A perturbation method and model order reduction for stochastic hydroelastic problems

Omar Bendaou,Othmane Bendaou,Bousselham Samoudi 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.4

This study aims to optimize computing time during numerical modal analysis of hydroelastic problems with uncertain parameters. We proposed a strategy that combines two methods adapted to hydroelastic problems. The first is the modal superposition method for reducing the finite element model order. The second one is a perturbation method that considers the design parameters uncertainties and evaluates without iterations the natural frequencies moments of the wetted structure. The proposed strategy was validated by applying it to the stochastic characterization of the vibratory behavior of a water storage tank. Results of the proposed strategy were compared with those from the classical one, which consists of modal analysis without model reduction combined with Monte Carlo simulation. The confrontation showed a good correlation between the results of the two strategies. However, as expected, the proposed one was considerably computationally time inexpensive.

State-Aware Re-configuration Model for Multi-Radio Wireless Mesh Networks

( Omar M. Zakaria ),( Aisha-hassan Abdalla Hashim ),( Wan Haslina Hassan ),( Othman Omran Khalifa ),( Mohammad Azram ),( Shidrokh Goudarzi ),( Lalitha Bhavani Jivanadham ),( Mahdi Zareei ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.1

Joint channel assignment and routing is a well-known problem in multi-radio wireless mesh networks for which optimal configurations is required to optimize the overall throughput and fairness. However, other objectives need to be considered in order to provide a high quality service to network users when it deployed with high traffic dynamic. In this paper, we propose a re-configuration optimization model that optimizes the network throughput in addition to reducing the disruption to the mesh clients` traffic due to the re-configuration process. In this multi-objective optimization model, four objective functions are proposed to be minimized namely maximum link-channel utilization, network average contention, channel re-assignment cost, and re-routing cost. The latter two objectives focus on reducing the re-configuration overhead. This is to reduce the amount of disrupted traffic due to the channel switching and path re-routing resulted from applying the new configuration. In order to adapt to traffic dynamics in the network which might be caused by many factors i.e. users` mobility, a centralized heuristic re-configuration algorithm called State-Aware Joint Routing and Channel Assignment (SA-JRCA) is proposed in this research based on our re-configuration model. The proposed algorithm re-assigns channels to radios and re-configures flows` routes with aim of achieving a tradeoff between maximizing the network throughput and minimizing the re-configuration overhead. The ns-2 simulator is used as simulation tool and various metrics are evaluated. These metrics include channel-link utilization, channel re-assignment cost, re-routing cost, throughput, and delay. Simulation results show the good performance of SA-JRCA in term of packet delivery ratio, aggregated throughput and re-configuration overhead. It also shows higher stability to the traffic variation in comparison with other compared algorithms which suffer from performance degradation when high traffic dynamics is applied.

A multi-institutional analysis of sternoclavicular joint coverage following osteomyelitis

Sammy Othman,Omar Elfanagely,Saïd C. Azoury,Geoffrey M. Kozak,Jessica Cunning,Arturo J. Rios-Diaz,Prashanth Palvannan,Patrick Greaney,Matthew P. Jenkins,Doraid Jarrar,Stephen J. Kovach,John P. Fischer 대한성형외과학회 2020 Archives of Plastic Surgery Vol.47 No.5

Background Sternoclavicular joint (SCJ) osteomyelitis is a rare pathology requiring urgent intervention. Several operative approaches have been described with conflicting reports. Here, we present a multi-institutional study utilizing multiple surgical pathways for SCJ reconstruction. Methods A multi-institutional retrospective cohort study was conducted to identify patients who underwent surgical repair for sternoclavicular osteomyelitis between 2008 and 2019. Patients were stratified according to reconstruction approach: single-stage reconstruction with advancement flap and delayed-reconstruction with flap following initial debridement. Demographics, operative approach, type of reconstruction, and postoperative outcomes were analyzed. Results Thirty-two patients were identified. Mean patient age was 56.2±13.8 years and 68.8% were male. The average body mass index (BMI) was 30.0±8.8 kg/m2. The most common infection etiologies were intravenous drug use and bacteremia (both 25%). Fourteen patients (43.8%) underwent one-stage reconstruction and 18 (56.2%) underwent delayed twostaged reconstruction. Both single and delayed-stage groups had comparable rates of reinfection (7.1% vs. 11.1%, respectively), surgical site complications (21.4% vs. 27.8%), readmissions (7.1% vs. 16.6%), and reoperations (7.1% vs. 5.6%; all P>0.05). The single-stage reconstruction group had a significantly lower BMI (26.2±5.7 kg/m2 vs. 32.9±9.1 kg/m2; P<0.05) and trended towards shorter hospital length of stay (11.3 days vs. 17.9 days; P=0.01). Conclusions Both single and delayed-stage approaches are appropriate methods with comparable outcomes for reconstruction for SCJ osteomyelitis. When clinically indicated, a singlestage reconstruction approach may be preferable in order to avoid a second operation as associated with the delayed phase, and possibly shortening total hospital length of stay.

Effect of EFB Biochar on Total Phenolics and Secondary Metabolites of L.pumila Benth

Siti Norayu Omar Baki,Hawa Ze Jaafar,Radziah Othman 한국토양비료학회 2014 한국토양비료학회 학술발표회 초록집 Vol.2014 No.6

Assessment of Muscle Fatigue Associated with Prolonged Standing in the Workplace

Halim, Isa,Omar, Abdul Rahman,Saman, Alias Mohd,Othman, Ibrahim Occupational Safety and Health Research Institute 2012 Safety and health at work Vol.3 No.1

Objectives: The objectives of this study were to determine the psychological fatigue and analyze muscle activity of production workers who are performing processes jobs while standing for prolonged time periods. Methods: The psychological fatigue experienced by the workers was obtained through questionnaire surveys. Meanwhile, muscle activity has been analyzed using surface electromyography (sEMG) measurement. Lower extremities muscles include: erector spinae, tibialis anterior, and gastrocnemius were concurrently measured for more than five hours of standing. Twenty male production workers in a metal stamping company participated as subjects in this study. The subjects were required to undergo questionnaire surveys and sEMG measurement. Results: Results of the questionnaire surveys found that all subjects experienced psychological fatigue due to prolonged standing jobs. Similarly, muscle fatigue has been identified through sEMG measurement. Based on the non-parametric statistical test using the Spearman's rank order correlation, the left erector spinae obtained a moderate positive correlation and statistically significant ($r_s$ = 0.552, p < 0.05) between the results of questionnaire surveys and sEMG measurement. Conclusion: Based on this study, the authors concluded that prolonged standing was contributed to psychological fatigue and to muscle fatigue among the production workers.

Hydrolysis of Empty Fruit Bunch of Oil Palm Using Cellulolytic Enzymes from Aspergillus terreus IMl 28243

(Jalil Kader),(Getha Krishnasamy),(Wan Mohtar),(Othman Omar) 한국미생물생명공학회 1999 Journal of microbiology and biotechnology Vol.9 No.4

N/A N/A

In vitro treatment of lipopolysaccharide increases invasion of Pasteurella multocida serotype B:2 into bovine aortic endothelial cells

Seng Kar Yap,Zunita Zakaria,Siti Sarah Othman,Abdul Rahman Omar 대한수의학회 2018 Journal of Veterinary Science Vol.19 No.2

Pasteurella multocida serotype B:2 causes hemorrhagic septicemia in cattle and buffalo. The invasion mechanism of the bacterium wheninvading the bloodstream is unclear. This study aimed to characterize the effects of immunomodulatory molecules, namely dexamethasoneand lipopolysaccharide, on the invasion efficiency of P. multocida serotype B:2 toward bovine aortic endothelial cells (BAECs) and theinvolvement of actin microfilaments in the invasion mechanism. The results imply that treatment of BAECs with lipopolysaccharide at 100ng/mL for 24 h significantly increases the intracellular bacteria number per cell (p < 0.01) compared with those in untreated anddexamethasone-treated cells. The lipopolysaccharide-treated cells showed a significant decrease in F-actin expression and an increase inG-actin expression (p < 0.001), indicating actin depolymerization of BAECs. However, no significant differences were detected in theinvasion efficiency and actin filament reorganization between the dexamethasone-treated and untreated cells. Transmission electronmicroscopy showed that P. multocida B:2 resided in a vacuolar compartment of dexamethasone-treated and untreated cells, whereas thebacteria resided in cellular membrane of lipopolysaccharide-treated cells. The results suggest that lipopolysaccharide destabilizes the actinfilaments of BAECs, which could facilitate the invasion of P. multocida B:2 into BAECs.

A Low-Profile Quasi-Loop Magneto-Electric Dipole Antenna Featuring a Wide Bandwidth and Circular Polarization for 5G mmWave Device-to-Device Communication

Kamal Shahanawaz,Ain Mohd Fadzil Bin,Ullah Ubaid,Mohammed Abdullahi S. B.,Hussin Roslina,Omar Mohamad Faiz Bin Mohamed,Najmi Fathul,Ahmad Zainal Arifin,Rahman Mohd Fariz Ab,Mahmud Mohd Nazri,Othman Mo 한국전자파학회 2022 Journal of Electromagnetic Engineering and Science Vol.22 No.4

The deployment of the millimeter (mmWave) frequency spectrum by fifth-generation (5G) device-to-device (D2D) wireless networks is anticipated to meet the growing demands for increased capacity. The antenna is regarded of as an important determinant that guarantees the maximum performance of wireless communication. This paper presents a low-profile magneto-electric (ME) dipole antenna for 5G mmWave D2D communication. A single-element quasi-loop radiator was designed to excite horizontal polarization, and a coaxial probe was used to produce vertical polarization. Subsequently, the structure of the radiator was transformed into a two-element quasi-loop an- tenna to achieve an omnidirectional radiation pattern with relatively enhanced gain. A coaxially fed T-junction microstrip element was implemented to equally distribute the signal between the two quasi-loop radiators and attain proper impedance matching. Furthermore, a pair of shorting pins was introduced into the two-element design to maintain the circularly polarized (CP) radiation. The finest values of the axial ratio and |S11| were derived by rigorously optimizing all the geometry parameters. Both single-element and two-element quasi- loop antennas were fabricated and characterized experimentally on the air substrate. The advantage of avoiding a physical substrate is to realize a wide bandwidth, circumvent dielectric losses, and ascertain the maximum gain. The measured and simulated results agree thor- oughly with each other. Stable in-band CP radiation were accomplished, thus confirming an appropriate field vector combination from the coaxial probe and the radiator. The finalized antenna engaged an area of ~7.6λ for operation at 23.9–30.0 GHz with an axial ratio <3 dB, radiation efficiency ~80%, and gain >5 dBic.