| 1. |
- Schael, S, et al.
(författare)
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Precision electroweak measurements on the Z resonance
- 2006
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Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
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Forskningsöversikt (refereegranskat)abstract
- We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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| 2. |
- Jo, Min-Seung, et al.
(författare)
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Aligned CuO nanowire array for a high performance visible light photodetector
- 2022
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Recently, copper oxide (CuO) has drawn much attention as a promising material in visible light photodetection with its advantages in ease of nanofabrication. CuO allows a variety of nanostructures to be explored to enhance the optoelectrical performance such as photogenerated carriers scattering and bandgap engineering. However, previous researches neglect in-depth analysis of CuO's light interaction effects, restrictively using random orientation such as randomly arranged nanowires, single nanowires, and dispersed nanoparticles. Here, we demonstrate an ultra-high performance CuO visible light photodetector utilizing perfectly-aligned nanowire array structures. CuO nanowires with 300 nm-width critical dimension suppressed carrier transport in the dark state and enhanced the conversion of photons to carriers; additionally, the aligned arrangement of the nanowires with designed geometry improved the light absorption by means of the constructive interference effect. The proposed nanostructures provide advantages in terms of dark current, photocurrent, and response time, showing unprecedentedly high (state-of-the-art) optoelectronic performance, including high values of sensitivity (S = 172.21%), photo-responsivity (R = 16.03 A/W, lambda = 535 nm), photo-detectivity (D* = 7.78 x 10(11) Jones), rise/decay time (tau(r)/tau(d) = 0.31 s/1.21 s).
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| 3. |
- Kim, Se-Hoon, et al.
(författare)
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Nanophase oxalate precursors of thermoelectric CoSb3 by controlled coprecipitation predicted by thermodynamic modeling
- 2016
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Ingår i: Advanced Powder Technology. - : Elsevier. - 0921-8831 .- 1568-5527. ; 27:2, s. 773-778
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Tidskriftsartikel (refereegranskat)abstract
- The precursors for the formation of thermoelectric skutterudite CoSb3 nanoparticles are predicted by thermodynamic modeling of the complex chemical species. Based on the results, equimolar mixture of CoC2O4 center dot 2H(2)O and Sb(C2O4) OH are successively co-precipitated under controlled conditions of pH = 2.7 and concentration of reactants. The as synthesized powder was decomposed at 350 degrees C to remove the organic molecules and further reduced to CoSb3 phase by heating at 530 degrees C under hydrogen flow. The obtained powder was consolidated by spark plasma sintering (SPS). CoSb3 prepared by controlled chemical co-precipitation has p-type behavior with a positive sign of the Seebeck coefficient. TE transport properties were measured, which revealed that the Seebeck coefficient increased 2.5 times with increasing the temperature and it is lower than the ball milled CoSb3. Thermal conductivity of sintered CoSb3 at 773 K starts from 0.06 W/cm K at room temperature and decreases to 0.04 W/cm K at 700 K, which is lower than the bulk counterpart. The ZT of coprecipitated CoSb3 and SPS consolidated at 773 K shows 2 times higher than the ball milled one. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.
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| 4. |
- Kim, Hwi-Min, et al.
(författare)
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Monolithic integration of self-aligned nanoisland laser with shifted-air-hole waveguide
- 2018
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Ingår i: Optics Express. - : OPTICAL SOC AMER. - 1094-4087. ; 26:10, s. 12569-12578
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel scheme for monolithic integration of a nanoisland laser with a shifted-air-hole waveguide by employing selective etching techniques. An active L3 laser cavity and passive shifted-air-hole waveguide are simultaneously formed through a single fabrication step. In the shifted-air-hole waveguide, the air-hole position is adjusted to be compatible with selective etching. The spectral overlap between the L3 laser resonance and guided mode is achieved by introducing small air holes at the nodes of the shifted-air-hole waveguide. Experiments show that >60% of the light is coupled from the nanoisland laser to the end of the 12-mu m-long waveguide.
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| 5. |
- Kim, Hyeri, et al.
(författare)
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Toward Sustaining Bioplastics : Add a Pinch of Seasoning
- 2023
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 11:5, s. 1846-1856
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Tidskriftsartikel (refereegranskat)abstract
- Modern society can no longer sustain accumulating plastic pollution without intervention; plastic waste has even found its way into the food that we consume. Unfortunately, biodegradable alternatives lack sound commercial and economic distinctiveness because mechanical strength and biodegradability are typically mutually exclusive. Inspired by fine cuisine, we introduce a novel synthetic method, referred to as “seasoning”, which consists of adding a minimal amount of a biobased multifunctional monomer to pinch the amorphous domains of poly(butylene succinate). Seasoning with only 0.03 mol % of a biobased monomer led to a significantly improved oxygen barrier, high strength (86 MPa), and excellent elongation at break (654%). To the best of our knowledge, this “seasoning” approach with the significant property improvement provided is unique in the bioplastics research field. The proposed approach is highly scalable, relies on existing industrial production, and has the potential to expand current biodegradable plastic applications through its simplicity.
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| 6. |
- Kim, S. H., et al.
(författare)
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A multi-hop pointer forwarding scheme for efficient location update in low-rate wireless mesh networks
- 2018
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Ingår i: Journal of Parallel and Distributed Computing. - : Academic Press Inc.. - 0743-7315 .- 1096-0848. ; 122, s. 109-121
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Tidskriftsartikel (refereegranskat)abstract
- Recently, a pointer forwarding scheme (PFS) was proposed to reduce location update overhead in wireless mesh networks. Using PFS, a location update is replaced with a simple forwarding pointer setup between two neighboring mesh routers (MRs). However, in PFS, if the two MRs are not one hop neighbors, PFS fails to set up a forwarding pointer, thus increasing location update overhead. To improve PFS, we present a multi-hop pointer forwarding scheme (MPFS). MPFS allows forwarding pointers to be constructed over multi-hop at once even if MRs are not one hop neighbor by using logical tree distance constructed during network formation. The tree distance is used to relay forwarding pointer packets over multi-hop links without additional control overhead during forwarding pointer setup and to estimate hop distance between two MRs. By doing so, MPFS improves the probability of success in forwarding pointer setup while ensuring k≤km, resulting in lowering the location update overhead. Also, we analyze pointer forwarding success probability and average chain length and discuss why MPFS is suitable for resource-constrained LRWMNs. Using ns-2, we show that MPFS significantly reduces the number of location update events, location update delay and signaling overhead, and packet losses during location updates. With real-world implementation, we also confirm feasibility of MPFS.
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| 7. |
- Kim, Su Min, et al.
(författare)
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Distributed MAC Based on Adaptive Sensing Period Adjustment in Overlay Cognitive Radio Networks
- 2013
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Ingår i: Proceedings of IEEE Asia-Pacific Wireless Communications Symposium (APWCS) 2013, Seoul, Korea.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose distributed MAC protocols based on adaptive sensing period adjustment in overlay cognitive radio (CR) networks. The proposed MAC protocols adjust the sensing period based on both primary sensing and secondary data channel information at each CR user. A user with the shortest adjusted sensing period accesses to the channel in a distributed manner through an exchange of RTS/CTS messages. We propose two kinds of sensing period adjustment (SPA) protocols: logarithmic SPA (LSPA) and exponential SPA (ESPA) protocols. Through Monte-Carlo simulations, we evaluate the performance of the proposed protocols in terms of spectral efficiency and collision probability. Numerical results show that the collision probability is the most dominant factor to determine the spectral efficiency. The proposed ESPA protocol efficiently reduces the collision probability with a moderate increase of the sensing period.
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| 8. |
- Kwon, Kiwoong, et al.
(författare)
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Traffic-aware stateless multipath routing for fault-tolerance in IEEE 802.15.4 wireless mesh networks
- 2018
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Ingår i: Wireless networks. - : Springer. - 1022-0038 .- 1572-8196. ; 24:5, s. 1755-1774
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Tidskriftsartikel (refereegranskat)abstract
- Single-path routing is widely used in wireless networks due to low resource consumption. However, it is vulnerable to link failure because such a failure may adversely affect an entire path. To overcome this, multipath routing has been proposed providing fault-tolerance. In this paper, we propose a novel multipath routing protocol called traffic-aware stateless multipath routing (TSMR) based on an overlaid tree topology comprising two topologies, namely, bounded degree tree (BDT) and root-oriented directional tree (RODT). BDT is strong on reducing routing overhead, and RODT is resilient against lossy links. By synergistically overlaying them, TSMR dynamically selects the local optimal path according to the given traffic flow and the failure on the primary path. In particular, TSMR enables stateless and low overhead routing despite multipath routing by keeping only one-hop neighbors to maintain multiple paths. To evaluate TSMR, we conducted simulations with a shadowing model reflecting lossy links, and compared with single and multipath routing protocols, such as ZTR, STR, AODV, and RPL. The simulation results show that the overall performance of TSMR surpasses that of others for packet delivery ratio, end-to-end delay, control overhead, memory consumption, and power consumption regardless of network size, number of sessions, and traffic flow.
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| 9. |
- Bang, I., et al.
(författare)
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Opportunistic user selection with adaptive jamming for secure communication in heterogeneous networks
- 2015
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Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC. - : IEEE conference proceedings. - 9781479949120 ; , s. 42-46
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Konferensbidrag (refereegranskat)abstract
- In this paper, we propose an opportunistic user selection criterion to obtain a multiuser diversity gain for secure communication. At the same time, we also propose a strategy for utilizing a small base station in heterogeneous networks as a helper or a jammer adaptively. Our approach is to maximize the secrecy achievable rate based on an analytically derived lower bound instead of the original objective function due to its complexity. Based on a simple proposed user selection criterion considering both macro and small base stations, we propose two jamming strategies according to knowledge of eavesdropper's channel: adaptive jamming and probabilistic jamming strategies. Through simulations in two scenarios, it is shown that our proposed user selection and jamming schemes provide a good performance gain in terms of secrecy achievable rate.
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| 10. |
- Charalambous, Themistoklis, et al.
(författare)
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Relay-pair selection in buffer-aided successive opportunistic relaying using a multi-antenna source
- 2019
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Ingår i: Ad hoc networks. - : ELSEVIER SCIENCE BV. - 1570-8705 .- 1570-8713. ; 84, s. 29-41
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Tidskriftsartikel (refereegranskat)abstract
- We study a cooperative network with a buffer-aided multi-antenna source, multiple half-duplex (HD) buffer-aided relays and a single destination. Such a setup could represent a cellular downlink scenario, in which the source can be a more powerful wireless device with a buffer and multiple antennas, while a set of intermediate less powerful devices are used as relays to reach the destination. The main target is to recover the multiplexing loss of the network by having the source and a relay to simultaneously transmit their information to another relay and the destination, respectively. Successive transmissions in such a cooperative network, however, cause inter-relay interference (IRI). First, by assuming global channel state information (CSI), we show that the detrimental effect of IRI can be alleviated by precoding at the source, mitigating or even fully cancelling the interference. A cooperative relaying policy is proposed that employs a joint precoding design and relay-pair selection. Note that both fixed rate and adaptive rate transmissions can be considered. For the case when channel state information is only available at the receiver side (CSIR), we propose a relay selection policy that employs a phase alignment technique to reduce the IRI. The performance of the two proposed relay pair selection policies are evaluated and compared with other state-of-the-art relaying schemes in terms of outage and throughput. The results show that the use of a powerful source can provide considerable performance improvements.
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