Comments on 'Increasing film-focus distance (FFD) reduces radiation dose for X-ray examinations' by P.C. Brennan, S. McDonnell and D. O'Leary

Sir, Comments on ‘Increasing film-focus distance (FFD) reducesradiation dose for X-ray examinations’ by P.C. Brennan,S. McDonnell and D. O'Leary. In a recent publication, Brennan et al.⁽¹⁾ claim that increasingthe film-focus distance (FFD) from 100 to 130 cm will reduceeffective doses (E) by 33% for a pelvic X-ray examination. Thisconclusion is based on a reported 33% reduction in the entrancesurface dose (ESD), by the use of the same effective dose perunit ESD conversion coefficient (E/ESD) at both FFD values.However, E/ESD values are only valid for the specific     

Delft Conference Proceedings Editorial 2008: safety and efficacy for new techniques and imaging using new equipment to support European Legislation

Radiation Protection Dosimetry, 129 (1-3): 1–2     

Radon transport through concrete and determination of its diffusion coefficient

Radiation Protection Dosimetry, 104 (1), 65–70 (2003) Dear Editor, We have published a paper treating radon diffusion through concreteslabs. Since some misunderstanding related to this paper hasarisen recently, we are writing to clarify     

Microdosimetric response of physical and biological systems to low- and high-let radiations. theory and applications to dosimetry: Y. Horowitz, Ed., 2006, Elsevier, The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, UK ISBN: 0-444-51643-3, 500 pp, 170.00 Euros (hardbound)

Microdosimetry deals with the deposition of energy by ionisingradiation in matter and its consequences on a small scale. Itshistorical role in radiation biology has been the measurementand characterisation of events and changes produced by radiationin cellular and subcellular environments. In early pioneeringefforts, Rossi and Rosenzweig succeeded in measuring energy-depositionspectra in proportional counters with micrometer dimensionson a scale of unit density [Radiology 64, 404–411 (1955)].The     

Letters to the Editor

Sir, The following are comments on ‘The ThermoluminescenceDose—Response and other characteristics of the high-temperatureTL in LiF:Mg,Ti (TLD-100)’, Radiat. Prot. Dosim., doi:10.1093/rpd/ncm241,and Letter to the Editor, doi:10.1093/rpd/ncm381, both of themavailable online, by Prof. Y. S. Horowitz. The first article, an Invited Review, includes a discussionon our published work about the TLD-100 response to gamma rays⁽¹⁾,whereas the second one analyses our measurements of the TLD-100response to intermediate-energy ions⁽²⁾. Given the criticaltone of both contributions, we felt it necessary to write thefollowing clarifying comments, which we kindly ask you to sharewith the readers of RPD. In the Invited Review, Horowitz et al. discuss two main aspectsof     

A note on: an optimal batch size for an imperfect production system with quality assurance and rework

In [Ojha, D., Sarker, B.R., and Biswas, P., 2007. An optimal batch size for an imperfect production system with quality assurance and network. International Journal of Production Research, 45 (14), 3191–3214] three models are introduced in the context of imperfect production systems. By analysing the proposed models we identify some problems. In particular we focus on six issues of the models developed in Ojha et al. and propose some modifications. All corrections are presented in detail and the numerical example of Ojha et al. is used to show the influence of the issues addressed in this paper.     

Response to Letter to the Editor

Sir, Response to ‘Are all photon radiations similar in largeabsorbers?—A comparison of electron spectra’ byA. M. Kellerer and H. Roos When the ICRP adopted a quality factor—and subsequentlya radiation weighting factor—that gives equal weight todifferent photon radiations, it did not, necessarily imply thatequal     

Fraunhofer Diffraction by Koch Fractals: The Dimensionality

Abstract

Some properties concerning the fractal dimension of generalized Koch fractals and their Fraunhofer diffraction patterns are investigated as a continuation of the previous paper by Uozumi et al. The methods are discussed for evaluating the fractal dimension of object fractals from the intensity distribution of their diffraction patterns. Experimental results are shown to demonstrate some properties in this context. The fractal dimension of fractal areas in the Fraunhofer diffraction patterns is also considered.     

Atomistic Modeling of the Structural and Thermal Conductivity of the InSb

A new parametrization for the previous empirical interatomic potential for indium antimonite is presented. This alternative parametrization is designed to correct the energetic sequence of structures. The effective empirical interatomic potential proposed consists of two and three body interactions which has the same functional form of the interatomic potential proposed by Vashishta et. al. to study other semiconductors (Branicio et al., 2003; Ebbsjo et al., 2000; Shimojo et al., 2000; Vashishta et al., 2008). Molecular dynamics simulations (MD) are performed to study high pressure phases of InSb up to 70 GPa and its thermal conductivity as a function of temperature. The rock-salt to cesium chloride, expected to occur at high pressures, is observed with the proposed interatomic potential.     

Analysis of volume expansion data for periclase, lime, corundum and spinel at high temperatures

We have presented an analysis of the volume expansion data for periclase (MgO), lime (CaO), corundum (Al₂O₃) and spinel (MgAl₂O₄) determined experimentally by Fiquet et al (1999) from 300K up to 3000K. The thermal equation of state due to Suzuki et al (1979) and Shanker et al (1997) are used to study the relationships between thermal pressure and volume expansion for the entire range of temperatures starting from room temperature up to the melting temperatures of the solids under study. Comparison of the results obtained in the present study with the corresponding experimental data reveal that the thermal pressure changes with temperature almost linearly up to quite high temperatures. At extremely high temperatures close to the melting temperatures thermal pressure deviates significantly from linearity. This prediction is consistent with other recent investigations. A quantitative analysis based on the theory of anharmonic effects has been presented to account for the nonlinear variation of the thermal pressure at high temperatures.     

Integrating a decomposition procedure with problem reduction for factory scheduling with disruptions: a simulation study

Dispatching rules are widely used in industry because schedules obtained from optimization procedures can be difficult to implement in the face of executional uncertainties. Barua et al. (Barua, A., Narasimhan, R., Upasani, A. and Uzsoy, R., Implementing global factory schedules in the face of stochastic disruptions. Int. J. Prod. Res., 2005, 43(4), 793–818) implement global schedules obtained from an optimization-based heuristic using a dispatching rule, and outperform myopic dispatching rules in the face of disruptions. However, the computation of the global schedules is still time-consuming for realistic instances. Upasani et al. (Upasani, A., Uzsoy, R. and Sourirajan, K., A problem reduction approach for scheduling semiconductor wafer fabrication facilities. IEEE Trans. Semicon. Manuf., 2006, 19, 216–225) develop a problem reduction scheme based on load disparity between work centres, and report significant reduction in CPU times with minimal loss of solution quality in deterministic experiments. In this paper we integrate the problem-reduction scheme to obtain global schedules with the dispatching approach of Barua et al. (Barua, A., Narasimhan, R., Upasani, A. and Uzsoy, R., Implementing global factory schedules in the face of stochastic disruptions. Int. J. Prod. Res., 2005, 43(4), 793–818) in a multi-product environment with stochastic machine breakdowns and job arrivals. A simulation model of a scaled-down wafer fabrication facility is used to evaluate the performance of the proposed procedures. Results show that the integrated procedure outperforms the benchmark dispatching rules while significantly reducing computation times.     

Constructing a new fuzzy classifier based on hierarchical fuzzy entropy

Abstract

In an earlier work, Lee et al. (Lee et al., 2001) presented a simple and fast fuzzy classifier that employed fuzzy entropy to evaluate pattern distribution information in a pattern space. In this paper, we extend his work to propose a new fuzzy classifier based on hierarchical fuzzy entropy (FC‐HFE). We retained the main parts of the original structure and modified some methods (e.g., methods for deciding the number of intervals in each dimension and for assigning class labels). In addition, the hierarchical fuzzy entropy is proposed for partitioning the decision region. The proposed FC‐HFE improves classification accuracy and overcomes some of the drawbacks in the Lee et al method (Lee et al., 2001). The simulation results show that the classification rate of the proposed FC‐HFE is better than earlier methods.     

Use of standardized sequences of flight-by-flight load spectra in fatigue testing of structural aircraft components

Following the initial proposal by Schütz et al., at the 1975 LAUSANNE ICAF Meeting, of a standardized load sequence to be used in fatigue tests of representative components of commercial aircraft wings, other standardized sequences are proposed. They correspond to the same global spectrum of cumulative frequency of load level exceedance used by Schütz et al, but besides $\text{s = 0.22}$ for the standard deviation of extreme load values per flight, other used $\text{s-}\text{values}$ are 0.17,0.12 and 0. These standardized load sequences are proposed for use in carrying out fatigue tests that might show whether or not the quality classification of several technological solutions, differing in the material or the detail design, is significantly modified by the selected value of the standard deviation of extreme load per flight values. So as to apply standardized random flight-by-flight loading programs to costly development tests, shortened sequences are proposed together with a simplified loading program simulating aircraft ground loads.     

Letter to the Editor

Sir, Comments on ‘Are all photon radiations similar in largeabsorbers?—A comparison of electron spectra’ byA. M. Kellerer and H. Roos In a recent publication⁽¹⁾, Kellerer and Roos demonstrate thatthe secondary electron spectrum inside a large absorber exposedto 1 MeV photons, compared to the secondary electron spectruminside a small absorber, is substantially shifted to lower energies.This phenomenon is     

Adoption of right turn on red—Effects on injury accidents at signalized intersections: A comment on Zador,Moshman and Marcus

Zador, Moshman and Marcus estimated an increase in right-turn accidents of 21% following the adoption of right turn on red. However, their study contained property damage only accidents, as well as injury accidents, and the change in injury accidents was not reported. An insignificant decrease (?0.7%) in accidents involving incapacitating injury was reported, however. It is suggested that Zador et al. report on the change in injury accidents in their sample.     

Convergence of implicit-explicit algorithms in nonlinear transient analysis

Recently introduced implicit-explicit algorithms in transient analysis are not covered by the standard convergence theorems. Convergence is established herein for the methods introduced by Hughes et al. The techniques employed are general and may be easily extended to encompass related formulations.     

Flexible kanbans to enhance volume flexibility in a JIT environment: a simulation based comparison via ANNs

Kanbans play an important role in the information and material flows in a JIT production system. The traditional kanban system with a fixed number of cards does not work satisfactorily in an unstable environment. In the flexible kanban-type pull control mechanism the number of kanbans is allowed to change with respect to the inventory and backorder level. Based on the need for the flexible kanban, a method was proposed by (Husseini, S.M.M., O’Brien, C., and Hosseini, S.T., 2006. A method to enhance volume flexibility in JIT production control. International Journal of Production Economics, 104 (2), 653–665), using an integer linear programming technique, to flexibly determine the number of kanbans for each stage of a JIT production system, minimising total inventory cost for a given planning horizon. Here, the effectiveness of the method proposed by Husseini et al. is examined by a case study and compared with the results for the conventional method of fixed kanban determination. This is also confirmed by a simulation study using artificial neural networks (ANNs). The main aim of this paper is to show the cost advantage for Husseini et al.'s method over the conventional method in fluctuating demand situations, and especially to prove that simulation via ANNs ensures a simplified representation for this method and is time saving.     

On the “limitations of the Petroski-Achenbach crack opening displacement approximation for the calculation of weight function” — Do they really exist?

The limitations of the Petroski Achenbach crack opening displacement approximation discussed by F. Görner, C. Mattheck and P. Morawietz (Engineering Fracture Mechanics, 22, 269 277 (1985)) have been re-analysed. It is shown that the Petroski-Achenbach crack opening displacement function can be determined from any reference stress intensity factor contrary to the conclusion drawn by Görner et al. Thus, the method does not need to be limited only to the cases where the reference stress intensity factors for the homogeneously distributed reference stresses are known.     

Deadlock avoidance algorithm for flexible manufacturing systems by calculating effective free space of circuits†

Modern flexible manufacturing systems (FMS) are highly automated and flexible in which raw parts of various types are processed concurrently. Deadlock issue arises easily in these systems due to shared equipment usage and high production flexibility. It was indicated in Wysk et al . (Wysk, R., Yang, N. and Joshi, S., Detection of deadlocks in flexible manufacturing cells. IEEE Trans. Rob. Auto., 1991, 7, 853–859.) that when a manufacturing system is modelled by a digraph, existence of circuits in such a graph is a necessary condition for deadlock. Deadlock avoidance for systems with free choice in part routing has been well studied in the Petri net formalism, however, we have not found that it has been studied systematically in the digraph formalism. Because of choices introduced, part flow dynamics become much more complex. Based on our previous work Zhang et al . (Zhang, W., Judd, R.P. and Paul P., Evaluating order of circuits for deadlock avoidance in a flexible manufacturing system. Int. J. Prod. Res., 2006, 44, 5247–5259.), this paper presents a deadlock avoidance algorithm for FMS, which allows free choices in part routing by calculation of effective free space of circuits of the digraph model. The algorithm is highly permissive since the effective free space calculation captures more parts flow dynamics, especially when there exist multiple knots in the digraph model. And it runs in polynomial time once the set of circuits of the digraph is computed offline. Simulation results on selected examples are given.     

Electron-induced transformation in an organic molecular crystal

Electron microscopic techniques reveal that at temperatures below 130 K the stable, triclinic phase of p-terphenyl, in which the molecules are non-planar, may be converted by electron irradiation (100 kev) to the monoclinic, room temperature characteristic structure in which the p-terphenyl molecule is thought to be effectively planar. The diffraction patterns and bright field images are interpretable in terms of the recent X-ray elucidation, by Baudour $\text{et al}$, of the structure at 113 K.