• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.409-412
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• 2011

본 논문에서는 Xen-ARM 기반의 가상화 환경에서 실시간 게스트 운영체제의 I/O를 지원하기 위한 방법을 제안한다. Xen-ARM 하이퍼바이저는 서버 환경에서 주로 사용되는 Xen 가상화 기법을 모바일 구조인 ARM에서 구현한 것으로, 분할 드라이버 모델과 크레딧 스케줄러를 지원한다. 하지만, 이러한 두 가지 특성은 I/O 처리 지연의 주요 원인이 된다. 특히, 장치 드라이버와 사용자 태스크의 실행 중에 하이퍼바이저의 도메인 간 스위칭이 필요하므로, 특정 시간으로 I/O 처리 지연을 제한하기 대단히 어렵다. 본 논문에서는 게스트 운영체제의 수정을 통해 I/O 처리 지연을 제한하는 기법을 제안한다. 게스트 운영체제는 현재 실행되는 태스크의 특성을 Xen-ARM 하이퍼바이저에게 간접적으로 전달하여, 전체 시스템의 모든 태스크에 대하여 우선순위를 부여하며, 하이퍼바이저의 스케줄러에서 인터럽트 처리를 위해 가장 응급한 태스크 실행을 스케줄링 할 수 있도록 한다. 제안하는 기법은 실험을 통해, I/O를 처리하는 도메인의 1ms 이상의 처리시간이 84%에서 99%까지 줄어들 수 있음을 보인다.

• Korean Journal of Pharmacognosy
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• v.32 no.4 s.127
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• pp.338-343
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• 2001

The extract and fractions of Rumex acetosa (Polygonaceae), a Korean medicinal plant, were examined for their cytotoxicities against five cultured human tumor cell lines, i.e. A549 (non-small cell lung), SK-OV-3 (ovary), SK-MEL-2 (melanoma), XF498 (central nerve system) and HCY15 (colon), using the SRB (sulforhodamine-B) method in vitro and antimutagenic activities by Ames test with Salmonella typhimurium TA98 and TA100 and SOS chromotest with E. coli PQ37. Among the tested samples, the methylene chloride fraction strongly inhibited the proliferation of each examined tumor cell line with $IC_{50}$ values ranged from 13.2 to $18.7\;{\mu}g/ml$ and showed potent antimutagenic activities with 96.1% and 96.7% at the concentration of 1 mg/plate against the mutagens, NPD and sodium azide, respectively. Its antigenotoxic activity was also very effective at the final concentration of $10\;{\mu}g/reaction$ tube against the mutagens, MNNG and NQO by SOS chromotest.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.516-519
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• 2011

현재 모바일 폰은 실시간 운영체제를 구동하는 CP(Communication Processor)와 범용 운영체제를 구동하는 AP(Application Processor}, 두 개의 프로세서를 사용하고 있다 임베디드 가상화는 하나의 칩 위에 실시간 운영체제와 범용 운영체제를 동시에 동작시킬 수 있는 솔루tus을 제공하면서, 각각의 운영체제가 서로 고립되어 동작하도록 한다. 따라서 임베디드 가상화 솔루션을 모바일 폰에 적용하면 하나의 집을 사용하여 비용을 절약하면서, 하이퍼바이저 위에 고립된 각각의 운영체제를 구동할 수 있기 때문에 각광을 받고 있다. Xen-ARM 은 모바일 기기에서 가장 많이 사용되는 ARM 프로세서에서 동작하는 하이퍼바이저로 임베디드 기기의 탑재를 목적으로 개발되었다. 그러나 현재의 Xen-ARM의 크레딧 스케쥴러는 CPU 공평성에 포커스를 맞추고 있어 실시간 IO를 제한된 시간 안에 처리할 수 없기 때문에, 실시간 IO를 처리해야 하는 임베디드 기기에 적용하기 어렵다. 본 논문에서는 현재 Xen-ARM이 실시간 IO를 지원할 수 없는 것을 실험을 통해 보여주고, 실시간 IO를 지원하기 위한 방안을 제시한다. 또한 수정된 Xen-ARM을 모바일 폰에 적용하는 방안에 대해 제시한다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06a
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• pp.328-330
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• 2006

동적 전력 관리 기법을 활용한 프로세서의 등장은 고성능 임베디드 장치들의 저전력 설계에 있어서 큰 영향을 주고 있다 특히, XSCALE과 같은 고성능 프로세서의 소비전력은 동작 클럭의 속도와 비례하여 빠르게 증가하고 있으며, 이를 극복하기 위한 다양한 기법이 제시되었다. 동적 전력 관리 기법은 크게 1) 동적 전압 관리 기법과 동적 프리퀀시 관리 기법으로 구분된다. 동적 프리퀀시 관리 기법을 사용한 프로세서는 필요에 따라 프로세서의 동작 클럭 속도를 변경한다. 이는 전체적인 프로세서 성능의 저하를 수반하게 된다 특히, 주변 장치들의 전력 관리가 동시에 이루어지지 않을 경우에는 시스템의 전체적인 성능에 큰 영향을 끼치게 된다. I/O 장치의 인터럽트는 CPU의 현재 실행을 잠시 멈추고, 인터럽트 처리를 우선적으로 수행하도록 한다. 따라서 CPU가 처리할 수 있는 양보다 많은 인터럽트 발생은 인터럽트 처리 이후에 실제 응용 프로그램들이 동작할 시간을 줄이게 되어 CPU는 살아있으나, 인터럽트 이외의 실제 프로세스 실행을 진행할 수 없는 라이브륵(livelock) 현상이 발생한다. 동적 프리퀀시 스케일링을 사용하는 경우, 프로세서의 동작 속도 저하로 인한 livelock 현상이 발생할 수 있으며 이를 막기 위하여, 인터럽트 처리를 제한하는 기법을 제시한다.

• KIISE Transactions on Computing Practices
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• v.23 no.8
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• pp.504-509
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• 2017

Preserving the integrity of the booting process is important. Recent rootkit attacks and subverting OS attacks prove that any post-OS security mechanism can be easily circumvented if the booting process is not properly controlled. Using an actual case as an example, the hacker of the Se-jong government office simply bypassed the user's password authentication by compromising the normal booting process. This paper analyzes existing pre-OS protection using secure boot and measured boot, and proposes another bootloader that overcomes the limitations. The proposed bootloader not only guarantees the integrity of all the pre-OS binaries, bootloaders, and kernel, it also makes explicit records of integrity in the booting process to the external TPM device, so that we can track modifications of BIOS configurations or unintended booting process modifications.

• Journal of KIISE:Computer Systems and Theory
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• v.37 no.1
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• pp.35-42
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• 2010

Guest operating systems running over the virtual machines share a variety of resources. Since CPU is allocated in a time division manner it consequently leads them to having the unknown physical time. It is not regarded as a serious problem in the server virtualization fields. However, it becomes critical in embedded systems because it prevents guest OS from executing real time tasks when it does not occupy CPU. In this paper we propose a hypercall to register a timer service to notify the timer request related real time. It enables hypervisor to schedule a virtual machine which has real time tasks to execute, and allows guest OS to take CPU on time to support real time. The following experiment shows its implementation on Xen-Arm and para-virtualized Linux. We also analyze the real time performance with response time of test application and frames per second of Mplayer.

• Korean Journal of Pharmacognosy
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• v.35 no.3 s.138
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• pp.239-243
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• 2004

The ameliorating effect of the MeOH extract of the root of Platycodon grandiflorum on the ethanol-induced cognitive dysfunction in mice was investigated. The total MeOH extract was devided into two fractions, saponin rich fraction and non-saponin fraction. The mice with repeated administration of the total MeOH extract and those with saponin rich fraction both showed a markedly prolongεd latency time upon the step-through test (passive avoidance performance) performed after acute ethanol intoxication, while those with non-saponin rich fraction did not. The results suggest that the extracts from the root of Platycodon grandiflorum exert a beneficial effect on ethanol-induced memory impairment in mice and also suggest that these effects of the extracts might be ascribed to the saponin constituents.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.2
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• pp.227-242
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• 2022

This paper presents a Cache-Coherency Interconnect(CCI)-based Android pattern screen lock(PSL) attack on modern ARM processors. CCI has been introduced to maintain the cache coherency between the big core cluster and the little core cluster. That is, CCI is the central interconnect inside SoC that maintains cache coherency and shares data. In this paper, we reveal that CCI can be a side channel in security, that an adversary can observe security-sensitive operations. We design and implement a technique to compromise Android PSL within only a few attempts using the information of CCI in user-level applications on Android Nougat. Further, we analyzed the relationship between the pattern complexity and security. Our evaluation results show that complex and simple patterns would have similar security strengths against the proposed technique.

• Journal of Sericultural and Entomological Science
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• v.13 no.2
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• pp.155-160
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• 1971

This experiment was carried out to investigate the cocoon reeling condiditions required to technical balance work on the automatic silk reeling machine. The results obtained were as follows. 1) Reasonable reeling velocity with regard to raw silk yield and to reeling efficiency varied according to cocoon reelability. It was observed to be about 150m/min on good reelability cocoon (850m of nonbreaking bave length), about 120m/min on medium reelability cocoon (650m of nonbreaking bave length) and from 90m/min to 120m/min on bad reelability cocoon (500m of nonbreaking bave length) 2) Low temperature drying of cocoon (T$_3$) improved the reelability of cocoon, but increased the reeling accidance with deteriorating the quality of raw silk more than the control(T$_1$) or high temperature drying of cocoon (T$_2$). No significant difference was observed in its raw silk yield and silk by-product with regard to cocoon drying temperature. 3) Incomplete drying of cocoon (T$_3$) improved the reelability of cocoon, but increased the reeling accidance with deteriorating the quality of raw silk more than the control(T$_1$) or over drying of cocoon(T$_2$). No significant difference was observed in its raw silk yield and silk by-product with regard to cocoon drying degree. It was cocoon drying condition of cocoon was the control(T$_1$) or high temperature(T$_2$) rather than low temperature (T$_3$) in cocoon drying process. Control (T$_1$) or over drying of cocoon (T$_2$) was adequate rather than incomplete drying of cocoon (T$_3$) for the improvement of the quality of raw silk on the automatic silk reeling process. 4) It was found that the reasonable cooking condition of cocoon was optimum cooking with 4$0^{\circ}C$ of reeling temperature or incomplete cooking with 45$^{\circ}C$ of the reeling temperature in the automatic silk reeling of the domestic cocoon.

• Journal of The Korean Society of Grassland and Forage Science
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• v.24 no.4
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• pp.323-334
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• 2004

Silage yield Potential and some agronomic characteristics of Korean improved and introduced corn hybrids from the United States were tested for five year in Gyeongsan, Gyeongsangbug-do and for one year in Hongcheon, Gangwon-do. 1. At 20 days after emergence, plant height and dry matter of hybrids were different, while the early growth of the hybrids was not correlated to the culm length and silage yield. 2. In Cyeongsan, silage yield potential of Suwon19 was relatively high, while most susceptible to rice black-streaked dwarf virus (RBSDV) disease and leaf senescence at harvest time. In contrast, silage yield potential and resistance to RBSDV of Cwanganok were moderate, while susceptible to leaf senescence at harvest. Generally, Suwon19 showed similar or higher yield than most introduced hybrids, while some introduced hybrids showed lower silage yield than Korean improved hybrids. Most introduced hybrids were more resistant to RBSDV and leaf senescence at harvest time compared to Korean improved hybrids. 3. In Hongcheon, silage yield of three Korean improved hybrids were lower than that of NC+5514 and DK729, while similar or higher than other introduced hybrids. af senescence of all Korean hybrids was severer compared to introduced hybrids.