Bulanık mantık yöntemi kullanılarak yakın alan probunun optimizasyonu

Bu tezin, veri tabanı üzerinden yayınlanma izni bulunmamaktadır.Sembolik hesaplama, EMC, Açıklık anteni, Tasarım, Sayısal analiz, Ölçüm. Sembolik analiz yöntemlerinin açıklık antenlerinin analizine uygulanması, geniş bantlı bir EMC anteninin tasarlanıp yapılması, yapılan antenin sayısal analizinin ve ölçümlerinin gerçekleştirilmesi bu çalışmanın amaçlarını oluşturmaktadır. Sembolik analiz yöntemlerinden biri olan Macsyma ilk defa anten analizi için kullanılarak, iki boyutlu açıklık antenlerinin analizi yapılmış, genel amaçlı sembolik bir kod oluşturulmuştur. Yapılan sembolik analiz, açıklık antenlerinin düzgün ve düzgün olmayan ışınlanma durumları için analizini kapsamaktadır. Açıklığın düzgün, üçgensel ve kosinüssel ışınlanma durumları için uygulamalar yapılmıştır. Yapılan uygulamaların her biri için manyetik alan ışınım Örüntüleri iki ve üç boyutlu olarak oluşturulmuştur. Her ışınım örüntüsü açıklığın farklı boyutları için ayrı ayrı oluşturularak, açıklık boyutlarının etkisi ortaya koyulmuştur. EMC laboratuarlarında verici anten olarak kullanılması amaçlanan, geniş bantlı yeni bir açıklık anteni tasarlanmış ve yapılmıştır. Antenin plakalarının hareketli olacak şekilde tasarlanmış olması sebebiyle, antenin açıklığının boyutları değiştirilebilmektedir. Yapılan antenin geometrisinin kompleks olması, analizinin sembolik veya analitik olarak yapılmasına imkan vermemektedir. Bu sebeple, Moment Yöntemini kullanarak sayısal analiz yapan NEC-WIN anten analiz programı ile antenin sayısal analizi gerçekleştirilmiştir. Sayısal analiz sonucunda farklı frekanslar için iki ve üç boyutlu ışınım örüntüleri elde edilmiştir. Antenin girişindeki, empedans değeri hesaplanmış ve frekansla değişimi ortaya koyulmuştur. Ayrıca farklı karakteristik empedans değerleri için VSWR analizi sonuçları, VSWR-frekans grafikleriyle sunulmuştur. Açıklık anteninin elektrik alan şiddeti ve VSWR ölçümleri yansımasız oda kullanılarak gerçekleştirilmiştir. VSWR ölçümleri antenin farklı açıklık boyutları için tekrarlanmıştır. Elektrik alan şiddeti ölçümleri, antenden uzaklıkları farklı olan iki noktada yapılmıştır.EMC ANTENNA DESIGN, ANALYSIS and MEASUREMENTS SUMMARY Keywords: Symbolic computation, EMC, Aperture antenna, Design, Numerical analysis, Measurement. The aim of this work contains the application of symbolic analysis methods to the aperture antennas, a wide band EMC antenna design, numerical analysis and measurements of the designed antenna. Macsyma, which is one of the symbolic analysis methods, is used to analyze the two dimensional aperture antennas first time and a general purpose symbolic code is developed. The symbolic analysis covers the uniformly and non-uniformly illuminated apertures. The symbolic analysis contains the applications for uniformly triangular and cosine type illuminated apertures. Magnetic field radiation patterns are formed in two and three dimensions for each of the applications. Forming each radiation pattern for different dimensions of apertures, effects of aperture dimensions are exposed. A new wide band aperture antenna is designed and built to use as a transmitter antenna at the EMC laboratories. Because the antenna has moving plates, the aperture dimensions of the antenna can be changed. The antenna geometry is complex and it cannot be analyzed using symbolic and analytical techniques. So, numerical analysis of the antenna is realized using NEC-WIN antenna analysis program that is based on Moment Method. As a result of the numerical analysis, two and three dimensional radiation patterns are obtained for different frequencies. Impedance values at the antenna input are computed and variation of the impedance with frequency is given. In addition, VSWR analysis results are represented as VSWR-frequency graphics for different characteristic impedances. The electric field strength and VSWR measurements of the aperture antenna are made in an anechoic chamber. VSWR measurements are repeated for different aperture dimensions. Electric field strength measurements are made at two points whose distances from the antenna are different. X

The effects of fabric lamination angle and ply number on electromagnetic shielding effectiveness of weft knitted fabric-reinforced polypropylene composites

In this study, it was aimed to investigate the effects of fabric lamination angle and fabric ply number on electromagnetic shielding effectiveness (EMSE) of weft knitted fabric-reinforced polypropylene composites. Knitted fabric-reinforced composites are composed of aramid yarn, polypropylene yarn, and copper wire. Polypropylene is the matrix phase and the aramid yarn and copper wires are the reinforcement phase of the composite materials. It was achieved to form 1.5 to 3 mm thickness composites. The composites have nearly 20-50 dB electromagnetic shielding values. To form the knitted fabrics, 7G semiautomatic flat knitting machine was used. The composites were formed by a laboratory-type hot press. EMSE of composites were tested by using ASTM D 4935 coaxial test fixture in 27-3000 MHz frequency band. Lamination angle and ply number parameters were examined related to EMSE of structures. For this study, three different structures were knitted and named as plain knit, 1 x 1 rib knit, and half cardigan knit. To determine the effect of lamination angle of composites on electromagnetic shielding performance, the composites were produced in two different lamination angles as 0 degrees/90 degrees/0 degrees/90 degrees and 0 degrees/45 degrees/0 degrees/45 degrees. To determine the effect of fabric ply number of composites on electromagnetic shielding performance, the composites were produced in two and four plies. It was observed that the fabric ply number and lamination angle does not affect the EMSE of composite materials very much. It was determined that weft knitted reinforced composite structures have appropriate and high EMSE values for electromagnetic applications. This knitted fabric-reinforced polypropylene composites are flexible and suitable for other industrial applications as civil engineering, aerospace, etc.Board of Project of Suleyman Demirel UniversitySuleyman Demirel University [1438-D-06]; Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [107-M-368]The authors would like to thank The Board of Project of Suleyman Demirel University (project number 1438-D-06) and The Scientific and Technological Research Council of Turkey (TUBITAK; project number 107-M-368) for the provision of a Ph.D. scholarship to one of us (D.S.). They also thank York EMC Services Ltd. for testing the shielding effectiveness tests

Effects of the wireless (2.45 GHz) electromagnetic fields on blood cells in rat

The study aims to investigate hematological parameters, blood cell diameters and shapes of rats exposed to 2.45 GHz wave frequency EMF. All of the subjects were divided in three groups as cage control group (n = 30), pseudo-exposure group (n = 30) and 2.45 GHz EMF exposed group (n = 30). The rats in the magnetic field group were exposed to a frequency of 2.45 GHz wave EMF power of 1 mW/cm2 for 120 minutes a day for 2 weeks. The effects of the electromagnetic field on blood levels in rats exposed to 2.45 GHz were compared. The mean lymphocyte count of 2.45 GHz group was lower than in the control group, the number of monocytes in the 2.45 GHz group was higher than the control group. The mean platelet count in the experimental group exposed 2.45 GHz was observed more intense than the control group. Exposure conditions of EMF emitted from wireless devices should be examined and in accordance with these terms the necessary corrections are being made and national standards should be determined. To continue research on this subject is important in terms of scientific and public health.No sponso

Biological Effect of Microwave on the Nervous System

This article presents an overview of the recent RT bioeffects literature dealing with the nervous system. Studies have evaluated the electroencephalography (EEG) of humans and laboratory animals during and after radiofrequency (RF) exposures. Exposure to high levels of RF energy can damage the structure and function of the nervous system. Much research has focused on the neurochemistry of the brain and the reported effects of RF exposure. Studies of individuals who are reported to be sensitive to electric and magnetic fields are discussed. The many exposure parameters such as frequency, orientation, modulation, power density, and duration of exposure make direct comparison of many experiments difficult. At high exposure power densities, thermal effects are prevalent and can lead to ad-verse consequences. At lower levels of exposure biological effects may still occur but thermal mechanisms are not ruled out. It is concluded that the diverse methods and experimental designs as well as lack of replication of many seemingly important studies prevents formation of definite conclusions concerning hazardous nervous system health effects from R-F exposure. The only firm conclusion that may be drawn is the potential for hazardous thermal consequences of high power RF exposure

The Passive Cable Modeling and Simulating of the Axon With Matlab(7.0.4)/Simulink

In this study the electrical theory of excitation propagation in excitable cell was investigated. The basic principals of linear cable theory were given and general differential equations concerning excitable cells were derived. The passive cable model simulation of axon was made through the programme of MATLAB(7.0.4)/Simulink. In order to reach the realistic model, which is one of the main targets of the study, two simplified and revised models were used. A realistic wave shape was produced in MATLAB(7.0.4)/Simulink as the action potential wave shape spreading in axon. As seen in the results, the more length increases in the values of minimum and maximum amplitude, the weaker. They are as expected in the simplified model. When the simulation results of the two simplified and revised models compared, in the output of the revised model the minimum amplitude is seen to decrease. In the revised model, an ideal capacity element which we recommend was found. However, the most crucial result is that this capacity shortens the hyperpolarization period

Manyetik Alanın Sıçanlardaki Sinir İleti Parametrelerine Etkileri

İyonize olmayan elektromanyetik radyasyonun insan sağlığı üzerindeki etkileri, son elli yılda manyetik alanların kullanım alanının genişlemesi ile birlikte, büyük bir araştırma konusu olmuştur. Manyetik alanların tabiatı çok iyi bilinmekle beraber, insan vücudunun karmaşık yapısı, bu etkilerin incelenmesini zorlaştırmaktadır. Bununla beraber yapılan deneysel ve teorik çalışmaların sonucunda, manyetik alanların insan sağlığı üzerindeki etkileri konusunda kayda değer bulgular elde edilmiştir. Ancak, henüz bilinmeyen etkilerinin olabileceği konusunda da şüpheler mevcuttur. Bu çalışma ile 50 Hz-1mT manyetik alanın izole sıçan siyatik siniri üzerindeki etkisinin incelenmesi amaçlanmıştır. İzole sinir 30 saniye 1mT Helmholtz bobini ile manyetik alana maruz bırakıldıktan sonra 0.1-0.5 msn süreli eşik ve supramaksimal pulslarla uyarılmış ve hücre dışı izole kayıt yöntemi kullanılarak değerler kaydedilmiştir (n=16). Elde edilen kayıtlardan ileti zaman farkı, maksimum genlik farkı, minimum genlik farkı, ortalama depolarizasyon süresi, ortalama repolarizasyon süresi ve ortalama hiperpolarizasyon süresi ölçülmüştür. 50 Hz-1 mT manyetik alan uygulanan sinirlerde, sinir ileti hızında bir değişme olmamıştır. Fakat manyetik alan uygulanan grubun; maksimum genlikler farkı (mV) ve ortalama hiperpolarizasyon süresi (msn), kontrol grubuna göre daha düşüktür (p=0,025). Anahtar Kelimeler: Manyetik Alan, Sinir İletimi, Siyatik Sini

Effects of 50 Hertz-1 mT magnetic field on action potential in isolated rat sciatic nerve

The aim of this study was to investigate possible effects of 50 Hz-1 mT magnetic field (MF) on action potential in isolated rat sciatic nerve. We used 16 Wistar rats in the study. They were divided into control (n = 10) and MF (n = 6) groups. The sciatic nerve of left legs in the MF group was exposed to 50 Hz-1 mT MF for 30 min by using a Helmholtz applicator and then action potentials in control and experimental groups were recorded extra-cellularly. Maximum amplitude and hyperpolarization time and action potential were significantly (p <= 0.025) lower in the MF group than in control. However, conduction time, minimum amplitude, depolarization and repolarization times of the action potential was not different between control and MF groups evaluated. In conclusion, 50-1 mT MF caused to decrease amplitude value and hyperpolarization time of action potential in the rat nerve

Matlab7.0.4/Simulink ile Aksonun Pasif Kablo Modellemesi ve Simülasyonu

Bu çalışmada uyarılabilir hücrelerde uyarı iletiminin elektriksel kuramı üzerinde durulmuştur. Pasif kablo teorisinin esaslarına yer verilmiş ve uyarılabilir hücreler ile ilgili genel diferansiyel denklemlerin türetilmesi yapılmıştır. Aksonun pasif kablo model simülasyonu, MATLAB7.0.4/Simulink programı ile gerçekleştirilmiştir. Çalışmanın ana hedeflerinden biri olan gerçekçi modele erişmek için, basitleştirilmiş ve revize edilmiş iki model kullanılmıştır. Aksonda yayılan aksiyon potansiyeli dalga şekli olarak, MATLAB7.0.4/Simulink'te gerçekçi dalga şekli üretilmiştir. Sonuçlardan görülmektedir ki; basitleştirilmiş modelde beklenildiği gibi minimum ve maksimum genlik değerlerinde, uzunluk arttıkça artan zayıflamaya neden olmaktadır. Basitleştirilmiş ve revize edilmiş iki modelin simülasyon sonuçları karşılaştırıldığında revize edilmiş model çıkışında, minimum genliğin azaldığı görülmektedir. Revize edilmiş modelde; önerdiğimiz, olması gereken bir kapasite elemanı bulunmuştur. Ama en önemli sonuç, bu kapasitenin hiperpolarizasyon süresini kısaltmasıdır

Influence of a 50 Hz-1 mT Magnetic Field on Human Median Nerve

With the increasing use of magnetic fields in recent five decades, the health effects of nonionized electromagnetic radiation is an important investigation subject. While the magnetic field is well known, it is difficult to investigate the health effects of radiation, because of the complex metabolism of human body. However, by the experimental and theorical studies, a lot of significant health effects of magnetic fields have been discovered. But, there are probabilities that can have much more adverse health effects. The purpose of this study is to evaluate the effect of 50 Hz-1 mT magnetic field on human median motor nerve conduction parameters. At this frequency, 1 mT value of magnetic field intensity is known and accepted as the marginal value where biological interaction starts. Standard nerve conduction techniques using constant measured distances were applied to evaluate the median nerve. Consequently in the measures conducted using the device of 4 channel NCS/EMG/EPS there was a significant decrease in motor distal amplitude after the magnetic field application in comparison to the one during the application (p=0,000573) and also in the motor distal amplitude/proximal amplitude in comparison to the ones before the application (p=0,037418)