• Korean Journal of Remote Sensing
• /
• v.35 no.3
• /
• pp.401-413
• /
• 2019

The purpose of this study is to generate DSM using the stereo matching algorithm of worldview-1 stereo images and verify the accuracy of the generated DSM. To generate DSM, RPC block modeling was performed to correct RPC errors, and image matching was performed using SGM, which is a stereo matching algorithm after the epipolar image was generated. The COST for SGM was calculated by using CENSUS, and 4-paths and 8-paths were applied for COST aggregation in SGM. To verify the quality and accuracy of the generated DSM, it was compared with the LiDAR-derived DSM and the DSM generated by commercial SW. The results showed that the vertical accuracy of the generated DSM using 4-paths of COST aggregation was 1.647 m to 3.689 m (RMSE). In case of using 8-paths of COST aggregation was 1.550 m to 3.106 m (RMSE).

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.12
• /
• pp.4799-4818
• /
• 2015

In this paper, we investigate the problem of achieving global optimization for distributed carrier aggregation (CA) in small cell networks, using a game theoretic solution. To cope with the local interference and the distinct cost of intra-band and inter-band CA, we propose a non-cooperation game which is proved as an exact potential game. Furthermore, we propose a spatial adaptive play learning algorithm with heterogeneous learning parameters to converge towards NE of the game. In this algorithm, heterogeneous learning parameters are introduced to accelerate the convergence speed. It is shown that with the proposed game-theoretic approach, global optimization is achieved with local information exchange. Simulation results validate the effectivity of the proposed game-theoretic CA approach.

• Proceedings of the KSME Conference
• /
• 2004.04a
• /
• pp.1678-1681
• /
• 2004

The light-transmission technique has been applied to a slit rheometer for measuring red blood cell aggregation as well as blood viscosity over a range of shear rates. For measurement of blood viscosity and aggregation, instantaneous pressure and transmit-light intensity are measured with time. Using a precision pressure measurement, one can determine the shear stress and shear rate. In addition, a transmitted light through a blood sample indicates degree of RBC aggregation. With abruptly flowing with high shear rate, RBCs rapidly disaggregate and the intensity of the transmitted light becomes low. When continuously flowing with decreasing shear rate, RBCs tend to re-aggregate and the corresponding transmit-intensity gradually increases with time. The light intensity as a degree of RBC aggregation is plotted against shear rate and compared with blood viscosity. The advantages of this design are dual measurement at a time, simplicity, i.e., ease of operation and no moving parts, low cost, short operating time, and the disposable kit which is contacted with blood sample.

• International Journal of Computer Science & Network Security
• /
• v.23 no.3
• /
• pp.31-48
• /
• 2023

The popularization of smart devices and subsequent optimization of their sensing capacity has resulted in a novel mobile crowdsensing (MCS) pattern, which employs smart devices as sensing nodes by recruiting users to develop a sensing network for multiple-task performance. This technique has garnered much scholarly interest in terms of sensing range, cost, and integration. The MCS is prevalent in various fields, including environmental monitoring, noise monitoring, and road monitoring. A complete MCS life cycle entails task allocation, data collection, and data aggregation. Regardless, specific drawbacks remain unresolved in this study despite extensive research on this life cycle. This article mainly summarizes single-task, multi-task allocation, and space-time multi-task allocation at the task allocation stage. Meanwhile, the quality, safety, and efficiency of data collection are discussed at the data collection stage. Edge computing, which provides a novel development idea to derive data from the MCS system, is also highlighted. Furthermore, data aggregation security and quality are summarized at the data aggregation stage. The novel development of multi-modal data aggregation is also outlined following the diversity of data obtained from MCS. Overall, this article summarizes the three aspects of the MCS life cycle, analyzes the issues underlying this study, and offers developmental directions for future scholars' reference.

• Journal of Information Technology Services
• /
• v.14 no.2
• /
• pp.69-86
• /
• 2015

The current contract awarding process regulated by laws and ordinances is analyzed and more reasonable processes are suggested. To this end, the principle of economic analysis is described with emphasis on the cost-effectiveness analysis, and the laws and ordinances regulating the process are thoroughly examined. The current contract awarding rule is based on the weighted sum of effectiveness score and cost score. This may not conform to the framework of economic analysis where effectiveness is supposed to be measured as an output and cost measured as an input. An improvement is attempted to the defense acquisition system and it is recognized that the economic analysis and policy consideration should be performed separately. Concept of statistical testing is introduced to see if the results of the cost effectiveness analyses show the significant difference between the alternatives. It is suggested that the contract awarding process can be improved by performing significance test followed by the aggregation of the two analyses. A minor improvement is also suggested on the application of current rules.

• The KIPS Transactions:PartC
• /
• v.18C no.5
• /
• pp.303-316
• /
• 2011

Data aggregation is important in wireless sensor networks. However, it also introduces many security problems, one of which is that a compromised node may inject false data or drop a message during data aggregation. Most existing solutions rely on encryption, which however requires high computation and communication cost. But they can only detect the occurrence of an attack without finding the attacking node. This makes sensor nodes waste their energy in sending false data if attacks occur repeatedly. Even an existing work can identify the location of a false data injection attack but it has a limitation that at most 50% of total sensor nodes can participate in data transmission. Therefore, a novel approach is required such that it can identify an attacker and also increase the number of nodes which participate in data transmission. In this paper, we propose a monitoring-based secure data aggregation protocol to prevent against a compromised aggregator which injects false data or drops a message. The proposed protocol consists of aggregation tree construction and secure data aggregation. In secure data aggregation, we use integration of abnormal data detection with monitoring and a minimal cryptographic technique. The simulation results show the proposed protocol increases the number of participating nodes in data transmission to 95% of the total nodes. The proposed protocol also can identify the location of a compromised node which injects false data or drops a message. A communication overhead for tracing back a location of a compromised node is O(n) where n is the total number of nodes and the cost is the same or better than other existing solutions.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.9
• /
• pp.1057-1059
• /
• 2016

A construction method of energy-efficient data aggregation tree is proposed by considering a tradeoff between acquisition time and energy consumption in wireless sensor networks. This proposed method constructs the data aggregation tree to minimize the link cost between the connected nodes for reducing energy consumption, while minimizing the maximum distance between sensor nodes and a sink node for rapid information gathering. Simulation results show that the proposed aggregation tree can be generated with low complexity and achieves high energy efficiency compared to conventional methods.

• Journal of Information Processing Systems
• /
• v.14 no.2
• /
• pp.396-417
• /
• 2018

GR-tree and query aggregation techniques have been proposed for spatial query processing in conventional spatial query processing for wireless sensor networks. Although these spatial query processing techniques consider spatial query optimization, time query optimization is not taken into consideration. The index reorganization cost and communication cost for the parent sensor nodes increase the energy consumption that is required to ensure the most efficient operation in the wireless sensor node. This paper proposes itinerary-based R-tree (IR-tree) for more efficient spatial-temporal query processing in wireless sensor networks. This paper analyzes the performance of previous studies and IR-tree, which are the conventional spatial query processing techniques, with regard to the accuracy, energy consumption, and query processing time of the query results using the wireless sensor data with Uniform, Gauss, and Skew distributions. This paper proves the superiority of the proposed IR-tree-based space-time indexing.

• Journal of the Korea Society of Computer and Information
• /
• v.17 no.2
• /
• pp.119-126
• /
• 2012

Local monitoring is an effective technique in securing data of wireless sensor networks. Existing solutions require high communication cost for detecting false data and this results in a network lifetime being shortened. This paper proposes novel techniques of monitoring based secure data aggregation and filtering false data in wireless sensor networks. The aim is to reduce energy consumption in securing data aggregation. An aggregator and its monitoring node perform data aggregation in a 60o sextant cluster. By checking Message Authentication Codes (MAC), aggregation data will be dropped by a forward aggregator if data aggregated by the aggregator and data monitored by the monitoring node are inconsistent. The simulation shows that the proposed protocol can reduce the amount of average energy consumption about 64% when comparing with the Data Aggregation and Authentication protocol (DAA)[1]. Additionally, the network lifetime of the proposed protocol is 283% longer than that of DAA without any decline in data integrity.

• Structural Engineering and Mechanics
• /
• v.30 no.4
• /
• pp.467-480
• /
• 2008

An aggregation multigrid method (AMM) is a leading iterative solver in solid mechanics. Recently, AMM is applied for solving Schur Complement system in the FE analysis of shell structures. In this work, an extended application of AMM for solving Schur Complement system in the FE analysis of continuum elements is presented. Further, the performance of the proposed AMM in multiple load cases, which is a challenging problem for an iterative solver, is studied. The proposed method is developed by combining the substructuring and the multigrid methods. The substructuring method avoids factorizing the full-size matrix of an original system and the multigrid method gives near-optimal convergence. This method is demonstrated for the FE analysis of several elastostatic problems. The numerical results show better performance by the proposed method as compared to the preconditioned conjugate gradient method. The smaller computational cost for the iterative procedure of the proposed method gives a good alternative to a direct solver in large systems with multiple load cases.