A study on the yield stress of perlite-filled high-density polyethylenes

Four different types of high-density polyethylenes were blended with expanded perlite at different compositions. -aminopropyltriethoxysilane was applied to perlite (2 wt%) from ether and water solutions to enhance the interfacial adhesion between the polymer and the filler. It was shown that silane treatment advances the yield stress with improving dispersion and increasing the interfacial adhesion of the filler with the polymer matrix. The experimental results were then checked with the expression of Turcsanyiet al.'s.     

Equilibrium distributions of key components of spearmint oil in sub/supercritical carbon dioxide

Effects of temperature (at 35, 45 or 55°C) and pressure (10–110 atm) on the relative distribution coefficients of the twelve key components of spearmint oil (essential oil ofMentha cardiaca; Scotch spearmint) at equilibrium in dense CO₂ were investigated under conditions ranging from subcritical to supercritical regions. Effects of vapor pressure, molecular weight and polarity of the key components on their equilibrium distributions in sub/supercritical CO₂ are discussed. At 35°C, all key components of spearmint oil are equally soluble in dense CO₂ within the 12–102 atm pressure region. At 45 and 55°C, the key components are equally soluble for pressures greater than about 60 atm. However, around either 45°C/27 atm or 55°C/35 atm conditions, the relative distribution coefficients of all monoterpene hydrocarbons and of isomenthone (an oxygenated monoterpene) exhibit maxima, which are due to significantly higher vapor pressures of these components and significantly lower solvating power of the dense-gas solvent at these particular temperatures and pressures. Vapor-pressure effects, coupled with the decrease in solvating power, dominate the effects of polarity and molecular mass of the key components. Deterpenation of spearmint oil with dense CO₂ is possible around either 45°C/27 atm or 55°C/35 atm, where the monoterpene hydrocarbons tend to concentrate in the CO₂-rich phase.     

Evaluation of an adaptive and intelligent educational hypermedia for enhanced individual learning of mathematics: A qualitative study

The purpose of this study is to design a personalized adaptive and intelligent web based tutoring system based on learning style and expert system named UZWEBMAT and to evaluate its effects on 10th grade students’ learning of the unit of probability. In the study, initially, learning objects were prepared in three different ways in relation to three sub-learning areas of Visual–Auditory–Kinesthetic (VAK) learning style for each subject of the probability unit. These were appropriate for secondary school mathematics curricula. Then, they were transferred into the digital environment. Each student’s dominant learning style determines the content to which s/he will be directed since s/he is directed to the content that is appropriate for his/her learning style. The course to be followed by the students within UZWEBMAT and their browsing around the pages are decided by expert system integrated into the system. This expert system sets the situations in which s/he will get solution supports and the course s/he will follow in accordance with the performance of the student. Hereby, each student may follow a different course, and the solution supports s/he will get may also differ highlighting the individual learning. The sample of the study consists of 81 10th grade students and 3 mathematics teachers from two high schools in Trabzon, Turkey. Qualitative data were obtained both from the teachers and students participating in the study in order to answer the research questions about the implementation and evaluation of UZWEBMAT for mathematics teaching in a high school classroom. Obtained data were analyzed using qualitative data analysis methods. According to the results of the present study, positive opinions of students and teachers such as taking into account the individual learning differences and deriving mathematical relations and formulas through exploration became prominent. In addition, there were also other positive opinions of students and teachers such as providing permanent learning and introducing learning responsibility to the students. In this sense, it was concluded that UZWEBMAT is a beneficial instrument for both students and teachers.     

Calculations of the Elastic Scattering Properties of Ultra-cold Francium Isotopes

The calculations of the elastic scattering properties of ultra-cold francium isotopes are reported in detail. A parametric model potential for the triplet molecular states of the Fr₂ is represented, and the scattering lengths a_t and the effective range r_e are calculated using WKB and Numerov methods for Fr--Fr in the triplet state. The convergence of these scattering properties depending on a K⁰ parameter and core radius is also investigated using two methods: Quantum Defect Theory and analytical formula of Symskoviski.     

Application of InP Neural Network to ECG BeatClassification

This paper presents an application of a hybrid neural network structure to the classification of the electrocardiogram (ECG) beats. Three different feature extraction methods are comparatively examined: discrete cosine transform, wavelet transform and a direct method. Classification performances, training times and the numbers of nodes of Kohonen network, Restricted Coulomb Energy (RCE) network and the hybrid neural network are presented. To increase the classification performance and to decrease the number of nodes, the hybrid neural network is trained by Genetic Algorithms (GAs). Ten types of ECG beats obtained from the MIT-BIH database and from a real-time ECG measurement system are classified with a success of 98% by using the hybrid neural network structure and discrete cosine transform together.     

On periodic resource scheduling for continuous-media databases

The Enhanced Pay-Per-View (EPPV) model for providing continuous-media services associates with each continuous-media clip a display frequency that depends on the clip's popularity. The aim is to increase the number of clients that can be serviced concurrently beyond the capacity limitations of available resources, while guaranteeing a constraint on the response time. This is achieved by sharing periodic continuous-media streams among multiple clients. The EPPV model offers a number of advantages over other data-sharing schemes (e.g., batching), which make it more attractive to large-scale service providers. In this paper, we provide a comprehensive study of the resource-scheduling problems associated with supporting EPPV for continuous-media clips with (possibly) different display rates, frequencies, and lengths. Our main objective is to maximize the amount of disk bandwidth that is effectively scheduled under the given data layout and storage constraints. Our formulation gives rise to -hard combinatorial optimization problems that fall within the realm of hard real-time scheduling theory. Given the intractability of the problems, we propose novel heuristic solutions with polynomial-time complexity. We also present preliminary experimental results for the average case behavior of the proposed scheduling schemes and examine how they compare to each other under different workloads. A major contribution of our work is the introduction of a robust scheduling framework that, we believe, can provide solutions for a variety of realistic EPPV resource-scheduling scenarios, as well as any scheduling problem involving regular, periodic use of a shared resource. Based on this framework, we propose various interesting research directions for extending the results presented in this paper. Received June 9, 1998 / Accepted October 13, 1998     

Systematic literature review on smart contracts in the construction industry: Potentials,benefits, and challenges

The development of digital transformation in the construction industry has led to the increasing adoption of smart contracts. As programmable applications to automatically write, verify, and enforce transaction conditions, smart contracts can be used in different areas mainly to improve automation level, information security, and built digital environment enhancement. However, the smart contract is commonly mentioned as a blockchain appendage, while its unique connotation and value in the construction industry have not been recognized. Therefore, this study carries out a systematic review based on 81 research articles published from 2014 to 2021 on smart contract applications in construction to explore and highlight their potentials under domain-specific requirements. Results are analyzed according to research type categorization and domain codification. Eight research domains are identified, where the three most highly explored domains are contract and payment, supply chain and logistics, and information management. The integration of smart contracts with other innovative concepts and advanced technologies is analyzed. The applicability, benefits, and challenges of smart contract applications regarding different research domains are discussed.     

Strain–Stress Analysis of AlGaN/GaN Heterostructures With and Without an AlN Buffer and Interlayer

Abstract: The strain–stress analysis of Al_xGa_1?xN/GaN (x = 0.3) heterostructures with and without a high‐temperature HT‐AlN interlayer (IL) grown on sapphire (Al₂O₃) substrates and AlN buffer/Al₂O₃ templates via metal organic chemical vapour deposition (MOCVD) was carried out based on the precise measurement of the lattice parameters by using high‐resolution X‐ray diffraction (HRXRD). The a‐ and c‐lattice parameters were measured from the peak positions that were obtained by rocking the theta axis at the vicinity of the symmetric and asymmetric plane reflection angles, followed by the in‐plane and out‐of‐plane strains. Then, the biaxial and hydrostatic components were extracted from the total strain values that were obtained and were then discussed in the present study as the effect of the HT‐AlN buffer and IL. The AlN buffer layer (BL) affects the strain values of the AlGaN ternary layer (TL). A further effect was realized by inserting an AlN IL between GaN BL and AlGaN TL. However, the experimental results also show that an AlN IL changes the strain behaviour in the a‐ and c‐directions of the AlGaN TL from the tensile to compressive and the compressive to tensile type, respectively. These similar behaviours were observed in hydrostatic strain, biaxial strain and stress. Their reasons are explained with an effective a‐lattice parameter, post‐growth cooling and lattice and thermal mismatches.     

Mode competition using TE03 gyrotron cavities

The gyrotron is a powerful source of millimetre wave radiation. Fusion applications require more power per tube than is currently available This in turn means that the resonator must be highly overmoded, with a dense mode spectrum, which leads to mode competition. The influence of external parameters, such as the applied magnetic field, electron beam, and resonator geometry, on mode competition in tubes designed to operate at 150 and 140 GHz in the TE⁰³ mode is investigated theoretically and experimentally. It can be shown that even when the mode spectrum is fairly dense, single mode operation of a gyrotron is possible. The influence of startup conditions on output power is investigated in the 150 GHz experiment. In some cases, modes with an axial index of 2 were excited.