Calibration and Characterization of Eddy Current Probes by Photoinductive Field Mapping

The calibration of eddy-current measurement systems is a long-standing problem in nondestructive evaluation. Eddy-current probe calibration is needed for several reasons: to compensate for different probe sensitivities, to set detection thresholds, to validate instrument setup and operation, and to perform quantitative flaw sizing.1,2 The most frequently used calibration method is to scan the probe being calibrated over simulated defects such as electrical-discharge-machined (EDM) slots, saw cuts, or laboratory-produced fatigue cracks. This method has the virtue of calibrating probe and instrument at the same time and it can be performed on the same material as that to be inspected. But it has a number of disadvantages as well. First, a large number of artifact standards must be generated, certified, and maintained, resulting in considerable expense. Second, the signals from EDM slots and saw cuts are not equivalent to the signals from actual defects.3 Third, it is questionable whether quantitative flaw sizing can be performed using such a calibration method. Even if laboratory-produced cracks were to be used for routine calibration (a prohibitively expensive option), the accuracy of calibration or quantitative sizing could be compromised by the occurrence of crack closure effects.

The role of brand loyalty and social media in e-commerce interfaces: survey results and implications for user interfaces

This paper explores the role of brand loyalty and social media in e-commerce interfaces. A survey consisting of 118 respondents was contacted to address the questions relating to online shopping and brand loyalty. Link between the frequency of access and time spent on an e-commerce user interface, and brand loyalty, gender and age profile differences, and the role of social media to branding and on-line shopping was analyzed. It was found that online loyalty differs from offline loyalty and loyalty also differed across genders, showing men were more loyal than women when shopping online. Information shared about products on social media by friends and family played an important role in purchase decision making. Website interface and ease of navigation were also key aspects for online shopping. The research concluded with recommendations to create multimodal websites which are more interactive and targeted so customer experience is enhanced and loyalty is achieved through the use of interactivity and social media

On post-Lie algebras, Lie--Butcher series and moving frames

Pre-Lie (or Vinberg) algebras arise from flat and torsion-free connections on differential manifolds. They have been studied extensively in recent years, both from algebraic operadic points of view and through numerous applications in numerical analysis, control theory, stochastic differential equations and renormalization. Butcher series are formal power series founded on pre-Lie algebras, used in numerical analysis to study geometric properties of flows on euclidean spaces. Motivated by the analysis of flows on manifolds and homogeneous spaces, we investigate algebras arising from flat connections with constant torsion, leading to the definition of post-Lie algebras, a generalization of pre-Lie algebras. Whereas pre-Lie algebras are intimately associated with euclidean geometry, post-Lie algebras occur naturally in the differential geometry of homogeneous spaces, and are also closely related to Cartan's method of moving frames. Lie--Butcher series combine Butcher series with Lie series and are used to analyze flows on manifolds. In this paper we show that Lie--Butcher series are founded on post-Lie algebras. The functorial relations between post-Lie algebras and their enveloping algebras, called D-algebras, are explored. Furthermore, we develop new formulas for computations in free post-Lie algebras and D-algebras, based on recursions in a magma, and we show that Lie--Butcher series are related to invariants of curves described by moving frames.Comment: added discussion of post-Lie algebroid

Calibration and Characterization of Eddy Current Probes by Photoinductive Field Mapping

The calibration of eddy-current measurement systems is a long-standing problem in nondestructive evaluation. Eddy-current probe calibration is needed for several reasons: to compensate for different probe sensitivities, to set detection thresholds, to validate instrument setup and operation, and to perform quantitative flaw sizing.1,2 The most frequently used calibration method is to scan the probe being calibrated over simulated defects such as electrical-discharge-machined (EDM) slots, saw cuts, or laboratory-produced fatigue cracks. This method has the virtue of calibrating probe and instrument at the same time and it can be performed on the same material as that to be inspected. But it has a number of disadvantages as well. First, a large number of artifact standards must be generated, certified, and maintained, resulting in considerable expense. Second, the signals from EDM slots and saw cuts are not equivalent to the signals from actual defects.3 Third, it is questionable whether quantitative flaw sizing can be performed using such a calibration method. Even if laboratory-produced cracks were to be used for routine calibration (a prohibitively expensive option), the accuracy of calibration or quantitative sizing could be compromised by the occurrence of crack closure effects.4</p

Sensing lead failure in implantable defibrillators: a comparison of two commonly used leads.

INTRODUCTION: Despite major technological advances, structural problems in implantable cardioverter defibrillator (ICD) endocardial sensing leads remain a significant problem. There are two types of ICD sensing leads: (1) dedicated bipolar leads and (2) integrated lead systems that include defibrillation coils. The long-term performance of these two lead systems has not been directly compared. METHODS AND RESULTS: We prospectively examined the incidence of lead failure manifested by inappropriate arrhythmia detection in 247 consecutive patients undergoing abdominal ICD implant at a single center between 1991 and 1995. A total of 107 patients received BT-10 (dedicated bipolar) leads and 140 patients received Endotak (integrated bipolar) leads. Over a mean follow-up of 860 +/- 442 days, there were 19 (17.8%) lead failures with the BT-10 lead (261 to 1,505 days postimplant) compared with only 6 (4.3%; P \u3c 0.01) with the Endotak lead (410 to 1,211 days postimplant). Lead failure was due to an insulation defect in all cases, with the problem occurring in the proximal lead (within the pulse generator pocket) in all but one case. Lead survival was significantly better with the Endotak lead (P = 0.015, risk ratio = 3.0, 95% confidence intervals 1.2 to 7.6). CONCLUSION: Late lead failure due to insulation defects in BT-10 sensing leads (causing inappropriate ICD activation) is a relatively common and progressive phenomenon, with difficulties becoming apparent as long as 4 years after implant. This problem is a likely cause of inappropriate shocks in patients with BT-10 leads. Implantation of a new sensing lead should be considered at the time of elective pulse generator replacement, even in the absence of demonstrable oversensing

Multiple Category Decision Making: Review and Synthesis

In many purchase environments, consumers use information from a number of product categories prior to making a decision. These purchase situations create dependencies in choice outcomes across categories. As such, these decision problems cannot be easily modeled using the single-category, single-choice paradigm commonly used by researchers in marketing. We outline a conceptual framework for categorization, and then discuss three types of cross-category dependence: cross-category consideration cross-category learning, and product bundling. We argue that the key to modeling choice dependence across categories is knowledge of the goals driving consumer behavior