Exact and efficient signal reconstruction in frequency-domain optical-coherence tomography

We address the problem of tomogram reconstruction in frequency-domain optical-coherence tomography. We propose a new technique for suppressing the autocorrelation artifacts that are commonly encountered with the conventional Fourier-transform-based approach. The technique is based on the assumptions that the scattering function is causal and that the intensity of the light reflected from the object is smaller than that of the reference. The technique is noniterative, nonlinear, and yields an exact solution in the absence of noise. Results on synthesized data and experimental measurements show that the technique offers superior quality reconstruction and is computationally more efficient than the iterative technique reported in the literature.     

Time-domain optical imaging: discrimination between scattering and absorption

A technique for discriminating between scattering and absorbing inclusions located in the center of a scattering slab is presented. The technique is based on an empirical model that provides a simple mathematical expression to describe the change in the time-resolved transmission resulting from the presence of an inclusion. Experimental results from various configurations show that the technique allows for proper recognition of the type of an inclusion whether it is scattering or absorbing. This technique is a significant step toward tissue differentiation.     

Identification and correction of analog-to-digital-converter nonlinearities and their implications for differential absorption lidar measurements

Differential absorption lidar (DIAL) is a powerful remote-sensing technique widely used to probe the spatial and temporal distribution of ozone and other gaseous atmospheric trace constituents. Although conceptually simple, the DIAL technique presents many challenging and often subtle technical difficulties that can limit its useful range and accuracy. One potentially serious source of error for many DIAL experiments is nonlinearity in the analog-to-digital converters used to capture lidar return signals. The impact of digitizer nonlinearity on DIAL measurements is examined, and a simple and inexpensive low-frequency dithering technique that significantly reduces the effects of ADC nonlinearity in DIAL and other applications in which the signal is repetitively averaged is described.     

低温液体贮运技术及其蒸发率的测算

低温液体贮运技术是获得和保持低温、实现低温技术应用中的必不可少的技术。简述了国内低温液体贮运技术的进展及航空兵部队低温液体贮运设备的典型结构，并就低温液体贮运过程中最为关注的蒸发率测定与计算问题，做了较为详细的分析。     

Size, velocity, and concentration in suspension measurements of spherical droplets and cylindrical jets

The principle of an optical technique for simultaneous velocity, size, and concentration in suspension measurements of spherical droplets and cylindrical jets is proposed. This technique is based on phase Doppler anemometry working in the dual burst technique configuration. The particle size and velocity are deduced from the reflected signal phase and frequency, whereas the amplitude ratio between the refracted and the reflected signals is used for measuring the concentration of small scatterers inside the particles. Numerical simulations, based on geometrical optics and a Monte Carlo model, and an experimental validation test on cylindrical jets made of various suspensions, are used to validate the principle of the proposed technique. It is believed that this new technique could be useful in investigating processes in which liquid suspensions are sprayed for surface coating, drying, or combustion applications.     

过盈配合数值分析与优化设计

围绕高速转盘的过盈配合问题，应用Ansys9．0有限元软件非线性接触技术和优化分析技术确定传递扭矩所需的最佳过盈配合量。实践证明，有限元技术在工程应用中能够优化过盈配合量，缩短设计周期，提高设计质量。     

Linearization and flattening technique for fringe analysis and its application to holographic interferometry

A simple technique for correcting the nonlinearity of a camera-digitizer system is presented. With this technique cameras that are extremely nonlinear but which enhance fringe contrast can be used. The technique can also reduce the number of phase-shifted interferograms required for quantitative analysis from three to two or (with some restrictions) to one. The last option is important for the interpretation of transient phenomena. The technique is demonstrated for the strain analysis of a pressure vessel by holographic interferometry (HI). The contribution to suitable noise elimination is also described.     

Lossless and lossy image compression using boolean function minimization

A novel approach for lossless as well as lossy compression of monochrome images using Boolean minimization is proposed. The image is split into bit planes. Each bit plane is divided into windows or blocks of variable size. Each block is transformed into a Boolean switching function in cubical form, treating the pixel values as output of the function. Compression is performed by minimizing these switching functions using ESPRESSO, a cube based two level function minimizer. The minimized cubes are encoded using a code set which satisfies the prefix property. Our technique of lossless compression involves linear prediction as a preprocessing step and has compression ratio comparable to that of JPEG lossless compression technique. Our lossy compression technique involves reducing the number of bit planes as a preprocessing step which incurs minimal loss in the information of the image. The bit planes that remain after preprocessing are compressed using our lossless compression technique based on Boolean minimization. Qualitatively one cannot visually distinguish between the original image and the lossy image and the value of mean square error is kept low. For mean square error value close to that of JPEG lossy compression technique, our method gives better compression ratio. The compression scheme is relatively slower while the decompression time is comparable to that of JPEG.     

Direct extraction of phase gradients from Fourier-transform and phase-step fringe patterns

An approach to computing pixel-by-pixel gradients of optical phase directly from digitally encoded Fourier-transform or phase-stepped fringe patterns is described. This approach can be classified as a phase unwrapping but is really a sine-cosine demodulation technique that finds its roots in the differential cross-multiplier phase-demodulation technique commonly used by the optical fiber sensor community. This technique is algorithmically simple, does not rely on a computation of the arctangent, and therefore is not subject to some of the limitations of the standard phase-unwrapping methodologies. The proposed phase-gradient technique is demonstrated by the calculation of strain fields from moir6 interferometric fringe patterns.     

某电泵装配厂生产线的改善及方案的评价

以某企业电泵装配生产线为研究对象,分别采用价值分析技术、“一个流”技术以及工作研究技术分析了企业现有生产线中存在的问题,提出了以上3种改善技术各自的改善方案。为了比较3种技术对该企业生产线的改善效果,运用TOPSIS法和灰色关联度法对改善方案进行综合评价,得出了“一个流”技术对该企业生产线改进取得的效果最佳,其次为工作研究技术,最后为价值分析技术的结论。     

掩模移动技术中的边框效应及其应用

掩模移动技术是一种通过移动掩模调制曝光量的连续面形微光学制作技术,其工作的局限性在于该技术对所制元件的对称性要求高,因此限制了制作复杂面形的功能。本文从分析掩模移动过程中的边框效应入手,阐明了消除这一效应负面影响的办法,并利用它来降低掩模移动技术的对称性要求,在实验中制作出了面形复杂的连续浮雕微光学元件。     

Computation of energy release rate components by the use of near-tip stress and displacement distributions

A simple method, called the two-term parameter technique, is introduced for the computation of the energy release rate in specimens made of composite materials. A cracked lap shear specimen with a zero degree stacking sequence was employed. The mode II energy release rate, calculated by the two-term parameter technique, was compared with that determined by using the crack closure method. The results show that the two-term parameter technique is very comparable to the crack closure method and does not require exact information of the stress and displacement distributions at the crack tip to get the energy release rate. Moreover, it is shown that while the crack closure method depends on the crack extension size, the two-term parameter technique is less affected by it.     

基于幅值和相位解调分析的齿轮箱起动过程故障诊断

针对齿轮箱升降速过程中振动信号非平稳的特点,将阶次跟踪、角域平均和幅值、相位解调分析技术相结合,提出了基于幅值和相位解调分析的齿轮箱故障诊断方法.首先对齿轮箱升降速瞬态信号进行时域同步采样,再对时域信号进行等角度重采样,转化为角域平稳信号,然后对角域信号进行角域平均,以消除干扰噪声的影响,最后对角域平均信号进行幅值和相位解调分析,根据幅值和相位解调函数图,就可提取齿轮的故障特征.通过对齿轮齿根裂纹故障实验信号的分析,表明该方法能有效地诊断齿轮的裂纹故障.     

A New and Unique Analog-to-Digital Conversion Technique

The analog-to-digital conversion technique which is used in the more accurate digital voltmeters available today is either potentiometric or integrating in nature. Both of these techniques are described in some detail, and their advantages and limitations are pointed out. A new technique is described which combines these two techniques so that the benefits of both are retained while the limitations of each are reduced or eliminated. The new technique, called potentiometric integrating, lends itself to high reading rates (7/sec) with 10 ppm resolution. A resolution of 1 ppm can be achieved with a reading rate of 1/second. Both cases retain the basic accuracy of 0.005 percent of reading and immunity to superimposed noise. This new technique has many applications in both systems and laboratory environments.     

An eigenvector method for estimating item parameters of the dichotomous and polytomous Rasch models

The purpose of this paper is to describe a technique for obtaining item parameters of the Rasch model, a technique in which the item parameters are extracted from the eigenvector of a matrix derived from comparisons between pairs of items. The technique can be applied to both dichotomous and polytomous data. In application to a previously published data set, it is shown that the technique provides item parameter estimates comparable to those produced by joint maximum likelihood estimation, and for the most difficult items, the technique appears to produce superior estimates. This method has several advantages. It easily accommodates missing data, and makes transparent the basis for item parameter estimation in the presence of missing data. Furthermore, the method provides a link to other methods in the social sciences and, in particular, provides the framework for application of graph theory to the analysis of assessment networks. Finally, it exploits several characteristics that are unique to the Rasch model.     

Presenting the several-release-problem and its cluster-based solution accelartion

This paper presents a novel technique for improving the runtime of metaheuristic search optimisations. The technique was applied on a new practical problem: several-release-problem (SRP) that characterises the modern industry. Many modern products are replaced by their next version due to incessant R&D activity, resulting in a short marketable life length. There are numerous such examples including the automotive industry, electronic devices and software products. These intermediate releases enable organisations to maximise their value for a given investment. The challenge faced by the industry is to decide which features to include in which version. The paper proves that SRP is NP-hard, thus cannot be solved practically using analytical approaches. A near-optimal, simple technique for determining the feature content of all version releases of the planning horizon is presented. The innovative approach utilises techniques adopted from the clustering domain to enhance the optimisation. The clustering enables skipping significant amounts of unattractive zones of the space. Verification and validation of the proposed technique are presented. The paper compares different heuristics and the shows that embedding the suggested clustering into general methods, yields significantly shorter runtime, and improves the solution’s quality. The enhancement technique can be applied to other combinatorial problems and metaheuristics.     

Fabrication of organic nanocrystals for electronics and photonics

We have presented a simple technique for the fabrication of nanocrystals of organic molecules and polymers and have shown that it is possible, using the liquid-phase technique, to fabricate organic nanocrystals ranging in size from 10 nm to 1 μm by manipulating the preparative conditions. In particular, nanocrystals of poly(4-BCMU) ranging from 20 nm to 350 nm were prepared by controlling the preparation conditions. The main advantages of the liquid-phase technique are the practicality and suitability of the technique for a wide range of materials. The fabrication of organic nanocrystals, though at a very early stage, seems a promising approach for producing low-dimensional organic materials and, like inorganic nanocrystals, another important objective for future study would be to incorporate organic nanocrystals into a variety of inorganic and organic media. It is hoped that extensive work will be done on organic nanocrystals to evaluate their potential for electronics and photonics.     

Near band-edge field-dependent absorption coefficient and refractive index determined by photocurrent and transmittance measurements

A technique is proposed for the extraction of precise values of field-dependent absorption coefficient alpha and refractive index n from photocurrent and transmittance measurements of optical modulator structures. The technique uses approximate results of alpha and n extracted from a simplified device as the initial input into an iterative procedure that utilizes the consistency between alpha and n to obtain successively better estimates of these parameters. The technique was applied to results that were measured experimentally, and we verified the accuracy by using synthetic data. Errors caused by measurement inaccuracy are also investigated. It is shown that the absorption coefficient has a modest sensitivity whereas the refractive index is insensitive to these errors.     

Evaluation of infrared-reflection absorption spectroscopy measurement and locally weighted partial least-squares for rapid analysis of residual drug substances in cleaning processes

The usefulness of infrared-reflection absorption spectroscopy (IR-RAS) for the rapid measurement of residual drug substances without sampling was evaluated. In order to realize the highly accurate rapid measurement, locally weighted partial least-squares (LW-PLS) with a new weighting technique was developed. LW-PLS is an adaptive method that builds a calibration model on demand by using a database whenever prediction is required. By adding more weight to samples closer to a query, LW-PLS can achieve higher prediction accuracy than PLS. In this study, a new weighting technique is proposed to further improve the prediction accuracy of LW-PLS. The root-mean-square error of prediction (RMSEP) of the IR-RAS spectra analyzed by LW-PLS with the new weighting technique was compared with that analyzed by PLS and locally weighted regression (LWR). The RMSEP of LW-PLS with the proposed weighting technique was about 36% and 14% smaller than that of PLS and LWR, respectively, when ibuprofen was a residual drug substance. Similarly, LW-PLS with the weighting technique was about 39% and 24% better than PLS and LWR in RMSEP, respectively, when magnesium stearate was a residual excipient. The combination of IR-RAS and LW-PLS with the proposed weighting technique is a very useful rapid measurement technique of the residual drug substances.     

Sequential Application of Simplex Designs in Optimisation and Evolutionary Operation

A technique for empirical optimisation is presented in which a sequence of experimental designs each in the form of a regular or irregular simplex is used, each simplex having all vertices but one in common with the preceding simplex, and being completed by one new point. Reasons for the choice of design are outlined, and a formal procedure given. The performance of the technique in the presence and absence of error is studied and it is shown (a) that in the presence of error the rate of advance is inversely proportional to the error standard deviation, so that replication of observations is not beneficial, and (b) that the “efficiency” of the technique appears to increase in direct proportion to the number of factors investigated. It is also noted that, since the direction of movement from each simplex is dependent solely on the ranking of the observations, the technique may be used even in circumstances when a response cannot be quantitatively assessed. Attention is drawn to the ease with which second-order designs having the minimum number of experimental points may be derived from a regular simplex, and a fitting procedure which avoids a direct matrix inversion is suggested. In a brief appendix one or two new rotatable designs derivable from a simplex are noted.