• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.11
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• pp.1629-1636
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• 2004

The continuous casting is primarily a heat-extraction process in which the heat transfer at various cooling zones profoundly influences quality of products. So development of numerical model is necessarily needed for more specific and clear investigations upon heat transfer mechanism at mold and secondary cooling zones. In this study, heat transfer coefficients which show the characteristic of heat transfer mechanism in mold are calculated for more exact analysis with temperature measured in bloom mold using optimal algorithm, and finally the validity of cooling conditions at secondary cooling zone actually used at field fur 30 Ton bloom type continuous casting of 0.187%C is investigated. From the results of solidification analysis, the characteristic of bloom mold shows a similar tendency with that of previous studies, and optimized cooling conditions for 0.187%C are presented.

• Journal of Korea Multimedia Society
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• v.19 no.8
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• pp.1597-1608
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• 2016

Recently, a number of solutions were proposed to address the challenges and issues of vehicular networks. Vehicular Cloud Computing (VCC) is one of the solutions. The vehicular cloud computing is a new hybrid technology that has a remarkable impact on traffic management and road safety by instantly using vehicular resources. In this paper, we study an important vehicular cloud service, content-based delivery, that allows future vehicular cloud applications to store, share and search data totally within the cloud. We design a VCC-based system architecture for efficient sharing of vehicular contents, and propose a Hierarchical Hybrid Content Delivery scheme using Bloom Filter (H2CDBF) for efficient vehicular content delivery in Vehicular Ad-hoc Networks (VANETs). The performance of the proposed H2CDBF is evaluated through an analytical model, and is compared to the proactive content discovery scheme, Bloom-Filter Routing (BFR).

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.672-675
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• 2012

SMART Highway 사업은 첨단 IT통신과 자동차 및 도로 기술이 접목된 세계 최고수준의 빠르고 편안한 지능형 녹색도로 실현을 목표로 하고 있다. SMART Highway의 도로-자동차 기반 교통운영에서 핵심기술인 VANET(Vehicular Ad-hoc Network)은 다수의 차량들이 무선통신을 이용하여 차량 간 통신 또는 차량과 RSU(Road Side Unit)사이의 통신을 제공하는 차세대 네트워킹 기술이다. 특히, 운전자의 안전에 직접적인 영향을 끼칠 수 있는 V2V 통신의 경우 차량 간의 안전한 통신을 위해 차량 간 상호인증이 반드시 고려되어야 한다. 이처럼 빠른 속도로 이동하는 차량 간 인증이 원활이 이루어지기 위해서는 기존의 네트워크에서 사용된 인증방식은 그대로 적용시키기 어렵다. 따라서 본 논문에서는 다수의 차량 간 통신 시에 보다 효율적인 차량 인증을 위해 카운팅 블룸필터를 이용한 차량 인증 기법을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.826-827
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• 2010

통신이 발전함에 따라 웹하드와 같은 원격 데이터 저장 서버에 PC에 사용되던 자료를 저장하여 언제 어디서든 접근할 수 있는 서비스가 발전하게 되었다. 하지만 데이터를 저장하는 서버의 신뢰 문재가 발생하게 되었고, 이를 해결하기위해 서버에 저장되는 데이터의 암호화 및 이를 검색할 수 있는 기술이 필요하게 되었다. 하지만 기존의 대칭키 검색 가능 암호 시스템은 결합 키워드 검색 시 연산의 효율성이 떨어지는 문제점이 존재한다. 따라서 본 논문은 블룸필터를 사용하여 효율적인 대칭키 기반 결합키워드 검색 가능 암호 시스템을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.869-870
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• 2011

통신이 발달로 인터넷 망을 이용해 고용량의 데이터를 빠르게 주고받을 수 있게 되었으며, 이로 인하여 데이터를 원격 저장소에 저장하여 언제 어디서든 빠르게 접근할 수 있는 서비스가 발전하게 되었다. 하지만 데이터를 저장하는 서버의 보안 및 서버관리자의 신뢰 문재가 발생하게 되었고, 이를 해결하기위해 서버에 저장되는 데이터의 암호화 및 이를 검색할 수 있는 기술이 필요하게 되었다. 기존의 검색 가능 암호의 경우 이메일 서비스를 기반으로 구성이 되어 하나의 데이터에 많은 키워드를 저장하게 되는 원격 저장소 서비스에 적용하기 어렵다. 또한 필드 기반 검색기능을 제공해 검색이 유연하지 않고 결합 키워드 검색 시 연산의 효율성이 떨어지는 문제점이 존재한다. 따라서 본 논문은 블룸필터를 사용하여 대량의 키워드를 효율적으로 저장 및 검색 할 수 있으며 필드 프리한 결합키워드 검색을 지원하는 공개키 검색 가능 암호 시스템을 제안한다.

• Journal of Internet Computing and Services
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• v.19 no.1
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• pp.37-47
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• 2018

The number of capabilities of Internet of Things (IoT) devices will exponentially grow over the next years. These devices may generate a vast amount of time-constrained data. In the context of IoT, data management should act as a layer between the objects and devices generating the data and the applications accessing the data for analysis purposes and services. In addition, most of IoT services will be content-centric rather than host centric to increase the data availability and the efficiency of data delivery. IoT will enable all the communication devices to be interconnected and make the data generated by or associated with devices or objects globally accessible. Also, fog computing keeps data and computation close to end users at the edge of network, and thus provides a new breed of applications and services to end users with low latency, high bandwidth, and geographically distributed. In this paper, we propose Edge-Fog cloud-based Hierarchical Data Delivery ($EFcHD^2$) method that effectively and reliably delivers IoT data to associated with IoT applications with ensuring time sensitivity. The proposed $EFcHD^2$ method stands on basis of fully decentralized hybrid of Edge and Fog compute cloud model, Edge-Fog cloud, and uses information-centric networking and bloom filters. In addition, it stores the replica of IoT data or the pre-processed feature data by edge node in the appropriate locations of Edge-Fog cloud considering the characteristic of IoT data: locality, size, time sensitivity and popularity. Then, the performance of $EFcHD^2$ method is evaluated through an analytical model, and is compared to fog server-based and Content-Centric Networking (CCN)-based data delivery methods.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.4
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• pp.739-751
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• 2014

We are using our smartphone for our business as well as ours lives. Thus, user's privacy data and a company secret are stored at smartphone. By the way, the saved data on smartphone database can be exposed to a malicous attacker when a malicous app is installed in the smartphone or a user lose his/her smartphone because all data are stored as form of plaintext in the database. To prevent this disclosure of personal information, we need a database encryption method. However, if a database is encrypted, it causes of declining the performance. For example, when we search specific data in condition with encrypted database, we should decrypt all data stored in the database or search sequentially the data we want with accompanying overhead[1]. In this paper, we propose an efficient and searchable encryption method using variable length bloom filter under limited resource circumstances(e.g., a smartphone). We compare with existing searchable symmetric encryption. Also, we implemented the proposed method in android smartphone and evaluated the performance the proposed method. As a result through the implementation, We can confirm that our method has over a 50% improvement in the search speed compared to the simple search method about encrypted database and has over a 70% space saving compared to the method of fixed length bloom filter with the same false positive rate.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.2
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• pp.65-72
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• 2015

An anti-virus is a widely used solution for detecting malicious software in client devices. In particular, signature-based anti-viruses detect malicious software by comparing a file with a signature of a malicious software. Recently, the number of malicious software dramatically increases and hence it results in a performance degradation issue: detection time of signature-based anti-virus increases and throughput decreases. In this paper, we summarize the research results of signature-based anti-viruses which are focusing on solutions overcoming of performance limitations, and propose a new solution. In particular, comparing our solution to SplitScreen which has been known with the best performance, our solution reduces client-side workload and decreases communication cost.

• School Mathematics
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• v.6 no.1
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• pp.21-35
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• 2004

This article was to develop a tool and apply it to the high school classrooms for the performance assessment in trigonometry Bloom(1956)'s cognitive domain and holistic rubric and analytic rubric(NCTM, 1999) were used to guide the development of 12 problems. To find validity and credibility of this developed tool, Cronbach n and Rasch's BIGSTEPS were used with the samples of high students, 208, using SPSS 10.0K. The results from the investigation, indicated that the tool was very worth assessing students' achievement and there was no difference between the areas where students lived, but were differences between genders as well as between a specialized high school and preparatory high schools.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2006.06a
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• pp.365-369
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• 2006

Multiple Message Authentication Codes can be represented by one of the Short MAC, Bloom Filter or Compressed Bloom Filler to reduce communication overheads. However, this will inevitably increase false positive rate (fpr) which is a false authentication probability of adversarial messages in trade-off of communication efficiency. While the simple short MAC scheme has the lowest fpr, one cannot choose arbitrary authenticator size. Bloom filter, randomized data structure often used for membership queries, can represent multiple MACs more flexibly with slightly higher fpr. Furthermore, compressed Bloom filter has the same fpr with the short MAC while maintaining its flexibility. Through our detailed analysis, we show that pros and cons of the three schemes are scenario specific. Therefore one can choose appropriate scheme under given parameters to achieve both communication efficiency and security based on our results.