Congestion due to Rate Variations in cdma2000 Data Networks

In order to support high data rate requirements and effectively manage the scarce wireless resources, additional bandwidth channels are allocated and taken away from mobile stations in 3G wireless data networks quite frequently. A TCP sender connected to the mobile, on seeing ACKs coming at a faster pace after additional bandwidth allocation, turns overtly optimistic and injects data into the network at a rate that might be excessive for an intermediate router, thereby leading to loss of multiple packets and subsequent prolonged recovery and periods of underutilization. In this work, we characterize this problem using an analytical model for losses based on continuous flow approximation as well as an extensive simulation setup. We also illustrate how bandwidth oscillations create more severe congestion than an increase in number of users to the extent that even RED algorithm is unable to check the sharp growth of queues. As a result, multiple packets are lost in a droptail fashion. We further demonstrate the dependence of congestion due to bandwidth allocation on the time during which mobiles' rates are increased and observe the degradation in performance for typical load scenarios. We also try to identify the boundary for stable operation of RED and finally present some possible methods for improving the performance. Vikas Paliwal graduated with a Bachelor of Technology degree in Electrical Engineering from IIT (Indian Institute of Technology), Kanpur, India and an M.S. in Systems and Computer Engineering from Carleton University, Ottawa, Canada. He has five years of research and work experience in telecommunications area in a variety of work environments across the globe. During his under-graduation he worked on a research project in micro-electronics area with IMS Research Labs, Hanover, Germany, and developed some innovative algorithms for circuit schematics and layouts. After graduating from IIT, Vikas was the core Engineering and Marketing Consultant for GMG Telecom Consultants India Limited, New Delhi, India, and helped GMG in developing a level of technical expertise in the areas of security systems that resulted in key research projects from firms such as ADT and Honeywell. Later, as part of his Masters research at Carleton University, Ottawa, Canada, Vikas worked on performance analysis of CDMA data networks and queue management techniques that resulted in five research papers in various academic journals/conferences. His Masters research project also attracted the interest of Nortel Networks, Ottawa, Canada, and helped in starting joint research projects in the area of wireless systems simulation, which was of particular interest to Nortel. Vikas then worked with Solana Networks, Ottawa, on network topology detection and on products that improve the performance of mission-critical IP networks and wireless LANs. This was followed by a year of work with Qualcomm, UK, on modem software design and implementation for Qualcomm's 3G chipsets. Currently he works with Qualcomm Inc., San Diego, CA, on physical layer of WCDMA and HSxPA systems. At Qualcomm, he continues his research activities in advanced wireless systems design and implementation by actively participating in various technical forums and conducting several training/discussion sessions on UMTS systems. Ioannis Lambadaris was born in Thessaloniki, Greece. He received a diploma in Electrical Engineering from the Polytechnic School of the Aristotle University of Thessaloniki in 1984. He was a recipient at a Fulbright Fellowship (1984–1985) for graduate studies in USA. He received a M.Sc. degree in Engineering from Brown University, Providence, RI, USA in 1985 and a Ph.D. degree in Electrical Engineering from the University of Maryland, College Park, MD, USA in 1991. He was employed as a research associate at Concordia University, Montreal, Quebec, Canada, in 1991–1992. Between September 1992 and July 1997 he has been an Assistant Professor in the Department of Systems and Computer Engineering at Carleton University, Ottawa, Ontario, Canada. Currently he is an associate professor in the same department and a member of IEEE. While at Carleton he received the Premier %92\,s Research Excellence Award (2000), and the Carleton University Research Excellence Award (2000–2001) for his research achievements in the area of modeling and performance analysis of computer networks. Professor Lambadaris' interests lie in the area of applied stochastic processes, stochastic control, queuing theory and their application for modeling and performance analysis of computer communication networks. His current research concentrates on quality of service (QoS) control for IP networks, resource allocation in optical networks, and optimal routing and flow control in ad-hoc wireless systems. Biswajit, a co-founder of Solana Networks, has15 years of experience in the area of data communication. He has worked at Nortel Networks, Bell Northern Research, Tropic Networks and Belair Networks. The primary focus of his work has been in the area of IP networking protocols and architecture. As an Independent Contributor at Nortel Networks, he spearheaded various advance technology programs and R&D projects in IP networking. He worked as a Network Architect with the MPLS team and as a member of the architecture team at Tropic Networks to address complex optical networking issues. He worked as a System Architect on WLAN mesh networking products at BelAir Networks. Dr. Nandy has a PhD in Electrical and Computer Engineering from the University of Waterloo and has been an Adjunct Research Professor with Systems and Computer Engineering at Carleton University since 2001. He holds an M.Tech in Electrical Engineering from Indian Institute of Technology, Kanpur and a B.E. in Electronics and Telecommunication Engineering from Jadavpur University, Calcutta. He has authored and presented over 25 research papers in International conferences and holds 12 US patents. He has actively participated in various Work Groups in IETF and author of several IETF proposals in the form of Internet Drafts and RFC.     

Impact of hot water treatment on sprouting,membrane permeability,sugar content and chip colour of reconditioned potato tubers following long‐term cold storage

BACKGROUND: The efficacy of hot water treatment in facilitating successful reconditioning of processing potato (Solanum tuberosum L.) cultivar Hermes following 6 months cold storage at 4.5 °C was examined. Tubers were subjected to hot water treatments (HWTs) at 52.5, 55.0, 57.5 and 60.0 °C for 0–60, 0–50, 0–40 and 0–20 min, respectively, and then reconditioned for 20 days at 16 °C before evaluated for sprouting, fresh weight loss, membrane permeability, sugar content and processing quality. RESULTS: The study demonstrates that in order to achieve complete inhibition of sprouting during potato reconditioning HWTs must exceed the thermal tolerance threshold of the tubers. Short‐duration HWT was effective in retarding sprout growth and tuber dehydration without significantly affecting storage parenchyma membrane permeability, tuber sugar content or processing quality. On the contrary, prolonged HWT caused extensive heat damage, loss of membrane integrity and induced an increase in tuber sucrose and reducing sugar content resulting in deterioration of chip colour in proportion to treatment duration. CONCLUSION: Although HWT at 52.5–60 °C following long‐term cold storage did not improve the processing quality of potato tubers after 20 days of reconditioning, future work is needed to evaluate the effect of short‐duration HWT on the permissible extent of reconditioning and subsequent processing quality. Copyright © 2008 Society of Chemical Industry     

Comprehensive risk assessment for rail transportation of dangerous goods: a validated platform for decision support

Currently, the most advanced and well documented risk assessments for the transportation of dangerous goods by railway take into account:

(i) statistics-based loss of containment frequencies,

(ii) specification of potential consequences for a given release situations using event tree methodology as an organisational tool and

(iii) consequence calculation models to determine a risk figure known as CCDF (Complementary Cumulative Distribution Function).

Such procedures for the risk assessment (including for example decision-making on preventive measures) may offer only a limited insight into the causes and sequences leading to an accident and do not allow for any kind of predictive analysis. The present work introduces an enhanced solution, and a related software platform, which attempts to integrate loss of containment causes and consequences with system's infrastructure and its environment. The solution features:

(i) the use of a detailed Master Logical Diagram, including fault/event tree analysis to determine a loss of containment frequency based on different initiating events, scenarios and specific basic data,

(ii) the characterization of a resulting source term following a release situation, and

(iii) the calculation of various potential impacts on the neighbouring site.

Results are wrapped into a CCDF format for each selected traffic segment. The risk-related results are integrated on a software platform, structured as a decision support system using intelligent maps and a variety of GIS (Geographical Information System) data processing procedures. The introduction of the hot spot approach, allows us to focus on the most risk-relevant areas and to use information on various railway infrastructure elements (e.g. points, tunnels), are the basis of the new models employed. The software is applicable to any railway transportation system, comprising its technical infrastructure, rolling stock, human actions, regulation and management procedures. It provides the determination of the annual societal risk due to potential accident scenarios, while also revealing information on the potential causes of an accident taking into account spatial parameters. The approach and software have been validated by a case study done for a particular traffic segment of the Swiss Federal Railway company.     

Introducing a Geometric Potential Theory for two-dimensional steady flows

It is demonstrated that the continuity and irrotationality conditions imply geometric constraints for two-dimensional steady flows. This fact leads to the formulation of an exclusively geometric criterion for these kinematical conditions. Thus, flow visualization can be conclusive on whether a flow possesses a potential or not. Moreover, the mutual relationship among the flow geometry, its kinematics and physics, can be expressed mathematically using an eikonal equation. Its analytical solution in the flow-streamline coordinate system enables the formulation of the `Geometric Potential Theory’. Accordingly, the determination of the physical quantities of velocity and static pressure throughout the flow is reduced to the purely geometrical problem of finding the streamline and potential line curvatures. These two functions are combined to introduce the `Global Curvature Vector’, a vector that can be mathematically and physically interpreted. Finally, it is shown that continuity and irrotationality are identically satisfied by the existence of a `Curvature Potential’, that is, the existence of an analytic expression from which the global curvature vector components can be found by partial differentiation.     

Display meets biology: A vision for ubiquitous healthcare platforms

Ever‐increasing demand for a healthy and sustainable life has been a traditional motivation behind state‐of‐the‐art medicines and precision diagnosis tools. Nowadays, the ultra‐connectivity and data‐centric initiatives that underpin the future Internet of Things is seen as another major driver of electronically enriched, highly customizable healthcare platforms. Especially, the information display technology, which already enjoys its position as an all‐round player in consumer electronics is poised to broaden its territory by envisioning a range of bio‐related features. In this review, the rising opportunities for next‐generation display‐based biotechnology and healthcare systems are critically assessed in light of recent literature. Clearly, smart combination of new materials, devices, and integration strategies has given rise to highly promising prototypes, and this article aims at highlighting some of these examples. Despite such progress, it is still unclear whether the resultant technologies will make a measurable impact in the near future, given both their own scientific limits and the lack of proper business model. In this regard, the final part of this contribution is dedicated to emergent challenges as well as development solutions that this potentially disruptive innovation may need to consider.     

Simulating and evaluating the local behavior of small pedestrian groups

Recent advancements in local methods have significantly improved the collision avoidance behavior of virtual characters. However, existing methods fail to take into account that in real life pedestrians tend to walk in small groups, consisting mainly of pairs or triples of individuals. We present a novel approach to simulate the walking behavior of such small groups. Our model describes how group members interact with each other, with other groups and individuals. We highlight the potential of our method through a wide range of test-case scenarios. We evaluate the results from our simulations using a number of quantitative quality metrics, and also provide visual and numerical comparisons with video footages of real crowds.     

Ex-Ante Optimal Design of Sustainable Phase Change Materials for Latent Heat Storage

Energy consumption for residential heating can be reduced using new insulation solutions in the form of phase change materials (PCMs) integrated within the building structure. This work proposes a framework for the optimal design of PCMs considering operational as well as sustainability aspects at the early stages of the material development process. The proposed framework applies computer-aided molecular design tools and considers a practical simulation model to calculate the functional performance of the PCM, as well as a variety of constraints to impose desirable bounds on the material thermophysical properties and its impact on environment and safety.     

Partially automated driving has higher workload than manual driving: An on-road comparison of three contemporary vehicles with SAE Level 2 features

Vehicles with SAE Level 2 automated features are already in active use on the road, and vehicles with Level 3 or 4 will be with us soon. Although the vehicles provide support for longitudinal and lateral control, partially automated driving experience is sometimes more demanding than manual driving. However, the effects of automated driving on workload in naturalistic conditions have not been extensively investigated, as most studies have been undertaken in driving simulators. This study aims to extend the current understanding about workload in partially automated driving on public roads. Drivers' perceived workload was assessed after conducting manual and automated driving activities using a small sample (N = 8). They performed driving tasks in three contemporary vehicles with SAE Level 2 features, in highway and urban environments. The comparative findings revealed that drivers' perceived workload was higher in partially automated driving than manual driving. Furthermore, perceived workload was higher in urban environments than highway environments and in less experienced drivers than more experienced drivers. Although the findings may need to be interpreted with caution due to the small sample size, they provide a future research agenda that can be built upon.