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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.

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

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Article
Publication date: 7 October 2021

Vadym Mozgovoy

The authors aim to develop a conceptual framework for longitudinal estimation of stress-related states in the wild (IW), based on the machine learning (ML) algorithms that…

Abstract

Purpose

The authors aim to develop a conceptual framework for longitudinal estimation of stress-related states in the wild (IW), based on the machine learning (ML) algorithms that use physiological and non-physiological bio-sensor data.

Design/methodology/approach

The authors propose a conceptual framework for longitudinal estimation of stress-related states consisting of four blocks: (1) identification; (2) validation; (3) measurement and (4) visualization. The authors implement each step of the proposed conceptual framework, using the example of Gaussian mixture model (GMM) and K-means algorithm. These ML algorithms are trained on the data of 18 workers from the public administration sector who wore biometric devices for about two months.

Findings

The authors confirm the convergent validity of a proposed conceptual framework IW. Empirical data analysis suggests that two-cluster models achieve five-fold cross-validation accuracy exceeding 70% in identifying stress. Coefficient of accuracy decreases for three-cluster models achieving around 45%. The authors conclude that identification models may serve to derive longitudinal stress-related measures.

Research limitations/implications

Proposed conceptual framework may guide researchers in creating validated stress-related indicators. At the same time, physiological sensing of stress through identification models is limited because of subject-specific reactions to stressors.

Practical implications

Longitudinal indicators on stress allow estimation of long-term impact coming from external environment on stress-related states. Such stress-related indicators can become an integral part of mobile/web/computer applications supporting stress management programs.

Social implications

Timely identification of excessive stress may improve individual well-being and prevent development stress-related diseases.

Originality/value

The study develops a novel conceptual framework for longitudinal estimation of stress-related states using physiological and non-physiological bio-sensor data, given that scientific knowledge on validated longitudinal indicators of stress is in emergent state.

Details

Applied Computing and Informatics, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2634-1964

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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.

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

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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…

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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.

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

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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).

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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.

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

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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.

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

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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.

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

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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.

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

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Article
Publication date: 13 October 2021

Liang Su, Zhenpo Wang and Chao Chen

The purpose of this study is to propose a torque vectoring control system for improving the handling stability of distributed drive electric buses under complicated…

Abstract

Purpose

The purpose of this study is to propose a torque vectoring control system for improving the handling stability of distributed drive electric buses under complicated driving conditions. Energy crisis and environment pollution are two key pressing issues faced by mankind. Pure electric buses are recognized as the effective method to solve the problems. Distributed drive electric buses (DDEBs) as an emerging mode of pure electric buses are attracting intense research interests around the world. Compared with the central driven electric buses, DDEB is able to control the driving and braking torque of each wheel individually and accurately to significantly enhance the handling stability. Therefore, the torque vectoring control (TVC) system is proposed to allocate the driving torque among four wheels reasonably to improve the handling stability of DDEBs.

Design/methodology/approach

The proposed TVC system is designed based on hierarchical control. The upper layer is direct yaw moment controller based on feedforward and feedback control. The feedforward control algorithm is designed to calculate the desired steady-state yaw moment based on the steering wheel angle and the longitudinal velocity. The feedback control is anti-windup sliding mode control algorithm, which takes the errors between actual and reference yaw rate as the control variables. The lower layer is torque allocation controller, including economical torque allocation control algorithm and optimal torque allocation control algorithm.

Findings

The steady static circular test has been carried out to demonstrate the effectiveness and control effort of the proposed TVC system. Compared with the field experiment results of tested bus with TVC system and without TVC system, the slip angle of tested bus with TVC system is much less than without TVC. And the actual yaw rate of tested bus with TVC system is able to track the reference yaw rate completely. The experiment results demonstrate that the TVC system has a remarkable performance in the real practice and improve the handling stability effectively.

Originality/value

In view of the large load transfer, the strong coupling characteristics of tire , the suspension and the steering system during coach corning, the vehicle reference steering characteristics is defined considering vehicle nonlinear characteristics and the feedforward term of torque vectoring control at different steering angles and speeds is designed. Meanwhile, in order to improve the robustness of controller, an anti-integral saturation sliding mode variable structure control algorithm is proposed as the feedback term of torque vectoring control.

Details

Assembly Automation, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0144-5154

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Article
Publication date: 16 April 2020

Sezer Çoban

This paper aims to investigate the autonomous performance optimization of a research-based hybrid unmanned aerial vehicle (i.e. HUAV) manufactured at Iskenderun Technical…

Abstract

Purpose

This paper aims to investigate the autonomous performance optimization of a research-based hybrid unmanned aerial vehicle (i.e. HUAV) manufactured at Iskenderun Technical University.

Design/methodology/approach

To maximize the autonomous performance of this HUAV, longitudinal and lateral dynamics were initially obtained. Then, the optimum magnitudes of the autopilot system parameters were estimated by considering the vehicle’s dynamic model and autopilot parameters.

Findings

After determining the optimum values of the longitudinal and lateral autopilots, an improved design for the autonomously controlled (AC) HUAV was achieved in terms of real-time flight.

Practical implications

Simultaneous improvement of the longitudinal and lateral can be used for better HUAV operations.

Originality/value

In this paper, the autopilot systems (i.e. longitudinal and lateral) of an HUAV are for the first time simultaneously designed in the literature. This helps the simultaneous improvement of the longitudinal and lateral flight trajectory tracking performances.

Details

Aircraft Engineering and Aerospace Technology, vol. 92 no. 4
Type: Research Article
ISSN: 1748-8842

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