DSpace collection: 期刊論文

Design of a General Type BSSO Fixation Plate Integrating Topology and Parameter Optimization for Various Severity Levels of Hemifacial Microsomia

Wed, 08 Apr 2026 04:05:25 GMT

title: Design of a General Type BSSO Fixation Plate Integrating Topology and Parameter Optimization for Various Severity Levels of Hemifacial Microsomia

Standardized Morphological Modeling and Simulation-Based Validation of a Novel Tibiotalar Fusion Implant. Bioengineering, 2025, 12(7), 705.

Wed, 08 Apr 2026 04:05:23 GMT

title: Standardized Morphological Modeling and Simulation-Based Validation of a Novel Tibiotalar Fusion Implant. Bioengineering, 2025, 12(7), 705.

A Self-Expanding Nitinol Fixation System for Atrial Leadless Pacemakers: Biomechanical Design and Evaluation.

Wed, 08 Apr 2026 04:05:15 GMT

title: A Self-Expanding Nitinol Fixation System for Atrial Leadless Pacemakers: Biomechanical Design and Evaluation.

Analysis of photocatalytic characteristics and mechanical properties of TiO2 thin films

Tue, 07 Apr 2026 04:05:25 GMT

title: Analysis of photocatalytic characteristics and mechanical properties of TiO2 thin films

Enhanced fracture fixation stability and osseointegration through over-compression: design of an annular compression plate for posterolateral tibial plateau fractures

Tue, 07 Apr 2026 04:05:23 GMT

title: Enhanced fracture fixation stability and osseointegration through over-compression: design of an annular compression plate for posterolateral tibial plateau fractures

Development of Active-Clamp Flyback Converter for Improving Light-Load Efficiency

Thu, 05 Mar 2026 04:07:06 GMT

title: Development of Active-Clamp Flyback Converter for Improving Light-Load Efficiency abstract: Conventional active-clamp flyback (ACF) converters suffer increased conduction losses due to the extended conduction time of the auxiliary switch during light loads. To tackle this problem and improve light-load efficiency, this article proposes a novel control strategy. This strategy is designed to limit the generation of excessive conduction losses by the auxiliary switch during light loads. The proposed control strategy also employs the quasi-resonant (QR) valley switching (VS) technique within a single switching cycle to activate the auxiliary switch. This enables the main switch to achieve zero-voltage switching (ZVS) characteristics during its operation. Moreover, once the converter reaches medium loads, the auxiliary and main switches operate in a complementary manner with a fixed frequency. This operation allows both switches to achieve ZVS, leading to a significant reduction in switching losses. The operating principle and control strategy of the 65-W ACF converter with the novel control approach have been thoroughly analyzed and discussed. Experimental results have confirmed the effectiveness of this strategy, validating its ability to improve the overall efficiency of the converter under various load conditions.

A Hybrid Bidirectional Full-Bridge CLLC Resonant Converter With Dual-Resonant Frequency for Enhancing Efficiency at Light-to-Medium loads

Thu, 05 Mar 2026 04:07:01 GMT

title: A Hybrid Bidirectional Full-Bridge CLLC Resonant Converter With Dual-Resonant Frequency for Enhancing Efficiency at Light-to-Medium loads abstract: The symmetric capacitor-inductor-inductor-capacitor (CLLC) resonant converter is a key component in electric power conversion systems, used for interfacing with dc voltage buses in applications such as renewable energy sources, battery energy storage in electric vehicles (EVs), and dc microgrids. It is favored for its bidirectional power transfer, high power density, zero-voltage switching (ZVS) for primary power switches, and soft commutation for output rectifiers. However, a significant drawback of the CLLC converter is the high operating frequency at light loads, leading to increased switching losses and reduced efficiency. To overcome this problem, this article introduces a hybrid CLLC converter that can dynamically switch between full-bridge (FB) and half-bridge (HB) configurations, as well as adjust the resonant frequency based on load conditions. This hybrid approach allows the converter to operate in an HB configuration and adjust its resonant frequency, reducing the switching frequency during light-to-medium loads and thus enhancing operating efficiency. A prototype with a 2-kW power rating, designed to connect a 400-Vdc bus to an 800-Vdc bus, was tested. The experimental results confirmed the proposed converter’s effectiveness, demonstrating improved efficiency under light-to-medium load conditions.

Development of vacuum-chamber-type capacitive micro-pressure sensors

Tue, 02 Dec 2025 04:05:14 GMT

title: Development of vacuum-chamber-type capacitive micro-pressure sensors abstract: This study presents the development of a capacitive pressure sensor tailored for measuring the dynamic pressure of flow fields. The sensor is fabricated using the UMC 0.18 µm CMOS-MEMS process, incorporated with additional post-processing steps such as metal wet etching, supercritical CO2 drying, and parylene encapsulation. The sensing architecture employs AD7746 as a capacitance-to-voltage converter (CVC), enabling the conversion of capacitance signals into voltage outputs for enhanced measurement fidelity. Structurally, the capacitive pressure sensor features a vacuum-sealed diaphragm capsule design with dual movable circular membranes functioning as sensing electrodes. A contact-mode capacitive configuration with a trapezoidal or Gong-like vacuum-chamber diaphragm is adopted to improve linearity and sensitivity. The output sensitivity was determined to be feasible for measuring dynamic pressure at 1–2 Pa resolution.

A high sensitive nanomaterial coated side polished fiber sensor for detection of Cardiac Troponin I antibody

Fri, 19 Sep 2025 04:07:43 GMT

title: A high sensitive nanomaterial coated side polished fiber sensor for detection of Cardiac Troponin I antibody abstract: The advent of evanescent field based fiber optic biosensor and advancements in nanotechnology has create an excellent opportunity in label-free detection of biomarkers which plays vital role in the early, rapid and accurate diagnosis of acute diseases. In this work, we demonstrate a high sensitive Molybdenum Tungsten Disulfide (MoWS2) coated side polished fiber (SPF) biosensor for accurate and early diagnosis of cardio vascular disease (CVD). The Cardiac Troponins I (cTnI) is identified as a biomarker of interest for early and rapid diagnosis of CVD. The proposed SPF biosensor exhibits surface plasmonic resonance (SPR) detection due to the evanescent field interaction between MoWS2 nano coated side polished region and anti-CTnI. The proposed SPF biosensor possess the high sensitivity of 82% to detect the cTnI antibody with a limit of detection (LOD) about 17.5 pg/mL. The peak SPR shift have been calculated as 61 nm for analyte concentrations of 500 pg/mL Moreover, the proposed SPF biosensor possess the high degree of selectivity and environmental stability to CTnI among three analytes such as CTnI, Estrogen and Glucose. The hydrophobic interactions of MoWS2 and cTnI antibody leads to chemical free biofunctionalization of antibody in the sensing region. Hence, the simulation results shows the surface interaction strength calculated as 1.29 KJ mol−1/nm2 in order to evaluate the hydrophobic interactions. Thus, the proposed optical biosensor is a promising candidate for “point-of-care” testing of CVD disorders and preclinical assessments.

An internal real-time microscopic monitoring and diagnostic tool for improved proton battery stacks

Fri, 19 Sep 2025 04:07:40 GMT

title: An internal real-time microscopic monitoring and diagnostic tool for improved proton battery stacks abstract: Proton batteries have brought new research directions in the field of fuel cells and energy storage. Although our R&D team has developed a prototype of the proton battery stack, there are still some problems to be solved, such as leakage and unstable power generation. In addition, simultaneously and accurately measuring multiple key physical parameters inside a proton battery stack remains challenging. The present measurement methods are external or single parameters, that has become a limiting factor. These parameters (voltage, current, temperature, flow, humidity, pressure, oxygen and hydrogen) significantly affect the performance, life and safety of the proton battery stack. To address these challenges, this study developed a micro hydrogen sensor using the Micro-electro-mechanical systems (MEMS) technology, which was integrated with the previously developed seven-in-one microsensor, the mask and layout were re-designed to increase the number of microsensors, which were combined with a Flexible Printed Circuit (FPC). Finally, the development of a flexible eight-in-one microsensor was completed, so as to improve the output and overall operating efficiency of the microsensor, and provide a reliable internal multi-parameter real-time microscopic monitoring and diagnostic tool for the development of proton battery stacks.

Sensors-on-flapping-wings (SOFW) using complementary-metal-oxide-semiconductor (CMOS) MEMS technology

Fri, 19 Sep 2025 04:07:36 GMT

title: Sensors-on-flapping-wings (SOFW) using complementary-metal-oxide-semiconductor (CMOS) MEMS technology abstract: This article presents a framework of using MEMS sensors to investigate unsteady flow speeds of a flapping wing or the new concept of sensors on flapping wings (SOFWs). Based on the implemented self-heating flow sensor using U18 complementary metal–oxide–semiconductor (CMOS) MEMS foundry provided by the Taiwan Semiconductor Research Institute (TSRI), the compact sensing region of the flow sensor was incorporated for in situ diagnostics of biomimetic flapping issues. The sensitivity of the CMOS MEMS flow sensor, packaged with a parylene coating of 10 μm thick to prolong the lifetime, was observed as −3.24 mV/V/(m/s), which was below the flow speed of 6 m/s. A comprehensive investigation was conducted on integrating CMOS MEMS flow sensors on the leading edge of the mean aerodynamic chord (m.a.c.) of the flexible 70-cm-span flapping wings. The interpreted flow speed signals were checked and demonstrated similar behavior with the (net) thrust force exerted on the flapping wing, as measured in the wind tunnel experiments using the force gauge. The experimental results confirm that the in situ measurements using the concept of SOFWs can be useful for measuring the aerodynamic forces of flapping wings effectively, and it can also serve for future potential applications.

A parametric study and tailored infill design for enhanced flame-retardant performance of SORPLAS in FFF 3D printing

Fri, 19 Sep 2025 04:07:32 GMT

title: A parametric study and tailored infill design for enhanced flame-retardant performance of SORPLAS in FFF 3D printing abstract: This study employs recycled polycarbonate-based SORPLAS Impact as the material for Fused Filament Fabrication (FFF) in order to systematically investigate the effect of multiple printing parameters on flame-retardant performance. Four key parameters—infill pattern, infill density, primary layer height, and external solid layer thickness—were varied to fabricate test specimens, which were then subjected to combustion tests, thermal imaging, and grayscale analyses for quantitative evaluation. Temperature distribution and char formation behaviors were recorded during burning, and analysis of variance (ANOVA) along with Tukey’s HSD comparisons was used to identify the critical factors influencing flame retardancy. The results show that infill density and external solid layer thickness significantly affect ignition time, flame propagation, and post-combustion structural integrity. While moderate increases in material content promote stable char formation and effective thermal insulation, excessive accumulation can lead to expansion and deformation. Grayscale variations in thermal images further verify how each parameter set influences heat conduction and char formation. Overall, the findings demonstrate that carefully balancing these printing parameters and material usage can enhance flame retardancy and mechanical properties of 3D-printed parts, while also aligning with sustainability objectives. This work provides practical guidelines for advancing recycled flame-retardant materials and their applications in additive manufacturing.

Investigating Experimental and Computational Fluid Dynamics of 3D-Printed TPMS and Lattice Porous Structures

Fri, 19 Sep 2025 04:07:28 GMT

title: Investigating Experimental and Computational Fluid Dynamics of 3D-Printed TPMS and Lattice Porous Structures abstract: This study investigates the capillary performance and wetting behavior of SLA (Stereolithography) 3D-printed porous structures, focusing on TPMS (triply periodic minimal surfaces)-Gyroid, Octet, Diamond, and Isotruss lattice designs. High-speed imaging was used to analyze droplet interactions, including penetration, spreading, and contact angles, with 16 μL water droplets dropping from 30 mm at 0.77 m/s. Results showed variable contact angles, with Isotruss and Octet having higher angles, while Diamond faced measurement challenges due to surface roughness. Numerical simulations of TPMS-Gyroid of 2 mm3 unit cells validated the experimental results, and Diamond, Octet, and Isotruss structures were simulated. Capillary performance was assessed through deionized (DI) water weight–time (w-t) measurements, identifying that the TPMS-Gyroid structure performed adequately. Structures with 4 mm3 unit cells had low capillary performance, excluding them from permeability testing, whereas smaller 2 mm3 structures demonstrated capillary effects but had printability and cleaning issues. Permeability results indicated that Octet performed best, followed by Isotruss, Diamond, and TPMS-Gyroid. Findings emphasize unit cell size, beam thickness, and droplet positioning as key factors in optimizing fluid dynamics for cooling, filtration, and fluid management.

Numerical Simulation of Permeability for Novel Lattice Structures Under Various Flow Conditions

Fri, 19 Sep 2025 04:07:21 GMT

title: Numerical Simulation of Permeability for Novel Lattice Structures Under Various Flow Conditions abstract: Porous materials are essential in applications like impact absorption, thermal management, tissue engineering, and vibration damping, making their detailed study crucial. Key parameters in pore structure characterization include porosity, pore distribution, types, aperture size, shape, tortuosity, pore size distribution, specific surface area, and permeability. This study numerically simulates the permeability of two Triply Periodic Minimal Surfaces (TPMS) structures—Primitive and Gyroid—and two strut-based lattice structures—Diamond and Iso-truss. The analysis was conducted under steady-state conditions, with variations in porosity levels (60%, 70%, 80%, 90%), Reynolds numbers (Re) of 10, 50, 100, 150, 200, and 250, and a lateral length of 3 mm. Results indicate that higher porosity correlates with higher permeability, while increasing Re lead to higher pressure drops, reducing permeability. Among the structures, the lattice Diamond shows the highest permeability, while TPMS Primitive generally has the lowest.

Enzymatic glucose fiber sensor for glucose concentration measurement with a heterodyne interferometry

Wed, 17 Sep 2025 04:07:11 GMT

title: Enzymatic glucose fiber sensor for glucose concentration measurement with a heterodyne interferometry abstract: In this study, we developed a glucose fiber sensor incorporating heterodyne interferometry to measure the phase difference produced by the chemical reaction between glucose and glucose oxidase (GOx). Both theoretical and experimental results showed that the amount of phase variation is inversely proportional to glucose concentration. The proposed method provided a linear measurement range of the glucose concentration from 10 mg/dL to 550 mg/dL. The experimental results indicated that the sensitivity is proportional to the length of the enzymatic glucose sensor, and the optimum resolution can be obtained at a sensor length of 3 cm. The optimum resolution of the proposed method is better than 0.6 mg/dL. Moreover, the proposed sensor demonstrates good repeatability and reliability. The average relative standard deviation (RSD) is better than 10% and satisfied the minimum requirement for point-of-care devices.

Notes on the uniqueness of Type II Yamabe metrics

Tue, 02 Sep 2025 04:05:32 GMT

title: Notes on the uniqueness of Type II Yamabe metrics abstract: In this paper, we study the uniqueness of type II Yamabe metrics in conformal classes on a compact connected manifold with boundary, and we investigate Obata-type theorems for type II Yamabe metrics. In particular, we establish a theorem which gives a sufficient condition for a metric to be the unique Type II Yamabe metric in its conformal class. We also prove the corresponding theorem for the CR Yamabe problem on closed manifolds.

Some results on the weighted Yamabe problem with or without boundary

Tue, 02 Sep 2025 04:05:28 GMT

title: Some results on the weighted Yamabe problem with or without boundary abstract: Abstract. Let (Mn,g,e− ϕdVg,e− ϕdAg,m) be a compact smooth metric measure space with boundary with n ⩾ 3. In this article, we consider several Yamabe-type problems on a compact smooth metric measure space with or without boundary: uniqueness problem on the weighted Yamabe problem with boundary, characterization of the weighted Yamabe solitons with boundary and the existence of positive minimizers in the weighted Escobar quotient.

Optimizing implant lattice design for large distal femur defects: Stimulating interface bone growth to enhance osseointegration

Wed, 30 Jul 2025 04:06:33 GMT

title: Optimizing implant lattice design for large distal femur defects: Stimulating interface bone growth to enhance osseointegration abstract: Large bone defects in the distal femur present a significant challenge due to the lack of inherent self-healing capabilities. Traditional approaches, such as utilizing polymethyl methacrylate (PMMA) in conjunction with a plate for distal femur reconstruction, have shown unsatisfactory osseointegration outcome, which leads to complications. To address this challenge, this study focuses on developing a lattice-structured implant for reconstructing distal femoral bone defects. The lattice geometry is based on the cuboctahedron lattice, with its design optimized through the adjustment of pillar diameter and arrangement angle. The lattice structure is designed to stimulate the surrounding bone, ultimately enhancing osseointegration in distal femur reconstruction. Finite element analysis revealed that for promoting bone ingrowth toward the implant, setting the optimal lattice structure parameters, i.e., a 45° arrangement angle and a 0.8 mm pillar diameter, is required. Fabricated using state-of-the-art metal three-dimensional printing, the implant underwent rigorous validation through biomechanical testing, in vitro biological assays, and animal experiments. The comprehensive results affirmed the bioactivity of the lattice-structured implant, underscoring its capability to improve osseointegration in distal femoral defect reconstruction.

Injectable ChitHCl-DDA tissue adhesive with high adhesive strength and biocompatibility for torn meniscus repair and regeneration

Wed, 30 Jul 2025 04:06:28 GMT

title: Injectable ChitHCl-DDA tissue adhesive with high adhesive strength and biocompatibility for torn meniscus repair and regeneration abstract: Suture pull-through is a clinical problem in meniscus repair surgery due to the sharp leading edge of sutures. Several tissue adhesives have been developed as an alternative to traditional suturing; however, there is still no suitable tissue adhesive specific for meniscus repair treatment due to unsatisfactory biosafety, biodegradable, sterilizable, and tissue-bonding characteristics. In this study, we used a tissue adhesive composed of chitosan hydrochloride reacted with oxidative periodate-oxidized dextran (ChitHCl-DDA) combined with a chitosan-based hydrogel and oxidative dextran to attach to the meniscus. We conducted viscoelastic tests, viscosity tests, lap shear stress tests, Fourier transform infrared (FTIR) spectroscopy, swelling ratio tests, and degradation behavior tests to characterize these materials. An MTT assay, alcian blue staining, migration assay, cell behavior observations, and protein expression tests were used to understand cell viability and responses. Moreover, ex vivo and in vivo tests were used to analyze tissue regeneration and biocompatibility of the ChitHCl-DDA tissue adhesive. Our results revealed that the ChitHCl-DDA tissue adhesive provided excellent tissue adhesive strength, cell viability, and cell responses. This tissue adhesive has great potential for torn meniscus tissue repair and regeneration.

A study to predict the hydrodynamic and thermal characteristics of hybrid mesh regenerator

Fri, 11 Jul 2025 04:05:14 GMT

title: A study to predict the hydrodynamic and thermal characteristics of hybrid mesh regenerator abstract: A Stirling engine is a heat engine that utilizes the cyclic compression and expansion of the working fluid caused by differential temperature for its operation. The regenerator heat exchanger is one of the core components in these Stirling engines, and the performance of the regenerator determines the performance of the Stirling engine. So, in this project, experimental and numerical simulations have been performed to study and compare the thermal and hydrodynamic properties of single mesh and hybrid mesh regenerators. Both single flow and oscillating flow characteristics were studied for single mesh regenerators with wire screens of mesh numbers 300, 400, 500 and hybrid mesh regenerators with wire mesh numbers 300-400-500 and 500-400-300. The oscillating flow study was carried out for 700 RPM, 500 RPM, 300 RPM and 200 RPM. It was observed that the single mesh regenerator with 500 mesh screens has the highest amount of energy storage but at the same time, it was also observed that the 500 mesh has the highest amount of pressure loss gradient. Upon comparing the pressure loss gradient and energy storage it was observed that the hybrid mesh has a better performance as it can store more heat energy with less pressure loss. A correlation was also developed for estimation of the Nusselt number.

Numerical Analysis to Find Permeability of Lattice Structures

Fri, 11 Jul 2025 04:05:10 GMT

title: Numerical Analysis to Find Permeability of Lattice Structures abstract: As the need for efficient heat extraction grows with decreasing extraction areas, enhancing heat transfer device performance is crucial. Porous structures in thermal devices like heat pipes and vapor chambers can significantly improve heat transfer. Permeability, vital in fluid dynamics, affects fluid flow in porous materials, such as lattice structures. This study uses numerical analysis to assess the permeability of lattice structures, created using nTopology and analyzed with ANSYS Fluent software. It focuses on Octet, Isotruss, and Diamond lattice geometries. The research considers lattice geometry, unit cell characteristics, flow conditions, and other factors to deeply understand these structures' behavior. Insights into how different parameters influence lattice behavior and permeability are gained. The study also examines the impact of beam thickness and porosity on lattice performance. By varying and comparing these aspects, the study seeks to develop a more thorough framework for permeability research, contributing to advancements in lattice structure design and engineering applications.

The weighted conformal mean curvature flow

Wed, 30 Apr 2025 04:05:25 GMT

title: The weighted conformal mean curvature flow

Equivariant CR Yamabe problem

Wed, 30 Apr 2025 04:05:22 GMT

title: Equivariant CR Yamabe problem abstract: As a generalization of the Yamabe problem, Hebey and Vaugon considered the equivariant Yamabe problem: for a subgroup G of the isometry group, find a G-invariant metric whose scalar curvature is constant in a given conformal class. In this paper, we introduce the equivariant CR Yamabe problem and prove some related results.

Extending CR Yamabe flow and Yamabe flow with boundary

Wed, 30 Apr 2025 04:05:19 GMT

title: Extending CR Yamabe flow and Yamabe flow with boundary

Deformations of the scalar curvature of a partially integrable pseudohermitian manifold

Wed, 30 Apr 2025 04:05:16 GMT

title: Deformations of the scalar curvature of a partially integrable pseudohermitian manifold abstract: We consider deformations of the scalar curvature of a partially integrable pseudohermitian manifold, in analogy with the work of Fischer and Marsden on Riemannian manifolds. In particular, we introduce and discuss R-singular spaces, give sufficient conditions for the stability of the scalar curvature, and give a partial infinitesimal rigidity result for the scalar curvature of a compact, torsion-free, scalar-flat, integrable pseudohermitian manifold

A rigidity result for the product of spheres

Wed, 30 Apr 2025 04:05:13 GMT

title: A rigidity result for the product of spheres abstract: In this paper, we prove a rigidity result for the product metric on the product of spheres S1×Sn−1.

The second Yamabe invariant with boundary

Wed, 30 Apr 2025 04:05:09 GMT

title: The second Yamabe invariant with boundary abstract: Let (M,∂M,g) be a compact Riemannian manifold with boundary. As a generalization of the Yamabe invariant with boundary Y(M,∂M,g) , we define the kth Yamabe invariant with boundary Yk(M,∂M,g). We prove some of its properties and study when it can be attained by the generalized metric. We also prove a version of conformal Schwarz lemma on (M,∂M,g)by using the Yamabe flow with boundary.

Additive Manufacturing of Vapor Chambers

Thu, 20 Mar 2025 01:30:11 GMT

title: Additive Manufacturing of Vapor Chambers abstract: The increasing power density of high-performance electronic devices poses significant thermal management challenges. Vapor chambers (VCs) offer efficient heat dissipation, but traditional manufacturing methods limit their structural precision and performance. This study investigates the thermal performance of VCs fabricated with additive manufacturing (AM), featuring triply periodic minimal surface (TPMS) Gyroid capillary structures at two fill ratios under varying thermal loads. Enhanced thermal stability and performance were observed in the higher fill ratio, particularly under higher heat loads, whereas the lower fill ratio excelled under low-heat conditions, achieving a thermal resistance as low as 0.3688 K/W at an 80Wheat load. Additionally, the research explored the advantages and challenges of horizontal and vertical printing techniques in VC fabrication. Horizontal printing was found to compromise cavity volume due to necessary support structures, whereas vertical printing enhanced mass production feasibility and maintained effective vapor circulation. This study proposes a novel approach using AM to manufacture VCs as a monolithic structure. By eliminating the need for welding, this method ensures seamless integration of the capillary structure with the housing, thereby avoiding issues related to poor contact or welding-induced damage. The study confirmed a 75% reduction in thermal resistance in VCs with capillary structures compared to those without under similar conditions, highlighting the significant potential of integrating precisely designed capillary structures and additive manufacturing in improving vapor chamber performance for advanced thermal management applications.

Exploring the self‑assembly behavior of polystyrene microspheres in ripple structures

Fri, 06 Dec 2024 04:05:29 GMT

title: Exploring the self‑assembly behavior of polystyrene microspheres in ripple structures abstract: To overcome the optical diffraction limit, combining micro-sized transparent spheres with photonic nanojet technology is able to achieve nanometer-level high-resolution imaging. To expand the imaging area, it is necessary to create a two-dimensional microsphere array. This paper presents a self-assembly method for fabricating two-dimensional transparent polystyrene microsphere arrays. The method uses radio frequency sputtering to deposit a low-friction graphite coating on the surface of a cured epoxy resin with a rippled structure. The wavelength of this rippled structure is slightly larger than the diameter of the polystyrene microspheres, allowing adjacent polystyrene microspheres in the one-dimensional array to make close contact. The amplitude of the rippled structure effectively prevents the polystyrene microspheres from flipping over. Next, 5 × 10-6 wt% of polystyrene microspheres are uniformly dispersed in 100 mL of a cosolvent consisting of ethylene glycol and deionized water in an 8:2 weight ratio, and the colloidal solution is heated to 100 °C before being dropped onto the graphite-coated surface with the rippled structure. After the solvent evaporates, a single-layer, ordered arrangement of polystyrene microspheres can form.

Recycled sand for sustainable 3D-printed sand mold processes

Wed, 16 Oct 2024 04:05:27 GMT

title: Recycled sand for sustainable 3D-printed sand mold processes abstract: Traditional casting methods are losing their appeal due to poor working conditions. Integrating additive manufacturing into traditional Casting is a popular solution. Among the seven additive manufacturing categories, binder jet 3D printing is most suitable for 3D printing sand molds. However, issues like waste management and environmental problems in binder jetting need to be solved. The investigation proves that utilizing recycled sand as a raw material for 3D printing sand products can reduce the environmental impacts associated with binder jet 3D printing while achieving adequate mechanical properties. This study shows that recycled sand can produce mechanical properties comparable to new sand, while reducing waste and environmental impact. The study examines samples of new sand and recycled sand obtained from one to nine cycles of recycling. It reveals that the compressive and flexural strengths of sand recycled one to three times outperform new sand, while surface hardness remains unaffected by the recycling cycle. However, the permeability of the sand decreases as the number of recycling cycles increases. Recycled sand required less binder and hardener, which reduced costs and improved the environmental impact. This study highlights the importance of waste management and sustainability in 3D-printed sand mold processes and offers a promising solution for recycled sand powders in binder jetting.

Simplified Model Predicts Binder Behavior in Sand Mold Printing

Wed, 16 Oct 2024 04:05:23 GMT

title: Simplified Model Predicts Binder Behavior in Sand Mold Printing abstract: Binder jetting is a crucial process in additive manufacturing (AM) and is widely used in sand mold casting. This study explores the challenges of simulating binder droplets in ANSYS Fluent, including complexity and computational time. To overcome these challenges, we propose a geometric approach that models the binder droplet as a circular shape instead of an actual droplet. Additionally, the dynamic mesh feature is employed to transform the initial boundary condition into a wall condition at a specified time interval (Δt). This simplified approach eliminates the need to simulate actual droplets, leading to significant computational resource and time savings. By adopting this geometric approach, we can accurately predict the diffusion and penetration behavior of binder droplets with varying materials and volumes in porous media with different porosities. Through data analysis, it was found that the main variables affecting the diffusion diameter and penetration depth are binder volume and porosity. The successful implementation of this simplified model enables researchers and engineers to expedite the simulation of binder behavior, facilitating process optimization and enhancing the understanding of binder jetting technology in the field of additive manufacturing.

Greyscale printing and characterization of the binder migration pattern during 3D sand mold printing

Wed, 16 Oct 2024 04:05:17 GMT

title: Greyscale printing and characterization of the binder migration pattern during 3D sand mold printing abstract: Binder jetting is an additive manufacturing process in which a liquid binder is deposited onto a sand bed to fabricate components of a desired geometry. After deposition, the permeation and migration of the liquid binder in the porous sand bed has a critical impact on the final performance of the printed part. The purpose of this two-part study is to determine whether greyscale printing can be adapted for use in binder jetting. First, using Furan resin as the liquid binder and silica particles for the sand bed, we fabricated six sets of samples with different droplet volumes and measured the resulting migration patterns and quantified them based on deposited liquid saturation. The migration patterns are then correlated with the dimension error, strength, and formability of the printed samples. The results show that a larger liquid saturation produces better strength and formability with the tradeoff of a significant decrease in dimension error. Within this quantitative framework, the authors then demonstrate that gray-level printing—adjusting the droplet size of the liquid binder independently at each print head—can achieve the desired dimension error, strength, and formability at any specific location. Future applications may include the binder jetting of ceramic and metallic powders.

Characterizing sliding wear behavior of A1100/AlFe (p) composites produced via repeated fold-forging and annealing

Mon, 14 Oct 2024 04:05:20 GMT

title: Characterizing sliding wear behavior of A1100/AlFe (p) composites produced via repeated fold-forging and annealing abstract: Aluminum matrix/aluminum-iron intermetallic composite materials pose challenges in plastic processing due to the susceptibility of hard intermetallic compound particles to fracture. This study introduces a novel fabrication method involving pure iron mesh, hot-dip aluminum plating, and solidification. Through ten consecutive folding, forging, and intermediate annealing cycles, aluminum matrix and iron undergo diffusion, leading to the formation of Fe2Al5 and FeAl3 interface reaction layers, as confirmed by X-ray diffraction analysis. Subsequent forging cycles cause the breakage or detachment of Fe2Al5 and FeAl3 particles from the interface, resulting in the formation of large-sized Fe2Al5 and small-sized Fe2Al5 intermetallic particles. FeAl3 intermetallic particles are observed via microscopic examination. These particles can be uniformly dispersed within the aluminum matrix through plastic flow, enabling the successful fabrication of A1100/Fe2Al5 and AlFe3 composite sheets. Furthermore, the study investigates the impact of intermetallic compound content, sliding speed, and forward load on the dry sliding wear of A1100/FeAl composites. It is found that Fe2Al5 and AlFe3 intermetallic compound particles effectively mitigate adhesive wear, plowing, and oxidative wear of the composites. With an AlFe intermetallic compound content of 4.3 wt.%, the volume wear rate remains low under conditions corresponding to PV = 56.652 (equivalent to a normal load of 19.6 kPa and a sliding speed of 2.87 m s−1).

Enhancing mechanical properties of surface hardness and abrasion resistance of Fe-Mn-Al alloy by using atmospheric pressure plasma jet nitriding

Fri, 20 Sep 2024 04:07:35 GMT

title: Enhancing mechanical properties of surface hardness and abrasion resistance of Fe-Mn-Al alloy by using atmospheric pressure plasma jet nitriding abstract: This study investigates the use of a N2/H2 mixture gas and an atmospheric pressure plasma jet (APPJ) for nitriding Fe-Mn-Al alloy. Pure metals, iron, manganese, and aluminum, were used as the reference metallic substrates. Various characterization techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Vickers hardness test, and optical emission spectroscopy (OES), were employed to analyze the material properties and plasma species. XRD analysis revealed the formation of nitride compounds on metals after the nitriding process. The plasma-nitrided Fe-Mn-Al alloy showed the mixture phases of Fe4N and Al, while plasma-nitrided pure metals possessed their specific metal nitrides. After nitriding process, the surface hardness increased to approximately 596 ± 6 HV0.025 for the Fe-Mn-Al alloy, 1307 ± 9 HV0.025 for manganese, 467 ± 4 HV0.025 for aluminum, 646 ± 5 HV0.025 for iron, and, compared to the pristine values of around 346 ± 4 HV0.025, 972 ± 6 HV0.025, 145 ± 3 HV0.025, and 125 ± 3 HV0.025, respectively. After the nitriding process, the Fe-Mn-Al alloy exhibited notable enhancements in both its resistance to abrasion and its capacity to endure impact loads, as indicated by the conducted tests. The OES test results identified NH radicals generated by the atmospheric pressure plasma jet beam as the active chemicals responsible for the success of the nitriding process. Overall, this study provides valuable insights into the strengthening of metal surfaces through nitriding using an N2/H2 mixture gas and APPJ. The results demonstrate significant improvements in surface hardness and surface free energy for iron, manganese, aluminum, and Fe-Mn-Al alloy, highlighting the effectiveness of NH radicals in the nitriding process.

A study to predict the hydrodynamic and thermal characteristics of hybrid mesh regenerator

Thu, 05 Sep 2024 04:05:25 GMT

Numerical Analysis to Find Permeability of Lattice Structures

Thu, 05 Sep 2024 04:05:21 GMT

Injectable ChitHCl-MgSO4-DDA hydrogel as a bone void filler to improve cell migration and osteogenesis for bone regeneration

Wed, 07 Aug 2024 04:06:19 GMT

title: Injectable ChitHCl-MgSO4-DDA hydrogel as a bone void filler to improve cell migration and osteogenesis for bone regeneration abstract: Suture pull-through is a clinical problem in meniscus repair surgery due to the sharp leading edge of sutures. Several tissue adhesives have been developed as an alternative to traditional suturing; however, there is still no suitable tissue adhesive specific for meniscus repair treatment due to unsatisfactory biosafety, biodegradable, sterilizable, and tissue-bonding characteristics. In this study, we used a tissue adhesive composed of chitosan hydrochloride reacted with oxidative periodate-oxidized dextran (ChitHCl-DDA) combined with a chitosan-based hydrogel and oxidative dextran to attach to the meniscus. We conducted viscoelastic tests, viscosity tests, lap shear stress tests, Fourier transform infrared (FTIR) spectroscopy, swelling ratio tests, and degradation behavior tests to characterize these materials. An MTT assay, alcian blue staining, migration assay, cell behavior observations, and protein expression tests were used to understand cell viability and responses. Moreover, ex vivo and in vivo tests were used to analyze tissue regeneration and biocompatibility of the ChitHCl-DDA tissue adhesive. Our results revealed that the ChitHCl-DDA tissue adhesive provided excellent tissue adhesive strength, cell viability, and cell responses. This tissue adhesive has great potential for torn meniscus tissue repair and regeneration.

Optimizing implant lattice design for large distal femur defects: Stimulating interface bone growth to enhance osseointegration

Wed, 07 Aug 2024 04:06:14 GMT

Initial Study of the Onsite Measurement of Flow Sensors on Turbine Blades (SOTB)

Wed, 07 Aug 2024 04:06:10 GMT

title: Initial Study of the Onsite Measurement of Flow Sensors on Turbine Blades (SOTB) abstract: This paper presents a new framework using MEMS flow sensors on turbine blades (SOTB) to investigate unsteady flow features of a rotating wind turbine. Self-heating flow sensors were implemented by the U18 complementary metal-oxide semiconductor (CMOS) MEMS foundry provided by Taiwan Semiconductor Research Institute (TSRI). Flow sensor chips with a size of 1.5 mm × 1.5 mm were parylene-coated, output via a wireless data acquisition system (WDAQ), and mounted at the root, middle and tip of a 1.2 m diameter semi-rigid turbine blade of a 400 W horizontal axis wind turbine (HAWT). The instantaneous angles of attack (AOAs) of the SOTB were found to be 46~62◦, much higher than the general stall AOA of 15◦, but were accurate considering the normal detection of the flow sensors. The computational fluid dynamics (CFD) simulation of the HAWT was also compared with the SOTB output. The onsite measurement herein revealed that the 3D secondary flow increment, mostly obvious near the middle part of the turbine blades, degraded both the sensor and the turbine performance and initially justified the onsite measurement application.

A New Silicon Mold Process for Polydimethylsiloxane Microchannels

Wed, 07 Aug 2024 04:06:06 GMT

title: A New Silicon Mold Process for Polydimethylsiloxane Microchannels abstract: As an alternative to SU-8 soft lithography, a new silicon mold process of fabricating PDMS microchannel chips was proposed. A picosecond laser is used to cut through a 550 μm thick silicon wafer and generate the original microchannel pattern with a 50 μm minimum feature size. This single-crystal silicon pattern, with the edge debris caused by laser cutting being trimmed off by a KOH solution and with the protection field oxide layer being removed by BOE afterwards, firmly resided on a glass substrate through the anodic bonding technique. Four-inch wafers with microchannel patterns as the PDMS mold cores were successfully bonded on Pyrex 7740 or Eagle XG glass substrates for the follow-up PDMS molding/demolding process. This new maskless process does not need a photolithography facility, but the laser cutting service must be provided by professional off-campus companies. One PDMS microchannel chip for particle separation was shown as an example of what can be achieved when using this new process.