3,562 research outputs found
Influence of erosional unloading on the state of stress for low amplitude single-layer buckle folds - implications for tensile fracture occurrence
The existence of fractures associated to buckle folds is related to the strain distribution of the fold. The erosional unloading process can amplify the remnant strain in the folded layer. Two-dimensional plane strain Finite Element Analysis (FEA) is used to investigate the influence of the erosional unloading step on both the evolution of the state of stress and the associated failure patterns in low amplitude buckle folds. Sensitivity analyses on different input parameters, including viscosity, shortening ratio, and overburden pressure, are performed. Based on the simulation results, tensile stress can be initiated both in the crest and in the limb of low amplitude buckle folds in high permeability models during the elastic erosional unloading process. Tensile failure can be initiated perpendicular to the bedding in the top of the fold crest. The type of fracture in the limb depends on the strength of the rock. Tensile failure is initiated in the fold limb more likely for strong rocks while shear failure is initiated more likely for weak rocks. The orientation of both the stresses and the subsequent fractures in low amplitude folds is not affected by the erosional unloading process. In summary, the initiation of both the tensile stress and the subsequent fractures depends on rock properties and strain history --Abstract, page iii
Seismic loss assessment of typical RC frame-core tube tall buildings in China and US using the FEMA P-58 procedure
Reinforced concrete (RC) frame-core tube buildings are widely constructed both in China and the United States (US). Their seismic performances greatly influence the economic loss of earthquakes. This study aims to compare the seismic losses of two typical RC frame-core tube tall buildings designed following the Chinese and the US seismic design codes. The prototype building is originally designed using the US seismic design codes, provided by the Tall Building Initiative (TBI) Project. Then the prototype building is redesigned according to the Chinese seismic design codes with the same design conditions and seismic hazard level. Detailed nonlinear finite element (FE) models are established for both designs. These models are used to evaluate their seismic responses at different earthquake intensities, including the service level earthquake (SLE), the design based earthquake (DBE) and the maximum considered earthquake (MCE). In addition, the collapse fragility functions of these two buildings are established using the incremental dynamic analysis (IDA). Subsequently, the seismic loss consequences (repair costs, repair workload, and casualties) of these two designs are calculated using the procedure proposed by FEMA P-58. The comparison shows that the Chinese design exhibits better seismic performances in most cases with smaller total repair cost, shorter repair time and a smaller number of casualties, except slightly longer repair time at the MCE level. For both designs, the repair cost of nonstructural components accounts for the majority of the total cost. The ceilings and elevators are the major causes of casualties at the MCE level
Performance Analysis of Sparse Traffic Grooming in WDM Mesh Networks
Sparse traffic grooming is a practical problem to be addressed in heterogeneous multi-vendor optical WDM networks where only some of the optical cross-connects (OXCs) have grooming capabilities. Such a network is called as a sparse grooming network. The sparse grooming problem under dynamic traffic in optical WDM mesh networks is a relatively unexplored problem. In this work, we propose the maximize-lightpath-sharing multi-hop (MLS-MH) grooming algorithm to support dynamic traffic grooming in sparse grooming networks. We also present an analytical model to evaluate the blocking performance of the MLS-MH algorithm. Simulation results show that MLSMH outperforms an existing grooming algorithm, the shortest path single-hop (SPSH) algorithm. The numerical results from analysis show that it matches closely with the simulation. The effect of the number of grooming nodes in the network on the blocking performance is also analyzed
An exploration of changing identity, linguistic challenges and cultural surprises -- a case study of a UK University group of diverse Chinese language students studying abroad
With the development of the internationalisation of China and Chinese
universities as well as Chinaās increasing prominence economically, there are
increasing numbers of international students who choose Chinese studies as their
major and come to China to learn the Chinese language. However, nowadays, in the
research field of teaching and learning Chinese as a second language, few
researchers concentrate on the beliefs, perspectives and sense of self of these
students of Chinese during their Study Abroad experiences. Therefore, this research
focuses on investigating the identity challenges, cultural engagement and linguistic
opportunities of students of Chinese in one Higher Education institution during this
important transitional experience, before, during and after studying Chinese in
Mainland China.
Drawing on poststructuralist perspectives to establish a theoretical position
and narrative identity theory as a key conceptual frame, an instrumental case study
formed the approach to data collection. The case study involved diverse learners of
Chinese as a second language on courses at a UK higher university and with
experience of studying abroad in China or other Chinese-speaking jurisdictions.
Interviews were used as a means of gaining rich data and insights into personal
experiences and conflicting interactions as the students attempted to develop
linguistically but also tried to negotiate a sense of belonging within this new
environment.
The results are reported using different narrative strands of the Chinese
language (CL) learners and how they defined and redefined the concept of who they
were and who they were becoming as they experienced Chinese language
interactions and Chinese culture during their experiences abroad and on their return.
The findings concluded with three main narrative strands: i) Linguistic self:
after studying in China, Chinese language learners (CLL) believed that they were
ānot afraid to speak Chineseā and felt a sense of achievement as they engaged in
diverse interactions and gradually achieved some degree of acceptance as new
Chinese speakers. ii) Social and cultural self: The acculturation process was very
much shaped by individualsā unique choices and experiences. The desire to speak
Chinese, the acceptance of and engagement with Chinese culture, and native
speakersā approval of their efforts, helped them to develop a sense of belonging,
creating a shift in CLLsā socio-cultural identity. iii) Hybrid self: Their original cultural
identity, whether monocultural or intercultural as part of the learnerās background,
played an important role in influencing the learnerās sense of self in the target
language community. Most of the CLLs believed that they came through this
transcultural journey with a more nuanced cultural hybrid identity after living in China,
but they always had some degree of still feeling like an āāoutsiderāā
A hybrid single-mode laser based on slotted silicon waveguides
An InGaAsP-Si hybrid single-mode laser based on etched slots in silicon waveguides was demonstrated operating at 1543 nm. The InGaAsP gain structure was bonded onto a patterned silicon-on-insulator wafer by selective area metal bonding method. The mode-selection mechanism based on a slotted silicon waveguide was applied, in which the parameters were designed using the simulation tool cavity modeling framework. The III-V lasers employed buried ridge stripe structure. The whole fabrication process only needs standard photolithography and inductively coupled plasma etching technology, which reduces cost for ease in technology transfer. At room temperature, a single mode of 1543-nm wavelength at a threshold current of 21 mA with a maximum output power of 1.9 mW in continuous-wave regime was obtained. The side mode suppression ratio was larger than 35 dB. The simplicity and flexibility of the fabrication process and a low cost make the slotted hybrid laser a promising light source
Rational design of dibenzo[a,c]phenazine-derived isomeric thermally activated delayed fluorescence luminophores for efficient orange-red organic light-emitting diodes
It is an immense challenge to develop efficient long-wavelength (orange-to-red) thermally activated delayed fluorescence (TADF) materials due to the increasing nonradiative decay rates following the energy-gap law. Herein, two pairs of asymmetric isomers; DPyPzTPA and TPAPzDPy, and PyPzDTPA and DTPAPzPy based on electron-deficient moieties dibenzo[a,c]phenazine (Pz) and pyridine (Py) combined with electron-donor units of triphenylamine (TPA) were designed and synthesized. Their photophysical properties could be finely modulated by changing the position and number of Py groups as well as TPA fragments onto Pz cores. DPyPzTPA and DTPAPzPy possess much more rigidity and thus less geometry relaxation and non-radiative decay between ground states and excited states than those of PyPzDTPA and TPAPzDPy. Intriguingly, DPyPzTPA exhibits the highest relative photoluminescence quantum yield (Ī¦PL) and the fastest reverse intersystem crossing (rISC) rate among them owing to relatively stronger rigidity and spin-orbit coupling (SOC) interactions between the lowest singlet (S1) and energetically close-lying excited triplet state and therefore, the device showed the highest maximum external quantum efficiency (EQEmax) of 16.6% (60.9 lm/W, 53.3 cd/A) with Commission Internationale de I'Eclairage (CIE) coordinates of (0.43, 0.55), peak wavelength 556 nm. In stark contrast, due to its lower rigidity and extremely weak delayed fluorescence (DF) characteristic and thus the much lower Ī¦PL, TPAPzDPy-based devices are only half as efficient (30.8 lm/W, 27.5 cd/A, 8.3% EQE) despite the isomers possessing equal singlet-triplet energy gaps (ĪEST) of 0.43 eV. On the other hand, the device based on DTPAPzPy also demonstrated a strongly enhanced performance (59.1 lm/W, 52.7 cd/A, 16.1% EQE) than its isomer PyPzDTPA-based device (39.5 lm/W, 35.2 cd/A, 10.3% EQE). This work explicitly implicates that the asymmetric and isomeric molecular design is a potential strategy for promoting the development of highly efficient long-wavelength TADF materials
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