• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제2권4호
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• pp.239-250
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• 2013

가용 센서를 내장하고 있는 모바일 디바이스의 사용이 많아지고 자동화, 자율화, 사용자 맞춤식 서비스의 요구가 커짐에 따라 컨텍스트 인지 모바일 컴퓨팅 (Context-Aware Mobile Computing)의 필요성이 증대하고 있다. 하지만 추론 시스템 설계는 컨텍스트 분석, 인지하고자 하는 상황분석 등의 복잡한 과정을 요구한다. 또한 모바일 디바이스의 제한된 자원 때문에 컴퓨팅 파워가 높은 서버에 탑재된 추론 엔진을 통해 추론을 수행하는 것이 적합하다. 본 논문에서는 이러한 과정을 간결하고 정확하게 표현하기 위한 컨텍스트-상황 추론 요소의 범용적 정형 모델을 제안하고 추론 요소들의 정형 모델을 실사례에 적용하여 본 논문에서 제안하고 있는 추론 요소들의 정형 모델이 실효성을 가지고 있으며 범용적임을 보여준다. 또한 제한한 추론 요소들을 컴퓨팅 환경에서 실현화하기 위해 제안한 정형 모델들을 기반으로 추론 엔진을 설계 및 구현하고 추론 실험을 통해 추론 엔진의 실효성과 재사용성을 검증한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권12호
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• pp.6169-6187
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• 2017

With the fast growth of mobile services, Mobile Cloud Computing(MCC) has gained a great deal of attention from researchers in the academic and industrial field. User authentication and privacy are significant issues in MCC environment. Recently, Tsai and Lo proposed a privacy-aware authentication scheme for distributed MCC services, which claimed to support mutual authentication and user anonymity. However, Irshad et.al. pointed out this scheme cannot achieve desired security goals and improved it. Unfortunately, this paper shall show that security features of Irshad et.al.'s scheme are achieved at the price of multiple time-consuming operations, such as three bilinear pairing operations, one map-to-point hash function operation, etc. Besides, it still suffers from two minor design flaws, including incapability of achieving three-factor security and no user revocation and re-registration. To address these issues, an enhanced and provably secure authentication scheme for distributed MCC services will be designed in this work. The proposed scheme can meet all desirable security requirements and is able to resist against various kinds of attacks. Moreover, compared with previously proposed schemes, the proposed scheme provides more security features while achieving lower computation and communication costs.

• 센서학회지
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• 제16권4호
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• pp.277-285
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• 2007

In this paper, we outline the research issues that we are pursuing towards building of location aware environments for mainly ubiquitous healthcare applications. Such location aware application can provide what is happening in this space. To locate an object, such as patient or elderly person, the active ceiling-mounted reference beacons were placed throughout the building. Reference beacons periodically publish location information on RF and ultrasonic signals to allow application running on mobile or static nodes to study and determine their physical location. Once object-carried passive listener receives the information, it subsequently determines it's location from reference beacons. The cost of the system was reduced while the accuracy in our experiments was fairly good and fine grained between 7 and 12 cm for location awareness in indoor environments by using only the sensor nodes and wireless sensor network technology. Passive architecture used here provides the security of the user privacy while at the server the privacy was secured by providing the authentication using Geopriv approach. This information from sensor nodes is further forwarded to base station where further computation is performed to determine the current position of object.

• 대한전자공학회논문지SD
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• 제46권7호
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• pp.22-28
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• 2009

멀티프로세서가 임베디드 시스템에서 널리 쓰임에 따라 지원되는 전력 최소화 기법을 이용하여 태스크를 수행하기 위해 필요한 에너지의 소모량을 줄여야 할 필요성이 대두된다. 본 논문은 동적 전압 스케일링 및 전력 셧다운을 이용하여 에너지 소모를 최소화 하는 태스크 스케줄링 알고리즘을 멀티프로세서 환경을 위해 제안하였다. 제안된 알고리즘에서는 전력 셧다운시의 에너지 및 타이밍 오버헤드를 고려하여 반복적으로 태스크 할당 및 태스크 순서화를 수행한다. 제안된 반복적인 태스크 스케줄링을 통해 전체 에너지 소모를 줄이는 가장 좋은 해를 얻을 수 있었다. 전체 에너지 소모는 리니어 프로그래밍 모델 및 전력 셧다운의 임계 시간을 고려하여 계산되었다. 실제 어플리케이션으로부터 추출된 표준 태스크 그래프에 기반을 둔 실험 결과를 통해 하드웨어 자원 및 시간제한에 따른 에너지 소모 관계를 분석하였다. 실험 결과를 볼 때 제안된 알고리즘은 기존의 우선권 기반의 태스크 스케줄링에 대해서 의미 있는 성능 향상을 얻을 수 있었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.1-8
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• 2009

This is a short review of how CFD contributed to hypersonic flights in the past 50 years. Two unexpected phenomena that occurred in the entry flights of the Apollo and Space Shuttle made us aware of the impact of the high temperature real-gas effects on hypersonic flights: pitching moment anomaly of up to 4 degrees, and radiation overshoot behind a shock wave. The so-called two-temperature nonequilibrium model was introduced to explain these phenomena. CFD techniques were developed to accommodate the two-temperature model. Presently, CFD can predict trim angle of attack to an accuracy of about 1 degree. A concerted effort was made to numerically reproduce the experimentally measured flow-field over a double-cone. As yet, perfect agreement between the experimental data and computation is not achieved. Scramjet technology development is disappointingly slow. The phenomenon of ablation during planetary entries is not yet predicted satisfactorily. In the future, one expects to see more research carried out on planetary entries and space tourism.

• 한국공간정보시스템학회:학술대회논문집
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• 한국공간정보시스템학회 2005년도 추계학술대회
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• pp.61-66
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• 2005

Spatiotemporal data mining represents the confluence of several fields including spatiotemporal databases, machine loaming, statistics, geographic visualization, and information theory. Exploration of spatial data mining and temporal data mining has received much attention independently in knowledge discovery in databases and data mining research community. In this paper, we introduce an algorithm Max_MOP for discovering moving sequences in mobile environment. Max_MOP mines only maximal frequent moving patterns. We exploit the characteristic of the problem domain, which is the spatiotemporal proximity between activities, to partition the spatiotemporal space. The task of finding moving sequences is to consider all temporally ordered combination of associations, which requires an intensive computation. However, exploiting the spatiotemporal proximity characteristic makes this task more cornputationally feasible. Our proposed technique is applicable to location-based services such as traffic service, tourist service, and location-aware advertising service.

• 한국정보통신학회논문지
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• 제24권1호
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• pp.141-144
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• 2020

Convolutional neural networks (CNNs) show high performance in computer vision tasks including object detection, but a lot of weight storage and computation is required. In this paper, a pruning scheme is applied to CNNs for object detection, which can remove much amount of weights with a negligible performance degradation. Contrary to the previous ones, the pruning scheme applied in this paper considers the base accelerator architecture. With the consideration, the pruned CNNs can be efficiently performed on an ASIC or FPGA accelerator. Even with the constrained pruning, the resulting CNN shows a negligible degradation of detection performance, less-than-1% point degradation of mAP on VOD0712 test set. With the proposed scheme, CNNs can be applied to objection dtection efficiently.

• 한국정보과학회논문지:소프트웨어및응용
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• 제37권10호
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• pp.736-744
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• 2010

모바일 기기에서 얻을 수 있는 로그 데이터는 다수의 유의미한 정보를 담고 있다. 그러나 모바일 기기의 연산능력 제약과 정보 분석 자체의 어려움 등으로 상황정보를 활용한 모바일 에이전트의 구현이 쉽지 않다. 본 논문에서는 제한적인 모바일 플랫폼에서 효율적인 상황인지를 위한 베이지안 네트워크 용용 기법을 제안한다. 베이지안 네트워크는 다수의 세부 모듈로 구성되며, 모듈간 인과성은 가상증거를 통해 보존된다. 각 모듈은 이전 증거값과 추론결과를 저장하고, 현재 증거값과 비교하여 전체 네트워크에 변화를 주는 경우에만 선택적으로 추론을 수행한다. 다양한 수집 주기의 모바일 데이터를 이용한 추론결과의 신뢰성을 높이기 위해 기억감소함수를 이용하여 결과를 보정하는 방법을 살펴본다. 마지막으로 실제 모바일 환경에서의 실험을 통해 제안하는 방법의 유용성을 확인한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.3916-3936
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• 2014

Smartphone applications like games, image processing, e-commerce and social networking are gaining exponential growth, with the ubiquity of cellular services. This demands increased computational power and storage from mobile devices with a sufficiently high bandwidth for mobile internet service. But mobile nodes are highly constrained in the processing and storage, along with the battery power, which further restrains their dependability. Adopting the unlimited storage and computing power offered by cloud servers, it is possible to overcome and turn these issues into a favorable opportunity for the growth of mobile cloud computing. As the mobile internet data traffic is predicted to grow at the rate of around 65 percent yearly, even advanced services like 3G and 4G for mobile communication will fail to accommodate such exponential growth of data. On the other hand, developers extend popular applications with high end graphics leading to smart phones, manufactured with multicore processors and graphics processing units making them unaffordable. Therefore, to address the need of resource constrained mobile nodes and bandwidth constrained cellular networks, the computations can be migrated to resourceful servers connected to cloud. The server now acts as a bridge that should enable the participating mobile nodes to offload their computations through Wi-Fi directly to the virtualized server. Our proposed model enables an on-demand service offloading with a decision support system that identifies the capabilities of the client's hardware and software resources in judging the requirements for offloading. Further, the node's location, context and security capabilities are estimated to facilitate adaptive migration.

• Journal of Information Processing Systems
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• 제10권1호
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• pp.103-118
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• 2014

Over the last couple of years, traditional VANET (Vehicular Ad Hoc NETwork) evolved into VANET-based clouds. From the VANET standpoint, applications became richer by virtue of the boom in automotive telematics and infotainment technologies. Nevertheless, the research community and industries are concerned about the under-utilization of rich computation, communication, and storage resources in middle and high-end vehicles. This phenomenon became the driving force for the birth of VANET-based clouds. In this paper, we envision a novel application layer of VANET-based clouds based on the cooperation of the moving cars on the road, called CaaS (Cooperation as a Service). CaaS is divided into TIaaS (Traffic Information as a Service), WaaS (Warning as a Service), and IfaaS (Infotainment as a Service). Note, however, that this work focuses only on TIaaS and WaaS. TIaaS provides vehicular nodes, more precisely subscribers, with the fine-grained traffic information constructed by CDM (Cloud Decision Module) as a result of the cooperation of the vehicles on the roads in the form of mobility vectors. On the other hand, WaaS provides subscribers with potential warning messages in case of hazard situations on the road. Communication between the cloud infrastructure and the vehicles is done through GTs (Gateway Terminals), whereas GTs are physically realized through RSUs (Road-Side Units) and vehicles with 4G Internet access. These GTs forward the coarse-grained cooperation from vehicles to cloud and fine-grained traffic information and warnings from cloud to vehicles (subscribers) in a secure, privacy-aware fashion. In our proposed scheme, privacy is conditionally preserved wherein the location and the identity of the cooperators are preserved by leveraging the modified location-based encryption and, in case of any dispute, the node is subject to revocation. To the best of our knowledge, our proposed scheme is the first effort to offshore the extended traffic view construction function and warning messages dissemination function to the cloud.