WorldWideScience

Sample records for optimal replacement policies

  1. Optimal Replacement Policies for Non-Uniform Cache Objects with Optional Eviction

    National Research Council Canada - National Science Library

    Bahat, Omri; Makowski, Armand M

    2002-01-01

    .... However, since the introduction of optimal replacement policies for conventional caching, the problem of finding optimal replacement policies under the factors indicated has not been studied in any systematic manner...

  2. A bivariate optimal replacement policy for a multistate repairable system

    International Nuclear Information System (INIS)

    Zhang Yuanlin; Yam, Richard C.M.; Zuo, Ming J.

    2007-01-01

    In this paper, a deteriorating simple repairable system with k+1 states, including k failure states and one working state, is studied. It is assumed that the system after repair is not 'as good as new' and the deterioration of the system is stochastic. We consider a bivariate replacement policy, denoted by (T,N), in which the system is replaced when its working age has reached T or the number of failures it has experienced has reached N, whichever occurs first. The objective is to determine the optimal replacement policy (T,N)* such that the long-run expected profit per unit time is maximized. The explicit expression of the long-run expected profit per unit time is derived and the corresponding optimal replacement policy can be determined analytically or numerically. We prove that the optimal policy (T,N)* is better than the optimal policy N* for a multistate simple repairable system. We also show that a general monotone process model for a multistate simple repairable system is equivalent to a geometric process model for a two-state simple repairable system in the sense that they have the same structure for the long-run expected profit (or cost) per unit time and the same optimal policy. Finally, a numerical example is given to illustrate the theoretical results

  3. Optimal Replacement and Management Policies for Beef Cows

    OpenAIRE

    W. Marshall Frasier; George H. Pfeiffer

    1994-01-01

    Beef cow replacement studies have not reflected the interaction between herd management and the culling decision. We demonstrate techniques for modeling optimal beef cow replacement intervals and discrete management policies by incorporating the dynamic effects of management on future productivity when biological response is uncertain. Markovian decision analysis is used to identify optimal beef cow management on a ranch typical of the Sandhills region of Nebraska. Issues of breeding season l...

  4. Optimal Overhaul-Replacement Policies for Repairable Machine Sold with Warranty

    Directory of Open Access Journals (Sweden)

    Kusmaningrum Soemadi

    2014-12-01

    Full Text Available This research deals with an overhaul-replacement policy for a repairable machine sold with Free Replacement Warranty (FRW. The machine will be used for a finite horizon, T (T <, and evaluated at a fixed interval, s (s< T. At each evaluation point, the buyer considers three alternative decisions i.e. Keep the machine, Overhaul it, or Replace it with a new identical one. An overhaul can reduce the machine age virtually, but not to a point that the machine is as good as new. If the machine fails during the warranty period, it is rectified at no cost to the buyer. Any failure occurring before and after the expiry of the warranty is restored by minimal repair. An overhaul-replacement policy is formulated for such machines by using dynamic programming approach to obtain the buyer’s optimal policy. The results show that a significant rejuvenation effect due to overhaul may extend the length of machine life cycle and delay the replacement decision. In contrast, the warranty stimulates early machine replacement and by then increases the replacement frequencies for a certain range of replacement cost. This demonstrates that to minimize the total ownership cost over T the buyer needs to consider the minimal repair cost reduction due to rejuvenation effect of overhaul as well as the warranty benefit due to replacement. Numerical examples are presented for both illustrating the optimal policy and describing the behavior of the optimal solution.

  5. Determining Optimal Replacement Policy with an Availability Constraint via Genetic Algorithms

    Directory of Open Access Journals (Sweden)

    Shengliang Zong

    2017-01-01

    Full Text Available We develop a model and a genetic algorithm for determining an optimal replacement policy for power equipment subject to Poisson shocks. If the time interval of two consecutive shocks is less than a threshold value, the failed equipment can be repaired. We assume that the operating time after repair is stochastically nonincreasing and the repair time is exponentially distributed with a geometric increasing mean. Our objective is to minimize the expected average cost under an availability requirement. Based on this average cost function, we propose the genetic algorithm to locate the optimal replacement policy N to minimize the average cost rate. The results show that the GA is effective and efficient in finding the optimal solutions. The availability of equipment has significance effect on the optimal replacement policy. Many practical systems fit the model developed in this paper.

  6. An optimal maintenance policy for machine replacement problem using dynamic programming

    Directory of Open Access Journals (Sweden)

    Mohsen Sadegh Amalnik

    2017-06-01

    Full Text Available In this article, we present an acceptance sampling plan for machine replacement problem based on the backward dynamic programming model. Discount dynamic programming is used to solve a two-state machine replacement problem. We plan to design a model for maintenance by consid-ering the quality of the item produced. The purpose of the proposed model is to determine the optimal threshold policy for maintenance in a finite time horizon. We create a decision tree based on a sequential sampling including renew, repair and do nothing and wish to achieve an optimal threshold for making decisions including renew, repair and continue the production in order to minimize the expected cost. Results show that the optimal policy is sensitive to the data, for the probability of defective machines and parameters defined in the model. This can be clearly demonstrated by a sensitivity analysis technique.

  7. An accurate approximate solution of optimal sequential age replacement policy for a finite-time horizon

    International Nuclear Information System (INIS)

    Jiang, R.

    2009-01-01

    It is difficult to find the optimal solution of the sequential age replacement policy for a finite-time horizon. This paper presents an accurate approximation to find an approximate optimal solution of the sequential replacement policy. The proposed approximation is computationally simple and suitable for any failure distribution. Their accuracy is illustrated by two examples. Based on the approximate solution, an approximate estimate for the total cost is derived.

  8. Optimal replacement policy of products with repair-cost threshold after the extended warranty

    Institute of Scientific and Technical Information of China (English)

    Lijun Shang; Zhiqiang Cai

    2017-01-01

    The reliability of the product sold under a warranty is usually maintained by the manufacturer during the warranty period. After the expiry of the warranty, however, the consumer confronts a problem about how to maintain the reliability of the product. This paper proposes, from the consumer's perspective, a replace-ment policy after the extended warranty, under the assumption that the product is sold under the renewable free replacement warranty (RFRW) policy in which the replacement is dependent on the repair-cost threshold. The proposed replacement policy is the replacement after the extended warranty is performed by the consumer based on the repair-cost threshold or preventive replacement (PR) age, which are decision variables. The expected cost rate model is derived from the consumer's perspective. The existence and uniqueness of the optimal solution that minimizes the expected cost rate per unit time are offered. Finally, a numeri-cal example is presented to exemplify the proposed model.

  9. An optimal maintenance policy for machine replacement problem using dynamic programming

    OpenAIRE

    Mohsen Sadegh Amalnik; Morteza Pourgharibshahi

    2017-01-01

    In this article, we present an acceptance sampling plan for machine replacement problem based on the backward dynamic programming model. Discount dynamic programming is used to solve a two-state machine replacement problem. We plan to design a model for maintenance by consid-ering the quality of the item produced. The purpose of the proposed model is to determine the optimal threshold policy for maintenance in a finite time horizon. We create a decision tree based on a sequential sampling inc...

  10. Determining Optimal Replacement Policy with an Availability Constraint via Genetic Algorithms

    OpenAIRE

    Zong, Shengliang; Chai, Guorong; Su, Yana

    2017-01-01

    We develop a model and a genetic algorithm for determining an optimal replacement policy for power equipment subject to Poisson shocks. If the time interval of two consecutive shocks is less than a threshold value, the failed equipment can be repaired. We assume that the operating time after repair is stochastically nonincreasing and the repair time is exponentially distributed with a geometric increasing mean. Our objective is to minimize the expected average cost under an availability requi...

  11. Optimal Replacement Policy of Jet Engine Modules from the Aircarrier's Point of View

    Directory of Open Access Journals (Sweden)

    Anita Domitrović

    2008-01-01

    Full Text Available A mathematical model for optimising preventive maintenanceof aircraft jet engine was developed by dynamic programming.Replacement planning for jet engine modules is regardedas a multistage decision process, while optimum modulereplacement is considered as a problem of equipment replacement.The goal of the optimal replacement policy of jet enginemodules is a defined series of decisions resulting in minimummaintenance costs. The model was programmed inC++ programming language and tested by using CFM56 jetengine data. The optimum maintenance strategy costs werecompared to costs of simpler experience-based maintenancestrategies. The results of the comparison j usti.JY further developmentand usage of the model in order to achieve significant costreduction for airline carriers.

  12. Simulation of an integrated age replacement and spare provisioning policy using SLAM

    International Nuclear Information System (INIS)

    Zohrul Kabir, A.B.M.; Farrash, S.H.A.

    1996-01-01

    This paper presents a SLAM simulation model for determining a jointly optimal age replacement and spare part provisioning policy. The policy, referred to as a stocking policy, is formulated by combining age replacement policy with a continuous review (s, S) type inventory policy, where s is the stock reorder level and S is the maximum stock level. The optimal values of the decision variables are obtained by minimizing the total cost of replacement and inventory. The simulation procedure outlined in the paper can be used to model any operating situation having either a single item or a number of identical items. Results from a number of case problems specifically constructed by 5-factor second order rotatory design have been presented and the effects of different cost elements, item failure characteristics and lead time characteristics have been highlighted. For all case problems, optimal (s, S) policies to support the Barlow-Proschan age policy have also been determined. Simulation results clearly indicate the separate optimizations of replacement and spare provisioning policies do not ensure global optimality when total system cost has to be minimized

  13. Replacement and inspection policies for products with random life cycle

    International Nuclear Information System (INIS)

    Yun, Won Young; Nakagawa, Toshio

    2010-01-01

    In this paper, we consider maintenance policies for products in which the economical life cycle of products is a random variable. First, we study a periodic replacement policy with minimal repair. The system is minimally repaired at failure and is replaced by new one at age T (periodic replacement policy with minimal repair of Barlow and Hunter). The expected present value of total maintenance cost of products with random life cycle is obtained and the optimal replacement interval minimizing the cost is found. Second, we consider an inspection policy for products with random life cycle to detect the system failure. The expected total cost is obtained and the optimal inspection interval is found. Numerical examples are also included.

  14. Age replacement policy based on imperfect repair with random probability

    International Nuclear Information System (INIS)

    Lim, J.H.; Qu, Jian; Zuo, Ming J.

    2016-01-01

    In most of literatures of age replacement policy, failures before planned replacement age can be either minimally repaired or perfectly repaired based on the types of failures, cost for repairs and so on. In this paper, we propose age replacement policy based on imperfect repair with random probability. The proposed policy incorporates the case that such intermittent failure can be either minimally repaired or perfectly repaired with random probabilities. The mathematical formulas of the expected cost rate per unit time are derived for both the infinite-horizon case and the one-replacement-cycle case. For each case, we show that the optimal replacement age exists and is finite. - Highlights: • We propose a new age replacement policy with random probability of perfect repair. • We develop the expected cost per unit time. • We discuss the optimal age for replacement minimizing the expected cost rate.

  15. Optimization on replacement and inspection period of plant equipment

    International Nuclear Information System (INIS)

    Takase, Kentaro; Kasai, Masao

    2004-01-01

    Rationalization of the plant maintenance is one of the main topics being investigated in Japanese nuclear power industries. Optimization of the inspection and replacement period of equipments is effective for the maintenance cost reduction. The more realistic model of the replacement policy is proposed in this study. It is based on the classical replacement policy model and its cost is estimated. Then, to consider the inspection for the maintenance, the formulation that includes the risk concept is discussed. Based on it, two variations of the combination of the inspection and the replacement are discussed and the costs are estimated. In this study the effect of the degradation of the equipment is important. The optimized maintenance policy depends on the existence of significant degradation. (author)

  16. Replacement policy of residential lighting optimized for cost, energy, and greenhouse gas emissions

    Science.gov (United States)

    Liu, Lixi; Keoleian, Gregory A.; Saitou, Kazuhiro

    2017-11-01

    Accounting for 10% of the electricity consumption in the US, artificial lighting represents one of the easiest ways to cut household energy bills and greenhouse gas (GHG) emissions by upgrading to energy-efficient technologies such as compact fluorescent lamps (CFL) and light emitting diodes (LED). However, given the high initial cost and rapidly improving trajectory of solid-state lighting today, estimating the right time to switch over to LEDs from a cost, primary energy, and GHG emissions perspective is not a straightforward problem. This is an optimal replacement problem that depends on many determinants, including how often the lamp is used, the state of the initial lamp, and the trajectories of lighting technology and of electricity generation. In this paper, multiple replacement scenarios of a 60 watt-equivalent A19 lamp are analyzed and for each scenario, a few replacement policies are recommended. For example, at an average use of 3 hr day-1 (US average), it may be optimal both economically and energetically to delay the adoption of LEDs until 2020 with the use of CFLs, whereas purchasing LEDs today may be optimal in terms of GHG emissions. In contrast, incandescent and halogen lamps should be replaced immediately. Based on expected LED improvement, upgrading LED lamps before the end of their rated lifetime may provide cost and environmental savings over time by taking advantage of the higher energy efficiency of newer models.

  17. Optimal household refrigerator replacement policy for life cycle energy, greenhouse gas emissions, and cost

    International Nuclear Information System (INIS)

    Kim, Hyung Chul; Keoleian, Gregory A.; Horie, Yuhta A.

    2006-01-01

    Although the last decade witnessed dramatic progress in refrigerator efficiencies, inefficient, outdated refrigerators are still in operation, sometimes consuming more than twice as much electricity per year compared with modern, efficient models. Replacing old refrigerators before their designed lifetime could be a useful policy to conserve electric energy and greenhouse gas emissions. However, from a life cycle perspective, product replacement decisions also induce additional economic and environmental burdens associated with disposal of old models and production of new models. This paper discusses optimal lifetimes of mid-sized refrigerator models in the US, using a life cycle optimization model based on dynamic programming. Model runs were conducted to find optimal lifetimes that minimize energy, global warming potential (GWP), and cost objectives over a time horizon between 1985 and 2020. The baseline results show that depending on model years, optimal lifetimes range 2-7 years for the energy objective, and 2-11 years for the GWP objective. On the other hand, an 18-year of lifetime minimizes the economic cost incurred during the time horizon. Model runs with a time horizon between 2004 and 2020 show that current owners should replace refrigerators that consume more than 1000 kWh/year of electricity (typical mid-sized 1994 models and older) as an efficient strategy from both cost and energy perspectives

  18. An optimal replacement policy for a repairable system based on its repairman having vacations

    Energy Technology Data Exchange (ETDEWEB)

    Yuan Li [School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092 (China); Xu Jian, E-mail: xujian@tongji.edu.c [School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092 (China)

    2011-07-15

    This paper studies a cold standby repairable system with two different components and one repairman who can take multiple vacations. If there is a component which fails and the repairman is on vacation, the failed component will wait for repair until the repairman is available. In the system, assume that component 1 has priority in use. After repair, component 1 follows a geometric process repair, while component 2 can be repaired as good as new after failures. Under these assumptions, a replacement policy N based on the failed times of component 1 is studied. The system will be replaced if the failure times of component 1 reach N. The explicit expression of the expected cost rate is given, so that the optimal replacement time N{sup *} is determined. Finally, a numerical example is given to illustrate the theoretical results of the model.

  19. Optimal Overhaul-Replacement Policies for Repairable Machine Sold with Warranty

    OpenAIRE

    Soemadi, Kusmaningrum; Iskandar, Bermawi P; Taroepratjeka, Harsono

    2014-01-01

    This research deals with an overhaul-replacement policy for a repairable machine sold with Free Replacement Warranty (FRW). The machine will be used for a finite horizon, T (T <), and evaluated at a fixed interval, s (s< T). At each evaluation point, the buyer considers three alternative decisions i.e. Keep the machine, Overhaul it, or Replace it with a new identical one. An overhaul can reduce the machine age virtually, but not to a point that the machine is as good as new. If the mac...

  20. Dynamic optimization of maintenance and improvement planning for water main system: Periodic replacement approach

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Woo; Choi, Go Bong; Lee, Jong Min [Seoul National University, Seoul (Korea, Republic of); Suh, Jung Chul [Samchully Corporation, Seoul (Korea, Republic of)

    2016-01-15

    This paper proposes a Markov decision process (MDP) based approach to derive an optimal schedule of maintenance, rehabilitation and replacement of the water main system. The scheduling problem utilizes auxiliary information of a pipe such as the current state, cost, and deterioration model. The objective function and detailed algorithm of dynamic programming are modified to solve the periodic replacement problem. The optimal policy evaluated by the proposed algorithm is compared to several existing policies via Monte Carlo simulations. The proposed decision framework provides a systematic way to obtain an optimal policy.

  1. A bi-objective model for optimizing replacement time of age and block policies with consideration of spare parts’ availability

    Science.gov (United States)

    Alsyouf, Imad

    2018-05-01

    Reliability and availability of critical systems play an important role in achieving the stated objectives of engineering assets. Preventive replacement time affects the reliability of the components, thus the number of system failures encountered and its downtime expenses. On the other hand, spare parts inventory level is a very critical factor that affects the availability of the system. Usually, the decision maker has many conflicting objectives that should be considered simultaneously for the selection of the optimal maintenance policy. The purpose of this research was to develop a bi-objective model that will be used to determine the preventive replacement time for three maintenance policies (age, block good as new, block bad as old) with consideration of spare parts’ availability. It was suggested to use a weighted comprehensive criterion method with two objectives, i.e. cost and availability. The model was tested with a typical numerical example. The results of the model demonstrated its effectiveness in enabling the decision maker to select the optimal maintenance policy under different scenarios and taking into account preferences with respect to contradicting objectives such as cost and availability.

  2. Optimal Repair And Replacement Policy For A System With Multiple Components

    Science.gov (United States)

    2016-06-17

    increases. A future research direction is to develop efficient heuristic methods that can produce near-optimal policy with much less computational...decision variables represent the long-run fraction of time for each state- action pair. The objective function is the linear combination of long-run...exists an optimal policy. To find this policy we solve the linear program. The solution shows that for each state only one state-action pair, represented

  3. Optimizing model. 1. Insemination, replacement, seasonal production and cash flow.

    NARCIS (Netherlands)

    Delorenzo, M.A.; Spreen, T.H.; Bryan, G.R.; Beede, D.K.; Arendonk, van J.A.M.

    1992-01-01

    Dynamic programming to solve the Markov decision process problem of optimal insemination and replacement decisions was adapted to address large dairy herd management decision problems in the US. Expected net present values of cow states (151,200) were used to determine the optimal policy. States

  4. A trivariate optimal replacement policy for a deteriorating system based on cumulative damage and inspections

    International Nuclear Information System (INIS)

    Tsai, Hsin-Nan; Sheu, Shey-Huei; Zhang, Zhe George

    2017-01-01

    In this article, we study a trivariate replacement model for a deteriorating system consisting of two units. Failures of unit 1 can be classified into two types. Type I failure (minor failure) is fixed by a minimal repair and type II failure (catastrophic failure) is removed by a replacement. Both types of failures can only be detected through inspection. Each type I failure of unit 1 will result in a random amount of damage to unit 2 and the damages are cumulative. The probability of type I failure or type II failure is assumed to depend on the number of failures since the last replacement. We formulate a replacement policy based on the number of type I failure, the occurrence of the first type II failure, and the amount of accumulative damages. Hence the system is replaced either preventively or correctively at any of the following four conditions depend on whichever occurs first; preventively (a) at the Nth type I failure; or (b) when the total damage of unit 2 exceeds a pre-specified level Z (but less than the failure level l); and, correctively (c) at the first type II failure; or (d) when the total damage of unit 2 exceeds a failure level l, where Z and l represent the thresholds of total damage level for unit 2 to preventive and corrective replacements, respectively. Although a type I failure can be fixed by a minimal repair, but the operating period is stochastically decreasing and repair time is stochastically increasing as time goes on. The minimal total expected long-run net cost per unit time of the system is derived and a computational algorithm for determining the optimal policy is developed. A real-world application from electric power industry is provided. Several past studied are shown to be special cases of our model. Finally, a numerical example is presented. - Highlights: • A trivariate replacement policy for a deteriorating system with two units is proposed. • A real-world application from the electric power industry is provided. • The

  5. Optimized preventive replacement policy for large cascade systems

    International Nuclear Information System (INIS)

    Kretzen, H.H.

    1986-01-01

    The repair-bottleneck problem as a limiting factor for system reliability can be overcome. Design need only cover the steady state, wearout induced accumulations of failures being precluded by preventive replacements with subsequent recycling. As a result, a reliable system appears to be feasible on an economic basis, optimization in detail to be left to more precised cost-benefit studies. As a reference system the radio-frequency-generator cascade of a single-cell linear accelerator is considered. (DG)

  6. Opportunity-based age replacement policy with minimal repair

    International Nuclear Information System (INIS)

    Jhang, J.P.; Sheu, S.H.

    1999-01-01

    This paper proposes an opportunity-based age replacement policy with minimal repair. The system has two types of failures. Type I failures (minor failures) are removed by minimal repairs, whereas type II failures are removed by replacements. Type I and type II failures are age-dependent. A system is replaced at type II failure (catastrophic failure) or at the opportunity after age T, whichever occurs first. The cost of the minimal repair of the system at age z depends on the random part C(z) and the deterministic part c(z). The opportunity arises according to a Poisson process, independent of failures of the component. The expected cost rate is obtained. The optimal T * which would minimize the cost rate is discussed. Various special cases are considered. Finally, a numerical example is given

  7. Optimization of costs for the DOEL 3 steam generator replacement

    International Nuclear Information System (INIS)

    Leblois, C.

    1994-01-01

    Several aspects of steam generator replacement economics are discussed on the basis of the recent replacement carried out in the Doel 3 unit. The choice between repair of replacement policies, as well as the selection of the intervention date were based on a comparison of costs in which various possible scenarios were examined. The contractual approach for the different works to be performed was also an important point, as well as the project organization in which CAD played an important role. This organization allowed to optimize the outage duration and to realize numerous interventions in the reactor building in parallel with the replacement itself. A last aspect of the optimization of costs is the possibility to uprate the plant power. In the case of Doel 3, the plant restarted with a nominal power increased by 10%, of which 5,7% were possible by the increase of the SG heat transfer area. (Author) 6 refs

  8. Optimal replacement policy for safety-related multi-component multi-state systems

    International Nuclear Information System (INIS)

    Xu Ming; Chen Tao; Yang Xianhui

    2012-01-01

    This paper investigates replacement scheduling for non-repairable safety-related systems (SRS) with multiple components and states. The aim is to determine the cost-minimizing time for replacing SRS while meeting the required safety. Traditionally, such scheduling decisions are made without considering the interaction between the SRS and the production system under protection, the interaction being essential to formulate the expected cost to be minimized. In this paper, the SRS is represented by a non-homogeneous continuous time Markov model, and its state distribution is evaluated with the aid of the universal generating function. Moreover, a structure function of SRS with recursive property is developed to evaluate the state distribution efficiently. These methods form the basis to derive an explicit expression of the expected system cost per unit time, and to determine the optimal time to replace the SRS. The proposed methodology is demonstrated through an illustrative example.

  9. An extended optimal replacement model for a deteriorating system with inspections

    International Nuclear Information System (INIS)

    Sheu, Shey-Huei; Tsai, Hsin-Nan; Wang, Fu-Kwun; Zhang, Zhe George

    2015-01-01

    This study considers a generalized replacement model for a deteriorating system in which failures can only be detected by inspection. The system is assumed to have two types of failures and is replaced at the occurrence of the Nth type I failure (minor failure), or the first type II failure (catastrophic failure), or at working age T, whichever occurs first. The probability of a type I or type II failure depends on the number of type I failures since the previous replacement. Such a system can be repaired after a type I failure, but is deteriorating stochastically. That is, the operating intervals are decreasing stochastically, whereas the durations of the repairs are increasing stochastically. Based on these assumptions, we determine the expected net cost rate and discuss various special cases of the model. Finally, we develop a computational algorithm for finding the optimal policy and present a numerical example to show the properties of the proposed model. - Highlight: • Replacement policy for system subject two types of failures or the system's working age. • Failures detected by inspections. • Decreasing operating times and increasing repair times. • Derive a cost function. • Determine the cost minimization policy

  10. Optimization on replacement period of plant equipment

    International Nuclear Information System (INIS)

    Kasai, Masao; Asano, Hiromi

    2002-01-01

    Optimization of the replacement period of plant equipment is one of the main items to rationalize the activities on plant maintenance. There are several models to replace the equipment and the formulations for optimizing the replacement period are different among these models. In this study, we calculated the optimum replacement periods for some equipment parts based on the replacement models and found that the optimum solutions are not so largely differ from the replacement models as far as the replacement period is not so large. So we will be able to use the most usable model especially in the early phase of rationalization on plant maintenance, since there are large uncertainties in data for optimization. (author)

  11. A Robust Bayesian Approach to an Optimal Replacement Policy for Gas Pipelines

    Directory of Open Access Journals (Sweden)

    José Pablo Arias-Nicolás

    2015-06-01

    Full Text Available In the paper, we address Bayesian sensitivity issues when integrating experts’ judgments with available historical data in a case study about strategies for the preventive maintenance of low-pressure cast iron pipelines in an urban gas distribution network. We are interested in replacement priorities, as determined by the failure rates of pipelines deployed under different conditions. We relax the assumptions, made in previous papers, about the prior distributions on the failure rates and study changes in replacement priorities under different choices of generalized moment-constrained classes of priors. We focus on the set of non-dominated actions, and among them, we propose the least sensitive action as the optimal choice to rank different classes of pipelines, providing a sound approach to the sensitivity problem. Moreover, we are also interested in determining which classes have a failure rate exceeding a given acceptable value, considered as the threshold determining no need for replacement. Graphical tools are introduced to help decisionmakers to determine if pipelines are to be replaced and the corresponding priorities.

  12. Pricing and inventory policies for Hi-tech products under replacement warranty

    Science.gov (United States)

    Tsao, Yu-Chung; Teng, Wei-Guang; Chen, Ruey-Shii; Chou, Wang-Ying

    2014-06-01

    Companies, especially in the Hi-tech (high-technology) industry (such as computer, communication and consumer electronic products), often provide a replacement warranty period for purchased items. In reality, simultaneously determining the price and inventory decisions under warranty policy is an important issue. The objective of this paper is to develop a joint pricing and inventory model for Hi-tech products under replacement warranty policy. In the first model, we consider a Hi-tech product feature in which the selling price is declining in a trend. We determine the optimal inventory level for each period and retail price for the first period while maximising the total profit. In the second model, we further determine the optimal retail price and inventory level for each period in the dynamic demand market. This study develops solution approaches to solve the problems described above. Numerical analysis discusses the influence of system parameters on the company's decisions and behaviours. The results of this study could serve as a reference for business managers or administrators.

  13. New one cycle criteria for optimizing preventive replacement policies

    International Nuclear Information System (INIS)

    Hamidi, Maryam; Szidarovszky, Ferenc; Szidarovszky, Miklos

    2016-01-01

    Models are introduced and examined for the optimum scheduling of preventive replacements. The “replace first” and “replace last” models are known from the literature if the long term expected cost per unit time is minimized. We will first introduce the one cycle counterparts of these models when the expected costs per unit time in a single cycle is minimized. If the unit performs identical projects sequentially then the “replace next” model assumes that the preventive replacement is postponed until the ongoing project is finished. The termination time of this project is random which also depends on the scheduled time of the preventive replacement in contrary to the “replace first” and “replace last” models. The mathematical models are formulated and conditions are given for the existence of finite optima. Numerical examples and a simulation study illustrate the methodology and the numerical results show interesting comparisons of the different models. - Highlights: • The Single cycle age replacement model is extended incorporating repairable failures. • In order to avoid project interruption costs, three model variants are discussed. • Model variants are replace first, replace last and replace next. • In many cases analytic solutions are derived and illustrated by numerical examples. • The different model variants and their results are compared based on simulation studies.

  14. Discrete-continuous analysis of optimal equipment replacement

    OpenAIRE

    YATSENKO, Yuri; HRITONENKO, Natali

    2008-01-01

    In Operations Research, the equipment replacement process is usually modeled in discrete time. The optimal replacement strategies are found from discrete (or integer) programming problems, well known for their analytic and computational complexity. An alternative approach is represented by continuous-time vintage capital models that explicitly involve the equipment lifetime and are described by nonlinear integral equations. Then the optimal replacement is determined via the opt...

  15. Optimal composition of fluid-replacement beverages.

    Science.gov (United States)

    Baker, Lindsay B; Jeukendrup, Asker E

    2014-04-01

    The objective of this article is to provide a review of the fundamental aspects of body fluid balance and the physiological consequences of water imbalances, as well as discuss considerations for the optimal composition of a fluid replacement beverage across a broad range of applications. Early pioneering research involving fluid replacement in persons suffering from diarrheal disease and in military, occupational, and athlete populations incurring exercise- and/or heat-induced sweat losses has provided much of the insight regarding basic principles on beverage palatability, voluntary fluid intake, fluid absorption, and fluid retention. We review this work and also discuss more recent advances in the understanding of fluid replacement as it applies to various populations (military, athletes, occupational, men, women, children, and older adults) and situations (pathophysiological factors, spaceflight, bed rest, long plane flights, heat stress, altitude/cold exposure, and recreational exercise). We discuss how beverage carbohydrate and electrolytes impact fluid replacement. We also discuss nutrients and compounds that are often included in fluid-replacement beverages to augment physiological functions unrelated to hydration, such as the provision of energy. The optimal composition of a fluid-replacement beverage depends upon the source of the fluid loss, whether from sweat, urine, respiration, or diarrhea/vomiting. It is also apparent that the optimal fluid-replacement beverage is one that is customized according to specific physiological needs, environmental conditions, desired benefits, and individual characteristics and taste preferences.

  16. Optimal post-warranty maintenance policy with repair time threshold for minimal repair

    International Nuclear Information System (INIS)

    Park, Minjae; Mun Jung, Ki; Park, Dong Ho

    2013-01-01

    In this paper, we consider a renewable minimal repair–replacement warranty policy and propose an optimal maintenance model after the warranty is expired. Such model adopts the repair time threshold during the warranty period and follows with a certain type of system maintenance policy during the post-warranty period. As for the criteria for optimality, we utilize the expected cost rate per unit time during the life cycle of the system, which has been frequently used in many existing maintenance models. Based on the cost structure defined for each failure of the system, we formulate the expected cost rate during the life cycle of the system, assuming that a renewable minimal repair–replacement warranty policy with the repair time threshold is provided to the user during the warranty period. Once the warranty is expired, the maintenance of the system is the user's sole responsibility. The life cycle of the system is defined on the perspective of the user and the expected cost rate per unit time is derived in this context. We obtain the optimal maintenance policy during the maintenance period following the expiration of the warranty period by minimizing such a cost rate. Numerical examples using actual failure data are presented to exemplify the applicability of the methodologies proposed in this paper.

  17. A general approach to total repair cost limit replacement policies

    Directory of Open Access Journals (Sweden)

    F. Beichelt

    2014-01-01

    Full Text Available A common replacement policy for technical systems consists in replacing a system by a new one after its economic lifetime, i.e. at that moment when its long-run maintenance cost rate is minimal. However, the strict application of the economic lifetime does not take into account the individual deviations of maintenance cost rates of single systems from the average cost development. Hence, Beichet proposed the total repair cost limit replacement policy: the system is replaced by a new one as soon as its total repair cost reaches or exceeds a given level. He modelled the repair cost development by functions of the Wiener process with drift. Here the same policy is considered under the assumption that the one-dimensional probability distribution of the process describing the repair cost development is given. In the examples analysed, applying the total repair cost limit replacement policy instead of the economic life-time leads to cost savings of between 4% and 30%. Finally, it is illustrated how to include the reliability aspect into the policy.

  18. Optimal replacement of residential air conditioning equipment to minimize energy, greenhouse gas emissions, and consumer cost in the US

    International Nuclear Information System (INIS)

    De Kleine, Robert D.; Keoleian, Gregory A.; Kelly, Jarod C.

    2011-01-01

    A life cycle optimization of the replacement of residential central air conditioners (CACs) was conducted in order to identify replacement schedules that minimized three separate objectives: life cycle energy consumption, greenhouse gas (GHG) emissions, and consumer cost. The analysis was conducted for the time period of 1985-2025 for Ann Arbor, MI and San Antonio, TX. Using annual sales-weighted efficiencies of residential CAC equipment, the tradeoff between potential operational savings and the burdens of producing new, more efficient equipment was evaluated. The optimal replacement schedule for each objective was identified for each location and service scenario. In general, minimizing energy consumption required frequent replacement (4-12 replacements), minimizing GHG required fewer replacements (2-5 replacements), and minimizing cost required the fewest replacements (1-3 replacements) over the time horizon. Scenario analysis of different federal efficiency standards, regional standards, and Energy Star purchases were conducted to quantify each policy's impact. For example, a 16 SEER regional standard in Texas was shown to either reduce primary energy consumption 13%, GHGs emissions by 11%, or cost by 6-7% when performing optimal replacement of CACs from 2005 or before. The results also indicate that proper servicing should be a higher priority than optimal replacement to minimize environmental burdens. - Highlights: → Optimal replacement schedules for residential central air conditioners were found. → Minimizing energy required more frequent replacement than minimizing consumer cost. → Significant variation in optimal replacement was observed for Michigan and Texas. → Rebates for altering replacement patterns are not cost effective for GHG abatement. → Maintenance levels were significant in determining the energy and GHG impacts.

  19. A Bayesian perspective on age replacement with minimal repair

    International Nuclear Information System (INIS)

    Sheu, S.-H.; Yeh, R.H.; Lin, Y.-B.; Juang, M.-G.

    1999-01-01

    In this article, a Bayesian approach is developed for determining an optimal age replacement policy with minimal repair. By incorporating minimal repair, planned replacement, and unplanned replacement, the mathematical formulas of the expected cost per unit time are obtained for two cases - the infinite-horizon case and the one-replacement-cycle case. For each case, we show that there exists a unique and finite optimal age for replacement under some reasonable conditions. When the failure density is Weibull with uncertain parameters, a Bayesian approach is established to formally express and update the uncertain parameters for determining an optimal age replacement policy. Further, various special cases are discussed in detail. Finally, a numerical example is given

  20. A useful framework for optimal replacement models

    International Nuclear Information System (INIS)

    Aven, Terje; Dekker, Rommert

    1997-01-01

    In this note we present a general framework for optimization of replacement times. It covers a number of models, including various age and block replacement models, and allows a uniform analysis for all these models. A relation to the marginal cost concept is described

  1. Analytical method for optimization of maintenance policy based on available system failure data

    International Nuclear Information System (INIS)

    Coria, V.H.; Maximov, S.; Rivas-Dávalos, F.; Melchor, C.L.; Guardado, J.L.

    2015-01-01

    An analytical optimization method for preventive maintenance (PM) policy with minimal repair at failure, periodic maintenance, and replacement is proposed for systems with historical failure time data influenced by a current PM policy. The method includes a new imperfect PM model based on Weibull distribution and incorporates the current maintenance interval T 0 and the optimal maintenance interval T to be found. The Weibull parameters are analytically estimated using maximum likelihood estimation. Based on this model, the optimal number of PM and the optimal maintenance interval for minimizing the expected cost over an infinite time horizon are also analytically determined. A number of examples are presented involving different failure time data and current maintenance intervals to analyze how the proposed analytical optimization method for periodic PM policy performances in response to changes in the distribution of the failure data and the current maintenance interval. - Highlights: • An analytical optimization method for preventive maintenance (PM) policy is proposed. • A new imperfect PM model is developed. • The Weibull parameters are analytically estimated using maximum likelihood. • The optimal maintenance interval and number of PM are also analytically determined. • The model is validated by several numerical examples

  2. Optimal patent policies: A survey

    DEFF Research Database (Denmark)

    Poulsen, Odile

    2002-01-01

    This paper surveys some of the patent literature, in particular, it focuses on optimal patent policies. We compare two situations. The first where the government only has a single policy tool to design the optimal patent policy, namely the optimal patent length. In the second situation......, the government uses two policy tools, the optimal breadth and length. We show that theoretical models give very different answers to what is the optimal patent policy. In particular, we show that the optimal patent policy depends among othet things on the price elasticity of demand, the intersectoral elasticity...... of research outputs as well as the degree of compettition in the R&D sector. The actual law on intellectual property, which advocates a unique patent length of 20 years is in general not supported by theoretical models....

  3. Adaptive Neuro-fuzzy Inference System as Cache Memory Replacement Policy

    Directory of Open Access Journals (Sweden)

    CHUNG, Y. M.

    2014-02-01

    Full Text Available To date, no cache memory replacement policy that can perform efficiently for all types of workloads is yet available. Replacement policies used in level 1 cache memory may not be suitable in level 2. In this study, we focused on developing an adaptive neuro-fuzzy inference system (ANFIS as a replacement policy for improving level 2 cache performance in terms of miss ratio. The recency and frequency of referenced blocks were used as input data for ANFIS to make decisions on replacement. MATLAB was employed as a training tool to obtain the trained ANFIS model. The trained ANFIS model was implemented on SimpleScalar. Simulations on SimpleScalar showed that the miss ratio improved by as high as 99.95419% and 99.95419% for instruction level 2 cache, and up to 98.04699% and 98.03467% for data level 2 cache compared with least recently used and least frequently used, respectively.

  4. Optimization of station battery replacement

    International Nuclear Information System (INIS)

    Jancauskas, J.R.; Shook, D.A.

    1994-01-01

    During a loss of ac power at a nuclear generating station (including diesel generators), batteries provide the source of power which is required to operate safety-related components. Because traditional lead-acid batteries have a qualified life of 20 years, the batteries must be replaced a minimum of once during a station's lifetime, twice if license extension is pursued, and more often depending on actual in-service dates and the results of surveillance tests. Replacement of batteries often occurs prior to 20 years as a result of systems changes caused by factors such as Station Blackout Regulations, control system upgrades, incremental load growth, and changes in the operating times of existing equipment. Many of these replacement decisions are based on the predictive capabilities of manual design basis calculations. The inherent conservatism of manual calculations may result in battery replacements occurring before actually required. Computerized analysis of batteries can aid in optimizing the timing of replacements as well as in interpreting service test data. Computerized analysis also provides large benefits in maintaining the as-configured load profile and corresponding design margins, while also providing the capability of quickly analyze proposed modifications and response to internal and external audits

  5. Impact of few failure data on the opportunistic replacement policy for multi-component systems

    International Nuclear Information System (INIS)

    Laggoune, Radouane; Chateauneuf, Alaa; Aissani, Djamil

    2010-01-01

    In continuous operating units, the production loss is often very large during the system shut down. Their economic profitability is conditioned by the implementation of suitable maintenance policy that could increase the availability and reduce the operating costs. In this paper, an opportunistic replacement policy is proposed for multi-component series system in the context of data uncertainty, where the expected total cost per unit time is minimized under general lifetime distribution. When the system is down, either correctively or preventively, the opportunity to replace preventively non-failed components is considered. To deal with the problem of the small size of failure data samples, the Bootstrap technique is applied, in order to model the uncertainties in parameter estimates. The Weibull parameters are considered as random variables rather than just deterministic point estimates. A solution procedure based on Monte Carlo simulations with informative search method is proposed and applied to the optimization of preventive maintenance plan for a hydrogen compressor in an oil refinery.

  6. 76 FR 27649 - HIV/AIDS Bureau Policy Notice 11-01 (Replaces Policy Notice 99-02)

    Science.gov (United States)

    2011-05-12

    ... Bureau Policy Notice 11-01 (Replaces Policy Notice 99- 02) AGENCY: Health Resources and Services.../AIDS Bureau (HAB) Policy Notice 99-02 established policies for the use of Ryan White HIV/AIDS Program... and short-term or emergency housing needs. Amendment 1 to Policy Notice 99-02, effective March 27...

  7. Age replacement models: A summary with new perspectives and methods

    International Nuclear Information System (INIS)

    Zhao, Xufeng; Al-Khalifa, Khalifa N.; Magid Hamouda, Abdel; Nakagawa, Toshio

    2017-01-01

    Age replacement models are fundamental to maintenance theory. This paper summarizes our new perspectives and hods in age replacement models: First, we optimize the expected cost rate for a required availability level and vice versa. Second, an asymptotic model with simple calculation is proposed by using the cumulative hazard function skillfully. Third, we challenge the established theory such that preventive replacement should be non-random and only corrective replacement should be made for the unit with exponential failure. Fourth, three replacement policies with random working cycles are discussed, which are called overtime replacement, replacement first, and replacement last, respectively. Fifth, the policies of replacement first and last are formulated with general models. Sixth, age replacement is modified for the situation when the economical life cycle of the unit is a random variable with probability distribution. Finally, models of a parallel system with constant and random number of units are taken into considerations. The models of expected cost rates are obtained and optimal replacement times to minimize them are discussed analytically and computed numerically. Further studies and potential applications are also indicated at the end of discussions of the above models. - Highlights: • Optimization of cost rate for availability level is discussed and vice versa. • Asymptotic and random replacement models are discussed. • Overtime replacement, replacement first and replacement last are surveyed. • Replacement policy with random life cycle is given. • A parallel system with random number of units is modeled.

  8. Optimal replacement time estimation for machines and equipment based on cost function

    Directory of Open Access Journals (Sweden)

    J. Šebo

    2013-01-01

    Full Text Available The article deals with a multidisciplinary issue of estimating the optimal replacement time for the machines. Considered categories of machines, for which the optimization method is usable, are of the metallurgical and engineering production. Different models of cost function are considered (both with one and two variables. Parameters of the models were calculated through the least squares method. Models testing show that all are good enough, so for estimation of optimal replacement time is sufficient to use simpler models. In addition to the testing of models we developed the method (tested on selected simple model which enable us in actual real time (with limited data set to indicate the optimal replacement time. The indicated time moment is close enough to the optimal replacement time t*.

  9. A summary of maintenance policies for a finite interval

    International Nuclear Information System (INIS)

    Nakagawa, T.; Mizutani, S.

    2009-01-01

    It would be an important problem to consider practically some maintenance policies for a finite time span, because the working times of most units are finite in actual fields. This paper converts the usual maintenance models to finite maintenance models. It is more difficult to study theoretically optimal policies for a finite time span than those for an infinite time span. Three usual models of periodic replacement with minimal repair, block replacement and simple replacement are transformed to finite replacement models. Further, optimal periodic and sequential policies for an imperfect preventive maintenance and an inspection model for a finite time span are considered. Optimal policies for each model are analytically derived and are numerically computed

  10. Optimal replacement policies for dairy cows based on daily yield measurements

    DEFF Research Database (Denmark)

    Nielsen, Lars Relund; Jørgensen, Erik; Kristensen, Anders Ringgaard

    2010-01-01

    describes the first step of developing an MDP model that can be integrated into a modern herd management system. A hierarchical MDP was formulated for the dairy cow replacement problem with stage lengths of 1 d. It can be used to assist the farmer in replacement decisions on a daily basis and is based...

  11. A model for an economically optimal replacement of a breeder flock.

    Science.gov (United States)

    Yassin, Hurria; Velthuis, Annet G J; Giesen, Gerard W J; Oude Lansink, Alfons G J M

    2012-12-01

    A deterministic model is developed to support the tactical and operational replacement decisions at broiler breeder farms. The marginal net revenue approach is applied to determine the optimal replacement age of a flock. The objective function of the model maximizes the annual gross margin over the flock's production cycle. To calculate the gross margin, future egg production, fertility, or hatchability of the eggs, revenues and variable costs of a flock were estimated. For tactical decisions, the optimal laying length is the age at which the average gross margin of an average flock is maximal. For operational decisions, a flock should be replaced when the marginal gross margin of a replaceable flock is less than the average gross margin of an average flock. To demonstrate the model, a broiler breeder flock from a Dutch breeder farm was used. A sensitivity analysis showed that the optimal replacement decision, for both tactical and operational management, is sensitive to the decrease in the weekly egg production after the peak and the prices of feed and hatching eggs. The effect of the decrease in weekly fertility after the peak on the replacement decision is related to the payment system for hatching eggs.

  12. Optimal timing of joint replacement using mathematical programming and stochastic programming models.

    Science.gov (United States)

    Keren, Baruch; Pliskin, Joseph S

    2011-12-01

    The optimal timing for performing radical medical procedures as joint (e.g., hip) replacement must be seriously considered. In this paper we show that under deterministic assumptions the optimal timing for joint replacement is a solution of a mathematical programming problem, and under stochastic assumptions the optimal timing can be formulated as a stochastic programming problem. We formulate deterministic and stochastic models that can serve as decision support tools. The results show that the benefit from joint replacement surgery is heavily dependent on timing. Moreover, for a special case where the patient's remaining life is normally distributed along with a normally distributed survival of the new joint, the expected benefit function from surgery is completely solved. This enables practitioners to draw the expected benefit graph, to find the optimal timing, to evaluate the benefit for each patient, to set priorities among patients and to decide if joint replacement should be performed and when.

  13. Asymptotically optimal production policies in dynamic stochastic jobshops with limited buffers

    Science.gov (United States)

    Hou, Yumei; Sethi, Suresh P.; Zhang, Hanqin; Zhang, Qing

    2006-05-01

    We consider a production planning problem for a jobshop with unreliable machines producing a number of products. There are upper and lower bounds on intermediate parts and an upper bound on finished parts. The machine capacities are modelled as finite state Markov chains. The objective is to choose the rate of production so as to minimize the total discounted cost of inventory and production. Finding an optimal control policy for this problem is difficult. Instead, we derive an asymptotic approximation by letting the rates of change of the machine states approach infinity. The asymptotic analysis leads to a limiting problem in which the stochastic machine capacities are replaced by their equilibrium mean capacities. The value function for the original problem is shown to converge to the value function of the limiting problem. The convergence rate of the value function together with the error estimate for the constructed asymptotic optimal production policies are established.

  14. Machine replacement, Network Externalities and Investment Cycles

    OpenAIRE

    Juan Ruiz

    2003-01-01

    This paper presents a model where agents decide on the timing of replacement of ageing machines. The optimal replacement policy for an agent is influenced by other agents' decisions because the productivity of a particular vintage displays network externalities that set in with a lag. In equilibrium, agents follow innovation cycles with a frequency that is lower than optimal, so there is too much delay. One extreme case is the possibility of inefficient collapse: for some parameters there is ...

  15. Optimal replacement time estimation for machines and equipment based on cost function

    OpenAIRE

    J. Šebo; J. Buša; P. Demeč; J. Svetlík

    2013-01-01

    The article deals with a multidisciplinary issue of estimating the optimal replacement time for the machines. Considered categories of machines, for which the optimization method is usable, are of the metallurgical and engineering production. Different models of cost function are considered (both with one and two variables). Parameters of the models were calculated through the least squares method. Models testing show that all are good enough, so for estimation of optimal replacement time is ...

  16. Investment, replacement and scrapping in a vintage capital model with embodied technological change

    OpenAIRE

    Bitros, George C.; Hritonenko, Natali; Yatsenko, Yuri

    2007-01-01

    This paper analyzes and compares two alternative policies of determining the service life and replacement demand for vintage equipment under embodied technological change. The policies are the infinite-horizon replacement and the transitory replacement ending with scrapping. The corresponding vintage capital models are formulated in the dynamic optimization framework. These two approaches lead to different estimates of the duration of replacements and the impact of technological change on the...

  17. Maintenance and replacement policies under technological obsolescence

    International Nuclear Information System (INIS)

    Clavareau, Julien; Labeau, Pierre-Etienne

    2009-01-01

    The technological obsolescence of a unit is characterized by the existence of challenger units displaying identical functionalities, but with higher performances. This paper aims to define and model in a realistic way, possible maintenance policies of a system including replacement strategies when one type of challenger unit is available. The comparison of these possible strategies is performed based on a Monte Carlo estimation of the costs they incur

  18. Maintenance and replacement policies under technological obsolescence

    Energy Technology Data Exchange (ETDEWEB)

    Clavareau, Julien [Service de Metrologie Nucleaire, Universite Libre de Bruxelles, Av. Franklin Roosevelt 50, CP165/84 Bruxelles B-1050 (Belgium)], E-mail: jclavare@ulb.ac.be; Labeau, Pierre-Etienne [Service de Metrologie Nucleaire, Universite Libre de Bruxelles, Av. Franklin Roosevelt 50, CP165/84 Bruxelles B-1050 (Belgium)], E-mail: pelabeau@ulb.ac.be

    2009-02-15

    The technological obsolescence of a unit is characterized by the existence of challenger units displaying identical functionalities, but with higher performances. This paper aims to define and model in a realistic way, possible maintenance policies of a system including replacement strategies when one type of challenger unit is available. The comparison of these possible strategies is performed based on a Monte Carlo estimation of the costs they incur.

  19. Policies for replacing long-term indwelling urinary catheters in adults.

    Science.gov (United States)

    Cooper, Fergus P M; Alexander, Cameron Edwin; Sinha, Sanjay; Omar, Muhammad Imran

    2016-07-26

    Long-term indwelling catheters are used commonly in people with lower urinary tract problems in home, hospital and specialised health-care settings. There are many potential complications and adverse effects associated with long-term catheter use. The effect of health-care policies related to the replacement of long-term urinary catheters on patient outcomes is unclear. To determine the effectiveness of different policies for replacing long-term indwelling urinary catheters in adults. We searched the Cochrane Incontinence Specialised Trials Register, which contains trials identified from the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, MEDLINE In-Process, MEDLINE Epub Ahead of Print, CINAHL, ClinicalTrials.gov, WHO ICTRP and handsearching of journals and conference proceedings (searched 19 May 2016), and the reference lists of relevant articles. All randomised controlled trials investigating policies for replacing long-term indwelling urinary catheters in adults were included. At least two review authors independently performed data extraction and assessed risk of bias of all the included trials. Quality of evidence was assessed by adopting the GRADE approach. Any discrepancies were resolved by discussion between the review authors or an independent arbitrator. We contacted the authors of included trials to seek clarification where required. Three trials met the inclusion criteria, with a total of 107 participants in three different health-care settings: A USA veterans administration nursing home; a geriatric centre in Israel; and a community nursing service in Hong Kong. Data were available for three of the pre-stated comparisons. Priefer and colleagues evaluated different time intervals between catheter replacement (n = 17); Firestein and colleagues evaluated the use of antibiotic prophylaxis at the time of replacement (n = 70); and Cheung and colleagues compared two different types of cleaning solutions (n = 20).All the included trials were

  20. Optimal Temporal Policies in Fluid Milk Advertising

    OpenAIRE

    Vande Kamp, Philip R.; Kaiser, Harry M.

    1998-01-01

    This study develops an approach to obtain optimal temporal advertising strategies when consumers' response to advertising is asymmetric. Using this approach, optimal strategies for generic fluid milk advertising in New York City are determined. Results indicate that pulsed advertising policies are significantly more effective in increasing demand than a uniform advertising policy. Sensitivity analyses show that the optimal advertising policies are insensitive to reasonable variations in inter...

  1. The influence of optimism on functionality after total hip replacement surgery.

    Science.gov (United States)

    Balck, Friedrich; Lippmann, Maike; Jeszenszky, Csilla; Günther, Klaus-Peter; Kirschner, Stephan

    2016-08-01

    Among other factors, optimism has been shown to significantly influence the course of some diseases (cancer, HIV, coronary heart disease). This study investigated whether optimism of a patient before a total hip replacement can predict the functionality of the lower limbs 3 and 6 months after surgery. A total of 325 patients took part in the study (age: 58.7 years; w: 55%). The functionality was measured with the Western Ontario and McMaster Universities arthrosis index, and optimism with the Life Orientation Test. To analyse the influences of age, gender and optimism, general linear models were calculated. In optimistic patients, functionality improved significantly over time. The study showed a clear influence of dispositional optimism on the recovery after total hip replacement in the first 3 months after surgery. © The Author(s) 2015.

  2. Optimal elastomeric scaffold leaflet shape for pulmonary heart valve leaflet replacement.

    Science.gov (United States)

    Fan, Rong; Bayoumi, Ahmed S; Chen, Peter; Hobson, Christopher M; Wagner, William R; Mayer, John E; Sacks, Michael S

    2013-02-22

    Surgical replacement of the pulmonary valve (PV) is a common treatment option for congenital pulmonary valve defects. Engineered tissue approaches to develop novel PV replacements are intrinsically complex, and will require methodical approaches for their development. Single leaflet replacement utilizing an ovine model is an attractive approach in that candidate materials can be evaluated under valve level stresses in blood contact without the confounding effects of a particular valve design. In the present study an approach for optimal leaflet shape design based on finite element (FE) simulation of a mechanically anisotropic, elastomeric scaffold for PV replacement is presented. The scaffold was modeled as an orthotropic hyperelastic material using a generalized Fung-type constitutive model. The optimal shape of the fully loaded PV replacement leaflet was systematically determined by minimizing the difference between the deformed shape obtained from FE simulation and an ex-vivo microCT scan of a native ovine PV leaflet. Effects of material anisotropy, dimensional changes of PV root, and fiber orientation on the resulting leaflet deformation were investigated. In-situ validation demonstrated that the approach could guide the design of the leaflet shape for PV replacement surgery. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. The optimal number of heifer calves to be reared as dairy replacements.

    Science.gov (United States)

    Mohd Nor, N; Steeneveld, W; Mourits, M C M; Hogeveen, H

    2015-02-01

    Dairy farmers often keep almost all their newborn heifer calves despite the high cost of rearing. By rearing all heifer calves, farmers have more security and retain flexibility to cope with the uncertainty in the availability of replacement heifers in time. This uncertainty is due to mortality or infertility during the rearing period and the variation in culling rate of lactating cows. The objective of this study is to provide insight in the economically optimal number of heifer calves to be reared as replacements. A herd-level stochastic simulation model was developed specific for this purpose with a herd of 100 dairy cows; the biological part of the model consisted of a dairy herd unit and rearing unit for replacement heifers. The dairy herd unit included variation in the number of culled dairy cows. The rearing unit incorporated variation in the number of heifers present in the herd by including uncertainty in mortality and variation in fertility. The dairy herd unit and rearing unit were linked by the number of replacement heifers and culled dairy cows. When not enough replacement heifers were available to replace culled dairy cows, the herd size was temporarily reduced, resulting in an additional cost for the empty slots. When the herd size reached 100 dairy cows, the available replacement heifers that were not needed were sold. It was assumed that no purchase of cows and calves occurred. The optimal percentage of 2-wk-old heifer calves to be retained was defined as the percentage of heifer calves that minimized the average net costs of rearing replacement heifers. In the default scenario, the optimal retention was 73% and the total net cost of rearing was estimated at €40,939 per herd per year. This total net cost was 6.5% lower than when all heifer calves were kept. An earlier first-calving age resulted in an optimal retention of 75%, and the net costs of rearing were €581 per herd per year lower than in the default scenario. For herds with a lower or

  4. Efforts for optimization of BWR core internals replacement

    International Nuclear Information System (INIS)

    Iizuka, N.

    2000-01-01

    The core internal components replacement of a BWR was successfully completed at Fukushima-Daiichi Unit 3 (1F3) of the Tokyo Electric Power Company (TEPCO) in 1998. The core shroud and the majority of the internal components made by type 304 stainless steel (SS) were replaced with the ones made of low carbon type 316L SS to improve Intergranular Stress Corrosion Cracking (IGSCC) resistance. Although this core internals replacement project was completed, several factors combined to result in a longer-than-expected period for the outage. It was partly because the removal work of the internal components was delayed. Learning a lesson from whole experience in this project, some methods were adopted for the next replacement project at Fukushima-Daiichi Unit 2 (1F2) to shorten the outage and reduce the total radiation exposure. Those are new removal processes and new welding machine and so on. The core internals replacement work was ended at 1F2 in 1999, and both the period of outage and the total radiation exposure were the same degree as expected previous to starting of this project. This result shows that the methods adopted in this project are basically applicable for the core internals replacement work and the whole works about the BWR core internals replacement were optimized. The outline of the core internals replacement project and applied technologies at 1F3 and 1F2 are discussed in this paper. (author)

  5. Optimum equipment maintenance/replacement policy. Part 2: Markov decision approach

    Science.gov (United States)

    Charng, T.

    1982-01-01

    Dynamic programming was utilized as an alternative optimization technique to determine an optimal policy over a given time period. According to a joint effect of the probabilistic transition of states and the sequence of decision making, the optimal policy is sought such that a set of decisions optimizes the long-run expected average cost (or profit) per unit time. Provision of an alternative measure for the expected long-run total discounted costs is also considered. A computer program based on the concept of the Markov Decision Process was developed and tested. The program code listing, the statement of a sample problem, and the computed results are presented.

  6. A model for an economically optimal replacement of a breeder flock

    NARCIS (Netherlands)

    Yassin, H.; Velthuis, A.G.J.; Giesen, G.W.J.; Oude Lansink, A.G.J.M.

    2012-01-01

    A deterministic model is developed to support the tactical and operational replacement decisions at broiler breeder farms. The marginal net revenue approach is applied to determine the optimal replacement age of a flock. The objective function of the model maximizes the annual gross margin over the

  7. Optimization of steam generator replacement with virtual reality modeling

    International Nuclear Information System (INIS)

    Kim, Jeong H.; Suh, Kune Y.

    2008-01-01

    Nuclear power plants (NPPs) have to be carefully examined and maintained up to the point of replacing major components during the overhaul period for continued operation. Most understandably the cost of maintenance and upgrading will tend to increase with the NPP power. There is thus an escalating need for developing an optimized process management method to reduce the cost involved. Albeit the steam generators (SGs) may not directly affect the expected lifespan of NPP, thousands of tubes with diameter on the order of 3 cm in the SG operating at 320degC and 16 MPa may well tend to be called Achilles' heel of the pressurized water reactors (PWRs). For instance, the SGs of Kori Nuclear Unit 1 (KNU 1) were replaced in October 1998 after 20 years of service on account of aging and potential threat to operational safety. In the same year the SG tubes of Ulchin Nuclear Units 1 and 2 were ruptured to result in leakage of the primary coolant to the secondary side. As a result their SGs are planned to be replaced in a few years. There is, however, a limit to improving the replacement process by trial and error in practice on account of the size of NPP with the ensuing complexity in process management. This paper proposes an optimization method for the SG replacement process based on the KNU 1 experience in 1998. The whole process was simulated accounting for interactions of each part in virtual reality utilizing the computer aided design solution CATIA, and the digital process management solution DELMIA. (author)

  8. Optimal serotype compositions for Pneumococcal conjugate vaccination under serotype replacement.

    Science.gov (United States)

    Nurhonen, Markku; Auranen, Kari

    2014-02-01

    Pneumococcal conjugate vaccination has proved highly effective in eliminating vaccine-type pneumococcal carriage and disease. However, the potential adverse effects of serotype replacement remain a major concern when implementing routine childhood pneumococcal conjugate vaccination programmes. Applying a concise predictive model, we present a ready-to-use quantitative tool to investigate the implications of serotype replacement on the net effectiveness of vaccination against invasive pneumococcal disease (IPD) and to guide in the selection of optimal vaccine serotype compositions. We utilise pre-vaccination data on pneumococcal carriage and IPD and assume partial or complete elimination of vaccine-type carriage, its replacement by non-vaccine-type carriage, and stable case-to-carrier ratios (probability of IPD per carriage episode). The model predicts that the post-vaccination IPD incidences in Finland for currently available vaccine serotype compositions can eventually decrease among the target age group of children replacement through herd effects, the decrease among the older population is predicted to be much less (20-40%). We introduce a sequential algorithm for the search of optimal serotype compositions and assess the robustness of inferences to uncertainties in data and assumptions about carriage and IPD. The optimal serotype composition depends on the age group of interest and some serotypes may be highly beneficial vaccine types in one age category (e.g. 6B in children), while being disadvantageous in another. The net effectiveness will be improved only if the added serotype has a higher case-to-carrier ratio than the average case-to-carrier ratio of the current non-vaccine types and the degree of improvement in effectiveness depends on the carriage incidence of the serotype. The serotype compositions of currently available pneumococcal vaccines are not optimal and the effectiveness of vaccination in the population at large could be improved by including

  9. Value maximizing maintenance policies under general repair

    International Nuclear Information System (INIS)

    Marais, Karen B.

    2013-01-01

    One class of maintenance optimization problems considers the notion of general repair maintenance policies where systems are repaired or replaced on failure. In each case the optimality is based on minimizing the total maintenance cost of the system. These cost-centric optimizations ignore the value dimension of maintenance and can lead to maintenance strategies that do not maximize system value. This paper applies these ideas to the general repair optimization problem using a semi-Markov decision process, discounted cash flow techniques, and dynamic programming to identify the value-optimal actions for any given time and system condition. The impact of several parameters on maintenance strategy, such as operating cost and revenue, system failure characteristics, repair and replacement costs, and the planning time horizon, is explored. This approach provides a quantitative basis on which to base maintenance strategy decisions that contribute to system value. These decisions are different from those suggested by traditional cost-based approaches. The results show (1) how the optimal action for a given time and condition changes as replacement and repair costs change, and identifies the point at which these costs become too high for profitable system operation; (2) that for shorter planning horizons it is better to repair, since there is no time to reap the benefits of increased operating profit and reliability; (3) how the value-optimal maintenance policy is affected by the system's failure characteristics, and hence whether it is worthwhile to invest in higher reliability; and (4) the impact of the repair level on the optimal maintenance policy. -- Highlights: •Provides a quantitative basis for maintenance strategy decisions that contribute to system value. •Shows how the optimal action for a given condition changes as replacement and repair costs change. •Shows how the optimal policy is affected by the system's failure characteristics. •Shows when it is

  10. The Impact of Assessment Policy on Learning: Replacement Exams or Grade Dropping

    Science.gov (United States)

    MacDermott, Raymond J.

    2013-01-01

    Instructors often debate the merits of alternate grading policies such as dropping the lowest exam or offering an additional exam to replace the lowest score. To date, there has been little research conducted on the impact of these policies on performance. In this study, the author investigates student performance in intermediate macroeconomics…

  11. Impact of biological and economic variables on optimal parity for replacement in swine breed-to-wean herds.

    Science.gov (United States)

    Rodriguez-Zas, S L; Davis, C B; Ellinger, P N; Schnitkey, G D; Romine, N M; Connor, J F; Knox, R V; Southey, B R

    2006-09-01

    Voluntary and involuntary culling practices determine the average parity when sows are replaced in a herd. Underlying these practices is the economic effect of replacing a sow at different parities. A dynamic programming model was used to find the optimal parity and net present value in breed-to-wean swine herds. The model included income and costs per parity weighted by the discount rate and sow removal rate. Three scenarios that reflect a wide range of cases were considered: low removal rates per parity with no salvage value (LRNS), high removal rates per parity with no salvage value (HRNS), and high removal rates per parity with a percentage of the sows having a salvage value (HRYS). The optimal parity of replacement for the base biological and economic conditions was 4 and 5 parities in the high and low removal scenarios, respectively. Sensitivity analyses identified the variables influencing the optimal replacement parity. Optimal parity of replacement ranged from 3 to 7 parities in the low replacement scenario, compared with 1 to 5 parities in the high replacement scenarios. Sow replacement cost and salvage value had the greatest impact on optimal parity of replacement followed by revenues per piglet weaned. The discount rate and number of parities per year generally had little influence on optimal parity. For situations with high sow costs, low salvage values, and low revenues per piglet, the optimal parity at removal was as high as 6 to 10 parities, and for situations with low sow cost, high salvage values, and high revenues per piglet, the optimal parity at removal was as low as 1 to 2 parities depending on removal rates. The modified internal rate of return suggested that, for most LRNS and HRYS scenarios considered, investment in a swine breed-to-wean enterprise was favored over other investments involving a similar risk profile. Our results indicate that in US breeding herds, sows are culled on average near the optimal parity of 4. However, the

  12. Setting the optimal type of equipment to be adopted and the optimal time to replace it

    OpenAIRE

    Albici, Mihaela

    2009-01-01

    The mathematical models of equipment’s wear and tear, and replacement theory aim at deciding on the purchase selection of a certain equipment type, the optimal exploitation time of the equipment, the time and ways to replace or repair it, or to ensure its spare parts, the equipment’s performance in the technical progress context, the opportunities to modernize it etc.

  13. Optimal Policy in OG Models

    DEFF Research Database (Denmark)

    Ghiglino, Christian; Tvede, Mich

    for generations, through fiscal policy, i.e. monetary transfers and taxes. Both situations with and without time discounting are considered. It is shown that if the discount factor is suffciently close to one then the optimal policy stabilizes the economy, i.e. the equilibrium path has the turnpike property...

  14. Optimal Policy in OG Models

    DEFF Research Database (Denmark)

    Ghiglino, Christian; Tvede, Mich

    2000-01-01

    for generations, through fiscal policy, i.e., monetary transfers and taxes. Situations both with and without time discounting are considered. It is shown that if the discount factor is sufficiently close to one then the optimal policy stabilizes the economy, i.e. the equilibrium path has the turnpike property...

  15. OPTIMIZATION OF THE RUSSIAN MACROECONOMIC POLICY FOR 2016-2020

    Directory of Open Access Journals (Sweden)

    Gilmundinov V. M.

    2016-12-01

    Full Text Available This paper is concerned with the methodological issues of economic policy elaboration and optimization of economic policy instruments’ parameters. Actuality of this research is provided by growing complexity of social and economic systems, important state role in their functioning as well as multi-targets of economic policy with limited number of instruments. Considering a big variety of internal and external restrictions of social and economic development of modern Russia it has wide range of applications. Extension of the dynamic econometric general equilibrium input-output model of the Russian economy with development of the sub-model of economic policy optimization is a key purpose of this study. The sub-model of economic policy optimization allows estimating impact of economic policy measures on target indicators as well as defining optimal values of their parameters. For this purpose, we extend Robert Mundell’s approach by considering dynamic optimization and wider range of economic policy targets and measures. Use of general equilibrium input-output model allows considering impact of economic policy on different aggregate markets and sectors. Approbation of suggested approach allows us to develop multi-variant forecast for the Russian economy for 2016-2020, define optimal values of monetary policy parameters and compare considered variants by values of social losses. The obtained results could be further used in theoretical as well as applied researches concerned with issues of economic policy elaboration and forecasting of social and economic development.

  16. Replacement model of city bus: A dynamic programming approach

    Science.gov (United States)

    Arifin, Dadang; Yusuf, Edhi

    2017-06-01

    This paper aims to develop a replacement model of city bus vehicles operated in Bandung City. This study is driven from real cases encountered by the Damri Company in the efforts to improve services to the public. The replacement model propounds two policy alternatives: First, to maintain or keep the vehicles, and second is to replace them with new ones taking into account operating costs, revenue, salvage value, and acquisition cost of a new vehicle. A deterministic dynamic programming approach is used to solve the model. The optimization process was heuristically executed using empirical data of Perum Damri. The output of the model is to determine the replacement schedule and the best policy if the vehicle has passed the economic life. Based on the results, the technical life of the bus is approximately 20 years old, while the economic life is an average of 9 (nine) years. It means that after the bus is operated for 9 (nine) years, managers should consider the policy of rejuvenation.

  17. Seeking optimal renal replacement therapy delivery in intensive care units.

    Science.gov (United States)

    Kocjan, Marinka; Brunet, Fabrice P

    2010-01-01

    Globally, critical care environments within health care organizations strive to provide optimal quality renal replacement therapy (RRT), an artificial replacement for lost kidney function. Examination of RRT delivery model literature and a case study review of the multidisciplinary-mixed RRT delivery model utilized within a closed medical surgical intensive care unit illustrates the organizational and clinical management of specialized resource and multidisciplinary roles. The successful utilization of a specific RRT delivery model is dependent upon resource availability.

  18. Optimization of inspection and replacement period by using Bayesian statistics

    International Nuclear Information System (INIS)

    Kasai, Masao; Watanabe, Yasushi; Kusakari, Yoshiyuki; Notoya, Junichi

    2006-01-01

    This study describes the formulations to optimize the time interval of inspections and/or replacements of equipment/parts taking into account the probability density functions (PDF) for failure rates and parameters of failure distribution functions (FDF) and evaluates the optimized results of these time intervals using our formulations by comparing with those using only representative values of failure rates and the parameters of FDF instead of using these PDFs. The PDFs are obtained with Bayesian method and the representative values are obtained with likelihood estimation method. However, any significant difference is not observed between both optimized results within our preliminary calculations. (author)

  19. Endogenous price flexibility and optimal monetary policy

    OpenAIRE

    Ozge Senay; Alan Sutherland

    2014-01-01

    Much of the literature on optimal monetary policy uses models in which the degree of nominal price flexibility is exogenous. There are, however, good reasons to suppose that the degree of price flexibility adjusts endogenously to changes in monetary conditions. This article extends the standard new Keynesian model to incorporate an endogenous degree of price flexibility. The model shows that endogenizing the degree of price flexibility tends to shift optimal monetary policy towards complete i...

  20. A condition-based maintenance policy for stochastically deteriorating systems

    International Nuclear Information System (INIS)

    Grall, A.; Berenguer, C.; Dieulle, L.

    2002-01-01

    We focus on the analytical modeling of a condition-based inspection/replacement policy for a stochastically and continuously deteriorating single-unit system. We consider both the replacement threshold and the inspection schedule as decision variables for this maintenance problem and we propose to implement the maintenance policy using a multi-level control-limit rule. In order to assess the performance of the proposed maintenance policy and to minimize the long run expected maintenance cost per unit time, a mathematical model for the maintained system cost is derived, supported by the existence of a stationary law for the maintained system state. Numerical experiments illustrate the performance of the proposed policy and confirm that the maintenance cost rate on an infinite horizon can be minimized by a joint optimization of the maintenance structure thresholds, or equivalently by a joint optimization of a system replacement threshold and the aperiodic inspection schedule

  1. OPTIMAL DATA REPLACEMENT TECHNIQUE FOR COOPERATIVE CACHING IN MANET

    Directory of Open Access Journals (Sweden)

    P. Kuppusamy

    2014-09-01

    Full Text Available A cooperative caching approach improves data accessibility and reduces query latency in Mobile Ad hoc Network (MANET. Maintaining the cache is challenging issue in large MANET due to mobility, cache size and power. The previous research works on caching primarily have dealt with LRU, LFU and LRU-MIN cache replacement algorithms that offered low query latency and greater data accessibility in sparse MANET. This paper proposes Memetic Algorithm (MA to locate the better replaceable data based on neighbours interest and fitness value of cached data to store the newly arrived data. This work also elects ideal CH using Meta heuristic search Ant Colony Optimization algorithm. The simulation results shown that proposed algorithm reduces the latency, control overhead and increases the packet delivery rate than existing approach by increasing nodes and speed respectively.

  2. A study on the optimal replacement periods of digital control computer's components of Wolsung nuclear power plant unit 1

    International Nuclear Information System (INIS)

    Mok, Jin Il; Seong, Poong Hyun

    1993-01-01

    Due to the failure of the instrument and control devices of nuclear power plants caused by aging, nuclear power plants occasionally trip. Even a trip of a single nuclear power plant (NPP) causes an extravagant economical loss and deteriorates public acceptance of nuclear power plants. Therefore, the replacement of the instrument and control devices with proper consideration of the aging effect is necessary in order to prevent the inadvertent trip. In this paper we investigated the optimal replacement periods of the control computer's components of Wolsung nuclear power plant Unit 1. We first derived mathematical models of optimal replacement periods to the digital control computer's components of Wolsung NPP Unit 1 and calculated the optimal replacement periods analytically. We compared the periods with the replacement periods currently used at Wolsung NPP Unit 1. The periods used at Wolsung is not based on mathematical analysis, but on empirical knowledge. As a consequence, the optimal replacement periods analytically obtained and those used in the field show a little difference. (Author)

  3. Condition-based inspection/replacement policies for non-monotone deteriorating systems with environmental covariates

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Xuejing [Universite de Technologie de Troyes, Institut Charles Delaunay and STMR UMR CNRS 6279, 12 rue Marie Curie, 10010 Troyes (France); School of mathematics and statistics, Lanzhou University, Lanzhou 730000 (China); Fouladirad, Mitra, E-mail: mitra.fouladirad@utt.f [Universite de Technologie de Troyes, Institut Charles Delaunay and STMR UMR CNRS 6279, 12 rue Marie Curie, 10010 Troyes (France); Berenguer, Christophe [Universite de Technologie de Troyes, Institut Charles Delaunay and STMR UMR CNRS 6279, 12 rue Marie Curie, 10010 Troyes (France); Bordes, Laurent [Universite de Pau et des Pays de l' Adour, LMA UMR CNRS 5142, 64013 PAU Cedex (France)

    2010-08-15

    The aim of this paper is to discuss the problem of modelling and optimising condition-based maintenance policies for a deteriorating system in presence of covariates. The deterioration is modelled by a non-monotone stochastic process. The covariates process is assumed to be a time-homogenous Markov chain with finite state space. A model similar to the proportional hazards model is used to show the influence of covariates on the deterioration. In the framework of the system under consideration, an appropriate inspection/replacement policy which minimises the expected average maintenance cost is derived. The average cost under different conditions of covariates and different maintenance policies is analysed through simulation experiments to compare the policies performances.

  4. Condition-based inspection/replacement policies for non-monotone deteriorating systems with environmental covariates

    International Nuclear Information System (INIS)

    Zhao Xuejing; Fouladirad, Mitra; Berenguer, Christophe; Bordes, Laurent

    2010-01-01

    The aim of this paper is to discuss the problem of modelling and optimising condition-based maintenance policies for a deteriorating system in presence of covariates. The deterioration is modelled by a non-monotone stochastic process. The covariates process is assumed to be a time-homogenous Markov chain with finite state space. A model similar to the proportional hazards model is used to show the influence of covariates on the deterioration. In the framework of the system under consideration, an appropriate inspection/replacement policy which minimises the expected average maintenance cost is derived. The average cost under different conditions of covariates and different maintenance policies is analysed through simulation experiments to compare the policies performances.

  5. Extreme Trust Region Policy Optimization for Active Object Recognition.

    Science.gov (United States)

    Liu, Huaping; Wu, Yupei; Sun, Fuchun; Huaping Liu; Yupei Wu; Fuchun Sun; Sun, Fuchun; Liu, Huaping; Wu, Yupei

    2018-06-01

    In this brief, we develop a deep reinforcement learning method to actively recognize objects by choosing a sequence of actions for an active camera that helps to discriminate between the objects. The method is realized using trust region policy optimization, in which the policy is realized by an extreme learning machine and, therefore, leads to efficient optimization algorithm. The experimental results on the publicly available data set show the advantages of the developed extreme trust region optimization method.

  6. Interactions between optimal replacement policies and feeding strategies in dairy herds

    NARCIS (Netherlands)

    Vargas, B.; Herrero, M.; Arendonk, van J.A.M.

    2001-01-01

    A dynamic performance model was integrated with a model that optimised culling and insemination policies in dairy herds using dynamic programming. The performance model estimated daily feed intake, milk yield and body weight change of dairy cows on the basis of availability and quality of feed and

  7. Optimization of Overflow Policies in Call Centers

    DEFF Research Database (Denmark)

    Koole, G.M.; Nielsen, B.F.; Nielsen, T.B.

    2015-01-01

    . A Markov decision chain is used to determine the optimal policy. This policy outperforms considerably the ones used most often in practice, which use a fixed threshold. The present method can be used also for other call-center models and other situations where performance is based on actual waiting times...

  8. Studies on the replacement policies in dairy cattle II.Optimum policy and influence of changes in production and prices

    NARCIS (Netherlands)

    Arendonk, van J.A.M.

    1985-01-01

    A dynamic programming model was developed to determine the optimum replacement policy of dairy cows. In the model cows were described in terms of lactation number, stage of lactation and the level of milk production during the previous and present lactations. The objective in determining the optimum

  9. Financing and funding health care: Optimal policy and political implementability.

    Science.gov (United States)

    Nuscheler, Robert; Roeder, Kerstin

    2015-07-01

    Health care financing and funding are usually analyzed in isolation. This paper combines the corresponding strands of the literature and thereby advances our understanding of the important interaction between them. We investigate the impact of three modes of health care financing, namely, optimal income taxation, proportional income taxation, and insurance premiums, on optimal provider payment and on the political implementability of optimal policies under majority voting. Considering a standard multi-task agency framework we show that optimal health care policies will generally differ across financing regimes when the health authority has redistributive concerns. We show that health care financing also has a bearing on the political implementability of optimal health care policies. Our results demonstrate that an isolated analysis of (optimal) provider payment rests on very strong assumptions regarding both the financing of health care and the redistributive preferences of the health authority. Copyright © 2015 Elsevier B.V. All rights reserved.

  10. Contribution to optimization of preventive replacement

    International Nuclear Information System (INIS)

    Legat, V.; Zaludova, A.H.; Cervenka, V.; Jurca, V.

    1996-01-01

    The paper presents a method for determining the optimal interval for preventive maintenance/replacement using either an age-based or diagnostic-based renewal strategy. For the case of a finite-time horizon, for which the computations are complicated, a simple formula is proposed for modifying the commonly used inifinite-time solution so that it gives a good approximation to the exact finite-time solution. Examples demonstrate that the method is sufficiently accurate and simple in practice for typical engineering components with Weibull life distributions and for a reasonable range of the cost factor (ratio of unit corrective to unit preventive maintenance costs). This paper investigates the problem of the accuracy of the results compared to the exact, finite-time solution for a selected matrix of time-to failure Weibull shape parameters and cost factors commonly occurring in technical practice. Applications offer substantial benefits to both manufacturer and user of technical equipment

  11. State dependent optimization of measurement policy

    Science.gov (United States)

    Konkarikoski, K.

    2010-07-01

    Measurements are the key to rational decision making. Measurement information generates value, when it is applied in the decision making. An investment cost and maintenance costs are associated with each component of the measurement system. Clearly, there is - under a given set of scenarios - a measurement setup that is optimal in expected (discounted) utility. This paper deals how the measurement policy optimization is affected by different system states and how this problem can be tackled.

  12. State dependent optimization of measurement policy

    International Nuclear Information System (INIS)

    Konkarikoski, K

    2010-01-01

    Measurements are the key to rational decision making. Measurement information generates value, when it is applied in the decision making. An investment cost and maintenance costs are associated with each component of the measurement system. Clearly, there is - under a given set of scenarios - a measurement setup that is optimal in expected (discounted) utility. This paper deals how the measurement policy optimization is affected by different system states and how this problem can be tackled.

  13. On Optimal Policies for Network-Coded Cooperation

    DEFF Research Database (Denmark)

    Khamfroush, Hana; Roetter, Daniel Enrique Lucani; Pahlevani, Peyman

    2015-01-01

    Network-coded cooperative communication (NC-CC) has been proposed and evaluated as a powerful technology that can provide a better quality of service in the next-generation wireless systems, e.g., D2D communications. Previous contributions have focused on performance evaluation of NC-CC scenarios...... rather than searching for optimal policies that can minimize the total cost of reliable packet transmission. We break from this trend by initially analyzing the optimal design of NC-CC for a wireless network with one source, two receivers, and half-duplex erasure channels. The problem is modeled...... as a special case of Markov decision process (MDP), which is called stochastic shortest path (SSP), and is solved for any field size, arbitrary number of packets, and arbitrary erasure probabilities of the channels. The proposed MDP solution results in an optimal transmission policy per time slot, and we use...

  14. Maintenance optimization for subsea oil pipelines

    International Nuclear Information System (INIS)

    Castanier, Bruno; Rausand, Marvin

    2006-01-01

    In this paper, the classical PF interval model, proposed for reliability centered maintenance, is used to optimize the preventive replacement policy of a subsea oil pipeline. The pipeline is subject to failure modes that may lead to oil release and pollution of the sea. The proposed replacement policy is based on regular condition measurements of the quality of an internal pipeline coating (lining). Holes in the coating will expose the pipe material (steel) to a corrosive environment. It is, therefore, important to identify holes in the coating and take action before the corrosion penetrates the pipe wall. The model proposed in the paper can be used to determine the inspection interval that minimizes the average maintenance cost per time unit. The model formulation is outlined and illustrative examples are solved. The mathematical evaluation of the replacement policy requires numerous assumptions. These assumptions have to be tailored to the specific application. The assumptions and the data provided are included for illustrative purposes to exemplify potential results that may be obtained by using the replacement policy

  15. Optimal Maintenance for Stochastically Degrading Staellite Constellations

    National Research Council Canada - National Science Library

    Cook, Timothy J

    2005-01-01

    .... Previous work has developed a methodology to compute an optimal replacement policy for a satellite constellation in which satellites were viewed as binary entities, either operational or failed...

  16. Optimal government policies in models with heterogeneous agents

    Czech Academy of Sciences Publication Activity Database

    Boháček, Radim; Kejak, Michal

    -, č. 272 (2005), s. 1-55 ISSN 1211-3298 Institutional research plan: CEZ:AV0Z70850503 Keywords : optimal macroeconomic policy * optimal taxation * distribution of wealth and income Subject RIV: AH - Economics http://www.cerge-ei.cz/pdf/wp/Wp272.pdf

  17. The determination of optimal climate policy

    International Nuclear Information System (INIS)

    Aaheim, Asbjoern

    2010-01-01

    Analyses of the costs and benefits of climate policy, such as the Stern Review, evaluate alternative strategies to reduce greenhouse gas emissions by requiring that the cost of emission cuts in each and every year has to be covered by the associated value of avoided damage, discounted by a an exogenously chosen rate. An alternative is to optimize abatement programmes towards a stationary state, where the concentrations of greenhouse gases are stabilized and shadow prices, including the rate of discount, are determined endogenously. This paper examines the properties of optimized stabilization. It turns out that the implications for the evaluation of climate policy are substantial if compared with evaluations of the present value of costs and benefits based on exogenously chosen shadow prices. Comparisons of discounted costs and benefits tend to exaggerate the importance of the choice of discount rate, while ignoring the importance of future abatement costs, which turns out to be essential for the optimal abatement path. Numerical examples suggest that early action may be more beneficial than indicated by comparisons of costs and benefits discounted by a rate chosen on the basis of current observations. (author)

  18. A model for calculating the optimal replacement interval of computer systems

    International Nuclear Information System (INIS)

    Fujii, Minoru; Asai, Kiyoshi

    1981-08-01

    A mathematical model for calculating the optimal replacement interval of computer systems is described. This model is made to estimate the best economical interval of computer replacement when computing demand, cost and performance of computer, etc. are known. The computing demand is assumed to monotonously increase every year. Four kinds of models are described. In the model 1, a computer system is represented by only a central processing unit (CPU) and all the computing demand is to be processed on the present computer until the next replacement. On the other hand in the model 2, the excessive demand is admitted and may be transferred to other computing center and processed costly there. In the model 3, the computer system is represented by a CPU, memories (MEM) and input/output devices (I/O) and it must process all the demand. Model 4 is same as model 3, but the excessive demand is admitted to be processed in other center. (1) Computing demand at the JAERI, (2) conformity of Grosch's law for the recent computers, (3) replacement cost of computer systems, etc. are also described. (author)

  19. Optimal Tax-Transfer Policies, Life-Cycle Labour Supply and Present-Biased Preferences

    DEFF Research Database (Denmark)

    Gunnersen, Lasse Frisgaard; Rasmussen, Bo Sandemann

    Using a two-period model with two types of agents that are characterized by present-biased preferences second-best optimal tax-transfer policies are considered. The paternalistic optimal tax-transfer policy has two main concerns: Income redistribution from high to low ability households...... consequences not only for optimal subsidies to savings but also for optimal marginal income taxes....

  20. Optimal inspection and replacement periods of the safety system in Wolsung Nuclear Power Plant Unit 1 with an optimized cost perspective

    International Nuclear Information System (INIS)

    Jinil Mok; Poong Hyun Seong

    1996-01-01

    In this work, a model for determining the optimal inspection and replacement periods of the safety system in Wolsung Nuclear Power Plant Unit 1 is developed, which is to minimize economic loss caused by inadvertent trip and the system failure. This model uses cost benefit analysis method and the part for optimal inspection period considers the human error. The model is based on three factors as follows: (i) The cumulative failure distribution function of the safety system, (ii) The probability that the safety system does not operate due to failure of the system or human error when the safety system is needed at an emergency condition and (iii) The average probability that the reactor is tripped due to the failure of system components or human error. The model then is applied to evaluate the safety system in Wolsung Nuclear Power Plant Unit 1. The optimal replacement periods which are calculated with proposed model differ from those used in Wolsung NPP Unit 1 by about a few days or months, whereas the optimal inspection periods are in about the same range. (author)

  1. Preventive maintenance optimization for a stochastically degrading system with a random initial age

    International Nuclear Information System (INIS)

    Sidibe, I.B.; Khatab, A.; Diallo, C.; Kassambara, A.

    2017-01-01

    This paper investigates the optimal age replacement policy for used systems, such as second-hand products, which start their second life-cycle in a more severe environment with an initial age that is uncertain. This uncertain age is modelled as a random variable following continuous probability distributions. A mathematical model is developed to minimize the total expected cost per unit of time for these systems on an infinite time horizon. Optimality and existence conditions for a unique optimal solution are derived and used in a numerical procedure to solve the problem. Numerical experiments are provided to demonstrate the added value and the impacts of the random initial age on the optimal replacement policy.

  2. A periodic inspection and replacement policy for systems subject to competing failure modes due to degradation and traumatic events

    Energy Technology Data Exchange (ETDEWEB)

    Huynh, K.T., E-mail: tuan.huynh@utt.f [Universite de technologie de Troyes, Institut Charles Delaunay and STMR UMR CNRS 6279-12, rue Marie Curie, BP2060, 10010 Troyes cedex (France); Barros, A., E-mail: anne.barros@utt.f [Universite de technologie de Troyes, Institut Charles Delaunay and STMR UMR CNRS 6279-12, rue Marie Curie, BP2060, 10010 Troyes cedex (France); Berenguer, C., E-mail: christophe.berenguer@utt.f [Universite de technologie de Troyes, Institut Charles Delaunay and STMR UMR CNRS 6279-12, rue Marie Curie, BP2060, 10010 Troyes cedex (France); Castro, I.T., E-mail: inmatorres@unex.e [Departamento de Matematicas, Escuela Politecnica, 10071 Caceres (Spain)

    2011-04-15

    This paper deals with the condition-based maintenance of single-unit systems which are subject to the competing and dependent failures due deterioration and traumatic shock events. The main aim is to provide a model to assess the value of condition monitoring information for the maintenance decision-making. A condition-based periodic inspection/replacement policy is developed and compared with a benchmark time-based block replacement policy. Numerical results show that it is indeed useful to follow closely the actual evolution of the system to adapt the maintenance decisions to the true system state to improve the performance of maintenance policies. The analysis of the maintenance costs savings can be used to justify or not the choice to implement a policy based on condition monitoring information and to invest in condition monitoring devices.

  3. A periodic inspection and replacement policy for systems subject to competing failure modes due to degradation and traumatic events

    International Nuclear Information System (INIS)

    Huynh, K.T.; Barros, A.; Berenguer, C.; Castro, I.T.

    2011-01-01

    This paper deals with the condition-based maintenance of single-unit systems which are subject to the competing and dependent failures due deterioration and traumatic shock events. The main aim is to provide a model to assess the value of condition monitoring information for the maintenance decision-making. A condition-based periodic inspection/replacement policy is developed and compared with a benchmark time-based block replacement policy. Numerical results show that it is indeed useful to follow closely the actual evolution of the system to adapt the maintenance decisions to the true system state to improve the performance of maintenance policies. The analysis of the maintenance costs savings can be used to justify or not the choice to implement a policy based on condition monitoring information and to invest in condition monitoring devices.

  4. The impact of uncertainty on optimal emission policies

    Science.gov (United States)

    Botta, Nicola; Jansson, Patrik; Ionescu, Cezar

    2018-05-01

    We apply a computational framework for specifying and solving sequential decision problems to study the impact of three kinds of uncertainties on optimal emission policies in a stylized sequential emission problem.We find that uncertainties about the implementability of decisions on emission reductions (or increases) have a greater impact on optimal policies than uncertainties about the availability of effective emission reduction technologies and uncertainties about the implications of trespassing critical cumulated emission thresholds. The results show that uncertainties about the implementability of decisions on emission reductions (or increases) call for more precautionary policies. In other words, delaying emission reductions to the point in time when effective technologies will become available is suboptimal when these uncertainties are accounted for rigorously. By contrast, uncertainties about the implications of exceeding critical cumulated emission thresholds tend to make early emission reductions less rewarding.

  5. Dynamic mobility applications policy analysis : policy and institutional issues for intelligent network flow optimization (INFLO).

    Science.gov (United States)

    2014-12-01

    The report documents policy considerations for the Intelligent Network Flow Optimization (INFLO) connected vehicle applications : bundle. INFLO aims to optimize network flow on freeways and arterials by informing motorists of existing and impen...

  6. Heuristic and optimal policy computations in the human brain during sequential decision-making.

    Science.gov (United States)

    Korn, Christoph W; Bach, Dominik R

    2018-01-23

    Optimal decisions across extended time horizons require value calculations over multiple probabilistic future states. Humans may circumvent such complex computations by resorting to easy-to-compute heuristics that approximate optimal solutions. To probe the potential interplay between heuristic and optimal computations, we develop a novel sequential decision-making task, framed as virtual foraging in which participants have to avoid virtual starvation. Rewards depend only on final outcomes over five-trial blocks, necessitating planning over five sequential decisions and probabilistic outcomes. Here, we report model comparisons demonstrating that participants primarily rely on the best available heuristic but also use the normatively optimal policy. FMRI signals in medial prefrontal cortex (MPFC) relate to heuristic and optimal policies and associated choice uncertainties. Crucially, reaction times and dorsal MPFC activity scale with discrepancies between heuristic and optimal policies. Thus, sequential decision-making in humans may emerge from integration between heuristic and optimal policies, implemented by controllers in MPFC.

  7. Muffins Elaborated with Optimized Monoglycerides Oleogels: From Solid Fat Replacer Obtention to Product Quality Evaluation.

    Science.gov (United States)

    Giacomozzi, Anabella S; Carrín, María E; Palla, Camila A

    2018-05-22

    This study demonstrates the effectiveness of using oleogels from high oleic sunflower oil (HOSO) and monoglycerides as solid fat replacers in a sweet bakery product. Firstly, a methodology to obtain oleogels with desired properties based on mathematical models able to describe relationships between process and product characteristics variables followed by multi-objective optimization was applied. Later, muffins were prepared with the optimized oleogels and their physicochemical and textural properties were compared with those of muffins formulated using a commercial margarine (Control) or only HOSO. Furthermore, the amount of oil released from muffins over time (1, 7, and 10 days) was measured to evaluate their stability. The replacement of commercial margarine with the optimized oleogels in muffin formulation led to the obtention of products with greater spreadability, higher specific volume, similar hardness values, and a more connected and homogeneous crumb structure. Moreover, these products showed a reduction of oil migration of around 50% in contrast to the Control muffins after 10 days of storage, which indicated that the optimized oleogels can be used satisfactorily to decrease oil loss in this sweet baked product. Fat replacement with the optimized monoglycerides oleogels not only had a positive impact on the quality of the muffins, but also allowed to improve their nutritional profile (without trans fat and low in saturated fat). The food industry demands new ways to reduce the use of saturated and trans fats in food formulations. To contribute to this search, oleogels from high oleic sunflower oil and saturated monoglycerides were prepared under optimized conditions in order to obtain a product with similar functionality to margarine, and its potential application as a semisolid fat ingredient in muffins was evaluated. Muffins formulated with oleogels showed an improved quality compare with those obtained using a commercial margarine with the added

  8. Choice of optimal replacement of equipment in the warehouse of the company

    Science.gov (United States)

    Baeva, Silvia; Tomov, Kiril

    2016-12-01

    The aim of this paper is to find an optimal replacement of equipment in the warehouse of the company. Real data for the machines are used and are processed with appropriate software. The mathematical model is made for this problem as problem for the shortest path from graph theory. The solution is made by Bellman's principle.

  9. Optimization of ACC system spacing policy on curved highway

    Science.gov (United States)

    Ma, Jun; Qian, Kun; Gong, Zaiyan

    2017-05-01

    The paper optimizes the original spacing policy when adopting VTH (Variable Time Headway), proposes to introduce the road curve curvature K to the spacing policy to cope with following the wrong vehicle or failing to follow the vehicle owing to the radar limitation of curve in ACC system. By utilizing MATLAB/Simulink, automobile longitudinal dynamics model is established. At last, the paper sets up such three common cases as the vehicle ahead runs at a uniform velocity, an accelerated velocity and hits the brake suddenly, simulates these cases on the curve with different curvature, analyzes the curve spacing policy in the perspective of safety and vehicle following efficiency and draws the conclusion whether the optimization scheme is effective or not.

  10. Trade Liberalization and Optimal Environmental Policies in Vertical Related Markets

    Directory of Open Access Journals (Sweden)

    Yan-Shu Lin

    2012-12-01

    Full Text Available This paper establishes a symmetric two-country model with vertically related markets. In the downstream market, there is one firm in each country selling a homogeneous good, whose production generates pollution, to its home and the foreign markets a la Brander (1981. In the intermediate good market, there is also one upstream firm in each country, supplying the intermediate good only to its own country’s downstream market. The upstream firms can choose either price or quantity to maximize their profits. With this setting, the paper examines the optimal environmental policy and how it is affected by the tariff on the final good. It is found that, under free trade, the optimal final-good output with imperfect intermediate-good market will have the same output level as that with perfect intermediate-good market after imposing the optimal emission tax. The optimal environmental tax is smaller and the optimal environmental policy is less likely to be a green strategy under trade liberalization if the market structure in the intermediate good market is imperfect than perfect competition. On the other hand, the optimal environmental tax is necessarily higher if the upstream firm chooses price than quantity. Moreover, the optimal environmental policy is less likely to be a green strategy under trade liberalization if the upstream firms choose quantity than price to maximize their profits.

  11. Machine Replacement, Technology Adoption and Convergence.

    OpenAIRE

    Boucekkine, Raouf; Martinez, Blanca

    1999-01-01

    In this paper, we introduce adoption costs in a canonical vintage capital model. Adoption costs take the form of a direct loss in production during a fixed period of time. We explicitly characterize the optimal machine replacement policy as a function of the adoption period. Using an explicit numerical method, we study the dynamics of the model. In particular, we find that while an increase in the adoption costs lowers the long run level of output, it also rises the magnitude of short run flu...

  12. Pipe replacement in a water supply network: coordinated versus uncoordinated replacement and budget effects

    NARCIS (Netherlands)

    Dijk, van D.; Hendrix, E.M.T.

    2016-01-01

    Operators of underground water supply networks are challenged with pipe replacement
    decisions, because pipes are subject to increased failure rates as they age and financial resources
    are often limited.We study the optimal replacement time and optimal number of pipe replacements
    such

  13. Input-output interactions and optimal monetary policy

    DEFF Research Database (Denmark)

    Petrella, Ivan; Santoro, Emiliano

    2011-01-01

    This paper deals with the implications of factor demand linkages for monetary policy design in a two-sector dynamic general equilibrium model. Part of the output of each sector serves as a production input in both sectors, in accordance with a realistic input–output structure. Strategic...... complementarities induced by factor demand linkages significantly alter the transmission of shocks and amplify the loss of social welfare under optimal monetary policy, compared to what is observed in standard two-sector models. The distinction between value added and gross output that naturally arises...... in this context is of key importance to explore the welfare properties of the model economy. A flexible inflation targeting regime is close to optimal only if the central bank balances inflation and value added variability. Otherwise, targeting gross output variability entails a substantial increase in the loss...

  14. Transparency and corruption: an optimal taxation policy

    OpenAIRE

    Jellal, Mohamed; Bouzahzah, Mohamed

    2013-01-01

    Under Principal-Agent-Supervisor paradigm, we examine in this paper how a tax collection agency changes optimal schemes in order to lessen the occurrence of corruption between the tax collector and the taxpayer. Indeed, the Principal, who maximizes the expected net fiscal revenue, reacts by decreasing tax rates when the supervisor is likely to engage in corrupt transaction with taxpayer. Therefore, the optimal policy against collusion and corruption may explain the rational of the greater rel...

  15. Optimal Monetary Policy Cooperation through State-Independent Contracts with Targets

    DEFF Research Database (Denmark)

    Jensen, Henrik

    2000-01-01

    Simple state-independent monetary institutions are shown to secure optimal cooperative policies in a stochastic, linear-quadratic two-country world with international policy spill-overs and national credibility problems. Institutions characterize delegation to independent central bankers facing...... quadratic performance related contracts punishing or rewarding deviations from primary and intermediate policy targets...

  16. Optimal policies for cumulative damage models with maintenance last and first

    International Nuclear Information System (INIS)

    Zhao, Xufeng; Qian, Cunhua; Nakagawa, Toshio

    2013-01-01

    From the economical viewpoint of several combined PM policies in reliability theory, this paper takes up a standard cumulative damage model in which the notion of maintenance last is applied, i.e., the unit undergoes preventive maintenances before failure at a planned time T, at a damage level Z, or at a shock number N, whichever occurs last. Expected cost rates are detailedly formulated, and optimal problems of two alternative policies which combine time-based with condition-based preventive maintenances are discussed, i.e., optimal T L ⁎ for N, Z L ⁎ for T, and N L ⁎ for T are rigorously obtained. Comparison methods between such maintenance last and conventional maintenance first are explored. It is determined theoretically and numerically which policy should be adopted, according to the different methods in different cases when the time-based or the condition-based PM policy is optimized.

  17. Optimal pricing policies for services with consideration of facility maintenance costs

    Science.gov (United States)

    Yeh, Ruey Huei; Lin, Yi-Fang

    2012-06-01

    For survival and success, pricing is an essential issue for service firms. This article deals with the pricing strategies for services with substantial facility maintenance costs. For this purpose, a mathematical framework that incorporates service demand and facility deterioration is proposed to address the problem. The facility and customers constitute a service system driven by Poisson arrivals and exponential service times. A service demand with increasing price elasticity and a facility lifetime with strictly increasing failure rate are also adopted in modelling. By examining the bidirectional relationship between customer demand and facility deterioration in the profit model, the pricing policies of the service are investigated. Then analytical conditions of customer demand and facility lifetime are derived to achieve a unique optimal pricing policy. The comparative statics properties of the optimal policy are also explored. Finally, numerical examples are presented to illustrate the effects of parameter variations on the optimal pricing policy.

  18. Optimising Age-Replacement and Extended Non-Renewing Warranty Policies in Lifecycle Costing

    OpenAIRE

    Wu, Shaomin; Longhurst, Phil

    2011-01-01

    This paper analyses the life cycle cost of equipment protected by both base and extended warranty policies from a consumer's perspective. We assume that the equipment has two types of failure: minor and catastrophic. A minor failure can be corrected with minimal repair whereas a catastrophic failure can only be removed by a replacement. It is assumed that equipment is maintained at no charge to the consumer during the warranty period, whereas the consumer is fully charged for any maintenance ...

  19. Chaotic dynamics in optimal monetary policy

    Science.gov (United States)

    Gomes, O.; Mendes, V. M.; Mendes, D. A.; Sousa Ramos, J.

    2007-05-01

    There is by now a large consensus in modern monetary policy. This consensus has been built upon a dynamic general equilibrium model of optimal monetary policy as developed by, e.g., Goodfriend and King [ NBER Macroeconomics Annual 1997 edited by B. Bernanke and J. Rotemberg (Cambridge, Mass.: MIT Press, 1997), pp. 231 282], Clarida et al. [J. Econ. Lit. 37, 1661 (1999)], Svensson [J. Mon. Econ. 43, 607 (1999)] and Woodford [ Interest and Prices: Foundations of a Theory of Monetary Policy (Princeton, New Jersey, Princeton University Press, 2003)]. In this paper we extend the standard optimal monetary policy model by introducing nonlinearity into the Phillips curve. Under the specific form of nonlinearity proposed in our paper (which allows for convexity and concavity and secures closed form solutions), we show that the introduction of a nonlinear Phillips curve into the structure of the standard model in a discrete time and deterministic framework produces radical changes to the major conclusions regarding stability and the efficiency of monetary policy. We emphasize the following main results: (i) instead of a unique fixed point we end up with multiple equilibria; (ii) instead of saddle-path stability, for different sets of parameter values we may have saddle stability, totally unstable equilibria and chaotic attractors; (iii) for certain degrees of convexity and/or concavity of the Phillips curve, where endogenous fluctuations arise, one is able to encounter various results that seem intuitively correct. Firstly, when the Central Bank pays attention essentially to inflation targeting, the inflation rate has a lower mean and is less volatile; secondly, when the degree of price stickiness is high, the inflation rate displays a larger mean and higher volatility (but this is sensitive to the values given to the parameters of the model); and thirdly, the higher the target value of the output gap chosen by the Central Bank, the higher is the inflation rate and its

  20. Better prevention than cure: optimal patient preparation for renal replacement therapy.

    Science.gov (United States)

    Huang, Xiaoyan; Carrero, Juan Jesús

    2014-03-01

    A generous proportion of end-stage renal disease patients may not be adequately prepared for initiation of renal replacement therapy (RRT). Here we review potential benefits of early patient referral to nephrologists and optimal preparation for RRT. We place this evidence in the context of the epidemiological study by Kurella Tamura et al., which shows that voluntary community kidney disease screening and education is associated with better patient preparation and, importantly, improved survival upon initiation of RRT.

  1. Modeling and optimizing periodically inspected software rejuvenation policy based on geometric sequences

    International Nuclear Information System (INIS)

    Meng, Haining; Liu, Jianjun; Hei, Xinhong

    2015-01-01

    Software aging is characterized by an increasing failure rate, progressive performance degradation and even a sudden crash in a long-running software system. Software rejuvenation is an effective method to counteract software aging. A periodically inspected rejuvenation policy for software systems is studied. The consecutive inspection intervals are assumed to be a decreasing geometric sequence, and upon the inspection times of software system and its failure features, software rejuvenation or system recovery is performed. The system availability function and cost rate function are obtained, and the optimal inspection time and rejuvenation interval are both derived to maximize system availability and minimize cost rate. Then, boundary conditions of the optimal rejuvenation policy are deduced. Finally, the numeric experiment result shows the effectiveness of the proposed policy. Further compared with the existing software rejuvenation policy, the new policy has higher system availability. - Highlights: • A periodically inspected rejuvenation policy for software systems is studied. • A decreasing geometric sequence is used to denote the consecutive inspection intervals. • The optimal inspection times and rejuvenation interval are found. • The new policy is capable of reducing average cost and improving system availability

  2. China's optimal stockpiling policies in the context of new oil price trend

    International Nuclear Information System (INIS)

    Xie, Nan; Yan, Zhijun; Zhou, Yi; Huang, Wenjun

    2017-01-01

    Optimizing the size of oil stockpiling plays a fundamental role in the process of making national strategic petroleum reserve (SPR) policies. There have been extensive studies on the operating strategies of SPR. However, previous literatures have paid more attention to a booming or stable international oil market, while few studies analyzed the impact of a long-term low oil price on SPR policy. As a supplement, this paper extends a static model to study China's optimal stockpiling policy under different oil price trends, and in response to different current oil prices. A new variable “FC”, which demonstrates the appreciation and depreciation of the reserved oil economic value, has been taken into account to assess the optimal size of SPR. In this paper, a more multi-perspective of view is provided to consider the policies of China's SPR, especially under the different trend of international oil price fluctuations. - Highlights: • We extended a static model to study optimal stockpiling size of China's SPR. • A new variable “FC” was applied to illustrate the shifting financial value of SPR. • We analyzed how current oil price and varied prediction influence optimal size. • Operational measures could be adjusted at the end of each decision-making period. • A more multifaceted of view might be provided for China's SPR policy-making.

  3. Fear of Floating: An optimal discretionary monetary policy analysis

    OpenAIRE

    Madhavi Bokil

    2005-01-01

    This paper explores the idea that “Fear of Floating” and accompanying pro-cyclical interest rate policies observed in the case of some emerging market economies may be justified as an optimal discretionary monetary policy response to shocks. The paper also examines how the differences in monetary policies may lead to different degrees of this fear. These questions are addressed with a small open economy, new- Keynesian model with endogenous capital accumulation and sticky prices. The economy ...

  4. Optimization of Simple Monetary Policy Rules on the Base of Estimated DSGE-model

    OpenAIRE

    Shulgin, A.

    2015-01-01

    Optimization of coefficients in monetary policy rules is performed on the base of the DSGE-model with two independent monetary policy instruments estimated on the Russian data. It was found that welfare maximizing policy rules lead to inadequate result and pro-cyclical monetary policy. Optimal coefficients in Taylor rule and exchange rate rule allow to decrease volatility estimated on Russian data of 2001-2012 by about 20%. The degree of exchange rate flexibility parameter was found to be low...

  5. Optimal selection of Orbital Replacement Unit on-orbit spares - A Space Station system availability model

    Science.gov (United States)

    Schwaab, Douglas G.

    1991-01-01

    A mathematical programing model is presented to optimize the selection of Orbital Replacement Unit on-orbit spares for the Space Station. The model maximizes system availability under the constraints of logistics resupply-cargo weight and volume allocations.

  6. On the Optimal Design of Distributed Generation Policies: Is Net Metering Ever Optimal?

    OpenAIRE

    Brown, David; Sappington, David

    2014-01-01

    Electricity customers who install solar panels often are paid the prevailing retail price for the electricity they generate. We show that this "net metering" policy typically is not optimal. A payment for distributed generation (w) that is below the retail price of electricity (r) will induce the welfare-maximizing level of distributed generation (DG) when centralized generation and DG produce similar (pollution) externalities. However, w can optimally exceed r when DG entails a substantial r...

  7. Optimal Operational Monetary Policy Rules in an Endogenous Growth Model: a calibrated analysis

    OpenAIRE

    Arato, Hiroki

    2009-01-01

    This paper constructs an endogenous growth New Keynesian model and considers growth and welfare effect of Taylor-type (operational) monetary policy rules. The Ramsey equilibrium and optimal operational monetary policy rule is also computed. In the calibrated model, the Ramseyoptimal volatility of inflation rate is smaller than that in standard exogenous growth New Keynesian model with physical capital accumulation. Optimal operational monetary policy rule makes nominal interest rate respond s...

  8. Maintenance overtime policies in reliability theory models with random working cycles

    CERN Document Server

    Nakagawa, Toshio

    2015-01-01

    This book introduces a new concept of replacement in maintenance and reliability theory. Replacement overtime, where replacement occurs at the first completion of a working cycle over a planned time, is a new research topic in maintenance theory and also serves to provide a fresh optimization technique in reliability engineering. In comparing replacement overtime with standard and random replacement techniques theoretically and numerically, 'Maintenance Overtime Policies in Reliability Theory' highlights the key benefits to be gained by adopting this new approach and shows how they can be applied to inspection policies, parallel systems and cumulative damage models. Utilizing the latest research in replacement overtime by internationally recognized experts, readers are introduced to new topics and methods, and learn how to practically apply this knowledge to actual reliability models. This book will serve as an essential guide to a new subject of study for graduate students and researchers and also provides a...

  9. The optimal hormonal replacement modality selection for multiple organ procurement from brain-dead organ donors.

    Science.gov (United States)

    Mi, Zhibao; Novitzky, Dimitri; Collins, Joseph F; Cooper, David Kc

    2015-01-01

    The management of brain-dead organ donors is complex. The use of inotropic agents and replacement of depleted hormones (hormonal replacement therapy) is crucial for successful multiple organ procurement, yet the optimal hormonal replacement has not been identified, and the statistical adjustment to determine the best selection is not trivial. Traditional pair-wise comparisons between every pair of treatments, and multiple comparisons to all (MCA), are statistically conservative. Hsu's multiple comparisons with the best (MCB) - adapted from the Dunnett's multiple comparisons with control (MCC) - has been used for selecting the best treatment based on continuous variables. We selected the best hormonal replacement modality for successful multiple organ procurement using a two-step approach. First, we estimated the predicted margins by constructing generalized linear models (GLM) or generalized linear mixed models (GLMM), and then we applied the multiple comparison methods to identify the best hormonal replacement modality given that the testing of hormonal replacement modalities is independent. Based on 10-year data from the United Network for Organ Sharing (UNOS), among 16 hormonal replacement modalities, and using the 95% simultaneous confidence intervals, we found that the combination of thyroid hormone, a corticosteroid, antidiuretic hormone, and insulin was the best modality for multiple organ procurement for transplantation.

  10. State-age-dependent maintenance policies for deteriorating systems with Erlang sojourn time distributions

    International Nuclear Information System (INIS)

    Yeh, R.H.

    1997-01-01

    This paper investigates state-age-dependent maintenance policies for multistate deteriorating systems with Erlang sojourn time distributions. Since Erlang distributions are serial combinations of exponential phases, the deteriorating process can be modeled by a multi-phase Markovian model and hence easily analyzed. Based on the Markovian model, the optimal phase-dependent inspection and replacement policy can be obtained by using a policy improvement algorithm. However, since phases are fictitious and can not be identified by inspections, two procedures are developed to construct state-age-dependent policies based on the optimal phase-dependent policy. The properties of the constructed state-age-dependent policies are further investigated and the performance of the policy is evaluated through a numerical example

  11. Guide to optimized replacement of equipment seals

    International Nuclear Information System (INIS)

    Gleason, J.F.

    1990-03-01

    A reevaluation of current scheduled replacement intervals of polymeric seals in plant equipment can achieve significant benefits. Information is provided which has the potential for increasing replacement intervals based on better information on how seals have performed through unique nuclear industry tests to qualify equipment, improved elastomers and increased knowledge of the failure mechanisms and related performance. The research was performed by reviewing applications of elastomeric seals in nuclear plants and practice associated with defining seal replacement intervals in the nuclear power and other industries. Performance indicators and how they predict degradation of seals were evaluated. Guidelines and a flow chart for reevaluating seal replacement intervals are provided. 29 refs., 38 figs., 8 tabs

  12. A sow replacement model using Bayesian updating in a three-level hierarchic Markov process. II. Optimization model

    DEFF Research Database (Denmark)

    Kristensen, Anders Ringgaard; Søllested, Thomas Algot

    2004-01-01

    improvements. The biological model of the replacement model is described in a previous paper and in this paper the optimization model is described. The model is developed as a prototype for use under practical conditions. The application of the model is demonstrated using data from two commercial Danish sow......Recent methodological improvements in replacement models comprising multi-level hierarchical Markov processes and Bayesian updating have hardly been implemented in any replacement model and the aim of this study is to present a sow replacement model that really uses these methodological...... herds. It is concluded that the Bayesian updating technique and the hierarchical structure decrease the size of the state space dramatically. Since parameter estimates vary considerably among herds it is concluded that decision support concerning sow replacement only makes sense with parameters...

  13. Policy Gradient Adaptive Dynamic Programming for Data-Based Optimal Control.

    Science.gov (United States)

    Luo, Biao; Liu, Derong; Wu, Huai-Ning; Wang, Ding; Lewis, Frank L

    2017-10-01

    The model-free optimal control problem of general discrete-time nonlinear systems is considered in this paper, and a data-based policy gradient adaptive dynamic programming (PGADP) algorithm is developed to design an adaptive optimal controller method. By using offline and online data rather than the mathematical system model, the PGADP algorithm improves control policy with a gradient descent scheme. The convergence of the PGADP algorithm is proved by demonstrating that the constructed Q -function sequence converges to the optimal Q -function. Based on the PGADP algorithm, the adaptive control method is developed with an actor-critic structure and the method of weighted residuals. Its convergence properties are analyzed, where the approximate Q -function converges to its optimum. Computer simulation results demonstrate the effectiveness of the PGADP-based adaptive control method.

  14. Optimal replacement and inspection periods of safety and control boards in Wolsung nuclear power plant unit 1

    International Nuclear Information System (INIS)

    Mok, Jin Il

    1993-02-01

    In nuclear power plants, the safety and control systems are important for operating and maintaining safety of nuclear power plants. Due to the failure of the instrument and control devices of nuclear power plants caused by aging, nuclear power plants occasionally trip. Since the start of first commercial operation of Kori nuclear power plant (NPP) unit 1, the trips caused by instrument and control systems account for 28% of total trips of NPPs in Korea. Even a single trip of a nuclear power plant causes an extravagant economical loss and deteriorates public acceptance of nuclear power plants. Therefore, the replacement of the instrument and control devices with proper consideration of the aging effect is necessary in order to prevent the inadvertent trip. In this work we investigated the optimal replacement periods of the digital control computer's (DCC) and the programmable digital comparator's (PDC) electronic circuit boards of Wolsung nuclear power plant Unit 1. We first derived mathematical models which calculate optimal replacement periods for electronic circuit boards of digital control computer (DCC) and for those of the programmable digital comparator (PDC) in Wolsung NPP unit 1. And we analytically obtained the optimal replacement periods of electronic circuit boards by using these models. We compared these periods with the replacement periods currently used at Wolsung NPP Unit. The periods used at Wolsung is not based on mathematical analysis, but on empirical knowledge. As a consequence, the optimal replacement periods analytically obtained for the electronic circuit boards of DCC and those used in the field shown small difference : the optimal replacement periods analytically obtained for the electronic circuit boards of PDC are shorter than those used in the field in general. The engineered safeguards of Wolsung nuclear power plant unit 1 contains redundant systems of 2-out-of-3 logic which are not operating under normal conditions but they are called

  15. Optimal timing for intravenous administration set replacement.

    Science.gov (United States)

    Gillies, D; O'Riordan, L; Wallen, M; Morrison, A; Rankin, K; Nagy, S

    2005-10-19

    Administration of intravenous therapy is a common occurrence within the hospital setting. Routine replacement of administration sets has been advocated to reduce intravenous infusion contamination. If decreasing the frequency of changing intravenous administration sets does not increase infection rates, a change in practice could result in considerable cost savings. The objective of this review was to identify the optimal interval for the routine replacement of intravenous administration sets when infusate or parenteral nutrition (lipid and non-lipid) solutions are administered to people in hospital via central or peripheral venous catheters. We searched The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, CINAHL, EMBASE: all from inception to February 2004; reference lists of identified trials, and bibliographies of published reviews. We also contacted researchers in the field. We did not have a language restriction. We included all randomized or quasi-randomized controlled trials addressing the frequency of replacing intravenous administration sets when parenteral nutrition (lipid and non-lipid containing solutions) or infusions (excluding blood) were administered to people in hospital via a central or peripheral catheter. Two authors assessed all potentially relevant studies. We resolved disagreements between the two authors by discussion with a third author. We collected data for the outcomes; infusate contamination; infusate-related bloodstream infection; catheter contamination; catheter-related bloodstream infection; all-cause bloodstream infection and all-cause mortality. We identified 23 references for review. We excluded eight of these studies; five because they did not fit the inclusion criteria and three because of inadequate data. We extracted data from the remaining 15 references (13 studies) with 4783 participants. We conclude that there is no evidence that changing intravenous administration sets more often than every 96 hours

  16. Optimal insemination and replacement decisions to minimize the cost of pathogen-specific clinical mastitis in dairy cows.

    Science.gov (United States)

    Cha, E; Kristensen, A R; Hertl, J A; Schukken, Y H; Tauer, L W; Welcome, F L; Gröhn, Y T

    2014-01-01

    Mastitis is a serious production-limiting disease, with effects on milk yield, milk quality, and conception rate, and an increase in the risk of mortality and culling. The objective of this study was 2-fold: (1) to develop an economic optimization model that incorporates all the different types of pathogens that cause clinical mastitis (CM) categorized into 8 classes of culture results, and account for whether the CM was a first, second, or third case in the current lactation and whether the cow had a previous case or cases of CM in the preceding lactation; and (2) to develop this decision model to be versatile enough to add additional pathogens, diseases, or other cow characteristics as more information becomes available without significant alterations to the basic structure of the model. The model provides economically optimal decisions depending on the individual characteristics of the cow and the specific pathogen causing CM. The net returns for the basic herd scenario (with all CM included) were $507/cow per year, where the incidence of CM (cases per 100 cow-years) was 35.6, of which 91.8% of cases were recommended for treatment under an optimal replacement policy. The cost per case of CM was $216.11. The CM cases comprised (incidences, %) Staphylococcus spp. (1.6), Staphylococcus aureus (1.8), Streptococcus spp. (6.9), Escherichia coli (8.1), Klebsiella spp. (2.2), other treated cases (e.g., Pseudomonas; 1.1), other not treated cases (e.g., Trueperella pyogenes; 1.2), and negative culture cases (12.7). The average cost per case, even under optimal decisions, was greatest for Klebsiella spp. ($477), followed by E. coli ($361), other treated cases ($297), and other not treated cases ($280). This was followed by the gram-positive pathogens; among these, the greatest cost per case was due to Staph. aureus ($266), followed by Streptococcus spp. ($174) and Staphylococcus spp. ($135); negative culture had the lowest cost ($115). The model recommended treatment for

  17. Optimal fleet conversion policy from a life cycle perspective

    International Nuclear Information System (INIS)

    Hyung Chul Kim; Ross, M.H.; Keoleian, G.A.

    2004-01-01

    Vehicles typically deteriorate with accumulating mileage and emit more tailpipe air pollutants per mile. Although incentive programs for scrapping old, high-emitting vehicles have been implemented to reduce urban air pollutants and greenhouse gases, these policies may create additional sales of new vehicles as well. From a life cycle perspective, the emissions from both the additional vehicle production and scrapping need to be addressed when evaluating the benefits of scrapping older vehicles. This study explores an optimal fleet conversion policy based on mid-sized internal combustion engine vehicles in the US, defined as one that minimizes total life cycle emissions from the entire fleet of new and used vehicles. To describe vehicles' lifetime emission profiles as functions of accumulated mileage, a series of life cycle inventories characterizing environmental performance for vehicle production, use, and retirement was developed for each model year between 1981 and 2020. A simulation program is developed to investigate ideal and practical fleet conversion policies separately for three regulated pollutants (CO, NMHC, and NO x ) and for CO 2 . According to the simulation results, accelerated scrapping policies are generally recommended to reduce regulated emissions, but they may increase greenhouse gases. Multi- objective analysis based on economic valuation methods was used to investigate trade-offs among emissions of different pollutants for optimal fleet conversion policies. (author)

  18. The optimal time path of clean energy R&D policy when patents have finite lifetime

    NARCIS (Netherlands)

    Gerlagh, R.; Kverndokk, S.; Rosendahl, K.E.

    We study the optimal time path for clean energy innovation policy. In a model with emission reduction through clean energy deployment, and with R&D increasing the overall productivity of clean energy, we describe optimal R&D policies jointly with emission pricing policies. We find that while

  19. A new multi-objective optimization model for preventive maintenance and replacement scheduling of multi-component systems

    Science.gov (United States)

    Moghaddam, Kamran S.; Usher, John S.

    2011-07-01

    In this article, a new multi-objective optimization model is developed to determine the optimal preventive maintenance and replacement schedules in a repairable and maintainable multi-component system. In this model, the planning horizon is divided into discrete and equally-sized periods in which three possible actions must be planned for each component, namely maintenance, replacement, or do nothing. The objective is to determine a plan of actions for each component in the system while minimizing the total cost and maximizing overall system reliability simultaneously over the planning horizon. Because of the complexity, combinatorial and highly nonlinear structure of the mathematical model, two metaheuristic solution methods, generational genetic algorithm, and a simulated annealing are applied to tackle the problem. The Pareto optimal solutions that provide good tradeoffs between the total cost and the overall reliability of the system can be obtained by the solution approach. Such a modeling approach should be useful for maintenance planners and engineers tasked with the problem of developing recommended maintenance plans for complex systems of components.

  20. Realistic nurse-led policy implementation, optimization and evaluation: novel methodological exemplar.

    Science.gov (United States)

    Noyes, Jane; Lewis, Mary; Bennett, Virginia; Widdas, David; Brombley, Karen

    2014-01-01

    To report the first large-scale realistic nurse-led implementation, optimization and evaluation of a complex children's continuing-care policy. Health policies are increasingly complex, involve multiple Government departments and frequently fail to translate into better patient outcomes. Realist methods have not yet been adapted for policy implementation. Research methodology - Evaluation using theory-based realist methods for policy implementation. An expert group developed the policy and supporting tools. Implementation and evaluation design integrated diffusion of innovation theory with multiple case study and adapted realist principles. Practitioners in 12 English sites worked with Consultant Nurse implementers to manipulate the programme theory and logic of new decision-support tools and care pathway to optimize local implementation. Methods included key-stakeholder interviews, developing practical diffusion of innovation processes using key-opinion leaders and active facilitation strategies and a mini-community of practice. New and existing processes and outcomes were compared for 137 children during 2007-2008. Realist principles were successfully adapted to a shorter policy implementation and evaluation time frame. Important new implementation success factors included facilitated implementation that enabled 'real-time' manipulation of programme logic and local context to best-fit evolving theories of what worked; using local experiential opinion to change supporting tools to more realistically align with local context and what worked; and having sufficient existing local infrastructure to support implementation. Ten mechanisms explained implementation success and differences in outcomes between new and existing processes. Realistic policy implementation methods have advantages over top-down approaches, especially where clinical expertise is low and unlikely to diffuse innovations 'naturally' without facilitated implementation and local optimization. © 2013

  1. Optimization of series-parallel multi-state systems under maintenance policies

    International Nuclear Information System (INIS)

    Nourelfath, Mustapha; Ait-Kadi, Daoud

    2007-01-01

    In the redundancy optimization problem, the design goal is achieved by discrete choices made from components available in the market. In this paper, the problem is to find, under reliability constraints, the minimal cost configuration of a multi-state series-parallel system, which is subject to a specified maintenance policy. The number of maintenance teams is less than the number of repairable components, and a maintenance policy specifies the priorities between the system components. To take into account the dependencies resulting from the sharing of maintenance teams, the universal generating function approach is coupled with a Markov model. The resulting optimization approach has the advantage of being mainly analytical

  2. Optimal timing for intravascular administration set replacement.

    Science.gov (United States)

    Ullman, Amanda J; Cooke, Marie L; Gillies, Donna; Marsh, Nicole M; Daud, Azlina; McGrail, Matthew R; O'Riordan, Elizabeth; Rickard, Claire M

    2013-09-15

    The tubing (administration set) attached to both venous and arterial catheters may contribute to bacteraemia and other infections. The rate of infection may be increased or decreased by routine replacement of administration sets. This review was originally published in 2005 and was updated in 2012. The objective of this review was to identify any relationship between the frequency with which administration sets are replaced and rates of microbial colonization, infection and death. We searched The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 6), MEDLINE (1950 to June 2012), CINAHL (1982 to June 2012), EMBASE (1980 to June 2012), reference lists of identified trials and bibliographies of published reviews. The original search was performed in February 2004. We also contacted researchers in the field. We applied no language restriction. We included all randomized or controlled clinical trials on the frequency of venous or arterial catheter administration set replacement in hospitalized participants. Two review authors assessed all potentially relevant studies. We resolved disagreements between the two review authors by discussion with a third review author. We collected data for seven outcomes: catheter-related infection; infusate-related infection; infusate microbial colonization; catheter microbial colonization; all-cause bloodstream infection; mortality; and cost. We pooled results from studies that compared different frequencies of administration set replacement, for instance, we pooled studies that compared replacement ≥ every 96 hours versus every 72 hours with studies that compared replacement ≥ every 48 hours versus every 24 hours. We identified 26 studies for this updated review, 10 of which we excluded; six did not fulfil the inclusion criteria and four did not report usable data. We extracted data from the remaining 18 references (16 studies) with 5001 participants: study designs included neonate and adult

  3. Spare parts sharing with joint optimization of maintenance and inventory policies

    DEFF Research Database (Denmark)

    Larsen, Christian; Wong, Hartanto Wijaya; Nielsen, Lars Relund

    We consider a collaborative arrangement where a number of companies are willing to share expensive spare parts, required for both failure replacement and preventive maintenance purposes. We develop a discrete-time Markov decision model for the joint optimization of maintenance and spare parts...

  4. A Bayesian perspective on some replacement strategies

    International Nuclear Information System (INIS)

    Mazzuchi, Thomas A.; Soyer, Refik

    1996-01-01

    In this paper we present a Bayesian decision theoretic approach for determining optimal replacement strategies. This approach enables us to formally incorporate, express, and update our uncertainty when determining optimal replacement strategies. We develop relevant expressions for both the block replacement protocol with minimal repair and the age replacement protocol and illustrate the use of our approach with real data

  5. Identification of Optimal Policies in Markov Decision Processes

    Czech Academy of Sciences Publication Activity Database

    Sladký, Karel

    46 2010, č. 3 (2010), s. 558-570 ISSN 0023-5954. [International Conference on Mathematical Methods in Economy and Industry. České Budějovice, 15.06.2009-18.06.2009] R&D Projects: GA ČR(CZ) GA402/08/0107; GA ČR GA402/07/1113 Institutional research plan: CEZ:AV0Z10750506 Keywords : finite state Markov decision processes * discounted and average costs * elimination of suboptimal policies Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.461, year: 2010 http://library.utia.cas.cz/separaty/2010/E/sladky-identification of optimal policies in markov decision processes.pdf

  6. 25 CFR 700.53 - Dwelling, replacement.

    Science.gov (United States)

    2010-04-01

    ... 25 Indians 2 2010-04-01 2010-04-01 false Dwelling, replacement. 700.53 Section 700.53 Indians THE... Policies and Instructions Definitions § 700.53 Dwelling, replacement. The term replacement dwelling means a dwelling selected by the head of a household as a replacement dwelling that meets the criteria of this...

  7. Capital Equipment Replacement Decisions

    OpenAIRE

    Batterham, Robert L.; Fraser, K.I.

    1995-01-01

    This paper reviews the literature on the optimal replacement of capital equipment, especially farm machinery. It also considers the influence of taxation and capital rationing on replacement decisions. It concludes that special taxation provisions such as accelerated depreciation and investment allowances are unlikely to greatly influence farmers' capital equipment replacement decisions in Australia.

  8. Optimization of hip joint replacement location to decrease maximum von Mi ses Stress

    International Nuclear Information System (INIS)

    Pourjamali, H.; Najarian, S.; Katoozian, H. R.

    2001-01-01

    Hip replacement is used for inoperable femur head injuries and femur fractures where internal fixation can not be used. This operation is one of the most common orthopedic operations that many research have been done about it. Among these we can mention implant and cement materials and composites optimization and also implant shape optimization. This study was designed to optimize artificial hip joint position (placement) to decrease maximal von mi sees stress. First, a model of femur and implant were made and then a computer program was written with the ability to change the position of implant through an acceptable range in the femur. In each of these positions, the program simulated femur and implant according to finite element method and made, applied forces were weight and muscle traction. Our findings show that a small deviation of the implant from femur bone center causes a considerable decrease in von mi sees stress that consequently results in longer maintenance of the implant

  9. Optimal climate policy is a utopia. From quantitative to qualitative cost-benefit analysis

    International Nuclear Information System (INIS)

    Van den Bergh, Jeroen C.J.M.

    2004-01-01

    The dominance of quantitative cost-benefit analysis (CBA) and optimality concepts in the economic analysis of climate policy is criticised. Among others, it is argued to be based in a misplaced interpretation of policy for a complex climate-economy system as being analogous to individual inter-temporal welfare optimisation. The transfer of quantitative CBA and optimality concepts reflects an overly ambitious approach that does more harm than good. An alternative approach is to focus the attention on extreme events, structural change and complexity. It is argued that a qualitative rather than a quantitative CBA that takes account of these aspects can support the adoption of a minimax regret approach or precautionary principle in climate policy. This means: implement stringent GHG reduction policies as soon as possible

  10. The optimal management of anti-thrombotic therapy after valve replacement: certainties and uncertainties.

    Science.gov (United States)

    Iung, Bernard; Rodés-Cabau, Josep

    2014-11-07

    Anti-thrombotic therapy after valve replacement encompasses a number of different situations. Long-term anticoagulation of mechanical prostheses uses vitamin K antagonists with a target international normalized ratio adapted to the characteristics of the prosthesis and the patient. The association of low-dose aspirin is systematic in the American guidelines and more restrictive in the European guidelines. Early heparin therapy is frequently used early after mechanical valve replacement, although there are no precise recommendations regarding timing, type, and dose of drug. Direct oral anticoagulants are presently contraindicated in patients with mechanical prosthesis. The main advantage of bioprostheses is the absence of long-term anticoagulant therapy. Early anticoagulation is indicated after valve replacement for mitral bioprostheses, whereas aspirin is now favoured early after bioprosthetic valve replacement in the aortic position. Early dual antiplatelet therapy is indicated after transcatheter aortic valve implantation, followed by single antiplatelet therapy. However, this relies on low levels of evidence and optimization of anti-thrombotic therapy is warranted in these high-risk patients. Although guidelines are consistent in most instances, discrepancies and the low-level of evidence of certain recommendations highlight the need for further controlled trials, in particular with regard to the combination of antiplatelet therapy with oral anticoagulant and the early post-operative anti-thrombotic therapy following the procedure. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.

  11. Note on ‘Combining an Improved Multi-delivery Policy into a Single-producer Multi-retailer Integrated Inventory System with Scrap in Production’

    OpenAIRE

    Chung-li Chou; Wen Kuei Wu; Singa W. Chiu

    2014-01-01

    In a recent study, Chiu et al. (2014) employed a mathematical modeling and conventional optimization technique to determine the optimal production-shipment policy for a single-producer multi-retailer integrated inventory system with scrap and an improved product distribution policy. This study replaces their optimization process of using differential calculus with an algebraic derivation. Such a simplified approach enables practitioners, who may have insufficient knowledge of calculus, to man...

  12. Optimal Control via Reinforcement Learning with Symbolic Policy Approximation

    NARCIS (Netherlands)

    Kubalìk, Jiřì; Alibekov, Eduard; Babuska, R.; Dochain, Denis; Henrion, Didier; Peaucelle, Dimitri

    2017-01-01

    Model-based reinforcement learning (RL) algorithms can be used to derive optimal control laws for nonlinear dynamic systems. With continuous-valued state and input variables, RL algorithms have to rely on function approximators to represent the value function and policy mappings. This paper

  13. The optimal hormonal replacement modality selection for multiple organ procurement from brain-dead organ donors

    Directory of Open Access Journals (Sweden)

    Mi Z

    2014-12-01

    Full Text Available Zhibao Mi,1 Dimitri Novitzky,2 Joseph F Collins,1 David KC Cooper3 1Cooperative Studies Program Coordinating Center, VA Maryland Health Care Systems, Perry Point, MD, USA; 2Department of Cardiothoracic Surgery, University of South Florida, Tampa, FL, USA; 3Thomas E Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA, USA Abstract: The management of brain-dead organ donors is complex. The use of inotropic agents and replacement of depleted hormones (hormonal replacement therapy is crucial for successful multiple organ procurement, yet the optimal hormonal replacement has not been identified, and the statistical adjustment to determine the best selection is not trivial. Traditional pair-wise comparisons between every pair of treatments, and multiple comparisons to all (MCA, are statistically conservative. Hsu’s multiple comparisons with the best (MCB – adapted from the Dunnett’s multiple comparisons with control (MCC – has been used for selecting the best treatment based on continuous variables. We selected the best hormonal replacement modality for successful multiple organ procurement using a two-step approach. First, we estimated the predicted margins by constructing generalized linear models (GLM or generalized linear mixed models (GLMM, and then we applied the multiple comparison methods to identify the best hormonal replacement modality given that the testing of hormonal replacement modalities is independent. Based on 10-year data from the United Network for Organ Sharing (UNOS, among 16 hormonal replacement modalities, and using the 95% simultaneous confidence intervals, we found that the combination of thyroid hormone, a corticosteroid, antidiuretic hormone, and insulin was the best modality for multiple organ procurement for transplantation. Keywords: best treatment selection, brain-dead organ donors, hormonal replacement, multiple binary endpoints, organ procurement, multiple comparisons

  14. Optimizing preventive maintenance policy: A data-driven application for a light rail braking system.

    Science.gov (United States)

    Corman, Francesco; Kraijema, Sander; Godjevac, Milinko; Lodewijks, Gabriel

    2017-10-01

    This article presents a case study determining the optimal preventive maintenance policy for a light rail rolling stock system in terms of reliability, availability, and maintenance costs. The maintenance policy defines one of the three predefined preventive maintenance actions at fixed time-based intervals for each of the subsystems of the braking system. Based on work, maintenance, and failure data, we model the reliability degradation of the system and its subsystems under the current maintenance policy by a Weibull distribution. We then analytically determine the relation between reliability, availability, and maintenance costs. We validate the model against recorded reliability and availability and get further insights by a dedicated sensitivity analysis. The model is then used in a sequential optimization framework determining preventive maintenance intervals to improve on the key performance indicators. We show the potential of data-driven modelling to determine optimal maintenance policy: same system availability and reliability can be achieved with 30% maintenance cost reduction, by prolonging the intervals and re-grouping maintenance actions.

  15. Studies on the replacement policies in dairy cattle

    NARCIS (Netherlands)

    Arendonk, van J.A.M.

    1985-01-01

    In The Netherlands dairy farmers replace on average 25-30% of their cows each year. The decision to replace instead of to keep a cow is based mainly on economic considerations rather than because a cow is no longer able to produce.

    The investigations described in this thesis were

  16. Patient perspectives on the optimal start of renal replacement therapy.

    Science.gov (United States)

    Henry, Shayna L; Munoz-Plaza, Corrine; Garcia Delgadillo, Jazmine; Mihara, Nichole K; Rutkowski, Mark P

    2017-09-01

    Healthcare systems and providers are encouraged to prepare their patients with advanced chronic kidney disease (CKD) for a planned start to renal replacement therapies (RRT). Less well understood are the socioemotional experiences surrounding the optimal start of RRT versus suboptimal haemodialysis (HD) starts with a central catheter. To characterise the experiences of patients beginning RRT. Qualitative, semi-structured phone interviews. A total of 168 patients with stage 5 CKD initiating RRT in an integrated, capitated learning healthcare system. Qualitative data from patients were collected as part of a quality improvement initiative to better understand patient-reported themes concerning preparation for RRT, patients' perceptions of their transition to dialysis and why sub-optimal starts for RRT occur within our healthcare system. Dual review and verification was used to identify key phrases and themes within and across each domain, using both deductive a priori codes generated by the interview guide and grounded discovery of emergent themes. From the patient perspective, preparing for RRT is an experience rooted in deep feelings of fear. In addition, a number of key factors contributed to patients' preparation (or failure to prepare) for RRT. While the education provided by our system was viewed as adequate overall, patients often felt that their emotional and psychosocial needs went unmet, regardless of whether or not, they experienced an optimal dialysis start. Future efforts should incorporate additional strategies for helping patients with advanced CKD achieve emotional and psychological safety while preparing for RRT. © 2017 European Dialysis and Transplant Nurses Association/European Renal Care Association.

  17. Replacement Models Revisited | Alabi | Journal of Research in ...

    African Journals Online (AJOL)

    The objective is to review the annual total cost and the cumulative annual total cost average hitherto used as replacement methods. The study showed some disparity in the optimal age of single replacement as used by some authors. Hence, an arithmetic mean method of finding the optimal single- replacement- age of an ...

  18. People adopt optimal policies in simple decision-making, after practice and guidance.

    Science.gov (United States)

    Evans, Nathan J; Brown, Scott D

    2017-04-01

    Organisms making repeated simple decisions are faced with a tradeoff between urgent and cautious strategies. While animals can adopt a statistically optimal policy for this tradeoff, findings about human decision-makers have been mixed. Some studies have shown that people can optimize this "speed-accuracy tradeoff", while others have identified a systematic bias towards excessive caution. These issues have driven theoretical development and spurred debate about the nature of human decision-making. We investigated a potential resolution to the debate, based on two factors that routinely differ between human and animal studies of decision-making: the effects of practice, and of longer-term feedback. Our study replicated the finding that most people, by default, are overly cautious. When given both practice and detailed feedback, people moved rapidly towards the optimal policy, with many participants reaching optimality with less than 1 h of practice. Our findings have theoretical implications for cognitive and neural models of simple decision-making, as well as methodological implications.

  19. Storage Policies and Optimal Shape of a Storage System

    NARCIS (Netherlands)

    Zaerpour, N.; De Koster, René; Yu, Yugang

    2013-01-01

    The response time of a storage system is mainly influenced by its shape (configuration), the storage assignment and retrieval policies, and the location of the input/output (I/O) points. In this paper, we show that the optimal shape of a storage system, which minimises the response time for single

  20. Optimal Drug Policy in Low-Income Neighborhoods

    Science.gov (United States)

    Chang, Sheng-Wen; Coulson, N. Edward; Wang, Ping

    2015-01-01

    The control of drug activity currently favors supply-side policies: drug suppliers in the U.S. face a higher arrest rate and longer sentences than demanders. We construct a simple model of drug activity with search and entry frictions in labor and drug markets. Our calibration analysis suggests a strong “dealer replacement effect.” As a result, given a variety of community objectives, it is beneficial to lower supplier arrests and raise the demand arrest rate from current values. A 10% shift from supply-side to demand-side arrests can reduce the population of potential drug dealers by 22–25,000 and raise aggregate local income by $380–400 million, at 2002 prices. (JEL Classification: D60, J60, K42, H70) PMID:27616878

  1. Off-Policy Reinforcement Learning: Optimal Operational Control for Two-Time-Scale Industrial Processes.

    Science.gov (United States)

    Li, Jinna; Kiumarsi, Bahare; Chai, Tianyou; Lewis, Frank L; Fan, Jialu

    2017-12-01

    Industrial flow lines are composed of unit processes operating on a fast time scale and performance measurements known as operational indices measured at a slower time scale. This paper presents a model-free optimal solution to a class of two time-scale industrial processes using off-policy reinforcement learning (RL). First, the lower-layer unit process control loop with a fast sampling period and the upper-layer operational index dynamics at a slow time scale are modeled. Second, a general optimal operational control problem is formulated to optimally prescribe the set-points for the unit industrial process. Then, a zero-sum game off-policy RL algorithm is developed to find the optimal set-points by using data measured in real-time. Finally, a simulation experiment is employed for an industrial flotation process to show the effectiveness of the proposed method.

  2. Optimal glucocorticoid replacement in adrenal insufficiency.

    Science.gov (United States)

    Øksnes, Marianne; Ross, Richard; Løvås, Kristian

    2015-01-01

    Adrenal insufficiency (glucocorticoid deficiency) comprises a group of rare diseases, including primary adrenal insufficiency, secondary adrenal insufficiency and congenital adrenal hyperplasia. Lifesaving glucocorticoid therapy was introduced over 60 years ago, but since then a number of advances in treatment have taken place. Specifically, little is known about short- and long-term treatment effects, and morbidity and mortality. Over the past decade, systematic cohort and registry studies have described reduced health-related quality of life, an unfavourable metabolic profile and increased mortality in patients with adrenal insufficiency, which may relate to unphysiological glucocorticoid replacement. This has led to the development of new modes of replacement that aim to mimic normal glucocorticoid physiology. Here, evidence for the inadequacy of conventional glucocorticoid therapy and recent developments in treatment are reviewed, with an emphasis on primary adrenal insufficiency. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Joint Optimization of Preventive Maintenance and Spare Parts Inventory with Appointment Policy

    Directory of Open Access Journals (Sweden)

    Jing Cai

    2017-01-01

    Full Text Available Under the background of the wide application of condition-based maintenance (CBM in maintenance practice, the joint optimization of maintenance and spare parts inventory is becoming a hot research to take full advantage of CBM and reduce the operational cost. In order to avoid both the high inventory level and the shortage of spare parts, an appointment policy of spare parts is first proposed based on the prediction of remaining useful lifetime, and then a corresponding joint optimization model of preventive maintenance and spare parts inventory is established. Due to the complexity of the model, the combination method of genetic algorithm and Monte Carlo is presented to get the optimal maximum inventory level, safety inventory level, potential failure threshold, and appointment threshold to minimize the cost rate. Finally, the proposed model is studied through a case study and compared with both the separate optimization and the joint optimization without appointment policy, and the results show that the proposed model is more effective. In addition, the sensitivity analysis shows that the proposed model is consistent with the actual situation of maintenance practices and inventory management.

  4. Optimal dynamic pricing and replenishment policy for perishable items with inventory-level-dependent demand

    Science.gov (United States)

    Lu, Lihao; Zhang, Jianxiong; Tang, Wansheng

    2016-04-01

    An inventory system for perishable items with limited replenishment capacity is introduced in this paper. The demand rate depends on the stock quantity displayed in the store as well as the sales price. With the goal to realise profit maximisation, an optimisation problem is addressed to seek for the optimal joint dynamic pricing and replenishment policy which is obtained by solving the optimisation problem with Pontryagin's maximum principle. A joint mixed policy, in which the sales price is a static decision variable and the replenishment rate remains to be a dynamic decision variable, is presented to compare with the joint dynamic policy. Numerical results demonstrate the advantages of the joint dynamic one, and further show the effects of different system parameters on the optimal joint dynamic policy and the maximal total profit.

  5. Loss-Averse Retailer’s Optimal Ordering Policies for Perishable Products with Customer Returns

    Directory of Open Access Journals (Sweden)

    Xu Chen

    2014-01-01

    Full Text Available We investigate the loss-averse retailer’s ordering policies for perishable product with customer returns. With the introduction of the segmental loss utility function, we depict the retailer’s loss aversion decision bias and establish the loss-averse retailer’s ordering policy model. We derive that the loss-averse retailer’s optimal order quantity with customer returns exists and is unique. By comparison, we obtain that both the risk-neutral and the loss-averse retailer’s optimal order quantities depend on the inventory holding cost and the marginal shortage cost. Through the sensitivity analysis, we also discuss the effect of loss-averse coefficient and the ratio of return on the loss-averse retailer’s optimal order quantity with customer returns.

  6. Handling Practicalities in Agricultural Policy Optimization for Water Quality Improvements

    Science.gov (United States)

    Bilevel and multi-objective optimization methods are often useful to spatially target agri-environmental policy throughout a watershed. This type of problem is complex and is comprised of a number of practicalities: (i) a large number of decision variables, (ii) at least two inte...

  7. Optimal environmental policy and the dynamic property in LDCs

    Directory of Open Access Journals (Sweden)

    Masahiro Yabuta

    2002-01-01

    Full Text Available This paper has provided a model framework of foreign assistance policy in the context of dynamic optimal control and investigated the environmental policies in LDCs that received some financial support from abroad. The model framework features a specific behavior of the social planner who determines the level of voluntary expenditure for preservation of natural environment. Because more financial needs for natural environmental protection means less allowance of growth-oriented investment, the social planner confronts a trade-off problem between economic growth and environmental preservation. To tackle with this clearly, we have built a dynamic model with two control variables: per-capita consumption and voluntary expenditure for natural environment.

  8. Optimizing renewable energy, demand response and energy storage to replace conventional fuels in Ontario, Canada

    International Nuclear Information System (INIS)

    Richardson, David B.; Harvey, L.D. Danny

    2015-01-01

    Electricity systems with high penetrations of renewable energy require a mix of resources to balance supply with demand, and to maintain safe levels of system reliability. A load balancing methodology is developed to determine the optimal lowest-cost mix of renewable energy resources, demand response, and energy storage to replace conventional fuels in the Province of Ontario, Canada. Three successive cumulative scenarios are considered: the displacement of fossil fuel generation, the planned retirement of an existing nuclear reactor, and the electrification of the passenger vehicle fleet. The results show that each of these scenarios is achievable with energy generation costs that are not out of line with current and projected electricity generation costs. These transitions, especially that which proposes the electrification of the vehicle fleet, require significant investment in new generation, with installed capacities much higher than that of the current system. Transitions to mainly renewable energy systems require changes in our conceptualization of, and approach to, energy system planning. - Highlights: • Model three scenarios to replace conventional fuels with renewables, storage and DR (demand response). • Determine optimal low-cost mix of resources for each scenario. • Scenarios require much higher installed capacities than current system. • Energy transitions require changes in approach to energy system planning.

  9. Clinical review: Optimal dose of continuous renal replacement therapy in acute kidney injury.

    Science.gov (United States)

    Prowle, John R; Schneider, Antoine; Bellomo, Rinaldo

    2011-01-01

    Continuous renal replacement therapy (CRRT) is the preferred treatment for acute kidney injury in intensive care units (ICUs) throughout much of the world. Despite the widespread use of CRRT, controversy and center-specific practice variation in the clinical application of CRRT continue. In particular, whereas two single-center studies have suggested survival benefit from delivery of higher-intensity CRRT to patients with acute kidney injury in the ICU, other studies have been inconsistent in their results. Now, however, two large multi-center randomized controlled trials - the Veterans Affairs/National Institutes of Health Acute Renal Failure Trial Network (ATN) study and the Randomized Evaluation of Normal versus Augmented Level (RENAL) Replacement Therapy Study - have provided level 1 evidence that effluent flow rates above 25 mL/kg per hour do not improve outcomes in patients in the ICU. In this review, we discuss the concept of dose of CRRT, its relationship with clinical outcomes, and what target optimal dose of CRRT should be pursued in light of the high-quality evidence now available.

  10. Monte Carlo modeling for realizing optimized management of failed fuel replacement

    International Nuclear Information System (INIS)

    Morishita, Kazunori; Yamamoto, Yasunori; Nakasuji, Toshiki

    2014-01-01

    Fuel cladding is one of the key components in a fission reactor to keep confining radioactive materials inside a fuel tube. During reactor operation, the cladding is however sometimes breached and radioactive materials leak from the fuel ceramic pellet into the coolant water through the breach. The primary coolant water is therefore monitored so that any leak is quickly detected, where the coolant water is periodically sampled and the concentration of, for example the radioactive iodine 131 (I-131), is measured. Depending on the measured concentration, the faulty fuel assembly with leaking rod is removed from the reactor and replaced by new one immediately or at the next refueling. In the present study, an effort has been made to develop a methodology to optimize the management for replacement of failed fuels due to cladding failures using the I-131 concentration measured in the sampled coolant water. A model numerical equation is proposed to describe the time evolution of I-131 concentration due to fuel leaks, and is then solved using the Monte-Carlo method as a function of sampling rate. Our results have indicated that, in order to achieve the rationalized management of failed fuels, higher resolution to detect a small amount of I-131 is not necessarily required but more frequent sampling is favorable. (author)

  11. Optimal reservoir operation policies using novel nested algorithms

    Science.gov (United States)

    Delipetrev, Blagoj; Jonoski, Andreja; Solomatine, Dimitri

    2015-04-01

    optimization algorithm into the state transition that lowers the starting problem dimension and alleviates the curse of dimensionality. The algorithms can solve multi-objective optimization problems, without significantly increasing the complexity and the computational expenses. The algorithms can handle dense and irregular variable discretization, and are coded in Java as prototype applications. The three algorithms were tested at the multipurpose reservoir Knezevo of the Zletovica hydro-system located in the Republic of Macedonia, with eight objectives, including urban water supply, agriculture, ensuring ecological flow, and generation of hydropower. Because the Zletovica hydro-system is relatively complex, the novel algorithms were pushed to their limits, demonstrating their capabilities and limitations. The nSDP and nRL derived/learned the optimal reservoir policy using 45 (1951-1995) years historical data. The nSDP and nRL optimal reservoir policy was tested on 10 (1995-2005) years historical data, and compared with nDP optimal reservoir operation in the same period. The nested algorithms and optimal reservoir operation results are analysed and explained.

  12. Optimal contant time injection policy for enhanced oil recovery and characterization of optimal viscous profiles

    Science.gov (United States)

    Daripa, Prabir

    2011-11-01

    We numerically investigate the optimal viscous profile in constant time injection policy of enhanced oil recovery. In particular, we investigate the effect of a combination of interfacial and layer instabilities in three-layer porous media flow on the overall growth of instabilities and thereby characterize the optimal viscous profile. Results based on monotonic and non-monotonic viscous profiles will be presented. Time permitting. we will also present results on multi-layer porous media flows for Newtonian and non-Newtonian fluids and compare the results. The support of Qatar National Fund under a QNRF Grant is acknowledged.

  13. Optimal policy for mitigating emissions in the European transport sector

    Science.gov (United States)

    Leduc, Sylvain; Piera, Patrizio; Sennai, Mesfun; Igor, Staritsky; Berien, Elbersen; Tijs, Lammens; Florian, Kraxner

    2017-04-01

    A geographic explicit techno-economic model, BeWhere (www.iiasa.ac.at/bewhere), has been developed at the European scale (Europe 28, the Balkans countries, Turkey, Moldavia and Ukraine) at a 40km grid size, to assess the potential of bioenergy from non-food feedstock. Based on the minimization of the supply chain from feedstock collection to the final energy product distribution, the model identifies the optimal bioenergy production plants in terms of spatial location, technology and capacity. The feedstock of interests are woody biomass (divided into eight types from conifers and non-conifers) and five different crop residuals. For each type of feedstock, one or multiple technologies can be applied for either heat, electricity or biofuel production. The model is run for different policy tools such as carbon cost, biofuel support, or subsidies, and the optimal mix of technologies and biomass needed is optimized to reach a production cost competitive against the actual reference system which is fossil fuel based. From this approach, the optimal mix of policy tools that can be applied country wide in Europe will be identified. The preliminary results show that high carbon tax and biofuel support contribute to the development of large scale biofuel production based on woody biomass plants mainly located in the northern part of Europe. Finally the highest emission reduction is reached with low biofuel support and high carbon tax evenly distributed in Europe.

  14. Optimization of fat-reduced ice cream formulation employing inulin as fat replacer via response surface methodology.

    Science.gov (United States)

    Pintor, Aurora; Severiano-Pérez, Patricia; Totosaus, Alfonso

    2014-10-01

    The use of new ingredients like inulin for fat replacement is of wide application in the food industry. The aim of the present work was to reduce the fat content on ice cream formulations. It was possible to reduce up to 25% of butyric and vegetable fats with 3% of inulin, with good textural and sensory characteristics of the final product. The substitution of fat with inulin increased the ice cream mix viscosity, improved air incorporation, and produced ice cream with soft and homogeneous textures. Color characteristics were not affected by the replacement. Hedonic sensory analysis showed that optimized fat-reduced inulin ice cream was not perceived different to commercial vanilla ice cream. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  15. Optimal subsidy policy for accelerating the diffusion of green products

    Directory of Open Access Journals (Sweden)

    Hongguang Peng

    2013-06-01

    Full Text Available Purpose: We consider a dynamic duopoly market in which two firms respectively produce green products and conventional products. The two types of product can substitute each other in some degree. Their demand rates depend on not only prices but the consumers’ increasing environmental awareness. Too high initial cost relative to conventional products becomes one of the major obstacles that hinder the adoption of green products. The government employs subsidy policy to trigger the adoption of green products. The purpose of the paper is to explore the optimal subsidy strategy to fulfill the government’s objective. Design/methodology/approach: We suppose the players in the game employ open-loop strategies, which make sense since the government generally cannot alter his policy for political and economic purposes. We take a differential game approach and use backward induction to analyze the firms’ pricing strategy under Cournot competition, and then focus upon a Stackelberg equilibrium to find the optimal subsidy strategy of the government. Findings: The results show that the more remarkable the energy or environmental performance, or the bigger the initial cost of green products, the higher the subsidy level should be. Due to the increasing environmental awareness and the learning curve, the optimal subsidy level decreases over time. Research limitations/implications: In our model several simplifying assumptions are made to keep the analysis more tractable. In particular, we have assumed only one type of green product. In reality several types of product with different energy or environmental performances exist. Our research can be extended in future work to take into account product differentiation on energy or environmental performance and devise a discriminatory subsidy policy accordingly. Originality/value: In the paper we set the objective of the government as minimizing the total social cost induced by the energy consumption or

  16. A delay time model for a mission-based system subject to periodic and random inspection and postponed replacement

    International Nuclear Information System (INIS)

    Yang, Li; Ma, Xiaobing; Zhai, Qingqing; Zhao, Yu

    2016-01-01

    We propose an inspection and replacement policy for a single component system that successively executes missions with random durations. The failure process of the system can be divided into two states, namely, normal and defective, following the delay time concept. Inspections are carried out periodically and immediately after the completion of each mission (random inspections). The failed state is always identified immediately, whereas the defective state can only be revealed by an inspection. If the system fails or is defective at a periodic inspection, then replacement is immediate. If, however, the system is defective at a random inspection, then replacement will be postponed if the time to the subsequent periodic inspection is shorter than a pre-determined threshold, and immediate otherwise. We derive the long run expected cost per unit time and then investigate the optimal periodic inspection interval and postponement threshold. A numerical example is presented to demonstrate the applicability of the proposed maintenance policy. - Highlights: • A delay time model of inspection is introduced for mission-based systems. • Periodic and random inspections are performed to check the state. • Replacement of the defective system at a random inspection can be postponed.

  17. Optimized Policies for Improving Fairness of Location-based Relay Selection

    DEFF Research Database (Denmark)

    Nielsen, Jimmy Jessen; Olsen, Rasmus Løvenstein; Madsen, Tatiana Kozlova

    2013-01-01

    For WLAN systems in which relaying is used to improve throughput performance for nodes located at the cell edge, node mobility and information collection delays can have a significant impact on the performance of a relay selection scheme. In this paper we extend our existing Markov Chain modeling...... framework for relay selection to allow for efficient calculation of relay policies given either mean throughput or kth throughput percentile as optimization criterium. In a scenario with static access point, static relay, and a mobile destination node, the kth throughput percentile optimization...

  18. Optimal strategies for a replacement model

    NARCIS (Netherlands)

    Bruns, P.B.

    2000-01-01

    We examine a replacement system with discrete-time Markovian deterioration and finite state space $\\{0,\\ldots,N\\}$. State 0 stands for a new system, and the higher the state the worse the system; a system in state $N$ is considered to be in a {\\it bad state}. We impose the condition that the

  19. Prediction of optimal deployment projection for transcatheter aortic valve replacement: angiographic 3-dimensional reconstruction of the aortic root versus multidetector computed tomography.

    OpenAIRE

    Binder Ronald K; Leipsic Jonathon; Wood David; Moore Teri; Toggweiler Stefan; Willson Alex; Gurvitch Ronen; Freeman Melanie; Webb John G

    2012-01-01

    BACKGROUND Identifying the optimal fluoroscopic projection of the aortic valve is important for successful transcatheter aortic valve replacement (TAVR). Various imaging modalities including multidetector computed tomography (MDCT) have been proposed for prediction of the optimal deployment projection. We evaluated a method that provides 3 dimensional angiographic reconstructions (3DA) of the aortic root for prediction of the optimal deployment angle and compared it with MDCT. METHODS AND RES...

  20. Why 'Optimal' Payment for Healthcare Providers Can Never be Optimal Under Community Rating.

    Science.gov (United States)

    Zweifel, Peter; Frech, H E

    2016-02-01

    This article extends the existing literature on optimal provider payment by accounting for consumer heterogeneity in preferences for health insurance and healthcare. This heterogeneity breaks down the separation of the relationship between providers and the health insurer and the relationship between consumers and the insurer. Both experimental and market evidence for a high degree of heterogeneity are presented. Given heterogeneity, a uniform policy fails to effectively control moral hazard, while incentives for risk selection created by community rating cannot be neutralized through risk adjustment. Consumer heterogeneity spills over into relationships with providers, such that a uniform contract with providers also cannot be optimal. The decisive condition for ensuring optimality of provider payment is to replace community rating (which violates the principle of marginal cost pricing) with risk rating of contributions combined with subsidization targeted at high risks with low incomes.

  1. Optimal Inventory Policy under Permissible Payment Delay in Fashion Supply Chains

    OpenAIRE

    Guo Li; Yuchen Kang; Mengqi Liu; Zhaohua Wang

    2014-01-01

    This paper investigates a retailer’s optimal inventory cycle and the corresponding time of payment in fashion supply chains where a supplier allows the payment delay. Here according to the established model we first analyze the retailer's reaction, and then find out the retailer’s optimal inventory policy and time of payment to maximize its total profit. Our result shows that it is not always the best choice for retailers of fashion supply chains to choose the discount way to replenish stocks...

  2. Experimental study of optimal self compacting concrete with spent foundry sand as partial replacement for M-sand using Taguchi approach

    Directory of Open Access Journals (Sweden)

    Nirmala D.B.

    2016-06-01

    Full Text Available This paper presents the application of Taguchi approach to obtain optimal mix proportion for Self Compacting Concrete (SCC containing spent foundry sand and M-sand. Spent foundry sand is used as a partial replacement for M-sand. The SCC mix has seven control factors namely, Coarse aggregate, M-sand with Spent Foundry sand, Cement, Fly ash, Water, Super plasticizer and Viscosity modifying agent. Modified Nan Su method is used to proportion the initial SCC mix. L18 (21×37 Orthogonal Arrays (OA with the seven control factors having 3 levels is used in Taguchi approach which resulted in 18 SCC mix proportions. All mixtures are extensively tested both in fresh and hardened states to verify whether they meet the practical and technical requirements of SCC. The quality characteristics considering “Nominal the better” situation is applied to the test results to arrive at the optimal SCC mix proportion. Test results indicate that the optimal mix satisfies the requirements of fresh and hardened properties of SCC. The study reveals the feasibility of using spent foundry sand as a partial replacement of M-sand in SCC and also that Taguchi method is a reliable tool to arrive at optimal mix proportion of SCC.

  3. Experimental study of optimal self compacting concrete with spent foundry sand as partial replacement for M-sand using Taguchi approach

    Science.gov (United States)

    Nirmala, D. B.; Raviraj, S.

    2016-06-01

    This paper presents the application of Taguchi approach to obtain optimal mix proportion for Self Compacting Concrete (SCC) containing spent foundry sand and M-sand. Spent foundry sand is used as a partial replacement for M-sand. The SCC mix has seven control factors namely, Coarse aggregate, M-sand with Spent Foundry sand, Cement, Fly ash, Water, Super plasticizer and Viscosity modifying agent. Modified Nan Su method is used to proportion the initial SCC mix. L18 (21×37) Orthogonal Arrays (OA) with the seven control factors having 3 levels is used in Taguchi approach which resulted in 18 SCC mix proportions. All mixtures are extensively tested both in fresh and hardened states to verify whether they meet the practical and technical requirements of SCC. The quality characteristics considering "Nominal the better" situation is applied to the test results to arrive at the optimal SCC mix proportion. Test results indicate that the optimal mix satisfies the requirements of fresh and hardened properties of SCC. The study reveals the feasibility of using spent foundry sand as a partial replacement of M-sand in SCC and also that Taguchi method is a reliable tool to arrive at optimal mix proportion of SCC.

  4. Strategic vehicle fleet management - the replacement problem

    Directory of Open Access Journals (Sweden)

    Adam Redmer

    2016-03-01

    Full Text Available Background: Fleets constitute the most important production means in transportation. Their appropriate management is crucial for all companies having transportation duties. The paper is the third one of a series of three papers that the author dedicates to the strategic vehicle fleet management topic. Material and methods: The paper discusses ways of building replacement strategies for companies' fleets of vehicles. It means deciding for how long to exploit particular vehicles in a fleet (the fleet replacement problem - FR. The essence of this problem lies in the minimization of vehicle / fleet exploitation costs by balancing ownership and utilization costs and taking into account budget limitations. In the paper an original mathematical model (an optimization method allowing for the FR analysis is proposed. Results: An application of the proposed optimization method in a real-life decision situation (the case study within the Polish environment and the obtained solution are presented. The solution shows that there exist optimal exploitation periods of particular vehicles in a fleet. However, combination of them gives a replacement plan for an entire fleet violating budget constraints. But it is possible to adjust individual age to replacement of particular vehicles to fulfill budget constraints without losing economical optimality of a developed replacement plan for an entire fleet. Conclusions: The paper is the last one of a series of three papers that the author dedicated to the strategic vehicle fleet management topic including the following managerial decision problems: MAKE-or-BUY, sizing / composition and replacement.

  5. A policy iteration approach to online optimal control of continuous-time constrained-input systems.

    Science.gov (United States)

    Modares, Hamidreza; Naghibi Sistani, Mohammad-Bagher; Lewis, Frank L

    2013-09-01

    This paper is an effort towards developing an online learning algorithm to find the optimal control solution for continuous-time (CT) systems subject to input constraints. The proposed method is based on the policy iteration (PI) technique which has recently evolved as a major technique for solving optimal control problems. Although a number of online PI algorithms have been developed for CT systems, none of them take into account the input constraints caused by actuator saturation. In practice, however, ignoring these constraints leads to performance degradation or even system instability. In this paper, to deal with the input constraints, a suitable nonquadratic functional is employed to encode the constraints into the optimization formulation. Then, the proposed PI algorithm is implemented on an actor-critic structure to solve the Hamilton-Jacobi-Bellman (HJB) equation associated with this nonquadratic cost functional in an online fashion. That is, two coupled neural network (NN) approximators, namely an actor and a critic are tuned online and simultaneously for approximating the associated HJB solution and computing the optimal control policy. The critic is used to evaluate the cost associated with the current policy, while the actor is used to find an improved policy based on information provided by the critic. Convergence to a close approximation of the HJB solution as well as stability of the proposed feedback control law are shown. Simulation results of the proposed method on a nonlinear CT system illustrate the effectiveness of the proposed approach. Copyright © 2013 ISA. All rights reserved.

  6. Optimal pricing and replenishment policies for instantaneous deteriorating items with backlogging and trade credit under inflation

    Science.gov (United States)

    Sundara Rajan, R.; Uthayakumar, R.

    2017-12-01

    In this paper we develop an economic order quantity model to investigate the optimal replenishment policies for instantaneous deteriorating items under inflation and trade credit. Demand rate is a linear function of selling price and decreases negative exponentially with time over a finite planning horizon. Shortages are allowed and partially backlogged. Under these conditions, we model the retailer's inventory system as a profit maximization problem to determine the optimal selling price, optimal order quantity and optimal replenishment time. An easy-to-use algorithm is developed to determine the optimal replenishment policies for the retailer. We also provide optimal present value of profit when shortages are completely backlogged as a special case. Numerical examples are presented to illustrate the algorithm provided to obtain optimal profit. And we also obtain managerial implications from numerical examples to substantiate our model. The results show that there is an improvement in total profit from complete backlogging rather than the items being partially backlogged.

  7. Social Optimization and Pricing Policy in Cognitive Radio Networks with an Energy Saving Strategy

    Directory of Open Access Journals (Sweden)

    Shunfu Jin

    2016-01-01

    Full Text Available The rapid growth of wireless application results in an increase in demand for spectrum resource and communication energy. In this paper, we firstly introduce a novel energy saving strategy in cognitive radio networks (CRNs and then propose an appropriate pricing policy for secondary user (SU packets. We analyze the behavior of data packets in a discrete-time single-server priority queue under multiple-vacation discipline. With the help of a Quasi-Birth-Death (QBD process model, we obtain the joint distribution for the number of SU packets and the state of base station (BS via the Matrix-Geometric Solution method. We assess the average latency of SU packets and the energy saving ratio of system. According to a natural reward-cost structure, we study the individually optimal behavior and the socially optimal behavior of the energy saving strategy and use an optimization algorithm based on standard particle swarm optimization (SPSO method to search the socially optimal arrival rate of SU packets. By comparing the individually optimal behavior and the socially optimal behavior, we impose an appropriate admission fee to SU packets. Finally, we present numerical results to show the impacts of system parameters on the system performance and the pricing policy.

  8. The feasibility of multisectoral policy options aimed at reducing trans fats and encouraging its replacement with healthier oils in India.

    Science.gov (United States)

    Downs, Shauna M; Thow, Anne-Marie; Ghosh-Jerath, Suparna; Leeder, Stephen R

    2015-05-01

    The World Health Organization recommends replacement of trans fat with polyunsaturated fat to reduce cardiovascular disease risk. Although several high-income countries have been successful in reducing trans fat in the food supply, low- and middle-income countries such as India may face additional contextual challenges such as the large informal sector, lack of consumer awareness, less enforcement capacity and low availability and affordability of healthier unsaturated fats. The objective of this study was to examine the feasibility and acceptability of multisectoral policy options aimed at supporting trans fat reduction and its replacement with polyunsaturated fats in India. Multisectoral policy options examined in this study were identified using food supply chain analysis. Semi-structured interviews (n = 17) were conducted with key informants from agriculture, trade, finance, retail, industry, food standards, non-governmental organizations and the health professions to gain their views on the feasibility and acceptability of the policy options. Purposive sampling was used to identify key informants. Data were coded and organized based on key themes. There was support for policies aimed at improving the quality of seeds, supporting farmer co-operatives and developing affordable farming equipment suited to smallholders to improve the production of healthier oils. Increasing the role of the private sector to improve links among producers, processors and retailers may help to streamline the fats supply chain in India. Blending healthier oils with oils high in saturated fat, which are currently readily available, could help to improve the quality of fat in the short term. Improving consumer awareness through mass media campaigns and improved labelling may help increase consumer demand for healthier products. Reorienting agricultural policies to support production of healthier oils will help increase their uptake by industry. Policy coherence across sectors will be

  9. Optimal harvesting policy of a stochastic two-species competitive model with Lévy noise in a polluted environment

    Science.gov (United States)

    Zhao, Yu; Yuan, Sanling

    2017-07-01

    As well known that the sudden environmental shocks and toxicant can affect the population dynamics of fish species, a mechanistic understanding of how sudden environmental change and toxicant influence the optimal harvesting policy requires development. This paper presents the optimal harvesting of a stochastic two-species competitive model with Lévy noise in a polluted environment, where the Lévy noise is used to describe the sudden climate change. Due to the discontinuity of the Lévy noise, the classical optimal harvesting methods based on the explicit solution of the corresponding Fokker-Planck equation are invalid. The object of this paper is to fill up this gap and establish the optimal harvesting policy. By using of aggregation and ergodic methods, the approximation of the optimal harvesting effort and maximum expectation of sustainable yields are obtained. Numerical simulations are carried out to support these theoretical results. Our analysis shows that the Lévy noise and the mean stress measure of toxicant in organism may affect the optimal harvesting policy significantly.

  10. Off-Policy Actor-Critic Structure for Optimal Control of Unknown Systems With Disturbances.

    Science.gov (United States)

    Song, Ruizhuo; Lewis, Frank L; Wei, Qinglai; Zhang, Huaguang

    2016-05-01

    An optimal control method is developed for unknown continuous-time systems with unknown disturbances in this paper. The integral reinforcement learning (IRL) algorithm is presented to obtain the iterative control. Off-policy learning is used to allow the dynamics to be completely unknown. Neural networks are used to construct critic and action networks. It is shown that if there are unknown disturbances, off-policy IRL may not converge or may be biased. For reducing the influence of unknown disturbances, a disturbances compensation controller is added. It is proven that the weight errors are uniformly ultimately bounded based on Lyapunov techniques. Convergence of the Hamiltonian function is also proven. The simulation study demonstrates the effectiveness of the proposed optimal control method for unknown systems with disturbances.

  11. OPTIMIZATION MODEL FOR VEHICLE ROUTING AND EQUIPMENT REPLACEMENT IN FARM MACHINERY

    OpenAIRE

    Grano, Carolina; Abensur, Eder

    2017-01-01

    ABSTRACT: An equipment replacement decision takes into account economic engineering models based on discounted cash flow (DCF) such as the Annual Equivalent Cost (AEC). Despite a large number of researches on industrial assets replacement, there is a lack of studies applied to farm goods. This study aimed at assessing an alternative model for economic decision analysis on farm machinery replacement, with no restrictions on the number of replacements and assessed goods during a defined timelin...

  12. Tax policy can change the production path: A model of optimal oil extraction in Alaska

    International Nuclear Information System (INIS)

    Leighty, Wayne; Lin, C.-Y. Cynthia

    2012-01-01

    We model the economically optimal dynamic oil production decisions for seven production units (fields) on Alaska's North Slope. We use adjustment cost and discount rate to calibrate the model against historical production data, and use the calibrated model to simulate the impact of tax policy on production rate. We construct field-specific cost functions from average cost data and an estimated inverse production function, which incorporates engineering aspects of oil production into our economic modeling. Producers appear to have approximated dynamic optimality. Consistent with prior research, we find that changing the tax rate alone does not change the economically optimal oil production path, except for marginal fields that may cease production. Contrary to prior research, we find that the structure of tax policy can be designed to affect the economically optimal production path, but at a cost in net social benefit. - Highlights: ► We model economically optimal dynamic oil production decisions for 7 Alaska fields. ► Changing tax rate alone does not alter the economically optimal oil production path. ► But change in tax structure can affect the economically optimal oil production path. ► Tax structures that modify the optimal production path reduce net social benefit. ► Field-specific cost functions and inverse production functions are estimated

  13. Optimal thromboprophylaxis following bioprosthetic aortic valve replacement: still a matter of debate?

    Science.gov (United States)

    Mydin, Muhammad I; Dimitrakakis, Georgios; Younis, Jenan; Nowell, Justin; Athanasiou, Thanos; Kourliouros, Antonios

    2012-07-01

    Optimal thromboprophylaxis following bioprosthetic aortic valve replacement (AVR) remains controversial. The main objective, which is the effective prevention of central nervous or peripheral embolic events, especially in the early postoperative period, will have to be weighed against the haemorrhagic risk that is associated with the utilization of different antithrombotic regimes. Most governing bodies in cardiovascular medicine have issued recommendations on thromboprophylaxis after the surgical implantation of aortic bioprostheses. However, the level of evidence to support these recommendations remains low, largely due to the inherent limitations of conducting appropriately randomized and adequately powered clinical research in this area. It is apparent from the recent surveys and large registries that there is a great variability in antithrombotic practice at an institutional or individual-clinician level reflecting this controversy and the lack of robust evidence. While organizational, financial or conceptual limitations could hinder the conduct and availability of conclusive research on optimal thromboprophylaxis after aortic bioprosthesis, it is imperative that all evidence is presented in a systematic way in order to assist the decision-making for the modern clinician. In this review, we provide an outline of the current recommendations for thromboprophylaxis, followed by a comprehensive and analytical presentation of all comparative studies examining anticoagulation vs. antiplatelet therapy after bioprosthetic AVR.

  14. Vertical integration and optimal reimbursement policy.

    Science.gov (United States)

    Afendulis, Christopher C; Kessler, Daniel P

    2011-09-01

    Health care providers may vertically integrate not only to facilitate coordination of care, but also for strategic reasons that may not be in patients' best interests. Optimal Medicare reimbursement policy depends upon the extent to which each of these explanations is correct. To investigate, we compare the consequences of the 1997 adoption of prospective payment for skilled nursing facilities (SNF PPS) in geographic areas with high versus low levels of hospital/SNF integration. We find that SNF PPS decreased spending more in high integration areas, with no measurable consequences for patient health outcomes. Our findings suggest that integrated providers should face higher-powered reimbursement incentives, i.e., less cost-sharing. More generally, we conclude that purchasers of health services (and other services subject to agency problems) should consider the organizational form of their suppliers when choosing a reimbursement mechanism.

  15. Opportunistic replacement of fusion power system parts

    International Nuclear Information System (INIS)

    Day, J.A.; George, L.L.

    1981-01-01

    This paper describes a maintenance problem in a fusion power plant. The problem is to specify which life limited parts should be replaced when there is an opportunity. The objective is to minimize the cost rate of replacement parts and of maintenance actions while satisfying a power plant availability constraint. The maintenance policy is to look ahead and replace all parts that will reach their life limits within a time called a screen. Longer screens yield greater system availabilities because more parts are replaced prior to their life limits

  16. Joint Optimal Production Planning for Complex Supply Chains Constrained by Carbon Emission Abatement Policies

    Directory of Open Access Journals (Sweden)

    Longfei He

    2014-01-01

    Full Text Available We focus on the joint production planning of complex supply chains facing stochastic demands and being constrained by carbon emission reduction policies. We pick two typical carbon emission reduction policies to research how emission regulation influences the profit and carbon footprint of a typical supply chain. We use the input-output model to capture the interrelated demand link between an arbitrary pair of two nodes in scenarios without or with carbon emission constraints. We design optimization algorithm to obtain joint optimal production quantities combination for maximizing overall profit under regulatory policies, respectively. Furthermore, numerical studies by featuring exponentially distributed demand compare systemwide performances in various scenarios. We build the “carbon emission elasticity of profit (CEEP” index as a metric to evaluate the impact of regulatory policies on both chainwide emissions and profit. Our results manifest that by facilitating the mandatory emission cap in proper installation within the network one can balance well effective emission reduction and associated acceptable profit loss. The outcome that CEEP index when implementing Carbon emission tax is elastic implies that the scale of profit loss is greater than that of emission reduction, which shows that this policy is less effective than mandatory cap from industry standpoint at least.

  17. Equipment Replacement Decision Making: Opportunities and Challenges

    OpenAIRE

    Fan, Wei (David); Gemar, Mason D.; Machemehl, Randy

    2012-01-01

    The primary function of equipment managers is to replace the right equipment at the right time and at the lowest overall cost. In this paper, the opportunities and challenges associated with equipment replacement optimization (ERO) are discussed in detail. First, a comprehensive review of the state-of-the art and state-of-the practice literature for the ERO problem is conducted. Second, a dynamic programming (DP) based optimization solution methodology is presented to solve the ERO problem. T...

  18. Nonparametric adaptive age replacement with a one-cycle criterion

    International Nuclear Information System (INIS)

    Coolen-Schrijner, P.; Coolen, F.P.A.

    2007-01-01

    Age replacement of technical units has received much attention in the reliability literature over the last four decades. Mostly, the failure time distribution for the units is assumed to be known, and minimal costs per unit of time is used as optimality criterion, where renewal reward theory simplifies the mathematics involved but requires the assumption that the same process and replacement strategy continues over a very large ('infinite') period of time. Recently, there has been increasing attention to adaptive strategies for age replacement, taking into account the information from the process. Although renewal reward theory can still be used to provide an intuitively and mathematically attractive optimality criterion, it is more logical to use minimal costs per unit of time over a single cycle as optimality criterion for adaptive age replacement. In this paper, we first show that in the classical age replacement setting, with known failure time distribution with increasing hazard rate, the one-cycle criterion leads to earlier replacement than the renewal reward criterion. Thereafter, we present adaptive age replacement with a one-cycle criterion within the nonparametric predictive inferential framework. We study the performance of this approach via simulations, which are also used for comparisons with the use of the renewal reward criterion within the same statistical framework

  19. Modeling investment uncertainty in the costs of global CO2 emission policy

    International Nuclear Information System (INIS)

    Birge, J.R.; Rosa, C.H.

    1995-01-01

    This paper investigates the effect that explicit modeling of stochastic returns to investment has on the CO 2 abatement policy returned by a large scale macroeconomic model of the United States economy. It was found that a policy derived from the mean value deterministic model in which the random variables of the stochastic model have been replaced by their expected value poorly approximates the optimal policy returned by solving the stochastic programming model. This nonoptimality is measured by determining the value of the stochastic solution and investigating the different evolutionary paths that various macroeconomic variables follow. Macroeconomic variables which stray far from their optimal paths when derived under the assumption of a certain mean valued future are as follows: the level of carbon taxation, investment in new energy production technologies, exploration for nonrenewable resources and investment in improved macroeconomic efficiency. 18 refs., 17 figs., 6 tabs

  20. An integrated DEA-COLS-SFA algorithm for optimization and policy making of electricity distribution units

    International Nuclear Information System (INIS)

    Azadeh, A.; Ghaderi, S.F.; Omrani, H.; Eivazy, H.

    2009-01-01

    This paper presents an integrated data envelopment analysis (DEA)-corrected ordinary least squares (COLS)-stochastic frontier analysis (SFA)-principal component analysis (PCA)-numerical taxonomy (NT) algorithm for performance assessment, optimization and policy making of electricity distribution units. Previous studies have generally used input-output DEA models for benchmarking and evaluation of electricity distribution units. However, this study proposes an integrated flexible approach to measure the rank and choose the best version of the DEA method for optimization and policy making purposes. It covers both static and dynamic aspects of information environment due to involvement of SFA which is finally compared with the best DEA model through the Spearman correlation technique. The integrated approach would yield in improved ranking and optimization of electricity distribution systems. To illustrate the usability and reliability of the proposed algorithm, 38 electricity distribution units in Iran have been considered, ranked and optimized by the proposed algorithm of this study.

  1. Environmentally Optimal, Nutritionally Aware Beef Replacement Plant-Based Diets.

    Science.gov (United States)

    Eshel, Gidon; Shepon, Alon; Noor, Elad; Milo, Ron

    2016-08-02

    Livestock farming incurs large and varied environmental burdens, dominated by beef. Replacing beef with resource efficient alternatives is thus potentially beneficial, but may conflict with nutritional considerations. Here we show that protein-equivalent plant based alternatives to the beef portion of the mean American diet are readily devisible, and offer mostly improved nutritional profile considering the full lipid profile, key vitamins, minerals, and micronutrients. We then show that replacement diets require on average only 10% of land, 4% of greenhouse gas (GHG) emissions, and 6% of reactive nitrogen (Nr) compared to what the replaced beef diet requires. Applied to 320 million Americans, the beef-to-plant shift can save 91 million cropland acres (and 770 million rangeland acres), 278 million metric ton CO2e, and 3.7 million metric ton Nr annually. These nationwide savings are 27%, 4%, and 32% of the respective national environmental burdens.

  2. Reliability Analysis of an Extended Shock Model and Its Optimization Application in a Production Line

    Directory of Open Access Journals (Sweden)

    Renbin Liu

    2014-01-01

    some important reliability indices are derived, such as availability, failure frequency, mean vacation period, mean renewal cycle, mean startup period, and replacement frequency. Finally, a production line controlled by two cold-standby computers is modeled to present numerical illustration and its optimal part-time job policy at a maximum profit.

  3. Optimal policies of non-cross-resistant chemotherapy on Goldie and Coldman's cancer model.

    Science.gov (United States)

    Chen, Jeng-Huei; Kuo, Ya-Hui; Luh, Hsing Paul

    2013-10-01

    Mathematical models can be used to study the chemotherapy on tumor cells. Especially, in 1979, Goldie and Coldman proposed the first mathematical model to relate the drug sensitivity of tumors to their mutation rates. Many scientists have since referred to this pioneering work because of its simplicity and elegance. Its original idea has also been extended and further investigated in massive follow-up studies of cancer modeling and optimal treatment. Goldie and Coldman, together with Guaduskas, later used their model to explain why an alternating non-cross-resistant chemotherapy is optimal with a simulation approach. Subsequently in 1983, Goldie and Coldman proposed an extended stochastic based model and provided a rigorous mathematical proof to their earlier simulation work when the extended model is approximated by its quasi-approximation. However, Goldie and Coldman's analytic study of optimal treatments majorly focused on a process with symmetrical parameter settings, and presented few theoretical results for asymmetrical settings. In this paper, we recast and restate Goldie, Coldman, and Guaduskas' model as a multi-stage optimization problem. Under an asymmetrical assumption, the conditions under which a treatment policy can be optimal are derived. The proposed framework enables us to consider some optimal policies on the model analytically. In addition, Goldie, Coldman and Guaduskas' work with symmetrical settings can be treated as a special case of our framework. Based on the derived conditions, this study provides an alternative proof to Goldie and Coldman's work. In addition to the theoretical derivation, numerical results are included to justify the correctness of our work. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Decommissioning and equipment replacement of nuclear power plants under uncertainty

    International Nuclear Information System (INIS)

    Takashima, Ryuta; Naito, Yuta; Kimura, Hiroshi; Madarame, Haruki

    2007-01-01

    This study examines the optimal timing for the decommissioning and equipment replacement of nuclear power plants. We consider that the firm has two options of decommissioning and equipment replacement, and determines to exercise these options under electricity price uncertainty. This problem is formulated as two optimal stopping problems. The solution of this model provides the value of the nuclear power plant and the threshold values for decommissioning and replacement. The dependence of decommissioning and replacement strategies on uncertainty and each cost is shown. In order to investigate the probability of events for decommissioning and replacement, Monte Carlo calculations are performed. We also show the probability distribution and the conditional expected time for each event. (author)

  5. An Optimization of (Q,r Inventory Policy Based on Health Care Apparel Products with Compound Poisson Demands

    Directory of Open Access Journals (Sweden)

    An Pan

    2014-01-01

    Full Text Available Addressing the problems of a health care center which produces tailor-made clothes for specific people, the paper proposes a single product continuous review model and establishes an optimal policy for the center based on (Q,r control policy to minimize expected average cost on an order cycle. A generic mathematical model to compute cost on real-time inventory level is developed to generate optimal order quantity under stochastic stock variation. The customer demands are described as compound Poisson process. Comparisons on cost between optimization method and experience-based decision on Q are made through numerical studies conducted for the inventory system of the center.

  6. A preventive maintenance policy based on dependent two-stage deterioration and external shocks

    International Nuclear Information System (INIS)

    Yang, Li; Ma, Xiaobing; Peng, Rui; Zhai, Qingqing; Zhao, Yu

    2017-01-01

    This paper proposes a preventive maintenance policy for a single-unit system whose failure has two competing and dependent causes, i.e., internal deterioration and sudden shocks. The internal failure process is divided into two stages, i.e. normal and defective. Shocks arrive according to a non-homogeneous Poisson process (NHPP), leading to the failure of the system immediately. The occurrence rate of a shock is affected by the state of the system. Both an age-based replacement and finite number of periodic inspections are schemed simultaneously to deal with the competing failures. The objective of this study is to determine the optimal preventive replacement interval, inspection interval and number of inspections such that the expected cost per unit time is minimized. A case study on oil pipeline maintenance is presented to illustrate the maintenance policy. - Highlights: • A maintenance model based on two-stage deterioration and sudden shocks is developed. • The impact of internal system state on external shock process is studied. • A new preventive maintenance strategy combining age-based replacements and periodic inspections is proposed. • Postponed replacement of a defective system is provided by restricting the number of inspections.

  7. Predictive maintenance policy for a gradually deteriorating system subject to stress

    Energy Technology Data Exchange (ETDEWEB)

    Deloux, E. [IRCCyN/Ecole des Mines de Nantes, Nantes (France); Castanier, B. [IRCCyN/Ecole des Mines de Nantes, Nantes (France)], E-mail: bruno.castanier@emn.fr; Berenguer, C. [Universite de Technologie de Troyes/CNRS, Troyes (France)

    2009-02-15

    This paper deals with a predictive maintenance policy for a continuously deteriorating system subject to stress. We consider a system with two failure mechanisms which are, respectively, due to an excessive deterioration level and a shock. To optimize the maintenance policy of the system, an approach combining statistical process control (SPC) and condition-based maintenance (CBM) is proposed. CBM policy is used to inspect and replace the system according to the observed deterioration level. SPC is used to monitor the stress covariate. In order to assess the performance of the proposed maintenance policy and to minimize the long-run expected maintenance cost per unit of time, a mathematical model for the maintained system cost is derived. Analysis based on numerical results are conducted to highlight the properties of the proposed maintenance policy in respect to the different maintenance parameters.

  8. Predictive maintenance policy for a gradually deteriorating system subject to stress

    International Nuclear Information System (INIS)

    Deloux, E.; Castanier, B.; Berenguer, C.

    2009-01-01

    This paper deals with a predictive maintenance policy for a continuously deteriorating system subject to stress. We consider a system with two failure mechanisms which are, respectively, due to an excessive deterioration level and a shock. To optimize the maintenance policy of the system, an approach combining statistical process control (SPC) and condition-based maintenance (CBM) is proposed. CBM policy is used to inspect and replace the system according to the observed deterioration level. SPC is used to monitor the stress covariate. In order to assess the performance of the proposed maintenance policy and to minimize the long-run expected maintenance cost per unit of time, a mathematical model for the maintained system cost is derived. Analysis based on numerical results are conducted to highlight the properties of the proposed maintenance policy in respect to the different maintenance parameters

  9. A comparison of alternative medicare reimbursement policies under optimal hospital pricing.

    Science.gov (United States)

    Dittman, D A; Morey, R C

    1983-01-01

    This paper applies and extends the use of a nonlinear hospital pricing model, recently posited in the literature by Dittman and Morey [1]. That model applied a hospital profit-maximizing behavior and studied the effects of optimal pricing of hospital ancillary services on the incidence of payment by private insurance companies and the Medicare trust fund. Here, we examine variations of the above model where both hospital profit-maximizing and profit-satisficing postures are of interest. We apply the model to three types of Medicare reimbursement policies currently in use or under legislative mandate to implement. The policies differ according to hospital size and whether cross-subsidies are allowed. We are interested in determining the effects of profit-maximizing and -satisficing behaviors of these three reimbursement policies on the levels of profits received, and on the respective implications for private payors and the Medicare trust fund. PMID:6347973

  10. Off-policy integral reinforcement learning optimal tracking control for continuous-time chaotic systems

    International Nuclear Information System (INIS)

    Wei Qing-Lai; Song Rui-Zhuo; Xiao Wen-Dong; Sun Qiu-Ye

    2015-01-01

    This paper estimates an off-policy integral reinforcement learning (IRL) algorithm to obtain the optimal tracking control of unknown chaotic systems. Off-policy IRL can learn the solution of the HJB equation from the system data generated by an arbitrary control. Moreover, off-policy IRL can be regarded as a direct learning method, which avoids the identification of system dynamics. In this paper, the performance index function is first given based on the system tracking error and control error. For solving the Hamilton–Jacobi–Bellman (HJB) equation, an off-policy IRL algorithm is proposed. It is proven that the iterative control makes the tracking error system asymptotically stable, and the iterative performance index function is convergent. Simulation study demonstrates the effectiveness of the developed tracking control method. (paper)

  11. Advances in the replacement and enhanced replacement method in QSAR and QSPR theories.

    Science.gov (United States)

    Mercader, Andrew G; Duchowicz, Pablo R; Fernández, Francisco M; Castro, Eduardo A

    2011-07-25

    The selection of an optimal set of molecular descriptors from a much greater pool of such regression variables is a crucial step in the development of QSAR and QSPR models. The aim of this work is to further improve this important selection process. For this reason three different alternatives for the initial steps of our recently developed enhanced replacement method (ERM) and replacement method (RM) are proposed. These approaches had previously proven to yield near optimal results with a much smaller number of linear regressions than the full search. The algorithms were tested on four different experimental data sets, formed by collections of 116, 200, 78, and 100 experimental records from different compounds and 1268, 1338, 1187, and 1306 molecular descriptors, respectively. The comparisons showed that one of the new alternatives further improves the ERM, which has shown to be superior to genetic algorithms for the selection of an optimal set of molecular descriptors from a much greater pool. The new proposed alternative also improves the simpler and the lower computational demand algorithm RM.

  12. Minimizing the dependency ratio in a population with below-replacement fertility through immigration

    Science.gov (United States)

    Simon, C.; Belyakov, A.O.; Feichtinger, G.

    2012-01-01

    Many industrialized countries face fertility rates below replacement level, combined with declining mortality especially in older ages. Consequently, the populations of these countries have started to age. One important indicator of age structures is the dependency ratio which is the ratio of the nonworking age population to the working age population. In this work we find the age-specific immigration profile that minimizes the dependency ratio in a stationary population with below-replacement fertility. It is assumed that the number of immigrants per age is limited. We consider two alternative policies. In the first one, we fix the total number of people who annually immigrate to a country. In the second one, we prescribe the size of the receiving country’s population. For both cases we provide numerical results for the optimal immigration profile, for the resulting age structure of the population, as well as for the dependency ratio. PMID:22781918

  13. Computation of a near-optimal service policy for a single-server queue with homogeneous jobs

    DEFF Research Database (Denmark)

    Johansen, Søren Glud; Larsen, Christian

    2001-01-01

    We present an algorithm for computing a near-optimal service policy for a single-server queueing system when the service cost is a convex function of the service time. The policy has state-dependent service times, and it includes the options to remove jobs from the system and to let the server...... be off. The systems' semi-Markov decision model has infinite action sets for the positive states. We design a new tailor-made policy-iteration algorithm for computing a policy for which the long-run average cost is at most a positive tolerance above the minimum average cost. For any positive tolerance...

  14. Computation of a near-optimal service policy for a single-server queue with homogeneous jobs

    DEFF Research Database (Denmark)

    Johansen, Søren Glud; Larsen, Christian

    2000-01-01

    We present an algorithm for computing a near optimal service policy for a single-server queueing system when the service cost is a convex function of the service time. The policy has state-dependent service times, and it includes the options to remove jobs from the system and to let the server...... be off. The system's semi-Markov decision model has infinite action sets for the positive states. We design a new tailor-made policy iteration algorithm for computing a policy for which the long-run average cost is at most a positive tolerance above the minimum average cost. For any positive tolerance...

  15. Is there room for geoengineering in the optimal climate policy mix?

    International Nuclear Information System (INIS)

    Bahn, Olivier; Chesney, Marc; Gheyssens, Jonathan; Knutti, Reto; Pana, Anca Claudia

    2015-01-01

    Highlights: • We investigate the optimal policy mix for dealing with climate change. • We consider jointly mitigation, adaptation, and solar radiation management (SRM). • SRM can control temperature, but brings environmental side-effects. • SRM is not robust due to uncertainty in magnitude and persistency of side-effects. • Implementing SRM with wrong assumptions about side-effects largely decreases welfare. - Abstract: We investigate geoengineering as a possible substitute for mitigation and adaptation measures to address climate change. Relying on an integrated assessment model, we distinguish between the effects of solar radiation management (SRM) on atmospheric temperature levels and its side-effects on the environment. The optimal climate portfolio is a mix of mitigation, adaptation, and SRM. When accounting for uncertainty in the magnitude of SRM side-effects and their persistency over time, we show that the SRM option lacks robustness. We then analyse the welfare consequences of basing the SRM decision on wrong assumptions about its side-effects, and show that total output losses are considerable and increase with the error horizon. This reinforces the need to balance the policy portfolio in favour of mitigation

  16. Welfare-based optimal monetary policy in a two-sector small open economy

    Czech Academy of Sciences Publication Activity Database

    Rychalovska, Yuliya

    -, č. 16 (2007), s. 1-46 ISSN 1803-2397 Institutional research plan: CEZ:AV0Z70850503 Keywords : DSGE models * optimal monetary policy * non-traded goods Subject RIV: AH - Economics http://www.cnb.cz/m2export/sites/www.cnb.cz/en/research/research_publications/cnb_wp/download/cnbwp_2007_16.pdf

  17. U.S. oil-import vulnerability: The technical replacement capability

    International Nuclear Information System (INIS)

    1991-10-01

    The report examines the changes that have taken place in world oil markets and the U.S. economy since 1984 and provides revised estimates of the technical oil replacement potential that might be attained in the event of a severe and long lasting cutoff of imported oil. The analysis focuses on technologies that are commercially available today or will be within the next 5 years and that are among the most cost-effective methods for replacing oil use in applicable sectors. It also considers the economic impacts of adopting an aggressive oil replacement strategy in a severe oil emergency. The report presents a variety of policy options that could help accelerate the adoption of oil replacement technologies in preparation for, or in response to, a severe supply disruption, or as part of a long-term national policy to reduce import vulnerability. The report concludes that U.S. capability to replace lost oil imports is shrinking. Market forces alone will not be sufficient to overcome the substantial economic and social dislocations that could result from a prolonged major oil disruption

  18. Application of capital replacement models with finite planning horizons

    NARCIS (Netherlands)

    Scarf, P.A.; Christer, A.H.

    1997-01-01

    Capital replacement models with finite planning horizons can be used to model replacement policies in complex operational contexts. They may also be used to investigate the cost consequences of technological change. This paper reviews the application of these models in various such contexts. We also

  19. Financial stability, wealth effects and optimal macroeconomic policy combination in the United Kingdom: A new-Keynesian dynamic stochastic general equilibrium framework

    Directory of Open Access Journals (Sweden)

    Muhammad Ali Nasir

    2016-12-01

    Full Text Available This study derives an optimal macroeconomic policy combination for financial sector stability in the United Kingdom by employing a New Keynesian Dynamic Stochastic General Equilibrium (NK-DSGE framework. The empirical results obtained show that disciplined fiscal and accommodative monetary policies stance is optimal for financial sector stability. Furthermore, fiscal indiscipline countered by contractionary monetary stance adversely affects financial sector stability. Financial markets, e.g. stocks and Gilts show a short-term asymmetric response to macroeconomic policy interaction and to each other. The asymmetry is a reflection of portfolio adjustment. However in the long-run, the responses to suggested optimal policy combination had homogenous effects and there was evidence of co-movement in the stock and Gilt markets.

  20. Penentuan Interval Waktu Penggantian Optimal Komponen Berdasarkan Model Opportunity Based-Age Replacement

    OpenAIRE

    Giatman, Muhammad

    2008-01-01

    Maintenance system, especially replacement that is not good, can cause much lose out for the company. The lose out is caused production process disturbing bay unexpectadly or unscheduled replacement. This will lose out for factory that have continue flow shop type, because replacement of the component that is need shut down machine will cause all machine in the process production stop. To anticipate of lose out that cause by replacement activity, so in this research will search interval of op...

  1. Optimal preventive maintenance and repair policies for multi-state systems

    International Nuclear Information System (INIS)

    Sheu, Shey-Huei; Chang, Chin-Chih; Chen, Yen-Luan; George Zhang, Zhe

    2015-01-01

    This paper studies the optimal preventive maintenance (PM) policies for multi-state systems. The scheduled PMs can be either imperfect or perfect type. The improved effective age is utilized to model the effect of an imperfect PM. The system is considered as in a failure state (unacceptable state) once its performance level falls below a given customer demand level. If the system fails before a scheduled PM, it is repaired and becomes operational again. We consider three types of major, minimal, and imperfect repair actions, respectively. The deterioration of the system is assumed to follow a non-homogeneous continuous time Markov process (NHCTMP) with finite state space. A recursive approach is proposed to efficiently compute the time-dependent distribution of the multi-state system. For each repair type, we find the optimal PM schedule that minimizes the average cost rate. The main implication of our results is that in determining the optimal scheduled PM, choosing the right repair type will significantly improve the efficiency of the system maintenance. Thus PM and repair decisions must be made jointly to achieve the best performance

  2. Practical considerations for optimizing cardiac computed tomography protocols for comprehensive acquisition prior to transcatheter aortic valve replacement.

    Science.gov (United States)

    Khalique, Omar K; Pulerwitz, Todd C; Halliburton, Sandra S; Kodali, Susheel K; Hahn, Rebecca T; Nazif, Tamim M; Vahl, Torsten P; George, Isaac; Leon, Martin B; D'Souza, Belinda; Einstein, Andrew J

    2016-01-01

    Transcatheter aortic valve replacement (TAVR) is performed frequently in patients with severe, symptomatic aortic stenosis who are at high risk or inoperable for open surgical aortic valve replacement. Computed tomography angiography (CTA) has become the gold standard imaging modality for pre-TAVR cardiac anatomic and vascular access assessment. Traditionally, cardiac CTA has been most frequently used for assessment of coronary artery stenosis, and scanning protocols have generally been tailored for this purpose. Pre-TAVR CTA has different goals than coronary CTA and the high prevalence of chronic kidney disease in the TAVR patient population creates a particular need to optimize protocols for a reduction in iodinated contrast volume. This document reviews details which allow the physician to tailor CTA examinations to maximize image quality and minimize harm, while factoring in multiple patient and scanner variables which must be considered in customizing a pre-TAVR protocol. Copyright © 2016 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

  3. An extended EPQ-based problem with a discontinuous delivery policy, scrap rate, and random breakdown.

    Science.gov (United States)

    Chiu, Singa Wang; Lin, Hong-Dar; Song, Ming-Syuan; Chen, Hsin-Mei; Chiu, Yuan-Shyi P

    2015-01-01

    In real supply chain environments, the discontinuous multidelivery policy is often used when finished products need to be transported to retailers or customers outside the production units. To address this real-life production-shipment situation, this study extends recent work using an economic production quantity- (EPQ-) based inventory model with a continuous inventory issuing policy, defective items, and machine breakdown by incorporating a multiple delivery policy into the model to replace the continuous policy and investigates the effect on the optimal run time decision for this specific EPQ model. Next, we further expand the scope of the problem to combine the retailer's stock holding cost into our study. This enhanced EPQ-based model can be used to reflect the situation found in contemporary manufacturing firms in which finished products are delivered to the producer's own retail stores and stocked there for sale. A second model is developed and studied. With the help of mathematical modeling and optimization techniques, the optimal run times that minimize the expected total system costs comprising costs incurred in production units, transportation, and retail stores are derived, for both models. Numerical examples are provided to demonstrate the applicability of our research results.

  4. Optimal Pricing and Advertising Policies for New Product Oligopoly Models

    OpenAIRE

    Gerald L. Thompson; Jinn-Tsair Teng

    1984-01-01

    In this paper our previous work on monopoly and oligopoly new product models is extended by the addition of pricing as well as advertising control variables. These models contain Bass's demand growth model, and the Vidale-Wolfe and Ozga advertising models, as well as the production learning curve model and an exponential demand function. The problem of characterizing an optimal pricing and advertising policy over time is an important question in the field of marketing as well as in the areas ...

  5. Replacement policy in a system under shocks following a Markovian arrival process

    International Nuclear Information System (INIS)

    Montoro-Cazorla, Delia; Perez-Ocon, Rafael; Carmen Segovia, Maria del

    2009-01-01

    We present a system subject to shocks that arrive following a Markovian arrival process. The system is minimally repaired. It is replaced when a certain number of shocks arrive. A general model where the replacements are governed by a discrete phase-type distribution is studied. For this system, the Markov process governing the system is constructed, and the interarrival times between replacements and the number of replacements are calculated. A special case of this system is when it can stand a prefixed number of shocks. For this new system, the same performance measures are calculated. The systems are considered in transient and stationary regime

  6. Replacement policy in a system under shocks following a Markovian arrival process

    Energy Technology Data Exchange (ETDEWEB)

    Montoro-Cazorla, Delia [Department of Statistics and Operational Research, University of Jaen (Spain); Perez-Ocon, Rafael [Department of Statistics and Operational Research, University of Granada, Granada (Spain)], E-mail: rperezo@ugr.es; Carmen Segovia, Maria del [Departamento de Estadistica e I.O., University of Granada, Granada (Spain)

    2009-02-15

    We present a system subject to shocks that arrive following a Markovian arrival process. The system is minimally repaired. It is replaced when a certain number of shocks arrive. A general model where the replacements are governed by a discrete phase-type distribution is studied. For this system, the Markov process governing the system is constructed, and the interarrival times between replacements and the number of replacements are calculated. A special case of this system is when it can stand a prefixed number of shocks. For this new system, the same performance measures are calculated. The systems are considered in transient and stationary regime.

  7. Optimal breastfeeding durations for HIV-exposed infants: the impact of maternal ART use, infant mortality and replacement feeding risk.

    Science.gov (United States)

    Mallampati, Divya; MacLean, Rachel L; Shapiro, Roger; Dabis, Francois; Engelsmann, Barbara; Freedberg, Kenneth A; Leroy, Valeriane; Lockman, Shahin; Walensky, Rochelle; Rollins, Nigel; Ciaranello, Andrea

    2018-04-01

    In 2010, the WHO recommended women living with HIV breastfeed for 12 months while taking antiretroviral therapy (ART) to balance breastfeeding benefits against HIV transmission risks. To inform the 2016 WHO guidelines, we updated prior research on the impact of breastfeeding duration on HIV-free infant survival (HFS) by incorporating maternal ART duration, infant/child mortality and mother-to-child transmission data. Using the Cost-Effectiveness of Preventing AIDS Complications (CEPAC)-Infant model, we simulated the impact of breastfeeding duration on 24-month HFS among HIV-exposed, uninfected infants. We defined "optimal" breastfeeding durations as those maximizing 24-month HFS. We varied maternal ART duration, mortality rates among breastfed infants/children, and relative risk of mortality associated with replacement feeding ("RRRF"), modelled as a multiplier on all-cause mortality for replacement-fed infants/children (range: 1 [no additional risk] to 6). The base-case simulated RRRF = 3, median infant mortality, and 24-month maternal ART duration. In the base-case, HFS ranged from 83.1% (no breastfeeding) to 90.2% (12-months breastfeeding). Optimal breastfeeding durations increased with higher RRRF values and longer maternal ART durations, but did not change substantially with variation in infant mortality rates. Optimal breastfeeding durations often exceeded the previous WHO recommendation of 12 months. In settings with high RRRF and long maternal ART durations, HFS is maximized when mothers breastfeed longer than the previously-recommended 12 months. In settings with low RRRF or short maternal ART durations, shorter breastfeeding durations optimize HFS. If mothers are supported to use ART for longer periods of time, it is possible to reduce transmission risks and gain the benefits of longer breastfeeding durations. © 2018 The Authors. Journal of the International AIDS Society published by John Wiley & sons Ltd on behalf of the International AIDS Society.

  8. Joint Optimal Production Planning for Complex Supply Chains Constrained by Carbon Emission Abatement Policies

    OpenAIRE

    He, Longfei; Xu, Zhaoguang; Niu, Zhanwen

    2014-01-01

    We focus on the joint production planning of complex supply chains facing stochastic demands and being constrained by carbon emission reduction policies. We pick two typical carbon emission reduction policies to research how emission regulation influences the profit and carbon footprint of a typical supply chain. We use the input-output model to capture the interrelated demand link between an arbitrary pair of two nodes in scenarios without or with carbon emission constraints. We design optim...

  9. Replacing penalties

    Directory of Open Access Journals (Sweden)

    Vitaly Stepashin

    2017-01-01

    Full Text Available УДК 343.24The subject. The article deals with the problem of the use of "substitute" penalties.The purpose of the article is to identify criminal and legal criteria for: selecting the replacement punishment; proportionality replacement leave punishment to others (the formalization of replacement; actually increasing the punishment (worsening of legal situation of the convicted.Methodology.The author uses the method of analysis and synthesis, formal legal method.Results. Replacing the punishment more severe as a result of malicious evasion from serving accused designated penalty requires the optimization of the following areas: 1 the selection of a substitute punishment; 2 replacement of proportionality is serving a sentence other (formalization of replacement; 3 ensuring the actual toughening penalties (deterioration of the legal status of the convict. It is important that the first two requirements pro-vide savings of repression in the implementation of the replacement of one form of punishment to others.Replacement of punishment on their own do not have any specifics. However, it is necessary to compare them with the contents of the punishment, which the convict from serving maliciously evaded. First, substitute the punishment should assume a more significant range of restrictions and deprivation of certain rights of the convict. Second, the perfor-mance characteristics of order substitute the punishment should assume guarantee imple-mentation of the new measures.With regard to replacing all forms of punishment are set significant limitations in the application that, in some cases, eliminates the possibility of replacement of the sentence, from serving where there has been willful evasion, a stricter measure of state coercion. It is important in the context of the topic and the possibility of a sentence of imprisonment as a substitute punishment in cases where the original purpose of the strict measures excluded. It is noteworthy that the

  10. Remaining lifetime modelling for replacement of power transformer populations

    NARCIS (Netherlands)

    Schijndel, van A.; Wetzer, J.; Wouters, P.A.A.F.

    2008-01-01

    The age of the majority of power transformers applied in the western electricity network varies between 25 and 50 years. Depending on the load history and time of operation, replacement on short term is imminent. A technically sound policy concerning the replacement of these assets must be based on

  11. Optimal replenishment policy for fuzzy inventory model with deteriorating items and allowable shortages under inflationary conditions

    Directory of Open Access Journals (Sweden)

    Jaggi Chandra K.

    2016-01-01

    Full Text Available This study develops an inventory model to determine ordering policy for deteriorating items with constant demand rate under inflationary condition over a fixed planning horizon. Shortages are allowed and are partially backlogged. In today’s wobbling economy, especially for long term investment, the effects of inflation cannot be disregarded as uncertainty about future inflation may influence the ordering policy. Therefore, in this paper a fuzzy model is developed that fuzzify the inflation rate, discount rate, deterioration rate, and backlogging parameter by using triangular fuzzy numbers to represent the uncertainty. For Defuzzification, the well known signed distance method is employed to find the total profit over the planning horizon. The objective of the study is to derive the optimal number of cycles and their optimal length so to maximize the net present value of the total profit over a fixed planning horizon. The necessary and sufficient conditions for an optimal solution are characterized. An algorithm is proposed to find the optimal solution. Finally, the proposed model has been validated with numerical example. Sensitivity analysis has been performed to study the impact of various parameters on the optimal solution, and some important managerial implications are presented.

  12. Optimal Control and Optimization of Stochastic Supply Chain Systems

    CERN Document Server

    Song, Dong-Ping

    2013-01-01

    Optimal Control and Optimization of Stochastic Supply Chain Systems examines its subject in the context of the presence of a variety of uncertainties. Numerous examples with intuitive illustrations and tables are provided, to demonstrate the structural characteristics of the optimal control policies in various stochastic supply chains and to show how to make use of these characteristics to construct easy-to-operate sub-optimal policies.                 In Part I, a general introduction to stochastic supply chain systems is provided. Analytical models for various stochastic supply chain systems are formulated and analysed in Part II. In Part III the structural knowledge of the optimal control policies obtained in Part II is utilized to construct easy-to-operate sub-optimal control policies for various stochastic supply chain systems accordingly. Finally, Part IV discusses the optimisation of threshold-type control policies and their robustness. A key feature of the book is its tying together of ...

  13. Optimal combination of energy crops under different policy scenarios; The case of Northern Greece

    International Nuclear Information System (INIS)

    Zafeiriou, Eleni; Petridis, Konstantinos; Karelakis, Christos; Arabatzis, Garyfallos

    2016-01-01

    Energy crops production is considered as environmentally benign and socially acceptable, offering ecological benefits over fossil fuels through their contribution to the reduction of greenhouse gases and acidifying emissions. Energy crops are subjected to persistent policy support by the EU, despite their limited or even marginally negative impact on the greenhouse effect. The present study endeavors to optimize the agricultural income generated by energy crops in a remote and disadvantageous region, with the assistance of linear programming. The optimization concerns the income created from soybean, sunflower (proxy for energy crop), and corn. Different policy scenarios imposed restrictions on the value of the subsidies as a proxy for EU policy tools, the value of inputs (costs of capital and labor) and different irrigation conditions. The results indicate that the area and the imports per energy crop remain unchanged, independently of the policy scenario enacted. Furthermore, corn cultivation contributes the most to iFncome maximization, whereas the implemented CAP policy plays an incremental role in uptaking an energy crop. A key implication is that alternative forms of motivation should be provided to the farmers beyond the financial ones in order the extensive use of energy crops to be achieved. - Highlights: •A stochastic and a deterministic LP model is formulated. •The role of CAP is vital in generated income. •Imports and cultivated areas are subsidy neutral. •The regime of free market results in lower income acquired from the potential crop mix. •Non – financial motivation is a key determinant of the farmers’ attitude towards energy crops.

  14. Prolonged Intermittent Renal Replacement Therapy.

    Science.gov (United States)

    Edrees, Fahad; Li, Tingting; Vijayan, Anitha

    2016-05-01

    Prolonged intermittent renal replacement therapy (PIRRT) is becoming an increasingly popular alternative to continuous renal replacement therapy in critically ill patients with acute kidney injury. There are significant practice variations in the provision of PIRRT across institutions, with respect to prescription, technology, and delivery of therapy. Clinical trials have generally demonstrated that PIRRT is non-inferior to continuous renal replacement therapy regarding patient outcomes. PIRRT offers cost-effective renal replacement therapy along with other advantages such as early patient mobilization and decreased nursing time. However, due to lack of standardization of the procedure, PIRRT still poses significant challenges, especially pertaining to appropriate drug dosing. Future guidelines and clinical trials should work toward developing consensus definitions for PIRRT and ensure optimal delivery of therapy. Copyright © 2016 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

  15. Maintaining environmental quality while expanding biomass production: Sub-regional U.S. policy simulations

    International Nuclear Information System (INIS)

    Egbendewe-Mondzozo, Aklesso; Swinton, Scott M.; Izaurralde, R. César; Manowitz, David H.; Zhang, Xuesong

    2013-01-01

    This paper evaluates environmental policy effects on ligno-cellulosic biomass production and environmental outcomes using an integrated bioeconomic optimization model. The environmental policy integrated climate (EPIC) model is used to simulate crop yields and environmental indicators in current and future potential bioenergy cropping systems based on weather, topographic and soil data. The crop yield and environmental outcome parameters from EPIC are combined with biomass transport costs and economic parameters in a representative farmer profit-maximizing mathematical optimization model. The model is used to predict the impact of alternative policies on biomass production and environmental outcomes. We find that without environmental policy, rising biomass prices initially trigger production of annual crop residues, resulting in increased greenhouse gas emissions, soil erosion, and nutrient losses to surface and ground water. At higher biomass prices, perennial bioenergy crops replace annual crop residues as biomass sources, resulting in lower environmental impacts. Simulations of three environmental policies namely a carbon price, a no-till area subsidy, and a fertilizer tax reveal that only the carbon price policy systematically mitigates environmental impacts. The fertilizer tax is ineffectual and too costly to farmers. The no-till subsidy is effective only at low biomass prices and is too costly to government. - Highlights: ► Bioeconomic optimization model predicts how biomass production affects environment. ► Rising biomass production could impair climate and water quality. ► Environmental protection policies compared as biomass supply grows. ► Carbon price protects the environment cost-effectively as biomass supply expands

  16. Energy efficiency optimization in distribution transformers considering Spanish distribution regulation policy

    International Nuclear Information System (INIS)

    Pezzini, Paola; Gomis-Bellmunt, Oriol; Frau-Valenti, Joan; Sudria-Andreu, Antoni

    2010-01-01

    In transmission and distribution systems, the high number of installed transformers, a loss source in networks, suggests a good potential for energy savings. This paper presents how the Spanish Distribution regulation policy, Royal Decree 222/2008, affects the overall energy efficiency in distribution transformers. The objective of a utility is the maximization of the benefit, and in case of failures, to install a chosen transformer in order to maximize the profit. Here, a novel method to optimize energy efficiency, considering the constraints set by the Spanish Distribution regulation policy, is presented; its aim is to achieve the objectives of the utility when installing new transformers. The overall energy efficiency increase is a clear result that can help in meeting the requirements of European environmental plans, such as the '20-20-20' action plan.

  17. On the effect of downtime costs and budget constraint on preventive and replacement policies

    International Nuclear Information System (INIS)

    Pascual, R.; Meruane, V.; Rey, P.A.

    2008-01-01

    This work proposes a general approach to study and improve the effectiveness of the system with respect to its expected life-cycle cost rate. The model we propose considers a production system which is protected against demand fluctuations and failure occurrences with elements like stock piles, line and equipment redundancy, and the use of alternative production methods. These design policies allow to keep or minimize the effect on the nominal throughput, while corrective measures are taken. The system is also subject to an aging process which depends on the frequency and quality of preventive actions. Making decisions is difficult because of discontinuities in intervention and downtime costs and the limited budget. We present a non-linear mixed integer formulation that minimizes the expected overall cost rate with respect to repair, overhaul and replacement times and the overhaul improvement factor proposed in the literature. The model is deterministic and considers minimal repairs and imperfect overhauls. We illustrate its application with a case based on a known benchmark example

  18. Examination of energy price policies in Iran for optimal configuration of CHP and CCHP systems based on particle swarm optimization algorithm

    International Nuclear Information System (INIS)

    Tichi, S.G.; Ardehali, M.M.; Nazari, M.E.

    2010-01-01

    The current subsidized energy prices in Iran are proposed to be gradually eliminated over the next few years. The objective of this study is to examine the effects of current and future energy price policies on optimal configuration of combined heat and power (CHP) and combined cooling, heating, and power (CCHP) systems in Iran, under the conditions of selling and not-selling electricity to utility. The particle swarm optimization algorithm is used for minimizing the cost function for owning and operating various CHP and CCHP systems in an industrial dairy unit. The results show that with the estimated future unsubsidized utility prices, CHP and CCHP systems operating with reciprocating engine prime mover have total costs of 5.6 and $2.9x10 6 over useful life of 20 years, respectively, while both systems have the same capital recovery periods of 1.3 years. However, for the same prime mover and with current subsidized prices, CHP and CCHP systems require 4.9 and 5.2 years for capital recovery, respectively. It is concluded that the current energy price policies hinder the promotion of installing CHP and CCHP systems and, the policy of selling electricity to utility as well as eliminating subsidies are prerequisites to successful widespread utilization of such systems.

  19. Adaptive optimal control of unknown constrained-input systems using policy iteration and neural networks.

    Science.gov (United States)

    Modares, Hamidreza; Lewis, Frank L; Naghibi-Sistani, Mohammad-Bagher

    2013-10-01

    This paper presents an online policy iteration (PI) algorithm to learn the continuous-time optimal control solution for unknown constrained-input systems. The proposed PI algorithm is implemented on an actor-critic structure where two neural networks (NNs) are tuned online and simultaneously to generate the optimal bounded control policy. The requirement of complete knowledge of the system dynamics is obviated by employing a novel NN identifier in conjunction with the actor and critic NNs. It is shown how the identifier weights estimation error affects the convergence of the critic NN. A novel learning rule is developed to guarantee that the identifier weights converge to small neighborhoods of their ideal values exponentially fast. To provide an easy-to-check persistence of excitation condition, the experience replay technique is used. That is, recorded past experiences are used simultaneously with current data for the adaptation of the identifier weights. Stability of the whole system consisting of the actor, critic, system state, and system identifier is guaranteed while all three networks undergo adaptation. Convergence to a near-optimal control law is also shown. The effectiveness of the proposed method is illustrated with a simulation example.

  20. The cost function for the preventive - maintenance replacement problem

    OpenAIRE

    Vilaplana, Jose Perez

    1994-01-01

    Let a discounted continuous review preventive-maintenance replacement model be such that its total discounted cost is given by means of two functional equations. We assume that downtime is caused by equipment breakdowns, and the length of a given downtime is the time necessary to repair the equipment and set it back in operation. The periodic preventive replacement policy is to replace the equipment by a new identical equipment when service age X is reached, or when the equipment ...

  1. Method for Determining Optimal Residential Energy Efficiency Retrofit Packages

    Energy Technology Data Exchange (ETDEWEB)

    Polly, B.; Gestwick, M.; Bianchi, M.; Anderson, R.; Horowitz, S.; Christensen, C.; Judkoff, R.

    2011-04-01

    Businesses, government agencies, consumers, policy makers, and utilities currently have limited access to occupant-, building-, and location-specific recommendations for optimal energy retrofit packages, as defined by estimated costs and energy savings. This report describes an analysis method for determining optimal residential energy efficiency retrofit packages and, as an illustrative example, applies the analysis method to a 1960s-era home in eight U.S. cities covering a range of International Energy Conservation Code (IECC) climate regions. The method uses an optimization scheme that considers average energy use (determined from building energy simulations) and equivalent annual cost to recommend optimal retrofit packages specific to the building, occupants, and location. Energy savings and incremental costs are calculated relative to a minimum upgrade reference scenario, which accounts for efficiency upgrades that would occur in the absence of a retrofit because of equipment wear-out and replacement with current minimum standards.

  2. Joint cost of energy under an optimal economic policy of hybrid power systems subject to uncertainty

    International Nuclear Information System (INIS)

    Díaz, Guzmán; Planas, Estefanía; Andreu, Jon; Kortabarria, Iñigo

    2015-01-01

    Economical optimization of hybrid systems is usually performed by means of LCoE (levelized cost of energy) calculation. Previous works deal with the LCoE calculation of the whole hybrid system disregarding an important issue: the stochastic component of the system units must be jointly considered. This paper deals with this issue and proposes a new fast optimal policy that properly calculates the LCoE of a hybrid system and finds the lowest LCoE. This proposed policy also considers the implied competition among power sources when variability of gas and electricity prices are taken into account. Additionally, it presents a comparative between the LCoE of the hybrid system and its individual technologies of generation by means of a fast and robust algorithm based on vector logical computation. Numerical case analyses based on realistic data are presented that valuate the contribution of technologies in a hybrid power system to the joint LCoE. - Highlights: • We perform the LCoE calculation with the stochastic component jointly considered. • We propose a fast an optimal policy that minimizes the LCoE. • We compare the obtained LCoEs by means of a fast and robust algorithm. • We take into account the competition among gas prices and electricity prices

  3. Optimal management of replacement heifers in a beef herd: a model for simultaneous optimization of rearing and breeding decisions.

    Science.gov (United States)

    Stygar, A H; Kristensen, A R; Makulska, J

    2014-08-01

    The aim of this study was to provide farmers an efficient tool for supporting optimal decisions in the beef heifer rearing process. The complexity of beef heifer management prompted the development of a model including decisions on the feeding level during prepuberty (age optimal rearing strategy was found by maximizing the total discounted net revenues from the predicted future productivity of the Polish Limousine heifers defined as the cumulative BW of calves born from a cow calved until the age of 5 yr, standardized on the 210th day of age. According to the modeled optimal policy, heifers fed during the whole rearing period at the ADG of 810 g/d and generally weaned after the maximum suckling period of 9 mo should already be bred at the age of 13.2 mo and BW constituting 55.6% of the average mature BW. Based on the optimal strategy, 52% of all heifers conceived from May to July and calved from February to April. This optimal rearing pattern resulted in an average net return of EUR 311.6 per pregnant heifer. It was found that the economic efficiency of beef operations can be improved by applying different herd management practices to those currently used in Poland. Breeding at 55.6% of the average mature BW, after a shorter and less expensive rearing period, resulted in an increase in the average net return per heifer by almost 18% compared to the conventional system, in which heifers were bred after attaining 65% of the mature BW. Extension of the rearing period by 2.5 mo (breeding at the age 15.7 mo), due to a prepubertal growth rate lowered by 200 g, reduced the average net return per heifer by 6.2% compared to the results obtained under the basic model assumptions. In the future, the model may also be extended to investigate additional aspects of the beef heifer development, such as the environmental impacts of various heifer management decisions.

  4. Automated procedure for selection of optimal refueling policies for light water reactors

    International Nuclear Information System (INIS)

    Lin, B.I.; Zolotar, B.; Weisman, J.

    1979-01-01

    An automated procedure determining a minimum cost refueling policy has been developed for light water reactors. The procedure is an extension of the equilibrium core approach previously devised for pressurized water reactors (PWRs). Use of 1 1/2-group theory has improved the accuracy of the nuclear model and eliminated tedious fitting of albedos. A simple heuristic algorithm for locating a good starting policy has materially reduced PWR computing time. Inclusion of void effects and use of the Haling principle for axial flux calculations extended the nuclear model to boiling water reactors (BWRs). A good initial estimate of the refueling policy is obtained by recognizing that a nearly uniform distribution of reactivity provides low-power peaking. The initial estimate is improved upon by interchanging groups of four assemblies and is subsequently refined by interchanging individual assemblies. The method yields very favorable results, is simpler than previously proposed BWR fuel optimization schemes, and retains power cost as the objective function

  5. Secondary water treatment optimization in French PWRs: Recent ways of investigation and policy

    Energy Technology Data Exchange (ETDEWEB)

    Millet, L.; Serres, F. [Electricite de France, Group des Laboratoires (France); Vermeeren, D. [Electricite de France, Groupe Ingenierie Process (France); Moreaux, D. [Electricite de France, Groupe Environnement (France)

    2002-07-01

    In French nuclear power plants, the secondary water conditioning is essentially based on the use of a volatile amine and a reducing reagent. The additional use of a corrosion inhibitor is limited to units with secondary side corrosion of Alloy 600 MA SG tubes. The main aim of secondary water treatment optimisation is to achieve the best compromise as follows: to minimize the different types of corrosion of the different PWRs materials (copper corrosion, flow assisted corrosion, SG fouling and secondary side corrosion), to reduce operation and maintenance costs (short term and long term), to minimise the impacts on the environment, to protect workers health. In a first part, this paper describes the studies recently carried out to try to optimise the secondary water treatment in French PWRs. They concern the possibility to use ethanolamine (ETA) in replacement of morpholine and ammonia and the possibility to use carbohydrazide (CBH) in replacement of hydrazine. In a second part, this paper presents the French secondary water treatment policy established in 2000, which is depending on the presence or not of copper alloys. (authors)

  6. Secondary water treatment optimization in French PWRs: Recent ways of investigation and policy

    International Nuclear Information System (INIS)

    Millet, L.; Serres, F.; Vermeeren, D.; Moreaux, D.

    2002-01-01

    In French nuclear power plants, the secondary water conditioning is essentially based on the use of a volatile amine and a reducing reagent. The additional use of a corrosion inhibitor is limited to units with secondary side corrosion of Alloy 600 MA SG tubes. The main aim of secondary water treatment optimisation is to achieve the best compromise as follows: to minimize the different types of corrosion of the different PWRs materials (copper corrosion, flow assisted corrosion, SG fouling and secondary side corrosion), to reduce operation and maintenance costs (short term and long term), to minimise the impacts on the environment, to protect workers health. In a first part, this paper describes the studies recently carried out to try to optimise the secondary water treatment in French PWRs. They concern the possibility to use ethanolamine (ETA) in replacement of morpholine and ammonia and the possibility to use carbohydrazide (CBH) in replacement of hydrazine. In a second part, this paper presents the French secondary water treatment policy established in 2000, which is depending on the presence or not of copper alloys. (authors)

  7. Optimal graft diameter and location reduce postoperative complications after total arch replacement with long elephant trunk for arch aneurysm.

    Science.gov (United States)

    Kondoh, Haruhiko; Funatsu, Toshihiro; Toda, Koich; Kainuma, Satoshi; Kuki, Satoru; Taniguchi, Kazuhiro

    2011-08-01

    Total arch replacement with an elephant trunk is a standard treatment for arch aneurysm, but serious complications, such as paraplegia and peripheral embolization caused by flapping of the elephant trunk, remain. Moreover, dilation of the descending aorta and retrograde flow into the peri-graft space at the distal elephant trunk are frequent problems. We hypothesized that optimal graft diameter and location would reduce complications after total arch replacement with a long elephant trunk by achieving complete thrombosis and minimal dilation of the descending aorta around the elephant trunk. We treated 65 patients with arch aneurysm by total arch replacement with a long elephant trunk anastomosed at the base of the innominate artery. The graft diameter was undersized (10%-20% of the distal aorta's diameter). Elephant trunk length was determined by preoperative computed tomography to locate the distal end at Th6 to Th8. Thrombosis around the elephant trunk, diameter of the descending aorta, and distance between the descending aorta and the graft near the distal end of the elephant trunk were evaluated using computed tomography. The distal end of the elephant trunk was located at Th 8 ± 1. There were no operative deaths, 3 patients (5%) died in the hospital, and 3 patients (5%) experienced spinal cord injury, including 1 in whom permanent paraplegia developed. Computed tomography revealed complete thrombosis around the elephant trunk in 58 patients (89%). The descending aorta did not dilate further, and distance between the descending aorta and the graft progressively decreased. Optimal graft diameter and location minimized postoperative complications, with complete thrombosis and no dilation of the descending aorta around the long elephant trunk in most patients. Copyright © 2011 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

  8. Energy efficiency optimization in distribution transformers considering Spanish distribution regulation policy

    Energy Technology Data Exchange (ETDEWEB)

    Pezzini, Paola [Centre d' Innovacio en Convertidors Estatics i Accionaments (CITCEA-UPC), E.T.S. Enginyeria Industrial Barcelona, Universitat Politecnica Catalunya, Diagonal, 647, Pl. 2, 08028 Barcelona (Spain); Gomis-Bellmunt, Oriol; Sudria-Andreu, Antoni [Centre d' Innovacio en Convertidors Estatics i Accionaments (CITCEA-UPC), E.T.S. Enginyeria Industrial Barcelona, Universitat Politecnica Catalunya, Diagonal, 647, Pl. 2, 08028 Barcelona (Spain); IREC Catalonia Institute for Energy Research, Josep Pla, B2, Pl. Baixa, 08019 Barcelona (Spain); Frau-Valenti, Joan [ENDESA, Carrer Joan Maragall, 16 07006 Palma (Spain)

    2010-12-15

    In transmission and distribution systems, the high number of installed transformers, a loss source in networks, suggests a good potential for energy savings. This paper presents how the Spanish Distribution regulation policy, Royal Decree 222/2008, affects the overall energy efficiency in distribution transformers. The objective of a utility is the maximization of the benefit, and in case of failures, to install a chosen transformer in order to maximize the profit. Here, a novel method to optimize energy efficiency, considering the constraints set by the Spanish Distribution regulation policy, is presented; its aim is to achieve the objectives of the utility when installing new transformers. The overall energy efficiency increase is a clear result that can help in meeting the requirements of European environmental plans, such as the '20-20-20' action plan. (author)

  9. An Extended EPQ-Based Problem with a Discontinuous Delivery Policy, Scrap Rate, and Random Breakdown

    Directory of Open Access Journals (Sweden)

    Singa Wang Chiu

    2015-01-01

    Full Text Available In real supply chain environments, the discontinuous multidelivery policy is often used when finished products need to be transported to retailers or customers outside the production units. To address this real-life production-shipment situation, this study extends recent work using an economic production quantity- (EPQ- based inventory model with a continuous inventory issuing policy, defective items, and machine breakdown by incorporating a multiple delivery policy into the model to replace the continuous policy and investigates the effect on the optimal run time decision for this specific EPQ model. Next, we further expand the scope of the problem to combine the retailer’s stock holding cost into our study. This enhanced EPQ-based model can be used to reflect the situation found in contemporary manufacturing firms in which finished products are delivered to the producer’s own retail stores and stocked there for sale. A second model is developed and studied. With the help of mathematical modeling and optimization techniques, the optimal run times that minimize the expected total system costs comprising costs incurred in production units, transportation, and retail stores are derived, for both models. Numerical examples are provided to demonstrate the applicability of our research results.

  10. Development of an approach to facilitate optimal equipment replacement.

    Science.gov (United States)

    1999-10-01

    The principle objective of this study was to develop a procedure using available departmental data on operation, maintenance and replacement costs to provide the Louisiana Department of Transportation and Development with guidelines for the identific...

  11. Optimizing Wind And Hydropower Generation Within Realistic Reservoir Operating Policy

    Science.gov (United States)

    Magee, T. M.; Clement, M. A.; Zagona, E. A.

    2012-12-01

    Previous studies have evaluated the benefits of utilizing the flexibility of hydropower systems to balance the variability and uncertainty of wind generation. However, previous hydropower and wind coordination studies have simplified non-power constraints on reservoir systems. For example, some studies have only included hydropower constraints on minimum and maximum storage volumes and minimum and maximum plant discharges. The methodology presented here utilizes the pre-emptive linear goal programming optimization solver in RiverWare to model hydropower operations with a set of prioritized policy constraints and objectives based on realistic policies that govern the operation of actual hydropower systems, including licensing constraints, environmental constraints, water management and power objectives. This approach accounts for the fact that not all policy constraints are of equal importance. For example target environmental flow levels may not be satisfied if it would require violating license minimum or maximum storages (pool elevations), but environmental flow constraints will be satisfied before optimizing power generation. Additionally, this work not only models the economic value of energy from the combined hydropower and wind system, it also captures the economic value of ancillary services provided by the hydropower resources. It is recognized that the increased variability and uncertainty inherent with increased wind penetration levels requires an increase in ancillary services. In regions with liberalized markets for ancillary services, a significant portion of hydropower revenue can result from providing ancillary services. Thus, ancillary services should be accounted for when determining the total value of a hydropower system integrated with wind generation. This research shows that the end value of integrated hydropower and wind generation is dependent on a number of factors that can vary by location. Wind factors include wind penetration level

  12. Optimal Policy under Restricted Government Spending

    DEFF Research Database (Denmark)

    Sørensen, Anders

    2006-01-01

    Welfare ranking of policy instruments is addressed in a two-sector Ramsey model with monopoly pricing in one sector as the only distortion. When government spending is restricted, i.e. when a government is unable or unwilling to finance the required costs for implementing the optimum policy...... effectiveness canexceed the welfare loss from introducing new distortions. Moreover, it is found that the investment subsidy is gradually phased out of the welfare maximizing policy, which may be a policy combining the two subsidies, when the level of government spending is increased.Keywords: welfare ranking......, indirect and direct policy instruments, restricted government spending JEL: E61, O21, O41...

  13. INDEXABILITY AND OPTIMAL INDEX POLICIES FOR A CLASS OF REINITIALISING RESTLESS BANDITS.

    Science.gov (United States)

    Villar, Sofía S

    2016-01-01

    Motivated by a class of Partially Observable Markov Decision Processes with application in surveillance systems in which a set of imperfectly observed state processes is to be inferred from a subset of available observations through a Bayesian approach, we formulate and analyze a special family of multi-armed restless bandit problems. We consider the problem of finding an optimal policy for observing the processes that maximizes the total expected net rewards over an infinite time horizon subject to the resource availability. From the Lagrangian relaxation of the original problem, an index policy can be derived, as long as the existence of the Whittle index is ensured. We demonstrate that such a class of reinitializing bandits in which the projects' state deteriorates while active and resets to its initial state when passive until its completion possesses the structural property of indexability and we further show how to compute the index in closed form. In general, the Whittle index rule for restless bandit problems does not achieve optimality. However, we show that the proposed Whittle index rule is optimal for the problem under study in the case of stochastically heterogenous arms under the expected total criterion, and it is further recovered by a simple tractable rule referred to as the 1-limited Round Robin rule. Moreover, we illustrate the significant suboptimality of other widely used heuristic: the Myopic index rule, by computing in closed form its suboptimality gap. We present numerical studies which illustrate for the more general instances the performance advantages of the Whittle index rule over other simple heuristics.

  14. Optimal repairable spare-parts procurement policy under total business volume discount environment

    International Nuclear Information System (INIS)

    Pascual, Rodrigo; Santelices, Gabriel; Lüer-Villagra, Armin; Vera, Jorge; Cawley, Alejandro Mac

    2017-01-01

    In asset intensive fields, where components are expensive and high system availability is required, spare parts procurement is often a critical issue. To gain competitiveness and market share is common for vendors to offer Total Business Volume Discounts (TBVD). Accordingly, companies must define the procurement and stocking policy of their spare parts in order to reduce procurement costs and increase asset availability. In response to those needs, this work presents an optimization model that maximizes the availability of the equipment under a TBVD environment, subject to a budget constraint. The model uses a single-echelon structure where parts can be repaired. It determines the optimal number of repairable spare parts to be stocked, giving emphasis on asset availability, procurement costs and service levels as the main decision criteria. A heuristic procedure that achieves high quality solutions in a fast and time-consistent way was implemented to improve the time required to obtain the model solution. Results show that using an optimal procurement policy of spare parts and accounting for TBVD produces better overall results and yields a better availability performance. - Highlights: • We propose a model for procurement of repairable components in single-echelon and business volume discount environments. • We used a mathematical model to develop a competitive heuristic that provides high quality solutions in very short times. • Our model places emphasis on using system availability, procurement costs and service levels as leading decision criteria. • The model can be used as an engine for a multi-criteria Decision Support System.

  15. U.S. oil import vulnerability: The technical replacement capability. Summary

    International Nuclear Information System (INIS)

    1991-10-01

    The report examines the changes that have taken place in world oil markets and the U.S. economy since 1984 and provides revised estimates of the technical oil replacement potential that might be attained in the event of a severe and long lasting cutoff of imported oil. The analysis focuses on technologies that are commercially available today or will be within the next 5 years and that are among the most cost-effective methods for replacing oil use in applicable sectors. It also considers the economic impacts of adopting an aggressive oil replacement strategy in a severe oil emergency. The report presents a variety of policy options that could help accelerate the adoption of oil replacement technologies in preparation for, or in response to, a severe supply disruption, or as part of a long-term national policy to reduce import vulnerability. The report's conclusion that U.S. capability to replace lost oil imports is shrinking should be sobering to those who believe that there are quick and easy technological solutions, or that market forces alone will be sufficient to overcome the substantial economic and social dislocations that could result from a prolonged major oil disruption

  16. Optimal Monetary Policy and Exchange Rate in a Small Open Economy with Unemployment

    Directory of Open Access Journals (Sweden)

    Hyuk-Jae Rhee

    2014-09-01

    Full Text Available In this paper, we consider a small open economy under the New Keynesian model with unemployment of Gali (2011a, b to discuss the design of the monetary policy. Our findings can be summarized in three parts. First, even with the existence of unemployment, the optimal policy is to minimize variance of domestic price inflation, wage inflation, and the output gap when both domestic price and wage are sticky. Second, stabilizing unemployment rate is important in reducing the welfare loss incurred by both technology and labor supply shocks. Therefore, introducing the unemployment rate as an another argument into the Taylor-rule type interest rate rule will be welfare-enhancing. Lastly, controlling CPI inflation is the best option when the policy is not allowed to respond to unemployment rate. Once the unemployment rate is controlled, however, stabilizing power of CPI inflation-based Taylor rule is diminished.

  17. A structural model for electricity prices with spikes: measurement of spike risk and optimal policies for hydropower plant operation

    International Nuclear Information System (INIS)

    Kanamura, Takashi

    2007-01-01

    This paper proposes a new model for electricity prices based on demand and supply, which we call a structural model. We show that the structural model can generate price spikes that fits the observed data better than those generated by other preceding models such as the jump diffusion model and the Box-Cox transformation model. We apply the structural model to obtain the optimal operation policy for a pumped-storage hydropower generator, and show that the structural model can provide more realistic optimal policies than the jump diffusion model. (author)

  18. A structural model for electricity prices with spikes: measurement of spike risk and optimal policies for hydropower plant operation

    Energy Technology Data Exchange (ETDEWEB)

    Kanamura, Takashi [Hitotsubashi University, Tokyo (Japan). Graduate School of International Corporate Strategy; Ohashi, Azuhiko [J-Power, Tokyo (Japan)

    2007-09-15

    This paper proposes a new model for electricity prices based on demand and supply, which we call a structural model. We show that the structural model can generate price spikes that fits the observed data better than those generated by other preceding models such as the jump diffusion model and the Box-Cox transformation model. We apply the structural model to obtain the optimal operation policy for a pumped-storage hydropower generator, and show that the structural model can provide more realistic optimal policies than the jump diffusion model. (author)

  19. Quantitative replacement of soybean meal with toasted African yam ...

    African Journals Online (AJOL)

    From the result, one can conclude that 25% AYB (treatment II) compared favourably with the control diets 0% AYB in starter broiler diets and is hereby recommended as optimal for quantitative replacement of soybean in broiler starter diet. Key words: Broiler Starter diet, African Yam Bean, Soyabean replacement ...

  20. Optimal operation and forecasting policy for pump storage plants in day-ahead markets

    International Nuclear Information System (INIS)

    Muche, Thomas

    2014-01-01

    Highlights: • We investigate unit commitment deploying stochastic and deterministic approaches. • We consider day-ahead markets, its forecast and weekly price based unit commitment. • Stochastic and deterministic unit commitment are identical for the first planning day. • Unit commitment and bidding policy can be based on the deterministic approach. • Robust forecasting models should be estimated based on the whole planning horizon. - Abstract: Pump storage plants are an important electricity storage technology at present. Investments in this technology are expected to increase. The necessary investment valuation often includes expected cash flows from future price-based unit commitment policies. A price-based unit commitment policy has to consider market price uncertainty and the information revealing nature of electricity markets. For this environment stochastic programming models are suggested to derive the optimal unit commitment policy. For the considered day-ahead price electricity market stochastic and deterministic unit commitment policies are comparable suggesting an application of easier implementable deterministic models. In order to identify suitable unit commitment and forecasting policies, deterministic unit commitment models are applied to actual day-ahead electricity prices of a whole year. As a result, a robust forecasting model should consider the unit commitment planning period. This robust forecasting models result in expected cash flows similar to realized ones allowing a reliable investment valuation

  1. Optimal Policies for Deteriorating Items with Maximum Lifetime and Two-Level Trade Credits

    Directory of Open Access Journals (Sweden)

    Nita H. Shah

    2014-01-01

    Full Text Available The retailer’s optimal policies are developed when the product has fixed lifetime and also the units in inventory are subject to deterioration at a constant rate. This study will be mainly applicable to pharmaceuticals, drugs, beverages, and dairy products, and so forth. To boost the demand, offering a credit period is considered as the promotional tool. The retailer passes credit period to the buyers which is received from the supplier. The objective is to maximize the total profit per unit time of the retailer with respect to optimal retail price of an item and purchase quantity during the optimal cycle time. The concavity of the total profit per unit time is exhibited using inventory parametric values. The sensitivity analysis is carried out to advise the decision maker to keep an eye on critical inventory parameters.

  2. Optimal Policy of Cross-Layer Design for Channel Access and Transmission Rate Adaptation in Cognitive Radio Networks

    Science.gov (United States)

    He, Hao; Wang, Jun; Zhu, Jiang; Li, Shaoqian

    2010-12-01

    In this paper, we investigate the cross-layer design of joint channel access and transmission rate adaptation in CR networks with multiple channels for both centralized and decentralized cases. Our target is to maximize the throughput of CR network under transmission power constraint by taking spectrum sensing errors into account. In centralized case, this problem is formulated as a special constrained Markov decision process (CMDP), which can be solved by standard linear programming (LP) method. As the complexity of finding the optimal policy by LP increases exponentially with the size of action space and state space, we further apply action set reduction and state aggregation to reduce the complexity without loss of optimality. Meanwhile, for the convenience of implementation, we also consider the pure policy design and analyze the corresponding characteristics. In decentralized case, where only local information is available and there is no coordination among the CR users, we prove the existence of the constrained Nash equilibrium and obtain the optimal decentralized policy. Finally, in the case that the traffic load parameters of the licensed users are unknown for the CR users, we propose two methods to estimate the parameters for two different cases. Numerical results validate the theoretic analysis.

  3. Optimal Policy of Cross-Layer Design for Channel Access and Transmission Rate Adaptation in Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Jiang Zhu

    2010-01-01

    Full Text Available In this paper, we investigate the cross-layer design of joint channel access and transmission rate adaptation in CR networks with multiple channels for both centralized and decentralized cases. Our target is to maximize the throughput of CR network under transmission power constraint by taking spectrum sensing errors into account. In centralized case, this problem is formulated as a special constrained Markov decision process (CMDP, which can be solved by standard linear programming (LP method. As the complexity of finding the optimal policy by LP increases exponentially with the size of action space and state space, we further apply action set reduction and state aggregation to reduce the complexity without loss of optimality. Meanwhile, for the convenience of implementation, we also consider the pure policy design and analyze the corresponding characteristics. In decentralized case, where only local information is available and there is no coordination among the CR users, we prove the existence of the constrained Nash equilibrium and obtain the optimal decentralized policy. Finally, in the case that the traffic load parameters of the licensed users are unknown for the CR users, we propose two methods to estimate the parameters for two different cases. Numerical results validate the theoretic analysis.

  4. Joint optimal inspection and inventory for a k-out-of-n system

    International Nuclear Information System (INIS)

    Bjarnason, Erik T.S.; Taghipour, Sharareh; Banjevic, Dragan

    2014-01-01

    Purpose: The objective of this paper is to develop a model, which optimizes jointly the inspection frequency and the inventory level for a k-out-of-n system with repairable components whose failures are hidden. Scope: The system is periodically inspected to detect failed components, and the components are either minimally repaired or replaced with spares from the inventory. The system fails between periodic inspections if n−k+1 components are down; in that case, all failed components are inspected and rectified if possible. Otherwise, the failed components are rectified at periodic inspections. An emergency spare is ordered at a system failure, if the inventory is empty and all failed components require replacement. Methodology: Using analytical approach to find the optimal solution is computationally intensive and not practical; a simulation model is developed to solve the problem. Results: The proposed model harmonizes the maintenance and inventory policies and finds the joint optimal solution which results in a minimum total cost. Conclusion: The joint optimization model results in a lower cost compared to separate maintenance and inventory optimization models. Novelty: Few joint models for k-out-of-n systems exist, and none of them investigate repairable components whose failures are hidden and follow a non-homogeneous Poisson process. - Highlights: • We model a k-out-of-n system with hidden failures and inventory. • The system is periodically inspected and the inventory is periodically replenished. • Failed components are either replaced or minimally repaired. • A simulation model is developed to calculate the total expected cost. • The inspection interval and inventory level that minimizes the total cost is found

  5. Replacement method and enhanced replacement method versus the genetic algorithm approach for the selection of molecular descriptors in QSPR/QSAR theories.

    Science.gov (United States)

    Mercader, Andrew G; Duchowicz, Pablo R; Fernández, Francisco M; Castro, Eduardo A

    2010-09-27

    We compare three methods for the selection of optimal subsets of molecular descriptors from a much greater pool of such regression variables. On the one hand is our enhanced replacement method (ERM) and on the other is the simpler replacement method (RM) and the genetic algorithm (GA). These methods avoid the impracticable full search for optimal variables in large sets of molecular descriptors. Present results for 10 different experimental databases suggest that the ERM is clearly preferable to the GA that is slightly better than the RM. However, the latter approach requires the smallest amount of linear regressions and, consequently, the lowest computation time.

  6. Optimization of Sugar Replacement with Date Syrup in Prebiotic Chocolate Milk Using Response Surface Methodology.

    Science.gov (United States)

    Kazemalilou, Sahar; Alizadeh, Ainaz

    2017-01-01

    Chocolate milk is one of the most commonly used non-fermentative dairy products, which, due to high level of sucrose, could lead to diabetes and tooth decay among children. Therefore, it is important to replace sucrose with other types of sweeteners, especially, natural ones. In this research, response surface methodology (RSM) was used to optimize the ingredients formulation of prebiotic chocolate milk, date syrup as sweetener (4-10%w/w), inulin as prebiotic texturizer (0-0.5%w/w) and carrageenan as thickening agent (0-0.04%w/w) in the formulation of chocolate milk. The fitted models to predict the variables of selected responses such as pH, viscosity, total solid, sedimentation and overall acceptability of chocolate milk showed a high coefficient of determination. The independent effect of carrageenan was the most effective parameter which led to pH and sedimentation decrease but increased viscosity. Moreover, in most treatments, date syrup and inulin variables had significant effects which had a mutual impact. Optimization of the variables, based on the responses surface 3D plots showed that the sample containing 0.48% (w/w) of inulin, 0.04% (w/w) of carrageenan, and 10% of date syrup was selected as the optimum condition.

  7. Performance of concrete with partial replacement of fine aggregates ...

    African Journals Online (AJOL)

    The study investigated the level of replacement of fine aggregate with waste glass that will result in optimal compressive strength. A total of 36 cubes were cast. 6 cubes without waste glass (control) and 30 cubes containing waste glass as partial replacement for fine aggregates at 15%, 25%, 35%, 45%, and 50%.

  8. An Optimization Model for Expired Drug Recycling Logistics Networks and Government Subsidy Policy Design Based on Tri-level Programming.

    Science.gov (United States)

    Huang, Hui; Li, Yuyu; Huang, Bo; Pi, Xing

    2015-07-09

    In order to recycle and dispose of all people's expired drugs, the government should design a subsidy policy to stimulate users to return their expired drugs, and drug-stores should take the responsibility of recycling expired drugs, in other words, to be recycling stations. For this purpose it is necessary for the government to select the right recycling stations and treatment stations to optimize the expired drug recycling logistics network and minimize the total costs of recycling and disposal. This paper establishes a tri-level programming model to study how the government can optimize an expired drug recycling logistics network and the appropriate subsidy policies. Furthermore, a Hybrid Genetic Simulated Annealing Algorithm (HGSAA) is proposed to search for the optimal solution of the model. An experiment is discussed to illustrate the good quality of the recycling logistics network and government subsides obtained by the HGSAA. The HGSAA is proven to have the ability to converge on the global optimal solution, and to act as an effective algorithm for solving the optimization problem of expired drug recycling logistics network and government subsidies.

  9. Optimizing Multireservoir System Operating Policies Using Exogenous Hydrologic Variables

    Science.gov (United States)

    Pina, Jasson; Tilmant, Amaury; Côté, Pascal

    2017-11-01

    Stochastic dual dynamic programming (SDDP) is one of the few available algorithms to optimize the operating policies of large-scale hydropower systems. This paper presents a variant, called SDDPX, in which exogenous hydrologic variables, such as snow water equivalent and/or sea surface temperature, are included in the state space vector together with the traditional (endogenous) variables, i.e., past inflows. A reoptimization procedure is also proposed in which SDDPX-derived benefit-to-go functions are employed within a simulation carried out over the historical record of both the endogenous and exogenous hydrologic variables. In SDDPX, release policies are now a function of storages, past inflows, and relevant exogenous variables that potentially capture more complex hydrological processes than those found in traditional SDDP formulations. To illustrate the potential gain associated with the use of exogenous variables when operating a multireservoir system, the 3,137 MW hydropower system of Rio Tinto (RT) located in the Saguenay-Lac-St-Jean River Basin in Quebec (Canada) is used as a case study. The performance of the system is assessed for various combinations of hydrologic state variables, ranging from the simple lag-one autoregressive model to more complex formulations involving past inflows, snow water equivalent, and winter precipitation.

  10. Suboptimal and optimal order policies for fixed and varying replenishment interval with declining market

    Science.gov (United States)

    Yu, Jonas C. P.; Wee, H. M.; Yang, P. C.; Wu, Simon

    2016-06-01

    One of the supply chain risks for hi-tech products is the result of rapid technological innovation; it results in a significant decline in the selling price and demand after the initial launch period. Hi-tech products include computers and communication consumer's products. From a practical standpoint, a more realistic replenishment policy is needed to consider the impact of risks; especially when some portions of shortages are lost. In this paper, suboptimal and optimal order policies with partial backordering are developed for a buyer when the component cost, the selling price, and the demand rate decline at a continuous rate. Two mathematical models are derived and discussed: one model has the suboptimal solution with the fixed replenishment interval and a simpler computational process; the other one has the optimal solution with the varying replenishment interval and a more complicated computational process. The second model results in more profit. Numerical examples are provided to illustrate the two replenishment models. Sensitivity analysis is carried out to investigate the relationship between the parameters and the net profit.

  11. Anticipating the uncertain: economic modeling and climate change policy

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, Svenn

    2012-11-01

    With this thesis I wish to contribute to the understanding of how uncertainty and the anticipation of future events by economic actors affect climate policies. The thesis consists of four papers. Two papers are analytical models which explicitly consider that emissions are caused by extracting scarce fossil fuels which in the future must be replaced by clean technologies. The other two are so called numerical integrated assessment models. Such models represent the world economy, the climate system and the interactions between those two quantitatively, complementing more abstract theoretical work. Should policy makers discriminate between subsidizing renewable energy sources such as wind or solar power, and technologies such as carbon capture and storage (CCS)? Focusing only on the dynamic supply of fossil fuels and hence Co{sub 2}, we find here that cheaper future renewables cause extraction to speed up, lower costs of CCS may delay it. CCS hence may dampen the dynamic inefficiency caused by the absence of comprehensive climate policies today. Does it matter whether uncertainty about future damage assessment is due to scientific complexities or stems from the political process? In paper two, I find that political and scientific uncertainties have opposing effects on the incentives to investment in renewables and the extraction of fossil fuels: The prospect of scientific learning about the climate system increases investment incentives and, ceteris paribus, slows extraction down; uncertainty about future political constellations does the opposite. The optimal carbon tax under scientific uncertainty equals expected marginal damages, whereas political uncertainty demands a tax below marginal damages that decreases over time. Does uncertainty about economic growth impact optimal climate policy today? Here we are the first to consistently analyze how uncertainty about future economic growth affects optimal emission reductions and the optimal social cost of carbon. We

  12. Optimization of fly ash as sand replacement materials (SRM) in cement composites containing coconut fiber

    Science.gov (United States)

    Nadzri, N. I. M.; Jamaludin, S. B.; Mazlee, M. N.; Jamal, Z. A. Z.

    2016-07-01

    The need of utilizing industrial and agricultural wastes is very important to maintain sustainability. These wastes are often incorporated with cement composites to improve performances in term of physical and mechanical properties. This study presents the results of the investigation of the response of cement composites containing coconut fiber as reinforcement and fly ash use as substitution of sand at different hardening days. Hardening periods of time (7, 14 and 28 days) were selected to study the properties of cement composites. Optimization result showed that 20 wt. % of fly ash (FA) is a suitable material for sand replacement (SRM). Meanwhile 14 days of hardening period gave highest compressive strength (70.12 MPa) from the cement composite containing 9 wt. % of coconut fiber and fly ash. This strength was comparable with the cement without coconut fiber (74.19 MPa) after 28 days of curing.

  13. Rehabilitation after total joint replacement: a scoping study.

    Science.gov (United States)

    L Snell, Deborah; Hipango, Julia; Sinnott, K Anne; Dunn, Jennifer A; Rothwell, Alastair; Hsieh, C Jean; DeJong, Gerben; Hooper, Gary

    2018-07-01

    The evidence supporting rehabilitation after joint replacement, while vast, is of variable quality making it difficult for clinicians to apply the best evidence to their practice. We aimed to map key issues for rehabilitation following joint replacement, highlighting potential avenues for new research. We conducted a scoping study including research published between January 2013 and December 2016, evaluating effectiveness of rehabilitation following hip and knee total joint replacement. We reviewed this work in the context of outcomes described from previously published research. Thirty individual studies and seven systematic reviews were included, with most research examining the effectiveness of physiotherapy-based exercise rehabilitation after total knee replacement using randomized control trial methods. Rehabilitation after hip and knee replacement whether carried out at the clinic or monitored at home, appears beneficial but type, intensity and duration of interventions were not consistently associated with outcomes. The burden of comorbidities rather than specific rehabilitation approach may better predict rehabilitation outcome. Monitoring of recovery and therapeutic attention appear important but little is known about optimal levels and methods required to maximize outcomes. More work exploring the role of comorbidities and key components of therapeutic attention and the therapy relationship, using a wider range of study methods may help to advance the field. Implications for Rehabilitation Physiotherapy-based exercise rehabilitation after total hip replacement and total knee replacement, whether carried out at the clinic or monitored at home, appears beneficial. Type, intensity, and duration of interventions do not appear consistently associated with outcomes. Monitoring a patient's recovery appears to be an important component. The available research provides limited guidance regarding optimal levels of monitoring needed to achieve gains following hip

  14. An approach to solve replacement problems under intuitionistic fuzzy nature

    Science.gov (United States)

    Balaganesan, M.; Ganesan, K.

    2018-04-01

    Due to impreciseness to solve the day to day problems the researchers use fuzzy sets in their discussions of the replacement problems. The aim of this paper is to solve the replacement theory problems with triangular intuitionistic fuzzy numbers. An effective methodology based on fuzziness index and location index is proposed to determine the optimal solution of the replacement problem. A numerical example is illustrated to validate the proposed method.

  15. A bivariate optimal replacement policy with cumulative repair cost ...

    Indian Academy of Sciences (India)

    Min-Tsai Lai

    Shock model; cumulative damage model; cumulative repair cost limit; preventive maintenance model. 1. Introduction ... with two types of shocks: one type is failure shock, and the other type is damage ...... Theory, methods and applications.

  16. US fiscal regimes and optimal monetary policy

    NARCIS (Netherlands)

    Mavromatis, K.

    2014-01-01

    Fiscal policy in the US has been documented to have been the leading authority in the ‘60s and the ‘70s (active fiscal policy), while committing to make the necessary fiscal adjustments following Volcker’s appointment (passive fiscal policy). Moreover, while passive, US fiscal policy has at times

  17. A multi-period optimization model for planning of China's power sector with consideration of carbon dioxide mitigation—The importance of continuous and stable carbon mitigation policy

    International Nuclear Information System (INIS)

    Zhang, Dongjie; Liu, Pei; Ma, Linwei; LI, Zheng

    2013-01-01

    A great challenge China's power sector faces is to mitigate its carbon emissions whilst satisfying the ever-increasing power demand. Optimal planning of the power sector with consideration of carbon mitigation for a long-term future remains a complex task, involving many technical alternatives and an infinite number of possible plants installations, retrofitting, and decommissioning over the planning horizon. Previously the authors built a multi-period optimization model for the planning of China's power sector during 2010–2050. Based on that model, this paper executed calculations on the optimal pathways of China's power sector with two typical decision-making modes, which are based on “full-information” and “limited-information” hypothesis, and analyzed the impacts on the optimal planning results by two typical types of carbon tax policies including a “continuous and stable” one and a “loose first and tight later” one. The results showed that making carbon tax policy for long-term future, and improving the continuity and stability in policy execution can effectively help reduce the accumulated total carbon emissions, and also the cost for carbon mitigation of the power sector. The conclusion of this study is of great significance for the policy makers to make carbon mitigation policies in China and other countries as well. - Highlights: • A multi-stage optimization model for planning the power sector is applied as basis. • Difference of ideal and actual decision making processes are proposed and analyzed. • A “continuous and stable” policy and a “loose first and tight later” one are designed. • 4 policy scenarios are studied applying the optimal planning model and compared. • The importance of “continuous and stable” policy for long term is well demonstrated

  18. CEP energy policy : Policy 917

    International Nuclear Information System (INIS)

    2002-10-01

    Some of the environmental challenges facing the world in the twenty-first century are energy and global warming. Vital human needs such as warmth, light and transportation require energy, which is also required in the production of goods. Absent from the debate concerning the energy industry and its efforts to stop climate change is the voice of energy workers. Previous policies from the Communications, Energy and Paperworkers Union of Canada (CEP) were replaced by this policy document. After providing a brief introduction, the document tackled global challenge: climate change. The following section dealt with global challenge: corporate rule. Canada's energy industries were examined from the workers' perspective, and the state of Canada's energy reserves was discussed. From national policies to national betrayal was the title of the following section of the document. Energy de-regulation and privatization was discussed, and an argument was made for a Canadian energy policy. The industrial policy was explored, as was the environment. A transition to sustainability was examined. refs

  19. Continuous Linguistic Rhetorical Education as a Means of Optimizing Language Policy in Russian Multinational Regions

    Science.gov (United States)

    Vorozhbitova, Alexandra A.; Konovalova, Galina M.; Ogneva, Tatiana N.; Chekulaeva, Natalia Y.

    2017-01-01

    Drawing on the function of Russian as a state language the paper proposes a concept of continuous linguistic rhetorical (LR) education perceived as a means of optimizing language policy in Russian multinational regions. LR education as an innovative pedagogical system shapes a learner's readiness for self-projection as a strong linguistic…

  20. Optimal results of aortic valve replacement with small mechanical valves (< 19 mm).

    Science.gov (United States)

    Kato, Yasuyuki; Hattori, Koji; Motoki, Manabu; Takahashi, Yosuke; Kotani, Shinsuke; Nishimura, Shinsuke; Shibata, Toshihiko

    2013-07-01

    Controversy exists regarding the optimal operative method or type of prosthesis for patients with a small aortic root. The aim of this retrospective study was to investigate the early and mid-term outcomes of standard aortic valve replacement (AVR) using 16 mm or 18 mm ATS Advanced Performance (AP) or 17 mm St. Jude Medical (SJM) Regent valves for a small aortic root. Between April 2003 and August 2009, 78 patients (age range: 50-86 years; 86% aged > or = 65 years) underwent AVR with 16 mm or 18 mm ATS AP valves (16AP group: n = 21, 18AP group: n = 32), or a 17 mm SJM Regent valve (17Regent group: n = 25). Fifty-six patients (72%) had a body surface area (BSA) of regression was similar among the groups (-30%, -25% and -28% in the 16AP, 17Regent and 18AP groups, respectively; p = 0.844). The early and mid-term results of AVR with 16 mm or 18 mm ATS AP valves, or with a 17 mm SJM Regent valve, were satisfactory. Therefore, standard AVR using these small mechanical prostheses, which avoids the need to enlarge the annulus or to conduct stentless bioprosthesis implantation, might represent an acceptable method, especially in elderly patients with a small aortic root.

  1. Human Health Safety Evaluation of Halon Replacement Candidates

    National Research Council Canada - National Science Library

    Dodd, D. E; Jepson, G. W; Macko, Jr, J. A

    2000-01-01

    .... The services within the Department of Defense (DoD) are directed to determine and evaluate suitable halon replacement candidates that will optimize performance of mission-essential equipment and operations...

  2. Vascular complications associated with transcatheter aortic valve replacement.

    Science.gov (United States)

    Sardar, M Rizwan; Goldsweig, Andrew M; Abbott, J Dawn; Sharaf, Barry L; Gordon, Paul C; Ehsan, Afshin; Aronow, Herbert D

    2017-06-01

    Transcatheter aortic valve replacement (TAVR) is now an accepted pathway for aortic valve replacement for patients who are at prohibitive, severe and intermediate risk for traditional aortic valve surgery. However, with this rising uptrend and adaptation of this new technology, vascular complications and their management remain an Achilles heel for percutaneous aortic valve replacement. The vascular complications are an independent predictor of mortality for patients undergoing TAVR. Early recognition of these complications and appropriate management is paramount. In this article, we review the most commonly encountered vascular complications associated with currently approved TAVR devices and their optimal percutaneous management techniques.

  3. The Free Senior High Policy: An Appropriate Replacement to the Progressive Free Senior High Policy

    Science.gov (United States)

    Abdul-Rahaman, Nurudeen; Rahaman, Abdul Basit Abdul; Ming, Wan; Ahmed, Abdul-Rahim; Salma, Abdul-Rahaman S.

    2018-01-01

    Governments all over the world have been improving their educational sector through funding programs aimed at reducing the financial burden on parents, increasing access and quality to education. The government of Ghana in 2017 switched policy to a free senior high school policy to reduce poverty by finally eliminating the financial burdens…

  4. An Optimization Model for Expired Drug Recycling Logistics Networks and Government Subsidy Policy Design Based on Tri-level Programming

    Directory of Open Access Journals (Sweden)

    Hui Huang

    2015-07-01

    Full Text Available In order to recycle and dispose of all people’s expired drugs, the government should design a subsidy policy to stimulate users to return their expired drugs, and drug-stores should take the responsibility of recycling expired drugs, in other words, to be recycling stations. For this purpose it is necessary for the government to select the right recycling stations and treatment stations to optimize the expired drug recycling logistics network and minimize the total costs of recycling and disposal. This paper establishes a tri-level programming model to study how the government can optimize an expired drug recycling logistics network and the appropriate subsidy policies. Furthermore, a Hybrid Genetic Simulated Annealing Algorithm (HGSAA is proposed to search for the optimal solution of the model. An experiment is discussed to illustrate the good quality of the recycling logistics network and government subsides obtained by the HGSAA. The HGSAA is proven to have the ability to converge on the global optimal solution, and to act as an effective algorithm for solving the optimization problem of expired drug recycling logistics network and government subsidies.

  5. The role of the safety analysis organization in steam generators replacement and reactor vessel head replacement evaluations

    International Nuclear Information System (INIS)

    Choe, Whee G.; Boatwright, W.J.

    2004-01-01

    When a major component in a nuclear power plant is replaced, especially the steam generators, the plant operator is presented a rare opportunity to learn from operating experience and significantly improve the performance, reliability and robustness of the plant. In addition to the use of improved materials, improved design margins can be built into the component specification that can later be used to provide meaningful operating margins. A Safety Analysis organization that is well-integrated with other plant organizations and possesses a detailed knowledge of the plant design and licensing bases can effectively balance the wants and needs of each organization to optimize the benefits realized by the plant as a whole. Knowledge of the assumptions, limitations, and available margins, both analytical and operating, can be used to specify a replacement steam generator design that optimizes costs and operating improvements. The work scope required to support the new design can be controlled through carefully selected and evaluated restrictions in operations, development of alternate operating strategies, and imposition of appropriate limitations. The important point is that the effective Safety Analysis organization must possess both the breadth and depth of knowledge of the plant design and operations and proactively use this information to support the replacement steam generator project. (author)

  6. Optimization Policy of Inventory Spare Parts Stocking and Provisioning

    International Nuclear Information System (INIS)

    Yun, Tae Sik; Park, Jong Hyuk; Hwang, Eui Youp; Yoo, Sung Soo; Kim, In Hwan

    2005-01-01

    Spare parts, especially safety related items, being used in Korea Nuclear Power Plants are largely from the United States, Canada, France and the like, meaning the inventory policy, stocking and provision, should be influenced by those countries' nuclear industry situation in a direct or indirect manner. As a result of nuclear industry downturn practices, lots of spare supply corporations have gone broke, which gave immediate signals we have to resolve inventory purchases in need. It is known for that nuclear maintenance spare items are particularly composed of many kinds with small quantities, which makes matters worse to Korea nuclear operation company (KHNP) to purchase them. Hence, Korea nuclear business is trying to change its exinventory purchasing paradigm into innovative schemes it did not have to consider in the past. In order to implement a new stocking policy, it should be kept in mind the factors such as not only how much to stock for a smooth operation but also economic point of view. Even though it has done a lot of studies to optimize the inventory stocking level in an academic curiosity, it is not easy to apply the researches in a real world. Since it is so tough job to anticipate when and how large scale even occurs. Hence, it would be thought that the nuclear inventory should be dealt in a different manner from the general manufacturing industry

  7. The optimal timing of continuous renal replacement therapy for patients with sepsis-induced acute kidney injury.

    Science.gov (United States)

    Tian, Huanhuan; Sun, Ting; Hao, Dong; Wang, Tao; Li, Zhi; Han, Shasha; Qi, Zhijiang; Dong, Zhaoju; Lv, Changjun; Wang, Xiaozhi

    2014-10-01

    High mortality in the intensive care unit (ICU) is probably associated with sepsis-induced acute kidney injury (AKI). The aim of this study is to explore which stage of AKI may be the optimal timing for continuous renal replacement therapy (CRRT). A retrospective analysis of 160 critically ill patients with septic AKI, treated with or without CRRT was performed in Binzhou medical college affiliated hospital ICU. The parameters including 28-days mortality rate, renal recovery, ventilation time and ICU stay between CRRT group and control group were assessed. Renal recovery, defined as independence from dialysis at discharge, was documented for 64/76 (84.2 %) of the surviving patients (48.1 % of total subjects included in the study). The mortality rate increased proportionally with acute kidney injury Network stages in CRRT subgroups (P = 0.001) and control groups (P = 0.029). CRRT initiation at stage 2 of AKI significantly reduced the 28-day mortality (P = 0.048) and increased the 28-day survival rate (P = 0.036) compared with those in control group. In addition, the ICU stay and ventilation time were shorter in CRRT group than that of control group in stage 2 of AKI. The stage 2 AKI might be the optimal timing for performing CRRT.

  8. Model for Quantitative Evaluation of Enzyme Replacement Treatment

    Directory of Open Access Journals (Sweden)

    Radeva B.

    2009-12-01

    Full Text Available Gaucher disease is the most frequent lysosomal disorder. Its enzyme replacement treatment was the new progress of modern biotechnology, successfully used in the last years. The evaluation of optimal dose of each patient is important due to health and economical reasons. The enzyme replacement is the most expensive treatment. It must be held continuously and without interruption. Since 2001, the enzyme replacement therapy with Cerezyme*Genzyme was formally introduced in Bulgaria, but after some time it was interrupted for 1-2 months. The dose of the patients was not optimal. The aim of our work is to find a mathematical model for quantitative evaluation of ERT of Gaucher disease. The model applies a kind of software called "Statistika 6" via the input of the individual data of 5-year-old children having the Gaucher disease treated with Cerezyme. The output results of the model gave possibilities for quantitative evaluation of the individual trends in the development of the disease of each child and its correlation. On the basis of this results, we might recommend suitable changes in ERT.

  9. A condition-based maintenance policy with non-periodic inspections for a two-unit series system

    International Nuclear Information System (INIS)

    Castanier, B.; Grall, A.; Berenguer, C.

    2005-01-01

    This paper considers a condition-based maintenance policy for a two-unit deteriorating system. Each unit is subject to gradual deterioration and is monitored by sequential non-periodic inspections. It can be maintained by good as new preventive or corrective replacements. Every inspection or replacement entails a set-up cost and a component-specific unit cost but if actions on the two components are combined, the set-up cost is charged only once. A parametric maintenance decision framework is proposed to coordinate inspection/replacement of the two components and minimize the long-run maintenance cost of the system. A stochastic model is developed on the basis of the semi-regenerative properties of the maintained system state and the associated cost model is used to assess and optimize the performance of the maintenance model. Numerical experiments emphasize the interest of a control of the operation groupings

  10. Optimal maintenance policy incorporating system level and unit level for mechanical systems

    Science.gov (United States)

    Duan, Chaoqun; Deng, Chao; Wang, Bingran

    2018-04-01

    The study works on a multi-level maintenance policy combining system level and unit level under soft and hard failure modes. The system experiences system-level preventive maintenance (SLPM) when the conditional reliability of entire system exceeds SLPM threshold, and also undergoes a two-level maintenance for each single unit, which is initiated when a single unit exceeds its preventive maintenance (PM) threshold, and the other is performed simultaneously the moment when any unit is going for maintenance. The units experience both periodic inspections and aperiodic inspections provided by failures of hard-type units. To model the practical situations, two types of economic dependence have been taken into account, which are set-up cost dependence and maintenance expertise dependence due to the same technology and tool/equipment can be utilised. The optimisation problem is formulated and solved in a semi-Markov decision process framework. The objective is to find the optimal system-level threshold and unit-level thresholds by minimising the long-run expected average cost per unit time. A formula for the mean residual life is derived for the proposed multi-level maintenance policy. The method is illustrated by a real case study of feed subsystem from a boring machine, and a comparison with other policies demonstrates the effectiveness of our approach.

  11. Policy Iteration for $H_\\infty $ Optimal Control of Polynomial Nonlinear Systems via Sum of Squares Programming.

    Science.gov (United States)

    Zhu, Yuanheng; Zhao, Dongbin; Yang, Xiong; Zhang, Qichao

    2018-02-01

    Sum of squares (SOS) polynomials have provided a computationally tractable way to deal with inequality constraints appearing in many control problems. It can also act as an approximator in the framework of adaptive dynamic programming. In this paper, an approximate solution to the optimal control of polynomial nonlinear systems is proposed. Under a given attenuation coefficient, the Hamilton-Jacobi-Isaacs equation is relaxed to an optimization problem with a set of inequalities. After applying the policy iteration technique and constraining inequalities to SOS, the optimization problem is divided into a sequence of feasible semidefinite programming problems. With the converged solution, the attenuation coefficient is further minimized to a lower value. After iterations, approximate solutions to the smallest -gain and the associated optimal controller are obtained. Four examples are employed to verify the effectiveness of the proposed algorithm.

  12. Optimal dynamic pricing and replenishment policies for deteriorating items

    Directory of Open Access Journals (Sweden)

    Masoud Rabbani

    2014-08-01

    Full Text Available Marketing strategies and proper inventory replenishment policies are often incorporated by enterprises to stimulate demand and maximize profit. The aim of this paper is to represent an integrated model for dynamic pricing and inventory control of deteriorating items. To reflect the dynamic characteristic of the problem, the selling price is defined as a time-dependent function of the initial selling price and the discount rate. In this regard, the price is exponentially discounted to compensate negative impact of the deterioration. The planning horizon is assumed to be infinite and the deterioration rate is time-dependent. In addition to price, the demand rate is dependent on advertisement as a powerful marketing tool. Several theoretical results and an iterative solution algorithm are developed to provide the optimal solution. Finally, to show validity of the model and illustrate the solution procedure, numerical results are presented.

  13. A note on optimal (s,S) and (R,nQ) policies under a stuttering Poisson demand process

    DEFF Research Database (Denmark)

    Larsen, Christian

    2015-01-01

    In this note, a new efficient algorithm is proposed to find an optimal (s, S) replenishment policy for inventory systems with continuous reviews and where the demand follows a stuttering Poisson process (the compound element is geometrically distributed). We also derive three upper bounds...

  14. AN OPTIMAL REPLENISHMENT POLICY FOR DETERIORATING ITEMS WITH RAMP TYPE DEMAND UNDER PERMISSIBLE DELAY IN PAYMENTS

    Directory of Open Access Journals (Sweden)

    Dr. Sanjay Jain

    2010-10-01

    Full Text Available The aim of this paper is to develop an optimal replenishment policy for inventory models of deteriorating items with ramp type demand under permissible delay in payments. Deterioration of items begins on their arrival in stock.  An example is also presented to illustrate the application of developed model.

  15. Optimal back-to-front airplane boarding

    Science.gov (United States)

    Bachmat, Eitan; Khachaturov, Vassilii; Kuperman, Ran

    2013-06-01

    The problem of finding an optimal back-to-front airplane boarding policy is explored, using a mathematical model that is related to the 1+1 polynuclear growth model with concave boundary conditions and to causal sets in gravity. We study all airplane configurations and boarding group sizes. Optimal boarding policies for various airplane configurations are presented. Detailed calculations are provided along with simulations that support the main conclusions of the theory. We show that the effectiveness of back-to-front policies undergoes a phase transition when passing from lightly congested airplanes to heavily congested airplanes. The phase transition also affects the nature of the optimal or near-optimal policies. Under what we consider to be realistic conditions, optimal back-to-front policies lead to a modest 8-12% improvement in boarding time over random (no policy) boarding, using two boarding groups. Having more than two groups is not effective.

  16. Optimal back-to-front airplane boarding.

    Science.gov (United States)

    Bachmat, Eitan; Khachaturov, Vassilii; Kuperman, Ran

    2013-06-01

    The problem of finding an optimal back-to-front airplane boarding policy is explored, using a mathematical model that is related to the 1+1 polynuclear growth model with concave boundary conditions and to causal sets in gravity. We study all airplane configurations and boarding group sizes. Optimal boarding policies for various airplane configurations are presented. Detailed calculations are provided along with simulations that support the main conclusions of the theory. We show that the effectiveness of back-to-front policies undergoes a phase transition when passing from lightly congested airplanes to heavily congested airplanes. The phase transition also affects the nature of the optimal or near-optimal policies. Under what we consider to be realistic conditions, optimal back-to-front policies lead to a modest 8-12% improvement in boarding time over random (no policy) boarding, using two boarding groups. Having more than two groups is not effective.

  17. Outcomes of pulmonary valve replacement in 170 patients with chronic pulmonary regurgitation after relief of right ventricular outflow tract obstruction: implications for optimal timing of pulmonary valve replacement.

    Science.gov (United States)

    Lee, Cheul; Kim, Yang Min; Lee, Chang-Ha; Kwak, Jae Gun; Park, Chun Soo; Song, Jin Young; Shim, Woo-Sup; Choi, Eun Young; Lee, Sang Yun; Baek, Jae Suk

    2012-09-11

    The objectives of this study were to evaluate outcomes of pulmonary valve replacement (PVR) in patients with chronic pulmonary regurgitation (PR) and to better define the optimal timing of PVR. Although PVR is effective in reducing right ventricular (RV) volume overload in patients with chronic PR, the optimal timing of PVR is not well defined. A total of 170 patients who underwent PVR between January 1998 and March 2011 for chronic PR were retrospectively analyzed. To define the optimal timing of PVR, pre-operative and post-operative cardiac magnetic resonance imaging (MRI) data (n = 67) were analyzed. The median age at the time of PVR was 16.7 years. Follow-up completeness was 95%, and the median follow-up duration was 5.9 years. Overall and event-free survival at 10 years was 98% and 70%, respectively. Post-operative MRI showed significant reduction in RV volumes and significant improvement in biventricular function. Receiver-operating characteristic curve analysis revealed a cutoff value of 168 ml/m(2) for non-normalization of RV end-diastolic volume index (EDVI) and 80 ml/m(2) for RV end-systolic volume index (ESVI). Cutoff values for optimal outcome (normalized RV volumes and function) were 163 ml/m(2) for RV EDVI and 80 ml/m(2) for RV ESVI. Higher pre-operative RV ESVI was identified as a sole independent risk factor for suboptimal outcome. Midterm outcomes of PVR in patients with chronic PR were acceptable. PVR should be considered before RV EDVI exceeds 163 ml/m(2) or RV ESVI exceeds 80 ml/m(2), with more attention to RV ESVI. Copyright © 2012 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  18. Electrocatalysts Prepared by Galvanic Replacement

    Directory of Open Access Journals (Sweden)

    Athanasios Papaderakis

    2017-03-01

    Full Text Available Galvanic replacement is the spontaneous replacement of surface layers of a metal, M, by a more noble metal, Mnoble, when the former is treated with a solution containing the latter in ionic form, according to the general replacement reaction: nM + mMnoblen+ → nMm+ + mMnoble. The reaction is driven by the difference in the equilibrium potential of the two metal/metal ion redox couples and, to avoid parasitic cathodic processes such as oxygen reduction and (in some cases hydrogen evolution too, both oxygen levels and the pH must be optimized. The resulting bimetallic material can in principle have a Mnoble-rich shell and M-rich core (denoted as Mnoble(M leading to a possible decrease in noble metal loading and the modification of its properties by the underlying metal M. This paper reviews a number of bimetallic or ternary electrocatalytic materials prepared by galvanic replacement for fuel cell, electrolysis and electrosynthesis reactions. These include oxygen reduction, methanol, formic acid and ethanol oxidation, hydrogen evolution and oxidation, oxygen evolution, borohydride oxidation, and halide reduction. Methods for depositing the precursor metal M on the support material (electrodeposition, electroless deposition, photodeposition as well as the various options for the support are also reviewed.

  19. Optimal Policies for Random and Periodic Garbage Collections with Tenuring Threshold

    Science.gov (United States)

    Zhao, Xufeng; Nakamura, Syouji; Nakagawa, Toshio

    It is an important problem to determine the tenuring threshold to meet the pause time goal for a generational garbage collector. From such viewpoint, this paper proposes two stochastic models based on the working schemes of a generational garbage collector: One is random collection which occurs at a nonhomogeneous Poisson process and the other is periodic collection which occurs at periodic times. Since the cost suffered for minor collection increases, as the amount of surviving objects accumulates, tenuring minor collection should be made at some tenuring threshold. Using the techniques of cumulative processes and reliability theory, expected cost rates with tenuring threshold are obtained, and optimal policies which minimize them are discussed analytically and computed numerically.

  20. The effect of replacing maize with cassava peel meal on the ...

    African Journals Online (AJOL)

    A 12-week feeding trial was conducted to determine the optimal replacement level(s) of dried cassava peel meal (DCPM) for maize in diets for weaner rabbits. Four experimentnl diets were formulated such that dried cassava peel meal replaced maize at 0, 50%, 75% and 100% levels, respectively. Each diet was fed to five ...

  1. Rational optimization of reliability and safety policies

    International Nuclear Information System (INIS)

    Melchers, Robert E.

    2001-01-01

    Optimization of structures for design has a long history, including optimization using numerical methods and optimality criteria. Much of this work has considered a subset of the complete design optimization problem--that of the technical issues alone. The more general problem must consider also non-technical issues and, importantly, the interplay between them and the parameters which influence them. Optimization involves optimal setting of design or acceptance criteria and, separately, optimal design within the criteria. In the modern context of probability based design codes this requires probabilistic acceptance criteria. The determination of such criteria involves more than the nominal code failure probability approach used for design code formulation. A more general view must be taken and a clear distinction must be made between those matters covered by technical reliability and non-technical reliability. The present paper considers this issue and outlines a framework for rational optimization of structural and other systems given the socio-economic and political systems within which optimization must be performed

  2. Apixaban or enoxaparin for thromboprophylaxis after knee replacement

    DEFF Research Database (Denmark)

    Lassen, Michael Rud; Raskob, Gary E; Gallus, Alexander

    2009-01-01

    BACKGROUND: The optimal strategy for thromboprophylaxis after major joint replacement has not been established. Low-molecular-weight heparins such as enoxaparin predominantly target factor Xa but to some extent also inhibit thrombin. Apixaban, a specific factor Xa inhibitor, may provide effective...... (P=0.03). CONCLUSIONS: As compared with enoxaparin for efficacy of thromboprophylaxis after knee replacement, apixaban did not meet the prespecified statistical criteria for noninferiority, but its use was associated with lower rates of clinically relevant bleeding and it had a similar adverse...

  3. Optimal human capital policies

    Czech Academy of Sciences Publication Activity Database

    Boháček, Radim; Kapička, M.

    2008-01-01

    Roč. 55, č. 1 (2008), s. 1-16 ISSN 0304-3932 Institutional research plan: CEZ:AV0Z70850503 Keywords : dynamic optimal taxation * income taxation Subject RIV: AH - Economics Impact factor: 1.429, year: 2008

  4. Reduction rules-based search algorithm for opportunistic replacement strategy of multiple life-limited parts

    Directory of Open Access Journals (Sweden)

    Xuyun FU

    2018-01-01

    Full Text Available The opportunistic replacement of multiple Life-Limited Parts (LLPs is a problem widely existing in industry. The replacement strategy of LLPs has a great impact on the total maintenance cost to a lot of equipment. This article focuses on finding a quick and effective algorithm for this problem. To improve the algorithm efficiency, six reduction rules are suggested from the perspectives of solution feasibility, determination of the replacement of LLPs, determination of the maintenance occasion and solution optimality. Based on these six reduction rules, a search algorithm is proposed. This search algorithm can identify one or several optimal solutions. A numerical experiment shows that these six reduction rules are effective, and the time consumed by the algorithm is less than 38 s if the total life of equipment is shorter than 55000 and the number of LLPs is less than 11. A specific case shows that the algorithm can obtain optimal solutions which are much better than the result of the traditional method in 10 s, and it can provide support for determining to-be-replaced LLPs when determining the maintenance workscope of an aircraft engine. Therefore, the algorithm is applicable to engineering applications concerning opportunistic replacement of multiple LLPs in aircraft engines.

  5. Optimal Ordering Policy of a Risk-Averse Retailer Subject to Inventory Inaccuracy

    Directory of Open Access Journals (Sweden)

    Lijing Zhu

    2013-01-01

    Full Text Available Inventory inaccuracy refers to the discrepancy between the actual inventory and the recorded inventory information. Inventory inaccuracy is prevalent in retail stores. It may result in a higher inventory level or poor customer service. Earlier studies of inventory inaccuracy have traditionally assumed risk-neutral retailers whose objective is to maximize expected profits. We investigate a risk-averse retailer within a newsvendor framework. The risk aversion attitude is measured by conditional-value-at-risk (CVaR. We consider inventory inaccuracy stemming both from permanent shrinkage and temporary shrinkage. Two scenarios of reducing inventory shrinkage are presented. In the first scenario, the retailer conducts physical inventory audits to identify the discrepancy. In the second scenario, the retailer deploys an automatic tracking technology, radiofrequency identification (RFID, to reduce inventory shrinkage. With the CVaR criterion, we propose optimal policies for the two scenarios. We show monotonicity between the retailer’s ordering policy and his risk aversion degree. A numerical analysis provides managerial insights for risk-averse retailers considering investing in RFID technology.

  6. Optimal pricing and promotional effort control policies for a new product growth in segmented market

    Directory of Open Access Journals (Sweden)

    Jha P.C.

    2015-01-01

    Full Text Available Market segmentation enables the marketers to understand and serve the customers more effectively thereby improving company’s competitive position. In this paper, we study the impact of price and promotion efforts on evolution of sales intensity in segmented market to obtain the optimal price and promotion effort policies. Evolution of sales rate for each segment is developed under the assumption that marketer may choose both differentiated as well as mass market promotion effort to influence the uncaptured market potential. An optimal control model is formulated and a solution method using Maximum Principle has been discussed. The model is extended to incorporate budget constraint. Model applicability is illustrated by a numerical example. P.C. Jha, P. Manik, K. Chaudhary, R. Cambini / Optimal Pricing and Promotional 2 Since the discrete time data is available, the formulated model is discretized. For solving the discrete model, differential evolution algorithm is used.

  7. Optimal inventory policy in a closed loop supply chain system with multiple periods

    International Nuclear Information System (INIS)

    Sasi Kumar, A.; Natarajan, K.; Ramasubramaniam, Muthu Rathna Sapabathy.; Deepaknallasamy, K.K.

    2017-01-01

    Purpose: This paper aims to model and optimize the closed loop supply chain for maximizing the profit by considering the fixed order quantity inventory policy in various sites at multiple periods. Design/methodology/approach: In forward supply chain, a standard inventory policy can be followed when the product moves from manufacturer, distributer, retailer and customer but the inventory in the reverse supply chain of the product with the similar standard policy is very difficult to manage. This model investigates the standard policy of fixed order quantity by considering the three major types of return-recovery pair such as commercial returns, end- of- use returns, end –of- life returns and their inventory positioning at multiple periods. The model is configured as mixed integer linear programming and solved by IBM ILOG CPLEX OPL studio. Findings: To find the performance of the model a numerical example is considered for a product with three Parts (A which of 2nos, B and C) for 12 multiple periods. The results of the analysis show that the manufacturer can know how much should to be manufacture in multiple periods based on Variations of the demand by adopting the FOQ inventory policy at different sites considering its capacity constraints. In addition, it is important how much of parts should be purchased from the supplier at the given 12 periods. Originality/value: A sensitivity analysis is performed to validate the proposed model two parts. First part of the analysis will focus on the inventory of product and parts and second part of analysis focus on profit of the company. The analysis which provides some insights in to the structure of the model.

  8. Optimal inventory policy in a closed loop supply chain system with multiple periods

    Energy Technology Data Exchange (ETDEWEB)

    Sasi Kumar, A.; Natarajan, K.; Ramasubramaniam, Muthu Rathna Sapabathy.; Deepaknallasamy, K.K.

    2017-07-01

    Purpose: This paper aims to model and optimize the closed loop supply chain for maximizing the profit by considering the fixed order quantity inventory policy in various sites at multiple periods. Design/methodology/approach: In forward supply chain, a standard inventory policy can be followed when the product moves from manufacturer, distributer, retailer and customer but the inventory in the reverse supply chain of the product with the similar standard policy is very difficult to manage. This model investigates the standard policy of fixed order quantity by considering the three major types of return-recovery pair such as commercial returns, end- of- use returns, end –of- life returns and their inventory positioning at multiple periods. The model is configured as mixed integer linear programming and solved by IBM ILOG CPLEX OPL studio. Findings: To find the performance of the model a numerical example is considered for a product with three Parts (A which of 2nos, B and C) for 12 multiple periods. The results of the analysis show that the manufacturer can know how much should to be manufacture in multiple periods based on Variations of the demand by adopting the FOQ inventory policy at different sites considering its capacity constraints. In addition, it is important how much of parts should be purchased from the supplier at the given 12 periods. Originality/value: A sensitivity analysis is performed to validate the proposed model two parts. First part of the analysis will focus on the inventory of product and parts and second part of analysis focus on profit of the company. The analysis which provides some insights in to the structure of the model.

  9. Optimal inventory policy in a closed loop supply chain system with multiple periods

    Directory of Open Access Journals (Sweden)

    SasiKumar A.

    2017-05-01

    Full Text Available Purpose: This paper aims to model and optimize the closed loop supply chain for maximizing the profit by considering the fixed order quantity inventory policy in various sites at multiple periods. Design/methodology/approach: In forward supply chain, a standard inventory policy can be followed when the product moves from manufacturer, distributer, retailer and customer but the inventory in the reverse supply chain of the product with the similar standard policy is very difficult to manage. This model investigates the standard policy of fixed order quantity by considering the three major types of return-recovery pair such as commercial returns, end- of- use returns, end –of- life returns and their inventory positioning at multiple periods.  The model is configured as mixed integer linear programming and solved by IBM ILOG CPLEX OPL studio. Findings: To find the performance of the model a numerical example is considered for a product with three Parts (A which of 2nos, B and C for 12 multiple periods. The results of the analysis show that the manufacturer can know how much should to be manufacture in multiple periods based on Variations of the demand by adopting the FOQ inventory policy at different sites considering its capacity constraints. In addition, it is important how much of parts should be purchased from the supplier at the given 12 periods. Originality/value: A sensitivity analysis is performed to validate the proposed model two parts. First part of the analysis will focus on the inventory of product and parts and second part of analysis focus on profit of the company. The analysis which provides some insights in to the structure of the model.

  10. The Optimal Replenishment Policy under Trade Credit Financing with Ramp Type Demand and Demand Dependent Production Rate

    Directory of Open Access Journals (Sweden)

    Juanjuan Qin

    2014-01-01

    Full Text Available This paper investigates the optimal replenishment policy for the retailer with the ramp type demand and demand dependent production rate involving the trade credit financing, which is not reported in the literatures. First, the two inventory models are developed under the above situation. Second, the algorithms are given to optimize the replenishment cycle time and the order quantity for the retailer. Finally, the numerical examples are carried out to illustrate the optimal solutions and the sensitivity analysis is performed. The results show that if the value of production rate is small, the retailer will lower the frequency of putting the orders to cut down the order cost; if the production rate is high, the demand dependent production rate has no effect on the optimal decisions. When the trade credit is less than the growth stage time, the retailer will shorten the replenishment cycle; when it is larger than the breakpoint of the demand, within the maturity stage of the products, the trade credit has no effect on the optimal order cycle and the optimal order quantity.

  11. Aorta-atria-septum combined incision for aortic valve re-replacement

    Science.gov (United States)

    Xu, Yiwei; Ye, Xiaofeng; Li, Zhaolong

    2018-01-01

    This case report illustrates a patient who underwent supra-annular mechanical aortic valve replacement then suffered from prosthesis dysfunction, increasing pressure gradient with aortic valve. She was successfully underwent aortic valve re-replacement, sub-annular pannus removing and aortic annulus enlargement procedures through combined cardiac incision passing through aortic root, right atrium (RA), and upper atrial septum. This incision provides optimal visual operative field and simplifies dissection. PMID:29850170

  12. Optimal timing of aortic valve replacement in elderly patients with severe aortic stenosis.

    Science.gov (United States)

    Marumoto, Akira; Nakamura, Yoshinobu; Kishimoto, Yuichiro; Saiki, Munehiro; Nishimura, Motonobu

    2014-01-01

    The elderly population with severe aortic stenosis (AS) requiring aortic valve replacement (AVR) is increasing. The optimal timing of AVR in these patients has been under discussion. We retrospectively reviewed the data from severe AS patients (n = 84) who underwent AVR with/without concomitant procedures from 2005 to 2010. The symptom status, preoperative data, operative outcome, late survival and freedom from cardiac events were compared between elderly patients (age ≥80 years [n = 31]) and younger patients (age <80 years [n = 53]). The operative mortality in elderly patients (3.2 %) and younger patients (3.8 %) was comparable. The symptoms in elderly patients were more severe and hospitalized heart failure (HF) was more frequently noted as the primary symptom (p = 0.017). Patients with and without hospitalized HF differed significantly in late survival and freedom from cardiac events (p = 0.001), but advanced age had no significant effect. The results of a Cox proportional hazards analysis revealed that hospitalized HF was a significant predictor for cardiac events after AVR, irrespective of age (hazard ratio 6.93, 95 % confidence interval 1.83-26.26, p < 0.004). In elderly patients with severe AS, surgery should be recommended even in the presence of minimal symptoms and should be performed before the onset of life-threatening HF.

  13. Energy policy in transport and transport policy

    International Nuclear Information System (INIS)

    Van Dender, Kurt

    2009-01-01

    Explanations for, and indirect evidence of, imperfections in the market for private passenger vehicle fuel economy suggest there is a reasonable case for combining fuel economy standards and fuel or carbon taxes to contribute to an energy policy that aims to reduce greenhouse gas emissions and improve energy security. Estimates of key elasticities, including the rebound effect, indicate that the positive and negative side-effects of fuel economy measures on transport activities and external costs are limited. However, an energy policy for transport does not replace a transport policy that aims to manage the main transport externalities including congestion and local pollution. Conventional marginal cost estimates and standard cost-benefit reasoning suggest that policies that address congestion and local pollution likely bring benefits at least as large as those from fuel economy measures. But the large uncertainty on the possible effects of greenhouse gas emissions constitutes a strong challenge for standard cost-benefit reasoning. Emerging results from methods to cope with this uncertainty suggest that policies to stimulate the widespread adoption of low-carbon technologies in transport are justified.

  14. Energy policy in transport and transport policy

    Energy Technology Data Exchange (ETDEWEB)

    Van Dender, Kurt [Joint Transport Research Centre of the International Transport Forum and the OECD, 2 rue Andre Pascale, F-75775 Paris Cedex 16 (France)

    2009-10-15

    Explanations for, and indirect evidence of, imperfections in the market for private passenger vehicle fuel economy suggest there is a reasonable case for combining fuel economy standards and fuel or carbon taxes to contribute to an energy policy that aims to reduce greenhouse gas emissions and improve energy security. Estimates of key elasticities, including the rebound effect, indicate that the positive and negative side-effects of fuel economy measures on transport activities and external costs are limited. However, an energy policy for transport does not replace a transport policy that aims to manage the main transport externalities including congestion and local pollution. Conventional marginal cost estimates and standard cost-benefit reasoning suggest that policies that address congestion and local pollution likely bring benefits at least as large as those from fuel economy measures. But the large uncertainty on the possible effects of greenhouse gas emissions constitutes a strong challenge for standard cost-benefit reasoning. Emerging results from methods to cope with this uncertainty suggest that policies to stimulate the widespread adoption of low-carbon technologies in transport are justified. (author)

  15. Development of an approach to facilitate optimal equipment replacement : technical summary.

    Science.gov (United States)

    1999-10-01

    The objective of the study was to determine a way or ways to assign an urgency rating to equipment that was currently in service but in need of replacement. This urgency rating must in some manner took into account the various costs associated with r...

  16. Update of Energy policy of Uruguay

    International Nuclear Information System (INIS)

    2004-08-01

    The National Energy Directorate from Uruguay called a contest for Update Policy L Energy of Uruguay so as to ensure energy supply at the lowest possible cost, with greater safety and lower environmental impact and taking account efficient use of the Energy. FIEL was selected to carry out the work planned within three months and responding to a broad agenda that included the following points in the order of the Terms of Reference of the contest (TORs): 3.1. Evaluation of the existing energy policy 3.2. relative price optimization fuel 3.3. Optimization of tax policy in fuel 3.4. assessment of cost and benefits of alternative import 3.5. strategic reserve 3.6. Ambiental impacts Identification 3.7. Recommendations to improve the framework regulatory 3.8. Institutional framework for the energy sector in Uruguay 3.9. Evaluation of potential of renewable national energy resources 3.10. Energy efficiency 3.11. Action Plan for the National Energy The report presents and order of the TORs. In the first chapter updates assessment of energy policy presented in the progress report. In point 3.2 approaching the economic costs of the various energy alternatives from the parities import and cost efficient products in non tradable. Along with the environmental costs estimated in Section 3.6 is evaluated in the 3.3 How should the taxes structure to take into account externalities generating energy. In Section 3.4 discusses different options imported and in 3.5 energy supply costs are assessed count a strategic reserve, which Uruguay has decided that it is in the form of capacity thermal generation. In paragraphs 3.7 and 3.8 governing institutions is analyzed and they plan the sector, not only from a regulatory point of view but also the organization Internal DNE. In 3.9 alternatives are discussed renewable resources from national and international studies existentes, and in 3.1 updating the results of a recent study on energy efficiency by the World Bank and the case of an eventual

  17. A model based on stochastic dynamic programming for determining China's optimal strategic petroleum reserve policy

    International Nuclear Information System (INIS)

    Zhang Xiaobing; Fan Ying; Wei Yiming

    2009-01-01

    China's Strategic Petroleum Reserve (SPR) is currently being prepared. But how large the optimal stockpile size for China should be, what the best acquisition strategies are, how to release the reserve if a disruption occurs, and other related issues still need to be studied in detail. In this paper, we develop a stochastic dynamic programming model based on a total potential cost function of establishing SPRs to evaluate the optimal SPR policy for China. Using this model, empirical results are presented for the optimal size of China's SPR and the best acquisition and drawdown strategies for a few specific cases. The results show that with comprehensive consideration, the optimal SPR size for China is around 320 million barrels. This size is equivalent to about 90 days of net oil import amount in 2006 and should be reached in the year 2017, three years earlier than the national goal, which implies that the need for China to fill the SPR is probably more pressing; the best stockpile release action in a disruption is related to the disruption levels and expected continuation probabilities. The information provided by the results will be useful for decision makers.

  18. Special features of total knee replacement in hemophilia.

    Science.gov (United States)

    Rodriguez-Merchan, Emerito Carlos

    2013-12-01

    Total knee replacement is an operation frequently needed by hemophilia patients, which greatly improves their quality of life. This operation, however, carries a higher risk of bleeding and infection for hemophiliacs than it does for osteoarthritis sufferers. It is advisable to implant prosthetic components using antibiotic-loaded cement. It is essential to maintain a level of 100% of the replacement clotting factor for 2 weeks. Hematological treatment must be established, depending on the patient's factor levels and other pharmacokinetic parameters such as recovery and half-life, optimal doses and treatment time. It is preferable to use general anesthesia due to the risk of spinal bleeding. The lifespan of total knee replacement in hemophilic patients is shorter than in patients with osteoarthritis because of the increased risk of infection.

  19. Age Replacement and Service Rate Control of Stochastically Degrading Queues

    National Research Council Canada - National Science Library

    Chapin, Patrick

    2004-01-01

    This thesis considers the problem of optimally selecting a periodic replacement time for a multiserver queueing system in which each server is subject to degradation as a function of the mean service...

  20. Optimal dividend policies with transaction costs for a class of jump-diffusion processes

    DEFF Research Database (Denmark)

    Hunting, Martin; Paulsen, Jostein

    2013-01-01

    his paper addresses the problem of finding an optimal dividend policy for a class of jump-diffusion processes. The jump component is a compound Poisson process with negative jumps, and the drift and diffusion components are assumed to satisfy some regularity and growth restrictions. Each dividend...... payment is changed by a fixed and a proportional cost, meaning that if ξ is paid out by the company, the shareholders receive kξ−K, where k and K are positive. The aim is to maximize expected discounted dividends until ruin. It is proved that when the jumps belong to a certain class of light...

  1. Emergency Diesel Generation System Surveillance Test Policy Optimization Through Genetic Algorithms Using Non-Periodic Intervention Frequencies and Seasonal Constraints

    International Nuclear Information System (INIS)

    Lapa, Celso M.F.; Pereira, Claudio M.N.A.; Frutuoso e Melo, P.F.

    2002-01-01

    Nuclear standby safety systems must frequently, be submitted to periodic surveillance tests. The main reason is to detect, as soon as possible, the occurrence of unrevealed failure states. Such interventions may, however, affect the overall system availability due to component outages. Besides, as the components are demanded, deterioration by aging may occur, penalizing again the system performance. By these reasons, planning a good surveillance test policy implies in a trade-off between gains and overheads due to the surveillance test interventions. In order maximize the systems average availability during a given period of time, it has recently been developed a non-periodic surveillance test optimization methodology based on genetic algorithms (GA). The fact of allowing non-periodic tests turns the solution space much more flexible and schedules can be better adjusted, providing gains in the overall system average availability, when compared to those obtained by an optimized periodic tests scheme. The optimization problem becomes, however, more complex. Hence, the use of a powerful optimization technique, such as GAs, is required. Some particular features of certain systems can turn it advisable to introduce other specific constraints in the optimization problem. The Emergency Diesel Generation System (EDGS) of a Nuclear Power Plant (N-PP) is a good example for demonstrating the introduction of seasonal constraints in the optimization problem. This system is responsible for power supply during an external blackout. Therefore, it is desirable during periods of high blackout probability to maintain the system availability as high as possible. Previous applications have demonstrated the robustness and effectiveness of the methodology. However, no seasonal constraints have ever been imposed. This work aims at investigating the application of such methodology in the Angra-II Brazilian NPP EDGS surveillance test policy optimization, considering the blackout probability

  2. Optimizing glucocorticoid replacement therapy in severely adrenocorticotropin-deficient hypopituitary male patients.

    LENUS (Irish Health Repository)

    Behan, Lucy-Ann

    2012-02-01

    BACKGROUND: The optimal replacement regimen of hydrocortisone in adults with severe ACTH deficiency remains unknown. Management strategies vary from treatment with 15-30 mg or higher in daily divided doses, reflecting the paucity of prospective data on the adequacy of different glucocorticoid regimens. OBJECTIVE: Primarily to define the hydrocortisone regimen which results in a 24 h cortisol profile that most closely resembles that of healthy controls and secondarily to assess the impact on quality of life (QoL). DESIGN: Ten male hypopituitary patients with severe ACTH deficiency (basal cortisol <100 nm and peak response to stimulation <400 nm) were enrolled in a prospective, randomized, crossover study of 3 hydrocortisone dose regimens. Following 6 weeks of each regimen patients underwent 24 h serum cortisol sampling and QoL assessment with the Short Form 36 (SF36) and the Nottingham Health Profile (NHP) questionnaires. Free cortisol was calculated using Coolen\\'s equation. All results were compared to those of healthy, matched controls. RESULTS: Corticosteroid binding globulin (CBG) was significantly lower across all dose regimens compared to controls (P < 0.05). The lower dose regimen C (10 mg mane\\/5 mg tarde) produced a 24 h free cortisol profile (FCP) which most closely resembled that of controls. Both regimen A(20 mg mane\\/10 mg tarde) and B(10 mg mane\\/10 mg tarde) produced supraphysiological post-absorption peaks. There was no significant difference in QoL in patients between the three regimens, however energy level was significantly lower across all dose regimens compared to controls (P < 0.001). CONCLUSIONS: The lower dose of hydrocortisone (10 mg\\/5 mg) produces a more physiological cortisol profile, without compromising QoL, compared to higher doses still used in clinical practice. This may have important implications in these patients, known to have excess cardiovascular mortality.

  3. Optimal sizing for SAPIEN 3 transcatheter aortic valve replacement in patients with or without left ventricular outflow tract calcification.

    Science.gov (United States)

    Maeno, Yoshio; Abramowitz, Yigal; Jilaihawi, Hasan; Israr, Sharjeel; Yoon, Sunghan; Sharma, Rahul P; Kazuno, Yoshio; Kawamori, Hiroyuki; Miyasaka, Masaki; Rami, Tanya; Mangat, Geeteshwar; Takahashi, Nobuyuki; Okuyama, Kazuaki; Kashif, Mohammad; Chakravarty, Tarun; Nakamura, Mamoo; Cheng, Wen; Makkar, Raj R

    2017-04-07

    The impact of left ventricular outflow tract calcification (LVOT-CA) on SAPIEN 3 transcatheter aortic valve replacement (S3-TAVR) is not well understood. The aims of the present study were to determine optimal device sizing for S3-TAVR in patients with or without LVOT-CA and to evaluate the influence of residual paravalvular leak (PVL) on survival after S3-TAVR in these patients. This study analysed 280 patients (LVOT-CA=144, no LVOT-CA=136) undergoing S3-TAVR. Optimal annular area sizing was defined as % annular area sizing related to lower rates of ≥mild PVL. Annular area sizing was determined as follows: (prosthesis area/CT annulus area-1)×100. Overall, ≥mild PVL was present in 25.7%. Receiver operating characteristic curve analysis for prediction of ≥mild PVL in patients with LVOT-CA showed that 7.2% annular area sizing was identified as the optimal threshold (area under the curve [AUC] 0.71). Conversely, annular area sizing for no LVOT-CA appeared unrelated to PVL (AUC 0.58). Aortic annular injury was seen in four patients (average 15.5% annular area oversizing), three of whom had LVOT-CA. Although there was no difference in one-year survival between patients with ≥mild PVL and without PVL (log-rank p=0.91), subgroup analysis demonstrated that patients with ≥moderate LVOT-CA who had ≥mild PVL had lower survival compared to patients with ≥mild PVL and none or mild LVOT-CA (log-rank p=0.010). In the setting of LVOT-CA, an optimally sized S3 valve is required to reduce PVL and to increase survival following TAVR.

  4. Survival comparison of the Ross procedure and mechanical valve replacement with optimal self-management anticoagulation therapy: propensity-matched cohort study.

    Science.gov (United States)

    Mokhles, M Mostafa; Körtke, Heinrich; Stierle, Ulrich; Wagner, Otto; Charitos, Efstratios I; Bogers, Ad J J C; Gummert, Jan; Sievers, Hans-Hinrich; Takkenberg, Johanna J M

    2011-01-04

    It is suggested that in young adults the Ross procedure results in better late patient survival compared with mechanical prosthesis implantation. We performed a propensity score-matched study that assessed late survival in young adult patients after a Ross procedure versus that after mechanical aortic valve replacement with optimal self-management anticoagulation therapy. We selected 918 Ross patients and 406 mechanical valve patients 18 to 60 years of age without dissection, aneurysm, or mitral valve replacement who survived an elective procedure (1994 to 2008). With the use of propensity score matching, late survival was compared between the 2 groups. Two hundred fifty-three patients with a mechanical valve (mean follow-up, 6.3 years) could be propensity matched to a Ross patient (mean follow-up, 5.1 years). Mean age of the matched cohort was 47.3 years in the Ross procedure group and 48.0 years in the mechanical valve group (P=0.17); the ratio of male to female patients was 3.2 in the Ross procedure group and 2.7 in the mechanical valve group (P=0.46). Linearized all-cause mortality rate was 0.53% per patient-year in the Ross procedure group compared with 0.30% per patient-year in the mechanical valve group (matched hazard ratio, 1.86; 95% confidence interval, 0.58 to 5.91; P=0.32). Late survival was comparable to that of the general German population. In comparable patients, there is no late survival difference in the first postoperative decade between the Ross procedure and mechanical aortic valve implantation with optimal anticoagulation self-management. Survival in these selected young adult patients closely resembles that of the general population, possibly as a result of highly specialized anticoagulation self-management, better timing of surgery, and improved patient selection in recent years.

  5. Multi-region optimal deployment of renewable energy considering different interregional transmission scenarios

    International Nuclear Information System (INIS)

    Wang, Ge; Zhang, Qi; Mclellan, Benjamin C.; Li, Hailong

    2016-01-01

    Renewable energy is expected to play much more important role in future low-carbon energy system, however, renewable energy has problems with regard to load-following and regional imbalance. This study aims to plan the deployment of intermittent renewable energy in multiple regions considering the impacts of regional natural conditions and generation capacity mix as well as interregional transmission capacity using a multi-region dynamic optimization model. The model was developed to find optimized development paths toward future smart electricity systems with high level penetration of intermittent renewable energy considering regional differences and interregional transmission at national scale. As a case study, the model was applied to plan power generation in nine interconnected regions in Japan out to 2030. Four scenarios were proposed with different supporting policies for the interregional power transmission infrastructures and different nuclear power phase-out scenarios. The analysis results show that (i) the government's support for power transmission infrastructures is vital important to develop more intermittent renewable energy in appropriate regions and utilize renewable energy more efficiently; (ii) nuclear and renewable can complement rather than replace each other if enough interregional transmission capacity is provided. - Highlights: • Plan the optimal deployment of intermittent renewable energy in multiple regions. • A multi-region dynamic optimization model was developed. • The impacts of natural conditions and interregional transmission are studied. • The government's support for transmission is vital important for renewable energy. • Nuclear and renewable can complement rather than replace each other.

  6. Optimizing Input/Output Using Adaptive File System Policies

    Science.gov (United States)

    Madhyastha, Tara M.; Elford, Christopher L.; Reed, Daniel A.

    1996-01-01

    Parallel input/output characterization studies and experiments with flexible resource management algorithms indicate that adaptivity is crucial to file system performance. In this paper we propose an automatic technique for selecting and refining file system policies based on application access patterns and execution environment. An automatic classification framework allows the file system to select appropriate caching and pre-fetching policies, while performance sensors provide feedback used to tune policy parameters for specific system environments. To illustrate the potential performance improvements possible using adaptive file system policies, we present results from experiments involving classification-based and performance-based steering.

  7. Evaluation of depreciation costs in replacement investments of nuclear power plants

    International Nuclear Information System (INIS)

    Nakada, Shoji; Takashima, Ryuta; Nagano, Koji; Kimura, Hiroshi; Madarame, Haruki

    2010-01-01

    Replacement of nuclear power plants has the possibility of affecting the management of electric power suppliers. Therefore, in the nuclear policy, a depreciation method as an equalization method, which means that part of the investment cost is accumulated as an allowance, and after the start of operation, the depreciation cost in the replacement project is equalized, has been introduced in Japan. In this paper, we evaluate the replacement of nuclear power plants by taking into account the uncertainty of operating costs and the depreciation cost in order to examine the effect of the depreciation method on the decision criteria of the replacement.We found that the equalization method is elective for inducing the acceleration of the replacement. Furthermore, we show the relationship between the uncertainty and the depreciation method. It turns out that as uncertainty increases, the difference in investment threshold between the equalization method and the existing depreciation method decreases, and that in option value increases. (author)

  8. A Global Optimizing Policy for Decaying Items with Ramp-Type Demand Rate under Two-Level Trade Credit Financing Taking Account of Preservation Technology

    Directory of Open Access Journals (Sweden)

    S. R. Singh

    2013-01-01

    Full Text Available An inventory system for deteriorating items, with ramp-type demand rate, under two-level trade credit policy taking account of preservation technology is considered. The objective of this study is to develop a deteriorating inventory policy when the supplier provides to the retailer a permissible delay in payments, and during this credit period, the retailer accumulates the revenue and earns interest on that revenue; also the retailer invests on the preservation technology to reduce the rate of product deterioration. Shortages are allowed and partially backlogged. Sufficient conditions of the existence and uniqueness of the optimal replenishment policy are provided, and an algorithm, for its determination, is proposed. Numerical examples draw attention to the obtained results, and the sensitivity analysis of the optimal solution with respect to leading parameters of the system is carried out.

  9. Performance and economic effects of partially replacing soybean ...

    African Journals Online (AJOL)

    The performance and economic effects of replacing soybean meal with palm kernel cake (PKC) in broiler diet was investigated in other to determine the optimal level of inclusion for maximum production in broilers. A total of 120 broiler chicks were randomly distributed into four treatment groups of 30 birds each.

  10. Optimal maintenance policy for a system subject to damage in a discrete time process

    International Nuclear Information System (INIS)

    Chien, Yu-Hung; Sheu, Shey-Huei; Zhang, Zhe George

    2012-01-01

    Consider a system operating over n discrete time periods (n=1, 2, …). Each operation period causes a random amount of damage to the system which accumulates over time periods. The system fails when the cumulative damage exceeds a failure level ζ and a corrective maintenance (CM) action is immediately taken. To prevent such a failure, a preventive maintenance (PM) may be performed. In an operation period without a CM or PM, a regular maintenance (RM) is conducted at the end of that period to maintain the operation of the system. We propose a maintenance policy which prescribes a PM when the accumulated damage exceeds a pre-specified level δ ( ⁎ and N ⁎ and discuss some useful properties about them. It has been shown that a δ-based PM outperforms a N-based PM in terms of cost minimization. Numerical examples are presented to demonstrate the optimization of this class of maintenance policies.

  11. Improved estimates of coordinate error for molecular replacement

    International Nuclear Information System (INIS)

    Oeffner, Robert D.; Bunkóczi, Gábor; McCoy, Airlie J.; Read, Randy J.

    2013-01-01

    A function for estimating the effective root-mean-square deviation in coordinates between two proteins has been developed that depends on both the sequence identity and the size of the protein and is optimized for use with molecular replacement in Phaser. A top peak translation-function Z-score of over 8 is found to be a reliable metric of when molecular replacement has succeeded. The estimate of the root-mean-square deviation (r.m.s.d.) in coordinates between the model and the target is an essential parameter for calibrating likelihood functions for molecular replacement (MR). Good estimates of the r.m.s.d. lead to good estimates of the variance term in the likelihood functions, which increases signal to noise and hence success rates in the MR search. Phaser has hitherto used an estimate of the r.m.s.d. that only depends on the sequence identity between the model and target and which was not optimized for the MR likelihood functions. Variance-refinement functionality was added to Phaser to enable determination of the effective r.m.s.d. that optimized the log-likelihood gain (LLG) for a correct MR solution. Variance refinement was subsequently performed on a database of over 21 000 MR problems that sampled a range of sequence identities, protein sizes and protein fold classes. Success was monitored using the translation-function Z-score (TFZ), where a TFZ of 8 or over for the top peak was found to be a reliable indicator that MR had succeeded for these cases with one molecule in the asymmetric unit. Good estimates of the r.m.s.d. are correlated with the sequence identity and the protein size. A new estimate of the r.m.s.d. that uses these two parameters in a function optimized to fit the mean of the refined variance is implemented in Phaser and improves MR outcomes. Perturbing the initial estimate of the r.m.s.d. from the mean of the distribution in steps of standard deviations of the distribution further increases MR success rates

  12. Fiscal Policy and the Implementation of the Walsh Contract for Central Bankers

    OpenAIRE

    Haizhou Huang; A. Jorge Padilla

    2002-01-01

    We develop a simple macroeconomic model where the time inconsistency of optimal monetary policy is due to tax distortions. If fiscal policy is exogenously fixed at its optimal level, a Walsh contract (Walsh, 1995) offered to an independent central bank implements the optimal monetary policy. When fiscal policy is determined endogenously, however, this contract is subject to strategic manipulation by the government, which results in a suboptimal policy mix. Implementing the optimal policy mix ...

  13. Fuel optimization of Qinshan nuclear power plant

    International Nuclear Information System (INIS)

    Liao Zejun; Li Zhuoqun; Kong Deping; Xue Xincai; Wang Shiwei

    2010-01-01

    Based on the design practice of the fuel replacement of Qin Shan nuclear power plant, this document effectively analyzes the shortcomings of current replacement design of Qin Shan. To address these shortcomings, this document successfully implements the 300 MW fuel optimization program from fuel replacement. fuel improvement and experimentation ,and achieves great economic results. (authors)

  14. Cultural Policy in Iceland

    DEFF Research Database (Denmark)

    Gudmundsson, Gestur

    2003-01-01

    on the continuing emphasis on central cultural institution and the Icelandic language. Since the 1970s Cold War conflicts have been replaced by a consensus on growing support to artists and an armth's length policy, and furthermore the 1990s have seen a strong move towards NPM and international participation.......The article examines the history of cultural policy in Iceland from a Nordic comparative perspective. National cultural policy takes form in the 19th and early 20th century as a part of the nation-building, emphasising the Icelandic language as the core of national identity, building cultural...

  15. On the Optimal Policy for the Single-product Inventory Problem with Set-up Cost and a Restricted Production Capacity

    NARCIS (Netherlands)

    Foreest, N. D. van; Wijngaard, J.

    2010-01-01

    The single-product, stationary inventory problem with set-up cost is one of the classical problems in stochastic operations research. Theories have been developed to cope with finite production capacity in periodic review systems, and it has been proved that optimal policies for these cases are not

  16. Inventory-transportation integrated optimization for maintenance spare parts of high-speed trains

    Science.gov (United States)

    Wang, Jiaxi; Wang, Huasheng; Wang, Zhongkai; Li, Jian; Lin, Ruixi; Xiao, Jie; Wu, Jianping

    2017-01-01

    This paper presents a 0–1 programming model aimed at obtaining the optimal inventory policy and transportation mode for maintenance spare parts of high-speed trains. To obtain the model parameters for occasionally-replaced spare parts, a demand estimation method based on the maintenance strategies of China’s high-speed railway system is proposed. In addition, we analyse the shortage time using PERT, and then calculate the unit time shortage cost from the viewpoint of train operation revenue. Finally, a real-world case study from Shanghai Depot is conducted to demonstrate our method. Computational results offer an effective and efficient decision support for inventory managers. PMID:28472097

  17. Optimal pricing of non-utility generated electric power

    International Nuclear Information System (INIS)

    Siddiqi, S.N.; Baughman, M.L.

    1994-01-01

    The importance of an optimal pricing policy for pricing non-utility generated power is pointed out in this paper. An optimal pricing policy leads to benefits for all concerned: the utility, industry, and the utility's other customers. In this paper, it is shown that reliability differentiated real-time pricing provides an optimal non-utility generated power pricing policy, from a societal welfare point of view. Firm capacity purchase, and hence an optimal price for purchasing firm capacity, are an integral part of this pricing policy. A case study shows that real-time pricing without firm capacity purchase results in improper investment decisions and higher costs for the system as a whole. Without explicit firm capacity purchase, the utility makes greater investment in capacity addition in order to meet its reliability criteria than is socially optimal. It is concluded that the non-utility generated power pricing policy presented in this paper and implied by reliability differentiated pricing policy results in social welfare-maximizing investment and operation decisions

  18. Process optimized minimally invasive total hip replacement

    Directory of Open Access Journals (Sweden)

    Philipp Gebel

    2012-02-01

    Full Text Available The purpose of this study was to analyse a new concept of using the the minimally invasive direct anterior approach (DAA in total hip replacement (THR in combination with the leg positioner (Rotex- Table and a modified retractor system (Condor. We evaluated retrospectively the first 100 primary THR operated with the new concept between 2009 and 2010, regarding operation data, radiological and clinical outcome (HOOS. All surgeries were perfomed in a standardized operation technique including navigation. The average age of the patients was 68 years (37 to 92 years, with a mean BMI of 26.5 (17 to 43. The mean time of surgery was 80 min. (55 to 130 min. The blood loss showed an average of 511.5 mL (200 to 1000 mL. No intra-operative complications occurred. The postoperative complication rate was 6%. The HOOS increased from 43 points pre-operatively to 90 (max 100 points 3 months after surgery. The radiological analysis showed an average cup inclination of 43° and a leg length discrepancy in a range of +/- 5 mm in 99%. The presented technique led to excellent clinic results, showed low complication rates and allowed correct implant positions although manpower was saved.

  19. Random maintenance policies

    CERN Document Server

    Nakagawa, Toshio

    2014-01-01

    Exploring random maintenance models, this book provides an introduction to the implementation of random maintenance, and it is one of the first books to be written on this subject.  It aims to help readers learn new techniques for applying random policies to actual reliability models, and it provides new theoretical analyses of various models including classical replacement, preventive maintenance and inspection policies. These policies are applied to scheduling problems, backup policies of database systems, maintenance policies of cumulative damage models, and reliability of random redundant systems. Reliability theory is a major concern for engineers and managers, and in light of Japan’s recent earthquake, the reliability of large-scale systems has increased in importance. This also highlights the need for a new notion of maintenance and reliability theory, and how this can practically be applied to systems. Providing an essential guide for engineers and managers specializing in reliability maintenance a...

  20. Economy of climate policy. Criticism and alternatives

    International Nuclear Information System (INIS)

    Van den Bergh, J.C.J.M.

    2002-01-01

    The economy of climate policy is characterized by notions as cost-benefit analysis, optimal policy and optimal timing. It is argued that the use of such notions reflects an unjustified optimism with respect to the contribution of economic science to the discussion on climate policy. The complexity of the biosphere and the uncertainty about climatic change, as well as their socio-economic consequences, are extensive. Another economic approach of the climate problem is suggested, based on complexity and historical justice. 12 refs [nl

  1. The optimal growth hormone replacement dose in adults, derived from bioimpedance analysis.

    Science.gov (United States)

    de Boer, H; Blok, G J; Voerman, B; de Vries, P; Popp-Snijders, C; van der Veen, E

    1995-07-01

    The prevalence of clinical signs and symptoms related to fluid retention is high in most studies evaluating the efficacy of GH treatment in GH-deficient (GHD) adults. This may be a consequence of supraphysiological GH replacement. To examine whether fluid retention is a dose-related phenomenon, we evaluated the impact of various GH substitution doses on body fluid status in 46 GHD men participating in a 1-yr, double blind, and placebo-controlled study. The patients were randomized to receive either placebo (n = 13) or GH in a dose of 1 (n = 11), 2 (n = 10), or 3 (n = 12) IU/m2.day, respectively. Treatment was started at one third of the predetermined dose and was subsequently increased by another third every month until the maintenance dose was reached. Tissue hydration was assessed by means of electrical impedance measurements. Normal values were obtained from 128 age- and sex-matched controls. In the untreated GHD state, whole body resistance was abnormally high (observed, 642 +/- 82 omega; predicted, 550 +/- 31 omega; P Regression analysis of the pooled data showed that GH replacement in a dose of 1.10 IU/m2.day (95% confidence interval, 0.85-1.45 IU/m2.day) resulted in a normalization of whole body resistance. In conclusion, GH replacement therapy in adults rapidly corrects the preexisting deficit in ECW. This rehydration process is dose dependent and may result in a substantial weight gain.(ABSTRACT TRUNCATED AT 400 WORDS)

  2. Optimization of Replacing Pork Meat with Yellow Worm (Tenebrio molitor L.) for Frankfurters

    Science.gov (United States)

    Paik, Hyun-Dong

    2017-01-01

    The effects of replacing pork meat with yellow mealworms on the physicochemical properties and sensory characteristics of frankfurters were investigated in this study. The control (50% pork ham), T1 (45% pork ham + 5% yellow mealworm), T2 (40% pork ham + 10% yellow mealworm), T3 (35% pork ham + 15% yellow mealworm), T4 (30% pork ham + 20% yellow mealworm), T5 (25% pork ham + 25% yellow mealworm), and T6 (20% pork ham + 30% yellow mealworm) were prepared, replacing lean pork meat with yellow mealworm. The moisture content, lightness, sarcoplasmic protein solubility, hardness, gumminess, chewiness, and apparent viscosity of frankfurters with yellow mealworm were lower than those of the control (pmealworm were higher than those of the control (pmealworm concentrations (pmealworm concentrations had lower color, flavor, off-flavor, and juiciness scores. The overall acceptability was not significantly different in the control, T1, and T2 (p>0.05). Thus, the results of this study showed that replacing lean pork meat with up to 10% yellow mealworm successfully maintained the quality of frankfurters at a level similar to that of the regular control frankfurters. PMID:29147084

  3. REGULATORY POLICY AND OPTIMIZATION OF INVESTMENT RESOURCE ALLOCATION IN THE MODEL OF FUNCTIONING OF RECREATION INDUSTRY

    Directory of Open Access Journals (Sweden)

    Hanna Shevchenko

    2017-11-01

    Full Text Available The research objective is the rationale of the theoretical and methodical approach concerning the improvement of regulatory policy as well as the process of distribution of financial investments using the model of the functioning of a recreational sector of the national economy. The methodology of the study includes the use of optimal control theory for the model formation of the functioning of the recreational industry as well as determining the behaviour of regulatory authorities and capabilities to optimize the allocation of investment resources in the recreational sector of the national economy. Results. The issue of equilibration of regulatory policy in the recreational sector of the national economy is actualized, including the question of targeted distribution of state and external financial investments. Also, it is proved that regulatory policy should establish the frameworks that on the one hand, do not allow public authorities to exercise extra influence on the economy of recreation, on the other hand, to keep the behaviour of the recreational business entities within the limits of normal socio-economic activity – on the basis of analysis of the continuum “recreation – work” by means of modified Brennan-Buchanan model. It is revealed that even with the condition of the tax reduction, the situation when the population resting less and works more than in the background of a developed economy is observed. However, according to the optimistic forecast, eventually on condition when the economy is emerging from the shade, we will obtain an official mode of the work in which, while maintaining taxes on proposed more advantageous for the population level, ultimately the ratio leisure and work will be established which is corresponding to the principles of sustainable development. Practical value. On the basis of methodical principles of the theory of optimal control, the model of the functioning of the recreational industry under the

  4. Optimal management strategies in variable environments: Stochastic optimal control methods

    Science.gov (United States)

    Williams, B.K.

    1985-01-01

    Dynamic optimization was used to investigate the optimal defoliation of salt desert shrubs in north-western Utah. Management was formulated in the context of optimal stochastic control theory, with objective functions composed of discounted or time-averaged biomass yields. Climatic variability and community patterns of salt desert shrublands make the application of stochastic optimal control both feasible and necessary. A primary production model was used to simulate shrub responses and harvest yields under a variety of climatic regimes and defoliation patterns. The simulation results then were used in an optimization model to determine optimal defoliation strategies. The latter model encodes an algorithm for finite state, finite action, infinite discrete time horizon Markov decision processes. Three questions were addressed: (i) What effect do changes in weather patterns have on optimal management strategies? (ii) What effect does the discounting of future returns have? (iii) How do the optimal strategies perform relative to certain fixed defoliation strategies? An analysis was performed for the three shrub species, winterfat (Ceratoides lanata), shadscale (Atriplex confertifolia) and big sagebrush (Artemisia tridentata). In general, the results indicate substantial differences among species in optimal control strategies, which are associated with differences in physiological and morphological characteristics. Optimal policies for big sagebrush varied less with variation in climate, reserve levels and discount rates than did either shadscale or winterfat. This was attributed primarily to the overwintering of photosynthetically active tissue and to metabolic activity early in the growing season. Optimal defoliation of shadscale and winterfat generally was more responsive to differences in plant vigor and climate, reflecting the sensitivity of these species to utilization and replenishment of carbohydrate reserves. Similarities could be seen in the influence of both

  5. A Jackson network model and threshold policy for joint optimization of energy and delay in multi-hop wireless networks

    KAUST Repository

    Xia, Li; Shihada, Basem

    2014-01-01

    This paper studies the joint optimization problem of energy and delay in a multi-hop wireless network. The optimization variables are the transmission rates, which are adjustable according to the packet queueing length in the buffer. The optimization goal is to minimize the energy consumption of energy-critical nodes and the packet transmission delay throughout the network. In this paper, we aim at understanding the well-known decentralized algorithms which are threshold based from a different research angle. By using a simplified network model, we show that we can adopt the semi-open Jackson network model and study this optimization problem in closed form. This simplified network model further allows us to establish some significant optimality properties. We prove that the system performance is monotonic with respect to (w.r.t.) the transmission rate. We also prove that the threshold-type policy is optimal, i.e., when the number of packets in the buffer is larger than a threshold, transmit with the maximal rate (power); otherwise, no transmission. With these optimality properties, we develop a heuristic algorithm to iteratively find the optimal threshold. Finally, we conduct some simulation experiments to demonstrate the main idea of this paper.

  6. A Jackson network model and threshold policy for joint optimization of energy and delay in multi-hop wireless networks

    KAUST Repository

    Xia, Li

    2014-11-20

    This paper studies the joint optimization problem of energy and delay in a multi-hop wireless network. The optimization variables are the transmission rates, which are adjustable according to the packet queueing length in the buffer. The optimization goal is to minimize the energy consumption of energy-critical nodes and the packet transmission delay throughout the network. In this paper, we aim at understanding the well-known decentralized algorithms which are threshold based from a different research angle. By using a simplified network model, we show that we can adopt the semi-open Jackson network model and study this optimization problem in closed form. This simplified network model further allows us to establish some significant optimality properties. We prove that the system performance is monotonic with respect to (w.r.t.) the transmission rate. We also prove that the threshold-type policy is optimal, i.e., when the number of packets in the buffer is larger than a threshold, transmit with the maximal rate (power); otherwise, no transmission. With these optimality properties, we develop a heuristic algorithm to iteratively find the optimal threshold. Finally, we conduct some simulation experiments to demonstrate the main idea of this paper.

  7. Strategies for the optimal timing to start renal replacement therapy in critically ill patients with acute kidney injury.

    Science.gov (United States)

    Bagshaw, Sean M; Wald, Ron

    2017-05-01

    Renal replacement therapy (RRT) is increasingly utilized to support critically ill patients with severe acute kidney injury (AKI). The question of whether and when to start RRT for a critically ill patient with AKI has long troubled clinicians. When severe complications of AKI develop, the need to commence RRT is unambiguous. In the absence of such complications but in the presence of severe AKI, the optimal time and thresholds for starting RRT are uncertain. The majority of existing data have largely been derived from observational studies. These have been limited due to confounding by indication, considerable heterogeneity in case mix and illness severity, and variably applied definitions for both AKI and for how "timing" was anchored relative to starting RRT. It is unclear whether a preemptive or earlier strategy of RRT initiation aimed largely at avoiding complications related to AKI or a more conservative strategy where RRT is started in response to developing complications leads to better patient-centered outcomes and health services use. This question has been the focus of 2 recently completed randomized trials. In this review, we provide an appraisal of available evidence, discuss existing knowledge gaps, and provide perspective on future research that will better inform the optimal timing of RRT initiation in AKI. Copyright © 2016 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

  8. An Adaptive Insertion and Promotion Policy for Partitioned Shared Caches

    Science.gov (United States)

    Mahrom, Norfadila; Liebelt, Michael; Raof, Rafikha Aliana A.; Daud, Shuhaizar; Hafizah Ghazali, Nur

    2018-03-01

    Cache replacement policies in chip multiprocessors (CMP) have been investigated extensively and proven able to enhance shared cache management. However, competition among multiple processors executing different threads that require simultaneous access to a shared memory may cause cache contention and memory coherence problems on the chip. These issues also exist due to some drawbacks of the commonly used Least Recently Used (LRU) policy employed in multiprocessor systems, which are because of the cache lines residing in the cache longer than required. In image processing analysis of for example extra pulmonary tuberculosis (TB), an accurate diagnosis for tissue specimen is required. Therefore, a fast and reliable shared memory management system to execute algorithms for processing vast amount of specimen image is needed. In this paper, the effects of the cache replacement policy in a partitioned shared cache are investigated. The goal is to quantify whether better performance can be achieved by using less complex replacement strategies. This paper proposes a Middle Insertion 2 Positions Promotion (MI2PP) policy to eliminate cache misses that could adversely affect the access patterns and the throughput of the processors in the system. The policy employs a static predefined insertion point, near distance promotion, and the concept of ownership in the eviction policy to effectively improve cache thrashing and to avoid resource stealing among the processors.

  9. Tranexamic acid: optimal blood loss management in surface replacement arthroplasty.

    Science.gov (United States)

    Sassoon, A; Nam, D; Jackups, R; Johnson, S R; Nunley, R M; Barrack, R L

    2016-02-01

    This study investigated whether the use of tranexamic acid (TXA) decreased blood loss and transfusion related cost following surface replacement arthroplasty (SRA). A retrospective review of patients treated with TXA during a SRA, who did not receive autologous blood (TXA group) was performed. Two comparison groups were established; the first group comprised of patients who donated their own blood pre-operatively (auto group) and the second of patients who did not donate blood pre-operatively (control). Outcomes included transfusions, post-operative haemoglobin (Hgb), complications, and length of post-operative stay. Between 2009 and 2013, 150 patients undergoing SRA were identified for inclusion: 51 in the auto, 49 in the control, and 50 in the TXA group. There were no differences in the pre-operative Hgb concentrations between groups. The mean post-operative Hgb was 11.3 g/dL (9.1 to 13.6) in the auto and TXA groups, and 10.6 g/dL (8.1 to 12.1)in the control group (p = 0.001). Accounting for cost of transfusions, administration of TXA, and length of stay, the cost per patient was $1731, $339, and $185 for the auto, control and TXA groups, respectively. TXA use demonstrated higher post-operative Hgb concentrations when compared with controls and decreased peri-operative costs. Tranexamic acid safely limits allogeneic transfusion, maintains post-operative haemoglobin, and decreases direct and indirect transfusion related costs in surface replacement arthroplasty. ©2016 The British Editorial Society of Bone & Joint Surgery.

  10. Optimizing two-dimensional renewable warranty policies for sensor embedded remanufactured products

    Directory of Open Access Journals (Sweden)

    Ammar Alqahtani

    2017-05-01

    Full Text Available Purpose: Remanufactured products, in addition to being environment friendly, are popular with consumers because they can offer the latest technology with lower prices in comparison to brand new products. However, some consumers are hesitant to buy remanufactured products because they are skeptical about the quality of the remanufactured product and thus are unsure of the extent to which the product will render services when compared to a new product. A strategy that remanufacturers may employ to entice customers is to offer warranties on remanufactured products. To that end, this paper studies and scrutinizes the impact of offering renewing warranties on remanufactured products. Specifically, the paper suggests a methodology which simultaneously minimizes the cost incurred by the remanufacturers and maximizes the confidence of the consumers towards buying remanufacturing products. Design/methodology/approach: This study uses discrete-event simulation to optimize the implementation of a two-dimensional renewing warranty policy for remanufactured products. The implementation is illustrated using a specific product recovery system called the Advanced Remanufacturing-To-Order (ARTO system. The experiments used in the study were designed using Taguchi’s Orthogonal Arrays to represent the entire domain of the recovery system so as to observe the system behavior under various experimental conditions. In order to determine the optimum strategy offered by the remanufacturer, various warranty and preventive maintenance scenarios were analyzed using pairwise t-tests along with one-way analysis of variance (ANOVA and Tukey pairwise comparisons tests for every scenario. Findings: The proposed methodology is able to simultaneously minimize the cost incurred by the remanufacturer, optimize the warranty price and period, and optimize the preventive maintenance strategy resulting in increased consumer confidence. Originality/value: This is the first study that

  11. Optimizing two-dimensional renewable warranty policies for sensor embedded remanufactured products

    International Nuclear Information System (INIS)

    Alqahtani, Ammar; Gupta, Surendra M.

    2017-01-01

    Remanufactured products, in addition to being environment friendly, are popular with consumers because they can offer the latest technology with lower prices in comparison to brand new products. However, some consumers are hesitant to buy remanufactured products because they are skeptical about the quality of the remanufactured product and thus are unsure of the extent to which the product will render services when compared to a new product. A strategy that remanufacturers may employ to entice customers is to offer warranties on remanufactured products. To that end, this paper studies and scrutinizes the impact of offering renewing warranties on remanufactured products. Specifically, the paper suggests a methodology which simultaneously minimizes the cost incurred by the remanufacturers and maximizes the confidence of the consumers towards buying remanufacturing products. Design/methodology/approach: This study uses discrete-event simulation to optimize the implementation of a two-dimensional renewing warranty policy for remanufactured products. The implementation is illustrated using a specific product recovery system called the Advanced Remanufacturing-To-Order (ARTO) system. The experiments used in the study were designed using Taguchi’s Orthogonal Arrays to represent the entire domain of the recovery system so as to observe the system behavior under various experimental conditions. In order to determine the optimum strategy offered by the remanufacturer, various warranty and preventive maintenance scenarios were analyzed using pairwise t-tests along with one-way analysis of variance (ANOVA) and Tukey pairwise comparisons tests for every scenario. Findings: The proposed methodology is able to simultaneously minimize the cost incurred by the remanufacturer, optimize the warranty price and period, and optimize the preventive maintenance strategy resulting in increased consumer confidence. Originality/value: This is the first study that evaluates in a

  12. Optimizing two-dimensional renewable warranty policies for sensor embedded remanufactured products

    Energy Technology Data Exchange (ETDEWEB)

    Alqahtani, Ammar; Gupta, Surendra M.

    2017-07-01

    Remanufactured products, in addition to being environment friendly, are popular with consumers because they can offer the latest technology with lower prices in comparison to brand new products. However, some consumers are hesitant to buy remanufactured products because they are skeptical about the quality of the remanufactured product and thus are unsure of the extent to which the product will render services when compared to a new product. A strategy that remanufacturers may employ to entice customers is to offer warranties on remanufactured products. To that end, this paper studies and scrutinizes the impact of offering renewing warranties on remanufactured products. Specifically, the paper suggests a methodology which simultaneously minimizes the cost incurred by the remanufacturers and maximizes the confidence of the consumers towards buying remanufacturing products. Design/methodology/approach: This study uses discrete-event simulation to optimize the implementation of a two-dimensional renewing warranty policy for remanufactured products. The implementation is illustrated using a specific product recovery system called the Advanced Remanufacturing-To-Order (ARTO) system. The experiments used in the study were designed using Taguchi’s Orthogonal Arrays to represent the entire domain of the recovery system so as to observe the system behavior under various experimental conditions. In order to determine the optimum strategy offered by the remanufacturer, various warranty and preventive maintenance scenarios were analyzed using pairwise t-tests along with one-way analysis of variance (ANOVA) and Tukey pairwise comparisons tests for every scenario. Findings: The proposed methodology is able to simultaneously minimize the cost incurred by the remanufacturer, optimize the warranty price and period, and optimize the preventive maintenance strategy resulting in increased consumer confidence. Originality/value: This is the first study that evaluates in a

  13. Can biofuels be a solution to climate change? The implications of land use change-related emissions for policy

    Science.gov (United States)

    Khanna, Madhu; Crago, Christine L.; Black, Mairi

    2011-01-01

    Biofuels have gained increasing attention as an alternative to fossil fuels for several reasons, one of which is their potential to reduce the greenhouse gas (GHG) emissions from the transportation sector. Recent studies have questioned the validity of claims about the potential of biofuels to reduce GHG emissions relative to the liquid fossil fuels they are replacing when emissions owing to direct (DLUC) and indirect land use changes (ILUC) that accompany biofuels are included in the life cycle GHG intensity of biofuels. Studies estimate that the GHG emissions released from ILUC could more than offset the direct GHG savings by producing biofuels and replacing liquid fossil fuels and create a ‘carbon debt’ with a long payback period. The estimates of this payback period, however, vary widely across biofuels from different feedstocks and even for a single biofuel across different modelling assumptions. In the case of corn ethanol, this payback period is found to range from 15 to 200 years. We discuss the challenges in estimating the ILUC effect of a biofuel and differences across biofuels, and its sensitivity to the assumptions and policy scenarios considered by different economic models. We also discuss the implications of ILUC for designing policies that promote biofuels and seek to reduce GHG emissions. In a first-best setting, a global carbon tax is needed to set both DLUC and ILUC emissions to their optimal levels. However, it is unclear whether unilateral GHG mitigation policies, even if they penalize the ILUC-related emissions, would increase social welfare and lead to optimal emission levels. In the absence of a global carbon tax, incentivizing sustainable land use practices through certification standards, government regulations and market-based pressures may be a viable option for reducing ILUC. PMID:22482030

  14. Determination of optimal environmental policy for reclamation of land unearthed in lignite mines - Strategy and tactics

    Science.gov (United States)

    Batzias, Dimitris F.; Pollalis, Yannis A.

    2012-12-01

    In this paper, optimal environmental policy for reclamation of land unearthed in lignite mines is defined as a strategic target. The tactics concerning the achievement of this target, includes estimation of optimal time lag between each lignite site (which is a segment of the whole lignite field) complete exploitation and its reclamation. Subsidizing of reclamation has been determined as a function of this time lag and relevant implementation is presented for parameter values valid for the Greek economy. We proved that the methodology we have developed gives reasonable quantitative results within the norms imposed by legislation. Moreover, the interconnection between strategy and tactics becomes evident, since the former causes the latter by deduction and the latter revises the former by induction in the time course of land reclamation.

  15. Optimal replenishment and credit policy in supply chain inventory model under two levels of trade credit with time- and credit-sensitive demand involving default risk

    Science.gov (United States)

    Mahata, Puspita; Mahata, Gour Chandra; Kumar De, Sujit

    2018-03-01

    Traditional supply chain inventory modes with trade credit usually only assumed that the up-stream suppliers offered the down-stream retailers a fixed credit period. However, in practice the retailers will also provide a credit period to customers to promote the market competition. In this paper, we formulate an optimal supply chain inventory model under two levels of trade credit policy with default risk consideration. Here, the demand is assumed to be credit-sensitive and increasing function of time. The major objective is to determine the retailer's optimal credit period and cycle time such that the total profit per unit time is maximized. The existence and uniqueness of the optimal solution to the presented model are examined, and an easy method is also shown to find the optimal inventory policies of the considered problem. Finally, numerical examples and sensitive analysis are presented to illustrate the developed model and to provide some managerial insights.

  16. Esophageal replacement by gastric tube: is three-stage surgery ...

    African Journals Online (AJOL)

    useful alternative under a resource-limited condition, with optimal outcome. Ann Pediatr Surg 10:7–9 c 2014 Annals of Pediatric Surgery. Annals of Pediatric Surgery 2014, 10:7–9. Keywords: esophageal replacement, gastric tube, long gap esophageal atresia, pure esophageal atresia. Departments of aPediatric Surgery ...

  17. Deep Learning Policy Quantization

    NARCIS (Netherlands)

    van de Wolfshaar, Jos; Wiering, Marco; Schomaker, Lambertus

    2018-01-01

    We introduce a novel type of actor-critic approach for deep reinforcement learning which is based on learning vector quantization. We replace the softmax operator of the policy with a more general and more flexible operator that is similar to the robust soft learning vector quantization algorithm.

  18. Replacing coal by tire powder in ceramic industry

    Energy Technology Data Exchange (ETDEWEB)

    Mothe, C.G. [Dept. de Processos Organicos, Escola de Quimica/CT/UFRJ, Rio de Janeiro, RJ (Brazil); Mothe Filho, H.F. [Dept. de Geociencias, Inst. de Agronomia/UFRRJ, Seropedica, RJ (Brazil)

    2005-07-01

    Nowadays preserving nature, recycling or reusing materials are good policies. Around ten million tires are put out by year in Brazil, and it is not known for how long they will remain in environment till their complete degradation. This research used tires to replace coal in ceramic processing. In this way it helps to protect environment, to reduce the consumption of mineral deposits and to save money. Results show that tire powder can replace coal to obtain ceramic material, using one percent of tire. Experiments were carried out using TA instruments SDT 2960, in air or nitrogen atmospheres, at heating rate of 10 C/min., flow 120 ml/min. TG/DTA curves of tire and coal have exothermic events at close temperatures between 450-600 C. At range of temperatures clay have endothermic events. (orig.)

  19. Robustness of climate metrics under climate policy ambiguity

    International Nuclear Information System (INIS)

    Ekholm, Tommi; Lindroos, Tomi J.; Savolainen, Ilkka

    2013-01-01

    Highlights: • We assess the economic impacts of using different climate metrics. • The setting is cost-efficient scenarios for three interpretations of the 2C target. • With each target setting, the optimal metric is different. • Therefore policy ambiguity prevents the selection of an optimal metric. • Robust metric values that perform well with multiple policy targets however exist. -- Abstract: A wide array of alternatives has been proposed as the common metrics with which to compare the climate impacts of different emission types. Different physical and economic metrics and their parameterizations give diverse weights between e.g. CH 4 and CO 2 , and fixing the metric from one perspective makes it sub-optimal from another. As the aims of global climate policy involve some degree of ambiguity, it is not possible to determine a metric that would be optimal and consistent with all policy aims. This paper evaluates the cost implications of using predetermined metrics in cost-efficient mitigation scenarios. Three formulations of the 2 °C target, including both deterministic and stochastic approaches, shared a wide range of metric values for CH 4 with which the mitigation costs are only slightly above the cost-optimal levels. Therefore, although ambiguity in current policy might prevent us from selecting an optimal metric, it can be possible to select robust metric values that perform well with multiple policy targets

  20. Corporate Accounting Policy Efficiency Improvement

    Directory of Open Access Journals (Sweden)

    Elena K. Vorobei

    2013-01-01

    Full Text Available The article is focused on the issues of efficient use of different methods of tax accounting for the optimization of income tax expenses and their consolidation in corporate accounting policy. The article makes reasoned conclusions, concerning optimal selection of depreciation methods for tax and bookkeeping accounting and their consolidation in corporate accounting policy and consolidation of optimal methods of cost recovery in production, considering business environment. The impact of the selected methods on corporate income tax rates and corporate property tax rates was traced and tax recovery was estimated.

  1. Safety benefits from CANDU reactor replacement - a case study

    International Nuclear Information System (INIS)

    Mottram, R.; Millard, J.W.F.; Purdy, P.

    2011-01-01

    Both total core replacement and core retubing have been used in the CANDU industry. For future plant refurbishments, based on experience both in new construction and in recent refurbishments, the concept of total core replacement has been revisited. This builds on practices for replacement of other large plant equipment like boilers. The Bruce CANDU reactors, with their local shield tanks built around the Calandria and containment closely located around that Calandria Shield Tank Assembly (CSTA), are believed to be good candidates for core replacement. A structured process was used to design a replacement CSTA suitable for Bruce A use. The work started with a study of opportunities for safety enhancements in the core. This progressed into design studies and related design assist safety analysis on the reactor. A key element of the work involved consideration of how verified features from later CANDU designs, and from our new reactor design work, could be tailored to fit this replacement core. The replacement reactor core brings in structural improvements in both calandria and end shield, and safety improvements like the natural circulation enhancing moderator cooling layout and further optimized reactivity layouts to improve shutdown system performance. Bruce Power are currently studying the business implications of this and retube techniques as part of preparation for future refurbishments. The work explained in this paper is in the context of the safety related changes and the work to choose and quantify them. (author)

  2. Safety benefits from CANDU reactor replacement. A case study

    International Nuclear Information System (INIS)

    Mottram, R.; Millard, J.W.F.; Purdy, P.

    2011-01-01

    Both total core replacement and core retubing have been used in the CANDU industry. For future plant refurbishments, based on experience both in new construction and in recent refurbishments, the concept of total core replacement has been revisited. This builds on practices for replacement of other large plant equipment like boilers. The Bruce CANDU reactors, with their local shield tanks built around the Calandria and containment closely located around that Calandria Shield Tank Assembly (CSTA), are believed to be good candidates for core replacement. A structured process was used to design a replacement CSTA suitable for Bruce A use. The work started with a study of opportunities for safety enhancements in the core. This progressed into design studies and related design assist safety analysis on the reactor. A key element of the work involved consideration of how verified features from later CANDU designs, and from our new reactor design work, could be tailored to fit this replacement core. The replacement reactor core brings in structural improvements in both calandria and end shield, and safety improvements like the natural circulation enhancing moderator cooling layout and further optimized reactivity layouts to improve shutdown system performance. Bruce Power are currently studying the business implications of this and retube techniques as part of preparation for future refurbishments. The work explained in this paper is in the context of the safety related changes and the work to choose and quantify them. (author)

  3. The optimal number of heifer calves to be reared as dairy replacements

    NARCIS (Netherlands)

    Mohd Nor, N.; Steeneveld, W.; Mourits, M.C.M.; Hogeveen, H.

    2015-01-01

    Dairy farmers often keep almost all their newborn heifer calves despite the high cost of rearing. By rearing all heifer calves, farmers have more security and retain flexibility to cope with the uncertainty in the availability of replacement heifers in time. This uncertainty is due to mortality or

  4. The optimal number of heifer calves to be reared as dairy replacements

    NARCIS (Netherlands)

    Mohd Nor, N; Steeneveld, W|info:eu-repo/dai/nl/304833169; Mourits, M C M; Hogeveen, H|info:eu-repo/dai/nl/126322864

    Dairy farmers often keep almost all their newborn heifer calves despite the high cost of rearing. By rearing all heifer calves, farmers have more security and retain flexibility to cope with the uncertainty in the availability of replacement heifers in time. This uncertainty is due to mortality or

  5. Use of Monte Carlo Simulations to Determine Optimal Carbapenem Dosing in Critically Ill Patients Receiving Prolonged Intermittent Renal Replacement Therapy.

    Science.gov (United States)

    Lewis, Susan J; Kays, Michael B; Mueller, Bruce A

    2016-10-01

    Pharmacokinetic/pharmacodynamic analyses with Monte Carlo simulations (MCSs) can be used to integrate prior information on model parameters into a new renal replacement therapy (RRT) to develop optimal drug dosing when pharmacokinetic trials are not feasible. This study used MCSs to determine initial doripenem, imipenem, meropenem, and ertapenem dosing regimens for critically ill patients receiving prolonged intermittent RRT (PIRRT). Published body weights and pharmacokinetic parameter estimates (nonrenal clearance, free fraction, volume of distribution, extraction coefficients) with variability were used to develop a pharmacokinetic model. MCS of 5000 patients evaluated multiple regimens in 4 different PIRRT effluent/duration combinations (4 L/h × 10 hours or 5 L/h × 8 hours in hemodialysis or hemofiltration) occurring at the beginning or 14-16 hours after drug infusion. The probability of target attainment (PTA) was calculated using ≥40% free serum concentrations above 4 times the minimum inhibitory concentration (MIC) for the first 48 hours. Optimal doses were defined as the smallest daily dose achieving ≥90% PTA in all PIRRT combinations. At the MIC of 2 mg/L for Pseudomonas aeruginosa, optimal doses were doripenem 750 mg every 8 hours, imipenem 1 g every 8 hours or 750 mg every 6 hours, and meropenem 1 g every 12 hours or 1 g pre- and post-PIRRT. Ertapenem 500 mg followed by 500 mg post-PIRRT was optimal at the MIC of 1 mg/L for Streptococcus pneumoniae. Incorporating data from critically ill patients receiving RRT into MCS resulted in markedly different carbapenem dosing regimens in PIRRT from those recommended for conventional RRTs because of the unique drug clearance characteristics of PIRRT. These results warrant clinical validation. © 2016, The American College of Clinical Pharmacology.

  6. Monetary Policy Implications of Electronic Money

    OpenAIRE

    Berentsen, Aleksander

    1997-01-01

    The term digital money refers to various proposed electronic payment mechanisms designed for use by consumers to make retail payments. Digital money products have the potential to replace central bank currency, thereby affecting the money supply. This paper studies the effect of replacing central bank currency on the narrowly defined stock of money under various assumptions regarding regulatory policies and monetary operations of central banks and the reaction of the banking system.

  7. Patellofemoral Joint Replacement and Nickel Allergy: An Unusual Presentation

    Directory of Open Access Journals (Sweden)

    Farhan Syed

    2015-01-01

    Full Text Available Metal allergy is an unusual complication of joint replacement that may cause aseptic loosening and necessitate joint revision surgery. We present the case of nickel allergy causing aseptic loosening following patellofemoral joint replacement (PFJR in a 54-year-old male. Joint revision surgery to a nickel-free total knee replacement was performed with good results. Our literature review shows that there is no evidence to guide the management of metal allergy in PFJR. The evidence from studies of total knee replacement is limited to retrospective case series and case reports and gives contradictory recommendations. The optimal management strategy for metal allergy in PFJR is not clear. We recommend allergy testing in patients with history of metal allergy and use of an allergen-free implant in those with positive tests. As there is no gold standard test to establish metal allergy, the choice of test should be guided by availability and recommendation from the local unit of dermatology and allergy testing. We recommend investigation for metal allergy in patients with implant loosening where other causes have been excluded.

  8. Strategic provisioning of replacement parts for CANDU power plants

    International Nuclear Information System (INIS)

    Mizuno, G.; Tume, P.; Prentice, J.

    2000-01-01

    Provisioning of replacement parts and management of critical spares are key factors in optimizing maintenance programs for CANDU power plants. With a view to supply assurance, Atomic Energy Canada Limited (AECL) has created a Spare Parts Branch (SPB) to provide a clear pipeline from the client to the delivered replacement part(s). SPB provides the client with assured access to a qualified supplier database, computer aided design, engineering and manufacturing services and material upgrades and design registration through the authorized inspection agency. The AECL spare parts strategic provisioning service plan that has four thrusts: 1) the efficient delivery of cost-effective replacement parts; 2) obsolete parts resolution; 3) a website that will provide our clients with real-time access to replacement part data; and 4) inventory recovery opportunities. Thrusts one and two are actively ensuring plant maintenance for on-shore and off-shore CANDU clients. Thrusts three and four are longer-term commitments. This paper will explore these thrusts in the context of our CANDU business practices. (author)

  9. Reliability tests for reactor internals replacement technology

    International Nuclear Information System (INIS)

    Fujimaki, K.; Uchiyama, J.; Ohtsubo, T.

    2000-01-01

    Structural damage due to aging degradation of LWR reactor internals has been reported in several nuclear plants. NUPEC has started a project to test the reliability of the technology for replacing reactor internals, which was directed at preventive maintenance before damage and repair after damage for the aging degradation. The project has been funded by the Ministry of International Trade and Industry (MITI) of Japan since 1995, and it follows the policy of a report that the MITI has formally issued in April 1996 summarizing the countermeasures to be considered for aging nuclear plants and equipment. This paper gives an outline of the whole test plans and the test results for the BWR reactor internals replacement methods; core shroud, ICM housing, and CRD Housing and stub tube. The test results have shown that the methods were reliable and the structural integrity was appropriate based on the evaluation. (author)

  10. Replenishment policy for Entropic Order Quantity (EnOQ model with two component demand and partial back-logging under inflation

    Directory of Open Access Journals (Sweden)

    Bhanupriya Dash

    2017-09-01

    Full Text Available Background: Replenishment policy for entropic order quantity model with two component demand and partial backlogging under inflation is an important subject in the stock management. Methods: In this paper an inventory model for  non-instantaneous  deteriorating items with stock dependant consumption rate and partial back logged in addition the effect of inflection and time value of money on replacement policy with zero lead time consider was developed. Profit maximization model is formulated by considering the effects of partial backlogging under inflation with cash discounts. Further numerical example presented to evaluate the relative performance between the entropic order quantity and EOQ models separately. Numerical example is present to demonstrate the developed model and to illustrate the procedure. Lingo 13.0 version software used to derive optimal order quantity and total cost of inventory. Finally sensitivity analysis of the optimal solution with respect to different parameters of the system carried out. Results and conclusions: The obtained inventory model is very useful in retail business. This model can extend to total backorder.

  11. Reward optimization of a repairable system

    International Nuclear Information System (INIS)

    Castro, I.T.; Perez-Ocon, R.

    2006-01-01

    This paper analyzes a system subject to repairable and non-repairable failures. Non-repairable failures lead to replacement of the system. Repairable failures, first lead to repair but they lead to replacement after a fixed number of repairs. Operating and repair times follow phase type distributions (PH-distributions) and the pattern of the operating times is modelled by a geometric process. In this context, the problem is to find the optimal number of repairs, which maximizes the long-run average reward per unit time. To this end, the optimal number is determined and it is obtained by efficient numerical procedures

  12. Reward optimization of a repairable system

    Energy Technology Data Exchange (ETDEWEB)

    Castro, I.T. [Departamento de Matematicas, Facultad de Veterinaria, Universidad de Extremadura, Avenida de la Universidad, s/n. 10071 Caceres (Spain)]. E-mail: inmatorres@unex.es; Perez-Ocon, R. [Departamento de Estadistica e Investigacion Operativa, Facultad de Ciencias, Universidad de Granada, Avenida de Severo Ochoa, s/n. 18071 Granada (Spain)]. E-mail: rperezo@ugr.es

    2006-03-15

    This paper analyzes a system subject to repairable and non-repairable failures. Non-repairable failures lead to replacement of the system. Repairable failures, first lead to repair but they lead to replacement after a fixed number of repairs. Operating and repair times follow phase type distributions (PH-distributions) and the pattern of the operating times is modelled by a geometric process. In this context, the problem is to find the optimal number of repairs, which maximizes the long-run average reward per unit time. To this end, the optimal number is determined and it is obtained by efficient numerical procedures.

  13. Optimum Replacement Policies for Kuwait Passenger Transport Company Busses: Case Study

    OpenAIRE

    Hilal A. Abdelwali; Elsayed E.M. Ellaimony; Ahmad E.M. Murad; Jasem M.S. Al-Rajhi

    2011-01-01

    Due to the excess of a vehicle operation through its life, some elements may face failure and deteriorate with time. This leads us to carry out maintenance, repair, tune up or full overhaul. After a certain period, the vehicle elements deteriorations increase with time which causes a very high increase of doing the maintenance operations and their costs. However, the logic decision at this point is to replace the current vehicle by a new one with minimum failure and maximum income. The import...

  14. Replacement team of mining drilling rigs

    OpenAIRE

    Hamodi, Hussan; Lundberg, Jan

    2014-01-01

    This paper presents a practical model to calculate the optimal replacement time (ORT) of drilling rigs used in underground mining. As a case study, cost data for drilling rig were collected over four years from a Swedish mine. The cost data include acquisition, operating, maintenance and downtime costs when using a redundant rig. A discount rate is used to determine the value of these costs over time. The study develops an optimisation model to identify the ORT of a mining drilling rig which ...

  15. Optimal policy for value-based decision-making.

    Science.gov (United States)

    Tajima, Satohiro; Drugowitsch, Jan; Pouget, Alexandre

    2016-08-18

    For decades now, normative theories of perceptual decisions, and their implementation as drift diffusion models, have driven and significantly improved our understanding of human and animal behaviour and the underlying neural processes. While similar processes seem to govern value-based decisions, we still lack the theoretical understanding of why this ought to be the case. Here, we show that, similar to perceptual decisions, drift diffusion models implement the optimal strategy for value-based decisions. Such optimal decisions require the models' decision boundaries to collapse over time, and to depend on the a priori knowledge about reward contingencies. Diffusion models only implement the optimal strategy under specific task assumptions, and cease to be optimal once we start relaxing these assumptions, by, for example, using non-linear utility functions. Our findings thus provide the much-needed theory for value-based decisions, explain the apparent similarity to perceptual decisions, and predict conditions under which this similarity should break down.

  16. Off-Policy Reinforcement Learning for Synchronization in Multiagent Graphical Games.

    Science.gov (United States)

    Li, Jinna; Modares, Hamidreza; Chai, Tianyou; Lewis, Frank L; Xie, Lihua

    2017-10-01

    This paper develops an off-policy reinforcement learning (RL) algorithm to solve optimal synchronization of multiagent systems. This is accomplished by using the framework of graphical games. In contrast to traditional control protocols, which require complete knowledge of agent dynamics, the proposed off-policy RL algorithm is a model-free approach, in that it solves the optimal synchronization problem without knowing any knowledge of the agent dynamics. A prescribed control policy, called behavior policy, is applied to each agent to generate and collect data for learning. An off-policy Bellman equation is derived for each agent to learn the value function for the policy under evaluation, called target policy, and find an improved policy, simultaneously. Actor and critic neural networks along with least-square approach are employed to approximate target control policies and value functions using the data generated by applying prescribed behavior policies. Finally, an off-policy RL algorithm is presented that is implemented in real time and gives the approximate optimal control policy for each agent using only measured data. It is shown that the optimal distributed policies found by the proposed algorithm satisfy the global Nash equilibrium and synchronize all agents to the leader. Simulation results illustrate the effectiveness of the proposed method.

  17. Effect of different economic support policies on the optimal synthesis and operation of a distributed energy supply system with renewable energy sources for an industrial area

    International Nuclear Information System (INIS)

    Casisi, Melchiorre; De Nardi, Alberto; Pinamonti, Piero; Reini, Mauro

    2015-01-01

    Highlights: • MILP model optimization identifies best structure and operation of an energy system. • Total cost of the system is minimized according to industrial stakeholders wills. • Effects of the adoption of economic support policies on the system are evaluated. • Social cost of incentives is comparted with correspondent CO 2 emission reduction. • Support schemes that promote an actual environmental benefit are highlighted. - Abstract: Economic support policies are widely adopted in European countries in order to promote a more efficient energy usage and the growth of renewable energy technologies. On one hand these schemes allow us to reduce the overall pollutant emissions and the total cost from the point of view of the energy systems, but on the other hand their social impact in terms of economic investment needs to be evaluated. The aim of this paper is to compare the social cost of the application of each incentive with the correspondent CO 2 emission reduction and overall energy saving. A Mixed Integer Linear Programming optimization procedure is used to evaluate the effect of different economic support policies on the optimal configuration and operation of a distributed energy supply system of an industrial area located in the north-east of Italy. The minimized objective function is the total annual cost for owning, operating and maintaining the whole energy system. The expectation is that a proper mix of renewable energy technologies and cogeneration systems will be included in the optimal solution, depending on the amount and nature of the supporting policies, highlighting the incentives that promote a real environmental benefit

  18. Future long-term trials of postmenopausal hormone replacement therapy - what is possible and what is the optimal protocol and regimen?

    Science.gov (United States)

    Purbrick, B; Stranks, K; Sum, C; MacLennan, A H

    2012-06-01

    The ideal long-term, randomized, placebo-controlled trial of hormone replacement therapy (HRT) from near menopause for up to 30 years to assess major morbidity and mortality is impractical because of high cost, participant retention, therapy compliance, and continuity of research staff and funding. Also the trial regimen may become outdated. It is nihilistic to demand such a long-term trial before endorsing HRT. However, medium-term trials using surrogate measures for long-term morbidity and mortality are possible and two are near completion. If these studies have been able to maintain reasonable participant retention, therapy compliance and minimal breach of protocol, they will set standards for trials of new HRT regimens. This paper discusses lessons learnt from past attempts at long-term trials and suggests the currently optimal protocol and cost of assessing new HRT regimens to optimize potential benefits and minimize adverse effects. A 5-7-year randomized, placebo-controlled trial of a flexible transdermal estrogen regimen ± either a selective estrogen receptor modulator, e.g. bazedoxifene, or micronized progesterone is discussed. Mild to moderately symptomatic women, 1-4 years post menopause, can be recruited via general practice and group meetings. Future trials should be funded by independent agencies and are high priority in women's health.

  19. Replacement Value of Feather Meal for Fishmeal on the ...

    African Journals Online (AJOL)

    Replacement Value of Feather Meal for Fishmeal on the Performance of Starter Cockerels. ... ratio and feed cost/kg weights gain. Considering the results of final live weight and daily weight gain, it appeared that the 7.5% level of FEM could be the optimal inclusion level feather meal in the diets of growing cockerels.

  20. Flat-plate photovoltaic array design optimization

    Science.gov (United States)

    Ross, R. G., Jr.

    1980-01-01

    An analysis is presented which integrates the results of specific studies in the areas of photovoltaic structural design optimization, optimization of array series/parallel circuit design, thermal design optimization, and optimization of environmental protection features. The analysis is based on minimizing the total photovoltaic system life-cycle energy cost including repair and replacement of failed cells and modules. This approach is shown to be a useful technique for array optimization, particularly when time-dependent parameters such as array degradation and maintenance are involved.

  1. Offshore wind farm repowering optimization

    DEFF Research Database (Denmark)

    Hou, Peng; Enevoldsen, Peter; Hu, Weihao

    2017-01-01

    is focused on optimization of offshore wind farm repowering, which is one option for the wind farm owner at end of life for the offshore wind farm. The LCoE is used as the evaluation index to identify whether it is economical to invest in such a way. In an optimized repowering strategy, different types...... of wind turbines are selected to replace the original wind turbines to reconstruct the wind farm, which is demonstrated to be better than the refurbishment approach which replaces the old wind turbines with the same type. The simulations performed in this research reveal that the reconstructed wind farm......, which consists of multiple types of wind turbine, has a smaller LCoE (10.43%) than the refurbishment approach, which shows the superiority of the proposed method. This research contributes an optimization tool to the wind industry, which consequently drives down the cost of energy produced by offshore...

  2. German nuclear policy reconsidered. Implications for the electricity market

    International Nuclear Information System (INIS)

    Fuersch, Michaela; Lindenberger, Dietmar; Malischek, Raimund; Nagl, Stephan; Panke, Timo; Trueby, Johannes

    2011-01-01

    In the aftermath of the nuclear catastrophe in Fukushima, German nuclear policy has been reconsidered. This paper demonstrates the economic effects of an accelerated nuclear phase-out on the German electricity generation sector. A detailed optimization model for European electricity markets is used to analyze two scenarios with different lifetimes for nuclear plants (phase-out vs. prolongation). Based on political targets, both scenarios assume significant electricity demand reductions and a high share of generation from renewable energy sources in Germany. Our principal findings are: First, nuclear capacities are mainly replaced by longer lifetimes of existing coal-fired plants and the construction of new gas-fired plants. Second, fossil fuel-based generation and power imports increase, while power exports are reduced in response to the lower nuclear generation. Third, despite the increased fossil generation, challenging climate protection goals can still be achieved within the framework of the considered scenarios. Finally, system costs and electricity prices are clearly higher. We conclude that the generation sector can generally cope with an accelerated nuclear phase-out under the given assumptions. Yet, we emphasize that such a policy requires a substantial and costly transformation of the supply and the demand side.

  3. Optimization of a sponge cake formulation with inulin as fat replacer: structure, physicochemical, and sensory properties.

    Science.gov (United States)

    Rodríguez-García, Julia; Puig, Ana; Salvador, Ana; Hernando, Isabel

    2012-02-01

    The effects of several fat replacement levels (0%, 35%, 50%, 70%, and 100%) by inulin in sponge cake microstructure and physicochemical properties were studied. Oil substitution for inulin decreased significantly (P cake structure development during baking. Cryo-SEM micrographs of cake crumbs showed a continuous matrix with embedded starch granules and coated with oil; when fat replacement levels increased, starch granules appeared as detached structures. Cakes with fat replacement up to 70% had a high crumb air cell values; they were softer and rated as acceptable by an untrained sensory panel (n = 51). So, the reformulation of a standard sponge cake recipe to obtain a new product with additional health benefits and accepted by consumers is achieved. Practical Application:  In this study, fat is replaced by inulin in cakes, which is a fiber mainly obtained from chicory roots. Sponge cake formulations with reductions in fat content up to 70% are achieved. These high-quality products can be labeled as "reduced in fat" according to U.S. FDA (2009) and EU regulations (European-Union 2006). © 2012 Institute of Food Technologists®

  4. The Theory of Optimal Taxation

    DEFF Research Database (Denmark)

    Sørensen, Peter Birch

    The theory of optimal taxation has often been criticized for being of little practical policy relevance, due to a lack of robust theoretical results. This paper argues that recent advances in optimal tax theory has made that theory easier to apply and may help to explain some current trends...... in international tax policy. Covering the taxation of labour income and capital income as well as indirect taxation, the paper also illustrates how some of the key results in optimal tax theory may be derived in a simple, heuristic manner....

  5. Boron-Coated Straw Collar for Uranium Neutron Coincidence Collar Replacement

    International Nuclear Information System (INIS)

    Hu, Jianwei; Croft, Stephen; McElroy, Robert Dennis

    2017-01-01

    The objective of this project was to design and optimize, in simulation space, an active neutron coincidence counter (or collar) using boron-coated straws (BCSs) as a non- 3 He replacement to the Uranium Neutron Coincidence Collar (UNCL). UNCL has been used by the International Atomic Energy Agency (IAEA) and European Atomic Energy Community (Euratom) since the 1980s to verify the 235 U content in fresh light water reactor fuel assemblies for safeguards purposes. This report documents the design and optimization of the BCS collar.

  6. BABAR IFR Replacement R and D

    CERN Document Server

    Berry, M

    2003-01-01

    The Instrumented Flux Return (IFR) of the BaBar detector will soon need to be replaced by a more robust muon detection system. Scintillator bars with embedded Wavelength Shifting (WLS) fibers and Limited Streamer Tubes are two replacement technology options. The scintillator bars are tested for attenuation length; and causes for the large width of the Photo Multiplier Tube (PMT) signal are analyzed by Monte Carlo simulation. Cooling techniques for Avalanche Photo Diodes (APD) are investigated. The fairly high attenuation length coupled with the narrow PMT signal make the scintillator a viable option for a muon detecting system. Continuing work will focus on increasing timing resolution using an APD to read the signal from the WLS fibers, and investigating the lifetime of the APD. The ability to read a signal from the LST on external copper strips is tested and signals are found to be clearly distinguishable from noise. The voltage is compared to count rate to find that the optimal operating voltage for the LS...

  7. Evaluation of genomic selection for replacement strategies using selection index theory.

    Science.gov (United States)

    Calus, M P L; Bijma, P; Veerkamp, R F

    2015-09-01

    Our objective was to investigate the economic effect of prioritizing heifers for replacement at the herd level based on genomic estimated breeding values, and to compute break-even genotyping costs across a wide range of scenarios. Specifically, we aimed to determine the optimal proportion of preselection based on parent average information for all scenarios considered. Considered replacement strategies include a range of different selection intensities by considering different numbers of heifers available for replacement (15-45 in a herd with 100 dairy cows) as well as different replacement rates (15-40%). Use of conventional versus sexed semen was considered, where the latter resulted in having twice as many heifers available for replacement. The baseline scenario relies on prioritization of replacement heifers based on parent average. The first alternative scenario involved genomic selection of heifers, considering that all heifers were genotyped. The benefits of genomic selection in this scenario were computed using a simple formula that only requires the number of lactating animals, the difference in accuracy between parent average and genomic selection (GS), and the selection intensity as input. When all heifers were genotyped, using GS for replacement of heifers was beneficial in most scenarios for current genotyping prices, provided some room exists for selection, in the sense that at least 2 more heifers are available than needed for replacement. In those scenarios, minimum break-even genotyping costs were equal to half the economic value of a standard deviation of the breeding goal. The second alternative scenario involved a preselection based on parent average, followed by GS among all the preselected heifers. It was in almost all cases beneficial to genotype all heifers when conventional semen was used (i.e., to do no preselection). The optimal proportion of preselection based on parent average was at least 0.63 when sexed semen was used. Use of sexed

  8. Biological aortic valve replacement: advantages and optimal indications of stentless compared to stented valve substitutes. A review.

    Science.gov (United States)

    Tavakoli, Reza; Danial, Pichoy; Oudjana, Ahmed Hamid; Jamshidi, Peiman; Gassmann, Max; Leprince, Pascal; Lebreton, Guillaume

    2018-05-01

    Controversy still surrounds the optimal biological valve substitute for aortic valve replacement. In light of the current literature, we review advantages and optimal indications of stentless compared to stented aortic bio-prostheses. Recent meta-analyses, prospective randomized controlled trials and retrospective studies comparing the most frequently used stentless and stented aortic bio-prostheses were analyzed. In the present review, the types and implantation techniques of the bio-prosthesis that are seldom taken into account by most studies and reviews were integrated in the interpretation of the relevant reports. For stentless aortic root bio-prostheses, full-root vs. sub-coronary implantation offered better early transvalvular gradients, effective orifice area and left ventricular mass regression as well as late freedom from structural valve deterioration in retrospective studies. Early mortality and morbidity did not differ between the stentless and stented aortic bio-prostheses. Early transvalvular gradients, effective orifice area and regression of left ventricular hypertrophy were significantly better for stentless, especially as full-root, compared to stented bio-prostheses. The long-term valve-related survival for stentless aortic root and Toronto SPV bio-prosthesis was as good as that for stented pericardial aortic bio-prostheses. For full-root configuration this survival advantage was statistically significant. There seems to be not one but different ideal biological valve substitutes for different subgroups of patients. In patients with small aortic root or exposed to prosthesis-patient mismatch full-root implantation of stentless bio-prostheses may better meet functional needs of individual patients. Longer follow-ups on newer generation of stented bio-prostheses are needed for comparison of their hemodynamic performance with stentless counterparts especially in full-root configuration.

  9. Cost Analysis Of Replacement And Bearing Trailer Maintenance In Sugar Group Companies

    OpenAIRE

    Mastur, Mastur; Masyhuri, Masyhuri; Waluyati, Lestari Rahayu

    2017-01-01

    The purpose of this study are to understand (i) the costs and periods optimal of grease used for the replacement and maintenance bearing trailer in Sugar Group Companies (SGC), and (ii) the effect of a period and frequency of grease, lifetime bearing, frequency of replacement bearing in a year, unit trailer, brand bearing, and location of plant. The basic method used is descriptive and analytical. The location determined were in Workshop Division PT. ILP, PT. SIL, and PT. GPM. The analytical ...

  10. Dislocation of total hip replacement in patients with fractures of the femoral neck

    OpenAIRE

    Enocson, Anders; Hedbeck, Carl-Johan; Tidermark, Jan; Pettersson, Hans; Ponzer, Sari; Lapidus, Lasse J

    2009-01-01

    Background Total hip replacement is increasingly used in active, relatively healthy elderly patients with fractures of the femoral neck. Dislocation of the prosthesis is a severe complication, and there is still controversy regarding the optimal surgical approach and its influence on stability. We analyzed factors influencing the stability of the total hip replacement, paying special attention to the surgical approach. Patients and methods We included 713 consecutive hips in a series of 698 p...

  11. Optimal trade-credit policy for perishable items deeming imperfect production and stock dependent demand

    Directory of Open Access Journals (Sweden)

    S. R. Singh

    2014-01-01

    Full Text Available Trade credit is the most succeeding economic phenomenon which is used by the supplier for encouraging the retailers to buy more quantity. In this article, a mathematical model with stock dependent demand and deterioration is developed to investigate the retailer’s optimal inventory policy under the scheme of permissible delay in payment. It is assumed that defective items are produced during the production process and delay period is progressive. The objective is to minimize the total average cost of the system. To exemplify hypothesis of the proposed model numerical examples and sensitivity analysis are provided. Finally, the convexities of the cost functions and the effects of changing parameters are represented through the graphs.

  12. Renewable Energy Policy Fact sheet - Finland

    International Nuclear Information System (INIS)

    2017-09-01

    The EurObserv'ER policy profiles give a snapshot of the renewable energy policy in the EU Member States. By 2014 Finland already surpassed its 2020 target for renewable energy use under the 2009 EU Renewable Energy Directive. The current feed-in premium system will be discontinued and is expected to be replaced with a competitive technology-neutral tendering scheme, in line with the requirements set in the 2014 State Aid guidelines

  13. Parallel island genetic algorithm applied to a nuclear power plant auxiliary feedwater system surveillance tests policy optimization

    International Nuclear Information System (INIS)

    Pereira, Claudio M.N.A.; Lapa, Celso M.F.

    2003-01-01

    In this work, we focus the application of an Island Genetic Algorithm (IGA), a coarse-grained parallel genetic algorithm (PGA) model, to a Nuclear Power Plant (NPP) Auxiliary Feedwater System (AFWS) surveillance tests policy optimization. Here, the main objective is to outline, by means of comparisons, the advantages of the IGA over the simple (non-parallel) genetic algorithm (GA), which has been successfully applied in the solution of such kind of problem. The goal of the optimization is to maximize the system's average availability for a given period of time, considering realistic features such as: i) aging effects on standby components during the tests; ii) revealing failures in the tests implies on corrective maintenance, increasing outage times; iii) components have distinct test parameters (outage time, aging factors, etc.) and iv) tests are not necessarily periodic. In our experiments, which were made in a cluster comprised by 8 1-GHz personal computers, we could clearly observe gains not only in the computational time, which reduced linearly with the number of computers, but in the optimization outcome

  14. Hip joint replacement

    Science.gov (United States)

    Hip arthroplasty; Total hip replacement; Hip hemiarthroplasty; Arthritis - hip replacement; Osteoarthritis - hip replacement ... Your hip joint is made up of 2 major parts. One or both parts may be replaced during surgery: ...

  15. Implementation strategy for achieving replacement level fertility.

    Science.gov (United States)

    1993-01-01

    The recommendation of the Bali Declaration on Population and Sustainable Development at the ESCAP regional conference was to adopt strategies for attaining replacement-level fertility of 2.1 or 2.2 children by 2010. East Asian countries, except Mongolia and the Democratic People's Republic of Korea, and the Southeast Asian countries Singapore and Thailand have already reached replacement-level fertility. Most larger Oceanic countries have also done so. Only South Asian Sri Lanka and southern India have attained replacement level. The following conditions slow or hinder the goal, but they do not provide an "absolute" barrier to fertility decline: social welfare schemes and old age security, son preference, lack of government family planning, poverty, relatively high mortality, low status of women, and education status. Theories of demographic transition have postulated that economic and social development initially brings a decline in mortality, and later brings a decline in fertility; and high fertility was an adaptation to high mortality. Policy gets caught in the lag between mortality and fertility decline. Eventually the cultural motives for high fertility are undercut by social and economic development. Although the generalization that economic growth slows fertility is true for South Asia, the correlation is uneven. Forceful government-sponsored family planning programs in Bangladesh and China may lead the way to strategies for decline in ESCAP region. A Thailand study suggested important factors were fundamental social change, the increased cost of children, cultural acceptance of birth control, a latent demand for fertility control, and government efforts in family planning. ESCAP countries have in common relatively high morality and inadequate public health programs, patriarchal structures, and limited female autonomy, poverty and landlessness, lack of community cohesiveness, and inadequate family planning programs. Weaknesses in programs are attributed to

  16. Boron-Coated Straw Collar for Uranium Neutron Coincidence Collar Replacement

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jianwei [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Croft, Stephen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); McElroy, Robert Dennis [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-01-01

    The objective of this project was to design and optimize, in simulation space, an active neutron coincidence counter (or collar) using boron-coated straws (BCSs) as a non-3He replacement to the Uranium Neutron Coincidence Collar (UNCL). UNCL has been used by the International Atomic Energy Agency (IAEA) and European Atomic Energy Community (Euratom) since the 1980s to verify the 235U content in fresh light water reactor fuel assemblies for safeguards purposes. This report documents the design and optimization of the BCS collar.

  17. TOTAL JOINT REPLACEMENT OF THE LOWER EXTREMITY IN PATIENTS WITH JUVENILE IDIOPATHIC ARTHRITIS

    Directory of Open Access Journals (Sweden)

    Стюарт Б. Гудмэн

    2014-03-01

    Full Text Available Joint replacement of the lower extremity in Juvenile Idiopathic Arthritis (JIA is becoming more commonly performed worldwide. These young adults experience severe pain and disability from end-stage arthritis, and require joint replacement of the hip or knee to alleviate pain, and restore ambulation and function. These procedures are very challenging from the anesthesia and surgical point of view, due to small overall proportions, numerous bony and other deformities and soft tissue contractures. Joint replacement operations for JIA are best performed by experienced teams, where pre-operative and peri-operative care, and post-operative rehabilitation can be optimized in a collaborative, patient-centered environment.

  18. Carbon Sequestration and Optimal Climate Policy

    International Nuclear Information System (INIS)

    Grimaud, Andre; Rouge, Luc

    2009-01-01

    We present an endogenous growth model in which the use of a non-renewable natural resource generates carbon-dioxide emissions that can be partly sequestered. This approach breaks with the systematic link between resource use and pollution emission. The accumulated stock of remaining emissions has a negative impact on household utility and corporate productivity. While sequestration quickens the optimal extraction rate, it can also generate higher emissions in the short run. It also has an adverse effect on economic growth. We study the impact of a carbon tax: the level of the tax has an effect in our model, its optimal level is positive, and it can be interpreted ex post as a decreasing ad valorem tax on the resource

  19. Prediction of optimal deployment projection for transcatheter aortic valve replacement: angiographic 3-dimensional reconstruction of the aortic root versus multidetector computed tomography.

    Science.gov (United States)

    Binder, Ronald K; Leipsic, Jonathon; Wood, David; Moore, Teri; Toggweiler, Stefan; Willson, Alex; Gurvitch, Ronen; Freeman, Melanie; Webb, John G

    2012-04-01

    Identifying the optimal fluoroscopic projection of the aortic valve is important for successful transcatheter aortic valve replacement (TAVR). Various imaging modalities, including multidetector computed tomography (MDCT), have been proposed for prediction of the optimal deployment projection. We evaluated a method that provides 3-dimensional angiographic reconstructions (3DA) of the aortic root for prediction of the optimal deployment angle and compared it with MDCT. Forty patients undergoing transfemoral TAVR at St Paul's Hospital, Vancouver, Canada, were evaluated. All underwent preimplant 3DA and 68% underwent preimplant MDCT. Three-dimensional angiographic reconstructions were generated from images of a C-arm rotational aortic root angiogram during breath-hold, rapid ventricular pacing, and injection of 32 mL contrast medium at 8 mL/s. Two independent operators prospectively predicted perpendicular valve projections. The implant angle was chosen at the discretion of the physician performing TAVR. The angles from 3DA, from MDCT, the implant angle, and the postdeployment perpendicular prosthesis view were compared. The shortest distance from the postdeployment perpendicular prosthesis projection to the regression line of predicted perpendicular projections was calculated. All but 1 patient had adequate image quality for reproducible angle predictions. There was a significant correlation between 3DA and MDCT for prediction of perpendicular valve projections (r=0.682, Pregression line of predicted angles to the postdeployment prosthesis view was 5.1±4.6° for 3DA and 7.9±4.9° for MDCT (P=0.01). Three-dimensional angiographic reconstructions and MDCT are safe, practical, and accurate imaging modalities for identifying the optimal perpendicular valve deployment projection during TAVR.

  20. Inequality and Optimal Redistributive Tax and Transfer Policies

    OpenAIRE

    Howell H Zee

    1999-01-01

    This paper explores the revenue-raising aspect of progressive taxation and derives, on the basis of a simple model, the optimal degree of tax progressivity where the tax revenue is used exclusively to finance (perfectly) targeted transfers to the poor. The paper shows that not only would it be optimal to finance the targeted transfers with progressive taxation, but that the optimal progressivity increases unambiguously with growing income inequality. This conclusion holds up under different a...

  1. Replacement of a vessel head, an operation which today gets easily into its stride

    International Nuclear Information System (INIS)

    Mardon, P.; Chaumont, J.C.; Lambiotte, P.

    1995-01-01

    In 1992, one year after the detection of a leak in a vessel head of the Electricite de France (EDF) Bugey 4 reactor, the head was replaced by the Framatome-Jeumont Industrie Group. Today, this group, which has developed new methods and new tools to optimize the cost, the time-delay and the dosimetry of this kind of intervention, has performed 11 additional replacements, two of which on 1300 MWe power units. This paper describes step by step the successive operations required for a complete vessel head replacement, including the testing of safety systems before starting up the reactor. (J.S.). 7 photos

  2. Endogenous Quality Effects of Trade Policy

    NARCIS (Netherlands)

    J.L. Moraga-Gonzalez (José Luis); J.M.A. Viaene (Jean-Marie)

    1999-01-01

    textabstractWe study the optimal trade policy against a foreign oligopoly with endogenous quality. We show that, under the Most Favoured Nation (MFN) clause, a uniform tariff policy is always welfare improving over the free trade equilibrium. However, a nonuniform tariff policy is always desirable

  3. Iron replacement therapy

    DEFF Research Database (Denmark)

    Nielsen, Ole Haagen; Coskun, Mehmet; Weiss, Günter

    2016-01-01

    PURPOSE OF REVIEW: Approximately, one-third of the world's population suffers from anemia, and at least half of these cases are because of iron deficiency. With the introduction of new intravenous iron preparations over the last decade, uncertainty has arisen when these compounds should...... be administered and under which circumstances oral therapy is still an appropriate and effective treatment. RECENT FINDINGS: Numerous guidelines are available, but none go into detail about therapeutic start and end points or how iron-deficiency anemia should be best treated depending on the underlying cause...... of iron deficiency or in regard to concomitant underlying or additional diseases. SUMMARY: The study points to major issues to be considered in revisions of future guidelines for the true optimal iron replacement therapy, including how to assess the need for treatment, when to start and when to stop...

  4. Agent-Based Optimization

    CERN Document Server

    Jędrzejowicz, Piotr; Kacprzyk, Janusz

    2013-01-01

    This volume presents a collection of original research works by leading specialists focusing on novel and promising approaches in which the multi-agent system paradigm is used to support, enhance or replace traditional approaches to solving difficult optimization problems. The editors have invited several well-known specialists to present their solutions, tools, and models falling under the common denominator of the agent-based optimization. The book consists of eight chapters covering examples of application of the multi-agent paradigm and respective customized tools to solve  difficult optimization problems arising in different areas such as machine learning, scheduling, transportation and, more generally, distributed and cooperative problem solving.

  5. Central alarm system replacement in NPP Krsko

    International Nuclear Information System (INIS)

    Cicvaric, D.; Susnic, M.; Djetelic, N.

    2004-01-01

    Current NPP Krsko central alarm system consists of three main segments. Main Control Board alarm system (BETA 1000), Ventilation Control Board alarm system (BETA 1000) and Electrical Control Board alarm system (BETA 1100). All sections are equipped with specific BetaTone audible alarms and silence, acknowledge as well as test push buttons. The main reason for central alarm system replacement is system obsolescence and problems with maintenance, due to lack of spare parts. Other issue is lack of system redundancy, which could lead to loss of several Alarm Light Boxes in the event of particular power supply failure. Current central alarm system does not provide means of alarm optimization, grouping or prioritization. There are three main options for central alarm system replacement: Conventional annunciator system, hybrid annunciator system and advanced alarm system. Advanced alarm system implementation requires Main Control Board upgrade, integration of process instrumentation and plant process computer as well as long time for replacement. NPP Krsko has decided to implement hybrid alarm system with patchwork approach. The new central alarm system will be stand alone, digital, with advanced filtering and alarm grouping options. Sequence of event recorder will be linked with plant process computer and time synchronized with redundant GPS signal. Advanced functions such as link to plant procedures will be implemented with plant process computer upgrade in outage 2006. Central alarm system replacement is due in outage 2004.(author)

  6. On jointly optimising the changes of seasonable goods and inventory replenishment

    Science.gov (United States)

    Li, Zhaolin; Tao, Feng; Sun, Daewon

    2012-06-01

    Retailers often need to replace soon-to-be-unseasonable products with new seasonable goods when the season changes. The trade-off for such activities involves choosing between the salvage loss of the unseasonable product and the profit of selling the seasonable product early. This article develops a periodic-review inventory model for planning the changes of seasonable goods with state-dependent demand and cost parameters. We show that the single-period optimal policy for product changes is a threshold policy based on the initial inventory of the unseasonable goods. The corresponding optimal inventory policy follows a Purchase-Keep-Dispose policy if the incumbent product is kept or a base-stock policy if the incumbent product is replaced. Numerically, we find that the structure of the multi-period optimal policy resembles that of the single-period model. We propose a heuristic to solve the multi-period model and demonstrate its effectiveness. Our research provides insights into dynamically managing seasonable goods.

  7. Optimal ordering and pricing policy for price sensitive stock–dependent demand under progressive payment scheme

    Directory of Open Access Journals (Sweden)

    Nita H. Shah

    2011-01-01

    Full Text Available The terminal condition of inventory level to be zero at the end of the cycle time adopted by Soni and Shah (2008, 2009 is not viable when demand is stock-dependent. To rectify this assumption, we extend their model for (1 an ending – inventory to be non-zero; (2 limited floor space; (3 a profit maximization model; (4 selling price to be a decision variable, and (5 units in inventory deteriorate at a constant rate. The algorithm is developed to search for the optimal decision policy. The working of the proposed model is supported with a numerical example. Sensitivity analysis is carried out to investigate critical parameters.

  8. Entrepreneurship Policies: Principles, Problems and Opportunities

    OpenAIRE

    Karlsson, Charlie; Andersson, Martin

    2009-01-01

    In this paper, we discuss the current status of the literature on entrepreneurship policy. The purpose is to discuss and assess several fundamental questions pertaining to entrepreneurship policies, such as “What is the optimal rate of entrepreneurship?” and “What entrepreneurship policies to pursue to remedy market failures and to avoid policy failures?”. In the entrepreneurship policies literature several contributors make distinctions between five types of entrepreneurship policy: governme...

  9. How do local governments decide on public policy in fiscal federalism?

    DEFF Research Database (Denmark)

    Köthenbürger, Marko

    2011-01-01

    Previous literature widely assumes that taxes are optimized in local public finance while expenditures adjust residually. This paper endogenizes the choice of the optimization variable. In particular, it analyzes how federal policy toward local governments influences the way local governments...... decide on public policy. Unlike the usual presumption, the paper shows that local governments may choose to optimize over expenditures. The result holds when federal policy subsidizes local taxation. The results offer a new perspective of the efficiency implications of federal policy toward local...

  10. How Do Local Governments Decide on Public Policy in Fiscal Federalism?

    DEFF Research Database (Denmark)

    Köthenbürger, Marko

    2008-01-01

    Previous literature widely assumes that taxes are optimized in local public finance while expenditures adjust residually. This paper endogenizes the choice of the optimization variable. In particular, it analyzes how federal policy toward local governments influences the way local governments...... decide on public policy. Unlike the presumption, the paper shows that local governments may choose to optimize over expenditures. The result most notably prevails when federal policy subsidizes local fiscal effort. The results offer a new perspective of the efficiency implications of federal policy...

  11. INSTITUTIONS, POLICIES AND EFFICIENCY IN ECONOMIES

    OpenAIRE

    Pavel Stoynov

    2007-01-01

    There are cases where the governments may not always serve the public interest. The implication seems to be that governments can help out but only if properly constrained. The impact of these ideas on monetary policy led to creation of Central banks. As far as fiscal policymaking is concerned, the evolution has been slower. It would seem that we are now ready to move to the next step, replacing rules with adequate incentives backed by institutions - fiscal policy committees.

  12. Dynamic optimization in environmental economics

    International Nuclear Information System (INIS)

    Moser, Elke; Tragler, Gernot; Veliov, Vladimir M.; Semmler, Willi

    2014-01-01

    This book contains two chapters with the topics: 1. Chapter: INTERACTIONS BETWEEN ECONOMY AND CLIMATE: (a) Climate Change and Technical Progress: Impact of Informational Constraints. (b) Environmental Policy in a Dynamic Model with Heterogeneous Agents and Voting. (c) Optimal Environmental Policy in the Presence of Multiple Equilibria and Reversible Hysteresis. (d). Modeling the Dynamics of the Transition to a Green Economy. (e) One-Parameter GHG Emission Policy With R and D-Based Growth. (f) Pollution, Public Health Care, and Life Expectancy when Inequality Matters. (g) Uncertain Climate Policy and the Green Paradox. (h) Uniqueness Versus Indeterminacy in the Tragedy of the Commons - A ''Geometric'' Approach. 2. Chapter: OPTIMAL EXTRACTION OF RESOURCES: (j) Dynamic Behavior of Oil Importers and Exporters Under Uncertainty. (k) Robust Control of a Spatially Distributed Commercial Fishery. (l) On the Effect of Resource Exploitation on Growth: Domestic Innovation vs. Technological Diffusion Through Trade. (m) Forest Management and Biodiversity in Size-Structured Forests Under Climate Change. (n) Carbon Taxes and Comparison of Trading Regimes in Fossil Fuels. (o) Landowning, Status and Population Growth. (p) Optimal Harvesting of Size-Structured Biological Populations.

  13. A shock and wear system under environmental conditions subject to internal failures, repair, and replacement

    International Nuclear Information System (INIS)

    Montoro-Cazorla, Delia; Pérez-Ocón, Rafael

    2012-01-01

    A system in a random environment is considered. The influence of the external conditions is governed by a Markovian arrival process. The internal structure of failure and repair are governed by phase-type distributions. The maintenance is performed by policy N. Under these assumptions, the Markov process governing the system is constructed, and it is studied in transient and stationary regime, calculating the availability and the rate of occurrence of failures. The renewal process due to the replacements of the system is studied, and expressions for the number of replacements and for the number of repairs between replacements are calculated. This paper extends other previously published since it incorporates a shock arrival process with dependence among the interarrival times and the renewal process associated to the replacements. A numerical application illustrates the calculations.

  14. An Economic and Environmental Assessment Model for Selecting the Optimal Implementation Strategy of Fuel Cell Systems—A Focus on Building Energy Policy

    Directory of Open Access Journals (Sweden)

    Daeho Kim

    2014-08-01

    Full Text Available Considerable effort is being made to reduce the primary energy consumption in buildings. As part of this effort, fuel cell systems are attracting attention as a new/renewable energy systems for several reasons: (i distributed generation system; (ii combined heat and power system; and (iii availability of various sources of hydrogen in the future. Therefore, this study aimed to develop an economic and environmental assessment model for selecting the optimal implementation strategy of the fuel cell system, focusing on building energy policy. This study selected two types of buildings (i.e., residential buildings and non-residential buildings as the target buildings and considered two types of building energy policies (i.e., the standard of energy cost calculation and the standard of a government subsidy. This study established the optimal implementation strategy of the fuel cell system in terms of the life cycle cost and life cycle CO2 emissions. For the residential building, it is recommended that the subsidy level and the system marginal price level be increased. For the non-residential building, it is recommended that gas energy cost be decreased and the system marginal price level be increased. The developed model could be applied to any other country or any other type of building according to building energy policy.

  15. Estimation of component redundancy in optimal age maintenance

    OpenAIRE

    Siopa, Jorge; Garção, José; Silva, Júlio

    2012-01-01

    The classical Optimal Age-Replacement defines the maintenance strategy based on the equipment failure consequences. For severe consequences an early equipment replacement is recommended. For minor consequences the repair after failure is proposed. One way of reducing the failure consequences is the use of redundancies, especially if the equipment failure rate is decreasing over time, since in this case the preventive replacement does not reduce the risk of failure. The estimation of an ac...

  16. Optimal Acquisition and Production Policy for End-of-Life Engineering Machinery Recovering in a Joint Manufacturing/Remanufacturing System under Uncertainties in Procurement and Demand

    Directory of Open Access Journals (Sweden)

    Haolan Liao

    2017-02-01

    Full Text Available The intensive shortage of natural resources and the inchoate phase of automobile remanufacturing in a closed-loop supply chain (CLSC are driving people to take cyclic manufacturing seriously. Aiming at maximizing resource utilization and produce profits, we apply an optimizing mathematical analysis to the modeling of automobile engine remanufacturing in a joint manufacturing system, in which the quantity and quality of procurement, and the demand of the market, are both uncertain. The manufacturer can either produce new products with raw materials or remanufacture the returned product taken back from customers; the raw materials are bought from two suppliers with certain probabilities of disruption in the supply. The returned products are classified into different quality levels according to the testing results after sorting, by considering the remanufacture-up-to strategy we obtained the optimal remanufacturing ratio, then the manufacturing quantity and corresponding maximized total profit of this joint system are determined. We also investigated a real-life case of auto engine remanufacturing, comparing it with the theory of optimal remanufacturing policy, and the results indicate that a material savings of more than 45% and a cost improvement of more than 40% could be achieved when the optimal remanufacturing policy of our model is implemented.

  17. Optimization of China's generating portfolio and policy implications based on portfolio theory

    International Nuclear Information System (INIS)

    Zhu, Lei; Fan, Ying

    2010-01-01

    This paper applies portfolio theory to evaluate China's 2020-medium-term plans for generating technologies and its generating portfolio. With reference to the risk of relevant generating-cost streams, the paper discusses China's future development of efficient (Pareto optimal) generating portfolios that enhance energy security in different scenarios, including CO 2 -emission-constrained scenarios. This research has found that the future adjustment of China's planned 2020 generating portfolio can reduce the portfolio's cost risk through appropriate diversification of generating technologies, but a price will be paid in the form of increased generating cost. In the CO 2 -emission-constrained scenarios, the generating-cost risk of China's planned 2020 portfolio is even greater than that of the 2005 portfolio, but increasing the proportion of nuclear power in the generating portfolio can reduce the cost risk effectively. For renewable-power generation, because of relatively high generating costs, it will be necessary to obtain stronger policy support to promote renewable-power development.

  18. Designing evaluation studies to optimally inform policy: what factors do policy-makers in China consider when making resource allocation decisions on healthcare worker training programmes?

    Science.gov (United States)

    Wu, Shishi; Legido-Quigley, Helena; Spencer, Julia; Coker, Richard James; Khan, Mishal Sameer

    2018-02-23

    In light of the gap in evidence to inform future resource allocation decisions about healthcare provider (HCP) training in low- and middle-income countries (LMICs), and the considerable donor investments being made towards training interventions, evaluation studies that are optimally designed to inform local policy-makers are needed. The aim of our study is to understand what features of HCP training evaluation studies are important for decision-making by policy-makers in LMICs. We investigate the extent to which evaluations based on the widely used Kirkpatrick model - focusing on direct outcomes of training, namely reaction of trainees, learning, behaviour change and improvements in programmatic health indicators - align with policy-makers' evidence needs for resource allocation decisions. We use China as a case study where resource allocation decisions about potential scale-up (using domestic funding) are being made about an externally funded pilot HCP training programme. Qualitative data were collected from high-level officials involved in resource allocation at the national and provincial level in China through ten face-to-face, in-depth interviews and two focus group discussions consisting of ten participants each. Data were analysed manually using an interpretive thematic analysis approach. Our study indicates that Chinese officials not only consider information about the direct outcomes of a training programme, as captured in the Kirkpatrick model, but also need information on the resources required to implement the training, the wider or indirect impacts of training, and the sustainability and scalability to other settings within the country. In addition to considering findings presented in evaluation studies, we found that Chinese policy-makers pay close attention to whether the evaluations were robust and to the composition of the evaluation team. Our qualitative study indicates that training programme evaluations that focus narrowly on direct training

  19. Policy development for biodiversity offsets: a review of offset frameworks.

    Science.gov (United States)

    McKenney, Bruce A; Kiesecker, Joseph M

    2010-01-01

    Biodiversity offsets seek to compensate for residual environmental impacts of planned developments after appropriate steps have been taken to avoid, minimize or restore impacts on site. Offsets are emerging as an increasingly employed mechanism for achieving net environmental benefits, with offset policies being advanced in a wide range of countries (i.e., United States, Australia, Brazil, Colombia, and South Africa). To support policy development for biodiversity offsets, we review a set of major offset policy frameworks-US wetlands mitigation, US conservation banking, EU Natura 2000, Australian offset policies in New South Wales, Victoria, and Western Australia, and Brazilian industrial and forest offsets. We compare how the frameworks define offset policy goals, approach the mitigation process, and address six key issues for implementing offsets: (1) equivalence of project impacts with offset gains; (2) location of the offset relative to the impact site; (3) "additionality" (a new contribution to conservation) and acceptable types of offsets; (4) timing of project impacts versus offset benefits; (5) offset duration and compliance; and (6) "currency" and mitigation replacement ratios. We find substantial policy commonalities that may serve as a sound basis for future development of biodiversity offsets policy. We also identify issues requiring further policy guidance, including how best to: (1) ensure conformance with the mitigation hierarchy; (2) identify the most environmentally preferable offsets within a landscape context; and (3) determine appropriate mitigation replacement ratios.

  20. Rationalizing method of replacement intervals by using Bayesian statistics

    International Nuclear Information System (INIS)

    Kasai, Masao; Notoya, Junichi; Kusakari, Yoshiyuki

    2007-01-01

    This study represents the formulations for rationalizing the replacement intervals of equipments and/or parts taking into account the probability density functions (PDF) of the parameters of failure distribution functions (FDF) and compares the optimized intervals by our formulations with those by conventional formulations which uses only representative values of the parameters of FDF instead of using these PDFs. The failure data are generated by Monte Carlo simulations since the real failure data can not be available for us. The PDF of PDF parameters are obtained by Bayesian method and the representative values are obtained by likelihood estimation and Bayesian method. We found that the method using PDF by Bayesian method brings longer replacement intervals than one using the representative of the parameters. (author)

  1. A model of residential energy end-use in Canada: Using conditional demand analysis to suggest policy options for community energy planners

    International Nuclear Information System (INIS)

    Newsham, Guy R.; Donnelly, Cara L.

    2013-01-01

    We applied conditional demand analysis (CDA) to estimate the average annual energy use of various electrical and natural gas appliances, and derived energy reductions associated with certain appliance upgrades and behaviours. The raw data came from 9773 Canadian households, and comprised annual electricity and natural gas use, and responses to >600 questions on dwelling and occupant characteristics, appliances, heating and cooling equipment, and associated behaviours. Replacing an old (>10 years) refrigerator with a new one was estimated to save 100 kW h/year; replacing an incandescent lamp with a CFL/LED lamp was estimated to save 20 kW h/year; and upgrading an old central heating system with a new one was estimated to save 2000 kW h/year. This latter effect was similar to that of reducing the number of walls exposed to the outside. Reducing the winter thermostat setpoint during occupied, waking hours was estimated to lower annual energy use by 200 kW h/°C-reduction, and lowering the thermostat setting overnight in winter relative to the setting during waking hours (night-time setback) was estimated to have a similar effect. This information may be used by policy-makers to optimize incentive programs, information campaigns, or other energy use change instruments. - Highlights: ► Conditional demand analysis (CDA) applied to data from 9773 Canadian households. ► Energy savings associated with certain appliance upgrades estimated. ► Energy savings associated with thermostat behaviours estimated. ► Policy-makers can use findings to optimize incentives and information campaigns

  2. Nutrition to Support Recovery from Endurance Exercise: Optimal Carbohydrate and Protein Replacement.

    Science.gov (United States)

    Moore, Daniel R

    2015-01-01

    Proper nutrition is vital to optimize recovery after endurance exercise. Dietary carbohydrate and protein provide the requisite substrates to enhance glycogen resynthesis and remodel skeletal muscle proteins, respectively, both of which would be important to rapidly restore muscle function and performance. With short recovery windows (optimal ingestion of both carbohydrate and protein.

  3. Shoulder replacement - discharge

    Science.gov (United States)

    Total shoulder arthroplasty - discharge; Endoprosthetic shoulder replacement - discharge; Partial shoulder replacement - discharge; Partial shoulder arthroplasty - discharge; Replacement - shoulder - discharge; Arthroplasty - shoulder - discharge

  4. A Petri net-based modelling of replacement strategies under technological obsolescence

    Energy Technology Data Exchange (ETDEWEB)

    Clavareau, Julien [Universite Libre de Bruxelles (U.L.B.), Service de Metrologie Nucleaire, Av. F.D. Roosevelt, 50 (CP165/84), Bruxelles B-1050 (Belgium)], E-mail: jclavare@ulb.ac.be; Labeau, Pierre-Etienne [Universite Libre de Bruxelles (U.L.B.), Service de Metrologie Nucleaire, Av. F.D. Roosevelt, 50 (CP165/84), Bruxelles B-1050 (Belgium)

    2009-02-15

    The technological obsolescence of a unit is characterised by the existence of challenger units displaying identical functionalities, but with higher performances. Though this issue is commonly encountered in practice, it has received little consideration in the literature. Previous exploratory works have treated the problem of replacing old-technology items by new ones, for identical components facing a unique new generation of items. This paper aims to define, in a realistic way, possible replacement policies when several types of challenger units are available and when the performances of these newly available units improve with time. Since no fully generic model can exist in maintenance optimisation, a modular modelling of the problem, allowing easy adaptations to features corresponding to specific applications is highly desirable. This work therefore proposes a modular Petri net model for this problem, underlying a Monte Carlo (MC) estimation of the costs incurred by the different possible replacement strategies under consideration.

  5. Policy Making While Paradigms Shift: Understanding the Development of Policy Drought in the U.S. Congress 1981-2013

    Science.gov (United States)

    McCurdy, K. M.

    2013-12-01

    Ronald Reagan famously announced in his 1981 inaugural address that 'government is not the solution to our problem; government is the problem.' For the scientific community and Members of Congress of that time, who were partners in working within the scientific management policy paradigm and the meritocracy on which its technical expertise depended, these words were outside their paradigm of good public service. Despite this announcement of a new paradigm by the incoming President, their policy world continued undisturbed, finding points of agreement to make incremental improvements in policy. Executive branch actions in Reagan's two terms as president were dismissed as peculiar, although they were the beginnings of realizing a policy goal of reducing the size and influence of the federal government. The important parameters influencing policy making in the U.S. Congress, which party holds the majority that sets the agenda and schedules votes, seniority that determines leadership positions in the conference and caucus, specialization on policy by committee jurisdictions, vary little annually and thereby were treated as constants by participants and observers alike. But member replacement has policy consequences that are infrequently noted. Members die in office, retire, and lose re-election bids, while the new members replacing them do not replicate any of their institutional characteristics. The policy process continues seemingly unchanged, but there are changes that become apparent with time. By 2013, scientists are no longer unquestioning partners in shaping federal public policy. They have been ridiculed in congressional hearings and in media attacks. Meanwhile new legislative strategies are being tried, e.g. shutting down government, increasing the use of earmarks instead of peer review, filibuster threats, and repeated attempts to repeal laws are now common tactics in Congress. Science and Congress no longer seem to act as partners in policy making, but as

  6. Integration scenarios of Demand Response into electricity markets: Load shifting, financial savings and policy implications

    International Nuclear Information System (INIS)

    Feuerriegel, Stefan; Neumann, Dirk

    2016-01-01

    Demand Response allows for the management of demand side resources in real-time; i.e. shifting electricity demand according to fluctuating supply. When integrated into electricity markets, Demand Response can be used for load shifting and as a replacement for both control reserve and balancing energy. These three usage scenarios are compared based on historic German data from 2011 to determine that load shifting provides the highest benefit: its annual financial savings accumulate to €3.110 M for both households and the service sector. This equals to relative savings of 2.83% compared to a scenario without load shifting. To improve Demand Response integration, the proposed model suggests policy implications: reducing bid sizes, delivery periods and the time-lag between market transactions and delivery dates in electricity markets. - Highlights: •Comparison of 3 scenarios to integrate Demand Response into electricity markets. •These are: optimize procurement, offer as control reserve, avoid balancing energy. •Ex post simulation to quantify financial impact and policy implications. •Highest savings from load shifting with a cost reduction of 3%. •Model suggests reducing bid sizes, delivery periods and time lags as policy issues.

  7. Reactor vessel closure head replacements in 1997

    International Nuclear Information System (INIS)

    Anon.

    1997-01-01

    The Framatome-Jeumont Industrie consortium have completed in 1997 28 reactor vessel (RV) closure head replacements, including five on 1300 MWe class PWR units. Framatome manages the operations and handles removal and reinstallation of equipment (not including the control rod drive mechanisms (CRDM)) and the requalification tests, while JI, which manufactures the CRDMs, is involved in the CRDM cutting, re-machining and welding operations, using tools of original design, in order to optimize the RV closure head operation in terms of costs, schedule and dosage

  8. A review on seashells ash as partial cement replacement

    Science.gov (United States)

    Mohammad, Wan Ahmad Soffian Bin Wan; Hazurina Othman, Nor; Ibrahim, Mohd Haziman Wan; Rahim, Masazurah A.; Shahidan, Shahiron; Rahman, Raha Abd

    2017-11-01

    This review paper emphasis on various sea shells ash such as cockle, clam, oyster, mollusc, periwinkle, snail, and green mussel shell ash as partial cement replacement and its objective is to create sustainable environment and reduce problems of global warming. Cement production give huge impact to environment in every stage of its production. These include air pollution in form of dust and, gases, sound and vibration during quarry crushing and milling. One of the solutions to solve this problem is by using modified cement. The modified cement is a cementitious material that meets or exceeds the Portland cement performance by combining and optimizes the recycle and wasted materials. This will indirectly reduce the use of raw materials and then, become a sustain construction materials. Therefore, the replacement of cement in concrete by various sea shell ash may create tremendous saving of energy and also leads to important environmental benefits. This study includes previous investigation done on the properties of chemical and mechanical such as specific gravity, chemical composition, compressive strength, tensile strength and flexural strength of concrete produced using partial replacement of cement by seashells ash. Results show that the optimum percentage of seashells as cement replacement is between 4 - 5%.

  9. A niching genetic algorithm applied to a nuclear power plant auxiliary feedwater system surveillance tests policy optimization

    International Nuclear Information System (INIS)

    Sacco, W.F.; Lapa, Celso M.F.; Pereira, C.M.N.A.; Oliveira, C.R.E. de

    2006-01-01

    This article extends previous efforts on genetic algorithms (GAs) applied to a nuclear power plant (NPP) auxiliary feedwater system (AFWS) surveillance tests policy optimization. We introduce the application of a niching genetic algorithm (NGA) to this problem and compare its performance to previous results. The NGA maintains a populational diversity during the search process, thus promoting a greater exploration of the search space. The optimization problem consists in maximizing the system's average availability for a given period of time, considering realistic features such as: (i) aging effects on standby components during the tests; (ii) revealing failures in the tests implies on corrective maintenance, increasing outage times; (iii) components have distinct test parameters (outage time, aging factors, etc.) and (iv) tests are not necessarily periodic. We find that the NGA performs better than the conventional GA and the island GA due to a greater exploration of the search space

  10. Optimal tax depreciation under a progressive tax system

    OpenAIRE

    Wielhouwer, J.L.; De Waegenaere, A.M.B.; Kort, P.M.

    2002-01-01

    The focus of this paper is on the effect of a progressive tax system on optimal tax depreciation. By using dynamic optimization we show that an optimal strategy exists, and we provide an analytical expression for the optimal depreciation charges. Depreciation charges initially decrease over time, and after a number of periods the firm enters a steady state where depreciation is constant and equal to replacement investments. This way, the optimal solution trades off the benefits of accelerated...

  11. Shadow Cost of Public Funds and Privatization Policies

    OpenAIRE

    Sato, Susumu; Matsumura, Toshihiro

    2017-01-01

    We investigate the optimal privatization policy in mixed oligopolies with shadow cost of public funds (excess burden of taxation). The government is concerned with both the total social surplus and the revenue obtained by the privatization of a public firm. We find that the relationship between the shadow cost of public funds and the optimal privatization policy is non-monotone. When the cost is moderate, then higher the cost is, the lower is the optimal degree of privatization. ...

  12. Welfare effects of deterrence-motivated activation policy

    DEFF Research Database (Denmark)

    Rasmussen, Martin

    We investigate whether activation policy is part of optimal policy of a benevolent government, when the motivation for introducing activation is to deter some people from collecting benefits. The government offers a pure benefit programme and an activation programme, and individuals self-select i......We investigate whether activation policy is part of optimal policy of a benevolent government, when the motivation for introducing activation is to deter some people from collecting benefits. The government offers a pure benefit programme and an activation programme, and individuals self......-select into programmes. Individuals differ with respect to disutility and wage. Activation programmes are relatively costly and favour individuals who are relatively well off. Hence, for activation policy to used, labour supply effects have to be relatively small. We discuss how labour supply effects depend...

  13. Optimal Implantation Depth and Adherence to Guidelines on Permanent Pacing to Improve the Results of Transcatheter Aortic Valve Replacement With the Medtronic CoreValve System: The CoreValve Prospective, International, Post-Market ADVANCE-II Study.

    Science.gov (United States)

    Petronio, Anna S; Sinning, Jan-Malte; Van Mieghem, Nicolas; Zucchelli, Giulio; Nickenig, Georg; Bekeredjian, Raffi; Bosmans, Johan; Bedogni, Francesco; Branny, Marian; Stangl, Karl; Kovac, Jan; Schiltgen, Molly; Kraus, Stacia; de Jaegere, Peter

    2015-05-01

    The aim of the CoreValve prospective, international, post-market ADVANCE-II study was to define the rates of conduction disturbances and permanent pacemaker implantation (PPI) after transcatheter aortic valve replacement with the Medtronic CoreValve System (Minneapolis, Minnesota) using optimized implantation techniques and application of international guidelines on cardiac pacing. Conduction disturbances are a frequent complication of transcatheter aortic valve replacement. The rates of PPI in the published reports vary according to bioprosthesis type and the indications for PPI. The primary endpoint was the 30-day incidence of PPI with Class I/II indications when the Medtronic CoreValve System was implanted at an optimal depth (≤6 mm below the aortic annulus). The timing and resolution of all new-onset conduction disturbances were analyzed. A total of 194 patients were treated. The overall rate of PPI for Class I/II indications was 18.2%. An optimal depth was reached in 43.2% of patients, with a nonsignificantly lower incidence of PPI in patients with depths ≤6 mm, compared with those with deeper implants (13.3% vs. 21.1%; p = 0.14). In a paired analysis, new-onset left bundle branch block and first-degree atrioventricular block occurred in 45.4% and 39.0% of patients, respectively, and resolved spontaneously within 30 days in 43.2% and 73.9%, respectively. In patients with new PPI, the rate of intrinsic sinus rhythm increased from 25.9% at 7 days to 59.3% at 30 days (p = 0.004). Optimal Medtronic CoreValve System deployment and adherence to international guidelines on cardiac pacing are associated with a lower rate of new PPI after transcatheter aortic valve replacement, compared with results reported in previous studies. (CoreValve Advance-II Study: Prospective International Post-Market Study [ADVANCE II]; NCT01624870). Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  14. Balancing Exploration, Uncertainty Representation and Computational Time in Many-Objective Reservoir Policy Optimization

    Science.gov (United States)

    Zatarain-Salazar, J.; Reed, P. M.; Quinn, J.; Giuliani, M.; Castelletti, A.

    2016-12-01

    As we confront the challenges of managing river basin systems with a large number of reservoirs and increasingly uncertain tradeoffs impacting their operations (due to, e.g. climate change, changing energy markets, population pressures, ecosystem services, etc.), evolutionary many-objective direct policy search (EMODPS) solution strategies will need to address the computational demands associated with simulating more uncertainties and therefore optimizing over increasingly noisy objective evaluations. Diagnostic assessments of state-of-the-art many-objective evolutionary algorithms (MOEAs) to support EMODPS have highlighted that search time (or number of function evaluations) and auto-adaptive search are key features for successful optimization. Furthermore, auto-adaptive MOEA search operators are themselves sensitive to having a sufficient number of function evaluations to learn successful strategies for exploring complex spaces and for escaping from local optima when stagnation is detected. Fortunately, recent parallel developments allow coordinated runs that enhance auto-adaptive algorithmic learning and can handle scalable and reliable search with limited wall-clock time, but at the expense of the total number of function evaluations. In this study, we analyze this tradeoff between parallel coordination and depth of search using different parallelization schemes of the Multi-Master Borg on a many-objective stochastic control problem. We also consider the tradeoff between better representing uncertainty in the stochastic optimization, and simplifying this representation to shorten the function evaluation time and allow for greater search. Our analysis focuses on the Lower Susquehanna River Basin (LSRB) system where multiple competing objectives for hydropower production, urban water supply, recreation and environmental flows need to be balanced. Our results provide guidance for balancing exploration, uncertainty, and computational demands when using the EMODPS

  15. Dynamic optimization in environmental economics

    Energy Technology Data Exchange (ETDEWEB)

    Moser, Elke; Tragler, Gernot; Veliov, Vladimir M. (eds.) [Vienna Univ. of Technology (Austria). Inst. of Mathematical Methods in Economics; Semmler, Willi [The New School for Social Research, New York, NY (United States). Dept. of Economics

    2014-11-01

    This book contains two chapters with the topics: 1. Chapter: INTERACTIONS BETWEEN ECONOMY AND CLIMATE: (a) Climate Change and Technical Progress: Impact of Informational Constraints. (b) Environmental Policy in a Dynamic Model with Heterogeneous Agents and Voting. (c) Optimal Environmental Policy in the Presence of Multiple Equilibria and Reversible Hysteresis. (d). Modeling the Dynamics of the Transition to a Green Economy. (e) One-Parameter GHG Emission Policy With R and D-Based Growth. (f) Pollution, Public Health Care, and Life Expectancy when Inequality Matters. (g) Uncertain Climate Policy and the Green Paradox. (h) Uniqueness Versus Indeterminacy in the Tragedy of the Commons - A ''Geometric'' Approach. 2. Chapter: OPTIMAL EXTRACTION OF RESOURCES: (j) Dynamic Behavior of Oil Importers and Exporters Under Uncertainty. (k) Robust Control of a Spatially Distributed Commercial Fishery. (l) On the Effect of Resource Exploitation on Growth: Domestic Innovation vs. Technological Diffusion Through Trade. (m) Forest Management and Biodiversity in Size-Structured Forests Under Climate Change. (n) Carbon Taxes and Comparison of Trading Regimes in Fossil Fuels. (o) Landowning, Status and Population Growth. (p) Optimal Harvesting of Size-Structured Biological Populations.

  16. Optimal policy of energy innovation in developing countries: Development of solar PV in Iran

    International Nuclear Information System (INIS)

    Shafiei, Ehsan; Saboohi, Yadollah; Ghofrani, Mohammad B.

    2009-01-01

    The purpose of this study is to apply managerial economics and methods of decision analysis to study the optimal pattern of innovation activities for development of new energy technologies in developing countries. For this purpose, a model of energy research and development (R and D) planning is developed and it is then linked to a bottom-up energy-systems model. The set of interlinked models provide a comprehensive analytical tool for assessment of energy technologies and innovation planning taking into account the specific conditions of developing countries. An energy-system model is used as a tool for the assessment and prioritization of new energy technologies. Based on the results of the technology assessment model, the optimal R and D resources allocation for new energy technologies is estimated with the help of the R and D planning model. The R and D planning model is based on maximization of the total net present value of resulting R and D benefits taking into account the dynamics of technological progress, knowledge and experience spillovers from advanced economies, technology adoption and R and D constraints. Application of the set of interlinked models is explained through the analysis of the development of solar PV in Iranian electricity supply system and then some important policy insights are concluded

  17. Ankle replacement

    Science.gov (United States)

    Ankle arthroplasty - total; Total ankle arthroplasty; Endoprosthetic ankle replacement; Ankle surgery ... Ankle replacement surgery is most often done while you are under general anesthesia. This means you will ...

  18. Optimal C-arm angulation during transcatheter aortic valve replacement: Accuracy of a rotational C-arm computed tomography based three dimensional heart model.

    Science.gov (United States)

    Veulemans, Verena; Mollus, Sabine; Saalbach, Axel; Pietsch, Max; Hellhammer, Katharina; Zeus, Tobias; Westenfeld, Ralf; Weese, Jürgen; Kelm, Malte; Balzer, Jan

    2016-10-26

    To investigate the accuracy of a rotational C-arm CT-based 3D heart model to predict an optimal C-arm configuration during transcatheter aortic valve replacement (TAVR). Rotational C-arm CT (RCT) under rapid ventricular pacing was performed in 57 consecutive patients with severe aortic stenosis as part of the pre-procedural cardiac catheterization. With prototype software each RCT data set was segmented using a 3D heart model. From that the line of perpendicularity curve was obtained that generates a perpendicular view of the aortic annulus according to the right-cusp rule. To evaluate the accuracy of a model-based overlay we compared model- and expert-derived aortic root diameters. For all 57 patients in the RCT cohort diameter measurements were obtained from two independent operators and were compared to the model-based measurements. The inter-observer variability was measured to be in the range of 0°-12.96° of angular C-arm displacement for two independent operators. The model-to-operator agreement was 0°-13.82°. The model-based and expert measurements of aortic root diameters evaluated at the aortic annulus ( r = 0.79, P optimal C-arm configuration, potentially simplifying current clinical workflows before and during TAVR.

  19. National Policy on Nuclear Fuel Cycle

    International Nuclear Information System (INIS)

    Soedyartomo, S.

    1996-01-01

    National policy on nuclear fuel cycle is aimed at attaining the expected condition, i.e. being able to support optimality the national energy policy and other related Government policies taking into account current domestic nuclear fuel cycle condition and the trend of international nuclear fuel cycle development, the national strength, weakness, thread and opportunity in the field of energy. This policy has to be followed by the strategy to accomplish covering the optimization of domestic efforts, cooperation with other countries, and or purchasing licences. These policy and strategy have to be broken down into various nuclear fuel cycle programmes covering basically assesment of the whole cycle, performing research and development of the whole cycle without enrichment and reprocessing being able for weapon, as well as programmes for industrialization of the fuel cycle stepwisery commencing with the middle part of the cycle and ending with the edge of the back-end of the cycle

  20. Nicotine replacement therapy

    Science.gov (United States)

    Smoking cessation - nicotine replacement; Tobacco - nicotine replacement therapy ... Before you start using a nicotine replacement product, here are some things to know: The more cigarettes you smoke, the higher the dose you may need to ...

  1. Research in Mobile Database Query Optimization and Processing

    Directory of Open Access Journals (Sweden)

    Agustinus Borgy Waluyo

    2005-01-01

    Full Text Available The emergence of mobile computing provides the ability to access information at any time and place. However, as mobile computing environments have inherent factors like power, storage, asymmetric communication cost, and bandwidth limitations, efficient query processing and minimum query response time are definitely of great interest. This survey groups a variety of query optimization and processing mechanisms in mobile databases into two main categories, namely: (i query processing strategy, and (ii caching management strategy. Query processing includes both pull and push operations (broadcast mechanisms. We further classify push operation into on-demand broadcast and periodic broadcast. Push operation (on-demand broadcast relates to designing techniques that enable the server to accommodate multiple requests so that the request can be processed efficiently. Push operation (periodic broadcast corresponds to data dissemination strategies. In this scheme, several techniques to improve the query performance by broadcasting data to a population of mobile users are described. A caching management strategy defines a number of methods for maintaining cached data items in clients' local storage. This strategy considers critical caching issues such as caching granularity, caching coherence strategy and caching replacement policy. Finally, this survey concludes with several open issues relating to mobile query optimization and processing strategy.

  2. Hip Replacement Surgery

    Science.gov (United States)

    ... Outreach Initiative Breadcrumb Home Health Topics English Español Hip Replacement Surgery Basics In-Depth Download Download EPUB ... PDF What is it? Points To Remember About Hip Replacement Surgery Hip replacement surgery removes damaged or ...

  3. Reducing CO2 emissions on the electric grid through a carbon disincentive policy

    International Nuclear Information System (INIS)

    Li, Chiao-Ting; Peng, Huei; Sun, Jing

    2013-01-01

    This paper studies the operation of an electric grid with renewable wind generation and plug-in electric vehicles (PEVs). In particular, PEVs will be the controllable demand that can mitigate the intermittency in wind generation and improve the capacity factors of the non-renewable generation assets on the grid. Optimization problems are formulated to minimize the costs of electricity generation, and two approaches are proposed to address the grid CO 2 emission in the optimization. The first approach directly penalizes CO 2 in the objective function, and the second approach adopts a carbon disincentive policy to alter the dispatch order of power plants, so that expensive low-CO 2 plants can replace cheap high-CO 2 plants. These two approaches result in very different outcomes: the first approach affects only the PEV charging demand on the grid and does not result in significant CO 2 reduction, whereas the second approach controls both the generation and load, and CO 2 can be reduced substantially. In addition, the carbon disincentive policy, unlike a carbon tax, does not collect any revenue; therefore, the increase in electricity cost is minimal. The effect of the proposed algorithms on the grid electricity cost and carbon emission is analyzed in details and reported. - Highlights: • We study the tradeoff between CO 2 emissions and generation cost on an electric grid. • The tradeoff was shown by Pareto fronts obtained from optimizations. • Pareto fronts shows that a carbon disincentive is effective in reducing emissions. • Controlling both supply and demand on the grid is necessary to reduce CO 2 and costs

  4. Nurses' perceptions of the challenges related to the Omanization policy.

    Science.gov (United States)

    Al-Riyami, M; Fischer, I; Lopez, V

    2015-12-01

    Human resource development has become a major concern in Oman since the inception of the 'Omanization' policy in 1988. The main goal of this policy was to replace the expatriate nursing workforce with similarly qualified local nurses to develop a sustainable workforce and achieve self-reliance. The aim of this study is to explore the nurses' perceptions of Omanization policy. A qualitative research design was used and 16 Omani registered nurses and 26 student nurses were interviewed in depth. Transcribed data were analysed using content analysis. Two main themes emerged from the data: 'Challenges of sustaining the local nursing workforce' and 'Challenges of educational preparation for local nurses'. The participants agreed that Omanization benefited national development, social stability and ensuring local workforce. The challenges faced were cultural and work life balance, preparation of nurses and pace of replacement. The participants were concerned that the pace of replacement could leave behind a marked experience gap. A slow-phased approach to Omanization of the nursing workforce was recommended by the participants. Results obtained from this study reflect the perceptions and voices of student nurses and registered nurses only from the Institute of Nursing and Oman Ministry of Health. A policy of this magnitude requires gradual establishment. The upgrading of the nursing education to degree level, continuous professional development, mentoring and role modeling of expert nurses should be established to prepare local nurses for the localization of the nursing workforce. © 2015 International Council of Nurses.

  5. Optimal Planning Method of On-load Capacity Regulating Distribution Transformers in Urban Distribution Networks after Electric Energy Replacement Considering Uncertainties

    Directory of Open Access Journals (Sweden)

    Yu Su

    2018-06-01

    Full Text Available Electric energy replacement is the umbrella term for the use of electric energy to replace oil (e.g., electric automobiles, coal (e.g., electric heating, and gas (e.g., electric cooking appliances, which increases the electrical load peak, causing greater valley/peak differences. On-load capacity regulating distribution transformers have been used to deal with loads with great valley/peak differences, so reasonably replacing conventional distribution transformers with on-load capacity regulating distribution transformers can effectively cope with load changes after electric energy replacement and reduce the no-load losses of distribution transformers. Before planning for on-load capacity regulating distribution transformers, the nodal effective load considering uncertainties within the life cycle after electric energy replacement was obtained by a Monte Carlo method. Then, according to the loss relation between on-load capacity regulating distribution transformers and conventional distribution transformers, three characteristic indexes of annual continuous apparent power curve and replacement criteria for on-load capacity regulating distribution transformers were put forward in this paper, and a set of distribution transformer replaceable points was obtained. Next, based on cost benefit analysis, a planning model of on-load capacity regulating distribution transformers which consists of investment profitability index within the life cycle, investment cost recouping index and capacity regulating cost index was put forward. The branch and bound method was used to solve the planning model within replaceable point set to obtain upgrading and reconstruction scheme of distribution transformers under a certain investment. Finally, planning analysis of on-load capacity regulating distribution transformers was carried out for electric energy replacement points in one urban distribution network under three scenes: certain load, uncertain load and nodal

  6. Regulatory aspects of the enforcement policy applied to teletherapy equipment obsolescence (1995-2002)

    International Nuclear Information System (INIS)

    Truppa, Walter A.; Rey, Hugo L.; Rojas, Carlos A.

    2004-01-01

    The paper describes the way in which the Nuclear Regulatory Authority (ARN) has implemented an 'enforcement' policy for the services of radiotherapy that operated obsolete cobalt therapy units. Without doubt one of the greater advances has been the simulation and planning of the treatment, indispensable tools in a system of quality in radiotherapy where the equipment acquires a preponderant paper. In Argentina the distribution of equipment was inhomogeneous, and within it coexisted, as primary and unique units, great amount with a technology today already obsolete. The Nuclear Regulatory Authority (ARN) took a strong regulatory attitude directed to change or to retire many of the units, as its characteristics of design and antiquity did not fulfill the criteria of radiological security established in the norms (optimization of the dose, distances source to skin, yield in surface, adequate maintenance, etc.). On this matter a policy was applied to impose within suitable terms, the change of the obsolete equipment for this practice, particularly those distances source to skin minor than 80 cm. As result of the applied coercive measures at this moment, 28 equipment of cobalt therapy in advanced degree of obsolescence were retired by regulatory decision. Part of these equipment were replaced by their owners by more modern equipment whose operation adjusts to the requirements of the radiological security norm, whereas the majority was replaced by linear accelerators. At the moment there are 86 of cobalt therapy units and 52 accelerators operating in our country, against 104 and 32 respectively, that operated in 1995. (author)

  7. Policy Development Fosters Collaborative Practice

    DEFF Research Database (Denmark)

    Meyer, Daniel M; Kaste, Linda M; Lituri, Kathy M

    2016-01-01

    This article provides an example of interprofessional collaboration for policy development regarding environmental global health vis-à-vis the Minamata Convention on Mercury. It presents an overview of mercury and mercury-related environmental health issues; public policy processes and stakeholde...... requiring dental engagement for interprofessional policy development include education, disaster response, HPV vaccination, pain management, research priorities, and antibiotic resistance.......; and specifics including organized dentistry's efforts to create global policy to restrict environmental contamination by mercury. Dentistry must participate in interprofessional collaborations and build on such experiences to be optimally placed for ongoing interprofessional policy development. Current areas...

  8. Political economy constraints on carbon pricing policies: What are the implications for economic efficiency, environmental efficacy, and climate policy design?

    International Nuclear Information System (INIS)

    Jenkins, Jesse D.

    2014-01-01

    Economists traditionally view a Pigouvian fee on carbon dioxide and other greenhouse gas emissions, either via carbon taxes or emissions caps and permit trading (“cap-and-trade”), as the economically optimal or “first-best” policy to address climate change-related externalities. Yet several political economy factors can severely constrain the implementation of these carbon pricing policies, including opposition of industrial sectors with a concentration of assets that would lose considerable value under such policies; the collective action nature of climate mitigation efforts; principal agent failures; and a low willingness-to-pay for climate mitigation by citizens. Real-world implementations of carbon pricing policies can thus fall short of the economically optimal outcomes envisioned in theory. Consistent with the general theory of the second-best, the presence of binding political economy constraints opens a significant “opportunity space” for the design of creative climate policy instruments with superior political feasibility, economic efficiency, and environmental efficacy relative to the constrained implementation of carbon pricing policies. This paper presents theoretical political economy frameworks relevant to climate policy design and provides corroborating evidence from the United States context. It concludes with a series of implications for climate policy making and argues for the creative pursuit of a mix of second-best policy instruments. - Highlights: • Political economy constraints can bind carbon pricing policies. • These constraints can prevent implementation of theoretically optimal carbon prices. • U.S. household willingness-to-pay for climate policy likely falls in the range of $80–$200 per year. • U.S. carbon prices may be politically constrained to as low as $2–$8 per ton of CO 2 . • An opportunity space exists for improvements in climate policy design and outcomes

  9. Knee Replacement

    Science.gov (United States)

    Knee replacement is surgery for people with severe knee damage. Knee replacement can relieve pain and allow you to ... Your doctor may recommend it if you have knee pain and medicine and other treatments are not ...

  10. OPTIMAL TRAINING POLICY FOR PROMOTION - STOCHASTIC MODELS OF MANPOWER SYSTEMS

    Directory of Open Access Journals (Sweden)

    V.S.S. Yadavalli

    2012-01-01

    Full Text Available In this paper, the optimal planning of manpower training programmes in a manpower system with two grades is discussed. The planning of manpower training within a given organization involves a trade-off between training costs and expected return. These planning problems are examined through models that reflect the random nature of manpower movement in two grades. To be specific, the system consists of two grades, grade 1 and grade 2. Any number of persons in grade 2 can be sent for training and after the completion of training, they will stay in grade 2 and will be given promotion as and when vacancies arise in grade 1. Vacancies arise in grade 1 only by wastage. A person in grade 1 can leave the system with probability p. Vacancies are filled with persons in grade 2 who have completed the training. It is assumed that there is a perfect passing rate and that the sizes of both grades are fixed. Assuming that the planning horizon is finite and is T, the underlying stochastic process is identified as a finite state Markov chain and using dynamic programming, a policy is evolved to determine how many persons should be sent for training at any time k so as to minimize the total expected cost for the entire planning period T.

  11. The employment effects of sustainable development policies

    International Nuclear Information System (INIS)

    McNeill, Judith M.; Williams, Jeremy B.

    2007-01-01

    This paper argues that it is time for ecological economists to bring the employment impacts of sustainable development policies to the forefront of the research agenda. Important conservation efforts continue to founder because of their perceived employment effects. The paper examines the evidence on the employment impacts of sustainable development policies and argues that maintaining or even increasing employment depends critically on appropriate policy design and attention to the political economy of implementation of policies. The paper concludes that a better understanding of these issues, fair labour market and structural adjustment programs, and especially forward planning to anticipate problem areas, must replace the piecemeal, 'knee-jerk' reactions to environmental issues, such as were evident in Australia during the last federal election. (author)

  12. Analysis for a two-dissimilar-component cold standby repairable system with repair priority

    International Nuclear Information System (INIS)

    Leung, Kit Nam Francis; Zhang Yuanlin; Lai, Kin Keung

    2011-01-01

    In this paper, a cold standby repairable system consisting of two dissimilar components and one repairman is studied. Assume that working time distributions and repair time distributions of the two components are both exponential, and Component 1 has repair priority when both components are broken down. After repair, Component 1 follows a geometric process repair while Component 2 obeys a perfect repair. Under these assumptions, using the perfect repair model, the geometric process repair model and the supplementary variable technique, we not only study some important reliability indices, but also consider a replacement policy T, under which the system is replaced when the working age of Component 1 reaches T. Our problem is to determine an optimal policy T* such that the long-run average loss per unit time (i.e. average loss rate) of the system is minimized. The explicit expression for the average loss rate of the system is derived, and the corresponding optimal replacement policy T* can be found numerically. Finally, a numerical example for replacement policy T is given to illustrate some theoretical results and the model's applicability. - Highlights: → A two-dissimilar-component cold standby system with repair priority is formulated. → The successive up/repair times of Component 1 form a decreasing/increasing geometric process. → Not only some reliability indices but also a replacement policy are studied.

  13. Analysis and Optimization of Distributed Real-Time Embedded Systems

    DEFF Research Database (Denmark)

    Pop, Paul; Eles, Petru; Peng, Zebo

    2006-01-01

    and scheduling policies. In this context, the task of designing such systems is becoming increasingly difficult. The success of new adequate design methods depends on the availability of efficient analysis as well as optimization techniques. In this paper, we present both analysis and optimization approaches...... characteristic to this class of systems: mapping of functionality, the optimization of the access to the communication channel, and the assignment of scheduling policies to processes. Optimization heuristics aiming at producing a schedulable system, with a given amount of resources, are presented....

  14. Optimal Network QoS over the Internet of Vehicles for E-Health Applications

    Directory of Open Access Journals (Sweden)

    Di Lin

    2016-01-01

    Full Text Available Wireless technologies are pervasive to support ubiquitous healthcare applications. However, a critical issue of using wireless communications under a healthcare scenario is the electromagnetic interference (EMI caused by RF transmission, and a high level of EMI may lead to a critical malfunction of medical sensors. In consideration of EMI on medical sensors, we study the optimization of quality of service (QoS within the whole Internet of vehicles for E-health and propose a novel model to optimize the QoS by allocating the transmit power of each user. Our results show that the optimal power control policy depends on the objective of optimization problems: a greedy policy is optimal to maximize the summation of QoS of each user, whereas a fair policy is optimal to maximize the product of QoS of each user. Algorithms are taken to derive the optimal policies, and numerical results of optimizing QoS are presented for both objectives and QoS constraints.

  15. Informing principal policy reforms in South Africa through data-based evidence

    Directory of Open Access Journals (Sweden)

    Gabrielle Wills

    2015-12-01

    Full Text Available In the past decade there has been a notable shift in South African education policy that raises the value of school leadership as a lever for learning improvements. Despite a growing discourse on school leadership, there has been a lack of empirical based evidence on principals to inform, validate or debate the efficacy of proposed policies in raising the calibre of school principals. Drawing on findings from a larger study to understand the labour market for school principals in South Africa, this paper highlights four overarching characteristics of this market with implications for informing principal policy reforms. The paper notes that improving the design and implementation of policies guiding the appointment process for principals is a matter of urgency. A substantial and increasing number of principal replacements are taking place across South African schools given a rising age profile of school principals. In a context of low levels of principal mobility and high tenure, the leadership trajectory of the average school is established for nearly a decade with each principal replacement. Evidence-based policy making has a strong role to play in getting this right.

  16. Multi-kilobase homozygous targeted gene replacement in human induced pluripotent stem cells.

    Science.gov (United States)

    Byrne, Susan M; Ortiz, Luis; Mali, Prashant; Aach, John; Church, George M

    2015-02-18

    Sequence-specific nucleases such as TALEN and the CRISPR/Cas9 system have so far been used to disrupt, correct or insert transgenes at precise locations in mammalian genomes. We demonstrate efficient 'knock-in' targeted replacement of multi-kilobase genes in human induced pluripotent stem cells (iPSC). Using a model system replacing endogenous human genes with their mouse counterpart, we performed a comprehensive study of targeting vector design parameters for homologous recombination. A 2.7 kilobase (kb) homozygous gene replacement was achieved in up to 11% of iPSC without selection. The optimal homology arm length was around 2 kb, with homology length being especially critical on the arm not adjacent to the cut site. Homologous sequence inside the cut sites was detrimental to targeting efficiency, consistent with a synthesis-dependent strand annealing (SDSA) mechanism. Using two nuclease sites, we observed a high degree of gene excisions and inversions, which sometimes occurred more frequently than indel mutations. While homozygous deletions of 86 kb were achieved with up to 8% frequency, deletion frequencies were not solely a function of nuclease activity and deletion size. Our results analyzing the optimal parameters for targeting vector design will inform future gene targeting efforts involving multi-kilobase gene segments, particularly in human iPSC. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

  17. Fish condensate as effective replacer of fish meal protein in diet for striped snakehead, Channa striata (Bloch).

    Science.gov (United States)

    Wattanakul, Wattana; Wattanakul, Uraiwan; Thongprajukaew, Karun; Muenpo, Chutchawan

    2017-02-01

    The optimal protein replacement of fish meal (FM) by fish condensate (FC) was investigated in striped snakehead, Channa striata (Bloch) (1.78 ± 0.02 g initial weight). The FM-based diet (0FC) was replaced by substituting protein from FC for 100 (100FC), 200 (200FC), 300 (300FC), 400 (400FC), 500 (500FC) or 600 (600FC) g kg -1 of the FM, and a commercial diet (CD) for carnivorous fish was included for comparison. The experiment was conducted indoors under completely randomized design (8 treatments × 3 replications × 60 fish per pond) over a 6-month trial. There were no significant differences in water quality during the experiment. The fish fed with 500FC had superior growth performance and feed utilization. This dietary treatment gave similar levels to all observed specific activities of digestive enzymes as did baseline 0FC. Survival, carcass composition, hematological parameters and liver histopathology were not negatively impacted by this protein replacement level. Economic analysis also supports the use of this by-product as a potent protein replacer in striped snakehead diet. Findings from the current study indicate that a 500 g kg -1 protein replacement of FM by FC is near optimal for striped snakehead, and similar use of it in the aquafeed of other species appears worth further studies.

  18. Hypogonadism and Sex Steroid Replacement Therapy in Girls with Turner Syndrome.

    Science.gov (United States)

    Gawlik, Aneta; Hankus, Magdalena; Such, Kamila; Drosdzol-Cop, Agnieszka; Madej, Paweł; Borkowska, Marzena; Zachurzok, Agnieszka; Malecka-Tendera, Ewa

    2016-12-01

    Turner syndrome is the most common example of hypergonadotropic hypogonadism resulting from gonadal dysgenesis. Most patients present delayed, or even absent, puberty. Premature ovarian failure can be expected even if spontaneous menarche occurs. Laboratory markers of gonadal dysgenesis are well known. The choice of optimal hormone replacement therapy in children and adolescents remains controversial, particularly regarding the age at which therapy should be initiated, and the dose and route of estrogen administration. On the basis of a review of the literature, we present the most acceptable schedule of sex steroid replacement therapy in younger patients with Turner syndrome. Copyright © 2016 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.

  19. An Optimization Model for Expired Drug Recycling Logistics Networks and Government Subsidy Policy Design Based on Tri-level Programming

    OpenAIRE

    Huang, Hui; Li, Yuyu; Huang, Bo; Pi, Xing

    2015-01-01

    In order to recycle and dispose of all people’s expired drugs, the government should design a subsidy policy to stimulate users to return their expired drugs, and drug-stores should take the responsibility of recycling expired drugs, in other words, to be recycling stations. For this purpose it is necessary for the government to select the right recycling stations and treatment stations to optimize the expired drug recycling logistics network and minimize the total costs of recycling and disp...

  20. Monetary policy and dynamic adjustment of corporate investment: A policy transmission channel perspective

    Directory of Open Access Journals (Sweden)

    Qiang Fu

    2015-06-01

    Full Text Available We investigate monetary policy effects on corporate investment adjustment, using a sample of China’s A-share listed firms (2005–2012, under an asymmetic framework and from a monetary policy transmission channel perspective. We find that corporate investment adjustment is faster in expansionary than contractionary monetary policy periods. Monetary policy has a significant effect on adjustment speed through monetary and credit channels. An increase in the growth rate of money supply or credit accelerates adjustment. Both effects are significantly greater during tightening than expansionary periods. The monetary channel has significant asymmetry, whereas the credit channel has none. Leverage moderates the relationship between monetary policy and adjustment, with a greater effect in expansionary periods. This study enriches the corporate investment behavior literature and can help governments develop and optimize macro-control policies.

  1. Seeking an optimal renal replacement therapy for the chronic kidney disease epidemic: the case for on-line hemodiafiltration.

    Science.gov (United States)

    Gatti, Emanuele; Ronco, Claudio

    2011-01-01

    The prevalence of chronic kidney disease (CKD) can be expected to increase dramatically in the foreseeable future, with suggestions that it has already reached epidemic proportions. The inadequate supply of donor organs, aggravated by an aging patient population, necessitates provision of sustainable dialysis treatment modalities. These treatment modalities must not only be of established clinical efficacy and effectiveness, but must simultaneously circumvent any potential treatment disparities due to geographical, social or other concurring factors. Home therapies might represent a partial solution to the complex issue of seeking optimal strategies to cope with the CKD epidemic. However, self-care renal replacement therapy (RRT), such as peritoneal dialysis (PD) and home therapies, can only be applied to a limited portion of the CKD population. Consequently, in preparation for coping with this CKD epidemic, specific large-scale plans need to be made that involve optimization of treatments already in use for the majority of the population requiring RRT, e.g. hemodialysis (HD). Extracorporeal chronic HD relies heavily on technology for its clinical success. Like the choice of the treatment modality and the complete medical approach to CKD patient care, the particular selection of the various components of the extracorporeal circuit has a significant impact on the well-being and survival of the patients. We present a medical-technological assessment of how best to treat vast numbers of dialysis patients under the financial restraints that are predicted to become even more severe as CKD entrenches itself as a more 'permanent epidemic'. A treatment modality is proposed that optimally addresses--and resolves--the debilitating effects of uremia, as well as of key clinical conditions closely linked to it. This treatment modality successfully tackles the issues of patient well-being, efficacy, effectiveness, safety and patient-nursing staff convenience--all in relation to

  2. Remote sensing estimates of stand-replacement fires in Russia, 2002–2011

    International Nuclear Information System (INIS)

    Krylov, Alexander; Potapov, Peter; Loboda, Tatiana; Tyukavina, Alexandra; Turubanova, Svetlana; Hansen, Matthew C; McCarty, Jessica L

    2014-01-01

    The presented study quantifies the proportion of stand-replacement fires in Russian forests through the integrated analysis of Landsat and Moderate Resolution Imaging Spectroradiometer (MODIS) data products. We employed 30 m Landsat Enhanced Thematic Mapper Plus derived tree canopy cover and decadal (2001–2012) forest cover loss (Hansen et al 2013 High-resolution global maps of 21st-century forest cover change Science 342 850–53) to identify forest extent and disturbance. These data were overlaid with 1 km MODIS active fire (earthdata.nasa.gov/data/near-real-time-data/firms) and 500 m regional burned area data (Loboda et al 2007 Regionally adaptable dNBR-based algorithm for burned area mapping from MODIS data Remote Sens. Environ. 109 429–42 and Loboda et al 2011 Mapping burned area in Alaska using MODIS data: a data limitations-driven modification to the regional burned area algorithm Int. J. Wildl. Fire 20 487–96) to differentiate stand-replacement disturbances due to fire versus other causes. Total stand replacement forest fire area within the Russian Federation from 2002 to 2011 was estimated to be 17.6 million ha (Mha). The smallest stand-replacement fire loss occurred in 2004 (0.4 Mha) and the largest annual loss in 2003 (3.3 Mha). Of total burned area within forests, 33.6% resulted in stand-replacement. Light conifer stands comprised 65% of all non-stand-replacement and 79% of all stand-replacement fire in Russia. Stand-replacement area for the study period is estimated to be two times higher than the reported logging area. Results of this analysis can be used with historical fire regime estimations to develop effective fire management policy, increase accuracy of carbon calculations, and improve fire behavior and climate change modeling efforts. (paper)

  3. 'Green' preferences as regulatory policy instrument

    International Nuclear Information System (INIS)

    Brennan, Timothy J.

    2006-01-01

    We examine here the suggestion that if consumers in sufficient numbers are willing to pay the premium to have power generated using low-emission technologies, tax or permit policies become less necessary or stringent. While there are implementation difficulties with this proposal, our purpose is more fundamental: Can economics make sense of using preferences as a regulatory instrument? If 'green' preferences are exogenously given, to what extent can or should they be regarded as a substitute for other policies? Even with 'green' preferences, production and consumption of polluting goods continue to impose social costs not borne in the market. Moreover, if green preferences are regarded as a policy instrument, the 'no policy' baseline would require a problematic specification of counterfactual 'non-green' preferences. Viewing green preferences as a regulatory policy instrument is conceptually sensible if the benchmark for optimal emissions is based on value judgments apart from the preferences consumers happen to have. If so, optimal environmental protection would be defined by reference to ethical theory, or, even less favorably, by prescriptions from policy advocates who give their own preferences great weight while giving those of the public at large (and the costs they bear) very little consideration. (author)

  4. Optimization of radioprotection in the nuclear power, industrial and medical domains

    International Nuclear Information System (INIS)

    Kalifa, G.

    2002-06-01

    These 3. SFRP days are devoted to the optimization of radioprotection in the context of the evolution of the regulation in this domain with the introduction of the ALARA (as low as reasonably achievable) principle in the public health regulations. First of all, the optimization of radioprotection is a principle of action aiming at elaborating a practical organization of risk taking based on the responsibility of the different actors and leading to an individual and collective management of the radiological risk. These days are oriented towards practical applications of this optimization and in a lesser extend towards the general radioprotection policies and the technical aspects, in particular the operational dosimetry: 1 - Alara bases and regulation: bases of radioprotection optimization; optimization and Belgium regulation: the contribution of the Royal by-law from July 20, 2001; status of the French regulation; 2 - Alara policies in the nuclear power domain: maintenance of PWR reactor vessels: exploratory approach of a joint safety and radioprotection control by the nuclear safety authority; implementation of the Alara approach at the CEA: status and perspectives; optimization of activities and Alara project at EdF; the file for the intervention in radioactive environment: an Alara tool; 3 - practical applications and experience feedback: optimization in interventional vascular radiology unit; forecast evaluation and personnel exposures optimization in the experiment hall of the laser integration line at CESTA; a French system of radioprotection experience feedback for radiological incidents; the European Alara network: a growing up dialogue and improvement structure; 4 - Alara policies in the medical and first aid services: dosimetry of radiodiagnosis personnel; integration of the radioactive waste management organization to the elimination files of hospital wastes; optimization of patient's radioprotection: a calculation approach of the specific risk by sex

  5. China's Population Policy at the Crossroads: Social Impacts and Prospects

    OpenAIRE

    Jiang, Quanbao; Li, Shuzhuo; Feldman, Marcus W.

    2013-01-01

    China's total fertility rate fell below replacement level in the 1990s. From the 1970s the fertility rate declined dramatically, mainly as a consequence of the national population policy whose aim has been to limit birth numbers, control population growth and boost economic growth. Having achieved such a low fertility rate, how will China's population policy evolve in the future? This paper first reviews the history of China's population policy since 1970 in terms of three stages: 1970-1979; ...

  6. Filters in topology optimization

    DEFF Research Database (Denmark)

    Bourdin, Blaise

    1999-01-01

    In this article, a modified (``filtered'') version of the minimum compliance topology optimization problem is studied. The direct dependence of the material properties on its pointwise density is replaced by a regularization of the density field using a convolution operator. In this setting...... it is possible to establish the existence of solutions. Moreover, convergence of an approximation by means of finite elements can be obtained. This is illustrated through some numerical experiments. The ``filtering'' technique is also shown to cope with two important numerical problems in topology optimization...

  7. Pavement maintenance optimization model using Markov Decision Processes

    Science.gov (United States)

    Mandiartha, P.; Duffield, C. F.; Razelan, I. S. b. M.; Ismail, A. b. H.

    2017-09-01

    This paper presents an optimization model for selection of pavement maintenance intervention using a theory of Markov Decision Processes (MDP). There are some particular characteristics of the MDP developed in this paper which distinguish it from other similar studies or optimization models intended for pavement maintenance policy development. These unique characteristics include a direct inclusion of constraints into the formulation of MDP, the use of an average cost method of MDP, and the policy development process based on the dual linear programming solution. The limited information or discussions that are available on these matters in terms of stochastic based optimization model in road network management motivates this study. This paper uses a data set acquired from road authorities of state of Victoria, Australia, to test the model and recommends steps in the computation of MDP based stochastic optimization model, leading to the development of optimum pavement maintenance policy.

  8. Optimizing Plutonium stock management

    International Nuclear Information System (INIS)

    Niquil, Y.; Guillot, J.

    1997-01-01

    Plutonium from spent fuel reprocessing is reused in new MOX assemblies. Since plutonium isotopic composition deteriorates with time, it is necessary to optimize plutonium stock management over a long period, to guarantee safe procurement, and contribute to a nuclear fuel cycle policy at the lowest cost. This optimization is provided by the prototype software POMAR

  9. ISASS Policy Statement – Lumbar Artificial Disc

    Science.gov (United States)

    Garcia, Rolando

    2015-01-01

    Purpose The primary goal of this Policy Statement is to educate patients, physicians, medical providers, reviewers, adjustors, case managers, insurers, and all others involved or affected by insurance coverage decisions regarding lumbar disc replacement surgery. Procedures This Policy Statement was developed by a panel of physicians selected by the Board of Directors of ISASS for their expertise and experience with lumbar TDR. The panel's recommendation was entirely based on the best evidence-based scientific research available regarding the safety and effectiveness of lumbar TDR. PMID:25785243

  10. English design policies: how have they fared?

    OpenAIRE

    Matthew Carmona

    2003-01-01

    In the wake of proposals in the 2002 Planning and Compulsory Purchase Bill to replace the current system of development plans with a new generation of planning policy tools, this is an appropriate moment to reconsider the role of design policies within English planning practice. As the era of local plans, structure plans, and unitary development plans (UDPs) comes to a close, the author looks at one part of the remit that development plans aim to address -- design. In doing so, he revisits th...

  11. Policies and Processes for Social Inclusion: Using EquiFrame and EquIPP for Policy Dialogue Comment on "Are Sexual and Reproductive Health Policies Designed for All? Vulnerable Groups in Policy Documents of Four European Countries and Their Involvement in Policy Development".

    Science.gov (United States)

    MacLachlan, Malcolm; Mannan, Hasheem; Huss, Tessy; Munthali, Alister; Amin, Mutamad

    2015-11-16

    The application of EquiFrame in the analysis of sexual and reproductive health policies by Ivanova et al to a new thematic area, their selection of only some of the Core Concepts of human rights in health service provision and the addition of new vulnerable groups relevant to the purpose of their analysis, are all very welcome developments. We also applaud their application of EquiFrame to policies in countries where it has not previously been used, along with their use of interviews with policy-makers to produce a deeper understanding of policy processes. We argue that clear justification for the inclusion of additional, or replacement of some exiting vulnerable groups within EquiFrame should be accompanied by clear definitions of such groups, along with the evidence-base that justifies their classification as a vulnerable or marginalised group. To illustrate the versatility of EquiFrame, we summarise a range of ways in which it has been used across a number of regions; including a brief Case Study of its use to develop the National Health Policy of Malawi. While EquiFrame focuses on policy content, we preview a new policy analysis tool - Equity and Inclusion in Policy Processes (EquIPP) - which assesses the extent of equity and inclusion in broader policy processes. Together, EquiFrame and EquIPP can be used to help governments and civil society ensure that policies are addressing the much stronger emphasis on social inclusion, now apparent in the Sustainable Development Goals (SDGs). © 2016 by Kerman University of Medical Sciences.

  12. How Intense Policy Demanders Shape Postreform Politics: Evidence from the Affordable Care Act.

    Science.gov (United States)

    Rocco, Philip; Haeder, Simon F

    2018-04-01

    The implementation of the Affordable Care Act (ACA) has been a politically volatile process. The ACA's institutional design and delayed feedback effects created a window of opportunity for its partisan opponents to launch challenges at both the federal and state level. Yet as recent research suggests, postreform politics depends on more than policy feedback alone; rather, it is shaped by the partisan and interest-group environment. We argue that "intense policy demanders" played an important role in defining the policy alternatives that comprised congressional Republicans' efforts to repeal and replace the ACA. To test this argument, we drew on an original data set of bill introductions in the House of Representatives between 2011 and 2016. Our analysis suggests that business contributions and political ideology affected the likelihood that House Republicans would introduce measures repealing significant portions of the ACA. A secondary analysis shows that intense policy demanders also shaped the vote on House Republicans' initial ACA replacement plan. These findings highlight the role intense policy demanders can play in shaping the postreform political agenda. Copyright © 2018 by Duke University Press.

  13. Conformationally constrained farnesoid X receptor (FXR) agonists: alternative replacements of the stilbene.

    Science.gov (United States)

    Akwabi-Ameyaw, Adwoa; Caravella, Justin A; Chen, Lihong; Creech, Katrina L; Deaton, David N; Madauss, Kevin P; Marr, Harry B; Miller, Aaron B; Navas, Frank; Parks, Derek J; Spearing, Paul K; Todd, Dan; Williams, Shawn P; Wisely, G Bruce

    2011-10-15

    To further explore the optimum placement of the acid moiety in conformationally constrained analogs of GW 4064 1a, a series of stilbene replacements were prepared. The benzothiophene 1f and the indole 1g display the optimal orientation of the carboxylate for enhanced FXR agonist potency. Copyright © 2011 Elsevier Ltd. All rights reserved.

  14. Dislocation of total hip replacement in patients with fractures of the femoral neck.

    Science.gov (United States)

    Enocson, Anders; Hedbeck, Carl-Johan; Tidermark, Jan; Pettersson, Hans; Ponzer, Sari; Lapidus, Lasse J

    2009-04-01

    Total hip replacement is increasingly used in active, relatively healthy elderly patients with fractures of the femoral neck. Dislocation of the prosthesis is a severe complication, and there is still controversy regarding the optimal surgical approach and its influence on stability. We analyzed factors influencing the stability of the total hip replacement, paying special attention to the surgical approach. We included 713 consecutive hips in a series of 698 patients (573 females) who had undergone a primary total hip replacement (n = 311) for a non-pathological, displaced femoral neck fracture (Garden III or IV) or a secondary total hip replacement (n = 402) due to a fracture-healing complication after a femoral neck fracture. We used Cox regression to evaluate factors associated with prosthetic dislocation after the operation. Age, sex, indication for surgery, the surgeon's experience, femoral head size, and surgical approach were tested as independent factors in the model. The overall dislocation rate was 6%. The anterolateral surgical approach was associated with a lower risk of dislocation than the posterolateral approach with or without posterior repair (2%, 12%, and 14%, respectively (p replacement in patients with femoral neck fractures.

  15. Effect of preoperative education of patients before hip or knee replacement surgery: A systematic review

    DEFF Research Database (Denmark)

    Aydin, Dogu; Klit, Jakob; Husted, Henrik

    2013-01-01

    Background Total hip (THA) and knee arthroplasty (TKA) are standard procedures for treatment of end stage osteoarthritis, and much is done to optimize results. It is usually hypothesized that education of patients before surgery reduces anxiety, secures more realistic patient expectations...... and enhances postoperative outcomes. Objectives To determine whether results reported in the literature proves an effect of preoperative education on postoperative outcomes in replacement surgery patients regarding anxiety, pain, length of hospital stay, patient satisfaction, postoperative complications...... visual) given by health professionals to patients were included. Results Seven studies involving 677 participants met the inclusion criteria. Two studies involved patients undergoing THA replacement, while five studies involved patients undergoing both THA and TKA replacement surgery. Mean number...

  16. Defining line replaceable units

    NARCIS (Netherlands)

    Parada Puig, J. E.; Basten, R. J I

    2015-01-01

    Defective capital assets may be quickly restored to their operational condition by replacing the item that has failed. The item that is replaced is called the Line Replaceable Unit (LRU), and the so-called LRU definition problem is the problem of deciding on which item to replace upon each type of

  17. Exponential Lower Bounds For Policy Iteration

    OpenAIRE

    Fearnley, John

    2010-01-01

    We study policy iteration for infinite-horizon Markov decision processes. It has recently been shown policy iteration style algorithms have exponential lower bounds in a two player game setting. We extend these lower bounds to Markov decision processes with the total reward and average-reward optimality criteria.

  18. Repair and replacement of reactor internals for plant life extension

    International Nuclear Information System (INIS)

    Graae, T.

    1998-01-01

    Recent experience from early Swedish BWRs corroborate that all components in a nuclear power plant can be repaired or replaced with new ones. Oskarshamn 1 has gone through a thorough refurbishment project. A number of internals were repaired or replaced including the core shroud support which was welded to the bottom of the reactor pressure vessel. The project verifies that it is fully possible to carry out complicated inspection and repair work inside a nuclear pressure vessel which has been in operation for more than 20 years. Along with increased capacity factor, operating nuclear power plants get the financial conditions needed for extensive repair and modernization projects. Large power output leads to short pay-back times for the investments. The FENIX project at Oskarshamn 1 is such a project. There are utilities whose policy is to keep their plants in as-new condition for an unlimited length of time. (orig.)

  19. Confronting hip resurfacing and big femoral head replacement gait analysis

    Directory of Open Access Journals (Sweden)

    Panagiotis K. Karampinas

    2014-03-01

    Full Text Available Improved hip kinematics and bone preservation have been reported after resurfacing total hip replacement (THRS. On the other hand, hip kinematics with standard total hip replacement (THR is optimized with large diameter femoral heads (BFH-THR. The purpose of this study is to evaluate the functional outcomes of THRS and BFH-THR and correlate these results to bone preservation or the large femoral heads. Thirty-one patients were included in the study. Gait speed, postural balance, proprioception and overall performance. Our results demonstrated a non-statistically significant improvement in gait, postural balance and proprioception in the THRS confronting to BFH-THR group. THRS provide identical outcomes to traditional BFH-THR. The THRS choice as bone preserving procedure in younger patients is still to be evaluated.

  20. Biocapacity optimization in regional planning

    Science.gov (United States)

    Guo, Jianjun; Yue, Dongxia; Li, Kai; Hui, Cang

    2017-01-01

    Ecological overshoot has been accelerating across the globe. Optimizing biocapacity has become a key to resolve the overshoot of ecological demand in regional sustainable development. However, most literature has focused on reducing ecological footprint but ignores the potential of spatial optimization of biocapacity through regional planning of land use. Here we develop a spatial probability model and present four scenarios for optimizing biocapacity of a river basin in Northwest China. The potential of enhanced biocapacity and its effects on ecological overshoot and water consumption in the region were explored. Two scenarios with no restrictions on croplands and water use reduced the overshoot by 29 to 53%, and another two scenarios which do not allow croplands and water use to increase worsened the overshoot by 11 to 15%. More spatially flexible transition rules of land use led to higher magnitude of change after optimization. However, biocapacity optimization required a large amount of additional water resources, casting considerable pressure on the already water-scarce socio-ecological system. Our results highlight the potential for policy makers to manage/optimize regional land use which addresses ecological overshoot. Investigation on the feasibility of such spatial optimization complies with the forward-looking policies for sustainable development and deserves further attention.

  1. Shipment Consolidation Policy under Uncertainty of Customer Order for Sustainable Supply Chain Management

    Directory of Open Access Journals (Sweden)

    Kyunghoon Kang

    2017-09-01

    Full Text Available With increasing concern over the environment, shipment consolidation has become one of a main initiative to reduce CO2 emissions and transportation cost among the logistics service providers. Increased delivery time caused by shipment consolidation may lead to customer’s order cancellation. Thus, order cancellation should be considered as a factor in order uncertainty to determine the optimal shipment consolidation policy. We develop mathematical models for quantity-based and time-based policies and obtain optimality properties for the models. Efficient algorithms using optimal properties are provided to compute the optimal parameters for ordering and shipment decisions. To compare the performances of the quantity-based policy with the time-based policy, extensive numerical experiments are conducted, and the total cost is compared.

  2. Replenishment policies for Empty Containers in an Inland Multi-depot System

    DEFF Research Database (Denmark)

    Dang, Quang-Vinh; Nielsen, Izabela Ewa; Yun, W. Y.

    2013-01-01

    . The objective is to obtain the optimal policy in order to minimize the expected total cost consisting of: inventory holding, overseas positioning, inland positioning and leasing costs. A simulation-based genetic algorithm is developed to find near-optimal policies. Numerical examples are given to demonstrate...

  3. SPES, Fuel Cycle Optimization for LWR

    International Nuclear Information System (INIS)

    1973-01-01

    1 - Nature of physical problem solved: Determination of optimal fuel cycle at equilibrium for a light water reactor taking into account batch size, fuel enrichment, de-rating, shutdown time, cost of replacement energy. 2 - Method of solution: Iterative method

  4. How adequate policies can push renewables

    International Nuclear Information System (INIS)

    Goldemberg, J.; Coelho, S.T.; Lucon, Oswaldo

    2004-01-01

    The growing interest in the establishment of a minimum share of renewable sources in the world energy matrix, after the Johannesburg's World Summit for Sustainable Development (WSSD), has raised the question about the means for such new technologies to compete with the traditional ones. The Brazilian experience in the last 25 years with ethanol as a replacement for gasoline can illustrate this possibility. Moreover, recent policies introduced by the Federal government for a minimum share of new renewable sources - wind, modern biomass and small hydro - in the Brazilian electricity matrix reinforces the country's commitment to utilize adequate policies for achieving sustainable development

  5. Optimizing pricing and ordering strategies in a three-level supply chain under return policy

    Science.gov (United States)

    Noori-daryan, Mahsa; Taleizadeh, Ata Allah

    2018-03-01

    This paper develops an economic production quantity model in a three-echelon supply chain composing of a supplier, a manufacturer and a wholesaler under two scenarios. As the first scenario, we consider a return contract between the outside supplier and the supplier and also between the manufacturer and the wholesaler, but in the second one, the return policy between the manufacturer and the wholesaler is not applied. Here, it is assumed that shortage is permitted and demand is price-sensitive. The principal goal of the research is to maximize the total profit of the chain by optimizing the order quantity of the supplier and the selling prices of the manufacturer and the wholesaler. Nash-equilibrium approach is considered between the chain members. In the end, a numerical example is presented to clarify the applicability of the introduced model and compare the profit of the chain under two scenarios.

  6. In Search for a Pronatalist Population Policy for Turkey

    Directory of Open Access Journals (Sweden)

    Yusuf YÜKSEL

    2015-06-01

    Full Text Available Turkey has witnessed high fertility rates and low mortality rates until 2000s. Young population structure, need for infrastructure for growing population and reproductive health issues were always on the agenda of policy makers throughout the history of Turkey. After the decline in total fertility rate below replacement level, vibrant discussions and search for a new policy framework began to be visible in the recent years. After the establishment of new Republic in Turkey in 1923 pronatalist policies were active until the beginning 1960s. After the First Development Plan in 1962, policy shift was towards an antinatalist direction until 2000. After a short period between 2000 and 2012 which can not be put any category in terms of fertility policy government clearly declared its position favouring pronatalist policies and mobilised bureaucracy for developing new policy options. This paper summarizes the fertility policies and demographic transition of Turkey and evaluates possible policy options

  7. A sow replacement model using Bayesian updating in a three-level hierarchic Markov process. I. Biological model

    DEFF Research Database (Denmark)

    Kristensen, Anders Ringgaard; Søllested, Thomas Algot

    2004-01-01

    that really uses all these methodological improvements. In this paper, the biological model describing the performance and feed intake of sows is presented. In particular, estimation of herd specific parameters is emphasized. The optimization model is described in a subsequent paper......Several replacement models have been presented in literature. In other applicational areas like dairy cow replacement, various methodological improvements like hierarchical Markov processes and Bayesian updating have been implemented, but not in sow models. Furthermore, there are methodological...... improvements like multi-level hierarchical Markov processes with decisions on multiple time scales, efficient methods for parameter estimations at herd level and standard software that has been hardly implemented at all in any replacement model. The aim of this study is to present a sow replacement model...

  8. The State Fiscal Policy: Determinants and Optimization of Financial Flows

    Directory of Open Access Journals (Sweden)

    Sitash Tetiana D.

    2017-03-01

    Full Text Available The article outlines the determinants of the state fiscal policy at the present stage of global transformations. Using the principles of financial science it is determined that regulation of financial flows within the fiscal sphere, namely centralization and redistribution of the GDP, which results in the regulation of the financial capacity of economic agents, is of importance. It is emphasized that the urgent measure for improving the tax model is re-considering the provision of fiscal incentives, which are used to stimulate the accumulation of capital, investment activity, innovation, increase of the competitiveness of national products, expansion of exports, increase of the level of the population employment. The necessity of applying the instruments of fiscal regulation of financial flows, which should take place on the basis of institutional economics emphasizing the analysis of institutional changes, the evolution of institutions and their impact on the behavior of participants of economic relations. At the same time it is determined that the maximum effect of fiscal regulation of financial flows is ensured when application of fiscal instruments is aimed not only at achieving the target values of parameters of financial flows but at overcoming institutional deformations as well. It is determined that the optimal movement of financial flows enables creating favorable conditions for development and maintenance of financial balance in the society and achievement of the necessary level of competitiveness of the national economy.

  9. Social Preferences and Labor Market Policy

    DEFF Research Database (Denmark)

    Filges, Trine; Kennes, John; Larsen, Birthe

    2006-01-01

    We find that the main featues of labor policy across OECD countries can be explained by a simple general equilibrium search model with risk neutral agents and a government that chooses policy to maximize a social welfare function. In equilibrum, policies are chosen to optimal redistribute income....... The model also explains why countries that appear to pursue equity spend more on both active and passive labor market programs....

  10. New staff contract policy

    CERN Document Server

    HR Department

    2006-01-01

    Following discussion at TREF and on the recommendation of the Finance Committee, Council approved a new staff contract policy, which became effective on 1 January 2006. Its application is covered by a new Administrative Circular No. 2 (Rev. 3) 'Recruitment, appointment and possible developments regarding the contractual position of staff members'. The revised circular replaces the previous Circulars No. 9 (Rev. 3) 'Staff contracts' and No. 2 (Rev. 2) 'Guidelines and procedures concerning recruitment and probation period for staff members'. The main features of the new contract policy are as follows: The new policy provides chances for long-term employment for all staff recruits staying for four years without distinguishing between those assigned to long-term or short-term activities when joining CERN. In addition, it presents a number of simplifications for the award of ICs. There are henceforth only 2 types of contract: Limited Duration (LD) contracts for all recruitment and Indefinite Contracts (IC) for...

  11. OPTIMAL IMPROVEMENT IN FUNCTION AFTER TOTAL HIP AND KNEE REPLACEMENT: HOW DEEP DO YOU KNOW YOUR PATIENT’S MIND?

    Science.gov (United States)

    De Caro, M F; Vicenti, G; Abate, A; Picca, G; Leoncini, V; Lomuscio, M; Casalino, A; Solarino, G; Moretti, B

    2015-01-01

    Osteoarthritis (OA) of the hip and knee causes pain and loss of joint mobility, leading to limitations in physical function. When conservative treatment fails total hip and knee replacement is a cost-effective surgical option. Patients have high expectations regarding functional outcome after these procedures. If such expectations are not met, they may still be dissatisfied with the outcome of a technically successful procedure. Recently, numerous studies reported that psychological factors can influence the outcome of total knee replacement (tkr) and total hip artrhoplasty with total hip replacement (thr). We conducted a prospective study on a consecutive sample of 280 patients affected by hip or knee OA who underwent total joint replacement. At patients’ admission, Harris Hip Score (HHS) and Knee Society Score (KSS) were used to assess pain and function. Furthermore, SF-36, Mini-Mental Status Examination (MMSE), Symptom Checklist-90-R (SCL-90-R), Coping Orientation to Problems Experienced (BRIEF-COPE) and the Amsterdam Preoperative Anxiety and Information Scale (APAIS) were administered. Patients had clinical and radio graphical follow up at 1, 3 and 6 months post-operatively. The HHS and KSS values before surgery showed a linear correlation with both SCL-90-R and MMSE. None of the investigated variables influenced post-operative HHS and KSS scores; however, the improvement of functional scores resulted conditioned by SCL-90-R values, VAS score, schooling and MMSE. Psychological factors and mental status in primary total hip and knee replacement can affect outcome and patient satisfaction. Strategies focused on identification and facing of these conditions must be considered to improve outcome of total replacement.

  12. COGEMA's employment and training policy for its foreign subsidiaries

    International Nuclear Information System (INIS)

    Hamani, A.

    2002-01-01

    COGEMA has actively pursued a policy of employing country nationals for its foreign subsidiaries in Niger, Gabon, Canada and Kazakhstan. The process of replacing foreign staff by nationals in Niger is first described, detailing the personnel management objectives and procedures, the main difficulties encountered, the current situation and the lessons to take from this experience. COGEMA's policies and ways applied in other countries to increase the proportions of nationals are then presented. (author)

  13. Development of explicit criteria for prioritization of hip and knee replacement.

    Science.gov (United States)

    Escobar, Antonio; Quintana, José M; Bilbao, Amaia; Ibañez, Berta; Arenaza, Juan C; Gutiérrez, Luis; Azkárate, Jesús; Güenaga, Jose I; Vidaurreta, Ignacio

    2007-06-01

    Among the problems to the publicly funded national health services are the waiting lists. Patients who need elective surgery generally have long waiting times before treatment. We aimed to develop a new prioritization tool for primary hip and knee replacement. Criteria were developed using a modified Delphi panel process. We convened a panel of nine members who scored the scenarios created by the research team and by patient focus groups. We studied the level of agreement among the panelists and the contribution of the variables to the ratings of the panel using linear and logistic regression models. The priority scores of the variables and their levels were synthesized using the optimal scaling and standard linear regression methods. Seven variables, pain on motion, walking functional limitations, abnormal findings on physical examination, pain at rest, other functional limitations, social role, and other pathologies that could improve with joint replacement, were considered to create the different scenarios. The panel scored 192 scenarios. The disagreement among the panelists was very low (1%) with an intra-class correlation coefficient of 0.72. Of the 192 scenarios, 45.8% were scored as urgent, 35.4% as preferred and 18.8% as ordinary. The variables that contributed most to the scores were pain on motion and walking functional limitations. When optimal scaling and regression techniques were applied, similar results were obtained. This tool can evaluate and prioritize patients on a waiting list for hip or knee replacement. We also provide a simple and easy way to use an algorithm to estimate the treatment priority for individual patients.

  14. Optimal Aquifer Pumping Policy to Reduce Contaminant Concentration

    Directory of Open Access Journals (Sweden)

    Ali Abaei

    2012-01-01

    Full Text Available Different sources of ground water contamination lead to non-uniform distribution of contaminant concentration in the aquifer. If elimination or containment of pollution sources was not possible, the distribution of contaminant concentrations could be modified in order to eliminate peak concentrations using optimal water pumping discharge plan. In the present investigation Visual MODFLOW model was used to simulate the flow and transport in a hypothetic aquifer. Genetic Algorithm (GA also was applied to optimize the location and pumping flow rate of wells in order to reduce contaminants peak concentrations in aquifer.

  15. Integrated dynamic policy management methodology and system for strategic environmental assessment of golf course installation policy in Taiwan

    International Nuclear Information System (INIS)

    Chen, Ching-Ho; Liu, Wei-Lin; Liaw, Shu-Liang

    2011-01-01

    Strategic environmental assessment (SEA) focuses primarily on assessing how policies, plans, and programs (PPPs) influence the sustainability of the involved regions. However, the processes of assessing policies and developing management strategies for pollution load and resource use are usually separate in the current SEA system. This study developed a policy management methodology to overcome the defects generated during the above processes. This work first devised a dynamic management framework using the methods of systems thinking, system dynamics, and Managing for Results (MFRs). Furthermore, a driving force-pressure-state-impact-response (DPSIR) indicator system was developed. The golf course installation policy was applied as a case study. Taiwan, counties of Taiwan, and the golf courses within those individual counties were identified as a system, subsystems, and objects, respectively. This study identified an object-linked double-layer framework with multi-stage-option to simultaneously to quantify golf courses in each subsystem and determine ratios of abatement and allocation for pollution load and resource use of each golf course. The DPSIR indicator values for each item of each golf course in each subsystem are calculated based on the options taken in the two decision layers. The summation of indicator values for all items of all golf courses in all subsystems according to various options is defined as the sustainability value of the policy. An optimization model and a system (IDPMS) were developed to obtain the greatest sustainability value of the policy, while golf course quantity, human activity intensity, total quantities of pollution load and resource use are simultaneously obtained. The solution method based on enumeration of multiple bounds for objectives and constraints (EMBOC) was developed for the problem with 1.95 x 10 128 combinations of possible options to solve the optimal solution in ten minutes using a personal computer with 3.0 GHz CPU

  16. Transcatheter aortic valve replacement

    Science.gov (United States)

    ... gov/ency/article/007684.htm Transcatheter aortic valve replacement To use the sharing features on this page, please enable JavaScript. Transcatheter aortic valve replacement (TAVR) is surgery to replace the aortic valve. ...

  17. Optimal allocation of energy sources for sustainable development in South Korea: Focus on the electric power generation industry

    International Nuclear Information System (INIS)

    Ahn, Joongha; Woo, JongRoul; Lee, Jongsu

    2015-01-01

    National energy planning has become increasingly complex owing to a pressing need to incorporate sustainability considerations. In this context, we applied least-cost and cost-risk optimization models to allocate energy sources for sustainable development in the Korean electric power generation industry. The least-cost model determined an electricity generation mix from 2012 to 2030 that incurs minimum generation cost to meet electricity demand. The cost-risk model determined electricity generation mixes in 2030 considering the risks associated with each energy source in order to lessen external risks. In deriving these optimal electricity generation mixes, we considered both conventional and renewable energy sources in conjunction with physical and policy constraints that realistically reflect Korean circumstances. Moreover, we accounted for CO 2 and external costs within the electricity generation costs for each energy source. For sustainable development in Korea, we conclude that a portion of the coal and gas in the electricity generation mix must be substituted with nuclear and renewable energy. Furthermore, we found that least-cost allocation is sub-optimal from cost-risk perspective and that it limits the adoption of renewables. Finally, we also discuss the implications of decisions taken by the Korean government regarding the electricity generation mix for next-generation energy planning to achieve sustainability. - Highlights: • Optimal least-cost/cost-risk energy mix for sustainable development in Korea. • We account for CO 2 and external costs of generation from each energy source. • Externalities and physical/policy constraints in Korea produce realistic energy mix. • Nuclear and renewables should replace coal and gas for sustainability in Korea. • Least-cost approach limits uptake of renewables and produces high-risk energy mix

  18. Beta-Cell Replacement: Pancreas and Islet Cell Transplantation.

    Science.gov (United States)

    Niclauss, Nadja; Meier, Raphael; Bédat, Benoît; Berishvili, Ekaterine; Berney, Thierry

    2016-01-01

    Pancreas and islet transplantation are 2 types of beta-cell replacement therapies for type 1 diabetes mellitus. Since 1966, when pancreas transplantation was first performed, it has evolved to become a highly efficient procedure with high success rates, thanks to advances in surgical technique and immunosuppression. Pancreas transplantation is mostly performed as simultaneous pancreas-kidney transplantation in patients with end-stage nephropathy secondary to diabetes. In spite of its efficiency, pancreas transplantation is still a major surgical procedure burdened by high morbidity, which called for the development of less invasive and hazardous ways of replacing beta-cell function in the past. Islet transplantation was developed in the 1970s as a minimally invasive procedure with initially poor outcomes. However, since the report of the 'Edmonton protocol' in 2000, the functional results of islet transplantation have substantially and constantly improved and are about to match those of whole pancreas transplantation. Islet transplantation is primarily performed alone in nonuremic patients with severe hypoglycemia. Both pancreas transplantation and islet transplantation are able to abolish hypoglycemia and to prevent or slow down the development of secondary complications of diabetes. Pancreas transplantation and islet transplantation should be seen as two complementary, rather than competing, therapeutic approaches for beta-cell replacement that are able to optimize organ donor use and patient care. © 2016 S. Karger AG, Basel.

  19. Replacement of heavy components of the Main Primary System (MPS). Recent innovations made by Framatome ANP

    International Nuclear Information System (INIS)

    Chanussot, J.M.; Thevenet, R.

    2006-01-01

    The replacement of heavy components is the result of widespread stress corrosion of Inconel 600 (and alloys 82/182) in the primary system. Following the corrosion of steam generator tubes, which led to the first steam generator replacement (SGR) operations, work has begun on reactor vessel head replacements (RVHR) and pressurizer replacements, pending treatment of the dissimilar butt welds (DBW). The replacement of sections of the Main Primary System is one way of optimizing plant lifetime besides preventing stress corrosion in primary components and combating phenomena as thermal fatigue or certain metallurgical weaknesses. The increase in the number of major operations carried out in the reactor building on PWR and BWR reactor geometries has called for major technical innovations. AREVA, has over the past twenty years carried out more than forty SGRs throughout the world, including the supply of 115 steam generators of all types. This equates to over 60% of all SGR operations performed in Europe and the USA. Today, most SGR operations are performed in the USA, though some still continue in Europe and Asia. Operations have been planned until 2015. The first RVHR operations were carried out in France in 1993, and have been widespread in Europe since 1996 (Spain and Belgium), and in the USA since 2002 (Davis Besse). Since 1993 AREVA, through its subsidiaries Framatome ANP, Jeumont SA and SGT, has performed 72 RVHRs, i.e. most of those carried out in Europe and the USA. Today, RVHR operations take place throughout the world and have been planned until 2014. The first pressurizer replacement took place in the fall of 2005 in Saint Lucie, USA. Others are to follow (Fort Calhoun, Millestone). A significant number of partial or complete pressurizer replacements are now being scheduled. Special focus must be given to this new operation, as a decision is required between the following types of replacements, taking into account the number of pressurizer heaters and the

  20. A linear programming model to optimize diets in environmental policy scenarios.

    Science.gov (United States)

    Moraes, L E; Wilen, J E; Robinson, P H; Fadel, J G

    2012-03-01

    The objective was to develop a linear programming model to formulate diets for dairy cattle when environmental policies are present and to examine effects of these policies on diet formulation and dairy cattle nitrogen and mineral excretions as well as methane emissions. The model was developed as a minimum cost diet model. Two types of environmental policies were examined: a tax and a constraint on methane emissions. A tax was incorporated to simulate a greenhouse gas emissions tax policy, and prices of carbon credits in the current carbon markets were attributed to the methane production variable. Three independent runs were made, using carbon dioxide equivalent prices of $5, $17, and $250/t. A constraint was incorporated into the model to simulate the second type of environmental policy, reducing methane emissions by predetermined amounts. The linear programming formulation of this second alternative enabled the calculation of marginal costs of reducing methane emissions. Methane emission and manure production by dairy cows were calculated according to published equations, and nitrogen and mineral excretions were calculated by mass conservation laws. Results were compared with respect to the values generated by a base least-cost model. Current prices of the carbon credit market did not appear onerous enough to have a substantive incentive effect in reducing methane emissions and altering diet costs of our hypothetical dairy herd. However, when emissions of methane were assumed to be reduced by 5, 10, and 13.5% from the base model, total diet costs increased by 5, 19.1, and 48.5%, respectively. Either these increased costs would be passed onto the consumer or dairy producers would go out of business. Nitrogen and potassium excretions were increased by 16.5 and 16.7% with a 13.5% reduction in methane emissions from the base model. Imposing methane restrictions would further increase the demand for grains and other human-edible crops, which is not a progressive