Effectiveness of clicker‐assisted teaching in improving the critical thinking of adolescent learners

The effect of the implementation of student response systems (SRSs) in teaching on the critical thinking (CT) of young students was investigated. The study benefited from a quasi‐experimental design and a pretest/posttest set‐up. Subjects consisted of 156 K‐8 students in Tehran during 2016–2017, selected through a multistage cluster sampling, and randomly assigned to either the experimental group (EG) or the control group (CG). The regular curriculum of the students contained a weekly session of a course titled “Thinking and Lifestyle.” Ten sessions of the course were conducted using SRS (aka clickers) for EG, whereas CG kept receiving the same content in the conventional form. The teaching period was followed by the posttest. ANCOVA showed that, in contrast with CG, EG scored significantly higher on CT test after the intervention. The effect was shown to be only significant for the students at the lower side of the performance spectrum. Thus, in this inaugural study of clickers in schools in Iran, it was empirically demonstrated that clickers, as a relatively new piece of technology, can be successfully utilized during early adolescence in the pedagogical strategies in general and for the improvement of CT of students in particular.     

Spark plasma sintering of WC-based cermets/titanium and vanadium added composites: A comparative study on the microstructure and mechanical properties

In an attempt to develop the composition and properties of W₂C-(W,Ti)C-TiC and WC-WC_1-x-VC-V super hardmetals, spark plasma sintering (SPS) method was implemented. WC powders were mixed separately with 10?wt% Ti and 10?wt% V in a high energy mixer mill and sintering processes were performed at temperatures of 2150 and 2000?°C, respectively. XRD investigations revealed the formations of TiC and (Ti,W)C as the reaction products in WC-10?wt% Ti composite. Moreover, the interfacial reaction between WC and V led to the formation of WC1-x and VC compounds. A higher bending strength (613?±?25?MPa) and fracture toughness (4.1?±?0.58?MPa?m^1/2) were obtained for WC-10?wt% V samples compared to WC-10?wt% Ti, While the WC-10?wt% Ti composite showed a higher value of hardness (3128?±?42 Vickers) in comparison to WC-10?wt% V (2632?±?39 Vickers), which can act as a super hard cermet.     

Synthesis of nano-crystalline NiO-YSZ by microwave-assisted combustion synthesis

Nano-crystalline NiO-YSZ composite powders have been successfully prepared by microwave-assisted combustion of a gel derived from an aqueous solution containing ZrO(NO₃)₂·6H₂O ,Y(NO₃)₃·6H₂O, Ni(NO₃)₂·6H₂O and glycine. The as-prepared powders were examined using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) techniques. It was found that the process took only a few seconds to obtain NiO-YSZ composite powders. The as synthesized composite powder was a homogeneous mixture of YSZ, NiO and Ni phases with crystallite size of 24.2, 33.6 and 25.3 nm respectively.     

Effect of Global Warming on Intensity and Frequency Curves of Precipitation, Case Study of Northwestern Iran

Predicting natural phenomena like flood and drought and consequently presenting an appropriate solution for fighting such natural hazards in northwestern Iran is considered in this study through clustering the precipitation regime. To compare the reference period (past) with the simulated data, the statistics of daily precipitation in six stations of Ardebil, Ghazvin, Hamedan, Kermanshah, Sanandaj, and Tabriz, have been provided for a 30-year period (1961–1990) and compared with the simulated data of 2021–2050. The simulated data was generated by general atmosphere circulation model HADCM3, A1scenario and was downscaled using the LARS-WG model. The method for comparing precipitations was done based on clustering in the form of 5 clusters for all the stations and study periods. One of the results of this research is the greater concentration of precipitation for the cold periods of the year (winter and fall) and the increase of annual precipitation by the amount of 20.62 mm for future period. Furthermore, the normality of two coordinates of precipitation and cluster frequency percentage was evaluated. The outputs of this section demonstrate that the precipitations of cluster 3 which have the features of light rain with average intensity, fall on this normal line for most of the stations and study periods. On the other hand, precipitations of cluster 1 indicating very heavy and intense precipitations, have the most distance to the normal line in most cases. Therefore, the precipitations of the third cluster need optimal exploitation management while those of the first cluster need required risk and crisis management.     

Effect of ball milling on reactive spark plasma sintering of B4C–TiB2 composites

The influence of mechanical activation by ball milling (BM) of Ti, B and graphite powders mixture on the synthesis of dense B₄C-41% vol. TiB₂ composite by Spark Plasma Sintering (SPS) is investigated. BM treatment produces grains size refinement (50–150 nm) in the processing powders and the formation of TiB and TiB₂, when milling times are longer than 6 h.     

Mullitization,microstructure and physical properties of mechanically activated andalusite sintered by microwave

In this work, the effects of mechanical activation and microwave heating of andalusite on mullite formation have been investigated. XRD results revealed that andalusite peaks disappeared after 60 h of milling and the peaks of alumina were observed. The formation of mullite from activated and as-received andalusite occurred at 800° and 1250 °C, respectively, while mullitization was completed at 1100° and 1400 °C in the former and latter, respectively. Mullite samples prepared from activated andalusite showed better densification with an elongated morphology.     

Classical flutter analysis of composite wind turbine blades including compressibility

For wind turbine blades with the increased slenderness ratio, flutter instability may occur at lower wind and rotational speeds. For long blades, at the flutter condition, relative velocities at blade sections away from the hub center are usually in the subsonic compressible range. In this study, for the first time for composite wind turbine blades, a frequency domain classical flutter analysis methodology has been presented including the compressibility effect only for the outboard blade sections, which are in the compressible flow regime exceeding Mach 0.3. Flutter analyses have been performed for the baseline blade designed for the 5‐MW wind turbine of NREL. Beam‐blade model has been generated by making analogy with the structural model of the prewisted rotating thin‐walled beam (TWB) and variational asymptotic beam section (VABS) method has been utilized for the calculation of the sectional properties of the blade. To investigate the compressibility effect on the flutter characteristics of the blade, frequency and time domain aeroelastic analyses have been conducted by utilizing unsteady aerodynamics via incompressible and compressible indicial functions. This study shows that with use of compressible indicial functions, the effect of compressibility can be taken into account effectively in the frequency domain aeroelastic stability analysis of long blades whose outboard sections are inevitably in the compressible flow regime at the onset of flutter.     

Sol-gel assisted synthesis of TiB2-B4C composite powder

Composite powders containing titanium diboride and boron carbide have been prepared by sol-gel method at 1450°C using titanium isopropoxide (titanium precursor), boric acid (Boron precursor), sucrose (carbon source), and acetic acid (AcOH) as a solvent. The effect of boron source (trimethyl borate and boric acid) and B₂O₃/TiO₂, C/B₂O₃ mole ratios of starting materials on the final phases has been studied. The progress of reactions was determined using thermal analysis (TGA-DTA). The resultant powders were characterized by X-ray diffraction (XRD) analysis and field-emission scanning electron microscope (FESEM). XRD patterns confirmed the formation of TiB₂, B₄C, and TiC phases after heat treatment at 1450°C at mole ratio of B₂O₃/TiO₂ = 4.5, C/B₂O₃ = 2.4. With increasing the content of boron oxide, the unwanted phases such as TiC and C were reduced. TiB₂ and B₄C composite powders (~5 µm diameter) containing residual carbon (<4 wt%) were synthesized using the mole ratio of B₂O₃/TiO₂ = 10 and C/B₂O₃ = 1.9 at low temperature of 1450°C.     

Semantic schema theory for genetic programming

Schema theory is the most well-known model of evolutionary algorithms. Imitating from genetic algorithms (GA), nearly all schemata defined for genetic programming (GP) refer to a set of points in the search space that share some syntactic characteristics. In GP, syntactically similar individuals do not necessarily have similar semantics. The instances of a syntactic schema do not behave similarly, hence the corresponding schema theory becomes unreliable. Therefore, these theories have been rarely used to improve the performance of GP. The main objective of this study is to propose a schema theory which could be a more realistic model for GP and could be potentially employed for improving GP in practice. To achieve this aim, the concept of semantic schema is introduced. This schema partitions the search space according to semantics of trees, regardless of their syntactic variety. We interpret the semantics of a tree in terms of the mutual information between its output and the target. The semantic schema is characterized by a set of semantic building blocks and their joint probability distribution. After introducing the semantic building blocks, an algorithm for finding them in a given population is presented. An extraction method that looks for the most significant schema of the population is provided. Moreover, an exact microscopic schema theorem is suggested that predicts the expected number of schema samples in the next generation. Experimental results demonstrate the capability of the proposed schema definition in representing the semantics of the schema instances. It is also revealed that the semantic schema theorem estimation is more realistic than previously defined schemata.     

A new real-coded stochastic Bayesian optimization algorithm for continuous global optimization

Estimation of distribution algorithms are considered to be a new class of evolutionary algorithms which are applied as an alternative to genetic algorithms. Such algorithms sample the new generation from a probabilistic model of promising solutions. The search space of the optimization problem is improved by such probabilistic models. In the Bayesian optimization algorithm (BOA), the set of promising solutions forms a Bayesian network and the new solutions are sampled from the built Bayesian network. This paper proposes a novel real-coded stochastic BOA for continuous global optimization by utilizing a stochastic Bayesian network. In the proposed algorithm, the new Bayesian network takes advantage of using a stochastic structure (that there is a probability distribution function for each edge in the network) and the new generation is sampled from the stochastic structure. In order to generate a new solution, some new structure, and therefore a new Bayesian network is sampled from the current stochastic structure and the new solution will be produced from the sampled Bayesian network. Due to the stochastic structure used in the sampling phase, each sample can be generated based on a different structure. Therefore the different dependency structures can be preserved. Before the new generation is generated, the stochastic network’s probability distributions are updated according to the fitness evaluation of the current generation. The proposed method is able to take advantage of using different dependency structures through the sampling phase just by using one stochastic structure. The experimental results reported in this paper show that the proposed algorithm increases the quality of the solutions on the general optimization benchmark problems.