Cafer Kırbaş - Academia.edu (original) (raw)

Papers by Cafer Kırbaş

Research paper thumbnail of Experimental analysis of sound absorption effect of specially developed elastomeric thin thermoplastic polyurethane sub-micron fibre web layers placed on rigid layer and flexible layers

Plastics, Rubber and Composites, 2021

The aim of this study is to determine the effect of sub-micron fibre web layers on sound absorpti... more The aim of this study is to determine the effect of sub-micron fibre web layers on sound absorption properties when they are placed on rigid substrate and flexible substrate. Elastomeric thermoplastic polyurethane (TPU) and composite TPU/PS (polystyrene) sub-micron fibre webs with both rigid glass fibre fabric reinforced epoxy composites (GFEC) and flexible polypropylene (PP) spunbond nonwovens have been examined. Elastomeric TPU sub-micron fibres and TPU/PS fibre web before and after soxhlet extraction were studied. Even though a thin layer of (less than 1 mm) electrospun sub-micron fibres were used with GFEC, sound absorption coefficient (SAC) improved from 0.1 to 0.4. Maximum SAC is drawn back to lower frequency (from 1250 to 500–630 Hz), when sub-micron fibre web is used on nonwoven. In conclusion, the mechanism of elastomeric thin sub-micron fibre webs on sound absorption for rigid GFEC and for flexible nonwoven is totally different than each other.

Research paper thumbnail of Monitoring of Crustal Deformations from 2003 to 2009 in Marmara Region, Turkey: Preliminary Results from Absolute Gravity and GPS Observations

The aim of this study is to develop methods that clarified the systematic relations between verti... more The aim of this study is to develop methods that clarified the systematic relations between vertical movements and mass changes by the help of absolute and relative gravity measurements as well as GPS observations. Using these relations, the anomalies about the vertical crustal deformation in the Marmara Region will be determined and obtained results will be used in connection with

Research paper thumbnail of Primary sound power sources for the realisation of the unit watt in airborne sound

At present, airborne sound power is not a directly measurable quantity. It is calculated from sou... more At present, airborne sound power is not a directly measurable quantity. It is calculated from sound pressure measurements performed in special environments, e.g. free or diffuse fields or from soun ...

Research paper thumbnail of Current Situations on Vibration Field at NMCC and Calibration of Signal Condioner

This paper introduces the current calibration and measurement capabilities (CMC) on vibration fie... more This paper introduces the current calibration and measurement capabilities (CMC) on vibration field in NMCC operating under the Saudi Standards, Metrology and Quality Organization (SASO) in Kingdom of Saudi Arabia. Calibration facilities operate for vibration pick-ups at primary and secondary level in accordance to relevant ISO standards. The calibration system is also capable of calibration of different type of signal conditioner. In order to show the consistency of the results for calibration of signal conditioner, the measurement results obtained at NMCC and TUBITAK UME is presented.

Research paper thumbnail of Primary Accelerometer Calibration in Ume by Sine Approximation Method

− − − − The traceability of the vibration measurements to SI units is maintained through the cali... more − − − − The traceability of the vibration measurements to SI units is maintained through the calibration of the reference transducers. Primary calibration of the reference transducers in the field of mechanical vibration and shock is performed in accordance with the international standard ISO 16063-11 [1]. In some applications beside magnitude of the transducer's sensitivity, the knowledge of phase shift is also required. Magnitude and phase shift of the complex sensitivity of the reference transducer could be obtained by applying the sine approximation method, described in ISO 16063-11 standard. In general, this method is applied in many leading National Metrology Institutes in the world. However, experimental implementation of the method varies from one institute to another. The experimental setup constructed in Turkish National Metrology Institute for the realization of sine approximation technique and calibration results for reference standard accelerometers are presented in this paper.

Research paper thumbnail of Influence of native structural defects activated by illumination and under the memory effect conditions on ultrasonic wave propagation in TlInS2 ferroelectric–semiconductor with incommensurate phase

This paper presents data about experimental observation and theoretical validation effect of nati... more This paper presents data about experimental observation and theoretical validation effect of native defect states activated by illumination and under the memory effect conditions on the velocity of longitudinal and shear elastic waves propagating in layered TlInS2 ferroelectric-semiconductor in different directions. These longitudinal and transverse ultrasonic velocities were worked out by using the pulse echo overlap technique in the range of temperature ~90–300 K and correspond to and elastic constants of TlInS2. The investigations reveal the illumination-induced spike-like peaks in the temperature dependence of longitudinal wave velocity centered at different temperatures in the range of temperature 225–300 K of high-temperature paraelectric phase. The temperature dependence of ultrasonic velocity of shear wave corresponding to mode exhibits a steep decrease in the slope under illumination at ~190 K. Influence of the memory effects on the velocities of ultrasonic waves, which is ...

Research paper thumbnail of Evaluation of Uncertainty Contributions of Measurement Surface and Number of Microphone Positions in Determination of Sound Power Levels

Acta Physica Polonica A, 2017

Sound power level of a noise source is determined by means of sound pressure level or sound inten... more Sound power level of a noise source is determined by means of sound pressure level or sound intensity level measurements performed in accordance to relevant ISO standards. The determination of sound power level according to ISO 3744, 3745 and 3746 standards is used for free field or for approximated free field conditions. Kinds of measurement surfaces, enveloping the noise source, number of microphones and their positions over the measurement surface are stated in the applied ISO standard. The effects of measurement surface and number of microphone positions on the determination of sound power level were investigated theoretically. As a measurement surface; hemisphere, parallelepiped rectangular box and cylindrical surfaces were selected. Key and additional microphone positions were taken into account in the calculations as well. Sound pressure levels of a commercially available reference sound source were measured in hemi-anechoic room using FFT with 4 Hz steps and also at 1/1, 1/3...

Research paper thumbnail of Experimental analysis of sound absorption effect of specially developed elastomeric thin thermoplastic polyurethane sub-micron fibre web layers placed on rigid layer and flexible layers

Plastics, Rubber and Composites, 2021

The aim of this study is to determine the effect of sub-micron fibre web layers on sound absorpti... more The aim of this study is to determine the effect of sub-micron fibre web layers on sound absorption properties when they are placed on rigid substrate and flexible substrate. Elastomeric thermoplastic polyurethane (TPU) and composite TPU/PS (polystyrene) sub-micron fibre webs with both rigid glass fibre fabric reinforced epoxy composites (GFEC) and flexible polypropylene (PP) spunbond nonwovens have been examined. Elastomeric TPU sub-micron fibres and TPU/PS fibre web before and after soxhlet extraction were studied. Even though a thin layer of (less than 1 mm) electrospun sub-micron fibres were used with GFEC, sound absorption coefficient (SAC) improved from 0.1 to 0.4. Maximum SAC is drawn back to lower frequency (from 1250 to 500–630 Hz), when sub-micron fibre web is used on nonwoven. In conclusion, the mechanism of elastomeric thin sub-micron fibre webs on sound absorption for rigid GFEC and for flexible nonwoven is totally different than each other.

Research paper thumbnail of Monitoring of Crustal Deformations from 2003 to 2009 in Marmara Region, Turkey: Preliminary Results from Absolute Gravity and GPS Observations

The aim of this study is to develop methods that clarified the systematic relations between verti... more The aim of this study is to develop methods that clarified the systematic relations between vertical movements and mass changes by the help of absolute and relative gravity measurements as well as GPS observations. Using these relations, the anomalies about the vertical crustal deformation in the Marmara Region will be determined and obtained results will be used in connection with

Research paper thumbnail of Primary sound power sources for the realisation of the unit watt in airborne sound

At present, airborne sound power is not a directly measurable quantity. It is calculated from sou... more At present, airborne sound power is not a directly measurable quantity. It is calculated from sound pressure measurements performed in special environments, e.g. free or diffuse fields or from soun ...

Research paper thumbnail of Current Situations on Vibration Field at NMCC and Calibration of Signal Condioner

This paper introduces the current calibration and measurement capabilities (CMC) on vibration fie... more This paper introduces the current calibration and measurement capabilities (CMC) on vibration field in NMCC operating under the Saudi Standards, Metrology and Quality Organization (SASO) in Kingdom of Saudi Arabia. Calibration facilities operate for vibration pick-ups at primary and secondary level in accordance to relevant ISO standards. The calibration system is also capable of calibration of different type of signal conditioner. In order to show the consistency of the results for calibration of signal conditioner, the measurement results obtained at NMCC and TUBITAK UME is presented.

Research paper thumbnail of Primary Accelerometer Calibration in Ume by Sine Approximation Method

− − − − The traceability of the vibration measurements to SI units is maintained through the cali... more − − − − The traceability of the vibration measurements to SI units is maintained through the calibration of the reference transducers. Primary calibration of the reference transducers in the field of mechanical vibration and shock is performed in accordance with the international standard ISO 16063-11 [1]. In some applications beside magnitude of the transducer's sensitivity, the knowledge of phase shift is also required. Magnitude and phase shift of the complex sensitivity of the reference transducer could be obtained by applying the sine approximation method, described in ISO 16063-11 standard. In general, this method is applied in many leading National Metrology Institutes in the world. However, experimental implementation of the method varies from one institute to another. The experimental setup constructed in Turkish National Metrology Institute for the realization of sine approximation technique and calibration results for reference standard accelerometers are presented in this paper.

Research paper thumbnail of Influence of native structural defects activated by illumination and under the memory effect conditions on ultrasonic wave propagation in TlInS2 ferroelectric–semiconductor with incommensurate phase

This paper presents data about experimental observation and theoretical validation effect of nati... more This paper presents data about experimental observation and theoretical validation effect of native defect states activated by illumination and under the memory effect conditions on the velocity of longitudinal and shear elastic waves propagating in layered TlInS2 ferroelectric-semiconductor in different directions. These longitudinal and transverse ultrasonic velocities were worked out by using the pulse echo overlap technique in the range of temperature ~90–300 K and correspond to and elastic constants of TlInS2. The investigations reveal the illumination-induced spike-like peaks in the temperature dependence of longitudinal wave velocity centered at different temperatures in the range of temperature 225–300 K of high-temperature paraelectric phase. The temperature dependence of ultrasonic velocity of shear wave corresponding to mode exhibits a steep decrease in the slope under illumination at ~190 K. Influence of the memory effects on the velocities of ultrasonic waves, which is ...

Research paper thumbnail of Evaluation of Uncertainty Contributions of Measurement Surface and Number of Microphone Positions in Determination of Sound Power Levels

Acta Physica Polonica A, 2017

Sound power level of a noise source is determined by means of sound pressure level or sound inten... more Sound power level of a noise source is determined by means of sound pressure level or sound intensity level measurements performed in accordance to relevant ISO standards. The determination of sound power level according to ISO 3744, 3745 and 3746 standards is used for free field or for approximated free field conditions. Kinds of measurement surfaces, enveloping the noise source, number of microphones and their positions over the measurement surface are stated in the applied ISO standard. The effects of measurement surface and number of microphone positions on the determination of sound power level were investigated theoretically. As a measurement surface; hemisphere, parallelepiped rectangular box and cylindrical surfaces were selected. Key and additional microphone positions were taken into account in the calculations as well. Sound pressure levels of a commercially available reference sound source were measured in hemi-anechoic room using FFT with 4 Hz steps and also at 1/1, 1/3...