Gupta M.,National University of Singapore |
Wong W.L.E.,Kio University
Magnesium Technology | Year: 2014
Magnesium is the lightest structural metal with tremendous potential in weight critical engineering and biomedical applications. To pave the way of magnesium based materials into multiple applications, it is important that: A) they can be processed cost effectively and using the existing infrastructure used for processing conventional light metal such as aluminum and b) there be enough formulations with wide range of combination of properties. In the first part of this paper, cost effective processing using disintegrated melt deposition technique and microwave assisted powder metallurgy technique will be highlighted. In the second part, mechanical characteristics of magnesium based formulations primarily focusing on nanocomposites will be presented with an aim to address their suitability in engineering applications. Finally this paper will conclude illustrating the current efforts that are made to replace aluminum alloys with magnesium based formulations.
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.
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.
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.
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.
Nagasawa T.,Kio University
Journal of Strength and Conditioning Research | Year: 2013
The purpose of this study was to examine whether differences in aerobic capacity and training status influence muscle reoxygenation after sprint exercise. We hypothesized that the muscle reoxygenation rate after sprint exercise is slower in long-distance runners with a high aerobic capacity. Five male long-distance runners, 5 male sprinters, and 6 healthy male controls performed a 30-second sprint exercise on a cycle ergometer. Oxygen saturation in muscle tissue (StO2) in the vastus lateralis muscles was measured by near-infrared spectroscopy. The muscle reoxygenation rate after the exercise was evaluated at half the time required for StO2 recovery (T 1/2 StO2). Aerobic capacity was evaluated by measuring maximal oxygen consumption (V̇O2max). The T1/2 StO2 in the long-distance runners (25.0 ± 4.5 seconds) was significantly longer than that in the controls (15.9 ± 1.6 seconds; p < 0.01) and in the sprinters (18.0 ± 4.6 seconds; p < 0.05). In all the subjects (long-distance runners, sprinters, and controls), the T 1/2 StO2 had a significant positive correlation with the V̇O2max (r = 0.75; p < 0.01) and was longer in subjects with a higher V̇O2max. These results suggest that reoxygenation after sprint exercise is influenced by aerobic capacity and training status, and that the subjects with a higher aerobic capacity have delayed muscle reoxygenation after sprint exercise. © 2013 National Strength and Conditioning Association.
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.
Kuroki Y.,Kio University |
Kanauchi K.,Narahigashi Hospital |
Kanauchi M.,Kio University
European Journal of Internal Medicine | Year: 2012
Background: As Japanese societies rapidly undergo Westernization, the prevalence of metabolic syndrome is increasing. We investigated the association between dietary habits and the prevalence of metabolic syndrome using a new adherence index to optimal dietary habits based on the American Heart Association Diet and Lifestyle Recommendation (AHA-DLR). Methods: We conducted a cross-sectional study of 503 male workers who completed a brief food frequency questionnaire. Adherence to the AHA-DLR was assessed using a 10-component adherence index (AI-84; a total possible score of 84 points). Metabolic syndrome was defined according to the most recently published harmonized criteria by the International Diabetes Federation in conjunction with the National Heart, Lung, and Blood Institute, American Heart Association, World Heart Federation, International Atherosclerosis Society, and International Association for the Study of Obesity. Results: The prevalence of metabolic syndrome was 26.6% and the AI-84 score ranged from 5 to 56 points. Subjects with metabolic syndrome had a significantly lower AI-84 score compared with those without (27.1 ± 9.1 vs. 28.9 ± 9.2, p = 0.042). After adjusting for age, energy intake, smoking habit and physical activity, a higher AI-84 score was associated with a significantly lower prevalence of metabolic syndrome, with an odds ratio of 0.778 (95% CI 0.614-0.986, p = 0.038) for each 10-point score increment. Conclusions: A lower AI-84 score was associated with increased prevalence of metabolic syndrome. Our findings support a potential beneficial impact of nutritional assessment using adherence to the AHA-DLR for prevention of metabolic syndrome.
Hiyamizu M.,Kio University |
Hiyamizu M.,Kobe University |
Morioka S.,Kio University |
Shomoto K.,Kio University |
Shimada T.,Kobe University
Clinical Rehabilitation | Year: 2012
Objective: To investigate the effects of dual task balance training in the elderly on standing postural control while performing a cognitive task.Design: A randomized two-group parallel controlled trial.Participants: Forty-three subjects (all >65 years old) were enrolled in the study and were assigned randomly to either an experimental group (n=21) or a control group (n=22).Interventions: Subjects in the experimental group were given strength and balance training while performing cognitive tasks simultaneously. Subjects in the control group were given strength and balance training only. The training was administered twice a week for three months.Measurements: The Chair Stand Test, Functional Reach Test, Timed Up and Go Test and Trail Making Test were measured. The sway length of the centre of gravity was measured during standing while performing the Stroop task. The rate of Stroop task was also measured. All measurements were collected at baseline and after the training period.Results: There were no significant differences in Functional Reach Test, Timed Up and Go Test and sway length at baseline and after training between the two groups. However, the rate of Stroop task (P<0.05) was significantly higher after training in the experimental group than in the control group.Conclusions: These results suggest that dual task balance training in elderly people improves their dual task performance during standing postural control. © SAGE Publications 2011.
Logenthiran T.,Kio University |
Woo W.L.,Kio University |
Phan V.T.,Kio University
International Journal of Electrical Power and Energy Systems | Year: 2015
Short-term generation scheduling is an important function in daily operational planning of power systems. It is defined as optimal scheduling of power generators over a scheduling period while respecting various generator constraints and system constraints. Objective of the problem includes costs associated with energy production, start-up cost and shut-down cost along with profits. The resulting problem is a large scale nonlinear mixed-integer optimization problem for which there is no exact solution technique available. The solution to the problem can be obtained only by complete enumeration, often at the cost of a prohibitively computation time requirement for realistic power systems. This paper presents a hybrid algorithm which combines Lagrangian Relaxation (LR) together with Evolutionary Algorithm (EA) to solve the problem in cooperative and competitive energy environments. Simulation studies were carried out on different systems containing various numbers of units. The outcomes from different algorithms are compared with that from the proposed hybrid algorithm and the advantages of the proposed algorithm are briefly discussed. © 2014 Elsevier Ltd. All rights reserved.