FOOTING FIXITY EFFECT ON PIER DEFLECTION

The rotational restraint coefficient at the top of a pier and the rotational restraint coefficient at the bottom of the pier (that is, the degree of fixity in the foundation of the pier) are used to determine the effective length factor of the pier. Moreover, the effective length factor of a pier is used to determine the slenderness ratio of the pier, while the degree of fixity in the foundation of a pier is used to perform the first-order elastic analysis in order to compute the pier deflection. Finally, the slenderness ratio of the pier is used to determine if the effect of slenderness shall be considered in the design of the pier, while the magnitude of the pier deflection resulting from the first-order analysis is used to determine if the second-order force effect (the p-∆ effect) shall be considered in the design of the pier. The computations of the slenderness ratio and the deflection of a pier, however, have conventionally been carried out by assuming that the base of the pier is rigidly fixed to the footing, and the footing in turn, is rigidly fixed to the ground. Other degrees of footing fixity have been neglected by the conventional approach. In this paper, two examples are demonstrated for the slenderness ratio computation and the first-order deflection analysis for bridge piers with various degrees of footing fixity (including footings anchored on rock, footings not anchored on rock, footings on soil, and footings on multiple rows of end-bearing piles) recommended by the AASHTO LRFD Bridge Design Specifications. The results from the examples indicate that the degree of footing fixity should not be neglected since it significantly affects the magnitude of the slenderness ratio and the deflection of the pier

Effective Seed-Guided Topic Discovery by Integrating Multiple Types of Contexts

Instead of mining coherent topics from a given text corpus in a completely unsupervised manner, seed-guided topic discovery methods leverage user-provided seed words to extract distinctive and coherent topics so that the mined topics can better cater to the user's interest. To model the semantic correlation between words and seeds for discovering topic-indicative terms, existing seed-guided approaches utilize different types of context signals, such as document-level word co-occurrences, sliding window-based local contexts, and generic linguistic knowledge brought by pre-trained language models. In this work, we analyze and show empirically that each type of context information has its value and limitation in modeling word semantics under seed guidance, but combining three types of contexts (i.e., word embeddings learned from local contexts, pre-trained language model representations obtained from general-domain training, and topic-indicative sentences retrieved based on seed information) allows them to complement each other for discovering quality topics. We propose an iterative framework, SeedTopicMine, which jointly learns from the three types of contexts and gradually fuses their context signals via an ensemble ranking process. Under various sets of seeds and on multiple datasets, SeedTopicMine consistently yields more coherent and accurate topics than existing seed-guided topic discovery approaches.Comment: 9 pages; Accepted to WSDM 202

Investigations on the micellization of amphiphilic dendritic copolymers: from unimers to micelles

Since the micellization kinetics is influenced by polymer structure, the spherical three-dimensional topology of amphiphilic dendritic copolymers (ADPs) which hinders the phase separation during micellization is assumed to make the micellization kinetics different. In the literatures, most of the attention has been paid to the morphology transition or the morphology at equilibrium and the micellization kinetics of ADPs is rarely reported. In this study, the micellization processes of amphiphilic dendritic copolymers from unimers to the final equilibrium micelles were monitored by laser light scattering. Based on the closed association mechanism, the thermodynamics of micellization was analysed. The negative thermodynamic quantities indicate that the micellization of ADPs is driven by enthalpy. Based on the change of scattering intensity and hydrodynamic radius (Rh) with time, the detailed micellization kinetics was analysed, which contains two steps. By controlling the temperature and type of solvent, a system in which the concentration has little influence on Rh is obtained. The relaxation times of the two steps decrease with concentration, indicating that at higher concentration the rate of micellization is quicker. With the increasing mass fraction of the hydrophobic part, the relaxation times decrease and the driving force of micellization increases

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

P-DELTA EFFECT ON MULTI-STORY STEEL FRAMES WITH UNSYMMETRICAL VERTICAL LOAD

The P-delta effect defined as a second order effect occurs on any structure displaced by lateral forces, such as seismic or wind force. The impact of extra vertical loads including gravity will cause additional moments on the deformed structure leading to further displacements. The purpose of this study is to investigate the P-delta effect on multi-story steel framed structure with different distributions of same amount of total vertical load setting conditions, symmetrically and unsymmetrical. Meanwhile computer models with finite element analysis method will be used for this study

Overview and analysis of PM starter/generator for aircraft electrical power systems

More Electrical Aircraft (MEA) which replaces the hydraulic and pneumatic power by electrical power leads to reducing emissions and fuel consumption. The MEA concept has led to a growing use of the starter/generator (S/G) system. Permanent magnet (PM) machines have been gaining interests for aircraft S/G system application over the last few years. This is mainly due to the several advantages, including high power density, high efficiency and high speed ability. The shortcoming of the PM machines is the de-excitation problem in case of a failure, which is a main issue for the aircraft application. However, by using a PM machine with high reactance or multiphase configuration, the fault-tolerant ability can be improved. In terms of the aircraft S/G system, this paper is going to present a comprehensive analysis of PM machines. Firstly, the state-of-the-art of PM starter/generator (PMS/G) is summarized and the basic structure of PMS/G system is analyzed. Next, key technologies of the PMS/G system are summarized and analyzed. Finally, a flux weakening fault protection strategy that is used to suppress the turn-to-turn short circuit (SC) current is studied, simulated and verified. With the breakthrough of key technologies based on the development of high temperature electromagnetic material and high temperature power electronics, the PMS/G will be a potential candidate for aircraft S/G system including the embedded power generation system