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Article
Publication date: 2 October 2020

Abraham Matthew Sagum Carandang, Lessandro Estelito O. Garciano, Osamu Maruyama and Richard De Jesus

Water distribution networks (WDNs) must deliver water to its customers 24/7. Disruption of this important service after a strong seismic event impedes post-disaster…

Abstract

Purpose

Water distribution networks (WDNs) must deliver water to its customers 24/7. Disruption of this important service after a strong seismic event impedes post-disaster activities and poses health and sanitation problems. Hence, WDNs must be able to quickly restore services after the occurrence of a major seismic event. This ability to return the water service can be a metric for resilience. The purpose of this paper is to quantify the resilience by developing a framework that translates various restoration strategies into an improved resilience measure for a multisource WDN.

Design/methodology/approach

This paper used a quantitative risk assessment method in developing the framework for the resilience quantification of WDN. Prim’s algorithm, Horn’s algorithm and maximum slope method are used for the restoration analysis conducted in this study.

Findings

This paper provides resilience indices of the WDN for each repair scenarios. Then, the resilience indices are used to determine the most efficient and optimized repair scenario to restore the hypothetically damaged WDN owing to Level 1 and Level 2 seismic events.

Research limitations/implications

The developed framework of this study only focuses on the robustness, rapidity and resourcefulness properties of resilience.

Practical implications

This study aims to help the water district in the maintenance, repair and evaluation of WDN against seismic events. The results from the study can be used in preparing the disaster management plan of the local water district to repair possible pipelines. This study also serves as a starting point to more complex and comprehensive research about the resilience quantification of WDNs with the consideration of optimal restoration sequence in the future.

Originality/value

The developed framework in the resilience quantification of WDN is original, as it uses optimal restoration strategies to represent the rapidity property of resilience.

Details

International Journal of Disaster Resilience in the Built Environment, vol. 12 no. 3
Type: Research Article
ISSN: 1759-5908

Keywords

Article
Publication date: 22 September 2020

Sotirios A. Argyroudis, Giorgos Nasiopoulos, Nikolaos Mantadakis and Stergios Aristoteles Mitoulis

Transport infrastructure resilience is of paramount importance for societies, therefore its quantification is urgently needed. A resilience assessment framework based on…

Abstract

Purpose

Transport infrastructure resilience is of paramount importance for societies, therefore its quantification is urgently needed. A resilience assessment framework based on well-informed resilience indices is presented and applied for assessing the resilience of representative bridges exposed to earthquakes.

Design/methodology/approach

The framework quantifies the robustness of bridges against different seismic hazard scenarios, by using realistic fragility functions and the rapidity of the recovery and/or retrofitting after the occurrence of a certain degree of damage, based on realistic restoration functions.

Findings

Two different approaches for the modeling of the restoration tasks are examined. Both direct losses due to structural damage and indirect losses due to traffic disruption are estimated.

Originality/value

A new cost-based resilience index is introduced and alternate approaches for expressing the restoration strategies are examined and assessed. The results facilitate owners to enhance cost-based resilience management toward more resilient infrastructure.

Details

International Journal of Disaster Resilience in the Built Environment, vol. 12 no. 2
Type: Research Article
ISSN: 1759-5908

Keywords

Article
Publication date: 1 October 1996

Roy H. Grieve

The recent publication of a sixth edition of Dornbusch and Fischer’s (D&F’s) Macroeconomics will be of interest to many teachers of macro theory. D&F’s text must currently…

1570

Abstract

The recent publication of a sixth edition of Dornbusch and Fischer’s (D&F’s) Macroeconomics will be of interest to many teachers of macro theory. D&F’s text must currently be one of the most widely used intermediate‐level guides to macroeconomics; as the authors themselves tell us, the book has been translated into many languages and is in use around the world “from Canada to Argentina and Australia, all over Europe, in India, Indonesia and Japan, from China and Albania to Russia”. The undogmatic “middle‐of‐the‐road” approach, together with the careful and clear presentation characteristic of this user‐friendly textbook, has won it many friends.

Details

Journal of Economic Studies, vol. 23 no. 4
Type: Research Article
ISSN: 0144-3585

Keywords

Article
Publication date: 20 March 2017

Jian Gao, Hao Wen, Zhiyuan Lin, Haidong Wu, Si Li, Xin Chen, Yun Chen and Yunbo He

Remanufacturing of worn blades with various defects normally requires processes such as scanning, regenerating a geometrical reference model, additive manufacturing (AM…

358

Abstract

Purpose

Remanufacturing of worn blades with various defects normally requires processes such as scanning, regenerating a geometrical reference model, additive manufacturing (AM) through laser cladding, adaptive machining and polishing and quality inspection. Unlike the manufacturing process of a new part, the most difficult problem for remanufacturing such a complex surface part is that the reference model adaptive to the worn part is no longer available or useful. The worn parts may suffer from geometrical deformation, distortion and other defects because of the effects of harsh operating conditions, thereby making their original computer aided design (CAD) models inadequate for the repair process. This paper aims to regenerate the geometric models for the worn parts, which is a key issue for implementing AM to build up the parts and adaptive machining to reform the parts. Unlike straight blades with similar cross sections, the tip geometry of the worn tip of a twist blade needs to be regenerated by a different method.

Design/methodology/approach

This paper proposes a surface extension algorithm for the reconstruction of a twist blade tip through the extremum parameterization of a B-spline basis function. Based on the cross sections of the scanned worn blade model, the given control points and knot vectors are firstly reconstructed into a B-spline curve D. After the extremum of each control point is calculated by extremum parameterization of a B-spline basis function, the unknown control points are calculated by substituting the extremum into the curve D. Once all control points are determined, the B-spline surface of the worn blade tip can be regenerated. Finally, the extension algorithm is implemented and validated with several examples.

Findings

The proposed algorithm was implemented and verified through the exampled blades. Through the extension algorithm, the tip geometry of the worn tip of a twist blade can be regenerated. This method solved a key problem for the repair of a twist blade tip. It provides an appropriate reference model for repairing worn blade tips through AM to build up the blade tip and adaptive machining/polishing processes to reform the blade geometry.

Research limitations/implications

The extension errors for different repair models are compared and analyzed. The authors found that there are several factors affecting the accuracy of the regenerated model. When the cross-section interval and the extension length are set properly, the restoration accuracy for the blade tip can be improved, which is acceptable for the repairing.

Practical implications

The lack of a reference geometric model for worn blades is a significant problem when implementing blade repair through AM and adaptive machining processes. Because the geometric reference model is unavailable for the repair process, reconstruction of the geometry of a worn blade tip is the first crucial step. The authors proposed a surface extension algorithm for the reconstruction of a twist blade tip. Through the implementation of the proposed algorithm, the blade tip model can be regenerated.

Social implications

Remanufacturing of worn blades with various defects is highly demeaned for the aerospace enterprises considering sustainable development. Unlike straight blades, repair of twist blades encountered a very difficult problem because the geometric reference model is unavailable for the repair processes. This paper proposed a different method to generate the reference model for the repair of a twist blade tip. With this model, repair of twist blades can be implemented through AM to build up the blade tip and adaptive machining to subtract the extra material.

Originality/value

The authors proposed a surface extension algorithm to reconstruct the geometric model for repair of twist blades.

Book part
Publication date: 18 February 2004

Daniele Besomi

The scientific correspondence between Harrod and Robertson was initiated by Harrod’s criticism of Robertson’s Banking Policy and the Price Level (1926).7 Harrod first…

Abstract

The scientific correspondence between Harrod and Robertson was initiated by Harrod’s criticism of Robertson’s Banking Policy and the Price Level (1926).7 Harrod first wrote on 18 May 1926 (letter 2) raising at once the following “salient point”: Much of your argument depends on the view that justifiable expansions and contractions as defined by you are desirable. Why are they desirable? You give reasons on p. 22 why you think some instability in output desirable. But the reasons mentioned there (and I can’t find any others) don’t seem particularly directed to show that the special form of instability constituted by the so-called “justifiable” expansions and contractions is desirable. They seem to me to show that perhaps some instability, that, presumably, of less degree than we have been accustomed to in the past, is good, but by no means precisely how much is good. Thus, suppose the “hypothetical group member” or “the actual workman” of p. 19 were able to govern output according to their own self interest, there would still, according to the arguments of ch. 2, be some instability. Would not that be enough? Or if you want more, why stop at the “justifiable”? Why not have some of that due to “secondary” causes? It seems to me that you have been led away by purely aesthetic interests to identify that more moderate amount of instability which we really need (as shown on p. 22.) with that which we would get: (i) if secondary causes were removed; and (ii) if control of output stayed where it is now – in the hands of the entrepreneur. I don’t see how you can say to the banks more than “damp down fluctuation a bit, but leave some fluctuation, as that is healthful for the body economic”.He added two notes to his letter, in the first of which he commented upon the four proposed courses of policy outlined by Robertson on pp. 25–26 of his book. In the second note Harrod suggested that Robertson’s calculations in Appendix I to Ch. 5 of Banking Policy assumed the following behaviour of the public: (i) People do not allow for the effect of their withholding on the price level (this is reasonable). (ii) They are ignorant as the future course of inflation (or do nothing to meet it). (iii) On this basis they decide what withholding is necessary to restore H, decide that it would be too much effort to restore it at once, and…spread the restoration over K – 1 days. It so happens that by choosing K – 1 their 2 errors (or failures to take everything into account) cancel each other out, and they do effect the restoration in that time. If K or K – 2 had been chosen, this would not have been so.Harrod further argued that Robertson’s “so-called reasonable assumption of a restoration in K – 1 days is purely arbitrary,” and that “all this reasoning is rendered of doubtful value by the fact that we must suppose an alteration in view as to ‘the appropriate proportion between Real Hoarding and Real Income’ during the process of inflation. Not only will people not replenish H at once, but they may well voluntarily reduce it.”

Details

A Research Annual
Type: Book
ISBN: 978-0-76231-089-0

Article
Publication date: 9 March 2010

Jie Liu, Biao Zhang, Chunze Yan and Yusheng Shi

The purpose of this paper is to report a study about the rapid prototyping method of dental glass‐ceramic restoration.

2034

Abstract

Purpose

The purpose of this paper is to report a study about the rapid prototyping method of dental glass‐ceramic restoration.

Design/methodology/approach

Dental glass‐ceramic restoration materials have excellent physical and chemical, mechanical, aesthetic and biocompatibility characteristics. However, casting methods adopted at present have complicated procedures and high costs; the forming qualities are especially difficult to control. These problems greatly restrict their clinical application and promotion. Therefore, a new forming process based on selective laser sintering (SLS) technology is proposed. First, dental glass‐ceramic is processed into fine powder through a special heat treatment process. Then, the dental restoration parts are manufactured using SLS without any moulds. In this paper, the effects of processing parameters including laser power, scan speed, scan spacing and preheating temperature on the relative density and mechanical properties of the sintered parts are studied.

Findings

The experimental results have shown that for the composite powder of epoxy resin binder E‐12 and K2O‐Al2O3‐SiO2 series of dental glass‐ceramics, when preheating temperature, layer thickness, laser power, scan speed and scan spacing are, respectively, 30∼35°C, 0.08 mm, 21 W, 1,800 mm/s and 0.10 mm/s, the relative densities of dental glass‐ceramic parts are relatively high; the mechanical properties and forming effect are excellent. The relative density and bending strength of SLS parts under the optimized processing parameters are 37.40 per cent and 2.08 MPa, respectively.

Research limitations/implications

This study only concerns the preparation and SLS of the dental glass‐ceramic powders. Further investigations are planned to be conducted on post processing, such as binder decomposition, isostatic press and high temperature sintering.

Originality/value

This study will provide a theoretical and technical basis for dental glass‐ceramic restorations of SLS.

Details

Rapid Prototyping Journal, vol. 16 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 6 November 2018

Carlos Alejandro Garcia Rosales, Hoejin Kim, Mario F. Garcia Duarte, Luis Chavez, Tzu-Liang Bill Tseng and Yirong Lin

Shape memory polymers (SMPs) are classified as smart materials owing to their inherent stimulus-induced response. SMPs are capable of recovering partially or totally to…

Abstract

Purpose

Shape memory polymers (SMPs) are classified as smart materials owing to their inherent stimulus-induced response. SMPs are capable of recovering partially or totally to its original shape after a high degree of deformation by external stimulus. The most used stimuli are thermal, light, magnetic field and electricity. This research aims to characterize the toughness property of thermo-responsive SMP specimens fabricated by the material extrusion (ME) process and to investigate the impact of ME parameters on specimen maximum load and load-displacement curves. Moreover, to investigate the recovery efficiency based on the initial and post toughness generated by the compact tension test.

Design/methodology/approach

A design of experiments with three parameters (temperature, velocity and layer height) defined the ME settings to fabricate the specimens. The ME raster orientation factor was also evaluated separately. In addition, one more specimen group assisted by a clamp during the recovery process was compared with a specimen control group. After fabrication, specimens were submitted to a thermo-mechanical cycle that encompasses a compact tension test and a thermo-recovery process. Comparison studies of load-displacement, toughness and recovery efficiency of the specimens were carried out to determine the optimized fabrication parameters.

Findings

It was found that ME parameters and raster orientation impacted the test results. Samples with the clamp support during recovery returned a higher toughness than samples without support. Finally, results showed that the shape memory effect can contribute with up to 43 per cent recovery efficiency in a first recovery and up to 23 per cent in a second recovery of damaged specimens.

Originality/value

This paper is a reference for toughness and recovery properties of SMP parts produced by the ME fabrication process.

Details

Rapid Prototyping Journal, vol. 25 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 1 December 2000

S. Ginzburg and E.M. Dar‐El

Some of the conventions regarding relearning of complex tasks (requiring both psychomotor and procedural skills) are well known, especially as relating to retention curves

1790

Abstract

Some of the conventions regarding relearning of complex tasks (requiring both psychomotor and procedural skills) are well known, especially as relating to retention curves. Still lacking, however, is information which better clarifies the relationship between relearning and skill retention. The purpose of this study was to examine this relationship while identifying the parameter affecting the duration between training intervals, in order to maintain a high level of performance. Two additional aspects were examined in this study: actual differences in the measure of decrease in the operator’s level for various task dimensions and the implication for integrating a simulator in the refresher training program. This study conducted a controlled field experiment in a military electronic warfare unit, examining refresher training of reserve soldiers operating a complex electronic system. Examination of the study’s hypotheses and analysis of the experiment’s results indicated a cyclical behavioral model of the retention curve and the relearning aspects involved (training intervals, “warming up” phenomenon, model boundaries etc.). This result necessitates the inclusion of the retention curve within the framework of the instruction task analysis (especially with training programs which include refresher training). It should be noted that the study’s conclusions are valid not merely for military tasks, but are also valid for implementation in complex civilian tasks.

Details

Journal of Workplace Learning, vol. 12 no. 8
Type: Research Article
ISSN: 1366-5626

Keywords

Article
Publication date: 5 May 2015

Archana Rethinam, Vinoo D. Shivakumar, L. Harish, M.B. Abhishek, G.V. Ramana, Madhusudana R., R. Sah and S. Manjini

The application of new technologies requires, however, modern rolling mills. Indeed, in manufacturing plants of older types, strict compliance with the developed rolling…

Abstract

Purpose

The application of new technologies requires, however, modern rolling mills. Indeed, in manufacturing plants of older types, strict compliance with the developed rolling regimes is not always feasible. Improving the mechanical properties in such cases is possible only by means of cooling. Compressive deformation behavior of carbon–manganese (C-Mn) grade has been investigated at temperatures ranging from 800-900°C and strain rate from 0.01-50 s−1 on Gleeble-3800, a thermo-mechanical simulator. Simulation studies have been conducted mainly to observe the microstructural changes for various strain rate and deformation temperatures at a constant strain of 0.5 and a cooling rate of 20°C s−1.

Design/methodology/approach

The project begins with simulation of a hot rolling condition using the thermo-mechanical simulator; this was followed by microstructural examination and identification of phases present by using an optical microscope for hot-rolled coil and simulated samples; grain size measurement and size distribution studies; and optimization of finishing temperature, coiling temperature and cooling rate by mimicking plant processing parameters to improve the mechanical properties.

Findings

As the strain rate and temperature increase, pearlite banding decreases gradually and finally gets completely eliminated, thereby improving the mechanical properties. True stress–strain curves were plotted to extrapolate the effect of strain-hardening and strain rate sensitivity on austenite (γ) and austenite–ferrite (γ-a) regions. To validate the effect of strain rate and temperature over the grain size, the hardness of simulated samples was measured using the universal hardness tester and the corresponding tensile strength was found from the standard hardness chart.

Practical implications

The results of the study carried out have projected a new technology of thermo-mechanical simulation for the studied C-Mn grade. These results were used to optimize the plant processing parameter like finishing and coiling temperature and finishing stands strain rate.

Originality/value

By controlling the hot rolling conditions like finishing, coiling temperature and cooling rate, structures differing in mechanical properties can be obtained for the same material. Accurate understanding of a structure being formed when different temperatures are applied enables the control of the process that assures intended structures and mechanical properties are achieved.

Details

Journal of Engineering, Design and Technology, vol. 13 no. 2
Type: Research Article
ISSN: 1726-0531

Keywords

Article
Publication date: 22 May 2020

Crislaine da Cruz, Ivan Mathias, Mariza Veiga Senk, Gelson Biscaia de Souza and Francisco Carlos Serbena

Lithium disilicate glass-ceramics (LS2 GC) are widely used as dental prosthetics and dental restorations. Based LS2 GC have hardness and translucency similar to that of…

Abstract

Purpose

Lithium disilicate glass-ceramics (LS2 GC) are widely used as dental prosthetics and dental restorations. Based LS2 GC have hardness and translucency similar to that of natural teeth. This study aims to investigate the tribological features of LS2 GC with crystalline volume fraction of 64% and different crystal sizes from 8 µm to 34 µm for different counterparts.

Design/methodology/approach

The tribological behavior was investigated using a pin-on-disc tribometer with alumina and tungsten carbide (WC) spheres, applied load of 5 N and sliding speed of 5 cm/s at normal conditions. The coefficient of friction was measured continuously up to 10,000 sliding cycles. The specific wear rate was calculated from tribological and profile measurements. The wear mechanism was investigated by surface morphology analysis.

Findings

The coefficient of friction during running-in varied from 0.8 to 1.0 for the alumina counterpart, because of severe wear. Afterwards, it reduced and reached a stationary regime, characterized by a mild wear regime and the formation of a tribolayer formed by the debris. For the WC counterpart, the coefficient of friction curves increased initially with sliding cycles up to a stationary regime. The samples tested against WC presented the lowest specific wear rate (k), and no variation of wear rate with crystal size was observed. For samples tested against the alumina, crystallization and crystal size increased the wear resistance.

Originality/value

This study evaluated the effect of different counterfaces on the tribological properties of the LS2 GC, an important glass-ceramic base for many dental prosthetics and dental restorations, discussing results in light of the contact mechanics. Different specific wear rates, wear regimes and dependence on the glass-ceramic microstructure were observed depending on the counterpart.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0352/

Details

Industrial Lubrication and Tribology, vol. 72 no. 9
Type: Research Article
ISSN: 0036-8792

Keywords

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