Naayagi R.T.,Kio University
Proceedings of the International Conference on Power Electronics and Drive Systems | Year: 2015
This paper presents the guidelines for selecting suitable power semiconductor devices for the dual active bridge (DAB) DC-DC converter targeting aerospace applications. The main power loss in a switching power supply is the loss associated with power semiconductor devices. The high frequency operation of power electronics reduces the size of magnetic components. As a result, a smaller and lighter circuit design is feasible. However, the high switching frequency increases the power device losses. Therefore, the selection of appropriate power devices is essential to design efficient power electronics. This paper clearly presents the guidelines for selecting suitable power devices (IGBTs) for a 20kW, 540V/125V, 20kHz DAB converter prototype meant for use in an aerospace application. © 2015 IEEE.
Fuyuki M.,Kio University
Journal of Luminescence | Year: 2016
The multiphoton photodegradation mechanism of indocyanine green (ICG) was investigated by using femtosecond near-infrared (NIR) pump and probe pulses. In the pump fluence region from 2 mJ/cm2 to 4 mJ/cm2, the photodegradation rate was higher in acetic acid than in ethanol, and the rate was proportional to pump fluence to the 2.3th power in acetic acid and the 3.9th in ethanol. Considering that the degree of auto-protolysis of acetic acid is much higher than that of ethanol, the experimental results indicate that self-ionized solvent molecules played an essential role in the degradation of ICG molecules excited by NIR multiphoton process. © 2015 Elsevier B.V. All rights reserved.
Gupta M.,National University of Singapore |
Wong W.L.E.,Northumbria University |
Wong W.L.E.,Kio University
Materials Characterization | Year: 2015
Magnesium and its alloys reinforced with nano-size reinforcements display improved mechanical properties without significant reduction in the ductility that is usually associated with the addition of micron size reinforcements, making them an attractive choice for lightweight structural applications. This paper provides a review of magnesium nanocomposites containing ceramic and metallic reinforcements synthesized using liquid based (Disintegrated Melt Deposition Technique) and solid based (Powder Metallurgy and Microwave Sintering) processing techniques. The properties of these nanocomposites will be discussed in terms of microstructure, grain size, hardness, tensile, compressive, dynamic, high temperature, corrosion, fatigue and wear. © 2015 Elsevier Inc.
Yamamoto T.,Kio University |
Ueji K.,Kio University
Frontiers in Systems Neuroscience | Year: 2011
Once the flavor of the ingested food (conditioned stimulus, CS) is associated with a preferable (e.g., good taste or nutritive satisfaction) or aversive (e.g., malaise with displeasure) signal (unconditioned stimulus, US), animals react to its subsequent exposure by increasing or decreasing ingestion to the food. These two types of association learning (preference learning vs. aversion learning) are known as classical conditioned reactions which are basic learning and memory phenomena, leading selection of food and proper food intake. Since the perception of flavor is generated by interaction of taste and odor during food intake, taste and/or odor are mainly associated with bodily signals in the flavor learning. After briefly reviewing flavor learning in general, brain mechanisms of conditioned taste aversion is described in more detail. The CS-US association leading to long-term potentiation in the amygdala, especially in its basolateral nucleus, is the basis of establishment of conditioned taste aversion. The novelty of the CS detected by the cortical gustatory area may be supportive in CS-US association. After the association, CS input is conveyed through the amygdala to different brain regions including the hippocampus for contextual fear formation, to the supramammillary and thalamic paraventricular nuclei for stressful anxiety or memory dependent fearful or stressful emotion, to the reward system to induce aversive expression to the CS, or hedonic shift from positive to negative, and to the CS-responsive neurons in the gustatory system to enhance the responsiveness to facilitate to detect the harmful stimulus. © 2011 Yamamoto and Ueji.
Do T.N.,Nanyang Technological University |
Tjahjowidodo T.,Nanyang Technological University |
Lau M.W.S.,Kio University |
Phee S.J.,Nanyang Technological University
Mechanical Systems and Signal Processing | Year: 2014
The tendon sheath mechanism plays an important role in many robotic systems from surgical devices to robot hands. However, many unexpected properties such as nonlinear hysteresis and backlash, which appear in the tendon sheath system, cause major losses in force transmission. This report deals with the characterization of hysteresis phenomenon, which is attributed to the presence of frictional effects on its elements, in a tendon-sheath driven surgical robot. Unlike various approaches presented in the literature that utilized multiple lumped mass elements, this proposed approach models the tendon sheath as one element. A new dynamic friction model that allows accurate description of friction lag and hysteresis behavior in two regimes, i.e. presliding and sliding regimes, for a sheath in arbitrary configuration such as helical and spatial shape has been developed. In both regimes, an advanced set of velocity and acceleration dependent functions in a form of the Stribeck function and the modified normalized Bouc-Wen model are used to model friction characteristics between the tendon and the sheath. The smooth transition between the two regimes is also assured. The proposed model is subsequently validated using experimental data. It shows a high degree of accuracy and fidelity in predicting the friction force in a tendon-sheath mechanism. The proposed model overcomes the current drawbacks in tendon sheath friction modeling approach when dealing with discontinuity as the system operates near areas of zero velocity. The new structure of this new model allows a simplified calculation, bringing more valuable practicability and providing an accurate prediction for haptic feedback and control purposes. © 2013 Elsevier Ltd. All rights reserved.