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Article
Publication date: 1 December 1970

S.N. Suciu

THE effect of higher turbine inlet temperature on the performance of an aircraft gas turbine engine can be quite dramatic. It can be used to increase the exhaust velocity of a dry…

156

Abstract

THE effect of higher turbine inlet temperature on the performance of an aircraft gas turbine engine can be quite dramatic. It can be used to increase the exhaust velocity of a dry turbojet to providea higher specific thrust; to increase the bypass ratio of a turbofan engine to improve its propulsive efficiency; to optimize the thermodynamic cycle at a higher pressure ratio to improve its specific fuel consumption; to reduce the amount of afterburner fuel flow in an augmented turbojet to improve its specific fuel consumption, or to increase the work output of a turboshaft engine. If the thrust or power of the engine is held constant, a size, cost and/or weight reduction can result. If the size of the engine is held constant growth capability can be provided.

Details

Aircraft Engineering and Aerospace Technology, vol. 42 no. 12
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 30 December 2021

Lorena Deleanu, Traian Florian Ionescu, George Catalin Cristea, Cornel Camil Suciu and Constantin Georgescu

This paper aims to present an analysis of several 3 D texture parameters for the entire wear scars obtained in severe regime, on a four-ball tester. The aim of this analysis is to…

71

Abstract

Purpose

This paper aims to present an analysis of several 3 D texture parameters for the entire wear scars obtained in severe regime, on a four-ball tester. The aim of this analysis is to correlate the tribological parameter as wear scar diameter to texture parameters.

Design/methodology/approach

Tested lubricants were rapeseed oil, rapeseed oil additivated with 1% Wt nano TiO2 and rapeseed oil additivated with 1%Wt nano ZnO. The severe regime was applied for 1400 rpm and for loads increasing in steps of 50 N, from 500 to 900 N. Several analyzed roughness parameters (height parameters and functional ones) could be related to the evolution of a wear parameter, the wear scar diameter. Comparing the values for neat rapeseed oil and additivated variants, the texture parameters allow for evaluating if the additives protect or not the worn surfaces.

Findings

Measurements pointed out two groups of roughness parameters: one that has an evolution depending on wear scar diameter (WSD) and load (Sa, St, functional parameters) and one including Ssk that has shown no dependence on load and WSD. Also, the functional parameters Spk and Svk follow in a similar manner the wear parameter, WSD, but Sk is the least dependent on load. For the highest load, amplitude parameters such as Sa and St are following the tendency of WSD. Each lubricant has its particular correlation between wear parameters and texture quality, expressed by the help of a set of roughness parameters.

Research limitations/implications

Such studies help tribologists to rank lubricants based on a combined analysis with wear parameters and texture parameters.

Practical implications

The results allow for evaluating new formulated lubricants.

Originality/value

The study on the quality on worn surfaces introduces the original idea of analyzing the entire wear scar surface (approximated by an ellipse with the axes as those experimentally measured) by the help of a set of 3 D roughness parameters.

Details

Industrial Lubrication and Tribology, vol. 74 no. 3
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 20 November 2009

Tomasz Müldner, Gregory Leighton and Jan Krzysztof Miziołek

The purpose of this paper is to consider the secure publishing of XML documents, where a single copy of an XML document is disseminated and a stated role‐based access control…

226

Abstract

Purpose

The purpose of this paper is to consider the secure publishing of XML documents, where a single copy of an XML document is disseminated and a stated role‐based access control policy (RBACP) is enforced via selective encryption. It describes a more efficient solution over previously proposed approaches, in which both policy specification and key generation are performed once, at the schema‐level. In lieu of the commonly used super‐encryption technique, in which nodes residing in the intersection of multiple roles are encrypted with multiple keys, it describes a new approach called multi‐encryption that guarantees each node is encrypted at most once.

Design/methodology/approach

This paper describes two alternative algorithms for key generation and single‐pass algorithms for multi‐encrypting and decrypting a document. The solution typically results in a smaller number of keys being distributed to each user.

Findings

The paper proves the correctness of the presented algorithms, and provides experimental results indicating the superiority of multi‐encryption over super‐encryption, in terms of encryption and decryption time requirements. It also demonstrates the scalability of the approach as the size of the input document and complexity of the schema‐level RBACP are increased.

Research limitations/implications

An extension of this work involves designing and implementing re‐usability of keyrings when a schema or ACP is modified. In addition, more flexible solutions for handling cycles in schema graphs are possible. The current solution encounters difficulty when schema graphs are particularly deep and broad.

Practical implications

The experimental results indicate that the proposed approach is scalable, and is applicable to scenarios in which XML documents conforming to a common schema are to be securely published.

Originality/value

This paper contributes to the efficient implementation of secure XML publication systems.

Details

International Journal of Web Information Systems, vol. 5 no. 4
Type: Research Article
ISSN: 1744-0084

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Article
Publication date: 29 August 2008

Wilma Penzo

The semantic and structural heterogeneity of large Extensible Markup Language (XML) digital libraries emphasizes the need of supporting approximate queries, i.e. queries where the…

355

Abstract

Purpose

The semantic and structural heterogeneity of large Extensible Markup Language (XML) digital libraries emphasizes the need of supporting approximate queries, i.e. queries where the matching conditions are relaxed so as to retrieve results that possibly partially satisfy the user's requests. The paper aims to propose a flexible query answering framework which efficiently supports complex approximate queries on XML data.

Design/methodology/approach

To reduce the number of relaxations applicable to a query, the paper relies on the specification of user preferences about the types of approximations allowed. A specifically devised index structure which efficiently supports both semantic and structural approximations, according to the specified user preferences, is proposed. Also, a ranking model to quantify approximations in the results is presented.

Findings

Personalized queries, on one hand, effectively narrow the space of query reformulations, on the other hand, enhance the user query capabilities with a great deal of flexibility and control over requests. As to the quality of results, the retrieval process considerably benefits because of the presence of user preferences in the queries. Experiments demonstrate the effectiveness and the efficiency of the proposal, as well as its scalability.

Research limitations/implications

Future developments concern the evaluation of the effectiveness of personalization on queries through additional examinations of the effects of the variability of parameters expressing user preferences.

Originality/value

The paper is intended for the research community and proposes a novel query model which incorporates user preferences about query relaxations on large heterogeneous XML data collections.

Details

International Journal of Web Information Systems, vol. 4 no. 3
Type: Research Article
ISSN: 1744-0084

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Article
Publication date: 31 July 2020

Oswald Mhlanga

The purpose of this paper is to examine the impacts of Airbnb on hotel employment.

812

Abstract

Purpose

The purpose of this paper is to examine the impacts of Airbnb on hotel employment.

Design/methodology/approach

A triple-difference regression framework was used to compare changes in hotel employment in three cities in South Africa where Airbnb started operating relative to cities without this home-sharing platform. Data on hotel employment was drawn from the survey on hotel service conducted by Smith Travel Research whereas the data on Airbnb’s listings was drawn from the Airbnb’s homepage for the period between July 2015 and December 2018. The analysis was restricted to 792 hotels.

Findings

Although prior studies have showed that Airbnb has an adverse impact on hotel performances, the findings show that total hotel employment expanded after the entry of Airbnb, accompanied by a marked relative shift towards self-employment. Airbnb supply negatively affected permanent employment, which was compensated by increase in temporary employment and self-employment. While the paper finds no evidence of adverse employment impacts, the hourly earnings declined for hotel employees were compensated by increase in income among self-employed Airbnb hosts. Although these findings might be contradictory to the general conjecture, such evidence calls for a comprehensive investigation of Airbnb’s overall economic impact.

Research limitations/implications

First, the study was based on the impact of Airbnb on hotel employment in South Africa. Caution is therefore required when generalising the findings of this study in other geographic areas. Second, some variables that may affect employment have not been included in this study because of the unavailability of data.

Practical implications

The results show that the sharing economy plays an important role in solving the unemployment problem, particularly in South Africa, where there is a high rate of unemployment. More practical implications are further discussed.

Originality/value

To the best of author’s knowledge, this paper provides the first systematic evidence of the impact of Airbnb on labour market outcomes in the hotel industry in South Africa.

研究目的

本论文研究Airbnb对酒店就业的影响。

研究涉及/方法/途径

研究采用三重差分回归模型, 对南非三个有Airbnb经营的城市与其他没有Airbnb经营的城市做酒店就业情况的对比分析。酒店就业数据来自于Smith Travel Research进行的Hotel Service问卷。Airbnb数据来自于2015年七月至2018年十二月之间的Airbnb主页上的租赁房屋数据。共792家酒店参与了数据分析。

研究结果

尽管之前的研究表明Airbnb对酒店绩效有着负面影响, 但是本论文研究表明, 在Airbnb进驻城市后, 该城市的酒店就业提升了, 并伴随着显著的自营就业。然而, Airbnb最终还是对长期的就业有着负面影响, 只是短期就业和自营就业的比重增大而已。虽然本论文未发现Airbnb对就业有负面影响, 但是酒店员工的时薪降低了, 随之弥补的是自营就业的收入增加。尽管本研究结果对整体的文献有着矛盾的地方, 但是仍需针对Airbnb经济影响的全面调研。

研究理论限制/意义

首先, 本论文仅研究了南非Airbnb对酒店就业情况的影响。其研究结果在其他地区的推广性则有待考察。第二, 受到数据限制, 一些可能会影响就业率的因素未被收录在本研究样本内。

研究实际意义

研究结果表明共享经济对解决就业问题有着重要影响, 尤其是在失业率较高的南非地区。更多的实际意义可以被深入讨论。

研究原创性/价值

本论文是首篇系统分析了Airbnb对南非酒店业劳动市场影响的文章。

Details

Journal of Hospitality and Tourism Technology, vol. 11 no. 3
Type: Research Article
ISSN: 1757-9880

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Details

Business and Management Doctorates World-Wide: Developing the Next Generation
Type: Book
ISBN: 978-1-78973-500-0

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Article
Publication date: 6 January 2022

Ahmad Latifian

Big data has posed problems for businesses, the Information Technology (IT) sector and the science community. The problems posed by big data can be effectively addressed using…

1063

Abstract

Purpose

Big data has posed problems for businesses, the Information Technology (IT) sector and the science community. The problems posed by big data can be effectively addressed using cloud computing and associated distributed computing technology. Cloud computing and big data are two significant past-year problems that allow high-efficiency and competitive computing tools to be delivered as IT services. The paper aims to examine the role of the cloud as a tool for managing big data in various aspects to help businesses.

Design/methodology/approach

This paper delivers solutions in the cloud for storing, compressing, analyzing and processing big data. Hence, articles were divided into four categories: articles on big data storage, articles on big data processing, articles on analyzing and finally, articles on data compression in cloud computing. This article is based on a systematic literature review. Also, it is based on a review of 19 published papers on big data.

Findings

From the results, it can be inferred that cloud computing technology has features that can be useful for big data management. Challenging issues are raised in each section. For example, in storing big data, privacy and security issues are challenging.

Research limitations/implications

There were limitations to this systematic review. The first limitation is that only English articles were reviewed. Also, articles that matched the keywords were used. Finally, in this review, authoritative articles were reviewed, and slides and tutorials were avoided.

Practical implications

The research presents new insight into the business value of cloud computing in interfirm collaborations.

Originality/value

Previous research has often examined other aspects of big data in the cloud. This article takes a new approach to the subject. It allows big data researchers to comprehend the various aspects of big data management in the cloud. In addition, setting an agenda for future research saves time and effort for readers searching for topics within big data.

Details

Kybernetes, vol. 51 no. 6
Type: Research Article
ISSN: 0368-492X

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Book part
Publication date: 2 September 2024

Nikola Ćurčić, Aleksandar Grubor and Vuk Miletić

Human resources (HR) are undoubtedly one of the most important factors of any organization. That is why making decisions on the HR policy is becoming a very sensitive issue, both…

Abstract

Human resources (HR) are undoubtedly one of the most important factors of any organization. That is why making decisions on the HR policy is becoming a very sensitive issue, both when hiring adequate candidates for the job and during the process work, i.e., during training and development of employees who work in the organization. The purpose of this study was to investigate the importance of HR and decisions on the HR policy as the premise for generating the organization’s expected business excellence. The starting assumption of this chapter is that appropriate decisions on the HR policy are predictors of engaging adequate employees and managing their potentials on the right way. The research is directed toward identifying differences in decisions on the personnel policy in organizations from Serbia that have different decision-makers and different management styles, which are directly related to their business success. Apart from the decision-maker, a significant role in profiling an organization’s personnel should also be done by the Human Resource Department, who take part in recruiting, selecting for education, building, and motivating personnel. In order to confirm the starting assumption, the comparative analysis method, the synthesis method, and the multiple comparison and statistical test methods are used.

Details

Emerging Patterns and Behaviors in a Green Resilient Economy
Type: Book
ISBN: 978-1-83549-781-4

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Article
Publication date: 25 October 2024

Burair Sajwani, Mohammad Al-Shboul and Aktham Maghyereh

This study aims to analyze the board characteristics–financial sustainability relationship in the largest US nonfinancial listed firms and the impact of the COVID-19 pandemic on…

116

Abstract

Purpose

This study aims to analyze the board characteristics–financial sustainability relationship in the largest US nonfinancial listed firms and the impact of the COVID-19 pandemic on this relationship.

Design/methodology/approach

Board characteristics such as attendance, cultural diversity, size, experience and gender diversity were assessed in relation to financial sustainability through various regression models, using 2007–2023 panel data of nonfinancial S&P 500 firms.

Findings

The examined board characteristics are positively associated with financial sustainability. The COVID-19 pandemic accentuated this association, which emphasizes the importance of effective board oversight during crises.

Practical implications

The findings provide guidance to shareholders, managers and regulators seeking to enhance corporate governance and financial sustainability. The adoption of effective supervisory and monitoring mechanisms can improve financial sustainability and reporting practices.

Social implications

Enhanced financial sustainability practices can lead to a more stable and secure financial future for companies, thus benefiting employees, shareholders and communities. This study offers insights for promoting the overall social and economic well-being of the US market.

Originality/value

This study enhances knowledge on how board characteristics influence financial sustainability, particularly during crises such as the COVID-19 pandemic. It provides insights into safeguarding stakeholder interests and improving financial sustainability in the US market.

Details

Journal of Financial Reporting and Accounting, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1985-2517

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Book part
Publication date: 23 April 2021

Kimberly W. O’Connor and Gordon B. Schmidt

Purpose – This chapter explores the topic of free speech protections and social media use in academia through an examination of the current legal landscape as it applies to…

Abstract

Purpose – This chapter explores the topic of free speech protections and social media use in academia through an examination of the current legal landscape as it applies to various stakeholders on university campuses in the United States. The authors focus this examination primarily on public universities. Methodology/Approach – Legal research methods were utilized, including an analysis of relevant United States federal and state laws, case law, and secondary sources such as law reviews. Non-legal sources, such as academic journals, were also reviewed, with particular emphasis on topics such as university policies, tenure protections, academic freedom, as well as current events. Findings – The law regarding personal social media communications in a university setting is a series of complex and interconnected legal questions. Courts are still flushing out how free speech protections, personal social media use, and other relevant legal protections (e.g., employment law) may interface in a university-related case. Outcomes of cases are highly fact driven, and legal precedent is still being established. Originality/Value – This chapter offers a comprehensive examination of the topic of free speech and social media use in United States academia by (1) examining legal protections as applied to various stakeholders on a college campus and (2) analyzing the current legal landscape of social media cases involving universities.

Details

Media and Law: Between Free Speech and Censorship
Type: Book
ISBN: 978-1-80071-729-9

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