This work presents the use of laser diode in the fiber distributed data interface FDDI networks. FDDI uses optical fiber as a transmission media. This solves the problems resulted from the EMI, and noise. In addition it increases the security of transmission. A network with a ring topology consists of three computers was designed and implemented. The timed token protocol was used to achieve and control the process of communication over the ring. Nonreturn to zero inversion (NRZI) modulation was carried out as a part of the physical (PHY) sublayer. The optical system consists of a laser diode with wavelength of 820 nm and 2.5 mW maximum output power as a source, optical fiber as a channel, and positive intrinsic negative (PIN) photodiode with maximum responsivity at wavelength of 820 nm as a detector. Practical tests were carried out on the laser diode showed that the output characteristics and spectral characteristics of the laser diode depend largely on the drive current. The maximum separation distance between successive stations in the ring was 5.4 km. From the performance tests, it was concluded that the maximum throughput and maximum access delay are directly proportional to length of the transmitted information. A trade off between the transmitted information length and the maximum access delay is needed.
The effect of different doses of gamma rays that emitted from 60Co on the development of different stages of lesser grain borer Rhyzopertha dominica (Fab.) was investigated . The results showed that the eggs in both early (1-3 days) and late (7-9) old were very sensitive to gamma rays and its hatch was zero at 10 Gy for both ages in comparison with 83.3% for the control group. Furthermore, the results illustrated that the larval stage in its two old ages were different in the radiosensitivity, the percent of its death were 100% & 96.6% when they exposed to 100 & 120 Gy, respectively. Moreover, the results showed that the sensitivity of pupal stage at age of 1-3 days was increased with increasing the doses of gamma rays, the percent of no
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Abstract
The entities responsible for regulating the financial market are seeking to provide high quality accounting information, to provide appropriate protection to investors, and thus encourage them and attract them to increase their investments. the research reached several conclusion, the most prominent of which comes :-
1-The production of high quality accounting information reduces investment costs and costs of processing accounting information.
2- The production of high quality accounting information helps investors identify the best investment opportunities.
3- The results of the statistical analysis showed that there is significant
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Over the course of six decades, Iraq exposed to many events that have affected the Iraqi people from the social, physical and mental aspects. In this study, two groups of people (2369), from Iraq (G1) and the Michigan, United States (U.S) of America (G2) selected to compare the prevalence rate and effects of trauma factors such as mental illness (anxiety, depression and PTS), somatic diseases (heart disease, hypertension, and diabetes), substances abuse (illicit drugs, alcohol and tobacco), and chemicals pollution), and self-rated health among the two groups. The study results reveals a significant different between the two groups in the all indicators for trauma. The study conclude that Iraqi in U.S. (G2) suffer from factors completely dif
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CuInSe2 (CIS)thin films have been prepared by use vacuum thermal evaporation technique, of 750 nm thickness, with rate of deposition 1.8±0.1 nm/sec on glass substrate at room temperature and pressure (10-5) mbar. Heat treatment has been carried out in the range (400-600) K for all samples. The optical properties of the CIS thin films are been studied such as (absorption coefficient, refractive index, extinction coefficient, real and imaginary dielectric constant)by determined using Measurement absorption and transmission spectra. Results showed that through the optical constants we can made to control it is wide applications as an optoelectronic devices and photovoltaic applications.
The fauna of bees (Hymenoptera, Apoidea) from different regions of Iraq is surveyed in this study; there were 16 species, 13 genera that belong to four families which are collected in this investigation.
Also, all the species that are recorded for Iraq in previous investigations are revised; totally there are 110 species, 32 genera belonging to five families: Apidae, Andernidae, Colletidae, Halictidae and Megachilidae were listed.
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The present study attempts to determine the effect of freezing for different periods on preserved bodies of fish in the laboratory to keep for the research and diagnosis of taxonomic studies and not for consumption. It also endeavors to identify the effect of freezing on some morphometric features of the preserved bodies of fishes. Planiliza abu fish were used to conduct the present study. Fish were frozen by regular freezing in the home refrigerator freezer with temperatures reaching four degrees centigrade below zero. Freezing time is distributed over four months; biometric measurements of frozen fish have been taken in these periods represented by body total length, Standard length, and Head length in centimeters using a ruler ve
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The paper presents an investigation to the flutter speed of composite wing for different ply orientation. Structurally the composite wing was idealized as a composite beam load carrying structure. Theodorsen’s expression was used to get the 2- dimension unsteady lifting force and pitching moment in the limit of incompressible flow and subsonic speed which were integrated over the wing span. A free vibration analysis was first carried out to get the natural frequencies and mode shapes .The velocity-damping (V-g) method was used to calculate the flutter speed and the flutter frequency. A wing of unmanned aerial vehicle was manufactured from woven glass and polyester resin where the flutter speed was calculated experimentally by the wind
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