실내 모형실험을 통한 토석류 퇴적 특성 연구

장형준(Hyungjoon Chang),유국현(Kukhyun Ryou),이호진(Hojin Lee) 한국지반환경공학회 2021 한국지반환경공학회논문집 Vol.22 No.2

본 연구는 토석류의 퇴적 특성을 파악하고 소단을 설치함에 따른 토석류 피해의 저감효과를 분석하기 위해 수행되었다. 다양한 수로경사 및 토사체적농도를 고려하여 수로실험을 수행하였으며, 소단 설치에 따른 토석류 피해의 저감효과를 분석하기 위해 소단을 설치하지 않은 경우와 소단을 설치한 경우를 비교하였다. 본 연구에서는 토석류의 퇴적 특성 중 도달거리, 총 이동거리 및 이동비에 대한 분석을 진행하였다. 먼저 수로경사 변화에 따른 토석류의 퇴적 특성을 분석하였고, 토사체적농도 변화에 따른 토석류의 퇴적 특성을 분석하였다. 또한, 소단을 설치하지 않은 경우를 기준으로 소단을 설치한 경우의 퇴적 특성 변화율을 산정하였다. 실험결과, 수로경사와 토사체적농도가 토석류의 퇴적 특성에 상당한 영향을 미치는 것을 확인하였다. 또한, 사면에 소단을 설치할 경우 토석류의 도달거리와 이동비가 크게 감소하였으며, 총 이동거리가 증가하였다. 이는 소단을 설치하는 것이 토석류의 이동을 지연시키고, 토석류의 잠재적인 이동성을 감소시키는 것을 의미한다. 본 연구의 결과는 토석류의 퇴적 특성을 이해하는 데 유용한 정보를 제공할 것이며, 나아가 소단의 설계에 도움을 줄 것으로 기대된다. This study was conducted to understand the deposition characteristics of debris flow and to analyze the reduction effect of debris flow damage by installing a berm. Flume experiments were performed in consideration of various channel slope and volumetric sediment concontration. In order to analyze the reduction effect of debris flow damage by installing a berm, the cases of not installing a berm and the cases of installing a berm were compared. In this study, the runout distance, total travel distance, and mobility ratio were analyzed among the deposition characteristics of debris flow. First, the deposition characteristics of debris flow according to the change of the channel slope were analyzed, and the deposition characteristics of debris flow due to the change of volumetric sediment concentration were analyzed. In addition, the change rate of debris flow deposition characteristics when a berm was installed was calculated based on the case when a berm was not installed. As a result of the experiments, it was confirmed that the channel slope and volumetric sediment concentration had a significant effect on the deposition characteristics of debris flow. In addition, when a berm is installed on the slope, the runout distance and mobility ratio of debris flow are greatly decreased, and the total travel distance is increased. This means that installing a berm delays the movement of debris flow and reduces the potential mobility of debris flow. The results of this study will provide useful information for understanding the deposition characteristics of debris flow. Furthermore, it is expected to help in the design of a berm.

키 교환을 이용한 경량화된 RFID 인증 프로토콜

이창보(Chang-bo Lee),장호진(Hojin Chang),김정재(Jungjae Kim),전문석(Moonseog Jun) 한국정보과학회 2005 한국정보과학회 학술발표논문집 Vol.32 No.2

유비쿼터스 사회를 만들기 위한 핵심 기술인 RFID는 시간과 공간을 초월하여 우리에게 정보를 제공해 줄 것으로 기대되고 있지만, RFID 시스템이 가지고 있는 특성으로 인하여 프라이버시를 침해할 수 있다는 심각한 문제를 안고 있다. 이를 해결하기 위한 방법으로 다양한 연구가 진행되어 왔지만 기존의 연구들은 보안상 문제점과 태그 및 백 엔드 데이터베이스의 과도한 처리능력을 요구하고 있다. 그러나 본 논문에서 제안하는 프로토콜은 해쉬함수와 XOR연산, 키 교환을 이용하여 스푸핑이나, 재전송 공격으로부터 안전 하면서도, 백 엔드 데이터베이스 안에서의 비교연산 횟수를 줄일 수 있는 경량화된 프로토콜을 제안한다.

항공우주 연구개발 투자의 성과와 파급효과 분석 : 한국항공우주연구원을 중심으로

정호진(Hojin Jung),임창호(Chang Ho Lim),장태진(Tae-Jin Chang),박정호(Jung Ho Park) 한국항공우주학회 2019 한국항공우주학회 학술발표회 논문집 Vol.2019 No.11

에세이영화에 대한 시각인류학적 접근

장호진(Hojin Chang) 동의대학교 영화·트랜스미디어연구소 2020 디스포지티프 Vol.7 No.-

This paper pays attention to the common area of essay film and visual anthropology, consideringtheoretical approaches crossing the two areas. Various efforts to define and explain the commonfeatures of essay film have been made in the contemporary film history, which mingle with thehistory of visual anthropology, particularly with the speculation on the ethnographic film andthe term of ethnofiction. The complex yet interesting journey leads us to fine multi-level layersof aesthetical issues and mutual influences in them, let alone the names of directors/authorsincluding Robert Flaherty, Jean Rouch, Sol Worth, or David MacDougall as well, who are commonlyspotlighted in both areas. This study efforts to illuminate the implication of essay film in the realmof visual anthropology today by analyzing the features of essay film such as subjectivity, reflexivity,and the intervention in the public sphere. Also, this paper aims to contribute to enforce the studyon essay film as well by suggesting the interrelation of the features of essay film which might seemincompatible, from the view of anthropology. A filme of Jean Rouch, Chronique d’un été will beexamined as an exemplary one to present how aesthetical inquiries in the area of essay film aredeeply associated with anthropological discussion.

항공유의 고온 분사 및 연소특성 시험기법 연구

최호진(Hojin Choi),이형주(Hyung Ju Lee),황기영(Ki-Young Hwang),박동창(Dong Chang Park) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5

연료를 초임계 상태로 가열하고 오리피스 인젝터와 압력선회형 인젝터를 통해 분사하면서 초고온과 초임계 상태에서의 연료분사 특성을 가시화 결과와 유출계수를 이용하여 분석하였다. 연료의 비등점 이하에서는 오리피스 인젝터와 압력선회형 인젝터이 분사패턴이 완전히 다르지만 기화가 시작되면서 유사한 패턴을 보이게 됨을 가시화를 통해 확인할 수 있었고, 유출계수 또한 액체상태에서 상당한 차이를 보이지만 기체 및 초임계 상태에서는 인젝터 형식에 따른 차이가 상당히 줄어들게 된다. 또한, 항공유의 가열에 따른 분사특성 변화와 함께 연소특성 변화를 확인하기 위해 분젠버너 형태의 시험장치를 구성하고 연료온도 상승에 따른 화염속도 변화를 관찰하였다. An experimental study was conducted to investigate fuel injection characteristics with temperature and pressure increase to supercritical phase using aviation fuel. Using orifice injector and pressure swirl injector, the visualization of spray pattern and analysis of discharge coefficient were conducted. At liquid status, spray patterns from two type of injectors are different from each other. As vaporization proceed, those are shown similar from visualization. The difference in Cd (discharge coefficient) also decreased in vapor or super-critical injection status. To study the combustion characteristics change with fuel temperature increase, flame speed in Bunsen burner was investigated.

인도태평양 지역내 한국의 한ㆍ미 동맹 전략

장호진 ( Chang Hojin ) 한국국가전략연구원 2022 한국국가전략 Vol.7 No.1

The Biden administration in Washington has taken over and further strengthened the policy to deter and compete with China through the Indo- Pacific Strategy initiated during the Trump era, while Beijing has made its stance and resolve very clear that it does not want to confront with the US but will continue to defend the core interests and expand its role in the international community notwithstanding any US pressures. This new development is posing a more complicated concern for Seoul than others. Seoul has kept its security under the continued North Korean nuclear threats through the sole allied partnership with Washington. However, it also neighbors with China that has the largest share in Seoul’s external trade and economic cooperation as well as the largest influence to North Korea. In fact, Seoul has declared its intention to develop a comprehensive strategic allied partnership with Washington through the Joint Vision for the Alliance of the Republic of Korea and the United States of America in 2009. It also has reflected such new developments in the security landscape as the cooperation for theIndo-Pacific Strategy and the advanced high technology and industry as well as the discussions on Taiwan and the South China Sea in the joint statement following a bilateral summit in Washington as recently as in May 2021. Nevertheless, the disputes in Seoul on how to cope with the Indo- Pacific Strategy and the US - China rivalry and conflicts have never ceased, which reflects its overall concern on the gravity of China and Korea-China relationship. Against this backdrop, it is necessary for Seoul to make an across-the board-review on its relationship with China and correct common fallacies, thus refine a cool-headed understanding that could help design Seoul’s strategy, in a more proactive manner, for the ROK-US alliance in the Indo-Pacific region, pursuant to its national interests. Those common fallacies would include such frail arguments that the US is important for security while China is important for economy and that it is essential to maintain good relations with Beijing in order to secure China’s help in the North Korean issue. Korea’s national interests in the Indo-Pacific region consists in the realization of the liberal, open and mature future order in which the universal values and norms prevail and great power’s egocentrism and unilateral overbearings could be held back. In the diplomatic reality, it leads to the task of how to get China to harmonize with and conform to the universal order in the region, even with its different ideology and such an overwhelming power and scale. Accordingly, it is natural and rightful for Korea to seek the realization of the desired future order in the region, based on its alliance with the US which shares common values and norms, while endeavoring to continue to develop its relation with China. Seoul needs to advance a democratic, cooperative and norm- based regional order in a subtle and smart manner through the tactful use of the nature of the individual issues and the causes related to values and norms as well as the pursuit of an open cooperation in which China could also eventually take part.

Therapeutic Potential of Stem Cells Strategy for Cardiovascular Diseases

Lee, Chang Youn,Kim, Ran,Ham, Onju,Lee, Jihyun,Kim, Pilseog,Lee, Seokyeon,Oh, Sekyung,Lee, Hojin,Lee, Minyoung,Kim, Jongmin,Chang, Woochul Hindawi Publishing Corporation 2016 Stem cells international Vol.2016 No.-

<P>Despite development of medicine, cardiovascular diseases (CVDs) are still the leading cause of mortality and morbidity worldwide. Over the past 10 years, various stem cells have been utilized in therapeutic strategies for the treatment of CVDs. CVDs are characterized by a broad range of pathological reactions including inflammation, necrosis, hyperplasia, and hypertrophy. However, the causes of CVDs are still unclear. While there is a limit to the currently available target-dependent treatments, the therapeutic potential of stem cells is very attractive for the treatment of CVDs because of their paracrine effects, anti-inflammatory activity, and immunomodulatory capacity. Various studies have recently reported increased therapeutic potential of transplantation of microRNA- (miRNA-) overexpressing stem cells or small-molecule-treated cells. In addition to treatment with drugs or overexpressed miRNA in stem cells, stem cell-derived extracellular vesicles also have therapeutic potential because they can deliver the stem cell-specific RNA and protein into the host cell, thereby improving cell viability. Here, we reported the state of stem cell-based therapy for the treatment of CVDs and the potential for cell-free based therapy.</P>

<i>Salvia miltiorrhiza</i> enhances the survival of mesenchymal stem cells under ischemic conditions

Kim, Ran,Lee, Seokyeon,Lee, Chang Youn,Yun, Hwayoung,Lee, Hojin,Lee, Min Young,Kim, Jongmin,Jeong, Jee‐,Yeong,Baek, Kyungmin,Chang, Woochul John Wiley and Sons Inc. 2018 Journal of pharmacy and pharmacology Vol.70 No.9

<P><B>Abstract</B></P><P><B>Objectives</B></P><P>To validate the enhanced therapeutic effect of <I>Salvia miltiorrhiza</I> Bunge (SM) for brain ischemic stroke through the anti‐apoptotic and survival ability of mesenchymal stem cells (MSCs).</P><P><B>Methods</B></P><P>The viability and the expression level of cell apoptotic and survival‐related proteins in MSCs by treatment of SM were assessed <I>in vitro</I>. In addition, the infarcted brain region and the behavioural changes after treatment of MSCs with SM were confirmed in rat middle cerebral artery occlusion (MCAo) models.</P><P><B>Key findings</B></P><P>We demonstrated that SM attenuates apoptosis and improves the cell viability of MSCs. In the rat MCAo model, the recovery of the infarcted region and positive changes of behaviour are observed after treatment of MSCs with SM.</P><P><B>Conclusions</B></P><P>The therapy using SM enhances the therapeutic effect for brain ischemic stroke by promoting the survival of MSCs. This synergetic effect thereby proposes a new experimental approach of traditional Chinese medicine and stem cell‐based therapies for patients suffering from a variety of diseases.</P>

실내 모형실험을 통한 토석류 흐름 특성 연구

유국현(Kukhyun Ryou),장형준(Hyungjoon Chang),이호진(Hojin Lee) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.4

최근 기후변화의 영향으로 집중호우의 발생빈도가 증가하여 많은 양의 토석류가 발생하고 있다. 본 연구의 목적은 수로경사와 토사체적농도의 변화에 따른 토석류의 흐름 특성을 파악하고, 소단의 설치가 토석류 흐름 특성에 미치는 영향을 분석하는 것이다. 본 연구에서는 실내 모형실험을 통해 토석류의 흐름 특성 중 유속, 흐름 깊이, Froude 수, 흐름저항계수를 산정하였으며, 소단의 영향을 확인하기 위해 소단을 설치하지 않은 직선수로와 소단을 설치한 1단 수로의 실험결과를 비교하였다. 실험결과, 수로경사가 토석류의 유속과 흐름 깊이에 영향을 미치는 것을 확인하였으며, 토사체적농도가 토석류의 유속, 흐름 깊이, Froude 수 및 흐름 저항계수에 영향을 미치는 것을 확인하였다. 또한, 소단을 설치함에 따라 토석류의 유속과 흐름 깊이가 최대 26.1%, 71.2%씩 감소하는 것을 확인하였다. 이는 소단을 설치하는 것이 토석류의 유속을 감소시켜 토석류의 이동성과 운동에너지를 감소시키는 것을 의미한다. 본 연구의 결과는 토석류의 흐름 특성을 파악하는 데 유용한 정보를 제공하며, 사면에서 소단의 효용성에 대한 정보를 제공한다. Recently, the frequency of torrential rain is increasing due to climate change, which causes a large amount of debris flows. The purpose of this study was to understand the flow characteristics of debris flow according to the change in channel slope and volumetric sediment concentration and to analyze the effects of a berm on the flow characteristics of debris flow. The flow characteristics of debris flow, such as flow velocity, flow depth, Froude number, and flow resistance coefficients, were calculated using laboratory tests. The effect of a berm was analyzed by comparing the experimental results of a linear channel with those of a one-stepped channel. The results showed that the channel slope affected the flow velocity and flow depth, and the volumetric sediment concentration affected the flow velocity and flow depth, Froude number, and flow resistance coefficient. Moreover, as a berm was installed, the flow velocity and flow depth decreased by up to 26.1% and 71.2%, respectively. This means that installing a berm reduces the flow velocity, thereby reducing the mobility and kinetic energy. These results provide useful information to understand better the flow characteristics of debris flow and the effectiveness of a berm.

Ethylene flame-holding in double ramp flows

Chang, Eric Won Keun,Yang, Sungmo,Park, Gisu,Choi, Hojin Elsevier 2018 AEROSPACE SCIENCE AND TECHNOLOGY Vol.80 No.-

<P><B>Abstract</B></P> <P>In this work, ethylene flame-holding in supersonic flows was investigated using a shock tunnel. The experiments were conducted at flow stagnation temperatures ranging from 1270 to 1810 K. The two-dimensional test model consisted of a double-ramp inlet and a constant-area combustor with a recessed wall cavity. The two fuel injectors were located at the inlet and the other upstream of the cavity. Shadowgraph and flame chemiluminescence images were captured for optical visualization. The inlet injection images showed various flame-holding patterns. At 1270 K, the flame was not maintained. At 1540 K, the flame was maintained inside the cavity, and the condition provided continuous combustion during the steady flow. At 1810 K, strong flame signals were observed from the inlet to the cavity and downstream. At 1540 K, the inlet injection with a low fuel pressure showed a gradual flame quenching in the cavity during flow establishment. On the other hand, the same injection in the combustor showed flame-holding in the shear layer above the cavity. The results showed that the flame patterns are strongly influenced by the flow stagnation temperature and the location of fuel-injection.</P>