Bottleneck Areas Research Articles

Sodium Ion Diffusion in Nasicon (Na3Zr2Si2PO12) Solid Electrolytes: Effects of Excess Sodium.

The Na superionic conductor (aka Nasicon, Na1+xZr2SixP3-xO12, where 0 ≤ x ≤ 3) is one of the promising solid electrolyte materials used in advanced molten Na-based secondary batteries that typically operate at high temperature (over ∼270 °C). Nasicon provides a 3D diffusion network allowing the transport of the active Na-ion species (i.e., ionic conductor) while blocking the conduction of electrons (i.e., electronic insulator) between the anode and cathode compartments of cells. In this work, the standard Nasicon (Na3Zr2Si2PO12, bare sample) and 10 at% Na-excess Nasicon (Na3.3Zr2Si2PO12, Na-excess sample) solid electrolytes were synthesized using a solid-state sintering technique to elucidate the Na diffusion mechanism (i.e., grain diffusion or grain boundary diffusion) and the impacts of adding excess Na at relatively low and high temperatures. The structural, thermal, and ionic transport characterizations were conducted using various experimental tools including X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). In addition, an ab initio atomistic modeling study was carried out to computationally examine the detailed microstructures of Nasicon materials, as well as to support the experimental observations. Through this combination work comprising experimental and computational investigations, we show that the predominant mechanisms of Na-ion transport in the Nasicon structure are the grain boundary and the grain diffusion at low and high temperatures, respectively. Also, it was found that adding 10 at% excess Na could give rise to a substantial increase in the total conductivity (e.g., ∼1.2 × 10-1 S/cm at 300 °C) of Nasicon electrolytes resulting from the enlargement of the bottleneck areas in the Na diffusion channels of polycrystalline grains.

IMPROVEMENT OF OVERALL EQUIPMENT EFFECTIVENESS OF BARREL PRE-HONING MACHINE LINE

Bosch Group is one of the leading global supplier of technology and services. The company was established in Stuttgart in the year 1886 by Robert Bosch a leading industrialist (1861-1942) as “Workshop for Precision Mechanics and Electrical Engineering.” Bosch Limited located at Adugodi, Bangalore manufactures one of the components of the diesel engine called an Element. It is made up of the assembly of two parts called the Barrel and the Plunger. When the plunger is inserted into the barrel, it creates a pressure drop in the pump which is used to inject the fuel into the engine. This paper reports the current Overall Equipment Effectiveness (OEE) and its improvement in the Barrel Pre-honing Machine Line, which is a process involved in the manufacture of a barrel. Improvement of the OEE is beneficial to improve the productivity. The scope of the project was to collect data to calculate the current OEE and create improvements. The project undertaken involved identifying the bottleneck area and eliminating the bottleneck. To do this, the Takt time chart of the various processes involved in the manufacture of the barrel was analyzed. The bottleneck was identified to be the Pre-Honing line which consisted of 12 machines. Preliminary analysis was carried out on the Pre-Honing line of barrels to obtain the current state data for the month of January and February. Graphical analysis of the collected data showed that two machines in particular had relatively lower OEE of the 12 machines. Any improvement on these two machines would lead to increased production, eliminating the bottleneck. Hence these two machines in particular were chosen as the subject of study. Thus the project aims at reducing Availability, Performance and Quality losses of the machines using SFMC (Shop Floor Management Cycle). Shop floor management cycle is a procedural system developed by Bosch to improve the Overall Equipment Efficiency in the troublesome process and hence the production and productivity. The identification of the bottleneck is done through Takt chart and then hourly monitoring is used to identify the losses. Further this data is analyzed to obtain the root causes of the problem. These causes are subjected to critical analysis, validated and appropriate actions are taken to reduce or eliminate them. The SFMC concepts include tracking all the activities that take place in the machine line. This includes creating a Takt time chart, maintaining hourly monitoring sheet, OEE tracking, creating a Pareto chart of the losses, problem solving (Ishikawa Diagram, 5-why) and PDCA sheet. The Hone Holder Tracking Sheet was designed and implemented to reduce the availability losses due to non-availability of hone holder sets. On implementation, the OEE of the line was improved from 70 to 84%.

ON OPERATION OF 740 M LONG FREIGHT TRAINS ON CZECH TEN-T RAILWAY NETWORK

Regulation (EU) No 1315/2013 defines actual scope of core and comprehensive TEN-T network, including both networks for railway freight transport. For the core network, possibility to operate 740 m long freight trains is required. The aim of this paper is to analyse availability of appropriate overtaking tracks for 740 m long freight trains. Due to ETCS braking curves and odometry, such trains, after ETCS implementation, will require 780-800 m long overtaking tracks. For practical reasons (e.g. bypass lines), whole Czech railway TEN-T network is analysed. The overtaking track, whose occupation means influence on scheduled traffic or threat to boarding passengers, are excluded. The data was collected from station schemes from Collection of Official Requisites for 2015/16 Timetable, issued by SŽDC, Czech state Infrastructure Manager. Most of appropriate tracks are over 800 m long, but their density in the network and in particular directions varies considerably. For freight traffic, gradient of the line is important, so in the resulting figure, there are marked significant peaks for particular lines as well. Czech TEN-T lines are further segmented on the basis of number of tracks and their traffic character. Then, specific issues on overtaking or crossing of 740 m long freight trains are discussed. As a conclusion, for long-term development of Czech TEN-T lines, targeted investment is recommended not only for passenger railway, but also for freight railway. An attractive capacity offer for railway undertakings, which can stimulate freight traffic on European Rail freight corridors, can be represented by network-bound periodic freight train paths with suitable long overtaking tracks outside bottlenecks. After the overtaking by passenger trains, a freight train should run without stop through large node station or a bottleneck area. Before the sections with high gradients, coupling of additional locomotives should be connected with the overtaking process. Next suitable overtaking tracks should be available behind every significant peak of the line.

Tracing Road Network Bottleneck by Data Driven Approach.

Urban road congestions change both temporally and spatially. They are essentially caused by network bottlenecks. Therefore, understanding bottleneck dynamics is critical in the goal of reasonably allocating transportation resources. In general, a typical bottleneck experiences the stages of formation, propagation and dispersion. In order to understand the three stages of a bottle neck and how the bottleneck moves on a road network, traffic flow data can be used to reconstruct these dynamics. However, raw traffic flow data is usually flawed in many ways. For instance some portion of data may be missing due to the failure of data collection devices, or some random factors in the data make it hard to identify real bottlenecks. In this paper a “user voting method” is proposed to deal with such raw-data-related issues. In this method, road links are ranked according to the weighed sum of certain performance measures and the links that are ranked relatively high are regarded as recurrent bottlenecks in a network, and several bottlenecks form a bottleneck area. A series of bottleneck parameters can be defined based on the identified bottleneck areas, such as bottleneck coverage, bottleneck link length, etc. Identifying bottleneck areas and calculating the bottleneck parameters for each time interval can reflect the evolution of the bottlenecks and also help trace how the bottlenecks move.

Crystal structure and oxygen permeation properties of (La, Ba, Sr)(Co, Ta)O3–δ

To clarify the influence of Ta-substitution on oxygen permeability (JO2) as well as ion conductivity (σi) in a cobaltite perovskite, we investigated detailed crystal structures of (La0.4Sr0.6)(Co1–yTay)O3–δ(y=0.0, 0.1, 0.2) and (La0.4BaxSr0.6–x)(Co0.8Ta0.2)O3–δ (x=0.1, 0.2) at room temperature using synchrotron x-ray powder diffractometry (XRPD). The crystal structure of the (La0.4Sr0.6)(Co1–yTay)O3–δ was modified from cubic (Pm3̅m) to rhombohedral (R3̅c) by substituting Ta ions into perovskite B-sites because the tolerance factor deviates from unity with the Ta-substitutions. The tilting angle ϕ of the CoO6 octahedra and strain parameters η estimated from the refined structural parameters suggest that the crystal structures of the Ta-substituted samples are improved to cubic at elevated temperatures of 800–900°C. Although the lattice volume, the lattice free volume, the O–O bond lengths, and the bottleneck areas gradually increased concomitantly with increasing Ta content, the activation energies estimated from both JO2 and σi increased with Ta-substitution. Results suggest that the electrostatic interaction between Ta5+ and O2− has greater impact than the crystallographic factors for the activation energy increase. Symmetry of the (La0.4BaxSr0.6–x)(Co0.8Ta0.2)O3–δ was improved from rhombohedral (R3̅c) to cubic (Pm3̅m) by substituting Ba ions for the A-sites because the tolerance factor approaches unity. The lattice constant, the O–O bond length, and the bottleneck area increased with the Ba-substitution. The lattice free volume depends on amount ratio between Co3+ and Co4+ cations in the samples. Both JO2 and σi increased with the Ba-substitution. The activation energy Ei of the σi slightly increased with the Ba-substitution.

Innovative financing for late-stage global health research and development: the Global Health Investment Fund

Innovative financing strategies for global health are urgently needed to reinvigorate investment and new tools for impact. Bottleneck areas along the research and development (R&D) pipeline require particular attention, such as the transitions from preclinical discovery to clinical study, and product development to implementation and delivery. Successful organizations mobilizing and disbursing resources through innovating financing mechanisms include UNITAID, the Global Fund, and Gavi, the Vaccine Alliance. Although precise numbers are poorly documented, estimated investment in low-income settings falls seriously short of local need. This commentary discusses the newly established Global Health Investment Fund as a case study to support late-stage global health R&D.

A quantification of illegal hunting of birds in Gipuzkoa (north of Spain)

The illegal hunting of wild birds is still today a major threat to the conservation of biodiversity on a global scale. This activity jeopardizes the survival of several migratory species. Our aims in this work were to (1) determine the spatial and temporal distribution of illegal hunting activities affecting bird species with regard to the location of fixed hunting posts in particular, and (2) identify the most affected species in Gipuzkoa (north of Spain), situated in a bottleneck area within one of the main routes of migration between Europe and Africa. All of our data came from birds with firearm injuries that were admitted to the Gipuzkoa Wildlife Rehabilitation Center (WRC). Over a period of 8 years (2006–2013), 421 birds belonging to 53 species were registered. The number of shot birds was found to be greater in more highly populated areas and during the months coinciding with hunting periods. Moreover, shot birds were recovered close to fixed hunting posts, suggesting that the illegal shooting of birds took place near or directly from these posts. Although the figures were not comparable to the high numbers of migrants shot annually in some other southern European areas, our results show that, even in small areas like Gipuzkoa, increased levels of protection are necessary.

Workers and Machine Performance Modeling in Manufacturing System Using Arena Simulation

This paper deals with the workers and machine performance measurements in manufacturing system. In simulating the manufacturing system, discrete event simulation involves the modeling of the system as it improves throughput time and is particularly useful for modeling queuing systems. In modeling this system, an ARENA simulation model was developed, verified, and validated to determine the daily production and potential problem areas for the various request levels in the case company (Ethiopia Plastic Factory). The results obtained show that throughput time in the existing system is low because of occurrence of bottlenecks, and waiting time identified. Therefore, some basic proposals have been drawn from the result to raise awareness of the importance of considering human and machine performance variation in such simulation models. It presents some conceptual ideas for developing a worker manager for representing worker and machine performance in manufacturing systems simulation models. The company workers’ and machine performance level is raised by identifying the bottle neck area. They were recommended to amend the main basic bottle necks identified.

Impact of long-stay beds on the performance of a tertiary hospital in emergencies.

ABSTRACTOBJECTIVE To assess the impact of implementing long-stay beds for patients of low complexity and high dependency in small hospitals on the performance of an emergency referral tertiary hospital.METHODS For this longitudinal study, we identified hospitals in three municipalities of a regional department of health covered by tertiary care that supplied 10 long-stay beds each. Patients were transferred to hospitals in those municipalities based on a specific protocol. The outcome of transferred patients was obtained by daily monitoring. Confounding factors were adjusted by Cox logistic and semiparametric regression.RESULTS Between September 1, 2013 and September 30, 2014, 97 patients were transferred, 72.1% male, with a mean age of 60.5 years (SD = 1.9), for which 108 transfers were performed. Of these patients, 41.7% died, 33.3% were discharged, 15.7% returned to tertiary care, and only 9.3% tertiary remained hospitalized until the end of the analysis period. We estimated the Charlson comorbidity index – 0 (n = 28 [25.9%]), 1 (n = 31 [56.5%]) and ≥ 2 (n = 19 [17.5%]) – the only variable that increased the chance of death or return to the tertiary hospital (Odds Ratio = 2.4; 95%CI 1.3;4.4). The length of stay in long-stay beds was 4,253 patient days, which would represent 607 patients at the tertiary hospital, considering the average hospital stay of seven days. The tertiary hospital increased the number of patients treated in 50.0% for Intensive Care, 66.0% for Neurology and 9.3% in total. Patients stayed in long-stay beds mainly in the first 30 (50.0%) and 60 (75.0%) days.CONCLUSIONS Implementing long-stay beds increased the number of patients treated in tertiary care, both in general and in system bottleneck areas such as Neurology and Intensive Care. The Charlson index of comorbidity is associated with the chance of patient death or return to tertiary care, even when adjusted for possible confounding factors.

A bottleneck analysis in the IFRC supply chain

Purpose– The purpose of this paper is to further the understanding of bottlenecks occurring when preparing for humanitarian operations in the humanitarian supply chain. The focus in this paper is set on the activities of aid supply procurement and aid consolidation into standardised deliveries of humanitarian aid.Design/methodology/approach– The paper follows a qualitative case study and builds a theoretical bottleneck analysis framework, using, e.g. the theory of constraints as an important building block. The case study as such involves the IFRC supply chain.Findings– The findings in the empirical study show that there is a need for long-term planning (practical and strategic planning) of the supply procurement, as well as organisational commitment in order to remove bottlenecks in a humanitarian operation.Research limitations/implications– The research framework built for the case study is applicable in similar future analyses of humanitarian supply chain operations and projects, as well as modifiable to other types of project or operation analyses.Practical implications– This paper gives a wide perspective insight into constraining bottleneck areas as well as areas of improvement in disaster preparedness. Additionally the paper provides an applicable tool for humanitarian practitioners to use for analysing process bottlenecks, to decide on corrective actions.Originality/value– The paper constructs a bottleneck analysis framework, which can be utilised beyond the humanitarian setting. Bottleneck analyses have not previously been conducted within the humanitarian context.

Adaptive quality of service aware multi‐mobility anchor point registration in hierarchical mobile IPv6 wireless access networks

In hierarchical mobile IPv6 (HMIPv6), mobility anchor points (MAPs) are introduced to reduce the signalling cost by localising the signalling traffic of mobile nodes (MNs). However, the presence of MAPs introduces areas of bottleneck within the network. This study evaluates the impact of overlapped domains of consecutive MAPs in HMIPv6 access networks. In this novel network architecture, an MAP registration algorithm is also proposed to enable MNs to register with more than one MAP simultaneously. For each flow, the proposed algorithm determines a primary and a secondary MAP according to the quality of service (QoS) requirements of the traffic flow. Load balancing is also introduced to provide an even distribution of load among MAPs. In addition, an extended router advertisement is proposed to enable multiple MAP registration of MNs. The impact of the proposed algorithm in the new HMIPv6 network architectures is compared with a non‐QoS aware multi‐MAP registration algorithm in access network with no overlapped MAP domains. The simulation‐based comparison study illustrates a maximum of 71 and 74% improvements in total amount of rejected bandwidth and the mean satisfied flow requests in network, respectively.

Process analysis and capacity utilization in a dental clinic in Kazakhstan

Purpose – The purpose of this paper is to investigate the service delivery system of a dental clinic in Kazakhstan to maximize the clinic’s efficiency. Design/methodology/approach – The study uses process analysis to determine the capacity utilization and areas of bottlenecks in the dental clinic’s system. Findings – The analysis shows that the most severe bottleneck is identified in step 16 of the 20-step patient flow process. The system efficiency is approximately 62 per cent. Practical implications – The study will help similar health-care organizations identify areas of bottlenecks in their operational system. This would allow management to deploy optimal resources that would improve systems’ performance. Originality/value – The paper provides a framework for health-care managers to identify how to reduce patient throughput time and increase patient satisfaction.

An optimal variable speed limits system to ameliorate traffic safety risk

Active Traffic Management (ATM) systems have been emerging in recent years in the US and Europe. They provide control strategies to improve traffic flow and reduce congestion on freeways. This study investigates the feasibility of utilizing a Variable Speed Limits (VSL) system, one key part of ATM, to improve traffic safety on freeways. A proactive traffic safety improvement VSL control algorithm is proposed. First, an extension of the METANET (METANET: A macroscopic simulation program for motorway networks) traffic flow model is employed to analyze VSL’s impact on traffic flow. Then, a real-time crash risk evaluation model is estimated for the purpose of quantifying crash risk. Finally, optimal VSL control strategies are achieved by employing an optimization technique to minimize the total crash risk along the VSL implementation corridor. Constraints are setup to limit the increase of average travel time and the differences of the posted speed limits temporarily and spatially. This novel VSL control algorithm can proactively reduce crash risk and therefore improve traffic safety. The proposed VSL control algorithm is implemented and tested for a mountainous freeway bottleneck area through the micro-simulation software VISSIM. Safety impacts of the VSL system are quantified as crash risk improvements and speed homogeneity improvements. Moreover, three different driver compliance levels are modeled in VISSIM to monitor the sensitivity of VSL effects on driver compliance. Conclusions demonstrated that the proposed VSL system could improve traffic safety by decreasing crash risk and enhancing speed homogeneity under both the high and moderate compliance levels; while the VSL system fails to significantly enhance traffic safety under the low compliance scenario. Finally, future implementation suggestions of the VSL control strategies and related research topics are also discussed.

Development of control strategy of variable speed limits for improving traffic operations at freeway bottlenecks

A control strategy of variable speed limits (VSL) was developed to reduce the travel time at freeway recurrent bottleneck areas. The proposed control strategy particularly focused on preventing the capacity drop and increasing the discharge flow. A cell transmission model (CTM) was developed to evaluate the effects of the proposed VSL control strategy on the traffic operations. The results show that the total travel time is reduced by 25.5% and the delay is reduced by 56.1%. The average travel speed is increased by 34.3% and the queue length is reduced by 31.0%. The traffic operation is improved by the proposed VSL control strategy. The way to use the proposed VSL control strategy in different types of freeway bottlenecks was also discussed by considering different traffic flow characteristics. It is concluded that the VSL control strategy is effective for merge bottlenecks but is less effective for diverge bottlenecks.

Spatially Distributed Multiagent Path Planning

Multiagent path planning is important in a variety of fields, ranging from games to robotics and warehouse management. Although centralized control in the joint action space can provide optimal plans, this often is computationally infeasi- ble. Decoupled planning is much more scalable. Traditional decoupled approaches perform a unit-centric decomposition, replacing a multi-agent search with a series of single-agent searches, one for each mobile unit. We introduce an orthogonal, significantly different approach, following a spatial distribution that partitions a map into high- contention, bottleneck areas and low-contention areas. Lo- cal agents called controllers are in charge with one local area each, routing mobile units in their corresponding area. Dis- tributing the knowledge across the map, each controller can observe only the state of its own area. Adjacent controllers can communicate to negotiate the transfer of mobile units. We evaluate our implemented algorithm, SDP, on real game maps with a mixture of larger areas and narrow, bottleneck gateways. The results demonstrate that spatially distributed planning can have substantial benefits in terms of makespan quality and computation speed.

Development of a Control Strategy of Variable Speed Limits to Reduce Rear-End Collision Risks Near Freeway Recurrent Bottlenecks

The primary objective of this paper was to develop a control strategy of variable speed limits (VSLs) to reduce rear-end collision risks near freeway recurrent bottlenecks. The risks of rear-end collisions were estimated using a crash risk prediction model that is specifically developed for rear-end collisions in freeway bottleneck areas. The effects of the VSL control strategy were evaluated using a cell transmission model. Several control factors were tested, including the start-up threshold of the collision likelihood, the target speed limit, the speed change rate, and the speed difference between adjacent links. A genetic algorithm was used to optimize critical control factors. For the high demand scenario, the proposed control strategy used 25% of the maximum collision likelihood for the start-up threshold, 35 mi/h for the target speed limit, 10 mi/h per 30 s for the speed change rate, and 10 mi/h for the speed difference between different links. For the moderate demand scenario, the strategy used 20% of the maximum collision likelihood for the start-up threshold, 40 mi/h for the target speed limit, 15 mi/h per 30 s for the speed change rate, and 10 mi/h for the speed difference between different links. The results of comparative analyses suggested that the proposed control strategy outperformed other strategies in reducing the rear-end collision risks near freeway recurrent bottlenecks. With the proposed control strategy, the VSL control reduced the rear-end crash potential by 69.84% for the high demand scenario and by 81.81% for the moderate demand scenario.

Troubleshooting a Full-scale Wastewater Treatment Plant for Biological Nutrient Removal

The International Association of Water Quality (IAWQ) Activated Sludge Model No.2 (ASM2) was applied to troubleshoot an existing underperforming full-scale wastewater treatment plant (WWTP) built for biological nutrient removal. The WWTP is operated in a 3-stage pho-redox process configuration (A2O). This study was undertaken with the aim of finding optimal operating conditions that will meet TP and TN concentration requirements in the effluent of the WWTP under study without the use of either chemical or external carbon sources and also to verify the applicability, capability and predictability of ASM2 as implemented in STOAT software. ASM2 was successfully used to troubleshoot bottle neck areas and to define the operational schedule for optimal performance of the wastewater treatment plant. Consequently, the costs of chemical and external carbon sources were eliminated and the effect of residual chemicals on the environment reduced.

Understanding Pedestrian Crowd Merging Behavior

Different behaviors of pedestrian under complex situations such as turning and crossing have been investigated in the past. However, few studies considered the behaviors of pedestrians in merging areas despite the fact that this situation is very common in built environment such as exit points of railway stations and stadium. Notwithstanding of the importance of this phenomenon in pedestrian movements in particular due to creating bottleneck areas, the existing research on merging area is limited to T-junctions or staircases. This study investigates the merging behaviors of pedestrians under different scenarios such as various angles and pedestrian speed. The outcome of this research provides an insight into the understanding of crowd behaviors in merging areas.

Mainstream Traffic Flow Control at Sags

Sags are freeway sections along which the gradient changes significantly from downward to upward. The capacity of sags is considerably lower than the capacity of normal sections. Consequently, sags are often freeway bottlenecks. Recently, several control measures have been proposed to improve traffic flow efficiency at sags. Those measures generally aim to increase the capacity of the bottleneck, to prevent traffic flow perturbations in nearly saturated conditions, or both. This paper presents an alternative type of measure based on the concept of mainstream traffic flow control. The proposed control measure regulates traffic density at the bottleneck area to keep it below the critical density and hence prevent traffic from breaking down while maximizing outflow. Density is regulated by means of a variable speed limit section that regulates the inflow to the bottleneck. Speed limits are selected on the basis of a feedback control law. The authors evaluate the effectiveness of the proposed control strategy by means of a simple case study by using microscopic traffic simulation. The results show a significant increase in bottleneck outflow, particularly during periods of high demand, which leads to a considerable decrease in total delay. This finding suggests that mainstream traffic flow control strategies that use variable speed limits have the potential to improve substantially the performance of freeway networks containing sags.

Control Strategy of Variable Speed Limits for Improving Traffic Efficiency at Merge Bottleneck on Freeway

Queue forms at merge bottleneck area on freeways if the mainline and on-ramp traffic demand exceeds the capacity of bottleneck. Then bottleneck discharge flow further drops below the capacity of bottleneck which is termed as the capacity drop phenomenon. This study aims to develop control strategies of Variable Speed Limits (VSL) for improving traffic efficiency at freeway merge bottleneck area via preventing the capacity drop. The Cell Transmission Model (CTM) was developed and calibrated with field traffic data to evaluate the effectiveness of VSL. The results showed that by reducing the speed limit in VSL at upstream area, the capacity drop at the merge bottleneck was prevented and the discharge flow rate was kept near the bottleneck capacity. The control strategy of VSL developed in this study significantly reduced the travel delay by 56.10% and was effective in improving the traffic efficiency at the merge bottleneck area.