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排序方式: 共有781条查询结果,搜索用时 15 毫秒
91.
92.
Comparative study of conventional and micro WEDM based on machining of meso/micro Sized Spur Gear 总被引:1,自引:0,他引:1
Mohammad Yeakub Ali A. N. Mustafizul Karim Erry Yulian T. Adesta Ahmad Faris Ismail ’Aisy Anuarin Abdullah Mohd Nazrol Idris 《International Journal of Precision Engineering and Manufacturing》2010,11(5):779-784
This paper discusses the comparison of micro machining process using conventional and micro wire electrical discharge machining
(WEDM) for fabrication of miniaturized components. Seventeen toothed miniaturized spur gear of 3.5 and 1.2 mm outside diameter
were fabricated by conventional and micro WEDM respectively. The process parameters for both conventional and micro WEDM were
optimized by preliminary experiments and analysis. The gears were investigated for the quality of surface finish and dimensional
accuracy which were used as the criteria for the process evaluation. An average surface roughness (Ra) of 50 nm and dimensional accuracy of 0.1–1 μm were achieved in micro WEDM. Whenever applied conventional WEDM for meso/micro
fabrication, a Ra surface roughness of 1.8 μm and dimensional accuracy of 2–3 μm were achieved. However, this level of surface roughness and
dimensional accuracy are acceptable in many applications of micro engineering. A window of conventional WEDM consisting of
low energy discharge parameters is identified for micromachining. 相似文献
93.
Ethanol and lactic acid production using sap squeezed from old oil palm trunks felled for replanting
Akihiko Kosugi Ryohei Tanaka Kengo Magara Yoshinori Murata Takamitsu Arai Othman Sulaiman Rokiah Hashim Zubaidah Aimi Abdul Hamid Mohd Khairul Azri Yahya Mohd Nor Mohd Yusof Wan Asma Ibrahim Yutaka Mori 《Journal of Bioscience and Bioengineering》2010,110(3):322-325
Old oil palm trunks that had been felled for replanting were found to contain large quantities of high glucose content sap. Notably, the sap in the inner part of the trunk accounted for more than 80% of the whole trunk weight. The glucose concentration of the sap from the inner part was 85.2 g/L and decreased towards the outer part. Other sugars found in relatively low concentrations were sucrose, fructose, galactose, xylose, and rhamnose. In addition, oil palm sap was found to be rich in various kinds of amino acids, organic acids, minerals and vitamins. Based on these findings, we fermented the sap to produce ethanol using the sake brewing yeast strain, Saccharomyces cerevisiae Kyokai no.7. Ethanol was produced from the sap without the addition of nutrients, at a comparable rate and yield to the reference fermentation on YPD medium with glucose as a carbon source. Likewise, we produced lactic acid, a promising material for bio-plastics, poly-lactate, from the sap using the homolactic acid bacterium Lactobacillus lactis ATCC19435. We confirmed that sugars contained in the sap were readily converted to lactic acid with almost the same efficiency as the reference fermentation on MSR medium with glucose as a substrate. These results indicate that oil palm trunks felled for replanting are a significant resource for the production of fuel ethanol and lactic acid in palm oil-producing countries such as Malaysia and Indonesia. 相似文献
94.
Mobile communications and wireless networks are developing at a fast pace. The increasing number of mobile subscribers and terminals are the real life evidence of the fast growing development in the area of wireless communication. Wireless communication technology is now pursuing 4G (fourth generation) and seeking a scheme to provide quality of service (QoS) to the various applications continuously even moving to another network. In this paper, we proposed a dynamic resource management architecture which considers vertical handoff situation with minimal disruption of service to the users considering seamless provision of QoS. The proposed scheme efficiently manages resources and provides stable services to the mobile terminal. The simulation results show that resource management enabled mobile terminals utilize system resources, CPU and memory, efficiently improved by 40% and 65%, respectively, rather than mobile terminals without resource tuning. 相似文献
95.
Fängström B Athanassiadis I Odsjö T Norén K Bergman A 《Molecular nutrition & food research》2008,52(2):187-193
Environmental and human exposures to brominated flame retardants (BFR) have been of emerging concern since some BFR are persistent and bioaccumulative compounds. Among those, polybrominated diphenyl ethers (PBDE) have frequently been reported in low to high ng/g concentrations in human blood around the world while hexabromocyclododecane (HBCDD) only occasionally has been reported and then in the low ppb concentrations in human blood. The present study concerns PBDE congener and HBCDD concentrations in human milk from Stockholm from 1980 to 2004. HBCDD concentrations has increased four to five times since 1980 until 2002 but seems to have stabilized at this concentration in the last years (2003/04). Similarly, BDE-153 has continued to increase at least to 2001, after which it has stabilized in the mother's milk. Other PBDE congeners with four to five bromine substituents peaked 5 years earlier (1995) and are all decreasing. DecaBDE (BDE-209) is not a suitable biomarker for time trend studies according to the present results, showing no changes over time. This is likely due to its short apparent half-life in humans and poor transfer from blood to milk. 相似文献
96.
The present work evaluates the potential of the natural filler peanut shell powder (PSP) on the properties and degradation behavior of alkaline‐treated PSP filled recycled polypropylene (RPP) composites. For this purpose, 0–40 wt% of untreated PSP and hydrogen peroxide‐treated PSP were incorporated into RPP composites that were fabricated via a melt‐mixing molding system. The fabricated composites were exposed to the natural environment of Penang, Malaysia for 6 months. The properties of both untreated and treated RPP/PSP composites were assessed. Results showed that the tensile properties of the treated RPP/PSP composites were higher than that of the untreated RPP/PSP composites. The treated RPP/PSP composites were less affected by weathering degradation compared to the untreated RPP/PSP composites. An increase in the carbonyl index of both composites also confirmed that some degradation had taken place. On comparing the crystallinity of both composites, the treated composites showed lower crystallinity than untreated composites. J. VINYL ADDIT. TECHNOL., 25:26–34, 2019. © 2018 Society of Plastics Engineers 相似文献
97.
Nur Aini Fauziyah Allif Rosyidy Hilmi Teuku Andi Fadly Mohamad Zainul Asrori Mashuri Mashuri Suminar Pratapa 《应用聚合物科学杂志》2019,136(17):47372
The effect of silica polymorphs on the thermomechanical properties of 0, 5, 10, and 20 wt % silica particles-reinforced-based poly(ethylene glycol) (PEG) composites have been studied as a function of temperature using dynamic mechanical analysis (DMA). The silica polymorphs exhibited quartz (Q), cristobalite (C), and amorphous (A) phases, which were obtained by processing natural silica sand. The DMA thermomechanical properties were determined in tensile (E) and shear (G) modes. The maximum storage moduli (E′ and G′) were achieved by samples with 20 wt % silica for all type of fillers. These values increased approximately 12 times for PEG/Q, 10 times for PEG/A, and 11 times for PEG/C composites compared to the pure PEG. Furthermore, the Poisson's ratio values of the composites were filler phase dependent, that is, 0.39–0.47 for PEG/Q, 0.15–0.18 for PEG/A, and somewhat anomalous for PEG/C composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47372. 相似文献
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