New Frontiers of Laser Welding Technology

With the advances in power sources and optic technologies, high-power laser welding has been utilized in many applications such as automotive, battery manufacturing, and electronic industries. The low-heat input of laser power and its precise control enables minimal thermal damage and geometric inaccuracy in the weldment. Recently, laser welding has evolved in combination with machine learning, monitoring and control technology, new materials, and new processes. This Special Issue aims to present the recent advances in the development in innovative laser welding technologies based on new laser power sources, laser optics, systems, and monitoring technologies. A total of six papers are presented in this Special Issue

Role of Binder on Yield Strength of polycaprolactone/dimethylsulfone composites for bio-applications

Polycaprolactone (PCL) and dimethylsulfone (DMSO2) composites can tailor the properties of scaffold materials, allowing their use in bone tissue engineering. With an increase in DMSO2 content, the modulus of the material increases but not the yield strength. In order to increase yield strength, a binder was added. However, the optimization of the content and the mixing process of the binder were not optimized in the previous studies. In this study, gamma-methacryloxypropyltrimethoxysilane (A-174) was used as a binder to increase the strength of a composite. Four different mixing processes were employed based on the binder mixing sequence. The binders with content of 0, 0.4, 0.5, 0.7, and 1.5 phr were employed. The yield strengths of composites were investigated in terms of the binder mixing sequence and binder content. When the binder and DMSO2 particle fillers were premixed in the PCL matrix consisting of a DMSO2 filler and an A-174 binder system, the filler surface was coated smoothly and uniformly, and less agglomeration occurred. The yield strength of the composites with the appropriate mixing sequence was 36.71 % higher than that of the specimen without a binder, which was attributed to the improved adhesion between the matrix and fillers. Upon increasing the binder content, elongation and tearing of the matrix surface were observed in the cross-sections after yield tests; however, the weakening of mechanical anchoring was caused by excessive binder content, and filler debonding was observed on the surface. Because of the use of the A-174 silane binder at a concentration of 0.5 phr and the premixing of the binder and filler, the highest performance in terms of strength improvement of a PCL-20 wt % DMSO2 composite was achieved

Improving I/O Performance in Smart TVs

Abstract-To use the XML file, it must be converted into a tree structure form in smart TV application. However, when the application is terminated, tree are eliminated in process address space. When application is restarted, XML file need to be converted to tree again in order to execute application. This study presents a Fast I/O technique that enables restarting a application without data conversion process by adding persistency in tree in a smart TV environment. Fast I/O technique provides an object, in which the tree are saved adding persistency in process address space. The data structure gains persistency by saving the tree in an object and reusing it without data conversion when restarting the application. Fast I/O technique was applied in the web browser to parse HTML and skip the process of composing a tree. Running time was reduced up to 61% in the test environment, consisting of CPU, memory, and an SSD

Enhancement of Mechanical Properties of PCL/PLA/DMSO2 Composites for Bone Tissue Engineering

Bone tissue engineering shows potential for regenerating or replacing damaged bone tissues by utilizing biomaterials renowned for their biocompatibility and structural support capabilities. Among these biomaterials, polycaprolactone (PCL) and polylactic acid (PLA) have gained attention due to their biodegradability and versatile applications. However, challenges such as low degradation rates and poor mechanical properties limit their effectiveness. Dimethyl sulfone (DMSO2) has emerged as a potential additive to address these limitations, offering benefits such as reduced viscosity, increased degradation time, and enhanced surface tension. In this study, we investigate tailored composites comprising PLA, PCL, and DMSO2 to enhance mechanical properties and hydrophilicity. Through material characterization and mechanical testing, we found that the addition of DMSO2 led to improvements in the yield strength, modulus, and hydrophilicity of the composites. PCL and DMSO2 10, 20, and 30 wt% were premixed, and 20 wt% PCL + 10, 20, and 30 wt% DMSO2 were mixed with PLA. Specifically, PLA/PCL/DMSO2 composites exhibited higher yield strengths and moduli compared to pure PLA, pure PCL, and PLA/PCL composites. Moreover, the hydrophilicity of the composites increased with DMSO2 concentration, facilitating cell attachment. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of –COOH and –COH bands in PLA/PCL/DMSO2 composites, indicating chemical interactions between DMSO2 and the polymer matrix. Fractography analysis revealed enhanced interface adhesion in PLA/PCL/DMSO2 composites due to the hydrogen bonding. Overall, this study demonstrates the potential of PLA/PCL/DMSO2 composites in bone tissue engineering applications, offering improved mechanical properties and enhanced cell compatibility. The findings contribute to the advancement of biomaterials for additive manufacturing in tissue engineering and regenerative medicine

Development of Prediction Method for Dimensional Stability of 3D-Printed Objects

Fused deposition modeling (FDM), as one of the additive manufacturing processes, is known for strong layer adhesion suitable for prototypes and end-use items. This study used a multiple regression model and statistical analysis to explore the dimensional accuracy of FDM objects. Factors such as inclination angle, layer thickness, support space, and raster angle were examined. Machine learning models (Gaussian process regression (GPR), support vector machines (SVM), and artificial neural network (ANN)) predicted dimensions using 81 datapoints. The mean squared dimensional error (MSDE) between the measured and designed surface profiles was selected as an output for the dimensional accuracy. Support spacing, layer thickness, and raster angle were determined to be statistically significant, and all factors were confirmed as significant predictors. The coefficients of determination for multiple linear regression, GPR, SVM, and ANN models were 76%, 98%, 93%, and 99%, respectively. The mean absolute errors (MAEs)—errors between the measured and the predicted MSDEs—were 0.020 mm and 0.034 mm, respectively, for GPR and SVM models. The MAEs for ANN models were 0.0055 mm for supporting cases and 2.1468 x 10 -5 mm for non-supporting cases

PCL and DMSO2 Composites for Bio-Scaffold Materials

Polycaprolactone (PCL) has been one of the most popular biomaterials in tissue engineering due to its relatively low melting temperature, excellent thermal stability, and cost-effectiveness. However, its low cell attraction, low elastic modulus, and long-term degradation time have limited its application in a wide range of scaffold studies. Dimethyl sulfone (DMSO2) is a stable and non-hazardous organosulfur compound with low viscosity and high surface tension. PCL and DMSO2 composites may overcome the limitations of PCL as a biomaterial and tailor the properties of biocomposites. In this study, PCL and DMSO2 composites were investigated as a new bio-scaffold material to increase hydrophilicity and mechanical properties and tailor degradation properties in vitro. PCL and DMSO2 were physically mixed with 10, 20, and 30 wt% of DMSO2 to evaluate thermal, hydrophilicity, mechanical, and degradation properties of the composites. The water contact angle of the composites for hydrophilicity decreased by 15.5% compared to pure PCL. The experimental results showed that the mechanical and degradation properties of PCL and DMSO2 were better than those of pure PCL, and the properties can be tuned by regulating DMSO2 concentration in the PCL matrix. The elastic modulus of the composite with 30 wt% of DMSO2 showed 532 MPa, and its degradation time was 18 times faster than that of PCL

Rheological Properties and 3D Printing Behavior of PCL and DMSO2 Composites for Bio-Scaffold

The significance of rheology in the context of bio three-dimensional (3D) printing lies in its impact on the printing behavior, which shapes material flow and the layer-by-layer stacking process. The objective of this study is to evaluate the rheological and printing behaviors of polycaprolactone (PCL) and dimethyl sulfone (DMSO2) composites. The rheological properties were examined using a rotational rheometer, employing a frequency sweep test. Simultaneously, the printing behavior was investigated using a material extrusion 3D printer, encompassing varying printing temperatures and pressures. Across the temperature range of 120–140 °C, both PCL and PCL/DMSO2 composites demonstrated liquid-like behavior, with a higher loss modulus than storage modulus. This behavior exhibited shear-thinning characteristics. The addition of DMSO2 10, 20, and 30 wt% into the PCL matrix reduced a zero-shear viscosity of 33, 46, and 74% compared to PCL, respectively. The materials exhibited extrusion velocities spanning from 0.0850 to 6.58 mm/s, with velocity being governed by the reciprocal of viscosity. A significant alteration in viscosity by temperature change directly led to a pronounced fluctuation in extrusion velocity. Extrusion velocities below 0.21 mm/s led to the production of unstable printed lines. The presence of distinct viscosities altered extrusion velocity, flow rate, and strut diameter. This phenomenon allowed the categorization of pore shape into three zones: irregular, normal, and no-pore zones. It underscored the importance of comprehending the rheological aspects of biomaterials in enhancing the overall quality of bio-scaffolds during the 3D printing process

In vitro development of mouse parthenogenetic embryos: Effect of temperature before oocyte activation

This study was conducted to establish the optimal temperature condition before oocyte activation in B6D2 F1 mouse. In experiment 1, two embryo culture media (CZB vs KSOM) were evaluated for the development of activated mouse oocytes. Parthenogenetic embryos cultured in KSOM showed better blastocyst development than ones cultured in CZB(56.2% vs 81.0%, p<0.01). Two-hour of pre-incubation before activation significantly reduced the number of hatched blastocysts in KSOM (22.0% versus 8.8%, p<0.05). In experiment 2, recovered oocytes were pre-incubated at different temperature conditions before activation. The experimental groups were divided by 5 as follows. Group A: pre-incubation for 120 min at 37℃, Group B: pre-incubation at 37℃ for 90 min then at 25℃ for 30 min, Group C: pre-incubation at 37℃ for 60 min then at 25℃ for 60 min, Group D: pre-incubation at 37℃ for 30 min then at 25℃ for 90 min, and Group E: pre-incubation at 25℃ for 120 min before activation. Group A (67.6%) and B (66.7%) showed better development to the blastocyst stage than other groups (Group C: 50.0%, Group D: 49.2%, Group E: 33.3%, p<0.05). The present study indicates that the temperature before activation affects the development of B6D2 F1 mouse parthenogenetic oocytes and exposure to room temperature should be limited to 30-min when the oocytes are left in HEPES-buffered medium for micromanipulation

New Frontiers of Laser Welding Technology

With the advances in power sources and optic technologies, high-power laser welding has been utilized in many applications such as automotive, battery manufacturing, and electronic industries [...

Existence of Amino Acids in Defined Culture Medium Influences In Vitro Development of Parthenogenetic and Nuclear Transfer Porcine Embryos

This study was designed to investigate the effect of essential amino acids (EAA) and/or non-essential amino acids (NEAA) on the development of parthenogenetic and somatic cell nuclear transfer (SCNT) porcine embryos in vitro. To evaluate the timing of amino acids supplementation, activated oocytes were cultured in NCSU23-PVA with EAA, NEAA or NEAA+EAA (AAs) during specific periods as below: EAA, NEAA or AAs were supplemented during Day 0 to 6 (whole culture period: ALL), Day 2 to Day 6 (post-maternal embryonic transition period: POST-MET), Day 5 to Day 6 (post-compaction period: POST-CMP), Day 0 to Day 2 (pre-maternal embryonic transition period: PRE-MET), or Day 0 to Day 4 (post-compaction period: PRE-CMP). Supplementation of NEAA decreased cleavage rates in PRE-MET and PRE-CMP and also decreased blastocyst rates in POST-CMP. On the other hand, EAA significantly enhanced blastocyst formation rate in POST-MET and no detrimental effect on embryonic development in other groups. Interestingly, NEAA and EAA had synergistic effect when they were supplemented to the medium during whole culture period. Supplementation of AAs also enhanced SCNT porcine embryo development whereas BSA-free medium without AAs could not supported blastocyst formation of SCNT embryos. In conclusion, existence of EAA and NEAA in defined culture medium variously influences the development of parthenogenetic and SCNT porcine embryos, and their positive effect are only occurred when both EAA and NEAA are supplemented to the medium during whole culture period. Additionally, AAs supplementation enhances the blastocyst formation of SCNT porcine embryos when they are cultured in the defined condition.This study was supported by the Korea Science and Engineering Foundation(KOSEF) grant funded by the Ministry of Education Science and Technology(MEST;R01-2007-000-20326-0 and 2008-04347)