Efficient end-to-end learning for quantizable representations

Embedding representation learning via neural networks is at the core foundation of modern similarity based search. While much effort has been put in developing algorithms for learning binary hamming code representations for search efficiency, this still requires a linear scan of the entire dataset per each query and trades off the search accuracy through binarization. To this end, we consider the problem of directly learning a quantizable embedding representation and the sparse binary hash code end-to-end which can be used to construct an efficient hash table not only providing significant search reduction in the number of data but also achieving the state of the art search accuracy outperforming previous state of the art deep metric learning methods. We also show that finding the optimal sparse binary hash code in a mini-batch can be computed exactly in polynomial time by solving a minimum cost flow problem. Our results on Cifar-100 and on ImageNet datasets show the state of the art search accuracy in precision@k and NMI metrics while providing up to 98X and 478X search speedup respectively over exhaustive linear search. The source code is available at https://github.com/maestrojeong/Deep-Hash-Table-ICML18Comment: Accepted and to appear at ICML 2018. Camera ready versio

Quantum Chaos and Pole-Skipping in Semi-Locally Critical IR

We investigate pole-skipping and its connection with quantum chaos, emphasizing the role of the IR fixed point in the established relationship between pole-skipping and a universal bound of the energy diffusion constant. Using the holographic Gubser-Rocha model, which features a semi-locally critical IR fixed point, we refine the pole-skipping argument to apply to generic fixed points. Additionally, we explore the reconstruction of the full hydrodynamic dispersion relation through pole-skipping. By considering conditions in which the dispersion relation exhibits the energy diffusive mode at low wave-vector and passes through a pole-skipping point, we propose an effective heuristic approximation that relies on three physical quantities: $(D_e, \, v_B, \, \lambda_L)$, determined from horizon data. Here, $D_e$ represents the energy diffusion constant, $v_B$ the butterfly velocity, and $\lambda_L$ the Lyapunov exponent. Remarkably, this approximation demonstrates excellent agreement with the quasi-normal mode, even extending its applicability beyond the hydrodynamic regime.Comment: 10 pages, 5 figure

Dynamic Wetting and Drag Reduction on Superhydrophobic and Liquid-Infused Surfaces

Reducing drag in fluid flow has been one of the most widely studied topics in fluid dynamics due to the significant impact on improving operational efficiencies and cutting cost in applications from the aerospace, automotive and naval industries. Over the past two decades, superhydrophobic surfaces have been in the spotlight due to their ability to reduce frictional drag on the wall surface in both laminar and turbulent flows. Despite the extensive work on superhydrophobic surfaces, there are still a number of open questions remaining. In this dissertation, we investigate how a moving contact line interacts with a superhydrophobic surface by performing the first dynamic contact angle measurements to better understand the dynamics of droplets and streams on the surfaces. Our measurements found that the dynamic advancing contact angles on a superhydrophobic surface remains constant independent on capillary number while the dynamic receding contact angles decreases with capillary number but at a rate much slower than on a smooth surface. Furthermore, we investigated the role of the air-water interface shapes on the drag reduction. A novel microfluidic device was designed to incorporate superhydrophobic pillars. The shape of the air-water interface was changed with change to the static pressure in the channel. Slip along interface trapped within the superhydrophobic surface was found to result in significant drag reduction. However, the changes in flow geometry due to changes in bubble shape dominated effects due to slip. Reducing the bubble size amplified drag reduction, while increasing bubble size reduced drag reduction and even resulted in drag enhancement. In this dissertation, we also studies liquid-infused superhydrophobic surfaces as an alternative to the air-infused superhydrophobic surfaces. In the studies presented here, various immiscible oils were infused into the structures of precisely patterned and randomly rough superhydrophobic surfaces. A series of experiments were performed to investigate how liquid-infused surface affect drag reduction and droplet impact dynamics. The pressure drop reduction and slip length on the liquid-infused surfaces in microchannels were found to increase as the ratio between viscosity of water and the infused oil was increased. The longevity of these surfaces was also studied with the most effective surface found to be randomly rough. The effect of the viscosity ratio was also investigated on the droplet impact dynamics onto liquid-infused superhydrophobic surfaces. The increase in the viscosity ratio was found to increase a maximum diameter and a spreading/retraction rates of droplets. Taken together, the experimental research presented in this dissertation have allowed us to better understand and optimize the design of air-infused and liquid-infused superhydrophobic surfaces for drag reduction, droplet spreading and liquid mobility. With this new-found knowledge, a sense of new innovative ideas and applications has been or soon will be realized

Doctor of Philosophy

dissertationThis dissertation is composed of three essays about style discourse in fashion consumption. For the first chapter I developed a conceptual model to unravel the political process of meaning making between marketers and consumers. In particular, I draw on the concepts in the discourse theory of Laclau and Mouffe to develop the conceptual model to analyze the data of Chapter 2 and 3. The second chapter explores the mainstream discourse of having personal style with respect to fashion. For this second study, data have been collected from the TLC TV series What Not to Wear, an American reality television show that is based on a British Show of the same name. I chose episodes selected in What Not to Wear: Best of DVD with run time of 10 hours and 45 minutes. Transcripts of these episodes were produced and I analyzed how the notions of self, fashion, and style are intertwined in the discourse of the program. In this program the conflicts between the nominee and fashion consultants are prevalent components and there is some extent of negotiation between the two parties. Therefore, I also focus on this negotiation process and reveal how the hosts of the show win over the nominees. For the third chapter, I turn to the fans of the show What Not to Wear. Using postings on the web forum of the program I examined the ways fans integrate the cultural discourse of fashion on the program into their lives. Since there was an ample amount of data on the web forum, I sampled only the postings that were related to the episodes used in the second study. The focus of analysis is on the identification process of audience members: who do audience members identify with and how does such identification lead to specific ways of incorporating the fashion knowledge of the program? This study is expected to contribute to better understanding of how fashion reality shows have influence on consumption behaviors of audience members

OVERTURE TO A DREAM

ABSTRACT Title of dissertation: OVERTURE TO A DREAM Hyun Jeong Kim, Doctor of Musical Arts, 2010 Dissertation directed by: Professor Lawrence Moss School of Music This piece is not intended as program music. The title does not literally represent the piece itself, but rather my thoughts (my "dreams") while I was writing the piece - in short, my vision, hope, and desires - - all the things that I have always dreamed of. In traditional opera, the overture raises the curtain on the action which will follow. It gives the audience a sense of expectancy as well as a hint of how the plot will turn out. Similarly, my "Overture to a Dream" raises the "curtain" of hope that opens on my journey to my life's dreams. I wrote this piece in a free-rondo structure. Then, I let my inner instinct guide me so that musical material comes into play "naturally" rather than following a rigid structural formula. I wanted to follow a flow which keeps coming back to the dynamic theme introduced in the beginning. Its last appearance brings down the curtain. A word that I¬¬ engraved in my mind while I was composing throughout this music was: contrast. The word led me to compose a Western piece that expresses an apparent contrast with an Eastern sensibility that uses thematic material and motive development from Western compositional technique. From the very beginning of this musical journey I have constantly strived towards an ideal orchestral sound using standard orchestral instruments, rather than pursuing distinctive, innovative, or experimental music. In conclusion, I had a wonderful opportunity to transform my Eastern way which emphasizes slow movement, chamber sonorities and absence of beat, with a dynamic Western language which emphasizes rhythm, "strong" sound and complicated texture