Do hands-free cell phone conversation while driving increase the risk of cognitive distraction among drivers? A cross-over quasi-experimental study

Background: Background: Conversation over the cell phone while driving is a known risk factor for road traffic crash. Using handsfree to talk on the cell phone may remove visual and manual distraction yet not the cognitive distraction. Objectives: The purpose of this study was to better understand the mechanisms of cognitive distraction due to hands-free cell phone conversation (HFPC) while driving. Methods: Twelve male and 12 female University students in Tehran, Iran, were selected via the consecutive convenient sampling method, and randomly assigned to one of the following administrations of cross-over quasi-experimental study design, during year 2016: Administration 1, participants performed the tests while involved in HFPC, took rest for 60 minute, and then performed the tests another time without HFPC; Administration 2, participants performed the tests without HFPC, took rest, and then performed the tests another time with HFPC. Each participant moved to the other administration after 7 to 10 days. The Vienna test system (VTS) was used to measure simple and choice reaction time, selective attention, visual orientation, and visual memory. Linear regression analysis was used to study the change in test scores due to HFPC. Results: The mean age of participants was 27.1±5.3 years. A history of road traffic crash (regardless of severity) was reported among 9 (37.5) participants in the previous year. Hands-free cell phone conversation while driving was directly associated with mean time correct rejection score (P < 0.01) (selective attention), omitted response (P < 0.01) and median reaction time (P < 0.01) (choice reaction time), and mean reaction time (P < 0.01) (Simple reaction time). Moreover, HPFC was inversely associated with sum hits (P = 0.05) (selective attention), incorrect (P < 0.02) and correct response (P < 0.01) (choice reaction time), score based on viewing and working time (P < 0. 01) (visual orientation), and visual memory performance (P < 0.01). Conclusions: Using hands-free devices to converse during driving, impaired reaction time, selective attention, visual orientation and visual memory, which are essential for safe driving. Thus, the use of these devices does not preclude cognitive distraction and should be restricted. © 2018, Iranian Red Crescent Medical Journal

Do hands-free cell phone conversation while driving increase the risk of cognitive distraction among drivers? A cross-over quasi-experimental study

Background: Background: Conversation over the cell phone while driving is a known risk factor for road traffic crash. Using handsfree to talk on the cell phone may remove visual and manual distraction yet not the cognitive distraction. Objectives: The purpose of this study was to better understand the mechanisms of cognitive distraction due to hands-free cell phone conversation (HFPC) while driving. Methods: Twelve male and 12 female University students in Tehran, Iran, were selected via the consecutive convenient sampling method, and randomly assigned to one of the following administrations of cross-over quasi-experimental study design, during year 2016: Administration 1, participants performed the tests while involved in HFPC, took rest for 60 minute, and then performed the tests another time without HFPC; Administration 2, participants performed the tests without HFPC, took rest, and then performed the tests another time with HFPC. Each participant moved to the other administration after 7 to 10 days. The Vienna test system (VTS) was used to measure simple and choice reaction time, selective attention, visual orientation, and visual memory. Linear regression analysis was used to study the change in test scores due to HFPC. Results: The mean age of participants was 27.1±5.3 years. A history of road traffic crash (regardless of severity) was reported among 9 (37.5) participants in the previous year. Hands-free cell phone conversation while driving was directly associated with mean time correct rejection score (P < 0.01) (selective attention), omitted response (P < 0.01) and median reaction time (P < 0.01) (choice reaction time), and mean reaction time (P < 0.01) (Simple reaction time). Moreover, HPFC was inversely associated with sum hits (P = 0.05) (selective attention), incorrect (P < 0.02) and correct response (P < 0.01) (choice reaction time), score based on viewing and working time (P < 0. 01) (visual orientation), and visual memory performance (P < 0.01). Conclusions: Using hands-free devices to converse during driving, impaired reaction time, selective attention, visual orientation and visual memory, which are essential for safe driving. Thus, the use of these devices does not preclude cognitive distraction and should be restricted. © 2018, Iranian Red Crescent Medical Journal

Ambient vibration testing and empirical relation for natural period of historical mosques. Case study of eight mosques in Kermanshah, Iran

Eight historical mosques of Kermanshah constructed in 18th or 19th century CE are investigated with ambient vibration tests on their sites and buildings. Conventional peak picking technique is used for determination of structures’ fundamental frequencies and spectral ratio of horizontal to vertical components along with ellipticity inversion of Rayleigh waves are considered to identify the natural frequency of ground and shear wave velocity profile to define the site conditions according to the national codes of Iran and Italy. The recorded motions on the buildings are used to calculate the fundamental frequencies of the structure. Afterward, buildings are modeled by macro-element method and material properties are tuned in the way that the fundamental frequencies from the modal analyses match with the measured values from AVTs. Finally, more modal analyses are performed by the calibrated models to present an empirical relation between the natural period of the mosques, the geometrical characteristics of the buildings, and the mechanical properties of the construction materials. The results show that the natural periods of the masonry buildings of the mosques are different from the values of empirical relations in the national codes. Meanwhile, the proposed empirical relation presents the natural periods of the buildings of this study reasonably well and can be used for other masonry buildings of similar architecture and materials

A unified small-strain shear stiffness model for saturated and unsaturated soils

This paper presents a model for calculating the small-strain shear stiffness of saturated and unsaturated fine-grained soils as the product of a dimensionless stiffness index and four individual functions of the mean average skeleton stress, the over-consolidation ratio, the reference saturated void ratio and the degree of saturation. The main element of novelty of the model resides in the introduction of a reference saturated state, which results in a dependency of the small-strain stiffness on the degree of saturation. The reference saturated state is calculated according to a recently published constitutive law that relates the quotient between the unsaturated void ratio and the reference saturated void ratio to the degree of saturation. The model requires only two extra parameters for unsaturated states, i.e. one parameter for the volumetric behaviour and one for the stiffness behaviour. These two parameters may also be correlated to the saturated parameters, which simplifies the calibration of the model. The proposed framework is validated against laboratory experiments on three different materials resulting in generally accurate predictions compared to other published models. The good predictive capabilities and the simplicity of the formulation justify the implementation of the model into numerical codes for the analysis of geotechnical problems