温度对果糖含量近红外光谱检测模型传递的影响

以果糖溶液为研究对象,采用斜率/截距(S/B)算法,通过不同温度的果糖含量检测模型在两台不同厂家的傅里叶变换近红外光谱仪间的传递,讨论了样品温度变化对模型传递的影响.主、从仪器直接建模时,预测集的均方根偏差(RMSEP)均随温度升高呈增大的趋势,但整体变化不显著.直接预测时,预测集的RMSEP均大于0.86,效果不理想;采用S/B算法传递后,预测结果得到改善,主、从仪器相同温度光谱间的传递结果优于不同温度光谱间的传递,15℃、22℃和28℃时相同温度光谱间传递后的RMSEP分别为0.317、0.389和0.416,差异显著.实验结果表明,进行模型传递时,样品温度变化会对模型传递产生较大影响;保证样品温度一致下,选择合适温度有利于取得最佳传递效果.     

Open air calibration with temperature compensation of a luminescence quenching-based oxygen sensor for portable instrumentation

This report addresses the task of calibrating an optical sensor for oxygen determination. Detailed analyses of the functional dependences from our measurement system results have been carried out with the additional aim of temperature compensation. As a result, an empirical calibration function has been successfully derived for the luminescent quenching-based oxygen sensor included in a self-designed portable instrument. This function also compensates for the temperature influence on the quenching luminescence process in the range from 0 to 45 degrees C. Moreover, the calibration procedure is extremely simple because only a single standard is needed. In fact, the oxygen measurement system can be calibrated with exposure to an open air atmosphere, and therefore, neither laboratory standards nor trained personnel are required. The method has been applied to a set of 11 units of the mentioned sensor (up to 24% oxygen concentration) giving an overall deviation between our calibrated system results and the laboratory standards of 0.3% oxygen concentration (calculated with 95% confidence level). The proposed calibration function has shown itself to be applicable for different sensing film thicknesses and luminophore concentrations using the same fittings parameter. Additionally, this function has been successfully applied to other oxygen dyes. Good agreement has also been found when the performance of the instrument was compared to a commercially available portable instrument based on an electrochemical sensor. We believe that this work could be an interesting finding for spreading the use of optical sensors for atmospheric oxygen determination in commercial measurement equipment for different purposes in confined working atmospheres, such as mines, undergrounds, warehouses, vehicles, and ships.     

星敏感器参数标定及误差补偿

针对CCD星敏感器光学系统存在焦距不准确、CCD平面倾斜和旋转及光学镜头畸变等误差因素,在理想针孔模型的基础上,用几何方法建立了星敏感器模型。利用地面实验数据,以最小二乘法解算该数学模型,求出焦距、CCD平面倾斜和旋转因子及畸变因子等待标定参数。将标定出的参数代回数学模型,便可由星象点测量坐标直接计算并修正入射光方向矢量,从而对光学系统的误差进行了补偿。计算结果表明:星对角距统计偏差由标定前41″降到了17″,提高了计算精度。     

A protocol for the calibration of gamma cameras to estimate internal contamination in emergency situations

The concern about accidents involving radioactive materials has led to the search of alternative methods to quickly identify and quantify radionuclides in workers and in the population. One of the options to face up an eventual demand for mass monitoring of internal contamination is the use of a nuclear medicine diagnostic equipment known as gamma camera, a device used to scan patients who have been administered specific amounts of radioactive materials for medical purposes. Although the gamma camera is used for image diagnosis, it can be calibrated with anthropomorphic phantoms or point sources for the quantification of radionuclide activities in the human body. This work presents a protocol for the calibration of gamma cameras for such application. In order to evaluate the suitability of this type of equipment, a gamma camera available in a public hospital located in Rio de Janeiro was calibrated for the in vivo measurement of 131I. The calibration includes the determination of detection efficiencies and minimum detectable activities for each radionuclide. The results show that the gamma camera presents enough sensitivity to detect activity levels corresponding to effective doses below 1 mSv. The protocol is the basis to establish a network of Nuclear Medicine Centres, located in public hospitals in eight countries of Latin America (Argentina, Brazil, Colombia, Cuba, Chile, Mexico, Peru and Uruguay) and in Spain that could be requested to collaborate in remediation actions in the event of an accident involving incorporation of radioactive materials. This protocol is one of the most significant outputs of the IAEA-ARCAL Project (RLA/9/049-LXXVIII) aimed to the Harmonization of Internal Dosimetry Procedures.     

New methodology to obtain a calibration model for noninvasive near-infrared blood glucose monitoring

This paper reports new methodology to obtain a calibration model for noninvasive blood glucose monitoring using diffuse reflectance near-infrared (NIR) spectroscopy. Conventional studies of noninvasive blood glucose monitoring with NIR spectroscopy use a calibration model developed by in vivo experimental data sets. In order to create a calibration model, we have used a numerical simulation of light propagation in skin tissue to obtain simulated NIR diffuse reflectance spectra. The numerical simulation method enables us to design parameters affecting the prediction of blood glucose levels and their variation ranges for a data set to create a calibration model using multivariate analysis without any in vivo experiments in advance. By designing the parameters and their variation ranges appropriately, we can prevent a calibration model from chance temporal correlations that are often observed in conventional studies using NIR spectroscopy. The calibration model (regression coefficient vector) obtained by the numerical simulation has a characteristic positive peak at the wavelength around 1600 nm. This characteristic feature of the regression coefficient vector is very similar to those obtained by our previous in vitro and in vivo experimental studies. This positive peak at around 1600 nm also corresponds to the characteristic absorption band of glucose. The present study has reinforced that the characteristic absorbance of glucose at around 1600 nm is useful to predict the blood glucose level by diffuse reflectance NIR spectroscopy. We have validated this new calibration methodology using in vivo experiments. As a result, we obtained a coefficient of determination, r2, of 0.87 and a standard error of prediction (SEP) of 12.3 mg/dL between the predicted blood glucose levels and the reference blood glucose levels for all the experiments we have conducted. These results of in vivo experiments indicate that if the parameters and their vibration ranges are appropriately taken into account in a numerical simulation, the new calibration methodology provides us with a very good calibration model that can predict blood glucose levels with small errors without conducting any experiments in advance to create a calibration model for each individual patient. This new calibration methodology using numerical simulation has promising potential for NIR spectroscopy, especially for noninvasive blood glucose monitoring.     

Spectrally constrained chromophore and scattering near-infrared tomography provides quantitative and robust reconstruction

A multispectral direct chromophore and scattering reconstruction technique has been implemented for near-infrared frequency-domain tomography in recovering images of total hemoglobin, oxygen saturation, water, and scatter parameters. The method applies the spectral constraint of the chromophores and scattering spectra directly in the reconstruction algorithm, thereby reducing the parameter space of the inversion process. This new method was validated by use of simulated and experimental data, and results show better robustness and stability in the presence of higher levels of noise. The method suppresses artifacts, especially those significant in water and scatter power images, and reduces cross talk between chromophore and scatter parameters. Variation in scattering was followed by this spectral approach successfully in experimental data from 90-mm-diameter cylindrical phantoms, and results show linear variation in scatter amplitude and reduced scattering coefficient (micro(s)'), with total hemoglobin, oxygen saturation, and water remaining constant and quantitatively accurate. Similar experiments were carried out for varying oxygen saturation and total hemoglobin. Accurate quantification was obtained with a mean error of 7.7% for oxygen saturation and 6.2% for total hemoglobin, with minimal cross talk between different parameters.     

Low-cost high-sensitivity strain and temperature sensing using graded-index multimode fibers

We report a low-loss, low-cost high-sensitivity all-fiber strain and temperature sensor based on mode interference in graded-index multimode fibers. Blueshifts with strain and temperature sensitivities of 18.6 pm/microstrain and 58.5 pm/ degrees C have been observed. Experimental results show that smaller core diameter graded-index fibers display greater strain-induced peak wavelength shifts than larger core diameter fibers.     

Dynamic temperature model and dynamic temperature compensation ofcrystal oscillators

In temperature-compensated crystal oscillators (TCXO), the compensating action is commonly estimated as a function of one variable-environmental temperature, At the same time, experimental data show that TCXO frequency stability is also dependent on the dynamics of the temperature process. The greater the temperature variation, the more pronounced Is the loss of temperature compensation. In this paper, the origins of this phenomenon are analyzed, and a method for reducing its effects is presented. A new approach is suggested according to which the compensating action is formed as a function of two variables: the temperature and the rate of its variation. A theoretical basis for this method is given. A functional model of the devices performing the dynamic temperature compensation is suggested. Experimental investigations of a TCXO with a microprocessor-based dynamic temperature compensation system confirmed the possibility of TCXO frequency stability improvement in nonstationary thermal conditions. In a system using an AT cut resonator and a separate Y-cut thermosensor, the application of dynamic temperature compensation resulted in an order of magnitude improvement as compared to conventional digital temperature compensation procedures. Even with dual-mode SC-cut resonators, the application of dynamic temperature compensation is shown to be useful     

Bayesian and regression approaches to on-line prediction of residual tool life

In this paper, two statistical approaches to on-line prediction of cutting tool life are presented and discussed. A Bayesian approach utilizes in-process information about the cutting tool state and constitutes a valuable basis for improved prediction. A second approach is based on the cutting forces and facilitates a prediction of the tool life with an uncertainty of 15% after 1.5–2.0 cutting minutes. Traditional tool condition monitoring can be improved by increased reliability of tool life predictions, increased utilization of the cutting tools together with reduced need for pre-process data and calibrating procedures. © 1998 John Wiley & Sons, Ltd.     

Nondestructive determination of solids and carotenoids in tomato products by near-infrared spectroscopy and multivariate calibration

Tomato is an important player in the agricultural market. It is the second most consumed vegetable in the world and is a source of important micronutrients such as lycopene and beta-carotene. Recent research has demonstrated that these carotenoids can act as free-radical quenchers in the body and prevent aging, tissue damage, heart disease, and certain cancers. Besides these microcomponents, tomato is composed of soluble and insoluble solids. In industry, these solids govern factory yield and play a major role in the tomato trade. Nowadays, standard methods for determining tomato solids and carotenoids are time and labor consuming. In this work, we present the development of a simultaneous and nondestructive method for determining total and soluble solids, as well as lycopene and beta-carotene, in tomato products by near-infrared spectroscopy. PLS-1 was the calibration technique chosen. For spectra preprocessing, MSC and second derivative were applied. As variable selection techniques, the correlogram cutoff, the successive projections algorithm, the dimension wise selection, and spectra splitting approach were applied. Best models presented satisfactory prediction abilities evaluated through its RMSEP and r values: total solids 0.4157, 0.9998; soluble solids 0.6333, 0.9996; lycopene 21.5779, 0.9996; beta-carotene 0.7296, 0.9981.     

Sandia Fracture Challenge: blind prediction and full calibration to enhance fracture predictability

The Impact and Crashworthiness Lab at Massachusetts Institute of Technology participated in the Sandia Fracture Challenge and predicted the crack initiation and propagation path during a tensile test of a compact tension specimen with three holes (B, C, and D), using a very limited number of material properties, including uniaxial tensile tests of a dog-bone specimen. The maximum shear stress and modified Mohr–Coulomb fracture models were used. The predicted crack path of A–C–E coincided with two out of thirteen experiments performed by Sandia National Laboratories, and the maximum load, as well as the load level at the first and second crack initiation, was accurately captured. However, the crack-tip opening displacements (CODs) corresponding to the initiation of the two cracks were overestimated by 12 and 24 %, respectively. After the challenge ended, we received the leftover material from Sandia and did full plasticity and fracture calibration by conducting extra fracture tests, including tensile tests, on a specimen with two symmetric round notches, a specimen with a central hole, and a butterfly specimen with double curvature. In addition, pure shear tests were carried out on a butterfly specimen. Newly identified fracture parameters again predicted the A–C–E crack path, but the force–COD response could be reproduced almost perfectly. Detailed calibration procedures and validation are discussed. Furthermore, in order to investigate the influence of the machining quality on the results, a pre-damage value was introduced to the first layer of finite elements around the starter notch, A, and the three holes, B, C, and D. This accelerated shear localization between holes A and D (and between D and C as well) and changed the crack path to A–D–C–E. Parametric study on the pre-damage value showed that there exist two competing crack paths, and the corresponding force–COD curve is influenced by the pre-damage value. The effect of mesh size and boundary conditions are also discussed.     

A comparison of stochastic programming and bi-objective optimisation approaches to robust airline crew scheduling

A prominent problem in airline crew scheduling is the pairings or Tour-of-Duty planning problem. The objective is to determine a set of pairings (or Tours-of-Duty) for a crew group to minimise the planned cost of operating a schedule of flights. However, due to unforeseen events the performance in operation can differ considerably from planning, sometimes causing significant additional recovery costs. In recent years there has been a growing interest in robust crew scheduling. Here, the aim is to find solutions that are “cheap” in terms of planned cost as well as being robust, meaning that they are less likely to be disrupted in case of delays. Taking the stochastic nature of delays into account, Yen and Birge (Transp Sci 40:3–14, 2006) formulate the problem as a two-stage stochastic integer programme and develop an algorithm to solve this problem. Based on the contradictory nature of the goals, Ehrgott and Ryan (J Multi-Criteria Decis Anal 11:139–150, 2002) formulate a bi-objective set partitioning model and employ elastic constraint scalarisation to enable the solution by set partitioning algorithms commercially used in crew scheduling software. In this study, we compare the two solution approaches. We improve the algorithm of Yen and Birge (Transp Sci 40:3–14, 2006) and implement both methods with a commercial crew scheduling software. The results of both methods are compared with respect to characteristics of robust solutions, such as the number of aircraft changes for crew. We also conduct experiments to simulate the performance of the obtained solutions. All experiments are performed using actual schedule data from Air New Zealand.     

Prediction of ethylene content in melt-state random and block polypropylene by near-infrared spectroscopy and chemometrics: influence of a change in sample temperature and its compensation method

This paper reports on the influence of a change in sample temperature, and a method for its compensation, for the prediction of ethylene (C2) content in melt-state random polypropylene (RPP) and block polypropylene (BPP) by near-infrared (NIR) spectroscopy and chemometrics. Near-infrared (NIR) spectra of RPP in the melt and solid states were measured by a Fourier transform near-infrared (FT-NIR) on-line monitoring system and an FT-NIR laboratory system. There are some significant differences between the solid and melt-state RPP spectra. Moreover, we investigated the predicted values of the C2 content from the RPP or BPP spectra measured at 190 degrees C and 250 degrees C using the calibration model for the C2 content developed using the RPP or BPP spectra measured at 230 degrees C. The errors in the predicted values of the C2 content depend on the pretreatment methods for each calibration model. It was found that multiplicative signal correction (MSC) is very effective in compensating for the influence of the change of temperature for the RPP or BPP samples on the predicted C2 content. From the suggestion of principal component analysis (PCA) and difference spectrum analysis, we propose a new compensation method for the temperature change that uses the difference spectra between two spectra sets measured at different temperatures. We achieved good results using the difference spectra between the RPP/BPP spectra sets measured at 190 degrees C and 250 degrees C after correction and the calibration model developed with the spectra measured at 230 degrees C. The comparison between the method using MSC and the proposed method showed that the predicted error in the latter is slightly better than those in the former.     

Two approaches to the continuous-radiation field calibration of a hydrophone in a nonanechoic water tank

A comparative analysis is carried out of a time-delay spectrometry method and a proposed method for the sliding complex weighted averaging of the frequency dependence of the transfer impedance of a radiator and receiver, which provide different approaches to the free-field continuous-radiation calibration of hydrophones in a nonanechoic water tank. The advantages of the second method are demonstrated.     

工业机器人校准技术与补偿方法发展现状及趋势

工业机器人因具有自动化程度高、定位精度好等优势,已成为我国工业智能化的攻关方向之一,并将逐步替代人工,在智能制造领域发挥不可替代的作用.在使用过程中,造成工业机器人准确度下降的因素众多,将直接影响其在叶片研磨、高精度钻铆等高精尖领域中的应用.文章在总结工业机器人通用校准模型的基础上,分析了工业机器人校准技术与误差补偿方...     

温度综合自动检定校测系统

本文主要介绍温度自动检定校准系统的基本组成，功能和基本原理特点。提出的综合自动检定系统的特点是二等标准水银温度计与工业用热电偶热电阻温度计的检定装置合二为一，一套测量系统可面对多个恒温场输送过来的信号进行测试，体现信息时代特征的高科技产品开发方向。一机多用和计管合一是自动检定系统的核心思路。     

Variations in predicted values from near-infrared spectra of samples in vials by using a calibration model developed from spectra of samples in vials: causes of the variations and compensation methods

The causes and compensation methods of variations in the predicted values from near-infrared (NIR) spectra of samples in vials by using a calibration model developed from spectra of samples in vials were studied. From the viewpoint of the path length and the peak height of spectra in the NIR region, vials with 1 mL volume (external diameter: 8 mm, inside diameter: about 6 mm, length: 40 mm) were selected as disposable vials for the samples. To investigate the causes of the variations in the predicted values, the optical path lengths and transmittance spectra of empty vials in five lots produced during the last four years were examined. The results showed that there were some differences in the path lengths of the vials and in the intensities of peaks near 7130 and 4515 cm-1, which were attributed to the hydroxyl groups in the spectra of the vials among the five lots. The calibration models for the concentration of isopropyl alcohol (IPA) in toluene contained in vials of the same lot were developed. To search the pretreatment methods for the best calibration model with small variations in the predictive values of the samples in the vials, six kinds of pretreatments (no pretreatment, baseline correction, first derivative, second derivative, multiplicative scattering correction (MSC), and standard normal variate (SNV)) were compared. The results indicated that MSC is a very effective method with small variation in the predicted values from the spectra of samples in vials. It was found that the variations in the predicted values are caused mainly by variations in the path lengths of vials. In real quality control, the NIR-chemometrics method is requested for long-term traceability and good reproducibility of the predictive value. Therefore, it is crucial to watch changes in the path length under a fixed path length as a reference. From this standpoint, modified MSC, which uses a particular spectrum as a reference instead of the average spectrum of a sample set, was proposed in the present study, and it was demonstrated that the variations due to the individual differences in the vials can not only be compensated, but the path lengths of vials could also be estimated by the modified MSC. Moreover, a calibration model for the toluene concentration in silicone oil was developed to confirm the effects of modified MSC by using another sample set. The results showed that the compensation of vial path lengths using the modified MSC is also useful for other samples, similar to the case of the sample of IPA in toluene.     

Resequencing orders on mixed-model assembly lines: Heuristic approaches to minimise the number of overload situations

In production systems that are based on mixed-model assembly lines, the product sequence has a crucial impact on the load distribution of the workstations, which constitutes one of the main cost drivers. Due to disturbances that occur during the production process, the carefully planned production sequence often cannot be performed as intended because certain orders are blocked and must be resequenced later. In this paper, we consider a realistic resequencing setting of a mixed-model assembly line in the automotive industry. A basic mixed-integer programming model is presented and extended to consider multi-station workplaces and to prevent the premature deployment of utility workers. We devise and evaluate several local search procedures that combine ideas from simulated annealing, variable neighbourhood search and tabu search. We demonstrate that the best procedure produces optimal or near-optimal results for small and medium-sized problem instances quickly and outperforms the other heuristics on large test instances.     

机载热电偶冷端补偿及校准方法研究

某型直升机试飞测试改装工作因飞机结构特殊性而改进,导致采用常规热电偶校准方法无法实现校准过程的冷端补偿。针对这一问题,该文通过对热电偶测温原理及PT100冷端补偿方法进行研究,提出一种新的热电偶测温校准方法。为验证该方法在飞行试验数据测试工作中的准确性及实用性,在该型试验机新旧改装方法基础上分别采用传统方法与新方法对机载热电偶测试通道进行校准。结果对比表明:两种方法所得校准曲线基本一致,相同参数最大偏差与量程比值小于0.1%。新校准方法准确可靠,满足飞行试验测试数据误差要求,可为机载热电偶参数校准提供新思路。     

Method of temperature error compensation in strain transducers

A method of compensation for the temperature error of semiconductor bridge strain transducers is described. It is based on the use of a strain gage bridge as the temperature-sensitive element and controllable source of current for supply to the bridge. The supply current is regulated to compensate for variation in temperature sensitivity in relation to bridge resistance by means of positive feedback while a correcting voltage proportional to the temperature is formed for correcting zero drift. The method facilitates the temperature error of strain transducers to be reduced up to 0.5% at 70–80°C.Translated from Izmeritel'naya Tekhnika, No. 7, pp. 39–40, July, 1993.