882 research outputs found
Ming Qing yi lai Hangzhou Wan nan an de she hui bian qian: Social transition of the south Hangzhou Bay area during the Ming and Qing dynasties.
No full text蔣宏達.Parallel title from added title page.Thesis (Ph.D.) Chinese University of Hong Kong, 2015.Includes bibliographical references (leaves 353-366).Jiang Hongda
Solidification Simulation of Binary Al-Si Alloys: Prediction of Primary Dendrite Arm Spacing with Macro-Scale Simulations (~1mm Length Scale)
No full textTitle: Solidification Simulation of Binary Al-Si Alloys: Prediction of Primary Dendrite Arm Spacing with Macro-Scale Simulations (~1mm Length Scale), Author: Hongda Wang, Location: ThodeA new and improved algorithm and numerical method has been developed and validated to simulate the solidification of binary alloys considering optimized thermophysical material properties, undercooling of the liquidus temperature prior to solidification event of the primary
phase, fluid flow induced by natural convection and shrinkage during solidification in the solidifying domain. The simulation was for a two dimensional unsteady state solidification process inside a cylindrical container. The validation was carried out with reliable experiment
results for both upward and downward solidification modes. An additional advantage of the present numerical algorithm is the estimation of the instantaneous primary dendrite arm spacing at any location in the solidified component. It has been shown that the Bouchard-Kirkaldy
model (unsteady state solidification) to evaluate the primary dendrite arm spacing in an unsteady solidification process coupled with the Lehmann model to evaluate the primary arm spacing with the effect of fluid velocity in the liquid phase is accurate within acceptable error. The results from simulations using these models have a good agreement with experiment results for instantaneous primary dendrite arm spacing in the solidified microstructure. The effect of fluid flow on the evaluation of primary arm spacing is pronounced during downward solidification. However, the effect of primary arm spacing on fluid flow is insignificant, so it is acceptable to
apply average primary arm spacing during macro-scale solidification simulations. To obtain a valid simulation, the thermophysical material properties of the solid phase should be considered as function of temperature and that of the liquid can be considered as an average constant value. The inclusion of solidification shrinkage in the simulation has negligible effect on the solidification parameters during the upward solidification mode. However, significantly changes the direction and magnitude of the fluid velocity in the liquid phase and the magnitude of
primary arm spacing in the downward solidification mode. A valid solidification simulation of binary alloys to estimate accurate primary dendrite arm spacing could be achieved only with the consideration of the undercooling of the liquidus temperature. Optimized thermophysical
properties, and fluid flow in the domain caused by both solidification shrinkage and natural convection effects.ThesisDoctor of Philosophy (PhD
RETRACTED ARTICLE: Mirt2 functions in synergy with miR-377 to participate in inflammatory pathophysiology of Sjögren's syndrome
No full textWe, the authors, Editors and Publisher of the journal Artificial Cells, Nanomedicine and Biotechnology have retracted the following article:Miaomiao Xin, Hongda Liang, Hongyue Wang, Dawei Wen, Liqin Wang, Lei Zhao, Mingshu Sun & Jibo Wang (2019) Mirt2 functions in synergy with miR-377 to participate in inflammatory pathophysiology of Sjögren’s syndrome. Artificial Cells, Nanomedicine, and Biotechnology, 47(1), 2473–2480, DOI: 10.1080/21691401.2019.1626413Following publication of the article, concerns were raised in 2019 regarding the western blots presented in the article; an Expression of Concern was issued as the authors were unable to provide the original data for review. In 2023, the authors alerted the Publisher that their Western Blots, in particular figures 1 (c,d), 3 (g,h,i,j), 5 (a,b) and 6 (a,b) had been edited prior to publication to unify the background of the blots. They also notified the publisher that they were unable to repeat their experiments to replicate their results.Upon further review, the Editor and Publisher found additional concerns regarding animal ethics and methodology. As this directly impacts the validity of the reported results and conclusions the authors alerted the issue to the Editor and Publisher, and all have agreed to retract the article to ensure the integrity of the scholarly record.We have been informed in our decision-making by our editorial policies and integrity and the COPE guidelines.The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as ‘Retracted’
Constructing ultra-stable photothermal plastics assisted by carbon dots with photocaged reactivity
No full textPhotothermal materials, especially photothermal plastics, are crucial building blocks for functional devices. Covalently immobilizing the photothermal carbon dots in plastic matrix is a promising method for producing efficient photothermal plastics. However, the reactive moieties of photothermal carbon dots are often destroyed because of harsh preparation conditions, preventing their covalent interaction with plastic matrix. Here, we conceptualized carbon dots with photocaged reactivity (P-CDs) for producing ultra-stable photothermal plastics. During the formation of P-CDs, hydroxyl moieties were maintained in the preparation environment. Upon UV irradiation, hydroxyl moieties of P-CDs were in situ converted into aldehyde groups and reacted with amino groups in the polysaccharide matrix, producing P-CD plastics. As-obtained P-CD plastics showed strong stability against solution immersion and UV aging. In particular, the P-CD plastics showed a high photothermal conversion efficiency of 46.6%. Such efficient and robust photothermal P-CD plastics were further applied to prepare a solar-driven thermoelectric generator (TEG) for energy generation
An integrated method for cell isolation and migration on a chip
No full textAbstractTumour cell migration has an important impact on tumour metastasis. Magnetic manipulation is an ascendant method for guiding and patterning cells. Here, a unique miniaturized microfluidic chip integrating cell isolation and migration assay was designed to isolate and investigate cell migration. The chip was fabricated and composed of a magnet adapter, a polytetrafluoroethylene(PDMS) microfluidic chip and six magnetic rings. This device was used to isolate MCF-7 cells from MDA-MB-231-RFP cells and evaluate the effects of TGF-β on MCF-7 cells. First, the two cell types were mixed and incubated with magnetic beads modified with an anti-EpCAM antibody. Then, they were slowly introduced into the chip. MCF-7 cells bond to the magnetic beads in a ring-shaped pattern, while MDA-MB-231-RFP cells were washed away by PBS. Cell viability was examined during culturing in the micro-channel. The effects of TGF-β on MCF-7 cells were evaluated by migration distance and protein expression. The integrated method presented here is novel, low-cost and easy for performing cell isolation and migration assay. The method could be beneficial for developing microfluidic device applications for cancer metastasis research and could provide a new method for biological experimentation.</jats:p
Design of a photonic crystal microcavity for biosensing
No full textWe have designed an air-bridged PhC microcavity with high sensitivity and a high quality factor. The structure parameters of the microcavity are optimized by three-dimensional finite-difference time-domain method. We compare the performance of a silicon-on-insulator PhC microcavity and an air-bridged PhC microcavity, and analyze the effect of the thickness of the slab and the radius of the defect hole on the performance of the air-bridged PhC microcavity. For a thinner slab and a larger defect hole, the sensitivity is higher while the quality factor is lower. For the air-bridged photonic crystal slab, the sensitivity can reach320-nm/RIU(refractive index unit) while the quality factor keeps a relatively high value of120 by selecting the proper slab thickness and the defect hole radius, respectively, when the refractive index is1.33. This is meaningful for low-detection-limit biosensing.?2011 Chinese Institute of Electronics
Federated Learning for Heterogeneous Networks: Algorithmic and System Design
No full textBuilding reliable machine learning models depends on access to data samples. With the increasingly advanced sensing and computing capabilities on edge devices, the ever-stringent data privacy legislation, and growing user privacy concerns, it is crucial to build learning models from separate, heterogeneous data sources without violating user privacy. Federated Learning (FL) can facilitate collaborative machine learning without accessing user-sensitive data and has emerged as an attractive paradigm for mobile edge networks. However, federated optimization builds on a heterogeneous environment, which brings challenges beyond traditional distributed learning. Though FL is viewed as a promising technique for enabling intelligent applications, the current FL system suffers from high communication costs, restricting it from being applied in mobile edge networks. To fully release the potential, the FL design must be communication-efficient, adaptive, and robust to the heterogeneous training environment.
In this thesis, we aim to address the practical challenges of FL in a conscientious manner. Particularly, we try to understand and address some of those challenges in federated networks and build FL systems that fulfill the accuracy, efficiency, and robustness requirements. Starting with the primary challenge, i.e., data heterogeneity, we study how it impacts the model accuracy and communication cost in the collaborative training system. To address this concern, we develop new and scalable algorithms that can quantify the contribution from participating devices, thus alleviating the negative impact of data heterogeneity and reducing the overall communication burden. To handle another major challenge, i.e., the heterogeneity of computation capabilities among different types of edge devices, we devise a new sub-model training method to enable devices with heterogeneous computation capabilities to participate in and contribute to the FL system, making it robust to the straggler effect. The proposed solutions are rigorously compared with popularly adopted benchmarks from theoretical and empirical perspectives. Finally, we provide a preliminary discussion on personalized FL and point out the potentially interesting research directions in the related fields. Although the proposed methods and designs originate from the practical application of FL, the theoretical insights gained from this thesis can be extended to a broader context of trustworthy machine learning
Wide Operation Range In-Phase Coherently Coupled Vertical Cavity Surface Emitting Laser Array Based on Proton Implantation
No full textHow the immune system learns from infections
No full textThe immune system is a complex system of cells and molecules that work cooperatively to protect us against pathogenic organisms. It can perform complicated tasks such as pattern recognition, learning, and memory, all of which require dynamical coordination among a large number of components across multiple scales. Nevertheless, the multitude of different components makes it challenging to unveil the mechanistic principles that give rise to these remarkable functions.My thesis focuses on how our immune system learns from infections and improves specificity of pathogens recognition on the fly. This process is known as affinity maturation, where the affinity of B cell receptor improves through Darwinian evolution. Although recent progresses in experiments revealed many details, what remains is a first-principle and quantitative understanding of how different elements come together to achieve the goal. Using statistical physics tools and computational modeling, I study various aspects of the maturation process, including molecular interactions, information extraction, and evolutionary dynamics. To understand how B cells with different affinities are discriminated during affinity maturation, we investigate the process of antigen extraction, where B cells use cytoskeleton forces to extract antigen molecules from other presenting cell surface. We show this process allows a B cell to infer its receptor affinity by measuring the number of extracted antigens.Our model highlights the regulatory role of mechanical force: Application of a constant force with proper magnitude can enhance discrimination fidelity, and usage of a dynamical force that introduces negative feedback can improve discrimination robustness with respect to fluctuations in antigen concentration. To illustrate how molecular interactions influence cellular evolution, we couple the physical theory of antigen extraction to a minimal model of affinity maturation and simulate ensembles of cell populations under different conditions. The multiscale model predicts that the affinity ceiling stems from the physical limit of antigen tether strength and identifies strategies to alleviate the constraint. Lastly, we present a study on the long-term coevolution between evolving pathogen and adaptive immune response. Our work reveals that the asymmetric reaction range between immunogenicity (the ability of pathogens to induce an immune response) and antigenicity (the ability of pathogens to interact with antibodies) is critical in determining the dynamics of coevolution
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