Optimizing thermography depth probing with a dynamic thermal point spread function

Derivation of two point spread functions PSFs suitable for infrared thermograms analysis is illustrated, based on two unique approaches, one based on depth decaying limit and one on diffusion limit. Experimental work using PMMA sample with back drilled holes and pulsed thermographic routine is utilized to show the effectiveness of deconvoluting pixel temperature transient history with suggested PSF’s. Synthetic second time derivative thermograms are utilized for comparison and the signal to noise ratio is used as a figure of merit for quantification.     

The uncertainty principle and Bekenstein–Hawking entropy corrections

There is much attention on the corrections to Bekenstein–Hawking entropy in area with a model-dependent coefficient. The corrections are generally composed of two parts: quantum corrections and thermal corrections. The generalized uncertainty principle (GUP), which will reduce to the conventional Heisenberg relation in situations of weak gravity, is one of the candidates to be utilized to obtain the quantum corrections to the Bekenstein–Hawking entropy. Recently the extended uncertainty principle (EUP) and generalized extended uncertainty principle (GEUP) are introduced to calculate entropy corrections with large length scales limit. In this paper, we obtain the quantum corrections to Bekenstein–Hawking entropy in four-dimensional Schwarzschild black holes based on the EUP and GEUP. Some attractive results are derived.     

Determination of iodine in foodstuffs consumed in Libya using instrumental and radiochemical neutron activation analysis

Iodine was determined in foodstuffs consumed in Libya employing two modes of NAA. The first mode was instrumental using short-time irradiation with epithermal neutrons behind a Cd shield (EINAA). The other mode utilized short-time irradiation with the reactor-pile neutrons followed by radiochemical separation (RNAA). The radiochemical separation procedure was based on the alkaline-oxidative fusion of samples and extraction of elemental iodine into chloroform. Separation yield determined using the radiotracer ¹³¹I was within the range of 90 to 95 %. For quality control purposes, standard reference materials were analyzed in both modes employed. Using RNAA, a detection limit of ～1 ng g^?1 could be obtained indicating superiority of the method in measuring ultra-trace levels of iodine. On the other hand, more than one order of magnitude higher detection limit did not allow sufficiently accurate determination of iodine in Libyan foodstuffs using EINAA.     

Determination of iodine in foodstuffs consumed in libya using instrumental and radiochemical neutron activation analysis

Iodine was determined in foodstuffs consumed in Libya employing two modes of NAA. The first mode was instrumental using short-time irradiation with epithermal neutrons behind a Cd shield (EINAA). The other mode utilized short-time irradiation with the reactor-pile neutrons followed by radiochemical separation (RNAA). The radiochemical separation procedure was based on the alkaline-oxidative fusion of samples and extraction of elemental iodine into chloroform. Separation yield determined using the radiotracer ¹³¹I was within the range of 90 to 95%. For quality control purposes, standard reference materials were analyzed in both modes employed. Using RNAA, a detection limit of ∼1 ng g⁻¹ could be obtained indicating superiority of the method in measuring ultra-trace levels of iodine. On the other hand, more than one order of magnitude higher detection limit did not allow sufficiently accurate determination of iodine in Libyan foodstuffs using EINAA.     

Identification des propriétés thermiques de composites fibres de verre/résines thermodurcissables: Application à l'optimisation des procédés de moulage

Identification of glass fiber/thermosetting resins composites thermal properties. Application to the optimization of molding processes. A procedure has been developed to optimize molding processes of thermosetting composite materials. Three stages have been distinguished. In the first one, some thermal and kinetic properties have been measured by differential scanning calorimetry. Thermal conductivities have been identified afterwards in thick instrumented pieces, placed in a thermally regulated press. High dependences of thermal conductivities on temperature and transformation degree have been shown. Secondly, coupled heat transfers have been numerically simulated and results have been satisfactorily compared with experimental thermograms. Finally, optimization technics based on effective inverse methods have been used.These points have been illustrated with two examples : glass fiber/epoxy resin and glass fiber/polyester. Sufficient mechanical characteristics of the first one, which is cured in oven, and good surface aspect of the second, that is made by injection in heated and closed molds, had to be obtained. The results let foresee real improvement of the corresponding molding processes.     

Fluctuations in the Weakly Asymmetric Exclusion Process with Open Boundary Conditions

We investigate the fluctuations around the average density profile in the weakly asymmetric exclusion process with open boundaries in the steady state. We show that these fluctuations are given, in the macroscopic limit, by a centered Gaussian field and we compute explicitly its covariance function. We use two approaches. The first method is dynamical and based on fluctuations around the hydrodynamic limit. We prove that the density fluctuations evolve macroscopically according to an autonomous stochastic equation, and we search for the stationary distribution of this evolution. The second approach, which is based on a representation of the steady state as a sum over paths, allows one to write the density fluctuations in the steady state as a sum over two independent processes, one of which is the derivative of a Brownian motion, the other one being related to a random path in a potential.     

Defects inspection of the solder bumps using self reference technology in active thermography

With the decrease of solder bumps in dimension and pitch, defects inspection of the solder bumps become more difficult. A nondestructive detection system based on the active thermography has been developed for solder bumps inspection. However, heating non-uniformities and emissivity differences may impede the defects recognition. In this paper, we propose a method using a self reference technology based on a source distribution image (SDI) to eliminate the influence of unevenness in emissivity values and heating power distribution. Three thermograms captured right after the heat pulse are averaged to create the SDI. Then the SDI is subtracted from the original thermograms, and we get the thermal contrast images, in which eight points on the edge of each hot spot are selected as the feature points for the corresponding bump. Thermal difference between the feature points and the central point are adopted to quantify the thermal behaviors of the solder bumps, by which the missing bump is distinguished from the reference bumps. The results show that it is effective using the method to eliminate the impacts of emissivity unevenness and heating non-uniformities on defects identification in the active infrared test.     

Limit cycles in quantum theories

Renormalization group limit cycles and more chaotic behavior may be commonplace for quantum Hamiltonians requiring renormalization, in contrast to experience based on classical models with critical behavior, where fixed points are far more common. We discuss the simplest quantum model Hamiltonian identified so far that exhibits a renormalization group with both limit cycle and chaotic behavior. The model is a discrete Hermitian matrix with two coupling constants, both governed by a nonperturbative renormalization group equation that involves changes in only one of these couplings and is soluble analytically.     

Analysis of thermograms for the estimation of dimensions of cracks in building envelope

In situ determination of global air leakage of the building envelope is presently done with the fan depressurization test. During such test, infrared thermography could also be used to dimension unintentional small openings (cracks). In this study, thermography was used to measure in laboratory the surface temperature of single-layer walls subjected to air flow through surrogates of cracks. Two image-processing methods were developed and applied to a dataset of 36 thermograms recorded in laboratory. First, using the edge detection technique, the opening length and large width (more than 4 mm) can be graphically estimated with an error of less than 8%. Second, for smaller openings, correlations for two image-processing characteristics, peak height and missing attenuation, were established. These relationships result in estimation with a relative error of less than 4% of the widths of small cracks on thermograms. The development of correlations for the spectrum of conditions found on site could be a step towards in situ quantification of air leakage areas.     

The conditional entropy in the microcanonical ensemble: The quantum lattice

The existence of the conditional entropy in the thermodynamic limit for a class of long range compatible observables operating on a quantum lattice is exhibited for the microcanonical ensemble. This limit is demonstrated first along a special sequence of cubes with a fixed contraction parameter. Properties of the parameter dependent limit are utilized to remove the parameter, and the results are extended to van Hove sequences approximable by cubes.     

On biomembrane electrodiffusive models

Two models are used in the literature, to study the electric behaviour of cellular membranes such as in protein aggregates, excitable media or ionic currents for examples. The first one is the Electroneutral Model based on Nernst-Planck and Poisson equations with a specific condition of microscopic electroneutrality. The second one is the Cable Model valid for long wavelengths based on an analogy between an electric cable and a cell. Convincing experiments have justified the Cable equation. First, we show that these two models are in contradiction. More precisely the assumption of electroneutrality is not considered in the Cable Model. The main difference between the two models is highlighted by the analysis of the well known voltage instability due to a negative differential conductance. Then, we derive a new semi-microscopic model (the Biomembrane Electrodiffusive Model, called BEM) valid for phenomena at any wavelength. The BEM is based on Nernst-Planck and Poisson equations but, doesn't imply microscopic electroneutrality. It reveals the capacitive behaviour of the membrane. In the limit of long wavelengths, one recovers the behaviour described within the Cable framework, as shown precisely in the study of the negative differential conductance analysis. Finally, we demonstrate the intimate link between the last models: the Cable Model appears as the limit of the BEM for large wavelengths with some prerequisites which are discussed. The effects of geometry and asymmetrical media are introduced. Received: 8 November 1996 / Revised: 23 July 1997 and 8 December 1997 / Accepted: 23 January 1998     

Resonant two‐magnon Raman scattering in high‐Tc cuprates

Resonance enhancement of one‐phonon, two‐phonon, and two‐magnon Raman scattering in a general, exactly solvable, multiband model is explained in a way that is in accordance with the general analytical properties of the total optical conductivity tensor. Using this approach, the charge‐transfer limit of the Emery three‐band model is examined to explain resonance enhancement of the two‐magnon Raman spectra of high‐T_c cuprates, which is found in experiments to be of 3 orders of magnitude. While previous Raman and optical conductivity analyzes of the cuprates, based on the single‐band Hubbard model, are found to be consistent with the picture where one hole per one CuO₂ unit is localized on the Cu ion, the present three‐band approach allows the study of the opposite, strong copper‐oxygen hybridization limit, which is found to be in agreement with the results of nuclear magnetic resonance (NMR) and one‐phonon Raman scattering experiments. Copyright © 2010 John Wiley & Sons, Ltd.     

利用带无标签数据的双支持向量机对恒星光谱分类

恒星光谱分类是天文技术与方法领域一直关注的热点问题之一。随着观测设备持续运行和不断改进,人类获得的光谱数量与日俱增。这些海量光谱为人工处理带来了极大挑战。鉴于此,研究人员开始关注数据挖掘算法,并尝试对这些光谱进行数据挖掘。近年来,神经网络、自组织映射、关联规则等数据挖掘方法广泛应用于恒星光谱分类。在这些方法中,支持向量机(SVM)以其强大的学习能力和高效的分类性能而备受推崇。SVM的基本思想是试图在两类样本之间找到一个最优分类面将两类分开。SVM在求解时,通过将其最优化问题转化为具有(QP)形式的凸问题,进而得到全局最优解。尽管该方法在实际应用中表现优良,但为了进一步提高其分类能力,有的学者提出双支持向量机(TSVM)。该方法通过构造两个非平行的分类面将两类分开,每一类靠近某个分类面,而远离另一个分类面。TSVM的计算效率较之传统SVM提高近4倍,因此,自TSVM提出后便受到研究人员的持续关注,并出现若干改进算法。在恒星光谱分类中,一般分类算法都是根据历史观测光谱来建立分类模型,其中最关键的是对光谱进行人工标注,这项工作极为繁琐,且容易犯错。如何利用已标记的光谱以及部分无标签的光谱来建立分类模型显得尤为重要。因此,提出带无标签数据的双支持向量机(TSVMUD)用以实现对恒星光谱智能分类的目的。该方法首先将光谱分为训练数据集和测试数据集两部分;然后,在训练集上进行学习,得到分类依据;最后利用分类依据对测试集上的光谱进行验证。继承了双支持向量机的优势,更重要的是,在训练集上学习分类模型过程中,不仅考虑有标记的训练样本,也考虑部分未标记的样本。一方面提高了学习效率,另一方面得到更优的分类模型。在SDSS DR8恒星光谱数据集上的比较实验表明,与支持向量机SVM、双支持向量机TSVM以及K近邻(KNN)等传统分类方法相比,带无标签数据的双支持向量机TSVMUD具有更优的分类能力。然而,该方法亦存在一定的局限性,其中一大难题是其无法处理海量光谱数据。该工作将借鉴海量数据随机采样思想,利用大数据处理技术,来对所提方法在大数据环境下的适应性展开进一步研究。     

红外双焦无热化空间相机光学镜头设计

针对空间碎片探测相机光学镜头的设计要求,提出了一种全新的紧凑型、小型化、轻量化、高像质、可全天候工作、使用环境恶劣的光学镜头,突破了以往该类系统结构复杂、体积大、重量重、仅有一个焦距的瓶颈。利用衍射光学元件特殊的特性进行消色差和消热差设计,并利用锗和硅混合来校正系统色球差,最终设计镜头的焦距为30, 120 mm,相对孔径为1/4。设计结果表明,在空间频率16 lp/mm处,－40～60 ℃温度范围内,短焦距、长焦距的传递函数值分别优于0.45和0.55,接近衍射极限;短焦距、长焦距的最大RMS弥散斑直径分别为15.8, 7.2 m,远小于探测器像元尺寸30 m,表明该系统在实际使用温度环境下具有良好的成像质量。     

Fiber optic loop buffer switch incorporating 3R regeneration

In this paper, an all-optical regenerator based, photonic packet switch architecture, which consists of fiber loop for the storage of the contending packets, is proposed. In the loop buffer, the available buffer space may not be fully utilized due to the re-circulation limit (maximum number of re-circulations that data can take before it can be correctly received at the output). The re-circulation limit arises due to the accumulated ASE (amplified spontaneous emission) noise of the optical amplifier and crosstalk of the optical components. This limit can be counteract by placing a pool of regenerators inside the buffer, which regenerates the signal after some fixed number of re-circulations. As optical regenerators are costly devices, hence they should be placed optimally in the buffer. To do so, in this paper an expression is presented to evaluate the minimum number of required regenerators, to be placed optimally in the buffer for different buffer configurations (B) and re-circulation limits (K), such that full buffer capacity can be utilized without any re-circulation constraints. The simulation results in terms of packet loss probability are presented by considering the detrimental effect of re-circulation limits. Finally, advantages gain due to the regenerator placement inside the buffer are shown.     

From Ballistic to Diffusive Behavior in Periodic Potentials

The long-time/large-scale, small-friction asymptotic for the one dimensional Langevin equation with a periodic potential is studied in this paper. It is shown that the Freidlin-Wentzell and central limit theorem (homogenization) limits commute. We prove that, in the combined small friction, long-time/large-scale limit the particle position converges weakly to a Brownian motion with a singular diffusion coefficient which we compute explicitly. We show that the same result is valid for a whole one parameter family of space/time rescalings. The proofs of our main results are based on some novel estimates on the resolvent of a hypoelliptic operator.     

基于DM8168的小型机载视频记录仪设计

针对飞行器搭载相机视频存储和传输的需求,设计了一种基于异构多核处理器DM8168的小型机载视频记录仪。首先,基于DM8168和FPGA处理器设计小型化低功耗的硬件系统;接着,基于McFW软件架构设计视频采集编码的数据流,充分发挥DM8168多核体系结构的优势,实现两路1080P60视频的采集,并且对每路视频分别进行主次码流的H.264编码;最后,采用GPMC总线,将视频码流传输到FPGA处理器,以实现本地视频存储和远程视频传输。本记录仪体积小功耗低、记录时间长、视频传输时延小,能够很好地满足飞行器多路视频记录的需求。     

层叠Blumlein线多开关导通时间分散性

高介电常数陶瓷储能脉冲形成线需要用到多开关触发的层叠Blumlein线结构。从形成线波过程理论出发，分析了多开关导通时间分散性对层叠Blumlein线及其输出波形的影响。主要包括两方面影响:其一是造成输出方波脉冲的前沿和后沿均出现阶梯形畸变；其二是使得各延迟导通的平行平板Blumlein线承受过电压，容易引起陶瓷储能介质的电击穿。在不单独考虑开关电感的理想情况下，利用PSpice电路程序模拟了开关导通时间分散性对四级层叠Blumlein线的影响，模拟结果与波过程理论分析一致。为减弱这些影响，提出了可行的解决方案。