Space Acceleration Measurement System (SAMS)/Orbital Acceleration Research Experiment (OARE)

The Life and Microgravity Spacelab (LMS) payload flew on the Orbiter Columbia on mission STS-78 from June 20th to July 7th, 1996. The LMS payload on STS-78 was dedicated to life sciences and microgravity experiments. Two accelerometer systems managed by the NASA Lewis Research Center (LERC) flew to support these experiments, namely the Orbital Acceleration Research Experiment (OARE) and the Space Acceleration Measurements System (SAMS). In addition, the Microgravity Measurement Assembly (NOAA), managed by the European Space Research and Technology Center (ESA/ESTEC), and sponsored by NASA, collected acceleration data in support of the experiments on-board the LMS mission. OARE downlinked real-time quasi-steady acceleration data, which was provided to the investigators. The SAMS recorded higher frequency data on-board for post-mission analysis. The MMA downlinked real-time quasi-steady as well as higher frequency acceleration data, which was provided to the investigators. The Principal Investigator Microgravity Services (PIMS) project at NASA LERC supports principal investigators of microgravity experiments as they evaluate the effects of varying acceleration levels on their experiments. A summary report was prepared by PIMS to furnish interested experiment investigators with a guide to evaluate the acceleration environment during STS-78, and as a means of identifying areas which require further study. The summary report provides an overview of the STS-78 mission, describes the accelerometer systems flown on this mission, discusses some specific analyses of the accelerometer data in relation to the various activities which occurred during the mission, and presents plots resulting from these analyses as a snapshot of the environment during the mission. Numerous activities occurred during the STS-78 mission that are of interest to the low-gravity community. Specific activities of interest during this mission were crew exercise, radiator deployment, Vernier Reaction Control System (VRCS) reboost, venting operations, Flight Control System (FCS) checkout, rack excitation, operation of the Life Sciences Laboratory Equipment Refrigerator/Freezer (LSLE R/F), operation of the JSC Projects Centrifuge, crew sleep, and attitude changes. The low-gravity environment related to these activities is discussed in the summary report

Three dimensional numerical modeling of flow around bridge piers using LES and RANS

River hydrodynamicsTurbulent open channel flow and transport phenomen

Investigation of the Dynamics Bed Shear Stress Distribution around a Circular Cylinder Using Various Turbulences Models

Scouring around cylinders is greatly affected by the value of bed shear stress entered on sediment materials of the bed around cylinders. Regarding the importance of the bed shear stress fluctuations and their influence on the initiation and development of scouring around cylinders, in this paper the dynamic bed shear stress distributions around a circular cylinder in high Reynolds numbers flow is investigated using various turbulence models. Since the bed shear stress can be regarded as one of the key parameters in scour and erosion predictions, then the accurate calculation of this parameter would be the first step in scour prediction and calculation. As the vortex shedding at the downstream of a cylinder depends on the turbulence intensity of flow, similar behavior may be anticipated for the dynamic bed shear stress. To evaluate the bed shear stress distribution, several numbers of numerical simulations are conducted to predict the bed shear stress around the circular cylinder using the CFD solver Fluent. Various turbulence models of time-and space-averaged types are used to simulate the turbulence effects. Regarding to the importance of the turbulence models inaccurate simulation of the cylinder wake region, three models of , RSM and LES are evaluated using a comparison of the flow pattern and fluctuation of near wake vortices. Results revealed that in simulation with LES turbulence model, the wake remains very symmetrical, consisting primarily of two large vortices in the near wake at two sides of the cylinder. With time passing, a transition occurs between the two states, from the initially symmetrical to the asymmetrical. Also, comparing the critical bed shear stress pattern in different phases shown that the bed shear stress is repeated again after a certain time period. This is in good agreement with the fluctuation time period of wake vortices. Evaluation of vortex and bed shear stress fluctuations shows that the pattern of bed shear stress fluctuation is in good agreement with vortex fluctuation phases in the near wake of a cylinder.Scouring around cylinders is greatly affected by the value of bed shear stress entered on sediment materials of the bed. Regarding the importance of the bed shear stress fluctuations and their influence on the initiation and development of scouring around cylinders, in this paper, the dynamic bed shear stress distributions around a circular cylinder in high Reynolds numbers flow is investigated using various turbulence closures. Since the bed shear stress can be regarded as one of the key parameters in scouring and erosion predictions, then the accurate calculation of this parameter would be the first step in scour prediction and calculation. As the vortex shedding at the downstream of a cylinder depends on the turbulence intensity of flow, a similar behavior may be anticipated for the dynamic bed shear stress. To evaluate the bed shear stress distribution, several numbers of numerical simulations are conducted to predict the bed shear stress using the CFD solver FLUENT. Various turbulence models of time-and space-averaged types are used to simulate the turbulence effects. Regarding the importance of the turbulence models in accurate simulation of the cylinder wake region, three models of k - ε, RSM and LES are evaluated using a comparison of the flow pattern and the fluctuation of near wake vortices. Results revealed that in the simulation with LES turbulence model, the wake remains very symmetrical, consisting primarily of two large vortices in the near wake at two sides of the cylinder. With time passing, a transition occurs between the two states, from the initially symmetrical to the asymmetrical. Also, comparing the critical bed shear stress pattern in different phases show that the bed shear stress is repeated again after a certain time period. This is in good agreement with the fluctuation time period of wake vortices

Measurement of the minority carrier diffusion length and edge surface-recombination velocity in InP

A scanning electron microscope (SEM) was used to measure the electron (minority carrier) diffusion length (L(sub n)) and the edge surface-recombination velocity (V(sub s)) in zinc-doped Czochralski-grown InP wafers. Electron-beam-induced current (EBIC) profiles were obtained in specimens containing a Schottky barrier perpendicular to the scanned (edge) surface. An independent technique was used to measure V(sub s), and these values were used in a theoretical expression for normalized EBIC. A fit of the experimental data with this expression enabled us to determine L(sub n)

Studija o rekonfiguraciji mreže distributivnog sustava korištenjem adaptivnog modificiranog \u27firefly\u27 algoritma

This paper suggests a new method based on the probabilistic load flow and Adaptive Modified Firefly Algorithm (AMFA) in order to evaluate the optimal management of the Distribution Feeder Reconfiguration (DFR) operation problems by considering a few Wind Turbines (WTs) in system and performance satisfaction of the proposed method is examined on the IEEE 32-bus standard test system. The significant objective functions in this paper includes: 1) Minimizing the total cost of active power losses in the network, 2) voltage profile improvement, 3) decreasing the present network total costs such as power production cost by the main network and distributed generations. Furthermore, a new stochastic solution based on Point Estimate Method (PEM) is proposed to effectively deal with the uncertainty related to the important random parameters such as active and reactive loads in addition to the wind speed variations. Thus, the suggested probabilistic framework must be considered in order to solve the reconfiguration problem with regard to uncertainties which caused by the wind turbines.U radu se predlaže novi pristup za optimalno rekonfiguriranje napojnih vodova u elektroenergetskim distributivnim sustavima temeljen na adaptivnom modificiranom \u27firefly\u27 algoritmu. Primjena obuhvaća problem s par vjetroagregata u sustavu, a učinkovitost je provjerena korištenjem standardnog testa za IEEE 32 sabirnicu. Značajniji razmatrani kriteriji su: 1) smanjenje ukupne cijene gubitaka aktivne snage u mreži, 2) poboljšanje profila napona, 3) smanjenje ukupne cijene postojeće mreže kroz smanjenje cijene proizvodnje snage glavne mreže i distribuiranih izvora. Nadalje, novo stohastičko rješenje temeljeno na \u27Point estimate\u27 metodi predloženo je za učinkovito savladavanje nesigurnosti povezanom s važnim stohastičkim parametrima kao što su aktivni i reaktivni teret u dodatku s varijacijama brzine vjetra. Predloženi stohastički okvir mora biti uzet u obzir prilikom rješavanja problema rekonfiguracije s obzirom na neodređenosti koje proizlaze iz vjetroagregata

A Comparative Study of Literacy Curriculum in Australia and New Zealand; Lessons for Iran’s Educational System

The present study, with the purpose to compare the literacy curriculum in Australia and New Zealand in order to benefit from the experiences of these countries to improve the level of literacy education in Iran in 2020. The approach used in the research is qualitative and comparative in which Australia and New Zealand, due to the high index of human development in 2020, obtaining favorable results in the PIRLS International assessment 2016 and effective activities in the field of literacy, by purposeful sampling have been selected. The data were collected by referring to valid scientific papers and websites of the Ministry of Education and the curriculum and valid documents related to literacy education in selected countries, and were analyzed and compared by Bereday’s four-step method and the similarity and difference method. The findings showed that the goals of literacy education in Iran are well explained and not much different from the literacy goals in selected countries, but determining the levels of literacy in each educational level and standards related to each level as well as education to thematic teachers have been neglected in extending concepts to other subjects that need to be revised and corrected

Dynamic Modeling and Simulation of a STATCOM/SMES Compensator in Power Systems

The advent of Flexible AC Transmission Systems (FACTS) is giving rise to a new family of electronic equipment emerging to controlling and optimizing the performance of power system, e.g. STATCOM. Static synchronous compensator (STATCOM) is one of the most widely used FACTS devices. This paper presents the integration of STATCOM coupled with superconducting magnetic energy storage (SMES) device in order to provide power oscillation damping in power systems. The additional of energy storage allows the combined compensator to exchange both reactive and active power with the ac network and also capability of the STATCOM is enhanced. This paper describes the structure and characteristics of STATCOM/SMES. In addition, using a proper control scheme, STATCOM/SMES is tested on an IEEE 3-bus system and more effective performance of the presented STATCOM/SMES compensator is evaluated with alone STATCOM through the dynamic simulation by using PSCAD/EMTDC software

Dynamic Modeling and Simulation of a STATCOM/SMES Compensator in Power Systems

The advent of Flexible AC Transmission Systems (FACTS) is giving rise to a new family of electronic equipment emerging to controlling and optimizing the performance of power system, e.g. STATCOM. Static synchronous compensator (STATCOM) is one of the most widely used FACTS devices. This paper presents the integration of STATCOM coupled with superconducting magnetic energy storage (SMES) device in order to provide power oscillation damping in power systems. The additional of energy storage allows the combined compensator to exchange both reactive and active power with the ac network and also capability of the STATCOM is enhanced. This paper describes the structure and characteristics of STATCOM/SMES. In addition, using a proper control scheme, STATCOM/SMES is tested on an IEEE 3-bus system and more effective performance of the presented STATCOM/SMES compensator is evaluated with alone STATCOM through the dynamic simulation by using PSCAD/EMTDC software