S U M M A R YTo provide quantitative information on the shear wave velocity structure of theİzmit Bay area, we conduct active-passive array surface wave and single-station microtremor measurements at 60 sites. We process these array measurements to produce combined Rayleigh wave dispersion curves that span a broad-frequency range (0.5-20 Hz). We also make use of horizontal-to-vertical spectral ratio (HVSR) curves obtained from the single-station microtremor measurements to benefit from their close relation to the ellipticity of Rayleigh waves. Using the dispersion curve sensitivity to the absolute velocities and the shape of the HVSR curve sensitivity to the velocity contrasts of the velocity-depth model, we have applied a combined inversion technique to derive better constrained shear velocity models at each site. The derived shear velocity models are used to provide a V s 30 site classification map and information on the sediment-bedrock structure for theİzmit Bay area. The V s 30 map shows that the entire shoreline regions including artificial infill areas of theİzmit Bay have V s 30 values less than 200 m s −1 , locally as low as 80 m s −1 . The older sediment areas of theİzmit basin have V s 30 values ranging between 250 and 350 m s −1 . The highest V s 30 values are associated with rock sites reaching about 950-1300 m s −1 . We also present a high correlation between the V s 30 values and the phase velocity of Rayleigh wave corresponding to the 40 m wavelength (C40). The important implication of this correlation is that V s 30 may be estimated from C40 without inverting the dispersion curve. The inferred sediment-bedrock interface along a crosssection shows an antisymmetric V shaped basin with a sedimentary cover thickness reaching about 1200 m at the deepest part of theİzmit basin. This deepest part coincides in the map view where the North Anatolian fault zone crosses the basin in the east-west direction. The sedimentary cover thickness is found to be 750 m in the Gölcük-Derince basin.

Polyethylene terephalate (PET) samples were modified by Cu, C, Ti, and Cr implantation using a metal vapor vacuum arc (MEVVA) implanter. The ions were implanted at an accelerating voltage of 30 kV with a dose ranging from 1 × 1014 to 1 × 1017 ions/cm2. In the first part of this study, Cu ions were implanted to improve the electrical properties of PET woven fabrics, and in the second part, C, Ti and Cr ions were implanted to enhance the mechanical properties of PET membrane fabrics. After implantation, the results showed that the half-charge decay time of implanted fabric lessened to milliseconds, and the friction coefficient and wear loss values decreased significantly. The surface morphologies of the samples were examined by scanning electron microscopy and atomic force microscopy. The changes in chemical structure were observed by IR spectra.

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Summary We present a new processing scheme that employs passive seismic interferometry followed by multichannel analysis of surface waves, which we call the 2D PSI-MASW method, to obtain Rayleigh wave phase velocity dispersion (PVD) information. In this scheme, we first use the principles of passive seismic interferometry to form multi-directional cross-correlations (CCs) then project the CCs onto a 1-D virtual array and apply the phase-shift transform as in MASW processing. We compare PVD information obtained by this method with those of the conventional beam-power based frequency–wavenumber decomposition (CVFK) method using ambient seismic noise (ASN) data collected by local-scale 2-dimensional (2D) arrays deployed at three selected sites in Bursa, Turkey. By analysing the ASN data from these sites, we show that similar multi-modal PVD curves can be obtained with the two methods over a broad frequency range (∼2-23 Hz) within the wavenumber resolution and aliasing limits. However, in one of our sites where the 2D array configuration has a considerable anti-symmetry, we show that the 1D virtual array used in the 2D PSI-MASW method has a better array response function in terms of wavenumber resolution and suppression of side-lobes leading to superior mode resolution and separation than that of the CVFK method, which shows strong directional variations. Furthermore, unlike the CVFK method, the 2D PSI-MASW method takes advantage of temporal stacking of CCs ensuring weak but coherent Rayleigh wave signals present in the ASN wavefield to be strengthened and has the potential for better extraction of PVD information. We conclude that by using a 2D array with spatial coverage providing a wide range of directions and distances, reliable PVD information can be obtained even if the ASN sources are not concentrated in the stationary phase zones. Thus, we suggest that the 2D PSI-MASW method is highly advantageous for the extraction of reliable PVD information owing to the multi-directional CCs provided by the 2D array configurations. We also report that using only a single receiver line in the interferometric approach results in biased and/or incomplete PVD information due to the non-isotropic ASN source distribution at all three sites we analysed. In conclusion, our results clearly indicate that the 2D PSI-MASW method can be used as complementary or alternative to the CVFK method to extract multi-modal Rayleigh wave PVD information in local-scale seismological studies.