• International Journal of Internet, Broadcasting and Communication
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• 제13권3호
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• pp.118-123
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• 2021

Recently, digital crime is becoming more intelligent, and efficient digital forensic techniques are required to collect evidence for this. In the case of important files related to crime, a specific person may intentionally delete the file. In such a situation, data recovery is a very important procedure that can prove criminal charges. Although there are various methods to recover deleted files, we focuses on the recovery technique using HxD editor. When recovering a deleted file using the HxD editor, check the file structure and access the file data area through calculation. However, there is a possibility that errors such as arithmetic errors may occur when a file approach through calculation is used. Therefore, in this paper, we propose an algorithm that automatically calculates the header and footer of a file after checking the file signature in the root directory for efficient file recovery. If the algorithm proposed in this paper is used, it is expected that the error rate of arithmetic errors in the file recovery process can be reduced.

• 한국기계가공학회지
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• 제21권4호
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• pp.46-52
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• 2022

In the existing wired communication network, wired communication is frequently interrupted by lightning, which accompanies rain, and remote management cannot be performed when it is actually necessary. In the case of communication interruption, field data stored in the database are lost, and data at an important point in time may go missing; this causes a decrease in the reliability of the stored data. Therefore, in this study, wireless communication using the Internet of Things (IoT) communication network of the 4^th industrial technology is installed in the prototype to reduce wired communication construction costs, prevent resource waste and environmental damage due to communication facility construction, and prepare for communication loss.

• 디지털산업정보학회논문지
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• 제4권2호
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• pp.101-108
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• 2008

In this paper, we develop system to backup automatically personal data by real time based on ECA model. This system backups data that is changed in user PC using CDP technology based on ECA model. Proposed ECA model defines file's change such as file creation, update, remove etc. in user PC to event for synchronization between server and user PC. If event is detected about file, proposed system examines condition that is defined and backup the file to server. Backup data that is stored to server can recovery on point of time that user wants. The proposed system can be applied to data management system for business, personal data management system, high-capacity contents management system etc.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권1호
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• pp.62-77
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• 2010

Emerging applications with high data rates will need to transport bulk data reliably in wireless sensor networks. ARQ (Automatic Repeat request) or Forward Error Correction (FEC) code schemes can be used to provide reliable transmission in a sensor network. However, the naive ARQ approach drops the whole frame, even though there is a bit error in the frame and the FEC at the bit level scheme may require a highly complex method to adjust the amount of FEC redundancy. We propose a bulk data transmission scheme based on erasure-resilient code in this paper to overcome these inefficiencies. The sender fragments bulk data into many small blocks, encodes the blocks with LT codes and packages several such blocks into a frame. The receiver only drops the corrupted blocks (compared to the entire frame) and the original data can be reconstructed if sufficient error-free blocks are received. An incidental benefit is that the frame error rate (FER) becomes irrelevant to frame size (error recovery). A frame can therefore be sufficiently large to provide high utilization of the wireless channel bandwidth without sacrificing the effectiveness of error recovery. The scheme has been implemented as a new data link layer in TinyOS, and evaluated through experiments in a testbed of Zigbex motes. Results show single hop transmission throughput can be improved by at least 20% under typical wireless channel conditions. It also reduces the transmission time of a reasonable range of size files by more than 30%, compared to a frame ARQ scheme. The total number of bytes sent by all nodes in the multi-hop communication is reduced by more than 60% compared to the frame ARQ scheme.

• 한국데이타베이스학회:학술대회논문집
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• 한국데이타베이스학회 2000년도 추계학술대회 E-Business와 정보보안
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• pp.216-223
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• 2000

본 연구에서는 외부와 유무선 접속기능을 갖는 무인창구 자동화기기(CD, ATM, 통장정리기, 발권기, 무인자동발급기, 지하철 게이트 등)를 인터넷망에 접속하여 기기의 장애/ 이력 관련정보를 Server의 데이터 베이스에 저장하고, 인터넷에 접속되어 있는 A/S 센터에서 필요한 정보를 쉽고 효율적으로 검색, 운용할 수 있는 시스템을 구현하는 방법을 제시한다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.288-295
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• 2003

An adaptive procedure in finite element analysis is presented by p-refinement of meshes in conjunction with a posteriori error estimator that is based on the recovery technique. In case of the recovery technique, the SPR(superconvergent patch recovery) approach has been modified for p-adaptive mesh refinement. The strategy of finding a nearly optimal distribution of polynomial degrees on a fixed finite element mesh is discussed such that a particular element has to be refined automatically to obtain an acceptable level of accuracy by increasing p-levels non-uniformly. To verify the proposed algorithm, the limit value approach is proposed which utilizes the exact strain energy computed from the extrapolation equation. A new pre-processor is developed for the p-version finite element program in which the vector graphic editor is used for the automatic generation of node connection and coordinate by halfedge solid data structure according to uniform or nonuniform p-distribution. The general 2-D algorithm is also developed to generate face modes and internal modes in accordance with different mesh types. The quality of the error estimator is investigated with the help of two mumerical examples. The results show that the sequences of p-distributions obtained by the proposed error indicator closely follow the optimal trajectory.

• 소성∙가공
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• 제18권3호
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• pp.210-216
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• 2009

Springback, an elastic material recovery after the unloading of stamping tools, causes variations and inconsistencies of final part dimensions. Recently, narrow and long surround molding parts around door frame are applied to high grade automobiles, but there are great difficulties in their die development, construction and tryout because of several springback modes including vertical movement and twist during flange forming process of them. So it is very important to predict springback's quantities of a surround molding part and, moreover, to compensate the die for them adequately, when they can't be corrected by the restrike operation. This paper presents a case study based on the die design for a surround molding part made of stainless steel. The forming and springback predictions, carried out using PAMSTAMP 2G, are reported and compared with the measurement data of the prototype. The predicted springback results were acceptable, so the processes of compensating die using Automatic Die Compensation Module of PAMSTAMP 2G were performed iteratively until the tolerances between the designed shape and the simulation data were satisfied.

• 한국컴퓨터정보학회논문지
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• 제17권3호
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• pp.41-50
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• 2012

웹 서비스 어플리케이션 기반 모니터링 시스템에서 빈번히 발생되는 데이터 구조 변경에 따른 코드 재생산에 확장성 및 오류 복구능력 향상을 위하여 DTD(Document Type Definition)자동 생성 기법을 이용한 모니터링 시스템 설계방법을 제안하였다. 제안한 DTD자동 생성 기법은 센서 데이터 구조가 수정되어도 서버 측에서 동적 서버사이드 스크립트(Dynamic Server-side Script)로 DTD정보를 자동으로 생성해 주기 때문에 데이터 손실과 오류에 대한 능동적인 대처가 가능하며, AJAX(Asynchronous JavaScript and XML)를 이용한 XML데이터 파싱(Parsing)을 구성하여 대단위 데이터 전송이나 다양한 모니터링 시스템 분야에 데이터 손실이나 손상 확인 등의 예외처리 및 데이터 구조의 확장과 축소가 용이하였다. 제안된 시스템은 일시적인 데이터 깨짐 상황에서 정상화 복구에 필요한 평균시간이 기존의 XML을 이용한 방법보다 약 44.8ms감소되어 오류 복구처리 속도가 향상됨을 알 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권8호
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• pp.3182-3202
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• 2015

Flexibly expanding the storage capacity required to process a large amount of rapidly increasing unstructured log data is difficult in a conventional computing environment. In addition, implementing a log processing system providing features that categorize and analyze unstructured log data is extremely difficult. To overcome such limitations, we propose and design a MongoDB-based unstructured log processing system (MdbULPS) for collecting, categorizing, and analyzing log data generated from banks. The proposed system includes a Hadoop-based analysis module for reliable parallel-distributed processing of massive log data. Furthermore, because the Hadoop distributed file system (HDFS) stores data by generating replicas of collected log data in block units, the proposed system offers automatic system recovery against system failures and data loss. Finally, by establishing a distributed database using the NoSQL-based MongoDB, the proposed system provides methods of effectively processing unstructured log data. To evaluate the proposed system, we conducted three different performance tests on a local test bed including twelve nodes: comparing our system with a MySQL-based approach, comparing it with an Hbase-based approach, and changing the chunk size option. From the experiments, we found that our system showed better performance in processing unstructured log data.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(4)
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• pp.13-16
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• 2001

In the Dedicated Short Range Communication (DSRC) system channel, a large number of bit errors occur because of Additive White Gaussian Noise (AWGN) and fading. When an image data is transmitted under the condition, reconstructed image quality is significantly degraded. In this paper, as an alternative to the error correcting code and/or automatic repeat request scheme, we propose an error recovery scheme for image data transmission. We first analyze how transmission errors in the DSRC system channel degrade image quality. Then, in order to improve image quality, we propose error resilient and concealment schemes for still image transmission using DCT-based fixed length coding, hamming code, cyclic redundancy check, and interleaver. Finally, we show its performance by an experiment.