| 45241. |
- Krusper, Aleksandra, 1967, et al.
(författare)
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Further development of the RED method to vehicle structural performance: assessment of crash compatibility
- 2015
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Ingår i: International Journal of Vehicle Safety. - 1479-3105 .- 1479-3113. ; 8:1, s. 65-84
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Tidskriftsartikel (refereegranskat)abstract
- An objective method for measuring compatibility is a prerequisite for improving crash performance and to further advance occupant safety in car-to-car collisions, but no suitable procedure has been developed to date. To date,based on car-to-car crashes, it is possible to conclude which pairs of cars are compatible, but it is not possible to quantify and compare the compatibility ofone pair of cars to another. This study presents a further development of the Relative Equivalent Energy Displacement (RED) method to assess vehiclecrash compatibility. The compatibility rating quantifies how the crash response of a car in barrier test differs from its crash response in a corresponding car-to-carcrash configuration with another car assessed in a same test. It was shown that the method can be used even in the development phase of a vehicle crash structure.
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| 45242. |
- Krusper, Aleksandra, 1967
(författare)
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Structural Interaction between Vehicles. An Investigation of Crash Compatibility between Cars and Heavy Goods Vehicles
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- While frontal collisions between Heavy Goods Vehicles (HGVs) and passenger cars are rarecompared to car-to-car frontal crashes, they are much more severe. Between 43% and 73% ofall frontal car-to-truck accidents result in fatalities. The severity is due to crashincompatibility between the vehicles that has been generally agreed to arise from differencesin mass, stiffness and geometry and it refers not only to car-to-truck collisions but also tomost vehicle-to-vehicle collisions. To address incompatibilities between passenger cars andHGVs, Front Underrun Protective Devices (FUPDs) are obligatory equipment for HGVsproduced after August 2003. To date, there is insufficient research describing the efficiency ofstatutory and energy absorbing (e.a.) FUPDs in real traffic collisions.The aim of the research presented in this thesis is to understand and suggest improvements forthe compatibility between trucks and passenger cars through parametric studies of differentdesign and collision configurations where the compatibility between trucks and cars is seen asan indivisible part of overall crash compatibility between vehicles. The focus was therequirements for energy absorbing FUPDs to overcome the unpredictable behaviour ofpassenger cars in frontal collisions by studying the links between geometry and stiffness asinfluenced by crash configuration and structural interaction. The bending stiffness of e.a.FUPD cross-beams, their height, and triggering force for energy absorbing elements werefound to be important characteristics of e.a. FUPD that influence the outcome in collisionsbetween HGVs and passenger cars.The stable response of vehicle structures was identified as an important issue to understand. Anew analysis approach, called the RED method, was developed and presented. Using energyabsorption and impact forces calculated in FE simulations, the RED method gives moreinsight into structural deformation processes than other methods and thereby improves theevaluation of vehicle structures. Information derived from the procedure was used to developtwo new assessment criteria - Structural Efficiency and Crash Stability – that can be used toobjectively quantify the crash response of vehicles. Because the method is based on FE crashsimulations it can be used in the development as well as production phase of a vehicle crashstructure or even other structures where deformation modes are important. It was shown thatthese criteria can be used in compatibility rating where a new perspective on compatibility isintroduced and applied.
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| 45243. |
- Krusper, Aleksandra, 1967, et al.
(författare)
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Truck frontal underride protection - compatibility factors influencing passenger car safety
- 2012
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Ingår i: International Journal of Crashworthiness. - : Informa UK Limited. - 1358-8265 .- 1754-2111. ; 17:2, s. 217-232
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Tidskriftsartikel (refereegranskat)abstract
- Frontal collisions between passenger cars and trucks are the severest vehicle-to-vehicle collisions observed in accident statistics. Regulation 93 was developed to reduce the risk of fatal injury by preventing passenger cars from underriding heavy truck structures. The regulation does not fully address the higher energy of content in these collisions where passenger car structures cannot be expected to have sufficient energy-absorbing capacity. The performance of a front underrun protective device (FUPD) incorporated into a finite element truck model was evaluated and compared with earlier studies by the authors. In particular, structural interaction of the car with the truck structures was investigated. The packing of the FUPD and truck structures was a critical factor for the FUPD performance. It was found that when the vertical offset between the FUPD and truck frame rails is too small, the efficiency of the FUPD is decreased. Incorporating deformable truck frame elements is only beneficial if the offset is at least 220 mm.
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| 45244. |
- Krusper, Aleksandra, 1967, et al.
(författare)
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Truck frontal underride protection-compatibility factors influencing passenger car safety
- 2010
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Ingår i: International Crashworthiness Conference, ICRASH 2010.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Frontal collisions between passenger cars and trucks are the most severe vehicle-vehicle collisions observed in accident statistics. Regulation 93 was developed to reduce the risk of fatal injury by preventing passenger cars from underriding heavy truck structures. The regulation does not fully address the higher energy of content in these collisions where passenger car structures cannot be expected to have sufficient energy absorbing capacity. The performance of a FUPD incorporated into a FE truck model was evaluated and compared to earlier studies by the authors. In particular, structural interaction of the car with the truck structures was investigated. The packing of the FUPD and truck structures was a critical factor for the FUPD performance. It was found that when the vertical offset between the FUPD truck frame rails is too small, the efficiency of the FUPD is decreased. Incorporating deformable truck frame elements is only beneficial if the offset is at least 220 mm.
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| 45245. |
- Krut, Jan Jessen, et al.
(författare)
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Biomarker Evidence of Axonal Injury in Neuroasymptomatic HIV-1 Patients
- 2014
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- Prevalence of neurocognitive impairment in HIV-1 infected patients is reported to be high. Whether this is a result of active HIV-related neurodegeneration is unclear. We examined axonal injury in HIV-1 patients by measuring the light subunit of neurofilament protein (NFL) in CSF with a novel, sensitive method.With a cross-sectional design, CSF concentrations of neurofilament protein light (NFL) (marker of neuronal injury), neopterin (intrathecal immunoactivation) and CSF/Plasma albumin ratio (blood-brain barrier integrity) were analyzed on CSF from 252 HIV-infected patients, subdivided into untreated neuroasymptomatics (n = 200), HIV-associated dementia (HAD) (n = 14) and on combinations antiretroviral treatment (cART) (n = 85), and healthy controls (n = 204). 46 HIV-infected patients were included in both treated and untreated groups, but sampled at different timepoints. Furthermore, 78 neuroasymptomatic patients were analyzed before and after treatment initiation. While HAD patients had the highest NFL concentrations, elevated CSF NFL was also found in 33% of untreated neuroasymptomatic patients, mainly in those with blood CD4+ cell counts below 250 cells/μL. CSF NFL concentrations in the untreated neuroasymptomatics and treated groups were equivalent to controls 18.5 and 3.9 years older, respectively. Neopterin correlated with NFL levels in untreated groups while the albumin ratio correlated with NFL in both untreated and treated groups. Increased CSF NFL indicates ongoing axonal injury in many neuroasymptomatic patients. Treatment decreases NFL, but treated patients retain higher levels than controls, indicating either continued virus-related injury or an aging-like effect of HIV infection. NFL correlates with neopterin and albumin ratio, suggesting an association between axonal injury, neuroinflammation and blood-brain barrier permeability. NFL appears to be a sensitive biomarker of subclinical and clinical brain injury in HIV and warrants further assessment for broader clinical use.
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| 45246. |
- Krut, Jan Jessen, et al.
(författare)
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No support for premature central nervous system aging in HIV-1 when measured by cerebrospinal fluid phosphorylated tau (p-tau).
- 2017
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Ingår i: Virulence. - : Informa UK Limited. - 2150-5608 .- 2150-5594. ; 8:5, s. 599-604
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Tidskriftsartikel (refereegranskat)abstract
- The prevalence of neurocognitive deficits are reported to be high in HIV-1 positive patients, even with suppressive antiretroviral treatment, and it has been suggested that HIV can cause accelerated aging of the brain. In this study we measured phosphorylated tau (p-tau) in cerebrospinal fluid (CSF) as a potential marker for premature central nervous system (CNS) aging. P-tau increases with normal aging but is not affected by HIV-associated neurocognitive disorders.
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| 45247. |
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| 45248. |
- Kruusmaa, Maarja, 1970
(författare)
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Repeated Path Planning for Mobile Robots in Dynamic Environments
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents a global navigation strategy for repeated traverse of mobile robots in dynamic environments. The research is motivated by the fact that most real-world applications of mobile robotics imply repeated traverse between predefined target points in large, uncertain real-world domains. The goal of this study is to develop a framework for navigation in large-scale dynamic environments that permits the robot to fulfill its assignment by adapting to use of easily traversable paths. While mobile robots usually tackle the problem of path planning in uncertain environments by implementing obstacle avoidance routines, in this approach the robot also learns to use routes along which obstacles occur less often. The few alternative approaches that consider the problem of global obstacle avoidance function in well-structured environments using an a priori known topological map. The approach reported in this thesis uses a grid-based map for path planning. It is argued that a grid-based map together with a stochastic wavefront planner offers a greater number of alternatives to the path planning problem and that the robot adapts to be able to use the best routes even when very little a priori knowledge of the environment is available. To adapt to dynamic environments the robot uses case-based reasoning to remember the paths followed and to reason about their traversability. While case-based reasoning is usually applied for planning problems in static environments, this approach also works in dynamic environments and uses a unique similarity measure to reduce the solution space. This thesis also offers an alternative decision-making strategy for mobile robots in hazardous environments that is based on the concept of irreversible decisions. The experiments made in simulated and real environments demonstrate that this approach to global navigation permits the robot to increase the predictability of its behavior and to minimize the risk of collision an time delays.
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| 45249. |
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| 45250. |
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