Seong-Il Jin

No-log recovery mechanism using stable memory for real-time main memory database systems

In this paper we propose a new recovery mechanism for real-time main memory database systems (RT-MMDBS) that improves the performance of the system while satisfying the real-time property by using shadow paging. Main memory database system (MMDBS) has been an attractive choice as a real-time database system (RTDBS) since if suggests the possibility of ensuring fast response time and predictability. But the recovery schemes used in existing MMDBS do not ensure fast responsiveness because of logging overhead. We propose a recovery mechanism that uses shadow-paging recovery scheme, stable memory, and sequential transaction processing. We also address how it can meet the real-time property of transactions by providing fast response time and fast recovery.

Branch-Based Centralized Data Collection for Smart Grids Using Wireless Sensor Networks

A smart grid is one of the most important applications in smart cities. In a smart grid, a smart meter acts as a sensor node in a sensor network, and a central device collects power usage from every smart meter. This paper focuses on a centralized data collection problem of how to collect every power usage from every meter without collisions in an environment in which the time synchronization among smart meters is not guaranteed. To solve the problem, we divide a tree that a sensor network constructs into several branches. A conflict-free query schedule is generated based on the branches. Each power usage is collected according to the schedule. The proposed method has important features: shortening query processing time and avoiding collisions between a query and query responses. We evaluate this method using the ns-2 simulator. The experimental results show that this method can achieve both collision avoidance and fast query processing at the same time. The success rate of data collection at a sink node executing this method is 100%. Its running time is about 35 percent faster than that of the round-robin method, and its memory size is reduced to about 10% of that of the depth-first search method.

Detecting and monitoring game bots based on large-scale user-behavior log data analysis in multiplayer online games

Online games with a variety of genres and game style have become popular. While the market for online games is growing, unauthorized program software is used and operated by some users. They damaged fair players and furthermore, bot program users have inflicted a huge loss to game service companies. Bot programs show various game play action styles and there are many users not only in Korea but also other countries, so it is not easy to trace. Also, as users of online game and smart device game which is focused recently are increasing, log data quantity are explosively increased and demands of analysis on not only bot information, but also statistical information which is necessary for game operation plan from log information. This paper examines bot program of online game, detection method and tendency of log data management technology for it. This paper introduces our method to detect game bots and manage game log data.

The Application of Visualization and Simulation in a Dismantling Process

The lack of as-built drawings and information for many old nuclear facilities impedes the planning for a decommissioning. Traditional manual walkthroughs subject workers to lengthy exposure to radiological and other hazards. And also there have been a delay in the dismantling schedules and that in an increase in the amount of waste, which have caused a heavy expenditure for the decommissioning cost. In order for a 3D model to represent the real dismantling operation environment, realistic dismantling activities and scenarios were modeled. We present a dismantling digital mock-up system that can show a dismantling process through an animation and enable us to evaluate the major parameters that can directly affect the cost in a static simulation as a preview to the dismantling activities on a hypothetical dismantling environment. We carried out a prototype 3D animation and a simulation system for dismantling the thermal column in Korean Research Reactor-1(KRR-1). The results show that the modeling of a realistic scenario makes it possible to demonstrate the adequacy of the design and can provide operators with a high fidelity under the real working conditions.

Kernel structuring using time-triggered message-triggered objects for real-time active DBMS in layered architecture

Real-time active database systems are systems that need the logical consistency of computation results and the timing constraint. Especially, real-time systems are generally highly interactive with their environment, reacting to stimuli in the environment. And a wealth of active database models has been proposed and several major prototypes have been produced However, no uniform method for specifying the rule and each manager of active database system in design has yet been proposed within the real-time research community: for an example, real-time object model. This paper presents an architecture of an real-time active database system using time-triggered message-triggered object with incorporating active functionality and real-time constraints into an active database kernel in layered architecture. Also this paper shows how real-time objects are designed to a manager as a module of active database and a rule in active database is represented as an object designed to appropriate to real-time active database.

Efficient data collection for smart grid using wireless sensor networks

Data collection is an essential operation in smart grids using wireless sensor networks. In a smart grid, a smart meter generates power usage and a data collection unit periodically collects it from every smart meter. This paper focuses on a central data collection problem of how to quickly collect every power usage from every smart meter without collisions. To solve the problem, we divide a tree that a sensor network constructs into several branches. Each branch consists of all meters included in a path from a data collection unit to a leaf meter, and a conflict-free query schedule is generated based on branches. The novel method avoids collisions between a query and a query response as well as between query responses. The experimental results show that this method can achieve both collision avoidance and fast query processing at the same time.

Adaptive Threshold-based Link Status Update Mechanism

The current Internet protocol (IP)-based networks face tremendous requirements such as quality of service (QoS) guarantees, efficient traffic engineering (TE), network scalability, and high network performance, in accordance with the emergence of diverse Internet services. A constraint-based routing path is determined based on network topology and link state information to guarantee QoS. It is necessary for constraint-based routing to disseminate and update link state information. Throughput can be reduced due to processing link state update messages if link update messages are generated excessively. On the other side, route setup requests can be rejected even though there are available routes in case that link state information is not updated appropriately. This paper proposes a new adaptive threshold-based link status update mechanism to reduce the volume of link state update traffic and to provide QoS-guaranteed path. In addition, the performance of the proposed mechanism is evaluated via simulations

UGS middleware for monitoring state of underground utilities

This paper describes UGS middleware (UGS-M) to support an underground safety service (UGS). UGS-M consists of communication manager, data translator, resource manager, sensing data manager, and monitoring manager. One of the most important roles of UGS-M is the abstraction of the various sensing devices installed in the underground. They are used to acquire the state changes of the underground utilities. To manage differences among the devices, UGS-M uses the standard interface, ISO/IEC 30128, which provides a single interface with them. UGS-M has been developed to provide a powerful tool that enhances the ability to monitor the underground environment and will help improve the efficiency of the underground safety management.

A Case Study: Online Game Testing Using Massive Virtual Player

Automated load tests for online games can resduce costs because it doesn’t need real players. We will introduce our online game testing tool, EasyQA and show a case study to testing real online game before it is published.

Inter-Domain QoS Routing Scheme using Link State Information

In the Internet, in order to guarantee Quality of Service (QoS), all routers have to manage their Link State Databases (LSDBs) and determine a routing path that satisfies service requirements based on the LSDB. In addition, routing protocols have to provide QoS not only in the intra- domain but also in the inter-domain to enable the end to end QoS guarantee. In the intra-domain routing, it is possible that a router manages its LSDB because the link state information is small in a domain. On the other hand, in inter- domain routing, since the amount of the link state information is very large, it is unrealistic to manage the whole link state information. The Border Gateway Protocol (BGP) is the most prominent inter-domain routing protocol in the current internet. However, it is difficult to guarantee the inter-domain QoS using BGP because the BGP is a path- vector based protocol. In this paper, we propose the inter- domain QoS routing schemes that can manage the LSDBs effectively and minimize a waste of the network system resources by Link State Update (LSU) massages. We evaluate the performance of the proposed schemes by simulations. From the results, the proposed schemes can reduce the blocking probability and amount of the link state update with a few link state information.