Wide angle reflections in OBC seismic physical model experiment

Wide angle acquisition has been taken as a significant measure to obtain high quality seismic data and is getting greater attention, In this paper, we discuss ocean bottom cable （OBC） seismic wide angle reflections on the basis of a layered model experiment. Some experiment results don＇t support theoretical conclusions. The main experimental conclusions are： 1. Wide angle reflection energies are stronger than non-wide-angle reflections （up to twice as strong） but there is a big difference between observations and theoretical calculations that suggest the wide angle reflection energies are 15 times the non- wide-angle reflection energy. The reflection energy increases gradually rather than sharply as the theoretical calculations suggest. 2. The reflection events remain hyperbolic when the offset increases. 3. Wide angle reflection dominant frequency is about 20-30% less than non- wide-angle reflections and decreases as the offset increases. The non-wide-angle reflection dominant frequency shows no obvious variation for small offsets. 4. There is no wave shape mutation or polarity reversal near the critical angle. 5. The reflection event group features are the same for both cases of incidence angle greater and less than the critical angle. 6. Direct arrivals, multiples, and water bottom refractions influence the wide angle reflections of the sea floor.

A NEW QUANTITATIVE WAY FOR DETERMINING LEAF AREA INDEX AND NET PRIMARY PRODUCTIVITY IN REGIONAL SCALE

An inversion of bidirectional reflection distribution fiJnedon (BRDF) wastested using NK Model and NOAA AVHRR datu. The test involVed sensitiveanalysis, optimum inversion selecting, ground simulated expenment, calibrahngmeasuremed with satellite and computer image processmg. Results of comparisonwith NDVI indicatal that inversion of BRDF will have brigh developing prospect inthe next decade.

Spectroscopic detection of forest diseases:a review(1970–2020)

Sustainable forest management is essential to confront the detrimental impacts of diseases on forest ecosystems.This review highlights the potential of vegetation spectroscopy in improving the feasibility of assessing forest disturbances induced by diseases in a timely and cost-effective manner.The basic concepts of vegetation spectroscopy and its application in phytopathology are first outlined then the literature on the topic is discussed.Using several optical sensors from leaf to landscape-level,a number of forest diseases characterized by variable pathogenic processes have been detected,identified and quantified in many country sites worldwide.Overall,these reviewed studies have pointed out the green and red regions of the visible spectrum,the red-edge and the early near-infrared as the spectral regions most sensitive to the disease development as they are mostly related to chlorophyll changes and symptom development.Late disease conditions particularly affect the shortwave-infrared region,mostly related to water content.This review also highlights some major issues to be addressed such as the need to explore other major forest diseases and geographic areas,to further develop hyperspectral sensors for early detection and discrimination of forest disturbances,to improve devices for remote sensing,to implement longterm monitoring,and to advance algorithms for exploitation of spectral data.Achieving of these goals will enhance the capability of vegetation spectroscopy in early detection of forest stress and in managing forest diseases.

Seismic volcanostratigraphy of large, extrusive complexes in continental rift basins of Northeast China：Analysis of general bedding patterns in volcanostratigraphy and their seismic reflection configurations

The aim of this work is to establish volcanic seismic reflection configuration models in the rift basins of Northeast China from a new perspective,the volcanostratigraphic structure.Accordingly,the volcanostratigraphic structure of an outcrop near the Hailaier Rift Basin was analyzed to understand the characteristics and causal factors of physical boundaries.Further,3D seismic reflection data and analysis of deep boreholes in the Songliao Rift Basin were used to establish the relationship between volcanic seismic reflection configurations and volcanostratigraphic structures.These studies suggested that in volcanic successions,physical boundaries coincide with volcanic boundaries,and their distributions are controlled by the stacking patterns of volcanic units.Therefore,volcanic seismic reflection configurations can be interpreted in terms of the stacking patterns of volcanic units.These are also referred to as general bedding patterns in volcanostratigraphy.Furthermore,four typical seismic reflection configurations were identified,namely,the chaotic,the parallel continuous,the hummocky,the multi-mound superimposed and the composite.The corresponding interpretation models comprised single massive unit,vertical,intersectional,lateral multi-mound,and composite stacking patterns.The hummocky and composite reflection configurations with intersectional and composite stacking patterns are the most favorable for the exploration of volcanic reservoirs in rift basins.

Altimetric Algorithm and Errors of Ocean Altimetry Using GNSS Reflection Signals

As a new remote sensing technology, the global navigation satellite system（GNSS） reflection signals can be used to collect the information of ocean surface wind, surface roughness and sea surface height. Ocean altimetry based on GNSS reflection technique is of low cost and it is easy to obtain large amounts of data thanks to the global navigation satellite constellation. We can estimate the sea surface height as well as the position of the specular reflection point. This paper focuses on the study of the algorithm to determine the specular reflection point and altimetry equations to estimate the sea surface height over the reflection region. We derive the error equation of sea surface height based on the error propagation theory. Effects of the Doppler shift and the size of the glistening zone on the altimetry are discussed and analyzed at the same time. Finally, we calculate the sea surface height based on the simulated GNSS data within the whole day and verify the sea surface height errors according to the satellite elevation angles. The results show that the sea surface height can reach the precision of 6 cm for elevation angles of 55° to 90°, and the theoretical error and the calculated error are in good agreement.

Novel single-transverse-mode control of VCSELs with dielectric mode filter

We establish a novel method of controlling the transverse modes of vertical cavity surface emitting lasers （VCSELs） to achieve 1 mW single-fundamental-mode lasing. A dielectric mode filter is installed on top of the VCSEL. The dielectric layer （SiO2） is deposited and patterned to modify the mirror reflectivity across the oxide aperture via antiphase reflections. This mode selection is nondestructive and universally applicable for other structures under single transverse mode. Destructive etching techniques （dry/wet） or epitaxial regrowth are also not required. This method simplifies the preparation process and improves the repeatability of the device. Measurements show that under continuous-wave current injection, the side-mode suppression ratio exceeds 30 dB.

Detection and Characterization of Defects in Additive Manufacturing by Polarization-Based Imaging System

Additive manufacturing (AM) technology such as selective laser melting (SLM) often produces a high refection phenomenon that makes defect detection and information extraction challenging. Meanwhile, it is essential to establish a characterization method for defect analysis to provide sufcient information for process diagnosis and optimization. However, there is still a lack of universal standards for the characterization of defects in SLM parts. In this study, a polarization-based imaging system was proposed, and a set of characterization parameters for SLM defects was established. The contrast, defect contour information, and high refection suppression efect of the SLM part defects were analyzed. Comparative analysis was conducted on defect characterization parameters, including geometric and texture parameters. The experimental results demonstrated the efects of the polarization imaging system and verifed the feasibility of the defect feature extraction and characterization method. The research work provides an efective solution for defect detection and helps to establish a universal standard for defect characterization in additive manufacturing.

GENERAL COUPLED MEAN-FIELD REFLECTED FORWARD-BACKWARD STOCHASTIC DIFFERENTIAL EQUATIONS

In this paper we consider general coupled mean-field reflected forward-backward stochastic differential equations(FBSDEs),whose coefficients not only depend on the solution but also on the law of the solution.The first part of the paper is devoted to the existence and the uniqueness of solutions for such general mean-field reflected backward stochastic differential equations(BSDEs)under Lipschitz conditions,and for the one-dimensional case a comparison theorem is studied.With the help of this comparison result,we prove the existence of the solution for our mean-field reflected forward-backward stochastic differential equation under continuity assumptions.It should be mentioned that,under appropriate assumptions,we prove the uniqueness of this solution as well as that of a comparison theorem for mean-field reflected FBSDEs in a non-trivial manner.

Control of visible‑range transmission and refection haze by varying pattern size,shape and depth in fexible metasurfaces

Cost-efective soft imprint lithography technique is used to prepare fexible thin polymeric surfaces containing a periodic arrangement of nanodimples and nanobumps of sub-micron size.Using a single master mold of self-assembled colloidal crystal,metasurfaces with diferent depths and heights of patterns with a fxed pitch are possible,which makes the process inexpensive and simple.These metasurfaces are studied for their difuse and total transmission and refection spectra in the visible range.The transmission haze and refection haze are calculated from the measurements.The surface containing nanobumps of lesser pattern height result in higher values of refection and transmission haze than from surfaces containing nanodimples of much higher depth for the same pitch.The haze is more dependent on the pattern depth or height and less dependent on the pitch of the pattern.Far-feld transmission profles measured in the same wavelength range from the patterned surfaces show that the scattering increases with the increase of the ratio of pattern depth/height to pitch,similar to the haze measurements conducted with a closed integrating sphere.These profles show that the angular spread of scattered light in transmission is within 10°,explaining the reason for the relatively low transmission haze in all the patterned surfaces.Simulation results confrm that the nanobump pattern gives higher transmission haze compared to nanodimple pattern.By controlling the ratio of pattern depth/height to pitch of the features on these surfaces,both an increase in optical haze and a balance between total refection intensity and total transmission intensity can be achieved.