Friction drilling of Cast Aluminum Alloy A380 without significant petal formation and radial fracture

Sara Ahmed El‑Bahloul 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.1

Cast aluminum alloy A380 is one of the most commonly specified alloys that has light weight and exhibits excellent resistance to hot cracking, which makes it necessary in many industrial applications. An idea is investigated to generate a cylindrical bushing without significant petal formation and radial fracture that are expected to be obtained by friction drilling of cast metals. Three materials; namely, 316 stainless steel, Al6060 aluminum alloy, and red copper alloy are used in which each of them is located on the upper and lower surfaces of A380 workpiece, so achieving the idea of the functionally graded material. The process parameters were studied for reducing the resultant axial force, the gap between surfaces, and achieving a longer bushing without petal formation and radial fracture. Lower feed rate achieves minimum axial force and gap thickness with maximum bushing length for all material sandwiches. An optimized decision making by the help of fuzzy logic techniques is performed, revealing that red copper sandwich exhibits the optimal multiple performance characteristic index based on axial force, bushing length, gap thickness, and gap divergence.

Gravity-induced ischemia in the brain and prone positioning for COVID-19 patients breathing spontaneously: still far from the truth!

Mabrouk Bahloul,Sana Kharrat,Kamilia Chtara,Hedi Chelly,Chokri Ben Hamida,Mounir Bouaziz 대한중환자의학회 2022 Acute and Critical Care Vol.37 No.1

Clinical characteristics and outcomes of critically ill COVID-19 patients in Sfax, Tunisia

Mabrouk Bahloul,Sana Kharrat,Kamilia Chtara,Malek Hafdhi,Olfa Turki,Najeh Baccouche,Rania Ammar,Nozha Kallel,Majdi Hsairi,Olfa Chakroun-Walha,Chokri Ben Hamida,Hedi Chelly,Khaiereddine Ben Mahfoudh,Ab 대한중환자의학회 2022 Acute and Critical Care Vol.37 No.1

Background: Africa, like the rest of the world, has been impacted by the coronavirus disease 2019 (COVID-19) pandemic. However, only a few studies covering this subject in Africa have been published. Methods: We conducted a retrospective study of critically ill adult COVID-19 patients—all of whom had a confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection—admitted to the intensive care unit (ICU) of Habib Bourguiba University Hospital (Sfax, Tunisia). Results: A total of 96 patients were admitted into our ICU for respiratory distress due to COVID-19 infection. Mean age was 62.4±12.8 years and median age was 64 years. Mean PaO2/FiO2 ratio was 105±60 and ≤300 in all cases but one. Oxygen support was required for all patients (100%) and invasive mechanical ventilation for 38 (40%). Prone positioning was applied in 37 patients (38.5%). Within the study period, 47 of the 96 patients died (49%). Multivariate analysis showed that the factors associated with poor outcome were the development of acute renal failure (odds ratio [OR], 6.7), the use of mechanical ventilation (OR, 5.8), and serum cholinesterase (SChE) activity lower than 5,000 UI/L (OR, 5.9). Conclusions: In this retrospective cohort study of critically ill patients admitted to the ICU in Sfax, Tunisia, for acute respiratory failure following COVID-19 infection, the mortality rate was high. The development of acute renal failure, the use of mechanical ventilation, and SChE activity lower than 5000 UI/L were associated with a poor outcome.

Temperature effect on the structural and the optical properties of sol gel CdTiO3 nanopowders

Radouane Bahloul 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.4

Sol gel processed cadmium titanate (CdTiO3) ceramic has been characterized by X-ray diffraction (XRD), infrared (IR) andRaman techniques. The results confirm that CdTiO3 crystallizes in the pure hexagonal ilmenite phase at 900 oC and undergoesa transition to the pure orthorhombic structure above this temperature. Furthermore, it was showed that a post-annealing atthe temperature of 1100 oC leads to a transition to a new phase with Pbn21 as space group, with the following latticeparameters: a = 5.30 Å, b = 5.43 Å and c = 7.57 Å. UV-Vis spectroscopy results show that CdTiO3 band gap energies arestrongly affected by the crystallite size and structural properties. The obtained band gap values of ilmenite and perovskitephases are higher than those reported in the literature, whereas that of Pbn21 is slightly lower than that related to Pbnm,probably due to the distortion of Pbnm structure or to the presence of TiO2 structure.

An Efficient Contour Parallel Tool Path Generation for Arbitrary Pocket Shape without Uncut Regions

Elhachemi- Bahloul,Mourad- Brioua,Cherif- Rebiai 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Abstract With the aim of improving productivity in pocket machining the uncut regions are one of the most influencing factors on the tool path length and cutting time. We are interested in two kinds of uncut regions; the corner uncuts that appear between the passes and the center uncut. In this paper we have developed a new analytical model of tool path for machining pockets in 2½D with contour parallel offset for an arbitrary shape of pocket boundary whether line-line or line-arc. For the corner uncuts we propose a novel coefficient which ensures the ideal cover area between passes without letting behind any uncut region. For the center uncut we propose an automatically additional reduced looping with a passage segment that depends on the center uncut region geometry. For the purpose of the validation of this new developed method some selected numerical examples are presented. The obtained results show that our new approach minimizes both the tool path length and the machining time compared to other methods. Thus this new method offers an efficient contour parallel offset of tool path generation and an optimized machining.

Impact of prone position on outcomes of COVID-19 patients with spontaneous breathing

Mabrouk Bahloul,Sana Kharrat,Malek Hafdhi,Anis Maalla,Olfa Turki,Kamilia Chtara,Rania Ammar,Basma Suissi,Chokri Ben Hamida,Hedi Chelly,Khaiereddine Ben Mahfoudh,Mounir Bouaziz 대한중환자의학회 2021 Acute and Critical Care Vol.36 No.3

Background: In this study, we explored whether early application of the prone position (PP) can improve severe hypoxemia and respiratory failure in coronavirus disease 2019 (COVID-19) patients with spontaneous breathing. Methods: This is a prospective observational study of severe, critically ill adult COVID-19 patients admitted to the intensive care unit. All vital parameters were recorded in real time for all patients. Moreover, the results of chest computed tomography (CT), when available, were analyzed. Results: PP was applied in 21 patients who were breathing spontaneously. The application of PP was associated with a significant increase in oxygen saturation measured by pulse oximetry (SpO2) from 82%±12% to 96%±3% (P<0.001) 1 hour later. Moreover, PP was associated with a significant reduction in respiratory rate from 31±10 to 21±4 breaths/min (P<0.001). Furthermore, the number of patients who exhibited signs of respiratory distress after PP was reduced from 10 (47%) to 3 (14%) (P=0.04). Early PP application also led to a clear improvement on CT imaging. It was not, however, associated with a reduction in mortality rate or in the use of invasive mechanical ventilation (P>0.05 for both). Conclusions: Our study confirmed that the early application of PP can improve hypoxemia and tachypnea in COVID-19 patients with spontaneous breathing. Randomized controlled trials are needed to confirm the beneficial effects of PP in COVID-19 patients with spontaneous breathing.

A Novel Heterozygous Missense Variant (c.667G>T;p.Gly223Cys) in USH1C That Interferes With Cadherin-Related 23 and Harmonin Interaction Causes Autosomal Dominant Nonsyndromic Hearing Loss

Ju Sun Song,Amel Bahloul,Christine Petit,Sang Jin Kim,Il Joon Moon,이진혁,Change-Seok Ki 대한진단검사의학회 2020 Annals of Laboratory Medicine Vol.40 No.3

Background: Pathogenic variants of USH1C, encoding a PDZ-domain-containing protein called harmonin, have been known to cause autosomal recessive syndromic or nonsyndromic hearing loss (NSHL). We identified a causative gene in a large Korean family with NSHL showing a typical pattern of autosomal dominant (AD) inheritance. Methods: Exome sequencing was performed for five affected and three unaffected individuals in this family. Following identification of a candidate gene variant, segregation analysis and functional studies, including circular dichroism and biolayer interferometry experiments, were performed. Results: A novel USH1C heterozygous missense variant (c.667G>T;p.Gly223Cys) was shown to segregate with the NSHL phenotype in this family. This variant affects an amino acid residue located in the highly conserved carboxylate-binding loop of the harmonin PDZ2 domain and is predicted to disturb the interaction with cadherin-related 23 (cdh23). The affinity of the variant PDZ2 domain for a biotinylated synthetic peptide containing the PDZ-binding motif of cdh23 was approximately 16-fold lower than that of the wild-type PDZ2 domain and that this inaccessibility of the binding site was caused by a conformational change in the variant PDZ2 domain. Conclusions: A heterozygous variant of USH1C that interferes with the interaction between cdh23 and harmonin causes novel AD-NSHL.

Fatigue crack growth behavior of AA2024T3 under mixed mode loading within the framework of EPFM

A. Remadi,A. Bahloul,C. H. Bouraoui 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4

In this paper, a fatigue crack growth (FCG) behavior under variable amplitude loadings and for mixed modes is analyzed in terms of residual compressive stress zone. For that, the Chaboche non-linear kinematic hardening model is used to evaluate the crack behavior on AA2024-T3. At first, a series of FCG simulation is performed for a single edge notched tension specimen to highlight the influences of the crack length, the overload ratio, the stress ratio, the mean stress, the mixed mode, and the load sequence on the crack tip residual -stress zone under variable amplitude loadings. Besides, the size and shape of crack tip residualstress zone are simulated for low/high, high/low block loadings and with / without overloads. Moreover, and according to the findings, a FCG code using the Python script and the extended finite element method (XFEM) Is improved. The developed code processes FCG behavior under variable amplitude loadings using the shape of residual stress distribution near the crack tip. The predicted results show a good agreement in simulating fatigue crack path under variable amplitude loadings with those published in the literature. The originality of this study is to simulate the fatigue crack path of cracked structures under variable amplitude loadings with the compressive residual stress model coupled with the XFEM for mode I and different mixed mode.

Simultaneously Achieving a Large Negative Dispersion and a High Birefringence Over Er and Tm Dual Gain Bands in a Square Lattice Photonic Crystal Fiber

Lee, Yong Soo,Lee, Chung Ghiu,Bahloul, Faouzi,Kim, Soeun,Oh, Kyunghwan IEEE 2019 Journal of Lightwave Technology Vol.37 No.4

<P>We proposed a novel photonic crystal fiber composed of a double-cladding square lattice that could be used in dual-band, Er and Tm optical gain bands, simultaneously supporting a large negative dispersion and a high birefringence. We theoretically investigated the light guiding property through the proposed photonic crystal fiber by using a vectorial finite-element method with a perfectly matched layer. By optimizing the structural parameters, we obtained an ultra-large negative dispersion of −20,186 ps/(nm·km) and a very high birefringence of 9.27 × 10<SUP>−3</SUP> at the wavelength of 1.55 <I>μ</I>m in the Er gain band and a very large negative dispersion of −8,067 ps/(nm·km) and a high birefringence of 1.0 × 10<SUP>−3</SUP> at the wavelength of 1.87 <I>μ</I>m in the Tm band. We further discussed the roles of waveguide parameters on the chromatic dispersion, its slope, and the birefringence of the fiber as well as the mode field diameter. The proposed fiber could be directly applied for dual-band dispersion and polarization control in fiber laser cavities as well as optical communications and sensors in the dual bands.</P>

Comparison of intraperitoneal versus intravenous dexamethasone on postoperative nausea and vomiting after gynecological laparoscopy: a randomized clinical trial

Eman A Ismail,Ghada M Abo Elfadl,Mustafa Bahloul 대한마취통증의학회 2019 Korean Journal of Anesthesiology Vol.72 No.1

Background: Postoperative nausea and vomiting (PONV) is a common complication following laparascopic surgery. This study compared the effect of intraperitoneal versus intravenous dexamethasone for reducing PONV after gynecological laparoscopic surgeries. Methods: Eighty adult female patients, American Society of Anesthesiologists physical status I–II, scheduled for gynecological laparoscopic surgery were randomized to receive 8 mg dexamethasone intravenously (IV) (n = 40) or intraperitoneally (IP) (n = 40). The primary outcome was the PONV incidence during the first 24 h after laparoscopy. Secondary outcomes included visual analogue scale (VAS) pain scores, total rescue analgesic consumption during the first 24 h postoperatively, the need for rescue antiemetic drugs, and the incidence of complications that may accompany these medications. Results: Eleven women (27.5%) in the IV group, versus only 3 (7.5%) women in the IP group, experienced nausea during the first 24 h postlaparoscopy (P = 0.037). However, 5 patients (12.5%) in the IV group, versus only 2 patients (5.0%) in the IP group, experienced vomiting (P = 0.424). No statistically significant differences were seen in the severity of nausea or the need for rescue antiemetics. The IV group had a higher rate of side-effects than the IP group (27.5% vs. 7.5%, P = 0.037). Headache and dizziness were common side effects in the IV dexamethasone group. The groups did not differ significantly in terms of mean VAS score for pain and total meperidine consumption during the first 24 h postoperatively. Conclusions: Intraperitoneal dexamethasone at a dose of 8 mg at the end of gynecological laparoscopy reduces the incidence of postoperative nausea.