Sandwich panels with aluminum honeycomb cores have emerged as an essential class of lightweight building materials in a wide variety of structural engineering areas, including marine, railway, ...aerospace, and automotive structures. Although sandwich structures offer remarkable mechanical properties, for instance, high specific strength and stiffness, these structures are open to the damage created by the low‐velocity impact. This study investigates the dynamic behavior of aluminum honeycomb sandwich panels with different core cell sizes based on neat and multi‐walled carbon nanotube (MWCNT) reinforced polyurethane (PU) adhesives that are aimed. The enhancement in impact performance of honeycomb sandwich structures obtained by the inclusion of MWCNTs in the PU adhesive is investigated. The effect of the MWCNT reinforcements on square sandwich panels at 50 J energy level is examined using an instrumented drop tower test setup. After acquiring load–time histories, the numerical integration method is implemented to obtain load–deflection and energy–time curves. Also, energy balance modeling (EBM) is utilized to characterize the effectualness of MWCNT reinforcement to PU adhesive on the impact behavior of sandwich panels. Theoretical EBM is confirmed that absorbed energy in the shear and bending deflections increased as the percentage of MWCNT‐added PU adhesive increases. Understanding the damage event implicated in absorbing and dissipating the impact energy is determined and compared for panels with different cell sizes, including nanoparticles, using the macroscopic optical images and microscopic scanning electron microscopy images of sandwich panels.
The stages of fabricating an aluminum honeycomb sandwich panel with nanoadhesive
In honeycomb core and composite face sheet sandwich panels, it is essential to understand the bonding characteristics of adhesive in relevance with its properties to observe synergistic effects of ...reinforcing nanoparticles such as multi-walled carbon nanotubes (MWCNTs). This study investigates the effects of MWCNT inclusion on polyurethane (PU) adhesive, which directly affects sandwich structures' structural and mechanical performance. MWCNTs are added to PU adhesive up to 0.2%, and their RAMAN spectroscopic analysis, Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analyses (TGA) and differential-scanning calorimetry analyses (DSC) are evaluated. Aluminum honeycomb carbon-fiber-reinforced composite (CFRC) sandwich panels are fabricated using an out-of-autoclave manufacturing process. Carbon-fiber prepreg is used for top/bottom face sheets. Mechanical strength of face/core bonding evaluated as a function of MWCNT addition and core cell sizes. Manufactured sandwich composite structures are investigated for flat-wise tensile strength and three-point bending strength. Results show that MWCNT reinforcement to PU adhesive and lower cell size increases bending and flat-wise tensile resistances.
PurposeThe purpose of this paper is to investigate the links among different forms of religiosity, family cohesion and ethical leadership in family firms operating in ...Turkey.Design/methodology/approachThe study was conducted with 210 respondents working in 51 family firms operating in Istanbul. Data regarding ethical leadership perceptions were collected separately from employees (non-family member) and managers (family member), and responses were matched in firm level to investigate the relations between variables calculated separately as perceptions of managers and employees. Confirmatory factor analysis and reliability statistics were used for ascertaining the dimensionality and factor structures of the constructs. Correlation analysis, structural equation modeling and bootstrapping method were used for investigating the relationships among variables.FindingsResults of the study demonstrated that family cohesion, intrinsic religiosity and spiritual well-being-oriented religiosity were positively, while secular religiosity was negatively related with ethical leadership levels rated by family member managers. Although none of these variables showed significant correlations with ethical leadership perceptions of non-family member employees, ethical leadership perceptions of the family managers and ethical leadership perceptions of employees were positively correlated, and intrinsic religiosity and spiritual well-being-oriented religiosity had significant indirect effects on ethical leadership perceptions of employees.Originality/valueGiven the lack of studies addressing the links between different forms of religiosity with ethical leadership especially in the Turkish context and the gap regarding research designs analyzing these relationships from the perspectives of managers and employees, the study provides important contributions.
Being a refugee or immigrant brings many difficulties that can detrimentally affect well-being. Participation in social life and feeling included in the host country can play an important role on ...well-being. This article aims to investigate the effects of religious participation and social inclusion on well-being levels of refugees and immigrants. Data were collected from 97 participants who were enrolled in voluntary Turkish language courses for refugees in Istanbul. Results of path analysis indicated that religious participation enhanced the level of social inclusion and social inclusion fostered existential well-being. Although religious participation demonstrated no direct effects on existential well-being, it showed a significant and positive indirect effect through social inclusion. Results of difference tests indicated that participants with higher level of education attended to religious activities significantly more often and their existential well-being and social inclusion levels were higher as well. Results also demonstrated that social inclusion scores of high attenders (to religious activities) were significantly higher.
Health services in the theater/district areas often contain difficulties. Although telemedicine has a huge potential to support medics in the area, there are challenges as well. Our aim is to ...evaluate the telemedicine support that can be provided to the medics from the perspective of course instructors.
Our study was carried out in The University of Health Sciences, Türkiye. All of the instructors of a medic course were asked to fill a 13-question questionnaire and Likert-type scale, sent via e-mail. Among 79 instructors, 71 of them (55 physicians, 16 nonphysicians) responded and were included in the study. The distributions of the categorical variables in the groups were analyzed with the Pearson Chi-square.
Of the 71 participants, 37 (52.11%) stated that there is a need for legal and ethical regulations for telemedicine (medical liability, malpractice, obtaining consent from the casualties, civilians, cross border missions, and rank-related problems) and patients' rights, additionally, to clarify the responsibilities of the doctors giving telemedicine support and the medics in the area. It was observed that physicians' and nonphysician group's opinions about the telepsychotherapy were statistically significantly different (χ2 = 8.675, P = .013).
Most of the instructors believed that telemedicine could carry the knowledge and skills of specialist physicians to the field of operation. Access to high-quality health services in a short time through telemedicine support can increase the courage and commitment of the personnel. It is thought that with telemedicine, medics will not feel alone in the field, their worries about making wrong decisions will decrease, and their knowledge and skills will increase. Participants were particularly concerned about who will be held responsible for problems arising from interventions carried out using telemedicine, and strict legal and medical regulations are needed.
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•Cu-based composites reinforced with different proportions of Co-CrC hybrid reinforcements.•The sharp-edged particle form of the ceramic particles decreased the density and ...strength.•Reinforcement particles maintained their thermal stability at high sintering temperature.•The strength and abrasion resistance of the composites were improved at the same time.
This study was carried out to assess the contribution of Co and CrC reinforcement particles to Cu main matrix powders by powder metallurgy (P/M) method as well as to mechanical properties, abrasion resistance and microstructure properties. For this purpose, the matrix material Cu powders, Co and CrC reinforcement particles, of which the weight percents are as follows: 5% (2% Co + 3% CrC), 10% (4% Co + 6% CrC) and 15% (6% Co + 9% CrC), were added. The samples were produced by cold pressing at room temperature and 450 MPa pressure, using the P/M method. Microstructure characterization of composite samples was performed by SEM-EDS and XRD analysis. Mechanical characterization of composite samples was carried out by analyzing the data of density determinations, hardness measurements, abrasion resistance tests and tensile tests. As a result of this study, it was observed that as the reinforcement ratio increased, the relative density of the samples decreased while the hardness of the samples increased. As a result of the findings obtained from the analysis of the tensile tests and other tests performed, it was clearly seen that the reinforcement particle ratio of wt. 10% was the optimum reinforcement ratio for this study.
This research aimed to examine the effects of daily work–family conflict and work–family enrichment on daily positive and negative affect levels of employees during the first phases of the COVID-19 ...pandemic in Turkey. The multilevel structure of the research design makes this study original. 730 day-level data were collected from 146 respondents during five consecutive workdays. One week later, a larger survey was delivered for assessing the person-level variables. The results indicated that both forms of work–family conflict significantly decreased positive affect and increased negative affect. Both types of work–family enrichment significantly increased positive affect; but only daily work to family enrichment significantly decreased daily negative affect. Findings also revealed that positive affect levels of respondents increase while negative affect levels decrease with time. On the days employees worked from distance, lower levels of positive and negative affect were experienced.
Biocomfort is limit values in which people feel comfortable in environmental conditions such as wind, humidity, temperature, and precipitation. Bioclimatic comfort areas are used in urban planning, ...rural planning, tourism purposes, urban area’s residential area, and landscape architecture. Bioclimatic comfort maps were made according to PET (Physiological Equivalent Temperature) index from meteorological station; also, data were obtained from satellite images to determine the bioclimatic comfort structure of the urban area in Bursa. For this data, average wind, temperature, and relative humidity values were converted to Geographic Information Systems (GIS) using ArcView GIS ™ 10 software and create thermal perception maps. The study integrates remote sensing (RS) and GIS to analyze land cover and use change in Bursa defining bioclimatic comfort. Utilizing Landsat (7 ETM and 8 OLITIRS) satellite data and Digital Elevation Model (DEM), the change map was analyzed and produced in 2002–2016. The objective was to understand the suitability of Change Vector Analysis (CVA) and elevation parameters in the region. The results indicate the appropriateness of change in vector analysis. With the help of a bioclimatic comfort conditions, map taking into account the temperature, humidity, and rainfall data and bioclimatic comfort zone for the 12-year period perceived for 30 years. The result maps of the study may serve as the basis for sustainable urban planning studies for Bursa.
Understanding the relationship between core/face adhesive interface and performance of MWCNT added nanoadhesives are essential for better designing and fabrication of aluminum honeycomb sandwich ...panels. In this study, we used multi-walled carbon nanotubes (MWCNTs) to prepare enhanced interfacial adhesion between honeycomb core and aluminum facesheet. MWCNTs are first introduced to isocyanate, and then MWCNTs/isocyanate blend poured into polyol to produce MWCNTs reinforced polyurethane (PU) nanoadhesives. The relationship between core/face adhesive interface and performance of MWCNT added nanoadhesives are investigated in detail in terms of thermogravimetric analyses (TGA), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, edge-wise compression tests, flat-wise tensile tests and three-point bending tests The experimental results showed that the MWCNT addition to PU adhesive led to enhanced thermal stability, flat-wise tensile strength and edge-wise compression strength for sandwich structures. This study gives a significant reference indicator on the fabrication of an improved core/face interface for obtaining sandwich panels with desired mechanical properties.
Given the unique nature and extreme work requirements of air traffic control units (e.g., high work demands, intolerance for mistakes, long working hours and night shifts), this study problematizes ...two critical yet understudied variables in this context, namely, workplace loneliness and work family conflict, and suggests a model in which paternalistic leadership mitigates them through boosted work engagement. Specifically, the study examined the mediating role of work engagement in the links between paternalistic leadership and workplace loneliness, and paternalistic leadership and work family conflict. Data were collected from air traffic controllers employed in İstanbul. The results of structural equation modeling analysis supported the hypothesis that work engagement fully mediated the links in the model. Paternalistic leadership, through increasing work engagement, decreases the workplace loneliness and work family conflict levels of air traffic controllers. The findings provide valuable insights and managerial implications.
•Paternalistic leadership fosters work engagement.•Work engagement fully mediates the relationship between paternalistic leadership and workplace loneliness.•Work engagement fully mediates the relationship between paternalistic leadership and work-family conflict.•Paternalistic leadership, though fostering work engagement, mitigates workplace loneliness and work family conflict.
