Capacity Limitation and Optimization Strategy for Flexible Point-to-Multi-Point Optical Networks

Point-to-multi-point (PtMP) optical networks become the main solutions for network-edge applications such as passive optical networks and radio access networks. Entropy-loading digital subcarrier multiplexing (DSCM) is the core technology to achieve low latency and approach high capacity for flexible PtMP optical networks. However, the high peak-to-average power ratio of the entropy-loading DSCM signal limits the power budget and restricts the capacity, which can be reduced effectively by clipping operation. In this paper, we derive the theoretical capacity limitation of the flexible PtMP optical networks based on the entropy-loading DSCM signal. Meanwhile, an optimal clipping ratio for the clipping operation is acquired to approach the highest capacity limitation. Based on an accurate clipping-noise model under the optimal clipping ratio, we establish a three-dimensional look-up table for bit-error ratio, spectral efficiency, and link loss. Based on the three-dimensional look-up table, an optimization strategy is proposed to acquire optimal spectral efficiencies for achieving a higher capacity of the flexible PtMP optical networks.Comment: The paper has been submitted to the IEEE Transactions on Communication

Flexible Coherent Optical Access: Architectures, Algorithms, and Demonstrations

To cope with the explosive bandwidth demand, significant progress has been made in the ITU-T standardization sector to define a higher-speed passive optical network (PON) with a 50Gb/s line rate. Recently, 50G PON becomes mature gradually, which means it is time to discuss beyond 50G PON. For ensuring an acceptable optical power budget, beyond 50G PON will potentially use coherent technologies, which can simultaneously promote the applications of flexible multiple access such as time/frequency-domain multiple access (TFDMA). In this paper, we will introduce the architectures, algorithms, and demonstrations for TFDMA-based coherent PON. The system architectures based on an ultra-simple coherent transceiver and specific signal spectra are designed to greatly reduce the cost of ONUs. Meanwhile, fast and low-complexity digital signal processing (DSP) algorithms are proposed for dealing with upstream and downstream signals. Based on the architectures and algorithms, we experimentally demonstrate the first real-time TFDMA-based coherent PON, which can support at most 256 end users, and peak line rates of 100Gb/s and 200Gb/s in the upstream and downstream scenarios, respectively. In conclusion, the proposed technologies for the coherent PON make it more possible to be applied in the future beyond 50G PON.Comment: The paper has been submitted to the Journal of Lightwave Technolog

Examining Space Usage for Developing a Current and Future State Representation of Patrons Needs: A Case Study in H.M. Briggs Library

A reasonable and patron-centered space design in an academic library with limited resources and budget provides more value for patrons. In an academic library, as a kind of public service organization, the patron is a key factor in its life. Therefore, it is important to consider the patron’s needs when contemplating improvement. This research is a single case study applied in Hilton M. Briggs Library on the main campus of South Dakota State University. The goal of this project is to gather data that can be used for redesigning spaces in H. M. Briggs Library to better meet the needs of patrons. To redesign the space, it is necessary to understand current usage of library space and to determine patron opinions of the spaces and what they think would improve the spaces. Ethnographic methods were used to determine the current state of the library, examining the physical space to explore ways in which they can improve the service to meet patrons’ needs. In order to minimize the limitations of a single method, triangulation methods were used to explore the research questions including a flipchart survey, a direct observation, a resource location analysis and a focus group study. The general population of participants in this research consists of students, faculty, researchers, and staff of SDSU, all of whom utilize the space and equipment in H. Briggs Library’s public spaces

A Pricing and Acquisition Strategy for New and Remanufactured High-Technology Products

New generations of high-technology products are frequently launched before the previous model is sold out. Customers have an incentive to end the use of their old product and purchase a new one with the latest technological innovations. The unsold old models become less attractive, while the supply of remanufactured products from end-of-use products is uncertain in time, quantity, and quality. Other than adjusting the price, upgrading the returning unsold new products may be a source of remedy. This study provides profit maximization models associated with customer choice demand functions based on manufacturer, retailer, and joint supply chain scenarios. Two acquisition strategies are compared: acquire end-of-use products only and collect both end-of-use products and unsold old-style new products. The results reveal that returning the optimal quantity of overstocked new products brings about a greater benefit in all scenarios. Compared to the remanufacturer, the retailer is the optimal undertaker for collecting used products. In addition to this, slow technological development of the new-generation model causes a decrease in profit for the manufacturer. The optimal quantity of new products to be bought back decreases, because both the manufacturer and the retailer prefer to promote unsold outmoded products rather than upgrade the used products

Molecular Cloning, Bioinformatics Analysis and Transcriptional Expression of Virulence-related Gene (exsA) of Vibrio alginolyticus

iology techniques to analyze its biological information. Fluorescence quantitative PCR technology was used to analyze the expression of exsA after different media stress. [Results] The exsA gene contains an open reading frame (ORF) of 861 bp, encoding 286 amino acids. The physico-chemical analysis shows that the molecular structural formula is C1442H2267N393O441S12, the theoretical molecular weight is 32.549 kD, the theoretical pI value is 6.0, and the protein is non-hydrophilic and unstable. The gene does not contain a transmembrane region, and there is no obvious signal peptide. The prediction result of protein subcellular localization shows that the protein is inside the cell. The deduced amino acid sequence and constructed phylogenetic tree show that V. alginolyticus has a close relationship with Vibrio antiquarius. The qPCR results show that the expression level of exsA in different media is different, highest in TSB medium containing bile salts, followed by DMEM medium, and lowest in ordinary TSB medium. [Conclusions] The gene sequence, molecular structure and isoelectric point of exsA, as well as its expression in three different media were obtained

Research Progress in Application of 2D Materials in Liquid-Phase Lubrication System

Two-dimensional (2D) materials are ultra-thin crystals with layered structures that have a monolayer and multiple layers of atomic thickness. Due to excellent performance, 2D materials represented by graphene have caused great interest from researchers in various fields, such as nano-electronics, sensors, solar cells, composite materials, and so on. In recent years, when graphite was used for liquid phase lubrication, there have been many disadvantages limiting its lubrication properties, such as stable dispersion, fluidity and so on. Therefore, 2D materials have been used as high-performance liquid-phase lubricant additives, which become a perfect entry point for high-performance nano-lubricants and lubrication applications. This review describes the application of 2D materials as additives in the field of liquid-phase lubrication (such as lubricating oil and water lubrication) in terms of experimental content, lubrication performance, and lubrication mechanism. Finally, the challenges and prospects of 2D materials in the lubrication field were also proposed

Recent advances in friction and lubrication of graphene and other 2D materials: Mechanisms and applications

Abstract Two-dimensional materials having a layered structure comprise a monolayer or multilayers of atomic thickness and ultra-low shear strength. Their high specific surface area, in-plane strength, weak layer-layer interaction, and surface chemical stability result in remarkably low friction and wear-resisting properties. Thus, 2D materials have attracted considerable attention. In recent years, great advances have been made in the scientific research and industrial applications of anti-friction, anti-wear, and lubrication of 2D materials. In this article, the basic nanoscale friction mechanisms of 2D materials including interfacial friction and surface friction mechanisms are summarized. This paper also includes a review of reports on lubrication mechanisms based on the film-formation, self-healing, and ball bearing mechanisms and applications based on lubricant additives, nanoscale lubricating films, and space lubrication materials of 2D materials in detail. Finally, the challenges and potential applications of 2D materials in the field of lubrication were also presented

Green Preparation of Aqueous Graphene Dispersion and Study on Its Dispersion Stability

The large-scale preparation of stable graphene aqueous dispersion has been a challenge in the theoretical research and industrial applications of graphene. This study determined the suitable exfoliation agent for overcoming the van der Waals force between the layers of expanded graphite sheets using the liquid-phase exfoliation method on the basis of surface energy theory to prepare a single layer of graphene. To evenly and stably disperse graphene in pure water, the dispersants were selected based on Hansen solubility parameters, namely, hydrophilicity, heterocyclic structure and easy combinative features. The graphene exfoliation grade and the dispersion stability, number of layers and defect density in the dispersion were analysed under Tyndall phenomenon using volume sedimentation method, zeta potential analysis, scanning electron microscopy, Raman spectroscopy and atomic force microscopy characterization. Subsequently, the long-chain quaternary ammonium salt cationic surfactant octadecyltrimethylammonium chloride (0.3 wt.%) was electrolyzed in pure water to form ammonium ions, which promoted hydrogen bonding in the remaining oxygen-containing groups on the surface of the stripped graphene. Forming the electrostatic steric hindrance effect to achieve the stable dispersion of graphene in water can exfoliate a minimum of eight layers of graphene nanosheets; the average number of layers was less than 14. The 0.1 wt.% (sodium dodecylbenzene sulfonate: melamine = 1:1) mixed system forms π–π interaction and hydrogen bonding with graphene in pure water, which allow the stable dispersion of graphene for 22 days without sedimentation. The findings can be beneficial for the large-scale preparation of waterborne graphene in industrial applications

Fast-Convergence Burst-Mode Digital Signal Processing for Coherent Passive Optical Networks

Optical access networks have been evolving to meet the explosive growth of data traffic. It is foreseeable that the 100Gb/s/λ and beyond passive optical network (PON) will be required in future optical access networks. Coherent optical communication is a promising solution for the future beyond 100G PON. However, the traditional digital signal processing (DSP) for coherent optical communication is difficult to realize fast convergence due to blind and complex algorithms. In this paper, we design a specific preamble structure and propose a burst-mode DSP to achieve fast convergence for the coherent PON. For verifying the feasibility of the proposed scheme, point-to-multi-point (P2MP) coherent PON is experimentally built up based on digital subcarrier multiplexing (DSCM), which is a kind of frequency division multiple access. When the allocated frequency of the optical network unit is suddenly changed, the DSP should converge fast to ensure a low handoff latency. In P2MP coherent PON, the proposed specific preamble structure and burst-mode DSP jointly implement the fast convergence using a short preamble with only 416 symbols. The experimental results show that the 8-Gbaud/SC×8-SCs 400Gb/s-net-rate coherent PON in burst-mode detection achieves the receiver sensitivity of approximately −27dBm at the 20% soft-decision forward error correction limit and approximately 35.5dB optical power budget with an optical pre-amplifier.</p