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Effects of Nanopowder Additives in Micro-electrical Discharge Machining
Peng-Cheong Tan,Swee-Hock Yeo,Yie-Voon Tan 한국정밀공학회 2008 International Journal of Precision Engineering and Vol.9 No.3
The use of electrical discharge machining(EDM) for micro-machining applications requires particular attention to the machined surface roughness and discharge gap distance, as these factors affect the geometrical accuracy of micro-parts. Previous studies of conventional EDM have shown that selected types of semi-conductive and nonconductive powder suspended in the dielectric reduced the surface roughness while ensuring a limited increase in the gap distance. Based on this, an extension of the technique to micro-EDM was studied. Such work is necessary since the introduction of nanopowders suspended in the dielectric is not well understood The experimental results showed that a statistically significant reduction in the surface roughness value was achieved at particular concentrations of the powder additives, depending on the powder material and the machining input energy setting. The average reduction in surface roughness using a powder suspended dielectric was between 14-24% of the average surface roughness generated using a pure dielectric. Furthermore, when these additive concentrations were used for machining, no adverse increase in the gap distance was observed.
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Optimal inspection frequency to mitigate the risk of building system failure
Cheong Peng Au-Yong,Azlan Shah Ali,Faizah Ahmad,Shirley Jin Lin Chua 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.64 No.3
The poor maintenance practice increases the possibility of system failure. Subsequently, the consequences of failure fall on the aspects of output, safety and healthy, environmental integrity, system quality, and customer satisfaction. Conditionbased maintenance is seen as a potential strategy to improve performance. Whereby, the key success factor of this maintenance strategy is identified as the system inspection. This study aims to investigate the association between system breakdown rate and frequency of inspection. A mixed method approach is implemented by distributing questionnaire and interviewing for data collection. Subsequently, descriptive analysis, correlation analysis and regression are adopted to analyse the collected data from 100 respondents and the results are validated with interview data of 10 interviewees. The research result establishes significant relationship between the system breakdown rate and the frequency of inspection. Additionally, the result of regression analysis confirms that the frequency of inspection is the significant predictor of system breakdown rate. Planning of accurate inspection frequency is crucial to secure the system performance. Hence, the research signifies the importance to carry out regular inspection towards the building systems and components. As a recommendation, the maintenance personnel should assess the risk criticality of the building systems. Then, continuously monitor the condition of critical building systems; regularly inspect the condition of non-critical building systems and randomly inspect all of them.
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Effects of Nanopowder Additives in Micro-electrical Discharge Machining
Tan, Peng-Cheong,Yeo, Swee-Hock,Tan, Yie-Voon Korean Society for Precision Engineering 2008 International Journal of Precision Engineering and Vol.9 No.3
The use of electrical discharge machining (EDM) for micro-machining applications requires particular attention to the machined surface roughness and discharge gap distance, as these factors affect the geometrical accuracy of micro-parts. Previous studies of conventional EDM have shown that selected types of semi-conductive and non-conductive powder suspended in the dielectric reduced the surface roughness while ensuring a limited increase in the gap distance. Based on this, an extension of the technique to micro-EDM was studied Such work is necessary since the introduction of nanopowders suspended in the dielectric is not well understood. The experimental results showed that a statistically significant reduction in the surface roughness value was achieved at particular concentrations of the powder additives, depending on the powder material and the machining input energy setting. The average reduction in surface roughness using a powder suspended dielectric was between 14-24% of the average surface roughness generated using a pure dielectric. Furthermore, when these additive concentrations were used for machining, no adverse increase in the gap distance was observed.
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Chen, Peng,Holinsworth, Brian S.,O’Neal, Kenneth R.,Luo, Xuan,Topping, Craig V.,Cheong, Sang W.,Singleton, John,Choi, Eun S.,Musfeldt, Janice L. American Chemical Society 2018 Inorganic Chemistry Vol.57 No.20
<P>We bring together <I>ac</I> susceptibility and <I>dc</I> magnetization to uncover the rich magnetic field-temperature behavior of a series of rare earth indium oxides, RInO<SUB>3</SUB> (R = Tb, Dy, and Gd). The degree of frustration is much larger than expected, particularly in TbInO<SUB>3</SUB>, and the ground states are glasslike with antiferromagnetic tendencies. The activation energy for spin reorientation is low. Chemical substitution with Mn<SUP>3+</SUP> ions to form TbIn<SUB>1-<I>x</I></SUB>Mn<SUB><I>x</I></SUB>O<SUB>3</SUB> (<I>x</I> ≤ 0.01) relieves much of the frustration that characterizes the parent compound and slightly enhances the short-range antiferromagnetic order. The phase diagrams developed from this work reveal the rich competition between spin orders and provide an opportunity to compare the dynamics in the RInO<SUB>3</SUB> and Mn-substituted systems. These structure-property relations may be useful for understanding magnetism in other geometrically frustrated multiferroics.</P><P>We combined <I>dc</I> magnetization and <I>ac</I> susceptibility to reveal the rich magnetic field-temperature phase diagrams of a series of rare earth indium oxides. These systems sport high degrees of frustration as described by the frustration index, <I>F</I>, as well as glasslike slow magnetic relaxation in combination with antiferromagnetic tendencies. Structure−composition−property investigations reveal that both the choice of rare earth center as well as introduction of a paramagnetic impurity like Mn<SUP>3+</SUP> can control frustration in this new class of geometrically frustrated multiferroics.</P> [FIG OMISSION]</BR>
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