• 한국멀티미디어학회논문지
• /
• 제24권12호
• /
• pp.1641-1652
• /
• 2021

To analyze the crime scene, the role of digital evidence such as CCTV and black box is very important. Such digital evidence is often damaged due to device defects or intentional deletion. In this case, the deleted video can be restored by well-known techniques like the frame-based recovery method. Especially, the data such as the video can be generally fragmented and saved in the case of the memory used almost fully. If the fragmented video were recovered in units of images, the sequence of the recovered images may not be continuous. In this paper, we proposed a new video restoration method to match the sequence of recovered images. First, the images are recovered through a frame-based recovery technique. Then, after analyzing the time information marked on the images, the time information was extracted and recognized via optical character recognition (OCR). Finally, the recovered images are rearranged based on the time information obtained by OCR. For performance evaluation, we evaluate the recovery rate of our proposed video restoration method. As a result, it was shown that the recovery rate for the fragmented video was recovered from a minimum of about 47% to a maximum of 98%.

• 응용통계연구
• /
• 제26권6호
• /
• pp.933-942
• /
• 2013

본 연구에서는 시뮬레이션 방법을 사용해서 다양한 조건에서 주성분분석이 얼마나 잘 요인 구조를 복원할 수 있는지를 공통요인분석과 비교하여 체계적으로 평가하였다. 이 연구에서 요인 대 변수 비율, 공통성, 그리고 표본크기를 실험변수로 설정하였다. 주성분분석은 표본의 크기가 200개 이하인 경우 공통적으로 공통요인분석에 비해 더 우수한 요인구조의 복원력을 보여주었다. 특히, 요인 당 변수 수가 적은 경우, 주성분분석은 50개의 표본에서도 만족할 만한 수준의 요인복원능력을 보여주었다. 이와 더불어 공통성 수준 또한 낮은 경우 필요한 표본수는 100개로 늘어난다. 본 연구결과는 요인추출방법으로서 주성분분석의 선택의 근거를 제시하고 타당한 사용에 관한 가이드라인을 제시해 준다.

• 한국멀티미디어학회논문지
• /
• 제19권5호
• /
• pp.918-923
• /
• 2016

IoT should be considered security risk environments such as various platforms and services including smart devices that can be mounted on household electric appliances, healthcare, car, and heterogeneous networks that are connected to the Internet, cloud services and mobile Apps.. In this paper, we provide analysis of new security threats, caused by open-platform of IoT and sensors via the Internet. Also, we present the key recovery mechanism that is applied to IoT. It results to have compatibility with given research, reduces network overhead, and performs key recovery without depending on key escrow agencies or authorized party.

• 한국유체기계학회 논문집
• /
• 제19권2호
• /
• pp.43-48
• /
• 2016

This study proves successes of Energy Service Company (ESCO) business by heat pump performance test. The purpose of ESCO business is recover investment costs through saving energy from installation of energy reduction facility. The most important technology assessment items are heat recovery and generator output. Experimental result shows that increase quality of heat recovery (11.52Gcal/h), while decrease generator output (0.234kw). In its final analysis, the ESCO business is successful according to our data.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2008년도 추계학술대회 논문집
• /
• pp.281-283
• /
• 2008

The superconducting fault current limiter (SFCL) using magnetic coupling of two coils with series connection, which was suggested by us, has the merit to increase the operational current and the limiting impedance of the SFCL through the adjustment of the inductance ratio and the winding direction of two coils. In addition, the recovery characteristics of the SFCL is affected by the winding direction of two coils as well as two coils' inductance ratio. In this paper, the fault current limiting and recovery characteristics of a SFCL using magnetic coupling of two coils with series connection were analyzed. Through the analysis based on the experimental results, the recovery characteristics and the current limiting characteristics of the SFCL were confirmed to be improved more in case of the additive polarity winding.

• 전기학회논문지
• /
• 제58권5호
• /
• pp.905-910
• /
• 2009

For proper application and operation of a SFCL(Superconducting Fault Current Limiter) in distribution systems, the prior investigation of fundamental characteristics and its effects analysis to the systems are very important. A point of view in coordination with recloser in distribution systems, characteristic about quenching and recovering of SFCL should be studied. Especially, its detailed study of recovery characteristic is particularly important to avoid conflict between the SFCL and the recloser. In this paper, the resistive type SFCL and recloser, which used in distribution system, were implemented using EMTP/ATPDraw and MODELS language. To analyze the recovery characteristics of SFCL according to recloser operation in distribution systems, case studies have been simulated and investigated.

• 한국정밀공학회지
• /
• 제14권2호
• /
• pp.145-151
• /
• 1997

In this paper, we discuss the cathode ray tube(CRT) glass bulb stress and sagging recovery by the contact band pressure using finite element method. We analyzed the band pressure and stress using contact element method between band and bulb before and after banding process which was conducted to decrease the stress concentration using finite element method, and calculated sagging recovery. The analysis results were confirmed by experiments using strain gauge and sagging recovery test apparatus.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제54권2호
• /
• pp.76-82
• /
• 2005

In this paper, a method for analyzing the thermal recovery characteristics of the nozzle of gas circuit breaker was described. In order to obtain thermal recovery characteristics, the transient simulation of SF6 arc plasma within the nozzle was carried out. In particular, the nozzle ablation was taken into account by simultaneously solving the PTFE concentration equation with the governing equations such as continuity, momentum and energy equation. After that, post arc current calculation was performed with the rate of rise of recovery voltage changed. From the calculated post arc current, it was possible to suggest the thermal recovery characteristics of the nozzle of gas circuit breaker.

• 소성∙가공
• /
• 제20권6호
• /
• pp.456-460
• /
• 2011

A major source of difficulty in die design for high strength steel is the high level of elastic recovery during unloading. The degree of elastic recovery is affected by factors such as material strength, bending angle, punch's corner radius and sheet thickness. Finite Element Method was used in the present work to quantitatively analyze the elastic recovery for various combinations of these parameters. In some cases elastic recovery happened in reverse direction. This phenomenon, which we call spring-go, was explained via changes in stress distribution in the panel occurring in the forming process.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제2권2호
• /
• pp.82-102
• /
• 2008

Packet losses tend to occur during short error bursts separated by long periods of relatively error-free transmission. There is also a significant spatial correlation in loss among the receiver nodes in a multicast session. To recover packet transmission errors at the transport layer, tree-based protocols construct a logical tree for error recovery before data transmission is started. The current tree construction scheme does not scale well because it overloads the sender node. We propose a scalable recovery tree construction scheme considering these properties. Unlike the existing tree construction schemes, our scheme distributes some tasks normally handled by the sender node to specific nodes acting as repair node distributors. It also allows receiver nodes to adaptively re-select their repair node when they experience unacceptable error recovery delay. Simulation results show that our scheme constructs the logical tree with reduced message and time overhead. Our analysis also indicates that it provides fast error recovery, since it can reduce the number of additional retransmissions from its upstream repair nodes or sender node.