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1 – 10 of over 52000Zhizhong Guo, Fei Liu, Yuze Shang, Zhe Li and Ping Qin
This research aims to present a novel cooperative control architecture designed specifically for roads with variations in height and curvature. The primary objective is to enhance…
Abstract
Purpose
This research aims to present a novel cooperative control architecture designed specifically for roads with variations in height and curvature. The primary objective is to enhance the longitudinal and lateral tracking accuracy of the vehicle.
Design/methodology/approach
In addressing the challenges posed by time-varying road information and vehicle dynamics parameters, a combination of model predictive control (MPC) and active disturbance rejection control (ADRC) is employed in this study. A coupled controller based on the authors’ model was developed by utilizing the capabilities of MPC and ADRC. Emphasis is placed on the ramifications of road undulations and changes in curvature concerning control effectiveness. Recognizing these factors as disturbances, measures are taken to offset their influences within the system. Load transfer due to variations in road parameters has been considered and integrated into the design of the authors’ synergistic architecture.
Findings
The framework's efficacy is validated through hardware-in-the-loop simulation. Experimental results show that the integrated controller is more robust than conventional MPC and PID controllers. Consequently, the integrated controller improves the vehicle's driving stability and safety.
Originality/value
The proposed coupled control strategy notably enhances vehicle stability and reduces slip concerns. A tailored model is introduced integrating a control strategy based on MPC and ADRC which takes into account vertical and longitudinal force variations and allowing it to effectively cope with complex scenarios and multifaceted constraints problems.
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Chongyi Chang, Gang Guo, Wen He and Zhendong Liu
The objective of this study is to investigate the impact of longitudinal forces on extreme-long heavy-haul trains, providing new insights and methods for their design and…
Abstract
Purpose
The objective of this study is to investigate the impact of longitudinal forces on extreme-long heavy-haul trains, providing new insights and methods for their design and operation, thereby enhancing safety, operational efficiency and track system design.
Design/methodology/approach
A longitudinal dynamics simulation model of the super long heavy haul train was established and verified by the braking test data of 30,000 t heavy-haul combination train on the long and steep down grade of Daqing Line. The simulation model was used to analyze the influence of factors on the longitudinal force of super long heavy haul train.
Findings
Under normal conditions, the formation length of extreme-long heavy-haul combined train has a small effect on the maximum longitudinal coupler force under full service braking and emergency braking on the straight line. The slope difference of the long and steep down grade has a great impact on the maximum longitudinal coupler force of the extreme-long heavy-haul trains. Under the condition that the longitudinal force does not exceed the safety limit of 2,250 kN under full service braking at the speed of 60 km/h the maximum allowable slope difference of long and steep down grade for 40,000 t super long heavy-haul combined trains is 13‰, and that of 100,000 t is only 5‰.
Originality/value
The results will provide important theoretical basis and practical guidance for further improving the transportation efficiency and safety of extreme-long heavy-haul trains.
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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 bending…
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.
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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 and…
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.
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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 process…
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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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 cyclic pitch…
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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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).
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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M. Grujicic, H. Marvi, G. Arakere and I. Haque
The purpose of this paper is to carry out a series of transient, non‐linear dynamics finite element analyses in order to investigate the interactions between a stereotypical…
Abstract
Purpose
The purpose of this paper is to carry out a series of transient, non‐linear dynamics finite element analyses in order to investigate the interactions between a stereotypical pneumatic tire and sand during off‐road vehicle travel.
Design/methodology/approach
The interactions were considered under different combined conditions of the longitudinal and lateral slip as encountered during “brake‐and‐turn” and “drive‐and‐turn” vehicle maneuvers. Different components of the pneumatic tire were modeled using elastic, hyper‐ and visco‐elastic material models (with rebar reinforcements), while sand was modeled using the CU‐ARL sand models developed by Grujicic et al. The analyses were used to obtain functional relations between the wheel vertical load, wheel sinkage, tire deflection, (gross) traction, motion resistance and the (net) drawbar pull. These relations were next combined with Pacejka magic formula for a pneumatic tire/non‐deformable road interaction to construct a tire/sand interaction model suitable for use in multi‐body dynamics analysis of the off‐road vehicle performance.
Findings
To rationalize the observed traction and motion resistance relations, a close examination of the distribution of the normal and shear contact stresses within the tire/sand contact patch is carried out and the results were found to be consistent with the experimental counter parts.
Originality/value
The paper offers insights into the interactions between a stereotypical pneumatic tire and sand during off‐road vehicle travel.
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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.
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Tobias Feldhoff, Falk Radisch and Linda Marie Bischof
The purpose of this paper is to focus on challenges faced by longitudinal quantitative analyses of school improvement processes and offers a systematic literature review of…
Abstract
Purpose
The purpose of this paper is to focus on challenges faced by longitudinal quantitative analyses of school improvement processes and offers a systematic literature review of current papers that use longitudinal analyses. In this context, the authors assessed designs and methods that are used to analyze the relation between school improvement processes and student outcomes. Based on this the authors point out to what extent the papers consider different aspects of the complex nature of school improvement (e.g. multilevel structure, indirect and nonlinear effects, reciprocity). The choice of study designs and methods of analysis substantially determines which aspects of this complexity are taken into account.
Design/methodology/approach
The authors searched in four international high-impact journals and in ERIC for articles reporting longitudinal school improvement studies. The database of the review consisted of a total of 428 journal articles. In total, 13 of the 428 papers met the selection criteria and were analyzed in detail.
Findings
The analyzed papers use a wide range of designs and methodological approaches. They support the assumption that sophisticated quantitative longitudinal designs and methods can be applied effectively in school improvement research. However, considering the complexity of school improvement is accompanied by high demands on designs and methods. Due to this none of the papers met the standards applied in this review completely.
Research limitations/implications
In particular, further research is needed to consider a long period of observation, reciprocal indirect and nonlinear processes in a multilevel structure. Moreover, research is required for a better and unambiguous theoretical foundation and empirical validation of the number of and intervals between measurement points.
Practical implications
If more consideration is given to the complex nature of school improvement in future studies, the broader knowledge base will allow a better understanding of the dynamic relation of school improvement and student learning. It would thus be possible to make more appropriate recommendations for the support of school improvement practice.
Originality/value
The original contribution of the paper is to show which aspects of the complexity of school improvement processes – and to what extent – are currently addressed in designs and methods of analysis applied in quantitative longitudinal studies that investigate the relation between schools’ capacity to managing change and student outcomes. Additionally the authors aim at deriving need for further research and giving guidelines how designs and methods in further studies can reflect the complexity appropriately. It is highly important to consider all aspects of this complexity to describe and understand the dynamic relation of school improvement processes and student outcomes.
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