| 1. |
- Bilstrup, Katrin, et al.
(författare)
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Evaluation of the IEEE 802.11p MAC method for vehicle-to-vehicle communication
- 2008
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Ingår i: 68th IEEE Vehicular Technology Conference, 2008. VTC 2008-Fall. - Piscataway, N.J. : IEEE Press. - 9781424417216 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- In this paper the medium access control (MAC) method of the upcoming vehicular communication standard IEEE 802.11p has been simulated in a highway scenario with periodic broadcast of time-critical packets (so-called heartbeat messages) in a vehicle-to-vehicle situation. The 802.11p MAC method is based on carrier sense multiple access (CSMA) where nodes listen to the wireless channel before sending. If the channel is busy, the node must defer its access and during high utilization periods this could lead to unbounded delays. This well-known property of CSMA is undesirable for time critical communications. The simulation results reveal that a specific node/vehicle is forced to drop over 80% of its heartbeat messages because no channel access was possible before the next message was generated. To overcome this problem, we propose to use self-organizing time division multiple access (STDMA) for real-time data traffic between vehicles. This MAC method is already successfully applied in commercial surveillance applications for ships (AIS) and airplanes (VDL mode 4). Our initial results indicate that STDMA outperforms CSMA for time-critical traffic safety applications in ad hoc vehicular networks.
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| 2. |
- Bilstrup, Katrin, et al.
(författare)
-
Medium access control in vehicular networks based on the upcoming IEEE 802.11p standard
- 2008
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Ingår i: 15th World Congress on Intelligent Transport Systems and ITS America Annual Meeting 2008. - : World Congress on ITS. - 9781615677566 ; , s. 4155-4167, s. 12-
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Konferensbidrag (refereegranskat)abstract
- In this paper, initial simulations are presented showing that the upcoming IEEE 802.11p standard is not suitable for traffic safety applications requiring reliable, low delay communication between vehicles. The medium access control procedure is one of the most important parts in the design of delay-constrained communication systems, and emerging vehicle safety applications put new stringent demands on timely and reliable delivery of data packets. The medium access procedure used in 802.11p is carrier sense multiple access, which is inherently unsuitable for time-critical data traffic since it is contention-based and cannot provide a finite upper bound on the time to channel access. The simulation results indicate that with IEEE 802.11p, channel access cannot be granted in a manner that is sufficiently predictable to support reliable, low-delay communications between vehicles on a highway.
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| 3. |
- Bilstrup, Katrin, et al.
(författare)
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On the ability of the 802.11p MAC method and STDMA to support real-time vehicle-to-vehicle communications
- 2009
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Ingår i: EURASIP Journal on Wireless Communications and Networking. - New York : Hindawi Publishing Corporation. - 1687-1472 .- 1687-1499. ; 2009:902414, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Traffic safety applications using vehicle-to-vehicle (V2V) communication is an emerging and promising area within the intelligent transportation systems (ITS) sphere. Many of these new applications require real-time communication with high reliability, meaning that packets must be successfully delivered before a certain deadline. Applications with early deadlines are expected to require direct V2V communications, and the only standard currently supporting this is the upcoming IEEE 802.11p, included in the wireless access in vehicular environment (WAVE) stack. To meet a real-time deadline, timely and predictable access to the channel is paramount. However, the medium access method used in 802.11p, carrier sense multiple access with collision avoidance (CSMA/CA), does not guarantee channel access before a finite deadline. In this paper, we analyze the communication requirements introduced by traffic safety applications, namely, low delay, reliable, real-time communications.We show by simulation of a simple, but realistic, highway scenario, that vehicles using CSMA/CA can experience unacceptable channel access delays and, therefore, 802.11p does not support real-time communications. In addition, we present a potential remedy for this problem, namely, the use of self-organizing time division multiple access (STDMA). The real-time properties of STDMA are investigated by means of the same highway simulation scenario, with promising results.
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| 4. |
- Bilstrup, Katrin, 1972, et al.
(författare)
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On the ability of the IEEE 802.11p and STDMA to provide predictable channel access
- 2009
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Ingår i: Proceedings of the 16<sup>th</sup> World Congress on Intelligent Transport Systems (ITS). ; , s. 10-
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Konferensbidrag (refereegranskat)abstract
- Emerging traffic safety applications requiring low delay communications will need vehicle ad-hoc networks. The only communication standard currently supporting this is IEEE 802.11p. However, 802.11p uses the medium access method CSMA/CA, which has a major drawback: unbounded worst case channel access delay. We therefore propose an algorithm already in commercial use in the shipping industry: STDMA. With STDMA, nodes always get predictable channel access regardless of the number of competing nodes and the maximum delay is deterministic. In this paper we elaborated with different parameter settings for the two protocols with the aim of improving performance without altering the standards.
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| 5. |
- Bilstrup, Katrin, et al.
(författare)
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Report on the Collaboration between CVIS and CERES in the Project Vehicle Alert System (VAS)
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In March 2007, an agreement was made for interchange of experiences between CVIS and the Centre for Research on Embedded Systems (CERES) at Halmstad University in Sweden. The majority of the work relating to this collaboration has been conducted within the CERES project Vehicle Alert System (VAS), aiming to use vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications to provide different types of warning messages. The main focus of the VAS project is on communication and in particular the lower layers of the communication stack are investigated. VAS involves academic researchers from Halmstad University as well as researchers from Volvo Technology, SP Technical Research Institute of Sweden and the company Free2move. This report presents the results of the VAS project, its publications, and other issues of interest both to the CVIS consortium as well as a broader scope.
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| 6. |
- Christensson, Kyllike, et al.
(författare)
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The Challenge of Improving Perinatal Care in settings with Limited Resources : Observations of Midwifery Practices in Mozambique
- 2006
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Ingår i: African Journal of Reproductive Health. - Benin City, Edo State, Nigeria : Women's Health and Action Research Centre. - 1118-4841. ; 10:1, s. 47-61
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to observe and analyze midwifery care routine related to asphyxia and hypothermia during the perinatal period and to investigate the effect of an in-service education program. A direct non-participant pre-and post intervention observation study of midwifery a performance during childbirth was conducted at a labour ward in Maputo. The observed groups consisted of 702 and 616 midwifery –attended deliveries. Examination was also conducted of the partographs (702 vs. 616). The quality of midwifery care related to prevention and early detection of asphyxia and hypothermia was found to be inadequate and the intervention had no significant effect upon the midwives' performances. This could be attributed to the quality of the intervention itself or to failure of implementing managerial decisions such as transfer to partograph documentation from obstetricians to midwives. Change in professional performance does not automatically follow awareness of evidence-based midwifery practices, but requires behavioural change, which may be more difficult to achieve.
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| 7. |
- Elgh-Dalgren, Kristin, et al.
(författare)
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Anaerobic bioremediation of a soil with mixed contaminants : Explosives degradation and influence on heavy metal distribution, monitored as changes in concentration and toxicity
- 2009
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Ingår i: Water, Air and Soil Pollution. - Dordrecht : Springer Netherlands. - 0049-6979 .- 1573-2932. ; 202:1-4, s. 301-313
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Tidskriftsartikel (refereegranskat)abstract
- Two soils with explosives and metals were evaluated for the degradation efficiency of explosives by native microorganisms under anaerobic conditions. The commercially available method Daramend®, amended with zero-valent iron (ZVI), was compared with a horse-manure amended compost and a treatment with ZVI alone. In a moderately contaminated soil, Daramend® and ZVI treatment gave significantly higher removal rates compared to compost and control treatments (Tukey’s test, P<0.05). The largest overall decrease in ecotoxicity, measured with bioluminescent bacteria (Vibrio fischeri), was achieved with ZVI-treatment. In a more contaminated soil no degradation of contaminants and no decline in soil toxicity could be distinguished after the same time period. Problems with establishment of anaerobic conditions during parts of the remediation process and low microbial activity due to acute toxicity of contaminants are plausible explanations. Redistribution that could potentially lead to mobilization of the co-contaminant Pb was not observed in either of the soils during the biological treatments.
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| 8. |
- Elgh-Dalgren, Kristin, 1980-, et al.
(författare)
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Laboratory and pilot scale soil washing of PAH and arsenic from a wood preservation site : Changes in concentration and toxicity
- 2009
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Ingår i: Journal of Hazardous Materials. - Amsterdam : Elsevier. - 0304-3894 .- 1873-3336. ; 172:2-3, s. 1033-1040
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Tidskriftsartikel (refereegranskat)abstract
- Soil washing of a soil with a mixture of both polycyclic aromatic hydrocarbons (PAH) and As was evaluated in laboratory and pilot scale, utilizing both single and mixtures of different additives. The highest level of decontamination was achieved with a combination of 0.213 M of the chelating agent MGDA and 3.2xCMC* of a nonionic, alkyl glucoside surfactant at pH 12 (Ca(OH)2). This combination managed to reach Swedish threshold values within 10 min of treatment when performed at elevated temperature (50°C), with initial contaminant concentrations of As = 105±4 mg/kg and US-EPA PAH16 = 46.0±2.3 mg/kg. The main mechanisms behind the removal were the pH-effect for As and a combination of SOM-ionization as a result of high pH and micellar solubilization for PAHs. Implementation of the laboratory results utilizing a pilot scale equipment did not improve the performance, which may be due to the shorter contact time between the washing solution and the particles, or changes in physical characteristics of the leaching solution due to the elevated pressure utilized. The ecotoxicological evaluation, Microtox®, demonstrated that all soil washing treatments increased the toxicity of soil leachates, possibly due to increased availability of contaminants and toxicity of soil washing solutions to the test organism.
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| 9. |
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Guiding and guided tours
- 2009
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Ingår i: Guiding and guided tours. - Göteborg : BAS Publishers. - 9789172462854 ; , s. 15-28
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- This book is based on the collaborative work and experience from Swedish researchers in an new and promising field of scientific and management oriented inquiry: guided tours. The book represents a wide range of scientific perspectives such as organizational theory, human geography, architecture, ethnology and technology.The chapters are divided into three themes: Guided tours as a phenomenon, Guided tours and guidebooks and finally Guided tours: their production, content and use. And your guides - the authors - will provide various kinds of insights. We will follow the history of guidebooks and their followers, experience the smell of sage and find out how a guided tour at a construction site can be performed. Let's take a walk...
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| 10. |
- Koslander, Tiburtius, 1969-, et al.
(författare)
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Existential and Spiritual Needs in Mental Health Care : An Ethical and Holistic Perspective
- 2009
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Ingår i: Journal of Holistic Nursing. - Thousand Oaks, CA : Sage Publications. - 0898-0101 .- 1552-5724. ; 27:1, s. 34-42
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Tidskriftsartikel (refereegranskat)abstract
- This study illuminates how existential needs and spiritual needs are connected with health care ethics and individuals’ mental health and well-being. The term existential needs is defined as the necessity of experiencing life as meaningful, whereas the term spiritual needs is defined as the need of deliverance from despair, guilt and/or sin, and of pastoral care. It discusses whether or not patients’ needs are holistically addressed in Western health care systems that neglect patients’ existential and spiritual needs, because of their biomedical view of Man which recognizes only patients’ physical needs. It excludes a holistic health care which considers all needs, expressed by patients in treatment of mental illness. Addressing all needs is important for patients’ improvement and recovery. For some patients, this is the only way to regain their mental health and well-being.
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