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Nanosecond pulse and dual-wavelength Q-switched 1.5 μm fiber laser using MAX phase Cr2TialC2 saturable absorber

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Optoelectronics Letters 2025年第1期21卷 7-12页

作者： ahmed Shakir al-HITI Hiba HASSAN Department of Electrical Engineering Faculty of Engineering University of Anbar Department of Laser and Optoelectronics Engineering University of Technology-Iraq

We demonstrated a new type of MAX phase material, chromium titanium aluminum carbide（Cr2TialC2） polymer film, to generate a passively Q-switched erbium-doped fiber laser（EDFL）. The film thickness was measured to be around 45 μm, which was fabricated using the embedding method with polyvinyl alcohol（PVA） polymer as hoster. The saturable absorber（SA） film demonstrates a dual-wavelength passively Q-switched EDFL which operates at 1 531 nm and 1 560.19 nm, respectively. The Q-switching pulse duration could be varied from 2.46 μs to 770 ns, while the repetition rate varied from 92.76 kHz to 106.6 kHz with an increasing input pumping range from 154 mW to 300 mW. The maximum output power and pulse energy of 15.05 mW and 141.18 nJ were obtained at the maximum input power of 300 mW, respectively.

关键词： Saturable absorbers

Vascular endothelial growth factor:a double-edged sword in the development of white matter lesions

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Neural Regeneration Research 2025年第1期20卷 191-192页

作者： Narek Manukjan Daniel Fulton Zubair ahmed WMatthijs Blankesteijn Sébastien Foulquier Department of Pharmacology and Toxicology Maastricht UniversityMaastrichtThe Netherlands CARIM-School for Cardiovascular Diseases Maastricht UniversityMaastrichtThe Netherlands Neuroscience and Ophthalmology Institute of Inflammation and AgeingUniversity of BirminghamEdgbastonBirminghamUK Centre for Trauma Sciences Research University of BirminghamEdgbastonBirminghamUK MHeNs-School for Mental Health and Neuroscience Maastricht UniversityMaastrichtThe Netherlands Department of Neurology Maastricht University Medical CenterMaastrichtThe Netherlands

As the population ages,the burden of age-related diseases becomes ***,over 55 million people suffer from dementia worldwide,with alzheimer’s disease being the most common ***,it is becoming clearer that underlying vascular pathology such as cerebral small vessel disease(cSVD)may be a more detrimental cause for dementia(Cuadrado-Godia et al.,2018).It is estimated that 10%-30%of the elderly population and 35%-90%of all dementia patients exhibit signs of *** term cSVD refers to pathology affecting the small vessels of the brain,which can lead to lacunar cerebral infarcts,enlarged perivascular spaces,and cortical hemorrhages(Cuadrado-Godia et al.,2018).CSVD is often associated with cognitive decline,gait problems,and dementia(Cuadrado-Godia et al.,2018).

关键词： pathology becoming white

CATIONIC RING-OPENING POLYMERIZATION OF TETRAHYDROFURAN WITH KEGGIN-TYPE HETEROPOLYCOMPOUNDS AS SOLID ACID CATalYSTS

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Chinese Journal of Polymer Science 2010年第3期28卷 305-310页

作者： ahmed Aouissi Salim Salem al-Deyab Hassan al-Shehri Chemistry Department College of ScienceKing Saud UniversityRiyadhKSA

Three Keggin-type heteropolyanions, namely H3PMo12O40-13H2O, （NH4）3PMo12O40·4H2O and H3PW12O40·13H2O were prepared and tested in the ring-opening polymerization reaction of tetrahydrofuran. The effects of the counter-cation （H＋, NH4＋） and the peripheral atoms （Mo, W） on the polymerization were investigated. It has been found that when the protons of H3PMo12O40·13H2O were replaced by the ammonium cations the polymerization rate decreased dramatically. Whereas, when the peripheral atoms （Mo） were replaced by their homologous （W）, the polymerization rate increased twofold. As for the viscosity average molecular weight （My） of polymer products, it was found that the high molecular weight （7930） was obtained by using H3PW12O40·13H2O. The molecular weight （My） obtained by H3PMo12O40·13H2O and （NH4）H3PMo12O40·13H2O was 6470 and 6810, respectively.

关键词： Tetrahydrofuran Heteropoly compounds Ring opening polymerization Cyclic ether Solid acid

Seismic retrofitting of severely damaged RC connections made with recycled concrete using CFRP sheets

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Frontiers of Structural and Civil Engineering 2020年第2期14卷 554-568页

作者： Yasmin MURAD Wassel al BODOUR ahmed ASHTEYAT Civil Engineering Department The University of JordanAmman 11942.Jordan

An experimental and numerical program is carried out in this research to investigate the influence of CFRP sheets on the cyclic behavior of unconfined connections made with recycled *** is partially replaced by silica fume,iron flling and pulverised fuel ash using two different percentages:15%and 20%.Each specimen is partially loaded at the first stage and then specimens are repaired using CFRP *** repaired specimens are then laterally loaded until *** addition,a finite element model is built in ABAQUS and verfed using the experimental *** experimental results have shown that the repaired specimens have regained almost double the capacity of the un-repaired specimens and hence the adopted repair configuration is recommended for retroftting seismically vulnerable RC *** cement replacement percentage by silica fume,fuel ash or iron flling from 15%to 20%has reduced joint carrying capacity and weakened the *** is recommended using 15%pulverised fuel ash or silica fume as cement partial replacement to enhance the strength and ultimate drift of beam-column joints under cyclic *** filling concrete is also recommended but the enhancement is relatively less than that found with pulverised fuel ash concrete and silica fume concrete.

关键词： retrofitting CFRP sheets recycled concrete pulverised fuel ash silica fume cyclic beam-column connections

A Participatory GIS Approach to Identify Critical Land Degradation Areas and Prioritize Soil Conservation for Mountainous Olive Groves(Case Study)

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Journal of Mountain Science 2014年第3期11卷 782-791页

作者： ahmed al-WADAEY Feras ZIADAT Soil and Water Department Faculty of Agriculture Sana’a University Sana’a 00967 the Republic of Yemen International Center for Agricultural Research in the Dry Areas (ICARDA) P.O. Box 950764 – Amman 11195 Jordan

Climate change scenarios predict an increase in the frequency of heavy rainfall events in some areas. This will increase runoff and soil erosion, and reduce agricultural productivity, particularly on vulnerable mountainous agricultural lands that is already exhibiting high rates of soil erosion. Haphazard implementation of soil and water conservation （SWC） interventions on scattered fields is inefficient in reducing soil erosion. The objective of this study was to identify areas at high risk of erosion to aid the design and implementation of sustainable SWC using GIS analysis and farmers＇ participation approach. A 25 m digital elevation model （DEM） was used to derive layers of flow accumulation, slope steepness and land curvature, which were used to derive an erosion-risk （priority） map for the whole watershed. Boundaries of farmers＇ fields were mapped and verified by the community and each field was classified into high, moderate or low erosion risk. Fields with low flow accumulation （top of hill） and/or steep slope and/or convex slope were assigned high erosion risk and therefore high implementation priority. The study showed that more than 54% of the fields were classified into high erosion risk areas. Accordingly, a community-watershed plan was established, revised and approved by the *** loans to implement SWC measures were distributed to 100 farmers based on the priorities of their fields. Judged by local farmers and using 16 randomly selected fields, 90% of the targeted areas were correctly identified using the erosion risk map. After two years, the conservation measures had led to marked improvement of soil conservation. The approach is simple and easy to comprehend by the community and provides scientific basis to prioritize the implementation of SWC and to target the most degraded areas, which amplify the impact of these in reducing the vulnerability to land degradation.

关键词： Flow accumulation Soil erosion Community-conservation plan Olive Priority map

Dynamical analysis and anti-synchronization of a new 6D model with self-excited attractors

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Applied Mathematics(A Journal of Chinese Universities) 2023年第1期38卷 27-43页

作者： Saad Fawzi al-Azzawi ahmed S.al-Obeidi Department of Mathematics College of Computer Science and MathematicsUniversity of MosulMosul 41002Iraq

A novel 6D dissipative model with an unstable equilibrium point is introduced *** of the dynamic characteristics of the proposed model were explored via analyses and numerical simulations including critical points,stability,Lyapunov exponents,time phase portraits,and circuit ***,anti-synchronization phenomena were implemented on the new ***,the error dynamics is ***,four different controllers are adopted to stabilize this error relying on the nonlinear control technique with two main ways:linearization and Lyapunov stability *** comparison with previous works,the present controllers realize anti-synchronization based on another method/linearization ***,a comparison between the two ways was *** simulation results show the effectiveness and accuracy of the first analytical strategy.

关键词： 6D hyperchaotic system self-excited attractor anti-synchronization Lyapunov stability theory

Numerical investigation on effect of various pump rotational speeds on performance of centrifugal pump based on CFD analysis technique

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International Journal of Modeling, Simulation, and Scientific Computing 2021年第5期12卷 210-233页

作者： ahmed Ramadhan al-Obaidi Department of Mechanical Engineering Faculty of Engineering Mustansiriyah UniversityBaghdadIraq

In this study,the flow structure and effect of different pump rotational speeds on a centrifugal pump’s performance are experimentally and numerically *** internal flow field pattern within the pump has been analyzed and discussed using the CFD *** numerical results are compared with experimental data under a wide range of operating *** comparison results between them have indicated a considerable *** pressure variations are gradually increasing from inlet to outlet impeller of the *** results note that when the impeller rotates near the tongue region,the pressure in this region was higher than in other ***,the interaction between the impeller and volute tongue region is actually according to the impeller blades’relative position concerning the tongue ***,the pressure and velocity variations within a centrifugal pump increase with rotational impeller speed.

关键词： Centrifugal pump pressure variations velocity variations pump rotational speed CFD

Sickle cell cholangiopathy:An endoscopic retrograde cholangiopancreatography evaluation

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World Journal of Gastroenterology 2009年第42期15卷 5316-5320页

作者： Hussain Issa ali al-Haddad ahmed al-Salem Department of Internal Medicine Division of GastroenterologyKing Fahad Specialist HospitalDammam 31444Saudi Arabia Department of Internal Medicine Qatif Central HospitalQatif 31911Saudi Arabia Department of Pediatric Surgery Maternity and Children HospitalDammamQatif 31911Saudi Arabia

AIM:To evaluate the role of endoscopic retrograde cholangiopancreatography(ERCP) in patients with sickle cell disease(SCD) .METHODS:Two hundred and twenty four SCD patients with cholestatic jaundice(CJ) had *** indications for ERCP were based on clinical and biochemical evidence of CJ and ultrasound ***:Two hundred and forty ERCPs were *** indications for ERCP were:CJ only in 79,CJ and dilated bile ducts without stones in 103,and CJ and bile duct stones in *** those with CJ only,ERCP was normal in 42(53.2%) ,and 13(16.5%) had dilated bile ducts without an obstructive *** the remaining 22,there were bile duct stones with or without *** those with CJ,dilated bile ducts and no stones,ERCP was normal in 17(16.5%) ,and 28(27.2%) had dilated bile ducts without an obstructive *** the remaining 58,there were bile ducts stones with or without *** those with CJ and bile duct stones,ERCP was normal in two(4.8%) ,and 14(33.3%) had dilated bile ducts without an obstructive *** the remaining 26,there were bile duct stones with or without ***:Considering the high frequency of biliary sludge and bile duct stones in SCD,endoscopic sphincterotomy might prove helpful in these patients.

关键词： Sickle cell disease Hepatobiliary Cholestsatic jaundice Sickle cell hepatopathy Sickle cell cholangiopathy Endoscopic retrograde cholangiopancreatography

Comparative study between gas phase and liquid phase for the production of DMC from methanol and CO_2

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Journal of Natural Gas Chemistry 2012年第2期21卷 189-193页

作者： ahmed Aouissi Salem S. al-Deyab Department of Chemistry King Saud University

Direct synthesis of dimethyl carbonate （DMC） from methanol and carbon dioxide over Co1.5PW12O40 in liquid and in gas phase is investigated. The synthesized catalyst has been characterized by means of FTIR and XRD. Liquid phase experiment results showed that high pressures are favorable for the synthesis of DMC. However, DMC formation is limited by the reaction with co-produced water. DMC selectivity is more strongly dependent on the temperature than on the pressure of CO2. As for the reactions in gas phase, it has been found that both CH3OH conversion and DMC selectivity decreased with increasing temperature, owing to the decomposition of DMC at high temperatures. High temperatures and more amount of Co1.5PW12O40 catalyst favor the formation of dimethoxymethane （DMM） and methyl formate （MF）.

关键词： heteropolyanion Keggin structure methanol dimethyl carbonate carbon dioxide