Preparation and characterization of new Ru-based dye-sensitizer for electrochromic devices

( Walid ),이익모 한국공업화학회 2005 한국공업화학회 연구논문 초록집 Vol.2005 No.1

Improved Reactive Power Sharing for Parallel-operated Inverters in Islanded Microgrids

Walid Issa,Suleiman Sharkh,Tapas Mallick,Mohammad Abusara 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

The unequal impedances of the interconnecting cables between paralleled inverters in the island mode of microgrids cause inaccurate reactive power sharing when the traditional droop control is used. Many studies in the literature adopt low speed communications between the inverters and the central control unit to overcome this problem. However, the losses of this communication link can be very detrimental to the performance of the controller. This paper proposes an improved reactive power-sharing control method. It employs infrequent measurements of the voltage at the point of common coupling (PCC) to estimate the output impedance between the inverters and the PCC and then readjust the voltage droop controller gains accordingly. The controller then reverts to being a traditional droop controller using the newly calculated gains. This increases the immunity of the controller against any losses in the communication links between the central control unit and the inverters. The capability of the proposed control method has been demonstrated by simulation and experimental results using a laboratory scale microgrid.

Switching to Aflibercept in Diabetic Macular Edema after Unsatisfactory Response to Other Anti-vascular Endothelial Growth Factor Drugs

Walid S. Ibrahim,Zeiad H. Eldaly,Mahmoud F. Rateb,Ahmed H. Aldoghaimy,Mohamed G. Saleh 대한안과학회 2019 Korean Journal of Ophthalmology Vol.33 No.2

Purpose: To evaluate the efficacy of switching to aflibercept in diabetic macular edema (DME) with suboptimalresponse to previous anti-vascular endothelial growth factor (anti-VEGF) injections. Methods: A prospective interventional case series study recruited patients from a single center diagnosedwith DME with suboptimal response to anti-VEGF injections. Three consecutive monthly injections of afliberceptwere performed. The primary outcome measure was mean change in visual acuity after switching toaflibercept. Results: Forty-two patients (42 eyes) were included. Baseline logarithm of the minimum angle of resolution(logMAR) visual acuity was 0.87 ± 0.23 and improved significantly to 0.62 ± 0.29, 0.56 ± 0.34, and 0.46 ±0.35 at 1, 2, and 3 months, respectively, after the first injection. Mean baseline retinal thickness was 451.57± 107.09 μm and decreased significantly at 1, 2, and 3 months after switching to aflibercept (346.52 ± 79.03,328.24 ± 81.98, and 313.71 ± 85.79 μm, respectively). Both visual improvement and mean change in retinalthickness were significant in patients with pre-aflibercept best-corrected visual acuity less than 1.0 logMARbut were not significant in patients with best-corrected visual acuity more than 1.0 logMAR. Conclusions: Switching to aflibercept in DME patients with an unsatisfactory response to previous anti-VEGFinjections provided acceptable short-term visual and retinal architectural improvement.

The Effects of Moon’s Uneven Mass Distribution on the Critical Inclinations of a Lunar Orbiter

Walid A. Rahoma,Fawzy A. Abd El-Salam 한국우주과학회 2014 Journal of Astronomy and Space Sciences Vol.31 No.4

The uneven mass distribution of the Moon highly perturbs the lunar spacecrafts. This uneven mass distribution leads to peculiar dynamical features of the lunar orbiters. The critical inclination is the value of inclination which keeps the deviation of the argument of pericentre from the initial values to be zero. Considerable investigations have been performed for critical inclination when the gravity field is assumed to be symmetric around the equator, namely for oblate gravity field to which Earth’s satellites are most likely to be subjected. But in the case of a lunar orbiter, the gravity field of mass distribution is rather asymmetric, that is, sectorial, and tesseral, harmonic coefficients are big enough so they can’t be neglected. In the present work, the effects of the first sectorial and tesseral harmonic coefficients in addition to the first zonal harmonic coefficients on the critical inclination of a lunar artificial satellite are investigated. The study is carried out using the Hamiltonian framework. The Hamiltonian of the problem is cconstructed and the short periodic terms are eliminated using Delaunay canonical variables. Considering the above perturbations, numerical simulations for a hypothetical lunar orbiter are presented. Finally, this study reveals that the critical inclination is quite different from the critical inclination of traditional sense and/or even has multiple solutions. Consequently, different families of critical inclination are obtained and analyzed.

Switching to Aflibercept in Diabetic Macular Edema after Unsatisfactory Response to Other Anti-vascular Endothelial Growth Factor Drugs

Walid S,Ibrahim,Zeiad H,Eldaly,Mohamed G,Saleh,Mahmoud F,Rateb,Ahmed H,Aldoghaimy 대한안과학회 2019 Korean Journal of Ophthalmology Vol.33 No.2

Purpose: To evaluate the efficacy of switching to aflibercept in diabetic macular edema (DME) with suboptimal response to previous anti-vascular endothelial growth factor (anti-VEGF) injections. Methods: A prospective interventional case series study recruited patients from a single center diagnosed with DME with suboptimal response to anti-VEGF injections. Three consecutive monthly injections of aflibercept were performed. The primary outcome measure was mean change in visual acuity after switching to aflibercept. Results: Forty-two patients (42 eyes) were included. Baseline logarithm of the minimum angle of resolution(logMAR) visual acuity was 0.87 ± 0.23 and improved significantly to 0.62 ± 0.29, 0.56 ± 0.34, and 0.46 ± 0.35 at 1, 2, and 3 months, respectively, after the first injection. Mean baseline retinal thickness was 451.57± 107.09 μm and decreased significantly at 1, 2, and 3 months after switching to aflibercept (346.52 ± 79.03, 328.24 ± 81.98, and 313.71 ± 85.79 μm, respectively). Both visual improvement and mean change in retinal thickness were significant in patients with pre-aflibercept best-corrected visual acuity less than 1.0 logMAR but were not significant in patients with best-corrected visual acuity more than 1.0 logMAR. Conclusions: Switching to aflibercept in DME patients with an unsatisfactory response to previous anti-VEGF injections provided acceptable short-term visual and retinal architectural improvement.

Optimizing the Unconnected Piled Raft Foundation for Soft Clay Soils: Numerical Study

Walid El Kamash,Hany El Naggar,Marwa Nabil,Alaa Ata 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.4

Over the past two decades, a number of researchers studied different aspects of the unconnected piled raft foundation (UPRF) system. In this system, a structural fill cushion is inserted between the raft and the concrete piles (PC) where the cushion transfers the loads from the superstructure to the piles. They showed that UPRF could increase the load-bearing share of the raft relative to that of the concrete piles, which leads to a favourable economic impact. Stone columns (SC) and deep-mixed columns (DMC) have also gained substantial popularity in the last few decades, and have shown pronounced success in substituting concrete pile foundations in numerous projects. This paper is an attempt to explore the viability of using SC and DMC in the UPRF system. Different column parameters such as material, stiffness, spacing, embedment length, configuration and raft thickness may affect the design considerations of UPRF systems. The current study investigates the effect of such parameters on the performance of the UPRF. In addition, two cushion alternatives were also studied: structural fill and EPS Geofoam. 3D finite element models of a 16-storey building on soft clay were used to compare the behaviour of different types of UPRF foundations embedded in different types of soft clays. A coupled hydraulic and mechanical model using the Modified Cam Clay soil model was used to model the soft soil.

Ultrasound does not shorten the duration of procedure but provides a faster sensory and motor block onset in comparison to nerve stimulator in infraclavicular brachial plexus block

walid Trabelsi,Mondher Belhaj Amor,Mohamed Anis Lebbi,Chiheb Romdhani,Sami Dhahri,Mustapha Ferjani 대한마취통증의학회 2013 Korean Journal of Anesthesiology Vol.64 No.4

Background: Infraclaviculr Brachial plexus (ICBP) block is useful for upper extremity surgery. The aim of this study was to compare the ultrasound (US) technique with the nerve stimulation (NS) technique in their success rates and times to perform ICBP block. Methods: 60 patients undergoing surgery of the upper limb were randomly allocated into two groups (n = 30 per group). Group 1; US, and Group 2; NS. Procedure time (including time for initial ultrasound examination), the success rate and the onset time of sensory and motor blockade were assessed. Results: The time needed to perform the ICBP block is similar in both groups (220 seconds ± 130 in US group versus 281 ± 134 seconds in NS group; P = 0.74). The success rate of all the nerve blocks in the US group was 100%. The success rate in the NS group was 73.3%, 76.7%, 76.7% and 100% for radial, ulnar, medial, and musculocutaneous nerve, respectively. A significantly faster onset of sensory block for the radial, ulnar, median, musculocutaneous, and the four nerves considered together were observed. The onset of motor block for the radial, ulnar, and medial nerves was faster in the US group. However, the onset of motor block for the musculocutaneous nerve and the four nerves considered together was comparable between the two groups. Conclusions: The ultrasound-guided infraclavicular brachial plexus block is a significantly efficacious method with faster onset but similar procedure time compared to the nerve stimulation technique.

The Effects of Moon’s Uneven Mass Distribution on the Critical Inclinations of a Lunar Orbite

Walid A. Rahoma,Fawzy A. Abd El-Salam 한국우주과학회 2014 Journal of Astronomy and Space Sciences Vol.31 No.4

The uneven mass distribution of the Moon highly perturbs the lunar spacecrafts. This uneven mass distribution leadsto peculiar dynamical features of the lunar orbiters. The critical inclination is the value of inclination which keeps thedeviation of the argument of pericentre from the initial values to be zero. Considerable investigations have been performedfor critical inclination when the gravity field is assumed to be symmetric around the equator, namely for oblate gravityfield to which Earth’s satellites are most likely to be subjected. But in the case of a lunar orbiter, the gravity field of massdistribution is rather asymmetric, that is, sectorial, and tesseral, harmonic coefficients are big enough so they can’t beneglected. In the present work, the effects of the first sectorial and tesseral harmonic coefficients in addition to the firstzonal harmonic coefficients on the critical inclination of a lunar artificial satellite are investigated. The study is carriedout using the Hamiltonian framework. The Hamiltonian of the problem is cconstructed and the short periodic termsare eliminated using Delaunay canonical variables. Considering the above perturbations, numerical simulations for ahypothetical lunar orbiter are presented. Finally, this study reveals that the critical inclination is quite different from thecritical inclination of traditional sense and/or even has multiple solutions. Consequently, different families of criticalinclination are obtained and analyzed.

Spectrum Sharing Method for Cognitive Radio in TV White Spaces: Enhancing Spectrum Sensing and Geolocation Database

( Walid A. Hassan ),( Han Shin Jo ),( Maziar Nekovee ),( Chee Yen Leow ),( Tharek Abd Rahman ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.8

This paper proposes a system called Wireless Link based on Global Communication Channel (WLGCC) to enhance the spectrum sharing between digital broadcasting (DB) services and the cognitive radio (CR) system in the licensed band of 470-790 MHz. The WLGCC aims to enhance the spectrum sensing and geolocation database (GLD) spectrum sharing methods in the CR system. Spectrum sensing can be enhanced by receiving the status of the used frequencies from the WLGCC, thereby eliminating the need for a low detection threshold (i.e., avoiding the hidden node problem). In addition, the GLD can be enhanced by providing a reliable communication link between the database and the CR device in the form of an unused TV white space that is reserved as the proposed Global Communication Channel (GCC). This paper analyzes the coexistence of the new WLGCC system and the DB service in terms of avoiding additional interference. Specifically, we mathematically determine the WLGCC parameters, such as the in-band and out-of-band power levels, and operation coverage, and verify them using Monte Carlo simulation. The results show that WLGCC does not degrade the existing DB service and reliably transmits information of the vacant (or used) frequency bands to the CR.

Simulation Model for Compatibility between LTE-Advanced and Digital Broadcasting in the Digital Dividend Band

Walid A Hassan,Han Shin Jo,Tharek Abd Rahman 한국산학기술학회 2013 SmartCR Vol.3 No.5

The switch from analog to digital television broadcasting (DB) has freed up a newly available spectrum called the digital dividend (DD) band. This band is expected to be used for both International Mobile Telecommunication-Advanced (IMT-A) and terrestrial DB, which could lead to performance degradation for both services. In this study, a simulation model is proposed to identify the requirements for coexistence between the new system (i.e., IMT-A) and the primary system (i.e., DB) in the DD band. Our model evaluates the compatibility between the two services by considering a feasible spectrum allocation: (i) the frequency plan for DB recommended by the International Telecommunication Union (ITU) in 2006 and (ii) the European preferred harmonized spectrum for mobile channel assignment proposed in 2009. Using the Monte Carlo method, we quantify the minimum distance between the systems to ensure reliable services for a given frequency guard band. We also propose a practical guideline for efficient spectrum sharing, which will increase the efficiency of DD spectrum usage between administrations. Unlike the previous studies where the services can coexist in all adjacent channels, our results show that coexistence is possible for a limited number of adjacent channels and for a specific sharing scenario.