21,233 research outputs found
Joint timing and channel estimation for bandlimited long-code-based MC-DS-CDMA: A low-complexity near-optimal algorithm and the CRLB
No full textJoint Timing and Channel Estimation (JTCE) for band limited long-code-aided Multi-Carrier Direct-Sequence Code Division Multiple Access (MC-DS-CDMA) systems is investigated. We establish the optimal multiuser timing and channel estimates for the uplink MC-DS-CDMA receiver by minimizing a weighted least squares cost function with respect to K independent parameters, where K is the number of active users. A guided random search procedure known as Repeated Weighted Boosting Search (RWBS) is invoked for numerically solving this challenging multivariate optimization problem, and thereby for producing near-optimal timing and channel estimates. The Cramér-Rao Lower Bound (CRLB) for the JTCE problem of interest is derived to benchmark the performance of the proposed RWBS based estimator. Quantitatively, for the scenario of K = 10 users, Eb/N0 ≥ 3 dB where Eb is the energy per bit and N0 the single-sided noise power spectral density, and for a near-far ratio of 10 dB, the RWBS based estimator using an observation window of 20 symbols is shown to approach the CRLB at a complexity 10 orders of magnitude lower in comparison to its full maximum likelihood search based counterpart. The proposed algorithm does not require the transmission of known pilots, yet it is capable of handling time-variant channel states
Growth Morphologies and Mechanisms of Non-Equilibrium Solidified MC Carbide
No full textGrowth morphologies and mechanisms of the carbide of group IVB and VB elements (MC carbide), a typical faceted crystal, were studied with an estimated cooling rate from 102 to 105 K/s. Results showed that although the growth morphologies of the MC carbide vary remarkably with solidification cooling rate, the solid/liquid interface is always atomically smooth, and the growth mechanisms are always lateral growth. The growth mechanism transition from lateral to continuous growth mode, which was predicted by the classic crystal growth theory, was not observed for the TiC type MC carbide within the estimated cooling rate range of 102?105 K/s
Eutectic MC Carbide Growth Morphologies of a Laser Clad TiC/FeAl Composite Coating
No full textIn this paper, eutectic MC carbide growth morphology and its evolution with laser scanning speed were studied comprehensively of a laser clad MC carbide reinforced FeAl intermetallic matrix composite coating. As the laser scanning speed increased, the growth morphology of eutectic MC carbide was found to be needle-aligned annulation, butterfly-like and well-developed dendrite
Methyl Cinnamate (MC) Alleviates Free Fatty Acids (FFAs) Induced Lipid Accumulation Through the AMPK Pathway in HepG2 Cells
No full textYingda Fu,1 Guangbing Li,1,2 Zichen Feng,1 Jun Liu,2 Xiaoyu Wang,1 Tao Wang,2 Jun Liu1,2 1Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong, People’s Republic of China; 2Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, Shandong, People’s Republic of ChinaCorrespondence: Jun Liu, Department of Hepatobiliary Surgery and Center of Organ Transplantation, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, Shandong, People’s Republic of China, Email [email protected]: AMP-activated protein kinase (AMPK) plays a critical role in energy metabolism. Its activation leads to the phosphorylation of downstream proteins such as acetyl-CoA carboxylase (ACC) and sterol regulatory element-binding protein-1 (SREBP1), subsequently inhibiting de novo fatty acid synthesis, thereby reducing intracellular triglyceride accumulation. MC is a compound found in extracts from Zanthoxylum armatum DC plants. Research has shown that MC can inhibit the differentiation of 3T3-L1 adipocytes through the CAMKK2-AMPK pathway. However, the biological effect of MC in HepG2 cells remains unknown.Methods: In this study, we utilized HepG2 cells to establish a model of MAFLD through FFAs stimulation. We investigated the biological effects of MC on HepG2 cells and studied its impact on lipid metabolism. Small interfering RNA was employed to explore the mechanism by which MC activates AMPK. Finally, molecular docking was conducted, establishing a model of the interaction between AMPK and MC.Results: We observed that MC can alleviate triglyceride accumulation in HepG2 cells. We observed the elevated p-AMPK/AMPK, P-ACC/ ACC, and elevated CPT1a after treatment of MC in HepG2 cells. The interference of CAMKK2 mRNA did not impact the ability of MC to phosphorylate AMPK. Compound C attenuates the ability of MC to increase p-AMPK. Molecular docking results led us to hypothesize that MC directly interacts with AMPK, resulting in AMPK phosphorylation and improved lipid accumulation in HepG2 cells.Keywords: AMPK, CAMKK2, FFAs, HepG2, methyl cinnamate, MAFL
Ant-Colony-Based Multiuser Detection for MC DS-CDMA Systems
Full text linkIn this contribution we present a novel ant colony optimization (ACO) based multi-user detector (MUD) designed for synchronous multi-carrier direct sequence code division multiple access (MC DSCDMA) systems. The operation of the ACO-based MUD is based on the behaviour of the ant colony in nature. The ACO-based MUD aims for achieving the same bit-error-rate (BER) performance as the optimum maximum likelihood (ML) MUD, without carrying out an exhaustive search of the entire MC DS-CDMA search space constituted by all possible combinations of the received multi-user vectors. We will demonstrate that the system is capable of supporting almost as many users as the number of chips in the spreading sequence, while searching only a small fraction of the entire ML search space. It will also be demonstrated that the number of floating point operations per second is a factor of 108 lower for the proposed ACO-based MUD than that of the ML MUD, when supporting K = 32 users in a MC DS-CDMA system employing 31-chip Gold codes as the T-domain spreading sequence
Ant-colony-based multiuser detection for multifunctional-antenna-array-assisted MC DS-CDMA systems
No full textA novel Ant Colony Optimization (ACO) based Multi-User Detector (MUD) is designed for the synchronous Multi-Functional Antenna Array (MFAA) assisted Multi-Carrier Direct-Sequence Code-Division Multiple-Access (MC DS-CDMA) uplink (UL), which supports both receiver diversity and receiver beamforming. The ACO-based MUD aims for achieving a bit-error-rate (BER) performance approaching that of the optimum maximum likelihood (ML) MUD, without carrying out an exhaustive search of the entire MC DS-CDMA search space constituted by all possible combinations of the received multi-user vectors. We will demonstrate that regardless of the number of the subcarriers or of the MFAA configuration, the system employing the proposed ACO based MUD is capable of supporting 32 users with the aid of 31-chip Gold codes used as the T-domain spreading sequence without any significant performance degradation compared to the single-user system. As a further benefit, the number of floating point operations per second (FLOPS) imposed by the proposed ACO-based MUD is a factor of 108 lower than that of the ML MUD. We will also show that at a given increase of the complexity, the MFAA will allow the ACO based MUD to achieve a higher SNR gain than the Single-Input Single-Output (SISO) MC DS-CDMA system. Index Terms—Ant Colony Optimization, Multi-User Detector, Multi-Functional Antenna Array, Multi-Carrier Direct-Sequence Code-Division Multiple-Access, Uplink, Near-Maximum Likelihood Detection
mc-Si : H/c-Si solar cell prepared by PECVD
No full textHetero-junction solar cells with an me-Si: H window layer were achieved. The open voltage is increased while short current is decreased with increasing the mc-Si:H layer's thickness of emitter layer. The highest of V-oc of 597 mV has obtained. When fixed the thickness of 30 nm, changing the N type from amorphous silicon layer to micro-crystalline layer, the efficiency of the hetero-junction solar cells is increased. Although the hydrogen etching before deposition enables the c-Si substrates to become rough by AFM images, it enhances the formation of epitaxial-like micro-crystalline silicon and better parameters of solar cell can be obtained by implying this process. The best result of efficiency is 13.86% with the V-oc of 549.8 mV, J(sc) of 32.19 mA center dot cm(-2) and the cell's area of 1 cm(2)
Hao Wang et Robert Mc Naughton, Les systèmes axiomatiques de la théorie des ensembles. Avec une préface par P. Destouches-Février
No full textBorgers A. Hao Wang et Robert Mc Naughton, Les systèmes axiomatiques de la théorie des ensembles. Avec une préface par P. Destouches-Février. In: Revue Philosophique de Louvain. Troisième série, tome 51, n°32, 1953. pp. 656-658
Multiple-Symbol Differential Sphere Detection for the Amplify-and-Forward Cooperative Uplink
Full text linkIt is widely recognized that the differential amplify-and-forward (DAF) transmission scheme is capable of providing a superior performance compared to classic direct transmissions employing differential detection in slow-fading channels and in fact it may even outperform coherent detection aided systems relying on realistic imperfect channel estimates. However, in reality the channels connecting the multiple nodes of a cooperative system typically become time-selective due to the relative mobility of the cooperating terminals. Hence, the performance gain achieved may erode as the environment becomes more time-selective. On the other hand, multiple-symbol based differential sphere detection (MSDSD) has been proposed to mitigate the channel-induced performance loss suffered by classic direct transmission schemes employing the conventional differential detection (CDD) scheme. Hence in this paper, we specifically design the MSDSD based on a multi-dimensional tree search, which is capable of achieving a significant performance gain in the context of a DAF-aided cooperative system for transmission over time-selective channels. For example, given a target BER of 10-3, a performance gain of about 10 dB can be attained by the proposed MSDSD for a two-user cooperative system in a channel having a normalized Doppler frequency of 0.03
Interactively using Semantic Web knowledge: Creating scalable abstractions with FacetOntology
No full textThe amount of knowledge accessible on the Semantic Web is growing, and there is a need for a scalable solution to facilitate exploring that data. Currently approaches to exploring Semantic Web data either focus on exploring resources individually, following links during exploration, and making little use of collated data, or take the approach of collating and aligning multiple sources into one store for one purpose, and hand-crafting a specific browsing interface onto it. We present an approach that provides a scalable browsing interface, which can browse knowledge from the Semantic Web at will. Our approach creates abstractions of knowledge, collated into facets, which are described using FacetOntology. FacetOntology facilitates describing facets from RDF data, suitable for use in creating datasets for faceted browsing
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