Kyungmin Cho

HiCon: a hierarchical context monitoring and composition framework for next-generation context-aware services

This article presents a hierarchical context monitoring and composition framework that effectively supports next-generation context-aware services. The upcoming ubiquitous space will be covered with innumerable sensors and tiny devices, which ceaselessly pump out a huge volume of data. This data gives us an opportunity for numerous proactive and intelligent services. The services require extensive understanding of rich and comprehensive contexts in real time. The framework provides three hierarchical abstractions: PocketMon (personal), HiperMon (regional), and EGI (global). The framework provides effective approaches to combining context from each level, thereby allowing us to create a rich set of applications, not possible otherwise. It deals with an extensively broad spectrum of contexts, from personal to worldwide in terms of scale, and from crude to highly processed in terms of complexity. It also facilitates efficient context monitoring and addresses the performance issues, achieving a high level of scalability. We have prototyped the proposed framework and several applications running on top of it in order to demonstrate its effectiveness.

Running or gaming

We developed Exertainer, a sensor-enabled, interactive running entertainment system to support advanced exercise applications. We designed Exertainer to be used in urban environments where outdoor running is often not convenient or practical; as such, Exertainer and Exertainer running applications represent an attractive alternative to traditional treadmill running. Exertainer effectively creates a robust design space around treadmill running. Developers can leverage Exertainers components, an advanced treadmill called Interactive Treadmill, Sensor Bracelet and the PSD game platform, to design interactive and immersive running games and other advanced running applications. We also developed Swan Boat, a multiplayer team racing game making the treadmill running an exciting social activity, and conducted a user study.

Defect formation in the solid phase epitaxial growth of GaAs films on Si (001) substrate

The defect structures of GaAs film on (001) Si substrate tilted ∼3° towards the [110] direction were investigated by the high‐resolution transmission electron microscopy. GaAs films were grown by the molecular beam epitaxy (MBE) on the Si (001) substrate by a modified two‐step process, in which amorphous GaAs buffer layers were grown first. High‐resolution electron micrographs show that stacking faults (and/or microtwins) are preferentially formed on the tilted step‐rich surface, whereas misfit dislocations are preferentially formed on the flat surface. However, the difference in the defect density on the two cross sections is small. Between the observed 90° edge and 60° misfit dislocations the density of the latter is higher irrespective of the substrate tilt. This occurrence is explained by the difference in distribution of initial nucleating islands between the present and the conventional two‐step MBE techniques.

DCF: an efficient data stream clustering framework for streaming applications

Streaming applications, such as environment monitoring and vehicle location tracking require handling high volumes of continuously arriving data and sudden fluctuations in these volumes while efficiently supporting multi-dimensional historical queries. The use of the traditional database management systems is inappropriate because they require excessive number of disk I/O in continuously updating massive data streams. In this paper, we propose DCF (Data Stream Clustering Framework), a novel framework that supports efficient data stream archiving for streaming applications. DCF can reduce a great amount of disk I/O in the storage system by grouping incoming data into clusters and storing them instead of raw data elements. In addition, even when there is a temporary fluctuation in the amount of incoming data, it can stably support storing all incoming raw data by controlling the cluster size. Our experimental results show that our approach significantly reduces the number of disk accesses in terms of both inserting and retrieving data.

SATI: A scalable and traffic-efficient data delivery infrastructure for real-time sensing applications

Upcoming ubiquitous technologies are expediting the advent of many real-time applications. Examples of such applications include physical world browsing, RFID-based supply chain management, city-wide road traffic monitoring, weather forecasting, and air pollution monitoring. These applications show different scales and characteristics in terms of sensing data delivery demands. They commonly demand a deep understanding on real-time data delivery from widely distributed data sources. Also, they have highly individualized and fine-grained delivery demands in terms of data and delay specifications, e.g., data value ranges of interest, spatial and temporal resolutions, and tolerable delay, etc. Due to the remarkable scale and complexity, however, existing data delivery systems cannot support such applications effectively. We present SATI (scalable and traffic-efficient data delivery infrastructure), a novel Internet-based sensing data delivery infrastructure that provides a common platform for data providers and consumers. Basically, it is comprised of a collection of proxy nodes forming an overlay network, where each proxy node conducts an in-network processing and efficient data delivery. It allows applications to specify their delivery requirements with intuitive and comprehensive delivery semantics. For scalable and efficient data delivery, SATI develops a novel delivery path management scheme based on an incremental relaxation method. The scheme enables SATI to construct and maintain efficient delivery paths satisfying a large number of delivery requests of high diversity. It fully exploits the diversity of delivery demands on both data and delay requirements, thus achieving a high level of service satisfaction and efficiency at the same time. The result from a large-scale simulation shows that SATI achieves a high level of scalability and bandwidth efficiency.

A Scalable and Efficient Path Management Scheme for Internet-Based Sensor Data Delivery Infrastructure

In upcoming ubiquitous environment, many real-time sensing applications will emerge. These applications show different scale and characteristics on delivery demands. The applications commonly depend on real-time understanding on data from widely distributed data sources. Also, they have highly diverse and complex delivery demands in terms of data and delay, e.g., data value ranges of interest, spatial and temporal resolution and tolerable delay, etc. Due to the remarkable scale and complexity, however, existing data delivery schemes cannot support the applications effectively. We present a novel data delivery scheme to support real-time sensing applications. Our scheme provides efficient delivery paths over Internet-based delivery infrastructure, which is comprised of a collection of dispersed nodes forming an overlay network. It fully exploits the diversity of delivery demands on both data and delay requirements, thus achieving high level of service satisfaction and efficiency at the same time. Also, it distributes path management overhead to multiple nodes by adopting a hierarchical path management approach. We evaluate our scheme through a large-scale simulation. The results show that it achieves a high level of scalability and bandwidth efficiency.

Sparse Rig Parameter Optimization for Character Animation

We propose a novel motion retargeting method that efficiently estimates artist‐friendly rig space parameters. Inspired by the workflow typically observed in keyframe animation, our approach transfers a source motion into a production friendly character rig by optimizing the rig space parameters while balancing the considerations of fidelity to the source motion and the ease of subsequent editing. We propose the use of an intermediate object to transfer both the skeletal motion and the mesh deformation. The target rig‐space parameters are then optimized to minimize the error between the motion of an intermediate object and the target character. The optimization uses a set of artist defined weights to modulate the effect of the different rig space parameters over time. Sparsity inducing regularizers and keyframe extraction streamline any additional editing processes. The results obtained with different types of character rigs demonstrate the versatility of our method and its effectiveness in simplifying any necessary manual editing within the production pipeline.

Age‐related gait motion transformation based on biomechanical observations

We present a novel approach for synthesizing human gait motions according to a range of input ages by transforming a given motion based on biomechanical observations. Given an original motion, our method first extracts gait cycles that are periodically defined by foot contact on the ground and then transforms the original motion to achieve a desirable posture and motions that respectively correspond to the input age. Among many biomechanical features that gradually change with aging, we mainly focus on spatiotemporal and kinematic features as well as postural changes. Exploiting these features, we formulate the biomechanical changes as continuous functions that reflect visually significant features corresponding to the input age. Finally, we demonstrate that our system can automatically generate plausible gait motions given a wide range of input ages.

CIGMA: aCtive Inventory service in Global e-MArket based on efficient catalog management

A fully Internet-connected business evironment is subject to frequent changes. To ordinary customers, online shopping under such a dynamic environment can be frustrating. We propose a new E-commerce service called the CIGMA to support online customers under such an environment. The CIGMA provides catalog comparison and purchase mediation services over multiple shopping sites for ordinary online customers. The service is based on up-to-date information by reflecting the frequent changes in catalog information in real-time. It also matches the desire of online customers for fast response. This paper describes the CIGMA along with an overview of its catalog management schemes.