Inversion Stage Research Articles

A time-domain multisource Bayesian/Markov chain Monte Carlo formulation of time-lapse seismic waveform inversion

Seismic waveform inversion has been shown to be well-suited for identification and characterization of time-lapse changes in a reservoir. However, the subtle medium variations associated with enhanced oil recovery and/or [Formula: see text] storage problems give uncertainty quantification within such inverse approaches a heightened importance. To analyze both of these features of the time-lapse inverse problem, we formulate a Bayesian full-waveform inversion (FWI) procedure, based on a Markov chain Monte Carlo (MCMC) algorithm. The formulation uses several existing strategies, such as the use of a double-difference time-lapse FWI (DDFWI), incorporation of time-domain multisource data, and application of a local-updating target-oriented inversion. However, it incorporates these within a stochastic framework, involving computation of model covariance with an adaptive Metropolis algorithm, and a method to estimate data error statistics based on the features of time-lapse difference data that is incorporated. A random walk Metropolis-Hastings MCMC is adopted for optimization. In conventional, i.e., deterministic, DDFWI, inversions are carried out for the baseline and monitoring models; in the MCMC approach, a deterministic FWI procedure is carried out for the baseline model, and the MCMC algorithm is applied in the monitoring inversion stage; and the final time-lapse model is the difference between these. A feasibility study is carried out using synthetic 2D acoustic models and data, including time-lapse model estimation and uncertainty quantification. We compare the MCMC approach with conventional deterministic optimization DDFWI and remark on benefits derived, which appear to justify the expanded complexity and cost of a global approach. In addition to the availability of posterior distributions, which are critical for the assessment of the estimations, we observe that the MCMC approach tends to produce monitoring images with clearer edges and fewer coherent errors.

The Iterative Extraction of the Boundary of Coherence Region and Iterative Look-Up Table for Forest Height Estimation Using Polarimetric Interferometric Synthetic Aperture Radar Data

In this paper, we introduce a refined three-stage inversion algorithm (TSIA) for forest height estimation using polarimetric interferometric synthetic aperture radar (PolInSAR). Specifically, the iterative extraction of the boundary of the coherence region (IEBCR) and iterative look-up table (ILUT) are proposed to improve the efficiency of traditional TSIA. A class of refined TSIA utilizes the boundary of the coherence region (BCR) to alleviate the underestimation phenomenon in forest height estimation. Given many eigendecompositions in the extraction of BCR (EBCR), we analyze the relationship of eigenvectors between the adjacent points on the BCR and propose the IEBCR utilizing the power methods. In the final inversion stage of TSIA, the look-up table (LUT) uses the exhaustive search method to minimize the loss function in the 2-D grid with defined step sizes and thus costs high computational complexity. To alleviate the deficiency, we define the random volume over ground (RVoG) function based on the RVoG model and prove its monotonicity and convergence from the analytical and numerical points of view. After analyzing the relationship between the RVoG function and the loss function, we propose the ILUT for the inversion stage. The simulation and experiments based on the BioSAR 2008 campaign data illustrate that the IEBCR and ILUT greatly improve the computational efficiency almost without compromising on accuracy.

Tectonics in the Greater Caucasus (Georgia – Russia): From an intracontinental rifted basin to a doubly verging fold-and-thrust belt

The Greater Caucasus doubly-vergent orogenic system has its origin in a Mesozoic-Early Cenozoic back-arc-type basin, floored by an extensively stretched and heavily intruded continental crust that has subsequently been inverted. Our field investigations along the Georgian Military Road in the eastern Central Greater Caucasus provide insights in its tectonic structure and reveal a bivergent orogenic wedge geometry. The southward propagating pro-wedge comprises the Southern Slope tectonic imbricate system developed in the Mesozoic-Early Cenozoic basin infill and the Transcaucasian Kartli foreland fold-and-thrust belt and is actively underthrust by the Transcaucasian Dzirula-Shatsky Block. The retro-wedge, on the other hand, incorporates the Northern Slope tectonic zones (including the Homocline Range) and the North Caucasian Terek-Sunzha foreland fold-and-thrust belt that developed in the Mesozoic-Cenozoic cover of the Scythian Platform. The Main Range forms the axial zone of the mountain belt where crystalline, pre-Mesozoic basement is locally brought to the surface at almost 3000 m altitude along the Main Caucasus Thrust.Our study of the regional geology, in combination with paleotectonic reconstructions suggests that the present-day tectonic units of the Caucasus correspond to distinct pre-collisional paleotectonic domains that existed in the Mesozoic-Early Cenozoic Neotethys-Eurasia ocean-continent convergence zone. The focus of our study lies on the tectonic interpretation of the Greater Caucasus fold-and-thrust belt. We propose to interprete the major thrusts of the orogen as former normal listric detachments occurring in the Greater Caucasus Basin, that were reactivated as reverse faults and thrusts during the collisional events of the Arabia-Eurasia convergence since the Late Eocene-Oligocene (Alpine inversion stage).

Types of Beixi slopes and the process of tectonic evolution

The phenomenon of oil and gas accumulation on the Beixi slope is obvious, which is one of the important directions of oil and gas pre-exploration and increasing reserves and production in the future. Taking the Beixi slope as the target area, according to the geological characteristics, the Beixi slope is divided into the differential subsidence type of the same fault depression, the reverse normal fault tilting and lifting slope and the compound slope. The evolution profile of Beixi slope is restored by using 2Dmove application software. based on the joint action of structure and deposition of Beixi slope, the fault evolution process of Beixi slope can be divided into four stages: rift stage 1 (Tongbamiao formation-N14 reflection layer), rift stage 2 (N14 reflection layer-T22 reflection layer), fault depression conversion stage (T22 reflection layer-T04 reflection layer) and depression inversion stage (above T04 reflection layer).

Study on the Optimization of Hyperspectral Characteristic Bands Combined with Monitoring and Visualization of Pepper Leaf SPAD Value.

Chlorophyll content is an important indicator of plant photosynthesis, which directly affects the growth and yield of crops. Using hyperspectral imaging technology to quickly and non-destructively estimate the soil plant analysis development (SPAD) value of pepper leaf and its distribution inversion is of great significance for agricultural monitoring and precise fertilization during pepper growth. In this study, 150 samples of pepper leaves with different leaf positions were selected, and the hyperspectral image data and SPAD value were collected for the sampled leaves. The correlation coefficient, stability competitive adaptive reweighted sampling (sCARS), and iteratively retaining informative variables (IRIV) methods were used to screen characteristic bands. These were combined with partial least-squares regression (PLSR), extreme gradient boosting (XGBoost), random forest regression (RFR), and gradient boosting decision tree (GBDT) to build regression models. The developed model was then used to build the inversion map of pepper leaf chlorophyll distribution. The research results show that: (1) The IRIV-XGBoost model demonstrates the most comprehensive performance in the modeling and inversion stages, and its , , and are 0.81, 2.76, and 2.30, respectively; (2) The IRIV-XGBoost model was used to calculate the SPAD value of each pixel of pepper leaves, and to subsequently invert the chlorophyll distribution map of pepper leaves at different leaf positions, which can provide support for the intuitive monitoring of crop growth and lay the foundation for the development of hyperspectral field dynamic monitoring sensors.

GaN-Based High-Power-Density AC–DC–AC Converter for Single-Phase Transformerless Online Uninterruptible Power Supply

This article introduces a new transformerless ac-dc-ac converter topology suitable for a high-power-density high-frequency single-phase online uninterruptible power supply (UPS) with a common neutral between the input and output ac ports. The proposed converter comprises an input power factor correction rectification (ac-dc) stage which is followed by an inversion (dc-ac) stage. The rectification stage operates in boost mode during the input positive half line cycle and buck-boost mode during the input negative half line cycle, while the inversion stage operates in buck and buck-boost modes in the output positive and negative half line cycles, respectively. The rectification stage utilizes boundary conduction mode control enabling soft-switching and allowing high-frequency operation. The inversion stage is operated in continuous conduction mode, wherein a digital controller regulates the output voltage of the converter across both resistive and reactive loads. The proposed online UPS utilizes a single (nonsplit) dc-bus between the rectification and inversion stages, resulting in a 50% reduction in dc-bus capacitance requirement compared to conventional split-bus online UPS topologies. Additionally, two battery interface solutions are also investigated which provide a trade-off between passive volume and additional switch-count. To verify the performance and control of the proposed online UPS, a GaN-based electrolytic-free 1-kVA prototype online UPS is designed, built, and tested. The prototype ac-dc-ac converter achieves a peak efficiency of 95.2% and maintains a high efficiency of above 92.3% across the full output power range. The electrolytic-free prototype ac-dc-ac converter for the online UPS achieves a power density of 26.4 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .

Guided Wave Tomography Based on Supervised Descent Method for Quantitative Corrosion Imaging.

Corrosion detection is a critical problem in many research areas. Guided wave tomography provides a powerful tool to estimate the remaining thickness of corroded structures. This article introduces an ultrasonic quantitative tomography method called fast inversion tomography (FIT) for corrosion mapping on plate-like structures. FIT consists of offline training and online inversion. The offline training stage uses the supervised descent method (SDM) to generate a series of average descent directions iteratively by minimizing the waveform misfit function between the fixed initial models and training examples. The minimization of the misfit function is equivalent to solving the linear least-squares problem. In the online inversion stage, we reconstruct the velocity map of testing examples using the learned descent directions in an iterative manner. Then, we convert the velocity map into the thickness map using the dispersive characteristics of a specific guided wave mode. The performance of this technique is evaluated using synthetic datasets which include both training and testing examples with different corrosion depths and shapes on an aluminum plate. We also compare the reconstruction accuracy and computation efficiency between FIT and time/frequency-domain full-waveform inversion. The results indicate that FIT exhibits great performance in the problem of quantitative corrosion imaging.

Synthesis and Characterization of Cellulose Acetate Membrane from Cotton Spinning Waste

Cellulose acetate membrane (CAM) was successfully synthesized and characterized from the cotton spinning waste of the textile industry. The membrane was produced through the isolation, acetylation, and phase inversion stages. The highest yields of cellulose fiber and α-cellulose contents were obtained using 3.0% and 6.0% v/v NaClO, respectively. The C–O acetyl bond detected by Fourier Transform Infrared (FTIR) analysis indicates the formation of the CAM. The resulting membrane can be potentially applied as an ultrafiltration membrane for water desalination purposes in water and wastewater treatment facilities. Furthermore, the utilization of cotton spinning waste as raw material aims to produce inexpensive products and recycle solid waste from the textile industry.

Impacts of recycled polysulfone on the salt separation performance of thin film poly(piperazine-amide) membranes

The reusability provisions for finding out the feasibility of a polysulfone (PS) membrane structure are considering the type of stimulating system. On the successive non-solvent phase inversion of PS, the Newtonian flow of PS solutions at different stages is well observed from the rheological study. The viscosities of PS solutions decrease with stages. The membranes (Memb.-I-Ps to Memb.-VIII-Ps) are prepared from PS, recycled from successive phase inversion stages. It develops better porosities and higher Molecular weight Cut-off (MWCO) (PEO 200,400KDa)). Poly(piperazine-amide) coating on different recycled stages of PS membranes (Memb.-I-Pip to Memb.-VIII-Pip) shows an MWCO (PEG 400 Da, 1000 Da) property. The wettability property, zeta potential, morphological features of the membranes vary with the number of recycled stages. The salt rejection profiles (NaCl and Na2SO4) increase with the successive stages of recycled PS, and the selectivity (Na2SO4/NaCl) decreases a little. The Marangoni effect can explain the rise in salt separation with the subsequent recycled stages. The study extends to the defluoridation of water and quite promising. The ~15% increase in separation for 10 mg/L fluoride from Memb.-I-Pip to Memb.-VIII-Pip. The maximum separation of fluoride is 84.9% for Memb.-VIII-Pip. The decrease in separation results when the fluoride concentration increases from 10 to 100 mg/L.

A Study on the Heterogeneity Characteristics of Geological Controls on Coalbed Methane Accumulation in Gujiao Coalbed Methane Field, Xishan Coalfield, China

Commercial exploration and exploitation of coalbed methane (CBM) in Gujiao coalbed methane (CBM) field, Xishan coalfield, have rapidly increased in recent decades. The Gujiao CBM field has shown strong gas distribution heterogeneity, low gas content, and wide distribution of wells with low production. To better understand the geological controlling mechanism on gas distribution heterogeneity, the coal reservoir evolution history and CBM accumulation process have been studied on the base of numerical simulation work. The burial history of coal reservoir can be classified into six stages: shallowly buried stage; deeply buried stage; uplifting stage; short-term tectonic subsidence stage; large-scale uplifting stage; and sustaining uplifting and structural inversion stage. Mostly, coal seams have experienced two-time thermal metamorphisms with twice hydrocarbon-generation processes in this area, whereas in the southwest part, the coal seams in there suffered three-time thermal metamorphisms and hydrocarbon-generation processes. The critical tectonic events of the Indosinian, Yanshanian, and Himalayan orogenies affect different stages of the CBM reservoir accumulation evolution process. The Indosinian orogeny mainly controls the primary CBM generation. The Yanshanian orogeny dominates the second and third gas generation and migration processes. The Himalayan orogeny mainly affects the gas dissipation process and current CBM distribution heterogeneity.

Features of the geological structure and petroleum potential of jurassic deposits of the sudoch trough

The article discusses the geological structure and prospects of the oil and gas potential of the Jurassic deposits of the Sudoch Trough, as well as issues related to neotectonic processes that were developed at the inversion stage of the geological development of this territory. The geological substantiation of the location of hydrocarbon accumulations and their confinement to certain tectonic elements is given.

Control of Nanostructured Polysulfone Membrane Preparation by Phase Inversion Method.

The preparation of membranes from polymer solutions by the phase inversion method, the immersion—precipitation technique has proved since the beginning of obtaining technological membranes the most versatile and simple possibility to create polymeric membrane nanostructures. Classically, the phase inversion technique involves four essential steps: Preparation of a polymer solution in the desired solvent, the formation of the polymer solution film on a flat support, the immersion of the film in a coagulation bath containing polymer solvents, and membrane conditioning. All phase inversion stages are important for the prepared membrane’s nanostructure and have been studied in detail for more than six decades. In this paper, we explored, through an electrochemical technique, the influence of the contact time with the polymer film’s environment until the introduction into the coagulation bath. The system chosen for membrane preparation is polysulfone-dimethylformamide-aqueous ethanol solution (PSf-DMF-EW). The obtained nanostructured membranes were characterized morphologically and structurally by scanning electron microscopy (SEM) and thermal analysis (TA), and in terms of process performance through water permeation and bovine serum albumin retention (BSA). The membrane characteristics were correlated with the polymeric film exposure time to the environment until the contact with the coagulation bath, following the diagram of the electrochemical parameters provided by the electrochemical technique.

The polyphase rifting and inversion of the Danube Basin revised

Abstract To track the evolution and formation of one of the major sub-basins of the Pannonian back-arc basin system, we re-evaluate pre-rift, syn-rift, post-rift, and inversion stages of the Danube Basin. This synthesis builds upon a new compilation of (i) geophysical measurements, (ii) current data about the substratum of the basin, (iii) recent advances in stratigraphic architecture of the basin fill, (iv) subsidence history, (v) geomorphological evolution, and (vi) new biostratigraphic and geochronological data.The history of the basin begins with the pre-rift stage represented by the pre-Neogene basement, which belongs to an Eo-Alpine mountain range uplifted at the end of the Cretaceous. The core of the mountain range was formed by pre-Alpine high-grade metamorphic complexes, with a dome-like structure. The crystalline complexes were overlain by late Paleozoic and Mesozoic cover and nappes, which were later eroded during the early Cenozoic. These pre-rift processes were triggered by (i) the late Cenozoic collision of the Alpine-Carpathian orogenic wedge with the European platform, (ii) the crustal extension resulting from the northeastward lateral extrusion of the Alpine-Carpathian-Pannonian lithospheric microplate, and (iii) the subsequent updoming of the lithospheric mantle. This stage was followed by the polyphase rifting of the basin associated with extensive volcanic activity. This syn-rift stage consists of four phases. The first syn-rift phase dated to the early Badenian (~15.2–13.8 Ma), with subsidence documented in the Blatne and Želiezovce depressions, was characterized by accommodation rates up to ~900 m·Ma-1. The second syn-rift phase dated to the late Badenian (~13.8–12.6 Ma), exhibited accelerated subsidence with accommodation rates up to ~2300 m·Ma-1, and mainly affected the Blatne depression. The third and fourth syn-rift phases took place during the Sarmatian (~12.6–11.6 Ma) and early Pannonian (~11.6–9.5 Ma) and the accommodation rates reached ~900 m·Ma-1 and ~1000 m·Ma-1, respectively. They were documented in the Risňovce, Komjatice and Gabcikovo-Győr depressions, confirming the eastward subsidence migration, up to the external zone of the middle Miocene mantle upheaval. The late Miocene post-rift stage, commonly refered to as a thermal subsidence stage (~9.5–6.0 Ma), was associated with formation of a widespread planation surface called the “Mid-mountain level” on the margins of the basin. The history of the Danube Basin terminates with the inversion stage which began after ~6.0 Ma and is still ongoing. It includes the continuous uplift of the basin margins and the subsidence of the central depocenters. The fluvial depositional systems did not behave steadily, because (i) lateral channel mobility and area of deposition increased progressively until ~4–3 Ma and caused onlaps on the base of the succession, followed by (ii) gradual confinement of the streams to the central part of the basin by uplifting basin margins, recorded by formation of river terrace staircases.

Full-waveform inversion with borehole constraints for elastic VTI media

The nonlinearity of full-waveform inversion (FWI) and parameter trade-offs can prevent convergence toward the actual model, especially for elastic anisotropic media. The problems with parameter updating become particularly severe if ultra-low-frequency seismic data are unavailable, and the initial model is not sufficiently accurate. We introduce a robust way to constrain the inversion workflow using borehole information obtained from well logs. These constraints are included in the form of rock-physics relationships for different geologic facies (e.g., shale, sand, salt, and limestone). We develop a multiscale FWI algorithm for transversely isotropic media with a vertical symmetry axis (VTI media) that incorporates facies information through a regularization term in the objective function. That term is updated during the inversion by using the models obtained at the previous inversion stage. To account for lateral heterogeneity between sparse borehole locations, we use an image-guided smoothing algorithm. Numerical testing for structurally complex anisotropic media demonstrates that the facies-based constraints may ensure the convergence of the objective function towards the global minimum in the absence of ultra-low-frequency data and for simple (even 1D) initial models. We test the algorithm on clean data and on surface records contaminated by Gaussian noise. The algorithm also produces a high-resolution facies model, which should be instrumental in reservoir characterization.

2D source rock maturity model with integrated geology, geophysics and geochemistry data in HL field Jambi Sub Basin, South Sumatra Basin

South Sumatra basin is one of the back arc tertiary basin in western part of Indonesia. It consists of 31 grabens and 2 grabens complexes which are divided into three general basin systems. Modeling of maturity generation has been performed in Jambi sub basin with Talang Akar formation as source rock target from 5 well along in HL field. This study aims to examine their hydrocarbon generation and expulsion history. Geochemical evaluation showed that Talang Akar formation is very potential as a source rock, with an average TOC value of around 1–8 wt %. The reconstruction of 2D modeling and thermal show that HL field evolved initially as a rift basin in Miocene with uplift in the Oligocene. The present-day calculation of heat flow in HL Field shows 7.27 HFU. The differences in the present-day heat flow with paleo heat flow have been corrected using vitrinite reflectance to know validate the paleo heat flow. In Paleo heat flow increased since the main rifting form late Oligocene until early Miocene. rifting finished, paleo heat flow will indirectly reduce the heat. During Middle Miocene there was a post rift phase which considered as influence on source rock maturation and hydrocarbon generation as quite Talang Akar formation is currently passing oil generation window. Thermal maturation model indicated that Talang Akar formation ware passed late oil generation stage and generated with oils to convert dry gas with the result % Ro is 2 %. The hydrocarbon explosion got result from transformation ratio model that source rock unit have probably completed all potential hydrocarbon since Pleistocene that in regional Sumatra has even inversion stage.

Detailed In Situ Hot Stage Transmission Electron Microscope Observations of the Localized Pinning of a Mobile Ferrite-Austenite Interface in a Fe-C-Mn Alloy by a Single Oxidic Particle

The current study reports the detailed analysis of an observation of the local pinning of a slowly moving austenite-ferrite interface by a single nanosized oxidic particle. The observations were made during an in situ cyclic partial phase transformation experiment on a Fe-0.1C-1.0Mn alloy close to the inversion stage at which the interface migrates at a rather low velocity. The low velocity allowed capturing the interface pinning effect over a period of no less than 16 seconds. From our observations, it was possible to follow the progression of the pinning effect from the initial stages all the way through to the release of the interface. The pinning force exerted by the individual particle having a diameter of 140 nm on the austenite-ferrite interface was estimated as 175 nJ m−1, while the maximum pinning length was approximately 750 nm to either side of the particle, leading to an interface line tension of 170 nJ m−1. The observed pinning behavior is compared with the most relevant models in the literature.

SLA developmental stages in the CEFR-related learner corpus MERLIN

Abstract Little is known about the link between Second Language Acquisition (SLA) developmental stages (Pienemann 1998) and the Common European Framework of Reference (CEFR) proficiency levels. Therefore, this study examines the inversion (INV) and verb-end (VEND) stages in L2 German MERLIN texts rated B1 (N = 104) or A2 (N = 32). Two acquisition criteria are applied to individual texts (emergence, Pienemann 1998; 75%-correct, Ellis 1989) and combined with analyses of texts grouped at CEFR levels. Results suggest links between developmental stages and CEFR levels: VEND was emerged in 44% of B1 texts, while most A2 texts did not contain VEND. Many B1 texts (61.5%), but only 37.5% of A2 texts showed emergence of INV. However, analyses also revealed persisting problems with INV accuracy at B1. More generally, the study points out shared challenges for Learner Corpus Research, SLA, and proficiency/assessment research related to the availability of linguistic evidence in learner texts.

Magmatic and Sedimentary Structure beneath the Klyuchevskoy Volcanic Group, Kamchatka, From Ambient Noise Tomography

AbstractThe Klyuchevskoy Volcanic Group is a cluster of the world's most active subduction volcanoes, situated on the Kamchatka Peninsula, Russia. The volcanoes lie in an unusual off‐arc position within the Central Kamchatka Depression (CKD), a large sedimentary basin whose origin is not fully understood. Many gaps also remain in the knowledge of the crustal magmatic plumbing system of these volcanoes. We conducted an ambient noise surface wave tomography, to image the 3‐D shear wave velocity structure of the Klyuchevskoy Volcanic Group and CKD within the surrounding region. Vertical component cross correlations of the continuous seismic noise are used to measure interstation Rayleigh wave group and phase traveltimes. We perform a two‐step surface wave tomography to model the 3‐D Vsv velocity structure. For each inversion stage we use a transdimensional Bayesian Monte Carlo approach, with coupled uncertainty propagation. This ensures that our model provides a reliable 3‐D velocity image of the upper 15 km of the crust, as well as a robust assessment of the uncertainty in the observed structure. Beneath the active volcanoes, we image small slow velocity anomalies at depths of 2–5 km but find no evidence for magma storage regions deeper than 5 km—noting the 15 km depth limit of the model. We also map two clearly defined sedimentary layers within the CKD, revealing an extensive 8 km deep sedimentary accumulation. This volume of sediments is consistent with the possibility that the CKD was formed as an Eocene‐Pliocene fore‐arc regime, rather than by recent (&lt;2 Ma) back‐arc extension.

Investigation of Standalone Solar Photovoltaic Water Pumping System With Reduced Switch Multilevel Inverter

Solar photovoltaic powered water pumping systems are becoming very successful in regions where there is no opportunity for connecting the grid. The photovoltaic technology converts solar energy into electrical energy for operating DC or AC motor-based water pump. In the case of a solar AC motor water pump, it engages two energy conversion stages (DC-DC and DC-AC) in the power conditioning unit. This usually resulted in increased size, cost, complexity and decreases efficiency of the entire system. In addition, the existing two-level inverter (DC-AC) stage generates higher harmonics in output voltage that deteriorates AC motor performance. As a consequence, a single energy conversion stage with more than two-level output voltage could be possible by utilizing multilevel inverters which replaces two-level inversion stage easily to get higher levels of output voltages as well for extracting best results from the motor. Moreover, they can able to operate with reduced switching frequency that certainly reduces switching losses. Still, the increased voltage levels comprise a higher number of power semiconductor switches, cumulative voltage stress and switching losses are making the system more complicated. In this paper an innovative seven-level inverter with five switches had been taken to investigate 0.5 H. P single phase induction motor water pump. This topology ensures minimum switching losses, lowering size along with less installation cost. In order to provide better insight into the working and performance of this proposed topology the simulation results performed in the MATLAB / Simulink environment and hardware implementation are depicted.

FlatNet: Towards Photorealistic Scene Reconstruction From Lensless Measurements.

Lensless imaging has emerged as a potential solution towards realizing ultra-miniature cameras by eschewing the bulky lens in a traditional camera. Without a focusing lens, the lensless cameras rely on computational algorithms to recover the scenes from multiplexed measurements. However, the current iterative-optimization-based reconstruction algorithms produce noisier and perceptually poorer images. In this work, we propose a non-iterative deep learning-based reconstruction approach that results in orders of magnitude improvement in image quality for lensless reconstructions. Our approach, called FlatNet, lays down a framework for reconstructing high-quality photorealistic images from mask-based lensless cameras, where the camera's forward model formulation is known. FlatNet consists of two stages: (1) an inversion stage that maps the measurement into a space of intermediate reconstruction by learning parameters within the forward model formulation, and (2) a perceptual enhancement stage that improves the perceptual quality of this intermediate reconstruction. These stages are trained together in an end-to-end manner. We show high-quality reconstructions by performing extensive experiments on real and challenging scenes using two different types of lensless prototypes: one which uses a separable forward model and another, which uses a more general non-separable cropped-convolution model. Our end-to-end approach is fast, produces photorealistic reconstructions, and is easy to adopt for other mask-based lensless cameras.