Comparison between orthogonal subspace projection and background subtraction techniques applied to remote-sensing data

The basic measurement equation r = B + alphad + n is solved for alpha (the weight or abundance of the spectral target vector d) by two methods: (a) by subtracting the stochastic spectral background vector B from the spectral measurement's vector r (subtraction solution) and (b) by orthogonal subspace projection (OSP) of the measurements to a subspace orthogonal to B (the OSP solution). The different geometry of the two solutions and in particular the geometry of the noise vector n is explored. The angular distribution of the noise angle between B and n is the key factor for determining and predicting which solution is better. When the noise-angle distribution is uniform, the subtraction solution is always superior regardless of the orientation of the spectral target vector d. When the noise is more concentrated in the direction orthogonal to B, the OSP solution becomes better (as expected). Simulations and one-dimensional hyperspectral measurements of vapor concentration in the presence of background radiation and noise are given to illustrate these two solutions.     

The chemical rank estimation for excitation-emission matrix fluorescence data by region-based moving window subspace projection technique and Monte Carlo simulation

A novel method, region-based on moving window subspace projection technique (RMWSPT) coupled with Monte Carlo simulation, was developed for the chemical rank estimation of excitation-emission matrix (EEM) fluorescence data arrays. RMWSPT determines the chemical rank by performing singular value decomposition (SVD) on the unfolded matrices of original data array and the subarrays yielded by a moving window, and through employing the subspace projection technique on the difference between the corresponding sub-bands of the significant eigenvectors and those of subarrays. Compared with the traditional methods, it utilizes the information from eigenvectors combined with the projection residual sum of squares values to estimate the rank of the EEM data arrays instead of using the eigenvalues. Two simulated and two real EEM data arrays were analyzed to demonstrate the excellent performance of the RMWSPT. Moreover, its performance was compared with that of other three factor-determining methods, i.e., factor indicator function (IND), the core consistency diagnostic (CORCONDIA) test and two-mode subspace comparison (TMSC) approaches. The results showed that the newly proposed method can accurately and quickly determine the chemical rank to fit the trilinear model, and it can deal with more complex situations in the presence of severe collinearity and trace concentration. The RMWSPT method thus lights a new avenue to determine the chemical rank of EEM data arrays and may hold great potential to be extended as a promising alternative for the chemical rank estimation.     

Response to "Comments on 'Quality of paraxial electromagnetic beams'"

The nonparaxial wave obtained by Seshadri [Appl. Opt.45, 5335 (2006)]APOPAI0003-693510.1364/AO.45.005335 is correct. The difference in the input field distributions of the nonparaxial wave and the corresponding paraxial beam is correct and is not caused by any error in the treatment. As is to be expected, in the appropriate limit, the nonparaxial wave reduces to the paraxial beam for 0相似文献   

神经网络获取三维面形研究

针对基于传统三角原理的结构光三维测量方法难以测量阶梯形物体的问题，应用神经网络对获取的变形条纹进行处理，获取物体的三维面形信息。该方法通过对神经网络的训练，直接建立条纹图分布与物体高度之间的对应关系，完成对物体的三维测量，即使在投影系统参数未知的情况下，也能取得较好的结果。论文中提出的神经网络三维面形测量方法测量时间短，测量过程中只需要一幅条纹图就能恢复阶梯物体的高度信息。计算机模拟及试验验证了方法的可行性。     

Circuit co-simulation and measurement techniques applied to voltage-controlled oscillator design

A voltage-controlled oscillator (VCO) was designed for operation in C-band for use in a microwave pointto- point radio system. Microstrip technology was chosen for resonator implementation since it offers ease of manufacturing and frequency adjustment. The design was performed using an electromagnetic harmonic balance co-design technique in conjunction with linear analysis in order to achieve first pass success. Emphasis in this work is the ability to use multiple design approaches and test techniques while validating in advance with co-simulation. The measured frequency against tune voltage data shows excellent agreement with simulation. Maximum deviation of 2% between the two was observed. The VCO tuned from 4.3 to 5.4 GHz as the tuning voltage was varied from 0 to 9 V representing a tuning bandwidth in excess of 20%. Power dissipation is 150 mW. Phase noise over the tune range was better than 2108 dBc/Hz at 100 kHz offset. The oscillator design efficiency, applicable to wider tune range designs, is greater than 2%. The hybrid oscillator figure-of-merit functions evaluated in this work exceeded comparable silicon-integrated implementations.     

BEM applied to damage models emphasizing localization and associated regularization techniques

In this work, the implicit BEM formulation, initially developed in the context of a plasticity analysis is extended to incorporate damage mechanics models. The algebraic equations adopted for the formulation are obtained either using displacement or traction equations, for the boundary nodes, and strain equations for the internal nodes. The formulation is modified to incorporate a regularization technique based on a non-local integral formulation. The consistent tangent operator has been obtained for local and non-local formulations. Arc-length strategy developed for BEM formulations is adopted to analyse problems exhibiting the snap-back effects.     

A comparison of the finite element and control volume numerical solution techniques applied to timber drying problems below the boiling point

Drying is a process which involves heat and mass transfer both inside the porous material, where a phase change in moisture occurs from the liquid to the gaseous state, and in the external boundary layer of the convected hot dry air, which heats the porous medium. The equations which govern this process consist of three tightly coupled, highly non-linear partial differential equations for the unknown system variables of moisture content, temperature and pressure. Due to the inherently complex boundary conditions and intricate physical geometries in any practical drying problem, an analytical solution is not possible. In order to obtain a transient drying solution it is necessary to resort to a numerical technique. The numerical solution techniques which were employed in this research were the finite element method and the control volume method. The transient numerical results were compared and contrasted for two timber drying problems, first, at a dry bulb temperature of 50°C, and secondly, at 80°C, both cases being below the boiling point of water.     

自然冷却技术应用于数据中心的方案分析

自然冷却技术是实现数据中心节能减排的重要途径。对于风冷冷水机组,采用冷冻水末端存在水进入数据中心的安全隐患,采用热管背板末端存在二次换热及蒸发温度低的问题。热管型冷水机组结构简单,具备小压比、变容量功能,机组配合风冷、水冷及蒸发冷等形式的选择及综合利用,可以发挥较好的节能效益;热管型制冷剂机组不仅可以解决水进入数据中心的安全隐患,而且可以解决多次换热性能效率低下以及分液不均的问题,提高系统蒸发温度,拓宽自然冷却利用时间,为大型数据中心全年冷却提供新的思考与方向。     

声波除灰与蒸汽吹灰的能量传播特性比较

蒸汽吹灰与声波除灰是目前锅炉运行中使用较多的两类除灰方式，本文重点讨论了两类除灰器的能量传播特性，并进行比较得出声波除灰在能量传输方面优于蒸汽吹灰的结论。     

Comments on "Frequency shifts in a resonator due to submersion in a fluid"

A critical analysis of the paper by Yang (see ibid., vol.53, no.3, p.662, 2006) is presented. The results presented in the paper are correct. Still, it is necessary to point out a few shortcomings that are possibly due to the fact that the author was not aware of some earlier papers when he submitted his paper