Search results for: vibration characteristics

Authors: Dmitry Lukyanov, Sergey Shevchenko, Alexander Kukaev

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Modern MEMS gyroscopes have strengthened their position in motion control systems and have led to the creation of tactical grade sensors (better than 15 deg/h). This was achieved by virtue of the success in micro- and nanotechnology development, cooperation among international experts and the experience gained in the mass production of MEMS gyros. This production is knowledge-intensive, often unique and, therefore, difficult to develop, especially due to the use of 3D-technology. The latter is usually associated with manufacturing of inertial masses and their elastic suspension, which determines the vibration and shock resistance of gyros. Today, consumers developing highly dynamic objects or objects working under extreme conditions require the gyro shock resistance of up to 65 000 g and the measurement range of more than 10 000 deg/s. Such characteristics can be achieved by solid-state gyroscopes (SSG) without inertial masses or elastic suspensions, which, for example, can be constructed with molecular kinetics of bulk or surface acoustic waves (SAW). Excellent effectiveness of this sensors production and a high level of structural integration provides basis for increased accuracy, size reduction and significant drop in total production costs. Existing principles of SAW-based sensors are based on the theory of SAW propagation in rotating coordinate systems. A short introduction to the theory of a gyroscopic (Coriolis) effect in SAW is provided in the report. Nowadays more and more applications require passive and wireless sensors. SAW-based gyros provide an opportunity to create one. Several design concepts incorporating reflective delay lines were proposed in recent years, but faced some criticism. Still, the concept is promising and is being of interest in St. Petersburg Electrotechnical University. Several experimental models were developed and tested to find the minimal configuration of a passive and wireless SAW-based gyro. Structural schemes, potential characteristics and known limitations are stated in the report. Special attention is dedicated to a novel method of a FEM modeling with piezoelectric and gyroscopic effects simultaneously taken into account.

Keywords: FEM simulation, gyroscope, OOFELIE, surface acoustic wave, wireless sensing

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Authors: Svetlana S. Saveysheva, Victoria E. Vasilenko

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The purpose of the research was to study the emotional and personal characteristics of preschool children in relation to the characteristics of child-parent interaction and deviant parental attitudes. The study involved 172 mothers and 172 children (85 boys and 87 girls) aged 4,5 to 7 years (mean age 6 years) living in St. Petersburg, Russia. Methods used were, demographic questionnaire, projective drawing method 'House-Tree-Man', Test of anxiety (Temml, Dorki, Amen), technique of studying self-esteem 'Ladder', expert evaluation of sociability and aggressiveness, questionnaire for children-parent emotional interaction (E.I. Zaharova) and questionnaire 'Analysis of family relationships' (E.G. Eidemiller, V.V. Yustitsky). Results. The greatest number of links with personal characteristics have received such parental deviant attitudes as overprotection and characteristics of authoritarian style (prohibitions, sanctions). If the mother has such peculiarities of the parental relationship, the child is characterized by lower self-esteem, increased anxiety, distrust of themselves and hostility. Children have more pronounced manifestations of aggression in a conniving and unstable style of parenting. The sensitivity of the mother is positively associated with children’s self-esteem. Unconditional acceptance of the child, the predominance of a positive emotional background, orientation to the state of the child during interaction promote the development of communication skills and reduce of aggressiveness. But the excessive closeness of the mother with the child can make it difficult to develop the communicative skills. Conclusions. The greatest influence on emotional and personal characteristics is provided by such features of the parental relation as overprotection, characteristics of authoritarian style, underdevelopment of the sphere of parental feelings, sensitivity of mother and behavioral manifestations of emotional interaction. Research is supported by RFBR №18-013-00990.

Keywords: characteristics of personality, child-parent interaction, children, deviant parental attitudes

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Authors: Babatunde Kasim Oladele

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This current study investigated students’ characteristics as factors that influence Mathematics Achievement of junior secondary school students. The study adopted a descriptive survey design. The population of the study was one hundred and twenty-three (123) JSS students of secondary schools in Ibadan North Local Government in Oyo State. A Mathematics achievement test and three questionnaires on student’s self-efficacy belief, attitude, and learning style were the instruments used. Prior to the administration of the constructed mathematics achievement test, 100-item mathematics was subjected to the expert review, and items analysis was carried out. Fifty items were retained. The Cronbach Alpha reliability coefficients of the instruments were 0.71, 0.76, and 0.83, respectively. Collected data were analysed using the frequency count, percentages, mean, standard deviation, and Path Analysis in Amos SPSS Version 20. Students characteristics: gender, age, self-efficacy, attitude and learning style had positive direct effects on students’ achievement in Mathematics as indicated by their respective beta weights (β = 0.36, 0.203, 0.92, 0.079, 0.69 p < 0.05). Consequently, the study concluded that student’s characteristics (Age, gender, and learning style) explained a significant part of the variability in students’ achievement in Mathematics.

Keywords: mathematics achievement, students’ characteristics, junior secondary school, Ibadan

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Authors: Kyeong Hoon Park, Taiji Mazuda

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High damping rubber (HDR) bearings are dissipating devices mainly used in seismic isolation systems and have a great damping performance. Although many studies have been conducted on the dynamic model of HDR bearings, few models can reflect phenomena such as dependency of experienced shear strain on initial history. In order to develop a model that can represent the dependency of experienced shear strain of HDR by Mullins effect, dynamic loading test was conducted using HDR specimen. The reaction of HDR was measured by applying a horizontal vibration using a hybrid actuator under a constant vertical load. Dynamic program analysis was also performed after dynamic loading test. The dynamic model applied in program analysis is a bilinear type double-target model. This model is modified from typical bilinear model. This model can express the nonlinear characteristics related to the initial history of HDR bearings. Based on the dynamic loading test and program analysis results, equivalent stiffness and equivalent damping ratio were calculated to evaluate the mechanical properties of HDR and the feasibility of the bilinear type double-target model was examined.

Keywords: base-isolation, bilinear model, high damping rubber, loading test

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Authors: Xiaobai Li, Li Li, Yujin Hu, Weiming Deng, Zhe Ding

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A size-dependent Euler–Bernoulli beam model, which accounts for nonlocal stress field, strain gradient field and higher order inertia force field, is derived based on the nonlocal strain gradient theory considering velocity gradient effect. The governing equations and boundary conditions are derived both in dimensional and dimensionless form by employed the Hamilton principle. The analytical solutions based on different continuum theories are compared. The effect of higher order inertia terms is extremely significant in high frequency range. It is found that there exists an asymptotic frequency for the proposed beam model, while for the nonlocal strain gradient theory the solutions diverge. The effect of strain gradient field in thickness direction is significant in low frequencies domain and it cannot be neglected when the material strain length scale parameter is considerable with beam thickness. The influence of each of three size effect parameters on the natural frequencies are investigated. The natural frequencies increase with the increasing material strain gradient length scale parameter or decreasing velocity gradient length scale parameter and nonlocal parameter.

Keywords: Euler-Bernoulli Beams, free vibration, higher order inertia, Nonlocal Strain Gradient Theory, velocity gradient

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Authors: Dinara F. Gaynutdinova, Vladimir Ya Modorsky, Nikolay A. Shevelev

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The problem under research is that of unpredictable modes occurring in two-stage centrifugal hydraulic pump as a result of hydraulic processes caused by vibrations of structural components. Numerical, analytical and experimental approaches are considered. A hypothesis was developed that the problem of unpredictable pressure decrease at the second stage of centrifugal pumps is caused by cavitation effects occurring upon vibration. The problem has been studied experimentally and theoretically as of today. The theoretical study was conducted numerically and analytically. Hydroelastic processes in dynamic “liquid – deformed structure” system were numerically modelled and analysed. Using ANSYS CFX program engineering analysis complex and computing capacity of a supercomputer the cavitation parameters were established to depend on vibration parameters. An influence domain of amplitudes and vibration frequencies on concentration of cavitation bubbles was formulated. The obtained numerical solution was verified using CFM program package developed in PNRPU. The package is based on a differential equation system in hyperbolic and elliptic partial derivatives. The system is solved by using one of finite-difference method options – the particle-in-cell method. The method defines the problem solution algorithm. The obtained numerical solution was verified analytically by model problem calculations with the use of known analytical solutions of in-pipe piston movement and cantilever rod end face impact. An infrastructure consisting of an experimental fast hydro-dynamic processes research installation and a supercomputer connected by a high-speed network, was created to verify the obtained numerical solutions. Physical experiments included measurement, record, processing and analysis of data for fast processes research by using National Instrument signals measurement system and Lab View software. The model chamber end face oscillated during physical experiments and, thus, loaded the hydraulic volume. The loading frequency varied from 0 to 5 kHz. The length of the operating chamber varied from 0.4 to 1.0 m. Additional loads weighed from 2 to 10 kg. The liquid column varied from 0.4 to 1 m high. Liquid pressure history was registered. The experiment showed dependence of forced system oscillation amplitude on loading frequency at various values: operating chamber geometrical dimensions, liquid column height and structure weight. Maximum pressure oscillation (in the basic variant) amplitudes were discovered at loading frequencies of approximately 1,5 kHz. These results match the analytical and numerical solutions in ANSYS and CFM.

Keywords: computing experiment, hydroelasticity, physical experiment, vibration

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Authors: N. Benabdeslam, N. Bouzidi, F. Atmani, R. Boucif, A. Sakhri

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The objective of this study was to provide answers for a better understanding of the mechanisms involved during grinding. To obtain a phosphate powder, we carry out sieving - grinding circuits for each parameter influencing the process. The analysis of the average particle size of the different tests carried out served in the first place as a basis for the determination of the granulometric curve area, the characteristics and the granular coefficients, then the exploitation of the different results for the calculation of the energies consumed for the fragmentation of different ore types, the energy coefficients as well as the ability to grind. Indeed, a time of 5 to 10 minutes can be chosen as the optimal grinding time in a disc mill for a % in weight of the highest pass. However, grinding time can influence the granular characteristics of ore.

Keywords: characteristic granular, grinding, mineralogical composition, phosphate ore, parameters

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Authors: Daniel P. Clayton, Edward A. Ball

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This paper describes an investigation into the isolation characteristics and bandwidth performance of RF combiners that are used as part of Chireix PA architectures, designed for use in the X-Band range of frequencies. Combiner designs investigated are the typical Chireix and Wilkinson configurations which also include simulation of the Wilkinson using manufacturer’s data for the isolation resistor. Another simulation was the less common approach of using a Branchline coupler to form the combiner, as well as simulation results from adding an additional stage. This paper presents the findings of this investigation and compares the bandwidth performance and isolation characteristics to determine suitability.

Keywords: bandwidth, Chireix, couplers, outphasing, power amplifiers, Wilkinson, X-Band

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Authors: Ardalan Sabamehr, Ashutosh Bagchi

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Recently, Structural Health Monitoring (SHM) based on the vibration of structures has attracted the attention of researchers in different fields such as: civil, aeronautical and mechanical engineering. Operational Modal Analysis (OMA) have been developed to identify modal properties of infrastructure such as bridge, building and so on. Frequency Domain Decomposition (FDD), Stochastic Subspace Identification (SSI) and Continuous Wavelet Transform (CWT) are the three most common methods in output only modal identification. FDD, SSI, and CWT operate based on the frequency domain, time domain, and time-frequency plane respectively. So, FDD and SSI are not able to display time and frequency at the same time. By the way, FDD and SSI have some difficulties in a noisy environment and finding the closed modes. CWT technique which is currently developed works on time-frequency plane and a reasonable performance in such condition. The other advantage of wavelet transform rather than other current techniques is that it can be applied for the non-stationary signal as well. The aim of this paper is to compare three most common modal identification techniques to find modal properties (such as natural frequency, mode shape, and damping ratio) of three story steel frame which was built in Concordia University Lab by use of ambient vibration. The frame has made of Galvanized steel with 60 cm length, 27 cm width and 133 cm height with no brace along the long span and short space. Three uniaxial wired accelerations (MicroStarin with 100mv/g accuracy) have been attached to the middle of each floor and gateway receives the data and send to the PC by use of Node Commander Software. The real-time monitoring has been performed for 20 seconds with 512 Hz sampling rate. The test is repeated for 5 times in each direction by hand shaking and impact hammer. CWT is able to detect instantaneous frequency by used of ridge detection method. In this paper, partial derivative ridge detection technique has been applied to the local maxima of time-frequency plane to detect the instantaneous frequency. The extracted result from all three methods have been compared, and it demonstrated that CWT has the better performance in term of its accuracy in noisy environment. The modal parameters such as natural frequency, damping ratio and mode shapes are identified from all three methods.

Keywords: ambient vibration, frequency domain decomposition, stochastic subspace identification, continuous wavelet transform

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Authors: Boualem Chetti

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The dynamic characteristics of a three-lobe journal bearing lubricated with micropolar fluids are determined by the linear stability theory. Lubricating oil containing additives and contaminants is modeled as micropolar fluid. The modified Reynolds equation is obtained using the micropolar lubrication theory and the finite difference technique has been used to solve it. The dynamic characteristics in terms of stiffness, damping coefficients, the critical mass and whirl ratio are determined for various values of size of material characteristic length and the coupling number. The computed results show compared with Newtonian fluids, that micropolar fluid exhibits better stability.

Keywords: three-lobe bearings, micropolar fluid, dynamic characteristics, stability analysis

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Authors: Chandra Gupt Porwal, Preeti C. Porwal

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Transient data reveals much about the machine's condition that steady-state data cannot. New technologies make this information much more available for evaluating the mechanical integrity of a machine train. Recent surveys at various stations indicate that simplicity is preferred over completeness in machine audits throughout the power generation industry. This is most clearly shown by the number of rotating machinery predictive maintenance programs in which only steady-state vibration amplitude is trended while important transient vibration data is not even acquired. Efforts have been made to explain what transient data is, its importance, the types of plots used for its display, and its effective utilization for analysis. In order to demonstrate the value of measuring transient data and its practical application in rotating machinery for resolving complex and persistent issues with turbine generators, the author presents a few case studies that highlight the presence of rotor instabilities due to the shaft moving towards the bearing centre in a 100 MM LMZ unit located in the Northern Capital Region (NCR), heavy misalignment noticed—especially after 2993 rpm—caused by loose coupling bolts, which prevented the machine from being synchronized for more than four months in a 250 MW KWU unit in the Western Region (WR), and heavy preload noticed at Intermediate pressure turbine (IPT) bearing near HP- IP coupling, caused by high points on coupling faces at a 500 MW KWU unit in the Northern region (NR), experienced at Indian power plants.

Keywords: transient data, steady-state-data, intermediate -pressure-turbine, high-points

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Authors: Jui-Pui Hung, Yong-Run Chen, Wei-Cheng Shih, Shen-He Tsui, Kung-Da Wu

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This paper presents the effect on the tooling conditions on the machining stabilities of a milling machine tool. The machining stability was evaluated in different feeding direction in the X-Y plane, which was referred as the orientation-dependent machining stability. According to the machining mechanics, the machining stability was determined by the frequency response function of the cutter. Thus, we first conducted the vibration tests on the spindle tool of the milling machine to assess the tool tip frequency response functions along the principal direction of the machine tool. Then, basing on the orientation dependent stability analysis model proposed in this study, we evaluated the variation of the dynamic characteristics of the spindle tool and the corresponding machining stabilities at a specific feeding direction. Current results demonstrate that the stability boundaries and limited axial cutting depth of a specific cutter were affected to vary when it was fixed in the tool holder with different overhang length. The flute of the cutter also affects the stability boundary. When a two flute cutter was used, the critical cutting depth can be increased by 47 % as compared with the four flute cutter. The results presented in study provide valuable references for the selection of the tooling conditions for achieving high milling performance.

Keywords: tooling condition, machining stability, milling machine, chatter

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Authors: Abdelhalem Shahen

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The world is now experiencing a digital revolution and greatly accelerated technological developments, in addition to the transition from the economy in its traditional form to the digital economy, which has resulted in the emergence of new tools that are appropriate to those developments, and from this, this paper attempts to explore the economic characteristics of the bitcoin currency that circulated recently. Due to the many advantages that distinguish it from money in its traditional forms, which have a range of economic effects. The study found that Bitcoin is among the technological innovations, which contain a set of characteristics that are worth studying, those that make it the focus of attention, such as the digital currency, the peer-to-peer property, Lower and Faster Transaction Costs, transparency, decentralized control, privacy, and Double-Spending, as well as security and Cryptographic, and finally mining.

Keywords: Digital Economics, Digital Currencies, Bitcoin, Features of Bitcoin

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Authors: Serges Mendomo Meye, Li Guowei, Shen Zhenzhong, Gan Lei, Xu Liqun

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Due to the characteristics of high-heap and large-volume, the complex layers of waste and the high-water level of leachate, environmental pollution, and slope instability are easily produced. It is therefore of great significance to research the heterogeneous seepage field and stability of landfills. This paper focuses on the heterogeneous characteristics of the landfill piles and analyzes the seepage field and slope stability of the landfill using statistical and numerical analysis methods. The calculated results are compared with the field measurement and literature research data to verify the reliability of the model, which may provide the basis for the design, safe, and eco-friendly operation of the landfill. The main innovations are as follows: (1) The saturated-unsaturated seepage equation of heterogeneous soil is derived theoretically. The heterogeneous landfill is regarded as composed of infinite layers of homogeneous waste, and a method for establishing the heterogeneous seepage model is proposed. Then the formation law of the stagnant water level of heterogeneous landfills is studied. It is found that the maximum stagnant water level of landfills is higher when considering the heterogeneous seepage characteristics, which harms the stability of landfills. (2) Considering the heterogeneity weight and strength characteristics of waste, a method of establishing a heterogeneous stability model is proposed, and it is extended to the three-dimensional stability study. It is found that the distribution of heterogeneous characteristics has a great influence on the stability of landfill slope. During the operation and management of the landfill, the reservoir bank should also be considered while considering the capacity of the landfill.

Keywords: heterogeneous characteristics, leachate levels, saturated-unsaturated seepage, seepage field, slope stability

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Authors: Salwa Abdelbaki

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This research investigated how leaders develop, asking whether they have been leaders due to their innate abilities or they gain leadership characteristics through interactions based on requirements of a situation. If the first is true, then a leader should be successful in any situation. Otherwise, a leader may succeed only in a specific situation. A series of experiments were carried out on three groups including of males and females. First; a group of 148 students with different specializations had to select a leader. Another group of 51 students had to recall their previous experiences and their knowledge of each other to identify who were leaders in different situations. Then a series of analytic tools were applied to the identified leaders and to the whole groups to find out how leaders were developed. A group of 40 young children was also experimented with to find young leaders among them and to analyze their characteristics.

Keywords: leadership, innate characteristics, situation, leadership theories

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Authors: Norshaffika I. Zaiedy Nor, Andrew P. Smith

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Background: Training is essential to develop individuals’ expertise to meet current and future job demands and to improve work performance. At the same time, individuals’ well-being is crucial to ensure that they can fully and positively carry out their daily duties. In addition to the studies that have examined what constitutes well-being and the factors behind it, many researchers have investigated the predictors of training effectiveness and transfer of training. However, there has been very little integration between them. This study was an attempt to bridge the gap between training effectiveness predictors and well-being. Purpose: This research paper aimed to investigate the association between well-being among employees and psychosocial characteristics, together with training variables. Training variables consist of motivation to learn; learning; implementation intention; and cognitive dissonance. Methodology: In total, 210 workers who had undergone various training programs completed an online survey measuring various psychosocial characteristics, four training variables, and level of well-being. Findings: The results showed that certain types of positive psychosocial characteristics (e.g., positive personality, positive work behaviors, positive work and resources) predict motivation to learn, learning and implementation intention. Meanwhile, negative psychosocial characteristics (e.g. negative work demands and resources, negative coping) predict cognitive dissonance. Also, all the training variables had a moderate to high correlation with well-being. However, after controlling other variables (age, gender, education and psychosocial characteristics), none of the training variables predicted well-being. Self-determination theory, cognitive dissonance theory, and the DRIVE model were used to explain these findings. Conclusion: As there is limited research on the integration of training variables with well-being, this study gives a new perspective in the field of both training and well-being. Further investigations are needed to examine the relationships between them.

Keywords: cognitive dissonance, implementation intention, learning, motivation to learn, psychosocial characteristics, well-being

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Authors: K. S. Agrawal

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The performance of jet ejector was studied in detail by different authors. Several authors have studied mass transfer characteristics like interfacial area, mass transfer coefficients etc. In this paper, we have made an attempt to develop PDE model by considering bubble properties and apply Lattice-Boltzmann technique for PDE model. We may present the results for the interfacial area which we have obtained from our numerical simulation. Later the results are compared with previous work.

Keywords: jet ejector, mass transfer characteristics, numerical simulation, Lattice-Boltzmann technique

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Authors: Abdelaziz Rabhi, Mohamed Amrani, Abderrazek Ziane, Nabil Belkadi, Abdelraouf Hocini

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In this paper, a bedimensional simulation program of the electric characteristics of reverse biased lateral polysilicon PIN diode is presented. In this case we have numerically solved the system of partial differential equations formed by Poisson's equation and both continuity equations that take into account the effect of impact ionization. Therefore we will obtain the current-voltage characteristics (I-V) of the reverse-biased structure which may include the effect of breakdown.The geometrical model assumes that the polysilicon layer is composed by a succession of defined mean grain size crystallites, separated by lateral grain boundaries which are parallel to the metallurgic junction.

Keywords: breakdown, polycrystalline silicon, PIN, grain, impact ionization

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Authors: Omar Juhmani

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This paper examines the relation between internal corporate governance and the level of corporate compliance with mandatory IFRS disclosure requirements. The internal corporate governance is measured by board and audit committee characteristics. Using data from Bahrain Stock Exchange, the results show that board independence is positively and significantly associated with level of compliance with IFRS disclosure requirements. This suggests that internal corporate governance mechanisms are effective in the financial reporting practices by increasing the level of compliance with IFRS disclosures. Also, the results of the regression analyses indicate that two of the control variables; company size and audit firm size are significantly positively associated with the level of corporate compliance with mandatory IFRS disclosure requirements in Bahrain.

Keywords: Bahrain, board and audit committee characteristics, compliance, disclosure, IFRS

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Authors: Naohiro Nakamura

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Analysis methods to accurately estimate the behavior of buildings when earthquakes occur is very important for improving the seismic safety of such buildings. Recently, the use of damping devices has increased significantly and there is a particular need to appropriately evaluate the behavior of buildings with such devices during earthquakes in the design stage. At present, however, the accuracy of the analysis evaluations is not sufficient. One reason is that the accuracy of current analysis methods has not been appropriately verified because there is very limited data on the behavior of actual buildings during earthquakes. Many types of shaking table test of large structures are performed at the '3-Dimensional Full-Scale Earthquake Testing Facility' (nicknamed 'E-Defense') operated by the National Research Institute of Earth Science and Disaster Prevention (NIED). In this study, simulations using 3- dimensional analysis models were conducted on shaking table test of a 5-story steel-frame structure with dampers. The results of the analysis correspond favorably to the test results announced afterward by the committee. However, the suitability of the parameters and models used in the analysis and the influence they had on the responses remain unclear. Hence, we conducted additional analysis and studies on these models and parameters. In this paper, outlines of the test are shown and the utilized analysis model is explained. Next, the analysis results are compared with the test results. Then, the additional analyses, concerning with the hysteresis curve of the dampers and the beam-end stiffness of the frame, are investigated.

Keywords: three-dimensional analysis, E-defense, full-scale experimen, vibration control damper

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Authors: Ferit Çakıcı, M. Kemal Leblebicioğlu

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In this study, characteristics and flight test analysis of a fixed-wing unmanned aerial vehicle (UAV) with hover capability is analyzed. The base platform is chosen as a conventional airplane with throttle, ailerons, elevator and rudder control surfaces, that inherently allows level flight. Then this aircraft is mechanically modified by the integration of vertical propellers as in multi rotors in order to provide hover capability. The aircraft is modeled using basic aerodynamical principles and linear models are constructed utilizing small perturbation theory for trim conditions. Flight characteristics are analyzed by benefiting from linear control theory’s state space approach. Distinctive features of the aircraft are discussed based on analysis results with comparison to conventional aircraft platform types. A hybrid control system is proposed in order to reveal unique flight characteristics. The main approach includes design of different controllers for different modes of operation and a hand-over logic that makes flight in an enlarged flight envelope viable. Simulation tests are performed on mathematical models that verify asserted algorithms. Flight tests conducted in real world revealed the applicability of the proposed methods in exploiting fixed-wing and rotary wing characteristics of the aircraft, which provide agility, survivability and functionality.

Keywords: flight test, flight characteristics, hybrid aircraft, unmanned aerial vehicle

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Authors: Khoo Shin Yee, Lian Yee Cheng, Ong Zhi Chao, Zubaidah Ismail, Siamak Noroozi

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Structural frequency response testing is accurate in identifying the dynamic characteristic of a machinery structure. In practical perspective, conventional structural frequency response testing such as experimental modal analysis with impulse technique (also known as “impulse testing”) has limitation especially on its long acquisition time. The high acquisition time is mainly due to the redundancy procedure where the engineer has to repeatedly perform the test in 3 directions, namely the axial-, horizontal- and vertical-axis, in order to comprehensively define the dynamic behavior of a 3D structure. This is unfavorable to numerous industries where the downtime cost is high. This study proposes to reduce the testing time by using oblique impact. Theoretically, a single oblique impact can induce significant vibration responses and vibration modes in all the 3 directions. Hence, the acquisition time with the implementation of the oblique impulse technique can be reduced by a factor of three (i.e. for a 3D dynamic system). This study initiates an experimental investigation of impulse testing with oblique excitation. A motor-driven test rig has been used for the testing purpose. Its dynamic characteristic has been identified using the impulse testing with the conventional normal impact and the proposed oblique impact respectively. The results show that the proposed oblique impulse testing is able to obtain all the desired natural frequencies in all 3 directions and thus providing a feasible solution for a fast and time effective way of conducting the impulse testing.

Keywords: frequency response function, impact testing, modal analysis, oblique angle, oblique impact

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Authors: Iva Buchberger, Vesna Kovač

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Global education policy trends and recommendations underline the importance of (distributive) school leadership as a school effectiveness key factor. In this context, the broader aim of this research (supported by the Croatian Science Foundation) is to identify school leadership characteristics in Croatian schools and to examine the correlation between school leadership and school effectiveness. The aim of the proposed conference paper is to focus on the school leadership characteristics which are additionally explained with school leadership facilitators that contribute to (distributive) school leadership development. The aforementioned school leadership characteristics include the following dimensions: (a) participation in the process of making different types of decisions, (b) influence in the decision making process, (c) social interactions between different stakeholders in the decision making process in schools. Further, the school leadership facilitators are categorized as follows: (a) principal’s activities (such as providing support to different stakeholders and developing mutual trust among them), (b) stakeholders’ characteristics (such as developed stakeholders’ interest and competence to participate in decision-making process), (c) organizational and material resources (such as school material conditions, the necessary information and time as resources for making decisions). The data were collected by a constructed and validated questionnaire for examining the school leadership characteristics and facilitators from teachers’ perspective. The main population in this study consists of all primary schools in Croatia while the sample is comprised of 100 primary schools, selected by random sampling. Furthermore, the sample of teachers was selected by an additional procedure taking into consideration the independent variables of sex, work experience, etc. Data processing was performed by standard statistical methods of descriptive and inferential statistics. Statistical program IBM SPSS 20.0 was used for data processing. The results of this study show that there is a (positive) correlation between school leadership characteristics and school leadership facilitators. Specifically, it is noteworthy to mention that all the dimensions of school leadership characteristics are in positive correlation with the categories of school leadership facilitators. These results are indicative for the education policy creators who should ensure positive and supportive environment for the school leadership development including the development of school leadership characteristics and school leadership facilitators.

Keywords: distributive school leadership, school effectiveness , school leadership characteristics, school leadership facilitators

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Authors: Cristina Bahón Arnaiz

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Many Asian languages, such as Korean and Japanese, are well-known for their wide use of sound symbolic words or ideophones. This is a very particular characteristic which enriches its lexicon hugely. Ideophones are a class of sound symbolic words that utilize sound symbolism to express aspects, states, emotions, or conditions that can be experienced through the senses, such as shape, color, smell, action or movement. Ideophones have very particular characteristics in terms of sound symbolism and morphology, which distinguish them from other words. The phonological characteristics of ideophones are vowel ablaut or vowel gradation and consonant mutation. In the case of Korean, there are light vowels and dark vowels. Depending on the type of vowel that is used, the meaning will slightly change. Consonant mutation, also known as consonant ablaut, contributes to the level of intensity, emphasis, and volume of an expression. In addition to these phonological characteristics, there is one main morphological singularity, which is reduplication and it carries the meaning of continuity, repetition, intensity, emphasis, and plurality. All these characteristics play an important role in both linguistics and literature as they enhance the meaning of what is trying to be expressed with incredible semantic detail, expressiveness, and rhythm. The following study will analyze the ideophones used in a single paragraph of a Korean novel, which add incredible yet subtle detail to the meaning of the words, and advance the expressiveness and rhythm of the text. The results from analyzing one paragraph from a novel, after presenting the phonological and morphological characteristics of Korean ideophones, will evidence the important role that ideophones play in literature. 

Keywords: ideophones, mimetic words, phonomimes, phenomimes, psychomimes, sound symbolism

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Authors: Odunjo Oluronke Omolola, Okanlawon Simon Ayorinde

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This study examines the relationship between house characteristics and socio-economic characteristics of developers in Ibadan, southwest, Nigeria. The research is borne out of the fact that social housing has not done much as a result of finance and housing poverty is on the increase in the country. Multistage random sampling was used in selecting 2,646 respondents in the area. The questionnaire forms the basic instrument for data collection and was administered to heads of households to collect information on socio-economic and demographic characteristics as well as characteristics of development. Both descriptive and inferential statistical analyses were employed in the presentation of the findings; MANOVA was used to analyse the relationship between house characteristics measured by wall materials (Y1-Yn) and socio-economic characteristics of developers measured by gender (X1), religion (X2), educational background (X3) and employment status (X4).The study found out that the bulk of the respondents (65.7%) were male, while 51.7% practiced Christianity. Also, 35.9% had HND/1st/Postgraduate degree, while 43.9% were self employed; Most households however, had membership size of 5 (26.9%). The significant wall material in the area was sandcrete block (71.2%) as opposed to mud (19.1%) and brick (0.6%). Multiple Analysis of Variance shows that there is a significant relationship between sandcrete block and each of gender (X1) and employment status (X3). The factor adduced to this is accessibility to cooperative societies which serve as the gravitational force of attraction for housing finance. The study suggests among others that, there should be re-invigoration of existing cooperative societies, while more should be established for the provision of housing finance.

Keywords: relationship, house development, developers, sandcrete block, cooperative societies

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Authors: Purna Singh, Vaibhav Tripathi, Vinayak Kalluri, Sumit Roy

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The present experimental work was carried out to investigate performance and emission characteristics of single cylinder diesel engine operating under dual-fuel mode with coconut oil blended with diesel. Coconut oil is one of the edible oil which is abundant in tropical countries and has properties like diesel. To this end, performance and emission parameters of diesel-coconut oil blends were reported in the current study. The results were drawn at different load steps of engine operation with 10% and 20% of coconut oil linearly blended with diesel. From the results, it was evident that coconut oil can be successfully replaced up to 20% of diesel without hampering the performance-emission characteristics of the existing diesel engine.

Keywords: coconut oil, alternative fuel, emissions, dual-fuel

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Authors: P. Intaracharoen, P. Chantraket, C. Detyothin, S. Kirtsaeng

Abstract:

Radar reflectivity data from Phimai weather radar station of DRRAA (Department of Royal Rainmaking and Agricultural Aviation) were used to analyzed the rainstorm characteristics via Thunderstorm Identification Tracking Analysis and Nowcasting (TITAN) algorithm. The Phimai weather radar station was situated at Nakhon Ratchasima province, northeastern Thailand. The data from 277 days of rainstorm events occurring from May 2016 to May 2017 were used to investigate temporal distribution characteristics of convective individual rainclouds. The important storm properties, structures, and their behaviors were analyzed by 9 variables as storm number, storm duration, storm volume, storm area, storm top, storm base, storm speed, storm orientation, and maximum storm reflectivity. The rainstorm characteristics were also examined by separating the data into two periods as wet and dry season followed by an announcement of TMD (Thai Meteorological Department), under the influence of southwest monsoon (SWM) and northeast monsoon (NEM). According to the characteristics of rainstorm results, it can be seen that rainstorms during the SWM influence were found to be the most potential rainstorms over northeastern region of Thailand. The SWM rainstorms are larger number of the storm (404, 140 no./day), storm area (34.09, 26.79 km²) and storm volume (95.43, 66.97 km³) than NEM rainstorms, respectively. For the storm duration, the average individual storm duration during the SWM and NEM was found a minor difference in both periods (47.6, 48.38 min) and almost all storm duration in both periods were less than 3 hours. The storm velocity was not exceeding 15 km/hr (13.34 km/hr for SWM and 10.67 km/hr for NEM). For the rainstorm reflectivity, it was found a little difference between wet and dry season (43.08 dBz for SWM and 43.72 dBz for NEM). It assumed that rainstorms occurred in both seasons have same raindrop size.

Keywords: rainstorm characteristics, weather radar, TITAN, Northeastern Thailand

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Authors: Mohamad R. Moshtagh, Ahmad Bagheri

Abstract:

Accurate fault detection in rotating machinery is of utmost importance to ensure optimal performance and prevent costly downtime in industrial applications. This study presents a robust fault detection system based on vibration data collected from rotating gears under various operating conditions. The considered scenarios include: (1) both gears being healthy, (2) one healthy gear and one faulty gear, and (3) introducing an imbalanced condition to a healthy gear. Vibration data was acquired using a Hentek 1008 device and stored in a CSV file. Python code implemented in the Spider environment was used for data preprocessing and analysis. Winner features were extracted using the Wiener feature selection method. These features were then employed in multiple machine learning algorithms, including Convolutional Neural Networks (CNN), Multilayer Perceptron (MLP), K-Nearest Neighbors (KNN), and Random Forest, to evaluate their performance in detecting and classifying faults in both the training and validation datasets. The comparative analysis of the methods revealed the superior performance of the Wiener-CNN approach. The Wiener-CNN method achieved a remarkable accuracy of 100% for both the two-class (healthy gear and faulty gear) and three-class (healthy gear, faulty gear, and imbalanced) scenarios in the training and validation datasets. In contrast, the other methods exhibited varying levels of accuracy. The Wiener-MLP method attained 100% accuracy for the two-class training dataset and 100% for the validation dataset. For the three-class scenario, the Wiener-MLP method demonstrated 100% accuracy in the training dataset and 95.3% accuracy in the validation dataset. The Wiener-KNN method yielded 96.3% accuracy for the two-class training dataset and 94.5% for the validation dataset. In the three-class scenario, it achieved 85.3% accuracy in the training dataset and 77.2% in the validation dataset. The Wiener-Random Forest method achieved 100% accuracy for the two-class training dataset and 85% for the validation dataset, while in the three-class training dataset, it attained 100% accuracy and 90.8% accuracy for the validation dataset. The exceptional accuracy demonstrated by the Wiener-CNN method underscores its effectiveness in accurately identifying and classifying fault conditions in rotating machinery. The proposed fault detection system utilizes vibration data analysis and advanced machine learning techniques to improve operational reliability and productivity. By adopting the Wiener-CNN method, industrial systems can benefit from enhanced fault detection capabilities, facilitating proactive maintenance and reducing equipment downtime.

Keywords: fault detection, gearbox, machine learning, wiener method

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Authors: Feng-jie Xie, Jian-hong Yan

Abstract:

Based on the complex network theory, we construct the air cargo network of the Belt and Road area, analyze its regional distribution and structural characteristics, measure the robustness of the network. The regional distribution results show that Southeast Asia and China have the most prominent development in the air cargo network of the Belt and Road area, Central Asia is the least developed. The structure characteristics found that the air cargo network has obvious small-world characteristics; the degree distribution has single-scale property; it shows a significant rich-club phenomenon simultaneously. The network robustness is measured by two attack strategies of degree and betweenness, but the betweenness of network nodes has a greater impact on network connectivity. And identified 24 key cities that have a large impact on the robustness of the network under the two attack strategies. Based on these results, recommendations are given to maintain the air cargo network connectivity in the Belt and Road area.

Keywords: air cargo, complex network, robustness, structure properties, The Belt and Road

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Authors: Ming-Kwei Lee, Chih-Feng Yen

Abstract:

The electrical characteristics of liquid phase deposited silicon oxynitride film on ammonium sulfide treated p-type (100) gallium arsenide substrate were investigated. Hydrofluosilicic acid, ammonia and boric acid aqueous solutions were used as precursors. The electrical characteristics of silicon oxynitride film are much improved on gallium arsenide substrate with ammonium sulfide treatment. With post-metallization annealing, hydrogen ions can further passivate defects in SiON/GaAs film and interface. The leakage currents can reach 7.1 × 10-8 and 1.8 × 10-7 at ± 2 V. The dielectric constant and effective oxide charges are 5.6 and -5.3 × 1010 C/cm2, respectively. The hysteresis offset of hysteresis loop is merely 0.09 V.

Keywords: liquid phase deposition, SiON, GaAs, PMA, (NH4)2S

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