Search results

1 – 10 of over 7000
To view the access options for this content please click here
Article
Publication date: 6 November 2017

Fahimeh Saberi Zafarghandi, Maryam Mohammadi, Esmail Babolian and Shahnam Javadi

The purpose of this paper is to introduce a local Newton basis functions collocation method for solving the 2D nonlinear coupled Burgers’ equations. It needs less computer…

Abstract

Purpose

The purpose of this paper is to introduce a local Newton basis functions collocation method for solving the 2D nonlinear coupled Burgers’ equations. It needs less computer storage and flops than the usual global radial basis functions collocation method and also stabilizes the numerical solutions of the convection-dominated equations by using the Newton basis functions.

Design/methodology/approach

A meshless method based on spatial trial space spanned by the local Newton basis functions in the “native” Hilbert space of the reproducing kernel is presented. With the selected local sub-clusters of domain nodes, an approximation function is introduced as a sum of weighted local Newton basis functions. Then the collocation approach is used to determine weights. The method leads to a system of ordinary differential equations (ODEs) for the time-dependent partial differential equations (PDEs).

Findings

The method is successfully used for solving the 2D nonlinear coupled Burgers’ equations for reasonably high values of Reynolds number (Re). It is a well-known issue in the analysis of the convection-diffusion problems that the solution becomes oscillatory when the problem becomes convection-dominated if the standard methods are followed without special treatments. In the proposed method, the authors do not detect any instability near the front, hence no technique is needed. The numerical results show that the proposed method is efficient, accurate and stable for flow with reasonably high values of Re.

Originality/value

The authors used more stable basis functions than the standard basis of translated kernels for representing of kernel-based approximants for the numerical solution of partial differential equations (PDEs). The local character of the method, having a well-structured implementation including enforcing the Dirichlet and Neuman boundary conditions, and producing accurate and stable results for flow with reasonably high values of Re for the numerical solution of the 2D nonlinear coupled Burgers’ equations without any special technique are the main values of the paper.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 11
Type: Research Article
ISSN: 0961-5539

Keywords

To view the access options for this content please click here
Article
Publication date: 1 April 1987

CONOR J. FITZSIMONS

This paper examines several modifications to Newton's method for the numerical solution of the nonlinear Poisson equation which describes the electrostatic potential…

Abstract

This paper examines several modifications to Newton's method for the numerical solution of the nonlinear Poisson equation which describes the electrostatic potential distribution in a semiconductor device. Two methods for a more efficient solution of the equation when the device is a Metal‐Oxide‐Semiconductor Field Effect Transistor are proposed. Their extension to the solution of the fully coupled system of equations is also discussed. The modifications to Newton's method are also compared numerically.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 6 no. 4
Type: Research Article
ISSN: 0332-1649

To view the access options for this content please click here
Article
Publication date: 20 May 2020

Houzhe Zhang, Defeng Gu, Xiaojun Duan, Kai Shao and Chunbo Wei

The purpose of this paper is to focus on the performance of three typical nonlinear least-squares estimation algorithms in atmospheric density model calibration.

Abstract

Purpose

The purpose of this paper is to focus on the performance of three typical nonlinear least-squares estimation algorithms in atmospheric density model calibration.

Design/methodology/approach

The error of Jacchia-Roberts atmospheric density model is expressed as an objective function about temperature parameters. The estimation of parameter corrections is a typical nonlinear least-squares problem. Three algorithms for nonlinear least-squares problems, Gauss–Newton (G-N), damped Gauss–Newton (damped G-N) and Levenberg–Marquardt (L-M) algorithms, are adopted to estimate temperature parameter corrections of Jacchia-Roberts for model calibration.

Findings

The results show that G-N algorithm is not convergent at some sampling points. The main reason is the nonlinear relationship between Jacchia-Roberts and its temperature parameters. Damped G-N and L-M algorithms are both convergent at all sampling points. G-N, damped G-N and L-M algorithms reduce the root mean square error of Jacchia-Roberts from 20.4% to 9.3%, 9.4% and 9.4%, respectively. The average iterations of G-N, damped G-N and L-M algorithms are 3.0, 2.8 and 2.9, respectively.

Practical implications

This study is expected to provide a guidance for the selection of nonlinear least-squares estimation methods in atmospheric density model calibration.

Originality/value

The study analyses the performance of three typical nonlinear least-squares estimation methods in the calibration of atmospheric density model. The non-convergent phenomenon of G-N algorithm is discovered and explained. Damped G-N and L-M algorithms are more suitable for the nonlinear least-squares problems in model calibration than G-N algorithm and the first two algorithms have slightly fewer iterations.

Details

Aircraft Engineering and Aerospace Technology, vol. 92 no. 7
Type: Research Article
ISSN: 1748-8842

Keywords

To view the access options for this content please click here
Article
Publication date: 20 November 2017

Katrina Elizabeth Champion, Emma Louise Barrett, Tim Slade, Maree Teesson and Nicola Clare Newton

Alcohol and cannabis are the two most commonly used substances by young people in many developed nations. The purpose of this paper is to explore the longitudinal…

Abstract

Purpose

Alcohol and cannabis are the two most commonly used substances by young people in many developed nations. The purpose of this paper is to explore the longitudinal relationships between risky substance use (binge drinking and cannabis use) and psychological distress, emotional and behavioural difficulties, and truancy among Australian adolescents.

Design/methodology/approach

A total of 527 students (Mage=13.4 years, SD=0.43; 67 per cent female) from seven Australian schools completed an online self-report survey on four occasions over two years (baseline, 6, 12 and 24 months). The survey assessed binge drinking (5+ standard drinks on one occasion), cannabis use in the past six months, psychological distress, emotional and behavioural difficulties (Strength and Difficulties Questionnaire), and truancy. Generalised estimating equations (GEEs) were conducted to examine the longitudinal relationship between the substance use outcomes and each predictor variable.

Findings

At baseline, 3 per cent of students reported binge drinking and 6 per cent had used cannabis in the past six months. Rates of binge drinking significantly increased over time (21.1 per cent at 24 months) however, rates of cannabis use remained relatively stable (8.8 per cent at 24 months). Multivariate GEE analyses indicated that higher levels of hyperactivity/inattention, more days of truancy and being female were independently and consistently associated with binge drinking over time. Conduct problems was the only factor to be independently associated with cannabis use over time.

Originality/value

These findings provide valuable information about psychosocial risk factors for harmful alcohol and cannabis use. A better understanding of these associations is critical for informing substance use prevention efforts in the future.

Details

Advances in Dual Diagnosis, vol. 10 no. 4
Type: Research Article
ISSN: 1757-0972

Keywords

To view the access options for this content please click here
Article
Publication date: 20 November 2017

Louise Elizabeth Birrell, Nicola Clare Newton, Lexine Stapinski, Katrina Prior, Katrina Elizabeth Champion, Clare J. Mackie, Maree Teesson and Tim Slade

The purpose of this paper is to explore how different trajectories of emotional symptoms relate to alcohol use in adolescence.

Abstract

Purpose

The purpose of this paper is to explore how different trajectories of emotional symptoms relate to alcohol use in adolescence.

Design/methodology/approach

In all, 431 participants (majority female), aged approximately 13 years at baseline were followed over three years and reported on their emotional symptoms and alcohol use. Latent class growth analyses explored different trajectories of emotional symptoms and regression models were run to relate these trajectories to alcohol use (full standard drink, and binge drinking) at 36-month follow-up (age 16 years).

Findings

While the majority of adolescents were best characterised by low-stable emotional symptoms, those with high-stable symptoms were more likely to be have consumed a full standard drink of alcohol and binge drunk when aged 16 years.

Research limitations/implications

Findings highlight the importance of prevention and early intervention, particularly targeting adolescents with elevated stable emotional symptoms who were more likely to be using alcohol at 16 years of age.

Originality/value

The present study is one of the first longitudinal investigations into the use of alcohol by community adolescents with different emotional symptom trajectories.

Details

Advances in Dual Diagnosis, vol. 10 no. 4
Type: Research Article
ISSN: 1757-0972

Keywords

To view the access options for this content please click here
Article
Publication date: 1 March 1978

Keith Newton

While concern for the quality of working life (QWL) is by no means new it is nevertheless true that there has been an enormous amount of research, experimentation and…

Abstract

While concern for the quality of working life (QWL) is by no means new it is nevertheless true that there has been an enormous amount of research, experimentation and commentary in this field in recent years. A particular confluence of forces—ever‐accelerating technological change; rapidly‐shifting attitudes, life‐styles, and social institutions; and the paradox in many countries of a customary prosperity threatened by doubts as to future economic performance—is at least in part responsible for the burgeoning interest in the field. But important also is its multidisciplinary nature, which has afforded to social scientists of varied orientations the opportunity to participate in a new intellectual growth industry.

Details

International Journal of Social Economics, vol. 5 no. 3
Type: Research Article
ISSN: 0306-8293

To view the access options for this content please click here
Article
Publication date: 4 April 2019

Ashley N. Newton and Vahap B. Uysal

The purpose of this paper is to examine the effects of political connections surrounding an exogenous Supreme Court decision (Citizens United) that lifted long-standing…

Abstract

Purpose

The purpose of this paper is to examine the effects of political connections surrounding an exogenous Supreme Court decision (Citizens United) that lifted long-standing restrictions on corporate political contributions.

Design/methodology/approach

This study examines key characteristics of politically connected firms compared to non-politically connected firms, including their market reaction to Citizens United, as well as cash holdings levels and governance characteristics before vs after the landmark decision.

Findings

The results indicate a significant negative market reaction to politically connected firms surrounding the announcement of Citizens United. Additionally, there is a significant increase in the cash holdings of politically connected firms relative to before the event and relative to non-politically connected firms. For politically connected firms, this result is exacerbated by poor corporate governance quality. Collectively, these findings are consistent with a positive association between agency costs and political connections.

Originality/value

This study provides novel evidence by exploiting an exogenous enhancement in the implications of political connections that accompanied the Citizens United decision. The use of this quasi-natural experiment offers an ideal research setting to extract fresh insights into the effects of corporate political connections.

Details

Managerial Finance, vol. 45 no. 5
Type: Research Article
ISSN: 0307-4358

Keywords

To view the access options for this content please click here
Book part
Publication date: 15 November 2016

Ewa McGrail, J. Patrick McGrail and Alicja Rieger

To explore the potential of conversations with an authentic audience through blogging for enriching in young writers the understanding of the communicative function of…

Abstract

Purpose

To explore the potential of conversations with an authentic audience through blogging for enriching in young writers the understanding of the communicative function of writing, specifically language and vocabulary use.

Design/methodology/approach

We situate our work in the language acquisition model of language learning, in which learners develop linguistic competence in the process of speaking and using language (Krashen, 1988; Tomasello, 2005). We also believe that language learning benefits from formal instruction (Krashen, 1988). As such, in our work, we likened engaging in blogging to learning a language (here, more broadly conceived as learning to write) through both natural communication (acquisition) and prescription (instruction), and we looked at these forms of learning in our study.

We were interested in the communicative function of language learning (Halliday, 1973; 1975; Penrod, 2005) among young blog writers, because we see language learning as socially constructed through interaction with other speakers of a language (Tomasello, 2005; Vygotsky, 1978).

Findings

The readers and commenters in this study supported young writers in their language study by modeling good writing and effective language use in their communication with these writers. Young writers also benefited from direct instruction through interactions with adults beyond classroom teachers, in our case some of the readers and commenters.

Practical implications

Blogging can extend conversations to audiences far beyond the classroom and make writing a more authentic endeavor for young writers. Teachers should take advantage of such a powerful tool in their writing classrooms to support their students’ language study and vocabulary development.

Details

Writing Instruction to Support Literacy Success
Type: Book
ISBN: 978-1-78635-525-6

Keywords

To view the access options for this content please click here
Book part
Publication date: 12 April 2007

Bert Van Wee

Abstract

Details

Threats from Car Traffic to the Quality of Urban Life
Type: Book
ISBN: 978-0-08-048144-9

To view the access options for this content please click here
Book part
Publication date: 25 March 2021

Kristjan Kikerpill, Andra Siibak and Suido Valli

Purpose: The study makes use of situational crime prevention framework for analyzing online community reactions to the banning of deepfake pornographic content from Reddit.…

Abstract

Purpose: The study makes use of situational crime prevention framework for analyzing online community reactions to the banning of deepfake pornographic content from Reddit.

Methodology/approach: Qualitative text analysis of user comments posted to Reddit’s rule-change announcement (N = 582) was carried out. Analysis relied on the original 25 techniques of situational crime prevention that were adapted into a table of activities and mechanisms meant specifically for use with online platforms.

Findings: Analysis indicates that Reddit users voiced several shortcomings that are currently present in Reddit’s platform management approach. In particular, users emphasized issues related to the lack of a consistent and transparent approach to community rule enforcement, as users believed the rule changes to be sudden and poorly reasoned. The general reactionary nature of Reddit’s approach to moderating community-harming actions also was a point of emphasis, alongside the platform’s continued rigid stance on freedom of expression, even with regard to illegal and demeaning content. Regarding Reddit and the new rules on involuntary pornography and the sexualization of minors, enforcement of sitewide policy appears contingent on external influences, such as attention from mainstream media or financial matters, rather than stemming from an inherent stance on decreasing community-harming activities.

Research limitations: The study only pertains to a specific rule change by Reddit and subsequent reactions from the platform’s community. Future research is needed to test the applicability of the adapted table of 25 techniques of situational crime prevention in the context of other online platforms.

Originality/value: First, the study applies the situational crime prevention approach in the context of moderating online platforms. Second, results from the study shed light on current practices in online content moderation from the perspective of criminological theory, as well as inform specific actions that can be taken to decrease the presence of community-harming phenomena and improve the enforcement of sitewide policy rules in general. Finally, by adapting the original 25 techniques of situational crime prevention to online content moderation, the study suggests a tentative roadmap for similar research in the future.

Details

Theorizing Criminality and Policing in the Digital Media Age
Type: Book
ISBN: 978-1-83909-112-4

Keywords

1 – 10 of over 7000