Recent advances in power electronics have significantly promoted the development of More Electric Aircraft. Power electronic converters for aircrafts include: DC to DC converters, DC to AC inverters, AC to DC rectifiers and AC to AC converters. In the present aircraft electrical systems, DC to DC converters are used for conversion between high-voltage DC (HVDC 270 VDC) to low voltage (28 VDC), secondary power or utilized for bi-directional power conversion between 28VDC and batteries. This work proposes a comparative analysis for some controller types used to stabilize a DC to DC Buck converter. Here are briefly presented the clasical control design strategies using state variables and also Sliding Mode control strategy. MATLAB/SIMULINK simulation schemes are implemented for a DC to DC Buck converter, using each control stategy proposed: classic control using state variables, with Sliding Mode Control and with P.I. Sliding Mode Controller. All these controllers aim to stabilize the output voltage when load varies. In order to comparative evaluate these control strategies, step load variations were applied to the Buck converter output. Closed loop functioning, both to load rise and decrease, and control strategies efficiency is studied by numerical simulation.
Purpose:We present our experience in the diagnosis, follow-up and planning therapy of thoracic, abdominal and retroperitoneal liquid collections in different emergency patients using conventional and interventional ultrasound. \n Material and Methods: The right and left oblique and polypositionning view was used in 235 patients/159 male and 76 female/ for US examination to identify fluids in the thorax and peritoneal or retroperitoneal space. The examination was performed after the clinical survey with patients supine. Positive findings of US were compared with those provided by CT, punctures under US control or surgery. US machine supplied with linear and convex transducers, CT machine, needles and catheters were used. \n Results. 197 of all 235 US examined patients had fluid collections, confirmed by CT scan, surgery or clinival course. In 156patients we performed FN diagnostic punctures under US control. There was 155 true-positives, 25 true-negatives, 5 false-positives and 2 false-negative results. Overall this demonstrated that ultrasonography hamaunt of d a sensitivity of 98.72%, specificity of 83.33% and accuracy of 96.25 %. The PPV is 96.87% and the NPV – 92.59%.\n Conclusions. Our experience and literature reports support the opinion that US examination can and should be used as a primary method for diagnosis and follow-up of clinically suspected free and organaised fluids in the thorax, abdomen and retroperitoneum.
This paper proposes evaluation model for building Learning Content Management System (LCMS) in Riyadh City universities. A literature and a practical survey of web development methodologies have been conducted to identify LCMS readiness in Riyadh city universities. The framework is evaluated by e-learning AHP evaluation model, which is proposed by Francesco Colace in 2006. The evaluation model is evaluating four main features (management, collaborative approach, Management of interactive learning objects and Adaptation of learning path). Every feature involves, in their determination, some sub-features. The results of evaluation model are outlined as follows: Total weights of the proposed framework in management feature is 16.7/25, in collaborative feature is 9/10, in adaption learning path is 5.5/10 and in interactive learning object is 5/5. The total weights of all features are 36.2/50. In this study an evaluation model was applied on Riyadh City universities like KSU, IMAMU, NAUSS, YU, KFU and PSU. Then, the results were compared with each other. The total weighs of each of KSU and PSU was 41. While the total weights of KFU, IMAMU, YU and NAUSS was 40, 37,36 and 32, respectively. Evaluation process shows that the proposed framework satisfied the objectives and the required functions of this work.
The development of Wireless Body Area Networks (WBANs) has significantly improved the quality of personal health care whilst enhancing the quality of life. A critical factor in the acceptance of WBANs is providing appropriate security and privacy protection of the wireless communication. It is a challenge to implement traditional security infrastructures in these types of lightweight networks, since they are by design limited in both computational and communication resources. \n In this paper, we propose to use the QRS Complex to generate and distribute securely and efficiently symmetric session keys to constituent sensors in WBAN with very high fidelity of key recoverability.
More personal software is our permanent goal. This means that more people should be\nconcerned with cryptography. We think that the encoding of cryptographic algorithms is an\nimportant step in it.\nIn this paper, our choice is encoding operation “Point doubling” on an Elliptic curve, over\nfinite field Fp (E(FP)), where p is odd prime, in order to intensify interest in ECC-Ellipse\ncurve cryptography.
Abstract\nIntroduction: Infertility is a problem that in addition to psychological effects, its high medical costs is also gripped the family and society. Regarding the role of the hormone oxytocin in stimulating ovulation and its less complications and cost, it may be considered substitutes for HCG. We decided to perform this study because the mechanism of effect of oxytocin on ovulation is not clear and no study has been conducted directly about its effect on LH surge. Methods: Of infertile women without ovulation, presenting to Iran North-West Gynecology specialized clinics, which had ovulation following excitation with Clomiphene, 200 patients were selected, and 200 patients received 5 U intra-muscular oxytocin. This was \"experimental\" and \"Case- Control\" study in which the subgroups were cased for: ultrasound study of follicular growth and follicle diameter measurement; serum LH levels measured periodically in both groups; Ovulation confirming using serum progesterone measurement in the middle of the luteal phase. The data obtained in the groups were analyzed by SPSS software version 15 using T-test. Results: The mean serum LH levels after 24 h was 21.87±21.71 mIu/ml in Control group and 23.77±34.51 mIu/ml in Case group, without significant difference (p=0.836); but U-Man- Whitney test showed significant difference (p=0.029) of mid-luteal average serum progesterone between the Control and Case groups (15.92 ng/ml and 23.88 ng/ml respectively). Conclusion: Although there was not significant difference in the mean serum LH after 24 h in two groups, but the presence of significant difference in mean mid- luteal progesterone levels in both groups suggest that administration of oxytocin is effective in the Ovulation induction.
XACML is an XML-based language for access\ncontrol that has been standardized by OASIS (Organization\nfor the Advancement of Structured Information Standards).\nXACML describes both an access control policy language that\nare ABAC and an access control decisions (request/response)\nlanguage. Although XACML is recognized as a precise and\ncomplete policy description method, the structure of an XACML\npolicy is complex and users need to understand XACML well\nand writes down the verbose policy all by hand, which make\nXACML difficult to master and use. In this paper, we present\na comprehensive description of XACML to support the future\nresearch and development work.
Oil revenue plays an important role in economy of Iran as an oil exporting country. This paper empirically investigates the effects of oil price fluctuations on real GDP in Iran. Overall, we find that the price of oil is a major determinant of economic activity of the country. Our impulse response functions suggest that negative oil shocks are much more effective than the positive oil shocks contemporaneously according to the size and statistical significance. Oil funds could help mitigate the transmission of oil price shocks to harsh changes in money aggregates, prices and exchange rates. When some sterilization in response to an oil price hike is conducted through oil funds, there are a lesser demands on monetary policy. When the exchange rate is the nominal anchor and the policy burden lies with the fiscal authorities, building up or drawing down stocks of the oil fund can be particularly effective in achieving macroeconomic stability.
Literature on soil erosion dynamics in abandoned farmlands of varying ages is not readily available. A study was carried out to evaluate the rate of sediment production in abandoned farmlands of 5yr-old and 3yr-old in a part of the rainforest zone in southern Nigeria. Measurements of 61 rainfall producing runoff and 54 rainfall producing sediment were carried out from the months of March to November in 2012 rainy season. Soil textural information showed that the 5yr-old fallow was silt loam, while soil in the 3yr-old fallow was sandy loam. The study showed that rainfall was the principal contributing factor of soil erosion on the fallow plots, and that greater proportion of the rainwater was absorbed by soil on the 3yr-old fallow plot due to its dense undergrowths (ground cover) and good soil structure. There were significant differences in the amount of runoff and sediment loss between the fallow plots (P<0.01). The high erosional loss on 5yr-old fallow plot was attributed to the canopy gaps that characterized its vegetation cover and scanty undergrowths as well as its clayey nature. The study concluded that vegetation on the 5yr-old fallow was not adequate in suppressing soil erosion. Stepwise regression identified rainfall as the primary cause of runoff on the 5yr-old fallow, while on the 3yr-old fallow plot, rainfall and crown cover were identified. For sediment loss, girth and ground cover were the prime causes on the 5yr-old fallow, while on the 3yr-old fallow, rainfall was the sole factor. The study revealed that vegetation cover alone did not afford the soil adequate cover, but the percentage of undergrowth (ground cover). Thus, to reduce soil erosional losses, the study suggested that fallow land with scanty ground cover should be managed through planted fallow and mulching.