球镜片的顶焦度的测量不确定度评定

球镜片的顶焦度检定是通过一级焦度计直接测量来实现的，检定时，将被检球镜片放在焦度计的镜片支座上，移动被检球镜片，使球镜片的光学中心与仪器十字中心重合，并使棱镜度为零或最小，此时的读数即为被检球镜片的球镜度。文章以分度值0.01D的一级焦度计对球镜片的顶焦度进行检定，分析其测量不确定度。     

球镜片的顶焦度的测量不确定度评定

球镜片的顶焦度检定是通过一级焦度计直接测量来实现的,检定时,将被检球镜片放在焦度计的镜片支座上,移动被检球镜片,使球镜片的光学中心与仪器十字中心重合,并使棱镜度为零或最小,此时的读数即为被检球镜片的球镜度.文章以分度值0.01D的一级焦度计对球镜片的项焦度进行检定,分析其测量不确定度.     

验光镜片检定方法的改进

在验光镜片组中，球镜片、柱镜片和棱镜片是最主要、最常用、并且数量最多的三种镜片。本文对《验光镜片组》（JJG579－88）检定规程中，这三种镜片的检定方法提出改进。一、球镜片检定方法的改进按照检定规程规定，球镜片有二项技术要求，即顶焦度偏差和光学中心位移。顶焦度偏差的检定是用焦度计在被检球镜片的光学中心处测得，光学中心位移的检定是用直尺测定被检球镜片的镜圈几何中心，再测得其镜圈几何中心与光学中心之间的距离，即为光学中心位移。现改为用焦度计在被检球镜片的镜圈几何中心处同时测得顶焦度偏差和光学中心位移。具…     

焦度计的检定与操作

一、焦度计的定义焦度计是用于测量眼镜和接触镜的顶焦度及棱镜度，确定未切边镜片的方位并打印标记，以及检查镜片是否正确安装在镜框中的仪器。定义里涉及￥1．的“顶焦度”其实应叫后顶焦度，它是以米为单位测得的近轴后顶焦距的倒数，表示单位为m‘，单位名称为屈光度，以D表示，习惯上称之为顶焦度。顶焦度是镜片的重要参数之一，它有球镜顶焦度和柱镜顶焦度之分。球镜顶焦度即我们常讲的近（远）视度数，柱镜顶焦度与球镜顶焦度的差值即常讲的散光变数。球镜的光学参数有球镜顶焦度、光学中心；柱菇的光学参数有柱镜顶焦度、柱镜轴位…     

焦度计的常见故障与维修

焦度计主要用于测量眼镜镜片(包括角膜接触镜片)的顶焦度(D)、棱镜度(△)，确定散光镜片的轴位方向，在未切边镜片上打印标记，并检查镜片是否正确安装在镜框中等。焦度计又称屈光度计、查片机、镜片测度仪等。焦度计的使用频率较高，在使用过程中容易出现一些故障，下面是焦度计的常见故障与简单的维修方法。     

焦度计的正确使用方法

焦度计是配装眼镜主要的检测设备，用于测量眼镜片的顶焦度，确定散光镜片的柱镜轴位方向，以及在镜片的光学中心上打印记。操作人员操作有误或不规范，将直接影响测量的准确性，造成配镜不合格。正确使用焦度计，是配装合格眼镜的关键。     

《焦度计计量检定规程》改进建议

焦度计用于测量眼镜的顶焦度,确定散光轴向以及在眼镜镜片上打印印记。按显示方式,分为连续显示     

学标准买太阳镜

QB2457-1999《太阳镜》是1999年10月14日发布,2000年9月1日实施的,该标准是参照美国标准ANSIZ80.3制定的。标准中的主要技术指标有:顶焦度偏差太阳镜的标称顶焦度值应为0.00D,镜片制造时的偏差或镜片与镜架的装配不符,都有可能产生顶焦度的偏差(即带有或正或负的顶焦度),若超出一定范围,则配戴者可能会感到视物变形,严重的则会影响配戴者的视力健康。对应于GB10810《眼镜镜片》国家标准要求,其球镜顶焦度允差为±0.08D,柱镜顶焦度允差为±0.06D。棱镜度太阳镜的棱镜度应为0.00Δ。若镜片具有棱镜度,则会产生视物移焦,若超过标准允许的…     

话说太阳镜产品标准

QB2457-1999《太阳镜》是1999年10月14日发布,2000年9月1日实施的国家强制性标准,该标准是参照美国标准ANSIZ80.3制定的。标准中的主要技术指标有:1.顶焦度偏差太阳镜的标称顶焦度值应为0.00D,镜片制造时的偏差或镜片与镜架的装配不符,都有可能产生顶焦度的偏差(即带有或正或负的顶焦度),若超出一定范围,则配戴者可能会感到视物变形,严重的则会影响配戴者的视力健康。对应于GB10810《眼镜镜片》国家标准(QB2457-1999《太阳镜》的引用标准,下同)要求,其球镜顶焦度允差为±0.08D;柱镜顶焦度允差为±0.06D。2.棱镜度太阳镜的棱镜度应为0.…     

老视镜和定配眼镜:多数标志不合格

<正>本次抽查共涉及山西省20家经销单位经销的20个批次的产品,检验不合格5个批次,不合格检出率25%。重点对老视镜的球镜顶焦度偏差(主子午面一、主子午面二)、柱镜顶焦度偏差、镜片材料和表面质量、可见光透射比、镜架外观质量、光学中心水平距离允差、光学中心单侧水平允差、光学中心垂直互差、两镜片     

An axiomatic approach to the measurement of accessibility

In this paper an axiomatic approach is developed for the task of measuring accessibility. The general mathematical form of a measure satisfying the postulated axioms is derived. This class of measure contains as a sub-class the so-called gravity potentials. A measure of the accessibility to employment opportunities is presented with applications to the Stockholm region. Finally some ideas on further development of accessibility measures are discussed.     

Coefficients of ergodicity for Markov chains with uncertain parameters

One of the central considerations in the theory of Markov chains is their convergence to an equilibrium. Coefficients of ergodicity provide an efficient method for such an analysis. Besides giving sufficient and sometimes necessary conditions for convergence, they additionally measure its rate. In this paper we explore coefficients of ergodicity for the case of imprecise Markov chains. The latter provide a convenient way of modelling dynamical systems where parameters are not determined precisely. In such cases a tool for measuring the rate of convergence is even more important than in the case of precisely determined Markov chains, since most of the existing methods of estimating the limit distributions are iterative. We define a new coefficient of ergodicity that provides necessary and sufficient conditions for convergence of the most commonly used class of imprecise Markov chains. This so-called weak coefficient of ergodicity is defined through an endowment of the structure of a metric space to the class of imprecise probabilities. Therefore we first make a detailed analysis of the metric properties of imprecise probabilities.     

Measuring scale efficiency from a parametric hyperbolic distance function

This paper shows how scale efficiency can be measured from an arbitrary parametric hyperbolic distance function with multiple outputs and multiple inputs. It extends the methods introduced by Ray (J Product Anal 11:183–194, 1998), and Balk (J Product Anal 15:159–183, 2001) and Ray (2003) that measure scale efficiency from a single-output multi-input distance function and from a multi-output and multi-input distance function, respectively. The method developed in the present paper is different from Ray’s and Balk’s in that it allows for simultaneous contraction of inputs and expansion of outputs. Theorems applicable to an arbitrary parametric hyperbolic distance function are introduced first, and then their uses in measuring scale efficiency are illustrated with the translog functional form.     

A Graph-Type Extension of Farrell Technical Efficiency Measure

We have two goals we wish to accomplish in this article. The first is the development of a framework for measuring efficiency in the full input–output space. This approach introduces a graph-type extension of the Farrell measure of technical efficiency. The second is the introduction of a weighting scheme for inputs and outputs, taking account of the particularity of the market summarized by input and output prices.     

Two-sided communication in competing mechanism games

We consider multiple-principal multiple-agent games of incomplete information. We identify a class of two-way communication mechanisms which mirror those considered in the single principal analysis of Myerson (1982). In such mechanisms, every agent truthfully reveals her type to all principals, and obeys the private recommendations she receives from each of them. We show that there is a rationale in restricting attention to this class of mechanisms: if principals use these mechanisms, there is no unilateral incentive to deviate towards more sophisticated ones. We develop three examples to analyze possible extensions and limits of our approach. The first two examples show that the restriction to direct and incentive compatible mechanisms is not sufficient to provide a complete characterization of all pure strategy equilibria. The third one shows that private recommendations play a fundamental role in competing mechanism games, suggesting that one cannot safely restrict to one-sided communication mechanisms.     

Measuring donor loyalty: key reasons why Net Promoter Score (NPS) is not the way

• Our paper reviewed the weaknesses of the Net Promoter Score (NPS) as a measure of donor loyalty for fundraisers working in nonprofit organizations, argued that the measure is fundamentally flawed and inappropriate for use in this context, and outlined six major critiques of the NPS approach and offered an alternative way of measuring future loyalty and value.

Copyright © 2013 John Wiley & Sons, Ltd.     

Measuring the Incidence of Over- and Undereducation

We deploy the unique opportunity of a dataset of Flemish school leavers to measure the incidence of over- and undereducation on the basis of the six applied measures in the literature. The incidence of overeducation in the first job after leaving school ranges from only 8% to 51%, undereducation ranges from 3% to 21%. While 66% is overeducated on the basis of at least one measure, only 3% is overeducated on the basis of every measure. Mismatch correlations range from 5% to 82%. Also the categories in terms of gender, educational level and region of residence with the highest likelihood of being overeducated depend on the measure. These findings clearly underline the weakness of the literature on this subject. However, measuring overeducation in different ways enables to derive some alternative concepts. Genuine overeducation amounts to about 20%. The incidence of over- and undereducation is both attributed to qualification inflation and deflation, and a credential gap. Finally, about 80% of the incidence of overeducation is classified as being structural.     

A multidimensional IRT approach for dimensionality assessment of standardised students’ tests in mathematics

Mathematics proficiency involves several content domains and processes at different levels. This essentially means that mathematics ability is a complex latent variable. In standardised testing, the complex, and unobserved, latent constructs underlying a test are traditionally appraised by expert panels through subjective measures. In the present research, we deal with the issue of dimensionality of the latent structure behind a test measuring the mathematics ability of Italian students from a statistical and objective point of view, within an IRT framework. The data refer to a national standardised test developed and collected by the Italian National Institute for the Evaluation of the Education System (INVALSI), and administered to lower secondary school students (grade 8). The model we apply is based on a class of multidimensional latent class IRT models, which allows us to ascertain the test dimensionality based on an explorative approach, and by concurrently accounting for non-constant item discrimination and a discrete latent variable formulation. Our results show that the latent abilities underlying the INVALSI test mirror the assessment objectives defined at the national level for the mathematics curriculum. We recommend the use of the proposed extended IRT models in the practice of test construction, primarily—but not exclusively—in the educational field, to support the meaningfulness of the inferences made from test scores about students’ abilities.     

Measuring dynamics and structural change of time-dependent socio-economic networks

This paper addresses the issue of measuring temporal dynamics of complex socio-economic relational systems, represented as time-dependent networks. Network dynamics is first splitted into a structural component, accounting for changes in the network topology, and a non-structural component, accounting for permutation of vertex labels. A quantitative measure of the dynamics and its components is then proposed and it is shown how it can be used to investigate and interpret the time evolution of networks. A real example is discussed, pertaining to the dynamics of a subnetwork of the Italian corporate board network.