检索结果-南通市图书馆

Positioning 2016年第2期7卷 63-74页

作者： akram afifi Ahmed El-Rabbany Department of Civil Engineering Ryerson University Toronto Canada

This paper introduces a new dual-frequency precise point positioning (PPP) model, which combines the observations of three different GNSS constellations, namely GPS, Galileo, and BeiDou. Our model is based on between-satellite single-difference (BSSD) linear combination, which cancels out some receiver-related biases, including receiver clock error and non-zero initial phase bias of the receiver oscillator. The reference satellite can be selected from any satellite system GPS, Galileo, and BeiDou when forming BSSD linear combinations. Natural Resources Canada’s GPS Pace PPP software is modified to enable a combined GPS, Galileo, and BeiDou PPP solution and to handle the newly introduced biases. A total of four data sets at four IGS stations are processed to verify the developed PPP model. Precise satellite orbit and clock products from the IGS-MGEX network are used to correct both of the GPS and Galileo measurements. It is shown that using the BSSD linear combinations improves the precision of the estimated parameters by about 25% compared with the GPS-only PPP solution. Additionally, the solution convergence time is reduced to 10 minutes for both BSSD scenarios, which represent about 50% improvement in comparison with the GPS-only PPP solution.

关键词： PPP BSSD GPS Galileo BeiDou

Simultaneous Localization and Mapping Solutions Using Monocular and Stereo Visual Sensors with Baseline Scaling System

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Positioning 2019年第4期10卷 51-72页

作者： akram afifi Brendan Woo Faculty of Applied Sciences and Technology Humber Institute of Technology and Advanced Learning Toronto Canada

In this paper, SLAM systems are introduced using monocular and stereo visual sensors. The SLAM solutions are implemented in both indoor and outdoor. The SLAM samples have been taken in different modes, such as a straight line that enables us to measure the drift, in addition to the loop sample that is used to test the loop closure and its corresponding trajectory deformation. In order to verify the trajectory scale, a baseline method has been used. In addition, a ground truth has been captured for both indoor and outdoor samples to measure the biases and drifts caused by the SLAM solution. Both monocular and stereo SLAM data have been captured with the same visual sensors which in the stereo situation had a baseline of 20.00 cm. It has been shown that, the stereo SLAM localization results are 75% higher precision than the monocular SLAM solution. In addition, the indoor results of the monocular SLAM are more precise than the outdoor. However, the outdoor results of the stereo SLAM are more precise than the indoor results by 30%, which is a result of the small stereo baseline cameras. In the vertical SLAM localization component, the stereo SLAM generally shows 60% higher precision than the monocular SLAM results.

关键词： SLAM Vision Kalman Filter Monocular Stereo

An Improved Model for Single-Frequency GPS/GALILEO Precise Point Positioning

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Positioning 2015年第2期6卷 7-21页

作者： akram afifi Ahmed El-Rabbany Department of Civil Engineering Ryerson University Toronto Canada

This paper introduces a new precise point positioning (PPP) model, which combines single-fre- quency GPS/Galileo observations in between-satellite single-difference (BSSD) mode. In the absence of multipath, all receiver-related errors and biases are cancelled out when forming BSSD for a specific constellation. This leaves the satellite originating errors and atmospheric delays un- modelled. Combining GPS and Galileo observables introduces additional biases that have to be modelled, including the GPS to Galileo time offset (GGTO) and the inter-system bias. This paper models all PPP errors rigorously to improve the single-frequency GPS/Galileo PPP solution. GPSPace PPP software of Natural Resources Canada (NRCan) is modified to enable a GPS/Galileo PPP solution and to handle the newly introduced biases. A total of 12 data sets representing the GPS/Galileo measurements of six IGS-MEGX stations are processed to verify the newly developed PPP model. Precise satellite orbit and clock corrections from IGS-MEGX networks are used for both GPS and Galileo measurements. It is shown that sub-decimeter level accuracy is possible with single-frequency GPS/Galileo PPP. In addition, the PPP solution convergence time is improved from approximately 100 minutes for the un-differenced single-frequency GPS/Galileo solution to approximately 65 minutes for the BSSD counterpart when a single reference satellite is used. Moreover, an improvement in the PPP solution convergence time of 35% and 15% is obtained when one and two reference satellites are used, respectively.

关键词： PPP GPS Galileo BSSD

Extra Renal Rhabdoid Tumor: A Rare Cause of Congenital Soft Tissue Tumor

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Pediatrics 2024年第3期14卷 579-584页

作者： Tazi Charki Mohammed Akammar Amal Dardar Hajar Abdellaoui Hicham Atarraf Karima Boubou Meryem afifi Moulay Abderrahmane Department of Pediatric Orthopedic and Traumatology University Hospital Hassan II Fez Morocco The Faculty of Medicine and Pharmacy Sidi Mohamed Ben Abdellah University Fez Morocco Department of Radiology University Hospital Hassan II Fez Morocco

Rhabdoid tumors (RTs) are a well-defined entity in the kidney or central nervous system of infants or children. However, soft-tissue involvement is uncommon. It’s an exceptional neonatal tumor of soft tissue. The imaging characteristics of this tumor are not specific. Biopsy allows diagnosis;the histomorphological characteristics of rhabdoid tumors, their immunoreactivity to epithelial markers and vimentin, and the INI-1 loss are important tools for diagnosis. RT tumors are aggressive and have a rapidly fatal clinical course in most cases. Despite multidisciplinary therapy, the survival rate is very low. We report a rare case occurring in a male neonate who presents at birth with a voluminous right axillary mass. A CT scan showed a well-limited tumor mass with lobulated contours. An ultrasound-guided biopsy was performed on day 8, showing the morphology and immunoprofile of RT. The mass showed rapid growth. The child was admitted for respiratory distress at 3 weeks. A thoraco-abdominal CT showed an increase in the size of the mass with the appearance of multiple lymph nodes and pleural, hepatic, and renal metastases. The child died two days later.

关键词： Congenital Rhabdoid Tumor Soft Tissue Diagnosis Immunohistochemistry INI-1

Infestation and morphological identification of the stalked epizoic barnacle Octolasmis on the blue crab Portunus pelagicus from the Red Sea

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Oceanology and Limnology 2018年第4期36卷 1374-1382页

作者： Rafat afifi KHATTAB Taibah University Faculty of Sciences Department of Biology Suez Canal University Faculty of Science Department of Marine Science

The intensity of infestation of the epizoic stalked barnacle Octolasmis on the blue crab was calculated for a total of 180 individuals collected around Jeddah, the western Red Sea Saudi coast. More than 90% of the crabs were found bearing the Octolasmis at a prevalence rate of 92% and mean intensity of 18.5 ? 18.6(0–127 epibiont per host). The intensity of infestation increased with host size in the range 90–135 mm. Generally, females were more infested(69%) than the males(31%). Octolasmis angulata occurred mostly on the gills, and the lower side of the gill chambers was more infested(84%) than the upper side(16%) and the left side of gills was also more infested than the right side in both males and females. Further studies are still needed to examine the commensal relationship and its impact on the fishery market of the Red Sea blue crab populations.

关键词： Octolasmis ecology commensal infestation Portunuspelagicus Red Sea

Exploring thermocline and water masses variability in southern South China Sea from the World Ocean Database(WOD)

在线全文

学校读者我要写书评

暂无评论

Acta Oceanologica Sinica 2019年第1期38卷 38-47页

作者： afifi Johari Mohd Fadzil Akhir Institute of Oceanography and Environmental Studies University Malaysia of Terengganu

Study about water characteristics(temperature and salinity) from the World Ocean Database(WOD) was conducted in the area of southern South China Sea(SSCS), covering the area of 0°–10°N, 100°–117°E. From interannual analysis, upper layer(10 m) and deep water temperature(50 m) increased from 1951 until 2014. Monthly averaged show that May recorded the highest upper layer temperature while January recorded the lowest. It was different for the deep water which recorded the highest value in September and lowest in February. Contour plot for upper layer temperature in the study area shows presence of thermal front of cold water at southern part of Vietnam tip especially during peak northeast season(December–January). The appearances of warm water were obviously seen during generating southwest monsoon(May–June). Thermocline study revealed the deepest isothermal layer depth(ILD) during peak northeast and southwest monsoon. Temperature threshold at shallow area reach more than 0.8°C during the transitional period. Water mass study described T-S profile based on particular region. Water mass during the southwest monsoon is typically well mixed compared to other seasons while strong separation according to location is very clear. During transitional period between northeast monsoon to southwest monsoon, the increasing of water temperature can be seen at Continental Shelf Water(CSW) which tend to be higher than 29°C and vice versa condition during transitional period between southwest monsoon to northeast monsoon. Dispersion of T-S profile can be seen during southwest monsoon inside Tropical Surface Water(TSW) where the salinity and temperature become higher than during northeast monsoon.

关键词： southern South China Sea upper layer temperature northeast monsoon southwest monsoon thermocline water mass

MPB:A modified Poisson blending technique

在线全文

学校读者我要写书评

暂无评论

Computational Visual Media 2015年第4期1卷 331-341页

作者： Mahmoud afifi Khaled F.Hussain Department of Information Technology Assiut University Department of Computer Science Assiut University

Image cloning has many useful applications,such as removing unwanted objects,fixing damaged parts of images,and panorama stitching. Instead of using pixel intensities,the gradient domain is used in Poisson image editing; however,it suffers from two main problems: color bleeding and bleeding *** this paper,a modified Poisson blending(MPB)technique is presented which ensures dependency on the boundary pixels of both target and source images rather than just those of the target. The problem of bleeding artifacts is reduced. This makes the proposed technique suitable for use in video compositing as it avoids the flickering caused by bleeding *** reduce the problem of color bleeding,we use an additional alpha compositing step. Our experimental results using the proposed technique show that MPB reduces the bleeding problems and generates more natural composited images than other techniques.

关键词： image processing image inpainting image blending image cloning image enhancement

Ameliorative effect of zinc oxide and silver nanoparticles on antioxidant system in the brain of diabetic rats

在线全文

学校读者我要写书评

暂无评论

Asian Pacific Journal of Tropical Biomedicine 2015年第10期5卷 874-877页

作者： Mohamed afifi Aaser Mohamed Abdelazim Department of Biological Sciences Faculty of ScienceUniversity of Jeddah Department of Biochemistry Faculty of Veterinary MedicineZagazig University

Objective: To test the ability of both zinc oxide nanoparticles(Zn ONPs) and silver nanoparticles(SNPs) to ameliorate the oxidative stress resulted from diabetes in diabetic ***: Fifty male albino rats were used; ten of them were served as control group and forty, as the experiment group, were injected with streptozotocin at the single intraperitoneal dose of 100 mg/kg. Then, the experiment group was subdivided into, diabetic,diabetic + Zn ONPs, diabetic + SNPs and diabetic + insulin groups. The activities and m RNA expression levels of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase were determined in brain tissues. Malondialdehyde, total antioxidant capacity, zinc and silver concentrations were estimated in the brain tissues of all ***: A significant increase in the activities and m RNA expression levels of superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase was *** levels were significantly decreased while there was a significant increase in the zinc, silver concentrations and total antioxidant capacity in brain of Zn ONPs and SNPs treated rats, compared with diabetic or diabetic + insulin group and their control ***: Zn ONPs and SNPs can be used to ameliorate the oxidative stress in brain resulted from diabetes mellitus.

关键词： glutathione antioxidant superoxide silver peroxida

Y^(3+) substituting-adjusted mechanical,dielectric,and impedance properties of cobalt copper zinc nanoferrites for high frequency applications

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Rare Earths 2023年第10期41卷 1597-1605,I0005页

作者： S.F.Mansour N.S.Al-Bassami M.afifi M.A.Abdo Physics Department Faculty of ScienceZagazig UniversityZagazigEgypt General Studies Department Jubail Industrial CollegeJubail Industrial CitySaudi Arabia Faculty of Nanotechnology for Postgraduate Studies Cairo UniversityEl-Sheikh Zayed12588Egypt

Upgrading mechanical-dielectric features of ferrites through rare-earth yttrium(Y^(3+))doping provides feasibility to evolving high-frequency electronic *** paper reports the mechanical and dielectric properties of Co_(0.5)Cu_(0.25)Zn_(0.25)Y_(x)Fe_(2-x)O_(4)ferrite nanoparticles labeled as CCZYF#0,CCZYF#1,CCZYF#2,CCZYF#3,CCZYF#4 and CCZYF#5 for x=0.***.0.02,0.04,0.06,0.08,and 0.1,*** frequency and temperature dependence of dielectric parameters and co nductivity of all CCZYF nanoferrites are well *** nanoferrite CCZYF#5 has the highest dielectric constant(enhancing ratio 170%)and the highest conductivity(enhancing ratio 7125.81%)compared with the undoped *** plots of all CCZYF nano ferrites manifest two arcs;the main reasons for the dielectric process are the grain boundaries and bulk *** impedance parameters were determined,which showed the effective role of Y^(3+)ions on their *** nanoferrite CCZYF#5 has the highest grain boundaries capacitance(with enhancing ratio of 59.40%)and the highest grains capacitance(with enhancing ratio of 22.53%)with a relaxation time decrement efficiency of 62.51%.An ultrasonic flaw detector was utilized to determine the elastic moduli of all CCZYF *** nanoferrite CCZYF#5 has the highest longitudinal modulus(with enhancing ratio of 20.95%),the highest shear modulus(with enhancing ratio of48.72%),highest Young's modulus(with enhancing ratio of 88.47%),the highest bulk modulus(with enhancing ratio 13.27%)and the highest micro hardness(with enhancing ratio 77.77%).Hence,Y3+tuned Co-Cu-Zn nanoferrites possess new opportunities for high-frequency and storage applications.

关键词： Nanoferrites Rare arth ions Mechanical properties Dielectric parameters Impedance spectroscopy

A Coordinated Search Algorithm for a Lost Target on the Plane

在线全文

学校读者我要写书评

暂无评论

Computer Systems Science & Engineering 2022年第1期40卷 127-137页

作者： Sundus Naji Al-Aziz Abd Al-Aziz Hosni El-Bagoury W.afifi Department of Mathematics College of SciencePrincess Nourah bint Abdulrahman UniversityRiyadhSaudi Arabia Department of Mathematics Faculty of ScienceTanta UniversityTantaEgypt Department of Mathematics and Statistics College of ScienceTaibah UniversityYanbuSaudi Arabia

Concepts in search theory have developed since World War *** study of search plans has found considerable interest among searchers due to its wide applications in our *** for lost targets either located or moved is often a time-critical issue,especially when the target is very *** many commercial and scientific missions at sea,it is of crucial importance to find lost targets *** illustrate a technique known as coordinated search,that completely characterizes the search for a randomly located target on a *** idea is to avoid wasting time looking for a missing *** searchers or robots start from the center of a circle to search out a lost target,the first searcher looks for the target on the right side of the circular area,and the second one looks for it on the left *** time taken to detect the target is obtained by assuming the target’s position has a symmetric *** procedures to facilitate the detection of the target are presented as an algorithm and as a *** application demonstrates the applicability of this search technique and the associated decrease in search *** effectiveness is illustrated by numerical results,which indicates considerable promise.

关键词： Expected value sensors lost target coordinated search search algorithm lost ship