Controlled Manipulation of Droplets on Fibers: Fundamentals and Printing Applications

In this dissertation, the drop interactions with a single fiber is discussed under an application angle for the development on new Drop-on-Demand (DOD) printhead using a fiber-in-a-tube platform[1] to print highly viscous materials[2]. To control the drop formation and manipulation on fiber, one needs to know how the fiber wetting properties and the fiber diameter influence drop formation. And then, one needs to know the effects of fiber movement in the device on drop formation. These two questions constitute the main theme of this dissertation. Before this study, it was accepted that the liquids could not form axisymmetric droplets if the liquid drop makes the contact angle greater than 90 degrees on a flat substrate of the same material. In Chapter 2, all possible configurations of an axisymmetric drop wrapping up the fiber were analyzed rigorously by studying all solutions of the Laplace equation of capillarity for small droplets for which gravity is insignificant. In Chapter 3, an experimental analysis of morphological transitions of droplet configurations has been systematically conducted. When the droplets are large and are able to wrap up the fiber, they form barreled configurations; when the volume of droplets is small, the barrels cannot be formed and droplets rest as clamshells on the fiber side. With these analyses in hands, one can design of a fiber-in-a-tube printhead taking advantage of the established diagrams for formation of barreled droplets. Drop-on-demand (DOD) printing is a versatile manufacturing tool, which has been widely used in applications ranging from graphic products to manufacturing of ceramics, even for cell engineering. However, the existing DOD methods cannot be applied for highly viscous materials: the printing technologies are typically limited to the inks with the water level viscosity and fall short of ejecting jets from thick fluids and breaking them into droplets. To address this challenge, a new wire-in-a-tube technology for drop generation has been developed replacing the nozzle generator with a wire-in-a-tube drop generator. In Chapter 4, we introduce the wire-in-a-tube generator and show successful printing results of droplets on-demand from highly viscous (~10 Pa*s) liquids. In Chapter 5, we study the drop formation mechanisms in the wire-in-a-tube drop generators. These mechanisms couple unique fluid mechanics, capillarity, and wetting phenomena providing a new platform that can be used in different microfluidic applications

An exotic fruit with high nutritional value: Kadsura coccinea fruit

This research was to determine nutritional composition, essential and toxic elemental content, and major phenolic acid with antioxidant activity in Kadsura coccinea fruit. The results indicated that Kadsura coccinea fruit exhibited the high contents of total protein, total fat, ash and essential elements such as calcium (Ca), ferrum (Fe) and phosphorus (P). The levels of four common toxic elements, i.e. cadmium (Cd), mercury (Hg), arsenic (As) and lead (Pb), were lower than legal limits. By high-performance liquid chromatography (HPLC) analysis, gallic acid was identified as major phenolic acid in peel and pulp tissues. Its contents were no significant difference in both tissues. In comparison with two commercial antioxidants, the major phenolic acid extracted from Kadsura coccinea exhibited stronger 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity and reducing power. Kadsura coccinea fruit is a good source of nutrition and natural antioxidant. It is worthwhile to popularize this exotic fruit around the world

Recommendation in Dialogue Systems

Dialogue system has been an active research field for decades and is developing fast in recent years, due to the recent breakthrough of the deep learning techniques. How to make recommendations in dialogue systems is attracting increasing attention because such systems could meet various user information needs and have much commercial potential.Current dialogue system researches typically focus on building systems for social conversation, question answering, and performing specific tasks. However, making recommendations to users, as important information need, has not been intensively researched. Meanwhile, traditional recommender systems are usually developed for non-conversation scenarios. In this dissertation, we explore how to integrate these two systems into one framework that specifically aims at making recommendations in dialogues. Such a system helps users find items by chatting with users to understand their preferences and recommending accordingly.First, we build conversational recommendation datasets, because existing dialogue datasets do not have user-item preference information or the dialogue utterances discussing facets of items, and current recommendation datasets do not have dialogue scripts associated with each user-item pair. We build the datasets by requesting crowdsourcing workers to compose dialogue utterances based on schemas and then use the delexicalization approach to simulate dialogues with the collected utterances. The datasets are used to train the natural language understanding component and provide recommendation information for our system.Based on collected datasets, we propose a reinforcement learning based conversational recommendation framework. Such a framework has three components, a belief tracker, a dialogue manager, and a recommender. The dialogue agent learns to first chat with a user to understand her preferences, and when it feels confident enough, it recommends a list of items to the user. We conduct both offline and online experiments to demonstrate the effectiveness of the framework.We further extend this framework with a personalized probabilistic recommender module. This recommender learns to predict the probability of a user likes an item given the dialogue utterance information and the personalized user preference information. By leveraging this hybrid information, the recommendation and dialogue performances are further improved. We evaluate the dialogue agent's strength in various simulated environments as well as in online user studies and demonstrate the advantages of this approach

Characterization of the fertilization independent endosperm (FIE) gene from soybean

Reproduction of angiosperm plants initiates from two fertilization events: an egg fusing with a sperm to form an embryo and a second sperm fusing with the central cell to generate an endosperm. The tryptophan-aspartate (WD) domain polycomb protein encoded by fertilization independent endosperm (FIE) gene, has been known as a repressor of hemeotic genes by interacting with other polycomb proteins, and suppresses endosperm development until fertilization. In this study, one Glycine max FIE (GmFIE) gene was cloned and its expression in different tissues, under cold and drought treatments, was analyzed using both bioinformatics and experimental methods. GmFIE showed high expression in reproductive tissues and was responsive to stress treatments, especially induced by cold. GmFIE overexpression lines of transgenic Arabidopsis were generated and analyzed. Delayed flowering was observed from most transgenic lines compared to that of wild type. Overexpression of GmFIE in Arabidopsis also leads to semi-fertile of the plants.Keywords: Polycomb proteins, fertilization independent endosperm (FIE), Glycine max, Arabidopsis thalian

3D numerical simulation of magnetization loss in multifilamentary MgB₂ wires at 20 K

High-power density all-superconducting rotating machines have potential for application in electrical aircraft motors. However, superconductors in the armature windings of such rotating machines carry AC currents under AC/rotating magnetic fields, resulting in AC losses. For reducing AC loss, low-cost, round magnesium diboride (MgB2) wires are one promising material due to their multifilamentary structure, fine filament size and tight twist. To date, previous 3D AC loss simulations have focused on MgB2 wires with a magnetic matrix operating at low frequency and 4.2 K, which are not relevant to aviation applications. In this work, 3D simulations of magnetization loss at 20 K of twisted 2-filament and 54-filament wires with a non-magnetic matrix are carried out using the finite element method, based on the H-formulation, with AC field amplitudes from 0.1 T to 2 T and frequencies up to 200 Hz. The measured Jc(B, 20 K) and n(B, 20 K) data of a non-magnetic MgB2 wire manufactured by Hyper Tech Research is assumed as input parameters. For the 2-filament wire, the operational frequency, the twist pitch, the filament size, the matrix resistivity, and inter-filament gap have been varied to systematically study their impacts on magnetization loss and its loss components (hysteresis loss, coupling loss and eddy currents). The simulation results show that the 2-filament wire with a 5 mm twist pitch and a higher resistivity matrix operated at 50 Hz has the lowest magnetization loss through decoupling the filaments. Furthermore, a lower coupling loss at 200 Hz for field amplitudes exceeding 1 T is observed, this is because critical coupling frequency fc shifts to small values with increasing field amplitudes. For the 54-filament MgB2 wire, the magnetization loss of a 5 mm twist pitch and a higher resistivity matrix wire operated at 50 Hz is estimated. The simulations show that the hysteresis loss of the 54-filament wire can be well predicted by the analytical hysteresis loss equation for a cylindrical superconductor multiplied by 54 (the number of filaments) because the filaments are in an uncoupled state. Good agreement is also observed between the simulated coupling loss and the analytical coupling loss equation from Wilson book for a circular-arranged multifilamentary superconducting wire

Effects of self-healing biomimetic subsoiler on tillage resistance, wear-corrosion performance and soil disturbance morphology under different soil types

Subsoiling has been widely used all over the world as an important operation method of no-tillage farming. For energy-saving and life-extension, the tillage resistance and wear-corrosion of subsoilers have attracted wide attention. In this study, the tillage resistance, soil disturbance, wear and corrosion of subsoiler with S-T-SK-2# biomimetic structures (S means subsoiler; T means tine; SK means shank; 2#, h/s=0.57, h=5 mm and α=45°.) and self-healing coating under two seasons, two locations with different soil properties (black loam and clay soil) and subsoiling speeds (2 km/h and 3.6 km/h) were investigated. The soil moisture content and compactness affected the tillage resistance and wear-corrosion. The tillage resistance and degree of corrosion on all subsoilers were much larger in clay soil than that in black loam soil. Compared with S-T-SK-2#, the tillage reduction rate of C-S-T-SK-2# (S-T-SK-2# with self-healing coating) was up to 14.32% in clay soil under the speed of 2 km/h. The significance tests of regression equation results showed that subsoiler type and soil properties had a significant impact on soil disturbance coefficient, swelling of total soil layer, bulkiness of the plough pan. It is of a guiding significance for the analysis of soil disturbance. Synergism mechanism of subsoiler coupling with biomimetic structures and self-healing coating was analyzed in following. It depicted the guiding effect of biomimetic structure and the shield function of self-healing coating, resulting in anticorrosion and wear resistance of subsoiler