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Deceleration behavior of multi‑layer cork composites intercalated with a non‑Newtonian material

Sheikhi Mohammad Rauf, Gürgen Selim

Archives of Civil and Mechanical Engineering

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2023

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Vol. 23, no. 1

art. no. e2, 2023

EN

Impact or sudden accelerations are strictly avoided by sensitive systems such as electronic devices, robotic structures and unmanned aerial vehicles (UAVs). In order to protect these systems, various composites have been developed in recent years. Due to its excellent energy absorbing capabilities as well as eco-friendly and sustainable properties, cork is one of promising materials dedicated to protective applications. In this study, we beneft from cork agglomerates in multi-layer design considering its advantages such as high fexural stifnesstoweight ratio and good buckling resistance over monolithic structures. In addition, a non-Newtonian material, namely shear thickening fuid (STF) was incorporated in this design. STF shows rapid increase in its viscosity under loading and thereby enabling a stifer texture that contributes to protective performance. At rest state, STF exhibit fuidic behavior and provides fexibility for composite. In the experimental stage, deceleration behavior of these composites was investigated. According to the analyses, STF exhibits promising results to lower peak decelerations while extending time period of deceleration under impact loading. STF contribution is pronounced by using this material in a closed medium such as in wrapped foam to avoid spilling out of composite during impact. The designed eco-friendly smart composites are suggested to cover internal parts in sensitive systems. Micro-mobility helmet is another prospective application area for cork/STF structures since they provide light-weight, excellent fexibility and good deceleration behavior.

2

Znaczenie pojęcia „pieszy wchodzący” - głos polemiczny

Krzemień Piotr

Paragraf na Drodze

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2022

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Nr 4

21--42

PL

Opracowanie jest kontynuacją publikacji autora dotyczących zmian ustawy Prawo o ruchu drogowym w zakresie pierwszeństwa pieszych. Jednocześnie stanowi polemikę z poglądem polegającym na stwierdzeniu, że pieszy wchodzący na przejście to taki „który zaraz wkroczy na przejście” i w praktyce znajduje się poza przejściem dla pieszych, czyli w małej odległości od krawędzi jezdni i przejścia.

EN

The article is a follow-up to the author’s publication on the amendments to the Act on Road Traffic in the field of pedestrians’ right of way. It is also a polemic against the view that a pedestrian entering a zebra crossing is one “that is about to enter the crossing” while he/she is actually outside the crossing proper, in other words at a small distance from the curb and the crossing.

3

Fakultatywny obowiązek zmniejszenia prędkości przed przejściem dla pieszych w kontekście zakazu wchodzenia bezpośrednio przed jadący pojazd

Krzemień Piotr

Paragraf na Drodze

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2022

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Nr 1

21--42

PL

Opracowanie jest kontynuacją publikacji autora dotyczącej zmian ustawy Prawo o ruchu drogowym w zakresie pierwszeństwa pieszych 1. Tym razem autor skupił się na obowiązku zmniejszenia prędkości przed przejściem dla pieszych, w taki sposób, aby nie narazić na niebezpieczeństwo pieszego wchodzącego lub znajdującego się na tym przejściu. Autor dowodzi, że obowiązek ten jest fakultatywny, tj. zależny od spełnienia się kilku czynników związanych zarówno z pieszym, jak i z ruchem pojazdu oraz warunkami zewnętrznymi, takimi jak widoczność i stan jezdni. W publikacji zaproponowano również „korektę” brzmienia przedmiotowego przepisu, w taki sposób, aby był lepiej dostosowany do sytuacji występujących w ruchu drogowym. Na zakończenie autor podaje przykładowe bezpieczne odległości wejścia pieszego przed pojazd dla różnych prędkości i warunków przyczepności, tak aby nie uchybić zasadom ruchu drogowego wskazując, że zmniejszenie prędkości przed przejściem dla pieszych nie zawsze zapobiegnie nieprawidłowemu zachowaniu pieszego - o ile takie nastąpi.

EN

The paper is a follow-up of the article by the author on the amendments to the Act on Road Traffic concerning pedestrian priority. The author focuses on the driver’s obligation to reduce the speed ahead of a pedestrian crossing so as not to endanger the pedestrian entering or walking across the crossing. The author argues that this obligation is optional, i.e. it depends on the occurrence of several factors concerning both pedestrians and vehicle movement as well as external conditions such as visibility and state of the road. The author also proposes a “correction” of the said regulation to make it more closely adapted to actual traffic situations. Finally, the author provides examples of safe distances for a pedestrian to walk in front of a vehicle versus various speeds of vehicles and the adhesion conditions, while obeying road traffic rules. The author points out that speed reduction by the driver in front of a pedestrian crossing does not always prevent incorrect behaviour of the pedestrian should this take place.

4

Empirical modeling of the relationship between decision sight distance and stopping sight distance based on AASHTO

Bassan S.

Archives of Transport

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2018

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Vol. 48, iss. 4

7--25

EN

The paper introduces implementation of highways' stopping sight distance (SSD) and decision sight distance (DSD) based on AASHTO modeling assumptions. SSD characterizes the necessary distance for highway vehicles to stop safely in front from an obstacle. SSD is a function of vehicle speed, perception reaction time, deceleration rate, and grade based on AASHTO and most highway design international guidelines. The deceleration rate which is assumed constant (3.4 m/sec2) based on AASHTO 2011 is generally controlled by the friction coefficient depending on the road surface conditions. A driver's demanded deceleration rate may not exceed the range of friction coefficient according to various pavement conditions. Although SSD is generally sufficient to allow skilled and alert drivers to the stop their vehicles under regular situations, this distance is insufficient when information is difficult to comprehend. A DSD should be provided in highways geometric design when the driver is required to detect an unexpected or difficult to perceive information source. Interchanges (specifically exit ramps) and intersections, and required changing in driver direction of travel, changes in the basic cross section such as toll plaza, lane drop, are typical scenarios where driver needs DSD in the safety manner. The introduction of the two sight distance types (SSD and DSD) is a perquisite for empirical modeling of the relationship between DSD and SSD. The modeling refers to DSD for rural highways, suburban roads, and urban roads based on AASHTO models. Specifically the paper covers DSD three avoidance maneuver types of stopping (types A, A1, B) and three maneuver types of speed, path, and direction changing (types C,D, E) for the three roadway categories. The major parameters that control these avoidance types are pre-maneuver times, and pre-maneuver plus maneuver times. The empirical relationship proposed in this study simplifies the process of evaluating the decision sight distance based on stopping sight distance record, based on AASHTO models, without the need of strenuous estimation of the DSD model maneuver and deceleration parameters. Such a simplified correlation has not been found in the literature except a rough approximation documented in the British highway design guidelines.

5

Experimental study on comparison of kinematic traffic characteristics of a road tractor and a passenger car at sub-zero temperatures

Waluś K.

Archives of Transport System Telematics

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2013

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Vol. 6, iss. 4

37--41

EN

Experimental studies on kinematic characteristics of the vehicle are usually performed using passenger cars, which is related to their availability and the ability to conduct tests on public roads. Road tests using trucks, due to the increased need for security, are performed less frequently and usually on special routes or public roads temporarily excluded from the traffic. The lack of tests performed together on various types of vehicles in similar environmental and weather conditions limits the possibility of direct comparison of the obtained results. Road tests conducted in December 2012 enabled the acquisition and recording of longitudinal acceleration values of passenger car and truck under identified environmental and surface conditions. Experimental studies were conducted on kinematic characteristics of the vehicle and a comparative analysis of the intensity of acceleration and breaking of a new passenger car and of a truck tractor without a trailer in sub-zero temperatures was carried out.