Automated Identification of Coronal Holes from Synoptic EUV Maps

Coronal holes (CHs) are regions of open magnetic field lines in the solar corona and the source of the fast solar wind. Understanding the evolution of coronal holes is critical for solar magnetism as well as for accurate space weather forecasts. We study the extreme ultraviolet (EUV) synoptic maps at three wavelengths (195 Å/193 Å, 171 Å and 304 Å) measured by the Solar and Heliospheric Observatory/Extreme Ultraviolet Imaging Telescope (SOHO/EIT) and the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) instruments. The two datasets are first homogenized by scaling the SDO/AIA data to the SOHO/EIT level by means of histogram equalization. We then develop a novel automated method to identify CHs from these homogenized maps by determining the intensity threshold of CH regions separately for each synoptic map. This is done by identifying the best location and size of an image segment, which optimally contains portions of coronal holes and the surrounding quiet Sun allowing us to detect the momentary intensity threshold. Our method is thus able to adjust itself to the changing scale size of coronal holes and to temporally varying intensities. To make full use of the information in the three wavelengths we construct a composite CH distribution, which is more robust than distributions based on one wavelength. Using the composite CH dataset we discuss the temporal evolution of CHs during the Solar Cycles 23 and 24.     

Glutamic Acid Modified Fenton System for Degradation of BTEX Contamination

The present study employed a modified Fenton system that aims to extend the optimum pH range towards neutral conditions for studying the oxidation of benzene, toluene, ethyl benzene, xylenes (BTEX) using glutamic acid (Glu) as an iron chelator. Addition of 20 mM Glu greatly enhanced the oxidation rate of BTEX in modified Fenton system at pH 5–7. A rapid mass destruction (>97% after 1 h) of BTEX as a water contaminant carried out in the presence of 500 mM H₂O₂, 10 mM Fe²⁺, and 20 mM Glu at pH 5 could be shown. The efficiency of this modified Fenton's system for mass destruction of BTEX in contaminated water was measured to estimate the impact of the major process variables that include initial concentrations of soluble Fe, H₂O₂, Glu (as metal chelating agent), and reaction time.     

A reanalysis of the AD 365 tsunami impact along the Egyptian Mediterranean coast

The historical tsunamigenic event of 21 July AD 365 destroyed several coastal locations in the Eastern Mediterranean region. The foremost destructive impacts were recorded in Crete and Egypt. The present study re-examines the effect of location, direction, height and time of travel of the tsunami towards the Egyptian coast. Evidently, this tsunamigenic event is related to an earthquake which is identified with a Hellenic Arc subduction-zone event of great magnitude, M > 8, as manifested by up to 9 m uplift in western Crete. The maximum run-up height distribution in the front of the Nile Delta was about 9.5 m in Alexandria, while those of the neighboring cities were 7.1 m, 4.9 m, and 1.9 m at Rashid, Damietta and El-Arish, respectively. Data obtained from this study is essential to evaluate the tsunami hazards along the Egyptian coast.     

Evaluating post-hurricane impacts in co-management areas: a framework for expert consensus

Natural Hazards - Natural ecosystems are characterized as dynamic systems that evolve through natural patterns of disturbance. Land managers can work within this system of natural disturbance by...     

Interface creep behavior of grouted anchors in clayey soils: effect of soil moisture condition

This study aims at investigating the influence of moisture conditions on interface shear behavior of element-grouted anchor specimens embedded in clayey soils. The tests involved comparatively short embedment lengths and a device that was specially designed to facilitate moisture conditioning. Rapidly loaded pullout tests as well as pullout tests under sustained (creep) loading were conducted to characterize both the short-term and long-term ultimate shear strength of anchor–soil interfaces. Both values of the interface shear strength were found to decrease exponentially with increasing moisture content values, although their ratio was found to show a linearly decreasing trend with increasing moisture content. The interface shear creep response under pullout conditions was characterized by a rheological hybrid model that could be calibrated using experimental measurements obtained under increasing stress levels. The accuracy of the hybrid model was examined by evaluating the stress-dependent prediction model as well as its governing parameters. This investigation uncovers the coupled impact of soil moisture condition and external stress state on the time-dependent performance of grouted anchors embedded in clayey soils by correlating the interface shear strength with soil moisture content and associating the creep model with stress levels applied to the grout–soil interface.

     

Sediment characteristics and water circulation of Big Jemsa Bay,Red Sea,Egypt

Big Jemsa Bay is one of the indentations dissecting the continuity of the Red Sea north-western shoreline. The data was collected from bathymetric survey, current meters and sediment samples. Analyses have been undertaken of coastal processes, seabed morphology, grain size characteristics and the effect of current circulation on the distribution of sediment characteristics. The sediment pattern varies from coarse sand in the southern part to silt and fine sand in the northern part. The central part of the study area is mainly composed of terrigenous isometric-medium sand facies. The sorting distribution of sediments varies from moderately well sorted to poorly sort. The significant factors that control the sediment transport process are downslope gravity and wave-induced currents that are affected by the seafloor configuration and the shoreline orientation. According to the circulation effect on the sediment transport of the study area where deposition of fine sand and silt was observed in the northern part. Because sediment transport mitigates the occurrence of pollutant deposition in this part of the bay, we recommend that future constructions along the bay should be in the southern part.     

Assessment of seismic hazards for Hurghada,Red Sea,Egypt

The entrance of the southern Suez Gulf of the Red Sea is known to be an area of high seismic activity in Egypt. The high rate of seismic activity in this area is mainly related to the adjustment in motion at the triple junction between the African plate, the Arabian plate, and the Sinai microplate. The present study attempts to estimate the Probabilistic Seismic Hazard Analysis (PSHA) for Hurghada site. This was done in two steps; the first one is by estimating specific parameters for the site, such as the mean seismic activity, λ, the Gutenberg-Richter parameter, b, and the maximum regional magnitude, m _max. The second step is by selecting a ground motion parameter that is applicable to Hurghada site. The procedure permits the combination of both historical and recent instrumental data. The results of the hazard assessment, expressed as the worst case scenario, detect that Hurghada is exposed to the maximum credible earthquake event of magnitude m _max = 7.1 ± 0.31, at hypocentral distance of 31.6 ± 10 km. The possibility of the maximum Peak Ground Acceleration (PGA), which occurred in relation to this event at Hurghada site, is equal to 0.29 g. The mean return periods with the selected accelerations for Hurghada, a horizontal acceleration of 0.1 g, is expected to occur once every 74–106 years, with an average of one every 90 years. This result which obtained from the hazard assessment can be used as an input data for a seismic risk assessment.     

Compactness,connectivity, and walking accessibility on the neighborhood level according to sustainability certifications: improvement or downgrade? A case study of Cairo,Egypt

Urban sustainability certifications (USCs) urge developers to exceed the local norms and regulatory requirements to attain sustainability. USCs are gaining international recognition as planning and policy support tools. This study aims to assess the relevance of four USCs (LEED for Neighborhood Development, BREAAM communities, CASBEE for Urban Development, and Pearl Community Rating System) in contexts outside their country of origin using Cairo Governorate as a case study. The study focuses on compactness, street connectivity, and walking accessibility as prominent components for sustainable mobility and urban form at the neighborhood level. The study examines 202 neighborhoods in Cairo in terms of compactness and then focuses on eight urban areas in different locations and with different characteristics to assess their connectivity and walking accessibility. Different analyses were performed with ArcGIS software using data about neighborhoods’ population, residential units, street networks, established buildings, buildings’ outlines and heights, and detailed uses. Results show that USCs’ indicators and thresholds are generally lenient and insensitive to the context of formal areas in Cairo Governorate, which are significantly more compact, mixed (horizontally and vertically), and connected. This study adds to the currently limited empirical evidence refuting the use of some USCs as global tools and questioning their utilization in different contexts either as they are or even through an adaptation process.     

A design‐variable‐based inelastic hysteretic model for beam–column connections

This paper presents a design‐variable‐based inelastic hysteretic model for beam–column connections. It has been well known that the load‐carrying capacity of connections heavily depends on the types and design variables even in the same connection type. Although many hysteretic connection models have been proposed, most of them are dependent on the specific connection type with presumed failure mechanisms. The proposed model can be responsive to variations both in design choices and in loading conditions. The proposed model consists of two modules: physical‐principle‐based module and neural network (NN)‐based module in which information flow from design space to response space is formulated in one complete model. Moreover, owing to robust learning capability of a new NN‐based module, the model can also learn complex dynamic evolutions in response space under earthquake loading conditions, such as yielding, post‐buckling and tearing, etc. Performance of the proposed model has been demonstrated with synthetic and experimental data of two connection types: extended‐end‐plate and top‐ and seat‐angle with double‐web‐angle connection. Furthermore, the design‐variable‐based model can be customized to any structural component beyond the application to beam–column connections. Copyright © 2007 John Wiley & Sons, Ltd.