|Cold-start Recommendation using Latent Space Mapping, Amazon|
Pure collaborative filtering recommenders cannot be used for cold-start users and items. To tackle this problem, we tried to learn a mapping from user or item feature space to the latent space discovered by matrix factorization. We observed significant improvement in Amazon Instant Video recommendation with user features such as book or DVD purchases.
|Leveraging Wikipedia semantics for Contextual Exploration, Microsoft Research
Contextual exploration is an entity recommendation problem given a query and context, in order to satisfy user's information need directly within an application. We leverage semantic signals from Wikipedia link structures as well as relate to the context with several graph mining techniques. A crowd-sourced experimental study indicates that the proposed method successfully mines contextually-relevant pages.
|Local Collaborative Ranking, Google Research [Best Student Paper at WWW 2014]
LLORMA found that local low-rank matrix assumption is more realistic in recommendation systems. We combine this local low-rank approximation based on the Frobenius norm with a general empirical risk minimization for ranking losses. Thanks to its local nature, it is easy to parallelize, making it a viable approach for large scale real-world rank-based recommendation systems.
|Local Low-Rank Matrix Approximation (LLORMA) |
A prevalent assumption in constructing matrix approximations was that the partially observed matrix is of low-rank. Instead, we assume that the matrix is locally of low-rank, leading to a representation of the observed matrix as a weighted sum of low-rank matrices. We verify our model both with theoretical analysis and with experimental study.
|Optimizing a Personalized Multigram Cellphone Keypad |
Making use of a genetic algorithm, an efficient mobile-phone keypad suiting for each individual is proposed. Frequently-used multigrams from text messages are introduced to keypads, improving typing speed and efficiency, especially for short message service (SMS) on the phone.
|Unified Communicator, LG Electronics |
This project is for building an application which downloads and merges address books from several webmails and friend lists from Social Network Services (SNS), based on Windows Mobile. I designed the merging algorithm with a customized L-Distance algorithm in order to check similarity of strings.
|Tantra: Game Server Log Analysis and Management System, NHN Corp. |
This system gathers scattered server logs into one log server, and analyze them with scripts. Useful information on server status such as CPU, memory, or disk status are extracted and reported in every second.
|Pandora: Abusing User Monitoring System, NHN Corp.|
Based on log management system Tantra, this module detects users who try to raise levels or to get money illegally, by analyzing game server logs. I suggested and led this project, and it was selected as an excellent project of the year.
|Multi-Baduk Game, NHN Corp.
Baduk game (known also as Go game) serviced in Hangame.com. Multi-Baduk project focuses on global services in China, Japan and United States, as well as Korea. It also contains multimedia features such as on-line lectures, real-time relay broadcasting, and advertisement.
|HanJanggi (Korean Chess) Game, NHN Corp. |
This is Korean traditional Chess-like game, also serviced in Hangame.com. For this service, I am in charge of general maintenance, periodic updates, and server platform control.
|Online Broadcasting System, NHN Corp. |
For a game relay service, we built an online broadcasting system, making use of a Linux-based open source Icecast. A proxy server for load balancing purpose and frame editing functions were implemented on original version of Icecast.
|Video Editor for Network Camera, TechnoVision Inc.|
I developed a video editor for recorded files from network camera using H.264 Codec. This program includes following functions: cutting several frames from many clips, merging them to one file, saving still-cuts, and filtering images.
|Real-Time Motion Tracking using Omni-Directional PTZ Camera, TechnoVision Inc. |
Motion tracking project, which observes and detects moving objects using a sensor, then tracks and records them using an omni-directional PTZ network camera on the ceiling. As a software engineer, I devised an efficient algorithm to distinguish each moving object, even when they are overlapped and separated again.
|Unified Monitoring System for Sewer Pipe, TechnoVision Inc.|
I participated in a project for gathering data on all sewer pipes in the country and for analyzing them. My role was developing a module analyzing data on precipitation and net flow of sewer pipes as well as visualizing the result. Optimization was the key issue because this application was on real-time basis.