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Author

Hyun Chul Roh

Other affiliations: Seoul National University
Bio: Hyun Chul Roh is an academic researcher from KAIST. The author has contributed to research in topics: Simultaneous localization and mapping & Mobile robot. The author has an hindex of 11, co-authored 35 publications receiving 415 citations. Previous affiliations of Hyun Chul Roh include Seoul National University.

Papers
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Journal ArticleDOI
Jinyong Jeong1, Younggun Cho1, Young-Sik Shin1, Hyun Chul Roh, Ayoung Kim1 
TL;DR: This paper presents 3D map data generated by the SLAM algorithm in the LASer (LAS) format for a wide array of research purposes, and a file player and a data viewer have been made available via the Github webpage to allow researchers to conveniently utilize the data in a Robot Operating System (ROS) environment.
Abstract: The high diversity of urban environments, at both the inter and intra levels, poses challenges for robotics research. Such challenges include discrepancies in urban features between cities and the ...

165 citations

Journal ArticleDOI
TL;DR: In this article, the microstructural changes of LixSi electrode with lithium insertion were observed and a chemomechanical model was employed to explain the mechanical degradation resulting from stresses in the LIXSi particles with lithium injection.
Abstract: We report the direct observation of microstructural changes of LixSi electrode with lithium insertion. HRTEM experiments confirm that lithiated amorphous silicon forms a shell around a core made up of the unlithiated silicon and that fully lithiated silicon contains a large number of pores of which concentration increases toward the center of the particle. Chemomechanical modeling is employed in order to explain this mechanical degradation resulting from stresses in the LixSi particles with lithium insertion. Because lithiation-induced volume expansion and pulverization are the key mechanical effects that plague the performance and lifetime of high-capacity Si anodes in lithium-ion batteries, our observations and chemomechanical simulation provide important mechanistic insight for the design of advanced battery materials.

62 citations

Journal ArticleDOI
TL;DR: It was observed that regardless of the aspect ratios of the nanostructure, all superhydrophobic surfaces became superHydrophilic after annealing at temperatures higher than 500°C.

46 citations

Journal ArticleDOI
TL;DR: In this article, a self-cleaning, transparent surface on poly(methyl methacrylate) (PMMA) using a dry etching with CF 4 plasma and a subsequent hydrolysis process with water immersion is presented.
Abstract: We report a method to create a self‐cleaning, transparent surface on poly(methyl methacrylate) (PMMA) using a dry etching with CF 4 plasma and a subsequent hydrolysis process with water immersion. During the CF 4 plasma treatment, nanoscale pillar structures were formed and its a...

36 citations

Proceedings ArticleDOI
Jinyong Jeong1, Younggun Cho1, Young-Sik Shin1, Hyun Chul Roh1, Ayoung Kim1 
21 May 2018
TL;DR: The presented LiDAR data set is unique in the sense it is able to capture the genuine features of an urban environment (e.g. metropolitan areas, large building complexes and underground parking lots).
Abstract: This paper presents a Light Detection and Ranging (LiDAR) data set that targets complex urban environments. Urban environments with high-rise buildings and congested traffic pose a significant challenge for many robotics applications. The presented data set is unique in the sense it is able to capture the genuine features of an urban environment (e.g. metropolitan areas, large building complexes and underground parking lots). Data of two-dimensional (2D) and three-dimensional (3D) LiDAR, which are typical types of LiDAR sensors, are provided in the data set. The two 16-ray 3D LiDARs are tilted on both sides for maximal coverage. One 2D LiDAR faces backward while the other faces forwards to collect data of roads and buildings, respectively. Raw sensor data from Fiber Optic Gyro (FOG), Inertial Measurement Unit (IMU), and the Global Positioning System (GPS) are presented in a file format for vehicle pose estimation. The pose information of the vehicle estimated at 100 Hz is also presented after applying the graph simultaneous localization and mapping (SLAM) algorithm. For the convenience of development, the file player and data viewer in Robot Operating System (ROS) environment were also released via the web page. The full data sets are available at: http://irap.kaist.ac.kr/dataset. In this website, 3D preview of each data set is provided using WebGL.

34 citations


Cited by
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768 citations

Proceedings ArticleDOI
Giseop Kim1, Ayoung Kim1
04 Oct 2018
TL;DR: Scan Context is proposed, a non-histogram-based global descriptor from 3D Light Detection and Ranging (LiDAR) scans that makes loop-detection invariant to LiDAR viewpoint changes so that loops can be detected in places such as reverse revisit and corner.
Abstract: Compared to diverse feature detectors and descriptors used for visual scenes, describing a place using structural information is relatively less reported. Recent advances in simultaneous localization and mapping (SLAM) provides dense 3D maps of the environment and the localization is proposed by diverse sensors. Toward the global localization based on the structural information, we propose Scan Context, a non-histogram-based global descriptor from 3D Light Detection and Ranging (LiDAR) scans. Unlike previously reported methods, the proposed approach directly records a 3D structure of a visible space from a sensor and does not rely on a histogram or on prior training. In addition, this approach proposes the use of a similarity score to calculate the distance between two scan contexts and also a two-phase search algorithm to efficiently detect a loop. Scan context and its search algorithm make loop-detection invariant to LiDAR viewpoint changes so that loops can be detected in places such as reverse revisit and corner. Scan context performance has been evaluated via various benchmark datasets of 3D LiDAR scans, and the proposed method shows a sufficiently improved performance.

399 citations

08 Jul 2010
TL;DR: In this paper, first-principles calculations for both amorphous and crystalline phases observed during lithiation of Si anodes were performed and the anisotropic elastic tensors as well as the homogenized Young's, shear, and bulk moduli and the Poisson's ratios were analyzed.
Abstract: Knowledge of the elastic properties of Li–Si alloys as a function of Li concentration is crucial in the development of reliable deformation and fracture mechanics models for Si anodes in Li-ion batteries. Here, we have studied these properties using first-principles calculations for both amorphous and crystalline phases observed during lithiation of Si anodes. In the case of crystalline alloys, we present the anisotropic elastic tensors as well as the homogenized Young's, shear, and bulk moduli and the Poisson's ratios. We find that while these moduli decrease in an approximately linear manner with increasing Li concentration leading to significant elastic softening (by about one order of magnitude) in both crystalline and amorphous systems, the Poisson's ratios remain in the range of 0.05–0.20 and 0.20–0.30 in the case of crystalline and amorphous systems, respectively. Further, for a given Li concentration, we find that the amorphous structures are elastically somewhat softer than their crystalline counterparts, the difference being more significant (about 30–40%) in Li-poor phases. Our results underscore the importance of including the concentration dependence of elastic constants in the analysis of stress and deformation fields during lithiation and de-lithiation of Si anodes.

324 citations

Journal ArticleDOI
TL;DR: This paper reviews the contributions to superhydrophobic nanocoatings reported in recent literature, mainly including materials, fabrication and applications, and introduces application examples, and briefly discusses the principle behind the phenomenon.
Abstract: Superhydrophobic nanocoatings, a combination of nanotechnology and superhydrophobic surfaces, have received extraordinary attention recently, focusing both on novel preparation strategies and on investigations of their unique properties. In the past few decades, inspired by the lotus leaf, the discovery of nano- and micro-hierarchical structures has brought about great change in the superhydrophobic nanocoatings field. In this paper we review the contributions to this field reported in recent literature, mainly including materials, fabrication and applications. In order to facilitate comparison, materials are divided into 3 categories as follows: inorganic materials, organic materials, and inorganic-organic materials. Each kind of materials has itself merits and demerits, as well as fabrication techniques. The process of each technique is illustrated simply through a few classical examples. There is, to some extent, an association between various fabrication techniques, but many are different. So, it is important to choose appropriate preparation strategies, according to conditions and purposes. The peculiar properties of superhydrophobic nanocoatings, such as self-cleaning, anti-bacteria, anti-icing, corrosion resistance and so on, are the most dramatic. Not only do we introduce application examples, but also try to briefly discuss the principle behind the phenomenon. Finally, some challenges and potential promising breakthroughs in this field are also succinctly highlighted.

307 citations