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Biomedical subjects

J Kajzer

Publications and source records attributed to J Kajzer.

13 recordsLinked to original sources

Analysis and comparison of reflex times and electromyograms of cervical muscles under impact loading using surface and fine-wire electroces.

Myoelectric signals [electromyograms (EMGs)] can be collected using either surface or fine-wire electrodes. Application of the latter results in higher-frequency contents of EMG. In the field of impact biomechanics, surface electrodes are more often utilized than fine-wire ones. However, the removal of motion artefacts from EMG recorded under transient loads requires application of high-pass filters with relatively high cutoff frequencies, which may eliminate a significant part of the surface EMG power spectra. Therefore, in the current study, both surface and fine-wire electrodes were utilized to record the EMG of cervical muscles under conditions simulating a rear-end car collision at low speed. The results indicated that application of high-pass filtering at 50 Hz can be necessary to remove motion artefacts from the EMG collected under such conditions. Such filtering resulted in a higher decrease in amplitude of the surface EMG than that of the fine-wire one. However, the reflex times obtained here were not significantly affected by the type of the electrodes utilized to collect EMG.

Artifacts↗

Compatibility problems in frontal, side, single car collisions and car-to-pedestrian accidents in Japan.

Compatibility problems in car-to-car frontal, side, single car and car-to-pedestrian collisions in Japan are discussed using traffic accident data. The number of serious and fatal injuries is investigated for the subject car and other cars, which are categorized by their class and mass. The aggressivity of the cars is calculated by the number of fatalities, fatality rates and by the number of car registrations. The results show that in car-to-car frontal collisions, cars with a mass of 1150 kg are the most compatible among the current car population. In both car-to-car frontal and side collisions, the sports utility vehicle and mini car are found to be the most incompatible car types with high and low aggressivity, respectively. On the other hand, the accident data show that the wagon and midsize sedan are the most compatible car types. The compatibility of fixed objects in the road environment with cars and cars with pedestrians is also discussed. In a single car collision with a fixed object, the guardrail is the most compatible object and can reduce the fatality rate on prefecture roads by about 60%. The front geometry of the car has large effect on compatibility with a pedestrian.

Accidents, Traffic↗

Impact modelling studies for a three-wheeled scooter taxi.

Three-wheeled scooter taxis (TSTs) are being used in many Asian countries and along with buses are the main mode of public transport for the urban middle class population. The TST chassis is made by the manufacturer and the body is fabricated by local body-makers. The vehicle is not subject to any crash safety specifications. This work is the first attempt to study the crash characteristics of TSTs using a crash simulation computer software (MADYMO) with the objective of developing practical guidelines to make the vehicle safer in collisions with other motorized road users and pedestrians. Impact modelling was done for the standard and modified TST occupied by a driver and one passenger at impact velocities of 10-30 km/h crashing with a pedestrian and a bus front. The results show that the passenger and the driver of the standard TST can sustain high HICs, face/head contact forces and tibia/knee contact forces in crashes with buses at velocities 20 km/h and greater. The magnitude of these parameters can be reduced slightly by small changes in the design of the interior and padding of critical surfaces. To increase the safety of the TST significantly major modifications need to be incorporated in the design of TSTs and bus fronts. Pedestrian impact simulations indicate that it may be possible to reduce the impact forces by changing the shape of the front of the TST. The results indicate that it should be possible to improve the crash safety properties of vehicles indigenously designed in Asian and African countries by the use of crash simulation models like MADYMO. This procedure is relatively inexpensive and can provide the first approximations for design of safer vehicles.

Accidents, Traffic↗

Simulation of car impact to pedestrian lower extremity: influence of different car-front shapes and dummy parameters on test results.

Sled impact tests on mechanical substitutes for a pedestrian were conducted as a preliminary study for the purpose of developing a subsystem test procedure for the assessment of car-front aggressiveness to pedestrian legs. Four mechanical substitutes for a pedestrian were used in the test: the leg of a rotationally symmetrical pedestrian dummy (RSPD) as the representation of a subsystem, a HYBRID-II pedestrian dummy, a modified HYBRID-II pedestrian dummy equipped with a steel bar serving as knee joint, and a RSPD - HYBRID-IIP combined dummy in which the lower part of the RSPD and the upper part of the HYBRID-IIP were connected by a joint in such a way that the movements of the upper part were similar to those in cadaver tests. In the tests the following were evaluated: (i) the influence of vehicle shape on knee response and on vehicle impact force; (ii) the influence of the upper body mass on knee response and on vehicle impact forces; (iii) the influence of the bumper system on knee response, the kinematics of pedestrian mechanical substitute, and on vehicle impact forces; (iv) the influence of pedestrian mechanical substitute characteristics on its kinematics and knee response, and on vehicle impact forces. This paper describes a primary concept when subsystem test methods for the assessment of car-front aggressiveness to pedestrian legs in a car-pedestrian collision are considered.

Acceleration↗