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Text-to-speech (TTS) synthesizers have been widely used as a vital assistive tool in various fields. Traditional sequence-to-sequence (seq2seq) TTS such as Tacotron2 uses a single soft attention mechanism for encoder and decoder alignment tasks, which is the biggest shortcoming that incorrectly or repeatedly generates words when dealing with long sentences. It may also generate sentences with run-on and wrong breaks regardless of punctuation marks, which causes the synthesized waveform to lack emotion and sound unnatural. In this paper, we propose an end-to-end neural generative TTS model that is based on the deep-inherited attention (DIA) mechanism along with an adjustable local-sensitive factor (LSF). The inheritance mechanism allows multiple iterations of the DIA by sharing the same training parameter, which tightens the token–frame correlation, as well as fastens the alignment process. In addition, LSF is adopted to enhance the context connection by expanding the DIA concentration region. In addition, a multi-RNN block is used in the decoder for better acoustic feature extraction and generation. Hidden-state information driven from the multi-RNN layers is utilized for attention alignment. The collaborative work of the DIA and multi-RNN layers contributes to outperformance in the high-quality prediction of the phrase breaks of the synthesized speech. We used WaveGlow as a vocoder for real-time, human-like audio synthesis. Human subjective experiments show that the DIA-TTS achieved a mean opinion score (MOS) of 4.48 in terms of naturalness. Ablation studies further prove the superiority of the DIA mechanism for the enhancement of phrase breaks and attention robustness. [ABSTRACT FROM AUTHOR]

The method of proximal VNIR-SWIR (with a spectral region of 400–2500 nm) spectroscopy in a laboratory setting has been widely employed in soil property estimations. Increasing attention has been focused recently on establishing an agreed-upon protocol for soil spectral measurement, fueled by the recognition that studies carried out under different laboratory settings have made future data sharing and model comparisons difficult. This study aimed to explore the key factors in a lab-based spectral measurement procedure to provide recommendations for enhancing the spectra quality and promoting the development of the spectral measurement protocol. To this aim, with the support of the standard spectral laboratory at Jilin University, China, we designed and performed control experiments on four key factors—the light interference in the measurement course, soil temperature, soil moisture, and soil particle size—to quantify the variation in the spectra quality by the subsequent estimation accuracies of different estimation models developed with different spectra obtained from control groups. The results showed that (1) the soil–probe contact measurement derived the optimum spectra quality and estimation accuracy; however, close-non-contact measurement also achieved acceptable results; (2) sieving the soil sample into particle sizes below 1 mm and drying before spectral measurement effectively enhanced spectra quality and estimation accuracy; (3) the variation in soil temperature did not have a distinct influence on spectra quality, and the estimation accuracies of models developed based on soil samples at 20–50 °C were all acceptable. Moreover, a 30-min warm-up of the spectrometer and contact probe was found to be effective. We carried out a complete and detailed control experiment process, the results of which offer a guide for optimizing the process of laboratory-based soil proximal spectral measurement to enhance spectra quality and corresponding estimation accuracy. Furthermore, we present theoretical support for the development of the spectral measurement protocol. We also present optional guidance with relatively lower accuracy but effective results, which are save time and are low cost for future spectral measurement projects. [ABSTRACT FROM AUTHOR]

Mobile wireless communication heavily relies on the radio frequency to convey message and data. However, its limited spectrum can hardly meet the demands for the future high data rate applications. Optical wireless communication, in particular visible light communication, opens up vast optical spectrum for communication, and meanwhile can retrofit the light sources as the communication transmitters in the existing working or living environments. In conjunction with the ubiquitous cameras in hand-held consumer electronics such as smartphones and pads, optical camera communication (OCC) further takes advantages of image sensors as the communication receivers and realizes low-cost communication systems. This article first provides an overview of OCC systems. It then addresses some practical constraints, ranging from sensor low frame rate and instability, rolling shutter readout, to visual qualities of displayed images and videos, and link blockage between the transmitter and receiver. Accordingly, it introduces existing and new solutions to deal with those constraints by data modulation, newly developed camera structures, post-processing of sensed signals and non-line of sight OCC as a new form. In particular, indirect paths by either the indoor surface reflection or the outdoor atmospheric scattering are explored for link connectivity under blockage. Finally, some future research directions are suggested. This article is part of the theme issue 'Optical wireless communication'. [ABSTRACT FROM AUTHOR]

The article focuses on the classification and analysis of the black soil through using ground spectral process. It discusses the high fertility and good properties of black soil and the distribution of its resources in the regions of South America, Eurasia and North America. The article also adds the sampling and spectral measurement of the soil using experimental and standardization methods.

We study geolocation based on biased range estimates. Positive bias arises using time delay ranging methods in a multipath fading environment, when the line of sight direct path is severely attenuated. We model the range measurement as contaminated with Gaussian noise and an additive nonnegative bias term, and consider deterministic and random bias cases. We develop weighted least squares (WLS) and maximum likelihood (ML) geolocation estimators, and show that in general they yield biased geolocation estimates. A perturbation analysis technique is applied to find bias and mean square error (MSE) expressions for the WLS and MLE algorithms. MLE generally outperforms WLS, because MLE exploits knowledge of the range measurement bias distribution. The location error expressions are functions of the measurement bias and variance, as well as the network geometry. These results are useful to study achievable geolocation performance, and are applied to optimize sensor placement for improving the overall geolocation accuracy. We also develop the Cramér-Rao bound (CRB) on geolocation for our model. The CRB is a bound on unbiased estimation, whereas the geolocation algorithms may be biased, and we show how the estimators approach the CRB in certain cases. Numerical examples are presented to verify the analysis and study some cases of interest. [ABSTRACT FROM AUTHOR]

Abstract: Singular Spectrum Analysis (SSA) has been exploited in different applications. It is well known that perturbations from various sources can seriously degrade the performance of the methods and techniques. In this paper, we consider the SSA technique based on the perturbation theory and examine its performance in both reconstructing and forecasting noisy series. We also consider the sensitivity of the technique to different window lengths, noise levels and series lengths. To cover a broad application range, various simulated series, from dynamic to chaotic, are used to verify the proposed algorithm. We then evaluate the performance of the technique using two real well-known series, namely, monthly accidental deaths in the USA, and the daily closing prices of several stock market indices. The results are compared with several classical methods namely, Box–Jenkins SARIMA models, the ARAR algorithm, GARCH model and the Holt–Winter algorithm. [Copyright &y& Elsevier]

Ziv–Zakai Bayesian lower bounds on time-delay estimation (TDE) are developed for frequency hopping waveforms. These wideband waveforms are readily employed for both communications and TDE. We consider random frequency-selective fading channels, described by a Gaussian tapped delay line model with inter-hop correlation. The receiver does not know the channel realization to assist in estimating the time delay but does know the channel statistics. The development incorporates a random uniform prior on the delay. The bounds provide tight mean-square error prediction for the maximum a posteriori (MAP) estimator performance over a large range of signal-to-noise ratios (SNRs). They also accurately predict the TDE frequency diversity gain from multi-frequency transmission in fading channels. The special case of independent fading is discussed, including both flat Rician and Rayleigh fading, and closed-form expressions enable easy study of the effects of SNR, frequency diversity, and channel statistics on TDE. [ABSTRACT FROM AUTHOR]

An essay is presented on the comparative dimensions of diverse approaches to regional cooperation and regionalism in Central Asia. It discusses the regional development patterns of the five Central Asian states of Kyrgyzstan, Kazakhstan, Uzbekistan, Tajikistan, and Turkmenistan. The author notes on the European Union (EU) approach in Central Asia as an optimal model to enhance regionalism in the area.

Barley is an important cereal crop worldwide. Its genetic transformation is now limited to very few cultivars because of the high genotype dependence of embryogenic callus. To reveal the key genes or factors controlling the callus induction and plantlet regeneration in barley, we compared the transcriptomic profiles of immature embryos of Golden Promise and ZU9, which differed dramatically in the efficiency of the genetic transformation. The samples were taken at 0, 5, 10 and 20 days of the culture, respectively. In total, 5386 up-regulated and 6257 down-regulated genes were identified in Golden Promise. Several genes, identified exclusively in GP callus, were selected for further investigation. These genes were mainly involved in protein metabolism, energy metabolism, stress response, detoxification and ubiquitin–proteasome. Four YUCCA flavin monooxygenases, one PIN-FORMED, one tryptophan aminotransferase related, three small auxin up RNA, three indole-3-acetic acid and one adenylate isopentenyl transferase, seven cytokinin oxidase/dehydrogenase, three Arabidopsis histidine kinase, three Arabidopsis histidine phosphotransfer protein, and one Arabidopsis response regulator were differentially expressed in the calli of the two barley genotypes, suggesting that biosynthesis, response and transport of auxin and cytokinin might be associated with cell reprogramming during callus induction. The current results provide insights into molecular mechanisms of callus induction at an early developmental stage and are helpful for optimizing the tissue culture system in barley. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes a middleware framework for integrating heterogeneous building automation systems (BAS) on the Internet. The proposed framework combines OPC (OLE for Process Control) and Web Services to integrate data and services on the Internet. It utilizes the OPC technologies in LAN and the powerful communication capability of Web Services to accommodate different communication interfaces/protocols and provide public Web Services methods. These public Web Services methods can be invoked by heterogeneous BAS or other enterprise applications to realize BAS integration and interoperation with enterprise applications on the Internet, thus filling the gap between BAS control network and data communication network. The design and implementation of the middleware technology are presented in this paper. Experiments and evaluation on performance of the middleware are also conducted and presented. [Copyright &y& Elsevier]

In blind and group-blind multiuser detection, different detectors can be designed using either the sample data covariance matrix directly or its eigen components. Due to finite-sample effect in practice, their performance deviates from the corresponding optimum. A perturbation technique is developed rigorously and systematically to analyze those detectors in this work. Subject to the assumption that the first-order perturbation dominates, corresponding results can be applied to a practical system of a given sample size. In particular, performance of the following typical detectors is studied for either flat or estimated multipath channels: direct-matrix-inversion (DM1) blind minimum meanssquare error (MMSE) detector, subspace blind MMSE detector, direct zero-forcing (ZF) detector, subspace ZF detector, and group-blind hybrid detector. Simulation examples further verify various analytical results. [ABSTRACT FROM AUTHOR]

In a code division multiple access (CDMA) system, signal detection under multipath distortion typically requires estimation of unknown channel parameters first. In such a scenario, performance of receivers highly relies on the accuracy of channel estimates. In this paper, effects of channel estimation errors on the performance of linear CDMA receivers due to finite data samples are studied when channel parameters are estimated blindly by a recently proposed covariance-matching technique. Those receivers include zero-forcing (ZF), direct matrix-inversion (DMI) minimum mean-square-error (MMSE), subspace MMSE, and RAKE receivers. Their output signal-to-interference-plus-noise ratios (SINRs) and bit-error-rates (BERs) are adopted for performance measures. Expressions for performance indicators under such an imperfect condition are derived from a perturbation perspective and verified by simulation examples. [ABSTRACT FROM AUTHOR]

This paper investigates the frustrating problems of integration and interoperability of Building Automation and Control System (BACS) and presents two possible solutions on the basis of the hierarchy architecture of BACS. One is to employ a unified protocol for the three levels of the BACS networks. The other is the integration at management level. For the first solution, as one candidate, BACnet and its relation with other protocols are evaluated. For the second solution, pros and cons of OPC and Web Services are analyzed and compared. The combination of these two technologies offers good prospects for this solution. A survey on the development of Intelligent Building (IB), the application of IB technologies and the IB standards in China is presented also. [Copyright &y& Elsevier]

Provides information on a study that generalized the blind subspace technique to two direct sequence code division multiple access (CDMA) systems to estimate possibly long channel impulse response of a desired user. Description on multirate direct-sequence CDMA model; Estimation of multipath channel parameters; Conclusions.

Presents information on a study which proposed the low complexity algorithms for estimating channel parameters in code-division multiple access systems using aperiodic spreading sequences. Problem formulation; Simulation results; Conclusions.

Presents information on a study which proposed blind adaptive algorithms for minimum variance code-division multiple-access (CDMA) receivers. Problem statement; Discrete-time model of a multiuser CDMA system; Preparation for the development of the proposed adaptive methods; Conclusions.

Presents a study which addressed the problem in estimating the correlations of frequency-selective fading channels. Algorithms developed in identifying time-varying channels; Autoregressive model considerations; Details on the proposed algorithm; Performance analysis; Channel tracking; Simulations.

Soil nitrogen (N) content plays a vital role in agriculture and biogeochemical processes, ranging from the N fertilization management for intensive agricultural production to the patterns of N cycling in agroecological systems. While proximal sensing in laboratory settings can achieve ideal soil N estimation accuracy, the estimation and mapping by using remote sensing methods in a large spatial scale diplays low ability. A new hyperspectral imager with 166 spectral channels, the ZY1-02D, makes possible the detection of subtle but important spectral features of soil. This study aimed at exploring the capability of the ZY1-02D to estimate and map the topsoil N content of the black soil-covered farmlands in northeast China. To this aim, 646 soil samples from study sites were collected, processed, spectrally and geochemically measured for the soil N sensitive bands detection and partial least squares regression (PLSR) calibration and validation. The sensitive bands detection results showed an appealing regularity of the variability and stable tendency of the soil N sensitive spectral bands with the change of the sample size. Based on this, we compared the estimation capacity of the models developed with the full wavelength spectra and the models developed with the sensitive bands. The estimation based on ZY1-02D full wavelength spectral reflectance were robust, with R2 of 0.64 in validation. Further, the results of model developed with the sensitive bands showed better validation accuracy with R2 of 0.66 and were applied to create a map of topsoil N content of farmlands in the northeast China black soil area. The results demonstrated that sensitive bands modelling could enhance the accuracy of the estimation and simplify model, and what is more, showed the ideal capability of ZY1-02D for soil N content estimation at the regional scale. [ABSTRACT FROM AUTHOR]

The assimilation of remote sensing data into mechanistic models of crop growth has become an available method for estimating yield. The objective of this study was to explore an effective assimilation approach for estimating maize grain protein content and yield using a canopy remote sensing data and crop growth model. Based on two years of field experiment data, the remote sensing inversion model using assimilation intermediate variables, namely leaf area index (LAI) and leaf nitrogen accumulation (LNA), was constructed with an R2 greater than 0.80 and a low root-mean-square error (RMSE). The different data assimilation approaches showed that when the LAI and LNA variables were used together in the assimilation process (VLAI+LNA), better accuracy was achieved for LNA estimations than the assimilation process using single variables of LAI or LNA (VLAI or VLNA). Similar differences in estimation accuracy were found in the maize yield and grain protein content (GPC) simulations. When the LAI and LNA were both intermediate variables in the assimilation process, the estimation accuracy of the yield and GPC were better than that of the assimilation process with only one variable. In summary, these results indicate that two physiological and biochemical parameters of maize retrieved from hyperspectral data can be combined with the crop growth model through the assimilation method, which provides a feasible method for improving the estimation accuracy of maize LAI, LNA, GPC and yield. [ABSTRACT FROM AUTHOR]

Single fatty chain conjugated paclitaxel prodrugs (PC) with disulfide bonds as linkers can self-assemble into stable nanoparticles and be rapidly converted into PC@albumin nanocomplexes by non-covalent binding to serum albumin. The PC@albumin nanocomplexes enhance prodrug activation and cytotoxicity, and exhibit enhanced tumor suppression with alleviated systemic toxicity. [Display omitted] • Modification with single or dual-chained fatty acids endows paclitaxel prodrug good self-assembly ability. • The formed prodrugs nanoparticles can convert into long-circulating nanocomplexes by noncovalent binding to serum albumin. • Single-chain conjugated PC NPs have faster prodrug activation and enhanced tumor inhibition effects after binding to albumin. • The study provides a facile approach to develop simple and effective nanoplatforms for enhanced chemotherapy. Improving drug delivery efficacy is the key point for enhancing the therapeutic index of medicines. Herein, we report fatty chain conjugated paclitaxel (PTX) prodrugs with a disulfide bond as linker. The formed prodrugs can self-assemble into stable nanoparticles in aqueous solutions, and rapidly transform into long-circulating nanocomplexes via the non-covalent binding to serum albumin in blood, enabling efficient drug delivery and robust antitumor effect. PTX prodrug (PC) with single-chain possess the improved self-assembly and interaction with albumins. The formed PC@albumin nanocomplexes reinforce the responsiveness of prodrug activation, and exhibit the enhanced tumor suppression ability. This strategy of hitchhiking albumin to deliver therapeutic agents holds great promise for enhanced chemotherapy. [ABSTRACT FROM AUTHOR]

• Sensitive cultivar showed more rapid leaf chlorophyll loss than the tolerant one in the mature leaves, but the youngest leaves of the two cultivars had a similar elongation rate. • Cultivar- and stress duration-specific DEGs were highly enriched in the ATP binding, oxidoreductase activity and iron transport pathways. • Photosystem II, thylakoid membrane and carbohydrate binding pathways were specific to the leaf age-specific DEGs. • Regulatory networks revealed the interactions of cultivar-, stress duration- and leaf age-specific hub genes and their co-expressed genes. Mature leaf degradation for supporting the younger leaf growth is a survival strategy for plants under waterlogging stress, but its molecular mechanism is rarely known. In this study, two barley cultivars Laurikka (B1) and Evergreen (B2), differing in waterlogging tolerance, were subjected to 6- or 10- day waterlogging stress during tillering stage. B1 was found more sensitive to waterlogging stress than B2, showing a more rapid leaf chlorophyll loss, but the elongation rate of the youngest leaf had little difference between the two cultivars. The youngest and mature leaves were sampled for dynamic transcriptome analysis. The results showed that 4384 genes were differentially expressed (DEGs) in the two cultivars, displaying significant enrichment of ATP binding, oxidoreductase and hydrolase activity and iron transport. More DEGs were identified between the waterlogging durations and leaf ages, whereas leaf age-specific DEGs were additionally enriched in the photosystem II, thylakoid membrane and carbohydrate binding pathways. A weighted gene co-expression network analysis (WGCNA) of 17669 highly expressed genes was performed to identify hub genes and construct regulatory networks. A cultivar-specific network was dominated by HST1 , MLH1 and SYP22 etc., while leaf age-specific networks were largely regulated by chlorophyll metabolism related hub genes CURT1B , PNSL4 , and PSY1 etc. This study provided a new insight into deciphering the role of hub genes, networks and pathways with relevance to whole leaves responses to waterlogging stress. [ABSTRACT FROM AUTHOR]

Presents a study that proposed a constrained optimization of the receiver's output variance as a method for designing blind multiuser detectors for DS-code division multiple access (DS-CDMA). Problem statement; Minimum variance receivers; Signal to interference and noise ratio (SINR) analysis.

Erectile dysfunction (ED) is closely related to oxidative stress, and antioxidant is a treatment and prevention method for erectile dysfunction. The Compound Dietary Antioxidant Index (CDAI) represents the overall dietary antioxidant intake of the human body. However, the link between CDAI and ED is unclear. The objective of this research was to examine the linkage between CDAI and ED. The research utilized information collected from the National Health and Nutrition Examination Survey (NHANES) spanning the years 2001 to 2004. To assess the association between CDAI and ED, the analysis employed weighted multivariate logistic regression along with weighted restricted cubic splines (RCS). Additionally, subgroup interaction analysis was conducted to confirm the findings. In this investigation, 3184 adults from the U.S., all above the age of 20, were part of the study cohort, with 863 of them identified as having ED. Adjustments for potential confounding variables revealed that the odds ratio (95% confidence interval) of CDAI associating with ED was 0.95 (0.92–0.99; P = 0.01). Besides, compared to the lowest tertile, the highest tertile of CDAI was associated with a lower risk of ED (0.63 [0.46–0.88]; P = 0.01). The application of weighted restricted cubic splines (RCS) analysis delineated a nonlinear inverse relationship between CDAI levels and the probability of ED. Subgroup analysis further demonstrated that the association between CDAI and ED remained consistent across subgroups. This cross-sectional analysis revealed a significant correlation, indicating that elevated levels of CDAI are closely linked with a lower likelihood of ED. [ABSTRACT FROM AUTHOR]

We extracted Sal B and TIIA from Salvia miltiorrhiza using enzymatic-assisted ethanol extraction. ACONN predicted optimal process conditions. Enzymolysis and alcohol extraction were used, optimizing conditions and evaluating antioxidant activity. ACONN analyzed data and ACO optimized conditions. Lab verification comprehensively evaluated the conditions. The correlation between Sal B, TIIA, and their antioxidant activities was examined. Weights of 0.5739 and 0.4260 evaluated Sal B and TIIA. ACONN had a 97.46% fitting degree. Optimized extraction conditions improved yield and quality, yielding a comprehensive evaluation value of 27.69 with 4.46% average errors. This approach enhances extraction and compound quality. Antioxidant activity strongly correlated with component yield, influenced by extraction conditions. ACONN-optimized extraction improved Sal B and TIIA yield and quality, with potential as natural antioxidants. Integrating machine learning and optimization algorithms in industrial extraction enhances efficiency and environmental preservation. [ABSTRACT FROM AUTHOR]

Consider a fixed orientation multi-user visible light communication (VLC) system with multi-color light emitting diodes (LEDs) where each transmitter serves a user with limited coordination impeding transmitter-side beamforming. In this paper, a multi-layer coding and constrained partial group decoding (CPGD) method is proposed to tackle strong color interference and increase the system throughput. After channel model formulation, user information rates are allocated and decoding order for all the received data layers is obtained by solving a max-min fairness problem using a greedy algorithm. An achievable rate is derived under the truncated Gaussian input distribution. To reduce the decoding complexity, a map on the decoding order and rate allocation is constructed for all positions of interest on the receiver plane parallel to the transmitter plane, and its size is reduced by a clustering algorithm. Meanwhile, the symmetrical geometry of LED arrays is exploited. Finally, the transmitter-user association problem is formulated and solved by a genetic algorithm. It is observed that the system throughput increases as the receivers are slightly misaligned with corresponding LED arrays due to the reduced interference level, but decreases afterwards due to the weakened link gain. [ABSTRACT FROM AUTHOR]

Abstract LED based visible light communication (VLC) has become a feasible technology for indoor high-speed access networks. Optical orthogonal frequency division multiplexing (O-OFDM) with high spectrum efficiency is often used to increase the data rate to overcome the limited bandwidth of LEDs. Due to the LED nonlinearity and high peak-to-average-power ratio (PAPR) of OFDM, the indoor broadcasting OFDM-VLC system suffers from not only the performance deterioration, but also the security issue. In this paper, we propose to use digital chaotic sequence pilot-assisted (CSPA) scheme to jointly improve the signal-to-noise-ratio (SNR) performance and the system security. The experimental results indicate that the proposed method can achieve 3 dB PAPR mitigation even up for OFDM 64-QAM signal and 2 dB SNR improvement. Meanwhile, the proposed digital CS offers a key space of ∼ 10106 for each OFDM symbol to guarantee the secure transmission. [ABSTRACT FROM AUTHOR]

Due to the extremely large path loss of non-line of sight optical wireless communication, the received signal exhibits the characteristics of discrete photoelectrons. In this paper, we investigate the achievable rates and signal detection of on-off keying modulation for discrete-time Poisson multiple access channel. Both non-orthogonal multiple access and code division multiple access are considered, for both single-rate and multi-rate multiple access channels. Maximum likelihood (ML) detections are adopted as the optimal criterion for signal detection, whose complexity grows exponentially with the number of users. Low computational complexity detections are proposed with $\mathcal {M}$ -order correction that can perform closely to the ML detection. Numerical and simulation results are presented to show the achievable rate regions, optimal power allocations, the performance of ML, and proposed low-complexity detections. Finally, the experimental results of the proposed detection approaches agree with the simulation results. [ABSTRACT FROM AUTHOR]

An interesting new physical phenomenon is uncovered—an open resonator array excited by an electron beam and able to generate a special kind of Smith–Purcell radiation (SPR). Although the frequency and direction satisfy the SPR relation, this is a single frequency radiation in a specific direction that is essentially different from ordinary SPR. The spectral density of this special radiation is also much higher than that of ordinary SPR. By means of theoretical analysis and digital simulations, the radiation mechanism together with its requirements are explored. This radiation may have great influence in modern physics and optics as it offers new ways to carry out coherent radiation generation and beam diagnostics. [ABSTRACT FROM AUTHOR]

We consider the secrecy rate for the multiple-input single-output optical wireless scattering communication, where the detected signal can be characterized by discrete photoelectrons. Assuming a legitimate receiver and an eavesdropper, we propose two secure communication protocols, the non-jamming protocol, and the cooperative jamming protocol, where for the former the transmitter does not send jamming signals but for the latter the transmitter sends jamming signals. We formulate the corresponding power and duty cycle optimization problems for both protocols. We also analyze the properties on the optimal solution, and adopt the alternating optimization to obtain a tractable solution. Moreover, we analyze the condition on the positive secrecy rate for the case where all the sub-channels to the receiver are weaker than their counterparts to the eavesdropper, where the secrecy transmission cannot be realized via a non-jamming protocol. The performance of the proposed two protocols is evaluated by numerical results. It is seen that for the iterative optimization solution, two to three iterations suffice for the convergence of the secrecy rate. [ABSTRACT FROM AUTHOR]

We aimed to investigate the pathological changes, clinicopathological correlation and prognostic factors of neoadjuvant programmed cell death 1 (PD-1) blockade camrelizumab combined with carboplatin and nab-paclitaxel (CCNP) which we have proved its effectiveness in previous research for resectable esophageal squamous cell carcinoma (ESCC). 108 patients of resectable ESCC, with a mean follow-up of 13 m (ranging 1–30 m), treated with neoadjuvant CCNP from March 2020 to October 2022 in the First Affiliated Hospital of Sun Yat-sen University were enrolled. One year overall survival (OS) and disease-free survival (DFS) were 96.4% and 84.7% respectively. Pathological complete response or major pathological response (pCR/MPR) of the primary tumour (T-pCR/T-MPR) and the metastatic lymph node (N-pCR/N-MPR) were 58.3% and 47.5%. Pathological response of both primary tumours (PT) and lymph nodes (LN) metastasis correlated with DFS. LN pathological response was consistent with PT in 70.0% and inconsistent in 30.0% metastatic cases. Higher ratio of CD8+ to FoxP3+ tumour-infiltrating lymphocytes (TILs), earlier ypT stage and PT invasion not beyond circular muscle correlated with better pathological response. Four types of regression patterns of PT and two types of metastatic LN regression were found. A total of 18 (16.7%) out of 108 developed recurrence with a mean time of 6.9 ± 5.3 months. PT pathological response plus ypN and PT invasion beyond circular muscle or not were independent prognostic factors of DFS. This study suggested that camrelizumab plus chemotherapy had a high rate of T-pCR/T-MPR for resectable ESCC. T-pCR/T-MPR plus ypN0 and tumour invasion not beyond circular muscle predicted better DFS. • Neoadjuvant camrelizumab plus chemotherapy is effective for ESCC. • Pathological response of PT was inconsistent with metastatic LN in 30% cases. • Higher ratio of CD8+ to FoxP3+ TILs correlated with better pathological response. • Tumour regression patterns of both PT and metastatic LN were summarised. • PT pathological response and ypN and circular muscle penetration were independent prognostic factors. [ABSTRACT FROM AUTHOR]

Channel estimation is conceived for optical wireless scattering channels associated with laser diode transmitters and photon-counting/photomultiplier tube receivers. The proposed channel estimation approach consists of two stages, namely, of the estimation of the channel tap second-order moments followed by the estimation of the channel taps based on the estimate of second-order moments. In the first stage, we provide the general framework of the moment estimation complemented by the conception of an estimation approach based on a sparse pilot structure, as well as by the analysis of the estimation error. We also propose a novel sparse pilot design as well as the associated low-complexity channel estimation, and prove the optimality of the proposed channel estimation. In the second stage, we conceive the associated channel tap estimation based on the eigenvalue decomposition of the matrix of estimated second-order moments, and analyze the associated performance. It is shown that as the length of the pilot sequence tends to infinity, the probability of having an estimation distortion above a certain threshold can be reduced arbitrarily small. Simulation results show that the proposed sparse pilot sequence can lead to a smaller estimation error than the pilot design using random 0–1 bits. [ABSTRACT FROM PUBLISHER]

Optical wireless communication (OWC) in the deep‐ultraviolet (DUV) band requires an efficient DUV light source with large bandwidth characteristics. In this work, a feasible approach is reported to enlarge the light output power as well as the bandwidth of a DUV light‐emitting diode (LED) by embedding a SiO2‐based microcavity on which an aluminum (Al) reflector is simultaneously deposited. Consequently, on the one hand, the microcavity with the Al‐reflector can facilitate photon escape from the LED to increase the light extraction efficiency, thus enhancing the light output power of the devices. On the other hand, the LED incorporated with a microcavity structure exhibits a reduced resistance–capacitance time constant, leading to an increase in the modulation bandwidth of the LED. Strikingly, the DUV LED incorporated with microcavities represents a significant enhancement of light output power by nearly 30% at 80 mA while exhibiting a higher modulation bandwidth of 12% in comparison to the conventional LED without microcavities. Thus, the implementation of the microcavity and Al reflector on top of a classic LED can enlarge the light output power and modulation bandwidth, eventually facilitating to establish viable high‐speed OWC systems. [ABSTRACT FROM AUTHOR]

Wetlands provide numerous ecosystem services essential for biodiversity conservation, climate change mitigation, and human well-being. Nevertheless, there are still no complete and uniform wetland maps providing information on the location, distribution, size, and changing status of wetlands in Africa. In this study, we used 130,000 Landsat satellite images and 270,000 sampling points evenly distributed across Africa to classify wetlands with a random forest classifier based on the Google Earth Engine (GEE) cloud platform. This resulted in the first systematic and comprehensive map of existing wetlands in Africa that quantified the area and distribution of these wetlands at a spatial resolution of 30 m, with an overall wetland producer accuracy of 90.22 % and user accuracy of 95.74 %. To address the seasonal variation in African wetlands, we used a dynamic threshold segmentation method based on the Otsu method, which can extract the extent of wetlands under different periods more accurately based on Landsat time series and African phenology data. Our results show that the total African existing wetlands extent from 2019 to 2021 (here in 2020), was approximately 1,341,500 km2, excluding shallow marine waters, comprises 3.98 % of Africa's total land area. Of these wetlands, inland wetlands account for 81 %, and coastal wetlands account for 19 %. The wetlands in Africa were symmetrically distributed around the equator and decreased with increasing latitude, accounting for 97 % of the total wetland area being within the 20°N and 20°S latitudes. African marshes were highly dynamic, expanding by 92.22 % from the dry to wet season. Our study demonstrates the substantial potential of large data samples, multiple wetland classification features (spectral-temporal, topographic, and hydrological features), and random forest classification in GEE for large-scale wetland mapping. The resulting wetland maps provide new baseline data for large-scale monitoring of seasonal dynamics and long-term trends in African wetlands. [ABSTRACT FROM AUTHOR]

As a revolutionizing technology, intelligent reflecting surfaces (IRS) are expected to enhance the physical layer security (PLS) by constructing a controllable wireless environment. In this paper, we consider an IRS-aided visible light communication (VLC) system with a legitimate user and a malicious eavesdropper, in which the IRS is implemented by an intelligent rotatable mirror array. Our objective is to provide a desired optical reflecting environment with enriched spatial degrees of freedom by jointly optimizing the rotation angles of arrayed mirrors. First, from the perspective of information theory, we derive the achievable secrecy rate for the IRS-aided VLC system. Then, we formulate an achievable secrecy rate maximization problem with the orientations of mirror elements as optimization variables. Since the effect of mirror elements' orientations on the IRS channel gain makes the formulated problem hard to solve, we propose a reflected spot search (RSS) method to transform the original problem into one with reduced dimension of optimization variables. Besides, bearing in mind that the VLC system has the dual task of communication and illumination, we define and analyze the illumination uniformity of the IRS-aided secure VLC system. Our simulation results show that by utilizing the proposed method, the VLC system can achieve significant secrecy enhancement, especially when the eavesdropper is close to the legitimate user. • The achievable secrecy rate for the mIRS-aided VLC system is derived. • An RSS method is proposed to handle the secrecy rate maximization problem. • Illumination uniformity is analyzed for the mIRS-aided secure VLC system. [ABSTRACT FROM AUTHOR]

As an alternative to radio-frequency (RF) communications, optical wireless communications can support high data rates and low power operations while providing good jamming resistance. Our focus in this paper is on deep ultraviolet (UV) outdoor communications (UVOC) where solar blind and non-line-of-sight operations are attractive. Light beams from UV light-emitting diode (LED) arrays serve as information carriers. In an abstract sense, this is similar to directional transmissions in RF; however, the physical (PHY) layer characteristics significantly differ due to atmospheric scattering. First, we perform extensive experiments on a UV testbed towards understanding signal propagation and the impact of the PHY on medium access. We find that UV propagation supports (a) fully duplex communications and (b) multiple data rate transmissions. Next, we propose a novel contention-based media access control (UVOC-MAC) protocol that inherently accounts for the UV PHY layer and fully exploits multi-fold spatial reuse opportunities. Evaluations via both simulations and analysis show that UVOC-MAC effectively mitigates collisions and achieves high throughput. In particular, up to a 4-fold increase in throughput and 50 % reduction in collision are possible compared to a MAC protocol agnostic to the UV PHY properties. [ABSTRACT FROM AUTHOR]

Abstract: Femotocell has been proposed and deployed to improve the indoor coverage and capacity of a cellular network. One big challenge in its deployment is the interference between the macrocell and femtocell cellular networks. In this paper we propose a new physical layer for the implementation of indoor femtocells – optical femtocells by LED-based visible light communication. A general system structure of the indoor optical femtocell network is first introduced. A combined wavelength division and code division multiple access scheme is proposed to differentiate cells and multiple users within a cell. This scheme coupled with directional beaming characteristics of the LEDs helps to mitigate intercell interference and intracell inference. The communication performance adopting the dimming compatible variable-PPM modulation suggested by the IEEE standard is analyzed. Monte-Carlo simulation is then carried out to reveal the system performance numerically under typical system settings and effects of various parameters. [Copyright &y& Elsevier]

The emerging photoelectrochemical‐type photodetector (PEC‐PD), because of its unique device architecture by using an aqueous electrolyte, is naturally applicable in the pursuit of underwater optical communication without sophisticated device packaging and assembling. Unfortunately, the traditional PEC detecting process typically involves a large electrochemical workstation with long cables and wire connections for photo signal acquisition, which hinders its applications in wireless optical communication. In this work, an AlGaN nanowire‐based self‐powered PEC‐PD is fabricated that uses seawater as an electrolyte, and then an optical communication system including the PEC‐PD and a portable electrochemical workstation as the signal receiver for data communication is built. Essentially, the self‐power PEC‐PD shows a high responsivity of −15.5 mA W–1, a fast response/recovery time of ≈100 ms, and high stability operation in the seawater electrolyte. Foremost, the optical communication system shows high accuracy in wireless transmission of ASCII code signals in a seawater environment. Such a demonstration offers a new device architecture for possible under‐seawater communication systems by leveraging the unique operation principle of photoelectrochemical devices in the future. [ABSTRACT FROM AUTHOR]

We adopt artificial $\Lambda $ -type three-level system with superconducting devices for microwave signal detection, where the signal intensity reaches the level of discrete photons instead of continuous waveform. Based on the state transition principles of the three-level system, we propose a statistical model for microwave signal detection. In addition, achievable transmission rates and signal detection based on the proposed statistical models are investigated for low temperature conditions in deep space communication scenario. It is predicted that high sensitivity can be achieved by the proposed system. We further characterize the received signal considering the saturation phenomenon of three-level system, which reveals negligible performance degradation caused by saturation under weak received power regime. [ABSTRACT FROM AUTHOR]

We investigate the achievable rate and capacity of a non-perfect photon-counting receiver assuming that the shot and thermal noise is negligible, and that the sampling interval is not shorter than the dead time. For long and fixed symbol duration, the achievable rate under on-off keying modulation is investigated based on Kullback-Leibler divergence and Chernoff divergence. We prove the tightness of the derived bounds for large peak power with zero background radiation at an exponential convergence rates, and for low peak power at an order-two convergence rates. Moreover, we propose an approximation on the achievable rate, which is more accurate compared with the derived bounds in the medium signal to noise ratio (SNR) regime. We also verify the accuracy of the proposed model on the achievable rate analysis via the comparison with the model with non-negligible shot and thermal noise. As for the capacity analysis, we assume that the symbol duration can be arbitrarily short, and demonstrate that the capacity approaches that of the continuous-time Poisson channel as both the sampling interval and the symbol duration approach zero, and the sampling interval equals the symbol duration. For large peak power, the capacity with a non-perfect receiver converges, while that of continuous Poisson capacity channel linearly increases. [ABSTRACT FROM AUTHOR]

Black soil in northeast China is gradually degraded and soil organic matter (SOM) content decreases at a rate of 0.5% per year because of the long-term cultivation. SOM content can be obtained rapidly by visible and near-infrared (Vis–NIR) spectroscopy. It is critical to select appropriate preprocessing techniques for SOM content estimation through Vis–NIR spectroscopy. This study explored three categories of preprocessing techniques to improve the accuracy of SOM content estimation in black soil area, and a total of 496 ground samples were collected from the typical black soil area at 0–15 cm in Hai Lun City, Heilongjiang Province, northeast of China. Three categories of preprocessing include denoising, data transformation and dimensionality reduction. For denoising, Svitzky-Golay filter (SGF), wavelet packet transform (WPT), multiplicative scatter correction (MSC), and none (N) were applied to spectrum of ground samples. For data transformation, fractional derivatives were allowed to vary from 0 to 2 with an increment of 0.2 at each step. For dimensionality reduction, multidimensional scaling (MDS) and locally linear embedding (LLE) were introduced and compared with principal component analysis (PCA), which was commonly used for dimensionality reduction of soil spectrum. After spectral pretreatments, a total of 132 partial least squares regression (PLSR) models were constructed for SOM content estimation. Results showed that SGF performed better than the other three denoising methods. Low-order derivatives can accentuate spectral features of soil for SOM content estimation; as the order increases from 0.8, the spectrum were more susceptible to spectral noise interferences. In most cases, 0.2–0.8 order derivatives exhibited the best estimation performance. Furthermore, PCA yielded the optimal predictability, the mean residual predictive deviation (RPD) and maximum RPD of the models using PCA were 1.79 and 2.60, respectively. The application of appropriate preprocessing techniques could improve the efficiency and accuracy of SOM content estimation, which is important for the protection of ecological and agricultural environment in black soil area. [ABSTRACT FROM AUTHOR]

Strong correlation of link gains over multiple wavelengths has been demonstrated in non-line-of-sight optical wireless scattering communication. In this paper, we further demonstrate the strong correlation of the channel impulse responses for different wavelengths. A novel channel estimation method is proposed based on such correlation, where only certain reference wavelengths are assigned with pilot signals. On each channel assigned by the pilot signal, we adopt an improved least-squares method to estimate the channel tap coefficients and the tap length. The channel tap coefficients for other wavelengths can be estimated based on the inter-wavelength correlation. Under the proposed channel estimation, the channel estimation accuracy can be improved as shown by the simulations. We further propose an optimization method for the correlation-based channel estimation pilot pattern based on the receiver channel state feedback. Simulation results show that optimized pilot pattern can achieve significant performance gain over the fixed pilot pattern. Moreover, the channel estimation performance is insensitive to the channel state feedback frequency. [ABSTRACT FROM AUTHOR]

Power allocation for optical wireless scattering communication over broad spectra is studied based on link gain correlation. We formulate two types of power allocation problems that aim to maximize the transmission rate and to minimize the linear minimum mean square error of detection. Two scenarios of power allocation problems are considered where the parallel channels are aggregated for single-user transmission and separated for different users. We solve the power optimization problems and show that the power allocation remains fixed if the link gain ratios are uniform over the broad spectra. Furthermore investigations show that for single-user transmission optimization, under imperfectly uniform link gain ratios, the optimal power allocation for one link gain realization performs close to optimality for other link gain realizations. Numerical results show that for the single-user transmission with parallel channels, fixed power allocation incurs negligible losses in terms of transmission rate, and signal distortion. Such a finding can significantly reduce the amount of channel feedback for single-user transmission optimization. However, for the multi-user transmission, these performance losses are noticeable. [ABSTRACT FROM AUTHOR]

In this paper, we study linear transceiver designs for indoor visible light communications (VLCs) with multiple light emitting diodes (LEDs). Specifically, we investigate VLCs including white emitting diodes and VLCs including red/green/blue (RGB) LEDs. The transmitter precoding and the offset are jointly designed by considering certain key practical lighting constraints, such as optical power, non-negativeness, and color illumination. Various non-convex transceiver design problems are formulated aiming to minimize total mean-square-error to improve transmission reliability. We show that for multi-input single-output white VLCs, the optimal precoding reduces to a simple LED selection strategy. For multi-input multi-output (MIMO) white VLCs, we prove that the optimization problem with multiple constraints can be equivalently simplified to a problem with single constraint, which enables us to propose efficient algorithms to search local optimal solutions. For MIMO RGB VLCs, by using certain useful transformations, we show that the precoding design is equivalent to covariance matrix design of transmit signals, which can be further transformed to a convex optimization problem. To develop an algorithm to find the optimal solution, we derive the optimal structure of the covariance matrix and show that the optimal solution can be obtained via a water-filling approach. Extensive simulation results are provided to verify the performance of the proposed designs. [ABSTRACT FROM PUBLISHER]

We proposed a lens design procedure to generate parallel light beams that facilitate optical MIMO communication with negligible interference between the un-intended transceiver pairs, in a 2×2 LED array. We designed an imaging receiver using two aspheric lenses instead of one single hemispherical lens to improve the light-beam separation performance. The proposed scheme can be extended to the scenario with ultra-dense LED array. Numerical results show that proper parameter setting in lens design can lead to negligible interference between un-intended transceiver pairs. The bit error rate performance is also evaluated. [ABSTRACT FROM AUTHOR]

In this paper, based on 1,3-bis[(3,3-dimethylindolin-2-ylidene)methyl]squaraine (ISQ), which has narrowband red-light absorption, and Rubrene, which possesses significant blue-light absorption, two color-selective organic photodetectors (OPDs) are developed. By quantum chemistry calculation, the mechanism of ISQ's sharp absorption spectrum is analyzed. Without input filtering, the two OPDs are well suited for two-channel visible light communications (VLC) system due to their good orthogonality of response spectrum and exceptional features, such as flexibility and ability to realize large-area thin-film manufacturing. With the two OPD as receivers and corresponding organic light emitting diodes (OLEDs) as data transmitters respectively, a two-channel VLC system delivering a bit-rate of 530 kb/s in the blue-light channel and 180 kb/s in the red-light channel was experimentally demonstrated. The two channels have good orthogonality when they operate together. This all-organic VLC system demonstrates the feasibility and benefit for the application of organic electronics in the communication field. [ABSTRACT FROM AUTHOR]

The use of satellite remote sensing could effectively predict maize yield. However, many statistical prediction models using remote sensing data cannot extend to the regional scale without considering the regional climate. This paper first introduced the hierarchical linear modeling (HLM) method to solve maize-yield prediction problems over years and regions. The normalized difference vegetation index (NDVI), calculated by the spectrum of the Landsat 8 operational land imager (OLI), and meteorological data were introduced as input parameters in the maize-yield prediction model proposed in this paper. We built models using 100 samples from 10 areas, and used 101 other samples from 34 areas to evaluate the model's performance in Jilin province. HLM provided higher accuracy with an adjusted determination coefficient equal to 0.75, root mean square error (RMSEV) equal to 0.94 t/ha, and normalized RMSEV equal to 9.79%. Results showed that the HLM approach outperformed linear regression (LR) and multiple LR (MLR) methods. The HLM method based on the Landsat 8 OLI NDVI and meteorological data could flexibly adjust in different regional climatic conditions. They had higher spatiotemporal expansibility than that of widely used yield estimation models (e.g., LR and MLR). This is helpful for the accurate management of maize fields. [ABSTRACT FROM AUTHOR]