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Open Access
Article
Publication date: 15 November 2022

Zhiqiang Zhang, Xingyu Zhu and Ronghua Wei

Large displacement misalignment under the action of active faults can cause complex three-dimensional deformation in subway tunnels, resulting in severe damage, distortion…

Abstract

Purpose

Large displacement misalignment under the action of active faults can cause complex three-dimensional deformation in subway tunnels, resulting in severe damage, distortion and misalignment. There is no developed system of fortification and related codes to follow. There are scientific problems and technical challenges in this field that have never been encountered in past research and practices.

Design/methodology/approach

This paper adopted a self-designed large-scale active fault dislocation simulation loading system to conduct a similar model test of the tunnel under active fault dislocation based on the open-cut tunnel project of the Urumqi Rail Transit Line 2, which passes through the Jiujiawan normal fault. The test simulated the subway tunnel passing through the normal fault, which is inclined at 60°. This research compared and analyzed the differences in mechanical behavior between two types of lining section: the open-cut double-line box tunnel and the modified double-line box arch tunnel. The structural response and failure characteristics of the open-cut segmented lining of the tunnel under the stick-slip part of the normal fault were studied.

Findings

The results indicated that the double-line box arch tunnel improved the shear and longitudinal bending performance. Longitudinal cracks were mainly distributed in the baseplate, wall foot and arch foot, and the crack position was basically consistent with the longitudinal distribution of surrounding rock pressure. This indicated that the longitudinal cracks were due to the large local load of the cross-section of the structure, leading to an excessive local bending moment of the structure, which resulted in large eccentric failure of the lining and formation of longitudinal cracks. Compared with the ordinary box section tunnel, the improved double-line box arch tunnel significantly reduced the destroyed and damage areas of the hanging wall and footwall. The damage area and crack length were reduced by 39 and 59.3%, respectively. This indicates that the improved double-line box arch tunnel had good anti-sliding performance.

Originality/value

This paper adopted a self-designed large-scale active fault dislocation simulation loading system to conduct a similar model test of the tunnel under active fault dislocation. This system increased the similarity ratio of the test model, improved the dislocation loading rate and optimized the simulation scheme of the segmented flexible lining and other key factors affecting the test. It is of great scientific significance and engineering value to investigate the structure of subway tunnels under active fault misalignment, to study its force characteristics and damage modes, and to provide a technical reserve for the design and construction of subway tunnels through active faults.

Details

Railway Sciences, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2755-0907

Keywords

Article
Publication date: 4 October 2022

Mojtaba Labibzadeh, Farhad Bostan Shirin and Amin Khajehdezfuly

This study aims to investigate the effects of using circular spirals as the longitudinal reinforcing bars on the performance of the concrete beams subjected to four-point…

Abstract

Purpose

This study aims to investigate the effects of using circular spirals as the longitudinal reinforcing bars on the performance of the concrete beams subjected to four-point bending load.

Design/methodology/approach

The effects of using circular spirals as the longitudinal reinforcing bars on the performance of the concrete beams subjected to four-point bending load are investigated in this study. Employing circular spirals as the main longitudinal reinforcement is a novel idea presented in this paper. In this regard, a finite element model of the beam with spiral longitudinal reinforcement was developed. After model verification, several configurations of concrete beams reinforced by longitudinal spirals were simulated under the four-point loading condition.

Findings

Obtained results showed that using the longitudinal spirals in place of the conventional longitudinal reinforcing bars can improve the bearing capacity of the concrete beam, but at the same time, increases its ductility unacceptably. In other words, the spirals reduce the initial stiffness of the beam significantly. To solve the problem, the authors decided to use the longitudinal spirals as the auxiliary bars added to the main conventional longitudinal bars in the beams. New gained results were satisfactory. By adding the longitudinal spirals to the conventional bars, not only the bearing capacity of the beam increases between 24% and 63%, but also the initial stiffness and ductility of the beam raises between 11%–29% and 3%–57%, respectively, in comparison to the corresponding beam reinforced with conventional longitudinal bars.

Originality/value

Employing circular spirals as the main longitudinal reinforcement is a novel idea presented in this paper.

Details

International Journal of Structural Integrity, vol. 13 no. 6
Type: Research Article
ISSN: 1757-9864

Keywords

Book part
Publication date: 1 August 2004

Henrich R. Greve and Eskil Goldeng

Longitudinal regression analysis is conducted to clarify causal relations and control for unwanted influences from actor heterogeneity and state dependence on…

Abstract

Longitudinal regression analysis is conducted to clarify causal relations and control for unwanted influences from actor heterogeneity and state dependence on theoretically important coefficient estimates. Because strategic management contains theory on how firms differ and how firm actions are influenced by their current strategic position and recent experiences, consistency of theory and methodology often requires use of longitudinal methods. We describe the theoretical motivation for longitudinal methods and outline some common methods. Based on a survey of recent articles in strategic management, we argue that longitudinal methods are now used more frequently than before, but the use is still inconsistent and insufficiently justified by theoretical or empirical considerations. In particular, strategic management researchers should use dynamic models more often, and should test for the presence of actor effects, autocorrelation, and heteroscedasticity before applying corrections.

Details

Research Methodology in Strategy and Management
Type: Book
ISBN: 978-1-84950-235-1

Article
Publication date: 1 December 2008

Suneeta Bhamra, Anthea Tinker, Gill Mein, Richard Ashcroft and Janet Askham

Research that follows people over a period of time (longitudinal or panel studies) is increasingly recognised as of great importance in helping us to understand the ageing…

Abstract

Research that follows people over a period of time (longitudinal or panel studies) is increasingly recognised as of great importance in helping us to understand the ageing process and changes over time in the lives of older people. If people drop out of studies ‐ which older people are more likely to do ‐ the value of the study diminishes. This research draws on evidence from ongoing and previous longitudinal studies of people aged 55 and over to examine what factors encourage the retention of participants and what causes them to drop out. The research is synthesising existing evidence, drawing together the experiences of researchers involved in longitudinal studies, and collecting some new evidence about the views of survey participants. This article reports on the first part of the research by drawing together evidence from other studies. These show that there are some factors that are related to attrition whereas for others the evidence is mixed. Methods employed by these studies to reduce attrition and retain participants are examined. It must be noted that apart from the consistent finding that attrition is associated with age, education, socio‐economic status and cognitive impairment, not all studies examined the same variables; some only being explored by one study. This makes it difficult to draw any further conclusions and indicates that attrition needs to be addressed in a uniform manner by more studies. This article identifies some implications for policy‐makers and practitioners.

Details

Quality in Ageing and Older Adults, vol. 9 no. 4
Type: Research Article
ISSN: 1471-7794

Keywords

Article
Publication date: 10 July 2007

Ranjan Ganguli, Beatrix Jehnert, Jens Wolfram and Peter Voersmann

To investigate the use of centre of gravity location on reducing cyclic pitch control for helicopter UAV's (unmanned air vehicles) and MAV's (micro air vehicles). Low…

1048

Abstract

Purpose

To investigate the use of centre of gravity location on reducing cyclic pitch control for helicopter UAV's (unmanned air vehicles) and MAV's (micro air vehicles). Low cyclic pitch is a necessity to implement the swashplateless rotor concept using trailing edge flaps or active twist using current generation low authority piezoceramic actuators.

Design/methodology/approach

An aeroelastic analysis of the helicopter rotor with elastic blades is used to perform parametric and sensitivity studies of the effects of longitudinal and lateral center of gravity (cg) movements on the main rotor cyclic pitch. An optimization approach is then used to find cg locations which reduce the cyclic pitch at a given forward speed.

Findings

It is found that the longitudinal cyclic pitch and lateral cyclic pitch can be driven to zero at a given forward speed by shifting the cg forward and to the port side, respectively. There also exist pairs of numbers for the longitudinal and lateral cg locations which drive both the cyclic pitch components to zero at a given forward speed. Based on these results, a compromise optimal cg location is obtained such that the cyclic pitch is bounded within ±5° for a BO105 helicopter rotor.

Originality/value

The reduction in the cyclic pitch due to helicopter cg location is found to significantly reduce the maximum magnitudes of the control angles in flight, facilitating the swashplateless rotor concept. In addition, the existence of cg locations which drive the cyclic pitches to zero allows for the use of active cg movement as a way to replace the cyclic pitch control for helicopter MAV's.

Details

Aircraft Engineering and Aerospace Technology, vol. 79 no. 4
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 25 May 2012

Markku Kuula and Antero Putkiranta

The purpose of this paper is to explore the possibilities and pitfalls of longitudinal studies in the field of operations management (OM).

1128

Abstract

Purpose

The purpose of this paper is to explore the possibilities and pitfalls of longitudinal studies in the field of operations management (OM).

Design/methodology/approach

A longitudinal study conducted in Finland was analyzed from the methodological point of view. In the theoretical part, a framework for analyses was created by studying the literature of longitudinal studies within and without the OM field.

Findings

Longitudinal studies are important in revealing root‐cause effects. They are particularly important in generating new ideas and theories and in questioning old ones. However, longitudinal studies are somewhat difficult to conduct and some unexpected challenges may arise, such as the effect of technology development on data retrieval.

Research limitations/implications

The analyses in this study are based on the data obtained in a longitudinal study conducted in the years 1993, 2004 and 2010. The sample in the longitudinal study is quite small for real quantitative statistical analysis, and therefore the conclusions made here are only indicative. However, the purpose of this study is to give some hints and guidance, and thus the lessons learned are valuable.

Originality/value

There are only a few studies describing methodological issues in longitudinal studies in the field of OM, and most of these studies are purely theoretical and do not refer to real experiences. This appears to be one of the first studies describing real experiences from a longitudinal study.

Details

Benchmarking: An International Journal, vol. 19 no. 3
Type: Research Article
ISSN: 1463-5771

Keywords

Book part
Publication date: 25 January 2021

Desalegn Abraha and Akmal S. Hyder

The method applied to carry out the study of the transformation of strategic alliances in emerging markets is discussed in this chapter. Specifically, this chapter…

Abstract

The method applied to carry out the study of the transformation of strategic alliances in emerging markets is discussed in this chapter. Specifically, this chapter discusses how the whole study is conducted, i.e. the identification and development of the research issues, the research aim and problem, the development of the conceptual framework, the development of the research method, how the empirical study is analyzed and conclusions are drawn. The specific research strategy applied to conduct the current study is a longitudinal research approach. A short discussion on how the ECE countries are classified into various groups is conducted in the current chapter and a detailed discussion on the classification of ECE countries into different groups is also conducted in chapter eight. Moreover, the logic for adopting a longitudinal research strategy to conduct the current study of the transformation of strategic alliances is also justified. The identification and choice of the case companies, the logic followed in the development of the questionnaire and how much and to what extent the questionnaire is modified are also discussed in detail. The identification of the interviewees, the execution of the interviews and the transcription of the interview materials and the structuring of the cases are also discussed in detail.

Details

Transformation of Strategic Alliances in Emerging Markets, Volume I
Type: Book
ISBN: 978-1-80043-745-6

Book part
Publication date: 28 August 2007

Michael C. Sturman

This article reviews the extensive history of dynamic performance research, with the goal of providing a clear picture of where the field has been, where it is now, and…

Abstract

This article reviews the extensive history of dynamic performance research, with the goal of providing a clear picture of where the field has been, where it is now, and where it needs to go. Past research has established that job performance does indeed change, but the implications of this dynamism and the predictability of performance trends remain unresolved. Theories are available to help explain dynamic performance, and although far from providing an unambiguous understanding of the phenomenon, they offer direction for future theoretical development. Dynamic performance research does suffer from a number of methodological difficulties, but new techniques have emerged that present even more opportunities to advance knowledge in this area. From this review, I propose research questions to bridge the theoretical and methodological gaps of this area. Answering these questions can advance both research involving job performance prediction and our understanding of the effects of human resource interventions.

Details

Research in Personnel and Human Resources Management
Type: Book
ISBN: 978-0-7623-1432-4

Book part
Publication date: 6 September 2021

Rachel S. Rauvola, Cort W. Rudolph and Hannes Zacher

In this chapter, the authors consider the role of time for research in occupational stress and well-being. First, temporal issues in studying occupational health…

Abstract

In this chapter, the authors consider the role of time for research in occupational stress and well-being. First, temporal issues in studying occupational health longitudinally, focusing in particular on the role of time lags and their implications for observed results (e.g., effect detectability), analyses (e.g., handling unequal durations between measurement occasions), and interpretation (e.g., result generalizability, theoretical revision) were discussed. Then, time-based assumptions when modeling lagged effects in occupational health research, providing a focused review of how research has handled (or ignored) these assumptions in the past, and the relative benefits and drawbacks of these approaches were discussed. Finally, recommendations for readers, an accessible tutorial (including example data and code), and discussion of a new structural equation modeling technique, continuous time structural equation modeling, that can “handle” time in longitudinal studies of occupational health were provided.

Details

Examining and Exploring the Shifting Nature of Occupational Stress and Well-Being
Type: Book
ISBN: 978-1-80117-422-0

Keywords

Open Access
Article
Publication date: 27 December 2021

Nengchao Lyu, Yugang Wang, Chaozhong Wu, Lingfeng Peng and Alieu Freddie Thomas

An individual’s driving style significantly affects overall traffic safety. However, driving style is difficult to identify due to temporal and spatial differences and…

Abstract

Purpose

An individual’s driving style significantly affects overall traffic safety. However, driving style is difficult to identify due to temporal and spatial differences and scene heterogeneity of driving behavior data. As such, the study of real-time driving-style identification methods is of great significance for formulating personalized driving strategies, improving traffic safety and reducing fuel consumption. This study aims to establish a driving style recognition framework based on longitudinal driving operation conditions (DOCs) using a machine learning model and natural driving data collected by a vehicle equipped with an advanced driving assistance system (ADAS).

Design/methodology/approach

Specifically, a driving style recognition framework based on longitudinal DOCs was established. To train the model, a real-world driving experiment was conducted. First, the driving styles of 44 drivers were preliminarily identified through natural driving data and video data; drivers were categorized through a subjective evaluation as conservative, moderate or aggressive. Then, based on the ADAS driving data, a criterion for extracting longitudinal DOCs was developed. Third, taking the ADAS data from 47 Kms of the two test expressways as the research object, six DOCs were calibrated and the characteristic data sets of the different DOCs were extracted and constructed. Finally, four machine learning classification (MLC) models were used to classify and predict driving style based on the natural driving data.

Findings

The results showed that six longitudinal DOCs were calibrated according to the proposed calibration criterion. Cautious drivers undertook the largest proportion of the free cruise condition (FCC), while aggressive drivers primarily undertook the FCC, following steady condition and relative approximation condition. Compared with cautious and moderate drivers, aggressive drivers adopted a smaller time headway (THW) and distance headway (DHW). THW, time-to-collision (TTC) and DHW showed highly significant differences in driving style identification, while longitudinal acceleration (LA) showed no significant difference in driving style identification. Speed and TTC showed no significant difference between moderate and aggressive drivers. In consideration of the cross-validation results and model prediction results, the overall hierarchical prediction performance ranking of the four studied machine learning models under the current sample data set was extreme gradient boosting > multi-layer perceptron > logistic regression > support vector machine.

Originality/value

The contribution of this research is to propose a criterion and solution for using longitudinal driving behavior data to label longitudinal DOCs and rapidly identify driving styles based on those DOCs and MLC models. This study provides a reference for real-time online driving style identification in vehicles equipped with onboard data acquisition equipment, such as ADAS.

Details

Journal of Intelligent and Connected Vehicles, vol. 5 no. 1
Type: Research Article
ISSN: 2399-9802

Keywords

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