In intensity modulated radiation treatment (IMRT) planning, the use of asymmetrically collimated fields that are placed on central axis or its off-set is mostly required. Output is the main topic discussed today for e...In intensity modulated radiation treatment (IMRT) planning, the use of asymmetrically collimated fields that are placed on central axis or its off-set is mostly required. Output is the main topic discussed today for extremely small and/or severe irregularly shaped fields. The air scatter data are involved directly or indirectly in obtaining the output. Despite the fact that extensive data have been published in many studies to provide a guide on the magnitude of output factor for clinical accelerators, there are very few data reviewed about output factor in-air or phantom for off-set fields. This study was aimed to investigate the impact of these conditions for small fields. This study was conducted in Elekta Synergy linear accelerator which produces 6 MV X-ray energy. The in-air output factor (Sc) has been measured by CC04 ion chamber with brass-alloy “build-up” cap and Dose-1 electrometer, and the total output (Scp) measurements were carried on at dose maximum depth in phantom by the same chamber and Thermoluminescence dosimeter (TLD) for 1 - 10 cm2 fields. The all measurements at center of isocenter and off-set fields at three directions (X2, Y1, Diagonal) were done. By decreasing field size from 10 to 2 cm2 at isocenter, the Sc value using CC04 was decreased to 5.4% and Scp using CC04 and TLD to 14.5% and 11% respectively. By increasing off-set value, the Sc and Scp values were increased in all directions comparing to central fields. The maximum increase was obtained in Y1 direction for Sc and Scp. TLD results for Scp is slightly higher than CC04. The dosimetric properties of small fields and their off-set should be evaluated and modelled appropriately in the treatment planning system to ensure accurate dose calculation in Intensity Modulated Radiation Treatment.展开更多
A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this techniq...A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this technique. However, very few studies have focused on the optimization of the nanocrystalline plasma electrolytic nitrocarburising process parameters. In this study, a design of experiment （DOE） technique, the Taguchi method, has been used to optimize the nanocrystalline plasma electrolytic nitrocarburising not only for surface hardening but also for the corrosion protection of 316L austenitic stainless steel by controlling the coating processes factors. The experimental design consisted of four factors （Urea concentration, electrical conductivity of electrolyte, voltage and duration of process）, each containing three levels. Potentiodynamic polarization measurements were carried out to determine the corrosion resistance of the coated samples. The results were analyzed with related software. An analysis of the mean of signal-to-noise （S/N） ratio indicated that the corrosion resistance of nanocrystalline plasma electrolytic nitrocarburised 316L stainless steel was influenced significantly by the levels in the Taguchi orthogonal array. The optimized coating parameters for corrosion resistance are 1150 g/L for urea concentration, 360 mS/cm for electrical conductivity of electrolyte, 260 V for applied voltage, 6 min for treatment time. The percentage of contribution for each factor was determined by the analysis of variance （ANOVA）. The results showed that the applied voltage is the most significant factor affecting the corrosion resistance of the coatings.展开更多
A novel heatsink based on a multilayer stack of thin metal plates with staggered honeycomb cell microchannels was investigated in this paper. A series of working-parametric tests such as different heat sink pipe diame...A novel heatsink based on a multilayer stack of thin metal plates with staggered honeycomb cell microchannels was investigated in this paper. A series of working-parametric tests such as different heat sink pipe diameter and pumping power were conducted for the microchannel cooling system to determine the heat transfer performance under small flow rate conditions. For the double fluid flow inlets and outlets heatsink design, experimental results showed that more uniform substrate temperature distribution was obtained than the single inlet and outlet ones. It showed that the heatsink design provided a good choice for electronic chips cooling applications.展开更多
In industry,the defective point data often make most surface reconstruction methods suffer from inherent problems that some specific aided information is difficult to obtain. To solve the problem,a novel implicit reco...In industry,the defective point data often make most surface reconstruction methods suffer from inherent problems that some specific aided information is difficult to obtain. To solve the problem,a novel implicit reconstruction method without any such information is proposed. This approach extends morphological operations into 3D space and provides an improved procedure to construct off-set gradient functions for indirect approximation. By this method,the dual relative functions guarantee a minimal crust surrounding the point data. They can generate a smooth and watertight resulting surface,filling holes and merging overlapping samples reasonably. Compared with other existing methods,the proposed method is better suited to handle defective point clouds in a convenient and efficient manner. The feasibility and effectiveness of the method are demonstrated through a series of practical examples.展开更多
文摘In intensity modulated radiation treatment (IMRT) planning, the use of asymmetrically collimated fields that are placed on central axis or its off-set is mostly required. Output is the main topic discussed today for extremely small and/or severe irregularly shaped fields. The air scatter data are involved directly or indirectly in obtaining the output. Despite the fact that extensive data have been published in many studies to provide a guide on the magnitude of output factor for clinical accelerators, there are very few data reviewed about output factor in-air or phantom for off-set fields. This study was aimed to investigate the impact of these conditions for small fields. This study was conducted in Elekta Synergy linear accelerator which produces 6 MV X-ray energy. The in-air output factor (Sc) has been measured by CC04 ion chamber with brass-alloy “build-up” cap and Dose-1 electrometer, and the total output (Scp) measurements were carried on at dose maximum depth in phantom by the same chamber and Thermoluminescence dosimeter (TLD) for 1 - 10 cm2 fields. The all measurements at center of isocenter and off-set fields at three directions (X2, Y1, Diagonal) were done. By decreasing field size from 10 to 2 cm2 at isocenter, the Sc value using CC04 was decreased to 5.4% and Scp using CC04 and TLD to 14.5% and 11% respectively. By increasing off-set value, the Sc and Scp values were increased in all directions comparing to central fields. The maximum increase was obtained in Y1 direction for Sc and Scp. TLD results for Scp is slightly higher than CC04. The dosimetric properties of small fields and their off-set should be evaluated and modelled appropriately in the treatment planning system to ensure accurate dose calculation in Intensity Modulated Radiation Treatment.
文摘A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this technique. However, very few studies have focused on the optimization of the nanocrystalline plasma electrolytic nitrocarburising process parameters. In this study, a design of experiment （DOE） technique, the Taguchi method, has been used to optimize the nanocrystalline plasma electrolytic nitrocarburising not only for surface hardening but also for the corrosion protection of 316L austenitic stainless steel by controlling the coating processes factors. The experimental design consisted of four factors （Urea concentration, electrical conductivity of electrolyte, voltage and duration of process）, each containing three levels. Potentiodynamic polarization measurements were carried out to determine the corrosion resistance of the coated samples. The results were analyzed with related software. An analysis of the mean of signal-to-noise （S/N） ratio indicated that the corrosion resistance of nanocrystalline plasma electrolytic nitrocarburised 316L stainless steel was influenced significantly by the levels in the Taguchi orthogonal array. The optimized coating parameters for corrosion resistance are 1150 g/L for urea concentration, 360 mS/cm for electrical conductivity of electrolyte, 260 V for applied voltage, 6 min for treatment time. The percentage of contribution for each factor was determined by the analysis of variance （ANOVA）. The results showed that the applied voltage is the most significant factor affecting the corrosion resistance of the coatings.
文摘不锈钢厂采用铁水罐喷吹脱磷工艺为70 tAOD提供优质的低磷铁水冶炼400系列不锈钢,取代原电弧炉冶炼环节,实现了新型一步法冶炼不锈钢工艺。生产实践表明,铁水罐喷吹脱磷起始[P]为0.20%,处理后铁水[P]为0.001%~0.010%,[C]≥3.2%,温度≥1 320℃,完全满足后续AOD冶炼400系不锈钢的需要,与原70 t EAF-AOD流程相比,生产成本大幅降低。
文摘A novel heatsink based on a multilayer stack of thin metal plates with staggered honeycomb cell microchannels was investigated in this paper. A series of working-parametric tests such as different heat sink pipe diameter and pumping power were conducted for the microchannel cooling system to determine the heat transfer performance under small flow rate conditions. For the double fluid flow inlets and outlets heatsink design, experimental results showed that more uniform substrate temperature distribution was obtained than the single inlet and outlet ones. It showed that the heatsink design provided a good choice for electronic chips cooling applications.
基金supported by the National Natural Science Fundation of China (Grant No. 50835004)
文摘In industry,the defective point data often make most surface reconstruction methods suffer from inherent problems that some specific aided information is difficult to obtain. To solve the problem,a novel implicit reconstruction method without any such information is proposed. This approach extends morphological operations into 3D space and provides an improved procedure to construct off-set gradient functions for indirect approximation. By this method,the dual relative functions guarantee a minimal crust surrounding the point data. They can generate a smooth and watertight resulting surface,filling holes and merging overlapping samples reasonably. Compared with other existing methods,the proposed method is better suited to handle defective point clouds in a convenient and efficient manner. The feasibility and effectiveness of the method are demonstrated through a series of practical examples.
