scholarly journals Analyze and improve the influence of geomagnetic gradient on aeromagnetic compensation in a towed bird

2021 ◽  
Author(s):  
Zhijian Zhou ◽  
Zhilong Liu ◽  
Wenduo Li ◽  
Yihang Wang ◽  
Chao Wang

Abstract. Aeromagnetic exploration is an important method of geophysical exploration. We study the compensation method of towed bird system and establish the towed bird interference model. Due to the low altitude of the helicopter, the geomagnetic gradient changes greatly, so the geomagnetic gradient is considered in the towed bird interference model. In this paper, we model the gradient of the geomagnetic field as vertical gradient and horizontal gradient components, analyze the influence of the towed bird system on the compensation results under different motion modes, and apply the ridge estimation method to solve the problem. We verify the feasibility of this compensation method through actual flight tests, and further improve the data quality of the towed bird interference.

2021 ◽  
Vol 10 (2) ◽  
pp. 257-264
Author(s):  
Zhijian Zhou ◽  
Zhilong Liu ◽  
Wenduo Li ◽  
Yihang Wang ◽  
Chao Wang

Abstract. Aeromagnetic exploration is an important method of geophysical exploration. We study the compensation method of the towed bird system and establish the towed bird interference model. Due to the geomagnetic gradient changing greatly, the geomagnetic gradient is considered in the towed bird interference model. In this paper, we model the geomagnetic field gradient and analyze the influence of the towed bird system on the aeromagnetic compensation results. Finally, we apply the ridge regression method to solve the problem. We verify the feasibility of this compensation method through actual flight tests and further improve the data quality of the towed bird interference.


2021 ◽  
pp. 0739456X2110067
Author(s):  
Siu Kei Wong ◽  
Kuang Kuang Deng

This study investigates how perceived school quality affects housing values, using a new estimation method. Our empirical design takes advantage of the mergers of school catchment zones initiated by the government to develop quasi-experiments. We find that, in zones that gained sudden access to higher ranked schools, housing prices increased by 1.3 to 4.1 percent. Larger and more expensive houses appreciated more in response to the improvement in perceived quality of available schools. The findings generate important policy implications regarding housing wealth redistribution and housing expenditures among different households. The study also enriches the literature on the capitalization effect of school quality.


2021 ◽  
Vol 26 (3-4) ◽  
pp. 291-301
Author(s):  
N.V. Stepanov ◽  

Operating quality of automated video control systems depends on optical specifications of video camera and peculiar features of video algorithm. Specified target function performance probability can serve as criterion of automated video control use efficiency. In this work, a new performance efficiency estimation method for automated equipment of target environment video control is suggested: to estimate the probability of target functions’ (object detection, capture, and auto tracking) performance. Theoretical prediction of target functions performance probability was built upon Johnson’s criterion and the use of optimal receiver model. The results of suggested method’s experimental verification have shown that target detection occurred when signal/noise ratio level was above 6. This level can be regarded as low value to ensure that object is detected with probability 0.9.


2017 ◽  
Vol 44 (5) ◽  
pp. 727-744
Author(s):  
Sujani Thrikawala ◽  
Stuart Locke ◽  
Krishna Reddy

Purpose The purpose of this paper is to examine the relationship between corporate governance (CG) and microfinance institution (MFI) performance, using a dynamic panel generalised method of moments (GMM) estimator to mitigate the serious issues with endogeneity. Design/methodology/approach Inconsistent findings and a general lack of empirical results for the microfinance industry leave an unclear message regarding the impacts of CG on MFI performance, especially in emerging economies. The authors use GMM estimation techniques to examine whether CG has an influence on MFI performance. Findings This study confirms that the MFIs’ contemporaneous performance and CG characteristics are statistically significantly positively linked with their past performance. This study finds statistically significant governance effects on MFI performance, including the presence of international directors and/or donor representatives on the board, client representatives on the board, percentage of non-executive directors and the quality of the national governance system. Practical implications These findings provide some insights for policy-makers and practitioners to develop suitable policies and guidelines to streamline MFIs’ operations in emerging countries. Moreover, national and international investors and donors may use these finding as a benchmark for their investment and funding decisions. Originality/value This paper is the first to estimate the CG and performance relationship of MFIs in a dynamic framework by applying the GMM estimation method. This approach improves upon traditional estimation methods by controlling the likely sources of endogeneity. Further, this paper examines whether quality of national-level governance characteristics is related to performance measures of profitability and outreach of MFIs.


2016 ◽  
Vol 5 ◽  
pp. 67-80 ◽  
Author(s):  
Nataly Zrazhevska

The most popular methods for dynamic risk measures – Value-at-Risk (VaR) and Conditional VaR (CVaR) estimating were analyzed, description and comparative analysis of the methods were fulfilled, recommendations on the use were given. Results of the research were presented in the form of a classification scheme of dynamic risk measures estimating that facilitates the choice of an estimation method. The GARCH-based models of dynamic risk measures VaR and CVaR evaluation for artificially generated series and two time series of log return on a daily basis of the most well-known Asian stock indexes Nikkey225 Stock Index and CSI30 were constructed to illustrate the effectiveness of the proposed scheme. A qualitative analysis of the proposed models was conducted. To analyze the quality of the dynamic VaR estimations the Cupets test and the Cristoffersen test were used. For CVaR estimations the V-test was used as quality test. The tests results confirm the high quality of obtained estimations. The proposed classification scheme of dynamic risk measures VaR and CVaR estimating may be useful for risk managers of different financial institutions.


2014 ◽  
Vol 4 (2) ◽  
pp. 195-206 ◽  
Author(s):  
Ruiting Xu ◽  
Zhigeng Fang ◽  
Jinyu Sun

Purpose – The purpose of this paper is to find out a scientific method to evaluate quality of complex products, whose quality is different from general products. Design/methodology/approach – Based on interval grey number theory, reliability analysis method and stochastic network theory, authors have established grey success tree analysis-graph evaluation and review technique (GSTA-GERT) model in this paper. Findings – Comparing complex products and general products, authors have found that complex products have two characters, i.e. quality of manufacture and quality of service. Furthermore, this paper has proved the GSTA-GERT model is a scientific and reasonable approach to estimate quality of complex products from the sight of manufacture-service network. Originality/value – This paper has established GSTA-GERT model, which surmounts the defect of traditional estimation method, such as lacking logic analysis in the method of analytic hierarchy process.


2016 ◽  
Vol 33 (5) ◽  
pp. 989-1004 ◽  
Author(s):  
Ya-Chien Feng ◽  
Frédéric Fabry ◽  
Tammy M. Weckwerth

AbstractAccurate radar refractivity retrievals are critical for quantitative applications, such as assimilating refractivity into numerical models or studying boundary layer and convection processes. However, the technique as originally developed makes some simplistic assumptions about the heights of ground targets () and the vertical gradient of refractivity (). In reality, the field of target phases used for refractivity retrieval is noisy because of varying terrain and introduces estimation biases. To obtain a refractivity map at a constant height above terrain, a 2D horizontal refractivity field at the radar height must be computed and corrected for altitude using an average . This is achieved by theoretically clarifying the interpretation of the measured phase considering the varying and the temporal change of . Evolving causes systematic refractivity biases, as it affects the beam trajectory, the associated target range, and the refractivity field sampled between selected targets of different heights. To determine and changes, a twofold approach is proposed: first, can be reasonably inferred based on terrain height; then, a new method of estimation is devised by using the property of the returned powers of a pointlike target at successive antenna elevations. The obtained shows skill based on in situ tower observation. As a result, the data quality of the retrieved refractivity may be improved with the newly added information of and .


Author(s):  
Loreta Abakoka

Nora Ikstena’s “Mātes piens” (Mother’s Milk; published in English as Soviet Milk) is one of the novels in the book series “MĒS. Latvija, XX gadsimts” (We. Latvia. The 20th Century). It describes the difficulties that can arise in the mother-daughter relationship, describes the Soviet time’s environment and its impact on everyday life. The historical novel “Mātes piens” has been published in 25 countries, which means that this novel has been translated into many different cultures, which are less familiar with the mentality of the Latvian people and the USSR times in Latvia. Therefore, it is crucial how the text is translated or whether the style and the particular poetics of Nora Ikstena’s language in this novel are accurately reproduced. Therefore, the scientific research work “Quality of Translated Comparisons of Nora Ikstena’s “Soviet Milk” and “Молоко матери”” was developed. Comparisons requiring the translator to take into account both the content and the meaning of the words were analysed, as well as the aspect of language imagery and culture. The novel was translated into English by Margita Gailīts, and into Russian by Ludmila Nukņeviča. The events of the novel “Soviet Milk” take place from the end of the Second World War until the 1980s. The main character is a daughter, whose story is intertwined with the life stories of her mother and grandmother. The novel portrays the daughter’s struggle with her mother’s depression, which has deprived her of emotional intimacy with her mother since birth; the daughter continues to hope and gain her mother’s love, helping in times of crisis and ignoring several rejections. Although the translation process is very old, the question about the translation quality is still relevant. Using sources of information and gaining theoretical knowledge of the translation process, an error estimation method was developed that allows the word “quality” to be quantified. Literary translation is mostly separated from other translation types and put into a separate category, usually because the meaning of a literary work cannot be clarified in simple terms presented today. It is also difficult to analyse what the reader expects from the translation. Since there cannot be one right way of translating literature, the sense of the translator’s ethical duty to the author is the most important. However, this is very limited by how well the translator understands the author’s intentions and what is said and how much freedom the translator is given to change the text to find the most appropriate way to express the idea in the language. (Sager 1994) Four groups were divided by Juliane House’s theory (House 2014; House 2017) about overt errors. Text translation errors are divided into 2 categories – covert and overt. Covert errors are difficult to notice because, superficially, from a grammatical point of view, the sentence is correct, but its content is not logical or acceptable. The overt errors detected are obvious, constitute a systematic error. Overt errors are divided into 7 groups: 1 – not translated; 2 – a slight change in meaning; 3 – a significant change in meaning; 4 – distortion of meaning; 5 – breach of SL system; 6 – creative translation; 7 – cultural filtering. 64 comparisons in Latvian, 64 equivalents in Russian, and 55 equivalents in English were excerpted (9 comparisons were not translated). Translations of comparisons were divided into 4 groups: 1) accurately translated, 2) translations with minor changes, 3) culturally harmonized translations, 4) untranslated comparisons. Translations of comparisons that scored 5 points or more are considered qualitatively translated, given that there are no significant errors. There is no single fundamental criterion for the quality of a translation against which all translated texts can be judged. There are several definitions of quality translation, and quality is affected by many factors. The translations of comparisons in both foreign languages (English and Russian) are of high quality; they received high marks if they were analysed according to the error evaluation table because the maximum number of points that could be obtained was 6 points and no comparative translation was lower than 5 points. The Russian translation is more successful (comparative translations more often scored 6 points) than the English translation, which can be justified by the fact that the Russian language is historically and geographically a neighbor of the Latvian language, but the English language and culture are remote. Phraseological comparisons are translated literally and also more accurately into Russian; there are more of the same equivalents in the target culture. When evaluating comparisons that use the concepts of biblical story motifs or images of Greek mythology, they are mostly accurately translated into the target languages, as the target cultures are well acquainted with this religion and Greek mythology. One of the most important findings – not only literal translations are of high quality; it is much more important to express them in a way that is understandable to the target culture while maintaining the author’s writing style and the text’s main idea, paying attention to details.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Ke Lu ◽  
Shanyong Zhao ◽  
YUjie Ma ◽  
Shangjing Wu ◽  
Cheng da Su

Purpose This paper aims to present an investigation on flight quality analysis and design of tilt-rotor aircraft combined with corresponding flight quality specifications. Design/methodology/approach From the perspective of modal characteristics of tilt-rotor aircraft, it focuses on the analysis of the change rules of the longitudinal short-term motion mode, lateral roll convergence mode, spiral mode and Dutch roll mode. Then, the flight quality design research is carried out using the explicit model tracking control method. The quantitative relationship between flight quality requirements and explicit model is established. Accordingly, the closed-loop flight quality of XV-15 tilt-rotor aircraft is evaluated. Findings The stability of spiral mode is the result of the interaction of various aerodynamic derivatives and spiral instability occurs in helicopter mode. The other motion modes are stable in full flight mode and meet the requirements of level 1 specified in ADS-33E-PRF and MIL-F-8785C flight quality specifications. There is a quantitative relationship between flight quality requirements and explicit model, and the flight quality of tilt-rotor aircraft is improved through the explicit model tracking control method. Practical implications The presented analysis results showed the influence of motion modes and flight quality and the effectiveness of explicit model tracking control method in flight quality improvement, which could be considered as new information for further flight quality design of tilt-rotor aircraft. Originality/value The originality of the paper lies in the proposed design and analysis method of the flight quality of tilt-rotor aircraft from the direction of the influence of its aerodynamic derivatives and motion modes.


2019 ◽  
Vol 29 (1) ◽  
pp. 1480-1495
Author(s):  
D. Khalandar Basha ◽  
T. Venkateswarlu

Abstract The image restoration (IR) technique is a part of image processing to improve the quality of an image that is affected by noise and blur. Thus, IR is required to attain a better quality of image. In this paper, IR is performed using linear regression-based support vector machine (LR-SVM). This LR-SVM has two steps: training and testing. The training and testing stages have a distinct windowing process for extracting blocks from the images. The LR-SVM is trained through a block-by-block training sequence. The extracted block-by-block values of images are used to enhance the classification process of IR. In training, the imperfections on the image are easily identified by setting the target vectors as the original images. Then, the noisy image is given at LR-SVM testing, based on the original image restored from the dictionary. Finally, the image block from the testing stage is enhanced using the hybrid Laplacian of Gaussian (HLOG) filter. The denoising of the HLOG filter provides enhanced results by using block-by-block values. This proposed approach is named as LR-SVM-HLOG. A dataset used in this LR-SVM-HLOG method is the Berkeley Segmentation Database. The performance of LR-SVM-HLOG was analyzed as peak signal-to-noise ratio (PSNR) and structural similarity index. The PSNR values of the house and pepper image (color image) are 40.82 and 36.56 dB, respectively, which are higher compared to the inter- and intra-block sparse estimation method and block matching and three-dimensional filtering for color images at 20% noise.


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