Establishment of the Model Widely Valid for the Melting and Vaporization Zones in Selective Laser Melting Printings Via Experimental Verifications

Chang-Shuo Chang,Kuan-Ta Wu,Chang-Fu Han,Tsung-Wen Tsai,Sung-Ho Liu,Jen-Fin Lin 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.1

The thermally affected material properties operating in the three phases and porosity variations in the SS316L steel powder have been introduced to the numerical analyses for the transient volumetric heat source (Q) models developed for the solid powder, melting, and vaporization regions in the selective laser melting (SLM). The bulk Q is thus a function of these heat sources and their ratio defined for the liquid and vapor phases. The heat conduction developed for the solid powders with porosity strings the heat convection with Q as the moving heat source to solve two-dimensional temperature distributions efficiently without the confinement of operating conditions and phase presumption. The specimens with single- and multiple-track printings are prepared to investigate the effects of incident energy density (E) and power intensity (I o) on the geometries of single-track printings and the areal surface roughness (Sa) values of the multiple-track printings with 0 and 50% overlap ratios. Laser power and scanning velocity are the controlling factors for the melting pool depth D and width W . D and W become the governing factors for the keyhole with evaporations, which affects the height H of single track after solidification. The W and D results predicted by the theoretical models developed in this study have an error range, 5–20%, compared to the experimental ones, which is much lower than those reported in the literatures (Gusarov et al. in J Heat Transf 131(7):072101, 2009. https ://doi.org/10.1115/1.31092 45 ; Hussein et al. in Mater Des 52:638–647, 2013. https ://doi.org/10.1016/j.matde s.2013.05.070 ; Yin et al. Int J Adv Manuf Technol 83(9–12): 1847–1859, 2016. https ://doi.org/10.1007/s0017 0-015-7609-x ; Andreotta et al. in Finite Elem Anal Des 135: 36–43, 2017. https ://doi.org/10.1016/j.finel .2017.07.002 ). The contact angle ( ϕ * ) is defined as a function of single-track width ( W ) and solidification height ( H ). ϕ * and Sa are significantly reduced as an E is applied beyond its critical value (47.62–57.14 J/mm 3 ). Significant change in Sa is ascribed to the big difference in the morphology and its surface pattern when E or I o reaches its critical value.

A hybrid finite element and analytical model for determining the mesh stiffness of internal gear pairs

Shuo Feng,Lehao Chang,Zhaoxia He 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.6

This work developed an efficient model for calculating the mesh stiffness of spur/helical internal gear pairs by combining the finite element method (FEM) and analytical formula. The tooth global deformation is obtained by separation of the deformation of a full finite element model and a partial model, and the local contact deformation is derived by an analytical line contact formula based on Hertz contact theory. The transmission error and mesh stiffness of the gear pair can be acquired after solving the nonlinear contact equilibrium equations. Compared with the conventional FEM, the proposed method has much smaller computational consumption. Furthermore, it also overcomes the disadvantage that the analytical method is difficult to consider different ring gear structures. Then the influences of ring thicknesses and the number of support pins of the ring gear on the mesh stiffness are discussed. The results show that the ring flexibility will change the amplitude-frequency components of the mesh stiffness a lot.

Dual 코일 하이브리드 제습 냉방 시스템 제안 및 성능 분석

유석(Shuo Liu),설염(Yan Xue),장휴산(Hyu San Jang),이태하(Tae Ha Leigh),정창호(Chang Ho Jeong),여명석(Myoung Souk Yeo) 대한설비공학회 2021 대한설비공학회 학술발표대회논문집 Vol.2021 No.6

Currently, the design and development of air conditioning systems increasingly requires consideration of indoor comfort, which makes the control of indoor humidity particularly important. Considering the miniaturization and complexity of the system structure, a heat pump assisted hybrid desiccant cooling system (HPDC system) using condenser waste heat to regenerate the desiccant was proposed in the previous study. Based on the problem of uncontrollable outlet temperature of this system, this paper has proposed an improved dual coil HPDC system and the corresponding system control logic and performed the thermal energy analysis by EnergyPlus software. The results show that the proposed system is able to maintain both the design indoor temperature and humidity. With the control logic, the increase in the number of cooling coil did not increase the cooling thermal energy consumption of the system, on the contrary, it was reduced by 2.1% compared to the previous system. But the design capacity of the second cooling coil should be larger than that of the previous system.

Manufacture of Precheese Powder by Use of Low-temperature Renneting Made from Raw Milk Using Spray Dryer

An, Shuo-Feng,Piao, Jing-Zhu,Chang, Oun-Ki Korean Society for Food Science of Animal Resource 2010 한국축산식품학회지 Vol.30 No.4

Among the food constituents, proteins differ in coagulation properties as compared to other constituents in food system. Especially milk protein coagulate through different pathways thus this coagulability can be used for manufacture of various dairy products or as a determinant of dairy product analysis. These milk coagulation methods include organic solvent, isoelectric point, trichloroacetic acid, Ca-sensitive casein, heavy metal ion and rennet coagulation. The coagulation experiment was performed using above parameters at $0^{\circ}C$ and $25^{\circ}C$ to find the dehydration conditions before coagulating for precheese powder making. After different chemical treatments, there was no coagulation at $0^{\circ}C$ rather at $25^{\circ}C$ whatever the mode of coagulation methods was. The appearance of precipitate with coagulation methods was quite different from above mentioned methods of coagulation illustrated by scanning electron microscope. These powders were used for fabrication of camembert cheese by renneting coagulation at $0^{\circ}C$, showing the possibility of cheese materials and of food additives for fabrication of products.

재열 시스템과 하이브리드 제습 냉방 시스템의 특성 비교 분석

유석(Shuo Liu),정창호(Chang Ho Jeong),여명석(Yeo Myoung Souk) 대한설비공학회 2020 대한설비공학회 학술발표대회논문집 Vol.2020 No.6

This study has compared the PTAC w/reheat system and the heat-pump assisted hybrid desiccant cooling (HPDC) system. EnergyPlus was applied to simulate the indoor thermal comfort and evaluate the system performance and dehumidification performance of HPDC system. As a result, compared with the PTAC w/reheat system, energy consumption of the HPDC system can be significantly reduced, and no additional heat source is needed to regenerate the desiccant wheel. The indoor temperature and humidity can be controlled within comfort range. There is the situation that indoor relative humidity exceeds the design relative humidity during the HPDC system operation, which accounts for 0.8% of the system operation time and only occurs when the outdoor temperature is low. The system performance of HPDC system improves with the increase of outdoor temperature and humidity, but the performance trend of the PTAC w/reheat system is opposite. The dehumidification performance of the HPDC system decreases with the increase of dehumidification load.

Bi-functional Al-doped ZnO@SnO2 heteronanowires as efficient substrates for improving photocatalytic and SERS performance

Yu-Cheng Chang,Shuo-Hsiu Wu 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.76 No.-

Bi-functional Al-doped ZnO@SnO2 heteronanowires systematically analyzed as high-performancesubstrates for photocatalytic and surface-enhanced Raman scattering (SERS) applications. For thephotocatalytic application, the Al-doped ZnO@SnO2 heteronanowires can exhibit highly efficient andreusable photocatalysts in the photodecomposition of rhodamine 6G solution under low-powered UVlightirradiation, which ascribed to improve the inhabitation of electron–hole pairs recombination andhigher surface active sites. For the SERS application, Al-doped ZnO@SnO2 heteronanowires revealedsuitable geometry to deposit Ag nanoparticles with higher density and more hot spots in threedimensionalstructures, which can provide high SERS enhancement, low detection limit (amoxicillin10 10 M), high reproducibility, and stability.

Biomechanical Evaluation of 2 Endoscopic Spine Surgery Methods for Treating Lumbar Disc Herniation: A Finite Element Study

Yang Zou,Shuo Ji,Hui Wen Yang,Tao Ma,Yue Kun Fang,Zhi Cheng Wang,Miao Miao Liu,Ping Hui Zhou,Zheng Qi Bao,Chang Chun Zhang,Yu Chen Ye 대한척추신경외과학회 2024 Neurospine Vol.21 No.1

Objective: This study aimed to evaluate the effects of 2 endoscopic spine surgeries on the biomechanical properties of normal and osteoporotic spines. Methods: Based on computed tomography images of a healthy adult volunteer, 6 finite element models were created. After validating the normal intact model, a concentrated force of 400 N and a moment of 7.5 Nm were exerted on the upper surface of L3 to simulate 6 physiological activities of the spine. Five types of indices were used to assess the biomechanical properties of the 6 models, range of motion (ROM), maximum displacement value, intervertebral disc stress, maximum stress value, and articular protrusion stress, and by combining them with finite element stress cloud. Results: In normal and osteoporotic spines, there was no meaningful change in ROM or disc stress in the 2 surgical models for the 6 motion states. Model N1 (osteoporotic percutaneous transforaminal endoscopic discectomy model) showed a decrease in maximum displacement value of 20.28% in right lateral bending. Model M2 (unilateral biportal endoscopic model) increased maximum displacement values of 16.88% and 17.82% during left and right lateral bending, respectively. The maximum stress value of L4–5 increased by 11.72% for model M2 during left rotation. In addition, using the same surgical approach, ROM, maximum displacement values, disc stress, and maximum stress values were more significant in the osteoporotic model than in the normal model. Conclusion: In both normal and osteoporotic spines, both surgical approaches were less disruptive to the physiologic structure of the spine. Furthermore, using the same endoscopic spine surgery, normal spine biomechanical properties are superior to osteoporotic spines.

Temperature enhanced growth of ultralong multi-walled carbon nanotubes forest

Tsung-Cho Wu,Shuo-Hung Chang 한국물리학회 2009 Current Applied Physics Vol.9 No.5

This work demonstrates a method to synthesize ultralong multi-walled carbon nanotubes (MW-CNTs) forest with high growth rate using the three-zone temperature chemical vapor deposition (TZT-CVD). The effect of temperature difference in the TZT-CVD is to sustain the lifetime of the catalyst and hence increase the growth efficiency. By optimizing the growth variables, TZT-CVD produced MW-CNTs forest with a height up to 4.27 mm in 60 min. The CNT synthesis ratio, an ultimate figure of merit is 712 times and the carbon source consumption is 4% compared to that of single-zone temperature CVD.

Possible coexistence of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and Diaeretiella rapae M'Intosh (Hymenoptera: Braconidae) in the biological control of Lipaphis erysimi (Homoptera: Aphididae)

Pengxiang Wu,Muhammad Haseeb,Chang Liu,Shuo Yan,Jing Xu,Runzhi Zhang 한국응용곤충학회 2019 Journal of Asia-Pacific Entomology Vol.22 No.1

To study the interactions between the aphidophagous predator Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and the specialist aphid parasitoid Diaeretiella rapae M'Intosh (Hymenoptera: Braconidae) in the biological control of mustard aphid, Lipaphis erysimi (Homoptera: Aphididae), the prey discrimination by H. axyridis among unparasitized, non-mummified parasitized and mummified aphids was examined under laboratory conditions. Prey/host selections were also tested by offering L. erysimi at various developmental stages to assess the possibility of coexistence between the two species, so the prey preference of H. axyridis when D. rapae parasitize aphids, and the host preference of D. rapae when H. axyridis interfered with the parasitization were detected. We found that H. axyridis could discriminate against mummies rather than non-mummified parasitized aphids. The ladybug showed a significantly positive preference for adult prey when D. rapae turned aphids into mummies, while D. rapae tended to parasitize younger nymphal aphids when H. axyridis was introduced. The present study suggests the prey discrimination against mummies by H. axyridis, and indicates that H. axyridis and D. rapae can avoid resource competition by attacking different and non-overlapping developmental stages of aphid. Thus, H. axyridis and D. rapae can potentially coexist and establish a stable ecosystem in the biological control of L. erysimi.

ZnO Nanowire Arrays on 3D Hierachical Graphene Foam: Biomarker Detection of Parkinson’s Disease

Yue, Hong Yan,Huang, Shuo,Chang, Jian,Heo, Chaejeong,Yao, Fei,Adhikari, Subash,Gunes, Fethullah,Liu, Li Chun,Lee, Tae Hoon,Oh, Eung Seok,Li, Bing,Zhang, Jian Jiao,Huy, Ta Quang,Luan, Nguyen Van,Lee, Y American Chemical Society 2014 ACS NANO Vol.8 No.2

<P>We report that vertically aligned ZnO nanowire arrays (ZnO NWAs) were fabricated on 3D graphene foam (GF) and used to selectively detect uric acid (UA), dopamine (DA), and ascorbic acid (AA) by a differential pulse voltammetry method. The optimized ZnO NWA/GF electrode provided a high surface area and high selectivity with a detection limit of 1 nM for UA and DA. The high selectivity in the oxidation potential was explained by the gap difference between the lowest unoccupied and highest occupied molecular orbitals of a biomolecule for a set of given electrodes. This method was further used to detect UA levels in the serum of patients with Parkinson’s disease (PD). The UA level was 25% lower in PD patients than in healthy individuals. This finding strongly implies that UA can be used as a biomarker for PD.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-2/nn405961p/production/images/medium/nn-2013-05961p_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn405961p'>ACS Electronic Supporting Info</A></P>