Search results for: high myopia

Authors: Lenka Bodnárová, Rudolf Hela, Michala Hubertová, Iveta Nováková

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This paper is concerning the issues of behaviour of lightweight expanded clay aggregates concrete exposed to high temperature. Lightweight aggregates from expanded clay are produced by firing of row material up to temperature 1050°C. Lightweight aggregates have suitable properties in terms of volume stability, when exposed to temperatures up to 1050°C, which could indicate their suitability for construction applications with higher risk of fire. The test samples were exposed to heat by using the standard temperature-time curve ISO 834. Negative changes in resulting mechanical properties, such as compressive strength, tensile strength, and flexural strength were evaluated. Also visual evaluation of the specimen was performed. On specimen exposed to excessive heat, an explosive spalling could be observed, due to evaporation of considerable amount of unbounded water from the inner structure of the concrete.

Keywords: expanded clay aggregate, explosive spalling, high temperature, lightweight concrete, temperature-time curve ISO 834

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Authors: D. Visuwan, B. Phruksaphanrat

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In this research, computer simulation is used for Electronic Manufacturing Service (EMS) plant layout analysis. The current layout of this manufacturing plant is a process layout, which is not suitable due to the nature of an EMS that has high-volume and high-variety environment. Moreover, quick response and high flexibility are also needed. Then, cellular manufacturing layout design was determined for the selected group of products. Systematic layout planning (SLP) was used to analyse and design the possible cellular layouts for the factory. The cellular layout was selected based on the main criteria of the plant. Computer simulation was used to analyse and compare the performance of the proposed cellular layout and the current layout. It is found that the proposed cellular layout can generate better performances than the current layout. In this research, computer simulation is used for Electronic Manufacturing Service (EMS) plant layout analysis. The current layout of this manufacturing plant is a process layout, which is not suitable due to the nature of an EMS that has high-volume and high-variety environment. Moreover, quick response and high flexibility are also needed. Then, cellular manufacturing layout design was determined for the selected group of products. Systematic layout planning (SLP) was used to analyse and design the possible cellular layouts for the factory. The cellular layout was selected based on the main criteria of the plant. Computer simulation was used to analyse and compare the performance of the proposed cellular layout and the current layout. It found that the proposed cellular layout can generate better performances than the current layout.

Keywords: layout, electronic manufacturing service plant, computer simulation, cellular manufacturing system

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Authors: Dacheng Li, Bo Huang, Qinjin Han, Ming Li

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Remotely sensed imagery with the high spatial and temporal characteristics, which it is hard to acquire under the current land observation satellites, has been considered as a key factor for monitoring environmental changes over both global and local scales. On a basis of the limited high spatial-resolution observations, challenged studies called spatiotemporal fusion have been developed for generating high spatiotemporal images through employing other auxiliary low spatial-resolution data while with high-frequency observations. However, a majority of spatiotemporal fusion approaches yield to satisfactory assumption, empirical but unstable parameters, low accuracy or inefficient performance. Although the spatiotemporal fusion methodology via sparse representation theory has advantage in capturing reflectance changes, stability and execution efficiency (even more efficient when overcomplete dictionaries have been pre-trained), the retrieval of high-accuracy dictionary and its response to fusion results are still pending issues. In this paper, we employ additional image pairs (here each image-pair includes a Landsat Operational Land Imager and a Moderate Resolution Imaging Spectroradiometer acquisitions covering the partial area of Baotou, China) only into the coupled dictionary training process based on K-SVD (K-means Singular Value Decomposition) algorithm, and attempt to improve the fusion results of two existing sparse representation based fusion models (respectively utilizing one and two available image-pair). The results show that more eligible image pairs are probably related to a more accurate overcomplete dictionary, which generally indicates a better image representation, and is then contribute to an effective fusion performance in case that the added image-pair has similar seasonal aspects and image spatial structure features to the original image-pair. It is, therefore, reasonable to construct multi-dictionary training pattern for generating a series of high spatial resolution images based on limited acquisitions.

Keywords: spatiotemporal fusion, sparse representation, K-SVD algorithm, dictionary learning

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Authors: Zarana Dave

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Cerium-doped lanthanum bromide, LaBr₃ (Ce), scintillator shows attracting properties for spectroscopy that makes it a suitable solution for security, medical, geophysics and high energy physics applications. Here, the performance parameters of a cylindrical LaBr₃ (Ce) scintillator was investigated. The first aspect is the determination of the efficiency for γ - ray detection, measured with GEANT4 simulation toolkit from 10keV to 10MeV energy range. The second is the detailed study of background radiation of LaBr₃ (Ce). It has relatively high intrinsic radiation background due to naturally occurring ¹³⁸La and ²²⁷Ac radioisotopes.

Keywords: LaBr₃(Ce), GEANT4, efficiency, background radiation

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Authors: Agata Tomaszewska, Timothy Kamps, Stephan R. Turnock, Nicola Symonds

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Bob skeleton is a highly competitive sport in which an athlete reaches speeds up to 40 m/s sliding, head first, down an ice track. It is believed that the friction between the runners and ice significantly contributes to the amount of the total energy loss during a bob skeleton descent. There is only limited available experimental data regarding the friction of bob skeleton runners or indeed steel on the ice at high sliding speeds ( > 20 m/s). Testing methods used to investigate the friction of steel on ice in winter sports have been outlined, and their accuracy and repeatability discussed. A system thinking approach was used to investigate the runner-ice interaction during sliding and create concept designs of three ice tribometers. The operational envelope of the bob skeleton system has been defined through mathematical modelling. Designs of a drum, linear and inertia pin-on-disk tribometers were developed specifically for bob skeleton runner testing with the requirement of reaching up to 40 m/s speed and facilitate fresh ice sliding. The design constraints have been outline and the proposed solutions compared based on the ease of operation, accuracy and the development cost.

Keywords: bob skeleton, ice friction, high-speed tribometers, sliding friction

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Authors: Yasir Ali, Farhatullah

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The present study was conducted to estimate the genetic variability, heritability and genetic advance in six parental lines and their 56 genotypes derived from five introgressed brassica populations on the basis of morphological and biochemical traits. The experiment was laid out in a randomized complete block design with two replications at The University of Agriculture Peshawar-Pakistan during growing season of 2015-2016. The ANOVA of all traits of F5:6 populations showed highly significant differences (P ≤ 0.01) for all morphological and biochemical traits. Among F5:6 populations, the genotype 2(526) was earlier in flowering (108.65 days), and genotype 14(485) was earlier in maturity (170 days). Tallest plants (182.5 cm), largest main raceme (91.5 cm) and maximum number of pods (80.5) on main raceme were recorded for genotype 17(34). Maximum primary branches plant-1(6.2) and longest pods (10.26 cm) were recorded for genotype 15, while genotype 16(171) had more seeds pod⁻¹ (22) and gave maximum yield plant-1 (30.22 g). The maximum 100-seed weight (0.60 g) was observed for genotype 10(506) while high protein content (22.61%) was recorded for genotype 4(99). Maximum oil content (54.08 %) and low linoleic acid (7.07 %) were produced by genotype (12(138) and low glucosinolate (59.01 µMg⁻¹) was recorded for genotype 21(113). The genotype 27(303) having high oleic acid content (51.73 %) and genotype 1(209) gave low erucic acid (35.97 %). Among the F5:6 populations moderate to high heritability observed for all morphological and biochemical traits coupled with high genetic advance. Cluster analysis grouped the 56 F5:6 populations along their parental lines into seven different groups. Each group was different from the other group on the basis of morphological and biochemical traits. Moreover all the F5:6 populations showed sufficient variability. Genotypes 10(506) and 16(171) were superior for high seed yield⁻¹, 100-seeds weight, and seed pod⁻¹ and are recommended for future breeding program.

Keywords: Brassicaceae, biochemical characterization, introgression, morphological characterization

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Authors: Sadık Ata, Kevser Dincer

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In this study, the performance of proton exchange membrane (PEM) fuel cell was experimentally investigated and modelled with Rule-Based Mamdani-Type Fuzzy (RBMTF) modelling technique. Coating on the anode side of the PEM fuel cell was accomplished with the spin method by using Yttria-stabilized zirconia (YSZ). Input-output parameters were described by RBMTF if-then rules. Numerical parameters of input and output variables were fuzzificated as linguistic variables: Very Very Low (L1), Very Low (L2), Low (L3), Negative Medium (L4), Medium (L5), Positive Medium (L6),High (L7), Very High (L8) and Very Very High (L9) linguistic classes. The comparison between experimental data and RBMTF is done by using statistical methods like absolute fraction of variance (R2). The actual values and RBMTF results indicated that RBMTF can be successfully used for the analysis of performance PEM fuel cell.

Keywords: proton exchange membrane (PEM), fuel cell, rule-based mamdani-type fuzzy (RMBTF) modelling, Yttria-stabilized zirconia (YSZ)

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Authors: El Oualid Mokhnache, Noureddine Ramdani

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The choice of gun barrel materials is crucial to ensure the maximum high rate of fire. The high rate of fire causes wear-out damage and shuts off mechanical properties (hardness, strength, wear resistance, etc.) and ballistic properties (bullet speed, dispersion and precision, longevity of barrel, etc). To overcome these kinds of problems, a deep understanding of the effect of the firing cycle on the mechanical and ballistic properties of the barrel is regarded as crucial to improving its characteristics. In the present work, a real experimental test of firing by using a high steel barrel with 7.62x39 ammunition was carried. Microstructural observations by using SEM were investigated. Hardness evolution through the barrel of both barrels labeled as reference barrels and as fired barrels were compared and discussed. Ballistic properties during the firing test, including speed of projectile and precision dispersion, are revealed and discussed as well. The aim of the present communication is about to discuss the relationship between pressure distribution versus mechanical properties through the wall barrel. Ballistic properties, including speed of the projectile, dispersion, and precision results during the shooting process, were investigated. Microstructure observations of the as-rifled barrel in comparison with the as-reference barrel were performed as well.

Keywords: barrel, ballistic, pressure, microstructure evolution, hardness

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Authors: Juliana Barcelos Cordeiro, Khashayar Mahani, Farbod Farzan, Mohsen A. Jafari

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Energy disaggregation has been focused by many energy companies since energy efficiency can be achieved when the breakdown of energy consumption is known. Companies have been investing in technologies to come up with software and/or hardware solutions that can provide this type of information to the consumer. On the other hand, not all people can afford to have these technologies. Therefore, in this paper, we present a methodology for breaking down the aggregate consumption and identifying the highdemanding end-uses profiles. These energy profiles will be used to build the forecast model for optimal control purpose. A facility with high cooling load is used as an illustrative case study to demonstrate the results of proposed methodology. We apply a high level energy disaggregation through a pattern recognition approach in order to extract the consumption profile of its rooftop packaged units (RTUs) and present a forecast model for the energy consumption.  

Keywords: energy consumption forecasting, energy efficiency, load disaggregation, pattern recognition approach

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Authors: Aedah Abd Rahman, Nurdatillah Hasim

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Software quality issues require special attention especially in view of the demands of quality software product to meet customer satisfaction. Software development projects in most organisations need proper defect management process in order to produce high quality software product and reduce the number of defects. The research question of this study is how to produce high quality software and reducing the number of defects. Therefore, the objective of this paper is to provide a framework for managing software defects by following defined life cycle processes. The methodology starts by reviewing defects, defect models, best practices and standards. A framework for defect management life cycle is proposed. The major contribution of this study is to define a defect management road map in software development. The adoption of an effective defect management process helps to achieve the ultimate goal of producing high quality software products and contributes towards continuous software process improvement.

Keywords: defects, defect management, life cycle process, software quality

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Authors: Reynald Contreras, Shaina Marie Bho, Kate Roan Dela Cruz, Marvin Dela Cruz

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This study was conducted with the aim of determining the skill level of grade ten (Grade 10) students in writing a reflective essay in selected secondary schools of Valenzuela. This research used descriptive and qualitative-quantitative research methods to systematically and accurately describe the level of writing skills of students and used a convenient sampling technique in selecting forty (40) students in grade ten. (Grade 10) at Polo, Wawang Pulo, and Arkong Batong high schools with a total of one hundred and twenty (120) students to assess the written reflective essay using modified rubrics developed based on 6+1 writing traits by Ruth Culham. According to the findings of the study, students at Polo and Wawang Pulo National high schools have low levels of writing skills that need to be developed or are not proficient. Meanwhile, Arkong Bato National High School has achieved a high degree of writing proficiency. Based on the study's findings, the researchers devised a suggested curriculum mapping for the suggested activity or intervention activity that would aid in the development and cultivation of the writing skills of children in grade ten (Grade 10).

Keywords: writing skills, reflective essay, intervention activity, 6+1 writing traits, modified rubrics

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Authors: Misun Kim, Beomsoo Park

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Korean government has strongly supported SMEs financially and technically. It has also changed R&D manpower management so that SMEs can benefit from the knowledge of highly qualified experts. This study evaluates the impacts of such policy on SMEs and analyzes the factors affecting the growth of the firms. Then we compare the characteristics of high growth companies to general companies. This factors could be use in the future for identifying firms that would significantly benefit from manpower help.

Keywords: dispatch human Ccapital, high growth, science and technology policy, SMEs

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Authors: Marinna Madrid, Nabiha Saklayen, Marinus Huber, Nicolas Vogel, Christos Boutopoulos, Michel Meunier, Eric Mazur

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Delivering material into cells is important for a diverse range of biological applications, including gene therapy, cellular engineering and imaging. We present a plasmonic substrate for delivering membrane-impermeable material into cells at high throughput and high efficiency while maintaining cell viability. The substrate fabrication is based on an affordable and fast colloidal self-assembly process. When illuminated with a femtosecond laser, the light interacts with the electrons at the surface of the metal substrate, creating localized surface plasmons that form bubbles via energy dissipation in the surrounding medium. These bubbles come into close contact with the cell membrane to form transient pores and enable entry of membrane-impermeable material via diffusion. We use fluorescence microscopy and flow cytometry to verify delivery of membrane-impermeable material into HeLa CCL-2 cells. We show delivery efficiency and cell viability data for a range of membrane-impermeable cargo, including dyes and biologically relevant material such as siRNA. We estimate the effective pore size by determining delivery efficiency for hard fluorescent spheres with diameters ranging from 20 nm to 2 um. To provide insight to the cell poration mechanism, we relate the poration data to pump-probe measurements of micro- and nano-bubble formation on the plasmonic substrate. Finally, we investigate substrate stability and reusability by using scanning electron microscopy (SEM) to inspect for damage on the substrate after laser treatment. SEM images show no visible damage. Our findings indicate that self-assembled plasmonic substrates are an affordable tool for high-throughput, high-efficiency delivery of material into mammalian cells.

Keywords: femtosecond laser, intracellular delivery, plasmonic, self-assembly

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Authors: Xiaoxu Liu, Yuwen Chen

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In this study, we investigated ethnic minority students’ perception of the implementation of preferential policies in China. Using a mixed methods design, we surveyed 320 students from an institute of education for ethnic minorities and conducted further in-depth interviews with seven respondents. Although interviewees were from 30 ethnic groups, most of them were from mainstream high schools. We found that minority students from preparatory classes have an overall positive attitude towards preferential policies and preparatory class but lack sense of belonging to the university for various reasons. Findings indicate that although preparatory class is regarded as being helpful for minority students’ academic development, there are differences of attitude mainly depending on the high schools they graduated from and their ethnic identities. Our analyses suggest that ethnicity, high school graduated from, hometown and family income are more important than gender, religion, and political affiliation when accounting for their perceptions of the implementation of preferential policies in China.

Keywords: Chinese minority education, higher education, preferential policies, survey analysis

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Authors: Karen Chad, Louise Humbert, Kenzie Friesen, Dave Sandomirsky

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Background: The pandemic of COVID-19 presented many historical challenges to the sporting community. For organizations and individuals, sport was put on hold resulting in social, economic, physical, and mental health consequences for all involved. High school sports are seen as an effective and accessible pathway for students to receive health, social, and academic benefits. Studies examining sport cessation due to COVID-19 found substantial negative outcomes on the physical and mental well-being of participants in the high school setting. However, the pandemic afforded an opportunity to examine sport participation and the value people place upon their engagement in high school sport. Study objectives: (1) Examine the experiences of students, parents, administrators, officials, and coaches during a year without high school sports; (2) Understand why participants are involved in high school sports; and (3) Learn what supports are needed for future involvement. Methodology: A mixed method design was used, including semi-structured interviews and a survey (SurveyMonkey software), which was disseminated electronically to high school students, coaches, school administrators, parents, and officials. Results: 1222 respondents completed the survey. Findings showed: (1) 100% of students participate in high school sports to improve their mental health, with >95% said it keeps them active and healthy, helps them make friends and teaches teamwork, builds confidence and positive self-perceptions, teaches resiliency, enhances connectivity to their school, and supports academic learning; (2) Top three reasons teachers coach is their desire to make a difference in the lives of students, enjoyment, and love of the sport, and to give back. Teachers said what they enjoy most is contributing to and watching athletes develop, direct involvement with student sport success, and the competitiveatmosphere; (3) 90% of parents believe playing sports is a valuable experience for their child, 95% said it enriches student academic learning and educational experiences, and 97% encouraged their child to play school sports; (4) Officials participate because of their enjoyment and love of the sport, experience, and expertise, desire to make a difference in the lives of children, the competitive/sporting atmosphere and growing the sport. 4% of officials said it was financially motivated; (5) 100% of administrators said high school sports are important for everyone. 80% believed the pandemic will decrease teachers coaching and increase student mental health and well-being. When there was no sport, many athletes got a part-time job and tried to stay active, with limited success. Coaches, officials, and parents spent more time with family. All participants did little physical activity, were bored; and struggled with mental health and poor physical health. Respondents recommended better communication, promotion, and branding of high school sport benefits, equitable funding for all sports, athlete development, compensation and recognition for coaching, and simple processes to strengthen the high school sport model. Conclusions: High school sport is an effective vehicle for athletes, parents, coaches, administrators, and officials to derive many positive outcomes. When it is taken away, serious consequences prevail. Paying attention to important success factors will be important for the effectiveness of high school sports.

Keywords: physical activity, high school, sports, pandemic

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Authors: Johannes Keil, Eric Mischorr, Veit Würfel, Jan Condé-Wolter, Alexander Liebsch, Maik Gude

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In the aviation sector wastewater pipes are subjected to many different mechanical and medial loads. Worst-case scenarios include high-velocity impacts resulting from the introduction of foreign objects into the system. The industry is seeking to reduce the weight of these pipes, which are currently manufactured from titanium. A promising alternative is the use of fiber-reinforced polymers (FRP), specifically carbon fiber (CF) reinforced polyaryletherketone (PAEK) laminates. This study employs an experimental methodology to investigate the impact resistance of CF/PAEK laminates, with a particular focus on three configurations: crimp, non-crimp, and interleaved matrix rich films in cross-ply laminates. High-velocity impacts were performed using a gas gun resulting in three-dimensional damage patterns. Afterwards the damage behavior was qualitatively and quantitatively analyzed using ultrasonic scans and computed tomography (CT). Samples with an interleaved matrix-rich film led to a reduction of the damage area by around 40% compared to the non-interleaved, non-crimp samples, while the crimp architecture resulted in a reduction of more than 60%. Therefore, these findings contribute to understanding the influence of laminate architecture on impact resistance, paving the way for more efficient materials in aviation applications.

Keywords: fracture toughness, high-velocity-impact, textile architecture, thermoplastic composites

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Authors: Branislav Timotijevic, Yves Petremand, Markus Luetzelschwab, Dara Bayat, Laurent Aebi

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Optical miniaturized sensors with remote readout are required devices for the monitoring in harsh electromagnetic environments. As an example, in turbo and hydro generators, excessively high vibrations of the end-windings can lead to dramatic damages, imposing very high, additional service costs. A significant change of the generator temperature can also be an indicator of the system failure. Continuous monitoring of vibrations, temperature, humidity, and gases is therefore mandatory. The high electromagnetic fields in the generators impose the use of non-conductive devices in order to prevent electromagnetic interferences and to electrically isolate the sensing element to the electronic readout. Metal-free sensors are good candidates for such systems since they are immune to very strong electromagnetic fields and given the fact that they are non-conductive. We have realized miniature optical accelerometer and temperature sensors for a remote sensing of the harsh environments using the common, inexpensive silicon Micro Electro-Mechanical System (MEMS) platform. Both devices show highly linear response. The accelerometer has a deviation within 1% from the linear fit when tested in a range 0 – 40 g. The temperature sensor can provide the measurement accuracy better than 1 °C in a range 20 – 150 °C. The design of other type of sensors for the environments with high electromagnetic interferences has also been discussed.

Keywords: optical MEMS, temperature sensor, accelerometer, remote sensing, harsh environment

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Authors: Siddegowda, Y. A. Sathish, G. Krishnegowda, T. M. Mohan Kumar

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Road accidents are a human tragedy. They involve high human suffering and monetary costs in terms of untimely death, injuries and social problems. India had earned the dubious distinction of having more number of fatalities due to road accidents in the world. Road safety is emerging as a major social concern around the world especially in India because of infrastructure project works. A case study was taken on NH – 07 which connects to various major cities and industries. The study shows that major cases of fatalities are due to bus, trucks and high speed vehicles. The main causes of accidents are due to high density, non-restriction of speed, use of mobile phones, lack of board signs on road parking, visibility restriction, improper geometric design, road use characteristics, environmental aspects, social aspects etc. Data analysis and preventive measures are enlightened in this paper.

Keywords: accidents, environmental aspects, fatalities, geometric design, road user characteristics

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Authors: Saad Ahmed, Sanjeev Khannaa

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Glass fiber reinforced polymers are widely used in structural systems as load-bearing elements at both high and low temperatures. This investigation presents the evaluation of glass fiber reinforced unsaturated polyurethane under harsh conditions of changing temperature and moisture content. This study Explores how these parameters affect the optical properties of the polymer matrix and the composite. Using the hand layup method, the polyurethane resin was modified by E-glass fibers (15 vol. %) to manufacture fiber-reinforced composite. This work includes the preparation of glass-like polyurethane resin sheets and estimates all light transmittance properties at high and very low temperatures and wet conditions. All-optical properties were retested to evaluate the level of improvement or failure. The results found that when comprising reinforced composite fiber to the unreinforced specimens, the reinforced composite shows a fair optical property at high temperatures and good performance at low temperatures.

Keywords: unsaturated polyurethane, extreme temperatures, light transmittance, haze number

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Authors: Ayoub Daoudi, Javad Eslami, Anne-Lise Beaucour, Martin Vigroux, Albert Noumowé

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As a fact, many cultural heritage masonry buildings have undergone violent fires during their history. In order to investigate the high temperature behaviour of stone masonry, six French limestones were heated to 600 °C at a rate of 9 °C/min. The main focus is the comparison between the high temperature behaviour of stones at the material and at the structural scale. In order to evaluate the risk of spalling, the tests have been carried out on the stone blocks (12x30x30 cm) instrumented with thermocouples and subjected to an unidirectional heating on one face. Thereafter, visual assessments and non-destructive measurements (dynamic elastic modulus) performed on blocks demonstrate a different behaviour from what was observed at the material scale. Finally, a series of thermo-mechanical computations, using finite element method, allowed us to highlight the difference between the behaviour of stones at material and block scales.

Keywords: limestones, hight temperature behaviour, damage, thermo-mechanical modeling, material and blocks scales, color change

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Authors: D. S. Mohale, A. V. Chandewar

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Anxiety is defined as an exaggerated feeling of apprehension, uncertainty and fear. Nerium indicum is a well-known ornamental and medicinal plant belonging to the family Apocynaceae. A wide spectrum of biological activities has been reported with various constituents isolated from different parts of the plant. This study was conducted to investigate antianxiety activity of flower extract. Flowers were collected and dried in shade and coarsely powdered. Powdered mixture was extracted with ethyl acetate by maceration process. Extract of flowers obtained was subsequently dried in oven at 40-50 °C. This extract is then tested for antianxiety activity at low and high dose using Elevated Plus Maze and Light & dark Model. Rats shown increased open arm entries and time spent in open arm in elevated Plus maze with treatment low and high dose of extract of Nerium indicum flower as compared to their respective control groups. In Light & dark Model, light box entries and time spent in light box increased with treatment low and high dose of extract of Nerium indicum flower as compared to their respective control groups. From result it is concluded that Ethyl acetate extract of flower of Nerium indicum possess antianxiety activity at low and high dose.

Keywords: anxiety, anxieolytic, social isolation, nerium indicum, kaner

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Authors: Pei-Hsing Huang, Wei-Ju Huang

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Investment casting is commonly used in the production of metallic components with complex shapes, due to its high dimensional precision, good surface finish, and low cost. However, the process is cumbersome, and the period between trial casting and final production can be very long, thereby limiting business opportunities and competitiveness. In this study, we replaced conventional wax injection with stereolithography (SLA) 3D printing to speed up the trial process and reduce costs. We also used silicone molds to further reduce costs to avoid the high costs imposed by photosensitive resin.

Keywords: investment casting, stereolithography, wax molding, 3D printing

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Authors: Hue Dinh, Binh Nguyen, Vivian Mendez, Phillip W. Taylor, Fleur Ponton

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Better understanding of how parental diet affects offspring traits is an important ecological and evolutionary question. In this study, we explored how maternal diet influences offspring physiology and resistance to infection using Bactrocera tryoni (Q-fly) as a system model. Female Q-flies were fed one of six single diets varying in their yeast-to-sugar ratio yielding six protein-to-carbohydrate ratios. As controls, we used females that were given a choice between yeast and sugar. Males were reared on a choice diet and allowed to mate with females 14 days post-emergence. Results showed that while maternal diet does not influence offspring developmental time, it has a strong effect on larval body weight. Mother fed either high-protein or high-sugar diet produced larger progeny. By challenging offspring with the bacterium Serratia marcescens, we found that female offspring from mothers fed high-sugar diet survived better the infection compared to those from mothers fed low-sugar diet. In contrast, male offspring produced by mother fed high-protein diet showed better resistance to the infection compared to those produced by mother fed low-protein diet. These results suggested sex-dependent transgenerational effects of maternal nutrition on offspring physiology and immunity.

Keywords: bacterial infection, Bactrocera tryoni, maternal diet, offspring, Serretia marcescens

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Authors: Armenuhi Ghazaryan, Qnarik Poghosyan, Tadevos Markosyan

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We have considered the high-order harmonic generation in-plane graphene quantum dots of hexagonal shape by the independent quasiparticle approximation-tight binding model. We have investigated how such a nonlinear effect is affected by a strong optical wave field, quantum dot typical band gap and lateral size, and dephasing processes. The equation of motion for the density matrix is solved by performing the time integration with the eight-order Runge-Kutta algorithm. If the optical wave frequency is much less than the quantum dot intrinsic band gap, the main aspects of multiphoton high harmonic emission in quantum dots are revealed. In such a case, the dependence of the cutoff photon energy on the strength of the optical pump wave is almost linear. But when the wave frequency is comparable to the bandgap of the quantum dot, the cutoff photon energy shows saturation behavior with an increase in the wave field strength.

Keywords: strong wave field, multiphoton, bandgap, wave field strength, nanostructure

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Authors: Abbas Nasir, Xiong Zhang, Sohail Ahmad, Yiping Cui

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Non-polar a-plane AlGaN epilayers of high structural quality have been grown on r-sapphire substrate by using metalorganic chemical vapor deposition (MOCVD). A graded non-polar AlGaN buffer layer with variable aluminium concentration was used to improve the structural quality of the non-polar a-plane AlGaN epilayer. The characterisations were carried out by high-resolution X-ray diffraction (HR-XRD), atomic force microscopy (AFM) and Hall effect measurement. The XRD and AFM results demonstrate that the Al-composition-graded non-polar AlGaN buffer layer significantly improved the crystalline quality and the surface morphology of the top layer. A low root mean square roughness 1.52 nm is obtained from AFM, and relatively low background carrier concentration down to 3.9×  cm^-3 is obtained from Hall effect measurement.

Keywords: non-polar AlGaN epilayer, Al composition-graded AlGaN layer, root mean square, background carrier concentration

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Authors: Noureddine Ramdani

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In recent years, extensive attention has been given to the study of conductive nanocomposites due to their unique properties, which are dependent on their size and shape. The potential applications of these materials include electromagnetic interference shielding, energy storage, photovoltaics, and others. These outstanding properties have led to increased interest and research in this field. In this work, a conductive poly benzoxazine nanocomposite, PBZ/Gr-Cu, was synthesized through a compression molding technique to achieve a high-performance material suitable for electromagnetic interference (EMI) shielding applications. The microstructure of the nanocomposites was analyzed using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The thermal stability, electrical conductivity, and EMI shielding properties of the nanocomposites were evaluated using thermogravimetric analysis, a four-point probe, and a VNA analyzer, respectively. The TGA results revealed that the thermal stability and electrical conductivity of the nanocomposites were significantly enhanced by the incorporation of Gr/Cu nanoparticles. The nanocomposites exhibited a low percolation threshold of about 3.5 wt.% and an increase in carrier concentration and mobility of the carriers with increasing hybrid nanofiller content, causing the composites to behave as n-type semiconductors. These nanocomposites also displayed a high dielectric constant and a high dissipation factor in the frequency range of 8-12 GHz, resulting in higher EMI shielding effectiveness (SE) of 25-44 dB. These characteristics make them promising candidates for lightweight EMI shielding materials in aerospace and radar evasion applications.

Keywords: polybenzoxazine matrix, conductive nanocomposites, electrical conductivity, EMI shielding

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Authors: Dilip Depan, Austin Simoneaux, William Chirdon, Ahmed Khattab

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In this study, we present a novel approach to synthesize polymer nanocomposites with nanohybrid shish-kebab architecture (NHSK). For this low-density and high density polyethylene (PE) was crystallized on various carbon nano-fillers using a novel and convenient method to prepare high-yield NHSK. Polymer crystals grew epitaxially on carbon nano-fillers using a solution crystallization method. The mixture of polymer and carbon fillers in xylene was flocculated and precipitated in ethanol to improve the product yield. Carbon nanofillers of varying diameter were also used as a nucleating template for polymer crystallization. The morphology of the prepared nanocomposites was characterized scanning electron microscopy (SEM), while differential scanning calorimetry (DSC) was used to quantify the amount of crystalline polymer. Interestingly, whatever the diameter of the carbon nanofiller is, the lamellae of PE is always perpendicular to the long axis of nanofiller. Surface area analysis was performed using BET. Our results indicated that carbon nanofillers of varying diameter can be used to effectively nucleate the crystallization of polymer. The effect of molecular weight and concentration of the polymer was discussed on the basis of chain mobility and crystallization capability of the polymer matrix. Our work shows a facile, rapid, yet high-yield production method to form polymer nanocomposites to reveal application potential of NHSK architecture.

Keywords: carbon nanotubes, polyethylene, nanohybrid shish-kebab, crystallization, morphology

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Authors: Huang Haoxin

Abstract:

Large dark current at room temperature has long been the major bottleneck that impedes the development of high-performance infrared photodetectors towards miniaturization and integration. Although infrared photodetectors based on layered 2D narrow bandgap semiconductors have shown admirable advantages compared with those based on conventional compounds, which typically suffer from expensive cryogenic operations, it is still urgent to develop a simple but effective strategy to further reduce the dark current. Herein, a tellurium (Te) based infrared photodetector is reported with a specifically designed asymmetric electrical contact area. The deliberately introduced asymmetric electrical contact raises the electric field intensity difference in the Te channel near the drain and the source electrodes, resulting in spontaneous asymmetric carrier diffusion under global infrared light illumination under zero bias. Specifically, the Te-based photodetector presents promising detector performance at room temperature, including a low dark current of≈1 nA, an ultrahigh photocurrent/dark current ratio of 1.57×10⁴, a high specific detectivity (D*) of 3.24×10⁹ Jones, and relatively fast response speed of ≈720 μs at zero bias. The results prove that the simple design of asymmetric electrical contact areas can provide a promising solution to high-performance 2D semiconductor-based infrared photodetectors working at room temperature.

Keywords: asymmetrical contact, tellurium, dark current, infrared photodetector, sensitivity

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Authors: Gajanan Bhat, Vincent Kandagor, Daniel Prather, Ramesh Bhave

Abstract:

Polyetherimide (PEI), an engineering plastic with very high glass transition temperature and excellent chemical and thermal stability, has been processed into a controlled porosity filter media of varying pore size, performance, and surface characteristics. A special grade of the PEI was processed by melt blowing to produce microfiber nonwovens suitable as filter media. The resulting microfiber webs were characterized to evaluate their structure and properties. The fiber webs were further modified by hot pressing, a post processing technique, which reduces the pore size in order to improve the barrier properties of the resulting membranes. This ongoing research has shown that PEI can be a good candidate for filter media requiring high temperature and chemical resistance with good mechanical properties. Also, by selecting the appropriate processing conditions, it is possible to achieve desired filtration performance from this engineering plastic.

Keywords: nonwovens, melt blowing, polyehterimide, filter media, microfibers

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Authors: Yudia Mailani Putri, Martalena Purba, B. J. Istiti Kandarina

Abstract:

Background: Obesity has been recognized as a global health problem. Individuals classified as overweight and obese are increasing at an alarming rate. This condition is associated with psychological and physiological problems. as a person reaches adulthood, somatic growth ceases. At this stage, the human body has developed fully, to a stable state. As the capital of Riau Province in Indonesia, Pekanbaru is dominated by Malay ethnic population habitually consuming cholesterol-rich fatty foods as a daily menu, a trigger to the onset of obesity resulting in high prevalence of degenerative diseases. Research objectives: The aim of this study is elaborating the relationship between high-fat consumption pattern, stress level, physical activity and the incidence of obesity in adult women in Pekanbaru city. Research Methods: Among the combined research methods applied in this study, the first stage is quantitative observational, analytical cross-sectional research design with adult women aged 20-40 living in Pekanbaru city. The sample consists of 200 women with BMI≥25. Sample data is processed with univariate, bivariate (correlation and simple linear regression) and multivariate (multiple linear regression) analysis. The second phase is qualitative descriptive study purposive sampling by in-depth interviews. six participants withdrew from the study. Results: According to the results of the bivariate analysis, there are relationships between the incidence of obesity and the pattern of high fat foods consumption (energy intake (p≤0.000; r = 0.536), protein intake (p≤0.000; r=0.307), fat intake (p≤0.000; r=0.416), carbohydrate intake (p≤0.000; r=0.430), frequency of fatty food consumption (p≤0.000; r=0.506) and frequency of viscera foods consumption (p≤0.000; r=0.535). There is a relationship between physical activity and incidence of obesity (p≤0.000; r=-0.631). However, there is no relationship between the level of stress (p=0.741; r=0.019-) and the incidence of obesity. Physical activity is a predominant factor in the incidence of obesity in adult women in Pekanbaru city. Conclusion: There are relationships between high-fat food consumption pattern, physical activity and the incidence of obesity in Pekanbaru city whereas physical activity is a predominant factor in the occurrence of obesity, supported by the unchangeable pattern of high-fat foods consumption.

Keywords: obesity, adult, high in fat, stress, physical activity, consumption pattern

Procedia PDF Downloads 233