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.     

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.     

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.     

INHOMOGENEOUS WAVES IN ANISOTROPIC POROUS LAYER OVERLYING SOLID BEDROCK

The problem of propagation of inhomogeneous waves in anisotropic porous layered medium is studied using transfer matrix. Firstly, transfer matrix for an anisotropic porous layer is derived. Biot's poro-elastic theory is incorporated to model the acoustics of anisotropic porous layer. The interface between porous layer and elastic half-space is considered as imperfect and modified boundary conditions are applied for this more realistic situation. The theory of transfer matrix is used to derive the analytical expression for the surface impedance. Numerical computation of results is done for different degrees of bonding in the low as well as high-frequency range. In the first case, which is relevant to geophysical studies, the surface impedance is predicted for low-frequency range and surface impedance for second model is computed in high-frequency range. It is observed that loose bondedness is accompanied by the loss of energy at the interface. The technique of transfer matrix is utilized to compute the surface impedance in both cases. The role of surface impedance in seismological studies and in the study of composites is discussed.     

Production or conservation in CHP networks?

In Sweden, Combined generation of Heat and Power (CHP) is in common practice. Different fuels are burnt in a boiler and the steam is used for generating electricity. The heat that has to be transferred from the condenser in the plant is used in the district heating grid. This grid is thus used as a cooling facility necessary for electricity production. However, energy conservation the Swedish building stock is also encouraged, and if this is utilized in district heated buildings it results in fewer possibilities for electricity production. This might be a major drawback when nuclear power is abolished, as is the result from a consensus some years ago. This paper deals with the question of whether it is better to conserve both heat and electricity, to save only one of the energy forms or if it is cheaper to produce more energy, instead of saving. A case study is presented dealing with Malmö, in the South of Sweden, and it is shown that energy conservation in district heated buildings cannot yield profitability: neither can conservation in the electricity grid, even if it gets closer to profitable savings. It is assumed that the total cost of heating, insulation and electricity is paid by the society and the minimum point for this cost will characterize the best solution.     

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.     

Study of fully developed wind wave spectrum by application of quantum statistics

The spectrum of fully developed wind waves is studied by application of the method of quantum statistics. A particle picture of water waves is introduced as an analogy of wave–particle duality. “Water wave particles” are conceived which are similar to phonons for elastic waves in solids. However, due to the property of wave breaking, the number of “water wave particles” in a quantum state is restricted. The spectrum of fully developed wind waves is studied on the basis of the maximum entropy principle. The similarity law of fully developed wind wave spectrum is proved. In the high frequency range, the spectral form is in agreement with the result of observations. In the particle picture, a saturated spectrum is introduced which is in conceptual consistency with the saturated spectrum introduced by Phillips in the wave picture, and the form of which is the same as Phillips’. It is further shown that in the high frequency range the spectrum is only half saturated for fully developed wind waves. The frequency downshifting phenomenon which cannot be explained by wave theory is explained in the particle picture.     

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.     

State reduction in quantum mechanics: A calculational example

The question is posed as to the role of the state reduction hypothesis in the passage of a molecular beam through a Stern-Gerlach apparatus of the ordinary sort, and of the sort proposed by Wigner, in which the beam is rejoined at the end of the apparatus. The effect of the magnetic field is calculated, as is the effect of a “detector” atom placed asymmetrically in the apparatus, and sensitive to the passage of the molecular beam nearby. It is shown that in the absence of the detector atom the rejoined beam is represented by a pure case density matrix. However, when the detector is present in one arm of our Stern-Gerlach apparatus, the beam is found to be in a statistical mixture approximating “reduction”, even if we never “look” at the detector atom. It is also seen that the beam density matrix is reduced to diagonal form even though it is not physically affected by the detector.     

Cluster perturbation theory in Hubbard model exactly taking into account the short-range magnetic order in 2 × 2 cluster

The cluster perturbation theory is presented in the 2D Hubbard model constructed using X operators in the Hubbard-I approximation. The short-range magnetic order is taken into account by dividing the entire lattice into individual 2 × 2 clusters and solving the eigenvalue problem in an individual cluster using exact diagonalization taking into account all excited levels. The case of half-filling taking into account jumps between nearest neighbors is considered. As a result of numerical solution, a shadow zone is discovered in the quasiparticle spectrum. It is also found that a gap in the density of states in the quasiparticle spectrum at zero temperature exists for indefinitely small values of Coulomb repulsion parameter U and increases with this parameter. It is found that the presence of this gap in the spectrum is due to the formation of a short-range antiferromagnetic order. An analysis of the temperature evolution of the density of states shows that the metal-insulator transition occurs continuously. The existence of two characteristic energy scales at finite temperatures is demonstrated, the larger scale is associated with the formation of a pseudogap in the vicinity of the Fermi level, and the smaller scale is associated with the metal-insulator transition temperature. A peak in the density of states at the Fermi level, which is predicted in the dynamic mean field theory in the vicinity of the metal-insulator transition, is not observed.     

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.     

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.     

PIV Measurements of side-cavity open-channel flows —Wando model in rivers—

PIV measurements in side-cavity open-channel flows that simulate “Wando” in rivers, were conducted in a laboratory flume. Five types of side cavities were built by using a transparent plate at the wando flow. The pattern of the instantaneous flow fields was quite different from that of time-averaged ones. It was found that a vortex, which is located in the side cavity, is stable when the junction mouth between the side-cavity and main channel is narrow. In contrast, large-scale unstable vortices are generated semi-periodically when the junction mouth is wide. The free-surface fluctuations in and outside the wando were also measured by three sets of supersonic wave gauges. The amplitude of the watersurface fluctuations is large when the junction mouth is wide as compared with when its mouth is narrow. When the elevation of the free surface in the side-cavity is rising, its elevation in the main channel is falling, and vice versa when the junction mouth is wide.     

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.     

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.     

原油含水率测量的光学计量仪

油井含水率是油田开发过程中的一个重要指标。光纤传感器具有体积小、重量轻、抗干扰能力强、实时、高效、准确等优点,将其应用于石油测井,有利于提高勘探效率。介绍测井应用中原油含水率计量仪的结构,分析了光纤传感器对混合液体含水率测量的基本原理。激光在弯曲光纤中的传输效率随外界混合介质折射率的变化而改变,根据光纤输出光功率的大小可以测量外界混合介质的组成成分。通过数值模拟,给出了光纤传感器中光束强度随混合液体含水率的变化现象,计算得到混合液体中含水率测量结果。结果表明,光纤传感器计量仪能实现0%～100%含水量的连续测量。最后基于数值模拟结果讨论了系统设计中的注意事项。     

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.     

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.     

Aharonov-Bohm shift as a shift in normal coordinates

The Aharonov-Bohm shift in a closed system is considered. The solenoid is a charged, rotating cylinder which is electrically neutral. This model of Henneberger and Opatrny has a Hamiltonian which is a quadratic form. This quadratic form is transformed to normal coordinates, so that the stationary states become self-evident. It is shown that, in the original system, it is the kinetic angular momentum which is quantized. Solutions of the problem for an electron inside the solenoid are discussed. It is shown that the rotating cylinder exhibits different behavior if the electron is in the magnetic field or if it is in the external region. An external field approximation which replaces the cylinder by a constant magnetic field therefore cannot yield a correct solution of the Schrödinger equation which is continuous at the surface of the solenoid.