Sharif Digital Repository

A thermo-mechanical multi-scale framework is presented in this study for simulating the compaction process of aluminum nanopowders coated with a surface oxide layer. The primary objective is to link atomistic-scale information with continuum-scale models in order to improve the accuracy of predictions of material response under varied mechanical loading and thermal conditions. This approach enables analysis of the role of atomic-scale mechanisms in the overall material response and aims to achieve improvements in both predictive accuracy and computational efficiency relative to conventional methods. In the first step, the mechanical properties of the nanopowders were extracted at 300, 400,... 

Annular combustion chambers used in small turbine motors which incorporate centrifugal (rotary) injectors for injecting fuel, are known as Slinger combustion chambers. The Slinger injector works in such a way that fuel enters from an inner tube in motor shaft and exits with high pressure from the holes on the cylinder connected to the shaft. Because of the high centrifugal force, the fuel is sprayed with high quality after entering the combustion chamber. Type and angle of spray, fuel-air mixing type, combustion phenomena and flame stability makes this different than other annular combustion chambers. The process of combustion in the Slinger chamber of YJ402 motor is numerically simulated in... 

Water shortage, population growth, and high levels of urban water demand are among main challenges of water demand management for developing countries and cities, and also for megacities. Urban water management systems, as they are complex adaptive systems, complex interactions exist among elements affecting the system. In other words, action from a subpart can trigger other parts, and also the whole system to respond in reaction. In this study, socio-economic water consumption behavior of households is studies and simulated in an agent-based modeling platform. First, households are interviewed and, using the qualitative data extracted from interviews and also the behavioral science... 

The water level of Lake Urmia has experienced a drop of 7.83 meters, from 1995 to 2017. According to previous studies, the uncontrolled development of agriculture, high consumption cultivation pattern, overuse of water resources for agricultural use and high water loss due to low irrigation efficiency, are the most important factors in the drying of Lake Urmia. Since agricultural sector is the largest water consumer (approximately 90%), the Lake Urmia Restoration Program has decided to study and implement the 40% reduction of water consumption in agricultural sector plans.Due to the inherent complexity of the Urmia Lake basin, accurate and realistic evaluation of the effectiveness of the... 

The spatiotemporal dynamic of salinity concentration (SC) in saline lakes is strongly dependent on the rate of water flow into the lake, water circulation, wind speed, evaporation rate, and the phenomenon of salt precipitation and dissolution. Although in-situ observations most reliably quantify water quality metrics, the spatiotemporal distribution of such data are typically limited and cannot be readily extrapolated for either long-term projections or extensive area. Alternatively, remotely sensed imagery has facilitated less expensive and a stronger ability to estimate water quality over a wide range of spatiotemporal resolutions. This study introduces an adaptive learning model that... 

Bathymetric maps are used for monitoring water bodies such as lakes, wetlands, and coastal areas, providing valuable information regarding changes in water storage volumes in these environments. For lakes prone to drying and salinity issues, where the lakebed elevation is constantly changing, the importance of these maps becomes even more pronounced as they play a crucial role in monitoring these lakes' conditions and assessing restoration efforts. Various methods exist for generating bathymetric maps, one of which is satellite remote sensing, which is more time- and cost-effective than traditional methods. One of the most common and accessible types of remote sensing data used for... 

Agriculture accounts for 70% of global freshwater consumption. However, precise data on irrigation water use (IWU) at the regional scale is often lacking, which hampers the development of effective water management plans. This study aims to estimate irrigation water use (IWU) by integrating remote sensing soil moisture (SM) and actual evapotranspiration (ET) data into a root-zone soil water model. Since irrigation influences both SM and actual ET, increases in SM and ET following irrigation events can be leveraged to frequently retrieve IWU from remotely sensed data. In this regard, we first developed an irrigation-free soil water model simulating root-zone SM dynamics during non-growing... 

This study analyzes the impact of climate-related stressors and water resources development projects in the Tigris-Euphrates Basin on regional dust storm intensity and frequency. To this end, we utilize remote sensing data for Aerosol Optical Depth (AOD), wind speed, surface temperature, soil moisture, precipitation intensity and inter-arrival time, Standardized Precipitation Evapotranspiration Index (SPEI), and vegetation cover to explore long-term trends. To identify dust hotspots, we introduce a normalized intensity-frequency index (NIFI). The NIFI combines the arithmetic mean of AOD values and the frequency of daily AOD measurements exceeding a predefined threshold, to identify potential... 

GB and Miankale Wetland are one of the most valuable water areas in the country from an ecological perspective, providing a habitat for a wide range of aquatic species and birds as well as providing a platform for fishing and tourism for locals. Recently, this wildlife refuge has experienced a crisis of reduced water levels and degraded water quality. Past studies have examined how fluctuations in the Caspian Sea water level affect GB's water quantity and quality. Due to the critical situation of Gorgan Bay, other factors affecting its water balance and upstream basin need to be examined, such as ground water flow and consumption, precipitation, and evaporation, and how they all affect the... 

This research aims to evaluate the capability of a physics-based machine learning model in forecasting PM₁₀ concentration (wich serves as dust particle concentration). Previous studies have primarily employed two methodological approaches for dust concentration prediction namely one based on the physical dynamics governing dust events and the other relying on data-driven techniques through machine learning. In this study, a Physics-Informed Neural Network (PINN) model was employed, integrating the strengths of both approaches. Training the PINN model required gridded meteorological inputs and corresponding gridded PM₁₀ data. To ensure reliability, correlation analyses were conducted between... 

In response to the growing energy consumptions levels in buildings, many countries have introduced standards and codes aimed at reducing their national building energy consumption levels as well as managing the amount of pollutants. Title 19 of Iran’s National Building Regulation (NBR) was first introduced in 1991. It is projected that Title 19 can lead to a 30 to 50% reduction in the amount of buildings energy consumption. Nevertheless, evidence suggests that the introduction of Title 19 NBR has not led to substantial reduction in building energy consumption in Iran. Unlike Title 19 NBR, similar standards in other countries have proven to be very effective in reducing the building energy... 

The purpose of this study is to introduce a new indicator to estimate the amount of irrigation water in excess of the need and also to determine the optimal irrigation pattern to reduce water loss in agriculture. According to the Food and Agriculture Organization of the United Nations, the major loss of fresh water takes place in agriculture, and the reduction of water resources is more significant in developing countries that do not have advanced agricultural equipment. One of the challenges in the studies related to reducing the amount of water used in agriculture is a lack of knowledge on the spatial distribution and temporal changes in water loss in a region. Although estimation of... 

This study aimed to investigate the efficiency of machine learning algorithms in capturing the dynamics of water particles' age distribution and in estimating the time series of median travel time (MTT) in river basins. The mechanism of solute transport in a catchment does not follow the hydrograph shape of the catchment and depends on the spatial and temporal distribution of solute resident time. The equations governing the age dynamics of water particles discharged from a catchment have been presented analytically in recent research. These equations showed that the transfer of solutes depends on various factors, including climatic conditions, basin topography, and basin vegetation. Also,... 

StorAge selection (SAS) functions describe the mechanism by which water particles with different ages exit a hydrological system through outfluxes such as streamflow and evapotranspiration (ET). The shape of the ET SAS functions affects the storage residence time distributions, ET travel time distributions, and discharge travel time distributions that control the hydrochemical dynamics of water. They also carry fundamental information to understand the response behavior of the system, and are affected by processes such as precipitation, outflow, ET, as well as the physical properties of the system. To better understand the shape of these functions, other important factors such as the type... 

This thesis describes a robust algorithm in speech recognition system based on phoneme recognition. Automatic speech recognition systems (ASR) can be divided into two main types: speaker-dependent continuous speech PC-based systems and speaker-independent continuous-speech server based systems. In speaker- independent systems, there is no need to have knowledge about the speaker(s) before using the system, on the other hand, in speaker dependent systems it is essential to have voice training by the speaker(s) supposed to work with the system. In this thesis, a speaker-independent continuous speech PC-based system has been chosen to work with. Acoustic-phonetic approach has been chosen among... 

Many of Iran's wetlands are going dry because of the expansion of anthropogenic activities like the exorbitant withdrawal of groundwater resources and excessive use of water for agricultural purposes. Bakhtegan, Hoor-ol-azim, Anzali, and Miankaleh are some of the most notable examples of this issue in the past two decades. The crucial role of wetlands in preserving the biodiversity of flora and fauna and supplying groundwater resources necessitates continuous monitoring of the quantitative and qualitative changes in the surface water of wetlands. The main focus of this research is quantifying the reduction in wetlands' surface water using K-means and random forest algorithms based on... 

In spite of succesfull achievements of standard quantum mechanics in describing variety of physical phenomenons, this theory has some conceptual problems in some areas. One of the important problems is the behavior of macroscopic objects and their interaction with microscopic systems, which is called “measurement problem”. Actually because the standard quantum mechanic is linear, it anticipates the occurrence of superposition of macroscopic states which is in contrast with our understanding of macroscopic objects. The standard theory answers this problem by using the wave function reduction principle.
There has been various proposals about the mechanism of wave function reduction,... 

Water-gas shift reaction (CO(g) + H2O(g) ↔ CO2(g) + H2(g)) is performed as the key step in the hydrogen and ammonia industrial plant. In this work, Fe/Cr/Cu high temperature water gas shift catalysts were synthesized by coprecipitation method, using sulfate precursors, in order to improve the catalytic performance and particular emphasis is placed on the catalytic activity affected by aging time, precipitating agent and ways of increasing the mechanical strength. Finally the prepared and industrial catalysts were compared when they were situated in the operating conditions (at 360oC and 2 bar) and were characterized by BET, XRD, TPR, TEM and crushing strength analysis. Catalysts being made... 

Numerical simulation of combustion in turbulent flow regimes is of high importance. The accuracy of numerical predictions depends on the quality of turbulence modeling and its interaction with combustion processes. In order to more accurately represent turbulent structures and mixing, the use of Large Eddy Simulation (LES) turbulence models is desirable, despite their relatively high computational cost. Premixed combustion at low equivalence ratios has gained widespread attention in recent years due to its high efficiency and reduced emissions. In this field, a significant portion of turbulent combustion simulations have focused on Flamelet-based models. Although these models have been... 

Recent years have seen the development of various remote sensing-based methods for river streamflow estimation. Among them, the C/M approach estimates streamflow by analyzing surface reflectance at two benchmark pixels, namely dry and wet. However, its efficiency heavily depends on the expert-selected dry and wet pixels, which cannot be chosen randomly. In this study, we introduced the Normalized Difference Streamflow Index (NDQI) as a novel proxy for streamflow estimation. This index, which utilizes the spectral bands of the Sentinel-2 satellite, is sensitive both to soil moisture changes along riverbanks and turbidity variations during high-flow events. Unlike the C/M approach, NDQI does...