Generalized in-line digital holographic technique based on intensity measurements at two different planes

In-line digital holography based on two-intensity measurements [Zhang Opt. Lett. 29, 1787 (2004)], is modified by introducing a pi shifting in the reference phase. Such an improvement avoids the assumption that the object beam must be much weaker than the reference beam in strength and results in a simplified experimental implementation. Computer simulations and optical experiments are carried out to validate the method, which we refer to as position-phase-shifting digital holography.     

Retrieval analysis of aerosol-size distribution with simulated extinction measurements at SAGE III wavelengths

The retrieval of aerosol-size distribution from simulated aerosol-extinction-coefficient measurements of the new satellite instrument, the Stratospheric Aerosol and Gas Experiment (SAGE) III, is investigated. A detailed discussion on the aerosol-size-distribution information content of the SAGE III aerosol-extinction-coefficient measurement is provided. Results of the investigation indicate that unimodal as well as bimodal log-normal size distributions can be inferred. In addition, it is shown that a shape-constraint-free size distribution can be derived from SAGE III aerosol measurements by use of the randomized minimization search technique and the optimal estimation theory.     

Thermal diffusivity measurements of building materials based on 2D models

This paper presents the results and experimental procedure used for obtaining the thermal diffusivity of building materials like cement, sand, expanded polystyrene, silicone and concrete. The determination of this important physical property is based on the solution of the 2D cartesian and cylindrical Fourier equation adapted to high surface conductances. Material samples are shaped as rectangular prisms or cylinders to accomplish these simple geometries. The measurement technique is based on the sample thermal response when it is suddenly submitted to baths of constant temperature. The uncertainty associated with this method is systematically estimated in both cases. Thermal diffusivity is obtained with a precision of about 6% using a simple proving bench. Such precision is good enough taking into account the typical low values of this property for such kind of materials and their strong dependence with temperature.     

Composite load models based on field measurements and their applications in dynamic analysis

The composite load model with an induction motor in parallel with a static load has been studied and applied in analysis of dynamics of power systems for a long time. However, the load parameters from field tests are still very limited. Based on the theoretical results of identifiability and estimation methodology of load parameters that have been achieved in the previous work, a project of load modelling based on field measurements is described. Eight sets of equipment for load modelling were installed in HeNan Electric Power Grid (HNEPG) Corporation, and the dynamics of the load were recorded and a dynamic index is proposed to evaluate the dynamic characteristics of the data measured. The load models derived from the field measurements are applied to stability analysis of HNEPG. The critical clearing time and power transfer capability analyses illustrate the enhancement of the stability analysis of the power grid using the load parameters derived from the field measurements and show the benefits of application of such model parameters in power system dynamic analysis.     

制冷机做冷源的低温热导率测量装置研制

设计研制了1套以4.2 K制冷机为冷源的低温热导率快速测量装置.该装置采用可拆卸的具有独立真空环境的样品测试杆,使得样品测试部件与低温冷源部件分离,从而实现不破坏制冷机冷源真空环境及制冷机不复温的情况下快速更换样品.高真空绝热恒温样品杆通过高导热柔性热桥与制冷机冷头良好热耦合.热导率测试采用稳态绝热纵向热流法.除快速测...     

Evaluation of two portable lead-monitoring methods at mining sites

Two methods for measuring airborne lead using field-portable instruments have been developed by the National Institute for Occupational Safety and Health (NIOSH): Method 7702 uses X-ray fluorescence (XRF), and Method 7701 employs ultrasonic extraction (UE) followed by anodic stripping voltammetry (ASV). The two portable methods were evaluated at mining sites. Area air samples were collected throughout two mills where ore from nearby mines was processed; the primary constituent of the ore was lead sulfide (galena). The air samples were collected on 37 mm mixed cellulose ester membrane filters housed within plastic filter cassettes. At the end of the work shift, the cassettes were collected and taken to a room off-site for analysis by the two portable methods. The filter samples were first analyzed by XRF and then by UE/ASV. Calibration was verified on both instruments according to standard procedures. The samples were then sent for confirmatory analysis via flame atomic absorption spectrometry (FAAS) according to NIOSH Method 7082. Pairwise comparisons between the methods using the paired t-test showed no statistically significant differences between ASV and FAAS (P>0.05); however, the comparison between XRF and FAAS was statistically significant (P<0.05). The elevated lead concentrations reported by XRF relative to FAAS were likely the result of the ability of XRF to report total lead, including lead silicates. This form of lead is not liberated in the digestion process prior to FAAS analysis, and is therefore not detected by this method. Despite this discrepancy, lead concentrations measured by both portable technologies were found to be highly correlated with the laboratory method (R2>0.96), suggesting that they are suitable as screening methods for airborne lead at mining sites.     

Natural attenuation of MTBE at two petroleum-hydrocarbon spill sites

Methyl tert-butyl ether (MTBE) has been used as a gasoline additive to improve the combustion efficiency and to replace lead since 1978. Because it is widely used and it has been disposed inappropriately, MTBE has become a prevalent groundwater contaminant worldwide. In this study, two petroleum-hydrocarbon contaminated sites (Sites A and B) were selected to evaluate the occurrence and effectiveness of natural attenuation of MTBE at these two sites. Field investigation results indicate that the natural attenuation mechanisms of MTBE at both sites were occurring with the first-order attenuation rates of 0.0021 and 0.0048 1day(-1) at Sites A and B, respectively. Results also reveal that the intrinsic biodegradation pattern was the most important mechanism among the natural attenuation processes at both sites. Results from BIOSCREEN simulation suggest that biodegradation was responsible for 78 and 59% of MTBE mass reduction at Sites A and B, respectively. Investigation results show that MTBE plume at Site B could be effectively controlled via natural attenuation processes. However, MTBE plume at Site A has migrated to a farther downgradient area and passed the boundary line of the site. Thus, more active groundwater remedial technologies should be applied at Site A to protect the downgradient environment. Results from this study suggest that natural attenuation might be feasible to be used as a remedial option for the remediation of MTBE-contaminated site on the premise that (1) detailed site characterization has been conducted and (2) the occurrence and effectiveness of natural attenuation processes have been confirmed.     

Simulation research on improved regularized solution of the inverse problem in spectral extinction measurements

We present further results of the simulation research on the constrained regularized least squares (CRLS) solution of the ill-conditioned inverse problem in spectral extinction (turbidimetric) measurements, which we originally presented in this journal [Appl. Opt. 49, 4591 (2010)]. The inverse problem consists of determining the particle size distribution (PSD) function of a particulate system on the basis of a measured extinction coefficient as a function of wavelength. In our previous paper, it was shown that under assumed conditions the problem can be formulated in terms of the discretized Fredholm integral equation of the first kind. The CRLS method incorporates two constraints, which the PSD sought will satisfy: nonnegativity of the PSD values and normalization of the PSD to unity when integrated over the whole range of particle size, into the regularized least squares (RLS) method. This leads to the quadratic programming problem, which is solved by means of the active set algorithm within the research. The simulation research that is the subject of the present paper is a continuation and extension of the research described in our previous paper. In the present research, the performance of the CRLS method variants is compared not only to the corresponding RLS method variants but also to other regularization techniques: the truncated generalized singular value decomposition and the filtered generalized singular value decomposition, as well as nonlinear iterative algorithms: The Twomey algorithm and the Twomey-Markowski algorithm. Moreover, two methods of selecting the optimum value of the regularization parameter are considered: The L-curve method and the generalized cross validation method. The results of our simulation research provide even stronger proof that the CRLS method performs considerably better with reconstruction of PSD than other inversing methods, in terms of better fidelity and smaller uncertainty.     

Testing linear models on spectral daylight measurements

We have analyzed the results of the reconstruction quality of 252 daylight spectral curves measured at Granada, Spain, using four bases obtained from measurements in different areas of the world. For these reconstructions we used two different methods (orthogonality of characteristic vectors and chromaticity coordinates) to study the influence of the wavelength range and spectral resolution. The reconstruction method from chromaticity coordinates presents difficulties for the spectral recovery of daylight spectral power distributions regardless of the basis used. The orthogonality method makes clear that the best bases were those proposed by the CIE, but more than two characteristic CIE vectors were needed for good reconstruction.     

Imaginary refractive-index effects on desert-aerosol extinction versus backscatter relationships at 351 nm: numerical computations and comparison with Raman lidar measurements

A numerical model is used to investigate the dependence at 351 nm of desert-aerosol extinction and backscatter coefficients on particle imaginary refractive index (mi). Three ranges (-0.005 < or = mi < or = -0.001, -0.01 < or = mi < or = -0.001, and -0.02 < or = mi < or = -0.001) are considered, showing that backscatter coefficients are reduced as /mi/ increases, whereas extinction coefficients are weakly dependent on mi. Numerical results are compared with extinction and backscatter coefficients retrieved by elastic Raman lidar measurements performed during Saharan dust storms over the Mediterranean Sea. The comparison indicates that a range of -0.01 to -0.001 can be representative of Saharan dust aerosols and that the nonsphericity of mineral particles must be considered.     

Characteristics of dust aerosols inferred from lidar depolarization measurements at two wavelengths

Lidar depolarization measurements were performed simultaneously at two wavelengths (532 and 1064 nm) in an Asian dust event. The observed particle depolarization ratio for 1064 nm was generally larger than that for 532 nm, and it was found that the mixing of Asian dust and other spherical aerosols must be taken into account. A simple two-component theory considering two types of aerosol (dust and spherical aerosols) was developed and applied to the observed data. The mixing ratio of dust and the backscatter-related Angstr?m exponents for dust and spherical aerosols was derived. These parameters can be used to infer characteristics of the aerosols and the mixed states.     

Fast dynamic performance optimization of complicated beam-type structures based on two new reduced physical models

In this article, two new model reduction methods for fast dynamic performance optimization of complicated beam-type structures are presented. In the new model reduction methods the projection of structural nodal degrees of freedom is carried out using the localized base vectors, which are obtained by physical hypothesis. The first new model reduction method constructs the base vectors based on the assumption of block-wise rigid body motion modified by minimizing the displacement error measured in strain energy. The second new model reduction method is based on the plane cross-section assumption, and the cross-sectional warp deformation is also taken into consideration. Then, two reduced optimization models based on each method and design variable decomposition are formulated and solved. Both reduced optimization models are compared with the response surface method-based structural optimization approach. Some examples are presented to demonstrate the feasibility and effectiveness of the proposed methods.     

Inclusion of a priori information in an analytic eigenfunction inversion of Mie extinction measurements

The analytic eigenfunction inversion technique to retrieve aerosol columnar size distributions from Mie extinction measurements has been extended to include a priori information, specifically surface area. The earlier (standard) and new (subtracted) techniques are compared by use of synthetic data that cover typical aerosol size distributions. Two different measurement wavelength ranges are considered. It is shown that the most appropriate inversion technique depends on the particle sizes, with the standard technique being more appropriate for small particles and the subtracted being more appropriate for large particles. Also presented is a simple method to determine whether a particular inversion technique is likely to produce meaningful results with a particular data set.     

Texture and secondary extinction measurements in Al\Ti stratified films by X-ray diffraction

In the present work the effects of secondary extinction has been studied using standard X-ray diffractometer and texture diffractometer techniques. For this purpose the texture of Al\Ti stratified films have been measured and evaluated. It is shown that these films have a very sharp single component texture. Therefore the evaluation and the interpretation of the measurement data is only possible when secondary extinction correction is carried out. The effect of secondary extinction is evaluated on the 111 pole figures of the stratified films with different layer pair numbers. The volume fraction of the main texture component is calculated from pole figures and it is shown that the grains of the films are practically completely oriented with 111 crystallographic direction parallel to the film surface normal. Moreover in the case of pole density measurements the secondary extinction values themselves are simultaneously calculated.     

Hydrocarbon vapor measurements in fuel sprays: a simplification of the infrared extinction technique

An equal optical thickness approximation that greatly simplifies the application and data reduction of the infrared extinction technique for measuring fuel vapor concentrations in sprays is investigated. A general approach is given, with specific results for a 3.39- and a 0.6328-μm-wavelength system. It is shown that the infrared (3.39-μm) drop optical thickness can be approximated by the use of the visible (0.6328-μm) optical thickness for drop size distributions with area mean diameters greater than 20 μm for hydrocarbon fuel sprays.     

A note on two process adjustment models

The idea of a process ‘adjustment’ has different connotations depending on whether one is talking from a statistical process control (SPC) or from an engineering process control (EPC) point of view. In SPC an adjustment implies the correction of some problem that has caused abnormal variation. The corrective action usually restores the process mean to a desired or ‘in-control’ level. In EPC an adjustment means the compensation of some observed deviation by manipulating a control variable. This paper analyses two models proposed for process adjustment useful for understanding these and other important differences. One model is based on assumptions common in EPC applications, the other is based on assumptions common in SPC applications. Adjustment policies for each model are presented and contrasted. © 1998 John Wiley & Sons, Ltd.     

Characterization of thin films based on reflectance and transmittance measurements at oblique angles of incidence

The optical parameters of a SiO2 thin-film coating determined from the spectral reflectance and transmittance measurements at various incidence angles, including the normal incidence and the Brewster's angle, are compared in this paper. The high-accuracy measurements were carried out through visible-near-infrared spectral regions by using our purpose-built instruments. The optical parameters obtained from the reflectance and the transmittance data are consistent over the angles of incidence and agree within 0.2%. The effect of important systematic factors in the oblique-incidence spectrophotometric measurements is also discussed.