25 research outputs found
The Social Status of Teaching and Kuwaiti Teachers from the Perspectives of School Teachers and Principals
No full textأجرى الباحث دراسة بهدف التعرف على تصورات معلمي ومديري المدارس الكويتية لمستوى المكانة الاجتماعية لمهنة التدريس والمعلم الكويتي. وقد قام الباحث بتطوير أداة عملية تفي بغرض الدراسة على نمط مقياس (ليكرت) وثم تحكيمها من قبل أساتذة متخصصين، وتم تطبيق أداة الدراسة على (600) مدير ومعلم في ست محافظات بجميع المراحل التعليمية بواقع 100 من كل محافظة (50 ذكور)، (50 إناث)، كما قام الباحث باستخدام أسلوب المقابلة العلمية مع مديري المدارس (المحددين بالعينة) للتعرف على آرائهم كإداريين نحو الأسباب التي تؤدي إلى انخفاض مستوى المكانة الاجتماعية للمعلم ومهنة التعليم، والأسباب التي تؤدي إلى عزوف الشباب عن الالتحاق بمهنة التعليم، وكيفية العمل على رفع مستوى المكانة الاجتماعية لمهنة التعليم والمعلم الكويتي، وتوصلت نتائج الدراسة إلى أن مستوى المكانة الاجتماعية لمهنة التدريس كان فوق الوسط، ووجدت فروق دالة إحصائياً في المتوسطات الحسابية تعزى لمتغير الجنس لصالح الإناث، كما وجدت فروق دالة إحصائياً تعزى لمتغير الخبرة التعليمية لصالح ذوي الخبرة الأقل، ولم تظهر الدراسة فروقاً دالة إحصائياً تعزى لمتغير المركز الوظيفي.
كما توصلت الدراسة إلى عدة أسباب تؤدي إلى انخفاض مستوى المكانة الاجتماعية لمهنة التعليم والمعلم منها ما يتصل بالمواصفات الشخصية والإعداد المهني للمعلم، ومنها ما يتصل بالظروف الاجتماعية والاقتصادية والأعباء الوظيفيةThis paper aimed at investigates the social status of Educators
and Kuwaiti teachers from the viewpoints of school teachers and
principals. The researcher designed an assessment tool that is based on
Likert's measuring scale. This tool was refereed by specialized
university professors. It was administered to 600 male and female
Kuwaiti teachers and principals representing all six Kuwaiti
governorates and all educational stages. Each governorate was
represented by 100 teachers (50 males, and 50 females). The study
concluded that the social status of education profession was above the
average on the scale. The results showed significant differences on the
mean scores of gender in favor of female teachers. They also showed
significant differences on the mean scores of the length of experience
in favor of those who had less experience. Finally, they showed no
significant differences for the position
The Social Status of Teaching and Kuwaiti Teachers from the Perspectives of School Teachers and Principals
No full textأجرى الباحث دراسة بهدف التعرف على تصورات معلمي ومديري المدارس الكويتية لمستوى المكانة الاجتماعية لمهنة التدريس والمعلم الكويتي. وقد قام الباحث بتطوير أداة عملية تفي بغرض الدراسة على نمط مقياس (ليكرت) وثم تحكيمها من قبل أساتذة متخصصين، وتم تطبيق أداة الدراسة على (600) مدير ومعلم في ست محافظات بجميع المراحل التعليمية بواقع 100 من كل محافظة (50 ذكور)، (50 إناث)، كما قام الباحث باستخدام أسلوب المقابلة العلمية مع مديري المدارس (المحددين بالعينة) للتعرف على آرائهم كإداريين نحو الأسباب التي تؤدي إلى انخفاض مستوى المكانة الاجتماعية للمعلم ومهنة التعليم، والأسباب التي تؤدي إلى عزوف الشباب عن الالتحاق بمهنة التعليم، وكيفية العمل على رفع مستوى المكانة الاجتماعية لمهنة التعليم والمعلم الكويتي، وتوصلت نتائج الدراسة إلى أن مستوى المكانة الاجتماعية لمهنة التدريس كان فوق الوسط، ووجدت فروق دالة إحصائياً في المتوسطات الحسابية تعزى لمتغير الجنس لصالح الإناث، كما وجدت فروق دالة إحصائياً تعزى لمتغير الخبرة التعليمية لصالح ذوي الخبرة الأقل، ولم تظهر الدراسة فروقاً دالة إحصائياً تعزى لمتغير المركز الوظيفي. كما توصلت الدراسة إلى عدة أسباب تؤدي إلى انخفاض مستوى المكانة الاجتماعية لمهنة التعليم والمعلم منها ما يتصل بالمواصفات الشخصية والإعداد المهني للمعلم، ومنها ما يتصل بالظروف الاجتماعية والاقتصادية والأعباء الوظيفيةThis paper aimed at investigates the social status of Educators and Kuwaiti teachers from the viewpoints of school teachers and principals. The researcher designed an assessment tool that is based on Likert's measuring scale. This tool was refereed by specialized university professors. It was administered to 600 male and female Kuwaiti teachers and principals representing all six Kuwaiti governorates and all educational stages. Each governorate was represented by 100 teachers (50 males, and 50 females). The study concluded that the social status of education profession was above the average on the scale. The results showed significant differences on the mean scores of gender in favor of female teachers. They also showed significant differences on the mean scores of the length of experience in favor of those who had less experience. Finally, they showed no significant differences for the position
Revenue-productive income tax structures and tax reforms in emerging market economies - evidence from Bulgaria
No full textUsing a household budget survey for 1992, The author shows the poor revenue performance and distributional impact of Bulgaria's personal income tax system. He explores the implications for revenue and income distribution of two alternative tax systems - a flat tax and a progressive but simpler three-brackets tax system. He demonstrates that simpler tax structures with lower tax rates could achieve at least equal revenue and distributional objectives and are superior in terms of efficiency and equity. (The findings are robust when Bulgaria's significant tax evasion is included). But tax changes since 1992 have, if anything, moved Bulgaria even further from a simple income tax system: the number of rates and brackets increased from 7 to 10, and the levels of exemption remain unchanged. (Complex, higher rates complicate administration and enforcement and provide incentives for tax evasions. And in the alternative systems the author explores, the poor are protected with higher exemptions.) Fortunately, the country's personal income tax structure began to move toward less nominal progressivity after Bulgaria's 1997 tax reform program. The tax rate in thetop income bracket was reduced from 52 percent to 40 percent, the number of tax brackets was halved, and the exemption level was increased 20 percent (reducing tax burdens on the poor).Environmental Economics&Policies,Public Sector Economics&Finance,Regional Governance,Tax Policy and Administration,Economic Theory&Research,Governance Indicators,Economic Theory&Research,Public Sector Economics&Finance,Environmental Economics&Policies,Tax Policy and Administration
Author Correction: Metaverse in surgery — origins and future potential (Nature Reviews Urology, (2024), 10.1038/s41585-024-00941-4)
No full textCorrection to: Nature Reviews Urologyhttps://doi.org/10.1038/s41585-024-00941-4, published online 30 September 2024. In the version of the article initially published, Enrico Checcucci was wrongly stated to be affiliated with the University of Verona. This has now been amended in the HTML and PDF versions of the article so that Enrico Checcucci’s only affiliation is Department of Surgery, Candiolo Cancer Institute, FPO-IRCCS, Candiolo, Turin, Italy
Study of surface complexation modeling on a novel hybrid enhanced oil recovery (EOR) method; smart-water assisted foam-flooding
No full textThis contribution focuses on surface complexes in the calcite-brine-surfactant system. This is relevant for the recovery of oil when using a new hybrid enhanced oil recovery (EOR) method, which combines smart-water (i.e., ionically modified brine) and foam-flooding (SWAF) of light oil with dissolved carbon dioxide (CO2) at high pressure in carbonate (i.e., calcite) reservoirs. Using this new hybrid EOR-method (i.e., the SWAF-process) is not only economically attractive (i.e., it reduces opex costs) but also enhances the effectiveness of the production process, and thus reduces the environmental impact. Ionically modified brine (i.e., low-salinity) has a dual improvement effect. It not only leads to more stable foam lamellae, but also helps to change the carbonate rock wettability, leading for some conditions to more favorable relative permeability behavior. The mechanism for the modified permeability behavior in the presence of ionically modified brine is only partly understood. Therefore, we study this process initially in a zero dimensional (thermodynamics) setting, which can be used for the one dimensional (1D) displacement process with an oleic phase that contains carbon dioxide (CO2) and an aqueous phase that contains both carbon dioxide (CO2) and all the ionic substances. Using DLVO theory and surface complexation modeling to better understand the mechanism(s) of ionically modified brine as wettability modifier and foam stabilizer. We perform simulations using both (NaCl) and (MgCl2) to show the effect of a divalent ion at the high-salinity (8500 mmol/kg-w) and low-salinity (0.4 mmol/kg-w) for both ambient-conditions at (25°C) and at the reservoir-conditions (80°C). We confine our analysis to a description that uses the Dzombak-Morel model of surface complexes, which is based on the Debye-Hückel theory (i.e., valid up to ionic strength of 0.3 (mol/kilogram of water)). We also investigate the effect of carbon dioxide (CO2) on the stability of low-salinity foam-laminae. We model the foam-laminae, which contain as surface complex a (cationic) surfactant in an aqueous phase. We use the PHREEQC-software to calculate the surface charge and the surface potential. The presence of a carbon dioxide (CO2) phase leads to dissolution of four valent C(IV) compounds in the aqueous film. PHREEQC also calculates the equilibrium concentrations and surface potential and allows the study of the effect of salinity and the carbon dioxide (CO2) gas pressure. For the soap-film (foam-film) in a carbon dioxide (CO2) atmosphere we do use Pitzer activity coefficients (i.e., valid up to 6 (mol/kilogram of water)). As our aim is to show the methodology and the versatility of this approach, we leave more realistic choices of these parameters for future work.sFor the conditions considered we can qualitatively state that, in the presence of (NaCl i.e., at pH > 10) and (MgCl2 i.e., pH > 10.3), the low-salinity case shows a more stable water-film behavior at (25°C) and at (80°C) than the high-salinity case for both (25°C) and (80°C). Moreover, high carbon dioxide (CO2) pressures have a destabilizing effect on the film, as they reduce the surface potential. A reduced surface potential leads to a decreasing electrostatic double layer repulsion and thus destabilizes the foam-film, whereas low-salinity leads to less screening of the surface potential and thus improves the stability of the foam-film. The low-salinity flow is characterized by a high residual oil saturation and low end-point permeability for the two phase oil-water flow. This leads to a more favorable mobility ratio and thus a more favorable displacement process. For the calcite surface an enhanced stability helps to stabilize the water film on the calcite surface if the oil-water surface charge has the same sign as the surface charge on the calcite surface. Our calculations show the pH range where the sign of these charges is the same or opposite at low-salinity and high-salinity conditions. Admittedly these calculations only show trends, but can be used to delineate optimal conditions for the application of “Smart Water Assisted Foam (SWAF) Flooding”. It is expected that the SWAF-process under the optimum conditions will make the proposed new hybrid Enhanced Oil Recovery (EOR) process environmentally and economically attractive.Reservoir Engineerin
Exergy return on exergy investment analysis of natural-polymer (Guar-Arabic gum) enhanced oil recovery process
No full textIt has been estimated that 17% of the recovered hydrocarbon exergy in oil fields [1]is spent on fluid handling and recovery costs. Therefore, improving the efficiency of oil production can give an some contribution to more efficient energy usage and therefore minimizing to some extent the carbon footprint. By way of example we present in this paper a work-flow, which can serve as a template for computing the fluid handling and recovery costs for natural polymer (Guar-Arabic Gum)flooding. The main contributors to the exergy investment in an Exergy Return on Exergy Investment analysis (ERoEI)are, the fluid circulation costs, the steel costs of the tubing and casing and to some degree the drilling costs. The main contributor to the exergy gain is the exergy of the produced oil. The fluid circulation costs represent the largest exergy investment and usually approximately accounts for 80% of the exergy used for the recovery of oil. For quantifying the circulation costs, the paper uses a 1-D displacement model of polymer flooding of oil to compare the enhanced oil recovery (EOR)history for three scenarios, i.e., (1)water injection, (2)natural-polymer water injection and (3)natural-polymer slug injection. The advantage of a 1-D model is that it allows multiple comparisons of many scenario's avoiding time consuming simulations but this goes at the expense of ignoring 3-D effects. The 1-D model can be extended to a 2-D or 3-D model, which makes it possible to include the improvement of vertical and areal sweep-efficiency. A numerical solution of the EOR model is obtained with COMSOL. We analyze the exergy balance of viscosified water, e.g., with natural-polymer. A comparison as to the displacement efficiency is made between the three scenarios, viz., water, Guar-Arabic gum, and slug injection. The viscosity behavior of Guar-Arabic gum is obtained from laboratory data. It is argued that an ERoEI analysis, which is used on its own or complementary to an economic analysis, can be used to show the advantage of using Guar-Arabic gum slugs with respect to permanent polymer-injection to enhance the oil recovery. Moreover, the analysis shows that at the end of the project, the concept of exergy-zero recovery time or zero-time marks, for each scenario the termination point, i.e., when the circulation exergy costs (exergy investment)become equal to the recovery exergy (exergy return), and thus recovery should be abandoned. For the conditions considered a single polymer injection displacement leads to optimal results.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Reservoir Engineerin
Aircraft Marshaling Signals Dataset of FMCW Radar and Event-Based Camera for Sensor Fusion
No full textDataset Introduction
The advent of neural networks capable of learning salient features from variance in the radar data has expanded the breadth of radar applications, often as an alternative sensor or a complementary modality to camera vision. Gesture recognition for command control is the most commonly explored application. Nevertheless, more suitable benchmarking datasets are needed to assess and compare the merits of the different proposed solutions. Furthermore, most current publicly available radar datasets used in gesture recognition provide little diversity, do not provide access to raw ADC data, and are not significantly challenging. To address these shortcomings, we created and made available a new dataset that combines two synchronized modalities: radar and dynamic vision camera of 10 aircraft marshalling signals at several distances and angles, recorded from 13 people. Moreover, we propose a sparse encoding of the time domain (ADC) signals that achieve a dramatic data rate reduction (>76%) while retaining the efficacy of the downstream FFT processing (<2% accuracy loss on recognition tasks). Finally, we demonstrate early sensor fusion results based on compressed radar data encoding in range-Doppler maps with dynamic vision data. This approach achieves higher accuracy than either modality alone.
Dataset Structure
The dataset has a common directory structure which contains additional information about the captures.
dataset_dir///--/ofxRadar8Ghz_yyyy-mm-dd_HH-MM-SS.rad
Identifiers
stage [train, test].
room: [conference_room, foyer, open_space].
person: [0-9]. Note that 0 stands for no person, and 1 for an unlabeled, random person (only present in test).
gesture: ['none', 'emergency_stop', 'move_ahead', 'move_back_v1', 'move_back_v2', 'slow_down' 'start_engines', 'stop_engines', 'straight_ahead', 'turn_left', 'turn_right'].
distance: ['xxx', '100', '150', '200', '250', '300', '350', '400', '450'] (in cm). Note that xxx is used for none gestures when there is no person present in front of the radar (i.e. background samples), or when a person is walking infront of the radar with varying distances but performing no gesture.If you use this dataset, please also cite our accompanying paper:
@inproceedings{mueller2023aircraft, title={Aircraft Marshalling Signals Dataset of Radar and Event-Based Camera for Sensor Fusion}, author={M\"uller, Leon and Sifalakis, Manolis and Eissa, Sherif and Yousefzadeh, Amirreza and Detterer, Paul and Stuijk, Sander, and Corradi, Federico}, journal={IEEE Radar Conference, San Antonio, TX}, volume={}, number={1}, pages={1--15}, year={2023}, publisher={IEE}
Development of an integrated RFID-IC technology for on-line viscosity measurements in enhanced oil recovery processes
No full textThis paper deals with on line viscosity measurements using integrated circuit technology, and is building on a previous paper on the use radio frequency identifier (RFID) technology for determining dielectric coefficients. It is asserted that the progress in RFID technology and integrated circuits, in particular in micro–electro–mechanical system (MEMS) makes it possible to combine them to perform physico-chemical property measurements using devices on centimeter scale. It can even be expected that these devices can be made increasingly smaller. An important property of interest is the viscosity, in this specific case, for the use of Arabic gum in enhanced oil recovery. Arabic gum, is an environmentally acceptable natural product. Natural-polymer solutions 1000 [ppm] are more viscous and therefore more efficient oil displacement agents. They require less invested exergy than non-viscosified water to recover oil. However, polymers, in particular environmentally acceptable natural-polymers (e.g., Guar–Arabic gum) available in large quantities in India and Sudan, are susceptible to microbial degradation. It is therefore important to monitor its quality at the injection and production side for real-time quality control. Natural-polymers based on plant products are promising EOR agents. They may have a lower environmental footprint because of the biodegradability. To provide a proof of concept, we use a state of the art acoustic wave sensor (AWS), which can determine acoustic viscosities. It is asserted that RFID technology can be used to record the acoustic wave signal (SenGenuity vismart acoustic wave Sensor AWS) to determine the viscosity at some distance (meters) away from the measurement device. A calibration with solutions of known viscosity behavior (i.e., Glycerol) can be used to relate the acoustic viscosity to the dynamic viscosity. We can calibrate the acoustic wave sensor using Guar–Arabic gum solutions to measurements with the Anton Paar viscometer (MCR-302). For the glycerol solution we also compare to reported literature data. The Newtonian viscosity measurements of the Paar density meter, and the literature values agree within a few percent. These favorable comparisons, are an important step in developing a methodology that allows cutting edge RFID-IC technology for real-time non-contact monitoring of viscosity degradation
Experimental investigation and performance evaluation of modified viscoelastic surfactant (VES) as a new thickening fracturing fluid
No full textIn hydraulic fracturing, fracturing fluids are used to create fractures in a hydrocarbon reservoir throughout transported proppant into the fractures. The application of many fields proves that conventional fracturing fluid has the disadvantages of residue(s), which causes serious clogging of the reservoir's formations and, thus, leads to reduce the permeability in these hydrocarbon reservoirs. The development of clean (and cost-effective) fracturing fluid is a main driver of the hydraulic fracturing process. Presently, viscoelastic surfactant (VES)-fluid is one of the most widely used fracturing fluids in the hydraulic fracturing development of unconventional reservoirs, due to its non-residue(s) characteristics. However, conventional single-chain VES-fluid has a low temperature and shear resistance. In this study, two modified VES-fluid are developed as new thickening fracturing fluids, which consist of more single-chain coupled by hydrotropes (i.e., ionic organic salts) through non-covalent interaction. This new development is achieved by the formulation of mixing long chain cationic surfactant cetyltrimethylammonium bromide (CTAB) with organic acids, which are citric acid (CA) and maleic acid (MA) at a molar ratio of (3:1) and (2:1), respectively. As an innovative approach CTAB and CA are combined to obtain a solution (i.e., CTAB-based VES-fluid) with optimal properties for fracturing and this behaviour of the CTAB-based VES-fluid is experimentally corroborated. A rheometer was used to evaluate the visco-elasticity and shear rate & temperature resistance, while sand-carrying suspension capability was investigated by measuring the settling velocity of the transported proppant in the fluid. Moreover, the gel breaking capability was investigated by determining the viscosity of broken VES-fluid after mixing with ethanol, and the degree of core damage (i.e., permeability performance) caused by VES-fluid was evaluated while using core-flooding test. The experimental results show that, at pH-value (6.17), 30 (mM) VES-fluid (i.e., CTAB-CA) possesses the highest visco-elasticity as the apparent viscosity at zero shear-rate reached nearly to 106 (mPa·s). Moreover, the apparent viscosity of the 30 (mM) CTAB-CA VES-fluid remains 60 (mPa·s) at (90 °C) and 170 (s-1) after shearing for 2-h, indicating that CTAB-CA fluid has excellent temperature and shear resistance. Furthermore, excellent sand suspension and gel breaking ability of 30 (mM) CTAB-CA VES-fluid at 90 (°C) was shown; as the sand suspension velocity is 1.67 (mm/s) and complete gel breaking was achieved within 2 h after mixing with the ethanol at the ratio of 10:1. The core flooding experiments indicate that the core damage rate caused by the CTAB-CA VES-fluid is (7.99%), which indicate that it does not cause much damage. Based on the experimental results, it is expected that CTAB-CA VES-fluid under high-temperature will make the proposed new VES-fluid an attractive thickening fracturing fluid.Reservoir Engineerin
Nano-modified cementitious binders reinforced with basalt fiber/polymer pellets as a stabilizer for weak soils
No full textConstructing on soft clay entails engineering challenges, such as significant volumetric changes; hence, stabilizing such problematic soil is essential. Since using lime in stabilizing soil is not recommended in some regions (e.g., Manitoba, Canada) due to some environmental concerns, there is a pressing need to explore suitable alternatives. This study investigates the efficiency of stabilizing soft clay using nano-modified cementitious binders (cement, slag, nano-silica), reinforced with a new class of fibers (basalt fiber pellets). The mechanical and durability properties of the mixtures have been tested in terms of California Bearing Ratio, compressive strength, unconsolidated-undrained triaxial stresses, and freezing-thawing resistance. Thermogravimetry and scanning electron microscope analyses were performed to interpret the bulk trends. The results showed significant improvement of soft clay specimens stabilized with the nano-modified cementitious binders and reinforced with the pellets. This demonstrates the potential of the proposed reinforced binders for field applications involving stabilization of soft soils.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
