The Experts below are selected from a list of 29586 Experts worldwide ranked by ideXlab platform
Lei Yang - One of the best experts on this subject based on the ideXlab platform.
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mechanical response of a triply periodic minimal surface Cellular structures manufactured by selective laser melting
International Journal of Mechanical Sciences, 2018Co-Authors: Lei Yang, Peng Chen, Shoufeng YangAbstract:Abstract Cellular structures with controllable mechanical properties and porous architecture are the most promising candidates for many applications such as bone implants. Selective laser melting (SLM), one of the additive manufacturing (AM) technologies, enables manufacturing of space filling lattice structures with exceptional load bearing efficiency, customizable stiffness, controllable Cell Topology, Cell size, and porosity. In this work, Schoen Gyroid (SG) unit Cell, a triply periodic minimal surface (TPMS) structure, was used to design the Cellular structures. As opposed to many other types of unit Cells, SG has superior characteristics of self-supporting and high manufacturability for AM technologies. The titanium alloy (Ti–6Al–4V) SG Cellular structures were manufactured by SLM. Finite element (FE) method was employed to predict the elastic modulus, compressive yield strength and stress/strain distributions of the SG Cellular structures, and the failure occurrence mechanisms were analyzed. The FE results were compared with the experimental data. The results show that through FE method, the mechanical responses of the SG Cellular structures can be accurately described and it is possible to customize the mechanical properties of SLM-produced titanium alloy TPMS lattices.
Yusheng Shi - One of the best experts on this subject based on the ideXlab platform.
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Effects of the unit Cell Topology on the compression properties of porous Co-Cr scaffolds fabricated via selective laser melting
Rapid Prototyping Journal, 2017Co-Authors: Changjun Han, Chunze Yan, Shifeng Wen, Jie Liu, Qingsong Wei, Yusheng ShiAbstract:Purpose Selective laser melting (SLM) is an additive manufacturing process suitable for fabricating metal porous scaffolds. The unit Cell Topology is a significant factor that determines the mechanical property of porous scaffolds. Therefore, the purpose of this paper is to evaluate the effects of unit Cell Topology on the compression properties of porous Cobalt–chromium (Co-Cr) scaffolds fabricated by SLM using finite element (FE) and experimental measurement methods. Design/methodology/approach The Co-Cr alloy porous scaffolds constructed in four different topologies, i.e. cubic close packed (CCP), face-centered cubic (FCC), body-centered cubic (BCC) and spherical hollow cubic (SHC), were designed and fabricated via SLM process. FE simulations and compression tests were performed to evaluate the effects of unit Cell Topology on the compression properties of SLM-processed porous scaffolds. Findings The Mises stress predicted by FE simulations showed that different unit Cell topologies resulted in distinct stress distributions on the bearing struts of scaffolds, whereas the unit Cell size directly determined the stress value. Comparisons on the stress results for four topologies showed that the FCC unit Cell has the minimum stress concentration due to its inclined bearing struts and horizontal arms. Simulations and experiments both indicated that the compression modulus and strengths of FCC, BCC, SHC, CCP scaffolds with the same Cell size presented in a descending order. These distinct compression behaviors were correlated with the corresponding mechanics response on bearing struts. Two failure mechanisms, cracking and collapse, were found through the results of compression tests, and the influence of topological designs on the failure was analyzed and discussed. Finally, the Cell initial response of the SLM-processed Co-Cr scaffold was tested through the in vitro Cell culture experiment. Originality/value A focus and concern on the compression properties of SLM-processed porous scaffolds was presented from a new perspective of unit Cell Topology. It provides some new knowledge to the structure optimization of porous scaffolds for load-bearing bone implants.
Kijeong Han - One of the best experts on this subject based on the ideXlab platform.
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Demonstration of Superior Static, Dynamic, and Short-Circuit Performance of 1.2 kV 4H-SiC Split-Gate Octagonal Cell MOSFETs Compared with Linear, Square, and Hexagonal Topologies
Materials Science Forum, 2020Co-Authors: Kijeong Han, B. Jayant Baliga, Ajit Kanale, Subhashish BhattacharyaAbstract:The electrical characteristics of the 1.2-kV rated 4H-SiC accumulation-channel split-gate octagonal Cell MOSFET (SG-OCTFET) are experimentally compared with linear, square, hexagonal, octagonal, and compact-octagonal Cell topologies. The specific on-resistance of the SG-OCTFET is 52% larger than the conventional linear Cell Topology. However, the SG-OCTFET has: (i) high-frequency figure-of-merit HFFOM[Ron×Cgd] 9.4×, 6.1×, 2.6×, 2.0×, and 1.8× superior to the square, hex, linear, octagonal, and compact-octagonal Cells; (ii) fastest switching performance among all Cell topologies, with 26% smaller switching energy loss than the conventional linear Cell Topology; and (iii) short circuit capability 1.5× longer than the conventional linear Cell Topology. The SG-OCTFET device is therefore an optimum candidate for high frequency applications of SiC MOSFETs.
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Impact of Cell Topology on Characteristics of 600V 4H-SiC Planar MOSFETs
IEEE Electron Device Letters, 2019Co-Authors: Aditi Agarwal, Kijeong Han, B. Jayant BaligaAbstract:This letter compares the measured electrical characteristics of 600 V planar-gate inversion-channel 4H-SiC power MOSFETs fabricated with four different Cell topologies (Linear, Square, Hexagonal, and Octagonal) for the first time. The High-Frequency Figures-of-Merit (HF-FOMs) of these devices were compared with the commercially available SiC device and the Si CoolMOS product. It was found that the HF-FOMs of the 600-V SiC product and our fabricated conventional Linear Cell device are much worse in comparison to the Si CoolMOS product. However, the 600 V SiC power MOSFET with comparable performance to the Si CoolMOS product could be achieved by using the Octagonal Cell Topology.
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The 1.2-kV 4H-SiC OCTFET: A New Cell Topology With Improved High-Frequency Figures-of-Merit
IEEE Electron Device Letters, 2019Co-Authors: Kijeong Han, Bantval Jayant BaligaAbstract:A 1.2 kV rated 4H-SiC OCTFET device with octagonal-Cell Topology is proposed and experimentally demonstrated for the first time. The device was first optimized using TCAD numerical simulations. Devices were then successfully fabricated in a 6-inch foundry. From the measured electrical characteristics, the OCTFET is demonstrated to have $\textsf {1.4}\times $ superior high frequency figures-of-merits (HF-FOM) [ $\textsf {R}_{\textsf {on}}\times \textsf {Q}_{\textsf {gd}}$ ], and $\textsf {2.1}\times $ superior HF-FOM [ $\textsf {R}_{\textsf {on}}\times \textsf {C}_{\textsf {gd}}$ ] compared with the conventional linear-Cell MOSFET.
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Comparison of New Octagonal Cell Topology for 1.2 kV 4H-SiC JBSFETs with Linear and Hexagonal Topologies: Analysis and Experimental Results
2019 31st International Symposium on Power Semiconductor Devices and ICs (ISPSD), 2019Co-Authors: Kijeong Han, Aditi Agarwal, B. Jayant BaligaAbstract:This paper compares experimentally obtained electrical characteristics of a novel Octagonal (Oct) Cell Topology for 1.2 kV-rated 4H-SiC JBSFETs with the Linear and Hexagonal (Hex) Cell topologies for the first time. The various Cell topologies were fabricated using the same process flow at a 6-inch foundry. The third quadrant on-state voltage drop for the JBS diode in the Oct JBSFET was matched with the Linear Cell design by using adequate JBS diode area within the Cell. Experimental results demonstrate that the Oct JBSFET has 1.7× and 2.2× better HF-FOM [ $\mathbf{R}_{\mathbf{on}}\times \mathbf{Q}_{\mathbf{gd}}$ ] compared with the Linear and Hex Cell JBSFETs, respectively. In addition, the Oct JBSFETs have a much superior [C iss /C rss ] ratio to suppress shoot through currents during high frequency switching.
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Comparison of Four Cell Topologies for 1.2-kV Accumulation- and Inversion-Channel 4H-SiC MOSFETs: Analysis and Experimental Results
IEEE Transactions on Electron Devices, 2019Co-Authors: Kijeong Han, Bantval Jayant BaligaAbstract:The electrical characteristics of 1.2-kV-rated 4H-SiC accumulation (Acc) and inversion (Inv) channel MOSFETs with linear, square, hexagonal, and octagonal Cell topologies fabricated using the same design rules and process flow in a 6-in foundry are compared for the first time. TCAD numerical simulations have been conducted to analyze the structures. For all the Cell topologies, it was found that the Acc MOSFETs have lower specific ON-resistance ( ${R}_{ \mathrm{\scriptscriptstyle ON},\textsf {sp}}$ ) than the Inv counterparts due to higher channel mobility resulting in 1.3– $2.0\times $ smaller high-frequency figure-of-merit (HF-FOM[ ${R} _{ \mathrm{\scriptscriptstyle ON}} \times {Q}_{\textsf {gd}}$ ]), where ${Q} _{\textsf {gd}}$ is the gate-to-drain charge. It is observed that the square and hexagonal Cell topologies with the same structural dimensions show similar electrical performance. When compared with the standard linear Cell Topology: 1) the hexagonal Cell Topology has $1.15\times $ better specific ON-resistance and $1.12\times $ worse HF-FOM[ $\text{R}_{ \mathrm{\scriptscriptstyle ON}} \times {Q}_{\textsf {gd}}$ ] and 2) the octagonal Cell Topology has $1.5\times $ worse specific ON-resistance and $1.4\times $ better HF-FOM[ $\text{R}_{ \mathrm{\scriptscriptstyle ON}} \times {Q}_{\textsf {gd}}$ ]. In addition, the octagonal Cell Topology has a much superior figure-of-merit (FOM[ ${C} _{\textsf {iss}}/{C} _{\textsf {rss}}$ ]), where ${C} _{\textsf {iss}}$ is the input capacitance and ${C} _{\textsf {gd}}$ is the reverse transfer capacitance.
Shoufeng Yang - One of the best experts on this subject based on the ideXlab platform.
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mechanical response of a triply periodic minimal surface Cellular structures manufactured by selective laser melting
International Journal of Mechanical Sciences, 2018Co-Authors: Lei Yang, Peng Chen, Shoufeng YangAbstract:Abstract Cellular structures with controllable mechanical properties and porous architecture are the most promising candidates for many applications such as bone implants. Selective laser melting (SLM), one of the additive manufacturing (AM) technologies, enables manufacturing of space filling lattice structures with exceptional load bearing efficiency, customizable stiffness, controllable Cell Topology, Cell size, and porosity. In this work, Schoen Gyroid (SG) unit Cell, a triply periodic minimal surface (TPMS) structure, was used to design the Cellular structures. As opposed to many other types of unit Cells, SG has superior characteristics of self-supporting and high manufacturability for AM technologies. The titanium alloy (Ti–6Al–4V) SG Cellular structures were manufactured by SLM. Finite element (FE) method was employed to predict the elastic modulus, compressive yield strength and stress/strain distributions of the SG Cellular structures, and the failure occurrence mechanisms were analyzed. The FE results were compared with the experimental data. The results show that through FE method, the mechanical responses of the SG Cellular structures can be accurately described and it is possible to customize the mechanical properties of SLM-produced titanium alloy TPMS lattices.
Matthew C. Gibson - One of the best experts on this subject based on the ideXlab platform.
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control of the mitotic cleavage plane by local epithelial Topology
Cell, 2011Co-Authors: William T. Gibson, Matthew C. Gibson, Jim H Veldhuis, Boris Rubinstein, Heather N Cartwright, Norbert Perrimon, Wayne G Brodland, Radhika NagpalAbstract:For nearly 150 years, it has been recognized that Cell shape strongly influences the orientation of the mitotic cleavage plane (e.g., Hofmeister, 1863). However, we still understand little about the complex interplay between Cell shape and cleavage-plane orientation in epithelia, where polygonal Cell geometries emerge from multiple factors, including Cell packing, Cell growth, and Cell division itself. Here, using mechanical simulations, we show that the polygonal shapes of individual Cells can systematically bias the long-axis orientations of their adjacent mitotic neighbors. Strikingly, analyses of both animal epithelia and plant epidermis confirm a robust and nearly identical correlation between local Cell Topology and cleavage-plane orientation in vivo. Using simple mathematics, we show that this effect derives from fundamental packing constraints. Our results suggest that local epithelial Topology is a key determinant of cleavage-plane orientation, and that cleavage-plane bias may be a widespread property of polygonal Cell sheets in plants and animals.
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Cell Topology, geometry, and morphogenesis in proliferating epithelia.
Current topics in developmental biology, 2009Co-Authors: William T. Gibson, Matthew C. GibsonAbstract:Epithelia are sheets of tightly adherent Cells that line both internal and external surfaces in a vast array of metazoans. During development, an intrinsic consequence of coupling tight adhesion with Cellular proliferation is the emergence of an epithelial form characterized by a stereotyped distribution of polygonal Cell shapes. Despite the near universality of this constraint on Cell shape and tissue organization, very little is known about the possible implications of Cell pattern geometry for mechanical properties of tissues or key biological processes, such as planar polarization, tissue remodeling, and Cell division. In this chapter, through an examination of increasingly complex models, we highlight what is known about the role of mitotic proliferation in the emergence of epithelial Cell geometry, and examine some possible implications for tissue morphogenesis. Ideally, continued progress in this area will address a major conceptual challenge in biology, which is to understand aspects of morphogenesis that are not explicitly directed by genetic control, but instead emerge from the complex interactions between geometric and biomechanical properties of epithelial tissues.