21 research outputs found
Experimental study of the impact of CO2 injection on the pore structure of coal: A case study from the Bowen Basin, Australia
No full textThis study investigates the impact of carbon dioxide (CO2) on the pore structure of coal during CO2 injection to understand the technical challenges associated with CO2 sequestration in depleted coal seam gas reservoirs. In an integrated approach, Micro-Computed Tomography (micro-CT) scanning, helium porosity and air permeability tests are performed on a coal sample prior to and after CO2 flooding experiments to identify both reversible and irreversible changes in cleat and fracture networks. The results indicate that irreversible changes contribute to a 43% reduction in effective porosity, which can be readily observed in the 3D model of the cleat and fracture networks constructed after CO2 flooding. At lower effective stresses, pore compressibility offsets the matrix swelling effect, resulting in improved permeability, which is beneficial for CO2 injection. Additionally, the analysis of borehole image logs of the study well reveals that most fractures and cleats terminate within coal intervals, with very few fractures extending into adjacent strata that are siltstone and fine sandstone with very low permeability.Alireza Salmachi, Abbas Zeinijahromi, Mohammed Said Algarni, Nawaf Abdullah Abahussain, Saad Abdullah Alqahtani, Alexander Badalyan, Mohammad Rezaee, Mojtaba Rajab
Spheres of Strings Under the Levenshtein Distance
No full textLet Σ be a nonempty set of characters, called an alphabet. The run-length encoding (RLE) algorithm processes any nonempty string u over Σ and produces two outputs: a k-tuple (b1,b2,…,bk), where each bi is a character and bi+1≠bi; and a corresponding k-tuple (q1,q2,…,qk) of positive integers, so that the original string can be reconstructed as u=b1q1b2q2…bkqk. The integer k is termed the run-length of u, and symbolized by ρ(u). By convention, we let ρ(ε)=0. In the Euclidean space (Rn,∥·∥2), the volume of a sphere is determined solely by the dimension n and the radius, following well-established formulas. However, for spheres of strings under the edit metric, the situation is more complex, and no general formulas have been identified. This work intended to show that the volume of the sphere SL(u,1), composed of all strings of Levenshtein distance 1 from u, is dependent on the specific structure of the “RLE-decomposition” of u. Notably, this volume equals (2l(u)+1)s−2l(u)−ρ(u), where ρ(u) represents the run-length of u and l(u) denotes its length (i.e., the number of characters in u). Given an integer p≥2, we present a partial result concerning the computation of the volume |SL(u,p)| in the specific case where the run-length ρ(u)=1. More precisely, for a fixed integer n≥1 and a character a∈Σ, we explicitly compute the volume of the Levenshtein sphere of radius p, centered at the string u=an. This case corresponds to the simplest run structure and serves as a foundational step toward understanding the general behavior of Levenshtein spheres
Lightweight multiscale information aggregation network for land cover land use semantic segmentation from remote sensing images
No full textAbstract Land Cover and Land Use (LCLU) segmentation plays a fundamental role in various remote sensing applications, including environmental monitoring, urban planning, and disaster management. Traditional models often face limitations in real-time processing and deployment on resource-constrained devices due to their high computational requirements. This paper presents a lightweight neural network designed to address these challenges by integrating dense dilated convolutions with pyramid depthwise convolutions for multiscale feature extraction. The proposed encoder-decoder architecture utilizes dense connections to aggregate spatial and contextual information across different resolutions, enhancing segmentation accuracy while minimizing computational overhead. The model’s performance was rigorously evaluated using the NITRDrone and UDD6 datasets, demonstrating a segmentation accuracy of 94.8%, with a significantly reduced parameter count compared to state-of-the-art methods. The compact design of the network facilitates its implementation on low-power devices, enabling real-time LCLU analysis across diverse environmental conditions. This work underscores the potential of lightweight neural networks to advance remote sensing image processing, offering scalable and efficient solutions for practical applications in geospatial analysis
New Evacuated Tube Solar Collector with Parabolic Trough Collector and Helical Coil Heat Exchanger for Usage in Domestic Water Heating
No full textBuildings represent approximately two-thirds of the overall energy needs, mainly due to the growing energy consumption of air conditioning and water heating loads. Hence, it is necessary to minimize energy usage in buildings. Numerous research studies have been carried out on evacuated tube solar collectors, but to our knowledge, no previous study has mentioned the combination of an evacuated tube solar collector with a parabolic trough collector and a helical coil heat exchanger. The objective of this paper is to evaluate the thermal behavior of an innovative evacuated tube solar collector (ETSC) incorporated with a helical coil heat exchanger and equipped with a parabolic trough collector (PTC) used as a domestic water heater. To design the parabolic solar collector, the Parabola Calculator 2.0 software was used, and the Soltrace software was used to determine the optical behavior of a PTC. Moreover, an analytical model was created in order to enhance the performance of the new model of an ETSC by studying the impact of geometric design and functional parameters on the collector’s effectiveness. An assessment of the thermal behavior of the new ETSC was performed. Thus, the proposed analytical model gives the possibility of optimizing ETSCs used as domestic water heaters with lower computational costs. Furthermore, the optimum operational and geometrical parameters of the new ETSC base-helical tube heat exchanger include a higher thermal efficiency of 72%. This finding highlights the potential of the heat exchanger as an excellent component that can be incorporated into ETSCs
Author biography.
No full textCloud computing is vital in various applications, such as healthcare, transportation, governance, and mobile computing. When using a public cloud server, it is mandatory to be secured from all known threats because a minor attacker’s disturbance severely threatens the whole system. A public cloud server is posed with numerous threats; an adversary can easily enter the server to access sensitive information, especially for the healthcare industry, which offers services to patients, researchers, labs, and hospitals in a flexible way with minimal operational costs. It is challenging to make it a reliable system and ensure the privacy and security of a cloud-enabled healthcare system. In this regard, numerous security mechanisms have been proposed in past decades. These protocols either suffer from replay attacks, are completed in three to four round trips or have maximum computation, which means the security doesn’t balance with performance. Thus, this work uses a fuzzy extractor method to propose a robust security method for a cloud-enabled healthcare system based on Elliptic Curve Cryptography (ECC). The proposed scheme’s security analysis has been examined formally with BAN logic, ROM and ProVerif and informally using pragmatic illustration and different attacks’ discussions. The proposed security mechanism is analyzed in terms of communication and computation costs. Upon comparing the proposed protocol with prior work, it has been demonstrated that our scheme is 33.91% better in communication costs and 35.39% superior to its competitors in computation costs.</div
Primary health care management of overweight and obese adults in Riyadh City, Saudi Arabia : current status and potential quality improvement through the fit and minimally disruptive medical model.
No full textBackground: Obesity is now one of the most important public health issues in Saudi Arabia, with 74.2% of women and 69% of men found to be overweight or obese, but there is limited research into the nature and effectiveness of overweight and obesity management in primary care in Saudi Arabia or elsewhere. International literature supports the role of primary health care in managing obesity through evidence-based interventions, yet also notes many barriers to health professionals helping patients achieve significant weight loss. A new collaborative and patient-centred approach to primary care management of chronic disease, Fit and Minimally Disruptive Medicine, appears potentially well-suited to helping patients manage their weight.
Research Aims: This thesis aimed to determine health professionals’ and patients’ views on the appropriateness and quality of current obesity management practices in primary health care in Riyadh, Saudi Arabia., and also their views on the acceptability, utility and applicability of Fit and Minimally Disruptive Medicine to assist successful weight management.
Research Methods: Preliminary informal interviews were held with representatives of key groups in primary health care in Riyadh, four senior primary health care officials, 10 primary health care centre managers, 20 doctors, 20 nurses and 20 patients from 10 primary health care centres. The main investigation used the interview material to develop two structured questionnaire surveys for a quantitative cross-sectional descriptive study on the management of overweight and obesity in primary health care. The first questionnaire, for doctors and nurses, addressed primary health care centre resources and services, use of weight loss strategies, and the health professionals’ views on overweight and obese patients, obesity management and the Fit and Minimally Disruptive Medicine approach. The second survey, for patients, addressed patients’ motivation and readiness to lose weight, support from family and friends, weight loss options used, satisfaction with services provided by their primary health care centre, and views on using the Fit and Minimally Disruptive Medicine approach. The surveys were conducted in
iv
53 primary health care centres in four out of five health sectors in Riyadh City; 10 centres were included in a pilot study and 43 in the main study. The main study was conducted with a sample of 77 doctors, 78 nurses and 80 patients.
Results: Findings showed that while primary care practice management of obesity in Riyadh incorporates some best practice recommendations, there are important elements that are rarely, or inconsistently, used. Only 44.2% of doctors and 55.1% of nurses, for example, always calculated patients’ body mass index, and only 10.4% of doctors and 12.8% of nurses always assessed the patient’s progress for more than six months. The main strategy for obesity management was the recommended combination of diet, exercise and behaviour modification (67.5% of doctors and 56.4% of nurses). Reported barriers to establishing obesity clinics included inadequate resources, and administrative and referral issues. The patient survey found 90% of patients said they were ready to lose weight, but identified various barriers, including lack of family and friend support, and dissatisfaction with their primary care centre’s staff and services (48%). The majority of health professionals and patients supported the use of Fit and Minimally Disruptive Medicine weight management.
Discussion: This thesis makes a major contribution to the literature on the effectiveness of primary care management of obesity, notably including the patient perspectives. The thesis is also the first to investigate health professionals’ and patients’ views on applying Fit and Minimally Disruptive Medicine to weight management. Recommendations for Saudi Arabia include further training of health professionals, the introduction of clinical practice guidelines on managing obesity, and a pilot study of using Fit and Minimally Disruptive Medicine for weight management in primary health care. This thesis provides valuable guidance for health care organisations seeking to improve the management of overweight and obesity in primary care, and for researchers interested in undertaking further investigations in this area
Heighting and distance accuracy with electronic digital levels
No full textCollege of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia
Phone: +966-146-770-03
Fax: +966-146-770-08
[email protected]
[email protected] Leica NA3000 electronic digital level, one of the newly-introduced heighting equipment, was evaluated for vertical and horizontal distance measurement. A well protected 170 m long 17-section test line was first established for this purpose using geodetic surveying techniques. The test instrument was then used to remeasure the line. Two approaches were followed. In the first, closed loops were run from one end of the line to each of the pegs on the line and back to the starting point in an out-and-back manner. Misclosure errors of loops were then computed and compared to known leveling standards. In the second approach, heights of some pegs on the line were re-established several times with the instrument erected on the one end of the line. Standard deviations of height measurement of each peg were then computed and compared with known standards. The results showed that in the first approach, the test instrument was able to achieve accuracy values commensurate with first order class I leveling standards as set out by the U.S.A.-based Federal Geodetic Control Committee (FGCC), i.e. better than oi3.0..Jk mm. In the second approach, for distances up to 64 m, standard deviations better than 01060 microns could easily be obtained. Again, this is within the requirements of first order class 1levelling standards. Overall, therefore, it can be said that digital electronic levels, as exemplified by the Leica NA3000 model, could be used to support high accuracy leveling operations being them of the geodetic ordinary type. The distance measuring stage of the test showed that, for up to 64 m from instrument station, the test instrument is capable of measuring distances to accuracy values better than 1/2000. This is sufficient accuracy for some localized survey works, e. g. site preparation in construction industry, pavement maintenance surveys, sewer pipe placement and monitoring etc. where distance errors of a few centimeters in several tens of meters are tolerable
Performance enhancement of evacuated U-tube solar collector integrated with phase change material
No full textIn this research, a numerical simulation was undertaken to assess the effectiveness of an Evacuated tube solar collector (ETSC). The study explored the efficacy of merging a parabolic trough solar collector (PTSC) and copper fins into the U-tube ETSC design. Two types of fins, namely annular fins and disk-shaped fins, were evaluated. Additionally, the study aimed to analyze the influence of operational and geometric parameters, such as the heat transfer fluid (HTF) mass flow rate and the U-tube bend radius, on the performance of the U-tube ETSC. Furthermore, a comparative examination was carried out to identify the most suitable type of phase change material (PCM) for the U-tube ETSC. Finally, a comparative analysis was conducted to assess the performance of the U-tube ETSC in comparison to that of the coaxial tubes ETSC. The results clearly demonstrated that the integration of an PTSC, PCM, and disk-shaped fins substantially improved the overall performance of the ETSC in comparison to the conventional solar collector. This improvement led to a remarkable increase in energy efficiency, with an impressive gain of 42.94 %. The ETSC displayed remarkable performance, particularly at lower HTF mass flow rates and a reduced U-tube bend radius, achieving an average HTF temperature of 430 K. Additionally, among the tested PCMs, RT 82 emerged as the most suitable choice, providing an energy gain of 9.27 % in comparison with the case without PCM
An Experimental Comparison of the Performance of Various Evacuated Tube Solar Collector Designs
No full textAn experimental study was carried out to assess the thermal performance of a few evacuated tube solar collectors (ETSCs) for water heating. The thermal performance of two kinds of ETSC (heat pipe ETSC and direct-flow ETSC) was investigated using an indoor experimental apparatus in lab testing conditions with a solar simulator. Several experimental tests were carried out for the heat pipe ETSC system under different operating conditions, such as the solar intensity (300, 500, and 1000 W/m2) and the tilt angle (0°, 30° and 90°) of the ETSC and the water flow rate (0.6, 1.2, and 2.4 LPM). Moreover, four configurations of direct-flow ETSC (U tube, double U tubes, coaxial tubes, and helical tube) were examined and compared to the conventional heat pipe ETSC. The results of the experiment proved that the ETSC system presents a great performance at higher solar irradiance and lower water flow rates, and the experiments indicated that with a 30° tilt angle, the ETSC reaches the maximum thermal efficiency of 36%. Furthermore, compared to the conventional heat pipe ETSC and the other proposed configurations of direct-flow ETSCs, the helical tube-based ETSC has a better thermal efficiency, 69%, and can be considered a greater potential heat exchanger that can be integrated in ETSCs. To the best of our knowledge, it is the first time this helical tube type been integrated into the ETSC and tested under these conditions.
TRANSLATE with x
English
Arabic
Hebrew
Polish
Bulgarian
Hindi
Portuguese
Catalan
Hmong Daw
Romanian
Chinese Simplified
Hungarian
Russian
Chinese Traditional
Indonesian
Slovak
Czech
Italian
Slovenian
Danish
Japanese
Spanish
Dutch
Klingon
Swedish
English
Korean
Thai
Estonian
Latvian
Turkish
Finnish
Lithuanian
Ukrainian
French
Malay
Urdu
German
Maltese
Vietnamese
Greek
Norwegian
Welsh
Haitian Creole
Persian
//
TRANSLATE with
COPY THE URL BELOW
Back
EMBED THE SNIPPET BELOW IN YOUR SITE
Enable collaborative features and customize widget: Bing Webmaster Portal
Back
/
Latency and energy-efficient multi-hop routing protocol for unmanned aerial vehicle networks
No full textUnmanned aerial vehicle is one of the main announced use cases of 5G/IMT2020, which is expected to have various applications in many fields. These devices have limited capabilities in terms of energy and processing. Due to the complex structure of unmanned aerial vehicle networks and the high mobility constraints, design of efficient routing protocol, for supporting such network, is a challenge. Thus, efficient routing of data among unmanned aerial vehicles between source and destination is an important issue in designing unmanned aerial vehicle networks. Proactive routing protocols are one of the main categories of routing protocols developed for mobile ad hoc networks and vehicular ad hoc networks. Optimized link state routing protocol is one of the most common proactive routing protocols that has been modified to support unmanned aerial vehicle networks, considering high mobility feature of the network. In this work, we propose a latency and energy-efficient proactive routing protocol for dense unmanned aerial vehicle networks, with high-density devices, based on optimized link state routing protocol algorithm, referred to as multi-objective optimized link state routing protocol. The proposed routing protocol is topology aware and can be used for low-latency and high-mobility applications. The proposed multi-objective optimized link state routing protocol routing algorithm considers all modified versions of optimized link state routing protocol and introduces a novel method for selecting multipoint relay nodes that considers the traffic load on the communication channel and the load on each unmanned aerial vehicle node. Moreover, the proposed algorithm considers the communication link stability and the energy constraints. The system is simulated over a reliable environment for various scenarios, and it is compared to the original optimized link state routing protocol and its modified versions. Simulation results indicate that the proposed protocol achieves higher efficiency in terms of latency, energy, and reliability. © The Author(s) 2019
