基于Roujean和Ross-Li模型算法的不同户外光照南疆冬枣BRDF特性研究

不同光照下,如何消除或减小反演数据差异,提高检测精度,是目前南疆冬枣户外检测中遇到的一大难题,因此通过用高光谱相机获得的南疆冬枣二向反射分布函数（BRDF）测量值,采用最小二乘法拟合Roujean模型和Ross-Li模型的参数,最后对比Roujean模型和Ross-Li模型反演的结果,提出何种天气何段波长用何种模型反演效果最好的建议,实验结果表明：（1）多云天气,反演南疆冬枣线偏振度（Dolp）时,Ross-Li模型的R2是0.974 8,Roujean模型的R2是0.969 9;反演南疆冬枣强度分量时,Ross-Li模型的R2是0.972 3,Roujean模型的R2是0.974 9。阴天反演南疆冬枣Dolp时,Ross-Li模型的R2是0.965 1,Roujean模型的R2是0.977 8;反演南疆冬枣强度分量时,Ross-Li模型的R2是0.942 0,Roujean模型的R2是0.968 8。晴天反演南疆冬枣Dolp时,Ross-Li模型的R2是0.965 5,Roujean模型的R2是0.926 2;反演南疆冬枣强度分量时,Ross-Li模型的R2是0.928 5,Roujean模型的R2是0.833 1。整体反演的最佳方案是多云天气下的南疆冬枣Dolp用Ross-Li模型反演,强度分量用Roujean模型反演;晴天南疆冬枣Dolp和强度分量均用Ross-Li模型反演;阴天南疆冬枣Dolp和强度分量均用Roujean模型反演。（2）多波段反演的最佳方案是：多云天气下,反演南疆冬枣强度分量时,波长为1 000~1 100 nm范围,需用Ross-Li模型,波长为1 450~1 600 nm范围,需用Roujean模型,其余波段处两种模型均可;反演南疆冬枣Dolp时,在波长为1 300 nm附近,需用Ross-Li模型,其余波段处两种模型均可。阴天反演南疆冬枣强度分量时,在1 000~1 350 nm范围,需用Roujean模型,在1 600 nm附近,需用Ross-Li模型,其余波段处两种模型均可;反演南疆冬枣Dolp时,在1 000~1 350 nm范围,需用Roujean模型,在1 600 nm附近,需用Ross-Li模型。晴天反演南疆冬枣强度分量时,波长为1 000~1 350和1 600 nm附近,需用Ross-Li模型,其余波段处则无特殊要求;反演南疆冬枣Dolp时,在1 000 nm附近,需用Roujean模型,在1 600 nm附近,需用Ross-Li模型。探索出消除或减小反演数据差异的方法,为南疆冬枣户外检测提高精度奠定基础。     

Acoustic streaming in a rotating fluid

Acoustic streaming theory is derived that is applicable to a fluid that is slow moving in a reference frame that rotates with a constant angular velocity omega. A simplified streaming equation is obtained for the special case in which the acoustic angular frequency omega is large relative to omega, and the change in fluid density due to rotation alone is negligible. For this special case it is shown that the "driving force" for the acoustic streaming is independent of omega. Thus, if no acoustic streaming is present in a fluid system that is stationary, then no steady-state acoustic streaming is predicted for a similar system that rotates with constant angular velocity. For a system in which acoustic streaming is present, the flow behavior depends on the relative magnitudes of the Coriolis forces and the viscous forces. If the Ekman number is large (that is, the viscous force dominates) then the predicted flow is identical to that which would exist in a stationary system. If, on the other hand, the Ekman number is small then the Coriolis force dominates and the component of flow in the direction of the axis of rotation can be much smaller in the rotating system than in a similar system at rest.     

Measurement of the dynamic structure function of fluorescently labeled complex fluids by fourier imaging correlation spectroscopy

The dynamics of the kicked rotor, which is a paradigm for a mixed system, where the motion in some parts of phase space is chaotic and in other parts is regular, is studied statistically. The evolution operator of phase space densities in the chaotic component is calculated in the presence of noise, and the limit of vanishing noise is taken in the end. The relaxation rates to the equilibrium density are calculated analytically within an approximation that improves with increasing stochasticity. The results are tested numerically. A global picture is presented of relaxation to the equilibrium density in the chaotic component when the system is bounded and to diffusive behavior when it is unbounded.     

Test of the weak cosmic censorship conjecture with a charged scalar field and dyonic Kerr–Newman black holes

A thought experiment considered recently in the literature, in which it is investigated whether a dyonic Kerr–Newman black hole can be destroyed by overcharging or overspinning it past extremality by a massive complex scalar test field, is revisited. Another derivation of the result that this is not possible, i.e. the weak cosmic censorship is not violated in this thought experiment, is given. The derivation is based on conservation laws, on a null energy condition, and on specific properties of the metric and the electromagnetic field of dyonic Kerr–Newman black holes. The metric is kept fixed, whereas the dynamics of the electromagnetic field is taken into account. A detailed knowledge of the solutions of the equations of motion is not needed. The approximation in which the electromagnetic field is fixed is also considered, and a derivation for this case is also given. In addition, an older version of the thought experiment, in which a pointlike test particle is used, is revisited. The same result, namely the non-violation of the cosmic censorship, is rederived in a way which is simpler than in earlier works.     

On the thermodynamics of contact interaction in an atomic force microscope

Contact interaction in an atomic force microscope is considered in terms of the thermodynamic approach. It is shown that hysteresis observed when a sample is probed in the vertical direction is due to the surface energy-work thermodynamic cycle. The force of sample-tip interaction is calculated for the case when the tip is a paraboloid of revolution. Fluctuations of the basic thermodynamic parameters are found. The role of electrocapillary forces is considered. A new method of spectroscopy in the lateral force mode is suggested.     

Gain studies of Coumarin 503 dye-doped polymer laser

Solid-state dye doped polymer is an attractive alternative to the conventional liquid dye solution. In this paper, the laser characteristics of Coumarin 503 (C503) doped polymethyl methacrylate (PMMA) rods modified with ethyl alcohol (EtOH) are studied under nitrogen laser excitation in a transverse pumping configuration and the variation of gain of the dye in solid medium for different pumping powers is studied. The gain of Coumarin 503 in solid medium is compared with the gain of Coumarin 503 in liquid medium and it is found that the gain of the dyes in the solid environment is less than that in the liquid environment. The photobleaching of dye in polymer medium under nitrogen laser excitation is also studied by keeping the rod in a fixed position and by rotating the rod about its cylindrical axis. It is found that the photobleaching rate is faster when the rod is in a fixed position.     

Bose-Einstein condensation and the glassy state

The distinction between a classical glass and a classical liquid is difficult, since both are disordered. The difference is in the fact that a glass is frozen while the liquid is not. In this Letter an equilibrium measure is suggested that distinguishes between a glass and a liquid. The choice of this measure is based on the idea that in a system which is not frozen symmetry under permutation of particles is physically relevant, because particles can be permuted by actual physical motion. This is not the case in a frozen system. In this Letter it is shown how to generalize naturally the quantum mechanical concept of Bose condensed fraction to classical systems in order to distinguish between the glass and the liquid. It is finite in the liquid and zero in the frozen state. The actual value of the condensed fraction in the liquid may serve also as a measure of the glassiness in the liquid.     

Quantum correlations in non-inertial cavity systems

Non-inertial cavities are utilized to store and send Quantum Information between mode pairs. A two-cavity system is considered where one is inertial and the other accelerated in a finite time. Maclaurian series are applied to expand the related Bogoliubov coefficients and the problem is treated perturbatively. It is shown that Quantum Discord, which is a measure of quantumness of correlations, is degraded periodically. This is almost in agreement with previous results reached in accelerated systems where increment of acceleration decreases the degree of quantum correlations. As another finding of the study, it is explicitly shown that degradation of Quantum Discord disappears when the state is in a single cavity which is accelerated for a finite time. This feature makes accelerating cavities useful instruments in Quantum Information Theory.     

新型1×N多模干涉分束器的三维设计与模拟

相比于传统的1×N对称型多模干涉（Mult-Mode Interference,MMI）分束器设计,提出了一种新型埋入式弱限制光波导分束器件.它的干涉区及输入输出波导采用倒锥形式,器件尺寸减小,且不均匀性与附加损耗也减小.以1×4的对称型MMI分束器为例,当只对干涉区采用倒锥形结构后,在TE偏振中心波长为1.55 μm时,器件长度减小了500 μm,均匀性增加了0.131 dB,而附加损耗仅增加了0.02 dB,波长响应较传统设计增加了40 nm.在此基础上,又在输入输出臂上也各增加倒锥形结构后,相比于传统设计附加损耗减小了0.02 dB,均匀性增加了0.139 dB,器件长度减小了500 μm.改进后的器件具有优越的容差性.器件采用掺氟型聚合物材料进行优化设计,通过在合理范围内偏离输出波导位置,使输出光强达到最大值.     

Hydrogen recombination in the early Universe in the presence of a magnetic field

Hydrogen recombination in the earlyUniverse in the presence of amagnetic field is studied. An equation for the recombination temperature in the presence of a magnetic field is obtained. The limiting cases of weak and strong magnetic fields are examined. A critical field above which the system being considered is in the atomic-hydrogen phase at any temperature is shown to exist. The relative shift of the recombination temperature in a magnetic field is estimated, and it is shown that this shift is small.     

Velocity autocorrelations and viscosity renormalization in sheared granular flows

The decay of the velocity autocorrelation function in a sheared granular flow is analyzed in the limit where the wavelength of fluctuations is larger than the "conduction length," so that energy is a nonconserved variable. The decay of the velocity autocorrelation function is much faster than that in a fluid at equilibrium for which energy is a conserved variable. Specifically, the autocorrelation function in a sheared granular flow decays proportional to t-3 in 2D and t-9/2 in 3D, in contrast with the decay proportional to t-1 in 2D and t-3/2 in 3D for a fluid at equilibrium. The renormalization of the viscosity due to mode coupling is evaluated using this form of the decay of the autocorrelation function. It is found that the logarithmic divergence in the viscosity in 2D, and the divergence of the Burnett coefficients in 3D, which is characteristic of a fluid of elastic particles at equilibrium, is absent in a sheared granular flow.     

Redistribution of energy flow in a material due to damping

The field lines of energy flow of the radiation emitted by a linear dipole in free space are straight lines, running radially outward from the source. When the dipole is embedded in a medium, the field lines are curves when the imaginary part of the relative permittivity is finite. It is shown that due to the damping in the material all radiation is emitted in directions perpendicular to the dipole axis, whereas for a dipole in free space the radiation is emitted in all directions except along the dipole axis. It is also shown that some field lines in the near field form semiloops. Energy flowing along these semiloops is absorbed by the material and does not contribute to the radiative power in the far field.     

Analysis of the Near-Anode Processes Characters in Argon Arc Discharges of High Pressure

In this paper the anode layer model including two zones is considered. It is suggested that in the collisionalless zone (the sheath) the potential drop is negative. For the collisional part of the anode layer the equation system is considered. This system takes into account the ionization non-equilibrium in this layer. Here side by side with the electrical field the complementary diffusion mechanism of the current transfer is examined. This mechanism is stipulated by the existence of the electron gas pressure gradients in the anode layer. It is shown that the potential drop in the collisional part of the anode layer is also negative because of the action of the diffusion mechanism of the current transfer. In this way the full potential drop in the anode layer of the discharge burning in argon by atmospere pressure is turned out to be negative. The character of the change of the energy and impulse equations terms is discussed.     

Analytical solution for multilayer assembly including heating and cooling cycles with laser pulse parameter variation

Laser heating of surfaces is involved with heating and cooling cycles. Material response to a laser pulse in the heating cycle is rapid while in the cooling cycle it is gradual. In this case, temperature rises rapidly in the heating cycle while temperature decay is gradual in the cooling cycle. Depending on the laser pulse properties (pulse length and intensity), the rise and fall of temperature profiles change in the surface region of the substrate material. In the present study, an analytical solution for laser heating pulse is presented and a closed-form solution for temperature distribution inside the multilayer assembly is obtained. Steel is considered as top layer while copper is situated below steel in the multilayer assembly. It is found that the analytical solution agrees well with the numerical predictions. Temperature rise in steel is higher than copper. This is due to the thickness of steel, which is larger than the absorption depth. In this case, internal energy gain dominates over the heat conduction in the energy transport process.     

核势和核子有效质量的同位旋相关性

在Dirac Brueckner Hartree-Fock (DBHF)理论框架下研究了核子光学势和核子有效质量的同位旋相关性. 非对称核物质的计算采用了DBHF的核子自能的Dirac结构的新的分解方法, 核子自能的实部是用G矩阵在Hartree-Fock近似下计算得到, 而虚部从极化图得到. 用核子的薛定谔等价势可以得到核子矢量有效质量. 研究表明考虑了核势的能量相关性在丰中子核物质情况下核子矢量有效质量比质子的大.     

A mixture theory for wave propagation in a laminated medium with debonding

In this paper wave propagation in the direction of the layering of a bi-laminated medium with the presence of imperfect bonding at the interfaces is investigated. The debonding mechanism is represented by a model which allows imperfect bonding both in the normal and tangential directions. A mixture theory is formulated in which every constituent has its own motion but is allowed to interact with the others. The resulting theory is applied to transient wave propagation in the laminated composite. It is shown that debonding in the tangential direction is significant in modifying the shape and amplitude of the propagating wave.     

轻型车载大口径光电跟测系统光学设计

设计了一套能实现机动式布站的大口径车载可见光、红外、激光光电跟踪测量光学系统。其主光学系统采用共口径光谱分光方式工作,系统有效口径1.2m,各成像通道成像质量均达到衍射极限;捕获电视系统采用连续变焦距光学系统,视场范围0.31°～4.57°;激光测距通道设计作用距离达20km。光学设计结果表明,此套光学系统能够用于空中和空间目标的运动轨迹、成像测量和实况景象记录。     

Frequency average loss factors of plates and shells

This paper describes a thorough investigation of the measurement of frequency band average loss factors of structural components for use in the statistical energy analysis (SEA) method of computation of vibration levels. The “traditional” method of measurement is to excite the structure by a random force having a flat spectral density in the frequency band of interest. The force is then cut off and the decay of the modes excited in the band is noted. The average loss factor is deduced from the decay curve. The alternative energy method is the subject of this study. In this test the power input from the band limited random force is measured and the spatial average vibration level of the structure is estimated from several surface accelerometers. It is shown that when the modes in the band have similar loss factors (as is usually the case) the energy method gives a result which is very close to that obtained from the decay method. These in turn are close to the arithmetic average of the loss factors of the individual modes in the band. It is shown that only when the band contains one or two very lightly damped modes amongst several more heavily damped modes is there a difference between the two methods. In this case it is better to use the energy result in the SEA calculations.     

Relativity of quantum states in entanglement swapping

The entanglement swapping protocol is analyzed in a relativistic setting, where shortly after the entanglement swapping is performed, a Bell test is performed. For an observer in the laboratory frame, a Bell violation is observed between the qubits with the swapped entanglement. In a moving frame, the order of the measurements is reversed, and a Bell violation is observed even though the particles are not entangled, directly or indirectly, or at any point in time. Although the measurement results are identical, the wavefunctions for the two frames are starkly different — one is entangled and the other is not. Furthermore, for boosts in a perpendicular direction, in the presence of decoherence, we show that the maximum Bell violation can occur across non-simultaneous points in time. This is a signature of entanglement that is spread across both space and time, showing both non-local and non-simultaneous aspects of entanglement.     

Some Aspects of Nuclear Structure in Relativistic Approach

The nucleon effective interaction in the nuclear medium is investigated in the framework of the DiracBrueckner-Hartree-Fock (DBHF) approach. A new decomposition of the Dirac structure of nucleon self-energy in the DBHF is adopted for asymmetric nuclear matter. The properties of finite nuclei are investigated with the nucleon effective interaction. The agreement with the experimental data is satisfactory. The relativistic microscopic optical potential in asymmetric nuclear matter is investigated in the DBHF approach. The proton scattering from nuclei is calculated and compared with the experimental data. A proper treatment of the resonant continuum for exotic nuclei is studied. The width effect of the resonant continuum on the pairing correlation is discussed. The quasiparticle relativistic random phase approximation based on the relativistic mean-field ground state in the response function formalism is also addressed.