Influence of processing parameters on warpage according to the Taguchi experiment

Guojian Zheng,Weiguo Dong,Qian Wang,Xiangyu Guo 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.10

An automotive triangle trim was chosen as a research model, and the influence of processing parameters was determined with the Taguchiexperimental method. An L27 (313) orthogonal array was constructed to investigate the significance of each factor (mold temperature,melt temperature, injection time, V/P switchover, packing pressure, and packing time). The computer-aided engineering softwareMoldflow was employed to determine the extent of warpage. The influence of processing parameters was analyzed by obtaining the signal-to-noise ratio and by conducting a range analysis. Furthermore, the processing parameters for minimizing warpage were optimized. Subsequently, the optimization packing condition for warpage minimization based on the filling conditions.

Diffusion mechanism of deep shale gas and its carbon isotope fractionation: a combined simulated and mathematical analysis

Yu Zou,Guojian Wang,Cheng Tao,Rui Zhou,Shangqing Zhang,Dongna Liu,Xiaohui Lin,Xuying Zheng 한국지질과학협의회 2023 Geosciences Journal Vol.27 No.3

Unlike the release pressure process in shale gas exploitation, in this study, the concentration diffusion process is deeply discussed under constant temperature-pressure conditions, which aims to evaluate the preservation conditions of shale gas reservoirs in combination with isotopic fractionation characteristics. The isobaric diffusion experiment emphasized that decreasing pressure can lead to enhanced diffusion and isotope fractionation. The established mathematical model not only confirms the results of the simulating experiment, but also suggests that the contributions of Fick, Knudsen and surface diffusion to the migration of methane (including 12CH4 and 13CH4) vary in the geological evolution of shale reservoirs, which are mainly controlled by the pore system and gas pressure. Based on the analysis of specific samples of Longmaxi shale (r = 11.7 nm) and Niutitang shale (r = 1.3 nm), we propose that: 1) high pressure condition (> 20 MPa) can significantly limit Knudsen diffusion, which is the reason for reducing the total diffusion coefficient (DTotal) and isotope fractionation, while low pressure (< 10 MPa) and small pore radius (ca. 1 nm) can strengthen the fractionation; 2) pore connectivity and heterogeneity can lead to an order of magnitude change in DTotal, while the influence of temperature is relatively small. According to the mathematical model, it can be expected that enhanced dissipation intensity and isotope fractionation of shale gas may occur in the process of basin uplift and pressure relief, which can potentially be used for the evaluation of reservoir preservation.

Study on the thermoelectric properties of porous Bi-Te films deposited using thermal evaporation on AAO template

Shiying Liu,GUOJIAN LI,Mingdi Lan,Yongjun Piao,Yanan Zhang,QIANG WANG 한국물리학회 2020 Current Applied Physics Vol.20 No.3

The application of thermoelectric films is limited to retain the temperature gradient. In this study, the Bi-Te films are deposited on the AAO template with a pore size of 100 nm using thermal evaporation. The results show that the conductive types of the Bi-Te film are tuned by source temperature. The power factor of the p-type porous film decreases 36% by comparing to that of the p-type nonporous film (1020 μW/mK2 at 250 °C). Meanwhile, the temperature difference in the porous device is maintained and is approximately 5.0 °C. Thus, the maximum output power is achieved in the porous device (about 25 pW), which is 5 times higher than that of the nonporous device. This provides a method to improve the conversion efficiency of thermoelectric film device by maintaining the temperature difference by using porous structure.

Flexible Composites: Carbon Nanotube Fiber Based Stretchable Conductor (Adv. Funct. Mater. 7/2013)

Zu, Mei,Li, Qingwen,Wang, Guojian,Byun, Joon‐,Hyung,Chou, Tsu‐,Wei WILEY‐VCH Verlag 2013 Advanced Functional Materials Vol.23 No.7

<P>Stretchable conductors based on buckled carbon nanotube (CNT) fibers are fabricated using a simple prestraining‐then‐buckling approach. The primary deformation mode of the CNT fibers is lateral kinking. This buckling shape is quite different from the sinusoidal shape observed previously in systems that are otherwise similar. As reported by Tsu‐Wei Chou and co‐workers on page 789, the prepared CNT fiber/poly(dimethylsiloxane) (PDMS) composite film shows excellent stability and repeatability in performance as a stretchable conductor. </P>

ENSO and greenhouse warming

Cai, Wenju,Santoso, Agus,Wang, Guojian,Yeh, Sang-Wook,An, Soon-Il,Cobb, Kim M.,Collins, Mat,Guilyardi, Eric,Jin, Fei-Fei,Kug, Jong-Seong,Lengaigne, Matthieu,McPhaden, Michael J.,Takahashi, Ken,Timmerm Nature Publishing Group, a division of Macmillan P 2015 Nature climate change Vol.5 No.9

The El Niño/Southern Oscillation (ENSO) is the dominant climate phenomenon affecting extreme weather conditions worldwide. Its response to greenhouse warming has challenged scientists for decades, despite model agreement on projected changes in mean state. Recent studies have provided new insights into the elusive links between changes in ENSO and in the mean state of the Pacific climate. The projected slow-down in Walker circulation is expected to weaken equatorial Pacific Ocean currents, boosting the occurrences of eastward-propagating warm surface anomalies that characterize observed extreme El Niño events. Accelerated equatorial Pacific warming, particularly in the east, is expected to induce extreme rainfall in the eastern equatorial Pacific and extreme equatorward swings of the Pacific convergence zones, both of which are features of extreme El Niño. The frequency of extreme La Niña is also expected to increase in response to more extreme El Niños, an accelerated maritime continent warming and surface-intensified ocean warming. ENSO-related catastrophic weather events are thus likely to occur more frequently with unabated greenhouse-gas emissions. But model biases and recent observed strengthening of the Walker circulation highlight the need for further testing as new models, observations and insights become available.

EFFECTS OF HIGH MAGNETIC FIELD ON THE STRUCTURAL EVOLUTION AND MAGNETIC PROPERTIES OF NANOCRYSTALLINE Ni FILMS

JIAOJIAO DU,QIANG WANG,GUOJIAN LI,YONGZE CAO,JICHENG HE 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.2

This paper studies the e®ects of a high magnetic feld on the structural evolution and magneticproperties of nanocrystalline Ni flms prepared on quartz substrates by a molecular beam vapordeposition (MBVD) method. Atomic force microscope, X-ray di®ractometer, transmission elecftron microscope and vibrating sample magnetometer were used to study the microstructures andmagnetic properties of the Ni flms. The results indicate that high magnetic feld has no obviousinfluence on crystal structures except changing the lattice constant of the Ni flms. However, thehigh magnetic feld can refne particle size. The flm deposited under magnetic feld tends to growthrough columnar mode because of the magnetized particles aligning along the direction ofmagnetic feld. Furthermore, the ordered and dense arrangement of Ni atoms results in more spinscontained in per unit volume and improves the saturation magnetization (Ms). Ms of the 6 T Ni¯lm increases by 70% (578 emu/cm3) than that of the ¯lm without magnetic ¯eld (341 emu/cm3),and the coercivity is also slightly increased for the 6 T flm.

Effect of Oxides on Characteristics of MnS and Transverse Mechanical Properties in Commercial Al‑Killed Non‑Quenched and Tempered Steel

Jinlong Lu,Guoguang Cheng,Julong Che,Liansheng Wang,Guojian Xiong 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.2

In this paper, the characteristics of tensile fractures and the typical inclusions in as-cast blooms and as-rolled bars are carefullyinvestigated to figure out the causes of different transverse tensile properties in two commercial non-quenched andtempered steels. In low Ca bearing steel (3 ppm), MgO–Al2O3 (MA) + MnS are main inclusions and MA oxides expresshigh ability for MnS heterogeneous nucleation. Consequently, the MnS inclusions in as-rolled bars are larger in size andsmaller in number, the transverse ductility is satisfied due to the high space distance between the MnS inclusions. However,the transverse ductility of high Ca bearing steel (9 ppm) is much poor because MnS inclusions are agminated in distribution,causing severe stress concentration. The calculation results show that CaO in CaO–MgO–Al2O3 oxides (CMA) wouldreact with Al and S in molten steels, suppressing the formation of MnS inclusions on surface of CMA oxides. An integratedillumination including the evolution processes of typical oxides in molten steels, the generation behaviors of MnS duringthe solidification, the deformation behaviors of sulfides and the relationship between sulfides and crack initiation have beenconducted based on observation results and thermodynamic calculation.

Dynamics of fungal community during silage fermentation of elephant grass (Pennisetum purpureum) produced in northern Vietnam

Viet Ha Vu,Xiyang Li,Mengyuan Wang,Rongmei Liu,Guojian Zhang,Wei Liu,Baixue Xia,Qun Sun 아세아·태평양축산학회 2019 Animal Bioscience Vol.32 No.7

Objective: This study aimed to gain deeper insights into the dynamic changes in spoilage fungi populations during fermentation and the influence of traditional additives on silage quality. Methods: Elephant grass (Pennisetum purpureum) was prepared without any additive (control), and with the addition of 0.5% salt, and 0.5% salt–0.2% sugar mixture. The fungal community was then determined using a classic culturing method and high-throughput sequencing at 0, 5, 15, and 60 days after ensiling. Results: The results showed that the fungal community of elephant grass silage varied significantly between the natural fermentation without any additive and the two additive groups. The diversity and relative abundance of spoilage molds in the control group were much higher than those in the two treatment groups (p<0.05). Three species of yeasts (Candida sp., Pichia sp., Trichosporon sp.) and four spoilage molds (Fusarium sp., Aspergillus sp., Muco sp. and Penicillin sp.) were the predominant fungi in elephant grass during natural fermentation from 0 to 60 days, which were found to be significantly decreased in salt and sugar additive groups (p<0.05). Meanwhile, the diversity and relative abundance of undesirable molds in the 0.5%-salt additive group were the lowest among all groups. Conclusion: Adding salt and sugar, particularly 0.5% salt, is a promising effective approach to reduce the amount of undesirable fungi thus, improving the silage quality of elephant grass in northern Vietnam.