92 research outputs found
Performance Evaluation Of Code Division Multiple Access (Cdma) Over Vsat Service Channel
No full textThe goal of this work is to evaluate the performance of Code Division Multiple
Access (CDMA) over VSAT Service Channel, to fulfill this; a simulation was
performed on MATLAB version-7.
The performance of a star-connected VSAT link (inbound) has been investigated by
using the most popular type of multiple access technique, Code Division Multiple
Access (CDMA) combined with multicarrier transmission system to achieve high data
rate, in the range of 64Kbps to 2 M bits/sec. The spectral efficiency is around 2
bit/sec/Hz and the required bandwidth is 84.48 MHz with the use of QPSK
modulation, in the usual frequency bands (14-17 GHz) and (10-13 GHz) respectively
allocated for uplink and downlink Fixed Satellite Services (FSS).
Bit Error Rate (BER) was the main parameter used to evaluate the performance of the
VSAT link (inbound) over the Rician channel. The results obtained showed that,
depending upon the number of active users (amount of loading) the BER performance
of the VSAT link (inbound) degrades gradually as a function of S/N. The degradation
in performance is more significant when going from a single user to three users
compared with going from three users to five users. The results obtained were
compared with the results of Yang and Hanzo[26], and they were found to agre
Visualization of deglutition and gastroesophageal reflux using real-time MRI: a standardized approach to image acquisition and assessment
No full textAbstract This study aims to develop a standardized algorithm for gastroesophageal image acquisition and diagnostic assessment using real-time MRI. Patients with GERD symptoms undergoing real-time MRI of the esophagus and esophagogastric junction between 2015 and 2018 were included. A 10 ml bolus of pineapple juice served as an oral contrast agent. Patients performed Valsalva maneuver to provoke reflux and hiatal hernia. Systematic MRI assessment included visual presence of achalasia, fundoplication failure in patients with previous surgical fundoplication, gastroesophageal reflux, and hiatal hernia. A total of 184 patients (n = 92 female [50%], mean age 52.7 ± 15.8 years) completed MRI studies without adverse events at a mean examination time of 15 min. Gastroesophageal reflux was evident in n = 117 (63.6%), hiatal hernia in n = 95 (52.5%), and achalasia in 4 patients (2.2%). Hiatal hernia was observed more frequently in patients with reflux at rest (n = 67 vs. n = 6, p < 0.01) and during Valsalva maneuver (n = 87 vs. n = 8, p < 0.01). Real-time MRI visualized a morphologic correlate for recurring GERD symptoms in 20/22 patients (90%) after fundoplication procedure. In a large-scale single-center cohort of patients with GERD symptoms undergoing real-time MRI, visual correlates for clinical symptoms were evident in most cases. The proposed assessment algorithm could aid in wider-spread utilization of real-time MRI and provides a comprehensive approach to this novel imaging modality
Real-time MRI for dynamic assessment of gastroesophageal reflux disease: Comparison to pH-metry and impedance.
No full textPURPOSE: To evaluate the diagnostic potential of real-time MRI for dynamic assessment of gastroesophageal reflux in patients with GERD (gastroesophageal reflux disease)-like symptoms compared to pH-metry and impedance. METHODS: Patients who underwent real-time MRI and pH-metry between 2015-2018 were included in this retrospective study. Real-time MRI at 3 T was achieved by undersampled radial FLASH acquisitions with iterative image reconstruction by NLINV. Real-time MRI visualized transit of pineapple juice through the gastroesophageal junction and during Valsalva maneuver. MRI results were compared to 24 h pH-metry to assess acidic reflux (following Lyon Consensus guidelines) and to impedance to assess non-acidic reflux. A standard 2 × 2 table was chosen to calculate diagnostic performance. RESULTS: 91/93 eligible patients fulfilled inclusion criteria (male n = 49; female n = 42; median age 55 y). All MRI studies were successfully completed without adverse events at a mean examination time of 15 min. On real-time MRI, reflux was evident in 60 patients (66 %). pH-metry revealed reflux in 41 patients (45 %), and impedance in 54 patients (59 %). Compared to pH-metry and impedance, real-time MRI sensitivity was 0.78 (95 % CI: 0.66-0.87), specificity 0.67 (95 % CI: 0.45-0.84) and PPV 0.87 (95 % CI: 0.75-0.94). CONCLUSION: Real-time MRI is an imaging method for assessment of gastroesophageal reflux in patients with GERD-like symptoms. Considering its high positive predictive value, real-time MRI can accurately identify patients in which further invasive testing with pH-metry and impedance might be considered
Improving Tale Blazer analytics
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (page 61).TaleBlazer is a platform for creating and playing augmented reality location-based mobile games. TaleBlazer Analytics is an automated system for collecting and analyzing anonymized player data from these games. This thesis presents additions and improvements made to TaleBlazer Analytics to allow for a more in-depth view of data from individual games, as well as aggregated across games. The updated system will ultimately help researchers, game designers, partner organizations, and the TaleBlazer development team in better understanding how users play TaleBlazer games.by Sarah R. Edris.M. Eng
Assessment of esophageal motility disorders by real-time MRI
No full textPurpose To investigate imaging findings of esophageal motility disorders on dynamic real-time. Material and methods 102 patients with GERD-like symptoms were included in this retrospective study between 2015−2018. Dynamic real-time MRI visualized the transit of a 10 mL pineapple juice bolus through the esophagus and EGJ with a temporal resolution of 40 ms. Dynamic and anatomic parameters were measured by consensus reading. Imaging findings were compared to HRM utilizing the Chicago classification of esophageal motility disorders, v3.0. Results All 102 patients completed real-time MRI in a median examination time of 15 min. On HRM, 14 patients presented with disorders with EGJ outlet obstruction (EGJOO) (13.7 %), 7 patients with major disorders of peristalsis (6.9 %), and 32 patients with minor disorders of peristalsis (31.4 %). HRM was normal in 49 patients (48.0 %). Incomplete bolus clearance was significantly more frequent in patients with esophageal motility disorders on HRM than in patients with normal HRM (p = 0.0002). In patients with motility disorders with EGJOO and major disorders of peristalsis, the esophageal diameter tended to be wider (23.6 ± 8.0 vs. 21.2 ± 3.5 mm, p = 0.089) and the sphincter length longer (19.7 ± 7.3 vs. 16.7 ± 3.0 mm, p = 0.091) compared to patients with normal HRM. 3/7 patients with achalasia type II were correctly identified by real-time MRI and one further achalasia type II patient was diagnosed with a motility disorder on MRI films. The other 3/7 patients presented no specific imaging features. Conclusion Real-time MRI is an auxiliary diagnostic tool for the assessment of swallowing events. Imaging parameters may assist in the detection of esophageal motility disorders
ZKPVM: a zero-knowledge authentication protocol for VMs' live migration in mobile cloud computing
No full textMobile cloud computing is a model in which mobile applications are built, powered and hosted using cloud computing technology. Mobile devices with their limited resources will be accessing a wide variety of these cloud-based services such as video/audio streaming and online gaming. In order to improve the performance of this model, cloud-based services need to become aware of the movement of the mobile devices and to be launched closer to the demand. Such a requirement becomes achievable through virtual machine live migration , a feature that is currently supported in all virtualization platforms. Virtual machine live migration is widely performed in the data centres of the Cloud, for the purposes of load balance, reliability, availability, hardware maintenance and system upgrade. It entails moving all the state information of the virtual machine being migrated, including memory state, network state and storage state, from one physical server to another within the same data center or across different data centers. The security aspect of live migration has not been fully addressed yet. Some proposals rely on trusted third-parties for generating and producing the security parameters. Others assume the presence of pre-shared security parameters between the source and destination cloud providers. The author argues that such assumptions might not always be feasible in open, large scale cloud environment. Therefore, this paper introduces ZKPVM, a new authentication and key agreement protocol for securing virtual machine migration. The protocol is based on zero-knowledge authentication; it requires no knowledge between the source and destination cloud providers prior to the migration and it also does not demand the presence of a third-party. ZKPVM is formally verified using AVISPA formal methods and it is proven to meet a number of desired security properties
Accuracy of oral exfoliative cytology in Sudanese patients undergoing oral biopsy
No full textIntroduction: Early detection of a premalignant or malignant oral lesions promises to improve the survival and the morbidity of patients suffering from these conditions. Oral exfoliative cytology (OEC) is a non-invasive method that is well accepted by the patient, and is therefore, suitable for screening at-risk population for early diagnosis of oral cancer. Objective: The purpose of this study is to investigate the value of OEC in the detection of oral premalignant and malignant lesions. Material and methods: In this hospital-based case-control study, cytological scrapes from buccal mucosa were obtained from 100 individuals, of whom 50 were patients with oral lesions ascertained as “cases” and 50 were clinically healthy volunteers ascertained as “controls”. All patients with oral lesions were also subjected to oral biopsy and histological examination. Results: Out of 50 cases studied, histopathology showed the presence of: Oral squamous cell carcinoma OSCC (n = 28), leukoplakia (n = 8), dysplasia (n = 3), and benign normal lesions (n = 11). In cytology, a specificity of 100%, sensitivity of 93% and accuracy of 92% were obtained for OSCC. Leukoplakia gave a specificity of 100%, a sensitivity of 87.5%, and an accuracy of 95%. Conclusion: Despite the small number of cases in this study, OEC is a useful method for detecting oral premalignant and malignant lesions. OEC can detect a number of pathological conditions that require management
A New Modular Multilevel Inverter Based on Step-Up Switched-Capacitor Modules
No full textA new structure of switched capacitor multilevel inverter (SCMLI) capable of voltage boosting and with self-balancing ability is introduced in this article. This advantage is the result of a step by step rise of capacitor voltages in each module, supplied by just one DC voltage source. The proposed topology generates a sinusoidal output waveform with a magnitude several times greater than the input one. Higher output staircase AC voltage is obtained by applying a nearest level control (NLC) modulation technique. The most significant features of this configuration can be mentioned as: fewer semiconductor devices, remarkably low total harmonic distortion (THD), desirable operating under high/low frequency, high efficiency, inherent bipolar voltage production, easy circuit expansion, ease of control and size reduction of the circuit thanks to utilizing neither bulky transformer nor inductor. Moreover, the proposed SCMLI is comprehensively surveyed through theoretical investigation and a comparison of its effectiveness to recent topologies. Eventually, the operating principle of a 25-level prototype of the suggested SCMLI is validated by simulation in the MATLAB SIMULINK environment and experimental results.Peer reviewe
Application of Moringa peregrina seed extract as a natural coagulant for phenol removal from aqueous solutions
No full textPhenol and its derivatives are toxic pollutants frequently found in surface and tap waters, and in aqueous effluents from various manufacturing processes such as petroleum and petrochemical, coal conversion, synthetic rubber, plastics, paper, oil refineries and phenol-producing industries. In the present study, the ability of Moringa peregrina seed extract to remove phenol from aqueous solutions in a batch system was investigated. The effects of major operating variables such as coagulant dose (0.05 - 4 ml//L), initial phenol concentration (5, 10, 20, 50 and 100 mg/L) and pH (3-9) were investigated. The optimum pH for phenol removal by coagulation using M. peregrina seed extract was 5, with coagulant dose of 0.1 and 0.3 ml/L and the highest removal was found to be 95.16, 95.84, 97.91, 98.27 and 99.9% at initial phenol concentration of 5, 10, 20, 50 and 100 mg/L, respectively, as a result of precipitation, co-precipitation and adsorption mechanisms. According to these results, it was defined that M. peregrina seed extract is not only an inexpensive coagulant, but also quite an effective factor in the removal of phenol from aqueous environments.Key words: Phenol removal, Moringa peregrina, coagulation, natural coagulants
Studies of Toxic and Heavy Metals Pollution of Karnafuli River and Its Impacts on Environment of Chittagong, Bangladesh
No full textThe present study was conducted to assess the toxic and heavy metals concentrations in water at different locations of the Karnafuli River. The assessment was carried out for various toxic and heavy metals concentrations in three seasons during pre-monsoon, monsoon and post-monsoon seasons for various continuous monitoring during the hydrological year 2014-2016. The statistical methods of sampling were used for collecting samples from different points of Karnafuli River. The samples were collected in high and low tide conditions. Since the water quality is expected to vary with season, multiple samples were collected at an interval of 2 to 3 weeks. The work has been carried out by traveling to the sampling sites for collection required water samples and the estimation of water discharge and determination of basic parameters of the sites. Samples were preserved with suitable preservation and transported to the laboratory. Standard methods were followed to determine the toxic and heavy metals concentrations. In the present study, seasonal variation hydrochemical character of Karnafuli River water has been evaluated and assessed the suitability of water for human & animal′s consumption, irrigation and industrial purposes. The study stress to access various essential heavy metals concentrations including arsenic, cadmium, cobalt, chromium, copper, iron, lead, manganese, nickel and zinc. Toxic and heavy metals concentrations were studied such as As, Cd, Co, Cr, Cu, Fe, Pb, Mn, Ni and Zn were found in variation from (0.01 - 0.05)-mgL-1, (0.12 - 0.75)-mgL-1, (0.01 - 0.013)-mgL-1, (0.051 -0.063)-mgL-1, (0.012 - 0.25)-mgL-1,(0.006 - 4.844)-mgL-1, (0.036 - 0.07)-mgL-1, (0.015 - 0.845)-mgL-1, (0.02 - 0.097)-mgL-1, (0.013 - 0.8)-mgL-1 respectively. The average of maximum heavy metals concentrations studied was found higher than those of the World Health Organization (WHO), Department of Environment (DoE) and BSTI drinking water guidelines. The laboratory finding of water quality parameters were also compared with the recommended values set by DoE and BSTI. From Pearson correlation program, significant positive and negative correlations were found in different parameters. These assessment data indicated that the water quality of Karnafuli River are highly polluted which are continuously polluting the coastal zone, sea and the Halda river of Chittagong. The environmental impact of water quality of Karnafuli River has been discussed. A strategic water quality management plan has been proposed
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