In gamma spectrometry of voluminous samples, inhomogeneous distribution of radioactivity caused by the presence of hot particles can create significant Bias in the results of activity determinations. We developed a no...In gamma spectrometry of voluminous samples, inhomogeneous distribution of radioactivity caused by the presence of hot particles can create significant Bias in the results of activity determinations. We developed a novel method to reduce this Bias using the gamma-peak ratio. We show that the peak area ratio of two gamma peaks of different energies, emitted by the same radionuclide, is a sensitive measure of emitting source location and thus the inhomogeneity. A new calibration formula was then derived for true gamma efficiency <em>p<sub>i</sub></em> as a function of efficiency ratio <em>p<sub>i</sub></em>/<em>p<sub>j</sub></em> of two peaks. This approach was verified by Monte Carlo simulations for a sample of 1-L volume containing from 1 up to 2048 of hot particles randomly distributed in a soil matrix. A <sup>152</sup>Eu radionuclide was selected for calculations and we used various combinations of two gamma spectral peaks selected from three gamma energies of 121.8, 344.3, and 1408.0 keV. This new method is shown to reduce the Bias range and Bias standard deviation by several times when compared with the traditional homogeneous calibration applied to measuring hot particles. The method is independent of the number, location, and distribution of hot particles in the samples, and can be applied to a mixture of radionuclides. It complements our previous calibration model based on the peak-to-total ratio.展开更多
A high peak power IPL system (Lumecca) was tested to determine the correlation between a high peak power and the successful treatment of pigmented and vascular lesions. Short pulse duration in the millisecond range an...A high peak power IPL system (Lumecca) was tested to determine the correlation between a high peak power and the successful treatment of pigmented and vascular lesions. Short pulse duration in the millisecond range and high peak power of 3.3 kW/cm<sup>2</sup> enabled selective and effective destruction, not only of pigment, but also of vessels in a comparable manner to a pulsed dye laser. Only one treatment session at a low fluence (8 - 16 J/cm<sup>2</sup>) was sufficient to achieve the desired results.展开更多
Pulsed microwaves are widely used inradar,navigation, and communication. The average power density is low at narrow pulse widths or large pulse intervals,but pulsed microwaves at certain peak densities exert numerous ...Pulsed microwaves are widely used inradar,navigation, and communication. The average power density is low at narrow pulse widths or large pulse intervals,but pulsed microwaves at certain peak densities exert numerous biological effects, including展开更多
In this article, the seismic records of Japan＇s Kik-net are selected to measure the acceleration, displacement, and effective peak acceleration of each seismic record within a certain time after P wave, then a contin...In this article, the seismic records of Japan＇s Kik-net are selected to measure the acceleration, displacement, and effective peak acceleration of each seismic record within a certain time after P wave, then a continuous estimation is given on earthquake early warning magnitude through statistical analysis method, and Wenchuan earthquake record is utilized to check the method. The results show that the reliability of earthquake early warning magnitude continuously increases with the increase of the seismic information, the biggest residual happens if the acceleration is adopted to fit earthquake magnitude, which may be caused by rich high-frequency components and large dispersion of peak value in acceleration record, the influence caused by the high-frequency components can be effectively reduced if the effective peak acceleration and peak displacement is adopted, it is estimated that the dispersion of earthquake magnitude obviously reduces, but it is easy for peak displacement to be affected by long-period drifting. In various components, the residual enlargement phenomenon at vertical direction is almost unobvious, thus it is recommended in this article that the effective peak acceleration at vertical direction is preferred to estimate earthquake early warning magnitude. Through adopting Wenchuan strong earthquake record to check the method mentioned in this article, it is found that this method can be used to quickly, stably, and accurately estimate the early warning magnitude of this earthquake, which shows that this method is completely applicable for earthquake early warning.展开更多
Using the ground motion attenuation relation, we calculated and compared the effective peak acceleration （EPA） generated by main shocks and their strong aftershocks of 21 earthquake sequences with Ms≥7 occurred in ...Using the ground motion attenuation relation, we calculated and compared the effective peak acceleration （EPA） generated by main shocks and their strong aftershocks of 21 earthquake sequences with Ms≥7 occurred in Chinese mainland and offing of China during 1966-2002. The result shows that EPA of strong aftershocks usually exceed that of main shock for 76.2% earthquake sequences and EPA of more than 50% strong aftershocks are greatly larger than that of main shocks in large area, which suggests that it is necessary to take damage produced by strong aftershock into account in the probabilistic seismic hazard analysis and the seismic design.展开更多
<strong>Introduction:</strong> Intense Pulsed Light (IPL) technology is well accepted in the medical aesthetic field for the treatment of various skin lesions, including pigmented and vascular lesions. The...<strong>Introduction:</strong> Intense Pulsed Light (IPL) technology is well accepted in the medical aesthetic field for the treatment of various skin lesions, including pigmented and vascular lesions. The light penetrates into the skin and is selectively absorbed by lesion chromophore. Absorbed energy is converted into heat, coagulating the lesion, which naturally fades following the treatment. The current article presents a retrospective efficacy evaluation of an IPL device with high peak power. <strong>Methods:</strong> Representative treatment results were collected from several clinics based on photographs taken at baseline and after treatments. Photos were evaluated and analyzed for aesthetic improvement of the various skin conditions in different facial and body areas. <strong>Results:</strong> Analysis included cases of pigmented and vascular lesions, textural lesions, and more specific conditions such as melasma and rosacea. The two evaluators’ scoring demonstrated improvement in all cases according to the Global Aesthetic Improvement Scale (GAIS) scale. <strong>Conclusion:</strong> The vast experience gathered from the market in treating various skin lesions supports the safety and efficacy of the investigated IPL device. The device’s particular specifications contribute to the successful results and ease of treatment for the practitioner and the patient.展开更多
The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pe...The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pellet was also introduced. The misorientation caused by the lattice mismatch between MgO and Gd123 melt was overcome by choosing suitable heat treatment program and Gd2BaCuO5 （Gd211） content of the buffer pellet. The doping effect of soft ferromagnetic NiFe alloy particles was also reported. The bulk sample with 0.4% （mole fraction） doping amount shows the best performance on the flux trapping. The critical current density is largely enhanced under the external field of 1-2 T, which is promising for large-scale applications. This effect is originated from the substitution of Fe and Ni ions for the Cu sites contributing to magnetic flux pinning.展开更多
The second magnetization peak(SMP)effect has been observed widely in many type‐Ⅱsuperconductors,but the reason remains elusive.This effect manifests an enhanced critical current density with magnetic field and shoul...The second magnetization peak(SMP)effect has been observed widely in many type‐Ⅱsuperconductors,but the reason remains elusive.This effect manifests an enhanced critical current density with magnetic field and should be very useful for applications.By measuring the magnetization of optimally doped Ba_(0.6)K_(0.4)Fe_(2)As_(2)single crystals with different thickness,it is found the SMP effect exists in thick samples and gradually becomes invisible when the sample thickness is reduced to the scale of micrometer.Detailed inves-tigation on the vortex dynamics on samples with different thickness clearly show that there is a common behav-ior of vortex dynamics in the low field region,which may be characterized by the Bragg glass like elastic vortex motion.This feature holds on in the whole field region for the thin samples,while it turns into the SMP effect for thicker samples when the field is increased.The results suggest that the SMP effect may be induced by the entanglement of the vortex system,and the absence of the SMP effect in thin samples is attributed to the cutoff of the entangled vortex length along c‐axis.展开更多
During pipe installation,compacting soil at pipe sides causes an initial pipe deformation which is known as the"peaking"effect.However,in conventional pipe design codes,only pipe deformation caused by vertic...During pipe installation,compacting soil at pipe sides causes an initial pipe deformation which is known as the"peaking"effect.However,in conventional pipe design codes,only pipe deformation caused by vertical overburden is considered while the"peaking"effect is ignored.In this study,a full-scale test was conducted on a Grade X52 steel pipe with a diameter of 600 mm to investigate the impacts of both soil compaction and vertical overburden on pipe deformation.Soil compaction and external load were found to elongate and shorten the vertical pipe diameter,respectively.The"peaking"effect was observed during the installation procedure accompanied by the highest pipe stress measured at the pipe crown.Then,a two-dimensional finite element model was created and validated based on the calculated pipe stresses from the experimental study.A parametric study was performed thereafter to numerically study the impacts of soil water content,pipe wall thickness,compaction pressure,and lift thickness on pipe responses due to soil compaction and external load.An increase in the"peaking"effect is observed with increasing soil water content and compaction pressure,while an increase in pipe wall thickness or lift thickness would cause a decrease in the"peaking"effect.展开更多
Volume pinning forces were determined for a variety of bulk high-Tc superconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various ...Volume pinning forces were determined for a variety of bulk high-Tc superconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various temperature ranges were identified. The Nd-based superconductors and some YBCO crystals exhibited a dominating pinning of the δTc-type (i.e. , small, superconducting pinning sites). In contrast to this, the addition of insulating 211 particles provided pinning of the δ/-type; providing effective pinning in the entire temperature range acting as a 'background' pinning mechanism for the peak effect. Due to the small coherence lengths of the high-Tc compounds, effective pinning sites are defects or particles of nanometer size relative to ζ3. Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) revealed that practically all high-Tc compounds were spatially inhomogeneous, which could be caused by oxygen deficiency (YBCO), solid solutions of Nd/Ba (NdBCO and other light rare earth compounds), intergrowths (Bi-based superconductors), and doping by pair-breaking dopants like Zn, Pr. This implies that the superconducting sample consists of stronger and weaker superconducting areas, coupled together. In large applied fields, this coupling gets broken and the magnetization versus temperature curves revealed more than one superconducting transition. In contrast, irradiation experiments by neutrons, protons, and heavy-ions enabled the artificial introduction of very effective pinning sites into the high-Tc superconductors, thus creating a large variety of different observations using magnetic data. From all these observations, we construct a pinning diagram for bulk high-Tc superconductors explaining many features observed in high-Tc samples.展开更多
文摘In gamma spectrometry of voluminous samples, inhomogeneous distribution of radioactivity caused by the presence of hot particles can create significant Bias in the results of activity determinations. We developed a novel method to reduce this Bias using the gamma-peak ratio. We show that the peak area ratio of two gamma peaks of different energies, emitted by the same radionuclide, is a sensitive measure of emitting source location and thus the inhomogeneity. A new calibration formula was then derived for true gamma efficiency <em>p<sub>i</sub></em> as a function of efficiency ratio <em>p<sub>i</sub></em>/<em>p<sub>j</sub></em> of two peaks. This approach was verified by Monte Carlo simulations for a sample of 1-L volume containing from 1 up to 2048 of hot particles randomly distributed in a soil matrix. A <sup>152</sup>Eu radionuclide was selected for calculations and we used various combinations of two gamma spectral peaks selected from three gamma energies of 121.8, 344.3, and 1408.0 keV. This new method is shown to reduce the Bias range and Bias standard deviation by several times when compared with the traditional homogeneous calibration applied to measuring hot particles. The method is independent of the number, location, and distribution of hot particles in the samples, and can be applied to a mixture of radionuclides. It complements our previous calibration model based on the peak-to-total ratio.
文摘A high peak power IPL system (Lumecca) was tested to determine the correlation between a high peak power and the successful treatment of pigmented and vascular lesions. Short pulse duration in the millisecond range and high peak power of 3.3 kW/cm<sup>2</sup> enabled selective and effective destruction, not only of pigment, but also of vessels in a comparable manner to a pulsed dye laser. Only one treatment session at a low fluence (8 - 16 J/cm<sup>2</sup>) was sufficient to achieve the desired results.
基金supported by the Foundation of Astronaut Research and Training Center of China [No.SMFA14B06 and No.14ZS017]
文摘Pulsed microwaves are widely used inradar,navigation, and communication. The average power density is low at narrow pulse widths or large pulse intervals,but pulsed microwaves at certain peak densities exert numerous biological effects, including
文摘In this article, the seismic records of Japan＇s Kik-net are selected to measure the acceleration, displacement, and effective peak acceleration of each seismic record within a certain time after P wave, then a continuous estimation is given on earthquake early warning magnitude through statistical analysis method, and Wenchuan earthquake record is utilized to check the method. The results show that the reliability of earthquake early warning magnitude continuously increases with the increase of the seismic information, the biggest residual happens if the acceleration is adopted to fit earthquake magnitude, which may be caused by rich high-frequency components and large dispersion of peak value in acceleration record, the influence caused by the high-frequency components can be effectively reduced if the effective peak acceleration and peak displacement is adopted, it is estimated that the dispersion of earthquake magnitude obviously reduces, but it is easy for peak displacement to be affected by long-period drifting. In various components, the residual enlargement phenomenon at vertical direction is almost unobvious, thus it is recommended in this article that the effective peak acceleration at vertical direction is preferred to estimate earthquake early warning magnitude. Through adopting Wenchuan strong earthquake record to check the method mentioned in this article, it is found that this method can be used to quickly, stably, and accurately estimate the early warning magnitude of this earthquake, which shows that this method is completely applicable for earthquake early warning.
基金Department of Science and Technology Important International Cooperate Subject (2004DFA06000)Joint seis-mological Science Foundation of China (604025).
文摘Using the ground motion attenuation relation, we calculated and compared the effective peak acceleration （EPA） generated by main shocks and their strong aftershocks of 21 earthquake sequences with Ms≥7 occurred in Chinese mainland and offing of China during 1966-2002. The result shows that EPA of strong aftershocks usually exceed that of main shock for 76.2% earthquake sequences and EPA of more than 50% strong aftershocks are greatly larger than that of main shocks in large area, which suggests that it is necessary to take damage produced by strong aftershock into account in the probabilistic seismic hazard analysis and the seismic design.
文摘<strong>Introduction:</strong> Intense Pulsed Light (IPL) technology is well accepted in the medical aesthetic field for the treatment of various skin lesions, including pigmented and vascular lesions. The light penetrates into the skin and is selectively absorbed by lesion chromophore. Absorbed energy is converted into heat, coagulating the lesion, which naturally fades following the treatment. The current article presents a retrospective efficacy evaluation of an IPL device with high peak power. <strong>Methods:</strong> Representative treatment results were collected from several clinics based on photographs taken at baseline and after treatments. Photos were evaluated and analyzed for aesthetic improvement of the various skin conditions in different facial and body areas. <strong>Results:</strong> Analysis included cases of pigmented and vascular lesions, textural lesions, and more specific conditions such as melasma and rosacea. The two evaluators’ scoring demonstrated improvement in all cases according to the Global Aesthetic Improvement Scale (GAIS) scale. <strong>Conclusion:</strong> The vast experience gathered from the market in treating various skin lesions supports the safety and efficacy of the investigated IPL device. The device’s particular specifications contribute to the successful results and ease of treatment for the practitioner and the patient.
文摘The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pellet was also introduced. The misorientation caused by the lattice mismatch between MgO and Gd123 melt was overcome by choosing suitable heat treatment program and Gd2BaCuO5 （Gd211） content of the buffer pellet. The doping effect of soft ferromagnetic NiFe alloy particles was also reported. The bulk sample with 0.4% （mole fraction） doping amount shows the best performance on the flux trapping. The critical current density is largely enhanced under the external field of 1-2 T, which is promising for large-scale applications. This effect is originated from the substitution of Fe and Ni ions for the Cu sites contributing to magnetic flux pinning.
基金supported by the National Natural Science Foundation of China(Grants No.A0402/11927809,No.A0402/11534005)National Key R and D Program of China(Grant No.2022YFA1403201)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB25000000).
文摘The second magnetization peak(SMP)effect has been observed widely in many type‐Ⅱsuperconductors,but the reason remains elusive.This effect manifests an enhanced critical current density with magnetic field and should be very useful for applications.By measuring the magnetization of optimally doped Ba_(0.6)K_(0.4)Fe_(2)As_(2)single crystals with different thickness,it is found the SMP effect exists in thick samples and gradually becomes invisible when the sample thickness is reduced to the scale of micrometer.Detailed inves-tigation on the vortex dynamics on samples with different thickness clearly show that there is a common behav-ior of vortex dynamics in the low field region,which may be characterized by the Bragg glass like elastic vortex motion.This feature holds on in the whole field region for the thin samples,while it turns into the SMP effect for thicker samples when the field is increased.The results suggest that the SMP effect may be induced by the entanglement of the vortex system,and the absence of the SMP effect in thin samples is attributed to the cutoff of the entangled vortex length along c‐axis.
基金support provided by the Natural Science and Engineering Council of Canada(Grant No.10021614)Enbridge Inc.(Grant No.10022179)University of Calgary.
文摘During pipe installation,compacting soil at pipe sides causes an initial pipe deformation which is known as the"peaking"effect.However,in conventional pipe design codes,only pipe deformation caused by vertical overburden is considered while the"peaking"effect is ignored.In this study,a full-scale test was conducted on a Grade X52 steel pipe with a diameter of 600 mm to investigate the impacts of both soil compaction and vertical overburden on pipe deformation.Soil compaction and external load were found to elongate and shorten the vertical pipe diameter,respectively.The"peaking"effect was observed during the installation procedure accompanied by the highest pipe stress measured at the pipe crown.Then,a two-dimensional finite element model was created and validated based on the calculated pipe stresses from the experimental study.A parametric study was performed thereafter to numerically study the impacts of soil water content,pipe wall thickness,compaction pressure,and lift thickness on pipe responses due to soil compaction and external load.An increase in the"peaking"effect is observed with increasing soil water content and compaction pressure,while an increase in pipe wall thickness or lift thickness would cause a decrease in the"peaking"effect.
文摘Volume pinning forces were determined for a variety of bulk high-Tc superconductors of the 123-type from magnetization measurements. By means of scaling of the pinning forces, the acting pinning mechanisms in various temperature ranges were identified. The Nd-based superconductors and some YBCO crystals exhibited a dominating pinning of the δTc-type (i.e. , small, superconducting pinning sites). In contrast to this, the addition of insulating 211 particles provided pinning of the δ/-type; providing effective pinning in the entire temperature range acting as a 'background' pinning mechanism for the peak effect. Due to the small coherence lengths of the high-Tc compounds, effective pinning sites are defects or particles of nanometer size relative to ζ3. Integral magnetic measurements of the magnetization as a function of temperature in large applied magnetic fields (up to 7 T) revealed that practically all high-Tc compounds were spatially inhomogeneous, which could be caused by oxygen deficiency (YBCO), solid solutions of Nd/Ba (NdBCO and other light rare earth compounds), intergrowths (Bi-based superconductors), and doping by pair-breaking dopants like Zn, Pr. This implies that the superconducting sample consists of stronger and weaker superconducting areas, coupled together. In large applied fields, this coupling gets broken and the magnetization versus temperature curves revealed more than one superconducting transition. In contrast, irradiation experiments by neutrons, protons, and heavy-ions enabled the artificial introduction of very effective pinning sites into the high-Tc superconductors, thus creating a large variety of different observations using magnetic data. From all these observations, we construct a pinning diagram for bulk high-Tc superconductors explaining many features observed in high-Tc samples.
