Sediment Yield Problems in Khassa Chai Watershed Using Hydrologic Models

Upland erosion and sedimentation are one of the severe problems which faces dams as sediments occupy spaces within reservoirs storage, hence, decreasing live water storage which is the main purpose of dam’s construction. Iraq is one of the countries that will face a significant shortage of water income as a result of both the increment in water demand and of the reduction of water shares from the source countries. Thus, the existing dams in Iraq represent a strategic resource to fulfill water demands, and the sedimentation at these dams is studied to assess the quantity of sediments that reach to these reservoirs and decrease available water volume and useful life of reservoir. In the current study, Khassa Chai Dam is located in the Northeast of Iraq and its main watershed basin covers an area of about 412 km2 between Kirkuk and Al Sulaymaniyah Governorates has been selected to estimate and predict the amount of sediment yield based on 30 years of daily climate data and the events of different intensity rainstorms. Automated geospatial watershed assessment (AGWA) tool model has been used to simulate Khassa Chai Dam catchment area. This model utilizes the geographic information system (GIS) application to analyze the required data from GIS layer for digital elevation model, soil type, land use, and land cover by interference with the required climate data. The key components of AGWA model are the soil and water assessment tool model and kinematic runoff and erosion (KINEROS) model which are able to simulate complex watershed behavior to explicitly account for spatial variability of soils, rainfall distribution patterns, and vegetation. The hydrologic characteristics for Khassa Chai catchment area according to the SWAT outputs show that the most erosive sub-basins are not able to deliver the eroded material or sediments to the reservoir due to their transmission losses, percolation, and other minor obstacles. KINEROS model simulation for sediment yield is much closer to the behavior of Khassa Chai watershed in erosion and sediment transport according to the single storm events and for individually selected sub-watersheds which are closed in their location to reservoir inlet

Five-Phase Line Commutated Rectifiers

Multiphase systems including multiphase generators or motors, especially five-phase, offer improved performance compared to three-phase counterpart. Five-phase generators could generate power in applications such as, but not limited to, wind power generation, electric vehicles, aerospace, and oil and gas. The five-phase generator output requires converter system such as AC-DC converters. This chapter introduces the basic construction and performance analysis for uncontrolled/controlled five-phase line commutated rectifier guided by numerical examples. This rectifier is suitable for wind energy applications to be the intermediate stage between five-phase generator and DC load or inverter stage. The filtration for AC side and effects of source inductances are detailed in other references. Here, this chapter gives the reader a quick idea about the analysis and performance of multiphase line commutated rectifiers and specifically five phase

The Factors that Lead to Cheating in Exams and How to Avoid Them

Cheating is one of the worst habitats that somestudents use it to pass their exams, and the biggest challenge toteachers and invigilators during tests to control the class andprohibit cheating. Students always try to find and create newmethods of cheating and invigilators try to find solutions for thisphenomenon. Many Educators discussed this phenomenon andinvestigated the reasons of cheating, but they couldn’t stop thisproblem. In this research we investigated the reasons behind thecheating, methods of cheating and we introduced somesuggestions to reduce cheating in exams.As a part of this paper, we distributed a questionnairecontained 19 questions among the students in Qatar University toinvestigate the reasons behind cheating and introduce somesuggestions to reduce it in the exams. Questions were grouped in6 categories and several study hypotheses were then analyzed byusing the Z-test. The study detected that the reasons of cheatingcan be divided into Physiological factors such as fear of failureand reprimand parents; and work related reasons such as largeclass sizes, the teacher, and Invigilator leniency. In addition, weintroduced some recommendations to reduce cheating during theexams