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Acoustic properties of natural fiber reinforced composite micro-perforated panel designed using 3D printing
No full textRole of Psychosocial Job Stressors on Sexual Function of Male Nurses: The Mediator Role of Work Ability
Full text linkThere is limited information on the specific psychosocial risks at work that can impact sexual function. The general aim of this study was to investigate the effects of multiple dimensions of psychosocial work stressors on the male sexual function. This was a cross-sectional study conducted among 153 male nurses working in two hospitals in Iran. Sexual function and psychosocial job stressors were measured using the Persian version of the International Index of Erectile Function (P-IIEF) and the Persian version of the Health and Safety Executive (P-HSE) Management Standards Indicator Tool. The Persian version of the Work Ability Index (P-WAI) was used to assess the mediating effect of work ability on the relationship between overall stress and subscales of sexual function. The data were analyzed using Pearson product–moment correlation, one-way analysis of variance (ANOVA), and multiple linear regressions. The subscales of psychosocial job stressors, especially the subscale of role, had a significant correlation with several domains of sexual function. The regression modeling indicated that the subscales of role and job demands were significant predictors of various domains of sexual function. The effect of overall stress on intercourse satisfaction was fully mediated by WAI. In the other indicators of sexual function, overall stress score had only a significant direct effect, not mediated by WAI. Intervention programs to improve sexual function should focus on increasing nurses’ involvement in making decisions related to jobs and on using ergonomic principles related to balancing job demands and the level of nurses’ capabilities
Acoustic properties of natural fiber reinforced composite micro-perforated panel (NFRC-MPP) made from cork fiber and polylactic acid (PLA) using 3D printing
Full text linkThe present study investigated the acoustic performance of biodegradable MPP absorbers made of natural fiber-reinforced composites (NFRC) using 3D printing. The novelty of this current research lies in the recent development of a methodology that aids industry professionals in optimizing the production of MPP (Micro-Perforated Panel) at a competitive cost. This is achieved by addressing and eliminating various issues commonly faced in traditional manufacturing processes, such as manual preparation and pressing. The FDM technique was used to fabricate test samples utilizing the PLA/corkwood composite. Using an impedance tube device with two microphones, the acoustic absorption coefficients of MPPs with different perforation diameters, thicknesses, and perforation rates were measured. Maa's analytical model was used to predict the acoustic absorption performance. Moreover, considering the average sound absorption and total cost of fabricating the samples, RSM-CCD was employed to optimize these samples. In the end, the parallel arrangement of MPP double layer and the combination of MPP with kenaf porous material were tested in order to improve the sound absorption performance. The results showed that the average sound absorption coefficient of the NFRC-MPP sound absorber is 25 % more than that of conventional MPP sound absorbers. The sample with a perforation diameter of 0.70 mm, a panel thickness of 0.90 mm, and an 8 mm distance between the perforations was selected as the optimal sound absorber. The measurement and model data for NFRC-MPP panels do not correspond well. The parallel arrangement of two layers of MPP and the addition of an optimized kenaf layer behind the MPP significantly improved the sound absorption performance in the intended frequency range. The findings of this study, coupled with data available in the literature for other types of biocomposite Micro-Perforated Panel (MPP), strongly indicate that Cork fiber-based MPP exhibits substantial promise for application, either independently or in conjunction with Kenaf materials, as a material for acoustic conditioning. Implementing smart manufacturing techniques for acoustic panels not only enhances engineering noise control efforts but also amplifies the overall effectiveness of Hearing Conservation Programs
Use of date palm waste fibers as sound absorption material
No full textAn increasing interest in the possibilities of converting agricultural wastes to value-added products has emerged. Annually, 200,000 tons of date palm waste are generated, which are charred or released as agricultural wastes. This work describes the efforts to fabricate low-cost sound-absorbing panels from date palm waste fibers and assess their performance for sound absorbing applications. Samples of different thicknesses (25, 35, 45, and 55 mm) and densities (125 and 175 kg/m3) were produced. The normal-incidence sound absorption coefficient was measured using the impedance tube and was modeled using both the Johnson-Champoux-Allard and the Attenborough models. The findings show that the samples with a thickness of 55 mm and a density of 175 kg/m3 have the highest sound absorbing performance. The acoustic behavior of this new material was investigated in a reverberation room. Moreover, the acoustic performance of the panels in a conference hall was modeled, assessing the improvements in its reverberation time (RT), early decay time (EDT), speech transmission index (STI), clarity (C80), and definition (D50). Finally, this paper shows that the acoustic performance of this material can be used to enhance room acoustics properties
Acoustic and thermal performance of wood strands-rock wool-cement composite boards as eco-friendly construction materials
No full textWith a growing emphasis on eco-friendly building materials, wood strands-rock wool-cement boards (WRCB) offer a promising solution due to their composition of renewable wood fibers and cementitious binder. This study delves into the intricate balance between sound absorption, thermal insulation, and cost-effectiveness of WRCB, all of which are crucial factors shaping indoor comfort, energy efficiency, and the economic viability of constructions. WRCB incorporating wood strands, Portland cement, rock wool, and calcium chloride were manufactured at various thicknesses (20–60 mm) and densities (400, 500, and 600 kg/m3). The WRCB exhibited sound absorption average (SAA) and effective thermal conductivity (Keff) values ranging from 0.28 to 0.56 and 0.285–0.381 W/(mK), respectively. These results underscore the remarkable SAA and Keff of the panels, showcasing their potential as sustainable construction materials. Notably, WRCB with thicknesses ranging from 30 mm to 50 mm and densities of 400–500 kg/m3 exhibited nearly ideal absorption levels between 1000 and 2000 Hz, indicating their practical suitability for speech-related scenarios in architectural environments. The utilization of the Response Surface Methodology allowed the optimal conditions for maximizing SAA while simultaneously minimizing Keff and cost to be identified through the optimization process. A density of 452.8 kg/m3 and a thickness of 37.8 mm were determined as the optimal parameters. Under these conditions, the resultant SAA reached 0.554, with a corresponding cost of 1724 IRR and Keff of 0.317 W/(mK). The results also demonstrated the significant impact of thickness and density on the acoustic and thermal performance of the WRCB. The acoustic performance of WRCB was further analyzed through predictive modeling using the Johnson-Champoux-Allard (JCA) and Delany-Bazley (DB) models. The results revealed that the JCA model exhibited superior predictive accuracy compared to the DB model
Measurement, Modeling, And Optimization Of Sound Absorption Performance Of Kenaf Fibers For Building Applications
No full textThe use of natural fibers in the buildings and construction industries as a sustainable and biodegradable product with the aim of noise pollution control has attracted the attention of many researchers. This work aims to study the acoustic behavior of porous absorbers made of natural Kenaf fibers. To this end, samples of sound absorber were fabricated with thicknesses of 10–40 mm at two different bulk densities of 150 and 200 kg/m3, and their sound absorption coefficient (SAC) was determined by standing wave sound impedance tube at different air gap cavities. A hybrid numerical-mathematical model was also proposed to investigate the acoustic behavior of the samples. To this end, a code was developed to simulate the 3D virtual structure of samples, and flow resistivity was calculated by numerically solving the flow of air in the structures. Tortuosity and two characteristic lengths were obtained using an inverse method programmed in MATLAB®. These parameters were then imported into the Johnson-Champoux-Allard (JCA) model to predict SACs at different frequencies. Afterward, considering the cost and sound absorption average (SAA), samples were optimized using factorial design. Consequently, the acoustic behavior of the optimized acoustic panels was investigated in the reverberation room in terms of reverberation time and random absorption coefficient. Moreover, in order to provide aesthetically and artistically pleasing appearance, the samples were covered with spacer fabrics, and their sound absorption behavior was also studied. The results revealed the promising sound absorption performance of Kenaf fibers. It was found that the SAC at low, mid, and high frequencies increases significantly with increasing the bulk density. The average of SACs for frequencies above 1250 Hz for samples of 40 mm thickness was found to be 0.95, while these values for samples of 30 and 20 mm thickness were respectively 0.85 and 0.7. The introduction of the air gap was found to improve the SAC at low-frequency bands and shift the peak of absorption toward low frequencies. Very good consistency was observed between the predicted and experimental data. The results of the statistical analysis suggested a thickness of 33 mm and a bulk density of 150 kg/m3 for the optimized panels. The results showed that the mean of SAC increased from 0.68 to 0.72 after covering the optimized panels with spacer fabrics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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