| 1. |
- Cao, J., et al.
(författare)
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Error-free spectral encoding and decoding operation of InP O-CDMA encoder
- 2006
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Ingår i: 2006 Optical Fiber Communication Conference, and the 2006 National Fiber Optic Engineers Conference. - : IEEE. - 1557528039 - 9781557528032
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Konferensbidrag (refereegranskat)abstract
- We report error-free spectral encoding and decoding operation of an InP monolithic, ultra-compact optical-CDMA encoder/decoder photonic chip pair. The experimental results demonstrate the strong potential for realizing high performance O-CDMA networks with InP micro-systems.
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| 2. |
- Yoo, S. J. B., et al.
(författare)
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Spectral phase encoded time spread optical code division multiple access technology for next generation communication networks Invited
- 2007
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Ingår i: Journal of Optical Networking. - 1536-5379. ; 6:10, s. 1210-1227
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Tidskriftsartikel (refereegranskat)abstract
- We overview and summarize the progress of the spectral phase encoded time spreading (SPECTS) optical code division multiple access (O-CDMA) technology. Recent progress included a demonstration of a 320 Gbit/s (32-user x 10 Gbit/s) all-optical passive optical network testbed based on the SPECTS O-CDMA technology and a theoretical prediction of the spectral efficiency at 100% and above. In particular, InP-based integrated photonics allows implementation of SPECTS O-CDMA transmitters and receivers monolithically integrated on a chip. The integrated InP chip technology not only allows robust and compact configurations for practical and low-cost O-CDMA network deployments but also offers code reconfigurations at rapid rates for secure communication applications.
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| 3. |
- Norrman, Jenny, 1971, et al.
(författare)
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Tracing sources of ammonium in reducing groundwater in a well field in Hanoi (Vietnam) by means of stable nitrogen isotope (δ15N) values
- 2015
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 61, s. 248-258
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Tidskriftsartikel (refereegranskat)abstract
- In the Southern part of Hanoi, high ammonium (NH4+) concentrations in reducing groundwater have been an issue over the last 25years. Elevated NH4+ concentrations in groundwater, in general, are an indicator of influences from anthropogenic sources, but the buried peat layers in the Red River delta formation are also hypothesized to contribute to the high NH4+ levels (up to 100mg/l). We traced the sources of NH4+ at the Nam Du well field of the Hanoi water works by means of isotope ratios (15N/14N). The δ15N values were determined for total sedimentary N and exchangeable NH4+ of the peat material, and for NH4+ dissolved in deep and shallow groundwater, sewage, and surface water. Groundwater NH4+ of the upper (Holocene) and the lower (Pleistocene) aquifers had higher δ15N values than did total N and NH4+ of the sediments, and were somewhat higher than the δ15N values of NH4+ in sewage and surface water. We conclude that the present conditions of temperature and pH tend to promote deprotonation of NH4+ to ammonia (NH3), which eventually degasses from the groundwater table to the unsaturated pore space. This can cause an enrichment of 15N in the remaining NH4+, as the lighter 14N in NH3 is volatilized at a slightly faster rate. The intermediate δ15N values within the Pleistocene aquifer can be explained by the recharge thereto, which is a mixture of the high δ15N values of the Holocene aquifer and the low δ15N values of water infiltrating from the Red River into the Pleistocene aquifer. Some part of the increased groundwater NH4+ is likely to arise from anthropogenic activities, as supported by several indications: a large drawdown in the Pleistocene aquifer caused by Hanoi's extensive water abstraction and subsequent downward gradient from the upper Holocene aquifer; the presence of coliforms in groundwater; and a positive correlation between ammonium and DOC, Cl, Br and Ni, but a lack of correlation with As. However, the much higher concentrations of NH4+ in the groundwater compared to the potential surface sources, the positive correlation between NH4+ and DOC, the abundance of natural organic matter (OM), the amount of exchangeable NH4+ in the sediments, and the highly reducing conditions in the aquifers indicate that N-mineralization of organic N from the peat contribute substantially to the high NH4+ levels in groundwater of the Nam Du well field.
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| 4. |
- Pham, T. -S, et al.
(författare)
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Declarative Local Search for Predicate Logic
- 2019
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Ingår i: 15th International Conference on Logic Programming and Nonmonotonic Reasoning, LPNMR 2019. - Cham : Springer Verlag. - 9783030205270 ; , s. 340-346
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Konferensbidrag (refereegranskat)abstract
- In this paper we introduce a framework built on top of the Knowledge Base System, which allows local search heuristics to be synthesized from their formal descriptions. It is introduced as a new inference to solve optimization problems in. To model a local search heuristic, users need to specify its components, among which neighbourhood moves are the most important. Two types of neighbourhood moves, namely standard moves and Large Neighbourhood Search moves, are supported. A set of built-in local search heuristics are provided, allowing users to combine neighbourhoods in different ways. We demonstrate how the new local search inference can be used to complement the existing solving mechanisms for logic programming.
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| 5. |
- Pham Van, Dung, et al.
(författare)
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Machine-to-machine communications over FiWi enhanced LTE networks : A power-saving framework and end-to-end performance
- 2016
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Ingår i: Journal of Lightwave Technology. - : IEEE Press. - 0733-8724 .- 1558-2213. ; 34:4, s. 1062-1071
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Tidskriftsartikel (refereegranskat)abstract
- To cope with the unprecedented acceleration of machine-to-machine (M2M) services over cellular networks, this paper envisions a highly converged network architecture based on the integration of high-capacity and reliable Ethernet fiber-wireless (FiWi) access networks with flexible and cost-effective 4G long term evolution (LTE) technology to support M2M connectivity in an end-to-end fashion, i.e., from air interface to transport (backhaul) network. In such emerging architecture, energy efficiency must be addressed in a comprehensive way, in which both wireless front-end and optical backhaul segments are considered at the same time to maximize the battery life of battery-constrained M2M devices as well as reduce operational expenditures for network operators, while maintaining acceptable network performance. Toward this end, an end-to-end power-saving framework is introduced in this paper that devises a timeout driven discontinuous reception (DRX) mechanism for LTE-enabled M2M devices and a polling-based power-saving mechanism for optical network units (ONUs) to improve the overall energy efficiency. End-to-end performance in terms of energy saving and packet delay is analytically modeled based on a semi-Markov process for the front-end and an M/G/1 queue for the backhaul. The obtained results indicate that the device battery life is significantly prolonged by extending the DRX cycle, whereas the backhaul energy consumption is minimized by incorporating the ONU power-saving modes into the dynamic bandwidth allocation process of the optical backhaul.
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| 6. |
- Rietzler, Barbara, et al.
(författare)
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Investigation of the decomplexation of polyamide/CaCl2 complex toward a green, nondestructive recovery of polyamide from textile waste
- 2021
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 0021-8995 .- 1097-4628. ; 138:40
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Tidskriftsartikel (refereegranskat)abstract
- The ‘circular economy’ concept envisages deriving the maximum value out of resources and reducing waste to a minimum. In textiles, that includes the recovery of fiber materials out of used clothing and reusing them in the construction of new clothes. Processes such as mechanical separation, depolymerization treatment, and selective dissolutions of individual polymers are applied. We investigate the approach of selective nondestructive dissolution and recovery of polyamide fiber from mixed textile waste by using the solvent system CaCl2/ethanol/water (CEW) based on complexation and decomplexation of polyamide (PA). The results show that PA is precipitated and decomplexed by simple addition of water and a substantial amount of previously incorporated calcium by complexation, is removed. The recovered polyamide shows properties similar to pristine polyamide. Investigation on a mixed textile waste model of polyamide/wool demonstrates that CEW treatment can successfully separate different fiber materials. The nondestructive approach in dissolving PA using CEW, clearly shows the benefit, that PA fiber can be separated by controlled complexation/decomplexation without degradation, thus avoiding the repolymerization step. Furthermore, the solvent system is made of abundantly available materials that are inexpensive and used widely in industrial-scale operations. Thus, the concept will make significant contribution to a green textile recycling approach.
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| 7. |
- Rimal, B. P., et al.
(författare)
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Cloudlet Enhanced Fiber-Wireless Access Networks for Mobile-Edge Computing
- 2017
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Ingår i: IEEE Transactions on Wireless Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 1536-1276 .- 1558-2248. ; 16:6, s. 3601-3618
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes to enhance capacity-centric fiber-wireless (FiWi) broadband access networks based on data-centric Ethernet technologies with computation- and storage-centric cloudlets to provide reliable cloud services at the edge of FiWi networks and thereby realize the vision of mobile-edge computing (MEC). To reduce offload delay and prolong battery life of edge devices, a novel cloudlet-aware resource management scheme is proposed that incorporates offloading activities into the underlying FiWi dynamic bandwidth allocation process. The whole system is designed in two time division multiple access layers to enhance the network performance. To allow for the efficient coexistence of FiWi and MEC traffic, the offloaded traffic is scheduled outside the FiWi transmission slots. To thoroughly study the scheme's performance, a comprehensive analytical framework is developed that covers a rich set of performance metrics, including packet delay of both FiWi and MEC traffic, response time efficiency, offload gain-overhead ratio, energy efficiency, and battery life. Analytical results demonstrate the feasibility and effectiveness of the cloudlet-enhanced FiWi networks for MEC by employing the proposed solution. Further, we develop an experimental testbed to validate the accuracy of our analytical model via real-world measurements.
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| 8. |
- Rimal, B. P., et al.
(författare)
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Mobile Edge Computing Empowered Fiber-Wireless Access Networks in the 5G Era
- 2017
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Ingår i: IEEE Communications Magazine. - : Institute of Electrical and Electronics Engineers (IEEE). - 0163-6804 .- 1558-1896. ; 55:2, s. 192-200
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Tidskriftsartikel (refereegranskat)abstract
- The expected stringent requirements of future 5G networks such as ultra-low latency, user experience continuity, and high reliability will drive the need for highly localized services within RANs in close proximity to mobile subscribers. In light of this, the mobile edge computing (MEC) concept has emerged, which aims to unite telco, IT, and cloud computing to deliver cloud services directly from the network edge. To facilitate better understanding of MEC, this article first discusses its potential service scenarios and identifies design challenges of MEC-enabled networks. Given the importance of scaling up research in the area of network integration and convergence in support of MEC toward 5G, the article explores the possibilities of empowering integrated fiber-wireless (FiWi) access networks to offer MEC capabilities. More specifically, envisioned design scenarios of MEC over FiWi networks for typical RAN technologies (i.e., WLAN, 4G LTE, LTE-A HetNets) are investigated, accounting for both network architecture and enhanced resource management. The performance of MEC over Ethernet-based FiWi networks in terms of delay, response time efficiency, and battery life of edge devices is then analyzed. The obtained results demonstrate the feasibility and effectiveness of the proposed MEC over FiWi concept.
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| 9. |
- Rimal, B. P., et al.
(författare)
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Mobile-edge computing vs. centralized cloud computing in fiber-wireless access networks
- 2016
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Ingår i: Proceedings - IEEE INFOCOM. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467399555 ; , s. 991-996
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Konferensbidrag (refereegranskat)abstract
- The advent of Internet of Things and 5G applications renders the need for integration of both centralized cloud computing and emerging mobile-edge computing (MEC) with existing network infrastructures to enhance storage, processing, and caching capabilities in not only centralized but also distributed fashions for supporting both delay-tolerant and mission-critical applications. This paper investigates performance gains of centralized cloud and MEC enabled integrated fiber-wireless (FiWi) access networks. A novel resource management scheme incorporating both centralized cloud and MEC offloading activities into the underlying FiWi dynamic bandwidth allocation process is proposed. An analytical framework is developed to model packet delay, response time efficiency, and gain-offload overhead ratio for both cloud and conventional broadband access traffic. The obtained results demonstrate the feasibility of implementing conventional cloud and MEC in FiWi access networks, while not affecting network performance of broadband access traffic.
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| 10. |
- Seo, S. W., et al.
(författare)
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Monolithically integrated InP photonic micro systems on a chip for O-CDMA and OAWG applications
- 2007
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Ingår i: 2007 Photonics in Switching, PS. - 142441122X - 9781424411221 ; , s. 97-98
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Konferensbidrag (refereegranskat)abstract
- A monolithically integrated InP chip for optical arbitrary waveform generation (OAWG) and/or pulse-coding/decoding is demonstrated using a 20-GHz AWG pair and 10 high-speed phase modulators. The fabrication and performance of the InP chip will be presented.
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