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Su, Quanyong, Juan Liu, Xianmou Xue, and Zheng Shi. "High power density thermal control design of onboard phased array antenna." Journal of Physics: Conference Series 2083, no. 2 (2021): 022034. http://dx.doi.org/10.1088/1742-6596/2083/2/022034.
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Abstract Thermal control of high power density phased array antenna [1] has become a critical problem for onboard seeker which is confined by compact structure and harsh flight condition [2-4], different from land-based or airborne seekers. As a key technology, thermal control of onboard phased array antenna faces the challenge of high density power element as well as worse operating temperature. Using finite volume method as theoretic foundation of numerical simulation, this paper firstly calculates temperature field and fluid field via discrete control equation group, which is transformed from continuous integration equation group according to energy reservation equation. Next,2 kinds of phased array antenna with phase change energy storage and water cooling are designed and evaluated by thermal control performance simulation. Then advice is given for reasonable assembly after temperature distribution of phased array antenna is quantified under different assembly state with the influence of contact thermal resistance. At the end, precision of temperature simulation is verified with temperature test result of phased array antenna.
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Liu, Ying, Wei Feng Tian, Jian Kang Zhao, Shi Qing Zhu, and Ge Wen Yang. "Line-of-Sight Angle Rate Reconstruction for Phased Array Strapdown Seeker." Advanced Materials Research 645 (January 2013): 196–201. http://dx.doi.org/10.4028/www.scientific.net/amr.645.196.
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The phased array strapdown radar seeker’s detecting information is coupled with missile attitude information. Hence, the measurement information can not be used for proportional navigation directly. The method of reconstructing inertial line of sight (LOS) rate in phased array strapdown seeker is presented using the missile-target relative motion geometric and filtering algorithm. Considering measurement noise and nonlinearity of the phased array strapdown radar guidance systems, the principle of unscented kalman filter (UKF) is introduced to estimate LOS rate. The simulation results show that the reconstruction method is correct and the extraction of LOS rate is effective.
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Du, Xiao, and Qunli Xia. "The calibration method of phased array seeker with the phantom-bit technology." Optik 127, no. 18 (2016): 7225–34. http://dx.doi.org/10.1016/j.ijleo.2016.05.066.
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Bai, Rui, Qunli Xia, and Xiao Du. "The study of guidance performance of a phased array seeker with platform." Optik 132 (March 2017): 9–23. http://dx.doi.org/10.1016/j.ijleo.2016.12.022.
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WEN, Qiuqiu, Tianyu LU, Qunli XIA, and Zedong SUN. "Beam-pointing error compensation method of phased array radar seeker with phantom-bit technology." Chinese Journal of Aeronautics 30, no. 3 (2017): 1217–30. http://dx.doi.org/10.1016/j.cja.2017.03.020.
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Lin, Shih-Yao, Jiang Wang, and Wei Wang. "Barrier Lyapunov Function Based Integrated Missile Guidance and Control Considering Phased Array Seeker Disturbance Rejection Rate." IEEE Access 10 (2022): 31070–83. http://dx.doi.org/10.1109/access.2022.3156292.
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Du, Xiao, and Qunli Xia. "The research of guidance performance of the phased array seeker with platform for air-to-air missile." Optik 127, no. 22 (2016): 10322–34. http://dx.doi.org/10.1016/j.ijleo.2016.08.071.
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Lin, Shih-Yao, Defu Lin, and Wei Wang. "A Novel Online Estimation and Compensation Method for Strapdown Phased Array Seeker Disturbance Rejection Effect Using Extended State Kalman Filter." IEEE Access 7 (2019): 172330–40. http://dx.doi.org/10.1109/access.2019.2956256.
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Lu, Tianyu, Qiuqiu Wen, and Jian Yin. "The effect of phantom-bit technology on the performance of phased array seeker detection in the case of the initial beam angle." Optik 127, no. 20 (2016): 9996–10003. http://dx.doi.org/10.1016/j.ijleo.2016.08.001.
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Guney, Kerim, and Ali Durmus. "Pattern Nulling of Linear Antenna Arrays Using Backtracking Search Optimization Algorithm." International Journal of Antennas and Propagation 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/713080.
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An evolutionary method based on backtracking search optimization algorithm (BSA) is proposed for linear antenna array pattern synthesis with prescribed nulls at interference directions. Pattern nulling is obtained by controlling only the amplitude, position, and phase of the antenna array elements. BSA is an innovative metaheuristic technique based on an iterative process. Various numerical examples of linear array patterns with the prescribed single, multiple, and wide nulls are given to illustrate the performance and flexibility of BSA. The results obtained by BSA are compared with the results of the following seventeen algorithms: particle swarm optimization (PSO), genetic algorithm (GA), modified touring ant colony algorithm (MTACO), quadratic programming method (QPM), bacterial foraging algorithm (BFA), bees algorithm (BA), clonal selection algorithm (CLONALG), plant growth simulation algorithm (PGSA), tabu search algorithm (TSA), memetic algorithm (MA), nondominated sorting GA-2 (NSGA-2), multiobjective differential evolution (MODE), decomposition with differential evolution (MOEA/D-DE), comprehensive learning PSO (CLPSO), harmony search algorithm (HSA), seeker optimization algorithm (SOA), and mean variance mapping optimization (MVMO). The simulation results show that the linear antenna array synthesis using BSA provides low side-lobe levels and deep null levels.
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Guney, K., and S. Basbug. "Seeker optimization algorithm for interference suppression of linear antenna arrays by controlling position-only, phase-only, and amplitude-only." International Journal of RF and Microwave Computer-Aided Engineering 21, no. 5 (2011): 505–18. http://dx.doi.org/10.1002/mmce.20536.
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Roy, Kalapi, Bingzhong (David) Guan, and Carl Sechen. "A Sea-of-Gates Style FPGA Placement Algorithm." VLSI Design 4, no. 4 (1996): 293–307. http://dx.doi.org/10.1155/1996/92380.
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Field Programmable Gate Arrays (FPGAs) have a pre-defined chip boundary with fixed cell locations and routing resources. Placement objectives for flexible architectures (e.g., the standard cell design style) such as minimization of chip area do not reflect the primary placement goals for FPGAs. For FPGAs, the layout tools must seek 100% routability within the architectural constraints. Routability and congestion estimates must be made directly based on the demand and availability of routing resources for detailed routing of the particular FPGA. We. present a hierarchical placement approach consisting of two phases: a global placement phase followed by a detailed placement phase. The global placement phase minimizes congestion estimates of the global routing regions and satisfies all constraints at a coarser level. The detailed placer seeks to maximize the routability of the FPGA by considering factors which cause congestion at the detailed routing level and to precisely satisfy all of the constraints. Despite having limited knowledge about the gate level architectural details, we have achieved a 90%reduction in the number of unrouted nets in comparison to an industrial tool (the only other tool) developed specifically for this architecture.
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Cook, Mylan R., Kent L. Gee, Carson F. Cunningham, and Grant W. Hart. "Vector acoustic intensity analysis of noise from the Delta IV Heavy launch vehicle during liftoff." Journal of the Acoustical Society of America 153, no. 3_supplement (2023): A42. http://dx.doi.org/10.1121/10.0018087.
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The noise sources within a turbulent rocket plume are not well understood, let alone the radiation from multiple rocket nozzles. Even less is known about the noise sources during launch vehicle liftoff. This paper seeks to simultaneously address these noise source analysis challenges using data collected during the NROL-82 Delta IV Heavy (DIVH) launch from Vandenberg Space Force Base. The three-core DIVH’s liftoff noise was measured by a ground-based four-microphone array at a distance of 330 m. Hart et al. [Proc. Mtgs. Acoust. 45, 040003 (2022)] previously used this array with a cross-correlation technique to identify the overall noise source radiation locus as it switched from the flame trench exit to about 55 m downstream of the nozzle exit plane. Here, vector intensity is used to localize the frequency-dependent noise source axial distribution using a variant of the phase and amplitude gradient estimator method for acoustic intensity [Thomas et al., J. Acoust. Soc. Am. 137, 3366–3376 (2015)]. The results help clarify a complex noise source generation process that is both time and frequency-dependent and involves both free and impinging jet noise phenomena.
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Raumer, Hans-Georg, and Carsten Spehr. "Wavenumber spectrum determination for aeroacoustic applications using FISTA." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, no. 4 (2023): 3754–62. http://dx.doi.org/10.3397/in_2022_0528.
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This conference paper deals with computational methods to determine the wavenumber spectrum of acoustic data measured by a phased microphone array. Such problems occur e.g. within the analysis of pressure fluctuations due to a turbulent boundary layer on a surface such as a wind-tunnel wall or the skin of an aircraft. The problem is closely related to the deconvolution of dirty beamforming maps in wavenumber domain, which seeks to determine the wavenumber spectrum by removing the influence of the shift-invariant point spread function from the beamforming result. Firstly, we recall how this task can be formulated as a minimization problem and then discuss a specific solver for this problem, provided by the framework of the generalized FISTA algorithm. The resulting method takes advantage of the convolutional structure of the gradient of the data misfit functional and allows further for a flexible regularization with L1 and L2 penalties as well as a nonnegativity constraint. Finally, the presented algorithmic framework is demonstrated with numerical examples.
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Raumer, Hans-Georg, Daniel Ernst, and Carsten Spehr. "Compensation of Modeling Errors for the Aeroacoustic Inverse Problem with Tools from Deep Learning." Acoustics 4, no. 4 (2022): 834–48. http://dx.doi.org/10.3390/acoustics4040050.
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In the field of aeroacoustic source imaging, one seeks to reconstruct acoustic source powers from microphone array measurements. For most setups, one cannot expect a perfect reconstruction. The main effects that contribute to this reconstruction error are data noise and modeling errors. While the data noise is accounted for in most advanced reconstruction methods, e.g., by a proper regularization strategy, the modeling error is usually neglected. This article proposes an approach that extends regularized inverse methods with a mechanism that takes the modeling error into account. The presented algorithmic framework utilizes the representation of the Fast Iterative Shrinkage Thresholding Algorithm (FISTA) algorithm by a neural network and uses standard gradient schemes from the field of deep learning. It is directly applicable to a single measurement, i.e., a prior training phase on previously generated data is not required. The capabilities of the method are illustrated by several numerical examples.
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Patnaik, Saroj Kumar, Pradeep Kumar, Priya Yadav, et al. "Can microRNA profiles predict corticosteroid responsiveness in childhood nephrotic syndrome? A study protocol." BMJ Paediatrics Open 2, no. 1 (2018): e000319. http://dx.doi.org/10.1136/bmjpo-2018-000319.
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IntroductionIn last few years, several studies have revealed the remarkable stability of extracellular microRNAs (miRNAs) circulating in the blood or excreted in the urine and underscored their key importance as biomarkers of certain diseases. Since miRNA in urinary sediment is relatively stable and easily quantified, it has the potential to be developed as a biomarker for disease diagnosis and monitoring. Identification of serum and urinary levels of certain miRNAs may assist in the diagnosis and assessment of disease activity in patients with nephrotic syndrome (NS). The global expression profile of miRNAs in childhood NS in Indian population remains unknown. Hence, further research is warranted in this area. This study seeks to prospectively evaluate whether a multipronged multiomics approach concentrating on microRNA expression profiles in children with NS vis-a-vis normal healthy children is discriminant enough to predict steroid responsiveness in childhood NS.Methods and analysisIn this prospective multicentric cohort study, subjects will be recruited from general paediatric and paediatric nephrology outpatient departments (OPDs) in tertiary care level referral hospitals. Age-matched and sex-matched healthy individuals with normal renal function (as assessed by normal serum creatinine and normal ultrasound of kidneys, ureter and bladder) in 1:1 ratio between study and control groups will be recruited from among the healthy siblings of children presenting to the OPDs. Differential microRNA expression profiles in urine and serum samples of children with steroid-sensitive NS (SSNS) and steroid-resistant NS (SRNS) with healthy children will be compared in a two-phased manner: a biomarker discovery phase involving pooled samples across SSNS, SRNS and healthy siblings analysed in triplicate using next-generation sequencing, slide microarray and quantitative reverse transcriptase PCR (qRT-PCR) arrays covering human miRNome followed by a validation phase with customised qRT-PCR primers based on the concordance in the discovery phase differential expression profiles and bioinformatics analysis.Ethics and disseminationThe study is funded after dueInstitutional Ethics Committee (IEC) clearance, and results will be available as open access.
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Raufi, Alexander, Winston Wong, Shing Mirn Lee, and Gulam Abbas Manji. "MEKiAUTO: A phase I/II open-label study of combination therapy with the MEK inhibitor cobimetinib, Immune-checkpoint blockade with atezolizumab, and the AUTOphagy inhibitor hydroxychloroquine in KRAS-mutated advanced malignancies." Journal of Clinical Oncology 39, no. 3_suppl (2021): TPS450. http://dx.doi.org/10.1200/jco.2021.39.3_suppl.tps450.
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TPS450 Background: Pancreatic ductal adenocarcinoma (PDAC) and colorectal carcinoma (CRC) are aggressive diseases which account for the third and second leading causes of cancer-related death, respectively. Limited progress has been made towards effective treatments or cure. K RAS is mutated or amplified in nearly 30% of all cancers, including up to 95% of PDAC and 45% of CRC. Although no successful KRAS directed therapy has been approved to date, data has emerged demonstrating that inhibition of downstream targets of KRAS, namely MEK/ERK, increases autophagic flux in KRAS-mutated tumors. This catabolic process is used by many tumors to maintain viability and recent preclinical studies have shown that combining MEK/ERK and autophagy inhibitors in KRAS-mutated tumors can synergistically suppress cancer cell proliferation. Inhibition of autophagy has demonstrated an increase in antigen presentation which sensitize tumors to immune checkpoint inhibitors. Presented here is a trial-in-progress that will evaluate combination of cobimetinib (MEK inhibitor), atezolizumab (anti-PDL1), and hydroxychloroquine (autophagy inhibitor) in KRAS-mutated advanced malignancies. Methods: This is a phase 1/2 multicenter, open-label study of combination cobimetinib (40-60mg) orally once daily on days 1-21, hydroxychloroquine (600mg) orally twice daily on days 1-28, and atezolizumab 840 mg IV on days 1 and 15 of each 28 day cycle. Patients with histologically confirmed metastatic or unresectable KRAS-mutant adenocarcinoma for which standard curative or meaningful life-prolonging treatment options do not exist or are no longer effective will be enrolled. The primary objective of the phase I portion of this trial, which seeks to enroll 18 patients, is to estimate the maximum tolerated dose (MTD) of these agents using a two-stage time-to-event continual reassessment method (TITE-CRM). The primary objective of the phase II portion of this trial, which seeks to enroll approximately 66-157 patients, is to evaluate the preliminary efficacy of this combination, based on the objective response by 16 weeks. Secondary endpoints include PFS, OS, and safety. Correlative aims include analyses of pre- and on-treatment biopsies with quantitative multiplex immunofluorescence, RNA-sequencing, reverse phase protein array for association with clinical benefit and to determine mechanisms of action/resistance. An interim analysis will be performed at the conclusion of the phase I portion of the study. This study is open with 4 patients enrolled at the time of submission. Clinical trial information: NCT04214418 . This trial is being conducted as part of the imCORE collaboration. Clinical trial information: NCT04214418.
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Cook, David, Ingibjörg Karlsdóttir, and Inga Minelgaite. "Enjoying the Heat? Co-Creation of Stakeholder Benefits and Sustainable Energy Development within Projects in the Geothermal Sector." Energies 15, no. 3 (2022): 1029. http://dx.doi.org/10.3390/en15031029.
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Analysis of the sustainability implications of the geothermal industry has tended to take a high-level or systemic overview of national performance rather than deeper, stakeholder-focused investigations. This study seeks to begin to fill this gap in the literature, investigating the following research question: how do projects in the Icelandic geothermal energy sector create co-benefits with stakeholders and reflect the integration of sustainable energy development (SED)? The focus of the analysis is identifying the stakeholders, what the sustainability benefits co-created with stakeholders are, and when in the projects’ life-cycle do these occur. Based on eleven semi-structured interviews with project managers in Iceland’s geothermal industry, the study identifies an array of stakeholders in the sector, including national and municipal governments, public sector institutions, businesses, the public, employees, and landowners. The sustainability co-benefits of Iceland’s geothermal power projects are broad and cut across all six aspects of SED and multiple phases of the project life-cycle. Although the sustainability benefits are apparent, trade-offs are reported between pursuing an economically efficient energy system and nature conservation. This relates to unsustainable utilization of the resources and the environmental externalities of power production and consumption. Efforts to mitigate these effects are ongoing, and further pursuit of SED is likely in Iceland given its recognition within the nation’s new energy policy and to meet ambitious greenhouse gas emissions reduction targets in the government’s climate action plan. These are prominent issues in other nations seeking to decarbonize energy systems through increased utilization of geothermal resources.
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Downs, Robert S., and Jens H. M. Fransson. "Tollmien–Schlichting wave growth over spanwise-periodic surface patterns." Journal of Fluid Mechanics 754 (July 30, 2014): 39–74. http://dx.doi.org/10.1017/jfm.2014.377.
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AbstractA novel type of surface roughness is deployed in a zero-pressure-gradient boundary layer with the goal of delaying the onset of laminar-to-turbulent transition for drag reduction purposes. This proof-of-concept experiment relies on forcing phase-triggered Tollmien–Schlichting (TS) waves across a range of initial amplitudes to produce amplified boundary-layer disturbances in a controlled and repeatable manner. Building on earlier work demonstrating attenuation of forced disturbances and delay of transition with spanwise arrays of discrete roughness and miniature vortex generators (MVGs), the present work seeks a roughness shape which might find success in a wider range of flows. Toward that end, streamwise-elongated humps are regularly spaced in the spanwise direction to form a wavy wall. By direct modulation of the mean flow, growth rates of the forced disturbances are increased or decreased, depending on the roughness configuration. Boundary-layer velocity measurements with hot-wire probes have been performed in a parametric study of the effects of roughness-field geometry and forcing amplitude on TS-wave growth and transition. The roughness field proves detrimental to passive flow control efforts in some configurations, while a reduction in the TS-wave amplitudes compared with the smooth-wall reference case is observed at other conditions. Substantial delays in the onset of transition are demonstrated when TS waves are forced with large amplitudes.
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Bonadio, Raffaele, Sergei Lebedev, Thomas Meier, et al. "Optimal resolution tomography with error tracking and the structure of the crust and upper mantle beneath Ireland and Britain." Geophysical Journal International 226, no. 3 (2021): 2158–88. http://dx.doi.org/10.1093/gji/ggab169.
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SUMMARY The classical Backus–Gilbert method seeks localized Earth-structure averages at the shortest length scales possible, given a data set, data errors, and a threshold for acceptable model errors. The resolving length at a point is the width of the local averaging kernel, and the optimal averaging kernel is the narrowest one such that the model error is below a specified level. This approach is well suited for seismic tomography, which maps 3-D Earth structure using large sets of seismic measurements. The continual measurement-error decreases and data-redundancy increases have reduced the impact of random errors on tomographic models. Systematic errors, however, are resistant to data redundancy and their effect on the model is difficult to predict. Here, we develop a method for finding the optimal resolving length at every point, implementing it for surface-wave tomography. As in the Backus–Gilbert method, every solution at a point results from an entire-system inversion, and the model error is reduced by increasing the model-parameter averaging. The key advantage of our method stems from its direct, empirical evaluation of the posterior model error at a point. We first measure inter-station phase velocities at simultaneously recording station pairs and compute phase-velocity maps at densely, logarithmically spaced periods. Numerous versions of the maps with varying smoothness are then computed, ranging from very rough to very smooth. Phase-velocity curves extracted from the maps at every point can be inverted for shear-velocity (VS) profiles. As we show, errors in these phase-velocity curves increase nearly monotonically with the map roughness. We evaluate the error by isolating the roughness of the phase-velocity curve that cannot be explained by any Earth structure and determine the optimal resolving length at a point such that the error of the local phase-velocity curve is below a threshold. A 3-D VS model is then computed by the inversion of the composite phase-velocity maps with an optimal resolution at every point. The estimated optimal resolution shows smooth lateral variations, confirming the robustness of the procedure. Importantly, the optimal resolving length does not scale with the density of the data coverage: some of the best-sampled locations display relatively low lateral resolution, probably due to systematic errors in the data. We apply the method to image the lithosphere and underlying mantle beneath Ireland and Britain. Our very large data set was created using new data from Ireland Array, the Irish National Seismic Network, the UK Seismograph Network and other deployments. A total of 11 238 inter-station dispersion curves, spanning a very broad total period range (4–500 s), yield unprecedented data coverage of the area and provide fine regional resolution from the crust to the deep asthenosphere. The lateral resolution of the 3-D model is computed explicitly and varies from 39 km in central Ireland to over 800 km at the edges of the area, where the data coverage declines. Our tomography reveals pronounced, previously unknown variations in the lithospheric thickness beneath Ireland and Britain, with implications for their Caledonian assembly and for the mechanisms of the British Tertiary Igneous Province magmatism.
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Parkin, Brian, Peter Ouillette, Yifeng Li, Cheng Li, Kerby Shedden, and Sami Malek. "Clonal Evolution and Devolution Following Chemotherapy in Adult Acute Myelogenous Leukemia." Blood 120, no. 21 (2012): 2487. http://dx.doi.org/10.1182/blood.v120.21.2487.2487.
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Abstract Abstract 2487 Introduction: Despite significant advances in the understanding of the biology of adult acute myelogenous leukemia (AML), overall survival remains poor due chiefly to the high rate of relapse after achieving complete remission as well as primary failure of induction chemotherapy. Efforts to further unravel the mechanisms leading to relapse and primary refractory disease are critical in order to guide the development of effective and durable treatment strategies for AML. To that end, this study seeks to elucidate the clonal relationship of AML in various disease phases. Methods: We employed SNP 6.0 array-based genomic profiling of acquired copy number aberrations (aCNA) and copy neutral LOH (cnLOH) together with sequence analysis of recurrently mutated genes to characterize paired AML genomes. We analyzed 28 AML sample pairs from patients that achieved complete remission with chemotherapy and subsequently relapsed (median remission duration 272 days [range 25 – 1249 days]) and 11 sample pairs from patients with persistent disease following induction chemotherapy. AML cell samples were isolated with a Ficoll gradient, negatively selected using Miltenyi microbead columns, and then further purified with flow cytometric cell sorting. Processed DNA isolated from highly purified AML blasts and paired buccal DNA was hybridized to Affymetrix SNP 6.0 arrays. aCNA were visually identified using the dChip program in paired data displays and corroborated by algorithmic lesion scoring, and cnLOH was detected using internally developed software. In addition, 11 genes known to be recurrently mutated in AML (CEBPA, DNMT3A, IDH1, IDH2, RUNX1, BCORL1, NPM1, NRAS, KRAS, FLT3 and TP53) were resequenced in all 39 presentation samples to identify somatically acquired mutations. Genes found mutated in individual AML cases were subsequently tested for the persistence of the mutation in paired samples. Results: For the 28 paired specimens in the relapsed cohort, comparison of aCNA and cnLOH occurrences, gene mutation patterns and karyotypes revealed 6 cases that carried no aCNA/cnLOH at either presentation or relapse, but at presentation carried at least 1 gene mutation, all of which but one were stable in relapse (1 case lost a RUNX1 mutation but carried a t(8;21) in both disease stages); 11 cases that were characterized by the presence of aCNA/cnLOH at presentation, of which 55% (6 of 11) gained additional aCNA/cnLOH at relapse; 6 cases without aCNA/cnLOH at presentation that gained aCNA/cnLOH at relapse, of which 2 concurrently lost a FLT3-ITD or CEPBA mutation; and 5 cases that carried no informative genomic events. For the 11 paired specimens in the persistent AML cohort, the same comparison revealed 2 cases without aCNA/cnLOH before or after chemotherapy and stable gene mutations; 5 cases with aCNA/cnLOH at presentation that carried the same genomic lesions and gene mutations before and after chemotherapy; 3 cases with aCNA/cnLOH present at enrollment that lost some but not all of these aCNA/cnLOH and gained none after initial induction therapy; and 1 additional case that lost a FLT3-ITD. Comparative analysis of these patterns demonstrates that relapsed AML invariably represents reemergence or evolution of an antecedent clone. Furthermore, all individual aCNA or cnLOH detected at presentation persisted at relapse indicating that this lesion type is proximally involved in AML evolution. Analysis of informative paired persistent AML disease samples uncovered at least two coexisting dominant clones of which at least one was chemotherapy sensitive and one resistant. Conclusion: This detailed genomic analysis supports the conclusion that incomplete eradication of AML founder clones rather than stochastic emergence of fully unrelated novel clones underlies AML relapse and persistence with direct implications for clinical AML research. Disclosures: No relevant conflicts of interest to declare.
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Iizuka, Kotaro, Yuichi S. Hayakawa, Takuro Ogura, Yasutaka Nakata, Yoshiko Kosugi, and Taichiro Yonehara. "Integration of Multi-Sensor Data to Estimate Plot-Level Stem Volume Using Machine Learning Algorithms–Case Study of Evergreen Conifer Planted Forests in Japan." Remote Sensing 12, no. 10 (2020): 1649. http://dx.doi.org/10.3390/rs12101649.
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The development of new methods for estimating precise forest structure parameters is essential for the quantitative evaluation of forest resources. Conventional use of satellite image data, increasing use of terrestrial laser scanning (TLS), and emerging trends in the use of unmanned aerial systems (UASs) highlight the importance of modern technologies in the realm of forest observation. Each technology has different advantages, and this work seeks to incorporate multiple satellite, TLS- and UAS-based remote sensing data sets to improve the ability to estimate forest structure parameters. In this paper, two regression analysis approaches are considered for the estimation: random forest regression (RFR) and support vector regression (SVR). To collect the dependent variable, in situ measurements of individual tree parameters (tree height and diameter at breast height (DBH)) were taken in a Japanese cypress forest using the nondestructive TLS method, which scans the forest to obtain dense and accurate point clouds under the tree canopy. Based on the TLS data, the stem volume was then computed and treated as ground truth information. Topographic and UAS information was then used to calculate various remotely sensed explanatory variables, such as canopy size, canopy cover, and tree height. Canopy cover and canopy shapes were computed via the orthoimages derived from the UAS and watershed segmentation method, respectively. Tree height was computed by combining the digital surface model (DSM) from the UAS and the digital terrain model (DTM) from the TLS data. Topographic variables were computed from the DTM. The backscattering intensity in the satellite imagery was obtained based on L-band (Advanced Land Observing Satellite-2 (ALOS-2) Phased Array type L-band Synthetic Aperture Radar-2 (PALSAR-2)) and C-band (Sentinel-1) synthetic aperture radar (SAR). All satellite (10–25 m resolution), TLS (3.4 mm resolution) and UAS (2.3–4.6 cm resolution) data were then combined, and RFR and SVR were trained; the resulting predictive powers were then compared. The RFR method yielded fitting R2 up to 0.665 and RMSE up to 66.87 m3/ha (rRMSE = 11.95%) depending on the input variables (best result with canopy height, canopy size, canopy cover, and Sentinel-1 data), and the SVR method showed fitting R2 up to 0.519 and RMSE up to 80.12 m3/ha (rRMSE = 12.67%). The RFR outperformed the SVR method, which could delineate the relationship between the variables for better model accuracy. This work has demonstrated that incorporating various remote sensing data to satellite data, especially adding finer resolution data, can provide good estimates of forest parameters at a plot level (10 by 10 m), potentially allowing advancements in precision forestry.
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Yu, Jing. "Performance Analysis of Beam Error Parasitic Loop of Phased Array Radar Seeker." International Journal of Performability Engineering, 2018. http://dx.doi.org/10.23940/ijpe.18.11.p21.27522759.
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Zhang, Quan, Yunfeng Chen, Fangxue Zhang, and Yangkang Chen. "Improving receiver function imaging with high-resolution Radon transform." Geophysical Journal International, March 22, 2022. http://dx.doi.org/10.1093/gji/ggac116.
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SUMMARY The receiver function (RF) method is one of the most widely used passive seismic approaches for imaging subsurface structures from shallow sedimentary basins to the deep Earth’s interior. RF is typically computed with a deconvolution operation that enables separating structural response from source-time function embedded in teleseismic wavefields. However, seismic recordings of temporary arrays are often contaminated with strong random noise and even amplitude bias due to poor installation conditions. Both factors can cause instability to deconvolution and severely degrade the accuracy, thereby the imaging quality, of the RF method. This underscores the importance of effective denoising algorithms in RF processing. In this study, we explore the application of high-resolution Radon transform (RT) to improve the conventional RF imaging workflow. Contrary to the commonly implemented post-processing (i.e., after deconvolution) noise suppression schemes, we introduce the RT to data pre-processing (i.e., before deconvolution). This method seeks a sparse representation of teleseismic wavefields in the τ-p domain by iteratively solving a least-squares minimization problem with a conjugate gradient algorithm. Synthetic test with a two-dimensional step-Moho model shows that non-linear phase arrivals including incoherent noise and diffraction energy are effectively removed in resulting RFs, with the signal-to-noise ratio increased by as much as ∼8 dB. Furthermore, real data experiments using the Hi-CLIMB network in the Tibetan Plateau demonstrate the superior performance of the proposed workflow in regularizing the wavefield and improving the coherence of converted phases across the recording array. Consequently, imaging results of common conversion point stacking using a single and a group of teleseismic events both recover subtle converted phases from the Moho and potential lithospheric discontinuities that are otherwise obscured by noise arising from the conventional processing workflow. This study highlights the necessity of wavefield regularization in RF method and calls for improved data processing techniques in array-based seismic imaging.
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Cho, In Ho, Sinchul Yeom, Tanmoy Sarkar, and Tae-Sik Oh. "Unraveling hidden rules behind the wet-to-dry transition of bubble array by glass-box physics rule learner." Scientific Reports 12, no. 1 (2022). http://dx.doi.org/10.1038/s41598-022-07170-y.
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AbstractA liquid–gas foam, here called bubble array, is a ubiquitous phenomenon widely observed in daily lives, food, pharmaceutical and cosmetic products, and even bio- and nano-technologies. This intriguing phenomenon has been often studied in a well-controlled environment in laboratories, computations, or analytical models. Still, real-world bubble undergoes complex nonlinear transitions from wet to dry conditions, which are hard to describe by unified rules as a whole. Here, we show that a few early-phase snapshots of bubble array can be learned by a glass-box physics rule learner (GPRL) leading to prediction rules of future bubble array. Unlike the black-box machine learning approach, the glass-box approach seeks to unravel expressive rules of the phenomenon that can evolve. Without known principles, GPRL identifies plausible rules of bubble prediction with an elongated bubble array data that transitions from wet to dry states. Then, the best-so-far GPRL-identified rule is applied to an independent circular bubble array, demonstrating the potential generality of the rule. We explain how GPRL uses the spatio-temporal convolved information of early bubbles to mimic the scientist’s perception of bubble sides, shapes, and inter-bubble influences. This research will help combine foam physics and machine learning to better understand and control bubbles.
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Köhler, A., E. B. Myklebust, and S. Mæland. "Enhancing seismic calving event identification in Svalbard through empirical matched field processing and machine learning." Geophysical Journal International, March 22, 2022. http://dx.doi.org/10.1093/gji/ggac117.
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SUMMARY Seismic signals generated by iceberg calving can be used to monitor ice loss at tidewater glaciers with high temporal resolution and independent of visibility. We combine the Empirical Matched Field (EMF) method and machine learning using Convolutional Neural Networks (CNNs) for calving event detection at the SPITS seismic array and the single broadband station KBS on the Arctic Archipelago of Svalbard. EMF detection with seismic arrays seeks to identify all signals generated by events in a confined target region similar to single P and/or S phase templates by assessing the beam power obtained using empirical phase delays between the array stations. The false detection rate depends on threshold settings and therefore needs appropriate tuning or, alternatively, post-processing. We combine the EMF detector at the SPITS array, as well as an STA/LTA detector at the KBS station, with a post-detection classification step using CNNs. The CNN classifier uses waveforms of the three-component record at KBS as input. We apply the methodology to detect and classify calving events at tidewater glaciers close to the KBS station in the Kongsfjord region in Northwestern Svalbard. In a previous study, a simpler method was implemented to find these calving events in KBS data, and we use it as the baseline in our attempt to improve the detection and classification performance. The CNN classifier is trained using classes of confirmed calving signals from four different glaciers in the Kongsfjord region, seismic noise examples, and regional tectonic seismic events. Subsequently, we process continuous data of 6 months in 2016. We test different CNN architectures and data augmentations to deal with the limited training data set available. Targeting Kronebreen, one of the most active glaciers in the Kongsfjord region, we show that the best performing models significantly improve the baseline classifier. This result is achieved for both the STA/LTA detection at KBS followed by CNN classification, as well as EMF detection at SPITS combined with a CNN classifier at KBS, despite of SPITS being located at 100 km distance from the target glacier in contrast to KBS at 15 km distance. Our results will further increase confidence in estimates of ice loss at Kronebreen derived from seismic observations which in turn can help to better understand the impact of climate change in Svalbard.
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Kolasinski, Kurt W. "Bubbles: A review of their relationship to the formation of thin films and porous materials." Open Material Sciences 1, no. 1 (2014). http://dx.doi.org/10.2478/mesbi-2014-0003.
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AbstractBubbles arise at the intersection of gases with other phases. Their role in the formation and applications of thin films and porous materials is complex. At times they are to be avoided. In other cases they are essential to the desired properties and outcomes. In many cases their function, form and production are misunderstood or disregarded. This review seeks to connect a diverse array of technical and fundamental aspects of bubbles so as to facilitate more control and understanding of their functions and utility