| 1. |
- An, Feng-Wei, et al.
(författare)
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Establishment of a Large Animal Model for Eustachian Tube Functional Study in Miniature Pigs
- 2019
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Ingår i: Anatomical Record Part A-discoveries in Molecular Cellular and Evolutionary Biology. - : WILEY. - 1552-4884 .- 1932-8494. ; 302:6, s. 1024-1038
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Tidskriftsartikel (refereegranskat)abstract
- This study was performed to investigate whether miniature pigs are a suitable animal model for studies of the Eustachian tube (ET). Sixteen Chinese experimental miniature pigs were used in this investigation. Ten animals were used for anatomical and morphometric analyses to obtain qualitative and quantitative information regarding the ET. Three animals were used for histological analysis to determine the fine structure of ET cross-sections. Three animals were used to investigate the feasibility of balloon dilation of the Eustachian tube (BDET). The anatomical study indicated that the pharyngeal orifice and tympanic orifice of the miniature pig ET are located at the posterior end of the nasal lateral wall and anterior wall of the middle ear cavity, respectively. The cartilaginous tube was seen to pass through the whole length of the ET, the length of the cartilaginous part of the ET and the diameter of the isthmus were similar between humans and miniature pigs. The inclination of the ET in miniature pigs was larger than that in humans. The gross histology seemed to be slightly different between miniature pig and human, but the fine structures were essentially the same in both species. BDET experiments verified that the miniature pig model is suitable as a model for clinical operations. The miniature pig ET corresponds very well to that of humans. In addition, the miniature pig ET is suitable as a model for clinical operations. Therefore, the miniature pig is a valid animal model for ET study.
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| 2. |
- Arvidsson, Therese
(författare)
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Train–Bridge Interaction : Literature Review and Parameter Screening
- 2014
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- New railway lines are continuously being constructed and existing lines are upgraded. Hence, there is a need for research directed towards efficient design of the supporting structures. Increasingly advanced calculation methods can be motivated, especially in projects where huge savings can be obtained from verifying that existing structures can safely support increased axle loads and higher speeds.This thesis treats the dynamic response of bridges under freight and passenger train loads. The main focus is the idealisation of the train load and its implications for the evaluation of the vertical bridge deck acceleration. To ensure the running safety of train traffic at high speeds the European design codes set a limit on the vertical bridge deck acceleration. By considering the train–bridge interaction, that is, to model the train as rigid bodies on suspension units instead of constant moving forces, a reduction in bridge response can be obtained. The amount of reduction in bridge deck acceleration is typically between 5 and 20% for bridges with a span up to 30 m. The reduction can be higher for certain train–bridge systems and can be important also for bridge spans over 30 m. This thesis aims at clarifying for which system parameter combinations the effect of train–bridge interaction is important.To this end, a thorough literature survey has been performed on studies in train–track–bridge dynamics. The governing parameters in 2D train–bridge systems have been further studied through a parameter screening procedure. The two-level factorial methodology was applied to study the effect of parameter variations as well as the joint effect from simultaneous changes in several parameters. The effect of the choice of load model was thus set in relation to the effect of other parameter variations.The results show that resonance can arise from freight train traffic within realistic speed ranges (< 150 km/h). At these resonance peaks, the reduction in bridge response from a train–bridge interaction model can be considerable.From the screening of key parameters it can furthermore be concluded that the amount of reduction obtained with a train–bridge interaction model depends on several system parameters, both for freight and passenger train loads. In line with the European design code’s guidelines for dynamic assessment of bridges under passenger trains an additional amount of damping can be introduced as a simplified way of taking into account the reduction from train–bridge interaction. The amount of additional damping is today given as function of solely the bridge span length, which is a rough simplification. The work presented in this thesis supports the need for a refined definition of the additional damping.
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| 3. |
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| 4. |
- Guo, Weiwei, et al.
(författare)
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Aerodynamic effect of wind barriers and running safety of trains on high-speed railway bridges under cross winds
- 2015
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Ingår i: Wind and Structures. - : Techno-Press. - 1226-6116 .- 1598-6225. ; 20:2, s. 213-236
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Tidskriftsartikel (refereegranskat)abstract
- For high-speed railways (HSR) in wind prone regions, wind barriers are often installed on bridges to ensure the running safety of trains. This paper analyzes the effect of wind barriers on the running safety of a high-speed train to cross winds when it passes on a bridge. Two simply-supported (S-S) PC bridges in China, one with 32 m box beams and the other with 16 m trough beams, are selected to perform the dynamic analyses. The bridges are modeled by 3-D finite elements and each vehicle in a train by a multi-rigid-body system connected with suspension springs and dashpots. The wind excitations on the train vehicles and the bridges are numerically simulated, using the static tri-component coefficients obtained from a wind tunnel test, taking into account the effects of wind barriers, train speed and the spatial correlation with wind forces on the deck. The whole histories of a train passing over the two bridges under strong cross winds are simulated and compared, considering variations of wind velocities, train speeds and without or with wind barriers. The threshold curves of wind velocity for train running safety on the two bridges are compared, from which the windbreak effect of the wind barrier are evaluated, based on which a beam structure with better performance is recommended.
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| 5. |
- Guo, Yiting, et al.
(författare)
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Effect of Side Groups on the Photovoltaic Performance Based on Porphyrin-Perylene Bisimide Electron Acceptors
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 10:38, s. 32454-32461
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we developed four porphyrin-based small molecular electron acceptors for non-fullerene organic solar cells, in which different side groups attached to the porphyrin core were selected in order to achieve optimized performance. The molecules contain porphyrin as the core, perylene bisimides as end groups, and the ethynyl unit as the linker. Four side groups, from 2,6-di(dodecyloxy)phenyl to (2-ethylhexyl)thiophen-2-yl, pentadecan-7-yl, and 3,5-di(dodecyloxy)phenyl unit, were applied into the electron acceptors. The new molecules exhibit broad absorption spectra from 300 to 900 nm and high molar extinction coefficients. The molecules as electron acceptors were applied into organic solar cells, showing increased power conversion efficiencies from 1.84 to 5.34%. We employed several techniques, including photoluminescence spectra, electroluminescence spectra, atomic force microscopy, and grazing-incidence wide-angle X-ray to probe the blends to find the effects of the side groups on the photovoltaic properties. We found that the electron acceptors with 2,6-di(dodecyloxy)phenyl units show high-lying frontier energy levels, good crystalline properties, and low nonradiative recombination loss, resulting in possible large phase separation and low energy loss, which is responsible for the low performance. Our results provide a detailed study about the side groups of non-fullerene materials, demonstrating that porphyrin can be used to design electron acceptors toward near-infrared absorption.
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| 6. |
- Lai, Dayi, et al.
(författare)
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A comprehensive review of thermal comfort studies in urban open spaces
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 742
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Forskningsöversikt (refereegranskat)abstract
- Urban open spaces provide various benefits to large populations in cities. Since thermally comfortable urban open spaces improve the quality of urban living, an increasing number of studies have been conducted to extend the existing knowledge of outdoor thermal comfort. This paper comprehensively reviews current outdoor thermal comfort studies, including benchmarks, data collection methods, and models of outdoor thermal comfort. Because outdoor thermal comfort is a complex issue influenced by various factors, a conceptual framework is proposed which includes physical, physiological and psychological factors as direct influences: and behavioral, personal, social, cultural factors, as well as thermal history, site, and alliesthesia, as indirect influences. These direct and indirect factors are further decomposed and reviewed, and the interactions among various factors are discussed. This review provides researchers with a systematic and comprehensive understanding of outdoor thermal comfort, and can also guide designers and planners in creating thermally comfortable urban open spaces.
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| 7. |
- Lan, Lei, et al.
(författare)
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Medial ElasticsElastics: Efficient and Collision-Ready Deformation via Medial Axis Transform
- 2020
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Ingår i: ACM Transactions on Graphics. - : Association for Computing Machinery (ACM). - 1557-7368 .- 0730-0301. ; 39:3
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Tidskriftsartikel (refereegranskat)abstract
- We propose a framework for the interactive simulation of nonlinear deformable objects. The primary feature of our system is the seamless integration of deformable simulation and collision culling, which are often independently handled in existing animation systems. The bridge connecting them is the medial axis transform (MAT), a high-fidelity volumetric approximation of complex 3D shapes. From the physics simulation perspective, MAT leads to an expressive and compact reduced nonlinear model. We employ a semireduced projective dynamics formulation, which well captures high-frequency local deformations of high-resolution models while retaining a low computation cost. Our key observation is that the most compelling (nonlinear) deformable effects are enabled by the local constraints projection, which should not be aggressively reduced, and only apply model reduction at the global stage. From the collision detection (CD)/collision culling (CC) perspective, MAT is geometrically versatile using linear-interpolated spheres (i.e., the so-called medial primitives (MPs)) to approximate the boundary of the input model. The intersection test between two MPs is formulated as a quadratically constrained quadratic program problem. We give an algorithm to solve this problem exactly, which returns the deepest penetration between a pair of intersecting MPs. When coupled with spatial hashing, collision (including self-collision) can be efficiently identified on the GPU within a few milliseconds even for massive simulations. We have tested our system on a variety of geometrically complex and high-resolution deformable objects, and our system produces convincing animations with all of the collisions/self-collisions well handled at an interactive rate.
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| 8. |
- Lee, Ben H, et al.
(författare)
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Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets.
- 2016
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 113:6, s. 1516-21
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Tidskriftsartikel (refereegranskat)abstract
- Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part of the Southern Oxidant and Aerosol Study. A large fraction of pONs is highly functionalized, possessing between six and eight oxygen atoms within each carbon number group, and is not the common first generation alkyl nitrates previously reported. Using calibrations for isoprene hydroxynitrates and the measured molecular compositions, we estimate that pONs account for 3% and 8% of total submicrometer organic aerosol mass, on average, during the day and night, respectively. Each of the isoprene- and monoterpenes-derived groups exhibited a strong diel trend consistent with the emission patterns of likely biogenic hydrocarbon precursors. An observationally constrained diel box model can replicate the observed pON assuming that pONs (i) are produced in the gas phase and rapidly establish gas-particle equilibrium and (ii) have a short particle-phase lifetime (∼2-4 h). Such dynamic behavior has significant implications for the production and phase partitioning of pONs, organic aerosol mass, and reactive nitrogen speciation in a forested environment.
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| 9. |
- Li, Cheng, et al.
(författare)
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A diketopyrrolopyrrole-based macrocyclic conjugated molecule for organic electronics
- 2019
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Ingår i: Journal of Materials Chemistry C. - : ROYAL SOC CHEMISTRY. - 2050-7526 .- 2050-7534. ; 7:13, s. 3802-3810
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the first diketopyrrolopyrrole (DPP) based donor-acceptor macrocyclic conjugated molecule was developed and its application in organic electronics was systematically studied. Macrocyclic molecules, as a fragment of armchair carbon nanotubes, have emerged as functional materials in materials chemistry, but the materials are always limited to cycloparaphenylenes. Using the donor-acceptor design strategy that has been widely used in high performance conjugated polymers for macrocyclic molecules, it will significantly broaden their species with tunable optical and electrical properties. Herein, we synthesize a well-defined macrocyclic molecule containing four electron-deficient DPP units alternating with electron-rich thiophenes. The new molecule was found to show high solubility, near-infrared absorption spectra and 3D charge transport properties. The new macrocyclic molecule as an electron acceptor was applied to non-fullerene organic solar cells, exhibiting an initial efficiency of 0.49%, while the linear molecule with a similar backbone only showed a very low efficiency of 0.03%. Our results demonstrate that donor-acceptor macrocyclic conjugated materials have great potential application in organic electronics.
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| 10. |
- Li, Shaohan, et al.
(författare)
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Pushing the limit of thermal conductivity of MAX borides and MABs
- 2022
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Ingår i: Journal of Materials Science & Technology. - : Elsevier. - 1005-0302. ; 97, s. 79-88
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of MAX borides as well as MAB phases attracted great attention because of the renewable developments of ternary ceramics and offering great opportunities in potential applications. However, the number of borides remains limited, and further fundamental descriptions and detailed investigations on various properties are still lacking. In this report, we employ an integrated computational scheme that combines density functional theory with the evolutional algorithm to search for the favorable structures of P- and S-glued ternary borides terminated by Nb metal. We discover that the structures of 212-type, as e.g. Nb2PB2 and Nb2SB2, belong to the P‾6m2 space group, while those of 211-type, as e.g. Nb2PB and Nb2SB, prefer to crystallize in the P63/mmc space group, and the corresponding carbides Nb2PC and Nb2SC are also considered for the sake of completeness and comparative analsys. The predicted Nb2PB2, Nb2PB, Nb2SB, Nb2PC and Nb2SC are energetically stable, as revealed by the negative formation energies and by the proposed reaction paths with respect to the most competing phases, as well as dynamically stable, as suggested by the non-imaginary phonon spectra. The thermal conductivities of the six materials show unusual behaviors, particularly for the acoustic and optical contributions, and are accompanied by a strong anisotropy. Most importantly, Nb2PB2 is found to be an excellent thermal conductor with a total thermal conductivity of ~65 W/(m K), while Nb2SC is found to be an ultra-low thermal conductor, with a total thermal conductivity of ~5 W/(m K). These values are clearly outside the currently reported range of thermal conductivities, which makes Nb2PB2 and Nb2SC extremely interesting for fundamental research as well as prospective applications with the aid of artificial tunings on the almost independent MB block and the A layer. The discovery of these novel materials is expected to contribute substantially to the rapid development of ternary ceramics and to accelerate attempts in the applicability of MAX phases for heat conduction.
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