An evaluation of radiation damage to solid state components flown in low earth orbit satellites

The effects of total ionising radiation dose upon commercial off-the-shelf semiconductors fitted to satellites operating in low Earth orbit (LEO) conditions was evaluated. The evaluation was performed for the Korea Institute of Technology SATellite-1, (KITSAT-1) which was equipped with commercial solid state components. Two approximate calculation models for space radiation shielding were developed. Verification was performed by comparing the results with detailed three-dimensional calculations using the Monte-Carlo method and measured data from KITSAT-1. It was confirmed that the developed approximate models were reliable for satellite shielding calculations. It was also found that commercial semiconductor devices, which were not radiation hardened, could be damaged within their lifetime due to the total ionising dose they are subject to in the LEO environment. To conclude, an intensive shielding analysis should be considered when commercial devices are used.     

A study on driver’s workload of telematics using a driving simulator: A comparison among information modalities

Recently, diffusion of telematics services and an explosive increase of in-vehicle display devices, such as Car Navigation Systems (CNSs), are becoming the new causes of traffic accidents. This is due to ‘inattention’ caused by an increase in the driver’s mental workload while he/she is driving. This situation has lead many countries to consider controlling the use of in-vehicle devices while driving through legislation. This research studies the effect of voice or display information systems on drivers through the Driver Eye Movement Analysis and the measurement of response ability. The experiment is carried out in a driving simulator and the results are presented through the comparative analysis of the driver’s visual field via the gaze tracking device and the average of correct answer rates for arithmetic problems.     

Loosening mechanism of threaded fastener for complex structures

Journal of Mechanical Science and Technology - Threaded fasteners are widely used in mechanical structures primarily owing to their easy disassembly for maintenance and low cost. However, the...     

Prediction of Dinghy Boom Direction Using Intelligent Predictor

International Journal of Control, Automation and Systems - In this study, an intelligent predictor is designed for predicting the direction of dinghy booms and coaching dinghy sailing using the...     

A study to maximize the crash energy absorption efficiency within the limits of crash space

The design of an engine room is important to protect the passenger from a crash impact by improving the absorption of the crash impact energy. The side member in the engine room absorbs most of the crash impact energy when the vehicle experiences a frontal crash. The side member is of two types: hat and ‘U.’ Analysis of the extent of energy absorption and the mechanism of the side member are necessary through a collapse mode in various load conditions. In this study, the design of experiments was used for evaluating the characteristics of the absorption of crash energy by side members through design variables. First, crash analysis was performed by experiment number extracted from the design of the experiment. Then, using the results of crash analysis, multiple regressions were conducted and sensitivity analysis performed for each design variable. Finally, the optimum design was developed for maximizing the absorption energy per unit weight considering various boundary conditions. In the present study, as a basic step for modeling the fatigue behavior of an extruded Al alloy cylinder, the fatigue crack growth data of the alloy was collected in two orientations. Microstructural analysis revealed that the material had recrystallized grains and clusters of constituent particles aligned in the direction of extrusion. Fatigue life of the samples revealed a shorter fatigue life representing a higher fatigue crack growth rate in the transverse direction.     

All solution processed organic thin film transistor-backplane with printing technology for electrophoretic display

In this study, solution processes were developed for backplane using an organic thin film transistor (OTFT) as a driving device for an electrophoretic display (EPD) panel. The processes covered not only the key device of OTFTs but also interlayer and pixel electrodes. The various materials and printing processes were adopted to achieve the requirements of devices and functioning layers. The performance of OTFT of the backplane was sufficient to drive EPD sheet by producing a mobility of 0.12 cm2/v x sec and on/off current ratio of 10(5).     

Spatial Stability of Nonsymmetric Thin-Walled Curved Beams. II: Numerical Approach

In a companion paper, for spatial stability of nonsymmetric thin-walled curved beams, a general formulation was derived based on a displacement field considering the second-order terms of semitangential rotations. Closed-form solutions were newly derived for in-plane and out-of-plane buckling of simply supported curved beams with monosymmetric sections subjected to pure bending or uniform compression. In this paper, to get numerical solutions for the buckling of thin-walled curved beams subjected to general loadings, finite-element procedures are developed using thin-walled curved beam elements and straight frame elements with nonsymmetric sections. Numerical examples for the spatial buckling of doubly symmetric, monosymmetric, and nonsymmetric thin-walled circular beams are presented and compared with previously published solutions to illustrate the accuracy and the practical usefulness of the analytical solutions and numerical procedures.     

Effects of Sodium Citrate Concentration on Electroless Ni-Fe Bath Stability and Deposition

In this research, electroless Ni-Fe bath stability and deposition characteristics were investigated for various sodium citrate concentrations. Complexing agents such as sodium citrate are one of the main components of such electroless plating baths. Since they could play various roles such as maintaining pH stability, preventing precipitation of metal salts, and reducing the concentrations of free metal ions, the concentration of complexing agents in the plating bath is an important parameter for electroless deposition processes. In this research, unstable baths were obtained for insufficient sodium citrate concentrations, and these phenomena were analyzed with ChemEQL. Moreover, the deposition characteristics of electroless Ni-Fe for under bump metallurgy diffusion barriers were also investigated using energy-dispersive spectroscopy and field-emission scanning electron microscopy.     

A study on the optimum design of high-speed low-floor bogie with independently rotating wheels

The low-floor bogie is a prior technology in countries and companies that want to develop the tram. The Low-floor tram (LFT), which includes low-floor bogies, is easy to embark and disembark because of the low floor height. In addition, it can be driven on urban as well as rural tracks. Furthermore, emissions such as NOx and SOx can be reduced. Due to these advantages, this innovative technology is expected to change the public transport system. To improve utilization in a downtown area, the technology for the low-floor bogie should satisfy conditions of a high-speed of over 80 km/h and minimum radius within a 25 mR curve for smooth running on a track that has a severe turning radius. Moreover, the wheelset should not be located in the bogie, and the components inside the bogie need to be wellarranged to satisfy the full low-floor condition. In this study, to develop an over-80 km/h class high-speed low-floor bogie that can be driven safely on a 25 mR curved track, a conceptual design of the LFT multibody dynamics model was constructed and dynamic characteristics were assessed by dynamic analysis. The modeling modification with Independently rotating wheels (IRW) needed to steer actively through semi-active suspension and the optimization using Design of experiments (DOE) were then performed. Through DOE method, the optimum combination of design parameters could be obtained and, the driving performances such as ride stability, comfort and safety of the LFT could then be improved about 7 %. The results of this work are available to detail design and development of LFT.     

Driving Performance Analysis of the Adaptive Cruise Controlled Vehicle with a Virtual Reality Simulation System

Nowadays, with the advancement of computers, computer simulation linked with VR (Virtual Reality) technology has become a useful method for designing the automotive driving system. In this paper, the VR simulation system was developed to investigate the driving performances of the ASV (Advanced Safety Vehicle) equipped with an ACC (Adaptive Cruise Control) system. For this purpose, VR environment which generates visual and sound information of the vehicle, road, facilities, and terrain was organized for the realistic driving situation. Mathematical models of vehicle dynamic analysis, which includes the ACC algorithm, have been constructed for computer simulation. The ACC algorithm modulates the throttle and the brake functions of vehicles to regulate their speeds so that the vehicles can keep proper spacing. Also, the real-time simulation algorithm synchronizes vehicle dynamics simulation with VR rendering. With the developed VR simulation system, several scenarios are applied to evaluate the adaptive cruise controlled vehicle for various driving situations.