Validation of Direct Beam Irradiance Measurements From Rotating Shadowband Irradiometers in a Region With Different Atmospheric Conditions

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Norbert Geuder ◽  
Roman Affolter ◽  
Olaf Goebel ◽  
Basel Dahleh ◽  
Mohamed Al Khawaja ◽  
...  
Keyword(s):  
United Arab Emirates ◽  
Reference Station ◽  
Atmospheric Conditions ◽  
Direct Normal Irradiance ◽  
Lower Accuracy ◽  
Remote Sites ◽  
Parallel Measurement ◽  
Class Reference ◽  
Radiation Sensors ◽  
Standard Instrumentation

Rotating shadowband irradiometers (RSIs) are a common type of radiation sensors for measurement of direct normal irradiance (DNI) at remote sites where daily maintenance of the instruments is not feasible or practicable. Their primordial lower accuracy due to systematic deviations of the photodiode response can be improved significantly with a thorough calibration of each RSI against high precision sensors and application of suitable corrections on the raw data. With different available correction functions for the systematic errors, RSI data coincide with first class reference sensors within 2–3% root mean square deviation (RMSD) for 10 min averages of DNI and meet the annual irradiation sum within 1.5%. Such comparisons of RSI data to reference irradiances have only been published for a small number of sites. To endorse the credibility of RSI measurements, it has to be shown that these accuracies derived for certain locations are also valid at other sites with differing atmospheric conditions. Therefore, a parallel measurement campaign with six RSIs and a reference station with first class and secondary standard instrumentation has been performed in the in the extreme climate of the United Arab Emirates (UAE). The results of this comparison are presented in this paper. The stated empiric accuracy could be validated and confirmed for the UAE.

scholarly journals Drone Image Segmentation Using Machine and Deep Learning for Mapping Raised Bog Vegetation Communities

2020 ◽  
Vol 12 (16) ◽  
pp. 2602 ◽  
Author(s):  
Saheba Bhatnagar ◽  
Laurence Gill ◽  
Bidisha Ghosh
Keyword(s):  
Image Segmentation ◽  
Deep Learning ◽  
Computation Time ◽  
Semantic Segmentation ◽  
Training Dataset ◽  
Atmospheric Conditions ◽  
Raised Bog ◽  
Vegetation Communities ◽  
Lower Accuracy ◽  
Cost Efficient

The application of drones has recently revolutionised the mapping of wetlands due to their high spatial resolution and the flexibility in capturing images. In this study, the drone imagery was used to map key vegetation communities in an Irish wetland, Clara Bog, for the spring season. The mapping, carried out through image segmentation or semantic segmentation, was performed using machine learning (ML) and deep learning (DL) algorithms. With the aim of identifying the most appropriate, cost-efficient, and accurate segmentation method, multiple ML classifiers and DL models were compared. Random forest (RF) was identified as the best pixel-based ML classifier, which provided good accuracy (≈85%) when used in conjunction graph cut algorithm for image segmentation. Amongst the DL networks, a convolutional neural network (CNN) architecture in a transfer learning framework was utilised. A combination of ResNet50 and SegNet architecture gave the best semantic segmentation results (≈90%). The high accuracy of DL networks was accompanied with significantly larger labelled training dataset, computation time and hardware requirements compared to ML classifiers with slightly lower accuracy. For specific applications such as wetland mapping where networks are required to be trained for each different site, topography, season, and other atmospheric conditions, ML classifiers proved to be a more pragmatic choice.

scholarly journals Urban area GPS positioning accuracy using ASG-EUPOS POZGEO service as a function of session duration

2014 ◽  
Vol 49 (1) ◽  
pp. 33-42 ◽  
Author(s):  
Karol Dawidowicz ◽  
Grzegorz Krzan ◽  
Krzysztof Świątek
Keyword(s):  
Geodetic Network ◽  
Reference Station ◽  
Gps Data ◽  
Dual Frequency ◽  
Post Processing ◽  
Positioning Accuracy ◽  
Gps Positioning ◽  
Session Duration ◽  
Lower Accuracy ◽  
Gnss Observations

ABSTRACT GNSS observations carried out in a network of Continuously Operating Reference Station (CORS) are a complex systems which offer post-processing as well as corrections sent in realtime. In Poland, such a system has been in operation since June 2008, known as the Polish Active Geodetic Network (ASG-EUPOS). Usually the measurements performed in real time characterized lower accuracy than static measurements. For users who demand the highest precision results the post-processing services are provided. The paper presents an analysis of the position determination accuracy using ASG-EUPOS POZGEO service. It is well known that the final accuracy is e.g. the measuring conditions, time of observations or number of measured frequencies dependent. We processed 4 consecutive days of GPS data to determine how the accuracy of derived positional coordinates depends on the length of the observing session, the characteristics of horizon visibility on points and the used in post-processing observations (L1 or L1+L2). The POZGEO results show that horizontal accuracies of about 1-2 cm and vertical accuracies of 4 cm are achievable provided 0.5 hours dual frequency GPS data. The accuracy clearly decreases for point measured under conditions of strongly limited satellite availability

scholarly journals New parameterized model for GPS water vapor tomography

2017 ◽  
Vol 35 (2) ◽  
pp. 311-323 ◽  
Author(s):  
Nan Ding ◽  
Shubi Zhang ◽  
Qiuzhao Zhang
Keyword(s):  
Water Vapor ◽  
Water Cycle ◽  
Weather Conditions ◽  
Reference Station ◽  
Atmospheric Conditions ◽  
Vapor Density ◽  
Spatiotemporal Resolution ◽  
Parameterized Model ◽  
Time Changes ◽  
Rainy Days

Abstract. Water vapor is the basic parameter used to describe atmospheric conditions. It is rarely contained in the atmosphere during the water cycle, but it is the most active element in rapid space–time changes. Measuring and monitoring the distribution and quantity of water vapor is a necessary task. GPS tomography is a powerful means of providing high spatiotemporal resolution of water vapor density. In this paper, a spatial structure model of a humidity field is constructed using voxel nodes, and new parameterizations for acquiring data about water vapor in the troposphere via GPS are proposed based on inverse distance weighted (IDW) interpolation. Unlike the density of water vapor that is constant within a voxel, the density at a certain point is determined by IDW interpolation. This algorithm avoids the use of horizontal constraints to smooth voxels that are not crossed by satellite rays. A prime number decomposition (PND) access order scheme is introduced to minimize correlation between slant wet delay (SWD) observations. Four experimental schemes for GPS tomography are carried out in dry weather from 2 to 8 August 2015 and rainy days from 9 to 15 August 2015. Using 14 days of data from the Hong Kong Satellite Positioning Reference Station Network (SatRef), the results indicate that water vapor density derived from 4-node methods is more robust than that derived from that of 8 nodes or 12 nodes, or that derived from constant refractivity schemes and the new method has better performance under stable weather conditions than unstable weather (e.g., rainy days). The results also indicate that an excessive number of interpolations in each layer reduce accuracy. However, the accuracy of the tomography results is gradually reduced with increases in altitude below 7000 m. Moreover, in the case of altitudes between 7000 m and the upper boundary layer, the accuracy can be improved by a boundary constraint.

scholarly journals Source Apportionment of Ambient Black Carbon during the COVID-19 Lockdown

2020 ◽  
Vol 17 (23) ◽  
pp. 9021
Author(s):  
Ismail Anil ◽  
Omar Alagha
Keyword(s):  
Black Carbon ◽  
United Arab Emirates ◽  
Fossil Fuel ◽  
Arabian Gulf ◽  
Receptor Site ◽  
Ground Level ◽  
Emission Sources ◽  
Atmospheric Conditions ◽  
Entire Study ◽  
High Concentrations

Black carbon (BC) particles being emitted from mobile and stationary emission sources as a result of combustion activities have significant impacts on human health and climate change. A lot of social activities have been halted during the COVID-19 lockdowns, which has evidently enhanced the ambient and indoor air quality. This paper investigates the possible emission sources and evaluates the meteorological conditions that may affect the dispersion and transport of BC locally and regionally. Ground-level equivalent BC (eBC) measurements were performed between January 2020 and July 2020 at a university campus located in Dammam city of the Kingdom of Saudi Arabia (KSA). The fossil fuel (eBCff) and biomass burning (eBCbb) fractions of total eBC (eBCt) concentrations were estimated as 84% and 16%, respectively, during the entire study period. The mean eBCbb, eBCff, and eBCt concentrations during the lockdown reduced by 14%, 24%, and 23%, respectively. The results of statistical analyses indicated that local fossil fuel burning emissions and atmospheric conditions apparently affected the observed eBC levels. Long-range potential source locations, including Iraq, Kuwait, Iran, distributed zones in the Arabian Gulf, and United Arab Emirates and regional source areas, such as the Arabian Gulf coastline of the KSA, Bahrain, and Qatar, were associated with moderate to high concentrations observed at the receptor site as a result of cluster analysis and concentration-weighted trajectory analysis methods.

Rainfall in the desert: anatomy of rainfall events in the United Arab Emirates

2021 ◽  
Author(s):  
Keri Nicoll ◽  
Martin Airey ◽  
R. Giles Harrison ◽  
Graeme Marlton
Keyword(s):  
United Arab Emirates ◽  
High Surface ◽  
Radar Data ◽  
Annual Rainfall ◽  
Cloud Base ◽  
Rain Event ◽  
Atmospheric Conditions ◽  
Rainfall Events ◽  
Al Ain ◽  
Water Scarce

<p>The occurrence and characteristics of rainfall events in arid and water scarce regions are of great interest to many, as it is vital to understand the efficient use of this finite resource, for example in terms of water management, agriculture, irrigation, and domestic food security. Fundamental to this is understanding the numerous environmental aspects that affect the generation and persistence of rain. These include the presence of cloud droplets, activation and growth processes,  temperature and relative humidity of the within and below cloud regions, and the cloud base height. Not only must what causes rainfall to be initiated be understood, but also the conditions that allow that rain to reach the surface.</p><p> </p><p>This work examines the conditions required for a successful rain event (i.e. one in which rainfall reaches the ground) to occur in the arid desert region of Al Ain, in the United Arab Emirates (UAE) (annual rainfall 76mm).  The high surface temperatures and dry air mean that rain events at Al Ain commonly occur as virga, as the rain droplets cannot survive evaporation under the local atmospheric conditions.  Here we examine individual rainfall events using backscatter data from a laser ceilometer, in conjunction with C-band radar data, to further understand the processes required for successful rain generation.  During the 2 year period of study, there was a total of 57.5 hours of rain (rainfall 0.5% of the time), with a total of 105 rainfall events.  Here we examine the effect on rainfall of (a) the initial size of the droplets falling from the cloud base, which must be large enough to survive the fall to the surface; and (b) the effect of the below cloud thermodynamic profile on the evaporation of the droplet (which also depends on the height of the cloud base). Preliminary conclusions find that smaller droplets, higher cloud bases, smaller cloud depths, and lower cloud base temperatures all favour the occurrence of a rain event terminating as virga before it reaches the surface. Understanding the details of why many potential rainfall events don’t reach the surface can ultimately lead to the more efficient implementation of rainfall enhancing measures such as cloud seeding.</p><p> </p>

Selective Corrosion of brazed joint between BNi-2 filler metal and stainless steel 316

1996 ◽  
Vol 54 ◽  
pp. 218-219
Author(s):  
H. S. Kim ◽  
R. U. Lee
Keyword(s):  
Stainless Steel ◽  
Filler Metal ◽  
Surface Preparation ◽  
Optical Microscope ◽  
Heating Element ◽  
Incomplete Fusion ◽  
Atmospheric Conditions ◽  
Leak Test ◽  
High Temperature Side ◽  
Inconel 600

A heating element/electrical conduit assembly used in the Orbiter Maneuvering System failed a leak test during a routine refurbishment inspection. The conduit, approximately 100 mm in length and 12 mm in diameter, was fabricated from two tubes and braze-joined with a sleeve. The tube on the high temperature side (heating element side) and the sleeve were made of Inconel 600 and the other tube was stainless steel (SS) 316. For the filler metal, a Ni-Cr-B brazing alloy per AWS BNi-2, was used. A Helium leak test spotted the leak located at the joint between the sleeve and SS 316 tubing. This joint was dissected, mounted in a plastic mold, polished, and examined with an optical microscope. Debonding of the brazed surfaces was noticed, more pronounced toward the sleeve end which was exposed to uncontrolled atmospheric conditions intermittently. Initially, lack of wetting was suspected, presumably caused by inadequate surface preparation or incomplete fusion of the filler metal. However, this postulation was later discarded based upon the following observations: (1) The angle of wetting between the fillet and tube was small, an indication of adequate wetting, (2) the fillet did not exhibit a globular microstructure which would be an indication of insufficient melting of the filler metal, and (3) debonding was intermittent toward the midsection of the sleeve.

Hepatocyte ultrastructural alterations in perimetastatic areas

1996 ◽  
Vol 54 ◽  
pp. 768-769
Author(s):  
H. J. Finol ◽  
M. E. Correa ◽  
L.A. Sosa ◽  
A. Márquez ◽  
N.L. Díaz
Keyword(s):  
Malignant Tumor ◽  
Malignant Tumors ◽  
Surrounding Tissue ◽  
Ultrastructural Changes ◽  
Pancreas Carcinoma ◽  
Duct Carcinoma ◽  
Tissue Samples ◽  
Primary Malignant Tumor ◽  
Transmission Electron ◽  
Remote Sites

In classical oncological literature two mechanisms for tissue aggression in patients with cancer have been described. The first is the progressive invasion, infiltration and destruction of tissues surrounding primary malignant tumor or their metastases; the other includes alterations produced in remote sites that are not directly affected by any focus of disease, the so called paraneoplastic phenomenon. The non-invaded tissue which surrounds a primary malignant tumor or its metastases has been usually considered a normal tissue . In this work we describe the ultrastructural changes observed in hepatocytes located next to metastases from diverse malignant tumors.Hepatic biopsies were obtained surgically in patients with different malignant tumors which metatastized in liver. Biopsies included tumor mass, the zone of macroscopic contact between the tumor and the surrounding tissue, and the tissue adjacent to the tumor but outside the macroscopic area of infiltration. The patients (n = 5), 36–75 years old, presented different tumors including rhabdomyosarcoma, leiomyosarcoma, pancreas carcinoma, biliar duct carcinoma and colon carcinoma. Tissue samples were processed with routine techniques for transmission electron microscopy and observed in a Hitachi H-500 electron microscope.

Recent Progress In High-Resolution Shadowing For Biological Transmission Electron Microscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 510-511 ◽  
Author(s):  
Heinz Gross ◽  
Katarina Krusche ◽  
Peter Tittmann
Keyword(s):  
Heavy Metal ◽  
High Resolution ◽  
Freeze Drying ◽  
Atmospheric Conditions ◽  
Vacuum Equipment ◽  
Transmission Electron ◽  
Gas Atmosphere ◽  
Gas Molecules ◽  
Residual Gas ◽  
Backing Layer

Freeze-drying followed by heavy metal shadowing is a long established and straight forward approach to routinely study the structure of dehydrated macromolecules. Very thin specimens such as isolated membranes or single macromolecules are directly adsorbed on C-coated grids. After rapid freezing the grids are transferred into a suitable vacuum equipment for freeze-drying and heavy metal shadowing.To improve the resolution power of shadowing films we introduced shadowing at very low specimen temperature (−250°C). To routinely do that without the danger of contamination we developed in collaboration with Balzers an UHV (p≤10-9 mbar) machine (BAF500K, Fig.2). It should be mentioned here that at −250°C the specimen surface acts as effective cryopump for practically all impinging residual gas molecules from the residual gas atmosphere.Common high resolution shadowing films (Pt/C, Ta/W) have to be protected from alterations due to air contact by a relatively thick C-backing layer, when transferred via atmospheric conditions into the TEM. Such an additional C-coat contributes disturbingly to the contrast at high resolution.

Ras al Khaimah: further archaeological discoveries

Antiquity ◽  
1976 ◽  
Vol 50 (200) ◽  
pp. 216-222
Author(s):  
Beatrice De Cardi
Keyword(s):  
United Arab Emirates ◽  
The State ◽  
Focused Attention ◽  
North East ◽  
The North ◽  
History Of ◽  
The City

Ras a1 Khaimah is the most northerly of the seven states comprising the United Arab Emirates and its Ruler, H. H. Sheikh Saqr bin Mohammad al-Qasimi, is keenly interested in the history of the state and its people. Survey carried out there jointly with Dr D. B. Doe in 1968 had focused attention on the site of JuIfar which lies just north of the present town of Ras a1 Khaimah (de Cardi, 1971, 230-2). Julfar was in existence in Abbasid times and its importance as an entrep6t during the sixteenth and seventeenth centuries-the Portuguese Period-is reflected by the quantity and variety of imported wares to be found among the ruins of the city. Most of the sites discovered during the survey dated from that period but a group of cairns near Ghalilah and some long gabled graves in the Shimal area to the north-east of the date-groves behind Ras a1 Khaimah (map, FIG. I) clearly represented a more distant past.

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