Blazars are characterized by large intensity and spectral variations across the electromagnetic spectrum It is believed that jets emerging from them are almost aligned with the line-of-sight. The major- ity of identif...Blazars are characterized by large intensity and spectral variations across the electromagnetic spectrum It is believed that jets emerging from them are almost aligned with the line-of-sight. The major- ity of identified extragalactic sources in γ-ray catalogs of EGRET and Fermi are blazars. Observationally, blazars can be divided into two classes： fiat spectrum radio quasars （FSRQs） and BL Lacs. BL Lacs usually exhibit lower γ-ray luminosity and harder power law spectra at γ-ray energies than FSRQs. We attempt to explain the high energy properties of FSRQs and BL Lacs from Fermi γ-ray space telescope observations. It was argued previously that the difference in accretion rates is mainly responsible for the large mismatch in observed luminosity in ＂7-ray. However, when intrinsic luminosities are derived by correcting for beaming effects, this difference in 7-ray luminosity between the two classes is significantly reduced. In order to ex- plain this difference in intrinsic luminosities, we propose that spin plays an important role in the luminosity distribution dichotomy of BL Lacs and FSRQs. As the outflow power of a blazar increases with increasing spin of a central black hole, we suggest that the spin plays a crucial role in making BL Lac sources low luminous and slow rotators compared to FSRQ sources.展开更多
The forming mechanism of hole flanging on a thick-wall heavy cylinder forging is simulated by DEFORM3D. The cylinder is 4 390 mm in diameter and 390 mm in thickness. The results show that the compound deformation with...The forming mechanism of hole flanging on a thick-wall heavy cylinder forging is simulated by DEFORM3D. The cylinder is 4 390 mm in diameter and 390 mm in thickness. The results show that the compound deformation with bending and expanding happens in the process of hole flanging. The diameter of pre-hole of the workpiece is one of the key parameters in the process of hole flanging. The optimal diameter is obtained for reverse-conical hole of average diameter 40 mm by simulation of hole flanging process on 5 pre-holes with different diameters and 3 pre-holes with different shapes. The results can provide the scientific base for engineering application of the process.展开更多
In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and pro...In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and process with computer graphics parameters design. The results that, as long as the appropriate parameters, using the above method not only can punch the square hole, can also be processed triangle, the five angle and hexagonal regular polygon holes. The square hole processing method can provide theoretical basis and engineering reliable reference for related engineering and technical personnel.展开更多
The increase in user mobility and density in modern cellular networks increases the risk of overloading certain base stations in popular locations such as shopping malls or stadiums,which can result in connection loss...The increase in user mobility and density in modern cellular networks increases the risk of overloading certain base stations in popular locations such as shopping malls or stadiums,which can result in connection loss for some users.To combat this,the traffic load of base stations should be kept as balanced as possible.In this paper,we propose an efficient load balancing-aware handover algorithm for highly dynamic beyond 5G heterogeneous networks by assigning mobile users to base stations with lighter loads when a handover is performed.The proposed algorithm is evaluated in a scenario with users having different levels of mobility,such as pedestrians and vehicles,and is shown to outperform the conventional handover mechanism,as well as another algorithm from the literature.As a secondary benefit,the overall energy consumption in the network is shown to be reduced with the proposed algorithm.展开更多
The joint adoption of sub-6GHz and millimeter wave(mmWave)technology can prevent the blind spots of coverage,enabling comprehensive coverage while realizing high-speed communication rate.According to the sensitivity o...The joint adoption of sub-6GHz and millimeter wave(mmWave)technology can prevent the blind spots of coverage,enabling comprehensive coverage while realizing high-speed communication rate.According to the sensitivity of mmWave,base stations should be more densely deployed,which is not well described by existing Poisson hole process(PHP)and the Poisson point process(PPP)models.This paper establishes a sub-6GHz and mmWave hybrid heterogeneous cellular network based on the modified Poisson hole process(MPHP).In our proposed model,the sub-6GHz base stations follow the PPP,and the mmWave base stations(MBSs)follow MPHP distribution.The expressions of the coverage probability are derived by using the interference calculation method of integrating the nearest sector exclusion area.Our theoretical analysis has been verified through simulation results,suggesting that the increase in the cell radius decreases the coverage probability of signal-to-interference-plus-noise ratio(SINR),whereas the increase in the sector parameter has the opposite effect.The variation of sub-6GHz base stations(SBSs)density imposes more significant impact than the MBSs on the SINR coverage probability.In addition,the decrease in MBSs density will reduce the average bandwidth allocated to the user equipment(UE),thus reducing the rate coverage probability.展开更多
基金partially supported by projects SB/S2HEP-001/2013funded by DST(DB)+1 种基金ISRO/RES/2/367/10-11funded by ISRO,India
文摘Blazars are characterized by large intensity and spectral variations across the electromagnetic spectrum It is believed that jets emerging from them are almost aligned with the line-of-sight. The major- ity of identified extragalactic sources in γ-ray catalogs of EGRET and Fermi are blazars. Observationally, blazars can be divided into two classes： fiat spectrum radio quasars （FSRQs） and BL Lacs. BL Lacs usually exhibit lower γ-ray luminosity and harder power law spectra at γ-ray energies than FSRQs. We attempt to explain the high energy properties of FSRQs and BL Lacs from Fermi γ-ray space telescope observations. It was argued previously that the difference in accretion rates is mainly responsible for the large mismatch in observed luminosity in ＂7-ray. However, when intrinsic luminosities are derived by correcting for beaming effects, this difference in 7-ray luminosity between the two classes is significantly reduced. In order to ex- plain this difference in intrinsic luminosities, we propose that spin plays an important role in the luminosity distribution dichotomy of BL Lacs and FSRQs. As the outflow power of a blazar increases with increasing spin of a central black hole, we suggest that the spin plays a crucial role in making BL Lac sources low luminous and slow rotators compared to FSRQ sources.
文摘The forming mechanism of hole flanging on a thick-wall heavy cylinder forging is simulated by DEFORM3D. The cylinder is 4 390 mm in diameter and 390 mm in thickness. The results show that the compound deformation with bending and expanding happens in the process of hole flanging. The diameter of pre-hole of the workpiece is one of the key parameters in the process of hole flanging. The optimal diameter is obtained for reverse-conical hole of average diameter 40 mm by simulation of hole flanging process on 5 pre-holes with different diameters and 3 pre-holes with different shapes. The results can provide the scientific base for engineering application of the process.
文摘In order to meet the rapid needs of processing square hole in mechanical equipment, the paper expounds the square hole processing method： planetary wheel method, and analyze the principle of tooling structure and process with computer graphics parameters design. The results that, as long as the appropriate parameters, using the above method not only can punch the square hole, can also be processed triangle, the five angle and hexagonal regular polygon holes. The square hole processing method can provide theoretical basis and engineering reliable reference for related engineering and technical personnel.
基金supported in part by the Istanbul Technical University Scientific Research Projects Coordination Unit under Grant FHD-2024-45764in part by TUBITAK 1515 Frontier R&D Laboratories Support Program for Turkcell 6GEN LAB under Grant 5229902Turkcell Technology R&D Center(Law no.5746)has partially supported this study。
文摘The increase in user mobility and density in modern cellular networks increases the risk of overloading certain base stations in popular locations such as shopping malls or stadiums,which can result in connection loss for some users.To combat this,the traffic load of base stations should be kept as balanced as possible.In this paper,we propose an efficient load balancing-aware handover algorithm for highly dynamic beyond 5G heterogeneous networks by assigning mobile users to base stations with lighter loads when a handover is performed.The proposed algorithm is evaluated in a scenario with users having different levels of mobility,such as pedestrians and vehicles,and is shown to outperform the conventional handover mechanism,as well as another algorithm from the literature.As a secondary benefit,the overall energy consumption in the network is shown to be reduced with the proposed algorithm.
基金supported in part by the National Key R&D Program of China(2018YFE0100500)by the National Natural Science Foundation of China(61871387,61861041,and 62171354)by the Natural Science Basic Research Program of Shaanxi(2019JM-019).
文摘The joint adoption of sub-6GHz and millimeter wave(mmWave)technology can prevent the blind spots of coverage,enabling comprehensive coverage while realizing high-speed communication rate.According to the sensitivity of mmWave,base stations should be more densely deployed,which is not well described by existing Poisson hole process(PHP)and the Poisson point process(PPP)models.This paper establishes a sub-6GHz and mmWave hybrid heterogeneous cellular network based on the modified Poisson hole process(MPHP).In our proposed model,the sub-6GHz base stations follow the PPP,and the mmWave base stations(MBSs)follow MPHP distribution.The expressions of the coverage probability are derived by using the interference calculation method of integrating the nearest sector exclusion area.Our theoretical analysis has been verified through simulation results,suggesting that the increase in the cell radius decreases the coverage probability of signal-to-interference-plus-noise ratio(SINR),whereas the increase in the sector parameter has the opposite effect.The variation of sub-6GHz base stations(SBSs)density imposes more significant impact than the MBSs on the SINR coverage probability.In addition,the decrease in MBSs density will reduce the average bandwidth allocated to the user equipment(UE),thus reducing the rate coverage probability.
