Homological stabilizer codes

In this paper we define homological stabilizer codes on qubits which encompass codes such as Kitaev’s toric code and the topological color codes. These codes are defined solely by the graphs they reside on. This feature allows us to use properties of topological graph theory to determine the graphs which are suitable as homological stabilizer codes. We then show that all toric codes are equivalent to homological stabilizer codes on 4-valent graphs. We show that the topological color codes and toric codes correspond to two distinct classes of graphs. We define the notion of label set equivalencies and show that under a small set of constraints the only homological stabilizer codes without local logical operators are equivalent to Kitaev’s toric code or to the topological color codes.     

The high-frequency description of scatter of a plane compressional wave by an elliptic crack

High-frequency approximations that can be interpreted in terms of the Uniform Geometrical Theory of Diffraction (UGTD) and Uniform Kirchhoff Approximation (UKA) are used to develop a code for modeling ultrasonic scatter of a plane compressional wave by an elliptic crack in the radiating near field. The approximations are intercompared and partially validated against a direct numerical code based on an FD (Finite-Difference) scheme. At present, in many realistic situations the approximate codes of the type described here offer the only viable simulation tool; purely numeric codes are not only much slower, they still require too much computer memory to simulate the complex structure of the radiating near fields.     

Testing a spatial model of the spectral radiance of combustion product plumes

The results of testing of the Plume-2D-MC and Plume-3D-MC computer codes for calculating the spectral radiance (signature) of combustion product plumes and various gas volumes with light-scattering particles and for predicting the degree of attenuation of this emission by atmospheric gases at a great distance away. These codes are based on various algorithms for modeling the characteristic of radiative heat transfer and various models of the thermal radiation of hot gases (the NASA IR radiation model, HITRAN and CDSD-1000 databases, and statistical models of wide and narrow bands). These codes were used to simulate experimental data on the spectral radiance of hot gases.     

Band absorption in nonhomogeneous,isotropically-scattering planetary atmospheres: theory and experiment

A computer program is developed which predicts the vertical distribution of an absorbing species in an isotropically-scattering, finite planetary atmosphere from measurements of the upwelling band radiance determined by a vertically traversing 2-channel radiometer. Comparison is made with experiment.     

Using the MARAS system for the in situ characterizing of the spectral optical properties of the North Sea

The MArine RAdiometric Spectrometer (MARAS) has been developed to perform in situ spectral marine radiometry. The vector and scalar components of the upwelling and downwelling light field are measured simultaneously over a constant separation, enabling the estimation of the apparent and inherent optical properties of a water body. When combined with the active MARAS sub-system, the transmissometer and scatterometer, MARAS is capable of more fully describing the optical properties of the ocean. Results from a 1994 cruise in the North Sea are illustrated. The spectral absorption coefficient, the spectral reflectance and the spectral upwelling radiance for a number of sample sites at different depths are shown with concurrent sea truth data.     

A single-scattering approximation for infrared radiative transfer in limb geometry in the Martian atmosphere

We present a single-scattering approximation for infrared radiative transfer in limb geometry in the Martian atmosphere. It is based on the assumption that the upwelling internal radiation field is dominated by a surface with a uniform brightness temperature. It allows the calculation of the scattering source function for individual aerosol types, mixtures of aerosol types, and mixtures of gas and aerosol. The approximation can be applied in a Curtis-Godson radiative transfer code and is used for operational retrievals from Mars Climate Sounder measurements. Radiance comparisons with a multiple scattering model show good agreement in the mid- and far-infrared although the approximate model tends to underestimate the radiances in realistic conditions of the Martian atmosphere. Relative radiance differences are found to be about 2% in the lowermost atmosphere, increasing to ∼10% in the middle atmosphere of Mars. The increasing differences with altitude are mostly due to the increasing contribution to limb radiance of scattering relative to emission at the colder, higher atmospheric levels. This effect becomes smaller toward longer wavelengths at typical Martian temperatures. The relative radiance differences are expected to produce systematic errors of similar magnitude in retrieved opacity profiles.     

AO3D: A Monte Carlo code for modeling of environmental light propagation

A Monte Carlo radiative transfer program (Atmosphere-Ocean 3-Dimensional, AO3D) for modeling the coupled atmosphere-ocean environment has been developed. The code allows for the specification of optical properties for the atmosphere, land and ocean. Light rays are tracked as they pass between the atmosphere and the ocean, reflect off the ocean surface, the ocean floor, and off land, or are absorbed. In this version the polarization of light rays is not considered. The optical properties of each horizontally homogeneous layer within the atmosphere and ocean can be set on a layer-by-layer basis with a choice of phase functions, absorption and scattering coefficients, and index of refraction. A wind-dependent Cox and Munk ocean surface realization (with whitecaps) is implemented to model refraction and reflection from surface waves. Either spherical- or flat-Earth models can be used, and all refraction and reflection are accounted for. The AO3D model has been tested by parts, and as a whole by comparison with single- and total-scattering calculations from other radiative transfer codes. Comparisons with Monte Carlo calculations by Adams and Kattawar (agreement in TOA radiance within the published precision ∼2%), MODTRAN4 (agreement in spherical-shell atmosphere (SSA) sky radiance within about 2%) and Coupled DIScrete Ordinate Radiative Transfer (COART) (agreement in plane-parallel (PP) sky radiance within 2%) are shown. Sun photometer measurements (including large air mass values) at the Mauna Loa Observatory are compared to AO3D simulations (for a spherical Earth) and suggest that a thin aerosol layer was present above the observatory at the time of the measurements.     

锚链式水下多光谱辐射计的设计

研发了一种向下光谱辐照度和向上光谱辐亮度的锚链式水下多光谱辐射计,主要用于深层海水的测量。解决了水下光学窗口的污染问题。采用高灵敏度光电探测器与高精度ADC相结合的方法探测了深层海水的微弱光信号。电池的使用采用了时钟控制和间断供电方式。通过电感式Modem实现了数据的实时传输。     

用于动物细胞和组织培养的新型LED生物光源系列

采用透镜组扩大光束、透镜阵列聚焦和点阵光曲面聚集光能三种光路设计,通过选择各光源中的四个工作参数调节光源输出的辐射照度,本文研制出可用于动物细胞和组织培养使用的、不同强度的三种新型LED生物光源,并使用统计分析软件SPSS拟合得出它们的辐射照度经验计算公式.     

CUDA-accelerated simulation of multiple scattering using decoupling approximation

Abstract  

In this research a CUDA-accelerated simulation method of multiple scattering in dense participating media based on decoupling approximation is proposed. Simulation of multiple scattering is important, in that it visually illustrates how radiance transfers between gaseous particles. The existing radiance transfer equation has poor computational performance because of its complicated integral calculation of in-scattering in each radiance update. However, this computation can be avoided using previous cached results proposed in this paper. To construct the cached results, we first decouple the phase function in radiance transfer equation with singular value decomposition (SVD) approximation. SVD approximates the multivariate phase function as a sum of products of incident light and outgoing light of lower dimensionality. Then the incident light and outgoing light data of current radiance update are cached independently in two textures. The cached two textures are used to replace integral calculation of in-scattering in the next radiance update to improve computation performance. The proposed method is designed in a parallelized way so that the parallel computing power of CUDA can be fully exploited. The simulation results show that our method allows fast rendering of dynamic scenes while high accuracy is maintained.     

起伏地形的高光谱遥感地气耦合辐射建模研究

邻近效应会影响高光谱遥感的定量化应用,而地气耦合辐射是邻近效应的重要组成部分。高光谱遥感数据多受地形背光和阴影的影响,不利于描述地物的光谱特性,并且地形的相互遮蔽使得辐射在大气、地表之间的耦合过程变得更加复杂。为了满足高光谱数据模拟快速性的要求,在深入分析辐射传输过程的基础上,利用邻近地物和目标地物的相对方位以及局地地形特征描述背景等效反射率,计算地气耦合辐射对传感器入瞳辐亮度的贡献,从而在起伏地形下实现了精确的地气耦合辐射建模。将此建模方法应用于高光谱遥感成像仿真,通过对实测图像的模拟,验证模型的有效性。结果表明,模拟图像与实测图像在视觉效果上具有较好的一致性;在地形起伏区域,仿真中采用改进后的地气耦合模型可提高模拟图像与实测图像的光谱相似度,同时在地形平坦区域保持了较高的仿真精度。     

A spectroscopic blackbody radiance calibration procedure with inherent source temperature calibration

Spectroscopic measurement in n (n > 2) narrow spectral bands of a calibration blackbody source at three different temperatures leads to a set of 3n equations of spectrometer signal as a function of Planck's radiance. Solution of this set is possible by balancing calculations and results in n values of spectrometer response, spectrometer radiance and the three source temperatures—no additional temperature measurement is required.     

Stabilization of a class of dynamical complex networks based on decentralized control

This paper deals with a stabilization problem for a class of dynamical complex networks with each node being a general Lur’e system. Based on a Lur’e-Postnikov function and a special decentralized control strategy, the problem of designing a linear feedback controller such that states of all nodes are globally stabilized onto an expected homogeneous state is addressed. A controller design method based on parameter-dependent Lur’e-Postnikov function is proposed in order to reduce the conservativeness and the controller can be constructed via feasible solutions of a certain set of linear matrix inequalities (LMIs). A dynamical network composed of identical Chua's circuits is adopted as a numerical example to demonstrate the effectiveness of the proposed results.     

Energy dissipation and violation of the fluctuation-response relation for harmonic oscillators described by the generalized Langevin equation

The generalized Langevin equation (GLE) satisfied by harmonic oscillators coupled to a heat bath is transformed into an equality between the rate of energy dissipation and an extent of violation of the fluctuation-response relation. Its significance is discussed. When the system reaches a stationary state and a single harmonic oscillator’s frequency is set to zero, the equality reduces to a fluctuation-dissipation relation, which is slightly different from the usual Kubo’s formalism.     

视场角和定位误差在光谱辐射亮度测量中的影响

为了减小不同光谱辐射计间瞄准区域差异带来的光谱辐射亮度不一致性,讨论了视场角及定位对于测量准确性的影响。通过建立太阳光白板和卤钨灯白板系统光路下的光谱辐射亮度测量模型,分析了不同几何光路视场区域平均辐射亮度与中心辐射亮度的差异。数值模拟表明,太阳光白板光路修正因子仅与视场角大小有关;卤钨灯白板光路修正因子随测量距离增大而减小,距离600 mm时8°和14°视场角的修正因子分别变为0.993 5和0.980 2。最后,实验验证了卤钨灯白板系统下角度误差和位移误差对光谱辐射亮度的影响。结果表明,修正因子对水平方向的角度误差和位移误差呈现非对称性,两侧差异高达2%。因此,依据视场角和几何定位可以对测量结果进行数据修正,有助于提升光谱辐射亮度测量不确定度水平。     

双通道数字红外辐射计的研究

 针对目前所使用的红外辐射强度测试系统的不足,提出双通道数字红外辐射计的方案,即在同一红外辐射计中设计两套相互独立的红外辐射强度测试通道,在红外辐射产品点火试验测试中,双通道测试同时工作,同时进行数据采集。用研制的双通道数字红外辐射计分别在室温（25℃）和低温（-15℃）条件下进行6次对比试验,结果表明：两系统测试的误差小于5%,双通道数字红外线辐射计两通道之间误差小于5％,原1905A测试系统出现2次漏测,双通道数字红外辐射计无漏测。     

An efficient method for computing atmospheric radiances in clear-sky and cloudy conditions

A computationally efficient method is developed to simulate the radiances in a scattering and absorbing atmosphere along an arbitrary path in the spectral region ranging from visible to far-infrared with a spectral resolution of 1 cm⁻¹. For a given spectral region, the method is based on fitting radiances pre-calculated from the discrete ordinate radiative transfer (DISORT) at several wavenumbers. Radiances at other wavenumbers are interpolated based on the pre-computed total absorption and scattering optical thicknesses and the surface albedo. The computational efficiency and accuracy of the method are tested in comparison with rigorous simulations for various scenarios under the same conditions. For both clear-sky and cloud atmospheres, the present method is at least 140 times faster than the direct application of DISORT. Across the spectral range, the standard relative differences between the new method and the DISORT are less than 2% for clear-sky conditions. Root-mean-square (RMS) differences of the top of the atmosphere (TOA) brightness temperatures between the new method and DISORT, for atmospheric infrared sounder (AIRS) channels over clear-sky, ice cloudy and water cloudy skies, are within the noise equivalent differential temperature (NEDT) of the AIRS sensor. The fast method is also applied to simulations of the spectral downwelling radiance measured by the Fourier transform infrared (FTIR) interferometer, and to the simulations of the AIRS upwelling radiances under clear-sky and cloudy conditions.     

基于高光谱辐亮度图像进行目标探测的大气状态影响分析

基于高光谱辐亮度图像直接进行目标探测可以提高数据处理效率,满足实时处理的要求。然而遥感器所获取的辐亮度光谱信息会受到大气的影响。通过对高光谱成像过程的模拟,分析大气状态变化对辐亮度图像中目标探测性能的影响。研究结果表明：高光谱辐亮度图像可以直接用于目标探测,不同的大气状态对RXD异常探测影响很小,而MF探测则受输入光谱准确度的影响,待检测目标的辐亮度光谱要求与辐亮度图像获取时的大气状态一致,才有良好的效果。     

Decoupling error for the atmospheric correction in ocean color remote sensing algorithms

This paper studies the decoupling error associated with the atmospheric correction procedures in the ocean color remote sensing algorithms. The decoupling error is caused by the lack of proper consideration of multiple scattering between the atmospheric and ocean components. In other words, the atmosphere and ocean are not coupled properly. A vector radiative transfer model for the coupled atmosphere and ocean (CAO) system based on the successive order of scattering (SOS) method is used to study the error. The inherent optical properties (IOPs) of the ocean are provided by the most updated bio-optical models. Two wavelengths are used in the study, 412 and 555 nm. For a detector located just above the ocean interface, the decoupling errors range from 0.3% to 7% at 412 nm; and from 0.3% to 3 % at 555 nm for zenith viewing angles smaller than 70°. The decoupling errors are significantly larger for larger zenith viewing angles for this detector. For a detector at the top of the atmosphere (TOA), it is hard to separate the decoupling error from the error introduced by the diffuse transmittance. If we assume the upwelling radiance is uniform just below the ocean surface when estimating the diffuse transmittance, the decoupling errors are from ?4% to 8% for zenith viewing angles smaller than 70°; and negative decoupling errors show up at mainly large zenith viewing angles.     

Uncertainties propagation for combustion diagnostics using infrared band models

The development of matrix equations for an uncertainty propagations analysis of an emission-absorption (E/A) band-model technique is described. The E/A technique is used for the determination of local values of temperature and species concentration from measurements of radiance and transmittance on axisymmetric gas flows. The approach used depends on linearization of the original nonlinear system of equations comprising the solution to the radiative transfer problem for an emitting-absorbing source such as a turbojet or rocket engine exhaust plume. The resultant linear transformation matrix provides a means for determination of the variance-covariance matrix for inverted temperature and partial pressure, based on the experimentally determined variance-covariance matrix of the measured radiance and transmittances. The diagonal elements of the propagated variance-covariance matrix yield the square of the standard deviation of the temperature and partial pressure. Although the equations are developed for uncertainty propagations analysis of the E/A band-model technique, the results are a general property of linear transformations. They are thus applicable to any situation in which the dependence of analysis on measurements can be approximated by a linear relationship. Inversion of radiance and transmittance lateral profiles obtained from a liquid-propellant rocket engine to radial profiles of temperature and partial pressure with the associated uncertainties propagations is included as an illustrative example.