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Article
Publication date: 1 January 1986

S. Rakheja and S. Sankar

The non‐linear damping mechanisms are expressed in two general forms: velocity dependent and displacement dependent. The non‐linear damping phenomena are expressed by an array of…

59

Abstract

The non‐linear damping mechanisms are expressed in two general forms: velocity dependent and displacement dependent. The non‐linear damping phenomena are expressed by an array of ‘local constants’, whose value depends upon excitation frequency, excitation amplitude, and type of non‐linearity. Thus, the non‐linear system is replaced by several localized linear systems corresponding to every discrete frequency and amplitude of excitation. Each of the localized linear systems, thus formulated, characterizes the response behaviour of the original non‐linear system, quite accurately in the vicinity of the specific frequency and amplitude of excitation. An algorithm is developed, which expresses the non‐linear damping by an array of ‘local constants’. The algorithm then employs the usual linear design tools to generate the response characteristics almost identical to the response behaviour of the non‐linear system.

Details

Engineering Computations, vol. 3 no. 1
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 April 1991

S. RAKHEJA and A.K.W. AHMED

A local equivalent linearization methodology is proposed to simulate non‐linear shock absorbers and dual‐phase dampers in the convenient frequency domain. The methodology based on…

122

Abstract

A local equivalent linearization methodology is proposed to simulate non‐linear shock absorbers and dual‐phase dampers in the convenient frequency domain. The methodology based on principle of energy similarity, characterizes the non‐linear dual‐phase dampers via an array of local damping constants as function of local excitation frequency and amplitude, response, and type of non‐linearity. The non‐linear behaviour of the dual‐phase dampers can thus be predicted quite accurately in the entire frequency range. The frequency response characteristics of a vehicle model employing non‐linear dual‐phase dampers, evaluated using local linearization algorithm, are compared to those of the non‐linear system, established via numerical integration, to demonstrate the effectiveness of the algorithm. An error analysis is performed to quantify the maximum error between the damping forces generated by non‐linear and locally linear simulations. The influence of damper parameters on the ride improvement potentials of dual‐phase dampers is further evaluated using the proposed methodology and discussed.

Details

Engineering Computations, vol. 8 no. 4
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 15 July 2021

Ramneek Sidhu and Mayank Kumar Rai

This paper aims to present the edge scattering dominant circuit modeling. The effect of crosstalk on gate oxide reliability (GOR), along with the mitigation using shielding…

43

Abstract

Purpose

This paper aims to present the edge scattering dominant circuit modeling. The effect of crosstalk on gate oxide reliability (GOR), along with the mitigation using shielding technique is further studied.

Design/methodology/approach

An equivalent distributed Resistance Inductance Capacitance circuit of capacitively coupled interconnects of multilayer graphene nanoribbon (MLGNR) has been considered for T Simulation Program with Integrated Circuit Emphasis (TSPICE) simulations under functional and dynamic switching conditions. Complementary metal oxide semiconductor driver transistors are modeled by high performance predictive technology model that drive the distributed segment with a capacitive load of 0.001 fF, VDD and clock frequency as 0.7 V and 0.2 GHz, respectively, at 14 nm technology node.

Findings

The results reveal that the crosstalk induced delay and noise area are dominated by the overall mean free path (MFP) (i.e. including the effect of edge roughness induced scattering), in contrary to, acoustic and optical scattering limited MFP with the temperature, width and length variations. Further, GOR, estimated in terms of average failure rate (AFR), shows that the shielding technique is an effective method to minimize the relative GOR failure rate by, 0.93e-7 and 0.7e-7, in comparison to the non-shielded case with variations in interconnect’s length and width, respectively.

Originality/value

Considering realistic circuit modeling for MLGNR interconnects by incorporating the edge roughness induced scattering mechanism, the outcomes exhibit more penalty in terms of crosstalk induced noise area and delay. The shielding technique is found to be an effective mitigating technique for minimizing AFR in coupled MLGNR interconnects.

Details

Circuit World, vol. 48 no. 4
Type: Research Article
ISSN: 0305-6120

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Available. Open Access. Open Access
Article
Publication date: 29 March 2024

Xingwen Wu, Zhenxian Zhang, Wubin Cai, Ningrui Yang, Xuesong Jin, Ping Wang, Zefeng Wen, Maoru Chi, Shuling Liang and Yunhua Huang

This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.

928

Abstract

Purpose

This review aims to give a critical view of the wheel/rail high frequency vibration-induced vibration fatigue in railway bogie.

Design/methodology/approach

Vibration fatigue of railway bogie arising from the wheel/rail high frequency vibration has become the main concern of railway operators. Previous reviews usually focused on the formation mechanism of wheel/rail high frequency vibration. This paper thus gives a critical review of the vibration fatigue of railway bogie owing to the short-pitch irregularities-induced high frequency vibration, including a brief introduction of short-pitch irregularities, associated high frequency vibration in railway bogie, typical vibration fatigue failure cases of railway bogie and methodologies used for the assessment of vibration fatigue and research gaps.

Findings

The results showed that the resulting excitation frequencies of short-pitch irregularity vary substantially due to different track types and formation mechanisms. The axle box-mounted components are much more vulnerable to vibration fatigue compared with other components. The wheel polygonal wear and rail corrugation-induced high frequency vibration is the main driving force of fatigue failure, and the fatigue crack usually initiates from the defect of the weld seam. Vibration spectrum for attachments of railway bogie defined in the standard underestimates the vibration level arising from the short-pitch irregularities. The current investigations on vibration fatigue mainly focus on the methods to improve the accuracy of fatigue damage assessment, and a systematical design method for vibration fatigue remains a huge gap to improve the survival probability when the rail vehicle is subjected to vibration fatigue.

Originality/value

The research can facilitate the development of a new methodology to improve the fatigue life of railway vehicles when subjected to wheel/rail high frequency vibration.

Details

Railway Sciences, vol. 3 no. 2
Type: Research Article
ISSN: 2755-0907

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Available. Open Access. Open Access
Article
Publication date: 27 August 2024

Wei Li, Xiaoxuan Yang, Peng Wang, Zefeng Wen and Jian Han

This study aims to investigate the cause of high-order wheel polygonization in a plateau high-speed electric multiple unit (EMU) train.

164

Abstract

Purpose

This study aims to investigate the cause of high-order wheel polygonization in a plateau high-speed electric multiple unit (EMU) train.

Design/methodology/approach

A series of field tests were conducted to measure the vibration accelerations of the axle box and bogie when the wheels of the EMU train passed through tracks with normal rail roughness after re-profiling. Additionally, the dynamic characteristics of the track, wheelset and bogie were also measured. These measurements provided insights into the mechanisms that lead to wheel polygonization.

Findings

The results of the field tests indicate that wheel polygonal wear in the EMU train primarily exhibits 14–16 and 25–27 harmonic orders. The passing frequencies of wheel polygonization were approximately 283–323 Hz and 505–545 Hz, which closely match the dominated frequencies of axle box and bogie vibrations. These findings suggest that the fixed-frequency vibrations originate from the natural modes of the wheelset and bogie, which can be excited by wheel/rail irregularities.

Originality/value

The study provides novel insights into the mechanisms of high-order wheel polygonization in plateau high-speed EMU trains. Futher, the results indicate that operating the EMU train on mixed lines at variable speeds could potentially mitigate high-order polygonal wear, providing practical value for improving the safety, performance and maintenance efficiency of high-speed EMU trains.

Details

Railway Sciences, vol. 3 no. 5
Type: Research Article
ISSN: 2755-0907

Keywords

Available. Open Access. Open Access
Article
Publication date: 29 May 2024

Lixia Sun, Yuanwu Cai, Di Cheng, Xiaoyi Hu and Chunyang Zhou

Under the high-speed operating conditions, the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed…

245

Abstract

Purpose

Under the high-speed operating conditions, the effects of wheelset elastic deformation on the wheel rail dynamic forces will become more notable compared to the low-speed condition. In order to meet different analysis requirements and selecting appropriate models to analyzing the wheel rail interaction, it is crucial to understand the influence of wheelset flexibility on the wheel-rail dynamics under different speeds and track excitations condition.

Design/methodology/approach

The wheel rail contact points solving method and vehicle dynamics equations considering wheelset flexibility in the trajectory body coordinate system were investigated in this paper. As for the wheel-rail contact forces, which is a particular force element in vehicle multibody system, a method for calculating the Jacobian matrix of the wheel-rail contact force is proposed to better couple the wheel-rail contact force calculation with the vehicle dynamics response calculation. Based on the flexible wheelset modeling approach in this paper, two vehicle dynamic models considering the wheelset as both elastic and rigid bodies are established, two kinds of track excitations, namely normal measured track irregularities and short-wave irregularities are used, wheel-rail geometric contact characteristic and wheel-rail contact forces in both time and frequency domains are compared with the two models in order to study the influence of flexible wheelset rotation effect on wheel rail contact force.

Findings

Under normal track irregularity excitations, the amplitudes of vertical, longitudinal and lateral forces computed by the flexible wheelset model are smaller than those of the rigid wheelset model, and the virtual penetration and equivalent contact patch are also slightly smaller. For the flexible wheelset model, the wheel rail longitudinal and lateral creepages will also decrease. The higher the vehicle speed, the larger the differences in wheel-rail forces computed by the flexible and rigid wheelset model. Under track short-wave irregularity excitations, the vertical force amplitude computed by the flexible wheelset is also smaller than that of the rigid wheelset. However, unlike the excitation case of measured track irregularity, under short-wave excitations, for the speed within the range of 200 to 350 km/h, the difference in the amplitude of the vertical force between the flexible and rigid wheelset models gradually decreases as the speed increase. This is partly due to the contribution of wheelset’s elastic vibration under short-wave excitations. For low-frequency wheel-rail force analysis problems at speeds of 350 km/h and above, as well as high-frequency wheel-rail interaction analysis problems under various speed conditions, the flexible wheelset model will give results agrees better with the reality.

Originality/value

This study provides reference for the modeling method of the flexible wheelset and the coupling method of wheel-rail contact force to the vehicle multibody dynamics system. Furthermore, by comparative research, the influence of wheelset flexibility and rotation on wheel-rail dynamic behavior are obtained, which is useful to the application scope of rigid and flexible wheelset models.

Details

Railway Sciences, vol. 3 no. 3
Type: Research Article
ISSN: 2755-0907

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Article
Publication date: 25 March 2020

Amit Singh, Mamata Jenamani and Jitesh Thakkar

This research proposes a text analytics–based framework that examines the utility of online customer reviews in evaluating automobile manufacturers and discovering their…

970

Abstract

Purpose

This research proposes a text analytics–based framework that examines the utility of online customer reviews in evaluating automobile manufacturers and discovering their consumer-perceived weaknesses.

Design/methodology/approach

The proposed framework integrates aspect-level sentiment analysis with the house of quality (HoQ), TOPSIS, Pareto chart and fishbone diagram. While sentiment analysis mines and quantifies review-embedded consumer opinions on various automobile attributes, the integrated HoQ-TOPSIS analyzes the quantified opinions and evaluates the manufacturers. The Pareto charts assist in discovering consumer-perceived weaknesses of the underperforming manufacturers. Finally, the fishbone diagram visually represents the results in the form with which the manufacturing community is acquainted.

Findings

The proposed framework is tested on a review data set collected from CarWale, a well-known car portal in India. Selecting five manufacturers from the mid-size car segment, the authors identified the worst-performing one and discovered its weak attributes.

Practical implications

The proposed framework can help the manufacturers in evaluating competitor; identifying consumers' contemporary interests; discovering own and their competitors' weak attributes; assessing the suppliers and sending early warnings; detecting the hazardous defects. It can assist the component suppliers in devising process improvement strategies; improving their customer network; comparing them with competitors. It can support the customers in identifying the best available alternative.

Originality/value

The proposed framework is first of its kind to integrate the sentiment analysis with (1) HoQ-TOPSIS to assess the manufacturers; (2) Pareto chart to discover their weaknesses; (3) fishbone diagram to visually represent the results.

Details

Journal of Enterprise Information Management, vol. 33 no. 5
Type: Research Article
ISSN: 1741-0398

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Article
Publication date: 23 October 2023

Mallikarjun S. Bhandiwad, B.M. Dodamani and Deepak M.D.

The present work involves analytical and experimental investigation of sloshing in a two-dimensional rectangular tank including the effect of porous baffles to control and/or…

83

Abstract

Purpose

The present work involves analytical and experimental investigation of sloshing in a two-dimensional rectangular tank including the effect of porous baffles to control and/or reduce the wave motion in the sloshing tank. The purpose of this study is to assess the analytical solutions of the drag coefficient effect on porous baffles performance to track free surface motion variation in the sloshing tank by comparison with experimental shake table tests under a range of sway excitation.

Design/methodology/approach

The linear second-order ordinary differential equations for liquid sloshing in the rectangular tank were solved using Newmark’s beta method and obtained the analytical solutions for liquid sloshing with dual vertical porous baffles of full submergence depths in a sway-oscillated rectangular tank following the methodology similar to Warnitchai and Pinkaew (1998) and Tait (2008).

Findings

The porous baffles significantly reduce wave elevation in the varying filled levels of the tank compared to the baffle-free tank under the range of excitation frequencies. It is observed that the Reynolds number-dependent drag coefficient for porous baffles in the tank can significantly reduce the sloshing elevations and is found to be effective to achieve higher damping compared to the porosity-dependent drag coefficient for porous baffles in the sloshing tank. The analytical model’s response to free surface elevation variations in the sloshing tank was compared with the experiment’s test results. The analytical results matched with shake table test results with a quantitative difference near the first resonant frequency.

Research limitations/implications

The scope of the study is limited to porous baffles performance under range sway motion and three different filling levels in the tank. The porous baffle performance includes Reynolds number dependent drag coefficient to explore the damping effect in the sloshing tank.

Originality/value

The porous baffles with low-level porosities in the sloshing tank have many engineering applications where the first resonant mode of sloshing in the tank is more important. The porous baffle drag coefficient is an important parameter to study the baffle’s damping effect in sloshing tanks. Hence, obtained analytical solution for liquid sloshing in the rectangular tank with Reynolds number as well as porosity-dependent drag coefficient (model 1) and porosity-dependent drag coefficient porous baffles (model 2) performance is discussed. The model’s test results were validated using a series of shake table sloshing experiments for three fill levels in the tank with sway motion at various excitation frequencies covering the first four sloshing resonant modes.

Details

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

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Article
Publication date: 31 May 2024

Haylim Chha and Yongbo Peng

Contemporary stochastic optimal control by synergy of the probability density evolution method (PDEM) and conventional optimal controller exhibits less capability to guarantee…

344

Abstract

Purpose

Contemporary stochastic optimal control by synergy of the probability density evolution method (PDEM) and conventional optimal controller exhibits less capability to guarantee economical energy consumption versus control efficacy when non-stationary stochastic excitations drive hysteretic structures. In this regard, a novel multiscale stochastic optimal controller is invented based on the wavelet transform and the PDEM.

Design/methodology/approach

For a representative point, a conventional control law is decomposed into sub-control laws by deploying the multiresolution analysis. Then, the sub-control laws are classified into two generic control laws using resonant and non-resonant bands. Both frequency bands are established by employing actual natural frequency(ies) of structure, making computed efforts depend on actual structural properties and time-frequency effect of non-stationary stochastic excitations. Gain matrices in both bands are then acquired by a probabilistic criterion pertaining to system second-order statistics assessment. A multi-degree-of-freedom hysteretic structure driven by non-stationary and non-Gaussian stochastic ground accelerations is numerically studied, in which three distortion scenarios describing uncertainties in structural properties are considered.

Findings

Time-frequency-dependent gain matrices sophisticatedly address non-stationary stochastic excitations, providing efficient ways to independently suppress vibrations between resonant and non-resonant bands. Wavelet level, natural frequency(ies), and ratio of control forces in both bands influence the scheme’s outcomes. Presented approach outperforms existing approach in ensuring trade-off under uncertainty and randomness in system and excitations.

Originality/value

Presented control law generates control efforts relying upon resonant and non-resonant bands, and deploys actual structural properties. Cost-function weights and probabilistic criterion are promisingly developed, achieving cost-effectiveness of energy demand versus controlled structural performance.

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Article
Publication date: 15 October 2020

Hangduo Gao, Zhao Yin, Jun Liu, Quansheng Zang and Gao Lin

The purpose of this paper is to analyze the liquid sloshing behaviors in two-dimensional tanks with various porous baffles under the external excitation.

379

Abstract

Purpose

The purpose of this paper is to analyze the liquid sloshing behaviors in two-dimensional tanks with various porous baffles under the external excitation.

Design/methodology/approach

Adopting the finite element method (FEM) and control variable method to study the impacts of the height, length, number, location, shape, porous-effect parameter of the porous baffle, the external load frequency and the shape of the tank on the liquid sloshing response.

Findings

The amplitude of the free surface can be reduced effectively when the baffle opening is appropriate. The anti-sway ability of the system increases in pace with the baffle’s height growing. Under the same conditions, the shapes of the baffles have an important effect on improving the anti-sway ability of the system.

Originality/value

As there exist the differences of the velocity potential between each side of the porous baffle, which means that there are two different velocity potentials at a point on the porous baffle, the conventional finite element modeling technologies are not suitable to be applied here. To deal with this problem, the points on the porous baffle are regarded as two nodes with the same coordinate to model and calculate.

Details

Engineering Computations, vol. 38 no. 5
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 9 June 2023

Haylim Chha and Yongbo Peng

In real life, excitations are highly non-stationary in frequency and amplitude, which easily induces resonant vibration to structural responses. Conventional control algorithms in…

3330

Abstract

Purpose

In real life, excitations are highly non-stationary in frequency and amplitude, which easily induces resonant vibration to structural responses. Conventional control algorithms in this case cannot guarantee cost-effective control effort and efficient structural response alleviation. To this end, this paper proposes a novel adaptive linear quadratic regulator (LQR) by integrating wavelet transform and genetic algorithm (GA).

Design/methodology/approach

In each time interval, multiresolution analysis of real-time structural responses returns filtered time signals dominated by different frequency bands. Minimization of cost function in each frequency band obtains control law and gain matrix that depend on temporal-frequency band, so suppressing resonance-induced filtered response signal can be directly achieved by regulating gain matrix in the temporal-frequency band, leading to emphasizing cost-function weights on control and state. To efficiently subdivide gain matrices in resonant and normal frequency bands, the cost-function weights are optimized by a developed procedure associated to genetic algorithm. Single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) structures subjected to near- and far-fault ground motions are studied.

Findings

Resonant band requires a larger control force than non-resonant band to decay resonance-induced peak responses. The time-varying cost-function weights generate control force more cost-effective than time-invariant ones. The scheme outperforms existing control algorithms and attains the trade-off between response suppression and control force under non-stationary excitations.

Originality/value

Proposed control law allocates control force amounts depending upon resonant or non-resonant band in each time interval. Cost-function weights and wavelet decomposition level are formulated in an elegant manner. Genetic algorithm-based optimization cost-efficiently results in minimizing structural responses.

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Article
Publication date: 4 January 2016

Dan Xu, James Ferris Whidborne and Alastair Cooke

The growing use of small unmanned rotorcraft in civilian applications means that safe operation is increasingly important. The purpose of this paper is to investigate the fault…

1624

Abstract

Purpose

The growing use of small unmanned rotorcraft in civilian applications means that safe operation is increasingly important. The purpose of this paper is to investigate the fault tolerant properties to faults in the actuators of an C 1 adaptive controller for a quadrotor vehicle.

Design/methodology/approach

C 1 adaptive control provides fast adaptation along with decoupling between adaptation and robustness. This makes the approach a suitable candidate for fault tolerant control of quadrotor and other multirotor vehicles. In the paper, the design of an C 1 adaptive controller is presented. The controller is compared to a fixed-gain LQR controller.

Findings

The C 1 adaptive controller is shown to have improved performance when subject to actuator faults, and a higher range of actuator fault tolerance.

Research limitations/implications

The control scheme is tested in simulation of a simple model that ignores aerodynamic and gyroscopic effects. Hence for further work, testing with a more complete model is recommended followed by implementation on an actual platform and flight test. The effect of sensor noise should also be considered along with investigation into the influence of wind disturbances and tolerance to sensor failures. Furthermore, quadrotors cannot tolerate total failure of a rotor without loss of control of one of the degrees of freedom, this aspect requires further investigation.

Practical implications

Applying the C 1 adaptive controller to a hexrotor or octorotor would increase the reliability of such vehicles without recourse to methods that require fault detection schemes and control reallocation as well as providing tolerance to a total loss of a rotor.

Social implications

In order for quadrotors and other similar unmanned air vehicles to undertake many proposed roles, a high level of safety is required. Hence the controllers should be fault tolerant.

Originality/value

Fault tolerance to partial actuator/effector faults is demonstrated using an C 1 adaptive controller.

Details

International Journal of Intelligent Unmanned Systems, vol. 4 no. 1
Type: Research Article
ISSN: 2049-6427

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Article
Publication date: 11 June 2020

Mohd Sabirin Rahmat, Khisbullah Hudha, Zulkiffli Abd Kadir, Noor Hafizah Amer, Muhammad Luqman Hakim Abd Rahman and Shohaimi Abdullah

The objective of this paper is to develop a fast modelling technique for predicting magneto-rheological fluid damper behaviour under impact loading applications.

96

Abstract

Purpose

The objective of this paper is to develop a fast modelling technique for predicting magneto-rheological fluid damper behaviour under impact loading applications.

Design/methodology/approach

The adaptive neuro-fuzzy inference system (ANFIS) technique was adopted to predict the behaviour of a magneto-rheological fluid (MRF) damper through experimental characterisation data. In this study, an MRF damper manufactured by Lord Corporation was used for characterisation using an impact pendulum test rig. The experimental characterisation was carried out with various impact energies and constant input currents applied to the MRF damper.

Findings

This research provided a fast modelling technique with relatively less error in predicting MRF damper behaviour for the development of control strategies. Accordingly, the ANFIS model was able to predict MRF damper behaviour under impact loading and showed better performance than the modified Bouc–Wen model.

Research limitations/implications

This study only focused on modelling technique for a single type of MRF damper used for impact loading applications. It is possible for other applications, such as cyclic loading, random loadings and system identification, to be studied in future experiments.

Original/Value

Future researchers could apply the ANFIS model as an actuator model for the development of control strategies and analyse the control performance. The model also can be replicated in other industries with minor modifications to suit different needs.

Details

Multidiscipline Modeling in Materials and Structures, vol. 16 no. 6
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 25 January 2023

Ranjan Kumar, Saikat Chaterjee, Vinayak Ranjan and Sanjoy K. Ghoshal

The present findings report a significant influence of disc profile and thickness on the order of excitation leading to critical speed condition. Certain transverse modes of…

62

Abstract

Purpose

The present findings report a significant influence of disc profile and thickness on the order of excitation leading to critical speed condition. Certain transverse modes of vibration of the disc have been obtained to be more susceptible to get excited while recording the lowest critical speeds.

Design/methodology/approach

Numerical simulation using finite-element method has been adopted due to the complicated geometry, complex loadings and intricate analytical formulation. A comprehensive analysis of exclusive as well as combination of thermal and centrifugal loads has been taken up to determine the intensity and characteristics of the individual/combined effects.

Findings

The typical gas turbine disc profile has been analyzed to predict the critical speed under the factual working condition of an aero-engine. FEM analysis of uniform and variable thickness discs have been carried out under stationary, rotating and rotating-thermal considerations while emphasizing the effect of disc profile and thickness. Centrifugal stresses developed due to rotational effect result in unceasing stiffening of the discs with higher stiffening for a greater number of nodal diameters. On the other hand, a role reversal of thermal effect from stiffening to softening is figured out with increasing numbers of nodal diameters. However, the discs are subjected to an overall stiffening effect on account of the combined centrifugal and thermal loading, with the effect decreasing with an increase in disc thickness. Under the combined loading, the order of excitation leading to critical speed condition is dependent on disc profile and thickness. Moreover, the vibrational modes (0,1) and (0,2) are identified as more prominent adverse modes corresponding to lowest critical speeds.

Practical implications

The present findings are expected to serve as guidelines during the design phase of gas turbine discs of aeroengine applications.

Originality/value

The present work deliberates on the simulation and analysis of gas turbine disc specific to aeroengine application. The real-life disc geometry has been analyzed with due consideration of major factual operating conditions to identify the critical speed. The identification of various critical speed using numerical analysis can help to reduce the number of experimental tests required for certification.

Details

Multidiscipline Modeling in Materials and Structures, vol. 19 no. 2
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 31 December 2020

Jianlei Yi, Kunjian Jin, Haiying Qin and Yuhong Cui

An ideal method for predicting the fatigue life of spherical thrust elastomeric bearings has not been reported, thus far. This paper aims to present a method for predicting the…

245

Abstract

Purpose

An ideal method for predicting the fatigue life of spherical thrust elastomeric bearings has not been reported, thus far. This paper aims to present a method for predicting the fatigue life of laminated rubber spherical thrust elastomeric bearings.

Design/methodology/approach

First, the mechanical properties of standard rubber samples were tested; the axial stiffness, cocking stiffness, torsional stiffness and fatigue life of several full-size spherical thrust elastomeric bearings were tested. Then, the stiffness results were calculated using the neo-Hookean, Mooney–Rivlin and Yoeh models. Using a modified Mooney–Rivlin constitutive model, this paper proposes an improved method for fatigue life prediction, which considers the laminated characteristics of a spherical thrust elastomeric bearing and loads of multiple multi-axle conditions.

Findings

The Mooney–Rivlin model could accurately describe the stiffness characteristics of the spherical thrust elastomeric bearings. A comparative analysis of experimental results shows that the model can effectively predict the life of a spherical thrust elastomeric bearing within its range of use and the prediction error is within 20%.

Originality/value

The fatigue parameters of elastomeric bearings under multiaxial loads were fitted and corrected using experimental data and an accurate and effective multiaxial fatigue-life prediction expression was obtained. Finally, the software was redeveloped to improve the flexibility and efficiency of modeling and calculation.

Details

Engineering Computations, vol. 38 no. 6
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 December 2002

C.M.A. Ashruf

This article gives an overview on the currently available techniques for the measurement of interface pressure or force between (soft) objects. These techniques make use of single…

5676

Abstract

This article gives an overview on the currently available techniques for the measurement of interface pressure or force between (soft) objects. These techniques make use of single sensor elements as well as integrated arrays of sensors to obtain pressure maps. Most of these devices originate from biomedical applications such as the evaluation of wheelchairs and the prevention of pressure ulcers in hospital beds. Today, these technologies are used in a wide range of applications such as computer peripherals, robotics, automotive systems and consumer electronics. These typical applications are considered in the first section. Next, the sensor technologies (and their suppliers) are briefly described and compared. The list of suppliers and technologies is intended as an overview and may not be complete. Finally, new developments in this field are discussed.

Details

Sensor Review, vol. 22 no. 4
Type: Research Article
ISSN: 0260-2288

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Article
Publication date: 15 June 2010

Van‐Tsai Liu, Chien‐Hung Liu, Hau‐Wei Li, Chieh‐Li Chen, Chun‐Liang Lin and Yu‐Chen Lin

The purpose of this paper is to develop the multi‐degree‐of‐freedom measurement system to test, verify, and control the nano‐measuring machine.

153

Abstract

Purpose

The purpose of this paper is to develop the multi‐degree‐of‐freedom measurement system to test, verify, and control the nano‐measuring machine.

Design/methodology/approach

A generic differential model approach is constructed to numerically describe the hysteresis effects of piezoelectric actuators. Based on the generic differential model, a feedforward compensator with a proportional integral (PI) type controller is designed to compensate for the hysteresis nonlinearity of a piezoelectric actuated three degree‐of‐freedom coplanar nanostage which can provide high‐precision applications.

Findings

The Z‐tilts (z, pitch, and roll motion) error compensation stage of the nano‐measuring machine is accomplished. Moreover, a high‐resolution laser interferometer is used to measure position accurately.

Originality/value

This paper contributes to develop a tracking control design method for the piezoelectric motion platform which combines a closed‐loop feedforward compensator with a PI type controller.

Details

Kybernetes, vol. 39 no. 6
Type: Research Article
ISSN: 0368-492X

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Article
Publication date: 3 June 2014

Xuan Wang, Aurélien Reysett, Valérie Pommier-Budinger and Yves Gourinat

Piezoelectric actuators (PEAs) exhibit hysteresis nonlinearity in open-loop operation, which may lead to unwanted inaccuracy and limit system performance. Classical Preisach model…

208

Abstract

Purpose

Piezoelectric actuators (PEAs) exhibit hysteresis nonlinearity in open-loop operation, which may lead to unwanted inaccuracy and limit system performance. Classical Preisach model is widely used for representing hysteresis but it requires a large number of first-order reversal curves to ensure the model accuracy. All the curves may not be obtained due to the limitations of experimental conditions, and the detachment between the major and minor loops is not taken into account. The purpose of this paper is to propose a modified Preisach model that requires relatively few measurements and that describes the detachment, and then to implement the inverse of the modified model for compensation in PEAs.

Design/methodology/approach

The classical Preisach model is modified by adding a derivative term in parallel. The derivative gain is adjusted to an appropriate value so that the measured and predicted hysteresis loops are in good agreement. Subsequently, the new inverse model is similarly implemented by adding another derivative term in parallel with the inverse classical Preisach model, and is then inserted in open-loop operation to compensate the hysteresis. Tracking control experiments are conducted to validate the compensation.

Findings

The hysteresis in PEAs can be accurately and conveniently described by using the modified Preisach model. The experimental results prove that the hysteresis effect can be nearly completely compensated.

Originality/value

The proposed modified Preisach model is an effective and convenient mean to characterize accurately the hysteresis. The compensation method by inserting the inverse modified Preisach model in open-loop operation is feasible in practice.

Details

Multidiscipline Modeling in Materials and Structures, vol. 10 no. 1
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 25 August 2023

Kali Charan Sabat and Som Sekhar Bhattacharyya

The purpose of this study was to empirically investigate the role of e-service quality factors in predicting e-satisfaction. The study context was spirituality and well-being…

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Abstract

Purpose

The purpose of this study was to empirically investigate the role of e-service quality factors in predicting e-satisfaction. The study context was spirituality and well-being over-the-top services. The e-service quality factors consisted of perceived functional completeness, perceived performance, perceived quality of interface and interaction, perceived quality of content and information and perceived quality of customer support. The study goal was to ascertain over-the-top services customers’ behavioral intention toward upgrading to premium subscription and the spread of electronic word of mouth.

Design/methodology/approach

This study was based upon the integrated stimulus-organism-response framework where e-service quality represented the stimulus, e-satisfaction the organism, behavioral intention and electronic word of mouth as the response. The study used a moderated-mediation approach with e-satisfaction as the mediator and the price value of a premium subscription as the moderator. To empirically test the model, the authors collected data from 312 spirituality and well-being over-the-top services users in India. Partial least squares-structured equation modeling was used to analyze the collected data.

Findings

The findings of the study supported the association between e-service quality factors and e-satisfaction while using spirituality and well-being over-the-top service. The results furthermore indicated that satisfied spirituality and well-being over-the-top customers were willing to upgrade to the premium subscription and spread favorable electronic word of mouth. The moderated-mediation study results revealed that the price value of premium subscriptions moderated the relationship between e-service quality and e-satisfaction but did not moderate the relationship between e-satisfaction and behavioral intention, and e-satisfaction and electronic word of mouth.

Research limitations/implications

This study offered a comprehensive stimulus-organism-response theoretical model by using the five e-service quality measurement factors as “stimuli” for motivating the internal state of spirituality and well-being over-the-top subscribers. This was toward sustained usage in over-the-top services subsequent to the end of the freemium period. Furthermore, in this study, both e-service quality theory and user satisfaction theory were integrated into the stimulus-organism-response model. This helped to better comprehend the impact of e-service quality factors in driving e-satisfaction among spirituality and well-being over-the-top service users.

Practical implications

This study revealed the significance of differentiating premium over-the-top subscriptions based on price value. To ensure a high level of e-satisfaction from a premium subscription, a greater emphasis on the e-service quality dimensions was required. This study provided insights to managers regarding the role of favorable electronic word of mouth in fostering effective customer acquisition.

Originality/value

This was one of the first studies which concurrently integrated perceived value of the premium subscription and e-satisfaction with customers’ behavioral intention and electronic word of mouth through the theoretical lens of stimulus-organism-response.

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Case study
Publication date: 28 November 2022

Deepa Kumari and Ritu Srivastava

The learning outcomes are as follows:1. enable students to appreciate how a platform company can navigate through diminishing network effects;2. enable students to foresee the…

Abstract

Learning outcomes

The learning outcomes are as follows:

1. enable students to appreciate how a platform company can navigate through diminishing network effects;

2. enable students to foresee the downside of scaling up a platform business;

3. enable students to appreciate the trade-off between an efficiency-centric and a novelty-centric business model for platform businesses; and

4. enable students to create a platform business model canvas for a company.

Case overview/synopsis

The teaching case discusses the dilemma of Akshay Chaturvedi, the founder of Leverage Edu, an artificial intelligence-enabled platform for students seeking admission to foreign universities. It had received nearly US$9.6m in funding until December 2021.

Chaturvedi wanted to make the best use of his funds, but was torn between turning Leverage Edu into an “efficient platform” and transforming it into a “novelty-centric platform”. The teaching note attempts to resolve Chaturvedi’s dilemma by analyzing competitors using the platform canvas model and determining how Chaturvedi could create and use network effects to Leverage Edu’s advantage. The case is based on secondary data that is freely available in the public domain.

Complexity academic level

This case is intended for MBA Entrepreneurship students taking a platform business elective. It can also be used in faculty and management development programs under the banner “Technology and Platform Businesses”.

Supplementary materials

Teaching notes are available for educators only.

Subject code

CSS 3: Entrepreneurship.

Details

Emerald Emerging Markets Case Studies, vol. 12 no. 4
Type: Case Study
ISSN:

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Case study
Publication date: 21 November 2022

Swapna Pradhan

The case study should enable the student:1. to assess the complexities of the Indian quick service restaurants (QSRs) market and its competitive dynamics;2. to infer the factors…

Abstract

Learning outcomes

The case study should enable the student:1. to assess the complexities of the Indian quick service restaurants (QSRs) market and its competitive dynamics;2. to infer the factors which have contributed to the growth of Domino’s Pizza in India;3. to apply different tools and techniques to assess and refine strategy;4. to evaluate Domino’s Pizza India in the context of the value chain analysis; and5. to examine the strategic options available to Domino’s India for achieving its future growth in India.

Case overview/synopsis

The case details the growth story of American pizza chain Domino’s in India. Jubilant Food Works Limited (JFL), a part of the Jubilant Bhartia Group, operates the Domino’s Pizza chain in India. The first restaurant was opened in India in 1996 and, in the initial years, the focus was on promoting and popularising “pizza” as an interesting meal replacement option. Over the years, through memorable advertising, operational efficiency and product innovation, Domino’s emerged as the market leader in the organised pizza market in India. The growth in competition both from domestic and international brands and the challenge posed by the growth of food aggregators posed challenges to its prospect of maintaining market leadership. The nationwide lockdown because of the pandemic severely impacted the foodservice industry. Significant changes were seen in the operations of the QSR and rapid growth was witnessed in online food ordering especially through food delivery apps. The management at JFL believed that the demand for QSR would increase rapidly in the country given the possibility of closure of 30%–35% of conventional restaurants. This company had raised the store addition target for FY22 to 150–175 from earlier 135 as it believed that there would be a greater demand for trusted brands. The management believed that the domestic market had the capacity to absorb 3,000 Domino’s outlets compared with the earlier estimate of 1,800–2,000 outlets. In the first quarter of FY22, it added 20 new Domino’s stores. Was the management correct in anchoring its future success on new physical retail outlets? Was there a need to revisit the strategy?

Complexity academic level

The case has been written with the objective of enabling the students to understand the dynamics of a rapidly changing emerging market. It is structured for use at a Master’s level course and an MBA audience in the subject of Business Strategy/Retail Strategy.

Supplementary materials

Teaching notes are available for educators only.

Subject code

CSS 11: Strategy.

Details

Emerald Emerging Markets Case Studies, vol. 12 no. 4
Type: Case Study
ISSN:

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Case study
Publication date: 4 August 2022

Sheela Bhargava and Parul Gupta

The case will help learners to analyse how effective handling of an extended marketing mix of 7Ps (product, price, place, promotion, physical evidence, participants and processes…

Abstract

Learning outcomes

The case will help learners to analyse how effective handling of an extended marketing mix of 7Ps (product, price, place, promotion, physical evidence, participants and processes) makes a startup profitable in its initial years of inception; understand the significance of the online marketing strategies like digital marketing and social media marketing implemented by firms to attain a competitive edge amongst established local and global competitors; examine the strategic challenges faced by a business enterprise while entering an emerging market; analyse the growth strategies of a startup relative to various market constraints; and propose long-term strategies for sustainable growth for a startup operating in the wearables market.

Case overview/synopsis

Founded in 2016, Boat Lifestyle is a Delhi-based Indian startup in fashionable consumer electronics. In the past five years, Boat earned remarkable profits and emerged as one of the most promising startups through its innovative products offerings and promotion. Aiming at its target customer segment, the millennials, it promoted its products through social media marketing such as influencer marketing and brand tie-ins with sports teams and music events. The case focuses on the dynamics of the Indian wearables market that is facing tough competition from global and local players. To ensure continued growth prospects, while maintaining a tight focus on product differentiation, quality, and customer satisfaction, there is a greater need for Boat to rethink its market development and growth strategies regarding new innovations and adopting long-term orientation like diversification and global expansion.

Complexity academic level

The case aims for teaching business management students at the Undergraduate, Postgraduate, and Executive education level. In addition, the case can be related to the Strategic Management course curriculum and Marketing course curriculum.

Supplementary materials

Teaching notes are available for educators only.

Subject code

CSS 11: Strategy

Details

Emerald Emerging Markets Case Studies, vol. 12 no. 2
Type: Case Study
ISSN: 2045-0621

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Case study
Publication date: 11 December 2023

Debajani Sahoo, Rachita Kashyap and Manish Agarwal

This case study is designed to enable students to formulate the strategic planning process in relation to an organization’s resources; assess the critical tasks required for the…

Abstract

Learning outcomes

This case study is designed to enable students to formulate the strategic planning process in relation to an organization’s resources; assess the critical tasks required for the company’s business planning for growth and market expansion; and examine the importance of the value delivery process for the company, its customer and its employees. At the end of the case discussion, students will learn how to plan their business in an emerging market by using their existing resources, where the business stands at present and where it may go in the coming future.

Case overview/synopsis

The case study discusses how Byju’s, an Indian multinational educational technology company, revolutionized student learning programs through its innovative strategic implementation. It explores the company’s growth and expansion strategy by considering a strength, weakness, opportunity and threats analysis. It elaborates on how Byju’s acquired various companies in India and other countries to become an international technology-based educational brand with 150 million users in 2022. The case study also highlights the marketing and promotional strategy used by the company on online and offline platforms. The case study elaborates on the value delivery process and its importance for customer and employee satisfaction. Despite its success in the Indian market, Byju’s faced tough challenges in the US and European markets, such as lower-than-expected growth rates and lower subscription numbers, even though it followed the same strategy as in the Indian market. The acquisition and celebrity strategy works in emerging economies such as India but not in developed countries. The company’s return on investment was down owing to the high costs it had incurred over the years on market acquisitions and marketing promotions. The growing competition was also expected to bring more challenges for Byju’s. New players such as Tata Studi and YouTube planned to enter the market. Byju Raveendran and his management group had to decide whether to maintain or change the current market offering to reflect market developments to satisfy their customers and employees. They also had to determine whether the main components of the marketing strategy, such as the company’s ongoing value delivery process and ongoing strategy toward the target audience, partners and rivals, are advantageous to the firm or not. The team was in dilemma whether the marketing planning process was going in the right direction and how to make all elements of its businesses more efficient in dealing with the issues. Raveendran kept asking questions about to what extent it is still possible to alter the marketing plan.

Complexity academic level

The case study is appropriate for discussion in courses such as marketing management, service marketing and strategic marketing management, whether they are part of an undergraduate program (Bachelor of Business Administration [BBA]), a postgraduate program in business management (Master of Business Administration [MBA]) or an executive-level program (executive MBA). The breadth of business topics addressed and the intricacy of the scenario make this case study best suited to be used after the semester as either a culminating project or as a seminar discussion for undergraduates (BBA). The case study can also be discussed in the marketing management course (graduation level) under the marketing and service strategy chapters.

Subject code

CSS8: Marketing

Supplementary material

Teaching notes are available for educators only.

Details

Emerald Emerging Markets Case Studies, vol. 13 no. 4
Type: Case Study
ISSN: 2045-0621

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Article
Publication date: 29 April 2021

Koorosh Gharehbaghi, Maged Georgy, Kathryn Mary Robson, Sara Wilkinson and Ken Farnes

Through an empirical study, this research proposes a multi-dimensional assessment method for Sustainable Building Design (SBD). This approach is adopted to investigate and…

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Abstract

Purpose

Through an empirical study, this research proposes a multi-dimensional assessment method for Sustainable Building Design (SBD). This approach is adopted to investigate and evaluate the current practices of SBD and to provide a basis for refining such processes while reducing existing shortfalls. In doing so, a holistic sustainable framework for rating the sustainable performance of buildings is proposed.

Design/methodology/approach

To achieve the aforementioned purpose, this research (1) investigates the most current trends in SBD including the use of Building Information Modelling (BIM); (2) examines the practical issues of SBD; (3) proposes a multi-dimensional assessment method; and (4) compares 18 separate case studies in the three countries of Australia, United Kingdom and USA, as part of the SBD implementation. To compare these case studies, an additional SBD tool, Green Building Rating and Certification System (GBELS) was carefully selected and applied. Five core values of SBD were identified based on functionality, accessibility and productivity, which align with the GBELS outcomes.

Findings

This research found that, for the 18 examined buildings, the main issues in SBD in the three countries concerned environmental and ecological issues. These included the impacts of buildings on the environment, as well as issues concerning the buildings' life cycle analysis and assessment. It was also determined that energy usage, pollution reduction and climate change concerns were important inclusions in establishing these buildings, particularly in the USA.

Originality/value

To support the research aim, this paper explores the most innovative trends in SBD assessments including their Structural Health Monitoring (SHM), grade (stars) classification, Relative Weight (RW) and particularly GBELS. GBELS was selected for this research, since it is relatively new and there is little available literature discussing its adaptation. Accordingly, this research further evaluates the application of GBELS as a part of versatility in SBD multi-dimensional assessment method. As the basis of these tests, a total of 18 separate case studies are closely evaluated.

Details

International Journal of Building Pathology and Adaptation, vol. 40 no. 5
Type: Research Article
ISSN: 2398-4708

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