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1 – 10 of 25Anton V. Ubaychin, Tilekbek Abdirasul Uulu and Grigory Zhuk
This paper aims to describe a new microwave radiometer designed for sensing natural mediums to solve various applied scientific problems. The research findings enable to make…
Abstract
Purpose
This paper aims to describe a new microwave radiometer designed for sensing natural mediums to solve various applied scientific problems. The research findings enable to make assertions about high efficiency of the described microwave radiometer being a part of mobile sensor systems with self-contained power supplies.
Design/methodology/approach
A new microwave radiometer is based on the modification of the null method. Modification of the null method has been implemented by using two reference noise generators. The first reference noise generator is passive and its implementation is based on the matched load. A low-noise amplifier is used as the second reference noise generator. The use of the low-noise amplifier as the reference noise generator is based on the noise wave generation effect at its input whereby the waves form low-temperature noise.
Findings
The use of the low-noise amplifier as the reference noise generator in the modified microwave radiometer has made it possible to simplify the device design at the system level while reducing the weight and power consumption and increasing sensitivity.
Originality/value
The novelty of the modified radiometer lies in the modification of the null method and the removal of high-temperature reference noise generators based on avalanche transit-time diodes. Further, the novelty lies in the invariance of measurement results toward changes in the receiver’s own noise and transmission factor while the design of the device has been simplified.
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Srinivasa Ramanujam, R. Chandrasekar and Balaji Chakravarthy
The purpose of this paper is to develop an algorithm, using PCA‐based neural network, to retrieve the vertical rainfall structure in a precipitating atmosphere. The algorithm is…
Abstract
Purpose
The purpose of this paper is to develop an algorithm, using PCA‐based neural network, to retrieve the vertical rainfall structure in a precipitating atmosphere. The algorithm is powered by a rigorous solution to the plane parallel radiative transfer equation for the atmosphere with thermodynamically consistent vertical profiles of humidity, temperature and cloud structures, together with “measured” vertical profiles of the rain structure derived from a radar.
Design/methodology/approach
The raining atmosphere is considered to be a plane parallel, radiatively participating medium. The atmospheric thermodynamic profiles such as pressure, temperature and relative humidity along with wind speed at sea surface and cloud parameters corresponding to Nargis, a category 4 tropical cyclone that made its landfall on May 2, 2008 at the Republic of Myanmar, are obtained by solving the flux form of Euler's equations in three‐dimensional form. The state‐of‐the‐art community software Weather Research and Forecasting has been used for solving the set of equations. The three‐dimensional rain profiles for the same cyclone at the same instant of time are obtained from National Aeronautics and Space Administration's space borne Tropical Rainfall Measuring Mission's precipitation radar over collocated pixels. An in‐house Micro‐Tropiques code is used to perform radiative transfer simulations for frequencies corresponding to a typical space borne radiometer, and hence to generate the database which is later used for training the neural network. The back propagation‐based neural network is optimized with reduced number of parameters using principal component analysis (PCA).
Findings
The results show that neural network is capable of retrieving the vertical rainfall structure with a correlation coefficient of over 0.99. Further, reducing the ill‐posedness in retrieving 56 parameters from just nine measurements using PCA has improved the root mean square error in the retrievals at reduced computational time.
Originality/value
The paper shows that combining numerically generated atmospheric profiles together with radar measurements to serve as input to a radiative transfer model brings in the much‐required synergy between numerical weather prediction, radar measurements and radiative transfer. This strategy can be gainfully used in satellite meteorology. Using principal components to reduce the ill‐posedness, thereby increasing the robustness in retrieving vertical rain structure, has been attempted for the first time. A well‐trained network can be used as one possible option for an operational algorithm for the proposed Indian climate research satellite Megha‐Tropiques, due to be launched in early 2011.
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Many types of sensing from satellites and aircraft are giving the offshore oil and gas industry increasingly comprehensive information.
Shuang Yu, Jun Miao, Hua Wang and Zhiyuan Qian
The purpose of this paper is to find the root cause of the current issue for a scan drive mechanism which is used to drive and to control the Microwave Radiometer Imager (MWRI…
Abstract
Purpose
The purpose of this paper is to find the root cause of the current issue for a scan drive mechanism which is used to drive and to control the Microwave Radiometer Imager (MWRI) equipment of the FY‐3 meteorological satellite in China.
Design/methodology/approach
In order to find the root cause of the irregularly unstable motor current, some possible reasons for this anomaly, including satellite dynamic, telemetry, electronics and mechanism system, are investigated. The root cause is focused on the mechanism that is increasing friction caused by limitation rollers striking the rotating part from time to time, which has been verified by simulation and test.
Findings
Findings gained from the simulations and tests results were: for a rotational space mechanism with high velocity accuracy requirement, if the moment of inertial (MOI) of the load is quite large, the balance is the key factor to the equipment performance. Moreover, thermal gradient and temperature difference are also important factors, especially to the space mechanism with large dimensions. Even a very small thermal deformation can lead to quite a number of unexpected results.
Practical implications
The better performance of the next optimized MWRI equipment in orbit showed that the performed measures are very effective and useful. The experience gained in settling this issue can be used for the design of a space scanning mechanism with high rotating speed and high accuracy.
Originality/value
The paper is an original work for the authors. The issue has not been found in the related literatures. It is based on research work on an engineering problem of unstable current issue, which is significant to the MWRI payload of the FY‐3 satellite.
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The purpose of this paper is to review the industrial sensing applications of electromagnetic radiation (EMR) and is in two parts. This, the second part, considers the infrared…
Abstract
Purpose
The purpose of this paper is to review the industrial sensing applications of electromagnetic radiation (EMR) and is in two parts. This, the second part, considers the infrared (IR) to radio‐frequency (RF) spectral regions.
Design/methodology/approach
This paper discusses the sensing applications of EMR in the IR to RF region, through reference to the techniques employed, products and their applications.
Findings
This paper shows that this spectral region is used in a diversity of sensors for the measurement of physical variables, gases and chemical compounds. The most widely used phenomena are absorption and reflection. Applications are found in a wide range of industries.
Originality/value
This paper provides a detailed review of the sensing uses of EMR with wavelengths longer than visible light.
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MATRAMarconi Space is the first fully integrated European space company (51 % Matra, 49 % GEC Marconi). It employs a staff of 3200 – 2000 in France and 1200 in Great Britain …
Abstract
MATRAMarconi Space is the first fully integrated European space company (51 % Matra, 49 % GEC Marconi). It employs a staff of 3200 – 2000 in France and 1200 in Great Britain — spread over five sites. In 1992, it achieved a turnover of 5.6 billion francs ($1.05 billion).
NASA's role in aeronautics is, by charter, to improve the usefulness, performance, speed, safety, and efficiency of U.S. civil and military aeronautical vehicles and to preserve…
Abstract
NASA's role in aeronautics is, by charter, to improve the usefulness, performance, speed, safety, and efficiency of U.S. civil and military aeronautical vehicles and to preserve U.S. leadership in aeronautical science and technology and its applications. To fill that role, NASA has oriented its aeronautics research and technology (R & T) programme to meet the near‐term and far‐term technology needs of the aviation industry, aircraft operators, government regulatory agencies, and the military services. NASA coordinates closely with those organizations in defining the R & T needs and the objectives for its aeronautics programme. The programme objective of potentially greatest interest to attendees of the International Air Safety Seminar is “To generate technology required for safer, more economical, efficient, fuel‐conservative, and environmentally acceptable air transportation systems to satisfy current and projected national needs.” In the spirit of this international meeting, I should note that certain NASA aeronautical research disciplines include cooperative efforts with the government aeronautical research organizations of several foreign countries.
Awel Haji Ibrahim, Dagnachew Daniel Molla and Tarun Kumar Lohani
The purpose of this study is to address a highly heterogeneous rift margin environment and exhibit considerable spatiotemporal hydro-climatic variations. In spite of limited…
Abstract
Purpose
The purpose of this study is to address a highly heterogeneous rift margin environment and exhibit considerable spatiotemporal hydro-climatic variations. In spite of limited, random and inaccurate data retrieved from rainfall gauging stations, the recent advancement of satellite rainfall estimate (SRE) has provided promising alternatives over such remote areas. The aim of this research is to take advantage of the technologies through performance evaluation of the SREs against ground-based-gauge rainfall data sets by incorporating its applicability in calibrating hydrological models.
Design/methodology/approach
Selected multi satellite-based rainfall estimates were primarily compared statistically with rain gauge observations using a point-to-pixel approach at different time scales (daily and seasonal). The continuous and categorical indices are used to evaluate the performance of SRE. The simple scaling time-variant bias correction method was further applied to remove the systematic error in satellite rainfall estimates before being used as input for a semi-distributed hydrologic engineering center's hydraulic modeling system (HEC-HMS). Runoff calibration and validation were conducted for consecutive periods ranging from 1999–2010 to 2011–2015, respectively.
Findings
The spatial patterns retrieved from climate hazards group infrared precipitation with stations (CHIRPS), multi-source weighted-ensemble precipitation (MSWEP) and tropical rainfall measuring mission (TRMM) rainfall estimates are more or less comparably underestimate the ground-based gauge observation at daily and seasonal scales. In comparison to the others, MSWEP has the best probability of detection followed by TRMM at all observation stations whereas CHIRPS performs the least in the study area. Accordingly, the relative calibration performance of the hydrological model (HEC-HMS) using ground-based gauge observation (Nash and Sutcliffe efficiency criteria [NSE] = 0.71; R2 = 0.72) is better as compared to MSWEP (NSE = 0.69; R2 = 0.7), TRMM (NSE = 0.67, R2 = 0.68) and CHIRPS (NSE = 0.58 and R2 = 0.62).
Practical implications
Calibration of hydrological model using the satellite rainfall estimate products have promising results. The results also suggest that products can be a potential alternative source of data sparse complex rift margin having heterogeneous characteristics for various water resource related applications in the study area.
Originality/value
This research is an original work that focuses on all three satellite rainfall estimates forced simulations displaying substantially improved performance after bias correction and recalibration.
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