基于Sandmeier模型的月球KAGUYA卫星高光谱数据地形校正

月球是人类深空探测的前哨站。月球卫星光谱测量是月表岩矿成分分析的主要技术方法。鉴于月表比地球地形起伏还要显著,有必要开展月球卫星高光谱数据的地形校正。通过顾及宏观地形起伏和周围地形反射辐射的影响,建立适合月表的Sandmeier辐照度模型,并由此推到了月表反射率地形校正模型。以月球虹湾地区KAGUYA卫星Spectral Profiler(SP)高光谱数据为例,借助美国Lunar Orbiter Laser Altimeter(LOLA)高程数据,计算了试验区坡度、坡向,以及入射角、反射角、地形可见因子等地形校正参数,结合平坦月表接收的太阳直接辐照度,实现了月球虹湾地区经向SP数据的反射率校正。通过比较发现,校正后反射率像元数量统计直方图近似高斯分布,而且光照区的月表反射率得到了抑制,阴影区的月表反射率有所增强,有效地消除了月表起伏地形的影响。     

Characterization of LSGM films obtained by electrophoretic deposition (EPD)

The application of the electrophoretic deposition (EPD) technique to the preparation of high quality electrolyte films for intermediate temperature solid oxide fuel cells (IT-SOFCs) was investigated. Films of La_0.83Sr_0.17Ga_0.83Mg_0.17O_2.83 (LSGM) were deposited on Pt and La_0.8Sr_0.2MnO₃ (LSM) substrates from suspensions in acetone/ethanol (3:1 by volume) mixture solvent and sintered at 1300 °C. Pt supported LSGM films, 10–20 μm thick, exhibited good adhesion to the Pt substrate, well-distributed microporosity and some surface roughness. LSM supported films exhibited cracking after sintering at 1300 °C for 3 h. Up to 900 °C the bulk conductivity of the Pt supported LSGM film showed the same behaviour of LSGM pellet (E_a = 0.93 eV and 0.99 eV, respectively). The LSGM film exhibited lower bulk electrical conductivity than the latter (4.1 × 10^− 3 and 4.4 × 10^− 2 Ω^− 1 cm^− 1, respectively, at 700 °C). This difference should be ascribed to the slight Ga depletion in the LSGM film. An important issue remains the selection of adequate electrode for LSGM electrolyte films.     

Optical properties of one-dimensional photonic crystals obtained by micromatchining silicon (a review)

The theoretical and experimental investigations of photonic band gaps in one-dimensional photonic crystals created by micromatchining silicon, which have been performed by the author as part of his doctoral dissertation, are presented. The most important result of the work is the development of a method of modeling photonic crystals based on photonic band gap maps plotted in structure–property coordinates, which can be used with any optical materials and in any region of electromagnetic radiation, and also for nonperiodic structures. This method made it possible to realize the targeted control of the optical contrast of photonic crystals and to predict the optical properties of optical heterostructures and three-component and composite photonic crystals. The theoretical findings were experimentally implemented using methods of micromatchining silicon, which can be incorporated into modern technological lines for the production of microchips. In the IR spectra of a designed and a fabricated optical heterostructure (a composite photonic crystal), extended bands with high reflectivities were obtained. In a Si-based three-component photonic crystal, broad transmission bands and photonic band gaps in the middle IR region have been predicted and experimentally demonstrated for the first time. Si–liquid crystal periodic structures with electric-field tunable photonic band-gap edges have been investigated. The one-dimensional photonic crystals developed based on micromatchining silicon can serve as a basis for creating components of optical processors, as well as highly sensitive chemical and biological sensors in a wide region of the IR spectrum (from 1 to 20 μm) for lab-on-a-chip applications.     

Mass distribution of meteoroids obtained by a meteor forward-scatter (MFS) radar method

Summary The cumulative distributions of the numbervs. duration of echoes belonging to main meteor showers (Lyrids, ν-Aquarids, δ-Aquarids, Perseids, Orionids, Leonids, Geminids) and sporadic background were investigated using a forward-scatter (FS) continuous-wave (CW) meteor radar link operational during 1992–95 over the long baseline Bologna-Lecce in Italy. The trend of the mass distribution of particles in the quoted meteoroid streams was derived, and the values of the mass indexs were compared for each meteor population with the steady-state condition (s<11/6). It was found that the mass indexs generally increases towards long-duration echoes, but many of the observed meteor streams appear to have unstable populations. The values of the mass index of the sporadic complex are generally higher (2.07≤s≤ 2.57) than the corresponding ones of meteor showers in the range of echo durations 0.1≤T≤10 s. This is a possible consequence of longer-lasting FS signals, indicating a shift of the mass distribution functionvs. higher echo durations. Moreover, non-gravitational forces in connection with solar radiation pressure, Poynting-Robertson effect, solar-wind particle streaming, mutual collisions, etc., appear to be responsible for the observed widespread radiants and for unstable populations in the meteoroid streams.     

High-pressure phases in nanocrystalline Co(C) films obtained by pulsed plasma vaporization

The phase composition of nanocrystalline Co(C) films obtained by a new pulsed plasma vaporization technique was found by studying their atomic structure and magnetic properties. The films deposited at the substrate temperature T=50°C were of heterophase structure and consisted of a supersaturated solid Co(C) solution and the metastable Co₃C carbide. The films obtained at T=150°C represented a mechanical mixture of the metastable Co₃C and Co₂C carbides. The metastable Co₃C and Co₂C carbides obtained in a nanocrystalline state were high-pressure phases (～100 kbar). The thermal stability ranges of these metastable phases were determined.     

Thoughts about next-generation (S)TEM instruments in science

Different aspects of desirable developments in (scanning) transmission electron microscopes are discussed. Topics are the issues with closed data and control channels, the fixed optical design, and the layout of the sample environment. A solution concept to some of these issues on the basis of current technology and already demonstrated concepts is presented and future possibilities in in situ and multi-dimensional microscopy with the new concept are laid out.     

CdS thin films obtained by thermal treatment of cadmium(II) complex precursor deposited by MAPLE technique

Thin films of [Cd{SSi(O-Bu^t)₃}(S₂CNEt₂)]₂, precursor for semiconducting CdS layers, were deposited on silicon substrates by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. Structural analysis of the obtained films by Fourier transform infrared spectroscopy (FTIR) confirmed the viability of the procedure. After the deposition of the coordination complex, the layers are manufactured by appropriate thermal treatment of the system (thin film and substrate), according to the thermal analysis of the compound. Surface morphology of the thin films was investigated by atomic force microscopy (AFM) and spectroscopic-ellipsometry (SE) measurements.     

Hydrogen isotope exchange in a coverage obtained on Ir(111) by ethylene adsorption

HREELS and SIMS studies of hydrogen isotopc exchange in a coverage obtained on Ir(111) by ethylene adsorption are carried out at 180–450 K and at a hydrogen (deuterium) pressure up to 8×10⁶ Pa. The ethylidyne species have shown a high stability towards hydration and structural changes upon hydrogen (deuterium) exposures. Under these conditions hydrogen exchange in the methyl groups is a slow process. With increasing temperature the hydrogen exchange in the decomposition products of ethylidyne (C₂H species) is quick and depends on the exchanged amount of atomically adsorbed hydrogen.     

New localized structures of a (2+1)-dimensional system obtained by variable separation approach

Starting from a quite universal formula, which is obtained by variable separation approach and valid for many (2+1)-dimensional nonlinear physical models, a new general type of solitary wave, i.e., semifolded solitary waves (SFSWs) and semifoldons, is defined and studied. We investigate the behaviors of the interactions for the new semifolded localized structures both analytically and graphically. Some novel features or interesting behaviors are revealed.     

Oxides of long carbon chains: Results obtained on IR and UV-vis absorptions

The IR and UV-vis absorptions of oxides of long carbon chains trapped in cryogenic matrices were investigated experimentally and theoretically. Some of the IR-lines were assigned to the oxides of certain carbon chains using the method of isotopic substitution of matrix material (¹⁶O₂/¹⁸O₂, ¹²CO/¹³CO) and the technique of selective UV-vis photo-bleaching. Our data, along with quantum chemical calculations suggest that the wavelength positions of the major UV-vis and IR absorptions of the oxides C_nO, OC_nO, and of the parent carbon chains C_n are located in close vicinity.     

T(1)--T(2) correlation spectra obtained using a fast two-dimensional Laplace inversion

Spin relaxation is a sensitive probe of molecular structure and dynamics. Correlation of relaxation time constants, such as T(1) and T(2), conceptually similar to the conventional multidimensional spectroscopy, have been difficult to determine primarily due to the absense of an efficient multidimensional Laplace inversion program. We demonstrate the use of a novel computer algorithm for fast two-dimensional inverse Laplace transformation to obtain T(1)--T(2) correlation functions. The algorithm efficiently performs a least-squares fit on two-dimensional data with a nonnegativity constraint. We use a regularization method to find a balance between the residual fitting errors and the known noise amplitude, thus producing a result that is found to be stable in the presence of noise. This algorithm can be extended to include functional forms other than exponential kernels. We demonstrate the performance of the algorithm at different signal-to-noise ratios and with different T(1)--T(2) spectral characteristics using several brine-saturated rock samples.     

Ultrasonic characterization of granites obtained from industrial quarries of Extremadura (Spain)

The industry of ornamental rocks, such as granites, represents one of the most important industrial activities in the region of Extremadura, SW Spain. A detailed knowledge of the intrinsic properties of this natural stone and its environmental evolution is a required goal in order to fully characterize its quality. In this work, two independent NDT acoustic techniques have been used to measure the acoustic velocity of longitudinal waves in different prismatic granitic-samples of industrial quarries. A low-frequency transceiver set-up, based on a high-voltage BPV Steinkamp instrument and two 50 kHz probes, has been used to measure pulse travel times by ultrasonic through-transmission testing. In complementary fashion, an Erudite MK3 test equipment with an electromagnetic vibrator and two piezoelectric sensors has also been employed to measure ultrasonic velocity by means of a resonance-based method, using the same types of granite varieties. In addition, a comprehensive set of physical/mechanical properties have also been analyzed, according to Spanish regulations in force, by means of alternative methods including destructive techniques such as strength, porosity, absorption, etc. A large number of samples, representing the most important varieties of granites from quarries of Extremadura, have been analyzed using the above-mentioned procedures. Some results obtained by destructive techniques have been correlated with those found using ultrasonic techniques. Our experimental setting allowed a complementary characterization of granite samples and a thorough validation of the different techniques employed, thus providing the industry of ornamental rocks with a non-destructive tool that will facilitate a more detailed insight on the properties of the rocks under study.     

High-phase-conjugate reflectivity (<800%) obtained by degenerate four-wave mixing in a continuous-wave diode-side-pumped Nd:YVO(4) amplifier

High-phase-conjugate reflectivities of >800% have been achieved through degenerate four-wave mixing in a cw diode-side-pumped Nd:YVO(4) amplifier. Reflectivity curves are shown as a function of input pump-beam intensity for three values of small-signal amplifier gain, and comparison is made with a numerical simulation.     

La(Fe,Si)13-based magnetic refrigerants obtained by novel processing routes

The structure and magnetic properties of LaFe_13−xSi_x and Co-substituted LaFe_11.8−xCo_xSi_1.2 alloys prepared by melt spinning, as well as of LaFe_11.57Si_1.43H_x hydrides prepared by reactive milling are investigated. The hysteresis in the temperature- and field-induced phase transitions is significantly reduced as compared with conventional bulk alloys, which makes these materials very attractive for magnetic refrigerant applications. The unusual combination of features characteristic of first- and second-order phase transitions in the La(Fe,Si)₁₃-based compounds is discussed on the basis of density-functional electronic structure calculations.     

Boson realizations for Sp(4) obtained from seniority-dictated similarity transformations

Similarity transformations are obtained which facilitate the construction of boson realizations of Sp(4) which directly link seniority and boson number. The boson number dependent terms which are encountered in IBM-operators of which the structure has been supported partly by microscopical considerations, appear here in a natural way.     

Optical phonons in Ge quantum dots obtained on Si(111)

The Raman light scattering from optical phonons of Ge quantum dots grown by molecular beam epitaxy on a Si(111) surface is studied. A series of Raman lines related to the quantization of phonon spectrum is observed. It is shown that phonon frequencies are adequately described in terms of the elastic properties and the dispersion of the optical phonons of bulk Ge. The strain experienced by the Ge quantum dots is estimated.     

La(Fe,Si)13-based magnetic refrigerants obtained by novel processing routes

The structure and magnetic properties of LaFe_13−xSi_x and Co-substituted LaFe_11.8−xCo_xSi_1.2 alloys prepared by melt spinning, as well as of LaFe_11.57Si_1.43H_x hydrides prepared by reactive milling are investigated. The hysteresis in the temperature- and field-induced phase transitions is significantly reduced as compared with conventional bulk alloys, which makes these materials very attractive for magnetic refrigerant applications. The unusual combination of features characteristic of first- and second-order phase transitions in the La(Fe,Si)₁₃-based compounds is discussed on the basis of density-functional electronic structure calculations.     

Hard magnetic properties of nanosized Sr(Fe,Al)12O19 hexaferrites obtained by Pechini method

In this work, we report the magnetic properties of isotropic M-type SrFe_12−xAl_xO₁₉ (x=0.0,1.5) hexaferrites synthesized by means of Pechini method. A polycrystalline distribution of fine grains was verified by Transmission Electron Microscopy for both compositions, with average sizes below 60 nm. Remarkable coercivity values within the range 500–850 kA/m were attained as a consequence of a combined effect of grain size refinement together with an enhancement of the anisotropy field afforded by the incorporation of the Al³⁺ cations into the hexagonal crystal structure.     

On the factors determining the pyrophoric stability of tungsten nanopowder obtained by plasma-chemical pyrolysis of W(CO)6

Nonpyrophoric tungsten powders with an average particle size of about 30 nm were obtained by pyrolysis of tungsten hexacarbonyl in a flow of microwave discharge nitrogen plasma. It is found that these powders are stable in air up to 300°C. The reason for such stability is that the structure of powder particles is of the core-double shell type, in which the metal core is covered with an oxide film approximately 1 nm in thickness, coated in turn with roentgenoamorphous layer consisting of carbon, oxygen, and nitrogen atoms. It is also established that the powders under investigation mainly release carbon oxides (CO and CO₂) and water into the gas phase upon heating in vacuum. Among the molecules present in the gas phase in small concentrations, nitrogen monoxide (NO) and formaldehyde (H₂CO) are worth mentioning apart from C1–C3 hydrocarbons.     

Results of studying metamorphic rock samples (Outokumpu,Finland Borehole) by the acoustic polarization method

When studying the elastic properties of anisotropic solid media, it is necessary to determine the spatial orientation of the elastic symmetry elements. This is particularly important for randomly inhomogeneous elastically anisotropic media, such as rock. By applying the acoustic polarization method, the possibility of determining the direction of the symmetry elements of deep rock samples extracted from the Outokumpu, Finland borehole was demonstrated. The anisotropy indices of samples were obtained, calculated from the velocity values of longitudinal and transverse waves. Additional inelastic effects were revealed that are widespread in rock.