• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.8
• /
• pp.3689-3700
• /
• 2016

It is not practically feasible to apply hardware-based fault-tolerant schemes, such as hardware replication, in mobile devices. Therefore, software-based fault-tolerance techniques, such as checkpoint and rollback schemes, are required. In checkpoint and rollback schemes, the optimal checkpoint interval should be applied to obtain the best performance. Most previous studies focused on minimizing the expected execution time or response time for completing a given task. Currently, most mobile applications run in real-time environments. Therefore, it is extremely essential for mobile devices to employ optimal checkpoint intervals as determined by the real-time constraints of tasks. In this study, we tackle the problem of determining the optimal inter-checkpoint interval of checkpoint and rollback schemes to maximize the deadline meet ratio in real-time systems and to build a probabilistic cost model. From this cost model, we can numerically find the optimal checkpoint interval using mathematical tools. The performance of the proposed solution is evaluated using analytical estimates.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.8
• /
• pp.748-754
• /
• 2004

In this paper, we propose the Triple Modular Redundancy (TMR) control system equipped with a checkpoint strategy. In this system, faults in a single processor are masked and faults in two or more processors are detected at each checkpoint time. When faults are detected, the rollback recovery is activated to recover from faults. The conventional TMR control system cannot overcome faults in two or more processors. The proposed system can effectively cope with correlated and independent faults in two or more processors. We develop a reliability model for this TMR control system under correlated and independent transient faults, and derive the reliability equation. Then we investigate the number of checkpoints that maximizes the reliability.

• Journal of Korean Society for Atmospheric Environment
• /
• v.24 no.1
• /
• pp.122-127
• /
• 2008

The purpose of this study is to calculate atmospheric environmental capacity for $PM_{10}$, $NO_2$ and $SO_2$ using a rollback model in Chungju. From the results of this study, the source contributions for $PM_{10}$ and $NO_2$ was the following order: line source > area source > point source. However, the source contributions for $SO_2$ was the following: point source > area source > line source. While the atmospheric environmental capacity of $NO_2$ and $SO_2$ was enough to meet the regional air quality target, $PM_{10}$ emission needs to be reduced by 5%.

• ETRI Journal
• /
• v.11 no.2
• /
• pp.120-136
• /
• 1989

최근의 데이터 베이스 응용분야에 있어서 시간에 따른 정보의 변화를 유지관리할 필요성이 대두되고 대용량의 기억장치 가격의 급속한 감소와 함께 이의 이용 기술이 향상되면서 시간주기에 따라 실세계의 상태에 대한 변경과정을 표현하는 시간 즉, 데이터의 변경이력을 지원하는 데이터베이스(Terporal Database)에 관심이 집중되고 있으며, 이러한 요구를 만족시키기 위한 여러 방법들이 연구되고 있다. 일반적으로 시간 지원 데이터베이스 모델은 지원되는 시간의 형태에 따라 Static, Static Rollback, Historical, Temporal, Revision 데이터베이스 모델로 나뉘어진다. 본 논문에서는 시간 및 변경이력을 지원하기 위한 데이터베이스 모델과 이를 위한 데이터베이스 시스템의 주요 설계 Issue들에 관하여 조사분석한 다음, Static Rollback 데이터베이스 모델을 기본으로 하는 "$SR^2DBS$: 시간 지원 데이터베이스 시스팀"의 설계 및 구현에 관하여 기술하였다. $SR^2DBS$은 기존의 관계형 데이터 베이스 시스팀"의 모델을 시간 애트리뷰트를 추가시킴으로서 데이터 베이스의 변경이력관리를 가능케 한 Direct Manipulation Database Processing System으로 데이터베이스의 현상태 뿐만 아니라 시간에 따른 변경이력에 대해서 Screenoriented Relation Browsing & Editing 기능을 제공하며, 다음과 같은 특징을 갖는다. - Screen oriented Processing - Directi-Manipulation of Objects - Object & Revision History of Interest Visibility - Rapid Reversible Actions - Transaction Time & Revision Number Supporting - Roll-back Query Supporting - Han-gul Data Supporting - Two level Storage Structure(Current Version & History Versions)

• ETRI Journal
• /
• v.46 no.1
• /
• pp.59-70
• /
• 2024

We introduce a high-performance named entity recognition (NER) model for written and spoken language. To overcome challenges related to labeled data scarcity and domain shifts, we use transfer learning to leverage our previously developed KorBERT as the base model. We also adopt a meta-pseudo-label method using a teacher/student framework with labeled and unlabeled data. Our model presents two modifications. First, the student model is updated with an average loss from both human- and pseudo-labeled data. Second, the influence of noisy pseudo-labeled data is mitigated by considering feedback scores and updating the teacher model only when below a threshold (0.0005). We achieve the target NER performance in the spoken language domain and improve that in the written language domain by proposing a straightforward rollback method that reverts to the best model based on scarce human-labeled data. Further improvement is achieved by adjusting the label vector weights in the named entity dictionary.

• Journal of the Korean Data and Information Science Society
• /
• v.22 no.1
• /
• pp.125-136
• /
• 2011

Ground-level ozone, an air pollutant that is monitored by the Environmental Protection Agency (EPA), damages human health by irritating the respiratory system, reducing lung function, damaging lung cells, and aggravating asthma and other chronic conditions. In March 2008, the EPA strengthened ozone standards by lowering acceptable limits from 84 parts per billion to 75 parts per billion. Here epidemiologic data is used to study the effects of ozone regulation on human health and assessed how various regulatory standards for ozone may affect nonaccidental mortality, including respiratory-related deaths during ozone season. The assessment uses statistical methods based on hierarchical Bayesian models to predict the potential effects of the different regulatory standards. It also analyzes the variability of the results and ho they are impacted by different modeling assumptions. We focused on the technical an statistical approach to assessing relationship between new ozone regulations and mortality while other researches have detailed the relationship between ozone and human mortality. We shows a statistical correlation between ozone regulations and mortality, with lower limits of acceptable ozone linked to a decrease in deaths, and projects that mortality is expected to decrease by reducing ozone regulatory standards.

• Proceedings of the Korea Society for Simulation Conference
• /
• 1992.10a
• /
• pp.5-5
• /
• 1992

The DEVS(discrete event system specification) formalism describes a discrete event system in a hierarchical, modular form. DEVSIM++ is C++ based general purpose DEVS abstract simulator which can simulate systems to be modeled by the DEVS formalism in a sequential environment. We implement P-DEVSIM++ which is a parallel version of DEVSIM++. In P-DEVSIM++, the external and internal event of models can be processed in parallel. To process in parallel, we introduce a hierarchical distributed simulation technique and some optimistic distributed simulation techniques. But in our algorithm, the rollback of a model is localized itself in contrast to the Time Warp approach. To evaluate its performance, we simulate a single bus multiprocessor architecture system with an external common memory. Simulation result shows that significant speedup is made possible with our algorithm in a parallel environment.

• Journal of the Korea Society for Simulation
• /
• v.1 no.1
• /
• pp.64-76
• /
• 1992

The DEVS(discrete event system specificaition) formalism specifies a discrete event system in a hierarchical, modular form. DEVSIM++ is a C++based general purpose DEVS abstract simulator which can simulate systems modeled by the DEVS formalism in a sequential environment. This paper describes P-DEVSIM++which is a parallel version of DEVSIM++ . In P-DEVSIM++, the external and internal event of DEVS models can by processed in parallel. For such processing, we propose a parallel, distributed optimistic simulation algorithm based on the Time Warp approach. However, the proposed algorithm localizes the rollback of a model within itself, not possible in the standard Time Warp approach. An advantage of such localization is that the simulation time may be reduced. To evaluate its performance, we simulate a single bus multiprocessor architecture system with an external common memory. Simulation result shows that significant speedup is made possible with our algorithm in a parallel environment.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.26 no.3
• /
• pp.202-207
• /
• 2016

Checkpoint placement is an effective fault tolerance technique against transient faults in which the task is re-executed from the latest checkpoint when a fault is detected. In this paper, we propose a new checkpoint placement strategy separating data saving and fault detection processes that are performed together in conventional checkpoints. Several fault detection processes are performed in one checkpoint interval in order to decrease the latency between the occurrence and detection of faults. We address the placement method of fault detection processes to maximize the probability of successful execution of a task within the given deadline. We develop the Markov chain model for a real-time task having the proposed checkpoints, and derive the optimal fault detection and checkpoint interval.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.18 no.3
• /
• pp.527-534
• /
• 2023

Triple modular redundancy (TMR) systems can continue their mission by virtue of their structural redundancy even if one processor is attacked by faults. In this paper, we propose a new fault tolerance strategy by introducing checkpoints into the TMR system in which data saving and fault detection processes are separated while they corporate together in the conventional checkpoints. Faults in one processor are tolerated by synchronizing the state of three processors upon detecting faults. Simultaneous faults occurring to more than one processor are tolerated by re-executing the task from the latest checkpoint. We propose the checkpoint placement and fault detection strategy to maximize the probability of successful execution of a task within the given deadline. We develop the Markov chain model for the TMR system having the proposed checkpoint strategy, and derive the optimal fault detection and checkpoint interval.