bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced manufacturing technology adoption and performance: the role of management information systems departments
Authors: Small Michael H. , Yasin Mahmoud
Published: July 2003

This study uses information obtained from the advanced manufacturing technology (AMT) literature to develop a conceptual framework that seeks to illustrate the impact of the management information systems (MIS) department on the different facets of AMT adoption. A detailed survey instrument was administered to a cross‐section of manufacturing firms in the USA to collect the data required to test five hypotheses relating to the efficacy of this framework. The results of this study indicate that the proposed framework is particularly useful in explaining the role of MIS departments in firms that are attempting to integrate advanced process and information technologies. This finding and other results of this study and their implications are discussed.
Analysis of the decision process for selecting ERP software: the case of Keller Manufacturing
Authors: Verville Jacques , Halingten Alannah
Published: July 2003

Keller Manufacturing, a mid‐sized furniture manufacturer, completed the purchase of an enterprise resource planning (ERP) software solution in August of 1996 at a cost of US$1 million. From 12 individuals who participated on Keller’s acquisition team, the four principals were interviewed for this case. The structure of the acquisition process that emerged from the data revealed six distinctive iterative, recursive and inter‐related processes that, together, form a complex web of activity and tasks for the acquisition of ERP software. These activities and tasks are described and analyzed as a function of the six processes. The ERP acquisition process developed by Keller for this purchase was atypical of their normal purchasing practices and proved to be a significant learning experience for the entire organization. This case provides a useful illustration of “good practice” and sets forth the framework for the ERP acquisition process.
Integrating ABC and TOC for better manufacturing decision making
Authors: Sheu Chwen , Chen Ming‐Hsiang , Kovar Stacy
Published: July 2003

This paper reviews and compares the concepts of theory of constraints (TOC) and activity‐based costing (ABC). The primary objective of this study is to investigate the integration of both theories so as to provide management with the capability of making better operations decisions in the presence of diverse activities and committed costs. First, the assumptions of each theory are discussed against traditional cost accounting. Next, based on numerical examples, we discuss the managerial implications of the two theories in various decisions such as pricing, make‐or‐buy and product mix. Numerical results show that both ABC and TOC can provide management with better performance measurement of diverse production activities especially when committed costs are a significant factor. Accordingly, suggestions for integrating the two theories are provided.
A micro‐AGV for flexible manufacturing in small enterprises
Authors: Collier M.
Published: July 2003

The extensive development of automated guided vehicles (AGVs) over the last two decades is outlined, and a vehicle for use in small assembly processes such as electronic equipment manufacturing is described. This micro‐AGV is intended for bench‐top use, and is guided by wall sensors between workstations. Traction is provided by two stepper motors, which receive their signals through appropriate drivers from an on‐board microcontroller. This device controls the vehicle in accordance with data stored in a non‐volatile memory, representing the node locations of the workstations in the path. Graphs of speed and electricity consumption against stepper pulse length are presented, and the issue of battery life is discussed. Circuitry for the stepper driver and the microcontroller interface is given. Specific applications of the vehicle in the electronics manufacturing industry are discussed, and a design of processing environment is presented.
Simulation workbench for analysing multi‐echelon supply chains
Authors: Kian Ng Woon , Piplani Rajesh , Viswanathan S.
Published: July 2003

End‐user demand information suffers from delay and distortion as it moves upstream in a supply chain. Co‐ordination between organisations in the supply chain, through sharing of demand information, is a possible solution to counter this distortion. Modelling and analysing supply chains, however, is not an easy task, as the supply chains contain multiple echelons and are faced with uncertain demand and lead‐times. For multi‐echelon supply chains adopting different inventory and forecasting policies at the echelon level, simulation is the most appropriate analysis tool. In this paper, we describe the development of a simulation workbench for modelling and analysing multi‐echelon supply chains. The workbench facilitates study of inventory and forecasting policies practised by the echelons, and models different information exchange mechanisms adopted by them. An experiment conducted, to test the workbench and demonstrate its capabilities, confirms that the workbench is a useful tool for gaining valuable insights into information exchange in a particular supply chain.
An approach to design of maintenance float systems
Authors: Chen Mu‐Chen , Tseng Hsien‐Yu
Published: July 2003

The paper offers an intelligent approach to analyze and determine the design parameters minimizing the total cost and achieving the desired performance measures in the maintenance float systems. The expected total cost in a maintenance float system includes the cost of lost production, the cost of repair persons and the cost of standby machines. The developed design procedure integrates simulation, metamodel and genetic algorithms. Neural networks are able to approximate functions based on a set of sample data, i.e. construct metamodels from simulation results in this study. The objective of metamodels is to predict simulation responses in order to significantly reduce the amount of simulation runs. The predictive performance of neural metamodels comparably outperforms the traditional regression metamodels. The neural metamodels are further extended to formulate a decision model for optimizing the maintenance float systems by using genetic algorithms.
Implementation of unidirectional functional dimensioning and tolerancing algorithm in CAD systems
Authors: Ciurana J. , Riba C. , Romeu M.L.G.
Published: July 2003

Functional dimensioning has a clear mission: to choose the correct dimension and tolerance in order to optimise the parts in the definition of the mechanical assembly for their functional purpose. The current development of computer systems allows us to introduce intelligent help in CAD systems, which makes the complex task of functional dimensioning a lot easier. The international technical literature offers a number of investigation projects that contribute to establishing the bases for implementing intelligent help for functional dimensioning in the design phase. The main aim of this study is to define a system of computer‐aided dimensioning, using graphic design (CAD) systems and the necessary programming language.
Online service marketing and delivery: the case of Swedish museums
Authors: Lagrosen Stefan
Published: July 2003

This article addresses service marketing and service delivery over the Internet. Some service activities – information, education and entertainment – can be delivered as well as promoted over the Internet. An empirical study focusing on museums has been carried out. The purpose has been to describe the current use of the Internet by Swedish museums and propose some strategies with regard to its value as a service delivery tool. The 371 Swedish museums that have a homepage have been examined. Of these, 156 museums operate their own Web site. The study has consisted of a content analysis of the sites as well as a questionnaire study and two preliminary in‐depth interviews. A cluster analysis was carried out, resulting in four groups being defined. It is found that the use of the Internet is still in its infancy. Three strategies for Internet service delivery are proposed.
Joining the backstage: locality and centrality in an online community
Authors: Lutters Wayne G. , Ackerman Mark S.
Published: July 2003

The design of viable, small‐scale community spaces on the Net is often a hit‐or‐miss affair. To better understand promising approaches in this design space, it is necessary to go back in time to examine an earlier community technology. A field study is presented of The Castle, a dial‐up bulletin board system, that focuses on Disneyland. As a “gathering place for Disney enthusiasts”, The Castle is a fascinating, albeit eccentric, online community. The Castle's centrality in the fans’ interest network allows it to function as a collecting point. Here people find similar enthusiasts and even those with insider knowledge. Yet, because of the cost structure of dial‐up access (an accidental side‐effect of the technology), participants are overwhelmingly geographically local, which has useful consequences for social maintenance. It is argued that the geographical locality and centrality of interest allow The Castle to thrive. Most importantly, however, the combination of the two together creates a powerful social dynamic which has been lost in most contemporary online communities.
Managing information systems for service quality: a study from the other side
Authors: Bharati Pratyush , Berg Daniel
Published: July 2003

System quality, information quality, user IS characteristics, employee IS performance and technical support are identified as important elements that influence service quality. A model interrelating these constructs is proposed. Data collected through a national survey of IS departments in electric utility firms was used to test the model using regression and path analysis methodology. The results suggest that system quality, information quality, user IS characteristics, through their effects on employee IS performance, influence service quality, while technical support influences service quality directly. The results also suggest that employee IS performance contributes more to service quality compared with technical support. Implications of this research for IS theory and practice are discussed.
Dangers inherent in the use of techniques: identifying framing influences
Authors: Adams Carl , Avison David
Published: July 2003

The literature about the development of information systems tends to concentrate on methodologies, techniques and tools. There is significant published research about the potential negative aspects of using methodologies and tools (along with that discussing their potential benefits). Techniques, on the other hand, are seen largely as benign, very often as simple aids to help carry out a task, and are used in many methodologies. They might be seen as supporting the collection, collation, analysis, representation or communication of information about system requirements and attributes (or a combination of these). However, it is argued in this paper that techniques also have negative aspects and there are as many dangers in their use as in using methodologies and tools. In particular, techniques may restrict understanding by framing the ways of thinking about the problem situation. In other words, people’s understanding of a problem can be profoundly influenced by how the problem is presented to them by the technique. Different development techniques can represent the same problem situation differently, and the way in which it is represented has considerable potential for influencing problem understanding and resultant decision making. Drawing on the cognitive psychology literature enables one to show how specific visual and linguistic characteristics of techniques may influence problem understanding. In addition, examining the taken‐for‐granted paradigm of a particular technique provides a further dimension influencing problem understanding. This knowledge of visual/language and paradigm attributes is applied to over 80 techniques used to a greater or lesser extent in IS development, indicating how different types of technique are likely to influence problem cognition. This serves two purposes. First, it exposes potential biases of a particular technique and makes users aware of the potential dangers. Second, the overall categorization may provide guidance to users in selecting appropriate techniques and combinations of techniques to help reduce any negative framing influences, provide a more holistic view of a problem situation and support a more appropriate problem‐learning environment.
Ten years of the UK ALMA: reflections on a decade of tumultuous change
Authors: Ashenhurst John
Published: July 2003

The author, one of the founders of the UK Asset and Liability Management Association ten years ago, looks back at developments since. He looks at how the embryo skills of asset and liability management used to be used and at the threats, like the international accounting standard dealing with financial instruments and proposals on liquidity ratios, and how they should be dealt with.
Ten years of the UK ALMA: a look forward via the rear view mirror
Authors: Hanlon Peter
Published: July 2003

The author looks back over ten years of the UK asset and liability management profession and compares the US and UK banking industries. He suggests that the value of ALM techniques is still undervalued and left to specialists rather than being embraced by the banking business.
A new look at investment risk – the organic risk management stance?
Authors: Yee Chong Yen
Published: July 2003

The author suggests that methods for rating investment risk are flawed. He suggests a risk analysis, management and projects (RAMP) approach. Number‐crunching will produce better results than listening to analysts.
IAS – the road to international (dis)harmony
Authors: Taylor Chris
Published: July 2003

As banks across Europe try to prepare for the introduction of international accounting standards in 2005, controversy over the rules continues to rage. The author traces the history of this process and shows where the problems for the global banking industry really lie.
Asset and liability management: what does the future have in store?
Authors: Black Richard , Brown Karl , Moloney James
Published: July 2003

Advances in market risk management have had a huge impact on asset liability management in recent years, enabling the most advanced institutions to analyze their balance sheet risks in a much more realistic and dynamic way. In future, as risk management develops still further and computing power increases, ALM could find itself with a new, broader function to perform.
Part 1: Investigating the concept of global responsibility
Authors: Biefnot Yvan
Published: July 2003

This article describes the views expressed about global responsibility by a variety of reputed individuals or groups: academics, political and religious authorities, NGO, private enterprises, etc. If there is, in the main, a rather common understanding of the word “global” (universal, borderless), the definition of responsibility varies much more. The main dichotomy is to be found between the private/business and the non‐private sector. The latter puts a humanistic dimension in the concept of responsibility, even if not always clearly defined. The private sector, clearly, thinks more in terms of business opportunities. The conclusion suggests that “man” should always be the center of the debate and the progress of mankind always the ultimate goal. Statements expressing this view and offering guidelines for action are already contained in the Universal Declaration of Human Rights, of which article 1 almost says it all.
Viewpoint: Questions on the theme of “global responsibility”
Authors: Pesqueux Yvon
Published: July 2003

The “global responsibility” theme is today in the same state of affairs as the “sustainability” theme, devised by the UNO, was in the 1990s. From a meaningless compromise situation, it has gradually acquired some sense, due to the interest shown by the actors, whether these belong to the political scene, non‐governmental organizations, enterprises, etc. Insofar as the “global responsibility” theme contains the word “responsibility”, it is necessary to propose an understanding of it, with reference to the various areas supporting it (its use in law, in philosophy) before underlining the development of the theme of responsible enterprise and the search for an underlying concept. This text ends on an analysis of the ideological function of the “global responsibility” theme.
Viewpoint: Global responsibility and total freedom
Authors: Cornuel Eric , Kletz Pierre
Published: July 2003

The notion of global responsibility is coming to light as it appears that the control of the economies by nation‐states has proved inefficient. Therefore, solutions are often sought by appealing to responsibility (for enterprises, individuals, interest groups …). In particular, global responsibility calls for firms to limit their own activities when it opposes the general interest. But it is generally admitted in the firms that a condition to maximize their profits is all about allowing the laws of economy to express themselves, without any restraint, in order to give their whole potential. In this sense, it refers to “total freedom”. This article tries to re‐examine the very concept of global responsibility versus total freedom. For that it addresses the question through two major issues: (1) responsibility as an external constraint, a source of improvement; (2) the responsibility of corporate governance for financial transparency.
Research: Big business, big responsibilities
Authors: Gardiner Louise , Rubbens Catherine , Bonfiglioli Elena
Published: July 2003

Focuses on “big business” and what is seen as its growing influence on the state of the world and argues that increasing globalization is posing significant challenges that require new thinking about global governance, particularly with regard to international trade. Businesses are required to operate within legislative and economic frameworks created by governments and should be helped to develop global, values‐based systems of management rooted in internationally accepted principles. Concludes that corporate social responsibility will only make a visible difference if the concept is fully integrated into corporate principles and practices, and if progress is monitored over time.
Research About “global responsibility” in management
Authors: Pérez Roland
Published: July 2003

The concept of global responsibility (GR) was devised to extend the traditional set of references for management responsibility. In analytical terms, we are forced to take externalities into account in management behavior, in a way, to try and externalize them. Two reference models have been explored: on model is based on the principle of dissociation between business and non‐business; the other model is based on the principle of their integration in the vision that managers have about their organizations’ strategy and in their concrete behaviors. However, some tendencies are emerging; they are common to both families of behavior models: the tendency to “legalize” contemporary companies, the increased constraint to “account” (accountability) and, finally, the risk of an increased risk aversion.
Viewpoint Global responsibility – vision from Central Asia/vision of Central Asia
Authors: Altaliyeva Akmaral
Published: July 2003

Focuses on global responsibility (GR) in Kazakhstan. Asserts, from analysis of the literature and interviews with students from the Executive MBA Program of one of the leading national business schools, that the subject of GR is not popular among Kazakhstani writers, nor well developed. Notes that the Kazakhstani national position with regard to GR is passive. Discusses the business culture structure of Kazakhstan.
Part 3: Implications in management education
Authors: Zsolnai Laszlo
Published: July 2003

Business activities considerably affect the fate and survival of natural ecosystems as well as the life conditions of present and future generations. Applying the imperative of responsibility developed by Jonas states that business has a one way, non‐reciprocal duty caring for the beings which are affected by its functioning. To meet its global responsibilities business should become sustainable, pro‐social and future‐enhancing.
Viewpoint: Foundations for a global management ethos
Authors: Capaldi Nicholas
Published: July 2003

An emerging global ethics is outlined that can serve as the foundation for a global management ethos. In so doing, what a global management ethos is is defined, what would make it possible discussed, and its benign and malignant forms distinguished. The global management ethos (GME) described and advocated combines macro libertarianism and micro diversity.
Viewpoint: Global responsibility and individual exemplarity
Authors: Thévenet Maurice
Published: July 2003

Discusses the concepts of global responsibility, sustainable growth and social responsibility. Concludes that key to the issue of global responsibility will be behavioral responsibility from people and notes that this is an issue not only of belief but of competencies and skills.
Case study: Global responsibility – business education and business schools – roles in promoting a global perspective
Authors: Lorange Peter
Published: July 2003

This article is based on the author’s experience as head of a leading international business school, with strong embedded values in providing the highest level of quality business education within a global perspective. The scope of the article is one of focusing on a global business school, i.e. one which is able to draw on professors and students to come together for teaching and learning in a “global meeting‐place” from all over the world. The article provides the following results, conclusions and recommendations: first, a distinction is made between local business schools, serving typically a national market, regional business schools, typically serving a number of national markets, but within the same language area, and global business schools, typically serving the entire world community. Then the content of a global curriculum is reviewed, and five items are being identified: a strategic competence, a partnership competence, a staffing competence, a learning competence, and an organizational competence. In order to pursue global growth and to develop the capabilities for this, a conceptual model by Chakravarthy and Lorange is then being introduced, where one’s strength will be the starting‐point/basis for further global expansion, either by leveraging one’s capability vis‐à‐vis new markets, or by building a new business by adding new competences to the existing ones, or as a next step by combining the two leveraging and building dimensions into a transform strategy. Four managerial challenges are then being reviewed for the leading global business school, namely the issue of language, the mix of the student body, the degree of internationalization of the teaching and administrative staff, as well as the global marketing challenge. The article concludes with a discussion regarding an optimal location for the global business school. It is argued that perhaps many of today’s leading business schools, being located in major markets, will not have an optimal location, due to the fact that these major markets can more or less explicitly lead to a nationally based bias of the teaching and research being undertaken, i.e. obstructing the globality focus of the business school. A small country location might therefore be preferable.
Efficient Modeling of An Anatomy‐Based Face and Fast 3D Facial Expression Synthesis
Authors: Zhang Yu , Prakash Edmond C. , Sung Eric
Published: July 2003

This paper presents new methods for efficient modeling and animation of an hierarchical facial model that conforms to the human face anatomy for realistic and fast 3D facial expression synthesis. The facial model has a skin–muscle–skull structure. The deformable skin model directly simulates the nonlinear visco‐elastic behavior of soft tissue and effectively prevents model collapse. The construction of facial muscles is achieved by using an efficient muscle mapping approach. Based on a cylindrical projection of the texture‐mapped facial surface and wire‐frame skin and skull meshes, this approach ensures different muscles to be located at the anatomically correct positions between the skin and skull layers. For computational efficiency, we devise an adaptive simulation algorithm which uses either a semi‐implicit integration scheme or a quasi‐static solver to compute the relaxation by traversing the designed data structures in a breadth‐first order. The algorithm runs in real‐time and has successfully synthesized realistic facial expressions.

ACM CSS:I.3.5 Computer Graphics: Computational Geometry and Object Modelling—physically based modelling;I.3.7 Computer Graphics: Three‐Dimensional Graphics and Realism—animation;
Development of a Framework for Web-Based Product Platform Customization
Authors: Simpson Timothy W. , Umapathy Karthikeyan , Nanda Jyotirmaya , Halbe Sachin , Hodge Barry
Published: July 2003

Product customization is a value-added activity that can significantly increase sales by increasing customer satisfaction. Many companies are using product platforms to increase product variety and customization while reducing development costs and time-to-market. While flooding the market with a variety of products may satisfy some customers by providing a substitute for customization, variety is not customization. This subtle, yet important, distinction between variety and customization motivates the need for investigating technologies to facilitate customer involvement during the product realization process, and our focus in this paper is on web-based platform customization strategies enabled by recent advances in information technology. Towards that end, we describe the development of an interactive web-based platform customization framework as an extension of product family design and present a prototype that has been created as part of on-going research with a company that produces customized refiner plates for pulp and paper processing. While the utility of the proposed web-based framework is demonstrated in the context of customizing a refiner plate design, the proposed framework is applicable to a variety of engineered products and enhances customer interaction during the product realization process while reducing design and manufacturing lead-time for custom orders.
Which accelerator photon beams are “clinic‐like” for reference dosimetry purposes?
Authors: Kalach N. I. , Rogers D. W. O.
Published: July 2003

Previous work has demonstrated that, for photon beam dosimetry,is not an ideal beam quality specifier for all bremsstrahlung beams, especially for lightly filtered beams in some standards laboratories. This paper addresses the following questions: Isan adequate beam quality specifier for all modern clinical therapy accelerators? When can nonclinical beams in standards laboratories be used to calibrate ion chambers or measurefactors as a function ofBased on detailed Monte Carlo simulations of Varian, Siemens, Elekta, and GE (Saturn) accelerators one can conclude thatis an adequate beam quality specifier for all these machines in the sense that for a given value ofthe value of stopping‐power ratios is the same. It is shown that, for the heavily filtered beams used in standards laboratories,is an adequate beam quality specifier. It is also demonstrated that, for a larger range of bremsstrahlung beams than previously,is a good beam quality specifier for all clinical beams as well as the lightly and heavily filtered beams in some standards laboratories. A criterion, based on the measured values ofandfor the beam, is proposed for determining whether a nonclinical beam is well specified byAgreement between calculations for specific accelerators and measured beam quality specifiers is shown to be good, but agreement with published data for a variety of clinical accelerators is not as good. Possible reasons for the discrepancy are discussed.
Feature‐guided analysis for reduction of false positives in CAD of polyps for computed tomographic colonography
Authors: Näppi Janne , Yoshida Hiroyuki
Published: July 2003

We evaluated the effect of our novel technique of feature‐guided analysis of polyps on the reduction of false‐positive (FP) findings generated by our computer‐aided diagnosis (CAD) scheme for the detection of polyps from computed tomography colonographic data sets. The detection performance obtained by use of feature‐guided analysis in the segmentation and feature analysis of polyp candidates was compared with that obtained by use of our previously employed fuzzy clustering technique. We also evaluated the effect of a feature called modified gradient concentration (MGC) on the detection performance. A total of 144 data sets, representing prone and supine views of 72 patients that included 14 patients with 21 colorectal polyps 5–25 mm in diameter, were used in the evaluation. At a 100% by‐patient (95% by‐polyp) detection sensitivity, the FP rate of our CAD scheme with feature‐guided analysis based on round‐robin evaluation was 1.3 (1.5) FP detections per patient. This corresponds to a 70–75 % reduction in the number of FPs obtained by use of fuzzy clustering at the same sensitivity levels. Application of the MGC feature instead of our previously used gradient concentration feature did not improve the detection result. The results indicate that feature‐guided analysis is useful for achieving high sensitivity and a low FP rate in our CAD scheme.
Statistical analysis of decorrelation‐based transducer tracking for three‐dimensional ultrasound
Authors: Smith Wendy , Fenster Aaron
Published: July 2003

The use of speckle decorrelation techniques to calculate the displacement of a moving transducer has shown promise. We describe a technique to estimate displacement between pairs of parallel planes without assuming that plane separation in the scan is uniform. We perform theoretical and empirical analyses of the bias and uncertainty in plane spacing estimates as a function of speckle size, patch size, and the number of planes used for normalization. Practically, only the central, linear region of the autocovariance curves can be used in this decorrelation method, which implies that distance between acquired image planes should be approximately half the speckle size. In this region, the uncertainty in estimated plane spacing was less than 15% for a 8.1 mm (axial) by 9.1 mm (lateral) patch and increased to 33% for an 8.1 mm (axial) by 1.5 mm (lateral) patch. The number of planes, used to calculate the normalization factors (averages of brightness andsquared brightness) was a major source of bias. Optimum was found to be five to ten planes, depending on distance between acquired image planes, with a poor choice of resulting in a bias of 10% or greater. A second source of bias is brightness gradients which, although they appear very slight on intensity images, can cause a large bias is the plane spacing estimates made using linearized data.
Ionization chamber volume averaging effects in dynamic intensity modulated radiation therapy beams
Authors: Low Daniel A. , Parikh Parag , Dempsey James F. , Wahab Sasha , Huq Saiful
Published: July 2003

The commercial cylindrical ionization chamber ionization integration accuracy of dynamically moving fields was evaluated. The ionization chambers were exposed to long (14 cm), narrow (0.6, 1.0, 2.0, and 4.0 cm) 6 MV and 18 MV fields. Rather than rely on the linear accelerator to reproducibly scan across the chamber, the chambers were scanned beneath fixed portals. A water‐equivalent phantom was constructed with cavities that matched the chambers and placed on a computer‐controlled one‐dimensional table. Computer‐controlled electrometers were utilized in continuous charge integrate mode, with 10 samples of the charge, along with time stamps, acquired for each chamber location. A reference chamber was placed just beneath the linear accelerator jaws to adjust for variations in linear accelerator dose rate. The scan spatial resolution was selected to adequately sample regions of steep dose gradient and second spatial derivative (curvature). A fixed measurement in a field was used to normalize the profiles to absolute chamber response. Three ionization chambers were tested, a microchamber a Farmer chamber and a waterproof scanning chamber The larger chambers exhibited severe under‐response at the small field's centers, but all of the chambers, independent of orientation, accurately integrated the ionization across the scanned portal. This indicates that the tested ionization chambers provide accurate integrated charges in regions of homogeneous dose regions. Partial integration (less than the field width plus the chamber length plus 2 cm), yielded integration errors of greater than 1% and 2% for 6 MV and 18 MV, respectively, with errors for the Farmer chamber of greater than 10% even for the 4 cm wide field.
Compensator quality control with an amorphous silicon EPID
Authors: Menon Geetha V. , Sloboda Ron S.
Published: July 2003

The calibration and quality control of compensators is conventionally performed with an ion chamber in a water‐equivalent phantom. In our center, the compensator factor and four off‐axis fluence ratios are measured to verify the central axis beam modulation and orientation of the compensator. Here we report the investigation of an alternative technique for compensator quality control using an amorphous silicon electronic portal imaging device (a‐Si EPID). Preliminary experiments were performed to identify appropriate EPID operating parameters for this relative dosimetric study and also to quantify EPID operation. The pixel value versus energy fluence response of the EPID for both open and compensated fields was then determined, and expressed via calibration curves. For open fields the response was seen to be linear, whereas for compensated fields it exhibited a small quadratic component. To account for field size effects, we measured EPID scatter factors. These exhibited small but non‐negligible dependencies on compensator thickness and source–detector distance. Finally, a number of test and clinical compensators were evaluated to assess the suitability of the EPID for compensator quality control. Our results indicate that the a‐Si EPID can measure clinical compensator factors and off‐axis energy fluence ratios to within 2% of values measured by a Farmer chamber on average, and so is a suitable ion chamber replacement.
Robustness and precision of an automatic marker detection algorithm for online prostate daily targeting using a standard V‐EPID
Authors: Aubin S. , Beaulieu L. , Pouliot S. , Pouliot J. , Roy R. , Girouard L.‐M. , Martel‐Brisson N. , Vigneault E. , Laverdière J.
Published: July 2003

An algorithm for the daily localization of the prostate using implanted markers and a standard video‐based electronic portal imaging device (V‐EPID) has been tested. Prior to planning, three gold markers were implanted in the prostate of seven patients. The clinical images were acquired with a2.1 V‐EPID for each field during the normal course radiotherapy treatment and are used off‐line to determine the ability of the automatic marker detection algorithm to adequately and consistently detect the markers. Clinical images were obtained with various dose levels from ranging 2.5 to 75 MU. The algorithm is based on marker attenuation characterization in the portal image and spatial distribution. A total of 1182 clinical images were taken. The results show an average efficiency of 93% for the markers detected individually and 85% for the group of markers. This algorithm accomplishes the detection and validation in 0.20–0.40 s. When the center of mass of the group of implanted markers is used, then all displacements can be corrected to within 1.0 mm in 84% of the cases and within 1.5 mm in 97% of cases. The standard video‐based EPID tested provides excellent marker detection capability even with low dose levels. The V‐EPID can be used successfully with radiopaque markers and the automatic detection algorithm to track and correct the daily setup deviations due to organ motions.
Prostate boundary segmentation from 3D ultrasound images
Authors: Hu Ning , Downey Dónal B. , Fenster Aaron , Ladak Hanif M.
Published: July 2003

Segmenting, or outlining the prostate boundary is an important task in the management of patients with prostate cancer. In this paper, an algorithm is described for semiautomatic segmentation of the prostate from 3D ultrasound images. The algorithm uses model‐based initialization and mesh refinement using an efficient deformable model. Initialization requires the user to select only six points from which the outline of the prostate is estimated using shape information. The estimated outline is then automatically deformed to better fit the prostate boundary. An editing tool allows the user to edit the boundary in problematic regions and then deform the model again to improve the final results. The algorithm requires less than 1 min on a Pentium III 400 MHz PC. The accuracy of the algorithm was assessed by comparing the algorithm results, obtained from both local and global analysis, to the manual segmentations on six prostates. The local difference was mapped on the surface of the algorithm boundary to produce a visual representation. Global error analysis showed that the average difference between manual and algorithm boundaries was −0.20±0.28 mm, the average absolute difference was 1.19±0.14 mm, the average maximum difference was 7.01±1.04 mm, and the average volume difference was 7.16%±3.45%. Variability in manual and algorithm segmentation was also assessed: Visual representations of local variability were generated by mapping variability on the segmentation mesh. The mean variability in manual segmentation was 0.98 mm and in algorithm segmentation was 0.63 mm and the differences of about 51.5% of the points comprising the average algorithm boundary are insignificantto the manual average boundary.
Particle selection for laser‐accelerated proton therapy feasibility study
Authors: Fourkal E. , Li J. S. , Ding M. , Tajima T. , Ma C.‐M.
Published: July 2003

In this paper we present calculations for the design of a particle selection system for laser‐accelerated proton therapy. Laser‐accelerated protons coming from a thin high‐density foil have broad energy and angular spectra leading to dose distributions that cannot be directly used for therapeutic applications. Our solution to this problem is a compact particle selection and collimation device that delivers small pencil beams of protons with desired energy spectra. We propose a spectrometer‐like particle selection and beam modulation system in which the magnetic field will be used to spread the protons spatially according to their energies and emitting angles. Subsequently, an aperture will be used to select the protons within a therapeutic window of energy (energy modulation). It will be shown that for the effective proton spatial differentiation, the primary collimation device should be used, which will collimate protons to the desired angular distribution and limit the spatial mixing of different energy protons once they have traveled through the magnetic system. Due to the angular proton distribution, the spatial mixing of protons of different energies will always be present and it will result in a proton energy spread with the width depending on the energy. For 250 MeV protons, the width (from the maximum to the minimum energy) is found to be 50 MeV for the magnetic field configuration used in our calculations. As the proton energy decreases, its energy width decreases as well, and for 80 MeV protons it equals 9 MeV. The presence of the energy width in the proton energy distribution will modify the depth dose curves needed for the energy modulation calculation. The matching magnetic field setup will ensure the refocusing of the selected protons and the final beam will be collimated by the secondary collimator. The calculations presented in this article show that the dose rate that the selection system can yield is on the order of D=260 Gy/min for a field size of 1×1 cm2.
Edge waves in poroelastic plate under plane stress conditions
Authors: Reddy P. Malla , Tajuddin M.
Published: July 2003

Employing Biot’s theory, the problem of edge waves in poroelastic plate under plane stress conditions is studied for both a pervious and an impervious surface. The equations for plane stress conditions are derived and discussed. The particle trajectory is obtained, which is an elliptic. The frequency equation is discussed for symmetric and antisymmetric motions and results of special interest are shown.
A guided wave technique for the characterization of highly attenuative viscoelastic materials
Authors: Simonetti F. , Cawley P.
Published: July 2003

The measurement of the acoustic properties of highly attenuative materials such as bitumen is very difficult. One possibility is to use measurements of the extent to which filling a cylindrical waveguide with the material affects the dispersion relationship of the cylinder. Torsional modes have been excited using piezoelectric transducers placed at one end of the cylinder, while the phase velocity and attenuation spectra have been measured by means of laser scanning. At each frequency, under the hypothesis of linear viscoelasticity, the phase velocity and attenuation of the fundamental torsional mode have been calculated as a function of the bulk shear velocity and the bulk shear attenuation of the inner core at that frequency. The resulting phase velocity and guided wave attenuation contour plots have been employed for deriving the unknown shear properties from the measured velocity and attenuation of the guided wave. The monochromaticity of the approach has not required a particular frequency dependence of the material properties to be assumed. Results for bitumen are given.
A diminished rate of “physiological decay” at noise offset contributes to age-related changes in temporal acuity in the CBA mouse model of presbycusis
Authors: Ison James R. , Allen Paul
Published: July 2003

The persistence of afferent activity at stimulus offset was examined in mice as a function of age (experiment 1) and noise level (experiment 2), using a procedure devised by von Bekesy to study the physiological decay of afferent activity. Noise offset was presented from 1 to 10 ms (the temporal gap) prior to an acoustic startle stimulus, with an abrupt edge or a linear ramp having the duration of the gap. Noise offset inhibited the startle reflex, this effect declining with age. For young (2–3 months old) and “young-old” mice (18–19 months old), the abrupt offset was always more inhibitory than the ramp, even for the one millisecond gap. In “old-old” mice (24–26 months old) abrupt and ramped offsets were not different until the gap exceeded 4 ms. The behavioral difference between abrupt and ramped decay times did not depend on noise level in young mice (4–5 months old), though overall inhibition increased with level. These data indicate that temporal acuity as measured by this gap detection method is limited in very old mice by their reduced ability to follow the abrupt change in noise level at the beginning of the gap.
Intensity discrimination and increment detection in cochlear-implant users
Authors: Wojtczak Magdalena , Donaldson Gail S. , Viemeister Neal F.
Published: July 2003

Intensity difference limens (DLs) were measured in users of the Nucleus 22 and Clarion v1.2 cochlear implants and in normal-hearing listeners to better understand mechanisms of intensity discrimination in electric and acoustic hearing and to evaluate the possible role of neural adaptation. Intensity DLs were measured for three modes of presentation: gated (intensity increments gated synchronously with the pedestal), fringe (intensity increments delayed 250 or 650 ms relative to the onset of the pedestal), and continuous (intensity increments occur in the presence of a pedestal that is played throughout the experimental run). Stimuli for cochlear-implant listeners were trains of biphasic pulses; stimuli for normal-hearing listeners were a 1-kHz tone and a wideband noise. Clarion cochlear-implant listeners showed level-dependent effects of presentation mode. At low pedestal levels, gated thresholds were generally similar to thresholds obtained in the fringe and continuous conditions. At higher pedestal levels, however, the fringe and continuous conditions produced smaller intensity DLs than the gated condition, similar to the gated-continuous difference in intensity DLs observed in acoustic hearing. Nucleus cochlear-implant listeners did not show consistent threshold differences for the gated and fringe conditions, and were not tested in the continuous condition. It is not clear why a difference between gated and fringe thresholds occurred for the Clarion but not the Nucleus subjects. Normal-hearing listeners showed improved thresholds for the continuous condition relative to the gated condition, but the effect was larger for the 1-kHz tonal carrier than for the noise carrier. Findings suggest that adaptation occurring central to the inner hair cell synapse mediates the gated-continuous difference observed in Clarion cochlear-implant listeners and may also contribute to the gated-continuous difference in acoustic hearing.
Empirical model of the acoustic impedance of a circular orifice in grazing mean flow
Authors: Lee Seong-Hyun , Ih Jeong-Guon
Published: July 2003

Although there are many analytical and empirical models for orifice impedance, the predicted acoustical performance when adopting any one of them sometimes shows a large discrepancy with the measured result in some cases. In order to obtain a new practical and precise empirical impedance model under grazing flow conditions, the acoustic impedance of circular orifices has been measured with a variation of the involved parameters under very carefully tested and controlled measurement conditions. The parameters involved in determining the acoustic impedance of an orifice are comprised of the orifice diameter, orifice thickness, perforation ratio, mean flow velocity, and frequency. The range of involved parameters is chosen to cover the practical data span of perforates in typical exhaust systems of internal combustion engines. The empirical impedance model is obtained by using nonlinear regression analysis of the various results of the parametric tests. The proposed empirical model of orifice impedance, with a very high correlation coefficient, is applied to the prediction of the transmission loss of concentric resonators, which have geometric configurations typical of acoustically short and long through-flow resonators. By comparing the measured and predicted results, in which the predictions are made by employing many previous orifice impedance models as well as the present model, it is confirmed that the proposed orifice impedance model yields the most accurate prediction among all other existing impedance models.