve the problem of customer congestion in a restaurant in the city of Ibadan, Nigeria that serves three different local delicacies. The three local delicacies constitute three different queues at the first stage. The second stage consists of only one queue which is for purchase of drinks and the third stage which is the last stage is for payment. Every customer in the restaurant passes through the three stages. Utilization factors for the five queues were determined and found to range from 70% to 97%. The average time spent by customers in the system was found to be 543.04 minutes. A simulation study using what-if scenario analysis was performed to determine the optimum service configuration for the system. The optimum configuration reduced average time for customers in the system from 543.04 minutes to 13.47 minutes without hiring new servers.
文摘There are many techniques for hazard identification and are divided into shortcut,standard and advanced techniques.Among these,HAZOP and What-If techniques are mostly engaged by practitioners in the chemical process industry.Both of these have certain advantages and limitations,i.e.,HAZOP is structured,and what-if covers broad range of scenarios.There is no hazard identification method,which can cover a broad range of scenarios and is structured in nature.For this purpose,a new technique namely integrated hazard identification(IHI)is proposed in this article that integrates HAZOP and What-If.The methodology is demonstrated via hazard identification study of urea synthesis section.Risk ranking is used to sort out the worst-case scenario.This worst-case scenario is further studied in detail for quantification that is performed using the ALOHA software.This quantification has assisted to detect ammonia concentrations in nearby control room and surroundings for worst-case scenario.It is revealed that if ammonia pump is not stopped within 10 minutes,concentration inside and outside the control room may reach to 384 ppm and 2630 ppm,compared to 1100 ppm(AEGL-3).Thus the proposed method would be easy,time saving and covers more details and would be handy for practicing engineers working in different chemical process industries.
