• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.27 no.2
• /
• pp.87-108
• /
• 2023

This is a review paper on recent development on the spectral theory of the Neumann-Poincaré operator. The topics to be covered are convergence rate of eigenvalues of the Neumann-Poincaré operator and surface localization of the single layer potentials of its eigenfunctions. Study on these topics is motivated by their relations with the cloaking by anomalous localized resonance. We review on this topic as well.

• KIPS Transactions on Computer and Communication Systems
• /
• v.7 no.8
• /
• pp.195-202
• /
• 2018

With the development of location-based applications such as smart phones and GPS navigation, active research is being conducted to protect location and trajectory privacy. To receive location-related services, users must disclose their exact location to the server. However, disclosure of users' location exposes not only their locations but also their trajectory to the server, which can lead to concerns of privacy violation. Furthermore, users request from the server not only location information but also multimedia information (photographs, reviews, etc. of the location), and this increases the processing cost of the server and the information to be received by the user. To solve these problems, this study proposes the EGTC (Enhanced Grid-based Trajectory Cloaking) technique. As with the existing GTC (Grid-based Trajectory Cloaking) technique, EGTC method divides the user trajectory into grids at the user privacy level (UPL) and creates a cloaking region in which a random query sequence is determined. In the next step, the necessary information is received as index by considering the sub-grid cell corresponding to the path through which the user wishes to move as c(x,y). The proposed method ensures the trajectory privacy as with the existing GTC method while reducing the amount of information the user must listen to. The excellence of the proposed method has been proven through experimental results.

• Proceedings of the Korean Information Science Society Conference
• /
• 2010.06a
• /
• pp.40-41
• /
• 2010

• Journal of Internet Computing and Services
• /
• v.18 no.5
• /
• pp.31-38
• /
• 2017

Recently with the rapid development of LBS (Location-based Services) technology, approaches of protecting user's location have gained tremendous attentions. For using LBS, users need to forward their real locations to LBS server. However, if the user sends his/her real location to LBS server, the server will have the all the information about user in LBS. Moreover, if the user opens it to LBS server for a long time, the trajectory of user may be released. In this paper, we propose GTC (Grid-based Trajectory Cloaking) method to address the privacy issue. Different from existing approaches, firstly the GTC method sets the predicting trajectory and divides the map into $2^n*2^n$ grid. After that we will generate cloaking regions according to user's desired privacy level. Finally the user sends them to LBS server randomly. The GTC method can make the cost of process less than sequential trajectory k-anonymity. Because of confusing the departure and destination, LBS server could not know the user's trajectory any more. Thus, we significantly improve the privacy level. evaluation results further verify the effectiveness and efficiency of our GTC method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.04a
• /
• pp.97-99
• /
• 2013

We introduced an earthquake-resistant design using acoustic rnetamaterials. There are two way in that field: one is a cloaking method and the other is a shadow zone method of seismic waves. Cloaking is a general property of a wave that changes the direction depending on the refractive index. Metamaterials control the propagation and transmission of specified parts of the wave and demonstrate the potential to render an object seemingly invisible. The shadow zone is a method of negative modulus using many huge resonators and it attenuates the amplitude of the wave exponentially. We compared and explained the fimdarnental principles of the two methods.

• Spatial Information Research
• /
• v.20 no.4
• /
• pp.93-101
• /
• 2012

Due to complexity of indoor space, the demand of Location Based Services (LBS) in indoor space is increasing as well as outdoor. However, it includes privacy problems of exposing personal location. Location K-anonymity technology is a method to solve the privacy problems with cloaking their locations by Anonymized Spatial Region(ASR). It guarantees K users within a region containing the location of a given user. However previous researches have dealt the problems based on Euclidean distance in outdoor space, and cannot be applied in indoor space where there are constraints of movement such as walls. For this reason, we propose in this paper a K-anonymity for cloaking indoor location in consideration of structures and representation of indoor space. The basic concept of our approach is to introduce a hierarchical structure as ASR for including K-1 users for cloaking their locations. We also proposed a cost model by K and attributes of hierarchical structure to analyze the performance of the method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.10a
• /
• pp.645-646
• /
• 2012

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.04a
• /
• pp.946-947
• /
• 2012

• The Journal of Society for e-Business Studies
• /
• v.15 no.3
• /
• pp.85-98
• /
• 2010

The prevailing infrastructure of ubiquitous computing paradigm on the one hand making significant development for integrating technology in the daily life but on the other hand raising concerns for privacy and confidentiality. This research presents a new privacy-preserving spatio-temporal query processing technique, in which location based services (LBS) can be serviced without revealing specific locations of private users. Existing location cloaking techniques are based on a grid-based structures such as a Quad-tree and a multi-layered grid. Grid-based approaches can suffer a deterioration of the quality in query results since they are based on pre-defined size of grids which cannot be adapted for variations of data distributions. Instead of using a grid, we propose a location-cloaking algorithm which uses the R-tree, a widely adopted spatio-temporal index structure. The proposed algorithm uses the MBRs of leaf nodes as the cloaked locations of users, since each leaf node guarantees having not less than a certain number of objects. Experimental results show the superiority of the proposed method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.6
• /
• pp.491-494
• /
• 2016

A design method is proposed to minimize the scattering cross section(SCS) of the electromagnetic cloak based on the quasi-conformal mapping. Often times in such cloaking structures, parts that require refractive index below one are approximated with free space because of the difficulty involved with realization. In this process, preformance degradation is inevitable. In this work, the size of the cloak is optimized to compensate for the deterioration, and thus to minimize the scattering cross section of a diamond shaped conductor. Proposed cloak is fabricated using a 3D printer, and verified by measuring the cloaking performance of a diamond shaped aluminum target.