Minimalist's Linux Cluster

Using barebone PC components and NIC's, we construct a linux cluster which has 2-dimensional mesh structure. This cluster has smaller footprint, is less expensive, and use less power compared to conventional linux cluster. Here, we report our experience in building such a machine and discuss our current lattice project on the machine.Comment: 3 pages, 2 figures, Proceedings of the Lattice 03 Conference (Tsukuba, Japan

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

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

E-government transformation and organisational learning: the case of Supreme Court Registry Office in Korea

This thesis critically reviews and evaluates theories of organisational learning and IT-related organisational change with particular reference to the task of explaining users’ acceptance (or rejection) of new technology. It seeks to develop a conceptual model of organisational learning and apply it to the particular case of recent IT-related (e-government) organisational change in Korea’s Supreme Court Registry Office (SCRO). Hitherto, there has been no systematic attempt to analyse the way in which management theories contribute to the electronic government (e-government) transformation effort within the public sector. This thesis seeks to fill this gap by synthesising perspectives drawn from the study of public sector organisation, IT, organisational transformation, and organisational learning. The analysis of the case study organisation (based on a qualitative research methodology) identifies various organisational learning phenomena occurring during the change project within the SCRO. In particular, it elaborates the interplay between the process of learning and change in the level of users’ acceptance (or rejection) of the new technology (the change over time is presented graphically in the form of a ‘support curve’). The research follows the organisational-transformation project since 1994 in terms of the process innovation diffusion model (Cooper and Zmud), which identifies the following key stages: initiation, adoption, adaptation, acceptance, routinisation and infusion (Cooper and Zmud). For each of these stages, processes of organisational learning are linked to the level of users’ acceptance. This aspect of the analysis involves considering the nature and scope of collective, mutual, situated, single-loop and double- loop learning; learning by doing; team learning; and leadership. These various approaches to organisational learning, which emerge from the analysis of the existing organisational-learning literature, are applied to the case analysis to bring out major developments in the SCRO’s organisational transformation. The findings derived from this study provide a framework that can be further applied and tested in future research, and that will also allow public sector management to continuously anticipate the problems involved in cultivating and sustaining users’ acceptance of new technology and nurturing appropriate organisational learning

EMI: Exploration with Mutual Information

Reinforcement learning algorithms struggle when the reward signal is very sparse. In these cases, naive random exploration methods essentially rely on a random walk to stumble onto a rewarding state. Recent works utilize intrinsic motivation to guide the exploration via generative models, predictive forward models, or discriminative modeling of novelty. We propose EMI, which is an exploration method that constructs embedding representation of states and actions that does not rely on generative decoding of the full observation but extracts predictive signals that can be used to guide exploration based on forward prediction in the representation space. Our experiments show competitive results on challenging locomotion tasks with continuous control and on image-based exploration tasks with discrete actions on Atari. The source code is available at https://github.com/snu-mllab/EMI .Comment: Accepted and to appear at ICML 201

The structure of gauge-invariant ideals of labelled graph C∗C^*-algebras

In this paper, we consider the gauge-invariant ideal structure of a $C^*$-algebra $C^*(E,\mathcal{L},\mathcal{B})$ associated to a set-finite, receiver set-finite and weakly left-resolving labelled space $(E,\mathcal{L},\mathcal{B})$, where $\mathcal{L}$ is a labelling map assigning an alphabet to each edge of the directed graph $E$ with no sinks. Under the assumption that an accommodating set $\mathcal{B}$ is closed under taking relative complement, it is obtained that there is a one to one correspondence between the set of all hereditary saturated subsets of $\mathcal{B}$ and the gauge-invariant ideals of $C^*(E,\mathcal{L},\mathcal{B})$. For this, we introduce a quotient labelled space $(E,\mathcal{L},[\mathcal{B}]_R)$ arising from an equivalence relation $\sim_R$ on $\mathcal{B}$ and show the existence of the $C^*$-algebra $C^*(E,\mathcal{L},[\mathcal{B}]_R)$ generated by a universal representation of $(E,\mathcal{L},[\mathcal{B}]_R)$. Also the gauge-invariant uniqueness theorem for $C^*(E,\mathcal{L},[\mathcal{B}]_R)$ is obtained. For simple labelled graph $C^*$-algebras $C^*(E,\mathcal{L},\bar{\mathcal{E}})$, where $\bar{\mathcal{E}}$ is the smallest accommodating set containing all the generalized vertices, it is observed that if for each vertex $v$ of $E$, a generalized vertex $[v]_l$ is finite for some $l$, then $C^*(E,\mathcal{L},\bar{\mathcal{E}})$ is simple if and only if $(E,\mathcal{L},\bar{\mathcal{E}})$ is strongly cofinal and disagreeable. This is done by examining the merged labelled graph $(F,\mathcal{L}_F)$ of $(E,\mathcal{L})$ and the common properties that $C^*(E,\mathcal{L},\bar{\mathcal{E}})$ and $C^*(F,\mathcal{L},\bar{\mathcal{F}})$ share