Task-based optimization and performance assessment in optical coherence imaging

Optimization of an optical coherence imaging (OCI) system on the basis of task performance is a challenging undertaking. We present a mathematical framework based on task performance that uses statistical decision theory for the optimization and assessment of such a system. Specifically, we apply the framework to a relatively simple OCI system combined with a specimen model for a detection task and a resolution task. We consider three theoretical Gaussian sources of coherence lengths of 2, 20, and 40 microm. For each of these coherence lengths we establish a benchmark performance that specifies the smallest change in index of refraction that can be detected by the system. We also quantify the dependence of the resolution performance on the specimen model being imaged.     

Design of Dyson imaging spectrometers based on the Rowland circle concept

We aim to show that Dyson imaging spectrometers can be easily designed by applying the concept of the Rowland circle to refracting surfaces. This allows us to conceive an analytical procedure that is based on the removal of astigmatism at two wavelengths. Following this procedure, high-optical-quality spectrometers can be designed even for high speeds. Root-mean-square spot radii less than 2.5 μm are obtained for speeds as high as f/1.5, slit lengths of 15 mm, and wavelength ranges of 0.4-1.7 μm. Design examples are presented for classical Dyson spectrometers in which the detector is glued to the glass plane surface and for spectrometers with an air gap between this surface and the image plane.     

消声室声学性能评价方法探讨

消声室和半消声室声学性能评价是通过比较室内的声源空间衰减的声压级与满足反平方律声压级的差值来确定的.在运用JJF 1147-2006《消声室和半消声室声学特性校准规范》时却出现了理论曲线与测量值呈现出“远端对齐”不合理现象,导致评估困难甚至无法评估.通过实验数据分析,发现JJF 1147-2006选择声压倒数标准偏差为最小二乘法判断依据是导致出现不合理现象的根本原因,并由此提出两个改进评价方法.     

Survey on performance assessment of cardiac angiography systems

Advances in imaging technology have facilitated the development of increasingly complex interventional cardiac equipment. Consequently, there is a need for definitive equipment requirements. The aim of the study is to assess the performances of different cardiac angiographic systems. A questionnaire was sent to centres participating in SENTINEL Project to collect dosimetry data (typical entrance dose rate in fluoroscopy and imaging mode), image quality evaluations (low and high contrast resolutions) and KAP calibration factors. Results from this survey could contribute to the explanation of patient dose variability in angiographic cardiac procedures and to derive reference levels for cardiac angiographic equipment performance parameters.     

Blue spot on the parhelic circle

We develop a theory for a new effect on the parhelic circle. We show that there is a colored segment on the parhelic circle at a certain large azimuth that depends on solar elevation. The color segment appears at solar elevations below 32 degrees and is explained as a transition between total and partial internal reflection in the main ray paths of the parhelic circle in oriented ice crystals. Based on our simple refraction theory and computer simulations, we find that the color of the segment is mainly green and blue. The theory is tested with available photographs of the effect.     

The effect of visual perception on the required performance of imaging systems

Abstract

Current performance measures for infrared imagers are applicable to linear mechanically scanned systems but not to those with focal plane arrays of detector elements, because these are nonlinear due to aliasing. The performance of an imager affects the ability of an observer to perform perception tasks using it. Psychophysical trials have been undertaken in an attempt to identify more appropriate performance measures. Simple shapes degraded by various degrees of Gaussian blurring and pixelation were selected at random and displayed on a computer monitor. A correlation has been found between the probability of recognition of an image and a quantity called ‘recognition contrast’ (C _R). This is related to the shape observed and a template of the equivalently degraded alternative shape most similar to it. This quantity C _R was refined following trials in which spatial noise was added to Gaussian blurred images. C _R is calculated from information about each of the two images and is directly proportional to the sensitivity index d' obtained from probability measurements. The results described are believed to have a wide range of applications such as in defining image quality and performance measures for imaging equipment.     

An empirical assessment of the influence of quality dimensions on organizational performance

While there are several conceptual models to suggest that there exists an association between quality dimensions (customer satisfaction, employee satisfaction, employee service quality) and organizational performance, no empirical study to date has verified such claims. This paper extends the literature by collecting hard data from 165 practising managers and testing their perceptions of the association among various quality dimensions and several organizational performance measures. The relationships between these quality dimensions and the nine component items that make up organizational performance were also investigated for both manufacturing and service firms. The data were grouped into four typologies to include type of firm, size, age, and presence of formal quality department. Multiple discriminant analysis was conducted to differentiate the typology of firms in a multivariate setting. Our results indicate that practising managers in manufacturing firms tend to perceive more widely a positive correlation between quality dimensions and the component items of organizational performance than managers in service firms. Also, managers from older manufacturing firms tend not to perceive a relationship between employee service quality and five component items of organizational performance such as competitiveness and market share.

The measures used for the three quality dimensions and organizational performance are shown to be valid and reliable. However, information derived from the study shows that practising managers in the service sector do not perceive some of the claims and expected benefits of quality management activities.     

Environmental performance assessment of manufacturing sectors

Clean Technologies and Environmental Policy - This study addresses to rank the environmental performance of manufacturing sectors using Preference Ranking Organization Method for Enrichment...     

绩效考核的两种创新方法

绩效考核作为企业人力资源管理最重要和核心的环节。从员工角度来说,绩效考核直接决定了其绩效薪酬的评定,间接影响到其晋升、调动及自身职业发展;从企业角度来说,绩效考核让企业了解每一位员工优劣势,从而制定不同的职业培养计划,同时为人力资源储备提供了关键依据。但     

National-scale research performance assessment at the individual level

There is an evident and rapid trend towards the adoption of evaluation exercises for national research systems for purposes, among others, of improving allocative efficiency in public funding of individual institutions. However the desired macroeconomic aims could be compromised if internal redistribution of government resources within each research institution does not follow a consistent logic: the intended effects of national evaluation systems can result only if a ??funds for quality?? rule is followed at all levels of decision-making. The objective of this study is to propose a bibliometric methodology for: (i) large-scale comparative evaluation of research performance by individual scientists, research groups and departments within research institution, to inform selective funding allocations; and (ii) assessment of strengths and weaknesses by field of research, to inform strategic planning and control. The proposed methodology has been applied to the hard science disciplines of the Italian university research system for the period 2004?C2006.     

A new time-domain narrowband velocity estimation technique for Doppler ultrasound flow imaging. II. Comparative performance assessment

For pt.I see ibid., vol.45, no.4, pp.939-54 (1998). The statistical performance of the new 2-D narrowband time-domain root-MUSIC blood velocity estimator described previously is evaluated using both simulated and flow phantom wideband (50% fractional bandwidth) ultrasonic data. Comparisons are made with the standard 1-D Kasai estimator and two other wideband strategies: the time domain correlator and the wideband point maximum likelihood estimator. A special case of the root-MUSIC, the "spatial" Kasai, is also considered. Simulation and flow phantom results indicate that the root-MUSIC blood velocity estimator displays a superior ability to reconstruct spatial blood velocity information under a wide range of operating conditions. The root-MUSIC mode velocity estimator can be extended to effectively remove the clutter component from the sample volume data. A bimodal velocity estimator is formed by processing the signal subspace spanned by the eigenvectors corresponding to the two largest eigenvalues of the Doppler correlation matrix. To test this scheme, in vivo common carotid flow complex Doppler data was obtained from a commercially available color flow imaging system. Velocity estimates were made using a reduced form of this data corresponding to higher frame rates. The extended root-MUSIC approach was found to produce superior results when compared to both 1- and 2-D Kasai-type estimators that used initialized clutter filters. The results obtained using simulated, flow phantom, and in vivo data suggest that increased sensitivity as well as effective clutter suppression can be achieved using the root-MUSIC technique, and this may be particularly important for wideband high frame rate imaging applications.     

Optimal planning of structural performance monitoring based on reliability importance assessment

Recently, the effective use of information from structural health monitoring (SHM) has been considered as a significant tool for rational maintenance planning of deteriorating structures. Since a realistic maintenance plan for civil infrastructure has to include uncertainty, reliable information from SHM should be used systematically. Continuous monitoring over a long-term period can increase the reliability of the assessment and prediction of structural performance. However, due to limited financial resources, cost-effective SHM should be considered. This paper provides an approach for cost-effective monitoring planning of a structural system, based on a time-dependent normalized reliability importance factor (NRIF) of structural components. The reliability of the system and the NRIFs of individual components are assessed and predicted based on monitored data. The total monitoring cost for the structural system is allocated to individual components according to the NRIF. These allocated monitoring costs of individual components are used in Pareto optimization to determine the monitoring schedules (i.e., monitoring duration and prediction duration).     

Channelized Hotelling observers for the assessment of volumetric imaging data sets

Current clinical practice is rapidly moving in the direction of volumetric imaging. For two-dimensional (2D) images, task-based medical image quality is often assessed using numerical model observers. For three-dimensional (3D) images, however, these models have been little explored so far. In this work, first, two novel designs of a multislice channelized Hotelling observer (CHO) are proposed for the task of detecting 3D signals in 3D images. The novel designs are then compared and evaluated in a simulation study with five different CHO designs: a single-slice model, three multislice models, and a volumetric model. Four different random background statistics are considered, both gaussian (noncorrelated and correlated gaussian noise) and non-gaussian (lumpy and clustered lumpy backgrounds). Overall, the results show that the volumetric model outperforms the others, while the disparity between the models decreases for greater complexity of the detection task. Among the multislice models, the second proposed CHO could most closely approach the volumetric model, whereas the first new CHO seems to be least affected by the number of training samples.     

Designs for high performance PAL-based imaging systems

In this study, we investigate methods to optimize the design of a panoramic annular lens (PAL) system. The design details of a PAL surveillance system, an anamorphic PAL surveillance system, a phone camera with a PAL attachment, and a PAL endoscope system are described. All these designs are optimized using a standard optical software package (Zemax). The results combine very good image quality with a modulation transfer function above 0.3, which is within the cutoff frequency of sensor chips.     

Optical performance at the thermodynamic limit with tailored imaging designs

Ultracompact concentrators and illuminators that approach the thermodynamic limit to optical performance can be realized with purely imaging strategies. We explore two-stage reflector systems where each optical surface is tailored to eliminate one order of aberration--the so-called aplanatic designs. The contours are monotonic functions that can be expressed analytically, which are important for the facilitation of optimization studies and practical fabrication. The radiative performance of the devices presented is competitive with, and even superior to, that of high-flux nonimaging systems. Sample results of practical value in solar concentration and light collimation are presented for systems that cover a wide range of numerical aperture.     

Dosimetric performance requirements for the routine dose assessment of external radiation

Dosimetric performance requirements must take the following into consideration: general radiation protection requirements established by the International Commission on Radiological Protection (ICRP), workplace conditions prevailing during (routine) work, and technical requirements set by international or national bodies. For performance tests the general requirements on the precision of dose measurements can be represented by the 'trumpet curves'. For photon radiation several measurements of the workplace conditions are reported. The main conclusions drawn from these measurements are the following: the photon energy range from 20 keV to 2 MeV, or even 7 MeV, is of importance for individual monitoring. The range of directions of radiation incidence on the dosemeter is very large, nearly the frontal hemisphere or even rotating, and almost all spectra are broad with respect to energy. In view of the great variety of workplace conditions, the scope of most of the technical requirements is not sufficiently great. No technical requirement is at present fully in accordance with the general principles of an uncertainty analysis.     

Regulatory basis for the Waste Isolation Pilot Plant performance assessment

The Waste Isolation Pilot Plant (WIPP) is the first operational repository designed for the safe disposal of transuranic (TRU) radioactive waste from the defense programs of the US Department of Energy (DOE). The US Environmental Protection Agency (EPA) is responsible for certifications and regulation of the WIPP facility for the radioactive components of the waste. The EPA has promulgated general radioactive waste disposal standards at 40 CFR Part 191, and WIPP-specific criteria to implement and interpret the generic disposal standards at 40 CFR Part 194. In October 1996, the DOE submitted its Compliance Certification Application (CCA) to the EPA to demonstrate compliance with the disposal standards at Subparts B and C of 40 CFR Part 191. This paper summarizes the development of the overall legal framework for radioactive waste disposal at the WIPP, the parallel development of the WIPP performance assessment (PA), and how the EPA disposal standards and implementing criteria formed the basis for the CCA WIPP PA. The CCA resulted in a certification in May 1998 by the EPA of the WIPP's compliance with the EPA's disposal standard, thus enabling the WIPP to begin radioactive waste disposal.     

Code performance assessment: application to the pull-out strength of concrete

This paper deals with the investigation into the best fitted program for solving a particular problem. We present a general method to assess the efficiency of a code in the general context where both experimental results (due to problems of experimental reproducibility and/or sample size) and theoretical results (predicted by the computer code) are uncertain. This method is based on the use of fuzzy sets to represent partial results and on a method to aggregate them into a global confidence degree. This method is applied to the problem of the pulling steel plugs out of a block of concrete or masonry, the code being based on limit analysis theory.