Low-complexity detectors play an essential role in massive multiple-input multiple-output (MIMO) transmissions. In this work, we discuss the perspectives of utilizing approximate message passing (AMP) algorithm to the...Low-complexity detectors play an essential role in massive multiple-input multiple-output (MIMO) transmissions. In this work, we discuss the perspectives of utilizing approximate message passing (AMP) algorithm to the detection of massive MIMO transmission. To this end, we need to efficiently reduce the divergence occurrence in AMP iterations and bridge the performance gap that AMP has from the optimum detector while making use of its advantage of low computational load. Our solution is to build a neural network to learn and optimize AMP detection with four groups of specifically designed learnable coefficients such that divergence rate and detection mean squared error (MSE) can be significantly reduced. Moreover, the proposed deep learning-based AMP has a much faster converging rate, and thus a much lower computational complexity than conventional AMP, providing an alternative solution for the massive MIMO detection. Extensive simulation experiments are provided to validate the advantages of the proposed deep learning-based AMP.展开更多
Rate Compatible Modulation(RCM)is an efficient technique for high spectral efficiency seamless transmission over highly dynamic wireless channels.However,its high decoding complexity at the receiver prevents it from b...Rate Compatible Modulation(RCM)is an efficient technique for high spectral efficiency seamless transmission over highly dynamic wireless channels.However,its high decoding complexity at the receiver prevents it from being applied in scenarios where computation resources are limited.To alleviate this problem,an RCM with variable weight sets(RCM-VWS)was presented in the literature to significantly reduce its complexity by employing weight sets of different complexities for channels at different signal-tonoise-ratio(SNR).However,RCM-VWS has to introduce an undesired feedback channel for the transmission of SNR information that is estimated at the receiver and transmitted back to the transmitter for weight set selection.To achieve a low computational complexity while avoiding feedback transmission at the same time,a novel RCM scheme with hybrid weight set(RCM-HWS)is introduced in this paper.A low complexity of decoding is allowed by gradually reducing the complexity of weight sets based on the number symbols already sent.It also avoids the feedback of SNRs since we can deduce SNRs from the number of the symbols transmitted and use a hybrid weight set we have designed.The theoretical analysisand simulation results show that the proposed scheme has the advantages of low demodulation complexity and not requiring feedback channel while maintaining the same transmission throughput as that of the conventional RCM.Therefore,the proposed scheme has a wider range of applications,especially in the case that feedback channel is not available.展开更多
Mg_(3)Sb_(2)-based thermoelectric materials have been the focus of widespread investigations as promising candidates for the harvesting of waste heat.Interface stability and service performance are key points for the ...Mg_(3)Sb_(2)-based thermoelectric materials have been the focus of widespread investigations as promising candidates for the harvesting of waste heat.Interface stability and service performance are key points for the commercial applications of these materials.We utilized Mg_(4.3)Sb_(3)Ni as a barrier layer to improve the thermal stability of Mg 3 Sb 2-based devices.However,its intrinsic high resistivity contributed nega-tively to the desired performance of the device.In this work,we investigated two other Mg-Sb-Ni ternary phases,MgSbNi and MgSbNi_(2),as new barrier layer materials to connect with Mg_(3.2)Sb_(2)Y_(0.05).The results show that the efficiency of the Mg_(1.2)SbNi/Mg_(3.2)Sb_(2)Y_(0.05)/Mg_(1.2)SbNi joint is increased by 33%relative to the higher Mg-content barriers due to lower resistivity.The system exhibited good interfacial compatibility and showed little change with aging at 673 K for 20 days.展开更多
Multimode waveguide bend is one of the key components for realizing high-density mode-division multiplexing systems on chip.However,the reported multimode waveguide bends are either large,bandwidth-limited or fabricat...Multimode waveguide bend is one of the key components for realizing high-density mode-division multiplexing systems on chip.However,the reported multimode waveguide bends are either large,bandwidth-limited or fabrication-complicated,which hinders their applications in future high-density multimode photonic circuits.Here we propose a compact multimode waveguide bend supporting four TE modes simply by shape-optimizing with transformation optics.The shape of the waveguide is optimized in the virtual space with gradient distribution of the refractive index,so that the scattering loss and intermode cross talk are well suppressed.After conformal mapping back into the physical space,a compact(effective radius of 17μm)multimode bending waveguide is obtained.Simulations show that the proposed multimode waveguide bend has little loss(<0.1 dB)and low cross talk(<−20 dB)throughout an ultrabroad wavelength range of 1.16–1.66μm.We also fabricated the shape-optimized multimode bending waveguide on a silicon-on-insulator wafer.At 1550 nm wavelength,the measured excess losses for the four lowest-order TE modes are less than 0.6 dB,and the intermode cross talks are all below−17 dB.Our study paves the way for realizing high-density and large-scale multimode integrated optical circuits for optical interconnect.展开更多
Connected-annular-rods photonic crystals(CARPCs) in both triangular and square lattices are proposed to enhance the two-dimensional complete photonic bandgap(CPBG) for chalcogenide material systems with moderate refra...Connected-annular-rods photonic crystals(CARPCs) in both triangular and square lattices are proposed to enhance the two-dimensional complete photonic bandgap(CPBG) for chalcogenide material systems with moderate refractive index contrast. For the typical chalcogenide-glass–air system with an index contrast of 2.8:1, the optimized square lattice CARPC exhibits a significantly larger normalized CPBG of about 13.50%, though the use of triangular lattice CARPC is unable to enhance the CPBG. It is almost twice as large as our previously reported result [IEEE J. Sel. Top. Quantum Electron. 22, 4900108(2016)]. Moreover, the CPBG of the square-lattice CARPC could remain until an index contrast as low as 2.24:1. The result not only favors wideband CPBG applications for index contrast systems near 2.8:1, but also makes various optical applications that are dependent on CPBG possible for more widely refractive index contrast systems.展开更多
Distribution of Paleogene lacustrine high-quality source rocks in the Bozhong sag in Bohai Bay Basin is analyzed through data of geochemistry,geology and well logging,and its differences under the control of climate a...Distribution of Paleogene lacustrine high-quality source rocks in the Bozhong sag in Bohai Bay Basin is analyzed through data of geochemistry,geology and well logging,and its differences under the control of climate and tectonics is also well discussed.Distribution characteristics of the high-quality source rocks developed in the saline environment controlled by the climate are quite different from that developed in the rapid subsidence environment controlled by tectonics.The high-quality source rocks in Member 1 of Shahejie Formation developed in the saline environment account for 81.9%of total subsag area,and are distributed widely and extensively.The high-quality source rocks in Member 3 of Shahejie Formation and Member 3 of Dongying Formation is developed in the tectonic subsidence environment,and horizontally,the subsag subsidence rates has a positive correlation with the area proportion of the high-quality source rocks in the sag;vertically,the reduction-oxidation interface of the lake controls the enrichment of highquality source rocks.Controlled by the saline environment and rapid subsidence environment,the highquality source rocks in the Bozhong sag and adjacent areas have three types of development condition:the saline water,the tectonic subsidence,and joint control of the saline water and the tectonic subsidence.The humid climate and low subsidence rate are not favorable for development of high-quality source rocks.展开更多
We present a novel method for engineering ultra-flattened-dispersion photonic crystal fibers with uniform air holes by rotations of inner air-hole rings around the fiber core.By choosing suitable rotation angles of ea...We present a novel method for engineering ultra-flattened-dispersion photonic crystal fibers with uniform air holes by rotations of inner air-hole rings around the fiber core.By choosing suitable rotation angles of each inner ring,theoretical results show that normal,anomalous,and nearly zero ultra-flattened-dispersion fibers in wide spectra ranges of interest can be obtained alternatively.Moreover,in our dispersion sensitive analysis,these types of fibers are robust to variations from optimal design parameters.The method is suitable for the accurate adjustment of fiber dispersion within a small range,which would be valuable for the fabrication of ultra-flattened-dispersion fibers and also have potential applications in wide-band high-speed optical communication systems.展开更多
Mechanical alloying （MA） and field-activated, pressure-assisted synthesis （FAPAS） were used for the in situ synthesis and densification of ultra-hard, super-abrasive AIMgB14 metallic ceramic, performed at 1500 ℃ ...Mechanical alloying （MA） and field-activated, pressure-assisted synthesis （FAPAS） were used for the in situ synthesis and densification of ultra-hard, super-abrasive AIMgB14 metallic ceramic, performed at 1500 ℃ under a pressure of 60 MPa with the elemental constituents of aluminum, magnesium, and boron. The microstructure and components of synthesized metallic ceramic were observed and determined by scanning electron microscopy （SEM）, energy dispersive X-ray analysis （EDX）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. The results showed that the main components of the samples were AIMgB14 with a few MgAI204.MgAI204 was derived from the contamination of the preliminary powders and the milling process. The average hardness of the samples that provided the results was 26.1 GPa. The average density of the samples was 2.62 g/cm^3, which is 98% of its theoretical density. The sample of AIMgB14-TiB2 composite with 30 wt% TiB2 had a hardness of 29.5 GPa, which is consistent with that of AIMgB14-TiB2 composite with 30 wt% TiB2 prepared by mechanical alloying/hot uniaxial pressing. Thus, a new approach was developed using the mechanical alloying and FAPAS process to synthesize AIMgB14 with fast heating, high efficiency, energy saving, and high yield.展开更多
The slab effective index difference between the transverse-electric(TE)and transverse-magnetic(TM)polarizations was utilized to obtain complete photonic bandgap(CPBG)in a silicon nitride(Si_(x)N_(y))photonic crystal s...The slab effective index difference between the transverse-electric(TE)and transverse-magnetic(TM)polarizations was utilized to obtain complete photonic bandgap(CPBG)in a silicon nitride(Si_(x)N_(y))photonic crystal slab.For this,coincident frequency range in the TE photonic bandgap(PBG)and TM PBG,which denotes the CPBGs of the slab,must be found with the same structure.Through adjusting the effective index pair of TE and TM polarizations by changing the thickness of the Si_(x)N_(y)core layer,and also optimizing the structure parameters within the photonic crystal plane,a large normalized CPBG of 5.62%was theoretically obtained in a slab of Si_(x)N_(y)with a refractive index of 2.5.Moreover,based on the obtained CPBG,a microcavity which could support both TE and TM polarization was theoretically demonstrated.The cavity modes for different polarizations were both well confined,which proved the reliability of the CPBG.In addition,using the same method,the lowest refractive index of Si_(x)N_(y)on silica slab for a CPBG could be extended to as low as 2.The results indicate that there is potential for development of various high-performance CPBG devices based on Si_(x)N_(y)slab technology.展开更多
基金supported by the National Natural Science Foundation of China under Grants 61801523, 61971452, and 91538203
文摘Low-complexity detectors play an essential role in massive multiple-input multiple-output (MIMO) transmissions. In this work, we discuss the perspectives of utilizing approximate message passing (AMP) algorithm to the detection of massive MIMO transmission. To this end, we need to efficiently reduce the divergence occurrence in AMP iterations and bridge the performance gap that AMP has from the optimum detector while making use of its advantage of low computational load. Our solution is to build a neural network to learn and optimize AMP detection with four groups of specifically designed learnable coefficients such that divergence rate and detection mean squared error (MSE) can be significantly reduced. Moreover, the proposed deep learning-based AMP has a much faster converging rate, and thus a much lower computational complexity than conventional AMP, providing an alternative solution for the massive MIMO detection. Extensive simulation experiments are provided to validate the advantages of the proposed deep learning-based AMP.
基金supported by the National Natural Science Foundation of China(NSFC)under Grant No.61971452 and Grant No.91538203supported by the Fundamental Research Funds for the Central Universities Grant SCUEC-CZY19038
文摘Rate Compatible Modulation(RCM)is an efficient technique for high spectral efficiency seamless transmission over highly dynamic wireless channels.However,its high decoding complexity at the receiver prevents it from being applied in scenarios where computation resources are limited.To alleviate this problem,an RCM with variable weight sets(RCM-VWS)was presented in the literature to significantly reduce its complexity by employing weight sets of different complexities for channels at different signal-tonoise-ratio(SNR).However,RCM-VWS has to introduce an undesired feedback channel for the transmission of SNR information that is estimated at the receiver and transmitted back to the transmitter for weight set selection.To achieve a low computational complexity while avoiding feedback transmission at the same time,a novel RCM scheme with hybrid weight set(RCM-HWS)is introduced in this paper.A low complexity of decoding is allowed by gradually reducing the complexity of weight sets based on the number symbols already sent.It also avoids the feedback of SNRs since we can deduce SNRs from the number of the symbols transmitted and use a hybrid weight set we have designed.The theoretical analysisand simulation results show that the proposed scheme has the advantages of low demodulation complexity and not requiring feedback channel while maintaining the same transmission throughput as that of the conventional RCM.Therefore,the proposed scheme has a wider range of applications,especially in the case that feedback channel is not available.
基金supported by the National Science Foundation of China(Grant No.52202277)the Special Project of Science and Technology Cooperation and Exchange of Shanxi Province(Grant No.202104041101007).
文摘Mg_(3)Sb_(2)-based thermoelectric materials have been the focus of widespread investigations as promising candidates for the harvesting of waste heat.Interface stability and service performance are key points for the commercial applications of these materials.We utilized Mg_(4.3)Sb_(3)Ni as a barrier layer to improve the thermal stability of Mg 3 Sb 2-based devices.However,its intrinsic high resistivity contributed nega-tively to the desired performance of the device.In this work,we investigated two other Mg-Sb-Ni ternary phases,MgSbNi and MgSbNi_(2),as new barrier layer materials to connect with Mg_(3.2)Sb_(2)Y_(0.05).The results show that the efficiency of the Mg_(1.2)SbNi/Mg_(3.2)Sb_(2)Y_(0.05)/Mg_(1.2)SbNi joint is increased by 33%relative to the higher Mg-content barriers due to lower resistivity.The system exhibited good interfacial compatibility and showed little change with aging at 673 K for 20 days.
基金National Natural Science Foundation of China(11504435,61975062)National Key Research and Development Program of China(2019YFB2205202)Innovation Fund of WNLO.
文摘Multimode waveguide bend is one of the key components for realizing high-density mode-division multiplexing systems on chip.However,the reported multimode waveguide bends are either large,bandwidth-limited or fabrication-complicated,which hinders their applications in future high-density multimode photonic circuits.Here we propose a compact multimode waveguide bend supporting four TE modes simply by shape-optimizing with transformation optics.The shape of the waveguide is optimized in the virtual space with gradient distribution of the refractive index,so that the scattering loss and intermode cross talk are well suppressed.After conformal mapping back into the physical space,a compact(effective radius of 17μm)multimode bending waveguide is obtained.Simulations show that the proposed multimode waveguide bend has little loss(<0.1 dB)and low cross talk(<−20 dB)throughout an ultrabroad wavelength range of 1.16–1.66μm.We also fabricated the shape-optimized multimode bending waveguide on a silicon-on-insulator wafer.At 1550 nm wavelength,the measured excess losses for the four lowest-order TE modes are less than 0.6 dB,and the intermode cross talks are all below−17 dB.Our study paves the way for realizing high-density and large-scale multimode integrated optical circuits for optical interconnect.
基金National Natural Science Foundation of China(NSFC)(11504435,11147014)Natural Science Foundation of Hubei Province,China(2013CFA052)+1 种基金King Abdullah University of Science and Technology(KAUST)(Baseline BAS/1/1664-01-01)Fundamental Research Funds for the Central Universities,South-Central University for Nationalities,China(CZY18001)
文摘Connected-annular-rods photonic crystals(CARPCs) in both triangular and square lattices are proposed to enhance the two-dimensional complete photonic bandgap(CPBG) for chalcogenide material systems with moderate refractive index contrast. For the typical chalcogenide-glass–air system with an index contrast of 2.8:1, the optimized square lattice CARPC exhibits a significantly larger normalized CPBG of about 13.50%, though the use of triangular lattice CARPC is unable to enhance the CPBG. It is almost twice as large as our previously reported result [IEEE J. Sel. Top. Quantum Electron. 22, 4900108(2016)]. Moreover, the CPBG of the square-lattice CARPC could remain until an index contrast as low as 2.24:1. The result not only favors wideband CPBG applications for index contrast systems near 2.8:1, but also makes various optical applications that are dependent on CPBG possible for more widely refractive index contrast systems.
基金supported by the National Science and Technology Major Project of China(No.2016ZX05024-002).
文摘Distribution of Paleogene lacustrine high-quality source rocks in the Bozhong sag in Bohai Bay Basin is analyzed through data of geochemistry,geology and well logging,and its differences under the control of climate and tectonics is also well discussed.Distribution characteristics of the high-quality source rocks developed in the saline environment controlled by the climate are quite different from that developed in the rapid subsidence environment controlled by tectonics.The high-quality source rocks in Member 1 of Shahejie Formation developed in the saline environment account for 81.9%of total subsag area,and are distributed widely and extensively.The high-quality source rocks in Member 3 of Shahejie Formation and Member 3 of Dongying Formation is developed in the tectonic subsidence environment,and horizontally,the subsag subsidence rates has a positive correlation with the area proportion of the high-quality source rocks in the sag;vertically,the reduction-oxidation interface of the lake controls the enrichment of highquality source rocks.Controlled by the saline environment and rapid subsidence environment,the highquality source rocks in the Bozhong sag and adjacent areas have three types of development condition:the saline water,the tectonic subsidence,and joint control of the saline water and the tectonic subsidence.The humid climate and low subsidence rate are not favorable for development of high-quality source rocks.
基金This work is supported by the National Natural Science Foundation of China under grant nos.11147014,61002013,and 11074082the Natural Science Foundation of Hubei Province under grant no.2013CFA052also partly by the open fund of Hubei Key Laboratory of Intelligent Wireless Communications under grant no.IWC2012009.
文摘We present a novel method for engineering ultra-flattened-dispersion photonic crystal fibers with uniform air holes by rotations of inner air-hole rings around the fiber core.By choosing suitable rotation angles of each inner ring,theoretical results show that normal,anomalous,and nearly zero ultra-flattened-dispersion fibers in wide spectra ranges of interest can be obtained alternatively.Moreover,in our dispersion sensitive analysis,these types of fibers are robust to variations from optimal design parameters.The method is suitable for the accurate adjustment of fiber dispersion within a small range,which would be valuable for the fabrication of ultra-flattened-dispersion fibers and also have potential applications in wide-band high-speed optical communication systems.
基金financially supported by the National Natural Science Foundation of China (No. 50975190, 51101111)
文摘Mechanical alloying （MA） and field-activated, pressure-assisted synthesis （FAPAS） were used for the in situ synthesis and densification of ultra-hard, super-abrasive AIMgB14 metallic ceramic, performed at 1500 ℃ under a pressure of 60 MPa with the elemental constituents of aluminum, magnesium, and boron. The microstructure and components of synthesized metallic ceramic were observed and determined by scanning electron microscopy （SEM）, energy dispersive X-ray analysis （EDX）, X-ray diffraction （XRD）, and transmission electron microscopy （TEM）. The results showed that the main components of the samples were AIMgB14 with a few MgAI204.MgAI204 was derived from the contamination of the preliminary powders and the milling process. The average hardness of the samples that provided the results was 26.1 GPa. The average density of the samples was 2.62 g/cm^3, which is 98% of its theoretical density. The sample of AIMgB14-TiB2 composite with 30 wt% TiB2 had a hardness of 29.5 GPa, which is consistent with that of AIMgB14-TiB2 composite with 30 wt% TiB2 prepared by mechanical alloying/hot uniaxial pressing. Thus, a new approach was developed using the mechanical alloying and FAPAS process to synthesize AIMgB14 with fast heating, high efficiency, energy saving, and high yield.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.11504435 and 62171478)the Natural Science Foundation of Hubei Province,China(No.2020CFB450).
文摘The slab effective index difference between the transverse-electric(TE)and transverse-magnetic(TM)polarizations was utilized to obtain complete photonic bandgap(CPBG)in a silicon nitride(Si_(x)N_(y))photonic crystal slab.For this,coincident frequency range in the TE photonic bandgap(PBG)and TM PBG,which denotes the CPBGs of the slab,must be found with the same structure.Through adjusting the effective index pair of TE and TM polarizations by changing the thickness of the Si_(x)N_(y)core layer,and also optimizing the structure parameters within the photonic crystal plane,a large normalized CPBG of 5.62%was theoretically obtained in a slab of Si_(x)N_(y)with a refractive index of 2.5.Moreover,based on the obtained CPBG,a microcavity which could support both TE and TM polarization was theoretically demonstrated.The cavity modes for different polarizations were both well confined,which proved the reliability of the CPBG.In addition,using the same method,the lowest refractive index of Si_(x)N_(y)on silica slab for a CPBG could be extended to as low as 2.The results indicate that there is potential for development of various high-performance CPBG devices based on Si_(x)N_(y)slab technology.
