Enhancing turbulence: a potential strategy for drag reduction based on ground transportation systems (GTS) model

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiaolong Yang ◽  
Zhuangzhi Liu ◽  
Yu Hu
Keyword(s):  
Drag Reduction ◽  
Transportation Systems ◽  
Small Scale ◽  
Content Type ◽  
Eddy Simulation ◽  
Heavy Trucks ◽  
Turbulence Transition ◽  
Potential Possibility ◽  
Potential Strategy ◽  
And Performance

Purpose The purpose of this paper is to investigate the mechanism and performance of a potential strategy, which is to enhance turbulence to carry out drag reduction for heavy trucks. Design/methodology/approach Enhancing turbulence deflector (ETD) was placed on the roof surface of an ground transportation system (GTS) to investigate the drag reduction mechanism of enhancing turbulence. Transition shear-stress transport improved delay detach eddy simulation model was adopted to simulate the unsteady small-scale flow around the ETD. Findings By optimizing the three influencing factors, diameter, streamwise length and streamwise position, the optimized ETD has achieved a maximum drag reduction of 7.04%. The analysis of flow field results shows that enhancing turbulence can effectively suppress flow separation and reduce the negative pressure intensity in the wake region of GTS. Originality/value The present work provides another potential possibility for the improvement of the aerodynamic performance of heavy trucks.

scholarly journals Followers’ personality, transformational leadership and performance

2015 ◽  
Vol 5 (1) ◽  
pp. 65-78 ◽  
Author(s):  
Emma Soane ◽  
Christina Butler ◽  
Emma Stanton
Keyword(s):  
Transformational Leadership ◽  
Leadership Style ◽  
Social Identity Theory ◽  
Effective Leadership ◽  
Leadership Effectiveness ◽  
Small Scale ◽  
Research Model ◽  
Content Type ◽  
And Performance ◽  
Perceptions Of Leadership

Purpose – Effective leadership is important to performance in both organisational and sporting arenas. The authors theorised that follower personality would influence perceptions of leadership, and that perceived effective leadership would be associated with performance. The authors drew on Social Identity Theory (Tajfel and Turner, 1986), Transformational Leadership and personality theory to develop a research model designed to assess leadership effectiveness and performance. The purpose of this paper is to test the research model in a sporting context. Design/methodology/approach – The context of the research was a round the world sailing race, a ten-month competitive circumnavigation with ten identical boats. Quantitative data were gathered concerning participants’ personality, their perceptions of transformational leadership and boat performance. Qualitative data on transformational leadership and leadership effectiveness were gathered from a subsample of crew members. Findings – Results showed that transformational leadership was associated with leadership effectiveness and performance. Personality influenced perceptions of leadership and, for moderate performing boats, there were associations between perceptions of leadership and performance. Research limitations/implications – The data have implications for the extension of transformational leadership theory. Further consideration of follower personality could enhance leadership effectiveness. A limitation is the relatively small scale of the study. Practical implications – The main implication is that leaders should take follower personality into account, and adapt their leadership style accordingly. Doing so has consequences for performance. Originality/value – This novel study examined personality, leadership, and performance and has implications for enhancing leadership and performance in sports and business.

scholarly journals Parenting and infant mental health promotion: teachers’ views

2017 ◽  
Vol 16 (2) ◽  
pp. 72-77
Author(s):  
Lynn Carol Cuddihy ◽  
Anna Waugh
Keyword(s):  
Mental Health ◽  
Focus Groups ◽  
Research Question ◽  
Infant Mental Health ◽  
Small Scale ◽  
Content Type ◽  
School Based ◽  
Teachers Experiences ◽  
Potential Strategy ◽  
And Training

Purpose The purpose of this paper is to critically examine school teachers’ experiences and beliefs regarding parenting and infant mental health (IMH) promotion, starting with the research question: How do teachers in two secondary schools view their roles regarding parenting and IMH promotion? Design/methodology/approach Qualitative, exploratory focus groups were used with two groups of teachers that delivered personal social education (PSE) in schools. Findings Teachers currently have varying roles in PSE delivery. Interaction within focus groups can generate changes of opinions. Teachers do not promote parenting and IMH but are keen for support and training to do so to enable them to benefit future parents. Research limitations/implications This was a small-scale study. There was limited breadth of knowledge and experience of participants. The study highlights the need for further research and support and training for school-based staff in parenting promotion. Social implications The significance of parenting and IMH is well evidenced by theory, practice and policies. A potential strategy to prevent child developmental difficulties is to educate young people about parenting and IMH before they become parents. Originality/value No similar research was found in this area at the time of the study.

scholarly journals Noise Reduction Effect of Superhydrophobic Surfaces with Streamwise Strip of Channel Flow

2021 ◽  
Vol 11 (9) ◽  
pp. 3869
Author(s):  
Chen Niu ◽  
Yongwei Liu ◽  
Dejiang Shang ◽  
Chao Zhang
Keyword(s):  
Reynolds Number ◽  
Drag Reduction ◽  
Noise Reduction ◽  
Channel Flow ◽  
Superhydrophobic Surface ◽  
Sound Field ◽  
Flow Noise ◽  
Slip Boundary ◽  
Eddy Simulation ◽  
Reduction Effect

Superhydrophobic surface is a promising technology, but the effect of superhydrophobic surface on flow noise is still unclear. Therefore, we used alternating free-slip and no-slip boundary conditions to study the flow noise of superhydrophobic channel flows with streamwise strips. The numerical calculations of the flow and the sound field have been carried out by the methods of large eddy simulation (LES) and Lighthill analogy, respectively. Under a constant pressure gradient (CPG) condition, the average Reynolds number and the friction Reynolds number are approximately set to 4200 and 180, respectively. The influence on noise of different gas fractions (GF) and strip number in a spanwise period on channel flow have been studied. Our results show that the superhydrophobic surface has noise reduction effect in some cases. Under CPG conditions, the increase in GF increases the bulk velocity and weakens the noise reduction effect. Otherwise, the increase in strip number enhances the lateral energy exchange of the superhydrophobic surface, and results in more transverse vortices and attenuates the noise reduction effect. In our results, the best noise reduction effect is obtained as 10.7 dB under the scenario of the strip number is 4 and GF is 0.5. The best drag reduction effect is 32%, and the result is obtained under the scenario of GF is 0.8 and strip number is 1. In summary, the choice of GF and the number of strips is comprehensively considered to guarantee the performance of drag reduction and noise reduction in this work.

scholarly journals Large-Eddy Simulation Study of Flow and Heat Transfer in Swirling and Non-Swirling Impinging Jets on a Semi-Cylinder Concave Target

2021 ◽  
Vol 11 (15) ◽  
pp. 7167
Author(s):  
Liang Xu ◽  
Xu Zhao ◽  
Lei Xi ◽  
Yonghao Ma ◽  
Jianmin Gao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Large Eddy Simulation ◽  
Wall Temperature ◽  
Target Surface ◽  
Impinging Jets ◽  
Small Scale ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Flow And Heat Transfer ◽  
Large Eddy

Swirling impinging jet (SIJ) is considered as an effective means to achieve uniform cooling at high heat transfer rates, and the complex flow structure and its mechanism of enhancing heat transfer have attracted much attention in recent years. The large eddy simulation (LES) technique is employed to analyze the flow fields of swirling and non-swirling impinging jet emanating from a hole with four spiral and straight grooves, respectively, at a relatively high Reynolds number (Re) of 16,000 and a small jet spacing of H/D = 2 on a concave surface with uniform heat flux. Firstly, this work analyzes two different sub-grid stress models, and LES with the wall-adapting local eddy-viscosity model (WALEM) is established for accurately predicting flow and heat transfer performance of SIJ on a flat surface. The complex flow field structures, spectral characteristics, time-averaged flow characteristics and heat transfer on the target surface for the swirling and non-swirling impinging jets are compared in detail using the established method. The results show that small-scale recirculation vortices near the wall change the nearby flow into an unstable microwave state, resulting in small-scale fluctuation of the local Nusselt number (Nu) of the wall. There is a stable recirculation vortex at the stagnation point of the target surface, and the axial and radial fluctuating speeds are consistent with the fluctuating wall temperature. With the increase in the radial radius away from the stagnation point, the main frequency of the fluctuation of wall temperature coincides with the main frequency of the fluctuation of radial fluctuating velocity at x/D = 0.5. Compared with 0° straight hole, 45° spiral hole has a larger fluctuating speed because of speed deflection, resulting in a larger turbulence intensity and a stronger air transport capacity. The heat transfer intensity of the 45° spiral hole on the target surface is slightly improved within 5–10%.

scholarly journals Solid Form and Phase Transformation Properties of Fexofenadine Hydrochloride during Wet Granulation Process

Pharmaceutics ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 802
Author(s):  
Suye Li ◽  
Hengqian Wu ◽  
Yanna Zhao ◽  
Ruiyan Zhang ◽  
Zhengping Wang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transformation ◽  
Water Content ◽  
Scale Up ◽  
Small Scale ◽  
Dissolution Behavior ◽  
Wet Granulation ◽  
Water Addition ◽  
Granulation Process ◽  
And Performance

The quality control of drug products during manufacturing processes is important, particularly the presence of different polymorphic forms in active pharmaceutical ingredients (APIs) during production, which could affect the performance of the formulated products. The objective of this study was to investigate the phase transformation of fexofenadine hydrochloride (FXD) and its influence on the quality and performance of the drug. Water addition was key controlling factor for the polymorphic conversion from Form I to Form II (hydrate) during the wet granulation process of FXD. Water-induced phase transformation of FXD was studied and quantified with XRD and thermal analysis. When FXD was mixed with water, it rapidly converted to Form II, while the conversion is retarded when FXD is formulated with excipients. In addition, the conversion was totally inhibited when the water content was <15% w/w. The relationship between phase transformation and water content was studied at the small scale, and it was also applicable for the scale-up during wet granulation. The effect of phase transition on the FXD tablet performance was investigated by evaluating granule characterization and dissolution behavior. It was shown that, during the transition, the dissolved FXD acted as a binder to improve the properties of granules, such as density and flowability. However, if the water was over added, it can lead to the incomplete release of the FXD during dissolution. In order to balance the quality attributes and the dissolution of granules, the phase transition of FXD and the water amount added should be controlled during wet granulation.

scholarly journals Numerical Investigation on the Influence of the Streamlined Structures of the High-Speed Train’s Nose on Aerodynamic Performances

2021 ◽  
Vol 11 (2) ◽  
pp. 784
Author(s):  
Zhenxu Sun ◽  
Shuanbao Yao ◽  
Lianyi Wei ◽  
Yongfang Yao ◽  
Guowei Yang
Keyword(s):  
Drag Reduction ◽  
Pressure Distribution ◽  
Flow Separation ◽  
High Speed ◽  
Leeward Side ◽  
Detached Eddy Simulation ◽  
Side Force ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Asymmetrical Design

The structural design of the streamlined shape is the basis for high-speed train aerodynamic design. With use of the delayed detached-eddy simulation (DDES) method, the influence of four different structural types of the streamlined shape on aerodynamic performance and flow mechanism was investigated. These four designs were chosen elaborately, including a double-arch ellipsoid shape, a single-arch ellipsoid shape, a spindle shape with a front cowcatcher and a double-arch wide-flat shape. Two different running scenes, trains running in the open air or in crosswind conditions, were considered. Results reveal that when dealing with drag reduction of the whole train running in the open air, it needs to take into account how air resistance is distributed on both noses and then deal with them both rather than adjust only the head or the tail. An asymmetrical design is feasible with the head being a single-arch ellipsoid and the tail being a spindle with a front cowcatcher to achieve the minimum drag reduction. The single-arch ellipsoid design on both noses could aid in moderating the transverse amplitude of the side force on the tail resulting from the asymmetrical vortex structures in the flow field behind the tail. When crosswind is considered, the pressure distribution on the train surface becomes more disturbed, resulting in the increase of the side force and lift. The current study reveals that the double-arch wide-flat streamlined design helps to alleviate the side force and lift on both noses. The magnitude of side force on the head is 10 times as large as that on the tail while the lift on the head is slightly above that on the tail. Change of positions where flow separation takes place on the streamlined part is the main cause that leads to the opposite behaviors of pressure distribution on the head and on the tail. Under the influence of the ambient wind, flow separation occurs about distinct positions on the train surface and intricate vortices are generated at the leeward side, which add to the aerodynamic loads on the train in crosswind conditions. These results could help gain insight on choosing a most suitable streamlined shape under specific running conditions and acquiring a universal optimum nose shape as well.

Leader–follower narcissism and subgroup formation in teams: a conceptual model

2019 ◽  
Vol 34 (6) ◽  
pp. 429-442 ◽  
Author(s):  
Manuel London
Keyword(s):  
Team Performance ◽  
Team Identification ◽  
Goal Congruence ◽  
Content Type ◽  
Team Outcomes ◽  
Performance Pressure ◽  
Proposed Model ◽  
Leaders And Followers ◽  
Trait Activation ◽  
And Performance

Purpose Drawing on existing theory, a model is developed to illustrate how the interaction between leaders and followers similarity in narcissism and goal congruence may influence subgroup formation in teams, and how this interaction influences team identification and team performance. Design/methodology/approach The proposed model draws on dominance complementary, similarity attraction, faultline formation and trait activation theories. Findings Leader–follower similarity in narcissism and goal congruence may stimulate subgroup formation, possibly resulting in conformers, conspirators, outsiders and victims, especially when performance pressure on a team is high. Followers who are low in narcissism and share goals with a leader who is narcissistic are likely to become conformers. Followers who are high in narcissism and share goals with a narcissistic leader are likely to become confederates. Followers who do not share goals with a narcissistic leader will be treated by the leader and other members as outsiders if they are high in narcissism, and victimized if they are low in narcissism. In addition, the emergence of these subgroups leads to reduced team identification and lower team performance. Practical implications Higher level managers, coaches and human resource professions can assess and, if necessary, counteract low team identification and performance resulting from the narcissistic personality characteristics of leaders and followers. Originality/value The model addresses how and under what conditions narcissistic leaders and followers may influence subgroup formation and team outcomes.

Does corporate governance affect the performance of Islamic banks? New insight into Islamic countries

2020 ◽  
Vol 20 (6) ◽  
pp. 1073-1090 ◽  
Author(s):  
Ejaz Aslam ◽  
Razali Haron
Keyword(s):  
Corporate Governance ◽  
Audit Committee ◽  
Positive Impact ◽  
Islamic Banks ◽  
Governance Mechanism ◽  
Method Of Moment ◽  
Content Type ◽  
Return On Equity ◽  
Islamic Countries ◽  
And Performance

Purpose Corporate governance plays a significant role to overcome agency issues and develop the culture of transparency and openness. In this context, this paper aims to examine how corporate governance mechanisms affect the performance of Islamic banks (IBs). Design/methodology/approach Stepwise, two-step system generalize method of moment estimation technique is used in the analysis in which control variables are added into the model sequentially. This study used data on 129 IBs from 29 Islamic countries (Middle East, South Asia and Southeast Asia) during the period of 2008 to 2017. Findings The findings suggest that the audit committee (AUDC) and Shariah board (SB) have positive impact on the performance of IBs (return on assets and return on equity). However, board size and risk management committee have negative and significant effect on the performance of IBs. CEO duality and non-executive directors have mixed relationship with the performance of IBs. These results support the argument that IBs need to improve their financial performance through appropriate governance mechanism. Research limitations/implications The findings of the study added a new dimension to the governance research that could be a valuable source of knowledge for policymakers and regulators to improve the existing governance mechanism for better performance of IBs. Originality/value The study fills the gap in the literature by addressing the issue of corporate governance on performance of IBs across countries. Agency theory is discussed to explain the relationship between corporate governance mechanism and performance.

scholarly journals Entrepreneurial knowledge, skills, competencies and performance

2019 ◽  
Vol 13 (1) ◽  
pp. 29-48 ◽  
Author(s):  
Abdullah Al Mamun ◽  
Syed Ali Fazal ◽  
Rajennd Muniady
Keyword(s):  
Market Orientation ◽  
Low Income ◽  
Mediation Effect ◽  
Enterprise Performance ◽  
Content Type ◽  
Entrepreneurial Skills ◽  
And Performance ◽  
Entrepreneurial Activities ◽  
Positive Effect ◽  
Entrepreneurial Competency

Purpose This study aims to examine the effect of entrepreneurial skills, market orientation, sales orientations and networking on entrepreneurial competency and performance of micro-enterprises in Kelantan, Malaysia. Design/methodology/approach Adopting a cross-sectional design, this paper collected data through structured interviews from 403 micro-entrepreneurs from “Majlis Amanah Rakyat,” Kelantan and “Majlis Agama Islam dan Adat Istiadat,” Kelantan. Findings The findings reveal that entrepreneurial skills, market orientation and networking have a positive effect on entrepreneurial competency. Then, entrepreneurial competency, entrepreneurial skills and networking have a positive effect on enterprise performance. The findings show a significant mediation effect of entrepreneurial competency on the relationships between entrepreneurial skills, market orientation and networking and enterprise performance. Originality/value Addressing the understudied “human factor” in entrepreneurship, this paper extends the resource-based view and enriches the existing entrepreneurship literature in Malaysia. It provides useful insights into the improvement of micro-enterprise performance, which is crucial for promoting entrepreneurial activities and for enhancing socio-economic conditions among low-income households in Malaysia. Thus, the government and developmental organizations should focus on the development of entrepreneurial skills, market-oriented approach, networking traits and entrepreneurial competencies and subsequently encourage poor households to perform entrepreneurial activities.

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