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Yasir Amer Al-Jawhar Khairun N. Ramli Montadar Abas Taher Nor Shahida M. Shah Salama A. Mostafa Bashar Ahmed Khalaf 《ETRI Journal》2021,43(2):209-220
The filtered orthogonal frequency division multiplexing (F-OFDM) system has been recommended as a waveform candidate for fifth-generation (5G) communications. The suppression of out-of-band emission (OOBE) and asynchronous transmission are the distinctive features of the filtering-based waveform frameworks. Meanwhile, the high peak-to-average power ratio (PAPR) is still a challenge for the new waveform candidates. Partial transmit sequence (PTS) is an effective technique for mitigating the trend of high PAPR in multicarrier systems. In this study, the PTS technique is employed to reduce the high PAPR value of an F-OFDM system. Then, this system is compared with the OFDM system. In addition, the other related parameters such as frequency localization, bit error rate (BER), and computational complexity are evaluated and analyzed for both systems with and without PTS. The simulation results indicate that the F-OFDM based on PTS achieves higher levels of PAPR, BER, and OOBE performances compared with OFDM. Moreover, the BER performance of F-OFDM is uninfluenced by the use of the PTS technique. 相似文献
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The evolution of local strains during shear of particles of a granular material is presented in this paper. A cylindrical specimen composed of 6.5-mm spherical plastic particles was loaded under an axisymmetric triaxial loading condition. Computed tomography (CT) was used to acquire three-dimensional images of the specimen at three shearing stages. The high-resolution CT images were used to identify the 3D coordinates of 400 particles. Nine strain components (normal, shear, and rotation), rotation angles, and local dilatancy angles for particle groups were calculated, and their frequency distribution histograms are presented and discussed. It was found that there is no preferred shear direction, and the standard deviation values for shear strain components (εxy, εxz, and εyz) were almost equal for the specific test shearing stage. Shear strains as high as 25.6% were recorded for some particle groups. Furthermore, granular particle groups rotated in the 3D space with almost equal amounts of rotation strains when loaded under axisymmetric triaxial condition. Rotation strain values are very close to the corresponding shear strains. Compared to particle sliding, rotation plays a major role in the shearing resistance of granular materials. The cumulative vertical rotation angles can be as high as 38° and the horizontal rotation angles have values as high as 60°. The statistical distributions of the local dilatancy angle (ψ1) of particle groups were calculated and found to be increasing as shearing continues. The “global” dilatancy angle value is very close to the mean local ψ1 during the first stage of shearing (i.e, when global εz = ?7.3%) 相似文献
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This investigation studies the influence of two different mineral admixtures, lithium nitrate (Li) and pozzolanic glass powder (PGP) on the expansion induced by alkali-silica reaction (ASR). Four numbers of concrete prisms were produced for each concrete mix to measure the expansion resulted from the ASR according to the test method of the BS 812-123:1999. Chemical analysis was performed using X-ray spectra. Test results confirmed that Li and PGP have significantly reduced the ASR expansion. Lower calcium to silica ratio (Ca/Si) was found in concrete mix contains (PGP) because of the high amorphous reactive silica and low calcium content in PGP compared to ordinary Portland cement CEM1. Similar components and minerals phases were obtained in different concrete mixes by using XRD. 相似文献
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In this paper, we report on our experiences of using lightweight formal methods for the partial validation of natural language requirements documents. We describe our approach to checking properties of models obtained by shallow parsing of natural language requirements, and apply it to a case study based on part of a NASA specification of the Node Control Software on the International Space Station. The experience reported supports our position that it is feasible and useful to perform automated analysis of requirements expressed in natural language. Indeed, we identified a number of errors in our case study that were also independently discovered and corrected by NASA's Independent Validation and Verification Facility in a subsequent version of the same document, and others that were not discovered. The paper describes the techniques we used, the errors we found and reflects on the lessons learned. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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Bashar H. Tarabieh Loay D. Khalaf 《AEUE-International Journal of Electronics and Communications》2009,63(3):179-187
The capacity of direct sequence code division multiple access (DS-CDMA) systems is limited by multiple access interference (MAI). Commercial CDMA systems regarded MAI as additive noise and employed the matched filter detectors. This technique limits the number of users that can be supported in a DS-CDMA system and causes an increase in the bit error rates for active users in the system as the number of users increases or as the spreading factor decreases. Thus, advanced signal processing solutions for interference suppression are necessary. In this paper, we propose a new multiuser detector (MUD) detector technique and compare between its performance to other popular MUD detectors for the universal mobile telecommunications system (UMTS) physical layer. 相似文献
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