Sharif Digital Repository

Local scouring at the downstream of sluice gates in the erosive beds is one of the main concerns of hydraulic engineers because of the significant damage that it can cause to the hydraulic structures. It is important to control the local scour depth at downstream of hydraulic structures to ensure safety operation of these systems. Many researchers have conducted various studies to predict the maximum depth and diameter of scour hole and develop new methods in order to control this phenomenon. One way to overcome this problem is the use of apron, or non-erosive bed. In order to shorten the apron length or decrease the effect of the... 

In this thesis, the satellite constellation orbit design for regional coverage is investigated. The orbits of satellites in a constellation for Earth observation missions play a crucial role in performance and characteristics of the mission; for example the image resolution, the area of coverage, and the coverage interval. In this thesis the problem is to find the optimal initial orbital elements for meeting the earth observation mission objectives for one or several sites. The cost functions are the total coverage time, the maximum gap time, time average gap, altitude, and number of satellites. The problem is solved in a multi-objective manner for different combination of two of the above... 

Many embedded multicore systems can benefit from a memory hierarchy to bridge the processor/memory speed gap. Embedded systems usually utilize a cacheless architecture to avoid the unpredictable behavior. Unlike caches, scratchpad memories (SPM) are software controlled and hence the execution time of applications on such systems can be accurately predicted. Scheduling the tasks of an embedded multicore application and partitioning the available SPM budget among these cores are two critical issues in such systems. Often, these are considered separately, such a decoupled approach may miss better quality schedules. In this paper, we present an integrated approach to task scheduling and SPM... 

Nowadays marine-tourism industry, especially under water tourism, has become very attractive. Thus, numerous under water vehicles are designed and constructed. The primary objective of the present study is to design an underwater vehicle capable of carrying ten passengers. Tow system is proposed as propulsion system. Due to the high costs, noise and vibrations of existing propulsion systems in medium size vehicles which contradicts the goal of calm atmosphere for passenger, the proposing system seems suitable and pragmatic. Two-part tow system is utilized to enhance the stability of the under water vehicle named Towfish. In this study the structure of towfish is being designed. Then,... 

In recent decades, the concentration of carbon dioxide in the atmosphere has increased. Carbon dioxide is a greenhouse gas that raises the Earth’s temperature, and it can endanger life on Earth. This study uses the 6.2 version of the Regional Atmospheric Modeling System (RAMS) with its simple biosphere model (SiB-2) to simulate and forecast the concentration of carbon dioxide over the Daintree rainforest in Australia. This analysis helps to better understand the interaction between the biosphere and the atmosphere. Results of the carbon dioxide simulation were compared and validated with the observed values of the satellite product (MultiInstrumentFusedXCO2). Based on effective parameters,... 

This study consists of two parts. In the first part, the performance of the LISFLOOD-FP model, which is raster-based, and the HEC-RAS model, are compared and evaluated. This work studied different scenarios under various digital models in two study areas, the Kashkan study basin with mountainous topography and the basin in Nebraska, which has a plain surface. The flood events are among the most severe floods in both study areas that occurred in March and April 2019. This study showed that in mountain topography, the performance of both models is good even with the 30 m high digital models. Although two models perform well, in the Nebraska basin, the performance of the two models in the... 

Forested areas can cause positive impacts on ecosystems and water supply for agriculture, electricity generation, industry, and human. On the other hand, large-scale deforestation affects the water and energy budget on a regional and global scale. Considering the importance of this issue, this study evaluates the impact of land use and land cover changes (LULC) on the water cycle components, including precipitation, evapotranspiration, runoff, and hydroclimatic variables such as soil moisture, air temperature, soil temperature, and sensible heat flux in southeastern Australia using an ecosystem model called Integrated Biosphere Simulator (IBIS). For this purpose, a two-year time span with... 

Wildfires are complex phenomena with many indeterminate and highly unpredictable driving factors that have remained unresolved. During the last decade, machine learning methods have successfully excelled in wildfire prediction as an alternative to traditional field research methods by elucidating the relationship between historical wildfire events and various important variables. The main purpose of this research is to evaluate the random forest machine learning approach and the logistic regression statistical approach to prepare a wildfire susceptibility map using data related to historical wildfires and effective variables in the Okanogan region in Washington province of the United States... 

Clustering presents valuable information in discovery of the climatic zones. To use clustering approaches, similarity measure, clustering algorithm, and clustering validity index should be determined. To find climatic zones over Middle East nad North Africa (MENA), this study performs k-means clustering with Euclidean distance as the similarity measure on four monthly precipitation datasets (CRU, GPCC, UDEL, and PREC/L) and two monthly temperature datasets (CRU, NOAA GHCN-CAMS). This study aims to validate clustering results and find a proper number of clusters. For this purpose, five traditional validity indices are examined on experimental datasets. Results show significant differences... 

In recent decades, the earth is affected by climate change and the seasons has been warmer than the last. Furthermore, the efficiency of agricultural irrigation is low, and it leads to surface water drought and decrease in groundwater level. The Middle East is known for its warm desert climate. Lack of water resources is considered the most limiting factor for sustainable agriculture and water management of irrigation is a crucial issue for agriculture in Middle East. So it’s necessary to devote the cropping pattern considering above changes. The FAO56 Penman-Monteith equation is the standardized ETo equation. A comparison was made between 8 selected methods and FAO56-PM. Thus the method... 

Heat waves and cold waves are among the most important extreme weather events, which could directly affect human health. The heat wave and cold wave are defined as a period of consecutive days (usually at least 3 days) when hot or cold air persists over a region. However, there is no universal definition of these two phenomena in different scientific references, and the available definitions differ depending on the type of temperature index, the minimum required duration, and the defined threshold temperature. This research aims to examine the main indices of heat waves and cold waves and analyze them in 6 major cities: Tehran, London, Madrid, New York, Shanghai, and Vancouver which have... 

Climate and extreme hydrometeorological studies are required to reduce risk and vulnerabilities. This study uses different cumulus and microphysics schemes in Weather Research and Forecasting (WRF) model to simulate heavy rainfall events and Cyclone Sidr in Bangladesh, where many extreme events occur. Results show that WRF can capture the cyclone track, intensity, and landfall position. In addition, regionalization and an ensemble method through Bayesian regression model (BRM) are used to improve WRF rainfall simulations. Although regionalization can improve results of the experiments with different schemes, BRM leads to the best performance. To consider uncertainty and evaluate hazards, a... 

Dry bed of lakes and surrounding areas play an important role in dust production. This work tries to develop an Aerosol Type Detection Index for the two regions of Lake Hamon in Sistan, Iran, and the Aral Sea in Central Asia. Using the parameters of Extinction Coefficient and Depolarization Ration of CALIPSO satellite, the proposed index differentiates and categorizes fine dust particles and clouds according to the physical behavior of each in absorbing and backscattering satellite rays. This index shows values between zero and 0.15 for desert dust and -0.3 to zero for polluted desert dust particles. In order to verify the accuracy of determining the type of particles by the proposed index,... 

In recent decades, especially with the increase of greenhouse gases and global warming, land degradation has become one of the important global environmental issues. Land degradation has significant impacts on soil performance, vegetation cover, crops, and even the dispersion of dust particles. Land degradation is a complex phenomenon that is affected by multiple factors. Thus, it is necessary to identify these factors and then assess the degree of vulnerability and resilience to it globally. Proper indicators can clarify the integration and effective linkage between related parameters. This study aims to develop a Land Degradation Vulnerability Index (LDVI) using parameters such as... 

Due to climate change and the increase in the emission of greenhouse gasses, the temperature of the large cities is increasing. Tehran, which is the capital of Iran and the most populated city of it, is no exception. One of the significant tools for characterizing heat in the cities is having access to the temperature field of the region. Different tools can be used for achieving the temperature field. Two methods for doing so are remote sensing and numerical models. Each one of the mentioned methods has their own strength and weaknesses. In this research, the WRF-ARW model (version 3.7) is used for deriving meteorological fields for the city of Tehran. One of the many merits of using... 

This study seeks to evaluate reliability of wind power density over Khouzestan province using WRF simulations. Based on 10 meter wind speed data extracted from eight synoptic stations over Khouzestan province, two different domains were selected in south and south-west of khouzestan as promising regions with strong wind speeds. WRF model were used to simulate atmospheric data during 2016 and over two selected regions with 2 kilometers grid spacing. Simulated data were verified with comparing to in-situ data via three parameters of RMSE, BIAS and correlation. Results indicate that model configuration had acceptable accuracy in simulating wind speed data. In this study, Monte Carlo... 

Lake Urmia, the largest domestic lake in Iran due to climate change and lack of attention to sustainable development in the past two decades, has lost a significant part of its area. The contaminated bed of dried lakes is one of the main centers of dust generation.These materials are transported along with the wind to distant areas and have an irreversible impact on human health and the environment, so it is very important to determine the sources of dust production on the lake of Urmia to reduce the adverse effects of it.In this study, after determining the arid areas in the Lake Urmia basin using the Angstrom Exponent (AE) and the Aerosol Optical Depth (AOD), an index has been introduced... 

This paper provides and empirical investigation of individual labor supply of Iranian spouses in a collective framework in which gender ratio and plays a central role in the decision process in household. The data set is taken from the socioeconomic characteristics of panel survey over 2001-2004 and ten yearly headcount of Iran. We have conducted the parameters estimation and hypothesis testing by Semykina, A. and Wooldridge, J.M., (2005) generalized procedure of sample selection in panel data model. Our findings explore that females’ labor supply is affected significantly and strongly by the gender ratio, (total number of males over the females in provinces, both in urban and rural areas)....