Transmittance of lithium disilicate ceramic of different thicknesses and opacities with different curing units

The aim of this study was to evaluate the amount of radiating energy transmitted through lithium disilicate discs of different thicknesses and opacities with different curing units (CU). Discshaped specimens 8 mm in diameter and 1.5 mm or 0.7 mm thick were designed with Zbrush® and Cura 3D® software, milled from HT and MO IPS e-maxCAD blocks (Ivoclar Vivadent) with Ceramill Mikro 4 (Amann Girrbach, Austria) and processed according to manufacturer instructions. Thickness was checked with a Mitutoyo (México) caliper. Four groups (n=4) were formed: G1(HT/1.5 mm), G2(MO/1.5 mm), G3(HT/0.7 mm) y G4(MO/0.7 mm), and the effect of three CUs: Coltolux (ColteneWhaledent), LED.C, (Woodpecker Medical Instrument Co.Ltd) and Deepcure L(3M-ESPE) was tested Measurements were taken with a halogen and LED radiometer (Woodpecker® LM-1-Guilin Woodpecker Medical Instrument Co.Ltd) after applying the guide of each CU directly on the reading window (d) and after interposing each of the specimens. The ratio of transmitted energy was determined in each case and data was analyzed with repeated measures ANOVA and Tukey test for multiple comparisons. LED.C: d:1600 mW/cm2, G1: 0.31(0.00), G2: 0.14(0.00) G3: 0.54(0.01), G4: 0.38(0.01); Deepcure L: d:1500 mW/cm2, G1: 0.34(0.01), G2: 0.20(0,00), G3: 0.56(0.01), G4: 0.41(0.02); Coltolux: d:1275 mW/cm2, G1: 0.44(0.01), G2: 0.24(0,00), G3: 0.65(0.01), G4: 0.47(0,00). Statistically significant differences were found among the curing units (P<0.001) and for the interaction CU-thickness (P<0.001) CU-opacity (P=0.023). Within the conditions of this study, the ratio of light transmitted through lithium disilicate structures is related to their thickness and opacity, and to the curing unit employed.

Quality Assessment of Acquired GEDI Waveforms: Case Study over France, Tunisia and French Guiana

The Global Ecosystem Dynamics Investigation (GEDI) full-waveform (FW) LiDAR instrument on board the International Space Station (ISS) has acquired in its first 18 months of operation more than 25 billion shots globally, presenting a unique opportunity for the analysis of LiDAR data across multiple domains (e.g., forestry, hydrology). Nonetheless, not all acquired GEDI shots provide exploitable waveforms due to instrumental (e.g., transmitted energy, viewing angle) and atmospheric conditions (e.g., clouds, aerosols). In this study, we analyzed the quality of all available GEDI acquisitions over France, Tunisia, and French Guiana, in order to determine the extent of the impact of instrumental and climatic factors on the viability of these acquisitions. Results showed that with favorable acquisition conditions (i.e., cloud-free acquisitions), the factor with the highest impact on the viability of GEDI data is the acquisition time, as acquisitions around noon were the least viable due to higher solar noise. In addition to acquisition time, the viewing angle, the transmitted energy, and the aerosol optical depth all affected, to a lesser extent, the viability of GEDI data. Nonetheless, the percentage of exploitable cloud-free GEDI acquisitions ranged from 75 to 91% of all total acquisitions, depending on the acquisition site. The analysis of the quality of GEDI shots acquired in the presence of clouds showed that clouds have a greater impact on their exploitability, with sometimes as much as 69% of acquired data being unusable. For cloudy acquisitions, the two factors that mostly affect the LiDAR signal are the cloud optical depth (or cloud opacity) and cloud water content. Overall, nonviable GEDI data represent less than 50% of total acquisitions across the different instrumental, climatic, and environmental conditions.

Study on Dynamic Behavior and Energy Dissipation of Rock considering Initial Damage Effect

To explore the influence of initial damage on the dynamic characteristics of rock mass, the Φ 50 mm split Hopkinson pressure bar (SHPB) test system was used, and the uniaxial impact compression tests on yellow sandstone specimens with different damage degrees were conducted, and then the variation law of mechanical properties of rock specimens with the initial damage was determined. The test results show that the dynamic stress-strain curve of rock specimens with initial damage can be roughly divided into compaction stage, elastic deformation stage, crack evolution stage, and strain-softening stage; the higher the initial damage degree of rock mass, the more significant the compaction stage. With the increase of the initial damage degree, the dynamic elastic modulus and peak stress of rock mass decrease gradually in a power number, while the peak strain of rock mass increases exponentially. With the increase of the initial damage degree, both the reflected energy ratio and the dissipated energy ratio decrease linearly, while the transmitted energy ratio increases linearly; the increasing rate of the transmitted energy ratio is greater than the decreasing rate of the reflected energy ratio.

Information–Theoretic Radar Waveform Design under the SINR Constraint

This study investigates the information–theoretic waveform design problem to improve radar performance in the presence of signal-dependent clutter environments. The goal was to study the waveform energy allocation strategies and provide guidance for radar waveform design through the trade-off relationship between the information theory criterion and the signal-to-interference-plus-noise ratio (SINR) criterion. To this end, a model of the constraint relationship among the mutual information (MI), the Kullback–Leibler divergence (KLD), and the SINR is established in the frequency domain. The effects of the SINR value range on maximizing the MI and KLD under the energy constraint are derived. Under the constraints of energy and the SINR, the optimal radar waveform method based on maximizing the MI is proposed for radar estimation, with another method based on maximizing the KLD proposed for radar detection. The maximum MI value range is bounded by SINR and the maximum KLD value range is between 0 and the Jenson–Shannon divergence (J-divergence) value. Simulation results show that under the SINR constraint, the MI-based optimal signal waveform can make full use of the transmitted energy to target information extraction and put the signal energy in the frequency bin where the target spectrum is larger than the clutter spectrum. The KLD-based optimal signal waveform can therefore make full use of the transmitted energy to detect the target and put the signal energy in the frequency bin with the maximum target spectrum.

Energy Evolution Law of Ore-Bearing Rock during Unloading under High Static Stress and Frequent Disturbance

Based on the complex engineering environment in deep rock engineering, preloaded high axial pressure, unloading of axial pressure, and impact loading were used to simulate high in situ stress, unloading of excavation, and blasting disturbance, respectively; the experimental study on frequent impact disturbances under unloading of high static load was carried out, which aimed at revealing the energy evolution law of rock. First, the equations of elastic property, plastic energy, and incident energy in the impact process are discussed by theoretical analysis. Then, it is found by further investigation that dynamic stress-strain curve and envelope curve of rock are with the same change tendency. The initial stage was short straight stage, and then linear stage appeared and was less influenced by unloading rate. The plastic energy, the ratio of reflected energy to incident energy, and the energy consumption per unit volume of rock increase during impact. The higher the preloaded axial pressure is, the greater the ratio of reflected energy to incident energy is, the smaller the ratio of transmitted energy to incident energy and the average energy dissipation per unit volume of rock are. When the unloading rate increased, the elastic energy generated by impact gradually increased, the plasticity gradually weakened, the ratio of transmitted energy to incident energy increased, and the ratio of reflection energy to incident energy decreased.

Retrieval of Vertical Foliage Profile and Leaf Area Index Using Transmitted Energy Information Derived from ICESat GLAS Data

The vertical foliage profile (VFP) and leaf area index (LAI) are critical descriptors in terrestrial ecosystem modeling. Although light detection and ranging (lidar) observations have been proven to have potential for deriving the VFP and LAI, existing methods depend only on the received waveform information and are sensitive to additional input parameters, such as the ratio of canopy to ground reflectance. In this study, we proposed a new method for retrieving forest VFP and LAI from Ice, Cloud and land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) data over two sites similar in their biophysical parameters. Our method utilized the information from not only the interaction between the laser and the forest but also the sensor configuration, which brought the benefit that our method was free from an empirical input parameter. Specifically, we first derived the transmitted energy profile (TEP) through the lidar 1-D radiative transfer model. Then, the obtained TEP was utilized to calculate the vertical gap distribution. Finally, the vertical gap distribution was taken as input to derive the VFP based on the Beer–Lambert law, and the LAI was calculated by integrating the VFP. Extensive validations of our method were carried out based on the discrete anisotropic radiative transfer (DART) simulation data, ground-based measurements, and the Moderate Resolution Imaging Spectroradiometer (MODIS) LAI product. The validation based on the DART simulation data showed that our method could effectively characterize the VFP and LAI under various canopy architecture scenarios, including homogeneous turbid and discrete individual-tree scenes. The ground-based validation also proved the feasibility of our method: the VFP retrieved from the GLAS data showed a similar trend with the foliage distribution density in the GLAS footprints; the GLAS LAI had a high correlation with the field measurements, with a determination coefficient (R2) of 0.79, root mean square error (RMSE) of 0.49, and bias of 0.17. Once the outliers caused by low data quality and large slope were identified and removed, the accuracy was further improved, with R2 = 0.85, RMSE = 0.35, and bias = 0.10. However, the MODIS LAI product did not present a good relationship with the GLAS LAI. Relative to the GLAS LAI, the MODIS LAI showed an overestimation in the low and middle ranges of the LAI and a saturation at high values of approximately LAI = 5.5. Overall, this method has the potential to produce continental- and global-scale VFP and LAI datasets from the spaceborne lidar system.

An offshore Gulf of Mexico case study applying full-waveform inversion

Full-waveform inversion (FWI) is a high-resolution earth model-building technique based on recorded seismic data. Conventional FWI usually relies on diving and refracted waves to update the low-wavenumber/background components of the model; however, the update based on transmitted energy is often depth limited due to the limited offset range of the acquired data. To extend the FWI updating depth beyond the transmitted energy limits, we must use reflection data. Recently, industry interest has resumed in the potential for automated subsurface model-building, especially in complex geologic settings (e.g., salts), through data-driven minimization such as FWI. The business impact of such an automatic model-building technique would be significant in that it is proposed to improve the efficiency of any model-building exercise involving structural complexity and high uncertainty in seismic image interpretation. An ultimate expectation for the FWI technique is to build or update the salt geometry because these complex bodies have a first-order impact on image quality. We evaluate several examples using FWI for building a subsurface model, including salt boundary and salt velocity delineation, in geologically complex areas in the western Gulf of Mexico. The geology there comprises rugose and deformed shallow salt bodies with intracanopy high dip and close-proximity structures, resulting from regional basinward gliding and associated compressional mechanisms. Given the challenges for model building in such a complex setting, a data-fitting approach such as FWI with access to the full reflectivity record is proposed to provide practical solutions for an effective salt model update. Improving confidence in the seismic image and subsequent geologic understanding remains the core objective.

Concurrent Coding A Reason to Think Differently About Encoding Against Noise, Burst Errors and Jamming

Concurrent coding is an unconventional encoding technique that simultaneously provides protection against noise, burst errors and interference. This simple-to-understand concept is investigated by distinguishing 2 types of code open and closed with the majority of the investigation concentrating on closed codes. Concurrent coding is shown to possess an inherent method of synchronisation thus requiring no additional synchronisation signals to be added. This enables an isolated codeword transmission to be synchronised and decoded in the presence of noise and burst errors. Comparisons are made with the spread spectrum technique CDMA. With a like-for-like comparison concurrent coding performs comparably against random noise effects, performs better against burst errors and is far superior in terms of transmitted energy efficiency.