To solve the problem that metal artifacts severely damage the clarity of the organization structure in computed tomography（CT） images, a sinogram fusion-based metal artifact correction method is proposed. First, the...To solve the problem that metal artifacts severely damage the clarity of the organization structure in computed tomography（CT） images, a sinogram fusion-based metal artifact correction method is proposed. First, the metal image is segmented from the original CT image by the pre-set threshold. The original CT image and metal image are forward projected into the original projection sinogram and metal projection sinogram, respectively. The interpolation-based correction method and mean filter are used to correct the original CT image and preserve the edge of the corrected CT image, respectively. The filtered CT image is forward projected into the filtered image sinogram. According to the position of the metal sinogram in the original sinogram and filtered image sinogram, the corresponding sinograms PM^D （ in the original sinogram） and PM^C （ in the filtered image sinogram）can be acquired from the original sinogram and filtered image sinogram, respectively. Then, PM^D and PM^C are fused into the fused metal sinogram PM^F according to a certain proportion.The final sinogram can be acquired by fusing PM^F , PM^D and the original sinogram P^O. Finally, the final sinogram is reconstructed into the corrected CT image and metal information is compensated into the corrected CT image.Experiments on clinical images demonstrate that the proposed method can effectively reduce metal artifacts. A comparison with classical metal artifacts correction methods shows that the proposed metal artifacts correction method performs better in metal artifacts suppression and tissue feature preservation.展开更多
Sinusoid curve fit is a very useful method in precise measurement, based on the modeling measurement. There are many valuable uses. But, what′s the specifications of the sinusoid curve fit software, and how to eval...Sinusoid curve fit is a very useful method in precise measurement, based on the modeling measurement. There are many valuable uses. But, what′s the specifications of the sinusoid curve fit software, and how to evaluate the uncertainty of it are still unknown yet, because they involve manifold factors and are complicated. Every one using the sinusoid curve fit software wants to know it. In this paper, the basic process and the uses of sinusoid curve fit are described, and some specifications and evaluation methods are introduced. One evaluation example of sinusoid curve fit software is discussed, the results and the specification are good.展开更多
The pulse width modulation (PWM) scheme is used in the staircase waveform inverters. The control strategy and system characteristics are analyzed. While the single pulse width modulation is used, the 12 stairs wavefo...The pulse width modulation (PWM) scheme is used in the staircase waveform inverters. The control strategy and system characteristics are analyzed. While the single pulse width modulation is used, the 12 stairs waveform inverter can achieve the output voltage regulated in a wide range of input voltage as well as the perfect output waveform. A 1 500 V input 80 kVA inverter has been deve loped. Experiments of the 80kVA inverter resulted in that the scheme is a perfect method for the development of high power converters with high efficiency.展开更多
The free energy at low temperature in 1D sine-Gordon-Thirring model with impurity coupling is studied by means of functional integrals method. For massive free sine-Gordon-Thirring model, free energy is obtained from ...The free energy at low temperature in 1D sine-Gordon-Thirring model with impurity coupling is studied by means of functional integrals method. For massive free sine-Gordon-Thirring model, free energy is obtained from perturbation expansion of functional determinant. Moreover, the free energy of massive model is calculated by use of an auxiliary Bose field method.展开更多
The shaping form of an untwisted yarn-end for the air splicer is analyzed and then a cosine curve form which will have practically good splicing effect is proposed. The yarn motion in the splicing nozzle by applying h...The shaping form of an untwisted yarn-end for the air splicer is analyzed and then a cosine curve form which will have practically good splicing effect is proposed. The yarn motion in the splicing nozzle by applying hydrodynamics and the splicing principle of the air splicer are also studied.展开更多
Planting plant such as Betung bamboo （Dendrocalamus asper （Schult f.） Backer ex Heyne） is one of the best ways for reducing global warming effect. Betung bamboo is giant grass （Poaceae） which has been traditiona...Planting plant such as Betung bamboo （Dendrocalamus asper （Schult f.） Backer ex Heyne） is one of the best ways for reducing global warming effect. Betung bamboo is giant grass （Poaceae） which has been traditionally used by Indonesian people for construction material since a long time ago. Poaceae family commonly has better carbon sink ability than trees because of its Ca photosynthesis mechanisms, but bamboo sub-family （Bambusoideae） lacks the Ca photosynthetic pathway and anatomy. In the absence of this feature the maximum possible productivity of bamboos is unlikely to greatly exceed that of other bioenergy crops with C3 photosynthesis such as fast growing tree species. This research proposed a sinusoidal equation as a basic equation for plant＇s daily photosynthesis light response curve fitting. The sinusoidal equation was success for Betung bamboo＇s daily photosynthesis light response curve fitting （R2 〉 60%）. It had similar result in estimating carbon sink （82.35 kg/clump/year） compared to those which calculated by annual increment （69.01-107.82 kg/clump/year）. It is better to choose sinusoidal equation than quadratic or cubic Betung bamboo is a good choice to be planted in order to resist the global warming effect because it has superior carbon sink capability （82.35 kg/clump/year） than slow growing tree, and equal to fast growing tree species, besides many other advantages.展开更多
A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by disc...A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by discrete points and the cutter figuration determined by analytic function was built for their geometrical relationship and conjugate motion during the machining process. Conjugate points in the cutter section corresponding to the discrete points on the cosine gear tooth surface and the conjugate movements were solved. By using the flexible control of the CNC procedure, the active control of the cutting trace of the slotting cutter was accomplished and the envelop forming of the cosine gear was obtained. Based on the software C++ and Matlab, the computer aided manufacturing(CAM) system of the cosine gear was developed, and the simulation of the slotting process was accomplished. Several examples were provided to illustrate the approach. The result of the simulation demonstrates that the proposed slotting method is feasible.展开更多
This paper focuses on a new rectangular waveguide grating Slow-Wave Structure (SWS) with cosine-shaped grooves and studies the propagation characteristics of the wave in the SWS. By using the approximate field-matchin...This paper focuses on a new rectangular waveguide grating Slow-Wave Structure (SWS) with cosine-shaped grooves and studies the propagation characteristics of the wave in the SWS. By using the approximate field-matching conditions,the dispersion equation and the coupling impedance of this circuit are obtained. The dispersion curves and coupling impedances of the fundamental wave are calculated and the influences of the various geometrical dimensions are discussed. The results show that the bandwidth of the cosine-shaped groove SWS is much wider than that of rectangular-shaped groove one. And reducing the groove width can broaden the frequency-band and decrease the phase-velocity,while increment of the groove-depth can also decrease phase-velocity. For above cases,the coupling impedance is more than 16Ω. The present analysis will be helpful on further study and design of the RF systems used in millimeter wave Traveling Wave Tube (TWT).展开更多
The present study summarizes the results of macro-and micro-mixing characteristics in an airlift internal loop reactor with low aspect ratio(H/D≤5) using the electrolytic tracer response technique and the method of p...The present study summarizes the results of macro-and micro-mixing characteristics in an airlift internal loop reactor with low aspect ratio(H/D≤5) using the electrolytic tracer response technique and the method of parallel competing reactions respectively. The micro-mixing has never been investigated in airlift loop reactors. The dual-tip electrical conductivity probe technique is used for measurement of local bubble behavior in the reactor. The effects of several operating parameters and geometric variables are investigated. It is found that the increase in superficial gas velocity corresponds to the increase in energy input, liquid circulation velocity and shear rate, decreasing the macro-mixing time and segregation index. Moreover, it is shown that top clearance and draft diameter affect flow resistance. However, the bubble redistribution with a screen mesh on the perforated plate distributor for macro-mixing is insignificant. The top region with a high energy dissipation rate is a suitable location for feeding reactants. The analysis of present experimental data provides a valuable insight into the interaction between gas and liquid phases for mixing and improves the understanding of intrinsic roles of hydrodynamics upon the reactor design and operating parameter selection.展开更多
基金Open Research Fund of the Key Laboratory of Computer Netw ork and Information Integration of Ministry of Education of Southeast University(No.K93-9-2014-10C)the Scientific Research Foundation of Education Department of Anhui Province(No.KJ2014A186,SK2015A433)the National Basic Research Program of China(973 Program)(No.2010CB732503)
文摘To solve the problem that metal artifacts severely damage the clarity of the organization structure in computed tomography（CT） images, a sinogram fusion-based metal artifact correction method is proposed. First, the metal image is segmented from the original CT image by the pre-set threshold. The original CT image and metal image are forward projected into the original projection sinogram and metal projection sinogram, respectively. The interpolation-based correction method and mean filter are used to correct the original CT image and preserve the edge of the corrected CT image, respectively. The filtered CT image is forward projected into the filtered image sinogram. According to the position of the metal sinogram in the original sinogram and filtered image sinogram, the corresponding sinograms PM^D （ in the original sinogram） and PM^C （ in the filtered image sinogram）can be acquired from the original sinogram and filtered image sinogram, respectively. Then, PM^D and PM^C are fused into the fused metal sinogram PM^F according to a certain proportion.The final sinogram can be acquired by fusing PM^F , PM^D and the original sinogram P^O. Finally, the final sinogram is reconstructed into the corrected CT image and metal information is compensated into the corrected CT image.Experiments on clinical images demonstrate that the proposed method can effectively reduce metal artifacts. A comparison with classical metal artifacts correction methods shows that the proposed metal artifacts correction method performs better in metal artifacts suppression and tissue feature preservation.
文摘Sinusoid curve fit is a very useful method in precise measurement, based on the modeling measurement. There are many valuable uses. But, what′s the specifications of the sinusoid curve fit software, and how to evaluate the uncertainty of it are still unknown yet, because they involve manifold factors and are complicated. Every one using the sinusoid curve fit software wants to know it. In this paper, the basic process and the uses of sinusoid curve fit are described, and some specifications and evaluation methods are introduced. One evaluation example of sinusoid curve fit software is discussed, the results and the specification are good.
文摘The pulse width modulation (PWM) scheme is used in the staircase waveform inverters. The control strategy and system characteristics are analyzed. While the single pulse width modulation is used, the 12 stairs waveform inverter can achieve the output voltage regulated in a wide range of input voltage as well as the perfect output waveform. A 1 500 V input 80 kVA inverter has been deve loped. Experiments of the 80kVA inverter resulted in that the scheme is a perfect method for the development of high power converters with high efficiency.
基金The project supported by the Natural Science Foundation of Sichuan Normal University
文摘The free energy at low temperature in 1D sine-Gordon-Thirring model with impurity coupling is studied by means of functional integrals method. For massive free sine-Gordon-Thirring model, free energy is obtained from perturbation expansion of functional determinant. Moreover, the free energy of massive model is calculated by use of an auxiliary Bose field method.
文摘The shaping form of an untwisted yarn-end for the air splicer is analyzed and then a cosine curve form which will have practically good splicing effect is proposed. The yarn motion in the splicing nozzle by applying hydrodynamics and the splicing principle of the air splicer are also studied.
文摘Planting plant such as Betung bamboo （Dendrocalamus asper （Schult f.） Backer ex Heyne） is one of the best ways for reducing global warming effect. Betung bamboo is giant grass （Poaceae） which has been traditionally used by Indonesian people for construction material since a long time ago. Poaceae family commonly has better carbon sink ability than trees because of its Ca photosynthesis mechanisms, but bamboo sub-family （Bambusoideae） lacks the Ca photosynthetic pathway and anatomy. In the absence of this feature the maximum possible productivity of bamboos is unlikely to greatly exceed that of other bioenergy crops with C3 photosynthesis such as fast growing tree species. This research proposed a sinusoidal equation as a basic equation for plant＇s daily photosynthesis light response curve fitting. The sinusoidal equation was success for Betung bamboo＇s daily photosynthesis light response curve fitting （R2 〉 60%）. It had similar result in estimating carbon sink （82.35 kg/clump/year） compared to those which calculated by annual increment （69.01-107.82 kg/clump/year）. It is better to choose sinusoidal equation than quadratic or cubic Betung bamboo is a good choice to be planted in order to resist the global warming effect because it has superior carbon sink capability （82.35 kg/clump/year） than slow growing tree, and equal to fast growing tree species, besides many other advantages.
基金Projects(51205335,50975242,51375411) supported by the National Natural Science Foundation of ChinaProject(2013J01209) supported by the Natural Science Foundation of Fujian Province,China
文摘A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by discrete points and the cutter figuration determined by analytic function was built for their geometrical relationship and conjugate motion during the machining process. Conjugate points in the cutter section corresponding to the discrete points on the cosine gear tooth surface and the conjugate movements were solved. By using the flexible control of the CNC procedure, the active control of the cutting trace of the slotting cutter was accomplished and the envelop forming of the cosine gear was obtained. Based on the software C++ and Matlab, the computer aided manufacturing(CAM) system of the cosine gear was developed, and the simulation of the slotting process was accomplished. Several examples were provided to illustrate the approach. The result of the simulation demonstrates that the proposed slotting method is feasible.
文摘This paper focuses on a new rectangular waveguide grating Slow-Wave Structure (SWS) with cosine-shaped grooves and studies the propagation characteristics of the wave in the SWS. By using the approximate field-matching conditions,the dispersion equation and the coupling impedance of this circuit are obtained. The dispersion curves and coupling impedances of the fundamental wave are calculated and the influences of the various geometrical dimensions are discussed. The results show that the bandwidth of the cosine-shaped groove SWS is much wider than that of rectangular-shaped groove one. And reducing the groove width can broaden the frequency-band and decrease the phase-velocity,while increment of the groove-depth can also decrease phase-velocity. For above cases,the coupling impedance is more than 16Ω. The present analysis will be helpful on further study and design of the RF systems used in millimeter wave Traveling Wave Tube (TWT).
基金Supported by the National Basic Research Program of China(2012CB224806)the National Science Fund for Distinguished Young Scholars(21025627)+2 种基金the National Natural Science Foundation of China(21206166,20990224)the National High Technology Research and Development Program of China(2012AA03A606)Beijing Natural Science Foundation(2112038)
文摘The present study summarizes the results of macro-and micro-mixing characteristics in an airlift internal loop reactor with low aspect ratio(H/D≤5) using the electrolytic tracer response technique and the method of parallel competing reactions respectively. The micro-mixing has never been investigated in airlift loop reactors. The dual-tip electrical conductivity probe technique is used for measurement of local bubble behavior in the reactor. The effects of several operating parameters and geometric variables are investigated. It is found that the increase in superficial gas velocity corresponds to the increase in energy input, liquid circulation velocity and shear rate, decreasing the macro-mixing time and segregation index. Moreover, it is shown that top clearance and draft diameter affect flow resistance. However, the bubble redistribution with a screen mesh on the perforated plate distributor for macro-mixing is insignificant. The top region with a high energy dissipation rate is a suitable location for feeding reactants. The analysis of present experimental data provides a valuable insight into the interaction between gas and liquid phases for mixing and improves the understanding of intrinsic roles of hydrodynamics upon the reactor design and operating parameter selection.
