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排序方式: 共有535条查询结果,搜索用时 15 毫秒
61.
The concept of implementation of Six Sigma methodology was pioneered at Motorola in the 1980s with the aim of reducing quality costs. Six Sigma methodology has evolved into a statistically oriented approach to process, product or service quality improvement. It is a business performance improvement strategy used to improve profitability, to drive out waste in business processes and to improve the efficiency of all operations that meet or exceed customers' needs and expectations. A performance level of Six Sigma equates to 3-4 defects per million opportunities, where sigma is a statistical measure of the amount of variation around the process average. The average sigma level for most companies is three sigma. The authors offer guidance as to how companies may achieve Six Sigma performance. Organisations that have adopted the principles and concepts of Six Sigma methodology have realised that once they have achieved Five Sigma quality levels the only way to surpass the Five Sigma quality level is to redesign their products, processes and services from scratch. These circumstances have led to the development of what we call today 'design for Six Sigma'. Design for Six Sigma is a powerful approach to designing products, processes and services in a cost-effective and simple manner, to meet the needs and expectations of the customer 相似文献
62.
Leo V. M. Antony Ramana G. Reddy 《JOM Journal of the Minerals, Metals and Materials Society》2003,55(3):14-18
Production of high-quality metal powders is becoming important to meet the increasing demand for manufacturing advanced materials.
A number of standard powder production techniques have been developed to meet the increasing demand for high-purity metal
powders. This paper discusses the different techniques of producing metal powder. 相似文献
63.
A. Manikandan M. Durka S. Arul Antony 《Journal of Superconductivity and Novel Magnetism》2014,27(12):2841-2857
Spinel Co x Mn1?x Fe2O4 (0≤x≤1) nano- crystals were successfully synthesized by a simple microwave-assisted combustion method. High-resolution scanning electron microscopy (HR-SEM) and transmission electron microscopy (HR-TEM) analysis was used to study the morphological variations and found the particle-like nanocrystal morphologies. Energy dispersive X-ray (EDX) results showed that the composition of the elements were relevant as expected from the combustion synthesis. Powder X-ray diffraction (XRD) analysis showed that all composition was found to have cubic spinel-type structure. Average crystallite size of the samples was found to be in the range of 10.36–21.16 nm. The lattice parameter decreased from 8.478 to 8.432 Å with increasing Co2+ content. Fourier transform infrared (FT-IR) spectra showed two strong absorption peaks observed at lower frequency (~435 to ~800 cm?1), which can be assigned to the M–O (Mn, Co, and Fe) bonds. UV-Visible diffuse reflectance spectroscopy (DRS) shows that the energy band gap of pure MnFe2O4 is 1.78 eV and with increase in the Co2+ ion, it increases from 1.87 to 2.33 eV. Addition of Co2+ in MnFe2O4 reduces the particle size, which can be confirmed by the blue shift in the photoluminescence (PL) spectra. Vibrating sample magnetometer (VSM) results that confirmed a weak ferromagnetic behavior for all composition with saturation magnetization values in the range of 50.05 ±04 to 67.09 °03 emu/g. All composition of spinel Co x Mn1?x Fe2O4 nano-crystals were successfully tested as catalyst for the oxidation of benzyl alcohol to benzaldehyde, which has resulted 87.32 and 94.28 % conversion efficiency of MnFe2O4 and Co0.6Mn0.4Fe2O4, respectively. 相似文献
64.
G. PanneerselvamR. Venkata Krishnan K. NagarajanM.P. Antony 《Materials Letters》2011,65(12):1778-1780
Samarium titanate (Sm2TiO5) was prepared by solid-state synthesis and characterized by X-ray diffraction (XRD). Heat capacity measurements were carried out by differential scanning calorimeter (DSC) in the temperature range 298-800 K. Thermal expansion characteristics have been studied by high temperature X-ray diffraction technique (HTXRD) in the temperature range 298-1573 K. The heat capacity value at 298 K is 170 J K− 1 mol− 1. The percentage linear thermal expansion in the temperature range 298-1573 K along a, b and c axes are 0.96, 0.89 and 1.07 respectively. The average coefficient of thermal expansion value obtained in the present study for samarium titanate up to 1573 K is 10.8 × 10− 6 K− 1. 相似文献
65.
We study the structural stability of surfactant coated ZnFe2O4 (ZF) nanoparticles of average particle size 10 nm annealed under different environments. The X-ray diffraction studies in oleic acid coated ZF (OC-ZF) show distinctly different phase transitions under different annealing conditions. The OC-ZF is reduced to α-Fe/ZnO phase under vacuum while it forms FeO/ZnO under argon whereas the ZnFe2O4 phase remains stable under air annealing. The simultaneous thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) coupled mass spectra (MS) in OC-ZF under argon atmosphere suggests that the residual carbon removes oxygen from the lattice to reduce the ZnFe2O4 phase into FeO/ZnO during argon annealing. Apart from CO and CO2 gas evolution at high temperature under argon annealing, creation of oxygen vacancies due to the random removal of oxygen under vacuum annealing, leads to direct interaction between Fe–Fe and the formation of metal Fe. It appears that the residual carbon aids the reduction of ZF and the formation of α-Fe/ZnO during vacuum annealing. After annealing at 1000 °C in vacuum, the magnetization is increased abruptly from 13.8 to 106.5 emu g−1. In sharp contrast, the air and argon annealed samples show a diminished magnetization of 1 emu g−1. The field cooled (FC) and zero FC magnetization of vacuum and argon annealed samples exhibit superparamagnetic and spin-glass type behavior respectively. Our results offer possibilities to switch a magnetically inactive material to an active one. 相似文献
66.
67.
Prygoski MP Pasang T Schmid SR Lozier AJ 《Journal of materials science. Materials in medicine》2011,22(12):2823-2832
A new method of bone fracture fixation is considered in which small pins/darts are dynamically inserted into bone to prevent
translation and rotation at the fracture site. An ABAQUS model was developed to analyze dart penetration in cortical and cancellous
bone for varying dart diameter, material, and velocity, and cortical thickness. The method is advocated for bioresorbable
darts, so polylactide (PLA) and magnesium are the materials examined in this study. Numerical results showed that magnesium
darts can achieve full penetration in bone while suffering little damage. The PLA darts penetrated thin bone well, but substantial
deformation was seen as the cortical thickness increased, especially for small diameter darts. As partial validation, prototype
PLA fixation darts were fired into cadaveric bone with a custom nailer. As in the model, the PLA darts could penetrate thin
cortices but saw gross deformation when impacted against thicker bone. 相似文献
68.
Selvakumar R Jothi NA Jayavignesh V Karthikaiselvi K Antony GI Sharmila PR Kavitha S Swaminathan K 《Water research》2011,45(2):583-592
The present study involves the development of adsorbent containing silver nanoparticles for arsenate removal using silver reducing property of a novel yeast strain Saccharomyces cerevisiae BU-MBT-CY1 isolated from coconut cell sap. Biological reduction of silver by the isolate was deduced at various time intervals. The yeast cells after biological silver reduction were harvested and subjected to carbonization at 400 °C for 1 h and its properties were analyzed using Fourier Transform Infra-Red spectroscopy, X-ray diffraction, scanning electron microscope attached with energy dispersive spectroscopy and transmission electron microscope. The average size of the silver nanoparticles present on the surface of the carbonized silver containing yeast cells (CSY) was 19 ± 9 nm. The carbonized control yeast cells (CCY) did not contain any particles on its surface. As(V) adsorption efficiency of CCY and CSY was deduced in batch mode by varying parameters like contact time, initial concentration, and pH. Desorption studies were also carried out by varying the pH. The experimental data were fitted onto Langmuir and D-R Isotherms and Lagergren and pseudo second order kinetic models. The CSY was more efficient in arsenate removal when compared to CCY. 相似文献
69.
The interaction of organic micropollutants with dissolved organic carbon (DOC) can influence their transport, degradation and bioavailability. While this has been well established for natural organic carbon, very little is known regarding the influence of DOC on the fate of micropollutants during wastewater treatment and water recycling. Dissolved organic carbon-water partition coefficients (KDOC) for wastewater derived and reference DOC were measured for a range of micropollutants using a depletion method with polydimethylsiloxane disks. For micropollutants with an octanol-water partition coefficient (log KOW) greater than 4 there was a significant difference in KDOC between reference and wastewater derived DOC, with partitioning to wastewater derived DOC over 1000 times lower for the most hydrophobic micropollutants. The interaction of nonylphenol with wastewater derived DOC from different stages of a wastewater and advanced water treatment train was studied, but little difference in KDOC was observed. Organic carbon characterisation revealed that reference and wastewater derived DOC had very different properties due to their different origins. Consequently, the reduced sorption capacity of wastewater derived DOC may be related to their microbial origin which led to reduced aromaticity and lower molecular weight. This study suggests that for hydrophobic micropollutants (log KOW > 4) a higher concentration of freely dissolved and thus bioavailable micropollutants is expected in the presence of wastewater derived DOC than predicted using KDOC values quantified using reference DOC. The implication is that naturally derived DOC may not be an appropriate surrogate for wastewater derived DOC as a matrix for assessing the fate of micropollutants in engineered systems. 相似文献
70.
Maarten Nijland Antony George Sean Thomas Evert P. Houwman Jing Xia Dave H. A. Blank Guus Rijnders Gertjan Koster Johan E. ten Elshof 《Advanced functional materials》2014,24(43):6853-6861
A process is developed that combines soft lithographic molding with pulsed laser deposition (PLD) to make heteroepitaxial patterns of functional perovskite oxide materials. Micro‐ and nanostructures of sacrificial ZnO are made by micro molding in capillaries (MiMiC) and nano transfer molding, respectively, and used to screen the single crystalline substrates during subsequent PLD. ZnO is used because of its compatibility with the high temperatures reached during PLD and because of the ease of its removal after use by benefiting from its amphoteric nature. Sub‐micrometer sized lines of La0.67Sr0.33MnO3 are made by the transfer molding approach, preserving the anisotropic features expected for a fully oriented thin film and taking account for the magnetostatic contribution from the line shapes. Different patterns of SrRuO3 are made with lateral dimensions of a few micrometers having individual features for which electrical isolation is illustrated. The bottom‐up soft lithographic methods can be compliantly utilized for making epitaxial structures of various shapes and sizes in the μm down to the nm range, and offer unique opportunities for fundamental studies as well as for realizing technological applications. 相似文献