Search

Based on a 3-D inhomogeneous simulative body torso model, the influence of various boundary conditions on inverse recovered epicardial potential maps (EPM) was studied by boundary element method (BEM). The result shows that the precision of EPM calculated under incomplete boundary conditions will meet the clinical requirements, as long as the incomplete boundary conditions still contain the extremum area which often appears at the breast area.

A conformal cooling channel (CCC) follows the mold core or cavity profile to carry out uniform cooling in the cooling stage. However, the significant pressure drop along the cooling channels is a distinct disadvantage of the CCC. In this study, an innovative waterfall cooling channel (WCC) was proposed and implemented. The WCC cools the injected products via surface contact, replacing the conventional line contact to cool the injected products. The WCC was optimized using numerical simulation software. Silicone rubber molds with two kinds of cooling channels were designed and implemented. The cooling time of the molded part was evaluated using a low-pressure wax injection molding machine. The experimental results of the cooling time of the molded part were compared with the simulation results from numerical simulation software. The results showed that the optimal mesh element count was about 1,550,000 with a mesh size of 1 mm. The simulation software predicted the filling time of the water cup injection-molded product to be approximately 2.008 s. The cooling efficiency for a silicone rubber mold with a WCC is better than that of the silicone rubber mold with a CCC since the core and cavity cooling efficiency is close to 50%. The pressure drop of the WCC is smaller than that of the CCC, which reduces the pressure drop by about 56%. Taking a water cup with a mouth diameter of 70 mm, a height of 60 mm, and a thickness of 2 mm as an example, the experimental results confirmed that the use of the WCC can save the cooling time of the product by about 265 s compared with the CCC. This shows how a WCC can increase cooling efficiency by approximately 17.47%. [ABSTRACT FROM AUTHOR]

This research established half of the finite element model to investigate the thermal and stress field evolution of single track cladding deposited by the wide-beam laser. The proposed FE model is validated by the molten pool temperature measured by a pyrometer. And the characteristic of the cladding shows good agreement with the temperature profile. Based on the temperature data, the molten pool length, width, and depth are calculated. Meanwhile, the effect of process parameters including laser power and scanning speed on the molten pool dimensions, temperature gradient G, cooling rate ε, solidification rate R, and G/R are discussed. Three experiments under different process parameters are conducted to verify the simulation results. Furthermore, the thermal stress distribution of the cladding in different direction and different path are discussed. The results indicate that laser power and scanning speed have a significant influence on the thermal and stress field evolution. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the temperature field evolution of the single track clad in wide-beam laser cladding. By using the birth and death element technique, a 3D transient finite element (FE) model was established to study the temperature field evolution, temperature gradient (G), cooling rate (ε), and solidifying rate (R) of the molten pool. The temperature field results of the molten pool were also validated by the temperature measurement and characteristics of the clad. Meanwhile, the effect of main parameters namely as laser power, scanning speed, laser absorptivity, laser power efficiency, and preheat temperature on the peak temperature of the molten pool and temperature variation rate were discussed in detail. Then, the effect of laser power and scanning speed on G, ε, R, and G/R were also investigated and the corresponding microstructure was analyzed. The results show that from the top surface of the clad to the interface between the clad and substrate, G/R decreases slightly at first and then increases sharply while the cooling rate continues to decrease. Moreover, the peak temperature of the molten pool increases with an increase of laser power, laser absorptivity, laser power efficiency, and preheat temperature, while with the increasing of scanning speed, the peak temperature decreases. [ABSTRACT FROM AUTHOR]

Magnetic flux leakage (MFL) response predicting is important for defect estimation. This paper first proposes a concept of basic signal by discovering the combination property of the MFL response. The basic signal can be used to predict the MFL response conveniently by a basic signal combination method (BSCM), which is also innovatively put forward in this paper. In this method, the basic signal is calculated in advance, and the MFL response can be calculated by several transformation and combination operations. Both the simulation and experimental results demonstrate the feasibility of BSCM. Compared with other traditional methods (magnetic dipole method and finite-element method), BSCM shows a good performance on both the computational speed and accuracy. [ABSTRACT FROM AUTHOR]

This paper is aimed to investigate the kinetic parameters matching and designing method for a multi-stage torsional stiffness dual mass flywheel (DMF) based on torsional vibration control. Using the numerical analysis methods, three critical technological problems are resolved subsequently. The first one is that the kinetics simulation model of vehicle drivetrain is established, and the actual torsional vibration excitation of crankshaft and different gear pairs engaged multi-operating conditions for drivetrain are taken into account during modeling. The second one is that the kinetic parameters sensitivity of DMF with respect to torsional vibration control are obtained and the range of each kinetic parameter (i.e. rotation inertia ratio, torsional stiffness and damping) is derived further. The last one is that the parameters matching and designing methods for a multi-stage torsional stiffness DMF, considering the constraint conditions that transmission torque, relative angle and distribution of natural frequencies of DMF-drivetrain, are carried out. The results show that the torsional vibration of drivetrain is controlled effectively after matching a three-stage torsional stiffness DMF and the amplitude of angular velocity at input end of gearbox decreases significantly, which verifies that the designing and matching methods are effective and the result can thus be used in vibration control for vehicle drivetrain. [ABSTRACT FROM AUTHOR]

Abstract: This study reports a piezoelectric polyvinylidene fluoride (PVDF) polymer-based sensor patch for simultaneous heartbeat and respiration detections. The principle is based on the piezoelectric sensing mechanism to detect the pulsatile vibrations, and periodical deformations on the chest wall of human body during heartbeats and respirations, respectively. In this study, the sensor patch with a structurally curved PVDF film was designed, and fabricated. The role of the curved structure design to enhance detection signals, and the capability of the sensor to faithfully detect the heartbeats and respirations were experimentally evaluated. Results revealed that the design of curved structure of PVDF film was capable of increasing detection signal by 151% for the respiration measurements compared with its flat counterpart. Moreover, the sensor was proved to be able to generate the heartbeat and respiration signals which were in concordance with those based on a commercial electrocardiogram (ECG), and respiratory effort transducer, respectively. Finally, the heart rate and respiratory rate measured through the sensor patch were proved to have no statistical significance compared with the reference data obtained from the ECG, and respiratory effort transducer-based detections, respectively. As a whole, this study has developed a PVDF-based sensor patch which was capable of monitoring the heartbeats and respirations with high fidelity. Other distinctive features include its small size, light weight, ease of use, low cost, and portability. All these make it a promising sensing device to monitor heartbeats and respirations either in medical centers, or home care units. [Copyright &y& Elsevier]