Search results for: Abbassi Mohamed Ammar
447 Modeling and Analyzing the WAP Class 2 Wireless Transaction Protocol Using Event-B
Authors: Rajaa Filali, Mohamed Bouhdadi
Abstract:
This paper presents an incremental formal development of the Wireless Transaction Protocol (WTP) in Event-B. WTP is part of the Wireless Application Protocol (WAP) architectures and provides a reliable request-response service. To model and verify the protocol, we use the formal technique Event-B which provides an accessible and rigorous development method. This interaction between modelling and proving reduces the complexity and helps to eliminate misunderstandings, inconsistencies, and specification gaps. As result, verification of WTP allows us to find some deficiencies in the current specification.
Keywords: Event-B, wireless transaction protocol, refinement, proof obligation, Rodin, ProB.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 961446 Solving Inhomogeneous Wave Equation Cauchy Problems using Homotopy Perturbation Method
Authors: Mohamed M. Mousa, Aidarkhan Kaltayev
Abstract:
In this paper, He-s homotopy perturbation method (HPM) is applied to spatial one and three spatial dimensional inhomogeneous wave equation Cauchy problems for obtaining exact solutions. HPM is used for analytic handling of these equations. The results reveal that the HPM is a very effective, convenient and quite accurate to such types of partial differential equations (PDEs).
Keywords: Homotopy perturbation method, Exact solution, Cauchy problem, inhomogeneous wave equation
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1808445 E-Books in Malaysian Primary Schools: The Terengganu Chapter
Authors: Azelin Mohamed Noor, Abd Mutalib Embong, Muhamad Ridhuan Tony Lim Abdullah
Abstract:
After the Terengganu state government decided to give a boost in teaching and learning through the allocation of free ebooks to all Primary five and six students; it was time to examine the presence of e-books in the classrooms. A survey was conducted on 101 students to determine how they felt about using the e-book and their experiences. It was discovered that a majority of these students liked using the e-book. However, although they had little problems using the e-book and the e-book helped to lighten the schoolbags, these new-age textbooks were not fully utilized. It is implied that perhaps the school administrators, teachers and students may not be able to overcome the unfamiliar characteristics of the e-book and its limitations.
Keywords: E-books, students, classroom, limitations
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 4223444 Expansion of A Finit Size Partially Ionized Laser-Plasma
Authors: Mohamed Fawzi Mahboub, Mourad Djebli
Abstract:
The expansion mechanism of a partially ionized plasma produced by laser interaction with solid target (copper) is studied. For this purpose we use a hydrodynamical model which includes a source term combined with Saha's equation. The obtained self-similar solution in the limit of quasi-neutrality shows that the expansion, at the earlier stage, is driven by the combination of thermal pressure and electrostatic potential. They are of the same magnitude. The initial ionized fraction and the temperature are the leading parameters of the expanding profiles,
Keywords: expansion, quasi-neutral, laser-ablated plasma, self- similar.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1306443 Adaptive MPC Using a Recursive Learning Technique
Authors: Ahmed Abbas Helmy, M. R. M. Rizk, Mohamed El-Sayed
Abstract:
A model predictive controller based on recursive learning is proposed. In this SISO adaptive controller, a model is automatically updated using simple recursive equations. The identified models are then stored in the memory to be re-used in the future. The decision for model update is taken based on a new control performance index. The new controller allows the use of simple linear model predictive controllers in the control of nonlinear time varying processes.
Keywords: Adaptive control, model predictive control, dynamic matrix control, online model identification
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1777442 On a Conjecture Regarding the Adam Optimizer
Authors: Mohamed Akrout, Douglas Tweed
Abstract:
The great success of deep learning relies on efficient optimizers, which are the algorithms that decide how to adjust network weights and biases based on gradient information. One of the most effective and widely used optimizers in recent years has been the method of adaptive moments, or Adam, but the mathematical reasons behind its effectiveness are still unclear. Attempts to analyse its behaviour have remained incomplete, in part because they hinge on a conjecture which has never been proven, regarding ratios of powers of the first and second moments of the gradient. Here we show that this conjecture is in fact false, but that a modified version of it is true, and can take its place in analyses of Adam.
Keywords: Adam optimizer, Bock’s conjecture, stochastic optimization, average regret.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 377441 A Primer to the Learning Readiness Assessment to Raise the Sharing of e-Health Knowledge amongst Libyan Nurses
Authors: Mohamed Elhadi M. Sharif, Mona Masood
Abstract:
The usage of e-health facilities is seen to be the first priority by the Libyan government. As such this paper focuses on how the key factors or elements of working size in terms of technological availability, structural environment, and other competence-related matters may affect nurses’ sharing of knowledge in e-health. Hence, this paper investigates learning readiness assessment to raise e-health for Libyan regional hospitals by using ehealth services in nursing education.
Keywords: Libyan nurses, e-Learning readiness, e-Health.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2172440 Attenuation in Transferred RF Power to a Biomedical Implant due to the Absorption of Biological Tissue
Authors: Batel Noureddine, Mehenni Mohamed, Kouadik Smain
Abstract:
In a transcutanious inductive coupling of a biomedical implant, a new formula is given for the study of the Radio Frequency power attenuation by the biological tissue. The loss of the signal power is related to its interaction with the biological tissue and the composition of this one. A confrontation with the practical measurements done with a synthetic muscle into a Faraday cage, allowed a checking of the obtained theoretical results. The supply/data transfer systems used in the case of biomedical implants, can be well dimensioned by taking in account this type of power attenuation.Keywords: Biological tissue, coupled coils, implanted device, power attenuation.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2324439 A Design and Implementation Model for Web Caching Using Server “URL Rewriting“
Authors: Mostafa E. Saleh, A. Abdel Nabi, A. Baith Mohamed
Abstract:
In order to make surfing the internet faster, and to save redundant processing load with each request for the same web page, many caching techniques have been developed to reduce latency of retrieving data on World Wide Web. In this paper we will give a quick overview of existing web caching techniques used for dynamic web pages then we will introduce a design and implementation model that take advantage of “URL Rewriting" feature in some popular web servers, e.g. Apache, to provide an effective approach of caching dynamic web pages.
Keywords: Web Caching, URL Rewriting, Optimizing Web Performance, Dynamic Web Pages Loading Time.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1928438 Determination of Optical Constants of Semiconductor Thin Films by Ellipsometry
Authors: Aïssa Manallah, Mohamed Bouafia
Abstract:
Ellipsometry is an optical method based on the study of the behavior of polarized light. The light reflected on a surface induces a change in the polarization state which depends on the characteristics of the material (complex refractive index and thickness of the different layers constituting the device). The purpose of this work is to determine the optical properties of semiconductor thin films by ellipsometry. This paper describes the experimental aspects concerning the semiconductor samples, the SE400 ellipsometer principle, and the results obtained by direct measurements of ellipsometric parameters and modelling using appropriate software.Keywords: Ellipsometry, optical constants, semiconductors, thin films.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1337437 Interfacing and Replication of Electronic Machinery Using MATLAB / SIMULINK
Authors: Abdulatif Abdusalam, Mohamed Shaban
Abstract:
This paper introduces Interfacing and Replication of electronic tools based on the MATLAB/ SIMULINK mock-up package. Mock-up components contain dc-dc converters, power issue rectifiers, motivation machines, dc gear, synchronous gear, and more entire systems. The power issue rectifier model includes solid state device models. The tools provide clear-cut structures and mock-up of complex energy systems, connecting with power electronic machines.
Keywords: Power electronics, Machine, Matlab/Simulink.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 3049436 Towards a Simulation Model to Ensure the Availability of Machines in Maintenance Activities
Authors: Maryam Gallab, Hafida Bouloiz, Youness Chater, Mohamed Tkiouat
Abstract:
The aim of this paper is to present a model based on multi-agent systems in order to manage the maintenance activities and to ensure the reliability and availability of machines just with the required resources (operators, tools). The interest of the simulation is to solve the complexity of the system and to find results without cost or wasting time. An implementation of the model is carried out on the AnyLogic platform to display the defined performance indicators.Keywords: Maintenance, complexity, simulation, multi-agent systems, AnyLogic platform.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1508435 Neutron Flux Characterization for Radioisotope Production at ETRR-2
Authors: A. M. Hassanain, Nader M. A. Mohamed, M. Naguib Aly, Alya A. Badawi, M. A. Gaheen
Abstract:
The thermal, epithermal and fast fluxes were calculated for three irradiation channels at Egypt Second Research Reactor (ETRR-2) using CITVAP code. The validity of the calculations was verified by experimental measurements. There are some deviations between measurements and calculations. This is due to approximations in the calculation models used, homogenization of regions, condensation of energy groups and uncertainty in nuclear data used. Neutron flux data for the three irradiation channels are now available. This would enable predicting the irradiation conditions needed for future radioisotope production.Keywords: ETRR-2, Neutron flux, Radioisotope production, CITVAP
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2242434 Exponential Stability of Linear Systems under a Class of Unbounded Perturbations
Authors: Safae El Alaoui, Mohamed Ouzahra
Abstract:
In this work, we investigate the exponential stability of a linear system described by x˙ (t) = Ax(t) − ρBx(t). Here, A generates a semigroup S(t) on a Hilbert space, the operator B is supposed to be of Desch-Schappacher type, which makes the investigation more interesting in many applications. The case of Miyadera-Voigt perturbations is also considered. Sufficient conditions are formulated in terms of admissibility and observability inequalities and the approach is based on some energy estimates. Finally, the obtained results are applied to prove the uniform exponential stabilization of bilinear partial differential equations.
Keywords: Exponential stabilization, unbounded operator, Desch-Schappacher, Miyadera-Voigt operator.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 368433 Fast Accurate Detection of Frequency Jumps Using Kalman Filter with Non Linear Improvements
Authors: Mahmoud E. Mohamed, Ahmed F. Shalash, Hanan A. Kamal
Abstract:
In communication systems, frequency jump is a serious problem caused by the oscillators used. Kalman filters are used to detect that jump, despite the tradeoff between the noise level and the speed of the detection. In this paper, an improvement is introduced in the Kalman filter, through a nonlinear change in the bandwidth of the filter. Simulation results show a considerable improvement in the filter speed with a very low noise level. Additionally, the effect on the response to false alarms is also presented and false alarm rate show improvement.
Keywords: Kalman Filter, Innovation, False Detection.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2226432 Analysis of Self Excited Induction Generator using Particle Swarm Optimization
Authors: Hassan E. A. Ibrahim, Mohamed F. Serag
Abstract:
In this paper, Novel method, Particle Swarm Optimization (PSO) algorithm, based technique is proposed to estimate and analyze the steady state performance of self-excited induction generator (SEIG). In this novel method the tedious job of deriving the complex coefficients of a polynomial equation and solving it, as in previous methods, is not required. By comparing the simulation results obtained by the proposed method with those obtained by the well known mathematical methods, a good agreement between these results is obtained. The comparison validates the effectiveness of the proposed technique.
Keywords: Evolution theory, MATLAB, optimization, PSO, SEIG.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2464431 Attenuation in Transferred RF Power to a Biomedical Implant due to the Misalignment Coils
Authors: Batel Noureddine, Mehenni Mohamed, Dekar Lies
Abstract:
In biomedical implant field, a new formula is given for the study of Radio Frequency power attenuation by simultaneous effects of side and angular misalignment of the supply/data transfer coils. A confrontation with the practical measurements done into a Faraday cage, allowed a checking of the obtained theoretical results. The DC supply systems without material connection and the data transmitters used in the case of biomedical implants, can be well dimensioned by taking into account the possibility of power attenuation by misalignment of transfer coilsKeywords: Biomedical implant field, misalignment coils, powerattenuation, transmitter and receiver coils.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1688430 Higher Order Statistics for Identification of Minimum Phase Channels
Authors: Mohammed Zidane, Said Safi, Mohamed Sabri, Ahmed Boumezzough
Abstract:
This paper describes a blind algorithm, which is compared with two another algorithms proposed in the literature, for estimating of the minimum phase channel parameters. In order to identify blindly the impulse response of these channels, we have used Higher Order Statistics (HOS) to build our algorithm. The simulation results in noisy environment, demonstrate that the proposed method could estimate the phase and magnitude with high accuracy of these channels blindly and without any information about the input, except that the input excitation is identically and independent distribute (i.i.d) and non-Gaussian.
Keywords: System Identification, Higher Order Statistics, Communication Channels.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1672429 Assessment of Performance Measures of Large-Scale Power Systems
Authors: Mohamed A. El-Kady, Badr M. Alshammari
Abstract:
In a recent major industry-supported research and development study, a novel framework was developed and applied for assessment of reliability and quality performance levels in reallife power systems with practical large-scale sizes. The new assessment methodology is based on three metaphors (dimensions) representing the relationship between available generation capacities and required demand levels. The paper shares the results of the successfully completed stud and describes the implementation of the new methodology on practical zones in the Saudi electricity system.
Keywords: Power systems; large-scale analysis, reliability; performance assessment, linear programming.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1846428 The removal of Ni, Cu and Fe from a Mixed Metal System using Sodium Hypophosphite as a Reducing Agent
Authors: Promise Sethembiso Ngema, Freeman Ntuli, Mohamed Belaid
Abstract:
The main objective of this study was to remove and recover Ni, Cu and Fe from a mixed metal system using sodium hypophosphite as a reducing agent and nickel powder as seeding material. The metal systems studied consisted of Ni-Cu, Ni-Fe and Ni-Cu-Fe solutions. A 5 L batch reactor was used to conduct experiments where 100 mg/l of each respective metal was used. It was found that the metals were reduced to their elemental form with removal efficiencies of over 80%. The removal efficiency decreased in the order Fe>Ni>Cu. The metal powder obtained contained between 97-99% Ni and was almost spherical and porous. Size enlargement by aggregation was the dominant particulate process.
Keywords: crystallization, electroless plating, heavy metal removal, wastewater treatment
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2039427 Teachers- Perceptions on the Use of E-Books as Textbooks in the Classroom
Authors: Abd Mutalib Embong, Azelin M Noor, Razol Mahari M Ali, Zulqarnain Abu Bakar, Abdur- Rahman Mohamed Amin
Abstract:
At the time where electronic books, or e-Books, offer students a fun way of learning , teachers who are used to the paper text books may find it as a new challenge to use it as a part of learning process. Precisely, there are various types of e-Books available to suit students- knowledge, characteristics, abilities, and interests. The paper discusses teachers- perceptions on the use of ebooks as a paper text book in the classroom. A survey was conducted on 72 teachers who use e-books as textbooks. It was discovered that a majority of these teachers had good perceptions on the use of ebooks. However, they had little problems using the devices. It can be overcome with some strategies and a suggested framework.Keywords: Classroom, E-books, perception, teacher.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 5749426 Comparative Study of QRS Complex Detection in ECG
Authors: Ibtihel Nouira, Asma Ben Abdallah, Ibtissem Kouaja, Mohamed Hèdi Bedoui
Abstract:
The processing of the electrocardiogram (ECG) signal consists essentially in the detection of the characteristic points of signal which are an important tool in the diagnosis of heart diseases. The most suitable are the detection of R waves. In this paper, we present various mathematical tools used for filtering ECG using digital filtering and Discreet Wavelet Transform (DWT) filtering. In addition, this paper will include two main R peak detection methods by applying a windowing process: The first method is based on calculations derived, the second is a time-frequency method based on Dyadic Wavelet Transform DyWT.Keywords: Derived calculation methods, Electrocardiogram, R peaks, Wavelet Transform.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2570425 Probability Density Estimation Using Advanced Support Vector Machines and the Expectation Maximization Algorithm
Authors: Refaat M Mohamed, Ayman El-Baz, Aly A. Farag
Abstract:
This paper presents a new approach for the prob-ability density function estimation using the Support Vector Ma-chines (SVM) and the Expectation Maximization (EM) algorithms.In the proposed approach, an advanced algorithm for the SVM den-sity estimation which incorporates the Mean Field theory in the learning process is used. Instead of using ad-hoc values for the para-meters of the kernel function which is used by the SVM algorithm,the proposed approach uses the EM algorithm for an automatic optimization of the kernel. Experimental evaluation using simulated data set shows encouraging results.
Keywords: Density Estimation, SVM, Learning Algorithms, Parameters Estimation.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2506424 Investigation of a Wearable Textile Monopole Antenna on Specific Absorption Rate at 2.45 GHz
Authors: Hasliza A. Rahim, Fareq Malek, Ismahayati Adam, Ahmad Sahadah, Nur B. M. Hashim, Nur A. M. Affendi, Azuwa Ali, Norshafinash Saudin, Latifah Mohamed
Abstract:
This paper discusses the investigation of a wearable textile monopole antenna on specific absorption rate (SAR) for bodycentric wireless communication applications at 2.45 GHz. The antenna is characterized on a realistic 8 x 8 x 8 mm3 resolution truncated Hugo body model in CST Microwave Studio software. The result exhibited that the simulated SAR values were reduced significantly by 83.5% as the position of textile monopole was varying between 0 mm and 15 mm away from the human upper arm. A power absorption reduction of 52.2% was also noticed as the distance of textile monopole increased.Keywords: Monopole antenna, specific absorption rate, textile antenna.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 2128423 Activation of Prophenoloxidase during Bacterial Injection into the Desert Locust, Schistocerca Gregaria
Authors: Shaiemaa, A. Momen, Dalia, A.M. Salem, Emad, M.S. Barakat, Mohamed, S. Salama
Abstract:
The present study has been conducted to characterize the prophenoloxidase (PPO) system of the desert locust, Schistocerca gregaria following injection of Bacillus thuringiensis kurstaki (Bt). The bulk of PPO system was associated with haemocytes and a little amount was found in plasma. This system was activated by different activators such as laminarin, lipopolysaccharide (LPS) and trypsin suggesting that the stimulatory mechanism may involve an enzyme cascade of one or more associated molecules. These activators did not activate all the molecules of the cascade. Presence of phenoloxidase activity (PO) coincides with the appearance of protein band with molecular weight (MW) 70.154 KD (Kilo Dalton).Keywords: Schistocerca gregaria, haemolymph, proteins, prophenoloxidase system, phenoloxidase
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1723422 Floating-Point Scaling for BSS Gain Control
Authors: Abdelmalek Fermas, Adel Belouchrani, Otmane Ait Mohamed
Abstract:
In Blind Source Separation (BSS) processing, taking advantage of scaling factor indetermination and based on the floatingpoint representation, we propose a scaling technique applied to the separation matrix, to avoid the saturation or the weakness in the recovered source signals. This technique performs an Automatic Gain Control (AGC) in an on-line BSS environment. We demonstrate the effectiveness of this technique by using the implementation of a division free BSS algorithm with two input, two output. This technique is computationally cheaper and efficient for a hardware implementation.Keywords: Automatic Gain Control, Blind Source Separation, Floating-Point Representation, FPGA Implementation.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1520421 Numerical Flow Simulation around HSP Propeller in Open Water and behind a Vessel Wake Using RANS CFD Code
Authors: Kadda Boumediene, Mohamed Bouzit
Abstract:
The prediction of the flow around marine propellers and vessel hulls propeller interaction is one of the challenges of Computational fluid dynamics (CFD). The CFD has emerged as a potential tool in recent years and has promising applications. The objective of the current study is to predict the hydrodynamic performances of HSP marine propeller in open water and behind a vessel. The unsteady 3-D flow was modeled numerically along with respectively the K-ω standard and K-ω SST turbulence models for steady and unsteady cases. The hydrodynamic performances such us a torque and thrust coefficients and efficiency show good agreement with the experiment results.
Keywords: Seiun Maru propeller, steady, unsteady, CFD, HSP.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 841420 A Comparative Study of Medical Image Segmentation Methods for Tumor Detection
Authors: Mayssa Bensalah, Atef Boujelben, Mouna Baklouti, Mohamed Abid
Abstract:
Image segmentation has a fundamental role in analysis and interpretation for many applications. The automated segmentation of organs and tissues throughout the body using computed imaging has been rapidly increasing. Indeed, it represents one of the most important parts of clinical diagnostic tools. In this paper, we discuss a thorough literature review of recent methods of tumour segmentation from medical images which are briefly explained with the recent contribution of various researchers. This study was followed by comparing these methods in order to define new directions to develop and improve the performance of the segmentation of the tumour area from medical images.
Keywords: Features extraction, image segmentation, medical images, tumour detection.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 590419 Plug and Play Interferometer Configuration using Single Modulator Technique
Authors: Norshamsuri Ali, Hafizulfika, Salim Ali Al-Kathiri, Abdulla Al-Attas, Suhairi Saharudin, Mohamed Ridza Wahiddin
Abstract:
We demonstrate single-photon interference over 10 km using a plug and play system for quantum key distribution. The quality of the interferometer is measured by using the interferometer visibility. The coding of the signal is based on the phase coding and the value of visibility is based on the interference effect, which result a number of count. The setup gives full control of polarization inside the interferometer. The quality measurement of the interferometer is based on number of count per second and the system produces 94 % visibility in one of the detectors.Keywords: single photon, interferometer, quantum key distribution.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1621418 Automatic Generation of Ontology from Data Source Directed by Meta Models
Authors: Widad Jakjoud, Mohamed Bahaj, Jamal Bakkas
Abstract:
Through this paper we present a method for automatic generation of ontological model from any data source using Model Driven Architecture (MDA), this generation is dedicated to the cooperation of the knowledge engineering and software engineering. Indeed, reverse engineering of a data source generates a software model (schema of data) that will undergo transformations to generate the ontological model. This method uses the meta-models to validate software and ontological models.
Keywords: Meta model, model, ontology, data source.
Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1998