2019 Cilt 24 Sayı 2

Permanent URI for this collectionhttps://hdl.handle.net/11452/12570

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Now showing 1 - 13 of 13

Asymptotic evaluation of scattering of inhomogeneous plane waves by a perfectly electric conducting half plane
(Bursa Uludağ Üniversitesi, 2019-04-26) Kara, Mustafa
In the present study, reflected and diffracted fields of an inhomogeneous plane wave obliquely incident on the surface of a perfectly electric conducting (PEC) half plane are evaluated for a two-dimensional case asymptotically and reexamined by considering the different aspects. Obtained results are plotted by Matlab numerically. Relationships between the complex angle of incidence and field intensities, and phase shifts in the fields are noted. Matlab plots are interpreted and compared to the theory for consistence.
Design and analysis of 28 GHz microstrip patch antenna for different type FR4 claddings
(Bursa Uludağ Üniversitesi, 2019-05-23) Hiçdurmaz, Bahadır; Gümüş, Ömer Faruk
In this study, rectangular patch microstrip antennas operating at 28 GHz frequency compatible with 5G mobile technology are designed with Computer Simulation Technology (CST) program for different patch materials and the performances of the designed antennas are compared. For each of the same sized antennas designed with the selected patch materials, it is found that they are suitable for the 28 GHz band and the best return loss performance is obtained by using the tantalum conductor while the silver conductor has the best antenna efficiency.
Design and realisation of a yarn tension sensor using strain gauge type load cells
(Bursa Uludağ Üniversitesi, 2019-08-02) Eren, Recep; Mutlu, Hüseyin Nizam; Çelik, Özge; Uludağ Üniversitesi/Mühendislik-Mimarlık Fakültesi/Tekstil Mühendisliği Bölümü.
Yarn tension sensors are used extensively in industrial applications as well as in laboratories for research purpose. In many textile processes like warping, winding, unwinding and knitting, yarn is subjected to cyclic forcing due to motion of mechanisms and nature of the process. This causes a cyclic change in yarn tension and frequency of tension signal depends on process speed. Therefore, it is required that yarn tension sensor detects even small tension changes caused by the process and rejects higher frequency variations called noise. This paper examines the general techniques used in constructing yarn tension sensors and then explains the design and realisation of a yarn tension sensor using strain gauge type load cell. After constructing the sensor, tension measurements are carried out at different yarn speeds up to 800 m/min and tension signals are analysed. After comparing the measured tension signals with the tension signals recorded by a commercial tensiometer, some suggestions are given for improving the measurement precision of the developed yarn tension sensor at high speeds.
A discovery-based case study to teach the concepts of computational simulation and measurement uncertainty in heat transfer
(Bursa Uludağ Üniversitesi, 2019-08-02) Çakmak, Mehmet Ekrem; Taylan, Çağkan
The present study was used to teach undergraduate students the concepts of computational simulation and measurement uncertainty via discovery based learning. The study included experimentaltheoretical-numerical examination of heat conduction along a cylindrical rod. Because it is a well-known fact that dealing with systems having complex theoretical background distracts students‟ attention, an easy to be comprehended experimental system had intentionally chosen to allow the students mainly focus on the computational simulations and measurement uncertainty. Students were requested to compare the results obtained at each step and to figure out the possible causes of discrepancies among the results if there was any. The steps were repeated several times until the students satisfied with the results.
Dynamic response analysis of a 3-story shear frame subjected to harmonic loading: An analytical approach
(Bursa Uludağ Üniversitesi, 2019-07-10) Tüken, Ahmet
The multi-story buildings are likely to be subjected to various types of dynamic loadings. A sinusoidal external force with a certain frequency applied to a system is considered as harmonic excitation. Since it is faced very commonly and also covers the concept of resonance, the response of a system to harmonic excitation is an important topic. In the present study, a three-story shear frame subjected to a harmonic force at the top floor is studied and the equations for the floor displacements as functions of time have been obtained. Then normalized response amplitudes under the applied harmonic loading is plotted against the frequency ratio / 1. These frequency-response curves show three resonance conditions at = 1, = 2 and = 3; at these exciting frequencies the steady-state response is unbounded. At other exciting frequencies, the vibration is finite and could be calculated from the derived equations. The structure experiences resonance at some frequency if the structure is excited with harmonic loading over a range of frequencies. When the frequency of the excitation is equal to the natural frequency of the structure, resonance occurs. The structure experiences its largest response at the resonant frequency as compared to any other frequency of loading. If the loading frequency is close to, not exactly equal to, the natural frequency of the system, a phenomenon known as "beating" may occur. In this kind of vibration, the amplitude builds up and then diminishes in a regular pattern.
Dynamic simulation of a pv/wind hybrid power generation system: Case study of Bursa province
(Bursa Uludağ Üniversitesi, 2019-08-02) Altun, Ayşe Fidan; Kılıç, Muhsin; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Makine Mühendisliği Bölümü.
In this study, a PV/Wind hybrid power generation system was studied using meteorological data of Bursa province. Reliability of the weather data is crucial when designing renewable-based power systems. As a result, weather data of the two specific years (2011, 2014) were chosen for the dynamic simulations. The designed hybrid system consists of PV panels and a wind turbine. The outcome of the study shows that with the proposed 1 MW PV + 2 MW wind turbine system, it is possible to generate enough electricity to compensate the annual electricity requirement of 450 households which can be considered as a small district area. Levelized cost of energy is found a value between 0.413-0.568 $/kWh. Payback period of the system is found a value around 20 years. It was concluded that it is essential to offer adequate incentives for renewable-based power applications to make them economically beneficial.
Effect of heat treatment and cross section on the crashworthiness of 51CRV4 spring steel
(Bursa Uludağ Üniversitesi, 2019-07-22) Dindar, Çiğdem; Beytüt, Hüseyin; Karagöz, Selçuk
In this study, 51CrV4 spring steel was used as a crash box material and its crashworthiness was investigated under axial dynamic loading. Crash boxes with cylinder and square geometries were designed in SolidWorks and crash analyses were performed by using RADIOSS/explicit and nonlinear Finite Element (FE) codes. In addition, 51CrV4 spring steel was subjected to three different heat treatments and their mechanical properties were determined by tensile and hardness tests. The crashworthiness of crash box was evaluated taking into account the energy absorption (EA), peak crushing force (PCF), mean crushing force (MCF) and crash force efficiency (CFE). Since the crash boxes had equal mass, their EA rates are equal to specific energy absorption (SEA) rates. It has been observed that heat treatment and cross-section geometry have a serious impact on crashworthiness.
An exact variance expression of the k-PHD singletone frequency estimator: Random phase case
(Bursa Uludağ Üniversitesi, 2019-06-10) Keyta, Betofe Mboyo; Uz, Sevim Hazal; Dilaveroğlu, Erdoğan; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.
The k-PHD method, a generalization of the well-known Pisarenko harmonic decomposition (PHD) method, is considered for frequency estimation of a single real random-phased sinusoid in noise. With the use of a simple variance analysis technique, an exact expression of the k-PHD frequency variance is derived. An approximate k-PHD variance formula for sufficiently large data lengths and signal-to-noise ratios is also given. Computer simulations are included to validate the theoretical development.
Experimental and simulating of dry-type transformer thermal analysis with a new approach for outdoor applications
(Bursa Uludağ Üniversitesi, 2019-05-17) Tören, Murat; Çelebi, Mehmet
Since dry type transformers (DTT) has many advantages over the oily ones, this study focuses on the realibity, feasibility and cost of DTT to be used at outdoor applications. On this respect the core and winding temperatures of the 1500 VA DTT transformer model is measured by thermal camera The operational highest temperature of the transformer is obtained by this way. The DTT is simulated by ANSYS with the design parameters based On the physical model, and the simulation values and the real ones are compared to satisfy the procedure. Then in the light of simulation results, an outer cover is designed for outdoor applications which is the goal of the paper. The real hot spot temperature of the 1500 VA DTT is 129 ° C remains the same with the new cover simulation designed DTT that naturally cooled. Furthermore, the temperature of the new design DTT is reduced by about 4.6% to 123 ° C by forced cooling. So the new cover design not only provide to be used at outdoors applications, it also increases the lifetime of the device, and reduces the operation costs.
Investigation of some mechanical and air permeability properties of shirting fabrics produced from compact yarns made of natural and synthetic fibres
(Bursa Uludağ Üniversitesi, 2019-07-10) Günaydın, Gizem Karakan; Çeven, Erhan Kenan; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.
Shirting fabrics are one of the most demanded product groups for textile consumers. Although cotton is the most preferred fibre as the raw material of shirting fabrics, fibres such as Polyester, Elastane, viscose and their blends with cotton may also be utilized in the shirting fabrics. For the convenience usage of shirting fabrics in apparel products, those fabrics’ durability and air permeability properties should be considered in detail. Fabric constructional parameters such as weave structure, warp and weft yarn density, yarn count, fibre type are the main influential factors on shirting fabrics’ mechanical and air permeability properties. This study has been performed in order to evaluate the effect of fabric construction on some mechanical properties such as tear strength, seam strength, crease recovery angle (°) as well as on air permeability of the shirting fabrics. Throughout the study, plain, dobby and satin shirting woven fabrics were produced from the compact yarns with several combinations of cotton, linen, polyamide, viscose and elastane fibre blends. Pre-treated samples were objected to tear strength test, seam strength test, crease recovery angle (°) test and finally to air permeability test. Randomized One –Way ANOVA test was performed in order to investigate the significant effect of fabric type on some mechanical and air permeability properties of shirting fabrics at significance level of 0.05. Test results were statistically evaluated and it was generally observed that there was a significant effect of fabric type on tear strength, seam strength, crease recovery angle and on air permeability features of the shirting fabrics at significant level of 0.05.
Investigation of the effects of some process parameters on the morphological properties of polyurethane nanofibrous mats containing black seed oil
(Bursa Uludağ Üniversitesi, 2019-06-27) Aras, Cansu; Gebizli, Şebnem Düzyer; Özer, Elif Tümay; Karaca, Esra; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Tekstil Mühendisliği Bölümü.; Bursa Uludağ Üniversitesi/Fen Edebiyat Fakültesi/Kimya Bölümü.
Black seed and its extracts have been used in alternative medicine since ancient times. The aim of this study is to produce and characterize composite nanofibrous surfaces by electrospinning with the addition of black seed oil (BSO) with different concentrations into the thermoplastic polyurethane polymer for wound dressings. During electrospinning the flow rate, and the distance between the needle and the collector were changed. The morphologies of the surfaces were analyzed by scanning electron microscopy (SEM). The nanofiber diameters, pore size and porosity of the nanofibrous mats were determined. The presence of black seed oil was investigated by FTIR analysis and the wettability of the surfaces was examined by contact angle measurements. As a result, optimum electrospinning process parameters and the most appropriate black seed oil concentration were determined to produce continuous, uniform and bead-free nanofibers.
Numerical investigation of the spray characteristics in an outwardly-opening piezoelectric gasoline injector for different ambient conditions
(Bursa Uludağ Üniversitesi, 2019-05-10) Taş, İbrahim; Karamangil, Mehmet İhsan; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Otomotiv Mühendisliği Bölümü.
In this study, the spray characteristics of an outwardly-opening injector have been investigated numerically. Numerical analyses are carried out by taking temperature and pressure statuses of the internal combustion engine in cold temperature operations into consideration. The effects of these parameters on the evaporation rate, penetration, spray morphology, angle of the fuel spray and the Sauter Mean Diameter were key issues to be addressed. N-heptane fuel was used and the Kelvin-Helmholtz / Rayleigh-Taylor breakup model was adopted. The analyses were performed in the comprehensive environment of Fluent software. It was observed that the results complied with experimental data taking part in literature. Consequences demonstrated that increasing the ambient pressure intensified vortex formation, decreased penetration and increased fuel cone angle by forming a more compact fuel bundle. In addition, it was ascertained that the effect of the temperature parameter on the evaporation was less effective than the pressure parameter.
The system stability software tool based on Routh-Hurwitz criterion
(Bursa Uludağ Üniversitesi, 2019-05-16) Vatansever, Fahri; Hatun, Metin; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.
Stability is one of the most important parameters / factors in the field of system analysis and design. For this reason, stability analysis should be well learned and understood in engineering education as well as need to be performed perfectly in practice. In this study; a software tool has been developed that can perform absolute, relative and conditional stability analysis for single input single output linear systems based on the Routh-Hurwitz criterion. Stability analysis of the systems defined by the user can be performed easy, fast and efficiently - including all possible general and special conditions - step-by-step in detail with the designed software tool, and the results can be obtained both numerically and graphically with many parameters.

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