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Friction Pendulum Bearing (FPB) with shearing keys will exhibit friction-coupling effect and collision phenomenon subjected to horizontal orthogonal ground motions. This paper establishes a numerical analysis model of FPB with four shear keys and viscous damping, considering the impact of the friction coupling effect and collision between the FPB and the shear keys on its displacement response. The influence of parameters of FPB on seismic displacement response with considering collision effect under horizontal orthogonal ground motions was studied. The results suggest that adjustments in damping and equivalent stiffness exclusively impact the amplitude of the displacement response, maintaining the response waveform. Conversely, variations in friction significantly alter the response waveform, as friction induces changes in the natural frequency of FPB. A heightened collision impact is noted with reduced spring stiffness. The displacement response is particularly amplified when the collision occurs at the vicinity of peak displacement in the time-history response of FPB. When the restoring stiffness and Peak Ground Acceleration (PGA) are low, the friction coupling effect significantly reduces the amplification of displacement response caused by collision effects. Viscous damping can considerably reduce the impact of collisions on the peak displacement of FPB and prevent the collision effects from noticeably amplifying or diminishing the peak displacement of FPB. • This paper proposes a numerical model of FPB considering shear key collisions. • Theoretical derivations and categorizations of collision and shearing scenarios involving shear keys are presented. • This model enables a decoupled analysis of the displacement response of FPB with shear keys under orthogonal horizontal seismic motions. [ABSTRACT FROM AUTHOR]

Heavy metal pollution is one of the most serious environmental problems, posing threats to human health. Here, we developed a magnetic hybrid aerogel by integrating nanocellulose and ferroferric oxide (Fe3O4) nanoparticles for effectively adsorbing heavy metal ions from water and realizing controllable recovery under magnetic condition. The magnetic behavior and adsorbing capacity of the hybrid aerogel on removal of heavy metal chromium (Cr)(VI) ion were examined. Results show that the ferroferric oxide nanoparticles physically adsorb the nanocellulose, each of which retains the original composition and structural characteristics. The magnetic hybrid aerogel possesses good ferromagnetic property with saturation magnetization value of 53.69 emu/g, enabling effective and controllable recovery of the aerogel under magnetic condition The adsorption efficiency of the hybrid aerogel on the Cr(VI) ion reaches the highest value of 2.2 mg/g when the mass ratio of the nanocellulose to ferroferric oxide nanoparticle is 1:1. Additionally, the hybrid aerogel presents similar adsorption behavior on plumbum (Pb)(II) and copper (Cu)(II) ions, suggesting extended applications of the hybrid aerogel on removal of heavy metal ions. Such strategy could provide new applications for the abundant nanocellulose resources and could be extended to integrate nanocellulose with other functional nanomaterials into novel hybrid aerogel for water purification. [ABSTRACT FROM AUTHOR]

Bit-interleaved coded modulation with iterative decoding (BICM-ID) is investigated, wherein a novel method of designing amplitude phase-shift keying (APSK) constellations is proposed, which is capable of outperforming both traditional quadrature amplitude modulation (QAM) and nonuniformly spaced QAM (NU-QAM). It is shown that the channel capacity can be approached by the proposed M-APSK constellation as M tends to infinity. Additionally, a new algorithm is introduced for finding the best bit-to-symbol mapping. Furthermore, when signal space diversity is also employed, our extrinsic information transfer (EXIT) chart analysis and Monte Carlo simulations demonstrate that the proposed BICM-ID schemes exhibit a near-Shannon-capacity performance for transmission over both additive white Gaussian noise (AWGN) and Rayleigh fading channels. For a block length of 64 800 bits, the bit-error-rate (BER) curve of the proposed BICM-ID 16/64-APSK scheme is only about 0.8 and 1.0 dB away from the Gaussian-input Shannon limit over AWGN and Rayleigh fading channels, respectively, at the BER of \10^-5 and for a code rate of 1/2. [ABSTRACT FROM PUBLISHER]

In the conventional digital television terrestrial multimedia broadcasting (DTMB) systems, all the transport streams (TS) from various programs are multiplexed in the level of TS packets, which have the same interleaving, constellation mapping, channel coding, and thus the same quality of service (QoS). Moreover, due to the convolutional interleaving mode, the receivers have to be turned on all the time to obtain the designated data until all the received signals are de-interleaved. In this paper, for DTMB systems, the concept of the physical sub-channel (PSC) in time-frequency domain is proposed, and the scheme to support services with different QoS requirements is also addressed. Based on these techniques, a novel approach to support multimedia services over DTMB systems in a backward compatible manner is proposed and evaluated by computer simulations. [ABSTRACT FROM PUBLISHER]

The state-of-the-art time domain synchronous OFDM (TDS-OFDM) transmit diversity schemes are only suitable either for fast time-varying but weakly frequency-selective channels, or deeply frequency-selective but slowly time-varying channels. In this paper, a novel TDS-OFDM transmit diversity scheme based on the space-time shifted constant amplitude zero autocorrelation (CAZAC) sequence is proposed over doubly selective broadcasting channels. The space-shifted CAZAC sequence is used for the unbiased maximum likelihood (ML) channel estimation. The time-shifted sequence is utilized for the low-complexity cyclicity reconstruction of the received inverse discrete Fourier transform (IDFT) block. Compared with the existing solutions, the signal-to-noise ratio (SNR) gain of about 2.5 dB can be achieved by the proposed scheme at the uncoded bit error rate (BER) of 10^-2 over the deeply frequency-selective single frequency network (SFN) broadcasting channel when the receiver velocity is 140 km/h, at the cost of the spectral efficiency penalty of about 2.88%. [ABSTRACT FROM PUBLISHER]

Background: Plant architecture is a critical factor that affects planting density and, consequently, grain yield in maize. The genes or loci that determine organ size are the key regulators of plant architecture. Thus, understanding the genetic and molecular mechanisms of organ size will inform the use of a molecular manipulation approach to improve maize plant architecture and grain yield. Results: A total of 18 unique quantitative trait loci (QTLs) were identified for 11 agronomic traits in the F2 and F2:3 segregating populations derived from a cross between a double haploid line with a small plant architecture (MT03-1) and an inbred line with a large plant architecture (LEE-12). Subsequently, we showed that one QTL, qLW10, for multiple agronomic traits that relate to plant organ size reflects allelic variation in ZmCSLD1, which encodes a cellulose synthase-like D protein. ZmCSLD1 was localized to the trans-Golgi and was highly expressed in the rapidly growing regions. The loss of ZmCSLD1 function decreased cell division, which resulted in smaller organs with fewer cell numbers and, in turn, pleiotropic effects on multiple agronomic traits. In addition, intragenic complementation was investigated for two Zmcsld1 alleles with nonsynonymous SNPs in different functional domains, and the mechanism of this complementation was determined to be through homodimeric interactions. Conclusions: Through positional cloning by using two populations and allelism tests, qLW10 for organ size was resolved to be a cellulose synthase-like D family gene, ZmCSLD1. ZmCSLD1 has pleiotropic effects on multiple agronomic traits that alter plant organ size by changing the process of cell division. These findings provide new insight into the regulatory mechanism that underlies plant organ development. [ABSTRACT FROM AUTHOR]

Divergent selection of KNR6 maximizes grain production by balancing the flowering-time adaptation and ear size in maize Keywords: flowering time; grain yield; trade-off; divergent selection; maize EN flowering time grain yield trade-off divergent selection maize 1311 1313 3 06/22/23 20230701 NES 230701 Domestication and improvement have led to dramatic changes in the plant architecture and inflorescence in maize. Collectively, we found that I KNR6 i underwent divergent selection during maize breeding to extend adaptation and increase grain yield, and offered a knowledge-driven strategy for engineering I KNR6 i to maximize maize grain production. [Extracted from the article]

A polar decomposition of mutual information between a complex-valued channel's input and output is proposed for an input whose amplitude and phase are independent of each other. The mutual information is symmetrically decomposed into three terms: 1) an amplitude term; 2) a phase term; and 3) a cross term, where the cross term is negligible. Theoretical bounds of the amplitude and phase terms are derived for additive white Gaussian noise channels with Gaussian inputs. This decomposition is applied to amplitude phase shift keying with product constellation (product-APSK) design and analysis. It facilitates the product-APSK to achieve a considerable shaping gain at some interesting rates over conventional quadrature amplitude modulation with a similar low complexity. [ABSTRACT FROM PUBLISHER]

Consumer electronics are expecting high-definition television (HDTV) services not only at home, but also in high-speed vehicles like cars, train, subways, etc. However, time domain synchronous OFDM (TDS-OFDM) could only provide HDTV services in static or low-speed channels, but not in fast fading channels due to the severe mutual interferences between the time-domain training sequence (TS) and the OFDM data block. Without changing the original TDS-OFDM signal structure, this paper firstly proposes the idea of regarding transmission parameter signaling (TPS) symbols embedded in the OFDM data block as frequency-domain pilots. This new perspective breaks the conventional concept that the training information of TDS-OFDM exists only in the time domain. Then, the two-dimensional channel estimation method jointly exploiting the time-domain TS as well as the frequency-domain pilots is proposed to improve the system reliability over fast fading channels. Simulation results demonstrate that reliable HDTV transmission could be achieved when the moving speed of consumer electronics is up to 120 km/h1. [ABSTRACT FROM PUBLISHER]

Experiments to characterize the constant-rate gas depleted production behavior in core samples were performed to study the areal gas flowing mechanism of a high-pressure low-permeability heterogeneous gas reservoir, including a newly designed long-core experiment on areal heterogeneity constant-rate gas depleted production considering fracturing. In the experiments, the fluid pressure increased up to 45 MPa, and the cores of the near-wellbore high permeability area before and after fracturing and the cores of the low permeability non fractured area were connected in series to simulate the gas flowing process of the dual-area composite gas reservoir. When the irreducible water saturation is considered, the gas permeability in a high permeability area cater fracturing increased threefold. Experimental results indicated that the pressure difference in the near-wellbore high permeability area decreased rapidly after fracturing and increased in the low permeability area. The recovery:factor of each area increased titter fracturing. Fracturing could have a significant effect on increasing the recovery factor when the average permeability is relatively low. The greater the gas rate, the higher is the built-up pressure alter shut-in. Fracturing in the near-wellbore area may cause a significant decrease in the shut-in built-up pressure value. [ABSTRACT FROM AUTHOR]

An improved frame structure for TDS-OFDM systems is presented by adopting cyclic block shifted training sequences. The guard interval needed for the training sequences could be shortened while the ability to combat the maximum channel delay spread is not sacrificed. Therefore the spectrum efficiency is increased. The corresponding channel estimation and equalisation schemes are also illustrated. [ABSTRACT FROM AUTHOR]

• We found the transport performance of FeSe 0.5 Te 0.5 tapes protected only by the thin silver layer was poor at high background field, while it could be significantly improved by soldering a stabilizing layer. • We investigated the influence of different stabilizing layers on the performance of tapes. • We investigated the influence of soldering temperature on the performance of tapes. The analysis of the influence of different stabilizing layers and solders on the transport current is very necessary for the engineering application of FeSe 0.5 Te 0.5 coated conductors. The soldering temperature and thermal stress caused by cooling from room temperature to liquid helium can affect the critical current values of the superconducting tapes. For this, FeSe 0.5 Te 0.5 coated conductors with four types of stabilizing layers and three types of solders were prepared. The stabilizing layer includes the copper layer with a thickness of 0.02 mm, 0.05 mm, 0.1 mm, and the silver layer with a thickness of 0.1 mm. The solders are respectively Bi 50 Pb 25 Sn 12.5 Cd 12.5 , Bi 51.2 Pb 30.6 Cd 18.2, and Sn 63 Pb 37. The experimental results show that the critical current of the tape encapsulated by the 0.02 mm thick copper layer and Bi 50 Pb 25 Sn 12.5 Cd 12.5 is about 400 A at self-field and about 25 A at 10 T, which is superior to other samples. The details of the fabrication process and performance test results were presented in this paper. [ABSTRACT FROM AUTHOR]

Device-to-device (D2D) communication has been proposed as a promising technology for future cellular communication systems due to its advantages of high spectrum efficiency, low energy consumption, and enhanced system capacity. Resource allocation for D2D communications, which occupies nonorthogonal channels with cellular transmissions, is an important problem in terms of achieving the aforementioned benefits. In this problem, there are two fundamental challenges to be addressed: 1) how to emulate cellular users to share their resources and 2) how to efficiently allocate resources in terms of channels for D2D pairs. In this paper, we exploit social ties in human-formed social networks to enhance D2D resource sharing and further propose a social-community-aware D2D resource allocation framework, where cellular users would like to share their channels with D2D communications in the same community formed by a group of people with close social ties. After that, we propose a two-step coalition game, where a coalition formulation is established for communities, and an optimal resource allocation problem is formulated for D2D pairs. Extensive simulations on random networks and real mobile trace verify the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Multiple-input multiple-output (MIMO), which can provide ultrahigh data transmission rate, is one of the key technologies for the next generation digital terrestrial television broadcasting (DTTB) standards. This paper proposes a near-capacity MIMO bit-interleaved coded modulation scheme with either independent or iterative demapping (BICM/BICM-ID) for the DTTB system. First, the amplitude phase shift keying (APSK) constellation with Gray mapping is proposed to replace the conventional Gray quadrature amplitude modulation (QAM) counterpart. From the perspective of average mutual information analysis, Gray-APSK has certain shaping gain compared to Gray-QAM for both independent and iterative demapping schemes. Besides the APSK constellation, a novel bit interleaver named bit mapping, which takes into account the unequal error protection of both APSK constellations and low-density parity-check codes, is proposed to further improve the system performance. The tool of extrinsic information transfer chart is utilized to analyze and design the optimal bit mapping for the BICM/BICM-ID scheme. Bit error rate simulations are finally carried out to verify the superiority of the proposed MIMO coded modulation scheme. [ABSTRACT FROM PUBLISHER]

As the key technology of Chinese national digital television terrestrial broadcasting (DTTB) standard, time domain synchronous OFDM (TDS-OFDM) has high spectral efficiency at the cost of performance loss over fast fading channels. In this paper, a novel time-frequency signal structure is proposed to improve the system performance of TDS-OFDM over fast time-varying channels. Each TDS-OFDM symbol adopts the time-domain one-sample shifted training sequence (TS) and the frequency-domain grouped pilots as the time-frequency training information. The modulable orthogonal sequence (MOS) with perfect autocorrelation property is adopted as the TS, while each pilot group has only one non-zero central pilot surrounded by several zero pilots. The corresponding joint time-frequency channel estimation utilizes the time-domain TS for path delay estimation and the frequency-domain grouped pilots for path gain estimation, thus accurate tracking of the fast time-varying wireless channel could be achieved. Only about 1% of the total subcarriers will be occupied by the redundant grouped pilots, thus the loss in spectral efficiency is negligible. Simulation results demonstrate that the proposed scheme outperforms the conventional solutions over fast fading channels. [ABSTRACT FROM PUBLISHER]

In the last two decades, digital television terrestrial broadcasting (DTTB) systems have been deployed worldwide. With the approval of the fourth DTTB standard called Digital Television/ Terrestrial Multimedia Broadcasting (DTMB) by International Telecommunications Union (ITU) in December 2011, the research on first-generation DTTB standards is coming to an end. Recently, with the rapid progress of advanced signal processing technologies, nextgeneration DTTB systems like Digital Video Broadcasting-Terrestrial-Second Generation (DVB-T2) have been extensively studied and developed to provide more types of services with higher spectral efficiency and better performance. This article starts from the brief review of the first-generation DTTB standards and the current status of emerging second-generation DTTB systems, then focuses on the common key technologies behind them instead of describing the specific techniques adopted by various standards. The state-of-the-art, technical challenges, and the most recent achievements in the field are addressed. The future research trends are discussed as well. In addition, the scheme of integrating DTTB and Internet is proposed to solve the crucial problem of information expansion. [ABSTRACT FROM AUTHOR]

Abstract: A space alternating generalized expectation–maximization (SAGE)-based estimation algorithm for doubly selective channel is proposed, which has very similar performance to the rectangular-windowed least squares methods introduced by Borah and Hart while providing large savings in computational complexity. Theoretical analysis shows that the proposed algorithm is always globally convergent. The convergence rate is also investigated through simulations. [Copyright &y& Elsevier]