Error Probability Analysis for Ultra-Massive MIMO System and Near-Optimal Signal Detection

In this paper,average bit error probability(ABEP)bound of optimal maximum likelihood(ML)detector is first derived for ultra massive(UM)multiple-input-multiple-output(MIMO)system with generalized amplitude phase modulation(APM),which is confirmed by simulation results.Furthermore,a minimum residual criterion(MRC)based lowcomplexity near-optimal ML detector is proposed for UM-MIMO system.Specifically,we first obtain an initial estimated signal by a conventional detector,i.e.,matched filter(MF),or minimum mean square error(MMSE)and so on.Furthermore,MRC based error correction mechanism(ECM)is proposed to correct the erroneous symbol encountered in the initial result.Simulation results are shown that the performance of the proposed MRC-ECM based detector is capable of approaching theoretical ABEP of ML,despite only imposing a slightly higher complexity than that of the initial detector.

A Unified Bit-to-Symbol Mapping for Generalized Constellation Modulation

Gray mapping is a well-known way to improve the performance of regular constellation modulation,but it is challenging to be applied directly for irregular alternative.To address this issue,in this paper,a unified bit-to-symbol mapping method is designed for generalized constellation modulation(i.e.,regular and irregular shaping).The objective of the proposed approach is to minimize the average bit error probability by reducing the hamming distance(HD)of symbols with larger values of pairwise error probability.Simulation results show that the conventional constellation modulation(i.e.,phase shift keying and quadrature amplitude modulation(QAM)with the proposed mapping rule yield the same performance as that of classical gray mapping.Moreover,the recently developed golden angle modulation(GAM)with the proposed mapping method is capable of providing around1 d B gain over the conventional mapping counterpart and offers comparable performance to QAM with Gray mapping.

Performance Analysis for Orthogonal Time Frequency Space Modulation Systems with Generalized Waveform

Orthogonal time-frequency space(OTFS),which exhibits beneficial advantages in high-mobility scenarios,has been considered as a promising technology in future wireless communication systems.In this paper,a universal model for OTFS systems with generalized waveform has been developed.Furthermore,the average bit error probability(ABEP)upper bounds of the optimal maximum likelihood(ML)detector are first derived for OTFS systems with generalized waveforms.Specifically,for OTFS systems with the ideal waveform,we elicit the ABEP bound by recombining the transmitted signal and the received signal.For OTFS systems with practical waveforms,a universal ABEP upper bound expression is derived using moment-generating function(MGF),which is further extended to MIMO-OTFS systems.Numerical results validate that our theoretical ABEP upper bounds are concur with the simulation performance achieved by ML detectors.

Stellate scar sign of renal cell carcinoma

Stellate scar sign is defined as the centrally-placed,welldefined,stellate area of low density on computed tomography(CT)appearance of solid tumors.This kind of radiating enhancement from the center of the tumor,which is also referred as“a spoke-wheel-like enhancement”or central scar sign,usually has been recognized as a specific finding of renal oncocytoma.We describe a patient who developed clear cell renal cell carcinoma(RCC)displaying typical stellate scar sign on CT scans,which was confirmed by gross pathologic appearance.

Synthesis and characterization of an amphiphilic chitosan bearing octyl and methoxy polyethylene

An amphiphilic N-octyl-O-methoxy poly (ethylene glycol) chitosan was successfully prepared by grafting successively octyl groups onto amino groups at chitosan’s C-2 position as hydrophobic moieties and methoxy polyethylene glycol (MPEG) groups onto hydroxyl groups at C-6, C-3 as hy-drophilic ones. A certain amount of -NH2 was retained in the structure of chitosan derivatives through protection by phthalic anhydride. The chemical structures and degree of N-and O-substitution of chitosan derivatives were characterized by FTIR, 1H NMR, GPC and elemental analysis, respectively. The amphiphilic property for convenient self-assembly and the preserved -NH2 groups for progressive chemical cross-linking make the resultant Nocyl-O-MPEG chitosan soluble in water and potentially applicable in preparing stable chitosan hollow microspheres, a demanding drug-carrier in medical and pharmaceutical sciences.

High toughness and CMAS resistance of REAlO_(3)/RE_(2)Zr_(2)O_(7)(RE=La,Nd,Sm,Eu,Gd,and Dy)composites with eutectic composition for thermal barrier coatings

Although rare earth zirconates(RE_(2)Zr_(2)O_(7))have garnered attention as viable candidates for thermal barrier coatings(TBCs),they suffer from low fracture toughness and accelerated calcium–magnesium–alumina–silicate(CMAS)melt corrosion at high service temperatures,which impedes their practical application.In this work,we developed a series of REAlO_(3)/RE_(2)Zr_(2)O_(7)(RE=La,Nd,Sm,Eu,Gd,and Dy)composites with a eutectic composition that not only significantly enhanced the fracture toughness by more than 40%relative to that of RE_(2)Zr_(2)O_(7)but also exhibited improved resistance to CMAS corrosion.The increase in toughness arises from multiple mechanisms,such as ferroelastic toughening,fine-grain strengthening,and residual stress toughening,all of which trigger more crack defects and energy consumption.Additionally,the CMAS penetration depth of the REAlO_(3)/RE_(2)Zr_(2)O_(7)composites is approximately 36%lower than that of RE_(2)Zr_(2)O_(7).Al–O constituents in composites can capture CaO,SiO_(2),and MgO in CMAS melts and increase their viscosity,resulting in enhanced CMAS corrosion resistance.The thermophysical properties of the REAlO_(3)/RE_(2)Zr_(2)O_(7)composites were also investigated,and their coefficient of thermal expansion and thermal conductivity are comparable to those of 7–8 wt%Y_(2)O_(3)partially stabilized ZrO2(YSZ),indicating their potential as TBC materials.

Synthesis of amorphous Pd-based nanocatalysts for efficient alcoholysis of styrene oxide and electrochemical hydrogen evolution

Amorphous nanomaterials with long-range disordered structures could possess distinct properties and promising applications,especially in catalysis,as compared with their conventional crystalline counterparts.It is imperative to achieve the controlled preparation of amorphous noble metal-based nanomaterials for the exploration of their phase-dependent applications.Here,we report a facile wet-chemical reduction strategy to synthesize various amorphous multimetallic Pd-based nanomaterials,including PdRu,PdRh,and PdRuRh.The phase-dependent catalytic performances of distinct Pd-based nanomaterials towards diverse catalytic applications have been demonstrated.Specifically,the usage of PdRu nanocatalysts with amorphous and crystalline face-centered cubic(fcc)phases can efficiently switch the ring-opening route of styrene oxide to obtain different products with high selectivity through alcoholysis reaction and hydrogenation reaction,respectively.Moreover,when used as an electrocatalyst for hydrogen evolution reaction(HER),the synthesized amorphous PdRh nanocatalyst exhibits low overpotential and high turnover frequency values,outperforming its crystalline fcc counterpart and most of the reported Pd-based HER electrocatalysts.

Digital-to-analog converter free architecture for digital reconfigurable intelligent surface

This research investigates the digital-to-analog converter(DAC)free architecture for the digital reconfigurable intelligent surface(RIS)system,where the transmission lines are implemented for reflection coefficient(RC)control to reduce power consumption.In the proposed architecture,the radio frequency(RF)switch based phase shifter is considered.By using a single-pole four-throw(SP4T)switch to simultaneously control the RCs of a group of elements,a 2-bit phase shifter is realized for passive beam steering.A novel modulation scheme is developed to explore the cost effectiveness,which approaches the performance of traditional quadrature amplitude modulation(QAM).Specifically,to overcome the limitation of the phase shift bits,joint frequency-shift and phase-rotation operations are applied to the constellation points.The simulation and experimental results demonstrate that the proposed architecture is capable of providing an ideal transmission performance.Moreover,64-and 256-QAM modulation schemes could be implemented by expanding the elements and phase bits.

Efficient signal detector design for OTFS with index modulation

In this paper,efficient signal detectors are designed for Orthogonal Time Frequency Space(OTFS)modulation with Index Modulation(IM)systems.Firstly,the Minimum Mean Squared Error(MMSE)based linear equalizer and its corresponding soft-aided decision are studied for OTFS-IM.To further improve the performance,a Vectorby-Vector-aided Message Passing(VV-MP)detector and its associated soft-decision are proposed,where each IM symbol is considered an entire vector utilized for message calculation and passing.Simulation results are shown that the OTFS-IM system relying on the proposed detectors is capable of providing considerable Bit Error Rate(BER)performance gains over the OTFS and Orthogonal Frequency Division Multiplex(OFDM)with IM systems.

Crystalline boron nitride nanosheets by sonication-assisted hydrothermal exfoliation

A simple method to prepare two-dimensional hexagonal boron nitride(h-BN) scalably is essential for practical applications. Despite intense research in this area, high-yield production of two-dimensional h-BN with large size and high crystallinity is still a key challenge. In the present work, we propose a simple exfoliation process for boron nitride nanosheets(BNNSs) with high crystallinity by sonication-assisted hydrothermal method, via the synergistic effect of the high pressure, and cavitation of the sonication. Compared with the method only by sonication, the sonication-assisted hydrothermal method can get the fewer-layer BNNSs with high crystallinity.Meanwhile, it can reach higher yield of nearly 1.68%, as the hydrothermal method with the yield of only 0.12%. The simple sonication-assisted hydrothermal method has potential applications in exfoliating other layered materials, thus opening new ways to produce other layered materials in high yield and high crystallinity.

Gas-discharge induced flash sintering of YSZ ceramics at room temperature

This is the first study to conduct the flash sintering of 3 mol%yttria-stabilized zirconia(3YSZ)ceramics at room temperature(25℃)under a strong electric field,larger than 1 kV/cm.At the standard atmospheric pressure(101 kPa),the probability of successful sintering is approximately half of that at low atmospheric pressure,lower than 80 kPa.The success of the proposed flash sintering process was determined based on the high electric arc performance at different atmospheric pressures ranging from 20 to 100 kPa.The 3YSZ samples achieved a maximum relative density of 99.5%with a grain size of~200 nm.The results showed that as the atmospheric pressure decreases,the onset electric field of flash sintering decreases,corresponding to the empirical formula of the flashover voltage.Moreover,flash sintering was found to be triggered by the surface flashover of ceramic samples,and the electric arc on the sample surfaces floated upward before complete flash sintering at overly high pressures,resulting in the failure of flash sintering.This study reveals a new method for the facile preparation of flash-sintered ceramics at room temperature,which will promote the application of flash sintering in the ceramic industry.