Genetic analysis of PARK2 gene in Korean patients with Parkinson's disease

박인원 忠南大學校 新藥專門大學院 2016 국내박사

Mutations in PARK2 are considered a common cause of Parkinson’s disease (PD). To assess the frequency of PARK2 mutations in the Korean population, we screened the PARK2 gene in 83 Korean PD patients: two young onset (YO, ≤49), 32 middle onset (MO, 50-69) and 49 late onset (LO, 70). Detection of the point mutations was performed by direct sequencing of the PARK2 exons, and exonic rearrangements were analyzed using multiplex ligation-dependent probe amplification (MLPA). Five known PARK2 variants were identified in 53 (63.9%) of the Korean PD patients: two missense mutations (Y267H and M458L) and three polymorphisms (S167N, L272I and V380L). We also found an increased frequency of PARK2 variants in PD patients and a lowered PD age at onset (AAO) in those having two variants, suggesting that the genetic variation in PARK2 gene might be a genetic risk factor of PD in Korean population.

공동주택 지하주차장 평면형태 및 환기구의 배치에 따른 공기유동에 관한 연구

박성원 부산대학교 2010 국내석사

The study on the airflow based on the array of ventilator and plan of the underground parking lot in apartment As demands of the residents have been variously changing according to the construction of the apartment house and the fast economic growth, the construction companies spurs the development of the apartment house flavored with environmental friendly factors. Also because of the multiple apartment project, the basement car park alone can not handle the rapid growth of the vehicles and the resident puts more and more emphasis on securing car park space for the freedom from the vehicles on the ground and for the safety of their children. Recently, as the interest about natural energy, the tendency minimizing the mechanical energy also appears. According to this trend, there has been growing attempts in order to apply the environmental friendly technologies to the apartment house. But the reality is that the systems doesn't virtually function well because the existing mechanical systems are applied. Consequently, the deterioration of the air and the brightness in the basement car park exacerbates the environments of the basement car park. And the study on the feasibility of the natural ventilation according to the unit-plan type of the basement car park and the performance of the skylight, is still insignificant. Thus, in this study, we intend to simulate, through the CFD, the air current by natural driving power by classifying the existing basement car parks into the unit-plan type and the direction of the vehicle traffic. Through classifying the existing basement car parks by the type of vehicle traffic that is the type of arrangement such as one-way or bidirectional traffic and deploying the ventilating openings by 3 types which enables the skylights, linked the ground for the purpose of collecting the light, play the role of ventilation at the same time, we forecast the air current of the basement car park by using CFD(Computational Fluids Dynamics) and, based on that, suggest the plan to improve the ventilating function of the basement car park by utilizing the natural ventilation. In this study, we research the general theories, that is 'the ventilation theory of underground space and the test method of ventilating performance' and interpret, through CFD, the air current of the target models according to the layout of the ventilation openings based on mean of air age and air exchange effectiveness by using computer simulation. As a result, we draw the conclusion as follows: (1) In respect of the air age according to the type of the vehicle traffic such as one way traffic and bidirectional traffic, the bidirectional traffic shows 30,405 seconds while 14,070 seconds in one way traffic indicating that the one way traffic abates by more than 50%. Therefore, the air of the basement car park with one way traffic has superior air quality because of its' shorter air age. (2) In case of the existing basement car parks, Case A' air exchange rate is 4.44 while 7.76 times/h in Case B and 1.94 times/h in Case C. It appears comparatively small in Case C. We can draw the conclusion, through this finding, that the placement of several natural ventilators in the middle and on the edge is more effective than the placement of the natural ventilator with big area in the middle when placing natural ventilator. (3) In case of Case B where the installation is in the middle and on the edge of the basement car park, it appears excellent in both the air exchange and the air age, but the effective area of the space on the ground abates. There requires a plan for the placement accordingly. (4) In case of Case C where the circular air-vent with the smallest area of air-vent is installed, the velocity of air current appears the fastest. Thus, it seems that there requires the research on the appropriate size and the layout plan of the circular air-vents for the purpose of the increase of effective space on the ground. It is also necessary to comprehend the appropriate locations in order to improve the performance of the natural ventilation, through examining the characteristic of the air current according to the type of ventilating openings installed in the basement car park, the velocity of the current, the pressure distribution and the installation of the auxiliary equipments for the natural ventilation.

How does the national park management deliver their services? The perspective of service marketing focused on gunung gede pangrango national park, Indonesia

Maulana, Firman 서울시립대학교 국제도시과학대학원 2018 국내석사

인도네시아에 설립된 가장 오래된 국립공원 중 하나인 구눙 게대 빵랑오 국립공원(GGPNP)은 관광 개발의 기초로 생태관광을 선택했다. 생태관광과 관련된 모든 혜택에 관계 없이 미래에 최적의 이익을 얻으려면 여전히 해결해야 할 과제가 있다. 정부기관으로서 GGPNP는 방문객에게 서비스를 제공하는 관광 활동을 지원하는 단순한 관리 이상의 또 다른 역할을 한다. 최근의 사실은 국립공원에 방문하는 관광객 수가 여전히 적다는 것을 보여주며 그 이유 중 하나는 국립공원에서 마케팅에 대한 관심이 낮기 때문이다. 국립공원은 또한 성과 중 하나인 방문 관광객 수에 대한 목표를 달성해야 하지만 GGPNP의 경영진은 서비스 마케팅을 시행하여 국립공원을 홍보하는 방법에 주목하기 시작해야 한다. 이러한 이유로 본 연구는 서비스 마케팅 관점에서 GGPNP가 서비스를 제공하는 방법을 조사하기 위해 실시되었다. 또한 이 논문은 생태관광 원리를 강조하는 경영진 측면과 인지된 서비스 성과 차원을 강조하는 방문객 관점에서 서비스 마케팅의 3가지 요소(인력, 물리적 증거, 프로세스 관리)를 탐구한다. 조사 결과에 따르면 GGPNP의 서비스 마케팅 구현은 전반적으로 중간 수준이다. 이는 GGPNP가 이미 표준 서비스 마케팅을 수행하지만 마케팅 가치를 높이기 위해 해결하고 개선해야 할 몇 가지 사항이 있다는 것을 의미한다. 인적 요소의 경우 GGPNP는 방문객에게 더 나은 서비스를 제공하기 위해 더 많은 인력을 충원하고 더 많은 교육을 제공해야 한다. 물리적 증거 요소의 경우 방문객은 GGPNP가 국립공원 지역에 머무는 동안 방문객에게 더 많은 지식과 편의를 제공하기 위해 국립공원 지역에 정보 표지판과 위생 시설을 개선하거나 추가해야 한다고 생각한다. 마지막으로, 프로세스 관리 요소에서 GGPNP는 더 많은 절차를 추가하고 고객 평가, 방문 우선순위 시민에 대한 대우(노인, 임산부, 장애인, 어린이), 방문객에게 피드백을 제공하는 방식에 대해 구체적인 사항을 추가해야 한다. GGPNP의 경영진에게 이 결과가 의미하는 바는 특히 인도네시아에서 국립공원의 서비스 마케팅에 대해 논의하는 이전 연구가 없었기 때문에 공식적인 계획 전략을 위한 마케팅 참조자료와 디딤돌을 제공하는 것이다. 또한 훌륭한 서비스 마케팅을 시행함으로써 장기적으로 국립공원을 방문하여 보존 메시지를 받고 환경에 대한 소속감을 높일 수 있는 사람들이 더 많아질 것이다. Gunung Gede Pangrango National Park (GGPNP) one of the oldest national parks established in Indonesia has chosen ecotourism as the basis of their strategy in developing tourism. Regardless of all of the benefits that come with ecotourism, there are challenges that are still need to be addressed to gain optimum benefit in the future. As a government agency, GGPNP has another role than just mere conservation which is supporting tourism activities which mainly about delivering a service to its visitors. The recent data shows that the number of tourist arrival to the national park is still low, and one of the reasons is the low interest of marketing for a national park. While the national park also needs to achieve the target for tourist arrival as one of their performance, the management of GGPNP needs to start their attention on how to market the national park through the implementation of service marketing. Due to these reasons, this research was conducted to examine how the GGPNP delivers their services from the perspective of services marketing. In particularly, this thesis explores the three elements of services marketing (personnel, physical evidence, and process management) from the perspective of management which emphasizes ecotourism principles and the perspective of visitor which emphasizes on perceived service performance dimension. The results of this survey show that as overall the implementation of service marketing in GGPNP is at a moderate level. This means that GGPNP already perform standard service marketing but there are several things that need to be addressed and improved to increase their marketing value. From the personnel element, the GGPNP need to consider adding more personnel and provide them with more training in order to deliver better services to the visitor. For the physical evidence element, the result also shows that the visitor thinks that GGPNP needs to improve or add more information signage and sanitary facilities in the national park area to give more knowledge and comfortability toward visitor during their stay in the area of national park. Lastly, from the process management element shown that GGPNP need to add more procedure and put more specific details on customer evaluation, treatment for priority citizen (elderly, pregnant woman, disabled person, and children) that come to visit, and how they provide their feedback to the visitor. This research is expected to serve as a stepping stone and reference on marketing and planning strategies of GGPNP since there was no previous research that discusses service marketing in the national park especially in Indonesia. Furthermore, by implementing good services marketing it is expected that for long-term outcome there will be more people to visit a national park to receive the message of conservation and hence increase their sense of belonging toward the environment.

Adequacy evaluation of urban park provision considering accessibility and amenity by age and gender cohorts

박시진 한양대학교 대학원 2022 국내석사

Characterization and evaluation of the gene expression profile for nontuberculous mycobacterial pulmonary disease

박영목 Graduate School, Yonsei University 2024 국내박사

Spatio-Temporal Patterns of Human-wildlife Conflict in Bardia National Park, Nepal

PAUDEL, Prabin University of Seoul, International School of Urban 2021 국내석사

지구 생태계의 균형을 이루기 위해서는 야생 생물 보존이 필수적이다. 하지만 야생 동물이 인간에게 피해를 입히면 인간은 그에 대한 복수로 야생 동물을 살상한다. 따라서 생태계 및 인간이 영위하는 생활의 지속 가능성을 위해서는 충돌을 최소화해야 한다. 인간과 야생 동물의 충돌은 바르디아 국립 공원(Bardia National Park)의 주요한 해결 과제이다. 효과적인 충돌 관리를 위해서는 구체적인 시공간 정보가 필수적이다. 그렇기 때문에, 본 연구에서는 바르디아 국립 공원의 완충 지대에서 11년(2010~2020) 동안 발생하여 기록된 충돌의 시공간적 분포를 조사하였다. 데이터 분석에는 기술 및 추론 통계를 사용하였다. 분석 결과에 따르면 기록된 충돌 횟수가 매년 증가하고 있다. 평균적으로 연간 806 건의 충돌이 기록되었다. 이 보호 구역에서 발생한 충돌의 주요 대상 종은 코끼리와 표범인데, 충돌의 59%가 남부 지역에서 기록되었다. 인간과 코끼리의 충돌 중 60% 이상이 8월, 9월, 10월 및 11월에 발생했다. 충돌이 가장 빈번한 계절은 종마다 다르지만, 코끼리, 표범, 호랑이 및 멧돼지의 경우 충돌의 계절적 분포가 유의미하다. 조사 대상 기간 동안의 손실 평가액 중 37%만이 보조금 형태로 지급되었다. 보조금을 받기까지의 과정도 길다. 따라서 지역을 바탕으로 주요 충돌 종을 관리하기 위한 월간 일정이 필수적이다. 초식 동물의 입맛에 덜 맞는 대체 작물을 재배하고 육식 동물의 침입을 막을 수 있는 축사를 장려하는 것이 필요하다. 전기 울타리를 설치하고 유지하며 대체 생계 수단을 제공함으로써 사람들의 삼림 출입을 줄이는 것 또한 중요하다. 이에 더해, 지역 사회를 대상으로 야생 동물의 행동에 대한 지식을 제공하고 교육을 실시하는 또한 바르디아 국립 공원 내에서의 충돌 사고를 축소하는 데 도움이 될 것이다. 주요어: 인간과 야생 동물의 충돌, 시공간 분포, 바르디아 국립 공권, 완충 지대 Human-wildlife conflict is one of the major conservation challenges. Detail spatial and temporal information is essential for effective conflict management. Therefore, this study examines the distribution of conflicts based on space and time for eleven years (2010 to 2020) in the buffer zone of Bardia National Park. Descriptive and inferential statistics were used to analyze the data. The result shows that the number of human-wildlife conflicts is increasing annually. Where on average, 806 conflicts per year were recorded. Elephant and leopard are the major conflicting species in this protected area, and 59 % of the conflict was recorded in the southern regions. More than sixty percent of human-elephant conflicts are recorded in August, September, October, and November. Major conflicting seasons vary with the species, where the distribution of conflict is significantly varied with the seasons for elephant, leopard, tiger, and wild boar. Attack due to carnivore is significantly higher in the new moon phase periods. Only 37 % of the evaluated loss was paid to the victim as a relief. A monthly calendar for the management of major conflicting species is essential. Farming of alternative crops that are less palatable for the herbivores and promoting predator-proof livestock shelter is needed. Where construction and maintenance of electric fences and reduction of dependency over forest resources by providing alternative sources of livelihood are crucial. Furthermore, providing knowledge and training about wildlife behavior to the local community will reduce the conflict and increase the harmony between people and wildlife.

First-Principles Characterization of Transition Metals on Oxide Films

Park, Jinwoo University of Seoul 2010 해외박사

Oxide-supported metal clusters and thin films have attracted a great deal of interest due to their importance in a wide range of technological applications, such as heterogeneous catalysis, gas sensors, corrosion-protective coatings, photovoltaic devices, and microelectronics. The adsorption, growth, and electronic characteristics of metal atoms adsorbed on oxides are of special interest, because these factors are supposed to help design and optimize methods for controlling processes concerning the desired chemical reaction and product. In this thesis, we performed ab initio electronic structure calculations to study the interactions of metal adatoms with ionic oxide atoms involving regular oxide surface atoms, surface oxygen defects like Fs centers, and metal supports. As an oxide, an MgO(001) surface, a prototype of an ionic oxide surface, was chosen here. All calculations were carried out using the density functional theory (DFT). First, a systematic approach was employed to investigate the adsorption geometries and electronic structures of late transition series (Cu, Ag, Au, Ni, Pd, and Pt) on ideal defect-free MgO(001) surfaces. For the above elements, the adsorption geometries, diffusion, and associated electronic structures were examined. Our calculations showed the favorable adsorption of the transition metal (TM) adatoms on top of the surface O atom. Further analysis showed that the TM-induced states formed in the gap region of MgO(001) vary significantly with the adsorption geometries. The DFT calculations have been also applied to investigate the adsorption of the TM adatoms (Cu, Ag, Au, Ni, Pd, and Pt) on defective MgO(001) surfaces with Fs centers as surface defects of oxides. The TM adatoms were found to favorably bind on the Fs centers. From the calculated adsorption structures and electronic structures, we carried out a systematic comparative analysis of the interactions of the metal adatoms with the surface oxygen vacancy and the regular surface oxygen atom of MgO(001). Finally, the adsorption of metal adatoms (Au and Pd) on Fe-supported ultrathin MgO(001) films was studied. Experimentally, it is well known that MgO films are epitaxially grown on Fe(001) due to their favorable physical properties. As such, the Fe/MgO/Fe junctions have been used as a system for magnetic tunnel junctions (MTJs) with huge tunneling-magnetoresistance (TMR) values. Interestingly, our calculations showed that the MgO/Fe(001) films we propose in this work can be used as a viable thin oxide model system. An analysis of the electronic structures in the systems reveals the negative charging even for Pd adatoms with a lower electron affinity. This indicates that the Fe substrate supporting the MgO films significantly influences charge and/or spin states of the metal adatoms. The physical origin of the negative charging of Pd was also discussed. These calculations demonstrate the importance of the interactions of the metal adatoms with underlying oxides for controlling the electronic and chemical properties of metal adatoms, such as charge and spin states.

North Korea's legal system and human rights

Park, Elisa Graduate School of International Studies, Yonsei U 2004 국내석사

In this study I will examine how the problem of human rights in North Korea runs deeper than the abuses themselves. The dilemma stems from North Korea's eschewed definition of human rights, and consequently, the political utility of it by the Kim Jong Il government to maintain unitary power. North Korea's definition of human rights is different, de jure and de facto from the universal definition, as outlined in the UN Declaration of Human Rights. I will be comparing international law with North Korean domestic law and practice. In examining domestic law there will be a focus on judicial proceedings, in particular due process. North Korea does, at least in rhetoric, attempt to follow international standards in order to avert criticism.In-depth studies, with respect to North Korean human rights violations covering prison camps, torture, execution, discriminatory ration distribution, and the refugee situation in China, have been carried out. However, these studies are based on political and sociological approaches. This study is unique because it narrows down on legal aspects of human rights violations in North Korea. It is necessary to see how the domestic legal system affects the human rights situation in North Korea. In order to understand, we must consider North Korea's view of international law and domestic law.Under international law, individuals have rights protecting their interests and survival. The International Covenant on Civil and Political Rights (ICCPR), of which the Democratic People's Republic of Korea (DPRK) is a member of, states the right of the individual in terms of various civil and political rights. Emphasized in the convention is the right to due process. Due process is defined as fairness in legal matters, including court proceedings that are guided by principles of justice and liberty. Substantive and procedural due process will be examined in application to the DPRK system. DPRK's violation of due process, a basic political right, diffuses its credibility and confidence as a state with whom other members of the international community can engage and trust. In particular, this study will examine infringement on due process as an indicator of other civil and political rights abuses and how it reflects the regime's attitude towards its people and its disregard for international laws. Domestic laws, their purpose and application will be inspected.The international trend for human rights is one of integration of values and progression of standard. The Declaration of Human Rights states that 'all human beings are born free and equal', 'free and equal in dignity', '(t)hey are endowed with reason and conscience', giving the individual 'free and equal personhood, equal dignity, equal creation and endowment, equal brotherhood, human agency' . Since the establishment of the High Commission of Human Rights, there has been an orchestration of efforts to establish a minimum standard and respect for the human spirit. In his Millenium Road Map Speech the role of the UN was redefined by the Secretary General, Kofi A. Annan . Two key points included freedom from want and freedom from fear. These are comprehensive rights that incorporate basic sustenance, social and political rights.Integration of values has been possible through the enmeshment of goals and pursuit by international organizations, NGO's and governments. Greater communication and cooperation has enabled this foundation of basic human rights. States that are party to international conventions and treaties are responsible for maintaining the standard and for ensuring accountability to other party members, so they strive for similar goals. Members have displayed a balance between taking steps to build up this standard while continuing to ensure that their national interests are met. Many of these members have come to an understanding that global interests often run parallel to national interests. The momentum towards greater integration and trust in the global system is evident in various areas, such as trade and aid.North Korea, as part of the UN and signatory to various international treaties and conventions is in a very particular situation. Even as a member to these organizations and treaties it regards international organizations and their members with a high level of suspicion. The doctrine of Juche, which acts as North Korea's guiding principle limits international effort in creating a working relationship with North Korea. The Juche ideology was created and developed by the founder of the North Korean system, Kim Il Sung. It is a concept centered in man's ability to shape his future through his own ability. The irony is that in its ideology North Korea exhorts self-reliance while in actuality it is growing more dependent on the international community for desperately needed aid.In examining the human rights abuses carried out through North Korea's penal system, violations surrounding prison camps will be explored in light of North Korean law and also a variety of laws that the international community upholds. Political human rights violations in North Korea are tantamount to crimes against humanity and the international community needs to be pro-active in finding a remedy that will end these arbitrary acts of injustice.Against the backdrop of international integration of values, North Korea faces a fork in the road. It will have to align its human rights standards to acceptable levels in order to continue to extract benefits from the international community. The alternative would be continual autarky and deterioration of its system. The international community must play an instigating role in pressuring North Korea to raise its human rights standards by imposing stricter conditions on aid.The issue of human rights abuses in North Korea has been pending for several years. It is a topic that cannot be examined in objectively verifiable detail due to its highly secretive government. The only sources of information come from non-governmental organizations and international organizations, which although restricted, are allowed to function in North Korean territory. Another source comes from the testimonies of defectors that have first hand experience of such abuses. The DPRK does not supply verifiable or refuting data on the inquiries made by international organizations or NGOs. Its defense thus far has been limited to basic denial of such accusations.Recent studies have reconfirmed the existence of gulags where thousands of prisoners are being held under conditions that drive the majority of them to illness and death. What is practiced in these prison-labor camps is clearly void of any regard for human rights, especially when the 'crimes' for which the accused were imprisoned for are disproportionate with how they are being castigated. As reported by human rights organizations, prisoners are often sentenced and executed extra-judicially. Under such conditions and practices North Korea is being pressured by the international community to make itself more transparent and to humanize its treatment of its citizens. North Korea denies such allegations and latches on sovereignty in dealing with its citizens. In doing so, North Korea excludes foreign governments and organizations from influencing its domestic policies. North Korea is in a quagmire because it realizes that it can no longer operate autonomously as its Juche ideology dictates.

Advanced ferroelectric memory technology on the van der waals material platform for in-memory computing

Park, Sangyong Sungkyunkwan University 2023 국내박사

전통적인 폰 노이만 방식의 컴퓨터는 데이터 저장공간과 처리공간이 분리되어 데이터를 처리하기 때문에 각 유닛간 데이터의 이동하는 과정이 필요하다. 하지만 각종 정보 기기와 서비스의 발달로 데이터의 크기가 증가함에 따라 연산 보다는 데이터의 이동이 데이터의 처리에 병목이 되고 있다. 이 문제를 해결하기 위하여 메모리 장치에서 연산, 처리까지 진행하는 인메모리 컴퓨팅이 제안되었다. 인메모리 컴퓨팅 구조에서는 데이터 이동에 소모되는 에너지를 최소화되고 크기가 크고 복잡한 데이터를 처리하기에 적합하여 차세대 구조로 관심을 받고 있다. 인메모리 컴퓨팅은 메모리 소자에서 저장과 연산이 모두 이루어지기 때문에 빠른 동작 속도와 안정적인 메모리 특성이 같이 요구된다. 본 논문에서는 인메모리 컴퓨팅에 사용될 새로운 동작 개념을 가지는 두 가지 강유전 메모리 소자를 소개한다. 두 소자는 모두 반데르발스(van-der-Waals) 물질을 기반으로 만들어졌으며 강유전 물질로 α-In2Se3 를 사용하였다. 반데르 발스 물질을 건식이동(Dry transfer) 방식으로 적층 하여 저온 공정으로 깨끗한 표면을 가지는 강유전 메모리 소자를 구현하였다. 첫 번째 소자는 강유전 막질을 전기적으로 고립시켜 전하를 저장하며 동시에 강유전 스위칭 동작을 하는 이중 동작 강유전 소자이다. α-In2Se3의 고유한 특성인 반도체 특성 (Eg=1.3 eV) 과 강유전 특성을 이용하였다. 저장되는 전하의 종류와 양에 따라 강유전 부유층의 전기적 에너지가 변화하여 강유전 스위칭 동작영역을 조절할 수 있다. 이러한 특성을 이용하여 넓은 동작 범위에서 전도도를 연속적으로 변화시킬 수 있다. 강유전 스위칭의 빠른 동작 속도와 낮은 동작 전압을 가지며 동시에 플래시 메모리의 안정적인 메모리 동작으로 전압 구간을 조절할 수 있는 것이 특징이다. 이를 이용하여 메모리 어레이에서 발생하는 산포를 균일하게 조절할 수 있음을 시뮬레이션을 통해 검증하였다. 또한, 연속적이고 넓은 전도도 대역대가 합성곱 신경망(CNN)에서 패턴 인식 정확도 향상에 효과적임을 검증하였다. 두번째 소자는 α-In2Se3의 수직 방향 잔류분극이 수평 방향 잔류분극과 연동되는 고유한 특징을 이용하여 강유전 물질의 측면에서 수평방향 전기장을 인가하여 강유전 메모리 소자를 동작시키는 측면 게이트 강유전 메모리 소자(LG-FeFET)이다. 수평 방향 전기장에 의한 분극이 수직 방향 전기장에 의한 분극보다 메모리 윈도우에 크게 기여함을 구현된 소자로 검증하였으며 분극의 연동 현상과 각 분극의 저장 유지 특성을 PFM과 KPFM 을 통하여 자세히 분석 하였다. 높이 방향의 축소가 중요한 적층형 메모리 구조에서 LG-FeFET을 적용한 3차원 적층형 메모리 구조를 디자인하여 제안하였고 실험적으로 2층으로 적층된 소자에서 곱셈 누산기 동작(MAC operation)을 구현하였다. 마지막으로 수직, 수평 방향에 의한 메모리 윈도가 인메모리 컴퓨팅의 정확도에 미치는 영향을 합성곱 패턴인식 시뮬레이션을 통하여 검증하였다. In-memory computing architecture, which stores and processes data in memory units, has emerged as a promising alternative to the traditional von-Neuman computing architecture because the new approach has the potential to eliminate the energy consumption caused by accessing and moving big data. The key part of the in-memory computing architecture is the performance of the memory device. The fast operation speed for computing tasks and stable memory characteristics for storage are essential characteristics. In this paper, two ferroelectric memory devices with new operational concepts are introduced for the application to in-memory computing. Both ferroelectric memory devices are built based on the van der Waals (vdW) material platform, and α-In2Se3 is used as a ferroelectric material. The vdW material platform allows clean surfaces, low-temperature processes, and thin films. The first device is a ferro-floating memory (FFM) which operates in dual mode. FFM uses an electrically isolated ferroelectric layer for both the ferroelectric switching and the charge storage at the same time. Due to the difference in the operation voltages, FFM operates as a ferroelectric memory in the low voltage range and as a floating gate flash memory in the high voltage range. In other words, FFM has both advantages of ferroelectric memory (fast operation speed) and flash memory (stable memory characteristics). Moreover, FFM can change the operation voltage region of the ferroelectric switching depending on the type and quantity of charges stored in the ferro-floating layer. The feature of the reconfigurable operation voltage was applied to the variation controlling of the threshold voltage in the memory array and to the wide range conductivity. The applications were emulated in pattern recognition neural network simulations. The second device is a laterally gated ferroelectric memory device (LG-FeFET). The LG-FeFET utilizes the interlocking effect of α-In2Se3 between the in-plane (IP) and the out-of-plane (OOP) directional polarizations. The gate of the device is placed on the lateral side of the ferroelectric material and operates ferroelectric switching by applying an IP directional electric field. The interlocking effect was confirmed with KPFM. Furthermore, the dependence of the direction of the electric field on the ferroelectric switching was confirmed by comparing the size of the memory window. The IP directional electric field shows a significantly larger memory window than the OOP directional electric field. A three-dimensional stacked memory structure was proposed, and the MAC operation was implemented in the two-tier stacked device with LG-FeFET devices. Finally, the advantages of the LG-FeFET were compared in an image recognition simulation with a convolutional neural network (CNN).

Phase Engineering of Two-dimensional Transition Metal Dichalcogenides for Electrocatalyst Application

Sanghyeon Park Graduate School of UNIST 2020 국내석사

Two Dimensional (2D) materials such as transition metal chalcogenides (TMDs) has been studied, but several problems still remain as disturbance for application to energy materials like electrocatalyst. In this work, we present a phase engineering of TMDs for electrocatalyst via highly reactive molten Potassium (K) metal intercalation. The 2H to 1T phase transition of TMDs has been exploited for application of the 1T phase with metallic property to applications such as electrocatalysts. However, the improving stability of thermodynamically metastable 1T TMDs remains an important challenge to overcome for using 1T phase properties. In addition, scalable synthesis methods of 1T TMDs, which are necessary for a wide range of applications, have to be developed. In this work, we presented a synthesis method of 1T phase MoS2 using molten K metal intercalation suitable for scalable method and confirmed the sucessfully phase transition 2H to 1T phase and improvement of 1T phase stability by K atom doping in the MoS2 basal plane. Furthermore, K atoms are doped in MoS2 basal plane, which can donate electron continuously to MoS2, which achieved long-term stability, thermal stability, and high power laser stability. Furthermore, we applied K doped 1T MoS2 to the hydrogen evolution reaction (HER) electrocatalyst and confirmed the improved HER performance owing to high electrical conductivity and basal plane activation of K-doped 1T MoS2 compared to 2H MoS2 and 1T MoS2 (n-BuLi), and high phase stability of K-doped 1T MoS2 exhibits high HER stability.