Iso-radioactivity curves of the water of the Hazar Lake, Elazig, Turkey

Alpha and beta radioactivity concentrations have been determined in the Hazar Lake (East of Turkey) surface, middle and bottom water. The total alpha-radioactivity concentration in the surface, middle and bottom levels varies from 0.32 to 2.52 Bq/l, from 0.21 to 2.70 Bq/l and from 0.12 to 0.96 Bq/l, respectively. The beta-radioactivity concentration in the surface, middle and bottom water levels varies from 0.01 to 0.16 Bq/l, from 0.01 to 0.27 Bq/l and from 0.03 to 0.23 Bq/l, respectively. The iso-radioactivity curves were drawn from the obtained data during 1998–2001. This revised version was published online in July 2006 with corrections to the Cover Date.     

Assessment of turbulent spectral bias in laser Doppler velocimetry

A critical evaluation is made of the spectral bias which occurs in the use of a laser Doppler velocimeter (LDV). In order to accommodate the randomly sampled LDV data, statistical treatments of particle arrival times are needed. This is modeled as a doubly stochastic Poisson process which includes the intensity function of the velocity field. Three processing algorithms are considered for spectral estimates: the sample and hold method (SH), the modified Shannon sampling technique (SR), and the direct transform (RG). Assessment is made of these for varying data densities (0.05 ≤ d.d ≤ 5) and turbulence levels (t.i.=30%, 100%). The effects of the values of the Reynolds stress coefficients and the transversal standard deviation on the spectral contents were examined. As an improved version of the spectral estimator, the utility of POCS (the projection onto convex sets) has been tested in the present study. This algorithm is found useful to be in the region when d.d. ? 3.     

Accumulative uncertainties in the quantitative evaluation of signals from fish

The accuracy of the acoustical method used in quantitative assessment of fish populations is mainly dependent on the measurement of the time varying echo signals and the evaluation of the fish target strengths. Various types of accumulative uncertainties involved in the measurement and estimation of different physical variables associated with the two way propagation of the acoustic signals between the fish target and the echo sounder system are investigated in this paper. The accumulative uncertainties are so high that an attempt to obtain an accuracy of, say, 0.5 dB in the conventional target strength calibration routines would have little meaning for any practical fishstock assessment survey. A new dynamic calibration method is proposed and discussed.     

A coupled-channels treatment of the positive-parity resonances in4He

The coupled-channels formalism, which has been previously applied successfully to interpret the negative-parity resonances in⁴He, has now been extended to the positiveparity 2?ω resonances in this system. The 1p-1h approach has been modified to include coupling to the 2p-2h configurations, which also belong to 2?ω excitations, by using the effective operator formalism. The effect of the Pauli term in thes-wave channel is examined and is found to be important in reproducing the 0⁺,T=0 resonance energy and width. Resonances with spins up toJ ^π=3⁺ have been studied, and the agreement with available data is satisfactory. In particular, from the good fit to the asymmetry coefficientβ(E), one establishes the presence of a 2⁺,T=0 resonance around 35-MeV excitation in the system.     

General semi-classical method for collective motion and its connection with the Rowe-Basserman and marumori theories,and adiabatic limits

In recent work, we have shown that in the adiabatic limit (large amplitude, small momentum), time-dependent Hartree-Fock theory (TDHF) yields a well-defined theory of large-amplitude collective motion which provides an essentially unique construction for a collective hamiltonian. An alternative theory, put forward by Rowe and Basserman and by Marumori is, apparently, not restricted to small momenta. We describe a general framework for the study of collective motion in the semi-classical limit without limitation on the size of coordinates or momenta, which includes all previous methods as limiting cases. We find it convenient, as in the past, to consider two general systems: first, a system with n degrees of freedom and no special permutation symmetry, and, second, a system of fermions described in TDHF. For both systems the problem can be formulated as a search for a hamiltonian flow confined to a finite-dimensional hypersurface in a phase space, which itself may be finite- or infinite-dimensional. Though, in general, there are no exact solutions to this problem, we can formulate consistent approximation schemes corresponding to both the adiabatic and Rowe-Basserman, and Marumori limits. We also show how to extend the momentum expansion, which underlies the adiabatic approximation, to higher orders in the momentum. We thereby confirm the structure of the theory found in our previous work.     

Effect of interference between anisotropic scattering entities on light scattering from polymer films. II. The correlation function approach

A theory is developed by use of the correlation function approach for calculating both the H_v and V_v intensity of scattered light for a concentrated assembly of spherulities. The scattering becomes a function of the radial and tangential polarizabilities of the spherulite α_r and α_t, the polarizability α_m of the medium, surrounding the spherulites, and the volume fraction ?_s of spherulites. The “effective polarizability of the surroundings” α_s, which appeared in previous theories, becomes function of these variables. The theory can explain, for example, why the V_v scattered intensity passes through a maximum during the course of crystallization.     

Analysis of machining characteristics in electrochemical etching using laser masking

Electrochemical etching using laser masking (EELM), which is a combination of laser beam irradiation for masking and electrochemical etching, allows the micro fabrication of stainless steel without photolithography technology. The EELM process can produce various micro patterns and multilayered structures. In this study, the machining characteristics of EELM were investigated. Changes in characteristics of recast layer formation and the protective effect of the recast layer according to the laser masking conditions and electrochemical etching conditions were investigated by field emission scanning electron microscopy (FE-SEM), focused ion beam (FIB) and X-ray photoelectron spectroscopy (XPS). The oxidized recast layer with a thickness of 500 nm was verified to yield a superior protective effect during electrochemical etching and good form accuracy. Finally, micro patterns and structures were fabricated by EELM.     

Transition of metallic and insulating Ti sub-oxides in bipolar resistive switching TiO x /TiO y frameworks due to oxygen vacancy drifts

Bilayer TiO _x (oxygen rich, region 1)/TiO _y (oxygen poor, region 2) homojunctions were evaluated as resistive switching elements where the TiO _x layers were designed with various oxygen contents. Depending on the oxygen ion content, controllable memory windows were observed by changing the off-state (high-resistance state), while the on-state (low resistance) was left with very little change. The cause of the variable memory windows in resistive switching phenomena appears to be the increasing amounts of movable oxygen ions between the TiO _x and TiO _y layers. In addition, the X-ray photoelectron spectroscopy measurements of the initial, low resistance, and high-resistance states in the homojunctions demonstrated the possible change of metallic and insulating Ti sub-oxide phases at the interfaces and oxygen ion rich region due to the migration of oxygen ions.