Optimal design to reduce torque ripple of IPM motor with radial based function meta-model considering design sensitivity analysis

In this study, optimum design process to reduce a torque ripple was presented for an interior permanent magnet (IPM) type electric traction motor. Firstly, 2-D electromagnetic finite element analysis was conducted to analyze the characteristics of the torque ripple in a view of magnetic saturation as well as cogging torque. Then, design factors of stator shape and rotor shape affecting to the torque ripple was selected as design variables. Secondly, using selected design variables, sensitivity analysis was performed to select design variable more affecting to the torque ripple and output torque by using design of experiments method. Thirdly, radial based function meta-model was constructed based on the results of the design of experiments (DOE). Finally, the optimum design was performed by using the constructed meta-model and method of feasible direction. By using the presented optimum design process, it is confirmed that the torque ripple of the optimum design was reduced to compare with the initial design and that output torque performance of the optimum design was maintained.

     

Reliability-based robust design optimization for torque ripple reduction considering manufacturing uncertainty of interior permanent magnet synchronous motor

Journal of Mechanical Science and Technology - This study performed reliability-based robust design optimization (RBRDO) of stator and rotor shape of the IPM type electric motor to reduce the...     

A Screening of the MMV Pandemic Response Box Reveals Epetraborole as A New Potent Inhibitor against Mycobacterium abscessus

Mycobacterium abscessus is the one of the most feared bacterial respiratory pathogens in the world. Unfortunately, there are many problems with the current M. abscessus therapies available. These problems include misdiagnoses, high drug resistance, poor long-term treatment outcomes, and high costs. Until now, there have only been a few new compounds or drug formulations which are active against M. abscessus, and these are present in preclinical and clinical development only. With that in mind, new and more powerful anti-M. abscessus medicines need to be discovered and developed. In this study, we conducted an in vitro-dual screen against M. abscessus rough (R) and smooth (S) variants using a Pandemic Response Box and identified epetraborole as a new effective candidate for M. abscessus therapy. For further validation, epetraborole showed significant activity against the growth of the M. abscessus wild-type strain, three subspecies, drug-resistant strains and clinical isolates in vitro, while also inhibiting the growth of M. abscessus that reside in macrophages without cytotoxicity. Furthermore, the in vivo efficacy of epetraborole in the zebrafish infection model was greater than that of tigecycline. Thus, we concluded that epetraborole is a potential anti-M. abscessus candidate in the M. abscessus drug search.     

A Highly Versatile and Adaptable Artificial Leaf with Floatability and Planar Compact Design Applicable in Various Natural Environments

As a promising means of solar energy conversion, photovoltaic (PV) cell‐based electrolysis has recently drawn considerable attention for its effective solar fuel generation; especially the generation of hydrogen by solar water splitting. Inspired by remarkable accomplishments in enhancing the solar‐to‐hydrogen conversion efficiency, various efforts have aimed at fostering convenient and practical uses of PV electrolysis to make this technology ubiquitous, manageable, and efficient. Here, the design and function of a monolithic photoelectrolysis system—a so‐called artificial leaf—for use in various environments are highlighted. The uniquely designed artificial‐leaf system facilitates an unbiased water‐splitting reaction by combining superstrate PV cells in series with single‐face electrodes in a compact 2D catalytic configuration. Floatability is a new feature of the water‐splitting artificial leaf; this feature maximizes solar light utilization and allows for easy retrieval for recycling. Additionally, its planar design enables operation of the device in water‐scarce conditions. These characteristics endow the artificial leaf with versatility and a high adaptability to natural environments, widening the applicability of the device.     

Thermal Stability and Ionic Conductivity of Calcia‐Stabilized Zirconia with Alumina Addition

The thermal expansion and ionic conduction of 15 mol% CaO‐stabilized zirconia (CSZ) with added Al₂O₃ were investigated. Specimens with 0.5 and 1 mol% Al₂O₃ maintained the cubic phase, and the thermal diffusivity increased from 0.499 to 0.661 mm²/s with a 1 mol% addition. The addition of 5 mol% caused a decrease in the thermal diffusivity (0.609 mm²/s) with the formation of the monoclinic phase. The thermal expansion coefficient of the CSZ decreased, and the thermal diffusivity increased with the addition of Al₂O₃. The ionic conductivity was increased up to the addition of 1 mol% due to scavenging of siliceous by Al₂O₃, while the 5 mol% addition showed a decrease in conductivity with the formation of the intergranular phase.     

Load analysis and structural strength evaluation of semi-submersible platform for wind turbines in Jeju Island sea states using hydrodynamic-structure interaction analysis

Journal of Mechanical Science and Technology - The present study conducted an analysis of waves and wind on the west coast of Jeju Island in South Korea to derive the loads for a structural...     

Design of end coil angular position and centerline shape of C-type side load coil spring for reducing side load of MacPherson strut suspension

Journal of Mechanical Science and Technology - MacPherson strut suspension, which is widely used vehicle suspension type, decreases the riding comfort and durability of strut module due to the side...     

Asymmetrical change in the pelvis and the spine during cross-legged sitting postures

People spend much time with cross-legged sitting by increasing the time spent in the chair. Prolonged cross-legged sitting postures might cause spinal disorders and trunk asymmetry problems. We investigated the biomechanical effects of cross-legged sitting postures on the pelvic and spinal regions. 3D-motion analyses were performed on 26 healthy subjects. Data were collected while the subjects sat in four different postures: the control posture (without crossed legs) of sitting upright on the chair; the knee-on-knee (KoK) posture (the right knee on the left knee), the ankle-on-knee (AoK) posture (the right ankle on the left knee) and the ankle-on-ankle (AoA) posture (the right ankle on the left ankle). EMG signals were also collected for abdominal muscles. Cross-legged sitting postures showed significantly greater kyphotic curves in the lumbar and the thoracic spines and pelvic posterior tilting, when compared with the control posture. The pressure on the right buttock area was greater in the AoK posture than in the control posture, and the pressure on the left buttock area in the KoK posture was greater than in the control posture. Cross-legged sitting postures showed significantly greater external oblique muscle activation when compared with the control posture.     

Preform design of hybrid-forming process to make sheet metal IT products with a sharp edge

Existing forging processes have limitations in forming products with sharp edges. Therefore, a new hybrid-forming process that combines drawing and forging processes was designed to form a sharp-edged product. First, a corner radius of a preform design was arranged to be smaller than the minimum bent area corner radius formed in general drawing processes. Then, the shape of the preform was planned to have the exact shape of the final product. Given that forming loads are a limiting condition in forging processes, they were set as an evaluation criterion to determine design requirements for final product shapes and the shapes of preforms. The reliability of finite element analysis results was verified by comparing analysis and experiment results, and a multistage preforming process was implemented to satisfy the determined evaluation criterion. This study demonstrates that IT products with sharp edges can be formed.