The influence of the inhomogeneous tissue layer on the generation of acoustic vortices (AV) is studied theoretically and experimentally based on the phase screen model. By considering the time-shift of a random phas...The influence of the inhomogeneous tissue layer on the generation of acoustic vortices (AV) is studied theoretically and experimentally based on the phase screen model. By considering the time-shift of a random phase screen, the formula of acoustic pressure for the AV beam generated by a circular array of eight planar piston sources is derived. With the actual correlation length of the abdominal wall, numerical simulations before and after the insertion of the inhomogeneous tissue layer are conducted, and also demonstrated by experimental measurements. It is proved that, when the thickness variation of the phase screen is less than one wavelength, no significant influence on the generation of AVs can be produced. The variations of vortex nodes and antinodes in terms of the location, shape, and size of AVs are not obvious. Although the circular pressure distribution might be deformed by the phase interference with a larger thickness variation, AVs can still be generated around the center axis with perfect phase spirals in a reduced effective radius. The favorable results provide the feasibility of AV generation inside the human body and suggest the application potential of AVs in object manipulation for biomedical engineering.展开更多
Gaussian models without intermittency are extensively used in estimating the effect of turbulence,but italso brings some puzzles,for example the observed pulse shape that disagrees with the result of the standard theo...Gaussian models without intermittency are extensively used in estimating the effect of turbulence,but italso brings some puzzles,for example the observed pulse shape that disagrees with the result of the standard theoryof interstellar scintillations.Indeed the property of intermittency is inherent in turbulence,i.e.,all the quantities thatcharacterize it suffer from strong fluctuations.So it is necessary to consider turbulent intermittency in many applications.In this paper we propose a non-Gaussian phase screen,which obeys log-Poisson statistics,and also offers the correspondingpoint spread function(PSF).These results describe that intermittency leads to the more extent and different directionaldistribution of PSF.Theoretical analysis is made under the hypothesis of the phase difference satisfying log-Poissonstatistics,and the average point spread function,which accord qualitatively with the result of the above generated phasescreen,is derived.展开更多
The Fresnel approximation in phase screen model is discussed and the coherencefunction is derived for k】】k.The application condition for Rino’s results is obtained,and it is|▽R<sub>△N<sub>e</sub>...The Fresnel approximation in phase screen model is discussed and the coherencefunction is derived for k】】k.The application condition for Rino’s results is obtained,and it is|▽R<sub>△N<sub>e</sub></sub>|/R<sub>△n<sub>e</sub></sub>【【1.展开更多
An x-ray scintillator screen with a special structure, functioning as detector and analyser grating, was proposed for collecting the interferogram of differential phase contrast imaging without absorption grating and ...An x-ray scintillator screen with a special structure, functioning as detector and analyser grating, was proposed for collecting the interferogram of differential phase contrast imaging without absorption grating and difficulty of fabrication by a state of the art technique. On the basis of phase grating diffraction, a detecting model of the scintillator screen was built for analysing the phase and absorption information of objects. According to the analysis, a new method of phase retrievals based on two-images and the optimal structure of screen were presented.展开更多
The purpose of this study is to improve the surface properties of austenitic stainless steel using the double-folded electrode screen plasma nitriding (SPN) process. In general, the S-phase is well-known for its excel...The purpose of this study is to improve the surface properties of austenitic stainless steel using the double-folded electrode screen plasma nitriding (SPN) process. In general, the S-phase is well-known for its excellent properties such as improved hardness and wear resistance along with sustained corrosion resistance. The concentrated nitrogen via SPN process was injected to form S-phase with time at 713 K. This study was carried out under the conditions of 44 at% of nitrogen injection, which was higher than 25 at% known as the condition of no precipitation of S-phase formed by the SPN process, and 20 K higher than the maximum temperature without precipitation phase. The hardness analysis of stainless steel sample treated by the SPN process at 713 K showed a much higher value than the typical nitriding hardness at a depth of lower nitrogen than the maximum nitrogen concentration. The SPN 20 hr treated specimen showed the average value of 2339 HV while 40 hr showed the average value of 2215 HV. The result is attributed to the concentrated nitrogen formed in the SPN process reacting with the alloying elements contained in the base material to form fine precipitates, thus producing a synergy effect of the extreme hardening effect;that is, the movement of precipitates and dislocations due to the GP-zone (Guinier-Preston zone).展开更多
目的探讨串联质谱(tandem mass spectrometry,MS/MS)联合气相质谱(gas phase mass spectrometry,GC-MS)在新生儿重症监护病房(neonatal intensive care unit,NICU)遗传代谢病(inherited metabolic disorders,IMD)筛查诊断中的应用价值...目的探讨串联质谱(tandem mass spectrometry,MS/MS)联合气相质谱(gas phase mass spectrometry,GC-MS)在新生儿重症监护病房(neonatal intensive care unit,NICU)遗传代谢病(inherited metabolic disorders,IMD)筛查诊断中的应用价值。方法选取2020年1月至2021年12月解放军总医院第七医学中心NICU收治的3682例新生儿(其中足月儿1794例,早产儿1888例)为观察对象,采集干血斑行MS/MS遗传代谢病筛查。初次筛查阳性者重新采样复查并行尿液GC-MS检测。根据患儿代谢谱结合临床表现进行生化诊断。统计学方法采用χ^(2)检验。结果3682例NICU患儿中初筛阳性率为5.65%(208/3682),复筛阳性率为1.33%(49/3682),共生化诊断IMD患儿14例,总检出率为0.38%(14/3682),其中足月儿检出率高于早产儿[0.67%(12/1794)与0.11%(2/1888),χ^(2)=7.697,P=0.006]。14例IMD中,有机酸代谢异常11例,包括甲基丙二酸血症8例(57.1%)、戊二酸血症2例(14.3%)、3-甲基戊二烯酸尿症1例(7.1%);氨基酸代谢异常3例,包括尿素循环障碍2例(14.3%)、高苯丙氨酸血症1例(7.1%)。MS/MS初筛假阳性率为5.29%(194/3668),阳性预测值为6.73%(14/208)。召回复查后,二次MS/MS复测,假阳性率为0.95%(35/3668),阳性预测值为28.57%(14/49)。在各类MS/MS指标异常中,丙酰肉碱及其比值增高、戊二酰肉碱增高的阳性预测值高于氨基酸类代谢异常。结论NICU人群IMD发病率较高,且存在早产、感染等多种非遗传因素,干扰MS/MS代谢筛查结果。及时进行MS/MS复查及尿GC-MS分析可以提高诊断效率,明确生化诊断。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61575095,11374155,and 11674173)
文摘The influence of the inhomogeneous tissue layer on the generation of acoustic vortices (AV) is studied theoretically and experimentally based on the phase screen model. By considering the time-shift of a random phase screen, the formula of acoustic pressure for the AV beam generated by a circular array of eight planar piston sources is derived. With the actual correlation length of the abdominal wall, numerical simulations before and after the insertion of the inhomogeneous tissue layer are conducted, and also demonstrated by experimental measurements. It is proved that, when the thickness variation of the phase screen is less than one wavelength, no significant influence on the generation of AVs can be produced. The variations of vortex nodes and antinodes in terms of the location, shape, and size of AVs are not obvious. Although the circular pressure distribution might be deformed by the phase interference with a larger thickness variation, AVs can still be generated around the center axis with perfect phase spirals in a reduced effective radius. The favorable results provide the feasibility of AV generation inside the human body and suggest the application potential of AVs in object manipulation for biomedical engineering.
基金Supported by the National Natural Science Foundation Science Foundation of China Academy of Engineering Physics (NSAF) under Grant No.10576005the National Natural Science Foundation of China under Grant No.10647127+1 种基金the Science Foundation of Hebei Education Department under Grant No.2009135the Science Foundation of Hebei Normal University
文摘Gaussian models without intermittency are extensively used in estimating the effect of turbulence,but italso brings some puzzles,for example the observed pulse shape that disagrees with the result of the standard theoryof interstellar scintillations.Indeed the property of intermittency is inherent in turbulence,i.e.,all the quantities thatcharacterize it suffer from strong fluctuations.So it is necessary to consider turbulent intermittency in many applications.In this paper we propose a non-Gaussian phase screen,which obeys log-Poisson statistics,and also offers the correspondingpoint spread function(PSF).These results describe that intermittency leads to the more extent and different directionaldistribution of PSF.Theoretical analysis is made under the hypothesis of the phase difference satisfying log-Poissonstatistics,and the average point spread function,which accord qualitatively with the result of the above generated phasescreen,is derived.
文摘The Fresnel approximation in phase screen model is discussed and the coherencefunction is derived for k】】k.The application condition for Rino’s results is obtained,and it is|▽R<sub>△N<sub>e</sub></sub>|/R<sub>△n<sub>e</sub></sub>【【1.
基金supported by the National Natural Science Foundation of China (Grant Nos. 60232090 and 10774102)the Science & Technology Project from Shenzhen Government of China (Grant Nos. 2008340 and 200717)
文摘An x-ray scintillator screen with a special structure, functioning as detector and analyser grating, was proposed for collecting the interferogram of differential phase contrast imaging without absorption grating and difficulty of fabrication by a state of the art technique. On the basis of phase grating diffraction, a detecting model of the scintillator screen was built for analysing the phase and absorption information of objects. According to the analysis, a new method of phase retrievals based on two-images and the optimal structure of screen were presented.
文摘The purpose of this study is to improve the surface properties of austenitic stainless steel using the double-folded electrode screen plasma nitriding (SPN) process. In general, the S-phase is well-known for its excellent properties such as improved hardness and wear resistance along with sustained corrosion resistance. The concentrated nitrogen via SPN process was injected to form S-phase with time at 713 K. This study was carried out under the conditions of 44 at% of nitrogen injection, which was higher than 25 at% known as the condition of no precipitation of S-phase formed by the SPN process, and 20 K higher than the maximum temperature without precipitation phase. The hardness analysis of stainless steel sample treated by the SPN process at 713 K showed a much higher value than the typical nitriding hardness at a depth of lower nitrogen than the maximum nitrogen concentration. The SPN 20 hr treated specimen showed the average value of 2339 HV while 40 hr showed the average value of 2215 HV. The result is attributed to the concentrated nitrogen formed in the SPN process reacting with the alloying elements contained in the base material to form fine precipitates, thus producing a synergy effect of the extreme hardening effect;that is, the movement of precipitates and dislocations due to the GP-zone (Guinier-Preston zone).
文摘目的探讨串联质谱(tandem mass spectrometry,MS/MS)联合气相质谱(gas phase mass spectrometry,GC-MS)在新生儿重症监护病房(neonatal intensive care unit,NICU)遗传代谢病(inherited metabolic disorders,IMD)筛查诊断中的应用价值。方法选取2020年1月至2021年12月解放军总医院第七医学中心NICU收治的3682例新生儿(其中足月儿1794例,早产儿1888例)为观察对象,采集干血斑行MS/MS遗传代谢病筛查。初次筛查阳性者重新采样复查并行尿液GC-MS检测。根据患儿代谢谱结合临床表现进行生化诊断。统计学方法采用χ^(2)检验。结果3682例NICU患儿中初筛阳性率为5.65%(208/3682),复筛阳性率为1.33%(49/3682),共生化诊断IMD患儿14例,总检出率为0.38%(14/3682),其中足月儿检出率高于早产儿[0.67%(12/1794)与0.11%(2/1888),χ^(2)=7.697,P=0.006]。14例IMD中,有机酸代谢异常11例,包括甲基丙二酸血症8例(57.1%)、戊二酸血症2例(14.3%)、3-甲基戊二烯酸尿症1例(7.1%);氨基酸代谢异常3例,包括尿素循环障碍2例(14.3%)、高苯丙氨酸血症1例(7.1%)。MS/MS初筛假阳性率为5.29%(194/3668),阳性预测值为6.73%(14/208)。召回复查后,二次MS/MS复测,假阳性率为0.95%(35/3668),阳性预测值为28.57%(14/49)。在各类MS/MS指标异常中,丙酰肉碱及其比值增高、戊二酰肉碱增高的阳性预测值高于氨基酸类代谢异常。结论NICU人群IMD发病率较高,且存在早产、感染等多种非遗传因素,干扰MS/MS代谢筛查结果。及时进行MS/MS复查及尿GC-MS分析可以提高诊断效率,明确生化诊断。