Search results

The purpose of this paper is to create models that predict exergetic sustainability index (ESI) and environmental effect factor (EEF) values with high accuracy according to various engine parameters.

In this study, models were created to estimate ESI and EEF sustainability parameters in various flight phases for a business jet with a turboprop engine using the cuckoo search algorithm (CSA) method. The database used for modeling includes the various engine parameters (torque, engine airflow, gas generator speed, fuel mass flow, power and air-fuel ratio) obtained by running a business aircraft engine more than once at different settings and the actual ESI and EEF values obtained depending on these parameters. In addition, sensitivity analysis was performed to measure the effect of engine parameters on the models. Finally, the effect of the CSA number of nest (n) parameter on the model accuracy was investigated.

It has been observed that the models predict ESI and EEF values with high accuracy. As a result of the sensitivity analysis, it was seen that the air-fuel ratio had a greater effect on the output parameters.

These models are thought to assist in the exergetic environment analysis used to find the greatest losses for turboprop business jets and identify their causes and further improve system performance. Thus, they will be a useful tool to minimize the negative impact of business jet on environmental sustainability.

To the best of the authors’ knowledge, this study stands out in the literature because it is the first exergo-metaheuristic approach developed with CSA for business aircraft engine; moreover, the data set used consists of real values.

This study aims to examine the relationship between market orientation and product innovation and the mediating role of technological capability in this relationship. It also aims to examine the effect of market orientation on product innovation within the framework of technological intensity classification of the fields of business activity.

The research data were obtained from 186 senior and mid-level managers of 627 manufacturing firms that are widely considered to be innovative, and that are ranked among Turkey's largest 1,000 manufacturing firms (ISO 1000). The data were analyzed using partial least squares structural equation modeling.

Customer orientation and interfunctional coordination, two distinct dimensions of market orientation, had positive effects on product innovation. Technological capability played a mediating role in the effect of customer orientation and interfunctional coordination on product innovation. In addition, interfunctional coordination positively affected product innovation in firms with low technological intensity, whereas customer orientation positively affected product innovation in firms with medium-high technological intensity.

For the success of product innovations, firms should establish mechanisms to obtain information about customer needs and expectations and to disseminate and effectively use this information among organizational functions. They also need to improve their technological capabilities to effectively transform market knowledge into product innovation.

The relationship between market orientation and product innovation has been examined in previous studies; however, there is an insufficient number of studies on the mediating role of technological capability in this relationship. This study aimed to eliminate the gap in the literature regarding the mediating role of technological capability. In addition, innovation activities of firms vary depending on the technological intensity, but only a limited number of evaluations have been conducted on this subject. This study contributes valuable knowledge to the relevant literature by examining the impact of market orientation dimensions on product innovation according to technological intensity.

The purpose of this paper is to present the results of a study on friction characteristics of plasma, salt‐bath and gas nitrided layers produced in AISI 304 type austenitic and AISI 420 type martensitic stainless steels.

Plasma nitriding processes were carried out with DC‐pulsed plasma in 80% N₂+20% H₂ atmosphere at 450°C and 520°C for 8 h at a pressure of 2 mbar. Salt‐bath nitriding was performed in a cyanide‐cyanate salt‐bath at 570°C for 1.5 h. Gas nitriding was also conducted in NH₃ and CO₂ atmosphere at 570°C for 13 h. Characterization of all nitrided samples has been carried out by means of microstructure, microhardness, surface roughness measurement and friction coefficient. The morphologies of the worn surfaces of the nitrided samples were also observed using a scanning electron microscope. Friction characteristics of the nitrided samples have been investigated using a ball‐on‐disc friction and wear tester with a WC‐Co ball as the counterface under dry sliding conditions.

The plasma nitrided and salt‐bath nitrided layers on the 420 steel surfaces were much thicker than on the 304 steel surfaces. However, there was no obvious and homogeneous nitrided layer on the gas nitrided samples' surface. The plasma and salt‐bath nitriding techniques significantly increased the surface hardness of the 304 and 420 samples. The highest surface hardness of the 304 nitrided samples was obtained by the plasma nitrided technique at 520°C. On the other hand, the highest surface hardness of the 420 nitrided layers was observed in the 450°C plasma nitrided layer. Experimental friction test results showed that the salt‐bath and 450°C plasma nitrided layers were more effective in reducing the friction coefficient of the 304 and 420 stainless steels, respectively.

The relatively poor hardness and hence wear resistance of austenitic and martensitic stainless steels needs to be improved. Friction characteristic is a key property of performance for various applications of austenitic and martensitic stainless steels. This work has reported a comparison of friction characteristics of austenitic 304 and martensitic 420 stainless steels, modified using plasma, salt‐bath and gas nitriding processes. The paper is of significances for improving friction characteristics, indirectly wear performances, of austenitic and martensitic stainless steels.

The study aims to assess the heater and cooler positional impacts systematically using four different quadrantal cavities filled with hybrid nanofluid, keeping the curved surface adiabatic under the orientated magnetic fields. Both heat transfer and entropy generation analyses are performed for a hybrid nanofluid flow in a quarter circular cavity considering different orientations of magnetic fields. The investigation is focused to assess the heater and cooler positional impacts systematically using four different quadrantal cavities (first to fourth quadrantal cavities), keeping the curved surface always adiabatic. The impacts of pertinent variables like Rayleigh number, Hartmann number and volumetric concentration of hybrid nanofluid on heat transfer characteristics are in consideration with the second law of thermodynamics. The analysis includes the thermal, viscous and magnetic aspects of entropy generation.

After validating against the experimental results, the present work explores numerically following the Galerkin weighted finite element technique. The solution is obtained through an iterative process satisfying the convergence limit of 10⁻⁸ and 10⁻¹⁰ for the maximum residuals and the mass defect, respectively.

It revealed that the mutual exchange of heater-cooler positions on the adjacent straight edges of the quadrant cavity does not have any impact on the flow direction. Although the magnitude of flow velocity enhances, the sidewall plays a decision-making role in the formation of a single circulation vortex. It also shows that thermal entropy production is the main cause behind thermodynamic irreversibility. The second or third quadrantal arrangement could have been opted as the best configuration of the heater-cooler position for achieving superior heat transfer. The Lorentz force plays a great role to moderate the heat transfer process. The maximum entropy generation is located, as expected, at the heating-cooling junction point.

There are plenty of prospects for extension of the present research concept numerically or experimentally, adopting three-dimensional analysis, working fluids, boundary conditions, etc. In fact, the study could be carried out for unsteady or turbulent fluid flow.

As the position of the heated source and cold sink on the enclosure geometry can significantly alter the thermo-fluid phenomena, this kind of analysis is of utmost relevance for the further development of efficient heating/cooling arrangements and proper management of the devices subjected to magnetic field applications. This original contribution could be a potentially valuable source for future research and exploration pertaining to a thermal system or device, like heat exchangers, solar collectors, thermal storage, electronic cooling, food and drying technologies and others.

In the literature, an inadequate number of works have focused on a quadrantal cavity, mostly considering the first quadrant of the circle. However, during practical applications, it is possible that the cavity can take the shape of the other three quadrants too, and the corresponding knowledge on relative performance is still missing. Furthermore, the present investigation includes the existence of magnetic fields at various orientations. The impact analysis of this field-induced Lorentz force on the nanofluid thermal performance is another major contribution from the present work that would enrich the domain knowledge and could be useful for thermal system engineers.

The purpose of this paper is to study the effects of additive on the tribological properties such as friction coefficient and wear loss in the journal bearings during start‐up (or shut‐down) and running‐in periods.

In this study, fully formulated commercial engine mineral oil (SAE 20W50) and commercial oil additives (3 per cent) added into this oil were tested to determine the tribological performances such as friction coefficient, wear loss and the effect of the additive on protective layers formed on the sliding bearing's surfaces.

This study presents an experimental procedure for obtaining practical results pertaining to the tribological performance of the journal bearing under running‐in and start‐up or shut down stages. Also, in this study, the authors have attempted to show the linkage between the oil additive and the running conditions such as running‐in and start‐up and shut‐down in effecting performance of the journal bearing. It is well known that one of the roles of an additive is to form a protective layer to reduce friction coefficient in lubricated contacts.

The paper is of value in presenting an experimental procedure for obtaining practical results pertaining to the tribological performance of the journal bearing under running‐in and start‐up or shut down stages.

This study aims to measure the effect of organizational culture perceptions of hotel employees on their organizational silence behavior and job performance, as well as the effect of their organizational silence behavior on their job performance.

A correlational survey model was used in this research and a questionnaire was distributed to collect the data from 389 sampled employees working in four- and five-star hotels in the Kusadasi region in Turkey.

It was found that organizational culture was not significantly related to organizational silence but that organizational culture and its dimensions were significantly related to job performance. It was also revealed that while organizational silence was not significantly related to job performance, its dimensions were significantly related to job performance.

The results of this study provide insight into organizational culture as an important factor in increasing job performance. The study also revealed how organizational silence behavior and its dimensions affect job performance. In this sense, accommodation establishments will be able to acquire new perspectives in terms of improving job performance.

This paper is deemed important, as it examined these three terms in one model in the field of tourism management. It is thought that it will contribute to the literature by closing the gap in the tourism literature while leading the way for future studies.

Introduction – In recent years virtual reality and augmented reality (AR) applications, which are widely used in many sectors, have become important tools in marketing communication. The change and differentiation that takes place in a revolutionary digital environment also affect social change. This change has led to the use of AR applications as a communication tool to affect all decisions of consumers in the purchasing process.

Purpose – The focus of this study is on AR applications using an experimental application in the context of marketing communication with experiential marketing and new technologies.

Method – This experimentation was carried out on over 2 million downloaded mobile applications by Turkish users of an AR brand of wall paint. The experiment included 32 consumers, painters, and interior designers in Istanbul. These formed the groups of the study. The authors aimed to determine whether AR mobile applications are seen differently between these three groups in terms of attitudes and buying intentions vis-a-vis other brands. Thus, the authors will determine the importance of AR applications in marketing communication, satisfaction of experience, and the effect on purchase intention in terms of the different groups. In line with the results, strategies will be presented to marketing practitioners. The literature review of the study enabled the formation and design of the research method and scales.

Findings – The preliminary study revealed that the attitudes toward experiential marketing, brand attitudes, and purchase intention using the AR application were significantly different from the catalog application.

The calculation and design of the structures are carried out with the aim of obtaining a sufficiently ductile behavior to allow the structure to undergo displacements, without risk of sudden breaks or loss of stability. The purpose of this study is to develop and validate a computer program (Thin beam2), allowing the modeling and simulation of the nonlinear behavior of reinforced concrete elements, on the other part, it is estimating the local and global ductility of the sections or elements constituting these structures.

The authors present two nonlinear analysis methods to carry out a parametric study of the factors influencing the local and global ductility of reinforced concrete structures. The first consists in evaluating the nonlinear behavior at the level of the cross-section of the reinforced concrete elements used in the elaborate Sectenol 1 program, it allows us to have the local ductility. The second, allows us to evaluate the nonlinear behavior of the element used in the modified thin beam 2 program, it allows us to estimate the overall ductility of the element.

The validation results of the Thin beam2 program are very satisfactory, by conferring the analytic and experimental results obtained by various researchers and the parametric study shows that each factor such as the compressive strength of the concrete has a favorable effect on ductility. Conversely, the normal compression force and the high resistance of tensioned reinforcements adversely affect ductility.

The reliability of the two programs lies in obtaining the local and global ductility of reinforced concrete structures because the calculation and design of the structures are carried out with the aim of obtaining ductile behavior without risk of breakage and instability.

Introduction – The rapid flow of information between the markets eliminates the possibility of diversifying the portfolio by bringing the markets closer, and may cause the volatility in a market to spread to another market. In this context, revealing the relationships between conventional and participation markets or financial assets is important in terms of portfolio diversification and risk management.

Purpose – The major aim of this work is to analyse the existence of volatility spillover between conventional stock index and participation index based on the indexes in Turkish Capital Markets. BIST-30 and Katılım-30 indexes are used as the representatives of conventional stock index and participation index, respectively.

Methodology – Firstly, the univariate HYGARCH (1,d,1) parameters are calculated, and secondly, the dynamic equicorrelation (DECO) methodology is applied. DECO model is proposed to simplify structural assumptions by introducing a structure in which all twosomes of returns take the same correlation for a given time period. In this way, DECO model enables to have an optimal portfolio selection in comparison to an unrestricted time varying-dynamic correlation approaches and gives more advanced forecasting ability for the duration of the financial crisis periods compared to the various portfolios.

Findings – There is a strong correlation between BIST-30 and Katılım-30. They are affected by the same shocks. We expect to see different investor behaviours for Katılım-30 and BIST-30. However, they seem to have almost the same investor profile. In addition, there is a causality in both ways and volatility spillover between them.