Safety and security are among the major basic needs for the public in daily life and transportation plays a crucial role in satisfying this need. According to the World Health Organization (WHO) data, estimates of 1.2 million people worldwide died as a result of road traffic injuries in 2013 and it is estimated that road traffic injuries will be the 6th leading cause of death by 2030. Among the various types of road traffic injuries, accidents between trains and road vehicles are the deadliest and are associated with high cost of accidents. As Railway transportation continues to be an important piece to the overall national transportation puzzle in Ethiopia and as congestion continues to increase on the nation’s roadways, commuters continue to flock to public transit as an alternative transportation mode. In Addis Ababa Light Rail Transit, there are over 20 level crossings, this represent a significant safety hazard to both road and rail users. In this paper, we used safety demonstration by complete system analysis to carry out safety demonstration for level crossing at Addis Ababa Light Rail Transit, and Failure mode effect analysis was used for identifying the potential hazards associated with the system and their root causes. Hazards associated with Addis Ababa Light Rail Transit level crossing are identified and classified, and results showed that 41% of the hazards are caused by Human errors, technical problems has 32%, non-compliance with standard operating procedures takes 18% and 9% are caused by other factors. Our Failure mode effect analysis result shows that safe redesign of the level crossing, management and operation of level crossings can reduce risks, and frequent orientation of road vehicle users to always give attention to traffic signal in level crossing can reduce the number of fatal and serious incidents and collisions.
In this paper, a refrigeration system using shell and tube evaporator will be converted to a refrigeration system using a plate type evaporator. The performance of the modified system will be evaluated and compared with the performance of the plate type evaporator. A refrigeration system working on a shell and tube evaporator was selected, charged with refrigerant R134a. Temperature and pressure readings were taken at both the inlet and outlet of both the evaporator and condenser unit respectively. The refrigeration system with shell and tube evaporator was then removed and replaced with a plate type evaporator. The system was evacuated, charged with refrigerant and readings were taken at both the inlet and outlet of the evaporator and condenser respectively. Experimental results obtained shows that the refrigeration efficiency of the shell and tube evaporator was 64.33% and that of the plate type evaporator was 85.24%. The result obtained shows that the COP of the refrigerator using the plate type evaporator is higher than that of the refrigerator using the shell and tube evaporator. The refrigeration system working on a plate type evaporator has higher refrigeration capacity and lower compressor work, low liquid hold up, higher surface area than the shell and tube evaporator system.
The aim of this analysis was to model the pantograph - catenary system
at static equilibrium and provide analytical solutions by computing the
natural frequencies of the system, mode functions, equivalent stiffness
of the catenary system and the deflections of the catenary wire as a
function of position, time and tensioning force. Furthermore, dynamic
analysis was conducted analytically and the results of the dynamic
performance were obtained. It was shown that the dynamic response of the
catenary system is dependent on the design parameters in which
tensioning force is included. It was also shown that low tensioning
forces result in high risk of contact loss and increased wave
propagation in the catenary wire while high tensioning forces result in
increased static stresses in the catenary system. The results in this
article can be used to select optimum tensioning forces and design
parameters for desired pantograph-catenary dynamic performance.
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