ISSN: 2250-3005 - ijcer

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International Journal Of Computational Engineering Research (ijceronline.com) Vol. 2 Issue. 8The HT12E encoder begins a 4-word transmission cycle upon receipt of a transmission enable (active low). Thiscycle will repeat itself as long as the transmission enable is held low. Once the transmission enable returns high, the encoderoutput completes its final cycle and then stops.The encoded data is transmitted through the RF transmitter i.e. ST-Tx01 receiver module.3.2 Receiver ModuleThe transmitted data is received through the ST-Rx04 receiver module and then it is given to the power sensingunit for detection RF signal.The received RF power is converted in voltage output using IC AD8318.The AD8318 is a demodulating logarithmic amplifier, capable of accurately converting an RF input signal to acorresponding decibel-scaled output voltage. It employs the progressive compression technique over a cascaded amplifierchain, each stage of which is equipped with a detector cell. The AD8318 maintains accurate log conformance for signals of1 MHz to 6 GHz and provides useful operation to 8 GHz. The input range is typically 60 dB (re: 50 Ω) with error less than±1 dB. The AD8318 is specified for operation up to 8 GHz. As a result, low impedance supply pins with adequate isolationbetween functions are essential. In the AD8318, VPSI and VPSO, the two positive supply pins, must be connected to thesame positive potential. The VPSI pin biases the input circuitry, while the VPSO pin biases the low noise output driver forVOUT. Separate commons are also included in the device. CMOP is used as the common for the output drivers. Pin CMIPand Pin CMOP should be connected to a low impedance ground plane.This voltage output is given for analog to digital conversion to the IC 7887 which is a 12-bit ADC.This digital data is given to the SPI to serial converter. Then, the data is serially transmitted to the FPGA platform.The double threshold energy detection algorithm is developed on the FPGA platform to reduce the collisionprobability between the primary user and femtocell user.The simulation result will be analyzed to see the improvement in the collision probability.4. CONCLUSIONThe review of cognitive femtocell network can be concluded as follows:- Cognitive radio is a solution for spectral crowding problem. It introduces the opportunistic usage of frequencybands that are not heavily occupied by licensed users. Cognitive radio can be incorporated in femtocell networks to solve the indoor coverage problem and to improve thesystem performance. The cognitive femtocells can achieve almost twice average capacity than the coloring method. Co-channel interference can be reduced significantly by using cognitive radio in femtocell networks. It will be interesting to see how the double threshold energy detection algorithm is useful in significantly reducingthe collision probability.REFERENCES[1] J.Xiang, Y.Zhang, T.Skeie, L.Xie, “Downlink spectrum sharing for cognitive radio femtocell networks”, IEEEsystems journal, Vol.4, No.4, Dec 10.[2] Akyildiz IF, Lee W, Vuran MC, Mohanty S. “Next generation/dynamic spectrum access/cognitive radio wirelessnetworks: a survey”. Int J Comput Telecommun Network 2006: 2127-59.[3] C.Stevenson, G.Chouinard, Z. Lei, W.Hu, S.Shellhammer, W.Caldwell, “IEEE 802.22: The First Cognitive RadioWireless Regional Area Network Standard”, IEEE communications magazine, Jan.09.[4] C.Sun, Y.Alemseged, H.Tran and H.Harada, “Cognitive Radio Sensing Architecture and A Sensor Selection CaseStudy”, IEEE communications magazine, 2009.[5] J.Wu, T.Luo, G.Yue, “An Energy Detection Algorithm Based on Double-threshold in Cognitive Radio Systems”,ICISE, 09.[6] V.Chandrasekhar, J.Andrews, A.Gatherer, “Femtocell networks: A survey”, IEEE communications magazine,Sept.08[7] Lamiaa Khalid, Alagan Anpalagan, “Emerging cognitive radio technology: Principles, challenges and opportunities”:2009: 358-366.||Issn 2250-3005(online)|| ||December||2012|| Page 161
International Journal Of Computational Engineering Research (ijceronline.com) Vol. 2 Issue. 8Exergy Requirements for the Manufacturing of Carbon NanotubesRenish M vekariya 1 , Rakesh P Ravani 21. HOD, A.I.E.T, MECH Dept., Rajkot-GJ, India,2. Lec.VVP, MECH, Rajkot-GJ, India,AbstractThe purpose of this paper is to address both the high values, and the large variation in reported values for the energyrequirements for the production of carbon nano tubes. The paper includes an estimate of the standard chemical exergy for singlewalled carbon nano tubes, as well as a historical look at how the minimum physical flow exergy improved as the HiPco processdeveloped.Keywords— Carbon Nanotubes, Exergy Analysis, SWNTI. IntroductionEarly estimates by Isaacs et al [1] indicated the potentially very large value of the specific energy requirements forcarbon single walled nano tubes (SWNT). More recently, energy estimates have been performed for a variety of carbon fibers(SWNTs, multiwall carbon nano tubes – MWNT, and carbon fibers) and a variety of manufacturing processes (Arc, CVD andHiPco) [2]–[6]. These studies show considerable variation in energy estimates (as much as 3 orders of magnitude), and almosttwo orders of magnitude variation between nominally identical processes. In this paper we review the available data and then lookfurther into the so called HiPco process, (for high pressure carbon mono xide process) [7]-[9] to attempt to explain the largevariation in specific energy requirements.II. Data SummaryIn Table 1 we summarize data for various carbon nanofiber production methods (synthesis only) from the literature [1 -4]. The Synthesis Reaction Carbon Yield (SRCY) is the amount of process carbon needed to produce carbon nano tubes/fibers. Itis based upon the flow rates of the process carbon and the carbon product output. Note that these values differ by almost threeorders of magnitude, while the specific electrical energy estimates for the synthesis reaction differ by more than three orders ofmagnitude. The purification step after synthesis may add up to 50% more to the value given in column four [2].Note: further that estimates for the HiPco process vary by almost two orders of magnitude. We will show that this variation is duein part to the changing nature of the HiPco process as it has been improved. Further, important details of the process are notgenerally available, and important assumptions in various analyses may differ, and in some cases are not reported.TABLE 1Results From The Literature For The Specific Work Input In The Form Of Electrical Energy Per Mass For The ProductionSynthesis Process For Carbon Nano-Tubes And Fibers.Process/Product Source SRCY1 GJ/kg2 Ref.HiPco/SWNT CO 50% 465.8 [1]HiPco/SWNT CO 0.08% 31.8 [2]HiPco/SWNT CO NA 5.8 [3]Arc/SWNT Carbon Anode 4.5% 458.7 [1]Arc/SWNT Carbon Anode 4.5% 83.7 [2]CVD/SWNT [ CH4 2.95% 915.8 [1]III. Standard Chemical Exergy Of SwntThe specific standard chemical exergy of a chemical compound is the minimum (reversible) work per mass to producethis component starting from the identified chemical components of the reference environment at the “dead state”. For theproduction of SWNTs the process would start from the carbon stored in the atmosphere as CO2 gas and include the followingsteps; 1) the concentrating of the CO2 from its reference concentration in the atmosphere to pure, 2) the reduction of CO2 intoits chemical constituents, carbon graphite) and oxygen,||Issn 2250-3005(online)|| ||December||2012 Page 162
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