| 45261. |
- Hansson, Ulf, 1967
(författare)
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Efficient Digital Communication over the Time Continuous Rayleigh Fading Channel
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Frequency flat, fast Rayleigh fading may be considered the most critical disturbance in a wireless communication system. In its most general form, it is modeled as a multiplicative time continuous random (zero mean complex Gaussian) distortion of the transmitted signal. In order to achieve an efficient communication here, each part of the communication link must be carefully designed based on the properties of the time continuous channel. Such an approach is distinct from most previous works, which have used strategies developed for the additive white Gaussian noise channel (AWGN) as starting points. Crucial in this development is how to deal with the deep fades and the rapid fluctuations of the received signal power. To reduce the influence of the deep fades on the error probability, diversity techniques must be used. Coded interleaved modulation can be regarded one such strategy, where the diversity effect arises as a result of nearby encoder output symbols being subjected to statistically independent fading. Central in achieving this independence is the interleaver, which spreads the symbols in time. A higher diversity order is obtained if the encoder output bits, instead of symbols, are interleaved. By also using codes of lower rates, the diversity is increased even further. To avoid bandwidth expansion here, the channel symbol constellation must be expanded accordingly. The resulting system is referred to as bit-interleaved channel symbol expansion diversity (CSED) and is the best low-complexity coded modulation scheme presented so far for the Rayleigh fading channel. On the fast fading channel, coding is only part of the solution, however. Here, matched filter detectors originally developed for AWGN are unable to efficiently handle the rapid (compared with the signaling rate) fluctuations of the received signal power. More sophisticated solutions are needed. It is essential to make the transition from the time continuous received signal to a discrete representation in the receiver, without losing too much accuracy. Both an adequate number of discrete observables and a sufficiently long observation interval are required. When this is fulfilled, error probability curves with steeper slopes and considerably lower error floors than those of matched filter based receivers are obtained. The steeper slopes are results of the implicit diversity of the random message component in the received signal, which is captured when multiple discrete observables (per symbol interval) are used. This effect is more pronounced the faster the fading is, therefore uncoded signaling has a potentially better performance at fast fading than in slow fading. Use of observation intervals larger than the symbol interval in the receiver, immediately leads to detectors based on sequence detection. The MAP (maximum aposteriori) sequence detector becomes prohibitively complex, consequently simpler suboptimal detectors are required. A near optimal detector needs to maintain only a small fixed number of candidate symbol sequences as the length of the received message increases. This is in contrast to the MAP sequence detector, where the number of sequences grows exponentially in the length of the message. By minor modifications, the suboptimal detector can also produce the bitwise soft outputs needed in the decoder part of a bit-interleaved CSED system.
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| 45262. |
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| 45263. |
- Hansted Andersen, Julie, et al.
(författare)
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Construction cost of timber buildings
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- There are increasing interests and practices in modern large timber constructions globally for the renewability and carbon storage function of wood. However, many stakeholders with limited knowledge and experience with timber still feel uncertain on how to carry out construction projects with timber. The common notion is that timber constructions would become more costly than a conventional alternative such as concrete. In order to inform wide spectrum of construction stakeholders in Scandinavia, this report presents a study on construction cost of cross laminated timber (CLT) buildings compared with concrete/steel buildings in Denmark, Norway and Sweden. The study investigated the actual cost of 9 recent multi-storey residential buildings, 5 constructed with a load-bearing system in primarily CLT and 4 constructed in primarily concrete in Norway and Sweden. Due to the nature of the chronological and geographical differences of market conditions, the cost data were evaluated separately for Norway and Sweden. In addition to the case building analysis, interviews were conducted with stakeholders from the case building projects as well as those from the industry with experiences with CLT buildings. The interviews contributed to a broader perspective of the cost analysis, with explanations of the projects and experiences of advantages and disadvantages for CLT building and concrete buildings. The results showed a tendency that the construction cost of the Norwegian CLT projects were higher than the Norwegian concrete projects. For the Swedish projects the concrete building had a higher cost compared to the CLT projects, however it can't be concluded as a tendency for the Swedish projects, since investigation only included one concrete project and two CLT projects. The results showed that often the material-related costs were higher for CLT buildings than concrete buildings. Such costs are for example the material cost itself and transportation cost for a long distance. Furthermore, the fire protection and measures for the finalized building according to fire safety resulted in a higher cost in the CLT cases. However, the construction time is often shorter for CLT buildings than concrete buildings, and CLT buildings are lighter and therefore the foundation can be dimensioned smaller. Although such observations were made, throughout the interviews it was stated that one should be careful comparing the cost of two buildings since the cost is very much depended on the specific project. Thus, the results shown in this report must be seen as tendencies and not as a forecast for specific cost difference between CLT building and concrete buildings. This study was an investigation of construction costs and advantages and disadvantages of CLT buildings in relation to the construction cost up till 2022. When there is a major change in the economy and legislations of the construction sector, the cost structure may be substantially affected. One of such factors may be the increasing focus on the reduction of greenhouse gas (GHG) emissions from the construction industry. The availability of resource might be also a key factor for the future cost development for both CLT and concrete.
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| 45264. |
- Hanzén, Ronnie, et al.
(författare)
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2nd Project on Damage Stability for RoRo Passenger ships
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Ro-ro passenger ship services constitute an important part of the European maritime infrastructure, and indeed play a crucial role for Sweden in connecting seaborne transport routes to and from our neighbouring countries. Moreover, northern European countries have been leading the development of, not only the ro-ro passenger ship concept as such, but also the development of relevant safety standards for this fleet. Understandably, it is therefore crucial for the Swedish maritime sector to take part of the legislative process that covers a significant share of the Swedish maritime infrastructure. Thus, in light of the IMO deliberations on the revisions of Chapter II-1 of the SOLAS Convention in general and proposals for an increased safety standard for passenger ships in particular, a first Triple-Helix project, partly funded by the Swedish Maritime Administration, was mobilized by the Swedish Shipowners’ Association, focusing on ro-ro passenger ship safety from a holistic perspective. The conclusions and findings of this Project can be found in the Report "Damage Stability Project for RoRo Passenger Ships – Final Report" [1.]. As the draft proposals for enhanced safety standards for passenger ships materialised into firm amendments to SOLAS Chapter II-1, which have now been adopted by the Marine Safety Committee of the International Maritime Organization during its 98th session, an extension of the Damage Stability Project was granted additional funding in the beginning of 2017 and consequently the 2nd Project on Damage Stability for Ro-Ro Passenger Ships (2nd RoPax DamStab Project) was mobilised. The aim of the 2nd RoPax DamStab Project has been to review and evaluate existing as well as future ro-ro passenger ship safety regulations from a theoretical perspective, with the objectives to: 1. provide in-depth knowledge about and facilitate the understanding of existing as well as future damage stability standards, 2. facilitate understanding of ship type specific characteristics from a safety standard aspect, and 3. assess the consequences for the ro-ro passenger ship fleet. This report outlines the work and findings of the 2nd RoPax DamStab Project as performed during the year of 2017.
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| 45265. |
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| 45266. |
- Hao, G. Z., et al.
(författare)
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Effect of Trapped Energetic Particles on the Resistive Wall Mode
- 2011
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Ingår i: Physical Review Letters. ; 107, s. 015001-
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Tidskriftsartikel (refereegranskat)abstract
- A stability analysis for the resistive wall mode is studied in the presence of trapped energetic particles (EPs). When the EPs’ beta exceeds a critical value, a fishbonelike bursting mode (FLM) with an external kink eigenstructure can exist. This offers the first analytic interpretation of the experimental observations [ Phys. Rev. Lett. 103 045001 (2009)]. The mode-particle resonances for the FLM and the q=1 fishbone occur in different regimes of the precession frequency of EPs. In certain ranges of the plasma rotation speed and the EPs’ beta, a mode conversion can occur between the resistive wall mode and FLM.
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| 45267. |
- Hao, G. Z, et al.
(författare)
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Stabilization of the Resistive Wall Mode Instability by Trapped Energetic Particles
- 2011
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Ingår i: Physics of Plasmas. - 1089-7674 .- 1070-664X. ; 18, s. 032513-
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical model for investigating the effect of the trapped energetic particles (EPs) on the resistive wall mode (RWM) instability is proposed. The results demonstrate that the trapped EPs have a dramatic stabilizing effect on the RWM because of resonant interaction between the mode and the magnetic precession drift motion of the trapped EPs. The results also show that the effect of the trapped EPs depends on the wall position. In addition, the stabilizing effect becomes stronger when the plasma rotation is taken into account. For sufficiently fast plasma rotation, the trapped EPs can lead to the complete stabilization of the RWM. Furthermore, the trapped EPs can induce a finite real frequency of the RWM in the absence of plasma rotation.
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| 45268. |
- Hao, Xian, et al.
(författare)
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Direct measurement and modulation of single-molecule coordinative bonding forces in a transition metal complex
- 2013
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Coordination chemistry has been a consistently active branch of chemistry since Werner’s seminal theory of coordination compounds inaugurated in 1893, with the central focus on transition metal complexes. However, control and measurement of metal–ligand interactions at the single-molecule level remain a daunting challenge. Here we demonstrate an interdisciplinary and systematic approach that enables measurement and modulation of the coordinative bonding forces in a transition metal complex. Terpyridine is derived with a thiol linker, facilitating covalent attachment of this ligand on both gold substrate surfaces and gold-coated atomic force microscopy tips. The coordination and bond breaking between terpyridine and osmium are followed in situ by electrochemically controlled atomic force microscopy at the single-molecule level. The redox state of the central metal atom is found to have a significant impact on the metal–ligand interactions. The present approach represents a major advancement in unravelling the nature of metal–ligand interactions and could have broad implications in coordination chemistry.
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| 45269. |
- Hapeta, Piotr, et al.
(författare)
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Nitrogen as the major factor influencing gene expression in Yarrowia lipolytica
- 2020
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Ingår i: Biotechnology Reports. - : Elsevier BV. - 2215-017X. ; 27
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Tidskriftsartikel (refereegranskat)abstract
- Yarrowia lipolytica is an important industrial microorganism used for the production of oleochemicals. The design of effective biotechnological processes with this cell factory requires an in-depth knowledge of its metabolism. Here we present a transcriptomic study of Y. lipolytica grown in the presence of glycerol and glucose, and mixture of both at different carbon to nitrogen ratios. It emerged that the transcriptomic landscape of Y. lipolytica is more sensitive to the nitrogen availability than to the utilized carbon source, as evidenced by more genes being differentially expressed in lower carbon to nitrogen ratio. Specifically, expression of hexokinase (HXK1) is significantly susceptible to changes in nitrogen concentrations. High HXK1 expression in low nitrogen seems to impact other genes which are implicated in tricarboxylic acid cycle and erythritol biosynthesis. We further show that expression of HXK1 and two genes belonging to the sugar porter family might be controlled by GATA-like zinc-finger proteins.
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| 45270. |
- Happel, Markus, 1985, et al.
(författare)
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SOx storage and release kinetics for ceria-supported Pt
- 2009
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Ingår i: Applied Catalysis B: Environmental. - : Elsevier BV. - 0926-3373 .- 1873-3883. ; 91:3-4, s. 679-682
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Tidskriftsartikel (refereegranskat)abstract
- The SOx storage and release kinetics on CeO2 have been studied by lean SOx adsorption and temperature programmed desorption for different pairwise configurations of individual monolith samples, i.e., Pt/CeO2 + SiO2, Pt/SiO2 + CeO2, CeO2 + Pt/SiO2 and CeO2 + SiO2. In the case of sole ceria, SOx adsorption proceeds both via SO2 and SO3 adsorption although the latter channel is kinetically favored. Hence, the rate of SO2 oxidation is crucial for the overall SOx storage kinetics. It is also found that physical contact between Pt and ceria is important for the storage process. This is attributed to efficient transport routes for SOx (surface diffusion and spill-over processes) and/or specific adsorption sites at the platinum–ceria interface. The main route for SOx release is found to be thermal decomposition where the effect of platinum is minor, although an indirect effect cannot be ruled out. Different mechanistic scenarios for SOx adsorption are discussed, which may serve as a guide for future experiments.
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