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Number of results: 7
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Method of high timing resolution pulse synthesis based on virtual sampling

Hanglin Liu Zaiming Fu Dexuan Kong Houjun Wang Yindong Xiao
Metrology and Measurement Systems | 2022 | vol. 29 | No 2 | 373-389 | DOI: 10.24425/mms.2022.140034
Keywords pulse synthesis high resolution virtual sampling digital-to-analogue conversion downsampling
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Abstract

Adjustable-width pulse signals are widely used in systems such as test equipment for hold time, response time and radar testing. In this study, we proposed a pulse generation method based on virtual sampling with ultra-high pulse width resolution. In the proposed method, the sampling rate of a digital-to-analogue converter (DAC) was adjusted to considerably improve pulse width resolution. First, the sampling rate was matched with the target pulse width resolution to digitally sample the ideal signal and generate digital waveform sampling points. Next, the signal bandwidth of the DAC was matched using a low-pass digital filter. Finally, the waveform sampling points were downsampled using an integer factor and output after digital-to-analogue conversion. The waveform pulse width information generated by high-frequency digital sampling was passed step by step and retained in the final output analogue signal. A DAC with a sampling rate of 1.25 GSa/s was used, and the pulse width resolution of the pulse signal was 0.1 ns. Theoretically, a sampling rate of 10 GSa/s is required to achieve 0.1 ns resolution. This method is simple, has a low cost, and exhibits excellent performance.
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Authors and Affiliations

Hanglin Liu
1
Zaiming Fu
1
Dexuan Kong
1
Houjun Wang
1
Yindong Xiao
1
  1. University of Electronic Science and Technology of China, School of Automation Engineering, Chengdu 611731, China

Dynamic sensor model of HRS Geo-images using parallel projection theory

Luong Chinh Ke
Geodesy and Cartography | 2007 | vol. 56 | No 2 | 73-82
Keywords High Resolution Satellite image orthorectification parallel projection dynamicaffine sensor model co-linearity condition
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Abstract

In last years, accurate spatial data from high resolution satellite images are getting more and more frequently used for modelling topography and other surveying purposes. To extract accurate spatial information, a sensor's mathematical models are needed. Those models classified to two branches: rigorous (parameirical or physical) models and non-rigorous models. In the paper a dynamic sensor model is proposed to extract spatial information from geo-rectified images named the geo-images which their geometry at the time of imaging have been lost. The developed model has been reconstructed basing on a transformation of central-perspective projection into a parallel one.
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Authors and Affiliations

Luong Chinh Ke

Mathematical model for bundle block adjustment of HRS images described by Keplerian parameters with orbital constraints

Luong Chinh Ke
Geodesy and Cartography | 2007 | vol. 56 | No 1 | 21-35
Keywords High Resolution Satellite image parametrical or physical model replacementsensor model block adjustment co-linearity condition
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Abstract

Nowadays, an orthomap destined for different purposes can be created from High Resolution Satellite (HRS) images using IKONOS, QuickBird and other satellite imageries having Ground Sampling Distance (GSD) lower than I m. The orthomap is one of the main sources for establishing GIS. Accuracy of the orthomap depends first of all on the parameters of Ground Control Points (GCPs) (the forms, number, accuracy and their distribution). In order to reduce the cost and number of GCP field measurements, the block of HRS images has been proposed. The accuracies of determined points in the block of HRS images are affected by the mathematical model used to build a block. The paper presents a general algorithm of bundle block adjustment model of HRS images using Keplerian parameters. In order to overcome strong correlation among exterior orientation elements of HRS images that causes the normal equation ill-conditioned, the ridge-stein estimator and orbital addition constraints have been proposed.
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Authors and Affiliations

Luong Chinh Ke

Review of practical accuracies of geometrical sensor models of very high resolution satellite imagery

Chinh Ke Luong
Geodesy and Cartography | 2006 | vol. 55 | No 4 | 193-207
Keywords Very high resolution satellite imagery orthorectification ground samplingdistance physical and polynomial model accuracy
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Abstract

Today, the new era with Very High Resolution Satellite (VHRS) imageries as IKON OS, QuickBird, EROS, Orb View etc., provides orthophoto in large scale of 1 :5 OOO, to update existing maps, to compile general-purpose or thematic maps. Orthophotomap in the scale of I :5 OOO with Ground Sampling Distance of 0.5 m is one of three important sources for establishing GIS together with a Digital Elevation Model of ±LO m accuracy in height and a topographic map in the scale of 1: IO OOO. Therefore, the accuracy of products of VHRS imageries affects reliability of GIS. Nevertheless, the accuracy of products of processing VHRS imageries is at first dependent on chosen geometrical sensor models. The understanding of geometrical sensor models of VHRS imageries is very important for improving processing of VHRS imageries. The polynomial models are to provide a simple, generic set of equations to represent the indirect relationship between the ground and its image. The polynomial models or replacement sensor models must not only model the ground-to-image relationship accurately. Physical (or parametrical) model describes dir~ctly strict geometrical relations between the terrain and its image, using satellite's orbital parameters and basing on the co-linearity condition. In such model, the above-mentioned multi-source distorting factors are taken into consideration. In this paper a review of practical accuracy of geometrical models of VHRS imageries taken from different research institutions in the world in last years has been presented.
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Authors and Affiliations

Chinh Ke Luong

Geometric models for satellite sensors

Chinh Ke Luong Wiesław Wolniewicz
Geodesy and Cartography | 2005 | vol. 54 | No 4 | 191-203
Keywords Very high resolution satellite imagery satellite sensors geometric models RPC model orthorectification
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Abstract

Since 2000 when first imageries of Space Imaging of one metre resolution satellite products appeared on the World market, many institutions started using them for cartographic production such as orthophotomaps on a large scale. A choice of the mathematic sensor models of imageries for their orthorectification in producing orthophotomaps is one of the main investigation directions. In order to restitute the functional relation between imageries and their ground space, the use of sensor models is required. They can be grouped into two classes, the generalized sensor models (geometric or replacement sensor models) and physical or parametric models. The paper presents a brief overview of the geometric models such as RPC (Rational Polynomial Coefficients). Their properties, and in particular their advantages and disadvantages are discussed. Also the parametric models, developed by the authors are presented in this paper. They are based on time-dependent collinearity equation of the mathematic relation between ground space and its imageries through parameters describing the sensor position in satellite orbit and position of the orbit in the geocentric system.
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Authors and Affiliations

Chinh Ke Luong
Wiesław Wolniewicz

The high resolution melting PCR protocol for rapid identification of single nucleotide substitutions in cytochrome c oxidase subunit II of Globodera pallida populations assigned to three pathotypes as an attempt of their differentiation

Marta Budziszewska
Journal of Plant Protection Research | 2021 | vol. 61 | No 4 | 430-433 | DOI: 10.24425/jppr.2021.139241
Keywords Globodera pallida high resolution melting (HRM) mtCOII genetic diversity pathotypes
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Abstract

The potato cyst nematode (PCN), Globodera pallida, originates from South America and is considered one of the most severe agricultural pests of potato crops and other Solanaceae plants globally. Based on their virulence and ability to reproduce on various potato cultivars, the populations of G. pallida are divided into three pathotypes, Pa1– Pa3. In this study, comparative sequence analyses of the fragment of mitochondrial cytochrome c oxidase subunit II ( mtCOII) gene for eight populations of G. pallida, representing three pathotypes, Pa1, Pa2 and Pa3, indicated genetic diversity between them. However, we did not identify significant mutations distinguishing Pa2 from Pa3. Interestingly, two single nucleotide substitutions, T441C and A468G, were characteristic only for populations assigned to Pa1. On this basis, we developed high resolution melting (HRM) PCR protocol. As a result, the melting curves obtained for samples of Pa1 populations varied from those obtained for populations designed as Pa2 and Pa3, allowing their differentiation. Thus, the HRM protocol developed here enables a rapid, very sensitive and low-cost screening assay for SNPs identification in mtCOII of G. pallida pathotypes. In effect, it might also be a helpful molecular tool in pathotype differentiation. However, further verification of the correlation of the occurrence of single nucleotide mutations in mtCOII in particular pathotypes should be carried out on a much larger number of samples of G. pallida, to determine if these mutations are characteristic only for this pathotype.
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Authors and Affiliations

Marta Budziszewska
1
ORCID: ORCID
  1. Department of Molecular Biology and Biotechnology, Institute of Plant Protection – National Research Institute, Poznań, Poland

Drought prediction in the Lepelle River basin, South Africa under general circulation model simulations

Darlington C. Ikegwuoha Megersa O. Dinka
Journal of Water and Land Development | 2020 | No 45 | 42-53 | DOI: 10.24425/jwld.2020.133044
Keywords drought high-resolution-climate-data Lepelle-River-Basin representative concentration pathways (RCPs) weather evaluation and planning (WEAP)
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Abstract

This study aims to evaluate changes in the frequency and severity of historical droughts (1980–2018) and then model future droughts occurrences (2019–2099) in the Lepelle River Basin (LRB), using Intergovernmental Panel on Climate Change (IPPC) General Circulation Model (GCM) simulations for two representative concentration pathways (RCP8.5 and RCP4.5). Firstly, the present-day and future hydrology of the LRB are modelled using the weather evaluation and planning (WEAP) model. Mann–Kendall tests are conducted to identify climate trends in the LRB. The reconnaissance drought in-dex (RDI) and the streamflow drought index (SDI) are employed to explore hydro-meteorological droughts in the Lepelle River Basin, South Africa. The RDI and SDI are plotted over time to assess drought magnitude and duration. The simulated temporal evolution of RDI and SDI show a significant decrease in wetting periods and a concomitant increasing trend in the dry periods for both the lower and middle sections of the LRB under RCP4.5 as the 22nd century is approached. Lastly, the Spearman and Pearson correlation matrix is used to determine the degrees of association between the RDI and SDI drought indices. A strong positive correlation of 0.836 is computed for the middle and lower sections of the LRB under the RCP8.5 forcing. Further findings indicate that severe to extreme drought above –2.0 magnitude are expected to hit the all three sec-tions of the LRB between 2080 and 2090 under RCP8.5. In the short term, it is suggested that policy actions for drought be implemented to mitigate possible impacts on human and hydro-ecological systems in the LRB.

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Authors and Affiliations

Darlington C. Ikegwuoha
Megersa O. Dinka
ORCID: ORCID

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