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Wind velocity is of great importance for weather monitoring, aviation hazard alerting, wind energy exploring, etc. Doppler radar is widely used to measure wind under rainy condition by sensing the raindrops entrained by the background wind. However, the Doppler velocity, which is a reflection of the raindrops’ velocity in radial direction, is not coincident with the background wind because of the strong inertia of raindrops. Efforts should be made to distinguish the difference between the raindrops’ velocity and the background wind velocity. In this article, we try to establish a relationship between the background wind velocity and the raindrops’ velocity by introducing a definition of the raindrops’ characteristic size, which is related to the velocity characterized by the strongest Doppler spectral component. It is found that the fusion of differential reflectivity and the depolarization ratio can serve as a good proxy for the estimation of the characteristic size. Simulation results for $S$/$C$/$X$-band radars and radar measurements verify the good performance of the proposed retrieval model for the characteristic size, which lays a solid foundation for the retrieval of the background wind velocity.

This paper discusses the effects of cross-polar radiation on the calibration methods usually employed for the calibration of the differential reflectivity. It is shown that cross-polar radiation has significant effects when simultaneous transmission and reception of horizontal and vertical polarizations are used to obtain polarimetric measurements. Additionally, it is shown that propagation through a transpolarizing medium considerably affects the results.

The mean axis ratio (length/width) and the degree of orientation of cloud ice particles are retrieved from radar differential reflectivity (ZDR) and the copolar correlation coefficient (ρhv) measured with the S-band WSR-88D radar. Hardware differential phases and amplifications in the polarimetric channels affect measured ZDR and ρhv and are taken into consideration in the retrieval procedure. The retrieval is performed for particles in shapes of hexagonal prisms, which are closer to shapes of real cloud particles than frequently used spheroids. The median retrieved axis ratio for prisms is larger than that for spheroids. The statistical 1σ retrieval errors caused by fluctuations of radar returns are about 40% in areas of signal-to-noise ratios stronger than 10 dB. The values of the degree of orientation lie in an interval from 2° to 23°, which points to significant perturbations in the orientations of ice particles most likely caused by the wind field.

For any quantitative applications that use reflectivity and/or differential reflectivity, radar observations need to be compensated for attenuation effects due to precipitation. This paper presents a robust attenuation correction system (ACS) for dual-polarization radars correcting the reflectivity factor as well as differential reflectivity profiles. The major advantage of the algorithm described in this paper is that the procedures are immune to the bias effect of reflectivity and differential reflectivity. In addition, this method is not very sensitive to the variation of temperature. The proposed ACS has been evaluated with X-band radar observations simulated from drop size distribution derived from high-resolution S-band measurements observed by the CSU-CHILL radar. The evaluation of the proposed retrieval algorithm shows that the retrieved reflectivity and differential reflectivity provide an improvement over the conventional self-consistent attenuation correction technique with the differential phase constraint.

Clouds consist of water particles (hydrometeors) in different aggregate states. Above the melting layer these hydrometeors are formed mainly as ice crystals and other completely or partly frozen particles. With measurements from the C-band dual polarimetric radar POLDIRAD (Oberpfaffenhofen, Germany) the backscattered signals of the ice particles in the horizontal/vertical polarisation base were analysed. The focus is lying on the co-polar reflectivities and therefore the differential reflectivity. In the next step a simulation of the backscattered signals deliver the physical ansatz for the creation of an ice crystal class. Finally the comparison of this class with a raindrop classification is shown.

The method for the daily monitoring of the differential reflectivity bias for polarimetric weather radars is developed further. Improved quality control is applied to the solar signals detected during the operational scanning of the radar, which efficiently removes rain and clutter-contaminated gates occurring in the solar hits. The simultaneous reflectivity data are used as a proxy to determine which data points are to be removed. A number of analysis methods to determine the differential reflectivity bias are compared, and methods based on surface fitting are found superior to simple averaging. A separate fit to the reflectivity of the horizontal and vertical polarization channels is recommended because of stability. Separate fitting also provides, in addition to the differential reflectivity bias, the pointing difference of the polarization channels. Data from the Finnish weather radar network show that the pointing difference is less than 0.02° and that the differential reflectivity bias is stable and determined to better than 0.04 dB. The results are compared to those from measurements at vertical incidence, which allows us to determine the total differential reflectivity bias including the differential receiver bias and the transmitter bias.

It is shown that the scattering resonance effects in echoes from migrating birds are so strong that a 10% frequency deviation within S-band can result in more than 10-dB changes in reflectivity values. Differential reflectivity values from adjacent polarimetric WSR-88D weather radars operating at offset frequencies can differ by several decibels in “clear air” echoes.

We consider weather radar measurements at simultaneous transmission and simultaneous reception of horizontal and vertical polarizations and show that the degree of polarization at simultaneous transmit (ps) is related to differential reflectivity and copolar correlation coefficient at simultaneous transmit (namely, ZDRs and ρhys). We evaluate the potential of degree of polarization at simultaneous transmit for weather radar applications. Ultimately, we explore the consequences of adjusting the transmit polarization state of dual-polarization weather radars to circular polarization.

A method is described for adjusting the far-field polarization of an electronically steered phased-array antenna. In this method, the polarization of a small subset of array elements is switched in order to reduce far-field cross-polarization of the overall array. The technique is intended for antennas used in polarimetric radars that measure quantities such as differential reflectivity (Zdr) and specific differential phase (KDP). In particular, it is appropriate for lower cost arrays where only one transmit or receive polarization is active at a time. In such arrays, it will reduce the number of measurements needed by one-third. Analysis of the tradeoffs in the technique is presented as well as examples in hypothetical large arrays. Measured results are presented for a small 4×4 array.

The conventional technique for calibrating Zdr using natural scatterers is based on vertical-looking observations. In some operational weather radar, this method is not applicable because of mechanical constraints that prohibit vertical measurement or choices in the scanning strategies. A technique for calibrating Zdr based on properties of rain returns is proposed and analyzed. The technique is based on an examination of properties of differential reflectivity measurements collected at increasing elevations. Differential reflectivity observed in rain decreases with increasing elevation due to the increasing view angle. Using the hypothesis of uniform microphysical profiles below the bright band, deviations of the profile of differential reflectivity with elevation with respect to the theoretical profile can be used to detect and quantify the presence of a bias on differential reflectivity. To apply this concept in the presence of a nonuniform microphysical profile, the contribution of vertical changes in microphysics to Zdr variation in height is also accounted for. An error parameter associated with the estimated Zdr bias can be used as a quality indicator of the bias estimation; it allows definition of a criterion based on a threshold of root-mean-square error that permits acceptance or rejection of a Zdr bias estimation obtained with the proposed method. The technique is demonstrated using data collected by an operational weather radar at Arpa Piemonte (Italy) and evaluated using independent disdrometer measurement. Results show that under certain conditions discussed in the paper, this method can provide Zdr calibration within an accuracy of 0.1 dB.

A calibration procedure of differential reflectivity on the Weather Surveillance Radar-1988 Doppler (WSR-88D) is described. It has been tested on NOAA's modified WSR-88D research and development polarimetric radar and is directly applicable to radars that simultaneously transmit and receive waves having horizontal and vertical polarization.

Techniques for the absolute calibration of radar reflectivity Z and differential reflectivity ZDR measured with dual-polarization weather radars are examined herein. Calibration of Z is based on the idea of self-consistency among Z, ZDR, and the specific differential phase KDP in rain. Extensive spatial and temporal averaging is used to derive the average values of ZDR and KDP for each 1 dB step in Z. Such averaging substantially reduces the standard error of the KDP estimate so the technique can be used for a wide range of rain intensities, including light rain. In this paper, the performance of different consistency relations is analyzed and a new self-consistency methodology is suggested. The proposed scheme substantially reduces the impact of variability in the drop size distribution and raindrop shape on the quality of the Z calibration. The new calibration technique was tested on a large polarimetric dataset obtained during the Joint Polarization Experiment in Oklahoma and yielded an accuracy of Z calibration within 1 dB. Absolute calibration of ZDR is performed using solar measurements at orthogonal polarizations and polarimetric properties of natural targets like light rain and dry aggregated snow that are probed at high elevation angles. Because vertical sounding is prohibited for operational Weather Surveillance Radar-1988 Doppler (WSR-88D) radars because of mechanical constraints, the existing methodology for ZDR calibration is modified for nonzenith elevation angles. It is shown that the required 0.1–0.2-dB accuracy of the ZDR calibration is potentially achievable.

This paper experimentally and theoretically examines the scattering properties of simulated non-spherical hydrometeors including water oblates, ice oblates and ice sphere–cone-oblates, in terms of the backscattering cross-section and the differential reflectivity. The experimental measurements of the backscattering cross-sections of non-spherical hydrometeor samples were performed in the Electromagnetic Scattering Laboratory of China National Space Industrial Corporation. Meanwhile, the backscattering cross-sections have been computed with the transition (T) matrix method. The theoretical results are compared with the experimental data, showing that the calculations are consistent with the observations in general. Experimental and theoretical analyses indicate that the backscattering cross-section of non-spherical particles increases as the particle size parameter increases, and fluctuates when the sizes are larger under the effect of resonance scattering. Differential reflectivity Z DR of water oblates in natural rainfall is always greater than 0 dB whereas Z DR of hailstones may be negative. There is a good linear relationship between differential reflectivity and aspect ratio of a particle. These derivations agree with the literature and can be used to identify the presence of hail particles and distinguish between plate-type and columnar-type hydrometeors. In this study, the measuring experiment and the T-matrix method calculations for the scattering of simulated raindrop and ice particles are also briefly described.

Original article can be found at : http://www3.interscience.wiley.com/ Copyright Royal Meterological Society / John Wiley & Sons [Full text of this article is not available in the UHRA]

We have carried out an ultrafast time-resolved differential reflectivity study of a ferromagnetic semiconductor InGaMnAs and made a systematic comparison with low-temperature grown and high-temperature grown InGaAs reference films. Very short carrier lifetimes (∼2 ps) were observed in InGaMnAs and the low-temperature grown InGaAs film, but not in the high-temperature grown InGaAs film. We attribute the short lifetimes to carrier trapping by mid-gap states introduced during low-temperature MBE growth. Furthermore, at long times, we observed periodic oscillations in the differential reflectivity signal with period ∼20 ps, which we interpret as coherent acoustic phonons.

The rain attenuation was calculated by using the Marshall and Palmer, the gamma and the Weibull raindrop-size distributions. The microwave experimental measurement data from 8.4 GHz (3.75 mm) to 312.5 GHz (0.96 mm) were compared with our calculations. The Weibull distribution has the best agreement with the measurements, especially above 100 GHz. The differential reflectivity ZDR was also calculated using these three distributions. To this end, we used the horizontal and vertical radar cross sections which were computed from Waterman's T-matrix method. It is shown that ZDR greatly depends on raindrop-size distributions and has potential for determing drop-size distributions with high accuracy.

This report presents anterior segment optical coherence tomography (AS-OCT) images of Kayser-Fleischer ring (KFR) in a child. The AS-OCT images highlight differential reflectivity of the KFR depending on amount of copper deposited in cornea, thus supporting the role of AS-OCT as a follow-up tool. Utility of AS-OCT for diagnosing and documenting the KFR in children otherwise uncooperative for detailed slit lamp examination is discussed.

BACKGROUND AND OBJECTIVE: To assess the feasibility of intraoperative OCT (iOCT) during pars plana vitrectomy with subretinal tissue plasminogen activator (tPA) injection for subretinal hemorrhage. PATIENTS AND METHODS: Eyes that underwent vitrectomy and subretinal injection of tPA were identified from the PIONEER study, a prospective clinical study assessing the feasibility and utility of iOCT in ophthalmic surgery. A microscope-mounted spectral-domain OCT system was utilized for iOCT imaging. Standardized scan protocol and image acquisition were followed for intraoperative imaging. RESULTS: iOCT was successfully obtained in four of four eyes. In all cases, increased subretinal fluid was noted, with differential reflectivity visualized between the hemorrhage–tPA interface confirming appropriate localization of tPA injection. Image quality variability was significant. CONCLUSION: iOCT can successfully be performed during pars plana vitrectomy with subretinal tPA injection. Utilizing iOCT, appropriate placement of tPA solution and corresponding retinal architectural changes were visualized. [ Ophthalmic Surg Lasers Imaging Retina . 2015;46:327–332].

An historical review of the development of optical spectroscopy of surface states in semiconductors is presented. The importance of symmetry considerations and of polarization properties is emphasized.

We report on the detection of a loss-inducing perturbation with variable localization accuracy along a test fiber based on the analysis of transmitted and reflected powers of an unmodulated continuous-wave light source. The required accuracy of localization is provided by suitable distribution of the differential reflectivity along the fiber. The localization accuracy for a strong disturbance has been estimated as /spl plusmn/ 1.0 m along the 3.939-km single-mode test fiber and as /spl plusmn/ 5.0 mm along a designated 10-cm fiber part for both strong and weak perturbations.

Surface differential reflectivity together with photoemissioii and Auger electron spectroscopies have been applied to observe and identify optical transitions among surface related states on CdTe(110) surfaces. The strongest contributions to the band of optical transitions have been revealed at the photon energies of 2.8, 3.4, and 3.9 eV. Their correspondence to excitations from the occupied S1 band to the unoccupied U1 one at the Γ, Χ and Χ ' points of the surface Brillouin zone is discussed. PACS numbers: 73.20.-r, 78.66.Hf

Surface differential reflectivity experiments with polarised light have been carried out for cleaved and then oxidised CdTe(110) surfaces. It was shown that the optical anisotropy of the surface investigated is small and almost independent from photon energy. The interpretation of the spectra in terms of optical transitions between surface states is discussed.

While radars measure several quantities closely coupled to the rainfall rate, for frequencies less than 15 GHz, estimates of the rainwater content W are traditionally computed from the radar reflectivity factor Z or the rate of attenuation A--quantities only weakly related to W. Consequently, instantaneous point estimates of W using Z and A are often erroneous. A more natural, alternative parameter for estimating W at these frequencies is the specific polarization propagation differential phase shift phi(sub DP), which is a measure of the change in the difference between phases of vertically (V) and horizontally (H) polarized waves with increasing distance from a radar. It is now well known that W is nearly linearly related to phi(sub DP) divided by (1 - reversed R), where reversed R is the mass-weighted mean axis ratio of the raindrops. Unfortunately, such relations are not widely used in part because measurements of phi(sub DP) are scarce but also because one must determine reversed R. In this work it is shown that this parameter can be estimated using the differential reflectivity (Z(sub H)/Z(sub V) at 3 GHz. An alternative technique is suggested for higher frequencies when the differential reflectivity becomes degraded by attenuation. While theory indicates that it should be possible using phi(sub DP) to estimate W quite accurately, measurement errors increase the uncertainty to +/- 18%-35% depending on reversed R. While far from ideal, it appears that these estimates are likely to be considerably more accurate than those deduced using currently available methods.

The roughness of Si(111) surfaces induced by heating at temperatures between 900 and 1000°C is studied by differential reflectivity measurements. For the lowest temperatures, the stepped-roughness of the surface is smoothed out by annealing the surface, leading to an increase of reflectivity for light energies below 3 eV. For the highest temperatures, a larger scale roughness (of the order of several tens of nm) is formed at the surface. This roughness increases with temperature and induces essentially a scattering of light leading to a decrease of reflectivity in the UV range.

Multilayer laserscanner sensors measure a precise range profile of road traffic situations. Moreover, they are able to detect different reflectivities of object surfaces. In addition to object detection and object tracking, these sensory features enable a roadway and lane detection function without requiring additional sensors. A special multilayer laserscanner prototype has been developed for this purpose. The roadway detection is based on an identification of changes in the distance profiles pattern at the borders of roadways. A classification and tracking of reflection posts extends the effective range of the roadway detection and enhances its robustness. The lane detection makes use of the differential reflectivity of lane markings and road surface. The lane detection operates within a distance range of 4m up to 30m and has been tested on highway scenarios.

We have measured the time-resolved differential reflectivity (TRDR) signal of ZnO epilayers and nanorods as a function of temperature and excitation wavelength. Non-exponential decays are observed, and relaxation times depend strongly on excitation wavelength.

The polarimetric technique consists of simultaneous transmission and reception of Horizontally and Vertically polarized waves. Thus, transmitted polarization will be elliptical with equal horizontal and vertical components and arbitrary phase between the two. This scheme has been tested at NSSL on the NOAA research and development WSR-88D radar. Here reports on backscatter differential phase measurements with this radar. The radar also has a mode of transmitting horizontal polarization and receiving both the strong H and the weak V component (for short we refer to this mode as Linear Depolarization Ratio mode, LDR). Backscatter differential phase is considered a secondary polarimetric variable of lesser value for precipitation measurements than (the forward) specific differential phase or differential reflectivity. This is because backscatter differential phase is seldom significant. At 10 cm wavelength the only precipitation that can cause appreciable backscatter differential phase is hail. But it turns out that backscatter differential phase from other scatters provides two benefits. (1) it is suitable for discrimination between nonmeteorological scatters and precipitation and (2) it offers a way to calibrate (measure) the system differential phase. Of relevant and special importance is that, for some scatters, the measured total differential phase in the SHV scheme can differ from the value obtained in the sequential H, V scheme. The radar system contributes two distinct phases to the total differential phase. One is the differential phase in the transmission channel, the other is the differential phase in the receiver channel

In this paper we present an overview of the method of surface differential reflectivity (SDR) for the study of semiconductor surfaces. We will describe the principles of the technique and the experimental apparatus together with some theoretical considerations concerning the connection of SDR with the microscopic properties of the surface. In particular, the analysis of SDR is done in the frame of a macroscopic three layers model in which the media involved (vacuum, surface and substrate) are assumed to have definite anisotropic dielectric functions. A few experimental results, indicative of the potential of the technique, will be shown.

We investigate pump induced modulation in the temporal evolution of the excitonic coherent polarization generated by a probe pulse in GaAs multiple quantum wells. For this, we perform fs time resolved pump-probe reflectivity measurements using frequency upconversion at both positive and negative pump-probe delays. A contribution arising from interference of excitonic linear and nonlinear polarization, which is usually not considered in describing pump-probe experiments, is required to understand the results., Comment: 7 pages, 6 figures, submitted to Phys. Rev. B

Some interesting aspects of millimeter-wave (35, 94, 220 GHz) scattering properties of various types of ice crystals are presented. These ice crystals include three types of bullet rosettes which are compared with hexagonal columns and hexagonal plates. The elevation angle dependence of differential reflectivity and linear depolarization ratio for certain bullet rosettes show distinct signatures that are different than columns and plates.

International audience; Band structure calculations of complete InAs monolayer in AlGaAs/GaAs quantum wells are performed within the framework of the extended-basis sp3d5s* tight-binding model. We show that the optical properties can be tuned from the quantum well energy below the GaAs band-gap depending on the well thickness and the position of the probe. The results are supported by differential reflectivity measurements and represent a concept for optoelectronic devices with an operation wavelength widely tuneable around 850 nm employing GaAs process technology.

Angle-resolved photoelectron spectroscopy and surface differential reflectivity have been used to study the electronic structure of Si(100):Sb-1\ifmmode\times\else\texttimes\fi{}1 and Si(100):Sb-2\ifmmode\times\else\texttimes\fi{}1 surfaces. For both surfaces, one occupied surface-state band has been mapped along the [010] and [011] directions. Both surfaces show a semiconducting behavior with a gap of 1.6 eV for the 1\ifmmode\times\else\texttimes\fi{}1-Sb and 1.4 eV for the 2\ifmmode\times\else\texttimes\fi{}1-Sb surface. A minimum-energy position at the Fermi level is derived for the empty surface-state band. The results are also compared with those obtained for the clean Si(100)2\ifmmode\times\else\texttimes\fi{}1 surface.

A brief account of the most important experimental and theoretical methods employed in surface physics is given. The use of optical spectroscopy in the study of clean semiconductor surfaces is described in detail.

New accurate surface differential reflectivity data of the GaAs and GaP cleavage faces are presented. Surface state transitions have been detected near 2.9 eV in GaAs(110), while in GaP(110) they appear at 2.8 and 3.5 eV. In both cases a small bulk-like Franz-Keldish effect is superimposed on the surface contribution to differential reflectivity. A method for subtracting this term out is described. The relevance of the present results in the context of the debate on surface excitons is also discussed.

The statistical characteristics of three estimators of the differential reflectivity (ZDR) radar signal are examined theoretically and compared with pulse-to-pulse measurements of reflectivity at horizontal and vertical polarizations. The square-law and log-ratio estimators provide satisfactory means for measuring ZDR while the log-ratio estimator does not. In addition, the theory is consistent with radar data, clearly showing that ZDR could be measured accurately from a sequence of alternately polarized waves.

A novel approach to making differential reflectivity measurements in multiple polarization planes has been proposed. This paper describes a versatile technique using a mechanical polarization switch and the systematic errors in differential reflectivity measurements which result. Initial results of simultaneous X band slant path measurements of attenuation and depolarization at 11.6 GHz and differential reflectivity measurements at 2.8 GHz using a slow polarization switch are presented.

Calculations have been made of the radar backscattering, differential reflectivity, and circular depolarization ratio of large oblate spheroids composed of spongy ice. Results are compatible with laboratory measurements by earlier investigators. As expected, scattering of 10-cm radiation depends to an important extent on the size, water content, and axial ratios of the spheroids. Observations of differential reflectivities close to zero in hailstorms can be explained, as was done by V. N. Bringi and his associates, as resulting from the irregular shapes and tumbling of hailstones. But such observations could also be explained by size-distributed oblate spheroids with equivalent diameters greater than about 3.5 cm, falling with vertical symmetry axes.

Backscatter amplitude ratios are defined for horizontal and vertical polarizations. These new parameters of linear polarization provide not only a coherent interpretation of the magnitude of the cross-correlation function between horizontally and vertically copolarized backscattered signals (ρL) but also give new meaning and applications for differential reflectivity (ζ). In particular, it is demonstrated that ρL and ζ can be used to determine the mean and variance of the amplitude ratios. In rain these quantities can be transformed into estimates of the mean and variance of drop axis ratios. This information can potentially improve polarization estimates of rainfall, provided ρL is measured accurately. Amplitude ratios also appear to be useful for investigating melting processes. Measurements indicate the presence of prolate-like scatterers even where ζ is greater than unity in some bright bands. It is hypothesized that this scattering from apparent prolates is, at least in part, a result of the...

The potential use of differential reflectivity measurements at orthogonal polarizations to determine rain-fall rate is examined. The method involves measurements of ZH and ZV, the radar reflectivity factors due to horizontally and vertically polarized incident waves respectively. The differential reflectivity, ZDR = 10 log (ZH/ZV), which should be precisely determinate, occurs as a result of the distortion of raindrops as they fall at terminal velocity. The approximate theory of Gans for electromagnetic scattering by spheroids is applied to the distorted raindrops. Assuming a general exponential form for the raindrop size distribution, equations are derived relating the distribution parameters to the measurements. The determination of rainfall rate follows directly. Finally, the sensitivity of the distribution parameters to radar inaccuracies is examined, and several methods of implementing the measurements are suggested. It is concluded that good estimates of rainfall rate using a single non-att...

We compute the optical properties of semiconductor surfaces starting from the self-consistent electronic structures determined using local pseudopotentials with a plane-wave basis set. Calculations for a 9 layer (110) slab of GaP are carried out with both clean and H covered surfaces. Differential reflectivity spectra and their anisotropies are interpreted in terms of transitions involving surface states.

An overview of the method of surface differential reflectivity (SDR) for the study of semiconductor surfaces is presented. This includes the principles of the technique, the experimental apparatus, and some theoretical considerations concerning the connection of SDR data with the microscopic properties of the surface. Experimental results are also presented as an example of the application of this spectroscopy to the study of semiconductor surfaces.

The optical properties of the GaAs(110) surface are studied by means of self-consistent local-density slab calculations. It is found that a large contribution to the calculated anisotropy of the clean surface reflectance is related to transitions which do not involve surface states. Comparison is made with differential reflectivity and reflectance anisotropy experiments.

We present a determination of surface dielectric functions (SDF) of Si(111)2×1, Ge(111)2×1, GaAs(110) and GaP(110) surfaces obtained using polarized surface differential reflectivity (SDR) technique.

Multiple parameter radar measurements (dual frequency hail signal DFR-HS or differential reflectivity ZDR) can be strongly affected by the mismatch of the antenna illumination functions at the two wavelengths or polarizations. The resulting instrumental error can be estimated, with some approximations, from the independently measured reflectivity at one wavelength or polarization by using the actual radar illumination functions. This objective estimation of the antenna-induced error is made in some real cases and its possible conseqences on the data analysis are discussed.

The results of an investigation by differential reflectivity of the reflectivity change due to the deposition of small amounts of Ag (10 to 200 A) on a cold (140 K) polycrystalline smooth Ag substrate are presented. The modifications of the optical properties due to the roughening of the surface are analysed, the annealing of the deposited Ag overlayers is investigated and their relationship with Surface-Enhanced Raman Scattering (SERS) is discussed Etude des variations de la reflectivite dues au depot de faibles quantites d'Ag (10 a 200 A) sur un support lisse d'Ag polycristallin refroidi a 140 K. Analyse des modifications des proprietes optiques causees par la rugosite a la surface et du recuit des couches d'argent; discussion de leur relation avec la diffusion Raman «geante»

Processing of simultaneous measurements of differential polarization parameters (differential reflectivity, ZDR, and differential phase shift, ϕDP) and Doppler spectral moments is discussed. It is shown how ZDR and ϕDP modulate the Doppler signal and what effects they have on the autocovariance at lag 1 if a sequence of alternately polarized fields (linear horizontal, H, and vertical, V) is transmitted. A scheme to overcome these effects is proposed and demonstrated on recorded time series data from a radar with polarization diversity.

A grazing incidence monochromator has been constructed using the principle of differential reflectivity for order sorting. Some difficulties associated with earlier designs of this type have been solved and various refinements incorporated. The instrument includes a phase grating of the laminar type, as developed for use in the X-ray region. Details of the design and construction of the monochromator together with measurements of performance are reported, and a comparison with the calculated properties of the grating and optical system is made.