Applied Mechanics and Materials Vols. 479-480

Abstract: A numerical study is conducted to predict the effects of physical parameters of a double layer microchannel heat sink on heat transfer. The physical parameters investigated are the channel height and channel width for different flow orientation at the upper and lower channels. For the range of Reynolds number investigated, results show that parallel flow configuration leads to better heat transfer performance than counter flow. Lower thermal resistance can be achieved in a double-layered microchannel heat sink with higher channel height and lower channel width.

Abstract: Magnetorheological (MR) brake is broadly applied in various fields. As the increase in demand of bicycle training equipment, this paper introduces a MR brake with multiple poles and outer rotor structure, which can be used as resistant source for bicycle-training equipment. With outer-rotor structure, the MR brake is suitable to use as a roller to fit the bike rear wheel on. The equipment is specifically designed for indoor exercise for users with their bikes. Magnetic circuit of the MR brake was built and analyzed. Key factors to affect brake torque were found. After that, two structures of the MR brake with different pole number were simulated to find the optimal one to harmonize between maximum output torque and input power. The simulation results confirm the feasibility of the designed MR brake. With compact design, its braking performance is enough to be use on bicycle-training equipment.

Abstract: Since the friction coefficient is critical to the seismic stability of a freestanding cask, cyclic loading tests of a 1/3 scale-down pedestal specimen of the INER-dry storage cask system, which will be used in Taiwan, were conducted to acquire the actual friction coefficient at the cask/pad interface as well as the effect of normal stress and sliding rate on it. Test results indicated that the cyclic frequency had few influence on the friction coefficient and the friction coefficient increased with the normal stress increased. The friction coefficient of the vertical cylindrical cask with an add-on shield, vertical cylindrical cask and add-on shield under actual loading condition was about 0.67, 0.60 and 0.73, respectively. Based on the frictional properties at the cask/pad interface obtained from the test results, it was performed to ensure the actual seismic stability of this INER-dry storage cask system under the design base earthquake.

Abstract: Permanent magnet (PM) brushless DC motors (BLDCMs) are widely applied in industrial drives. However, the price rising of rare earth resource resulted in country policy restriction, so it is detrimental for mass production of PM-BLDCMs. As a result, the design and manufacture tendency of PM-BLDCMs are smaller and slighter in adopting rare earth materials of PMs. Additional, the magnetic flux density of PMs are difficult to improve in the near future. The effective method is to decrease stator reluctance and to adjust magnetic flux distribution of the air gap in stator design. Hence, the surface permanent magnets (SPMs) and tooth surface stators (TSSs) are designed to improve the motor performance, and are calculated by finite-element analysis (FEA) software in this study. Various hemicycle groove microstructures of SPMs and TSSs for designing, analyzing and optimizing are considered to observe the magnetic field strength distribution and to reduce the cogging torque in PM-BLDCMs, and the FEA result can be regarded as important references of motor structure design. The cogging torque can be reduced 80.9% in SPM3-model and can be decayed 89.2% in TSS2-model versus original model separately, and the cogging torque of the optimal combination of SPM-BLDCM can be abated 62.4%. Furthermore, the usage amount of rare earth material volume in designed SPM-BLDCMs can be reduced 5.3% in average. Finally, a prototype of the SPM- BLDCM has been constructed to prove the simulation design.

Abstract: The nonlinear dynamic behavior of the micro actuators is analyzed in this paper. In general, analysis of the electrostatic device is quite difficult and complicated due to the electrostatic coupling effect and the nonlinear electrostatic force. In this study, a hybrid method for the micro-structure system, which combines the differential transformation and finite difference approximation techniques, is used to overcome the nonlinear electrostatic coupling phenomenon. The analysis takes account of the electrostatic coupling effect, the fringing field effect, the residual stress, the nonlinear electrostatic force and squeeze-film damping effect. Finally, the actuating conditions which ensure the stability of the micro actuators are identified by reference to phase portraits.

Abstract: This paper applies planar inverted-F antenna (PIFA) to design a smart handset antenna in accordance with octa-band operations, as GSM 850 (824-894 MHz), GSM 900 (880-960 MHz), GSM 1800/1900, DCS 1800 (1710-1880 MHz), PCS 1900 (1850-1990 MHz), UMTS (1920-2170 MHz), IEEE 802.11b WLAN (2400-2484 MHz) and LTE (700 MHz/2300 MHz/2600 MHz) band operations for S₁₁ -6 dB. The entire antenna is 75 × 22 × 5.8 mm³ with one-quarter wavelength design of hub. With the inter-coupling between dual branch circuit radiation and multiple branch circuit radiation, the wideband for GSM 1800/1900, DCS, PCS, UMTS, IEEE 802.11b WLAN and LTE 700/2300/2600 is generated. When integrating with mobiles, the designed ground plane area is also taken into consideration. In this case, the ground plane area can be increased in accordance to the system motherboard.

Abstract: The purpose of this study is to develop an appendicitis diagnosis system, by using artificial neural networks (ANNs). Acute appendicitis is one of the most common surgical emergencies of the abdomen. Various methods have been developed to diagnose appendicitis, but these methods have not shown good performance in the Middle East and Asia, or even in the West. We used the structures of ANNs with 801 patients. These various structures are a multilayer neural network structure (MLNN), a radial basis function neural network structure (RBF), and a probabilistic neural network structure (PNN). The Alvarado clinical scoring system was used for comparison with the ANNs. The accuracy of MLNN, RBF, PNN, and Alvarado was 97.84%, 99.80%, 99.41% and 72.19%, respectively. The AUC of MLNN, RBF, PNN, and Alvarado was 0.985, 0.998, 0.993, and 0.633, respectively. The performance of ANNs was significantly better than the Alvarado clinical scoring system (P<0.001). The models developed to diagnose appendicitis using ANNs showed good performance. We consider that the developed models can help junior clinical surgeons diagnose appendicitis.

Abstract: The development and utilization of energy has played a key role in the human civilization process, and fossil fuels have become the major energy supply after Industrial Revolution. However, with the massive utilization of fossil fuels, petroleum and natural gas will be exhausted, and people will face the risk of energy shortages. For this reason, the development of clean, efficient, and renewable energy should be a priority. Hydrogen is considered a safe and secure energy source for human health and the global environment, as it does not emit any pollutants while burning. Hence, this study combines biohydrogen production of dark fermentation with ultrasonic to explore the effects of ultrasonic frequency, amplitude and exposure time on biohydrogen production of dark fermentation. The experimental results show that the largest biohydrogen production appears when the ultrasonic frequency being 1MHz and the ultrasonic exposure time is 15 min for exposure and 15 min for termination. It is therefore possible to find the optimal hydrogen production condition and to further understand the effect of ultrasonic on microorganisms.

Abstract: This study presents a method for reconstructing respiration signals from ECG tracings based on average electrical-cardiac-axis theory with heart rate variability. The algorithm is simplified to use QRS characteristic points and subsequent spectrum analysis. The experiments were conducted on eight healthy patients during rest with spontaneous (voluntarily) and paced breathings. Five QRS characteristic series are constructed, and the corresponding electrocardiography (ECG)-derived respiration (EDR) is compared with measured data. The experiment results show the R-Q-S series-derived respiration exhibited superior correlation with the original respiration from the perspective of breathing frequency.

Abstract: Polyurethane prosthetic heart valve tried to imitate the geometry of native valve that might perhaps show better performance which is close to natural valve. However, the geometry of natural valve is very complex and there are variety of parameters can affect performances of the valves. This study has simplified the geometry of natural valve so that there are only four parameters needs to be considered. The four parameters include the fundamental curve, the free edge angle, the valve height, and the leaflet thickness. The study investigated the influence of these four parameters on biomechanics of the polyurethane prosthetic valves.