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Consideration of corneal biomechanics in the diagnosis and management of keratoconus: is it important?

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Eye and Vision 2016年第1期3卷 141-146页

作者： FangJun Bao Brendan Geraghty Qinmei Wang ahmed elsheikh The Affiliated Eye Hospital of Wenzhou medical University Wenzhou City 325027China The Institution of Ocular Biomechanics Wenzhou Medical UniversityWenzhou City 325027China School of Engineering University of LiverpoolLiverpool City L693GHUK NIHR Biomedical Research Centre for Ophthalmology Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of OphthalmologyLondon CityUK

Keratoconus is a bilateral,non-inflammatory,degenerative corneal *** occurrence and development of keratoconus is associated with corneal thinning and conical protrusion,which causes irregular *** the disruption of the collagen organization,the cornea loses its shape and function resulting in progressive visual ***,corneal topography is the most important tool for the diagnosis of keratoconus,which may lead to false negatives among the patient population in the subclinical ***,it is now hypothesised that biomechanical destabilisation of the cornea may take place ahead of the topographic evidence of keratoconus,hence possibly assisting with disease diagnosis and *** article provides a review of the definition,diagnosis,and management strategies for keratoconus based on corneal biomechanics.

关键词： Keratoconus In vivo Corneal biomechanics Corneal collagen cross-linking

Fast segmentation of anterior segment optical coherence tomography images using graph cut

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Eye and Vision 2015年第1期2卷 1-6页

作者： Dominic Williams yalin Zheng Fangjun Bao ahmed elsheikh Ocular Biomechanics and Biomaterials Group School of EngineeringUniversity of LiverpoolBrownlow HillLiverpool L693GHUK Department of Eye and Vision Science University of Liverpool3rd FloorUCD BuildingDaulby StreetLiverpool L693GAUK School of Optometry and Ophthalmology and Eye Hospital Wenzhou Medical UniversityNo.270Xueyuanxi RoadWenzhou CityZhejiang Province 325027China

Background:Optical coherence tomography(OCT)is a non-invasive imaging system that can be used to obtain images of the anterior *** segmentation of these images will enable them to be used to construct patient specific biomechanical models of the human *** models could be used to help with treatment planning and diagnosis of ***:A novel graph cut technique using regional and shape terms was *** was evaluated by segmenting 39 OCT images of the anterior *** results of this were compared with manual segmentation and a previously reported level set segmentation *** different comparison techniques were used:Dice’s similarity coefficient(DSC),mean unsigned surface positioning error(mSPE),and 95%Hausdorff distance(HD).A paired t-test was used to compare the results of different segmentation ***:When comparison with manual segmentation was performed,a mean DSC value of 0.943±0.020 was achieved,outperforming other previously published techniques.A substantial reduction in processing time was also achieved using this ***:We have developed a new segmentation technique that is both fast and *** has the potential to be used to aid diagnostics and treatment planning.

关键词： Optical coherence tomography Anterior segment Image segmentation Cornea Graph cut Shape prior

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

In vivo study of corneal responses to increased intraocular pressure loading

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Eye and Vision 2015年第1期2卷 177-186页

作者： ahmed elsheikh Charles W.mcmonnies Charles Whitford Gavin C.Boneham School of Engineering University of LiverpoolBrownlow HillLiverpool L693GHUK National Institute for Health Research(NIHR)Biomedical Research Centre Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of OphthalmologyLondonUK School of Optometry and Vision Science University of New South WalesSydneyAustralia

Background:The cornea is responsible for two-thirds of the eye's refractive power which is a function of the shape and refractive *** aim of this present study is to examine human eyes in vivo for corneal shape changes in response to short-term elevation in intraocular ***:Videokeratographic and tonometric assessments at baseline were compared with the same assessments when intraocular pressure was elevated to approximately double(199±22%)the baseline levels using ophthalmodynamometer applanation of the *** maps of the cornea and limbus were created by combining topographical assessments for central,nasal,temporal,inferior and superior *** finiteelement simulations were custom built for each subject and the stiffness distribution across corneal surface modified to achieve matches between simulated and experimental ***:The stiffness distributions required to achieve simulation-experimental matches showed a consistent trend with the 2.5 mm annulus bounded by the limbus showing a mean stiffness reduction of 47.3±10.8%compared with the central cornea(P=0.001).Conclusions:Corneal structure appears to provide the central cornea with a greater stiffness compared with the peripheral cornea and associated greater tolerance to elevation in intraocular pressure,consistent with the need for stable corneal refraction and *** method adopted to examine corneal biomechanical performance in vivo may have applications in additional studies.

关键词： Corneal biomechanics Topography Numerical simulation

Frailty in end-stage liver disease:Understanding pathophysiology,tools for assessment,and strategies for management

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World Journal of Gastroenterology 2023年第46期29卷 6028-6048页

作者： mazen elsheikh ahmed El Sabagh Islam B mohamed megha Bhongade manal m Hassan Prasun Kumar Jalal Department of Gastroenterology and Hepatology Baylor College of MedicineHoustonTX 77030United States Department of Epidemiology Division of Cancer Prevention and Population SciencesThe University of TexasMD Anderson Cancer CenterHoustonTX 77030United States

Frailty and sarcopenia are frequently observed in patients with end-stage liver *** is a complex condition that arises from deteriorations across various physiological systems,including the musculoskeletal,cardiovascular,and immune systems,resulting in a reduced ability of the body to withstand *** condition is associated with declined resilience and increased vulnerability to negative outcomes,including disability,hospitalization,and *** cirrhotic patients,frailty is influenced by multiple factors,such as hyperammonemia,hormonal imbalance,malnutrition,ascites,hepatic encephalopathy,and alcohol *** frailty is crucial in predicting morbidity and mortality in cirrhotic *** can aid in making critical decisions regarding patients’eligibility for critical care and ***,in turn,can guide the development of an individualized treatment plan for each patient with cirrhosis,with a focus on prioritizing exercise,proper nutrition,and appropriate treatment of hepatic complications as the primary lines of *** this review,we aim to explore the topic of frailty in liver diseases,with a particular emphasis on pathophysiology,clinical assessment,and discuss strategies for preventing frailty through effective treatment of hepatic ***,we explore novel assessment and management strategies that have emerged in recent years,including the use of wearable technology and telemedicine.

关键词： End-stage liver disease Frailty Liver cirrhosis malnutrition Sarcopenia

Ex vivo testing of intact eye globes under inflation conditions to determine regional variation of mechanical stiffness

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Eye and Vision 2016年第1期3卷 166-177页

作者： Charles Whitford Akram Joda Steve Jones Fangjun Bao Paolo Rama ahmed elsheikh School of Engineering University of LiverpoolLiverpool L693GHUK Department of mechanical Engineering King Faisal UniversityHofufSaudi Arabia Eye Hospital WenZhou Medical UniversityWenZhouChina Ophthalmology Department San Raffaelle HospitalMilanItaly National Institute for Health Research(NIHR)Biomedical Research Centre at moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology LondonUK

Background:The eye globe exhibits significant regional variation of mechanical *** aim of this present study is to develop a new experimental technique for testing intact eye globes in a form that is representative of in vivo conditions,and therefore suitable for determining the material properties of the complete outer ocular ***:A test rig has been developed to provide closed-loop control of either applied intra-ocular pressure or resulting apical displacement;measurement of displacements across the external surface of the eye globe using high-resolution digital cameras and digital image correlation software;prevention of rigid-body motion and protection of the ocular surface from environmental *** method has been demonstrated on one human and one porcine eye globe,which were cyclically *** element models based on specimen specific tomography,free from rotational symmetry,were used along with experimental pressure-displacement data in an inverse analysis process to derive the mechanical properties of tissue in different regions of the eye’s outer ***:The test method enabled monitoring of mechanical response to intraocular pressure variation across the surface of the eye *** the two eyes tested,the method showed a gradual change in the sclera’s stiffness from a maximum at the limbus to a minimum at the posterior pole,while in the cornea the stiffness was highest at the centre and lowest in the peripheral ***,for both the sclera and cornea,the load–displacement behaviour did not vary significantly between loading ***:The first methodology capable of mechanically testing intact eye globes,with applied loads and boundary conditions that closely represent in vivo conditions is *** method enables determination of the regional variation in mechanical behaviour across the ocular surface.

关键词： Ocular biomechanics Experimental testing Digital image correlation

Voltage imbalance mitigation in an active distribution network using decentralized current control

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Protection and Control of modern Power Systems 2023年第2期8卷 68-84页

作者： ahmed m.m.Nour ahmed A.Helal magdi m.El-Saadawi ahmed y.Hatata Alexandria Higher Institute of Engineering and Technology(AIET) AlexandriaEgypt Department of Electrical and Control Engineering Arab Academy for Science and Technology and Maritime TransportAlexandriaEgypt Department of Electrical Engineering Faculty of EngineeringMansoura UniversityMansouraEgypt Department of Electrical Engineering College of EngineeringShaqra UniversityShaqraKingdom of Saudi Arabia

Voltage imbalance(VI)is caused by the difference in connected single-phase load or generation in a low voltage distribution network(DN).VI increase in a smart distribution grid is due to the current practice of increasing single-phase distributed generators such as photovoltaic(PV)*** paper proposes a decentralized control method to mitigate VI using distributed batteries included in smart grid interfaced residential PV *** mitigate VI using the batteries in this way,five challenges must be overcome,i.e.,equalizing all battery stress currents within the DN,mitigating VI in abnormal conditions such as signal loss among bus controllers,being immune from the distorted feedback measurements,minimizing the steady-state error at different loads,and overcoming the insufficient number or capacity of the distributed batteries at the same *** fuzzy logic controllers(FLC)are proposed at each bus to overcome these five tasks based on a decentralized control *** proposed decentralized control based on FLC is compared with centralized control based on a PI *** proposed control method is tested and verified using simulations in the mATLAB/Simulink software,and the results validate the ability of the scheme to alleviate VI on a smart distribution network under both normal and abnormal conditions.

关键词： Fuzzy controller Distributed batteries Decentralized control Voltage imbalance Distributed PV

A comprehensive review on residual stresses in turning

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Advances in manufacturing 2022年第2期10卷 287-312页

作者： Ammar H.elsheikh S.Shanmugan T.muthuramalingam Amrit Kumar Thakur F.A.Essa ahmed mohamed mahmoud Ibrahim ahmed O.mosleh Department of Production Engineering and mechanical Design Facultyof EngineeringTanta UniversityTanta 31527Egypt Research Centre for Solar Energy Department of PhysicsKoneru Lakshmaiah Education FoundationVaddeswaramAndhra Pradesh 522502India Department of mechatronics Engineering SRM Institute of Science and TechnologyChennai 603203India Department of mechanical Engineering KPR Institute Engineering and TechnologyCoimbatoreTamilnaduIndia Department of mechanical Engineering Faculty of EngineeringKafrelsheikh UniversityKafrelsheikh 33516Egypt Production Engineering and mechanical Design Department Faculty of EngineeringMinia UniversityMinya 61519Egypt Shoubra Faculty of Engineering Benha UniversityBenhaEgypt

Residual stresses induced during turning processes can affect thequality and performance of machined products,depending on its direction and *** stresses can be highly detrimental as they can lead to creeping,fatigue,and stress corrosion *** final state of residual stresses in a workpiece depends on its material as well as the cutting-tool configuration such as tool geometry/coating,cooling and wear conditions,and process parameters including the cutting speed,depth-ofcut and ***,there have been disagreements in some literatures regarding influences of the abovementioned factors on residual stresses due to different cutting conditions,tool parameters and workpiece materials used in the specific *** review paper categorizes different methods in experimental,numerical and analytical approaches employed for determining induced residual stresses and their relationships with cutting conditions in a turning *** is presented for the effects of different cutting conditions and parameters on the final residual stresses state.

关键词： Residual stresses machining Turning:Process parameters

Production of porous silica by the combustion of rice husk ash for tundish lining

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Journal of University of Science and Technology Beijing 2008年第3期15卷 307-313页

作者： y.m.Z.ahmed E.m.Ewais Z.I.Zaki Central metallurgical Research and Development Institute(CmRDI)

In order to study the production of porous silica compacts by the combustion of rice husk ash （RHA） for tundish lining, the experimental design technique was used to evaluate the effect of firing temperature, soaking time and compaction pressure on controlling both the porosity degree and compressive strength of rice husk ash compacts. The results revealed that while the porosity degree of the compacts decreased with the increase in the entire studied parameters, the compressive strength exhibited another trend especially at a lower soaking time. At a lower soaking time, the increase in firing temperature led to a slight decrease in compressive strength and then increasing thereafter. The porous silica compacts having 30% porosity and 〉 2.5 mPa compressive strength suitable for tundish lining could be obtained from the combustion of rice husk ash compacts.

关键词： porous silica rice husk ash tundish lining compressive strength porosity