Littérature scientifique sur le sujet « Index-partitioned modulation »

Gochujang is a traditional Korean fermented soy-based spicy paste made of meju (fermented soybean), red pepper powder, glutinous rice, and salt. This study investigated the anti-inflammatory effects of Gochujang containing salt in DSS-induced colitis. Sprague–Dawley (SD) rats were partitioned into five groups: normal control, DSS control, DSS + salt, DSS + mesalamine, and DSS + Gochujang groups. They were tested for 14 days. Gochujang improved the disease activity index (DAI), colon weight/length ratio, and colon histomorphology, with outcomes similar to results of mesalamine administration. Moreover, Gochujang decreased the serum levels of IL-1β and IL-6 and inhibited TNF-α, IL-6, and IL-1β mRNA expression in the colon. Gochujang downregulated the expression of iNOS and COX-2 and decreased the activation of NF-κB in the colon. Gochujang induced significant modulation in gut microbiota by significantly increasing the number of Akkermansia muciniphila while decreasing the numbers of Enterococcus faecalis and Staphylococcus sciuri. However, compared with the DSS group, the salt group did not significantly change the symptoms of colitis or cytokine levels in serum and colon. Moreover, the salt group significantly decreased the gut microflora diversity. Gochujang mitigated DSS-induced colitis in rats by modulating inflammatory factors and the composition of gut microflora, unlike the intake of salt alone.

This paper presents a lifting wavelet transform (LWT)-based blind audio watermarking scheme designed for tampering detection and self-recovery. Following 3-level LWT decomposition of a host audio, the coefficients in selected subbands are first partitioned into frames for watermarking. To suit different purposes of the watermarking applications, binary information is packed into two groups: frame-related data are embedded in the approximation subband using rational dither modulation; the source-channel coded bit sequence of the host audio is hidden inside the 2nd and 3rd -detail subbands using 2N-ary adaptive quantization index modulation. The frame-related data consists of a synchronization code used for frame alignment and a composite message gathered from four adjacent frames for content authentication. To endow the proposed watermarking scheme with a self-recovering capability, we resort to hashing comparison to identify tampered frames and adopt a Reed–Solomon code to correct symbol errors. The experiment results indicate that the proposed watermarking scheme can accurately locate and recover the tampered regions of the audio signal. The incorporation of the frame synchronization mechanism enables the proposed scheme to resist against cropping and replacement attacks, all of which were unsolvable by previous watermarking schemes. Furthermore, as revealed by the perceptual evaluation of audio quality measures, the quality degradation caused by watermark embedding is merely minor. With all the aforementioned merits, the proposed scheme can find various applications for ownership protection and content authentication.

AbstractMany recent studies have aimed to better understand changes in the characteristics of the intertropical convergence zone (ITCZ), including ITCZ location, width, and precipitation intensity. However, very few studies have looked at the relationship between characteristics of convection within the ITCZ and ITCZ width. The present work uses information from an ITCZ identification database and Tropical Rainfall Measuring Mission (TRMM) precipitation feature (PF) database to quantify variations in convective characteristics across the ITCZ in the Pacific Ocean. Data are partitioned into wide and narrow ITCZ regimes to quantify differences in convection between different ITCZ regimes. Under the wide regime, convection deeper than 5 km, with areas greater than 100 km2, or stratiform rain fractions greater than 0.5 is, on average, 24%, 23%, and 12% more frequent, respectively. In the narrow regime, the signal is reversed, with average increases in the frequency of convection with heights below 5 km, areas less than 100 km2, or stratiform rain fractions less than 0.5 of 15%, 4%, and 6%, respectively. Positive and negative anomalies in columnar water vapor (CWV) and sea surface temperature (SST) across the ITCZ are observed in the wide and narrow regimes, respectively. There is also a strong positive correlation between an El Niño–Southern Oscillation (ENSO) index and ITCZ width anomalies, with wide (narrow) ITCZs occurring during warm (cold) phases of ENSO. This implies that the strengthening and weakening of the Walker circulation associated with ENSO may play a role in modulating the convective populations that contribute to the Pacific ITCZ width variations.

Abstract. Crop phenology exerts measurable impacts on soil surface properties, biophysical processes and climate feedbacks, particularly at local or regional scales. Nevertheless, the response of surface biophysical processes to climate feedbacks as affected by sowing date in winter wheat croplands has been overlooked, especially during winter dormancy. The dynamics of leaf area index (LAI), surface energy balance and canopy temperature (Tc) were simulated by a modified SiBcrop (Simple Biosphere) model under two sowing date scenarios (early sowing, EP; late sowing, LP) at 10 stations in the North China Plain. The results showed that the SiBcrop model with a modified crop phenology scheme well simulated the seasonal dynamic of LAI, Tc, phenology and surface heat fluxes. An earlier sowing date had a higher LAI with earlier development than a later sowing date. But the response of Tc to the sowing date exhibited opposite patterns during the dormancy and active-growth periods: EP led to higher Tc (0.05 K) than LP in the dormancy period and lower Tc (−0.2 K) in the growth period. The highest difference (0.6 K) between EP and LP happened at the time when wheat was sown in EP but was not in LP. The higher LAI captured more net radiation with a warming effect but partitioned more energy into latent heat flux with cooling. The climate feedback of the sowing date, which was more obvious in winter in the northern areas and in the growing period in the southern areas, was determined by the relative contributions of the albedo radiative process and partitioning non-radiative process. The study highlights the surface biophysical process of land management in modulating climate.

La sécurité de la couche physique (PLS) est un paradigme émergent qui se concentre sur l'utilisation des propriétés de la communication sans fil, telles que le bruit, l'évanouissement, la dispersion, l'interférence, la diversité, etc. pour assurer la sécurité entre les utilisateurs légitimes en présence d'un espion. Comme le PLS utilise des techniques de traitement du signal et de codage, il intervient au niveau de la couche physique et peut donc garantir le secret quelle que soit la puissance de calcul de l'espion. Cela en fait une approche intéressante pour compléter la cryptographie traditionnelle dont le principe de sécurité est basé sur la dureté informatique de l'algorithme de cryptage qui ne peut pas être facilement cassé par un espion. En outre, les récents progrès rapides des technologies de communication sans fil ont permis l'émergence et l'adoption de technologies telles que l'internet des objets, les communications ultra-fiables et à faible latence, les communications massives de type machine, les véhicules aériens sans pilote, etc. La plupart de ces technologies sont décentralisées, limitées en ressources de calcul et de puissance, et sensibles aux délais. La plupart de ces technologies sont décentralisées, limitées en ressources de calcul et de puissance, et sensibles aux délais. Cela fait du PLS une alternative très intéressante pour assurer la sécurité dans ces technologies. À cette fin, dans cette thèse, nous étudions les limites de la mise en œuvre pratique de la PLS et proposons des solutions pour relever ces défis. Tout d'abord, nous étudions le défi de l'efficacité énergétique de la PLS par l'injection de bruit artificiel (AN) dans un contexte massif d'entrées multiples et de sorties multiples (MIMO). La grande matrice de précodage dans le contexte MIMO massif contribue également à un signal d'émission avec un rapport élevé entre la puissance de crête et la puissance moyenne (PAPR). Cela nous a incités à proposer un nouvel algorithme, appelé PAPR-Aware-Secure-mMIMO. Dans ce schéma, les informations instantanées sur l'état du canal (CSI) sont utilisées pour concevoir un AN tenant compte du PAPR qui assure simultanément la sécurité tout en réduisant le PAPR. Ensuite, nous considérons le PLS par adaptation du canal. Ces schémas PLS dépendent de la précision de la CSI instantanée et sont inefficaces lorsque la CSI est imprécise. Toutefois, la CSI peut être inexacte dans la pratique en raison de facteurs tels qu'un retour d'information bruyant, une CSI périmée, etc. Pour résoudre ce problème, nous commençons par proposer un schéma PLS qui utilise le précodage et la diversité pour fournir le PLS. Nous proposons ensuite un réseau neuronal autoencodeur peu complexe pour débruiter la CSI imparfaite et obtenir des performances PLS optimales. Les modèles d'autoencodeur proposés sont appelés respectivement DenoiseSecNet et HybDenoiseSecNet. Enfin, nous étudions les performances de la PLS dans le cas d'une signalisation à alphabet fini. Les signaux gaussiens ont une grande complexité de détection parce qu'ils prennent un continuum de valeurs et ont des amplitudes non limitées. Dans la pratique, on utilise des entrées de canal discrètes parce qu'elles permettent de maintenir une puissance de transmission de crête et une complexité de réception modérées. Cependant, elles introduisent des contraintes qui affectent de manière significative la performance du PLS, d'où la contribution de cette thèse. Nous proposons d'utiliser des clés dynamiques pour partitionner les espaces de modulation de manière à ce qu'ils profitent à un récepteur légitime et non à un espion. Ces clés sont basées sur le canal principal indépendant et leur utilisation pour la partition conduit à des régions de décision plus grandes pour le récepteur prévu et plus petites pour l'espion. Ce système est appelé modulation partitionnée par index (IPM)
Physical layer security (PLS) is an emerging paradigm that focuses on using the properties of wireless communication, such as noise, fading, dispersion, interference, diversity, etc., to provide security between legitimate users in the presence of an eavesdropper. Since PLS uses signal processing and coding techniques, it takes place at the physical layer and hence can guarantee secrecy irrespective of the computational power of the eavesdropper. This makes it an interesting approach to complement legacy cryptography whose security premise is based on the computational hardness of the encryption algorithm that cannot be easily broken by an eavesdropper. The advancements in quantum computing has however shown that attackers have access to super computers and relying on only encryption will not be enough. In addition, the recent rapid advancement in wireless communication technologies has seen the emergence and adoption of technologies such as Internet of Things, Ultra-Reliable and Low Latency Communication, massive Machine-Type Communication, Unmanned Aerial Vehicles, etc. Most of these technologies are decentralized, limited in computational and power resources, and delay sensitive. This makes PLS a very interesting alternative to provide security in such technologies. To this end, in this thesis, we study the limitations to the practical implementation of PLS and propose solutions to address these challenges. First, we investigate the energy efficiency challenge of PLS by artificial noise (AN) injection in massive Multiple-Input Multiple-Output (MIMO) context. The large precoding matrix in massive MIMO also contributes to a transmit signal with high Peak-to-Average Power Ratio (PAPR). This motivated us to proposed a novel algorithm , referred to as PAPR-Aware-Secure-mMIMO. In this scheme, instantaneous Channel State Information (CSI) is used to design a PAPR-aware AN that simultaneously provides security while reducing the PAPR. This leads to energy efficient secure massive MIMO. The performance is measured in terms of secrecy capacity, Symbol Error Rate (SER), PAPR, and Secrecy Energy Efficiency (SEE). Next, we consider PLS by channel adaptation. These PLS schemes depend on the accuracy of the instantaneous CSI and are ineffective when the CSI is inaccurate. However, CSI could be inaccurate in practice due to such factors as noisy CSI feedback, outdated CSI, etc. To address this, we commence by proposing a PLS scheme that uses precoding and diversity to provide PLS. We then study the impact of imperfect CSI on the PLS performance and conclude with a proposal of a low-complexity autoencoder neural network to denoise the imperfect CSI and give optimal PLS performance. The proposed autoencoder models are referred to as DenoiseSecNet and HybDenoiseSecNet respectively. The performance is measured in terms of secrecy capacity and Bit Error Rate (BER). Finally, we study the performance of PLS under finite-alphabet signaling. Many works model performance assuming that the channel inputs are Gaussian distributed. However, Gaussian signals have high detection complexity because they take a continuum of values and have unbounded amplitudes. In practice, discrete channel inputs are used because they help to maintain moderate peak transmission power and receiver complexity. However, they introduce constraints that significantly affect PLS performance, hence, the related contribution in this thesis. We propose the use of dynamic keys to partition modulation spaces in such a way that it benefits a legitimate receiver and not the eavesdropper. This keys are based on the independent main channel and using them to partition leads to larger decision regions for the intended receiver but smaller ones for the Eavesdropper. The scheme is referred to as Index Partitioned Modulation (IPM). The performance is measured in terms of secrecy capacity, mutual information and BER