Rheological, Mechanical and Structural Performances of Crushed Limestone Sand Concrete

Khaoula Akrout,Pierre Mounanga,Mounir Ltifi,Nejib Ben Jamaa 한국콘크리트학회 2010 International Journal of Concrete Structures and M Vol.4 No.2

The crushed limestone sand is an abundant material in Tunisia, which induces many environmental problems. Indeed, available stocks of siliceous sand drastically decrease because of its massive use in hydraulic concrete. Some recent research works, carried out in Tunisia, concluded that crushed limestone sand may be used in concrete manufacture instead of siliceous sand traditionally used. In this context, an experimental study was achieved in order to quantify the influence of a partial or total substitution of siliceous sand by crushed limestone sand on hydraulic concrete performances. Preliminary chemical and physical tests on crushed sand indicated that it presented the minimum requirement for its use as aggregate in hydraulic concrete. 79 concretes were then prepared with siliceous sand, crushed limestone sand and a mix of the two sands. Their slump value and compressive strengths were measured on plain concretes. Complementary structural tests on reinforced concrete beam were also performed. The results proved that crushed limestone sand concretes showed workability and mechanical performances closed to those of siliceous sand concretes.

Chloride Diffusion in Mortars - Effect of the Use of Limestone Sand Part I

Khaoula Akrout,Mounir Ltifi,Mongi Ben Ouezdou 한국콘크리트학회 2010 International Journal of Concrete Structures and M Vol.4 No.2

In order to determine the effect of the use of limestone sand on chloride ion ingress in mortar, specimens were cast with two different sands: siliceous sand (used as reference) and limestone crushed sand (used for this study). To compare and assess the resistance of this mortar to chloride penetration, two different diffusions tests were employed: slow migration and rapid migration (AASHTO test). In this study, calculation of the effective diffusion coefficient is proposed using a model based on Nernst?Planck equation. The diffusion coefficients from each sample were compared. The results for all tests show that the diffusion coefficients for siliceous sand mortar are larger than those obtained with limestone sand. It appears also that the diffusion coefficient varies as a function of the W/C ratio.

Improvement of thermal conductivity and energy stored by paraffin with different metallic additives

Khaoula Missoum,Hocine Guellil,Abdel Illah Nabil Korti 대한설비공학회 2020 International Journal Of Air-Conditioning and Refr Vol.28 No.3

Phase change thermal storage is an innovative technology for saving energy. It is one of the new areas of research because it provides the solution to problems related between the provided and the required energies. Praffin is a common phase change material(PCM) that used in many applications in thermal energy storage(TES) systems. However, the main disadvantage is their low thermal conductivities. However, using metallic additives to improve effective energy stored. An experimental study is carried out to analyze the thermal behavior of the paraffin melting in a thermal cavity integrating different metals (zamak, aluminum and copper) with different configuration. The originality of study is to try to predict the best duo that respects both the improvement of thermal conductivity and energy stored. The expetiments shows that addind the aluminum perforated plate in the paraffin can accelerates the melting process by about 19% and increases the energy sored by 5.18%.

On numerical range and numerical radius of convex function operators

Khaoula Zaiz,Abdelouahab Mansour 강원경기수학회 2019 한국수학논문집 Vol.27 No.4

In this paper we prove some interesting inclusions concerning the numerical range of some operators and the numerical range of theirs ranges with a convex function. Further, we prove some inequalities for the numerical radius. These inclusions and inequalities are based on some classical convexity inequalities for non-negative real numbers and some operator inequalities.

Generic Framework for Hybrid Fault Diagnosis and Health Monitoring of the Tennessee Eastman Process

Khaoula Tidriri,Nizar Chatti,Sylvain Verron,Teodor Tiplica 제어로봇시스템학회 2017 제어로봇시스템학회 국제학술대회 논문집 Vol.2017 No.10

Fault Diagnosis and Health Monitoring (FD-HM) based on hybrid approaches have been an active field of research and a key challenge over the last few years. In many applications, generic and unified approaches are usually required for designing a complete robust FD-HM system. The main contribution of this article is to develop a hybrid approach properly tailored for such challenge, by bridging the Bond-Graph (BG), the Signed Bond-Graph (SBG) and the Bayesian Network (BN) methods, through a probabilistic common framework for decision-making. This new hybrid methodology benefits from different types of information emanating from the quantitative model, the qualitative reasoning and the available data, in order to increase the overall confidence in the diagnosis performances. The effectiveness of the proposed hybrid approach is validated by the well-known Tennessee Eastman Process.

Rheological, Mechanical and Structural Performances of Crushed Limestone Sand Concrete

Akrout, Khaoula,Mounanga, Pierre,Ltifi, Mounir,Jamaa, Nejib Ben Korea Concrete Institute 2010 International Journal of Concrete Structures and M Vol.4 No.2

The crushed limestone sand is an abundant material in Tunisia, which induces many environmental problems. Indeed, available stocks of siliceous sand drastically decrease because of its massive use in hydraulic concrete. Some recent research works, carried out in Tunisia, concluded that crushed limestone sand may be used in concrete manufacture instead of siliceous sand traditionally used. In this context, an experimental study was achieved in order to quantify the influence of a partial or total substitution of siliceous sand by crushed limestone sand on hydraulic concrete performances. Preliminary chemical and physical tests on crushed sand indicated that it presented the minimum requirement for its use as aggregate in hydraulic concrete. 79 concretes were then prepared with siliceous sand, crushed limestone sand and a mix of the two sands. Their slump value and compressive strengths were measured on plain concretes. Complementary structural tests on reinforced concrete beam were also performed. The results proved that crushed limestone sand concretes showed workability and mechanical performances closed to those of siliceous sand concretes.

Chloride Diffusion in Mortars - Effect of the Use of Limestone Sand Part II: Immersion Test

Akrout, Khaoula,Ltifi, Mounir,Ouezdou, Mongi Ben Korea Concrete Institute 2010 International Journal of Concrete Structures and M Vol.4 No.2

Part I of this study was devoted to the electrical accelerated chloride diffusion in mortars. In this second part, natural chloride diffusion has been investigated for four types of mortars under exposure to a 0.5 mol/L NaCl solution for a period of up to 35 days. Two different types of sand were used for the production of test samples: siliceous sand (used as a reference) and limestone sand (used in this study). The effect of water to cement ratio and exposure time on the diffusion coefficients of mortars was also investigated. In this study, the total and free chloride content and penetration depth of mortar were measured after immersion, and Fick's second law of diffusion was fitted to the experimental data to determine the diffusion coefficient. Their results show that the use of crushed limestone sand in mortar had a positive effect on the chloride resistance. The apparent diffusion coefficient in all specimens was smaller than that in siliceous sand mortar. However, the chloride penetration of these mortars was increased as exposure time progressed.

Chloride Diffusion in Mortars - Effect of the Use of Limestone Sand Part I: Migration Test

Akrout, Khaoula,Ltifi, Mounir,Ouezdou, Mongi Ben Korea Concrete Institute 2010 International Journal of Concrete Structures and M Vol.4 No.2

In order to determine the effect of the use of limestone sand on chloride ion ingress in mortar, specimens were cast with two different sands: siliceous sand (used as reference) and limestone crushed sand (used for this study). To compare and assess the resistance of this mortar to chloride penetration, two different diffusions tests were employed: slow migration and rapid migration (AASHTO test). In this study, calculation of the effective diffusion coefficient is proposed using a model based on Nernst. Planck equation. The diffusion coefficients from each sample were compared. The results for all tests show that the diffusion coefficients for siliceous sand mortar are larger than those obtained with limestone sand. It appears also that the diffusion coefficient varies as a function of the W/C ratio.

Awake prone positioning for COVID-19 acute hypoxemic respiratory failure in Tunisia

Ismail Khaoula Ben,Essafi Fatma,Talik Imen,Slimene Najla Ben,Sdiri Ines,Dhia Boudour Ben,Merhbene Takoua 대한중환자의학회 2023 Acute and Critical Care Vol.38 No.3

Background: In this study, we explored whether awake prone position (PP) can impact prognosis of severe hypoxemia coronavirus disease 2019 (COVID-19) patients. Methods: This was a prospective observational study of severe, critically ill adult COVID-19 patients admitted to the intensive care unit. Patients were divided into two groups: group G1=patients who benefited from a vigilant and effective PP (>4h minimum/24) and group G2=control group. We compared demographic, clinical, paraclinical and evolutionary data. Results: Three hundred forty-ninepatients were hospitalized during the study period, 273 met the inclusion criteria. PP was performed in 192 patients (70.3%). The two groups were comparable in terms of demographic characteristics, clinical severity and modalities of oxygenation at ICU admission.The mean PaO2/FIO2ratios were respectively 141 and 128 mmHg, (P=0.07). The computed tomography scan was comparable with a critical >75% in 48.5% (G1) versus 54.2% (G2). The median duration of the daily PP session was 13±7 hours per day. The average duration of spontaneous PP days was 7 days [4–19]. Use of invasive ventilation was lower in the G1 group (27% vs. 56%, P=0.002). Healthcare-associated infections were significantly lower in G1 (42.1% vs. 82%, P=0.01). Duration of total mechanical ventilation and length of ICU stay were comparable between the two groups. Mortality was significantly higher in G2 (64% vs. 28%, P=0.02). Conclusions: Our study confirmed that awake PP can improve prognosis in COVID-19 patients. Randomized controlled trials are needed to confirm this result.

Monitoring Mental Healthcare Services Using Business Analytics

Samy Housbane,Adil Khoubila,Khaoula Ajbal,Zineb Serhier,Mohamed Agoub,Omar Battas,Mohamed Bennani Othmani 대한의료정보학회 2020 Healthcare Informatics Research Vol.26 No.2

Objectives: Monitoring healthcare activities is the first step for health stakeholders and health professionals to improve the quality and performance of healthcare services. However, monitoring remains a challenge for healthcare facilities, especially in developing countries. Fortunately, advances in business analytics address this need. This paper aims to describe the experience of a lowincome healthcare facility in a developing country in using business analytics descriptive techniques and to discuss business analytics implementation challenges and opportunities in such an environment. Methods: Business analytics descriptive techniques were applied on 3 years’ electronic medical records of outpatient consultation of the University Psychiatric Centre (CPU) of Casablanca. Statistical analysis was conducted to compare results over years. Results: Over the 3 monitored years, the monthly number of computerized physician order entries increased significantly (p < 0.001). Physicians improved their personal recording over years. Schizophrenia as well as depressive and bipolar disorders were noted at the top of outpatient mental disorders. Antipsychotics are the most prescribed drugs, and a significant annual decrease in outpatient care wait time was noted (p < 0.001). Conclusions: Business analytics allowed CPU to monitor mental healthcare outpatient activity and to adopt its business processes according to outcomes. However, challenges mainly in the organizational dimension of the decision-making process and the definition of strategic key metrics, data structuration, and the quality of data entry had to be considered for the optimal use of business analytics.