스마트설계 플랫폼의 비즈니스 모델에 관한 연구 : 비즈니즈 모델의 고도화

이욱현,이성곤,구기관,한경진,이민규,유재경,이대근 한국에너지학회 2022 한국에너지공학회 학술발표회 Vol.2022 No.4

클라우드 기반 지능형 원격 디지털 헬스케어 시스템에 관한 연구

이욱현 한국지식정보기술학회 2022 한국지식정보기술학회 논문지 Vol.17 No.6

Population growth and demand for high levels of well-being and health care are significant challenges for new technologies in the health care sector. Monitoring of the patient's health status and medical parameters is essential in the doctor's diagnosis process. This paper proposes a new approach for intelligent remote patient monitoring (RPM), a remote digital healthcare solution. This approach centralizes a cloud-based intelligent remote patient monitoring architecture method to collect and analyze patient data so that healthcare organizations can make better decisions. This paper proposes a system architecture that includes all major groups of components of a healthcare service system, such as patients, hospitals, insurance companies, and controllers. The proposed solution will be fully cloud-based, allowing hospitals to achieve more cost-effective management, speeding up medical processes and improving the quality of healthcare services. The main purpose of the proposed solution is to monitor patients' health status and generate alerts when undesirable medical conditions are predicted through AI-based data analysis. The solutions proposed in this way help reduce waiting times in emergency rooms in hospitals. It also helps prevent patients from staying in the hospital for long periods of time. The IRPM (Intelligent Remote Patient Monitoring) cloud-based architecture helps to perform continuous health monitoring in daily life and achieve higher diagnostic accuracy and higher quality of life.

클라우드 전자기록관리를 위한 품질요인과 SLA

이욱현,이영곤 한국지식정보기술학회 2018 한국지식정보기술학회 논문지 Vol.13 No.6

Recently, many companies or organizations are introducing cloud services for managing digital records. Cloud services can dramatically reduce the cost of archiving and managing digital records, and provide a foundation for resilient management of digital records, depending on the business environment. Many companies and organizations outsource management of digital records to the cloud. Generally, companies sign SLA contracts when outsourcing computing systems to the cloud. This means that they will pay for the usage of the service while expecting cloud service more or less quantitative level. Customers who request cloud record management services want to be assured that their records are kept in trust in the cloud while meeting records requirements. The cloud record management service provider wants to know which quality items or criteria associated with records should be used to manage records. To establish a cloud record management service SLA, customers and service providers must be aware of each other's interrelationships, make a clear statement of their requirements and expectations, and agree on them. Because cloud services pay for service usage and satisfaction, the SLA must be defined for the purpose so that the customer and service provider can provide services that are mutually satisfactory. This paper describes the requirements for ensuring the quality of cloud record management services and the quality items and classification schemes and key indicators and values required for establishing SLAs.

클라우드 서비스를 활용한 전자기록관리에 있어서의 위험요소 분석

이욱현,이영곤 한국지식정보기술학회 2017 한국지식정보기술학회 논문지 Vol.12 No.6

Recently, many companies or organizations are introducing cloud services for managing digital records. Cloud services can dramatically reduce the cost of archiving and managing digital records, and provide a foundation for resilient management of digital records, depending on the business environment. However, due to the nature of the services provided by the cloud and the inherent risk inherent in the cloud, many companies are reluctant to apply cloud services to digital records management. In particular, the characteristics of digital records that should be stable and long-term preserved, and the characteristics of the cloud that needs to change the configuration of the server and storage from time to time in accordance with the user's request, often conflict with each other. These risk factors can vary widely depending on the nature and type of the cloud, which can seriously jeopardize the stability of digital records. In addition, cloud record management can be based on network-based locations where records are used and where they are stored locally or nationally, creating new legal and social issues that have not been experienced before in record management. In this paper, we analyze the risk factors of digital records management using cloud service and propose the countermeasures to solve them.

방송환경에서 타임스탬프 구간에 기반을 둔 낙관적 동시성 제어 기법

이욱현,황부현 한국정보과학회 2002 정보과학회논문지 : 데이타베이스 Vol. No.

The broadcast environment has asymmetric communication aspect that is typically much greater communication bandwidth available from server to clients than in the opposite direction. In addition, mobile computing systems generate mostly read-only transactions from mobile clients for retrieving different types of information such as stock data, traffic information and news updates. Since previous concurrency control protocols, however, do not consider such a particular characteristics, the performance degradation occurs when previous schemes are applied to the broadcast environment. In this paper, we propose optimistic concurrency control based on timestamp interval for broadcast environment. The following requirements are satisfied by adapting weak consistency that is the appropriate correctness criterion of read-only transactions: (1) the mutual consistency of data maintained by the server and read by clients (2) the currency of data read by clients. We also adopt the timestamp Interval protocol to check the weak consistency efficiently. As a result, we improved a performance by reducing unnecessary aborts and restarts of read-only transactions caused when global serializability was adopted. 방송환경은 서버와 클라이언트간 대역폭이 서버에서 클라이언트쪽으로는 크고 클라이언트에서 서버쪽으로의 대역폭은 상대적으로 많이 작은 비대칭적(asymmetric) 특수한 환경이다. 또한 대부분의 방송 환경 응용 시스템들은 클라이언트측에서 발생한 주식 데이타, 교통 정보와 새로운 뉴스와 같은 여러 가지 다양한 정보를 검색하는 주로 읽기전용 즉 질의 거래들을 허락한다. 그러나, 기존의 여러 가지 동시성 제어 기법들은 이러한 특수성을 고려하지 않음으로써 방송 환경에 적용될 때 거래들의 불필요한 철회를 일으킨다. 이 논문에서는 방송환경에서 타임스탬프 구간에 기반을 둔 낙관적 동시성 제어 기법을 제안한다.이 기법은 서버에 의해 관리 유지되고 클라이언트에 의해 읽혀지는 데이타의 상호 일관성과 데이타의 현재성을 만족시키기에 적절한 정확성 검증 기준인 약한 일관성(weak consistency)을 채택하였다. 또한, 그것을 효율적으로 실행할 수 있는 타임스탬프 구간 기법을 적용하였다. 그 결과, 전역적 직렬화를 적용할 때 발생되는 질의 거래의 불필요한 철회 및 재시작의 횟수를 줄임으로써 성능향상을 도모하였다.

저온 폐열회수용 진동세관형 히트파이프 열교환기의 작동 유체에 따른 열전달 특성

이욱현,임용빈,김정훈,김종수 대한설비공학회 2000 설비공학 논문집 Vol.12 No.7

Heat transfer characteristics of a heat exchanger for low temperature waste heat recovery using oscillating capillary tube heat pipe were evaluated against the charge ratio variation of working fluid and various working fluids. R-l42b, R-22 and R-290 were used as working fluids. The heat exchanger was composed of heat pipe with capillary tube bundles, having a 2.6mm in outer diameter, 1.4mm in inner diameter with 101m long, and 40 turns. Charge ratio of working fluid was 40% and 50%. Water was used as secondary fluid. Inlet temperature and mass velocity for each secondary fluid were 297 K, 280 K and9~27 kg /$m^2s$,, respectively. From experimental results, it was found that heat transfer performance of R-22 was higher than those of R-l42b and R-290 and it was proportional to Figure of merit for thermosyphons. As a result, it was thought that R-22 was the most suitable working fluid of waste heat recovery for low temperature waste heat recovery.

AMTEC용 모세관 순환윅 설계

이욱현,조종표,김강출,이석호 한국에너지학회 2015 한국에너지공학회 학술발표회 Vol.2015 No.11

Current Status of Alkali Metal Thermal to Electric Conversion Technology Developments in Korea

이욱현,서민수,이계중 한국에너지학회 2017 한국에너지공학회 학술발표회 Vol.2017 No.4

Theoretical Optimization of Vertical Quantum Dot Infrared Photodetector Structure

이욱현,강용훈 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.45 No.2

A parametric study of vertical quantum dot infrared photodetectors (QDIPs) is presented. The properties of QDIPs are functions of the period of QD layers, the barrier thickness, and the buer thickness. Optimum periods are found to exist for the responsivity (R) and the detectivity (D), respectively. The optimum period for D is larger than that for R because the noise decreases as the number of periods increases. Stacking of many QD layers is necessary for a higher D because the optimum period for D is quite large. In addition, a high absorption coecient for the QD layers is very important because that improves both R and D and decreases the optimum period.

양자점 원적외선 수광소자 전망

이욱현,강용훈,엄준호,홍성철,최원준,이동한,김문덕,노삼규,이정일 대한전자공학회 2003 전자공학회지 Vol.30 No.5

실제 실험에 사용한 대표적인 InAs/GaAs QUDIP에 대해서 detector를 평가하는데 사용하는 responsitity D*뿐만 아니라 이두 값을 좌우하는 phottoconductive gain 양자효율 noise current에 대해 정량적으로 살펴보고 QWIP와 비교해보았다 우선 가장 중요한 것은 QDIP의 온도가 약 10K에서 거의 200K까지 올라가도 responsivity와 D* 모두 온도에 따라 민감하게감소하지 않는다는 사실이다(거의 10배 정도만 감소했음). 이러한 측정결과는 QDIP의 가장 큰 장점인 실온 동작 가능성이 아주 높음을 확인시켜 준다. 참고로, 이미 사용되고 있는 QWIP나 MCT detector는 낮은 온도 영역에서도 온도가 증가함에 따라 responsivity와 D*가 민감하게 감소해서 77K 이상에서는 동작하지 않는다. 두번째로, QWIP는 시료의 표면에 수직 입사되는 IR에 반응하지 않는데, QDIP는 시료의 표면에 수직 입사되는 IR에도 잘 반응함을 확인하였다. 이러한 두 가지 특성은 QDIP가 가질 것이라고 예상되던 QDIP의 가장 큰 장점으로, QDIP가 mid IR이나 far IR detector로서의 전망이 아주 밝음을 보여준다. 저온에서 QDIP의 responsivity는 수 A/W 로, 보통의 QWIP의 responsivity가 수십 mA/W인 것을 고려할 때, 충분히 큰 값이었다. QDIP의 responsivity가 이렇게 큰 이유는 photo-conductive gain이 1000 이상으로 매우 컸기 때문이었다. 반면에, 양자효율은 0.01% 이하로 아주 작았는데, 이것은 흡수 계수 자체보다는 흡수 두께가 작기 때문인 것 같고, 따라서 QDIP의 주기 수를 늘릴 필요가 있음을 알았다. Detector를 평가하는데 가장 중요한 것은 responsivity보다는 D*인데, photoconductive gain과 양자효율의 곱에 비례하는 responsivity는 $\sim$A/W로 충분히 컸지만, 반면에 D*는 $\sim$2E8으로 QWIP에 비해 작았다. 이것은 noise current가 컸기 때문이며 이를 줄이는 것이 중요하다. Noise current의 주된 요인이 dark current에 비례하는 g-r noise이므로, dark current를 줄이는 구조가 필요하다. 대표적인 예가 AlGaAs 같은 additional barrier를 넣어 dark current를 줄이는 방법이다. QDIP의 주기 수를 늘리는 것도 dark current를 줄이는 데 도움이 될 것이다.