排序方式: 共有62条查询结果,搜索用时 15 毫秒
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M. Hasbullah Mazlan Mehran Behjati Rosdiadee Nordin Mahamod Ismail 《Telecommunication Systems》2018,67(3):387-399
One of the challenges in massive-MIMO system is pilot contamination during the channel estimation process. Pilot contamination can cause error or inaccurate channel estimation process for future fifth generation (5G) downlink transmissions. This paper considers using a Wiener-based filter to smooth and predict the channel estimation to reduce the pilot contamination for more accurate CSI during channel estimation. The simulation results show that the Wiener-based smoothing and predicting technique reduces the effect of pilot contamination and increases the accuracy of CSI during channel estimation process. Wiener smoother (WS) is implemented based on Wiener-based filtering technique. The previous estimated CSI and weight coefficient vector are used to smooth the current estimated CSI by using block data formulation to reduce the effect of pilot contamination. However, WS technique suffers from pilot contamination due to pilot training. This motivates the development of two Wiener predictors (WP), known as WP1 and WP2. The WP1 and WP2 run a prediction technique for CSI and number of pilot training during the prediction period, which is missing from the original WS. Comparison results show that the proposed WS and WP outperforms the conventional minimum mean square error and least square, in terms of channel estimation error and per-cell rate. WP2 perform better than WS and WP1 because of the algorithm complexity that required more information to be updated, stored and processed for prediction. Thus, WP2 requires large computation and matrix operation compared to WS and WP1. The results indicate that the channel estimation error due to pilot contamination can be reduced by using the Wiener-based approaches. 相似文献
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Ali Shokuhi Rad Saeed Ghasemi Ateni Habib-allah Tayebi Peiman Valipour Vahid Pouralijan Foukolaei 《Journal of Sulfur Chemistry》2016,37(6):622-631
Interaction of SOx (x?=?2,3) molecules on active sites of dianiline (as a model for polyaniline, denoted here as 2PANI) was studied using density functional theory at the BLYP-D/6-31+G(d) level of theory. Natural population analysis was used to find out the charge distribution as well as the net transferred charge of SOx upon adsorption on 2PANI and the result has been compared with Mulliken charge analysis to evaluate the sensing ability of 2PANI. The computed density of states point to the remarkable orbital hybridization between SOx and 2PANI during the adsorption process. As a consequence, the results of UV–VIS confirm the sensing ability of 2PANI toward SO2 and SO3. Based on our results, it can be found that at proper configuration the SO2 and SO3 molecules can be adsorbed on 2PANI with adsorption energies (Eads) of ?18.2 and ?62.9?kJ/mol (BSSE), respectively. 相似文献
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The static and dynamic coefficient of friction between two flat surfaces at elevated temperature is under investigation. The equipment used in this study was originally designed for the precision glass molding (PGM) process and was then modified for friction measurement. The ultimate aim of this research is to study and characterize the frictional behavior between glass and a mold surface at elevated temperatures typical of the PGM process and under conditions similar to those for this process. This paper describes the design of the apparatus, and validation experiments using a steel-steel material pair at room temperature for comparison with values reported in the literature. The average friction coefficient between the steel-steel pair was found to be 0.17. Subsequent experiments using steel against steel and BK-7 glass against steel, found the stick-slip phenomena is happening at 577 °C. 相似文献
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Sasan Khalaj Amineh Alireza Fadaei Tehrani Peiman Mosaddegh Aminollah Mohammadi 《Materials and Manufacturing Processes》2015,30(1):93-98
In this paper, a new noncontact ultrasonic magnetic abrasive finishing mechanism is presented. An ultrasonic vibration producer is used to vibrate the permanent magnets. The ferromagnetic steel grits in the created magnetic field form a flexible finishing tool. To take advantage of cavitation collapse pressure, the finishing zone components are immersed in water. The present work also studies the effect of parameters, i.e., time duration for finishing and working gap between magnetic poles and the workpiece on the surface roughness (Ra). The microscopic pictures and the roughness profile diagrams demonstrate the advantages of the proposed method. 相似文献
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In this paper, we propose new universal designs of ternary-valued logic (TVL) with high-speed, low-power and full swing output using carbon nanotube FETs (CNTFETs). All of the TVL functions (39 functions) can be implemented in these designs. Ternary value logic is a promising alternative to binary logic due to the reduced integrated circuit (IC) interconnects and chip area. Therefore, a universal design of TVL is a good direction for the future of FPGA design using CNTFET. In this paper, new universal designs of ternary-valued logic based on CNTFETs are proposed and compared with the existing resistive-load CNTFET universal TVL designs. Extensive simulations have been performed in HSPICE to investigate the distribution of power consumption and the delay of the CNTFET-based universal cells due to variations in the supply voltage, the diameter of the CNT, and the room temperature. Simulation results show that the proposed universal TVL designs result in significantly lower power consumption and delay compared with previous resistive-load CNTFET universal TVL implementations. 相似文献
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Peiman Aliparast Nasser Nasirzadeh 《Analog Integrated Circuits and Signal Processing》2009,60(3):195-204
In this paper a 10-bit 1.2-GSample/s Nyquist current-steering CMOS digital-to-analog converter (DAC) is presented. Segmentation
(90%) has been used to get the best DNL and reduce glitch energy. This segmentation ratio guarantees the monotonicity. Higher
performance is achieved using a novel 3-D thermometer decoding method which reduces the area, power consumption, and the number
of control signals of the digital section. Simulation results show that the spurious-free-dynamic-range (SFDR) in Nyquist
rate is better than 65 dB for sampling frequency up to 1.2-GSample/s. The analog voltage supply is 3.3 V while the digital
part of the chip operates at only 2.4 V. Total power consumption in Nyquist rate measurement is 149 mW. The chip has been
processed in a standard 0.35 μm CMOS technology. Active area of chip is 1.97 mm2. 相似文献
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Jannesari Mohammad Mosaddegh Peiman Kadkhodaei Mahmoud Kasprzak Henryk Jabbarvand Behrouz Mahmoud 《Mechanics of Time-Dependent Materials》2019,23(3):373-384
Mechanics of Time-Dependent Materials - Non-contact tonometers, including ORA and Corvis ST, are not only used to estimate intraocular pressure (IOP) in clinical surveys but are also utilized to... 相似文献