Search

In this study, it was aimed to determine the effects of machining parameters on the surface integrity and fatigue life of the machined part in electrical discharge turning (EDT). Initially, a mechanism was designed and manufactured to ensure rotation of the workpiece. EDT experiments were carried out on AISI L2 tool steel using three different discharge currents, pulse on time, pulse off time and constant rotational speed. The experiments were carried out according to the L9 orthogonal array, and Rz, Sm and hardness values were measured as processing performance outputs. Finally, the fatigue life of the machined parts was estimated by applying the √area model and the change of theoretical fatigue life according to the machining parameters was investigated. According to experimental results, an increase in Rz and Sm parameters was determined with increasing the discharge current and pulse on time. The lowest Rz and Sm values were obtained at 3 A discharge current, 3 µs pulse on time and 5 µs pulse off time. Based on Taguchi analysis, the optimum theoretical fatigue stress was calculated as 643.932 MPa with √area model for the machined workpiece in the A1Ton1Toff3 experiment sequence., Bu çalışmada, elektro erozyon ile tornalamada (EET) işleme parametrelerinin yüzey bütünlüğü ve işlenmiş parçanın yorulma ömrüne etkilerinin belirlenmesi amaçlanmıştır. İlk olarak, iş parçasının dönmesini sağlamak amacıyla bir mekanizma tasarlanarak imal edilmiştir. EET deneyleri, AISI L2 takım çeliği üzerinde üçer farklı boşalım akımı, vurum süresi ve bekleme süresi ile sabit devir sayısı kullanılarak yapılmıştır. Deneyler, L9 dikey dizisine göre yapılmış olup, işleme performans çıktıları olarak Rz, Sm ve sertlik değerleri ölçülmüştür. Son olarak, √area modeli uygulanarak işlenen parçaların yorulma ömrü tahmin edilmiş ve işleme parametrelerine göre teorik yorulma ömrünün değişimi araştırılmıştır. Deneysel sonuçlara göre, boşalım akımı ve vurum süresinin artmasıyla Rz ve Sm parametrelerinde bir artış belirlenmiştir. En düşük Rz ve Sm değerleri 3 A boşalım akımı, 3µs vurum süresi ve 5 µs bekleme süresinde elde edilmiştir. Taguchi analizine göre optimum teorik yorulma gerilmesi A1Ton1Toff3 deney dizisinde işlenen parça için √area modeli ile 643.932 MPa olarak hesaplanmıştır.

Date of Conference: 2-5 May 2018 In this work, a new method for estimating the modulation parameters of radar pulses which make interpulse phase/frequency stepping for pulse compression. Proposed method first applies special filters, which magnifies phase/frequency stepping instants, to the instantaneous phase of the measured radar pulse. Then, Robust Least Squares (RobLS) algorithm is utilized for anomaly detection. The local maximum of the detected anomaly points provides the high resolution estimates of the phase/frequency stepping instants. Extensive experiments conducted on synthetic data sets for different SNR (Signal-to-Noise Ratio) levels and phase/frequency stepping values show that proposed method can successfully estimate phase/frequency stepping instants.

A Gaussian laser pulse propagating through plasma in the presence of a magnetic wiggler produces third-harmonic radiation. The wiggler's magnetic field provides additional momentum required for phase matching. The required wiggler wave number is sensitive to pulse duration and amplitude. The efficiency of the process is significant at the instant at which the phase matching condition is satisfied.

Date of Conference: 18-20 April 2012 Ultra-Wideband (UWB) communication systems have been developed for short distance, high data rate communications. To avoid interfering with the existing systems in the same environment, very short duration pulses used by these systems should satisfy a predefined spectral mask. Data rate of UWB systems can be increased by using multiple pulse shapes simultaneously. Orthogonality of the simultaneously used pulse shapes simplifies the receiver design. In this work, design of orthogonal pulse shapes which satisfy the spectral mask is modelled as an optimization problem. First, it is converted to a convex optimization problem by constraining the pulse shapes to lie in a subspace spanned by the Hermite-Gaussian (HG) functions. Then the optimal solution is obtained. It is shown that a larger pulse shape set can be designed compared to the existing approaches, and hence, a higher data rate can be achieved. © 2012 IEEE.