Capacity Savings Research Articles

Capacity management of nursing staff as a vehicle for organizational improvement

BackgroundCapacity management systems create insight into required resources like staff and equipment. For inpatient hospital care, capacity management requires information on beds and nursing staff capacity, on a daily as well as annual basis. This paper presents a comprehensive capacity model that gives insight into required nursing staff capacity and opportunities to improve capacity utilization on a ward level.MethodsA capacity model was developed to calculate required nursing staff capacity. The model used historical bed utilization, nurse-patient ratios, and parameters concerning contract hours to calculate beds and nursing staff needed per shift and the number of nurses needed on an annual basis in a ward. The model was applied to three different capacity management problems on three separate groups of hospital wards. The problems entailed operational, tactical, and strategic management issues: optimizing working processes on pediatric wards, predicting the consequences of reducing length of stay on nursing staff required on a cardiology ward, and calculating the nursing staff consequences of merging two internal medicine wards.ResultsIt was possible to build a model based on easily available data that calculate the nursing staff capacity needed daily and annually and that accommodate organizational improvements. Organizational improvement processes were initiated in three different groups of wards. For two pediatric wards, the most important improvements were found to be improving working processes so that the agreed nurse-patient ratios could be attained. In the second case, for a cardiology ward, what-if analyses with the model showed that workload could be substantially lowered by reducing length of stay. The third case demonstrated the possible savings in capacity that could be achieved by merging two small internal medicine wards.ConclusionA comprehensive capacity model was developed and successfully applied to support capacity decisions on operational, tactical, and strategic levels. It appeared to be a useful tool for supporting discussions between wards and hospital management by giving objective and quantitative insight into staff and bed requirements. Moreover, the model was applied to initiate organizational improvements, which resulted in more efficient capacity utilization.

Resilience design in all-optical ultralong-haul networks

Feature Issue on High Availability in Optical NetworksAfter many years of research and industry efforts, ultralong-haul (ULH) technologies for DWDM transport are maturing, and carriers are deploying them for high capacity and capital savings. Unlike opaque optical networks, it is still uncertain how best to restore an all-optical ULH network after failure. This paper focuses on this issue and proposes a standby restoration scheme and its variants with different restoration speed and associated restoration cost. Our observations suggest that the proposed hot standby scheme would yield both faster restoration and cost efficiencies compared with other schemes.

Efficiency and quality of service issues in MPLS transport for the UMTS access network

Multiprotocol Label Switching (MPLS) offers a simple and flexible transport solution for multiservice networks, and many operators are currently using or considering the use of an MPLS backbone. In UMTS networks, MPLS can be used both in the access part (i.e. the links that provide connectivity to each base station) and in the core. However, the efficient transport of short voice and data packets in the UMTS access network requires multiplexing and segmentation functions not provided by MPLS. This paper investigates the use of ATM Adaptation Layer 2 (AAL2) over MPLS to perform both functions. The efficiency of AAL2/MPLS is analyzed for different traffic types and compared with other transport options. The results indicate that significant capacity savings can be obtained with this solution.

Quantifying trade-offs in resource allocation for VPNs

Virtual Private Networks (VPNs) feature notable characteristics in structure and traffic patterns that allow for efficient resource allocation. A strategy that exploits the underlying characteristics of a VPN can result in significant capacity savings to the service provider.There are a number of admission control and bandwidth provisioning strategies to choose from. We examine trade-offs in design choices in the context of distinctive characteristics of VPNs. We examine the value of signaling-based mechanisms, traffic matrix information and structural characteristics of VPNs in the way they impact resource utilization and service quality. We arrive at important conclusions which could have an impact on the way VPNs are architected. We show that the structure of VPNs profoundly influences achievable resource utilization gains with various admission control and provisioning schemes.

Benefits of traffic engineering using QoS routing schemes and network controls

We demonstrate the benefits of traffic engineering by studying three realistic network models derived from an actual service provider network. We evaluate traffic engineering in the presence of QoS-based routing schemes compared with Destination-Based Routing, the default routing behavior for the Internet. We also simulate prioritization of important traffic flows by implementing priority in one or more of the path caching, path ordering, and actual route selection phases of the constraint-based routing framework. We observe that traffic engineering can provide 20–50% network capacity savings. We also observe that prioritization in more than one phase of constraint-based routing can provide even more significant benefits.

Survivable WDM mesh networks

In a wavelength-division-multiplexing (WDM) optical network, the failure of network elements (e.g., fiber links and cross connects) may cause the failure of several optical channels, thereby leading to large data losses. This study examines different approaches to protect a mesh-based WDM optical network from such failures. These approaches are based on two survivability paradigms: 1) path protection/restoration and 2) link protection/restoration. The study examines the wavelength capacity requirements, and routing and wavelength assignment of primary and backup paths for path and link protection and proposes distributed protocols for path and link restoration. The study also examines the protection-switching time and the restoration time for each of these schemes, and the susceptibility of these schemes to multiple link failures. The numerical results obtained for a representative network topology with random traffic demands demonstrate that there is a tradeoff between the capacity utilization and the susceptibility to multiple link failures. We find that, on one hand, path protection provides significant capacity savings over link protection, and shared protection provides significant savings over dedicated protection; while on the other hand, path protection is more susceptible to multiple link failures than link protection, and shared protection is more susceptible to multiple link failures than dedicated protection. We formulate a model of protection-switching times for the different protection schemes based on a fully distributed control network. We propose distributed control protocols for path and link restoration. Numerical results obtained by simulating these protocols indicate that, for a representative network topology, path restoration has a better restoration efficiency than link restoration, and link restoration has a faster restoration time compared with path restoration.

Public Benefits Charges to Fund Resource Acquisition Programs: An Orwellian Tale

It’s time for less Orwellian double-speak and more straight talk. We need to be sure that claims of avoided energy and capacity savings are true savings—not merely paper “negawatts” or pure wind. We shouldn’t seek the accomplishment of good social objectives through costly programs, bureaucratic administration, a central planning approach that ignores market incentives, high rebates, and cross-subsidies.

Implications of proxy caching for provisioning networks and servers

In this paper, we examine the potential benefits of Web proxy caches in improving the effective capacity of servers and networks. Since networks and servers are typically provisioned based on a high percentile of the load, we focus on the effects of proxy caching on the tail of the load distribution. We find that, unlike their substantial impact on the average load, proxies have a diminished impact on the tail of the load distribution. The exact reduction in the tail and the corresponding capacity savings depend on the nature of the workload and the percentile of the load distribution chosen for provisioning networks and servers-the higher the percentile, the smaller the savings. For workloads considered in this study, compared with over a 50% reduction in the average load, the savings in network and server capacity was only 20%-35% for the 99th percentile of the load distribution. We also find that while proxies can be somewhat useful in smoothing out some of the burstiness in Web workloads; the resulting workload continues, however, to exhibit substantial burstiness and a heavy-tailed nature. We identify one-time requests for large objects to be the limiting factor that diminishes the impact of proxies on the tail of load distribution. We conclude that, while proxies are immensely useful to users due to the reduction in the average response time, they are less effective in improving the capacities of networks and servers.

Wavelength-assignment algorithms for service and restoration in wavelength-division-multiplexing rings

We consider off-line capacity assignment in wavelength-routed ring networks with path restoration under arbitrary traffic patterns. We present service and restoration wavelength-assignment (WA) algorithms under shortest-path routing and analyze their performance in terms of the wavelength requirement. We obtain bounds to the wavelength requirement, using a routing-independent traffic parameter, and we show that both the service wavelength requirement and the total wavelength requirement under these algorithms lie within a factor of 2 of the optimal that can be achieved by any routing and WA algorithm. These results are among the few analytical results regarding the wavelength requirement in rings without wavelength conversion. We also propose vertex-coloring-based WA algorithms and demonstrate their efficiency through performance bounds and simulations. Results also show that knowledge of which link failed provides little capacity savings, and hence our algorithm with failure-independent restoration WA offers an attractive solution to reduce the fault-monitoring costs and the restoration signaling complexity.

Environmental Implications and Potential of International High-Voltage Connections

This paper reviews the potential of international High-Voltage connections and their impact and implications on the environment. It considers the proposed North African Super-grid, ways of creating connections in East Asia, HighVoltage connections in Eastern Europe, together with emissions from different types of power plant, and aspects which are considered in system interconnection feasibility studies. A case study highlighting environmental issues and High-Voltage interconnections considering electromagnetic fields, greenhouse gas emissions, rare and endangered species, and public participation programs in Quebec is summarized. First, the advantages of power system interconnections between the power systems of Algeria and Tunisia, Algeria and Morocco, Tunisia and Libya, and Egypt and Libya, together with the potential of creating a North African Supergrid, are reviewed. The interconnection would be used mainly for reserve sharing, which may result in savings in reserve capacity of more than 12GW in 2015. Then, ways of creating international connections in East Asia and environmental implications of the connections are discussed: specific features of the region, state of the East Asian Electric Utility industry, and proposed main interstate ties in the region, including the Russia-Japan tie, Russia-China-South Korea tie, and East Siberia-China tie. The paper goes on to discuss ecological benefits of HVDC in comparison with HVAC, together with the main environmental advantages of the use of hydro power resources instead of thermal power plants (with their pollution) in the eastern parts of Russia, China, Korea, and Japan. CO 2 emissions from different types of electricity generation power plants in Europe are discussed. Also discussed are the advantages of enlargement of the UCTE system to the CENTREL countries; a five-terminal HVDC project connecting the systems of Russia, Belarus, Poland and Germany; and the building of the Baltic Ring. Environmental, social development, and gender considerations in feasibility studies for High-Voltage interconnections is also discussed, where feasibility study considerations, the identification of essential organizations, identifying guidelines, defining preferred corridors, and the evaluation of costs are among the considerations that are examined. A case study on environmental implications of cross-border power lines created by free trade and regulation in Quebec in which environmental management systems, environmental issues, and advantages and disadvantages of the alternatives are examined is also discussed.

Implications of proxy caching for provisioning networks and servers

In this paper, we examine the potential benefits of web proxy caches in improving the effective capacity of servers and networks. Since networks and servers are typically provisioned based on a high percentile of the load, we focus on the effects of proxy caching on the tail of the load distribution. We find that, unlike their substantial impact on the average load, proxies have a diminished impact on the tail of the load distribution. The exact reduction in the tail and the corresponding capacity savings depend on the percentile of the load distribution chosen for provisioning networks and servers—the higher the percentile, the smaller the savings. In particular, compared to over a 50% reduction in the average load, the savings in network and server capacity is only 20-35% for the 99 th percentile of the load distribution. We also find that while proxies can be somewhat useful in smoothing out some of the burstiness in web workloads; the resulting workload continues, however, to exhibit substantial burstiness and a heavy-tailed nature. We identify large objects with poor locality to be the limiting factor that diminishes the impact of proxies on the tail of load distribution. We conclude that, while proxies are immensely useful to users due to the reduction in the average response time, they are less effective in improving the capacities of networks and servers.

Using different response-time requirements to smooth time-varying demand for service

Many service systems have demand that varies significantly by time of day, making it costly to provide sufficient capacity to be able to respond very quickly to each service request. Fortunately, however, different service requests often have very different response-time requirements. Some service requests may need immediate response, while others can tolerate substantial delays. Thus it is often possible to smooth demand by partitioning the service requests into separate priority classes according to their response-time requirements. Classes with more stringent performance requirements are given higher priority for service. Lower capacity may be required if lower-priority-class demand can be met during off-peak periods. We show how the priority classes can be defined and the resulting required fixed capacity can be determined, directly accounting for the time-dependent behavior. For this purpose, we exploit relatively simple analytical models, in particular, M t / G/∞ and deterministic offered-load models. The analysis also provides an estimate of the capacity savings that can be obtained from partitioning time-varying demand into priority classes.

Kinetic analysis of thermophilic anaerobic digestion of wastewater sludge

Conventional mesophilic anaerobic digesters are sometimes subject to process upset and have earned the reputation of being difficult to cope with sludge overloading. This study was conducted to examine the thermophilic process as a viable alternative. An analysis of field data from an operating mesophilic sludge digester was conducted in parallel with experimental runs on a laboratory thermophilic reactor using similar sludge. The results showed that thermophilic anaerobic digestion was a viable alternative to the mesophilic process especially for overloaded digesters in warm climates. The optimum hydraulic retention time for the thermophilic process was 10 days which can lead to substantial savings in digester capacity. A simplified kinetic model was developed and applied in the analysis of steady-state operation of thermophilic anaerobic sludge digesters.

Dependence of network capacity requirements on the allowable flow convergence overloads in ATM backup VP restoration

Work on capacity design for VP restoration in ATM has to date either been heuristic in nature or has treated the capacity design problem in a 1 for 1 VP replacement manner that is essentially the same as for STM path restorable networks. However, the inherently statistical nature of the traffic in ATM should allow formulation of a backup VP restoration capacity design that permits a controlled maximum of convergent flow overloads on spans during restoration. Results show that significant capacity savings can be obtained relative to STM if ATM restoration is allowed even modest restoration overload factors. We give an integer program formulation permitting controlled exploitation of this intrinsic difference between ATM and STM transport and present results showing the significant capacity benefits motivating this approach.

DSM accomplishments in California: PG&E's experience

The recent demand-side management (DSM) emphasis and, more specifically, the advent of utility shareholder incentive/penalty mechanisms for utility's performance in implementing DSM programs has increased the importance of DSM programs to Pacific Gas & Electric (PG&E) Company. Over the period 1990–1995, PG&E's expenditures on DSM programs and evaluation of these programs accounted for half of all DSM funds expended by the four largest California investor-owned utilities. Because the energy and capacity savings are intended to offset supply-side resources in the long run, it is important to ascertain the extent to which these savings can be relied on over time. This paper shares PG&E's DSM experiences gained from the operational and measurement trenches in residential and nonresidential energy-efficiency activities and looks at the future of DSM.

Interconnection of electric power systems in the Arab world

Economic and technical considerations are usually the underlying factors for interconnecting neighbouring electric power systems. Among some of the benefits that may be realised are plant capacity savings, interchange due to diversity, emergency power interchange, spinning reserve savings. However, planning of interconnections is a demanding task and must cover a wide range of technical aspects. This article presents the advantages, requirements and problems arising from the interconnection of electric power systems in the Arab world. It also presents the planning principles for grid systems, procedures for power system development planning, technical aspects of interconnection and possibilities of increasing interconnection capacity by limited means. The results of studies investigating the feasibility of interconnecting the power networks of the six countries which form the Gulf Go-operation Council (GCC) are presented. The article also shows existing and future interconnections of power systems in the Arab world.

Channel Allocation under Batching and VCR Control in Video-on-Demand Systems

In order to guarantee continuous delivery of a video stream in an on-demand video server environment, a collection of resources (referred to as a logical channel) are reserved in advance. To conserve server resources, multiple client requests for the same video can be batched together and served by a single channel. Increasing the window over which all requests for a particular video are batched results in larger savings in server capacity; however, it also increases the reneging probability of a client. A complication introduced by batching is that if a batched client pauses, a new stream (which may not be immediately available) needs to be started when the client resumes. To provide short response time to resume requests, some channels are set aside and are referred to as contingency channels. To further improve resource utilization, even when a nonbatched client pauses, the channel is released and reacquired upon resume. In this paper, we first develop an analytical model that predicts the reneging probability and expected resume delay, and then use this model to optimally allocate channels for batching, on-demand playback, and contingency. The effectiveness of the proposed policy over a scheme with no contingency channels and no batching is also demonstrated.

Multiplexing gains in bit stream multiplexors

We are concerned with characterizing the variation of multiplexing gains with source type and burstiness in integrated service systems such as ATM. We model a fixed capacity high speed bit pipe that multiplexes a moderate number of bit streams with minimal buffer under a low loss constraint. Each service type is defined by its instantaneous bitrate distribution, but the bitrate distribution of multiplexed streams is approximated as Gaussian. The Gaussian approximation is not as accurate as Chernoff bounds, but it allows for stronger characterization of multiplexing gains. We consider three schemes for allocating bandwidth to services: by individual user, by path and service type, and by path only. We find explicit formulae for sensitivities of required capacity to source rate mean and variance and to loss rate. We characterize multiplexing gains and costs to identify the benefits of each allocation policy. We find that the capacity savings resulting from sharing resources is proportional to the square root of the ratio of source rate variance to source rate mean. This suggests that although bursty sources require more bandwidth, multiplexing gains are increasing with burstiness. We also find that the extra capacity required to multiplex dissimilar source types is increasing with the difference between their burstinesses. This suggests that when bit streams are partially grouped, it is most important first, to group similar source types.

Engineering-Economic Optimization of a Fuel Cell Cogeneration Plant

The feasibility of fuel cells in cogeneration applications is studied from engineering and economic viewpoints by using an optimization approach. Capacities of fuel cell cogeneration units and auxiliary devices are determined together with maximum utility demands so as to minimize the annual total cost by considering the plant’s annual operational strategy. This optimization problem is solved efficiently by considering the hierarchical relationship between unit sizing and operational planning problems. Through a numerical study on a plant for installation in a hotel and office building with a maximum electrical demand of 1000 kW, the effect of initial capital cost of fuel cell cogeneration units is examined from the perspective of the plant capacity, economics, and energy savings. The results show that a fuel cell cogeneration plant may have better economic and energy-saving characteristics than a conventional gas engine cogeneration plant with a reduction in the capital cost of fuel cell.

Storage Conditions for Stability Testing in the Ec, Japan and Usa; the Most Important Market for Drug Products

Strong efforts have been undertaken to harmonise the requirements for the investigation of the stability of drug substances and drug products. Since the results of these investigations are used to assign labelling which properly reflects the stability of the substances/products under the climatic conditions encountered in the region of distribution and use, a thorough examination of the climatic conditions in the EC, Japan and the USA was conducted. According to this study, the EC, Japan and the USA may be practically assigned to a region for which there is an annual mean kinetic temperature of up to 25 degrees C.In fact, the climatic study indicates that 25 degrees C/60 per cent RH is general well above the mean kinetic temperature for the 35 major European, Japanese and American cities in the study. In addition the mean kinetic temperature encompasses the data in warehouses as well as measured seasonal and daily fluctuations up to and above the extreme temperature of 30 degrees C allowed by the USP definition of controlled room temperature. Based upon the above, it can therefore be concluded that long term controlled room temperature labelling for the USA, Japan and the EC can be accurately assigned by applying storage condition of 25 degrees C/60 per cent RH.Since the applied procedure to calculate and derive climatic conditions is based on the Arrhenius equation in the modified version of Hayne's relates mainly to chemical stability. In order to follow also organoleptic and physico-chemical changes storage at higher conditions is necessary for up to 6 months (40°C/75%) if a shelf live of at least three years is anticipated.The described procedure and derived storage conditions allow considerably savings in capacity and cutting costs.