517 research outputs found

    (In Press) A new house wall system for residential buildings

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    The residential housing sector consumes a significant amount of fossil fuel energy and thereby produces a large percentage of greenhouse gas emissions that contribute to global warming and climate change. At present, approximately 40% of the total household energy used is required for space heating/cooling and a substantial amount of that energy is lost through the house walls. Despite the importance of house walls for energy efficiency, most published literature focuses mainly on thermal comfort, environmental impact and economic costs of residential buildings. Little information is available on energy efficient house wall systems that can be used and adapted for varied climate conditions with minimal design change and associated cost. Therefore, the primary objective of this paper was to undertake a thermal performance study of two house wall systems with single and double glazed windows under variable climate conditions. The study was undertaken using thermal performance simulation software AccuRate®. The findings indicate that a significant energy saving can be achieved using the new house wall system compared to currently used brick veneer house wall system

    Energy efficient residential house wall system

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    The energy consumption and greenhouse gas emission by the residential housing sector are considered to be one of the largest in economically developed countries. The larger energy consumption and greenhouse gas emission not only put additional pressure on finite fossil fuel resources but also cause global warming and climate change. Additionally, the residential housing sector will be consuming more energy as the house demand and average house floor area are progressively increasing. With currently used residential house wall systems, it is hard to reduce energy consumption for ongoing house space heating and cooling. A smart house wall envelope with optimal thermal masses and insulation materials is vital for reducing our increasing energy consumption. The major aim of this study is to investigate thermal performance and energy saving potential of a new house wall system for variable climate conditions. The thermal performance modelling was carried out using commercially developed software AccuRate®. The findings indicate that a notable energy savings can be accomplished if a smart house wall system is used

    Evaluating Teaching Strategies in Higher Education From Students\u27 Perspectives

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    This study was conducted to investigate students\u27 perception of learning experiences at one of the largest government universities in the eastern province of Saudi Arabia. The sample consisted of male and female students and their instructors enrolled in four main colleges (Arts, Education, Preparatory year, and Science). Data were collected through a survey and focus group interviews during the fall semester of 2014-2015 academic year. The results provide feedback to faculty members about the quality of content, format, and structure of their courses, and can contribute to teaching and learning processes by facilitating faculty growth, development, and self-improvement

    HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC DETERMINATION OF GLIMEPIRIDE AND TIMOLOL IN PHARMACEUTICAL FORMULATIONS USING BRITTON -ROBINSON BUFFER IN MOBILE PHASES

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    Actually, Glimepiride (GLI) and Timolol (TIM) are analysed by several analytical techniques such as HPLC, Uv Vis and electrochemical methods, but in this study these compounds were determined by use Britton-Robinson (B-R) buffer pH3 in mobile phases as a new work. B-R pH3 : Acetonitrile : Water : Methanol (10 : 30 : 10 : 50 % v/v/v/v) and B-R pH3 : Acetonitrile : Methanol (30 : 15 : 55 % v/v/v), were used as mobile phases for chromatographic studies of GLI and TIM respectively. 1´10-3 mol L-1 of GLI and TIM were prepared  by dissolving the suitable weight of analyte in methanol and distilled water respectively, in 50 ml volumetric flask. GLI and TIM were HPLC separated from interferences and analytical determined using C-18 (5µm) with UV detector at 254 nm and 1.00 mL min-1 flow rate by 10 µL injection volume. The calibration curves for GLI and TIM  were studied over the range 1×10-4 to 1×10-3 mol L-1 (correlation coefficient = 0.994, n=6) for GLI and (correlation coefficient = 0.996, n=6) for TIM. The HPLC reproducibility and stability were evaluated for 5×10-4 mol L-1 of GLI and TIM , yielded good results for ten HPLC measurements with relative standard deviations RSD% were 0.43 and 1.1%, and good stability observed. The developed HPLC was applied to determine of GLI and TIM in pharmaceutical formulations with mean recoveries 103% ±0.71 and 99% ±1.0, respectively.  

    Active Expert Learning for the Digital Humanities

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    Current platforms for paper sharing among scholars, such as Research Gate, could support Active Expert Learning, whereby the paper being uploaded is processed using human language technology techniques, and feedback is asked of the scholar doing the upload using active learning techniques to minimize the amount of feedback requested. We show that this approach could outperform traditional active learning as well as randomly asking for feedback

    “The accuracy of the EOS imaging system to assess hip abnormalities in adolescents and adults:” a systematic review and meta-analysis

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    Objectives To determine the accuracy of the EOS imaging system compared to the gold standard computed tomography (CT) scan, for the measurement of native and postoperative/prosthetic hip parameters in adolescents and adults. Methods Medline, Cochrane Systematic Review, and Web of Science databases were searched to obtain relevant articles published between January 1964 and February 2021. All articles published in English. Inclusion and exclusion criteria were developed according to the Population, Intervention, Comparator, Outcome (PICO) framework. Three reviewers independently assessed the quality of included studies using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) checklist. A narrative synthesis of the articles and a meta-analysis were conducted. The heterogeneity exhibited by the effect sizes was obtained using a forest plot, the Q statistic and the I2 index. Reliability coefficients were transformed into Fisher’s Z to normalise their distribution and stabilise the variances. For each meta-analysis, an effect size (average reliability coefficient) and a 95% confidence interval were calculated and presented in a forest plot. The amount of radiation dose between modalities was compared. Results The search retrieved 75 articles, six of which met inclusion and exclusion criteria. The meta-analysis included five of these six studies (sample size from 20 to 90). Comparing EOS and CT, the estimated average correlation (effect size) for combined studies was significantly high (r = 0.84, 95% CI = 0.78 to 0.88, p-value < 0.001). With respect to Pearson’s correlation between EOS and CT, the estimated average correlation for combined studies was significantly high (r = 0.86, 95% CI = 0.80 to 0.90, p-value < 0.001). Average radiation dose for EOS was 0.18 ± 0.05 mGy for the anteroposterior view (AP) and 0.45 ± 0.08 mGy for the lateral view; and for CT was 8.4 to 15.6 mGy. Conclusion The EOS imaging system has a high correlation with CT for preoperative and postoperative/prosthetic hip measurements, with considerably lower irradiation of patients

    Intensity noise in ultra-high frequency modulated semiconductor laser with strong feedback and its influence on noise figure of RoF links

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    We characterize the intensity noise associated with the ultra-high frequency direct modulation of semiconductor lasers under strong optical feedback over a millimeter-wave frequency passband between 54.5 and 56.5 GHz. Enhancement of the modulation response over this millimeter wave band due to optical feedback is clearly shown by time-delay rate equation analysis fully involving the strong optical feedback effect. The contribution of the relative intensity noise of the laser to the noise figure of an ultra-high speed radio over fiber link is evaluated. We show that subjecting the laser diode to strong feedback improves the noise figure of a 55.8-GHz radio over fiber link nearly by 20 dB in the regime of small-signal modulation and 10 dB under large-signal modulation

    EPR detection and characterisation of a paramagnetic Mo(III) dihydride intermediate involved in electrocatalytic hydrogen evolution

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    EPR spectroscopy and theoretical data show that the slow heterogeneous electron-transfer kinetics associated with the reduction of an 18-electron Mo(IV) acetato dihydride are a consequence of an η2−η1 rearrangement of the carboxylate ligand which gives a unique paramagnetic 17-electron Mo(III) dihydride

    Optimal Design and Techno-economic Analysis of a Hybrid Solar-wind Power Resource: A Case Study at Al Baha University, KSA

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    This study presents a feasibility analysis of supplying the measured load of Al Baha University in Saudi Arabia by renewable resources including solar photovoltaic (PV), wind turbine (WT), and storage banks instead of the current conventional grid. The objective of this paper is to find the optimum system that has the lowest net present cost (NPC) and greenhouse emission CO2. The metrological data and load profile are collected at the desired location. The simulation results show that NPC of a proposed combination of Grid/PV/WT system, at the current grid’s tariff of 0.085/kWh,ismoreefficientthanotherconfigurationswithpowerloadshortage(<0.1/kWh, is more efficient than other configurations with power load shortage (<0.1%), with more than 30% reduction in CO2 emission, and lower cost of energy (COE). The results also show that the integration of PV and WT sources with the main grid is the best configuration that leads to the minimum COE of 0.0772 /kWh, 0.075 /kWh,and0.048/ kWh, and 0.048 /kWh at the educational building, administration building, and total campuses’ load, respectively. The developed methods conclude that the objective function and simulation results are feasible for the selected loads at Al Baha University. The current analyses can be adopted to install the real renewable energy system at the desired University

    Prognosis and distribution of ischemic stroke with negative diffusion-weighted imaging: a systematic review and meta-analysis

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    BackgroundMagnetic resonance diffusion-weighted imaging (DWI) is the most sensitive modality for ischemic stroke diagnosis. However, DWI may fail to detect ischemic lesions in a proportion of patients.MethodsFollowing PRISMA statement, a systematic search of Medline, Embase, and Web of Science was conducted until January 3, 2024. The inclusion was confined to English literature with sufficient reporting. Proportions of DWI-negative ischemic stroke were pooled. For binary variables, odds ratios (ORs) were computed using the random-effects model.ResultsFourteen studies constituting 16,268 patients with a clinical diagnosis of ischemic stroke and available DWI findings were included. Intravenous thrombolysis (IVT) was administered to 19.6% of the DWI-negative group and 15.3% of the DWI-positive group. DWI-negative ischemic stroke was reported in 16% (95% CI: 10–24%; after sensitivity analysis: 11% [95% CI: 8–15%]) of stroke patients. Among minor stroke patients (National Institutes of Health Stroke scale [NIHSS] of 5 or less), 24% (95% CI 12–42%) had negative DWI findings. Predictors of DWI-negative scans included posterior circulation stroke, history of ischemic heart disease, prior stroke, or prior transient ischemic attack. Cardioembolic stroke (OR, 0.62, 95% CI: 0.41–0.93) and history of atrial fibrillation increased the likelihood of positive DWI findings (OR, 0.56, 95% CI: 0.45–0.71). Patients with DWI-negative ischemic stroke had higher odds of good functional outcomes (modified Rankin scale [mRS] of 0–1) (OR, 2.26; 95% CI: 1.03–4.92), lower odds of stroke recurrence (OR, 0.68; 95% CI: 0.48–0.96), and lower odds of severe disability or mortality (mRS of 3–6) (OR, 0.44; 95% CI: 0.34–0.57) compared to patients with positive DWI. Rates of symptomatic intracerebral hemorrhage after IVT were comparable between groups.ConclusionDWI-negative findings were present in a significant proportion of ischemic stroke patients and may be utilized as a marker for favorable prognosis
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