Modeling of tubes containing fluid flow is widely used in the study of heat exchangers, nuclear reactors, micro and nano tools, etc. This system is structurally simple but very complex in terms of dynamic behavior and vibrations. In this paper, an analytical relationship for nonlinear vibrations of self-excitation of a nanocomposite conical tube containing fluid flow is extracted, one end of which is free and the other side is fixed and is under gravitational force. The base material is assumed to be 1200 series aluminum, which is reinforced with carbon nanotubes. The Hamiltonian equations are obtained, assuming the Euler–Bernoulli beam theory and the use of the Galerkin method, dissected the partial derivative equations into Ordinary Differential Equations (ODE), then solved by MATLAB coding and investigated the effect of various parameters on system behavior. As the fluid velocity increases, the amplitude of the vibration increases and the nonlinear effects of the system increase, so more modes are needed to converge the responses. In a conical tube, the ßT coefficient increases with increasing inner diameter along the tube and the system becomes more stable. Increasing the length of the pipe makes the opening conical pipe more stable and the closing conical pipe more unstable. The change in length has no effect on the stability of the cylindrical tube.

Screw loosening in spine surgery is a clinical complication in patients with poor bone quality. Pedicle screws are subjected to bending moments and axial loads that may cause toggling during daily movements of spine. The purpose of this study was to assess the previous studies related to toggling effect on pullout performance of pedicle screws by surveying the whole literature and to provide some discussion for new studies about pullout performance of pedicle screws after toggling. The search was performed by combining terms of pedicle screw, toggling, screw loosening, fatigue, cyclic loading, and pullout. The retrieved articles dealing with determined terms and also their references were reviewed. Some of these articles were eliminated after review process. Toggling was determined to be crucial for the stabilization performance of pedicle screw because the loosening mechanism of screws was affected directly by cyclic loading. The toggling or cyclic loading affected the holding capacity of pedicle screws negatively, and the possibility of loosening or failure problem for pedicle screws increased with cyclic loading magnitude. Loading conditions, screw properties, test medium, level of spinal region, and cement usage were determined by many researchers as the most important parameters affecting the toggling performance as well as the pullout strength of pedicle screws. The pullout strength of pedicle screws generally decreased with cyclic loading. The parameters of cyclic loading were fairly important for pullout performance of pedicle screws. Screw properties and cement augmentation had critical effects on the stability of screws under cyclic loading, as well.

In this study, compressibility, and conventional and ultra-high frequency induction sintering behaviors of 99.8% purity and 50-70 µm size range aluminum powders were investigated. In the compressibility studies, uniaxial-cold pressing method was used. Green samples were produced in the range of 50-275 MPa using different pressures. By measuring the apparent densities of the produced samples, the optimum compressibility pressure was determined as 200 MPa. Pure aluminum powder metal samples produced with this ideal pressing pressure were sintered in both classical and ultra-high frequency induction methods in the range of 500-600 oC. Sintering was performed as 40 min in the traditional method and 5 min in the ultra-high frequency induction sintering method. As a result of the tests carried out in this study, it was determined that pure aluminum samples were successfully sintered with a high frequency induction system in a shorter time than traditional sintering method.

In this study, the axially moving string with spring-loaded middle support is discussed. The supports assumed as simple support on the string both ends. The intermediate support shows the characteristics of the spring. The string velocity is accepted as harmonically varying around a mean value. The Hamiltonian principle is used to find the equations of motion. The equations of motion become nonlinear, considering the nonlinear effects caused by string extensions. The equations of motion and boundary conditions are become dimensionless by nondimensionalization. Approximate solutions were found by using multiple time scales which is one of the perturbation methods. By solving the linear problem that is obtained by the first terms of the perturbation series, the exact natural frequencies were calculated for the different locations of the mid-support, various spring coefficients, and various axial velocity values. The second-order nonlinear terms reveal the correction terms for the linear problem. Stability analysis is carried out for cases where the velocity change frequency is away from zero and two times the natural frequency. Stability boundaries are determined for the principal parametric resonance case.

Sign language is a way for hearing-impaired people to communicate among themselves and with people without hearing impairment. Communication with the sign language is difficult because few people know this language and the language does not have universal patterns. Sign language interpretation is the translation of visible signs into speech or writing. The sign language interpretation process has reached a practical solution with the help of computer vision technology. One of the models widely used for computer vision technology that mimics the work of the human eye in a computer environment is deep learning. Convolutional neural networks (CNN), which are included in deep learning technology, give successful results in sign language recognition as well as other image recognition applications. In this study, the dataset containing 2062 images consisting of Turkish sign language digits was classified with the developed CNN model. One of the important parameters used to minimize network error of the CNN model during the training is the learning rate. The learning rate is a coefficient used to update other parameters in the network depending on the network error. The optimization of the learning rate is important to achieve rapid progress without getting stuck in local minimums while reducing network error. There are several optimization techniques used for this purpose. In this study, the success of four different training and test processes performed with SGD, RMSprop, Adam and Adamax optimizers were compared. Adam optimizer, which is widely used today with its high performance, was found to be the most successful technique in this study with 98.42% training and 98.55% test accuracy.

Nowadays, the problem of power quality increases day by day. Harmonic current and reactive power are the important factors disturbing the power quality. The induction motors draw both harmonic current and reactive power from the grid. Reactive power and harmonic current lead to heat losses and decrease in the efficiency of the transmission lines. Passive and active filter applications have been used to solve these problems. There are some disadvantages of passive filters. Large physical dimensions and resonance with load can be shown as examples for these disadvantages. Therefore, the application areas of Active Power Filter (APF) are rapidly developing due to the fact that they can be applied together with harmonic and reactive power compensation as appropriate control methods. This paper proposes a MATLAB/Simulink simulation to perform power factor correction and reactive power compensation of three-phase induction motor by using three-phase Parallel Active Power Filter (PAPF). In order to generate PAPF’s reference currents the Sine Multiplication Technique (SMT) is used. Simulation studies are presented to be able to assess the performances under different motor operating conditions. The proposed hysteresis controller based PAPF filter makes the power factor up to 1 and the reactive power compensation of the three-phase induction motor.

Understanding the dynamics of coupled neurons is one of the fundamental problems in the analysis of neuronal model dynamics. The transfer entropy (TE) method is one of the primary analyses to explore the information flow between the neuronal populations. We perform the TE analysis on the two-neuron conductance-based Hodgkin-Huxley (HH) neuronal network to analyze how their connectivity changes due to conductances. We find that the information flow due to underlying synaptic connectivity changes direction by changing conductances individually and/or simultaneously as a result of TE analysis through numerical simulations.

Liquid level control is needed in many areas, from simple to complex, from daily life to industry. With the developed system in this study, it was aimed to ensure the students of the control system course to learn the concepts of a closed-loop control system and to observe the effect of changes in the system in real-time. The system consists of two tanks, a pump, a pressure sensor, a power supply, a regulated voltage source, a computer, and an Arduino Due board. By using the Matlab/Simulink and added Arduino blocks, software of the control system was created without code need. It is possible to control the liquid level system via the control board through the computer, as well as to control it without a computer by the embedded software. Liquid level control is carried out with different types of control methods from basic level to advanced level (On-off, PID, ANN-PID, and Fuzzy-PID controller). It is also possible to record the desired parameters in real-time, such as reference level, actual level, error signal, and control signal, in the liquid level control system. In this study, an interface for a PID controller was prepared using Matlab/Gui. It was concluded that with Matlab/Simulink blocks added to the system, different control methods could be applied easily.

In satellite communication, link margin and therefore antenna radiation characteristics are key factors to ensure providing a robust communication link between space and ground segment. For telemetry/telecommand and payload data transfer, isoflux antennas are employed widely in satellite communication systems to direct electromagnetic wave efficiently. To decrease complexity and manufacturing cost, simple antenna structures are preferred. In this study, after a detailed literature survey, a polyrod antenna has been designed to use in the space segment of Low Earth Orbit satellite communication subsystem. The proposed polyrod antenna has maximum gain at about 600 elevation angle of the antenna. Moreover, its impedance bandwidth is 750MHz (11%) that is fairly adequate to use in high data rate transmitters. By using CST Microwave StudioTM which is a commercially available 3-D electromagnetic time-domain solver, directivity, gain, axial ratio for elevation plane at X-Band, and return loss characteristic have been presented. Based on the obtained results, the designed polyrod antenna can be used where a conical shaped beam radiation pattern is needed.

In this paper, the selective mapping (SLM) technique possessing the powerful and distortionless peak to average power ratio (PAPR) reduction capability was employed in universal filtered multicarrier (UFMC) waveform that is considered as one of the most promising fifth generation (5G) waveform candidates in order to provide a solution to the PAPR issue encountered in the related waveform. Owing to our SLM-based PAPR reduction implementation performed by employing the SLM scheme between the quadrate amplitude modulation (QAM) mapping and bandwidth-subdivision operations at the transmitter side, successful PAPR reduction results were achieved in a straightforward and effective manner. In the simulations, the effect of the related way of SLM application on alleviating the PAPR and spectral leakages of the UFMC signal amplified via the solid state power amplifier (SSPA) was investigated for various number of phase factor combinations. Besides, the impact of SLM on the bit error rate (BER) of the UFMC waveform was analyzed for varied values of SSPA parameters called smoothness (p) and input back off (IBO) controlling the linearity and operation point of the SSPA, respectively.

Consistency limits are essential and simple design parameters that are utilized as standard entries of all kinds of soil investigation programs conducted for geotechnical projects which are constructed in/on fine grained soils. These limits also represent mineralogical and physical properties of clayey soils directly and used to estimate their strength and rigidity properties indirectly. However, the consistency tests are assumed as the simple and basic tests of geotechnical engineering investigations, but the effects of operator, calibration of the device and environmental aspects at the tests damage the reliability and correctness of results. In this paper, it is aimed to overcome these challenges by evaluating the consistency characteristics of clayey soils considering only the values of liquid limit of specific clays with the use of simple regression analysis. A database is prepared by using 500 soil investigation reports that are involving the site characterization information, laboratory and field tests of Istanbul Province European side clayey soils, including Avcilar, Esenyurt, Küçükçekmece, Büyükçekmece, Çatalca, Zeytinburnu, Bahçelievler, Bakirköy districts. 1523 liquid limit tests are obtained from the mentioned database for high and very high plastic clays. The regression analyses have been applied to query the parameter effect ratio on the consistent characteristics and relationships have been tried to be developed to evaluate the values of plastic limit and plasticity index directly from only liquid limit test applications. The effects of fine material content, depth and natural water content is also investigated. Verifications of the suggested equations have been done for different cases and comparisons are made with the well-known sources of literature. Consequently, strong equations are acquired to determine the plasticity index value in terms of liquid limit, liquid limit-depth, liquid limit-fine content, natural water content-fine content respectively based on the actual experimental tests conducted in Istanbul.

Chaos is one of the important research areas in recent years. The chaotic signal generator is one of the most basic structure in the chaos-based researches and applications. In this study, Sundarapandian-Pehlivan Chaotic Oscillator (SPCO) designs have been implemented in 2 different platforms as analog-based using Second-Generation Current Controlled Current Conveyor (CCII) and FPGA-based with one of the chaotic oscillator that has been presented to the literature namely Sundarapandian-Pehlivan system. The structure used for the design of CCII-based chaotic oscillator and the results obtained from the study have been presented. In the second phase, the design of SPCO has been realized in order to utilize for running in FPGA chips using Dormand-Prince (DP) numeric algorithm. The design has been coded in VHDL using 32-bit IEEE-754-1985 floating point representation. The designed system has been tested by synthesizing it in Xilinx ISE Design Tools program. Then, the test results obtained from DP-based SPCO structure have been presented. In the last phase, the designed system has been synthesized for VIRTEX-7 FPGA. FPGA chip resource consumption values that obtained after the Place-Route process are presented. According to the results, the maximum operating frequency of DP-based SPCO unit on FPGA is obtained as 362.608 MHz. In future studies, the designs of Pseudo Random Number Generator (RNG) and True RNG can be performed using DP-based SPCO unit implemented successfully in this study.