In an open-circuit dissipative photovoltaic （PV） crystal, by considering the diffusion effect, the deflection of bright dissipative photovoltaic （DPV） solitons has been investigated by employing numerical techniqu...In an open-circuit dissipative photovoltaic （PV） crystal, by considering the diffusion effect, the deflection of bright dissipative photovoltaic （DPV） solitons has been investigated by employing numerical technique and perturbational procedure. The relevant results show that the centre of the optical beam moves along a parabolic trajectory, while the central spatial-frequency component shifts linearly with the propagation distance; furthermore, both the spatial deflection and the angular derivation are associated with the photovoltaic field. Such DPV solitons have a fixed deflection degree completely determined by the parameters of the dissipative system. The small bending cannot affect the formation of the DPV soliton via two-wave mixing.展开更多
The dynamical evolution of both signal and pump beams are traced by numerically solving the coupled-wave equation for a photorefractive two-wave mixing system. The direct simulations show that, when the intensity rati...The dynamical evolution of both signal and pump beams are traced by numerically solving the coupled-wave equation for a photorefractive two-wave mixing system. The direct simulations show that, when the intensity ratio of the pump beam to the signal beam is large enough, the pump beam presents a common decaying behaviour without modulational instability （MI）, while the signal beam can evolve into a quasistable spatial soliton within a regime in which the pump beam is depleted slightly. The larger the ratio is, the longer the regime is. Such quasistable solitons can overcome the initial perturbations and numerical noises in the course of propagation, perform several cycles of slow oscillation in intensity and width, and persist over tens of diffraction lengths. From physical viewpoints, these solitons actually exist as completely rigorous physical objects. If the ratio is quite small, the pump beam is apt to show MI, during which the signal beam experiences strong expansion and shrinking in width and a drastic oscillation in intensity, or completely breaks up. The simulations using actual experimental parameters demonstrate that the observation of an effectively stable soliton is quite possible in the proposed system.展开更多
In a biased photorefractive crystal, the process of two one-dimensional waves mixing, i.e., the dynamical evolution of both pump beam and signal beam, is traced by numerically solving the coupled-wave equation. Direct...In a biased photorefractive crystal, the process of two one-dimensional waves mixing, i.e., the dynamical evolution of both pump beam and signal beam, is traced by numerically solving the coupled-wave equation. Direct simulations show that the propagation and stability of the two beams are completely determined by the system parameters, such as the external bias field, the intensity and the beam waist of the pump beam. By adjusting these parameters, one can control the state of two Gaussian waves mixing. The numerical results are helpful for performing a two-wave mixing experiment.展开更多
The dynamical evolution and stability of bright dissipative holographic solitons in biased photorefractive materials in which the self-trapping beam obtains a gain from the pump beam via two-wave mixing has been inves...The dynamical evolution and stability of bright dissipative holographic solitons in biased photorefractive materials in which the self-trapping beam obtains a gain from the pump beam via two-wave mixing has been investigated numerically. Results show that these solitons are stable relative to small perturbations. Adjusting some system parameters, such as the bias field and the angle between beams, can easily control the generation of such solitons. Potential applications in optical switches or repeaters are discussed.展开更多
In this paper, a nonlocal two-wave interaction system from the Manakov hierarchy is investigated via the Riemann–Hilbert approach. Based on the spectral analysis of the Lax pair, a Riemann–Hilbert problem for the no...In this paper, a nonlocal two-wave interaction system from the Manakov hierarchy is investigated via the Riemann–Hilbert approach. Based on the spectral analysis of the Lax pair, a Riemann–Hilbert problem for the nonlocal two-wave interaction system is constructed. By discussing the solutions of this Riemann–Hilbert problem in both the regular and nonregular cases, we explicitly present the N-soliton solution formula of the nonlocal two-wave interaction system. Moreover,the dynamical behaviour of the single-soliton solution is shown graphically.展开更多
Single crystals subjected to shock compression exhibit responses with distinct two-wave structures for certain crystal orientations.However,little is known to date regarding how the shock response depends on crystal o...Single crystals subjected to shock compression exhibit responses with distinct two-wave structures for certain crystal orientations.However,little is known to date regarding how the shock response depends on crystal orientation,and especially why the two-wave structure depends on the crystal orientation.In this work,molecular dynamics simulations of shock compressions in copper single crystals are performed to investigate the orientation dependence of shock responses and the corresponding deformation mechanisms.Four copper single crystals with[001],[011],[012],and[123]crystal orientations along the depth direction are investigated.The[011],[012],and[123]crystal orientations of copper single crystals show distinct two-wave structures in their shock responses,while such a two-wave structure in the shock response is not seen for those orientations having a[001]crystal orientation.The potential causes are analyzed by considering the propagation velocities of both elastic and plastic waves.We develop a technique for identifying twin structures in face-centered cubic crystals and this technique can effectively identify the twin structure.The morphology of shock-induced defects(e.g.,dislocations and twins)shows the significant dependence of crystal orientation and the mechanisms behind these are discussed in detail.Finally,the Johnson-Cook constitutive model describing dynamic deformations at high temperatures and high strain rates is used to analyze the relationships between the shock responses and microscopic defects.The predictions of the Johnson-Cook constitutive model are consistent with the results of the molecular dynamics simulations.展开更多
The transverse effects of two Gauss waves mixing in a photovoltaic photorefractive crystal,i.e.,the dynamical evolutions of signal beam with different parameters,are traced numerically and experimentally.Both the one-...The transverse effects of two Gauss waves mixing in a photovoltaic photorefractive crystal,i.e.,the dynamical evolutions of signal beam with different parameters,are traced numerically and experimentally.Both the one-dimensional numerical simulations and two-dimensional experimental investigations show that the self-focusing effect of signal beam becomes more obvious as the intensity of pump beam and the angle between the signal and pump beams increase.In accordance with these results,the state of two Gaussian waves mixing is controllable.展开更多
When the magnitude of sub-scale ographic forcing is comparable with explicitly ordinary dynamic forcing, the drag effect reduced by ographic gravity wave is to be significant for maintaining dynamic balance of atmosph...When the magnitude of sub-scale ographic forcing is comparable with explicitly ordinary dynamic forcing, the drag effect reduced by ographic gravity wave is to be significant for maintaining dynamic balance of atmospheric circulation, as well as the momentum and energy transport. Such sub-scale ographic forcing should be introduced into numerically atmospheric model by means of drag being parameterized. Furthermore, the currently mature ographic gravity wave drag （OGWD） parameterization, i.e., the so-called first-generation （based on lineal single-wave theoretical framework） or the second-generation drag parameterization （including an important extra forcing by the contribution of critical level absorption）, cannot correctly and effectly describe the vertical profile of wave stress under the influence of ambient wind shearing. Based on aforementioned consideration, a new two-wave scheme was proposed to parameterize the ographic gravity wave drag by means of freely propagating gravity waves. It starts with a second order WKB approximation, and treats the wave stress attenuations caused by either the selective critical level absorption or the classical critical level absorption explicitly; while in the regions where critical levels are absent, it transports the wave stress vertically by two sinusoidal waves and deposits them and then damps them according to the wave saturation criteria. This scheme is thus used to conduct some sample computations over the Dabie Mountain region of East China, as an example. The results showed that the new two-wave scheme is able to model the vertical distribution of the wave stress more realistically.展开更多
The current study employs the novel Hirota bilinear scheme to investigate the nonlinear model.Thus,we acquire some two-wave and breather wave solutions to the governing equation.Breathers are pulsating localized struc...The current study employs the novel Hirota bilinear scheme to investigate the nonlinear model.Thus,we acquire some two-wave and breather wave solutions to the governing equation.Breathers are pulsating localized structures that have been used to mimic extreme waves in a variety of nonlinear dispersive media with a narrow banded starting process.Several recent investigations,on the other hand,imply that breathers can survive in more complex habitats,such as random seas,despite the attributed physical restrictions.The authenticity and genuineness of all the acquired solutions agreed with the original equation.In order to shed more light on these novel solutions,we plot the 3-dimensional and contour graphs to the reported solutions with some suitable values.The governing model is also stable because of the idea of linear stability.The study’s findings may help explain the physics behind some of the challenges facing ocean engineers.展开更多
目的:观察实时剪切波弹性成像(Sensor Web Enablement,SWE)技术与二维超声技术在桥本甲状腺炎背景下甲状腺癌中的联合诊断效能。方法:选取我院2022年1月至2023年12月收治的80例甲状腺结节且伴桥本甲状腺炎患者,均行二维超声、SWE检查,...目的:观察实时剪切波弹性成像(Sensor Web Enablement,SWE)技术与二维超声技术在桥本甲状腺炎背景下甲状腺癌中的联合诊断效能。方法:选取我院2022年1月至2023年12月收治的80例甲状腺结节且伴桥本甲状腺炎患者,均行二维超声、SWE检查,分析二维超声与SWE联合诊断价值。结果:病理结果示80例患者共检出80个结节,其中良性52个,恶性28个;联合诊断灵敏度、准确率均明显高于SWE或二维超声(P<0.05);二维超声联合SWE技术的曲线下面积(Area Under the Curve,AUC)最大。结论:二维超声联合SWE在桥本甲状腺炎背景下甲状腺癌患者中诊断效能较高,可同时开展二维超声与SWE技术检查,以提高甲状腺癌的检出。展开更多
地震波在储层岩石中传播会形成流体压力梯度,引起孔隙间流体相对流动,表现为速度频散及衰减现象,进而影响地震波场特征.然而,传统考虑流体赋存影响的衰减岩石物理模型均假设孔隙中流体不相溶,而实际上流体之间必然发生溶解及扩散作用,...地震波在储层岩石中传播会形成流体压力梯度,引起孔隙间流体相对流动,表现为速度频散及衰减现象,进而影响地震波场特征.然而,传统考虑流体赋存影响的衰减岩石物理模型均假设孔隙中流体不相溶,而实际上流体之间必然发生溶解及扩散作用,导致其无法有效刻画孔隙流体赋存影响,影响了地震岩石物理模型精度.波致气体溶解出溶机制(Wave Induced Gas Exsolution and Dissolution,WIGED)能够很好地解释在多相流体相互溶解和扩散导致的衰减作用.目前,尚无针对性的岩石物理实验观测在双相流体中压力梯度引起的溶解-扩散作用,制约了基于该衰减理论的岩石物理模型应用.本文针对双相(气、液)、可相溶流体饱和岩石中的地震波衰减展开测量及衰减特征分析.通过搭建岩石物理衰减测量仪器,观测到了气泡随压力(地震波产生的压力扰动)变化而发生的形变,理论模型数值计算验证了波致气体溶解出溶(WIGED)机制描述地震频带内衰减的有效性.这种地震波衰减特征与地层温度、压力、流体赋存状态、孔隙结构、裂缝发育等因素关系密切,衰减曲线特征可基于标准线性固体模型有效刻画.展开更多
立体摄影技术可实现三维海浪的连续观测,但目前基于立体摄影海浪观测数据开展二维海浪方向谱估计的研究却相对匮乏,从而束缚了立体摄影技术在海洋观测中的进一步深入应用。鉴于此,本文基于中国海洋大学微波遥感实验室开发的立体摄影海...立体摄影技术可实现三维海浪的连续观测,但目前基于立体摄影海浪观测数据开展二维海浪方向谱估计的研究却相对匮乏,从而束缚了立体摄影技术在海洋观测中的进一步深入应用。鉴于此,本文基于中国海洋大学微波遥感实验室开发的立体摄影海浪观测系统,并结合海浪方向谱阵列测量的扩展本征矢方法,系统性研究了基于立体摄影海浪观测数据反演二维海浪方向谱的可行性,并分析了不同海面采样点阵列排列方式、采样点间距及观测误差等因素对二维海浪方向谱反演结果的影响。立体摄影实测海浪数据反演结果显示:阵列中采样点间距小于1/3波浪的波长,海面采样点阵列排列方式为五边形时可得到较好的海浪方向谱反演结果。通过将立体摄影数据反演所得二维海浪方向谱与Signature1000型声学多普勒波浪流速剖面仪(Acoustic Doppler Wave and Current Profiler, AWAC)测量结果进行比较,结果显示二者具有较高的相关性和良好的一致性。立体摄影所得有效波高、平均波向和AWAC测量的有效波高、平均波向的相关系数分别为0.988和0.983,平均偏差分别为0.029 m和0.010°,均方根误差分别为0.089 m和8.844°。展开更多
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10574051 and 10174025）.
文摘In an open-circuit dissipative photovoltaic （PV） crystal, by considering the diffusion effect, the deflection of bright dissipative photovoltaic （DPV） solitons has been investigated by employing numerical technique and perturbational procedure. The relevant results show that the centre of the optical beam moves along a parabolic trajectory, while the central spatial-frequency component shifts linearly with the propagation distance; furthermore, both the spatial deflection and the angular derivation are associated with the photovoltaic field. Such DPV solitons have a fixed deflection degree completely determined by the parameters of the dissipative system. The small bending cannot affect the formation of the DPV soliton via two-wave mixing.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10574051 and 10174025）.
文摘The dynamical evolution of both signal and pump beams are traced by numerically solving the coupled-wave equation for a photorefractive two-wave mixing system. The direct simulations show that, when the intensity ratio of the pump beam to the signal beam is large enough, the pump beam presents a common decaying behaviour without modulational instability （MI）, while the signal beam can evolve into a quasistable spatial soliton within a regime in which the pump beam is depleted slightly. The larger the ratio is, the longer the regime is. Such quasistable solitons can overcome the initial perturbations and numerical noises in the course of propagation, perform several cycles of slow oscillation in intensity and width, and persist over tens of diffraction lengths. From physical viewpoints, these solitons actually exist as completely rigorous physical objects. If the ratio is quite small, the pump beam is apt to show MI, during which the signal beam experiences strong expansion and shrinking in width and a drastic oscillation in intensity, or completely breaks up. The simulations using actual experimental parameters demonstrate that the observation of an effectively stable soliton is quite possible in the proposed system.
基金supported by the National Natural Science Foundations of China(Grant Nos 10174025 and 10574051)
文摘In a biased photorefractive crystal, the process of two one-dimensional waves mixing, i.e., the dynamical evolution of both pump beam and signal beam, is traced by numerically solving the coupled-wave equation. Direct simulations show that the propagation and stability of the two beams are completely determined by the system parameters, such as the external bias field, the intensity and the beam waist of the pump beam. By adjusting these parameters, one can control the state of two Gaussian waves mixing. The numerical results are helpful for performing a two-wave mixing experiment.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574051）.
文摘The dynamical evolution and stability of bright dissipative holographic solitons in biased photorefractive materials in which the self-trapping beam obtains a gain from the pump beam via two-wave mixing has been investigated numerically. Results show that these solitons are stable relative to small perturbations. Adjusting some system parameters, such as the bias field and the angle between beams, can easily control the generation of such solitons. Potential applications in optical switches or repeaters are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11331008 and 11522112)
文摘In this paper, a nonlocal two-wave interaction system from the Manakov hierarchy is investigated via the Riemann–Hilbert approach. Based on the spectral analysis of the Lax pair, a Riemann–Hilbert problem for the nonlocal two-wave interaction system is constructed. By discussing the solutions of this Riemann–Hilbert problem in both the regular and nonregular cases, we explicitly present the N-soliton solution formula of the nonlocal two-wave interaction system. Moreover,the dynamical behaviour of the single-soliton solution is shown graphically.
基金supported by the National Natural Science Foundation of China(Grant Nos.11972165,and 11502085)the Japan Society for the Promotion of Science(Grant No.P18067)the Fundamental Research Funds for the Central Universities of China(Grant No.2016YXMS097)。
文摘Single crystals subjected to shock compression exhibit responses with distinct two-wave structures for certain crystal orientations.However,little is known to date regarding how the shock response depends on crystal orientation,and especially why the two-wave structure depends on the crystal orientation.In this work,molecular dynamics simulations of shock compressions in copper single crystals are performed to investigate the orientation dependence of shock responses and the corresponding deformation mechanisms.Four copper single crystals with[001],[011],[012],and[123]crystal orientations along the depth direction are investigated.The[011],[012],and[123]crystal orientations of copper single crystals show distinct two-wave structures in their shock responses,while such a two-wave structure in the shock response is not seen for those orientations having a[001]crystal orientation.The potential causes are analyzed by considering the propagation velocities of both elastic and plastic waves.We develop a technique for identifying twin structures in face-centered cubic crystals and this technique can effectively identify the twin structure.The morphology of shock-induced defects(e.g.,dislocations and twins)shows the significant dependence of crystal orientation and the mechanisms behind these are discussed in detail.Finally,the Johnson-Cook constitutive model describing dynamic deformations at high temperatures and high strain rates is used to analyze the relationships between the shock responses and microscopic defects.The predictions of the Johnson-Cook constitutive model are consistent with the results of the molecular dynamics simulations.
基金supported by the National Natural Science Foundation of China(Grant Nos.10174025 and 10574051)
文摘The transverse effects of two Gauss waves mixing in a photovoltaic photorefractive crystal,i.e.,the dynamical evolutions of signal beam with different parameters,are traced numerically and experimentally.Both the one-dimensional numerical simulations and two-dimensional experimental investigations show that the self-focusing effect of signal beam becomes more obvious as the intensity of pump beam and the angle between the signal and pump beams increase.In accordance with these results,the state of two Gaussian waves mixing is controllable.
基金the State Natural Science Foundation of China under Grant Nos.40775034,40575017,and 90715031the Natural Science Foundation of Jiangsu under Grant No.BK99020the open project of State Key Laboratory of Severe Weather,Chinese Academy of Meteorological Sciences.
文摘When the magnitude of sub-scale ographic forcing is comparable with explicitly ordinary dynamic forcing, the drag effect reduced by ographic gravity wave is to be significant for maintaining dynamic balance of atmospheric circulation, as well as the momentum and energy transport. Such sub-scale ographic forcing should be introduced into numerically atmospheric model by means of drag being parameterized. Furthermore, the currently mature ographic gravity wave drag （OGWD） parameterization, i.e., the so-called first-generation （based on lineal single-wave theoretical framework） or the second-generation drag parameterization （including an important extra forcing by the contribution of critical level absorption）, cannot correctly and effectly describe the vertical profile of wave stress under the influence of ambient wind shearing. Based on aforementioned consideration, a new two-wave scheme was proposed to parameterize the ographic gravity wave drag by means of freely propagating gravity waves. It starts with a second order WKB approximation, and treats the wave stress attenuations caused by either the selective critical level absorption or the classical critical level absorption explicitly; while in the regions where critical levels are absent, it transports the wave stress vertically by two sinusoidal waves and deposits them and then damps them according to the wave saturation criteria. This scheme is thus used to conduct some sample computations over the Dabie Mountain region of East China, as an example. The results showed that the new two-wave scheme is able to model the vertical distribution of the wave stress more realistically.
文摘The current study employs the novel Hirota bilinear scheme to investigate the nonlinear model.Thus,we acquire some two-wave and breather wave solutions to the governing equation.Breathers are pulsating localized structures that have been used to mimic extreme waves in a variety of nonlinear dispersive media with a narrow banded starting process.Several recent investigations,on the other hand,imply that breathers can survive in more complex habitats,such as random seas,despite the attributed physical restrictions.The authenticity and genuineness of all the acquired solutions agreed with the original equation.In order to shed more light on these novel solutions,we plot the 3-dimensional and contour graphs to the reported solutions with some suitable values.The governing model is also stable because of the idea of linear stability.The study’s findings may help explain the physics behind some of the challenges facing ocean engineers.
文摘目的:观察实时剪切波弹性成像(Sensor Web Enablement,SWE)技术与二维超声技术在桥本甲状腺炎背景下甲状腺癌中的联合诊断效能。方法:选取我院2022年1月至2023年12月收治的80例甲状腺结节且伴桥本甲状腺炎患者,均行二维超声、SWE检查,分析二维超声与SWE联合诊断价值。结果:病理结果示80例患者共检出80个结节,其中良性52个,恶性28个;联合诊断灵敏度、准确率均明显高于SWE或二维超声(P<0.05);二维超声联合SWE技术的曲线下面积(Area Under the Curve,AUC)最大。结论:二维超声联合SWE在桥本甲状腺炎背景下甲状腺癌患者中诊断效能较高,可同时开展二维超声与SWE技术检查,以提高甲状腺癌的检出。
文摘地震波在储层岩石中传播会形成流体压力梯度,引起孔隙间流体相对流动,表现为速度频散及衰减现象,进而影响地震波场特征.然而,传统考虑流体赋存影响的衰减岩石物理模型均假设孔隙中流体不相溶,而实际上流体之间必然发生溶解及扩散作用,导致其无法有效刻画孔隙流体赋存影响,影响了地震岩石物理模型精度.波致气体溶解出溶机制(Wave Induced Gas Exsolution and Dissolution,WIGED)能够很好地解释在多相流体相互溶解和扩散导致的衰减作用.目前,尚无针对性的岩石物理实验观测在双相流体中压力梯度引起的溶解-扩散作用,制约了基于该衰减理论的岩石物理模型应用.本文针对双相(气、液)、可相溶流体饱和岩石中的地震波衰减展开测量及衰减特征分析.通过搭建岩石物理衰减测量仪器,观测到了气泡随压力(地震波产生的压力扰动)变化而发生的形变,理论模型数值计算验证了波致气体溶解出溶(WIGED)机制描述地震频带内衰减的有效性.这种地震波衰减特征与地层温度、压力、流体赋存状态、孔隙结构、裂缝发育等因素关系密切,衰减曲线特征可基于标准线性固体模型有效刻画.
文摘立体摄影技术可实现三维海浪的连续观测,但目前基于立体摄影海浪观测数据开展二维海浪方向谱估计的研究却相对匮乏,从而束缚了立体摄影技术在海洋观测中的进一步深入应用。鉴于此,本文基于中国海洋大学微波遥感实验室开发的立体摄影海浪观测系统,并结合海浪方向谱阵列测量的扩展本征矢方法,系统性研究了基于立体摄影海浪观测数据反演二维海浪方向谱的可行性,并分析了不同海面采样点阵列排列方式、采样点间距及观测误差等因素对二维海浪方向谱反演结果的影响。立体摄影实测海浪数据反演结果显示:阵列中采样点间距小于1/3波浪的波长,海面采样点阵列排列方式为五边形时可得到较好的海浪方向谱反演结果。通过将立体摄影数据反演所得二维海浪方向谱与Signature1000型声学多普勒波浪流速剖面仪(Acoustic Doppler Wave and Current Profiler, AWAC)测量结果进行比较,结果显示二者具有较高的相关性和良好的一致性。立体摄影所得有效波高、平均波向和AWAC测量的有效波高、平均波向的相关系数分别为0.988和0.983,平均偏差分别为0.029 m和0.010°,均方根误差分别为0.089 m和8.844°。
