• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.481-482
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• 2006

Chemical-mechanical polishing, the dominant technology for LSI planarization, is trending to play an important function in micro-electro mechanical systems (MEMS). However, MEMS CMP process has a couple of different characteristics in comparison to LSI device CMP since the feature size of MEMS is bigger than that of LSI devices. Preliminary CMP tests are performed to understand material removal rate (MRR) with blanket wafer under a couple of polishing pressure and velocity. Based on the blanket CMP data, this paper focuses on the consumable approach to enhance MEMS CMP by the adjustment of slurry and pad. As a mechanical tool, newly developed microstructured (MS) pad is applied to compare with conventional pad (IC 1400-k Nitta-Haas), which is fabricated by micro melding method of polyurethane. To understand the CMP characteristics in real time, in-situ friction force monitoring system was used. Finally, the topography change of poly-si MEMS structures is compared according to the pattern density, size and shape as polishing time goes on.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.723-743
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• 2016

Indoor positioning is considered an enabler for a variety of applications, the demand for an indoor positioning service has also been accelerated. That is because that people spend most of their time indoor environment. Meanwhile, the smartphone integrated powerful camera is an efficient platform for navigation and positioning. However, for high accuracy indoor positioning by using a smartphone, there are two constraints that includes: (1) limited computational and memory resources of smartphone; (2) users' moving in large buildings. To address those issues, this paper uses the TC-OFDM for calculating the coarse positioning information includes horizontal and altitude information for assisting smartphone camera-based positioning. Moreover, a unified representation model of image features under variety of scenarios whose name is FAST-SURF is established for computing the fine location. Finally, an optimization marginalized particle filter is proposed for fusing the positioning information from TC-OFDM and images. The experimental result shows that the wide location detection accuracy is 0.823 m (1σ) at horizontal and 0.5 m at vertical. Comparing to the WiFi-based and ibeacon-based positioning methods, our method is powerful while being easy to be deployed and optimized.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2217-2226
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• 2007

In this paper, we propose a microstrip antenna with sufficient impedance bandwidths and gains for the 2.65GHz antenna which can be used in the satellite digital multimedia broadcasting. The prposed 2.65GHz satellite DMB bandwidth microstrip antenna is implemented on a substrate, which is small enough to be installed in practical mobile phones, and described simulation feature using by CST MicroWave Studio program. And also, we measured the antenna performance between the proposed antenna and the commercial antenna. From the analysis, it was found that the radiation pattern of proposed antenna is superior to the commercial antenna and an acceptable frequency band is more wider than the existing products.

• Transactions of Materials Processing
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• v.32 no.4
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• pp.180-190
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• 2023

This study deals with residual stress prediction and hardness evaluation within cross ball grooved inner race fabricated by cold upsetting process consisted of upsetting and ejection steps. A raw workpiece material of AISI 5120H (SCr420H) is first spheroidized and annealed, then phosphophyllite coated to form solid lubricant layer on its outer surface. To investigate influences of the heat treatment, uni-axial compression tests and Vickers micro-hardness measurements are conducted. Three-dimensional elasto-plastic FE simulations on the upsetting step and the ejection one are performed to visualize the residual stress and the ductile (plastic deformation) damage. External feature of the fabricated inner race is fully captured by using an optical 3D scanner, and the micro-hardness is measured on internal cross-sections. Consequently, the dimensional compatibility between the simulated inner race and the fabricated one is ensured with a difference of under 0.243mm that satisfied permissible error range of ±0.50mm on the grooved surface, and the predicted residual stress is verified to have similar distribution tendency with the measured Vickers micro-hardness.

• Journal of KIISE
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• v.43 no.9
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• pp.1008-1014
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• 2016

Data such as Twitter, Facebook, and customer reviews belong to the informal document group, whereas, newspapers that have grammar correction step belong to the formal document group. Finding consistent rules or patterns in informal documents is difficult, as compared to formal documents. Hence, there is a need for additional approaches to improve informal document analysis. In this study, we classified Twitter data, a representative informal document, into ten categories. To improve performance, we revised and expanded features based on LDA(Latent Dirichlet allocation) word distribution. Using LDA top-ranked words, the other words were separated or bundled, and the feature set was thus expanded repeatedly. Finally, we conducted document classification with the expanded features. Experimental results indicated that the proposed method improved the micro-averaged F1-score of 7.11%p, as compared to the results before the feature expansion step.

• Journal of IKEEE
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• v.24 no.1
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• pp.200-207
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• 2020

In this paper, an area-efficient feature extractor was proposed for security surveillance radar systems and FPGA-based implementation results were presented. In order to reduce the memory requirements, features extracted from Doppler profile for FFT window-size are used, while those extracted from total spectrogram for frame-size are excluded. The proposed feature extractor was design using Verilog-HDL and implemented with Xilinx Zynq-7000 FPGA device. Implementation results show that the proposed design can reduce the logic slice and memory requirements by 58.3% and 98.3%, respectively, compared with the existing research. In addition, security surveillance radar system with the proposed feature extractor was implemented and experiments to classify car, bicycle, human and kickboard were performed. It is confirmed from these experiments that the accuracy of classification is 93.4%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.9
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• pp.1043-1048
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• 2014

As micro screws feature reduced screw lengths and pitches, the resulting clamping force diminishes because of the reduced length of the actual joints. The elements of the clamping force are material, geometry, and friction. We studied the shrinking size of the screw and the methods to improve the clamping force by changing the material. We developed a micro screw using SWCH18A and SUS XM7 materials, and obtained the precision and thickness of the pitch through three-dimensional measurement. We also measured the external resistance of the micro screw by applying the Vicker's hardness test and conducted a break surface analysis using a break torque test and SEM for obtaining the break characteristics.

• Journal of computational fluids engineering
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• v.22 no.1
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• pp.43-50
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• 2017

Thermal flowfield of a micro turbojet engine was computationally investigated for exhaust nozzles with different aspect ratio and curvature. Special attention was paid to maximum and average temperature of the nozzle surface and the exhaust nozzle plume. The IR signatures of the micro turbojet engine nozzle were then calculated through the narrow-band model based on thermal flowfield data obtained through CFD analysis. Finally, in order to check the similarity of thermal flowfields and IR signature of the sub-scale micro turbojet engine model and the full-scale UCAV propulsion system, several non-dimensional parameters associated with temperature and optical property of plume were introduced. It was shown that, in spite of some differences in actual values of non-dimensional parameters, the scaling characteristics on spectral feature of IR signature and effects of aspect ratio and curvature of nozzle configuration remain similar in sub-scale and full-scale cases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.587-588
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• 2012

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.862-865
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• 2005

해면골에 대한 평가는 일반적으로 골밀도를 기준으로 평가하지만, 골밀도는 뼈의 특성을 70-80% 정도만 설명하는 것으로 알려져 있다. 이에 따라 골밀도로 설명이 되지 않는 나머지 특성을 뼈 미세구조의 형태학적 특성을 이용하여 설명하려는 노력이 생체역학 분야에서 오랫동안 있어 왔다. 본 연구는 CAD/CAM 분야의 feature extraction 기술을 이러한 생체역학 분야에 접목함으로써 뼈의 미세구조 평가를 위한 새로운 형태학적 지수 개발의 가능성을 탐색하고자 한다.