• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.972-974
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• 2016

최근 전 세계적으로 IoT(Internet of Things) 기술이 활발히 연구되고 있다. IoT 환경은 임베디드나 센서 등의 시스템에 적용되는 경우가 많다. 그 특성으로 인해, 적용된 장치들은 경량화되기 때문에 통신을 위한 프로토콜로 UDP 기반 프로토콜을 많이 사용한다. UDP 기반 프로토콜은 TCP 기반 프로토콜보다 보안 기능이 미비하므로 UDP 상에서도 보안 기능을 제공해 줄 수 있는 DTLS(Datagram Transport Layer Security)가 권고된다. 하지만 DTLS는 저전력 IoT 환경을 고려하여 만들어진 프로토콜이 아니다. 그래서 저전력 IoT 환경에서 사용하기에는 힘들다. 하지만 HIGHT(HIGh security and light weigHT) 알고리즘을 사용하면 보안적인 측면을 고려하면서도 DTLS의 알고리즘인 AES(Advanced Encryption Standard)의 높은 에너지 소모량이 해결된다. 본 논문에서는 보안 측면을 고려하면서 에너지 효율까지 고려한 KISA(Korea Internet & Security Agency, 한국인터넷진흥원)의 HIGHT 암호화 알고리즘을 기반으로 DTLS를 경량화하여 저전력 기기에서 적용할 수 있는 방안을 제안한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.463-466
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• 2005

While recent display devices are becoming light and slim, the size of a screen is especially the important issue in the field of display devices. Furthermore, it is also required that the projection TV, a large screen display device, be able to represent higher resolutions as the digital broadcasting is set off. In order to realize high resolutions in a DLP projection TV, the number of pixel on DMD should be increased. However, a large number of pixels make it difficult to realize resulting small sized pixels and this cause the increase in cost. Therefore, we propose a simple and improved pixel enhancement actuator using the existing DMD by offsetting half pixels repeatedly in the vertical direction.

• Journal of Information Processing Systems
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• v.14 no.6
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• pp.1445-1456
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• 2018

Environment perception and three-dimensional (3D) reconstruction tasks are used to provide unmanned ground vehicle (UGV) with driving awareness interfaces. The speed of obstacle segmentation and surrounding terrain reconstruction crucially influences decision making in UGVs. To increase the processing speed of environment information analysis, we develop a CPU-GPU hybrid system of automatic environment perception and 3D terrain reconstruction based on the integration of multiple sensors. The system consists of three functional modules, namely, multi-sensor data collection and pre-processing, environment perception, and 3D reconstruction. To integrate individual datasets collected from different sensors, the pre-processing function registers the sensed LiDAR (light detection and ranging) point clouds, video sequences, and motion information into a global terrain model after filtering redundant and noise data according to the redundancy removal principle. In the environment perception module, the registered discrete points are clustered into ground surface and individual objects by using a ground segmentation method and a connected component labeling algorithm. The estimated ground surface and non-ground objects indicate the terrain to be traversed and obstacles in the environment, thus creating driving awareness. The 3D reconstruction module calibrates the projection matrix between the mounted LiDAR and cameras to map the local point clouds onto the captured video images. Texture meshes and color particle models are used to reconstruct the ground surface and objects of the 3D terrain model, respectively. To accelerate the proposed system, we apply the GPU parallel computation method to implement the applied computer graphics and image processing algorithms in parallel.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.2
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• pp.39-46
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• 2001

In this paper we propose a new method that can be estimation the spectral power distribution of the light source from three-band images. the light source is estimated by dividing the reflected spectral power distribution of the maximum achromatic region(L(λ)) by the corresponding surface reflectance(Ο(λ)). In order to obtain reflected spectral power distribution of the maximum achromatic region from three-bend images, a modified gray world assumption algorithm is adapted. And the maximum surface reflectance is estimated using the principal component analysis method along with achromatic population. The achromatic population is created from a set of given Munsell color chips whose chroma vector is less than threshold. Cumulative contribution ratio of principal components from the first to the third for classified achromatic population was about 99.75%. The reconstruction of illumination spectral power distribution by using achromatic population and three-band digital images captured under various light source was examined, and evaluated by RMSE between the original and reconstructed illumination spectral power distribution. This work was supported by grant No (2000-1-30200-005-3) from the Basic Research Program of the Korea Science & Engineering Foundation.

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.77-83
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• 2021

Purpose: The purpose of this in vitro study was to measure and compare the thickness-dependent color dimensions of digital light processing (DLP) three-dimensional (3D) printer and conventional interim restorative resin. Methods: Specimens (N=60) were fabricated using either subtractive manufacturing (S group) or DLP 3D printing (D group) material. All milled and 3D-printed specimens were allocated into three different groups (n=10) according to different thicknesses as follows: 1.0, 1.5, and 2.0 mm. Color measurements in the CIELab coordinates were made using a spectrophotometer under room light conditions (1,003 lux). The color differences (𝚫E^*) between the specimen and control target data were calculated. Data were analyzed using the oneway analysis of variance (ANOVA). Post hoc comparisons were conducted using Tukey's honestly significant difference method (α=0.05 for all tests). Results: The 𝚫L^*, 𝚫a^*, 𝚫b^*, and 𝚫E^* values of interim restorative resin produced by DLP 3D printing were obtained in terms of the specimen's thickness increased compared with the increases by subtractive manufacturing. When the thickness was similar, the color difference between subtractive manufacturing and DLP 3D printing was ≥5.5, which is a value required by the dentist for remanufacturing. Conclusion: Color was influenced by the thickness of the interim restorative resin produced by DLP 3D printing.

• The Journal of Advanced Prosthodontics
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• v.15 no.5
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• pp.248-258
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• 2023

PURPOSE. This study aims to evaluate the effects of exposure energy on the lateral resolution and mechanical strength of dental zirconia manufactured using digital light processing (DLP). MATERIALS AND METHODS. A zirconia suspension and a custom top-down DLP printer were used for in-office manufacturing. The viscosity of the suspension and uniformity of the exposed light intensity were controlled. Based on the exposure energy dose delivered to each layer, the specimens were classified into three groups: low-energy (LE), medium-energy (ME), and high-energy (HE). For each energy group, a simplified molar cube was used to measure the widths of the outline (X_o and Y_o) and isthmus (X_i and Y_i), and a bar-shaped specimen of the sintered body was tested. A Kruskal-Wallis test for the lateral resolution and one-way analysis of variance for the mechanical strength were performed (α = .05). RESULTS. The zirconia green bodies of the ME group showed better lateral resolution than those of the LE and HE groups (both P < .001). Regarding the flexural strength of the sintered bodies, the ME group had the highest mean value, whereas the LE group had the lowest mean value (both P < .05). The ME group exhibited fewer agglomerates than the LE group, with no distinctive interlayer pores or surface defects. CONCLUSION. Based on these findings, the lateral resolution of the green body and flexural strength of the sintered body of dental zirconia could be affected by the exposure energy dose during DLP. The exposure energy should be optimized when fabricating DLP-based dental zirconia.

• International journal of advanced smart convergence
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• v.1 no.1
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• pp.52-56
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• 2012

As inexhaustible clean energy, solar energy will be the most ideal green energy in the 21st century. The effective method to convert solar energy into electrical energy is by solar photovoltaic power generation technologies. LED Emitting Diode is a kind of component which can transform electricity into visible light. As the smart current control system for photovoltaic street lights, the proposed system has improved the battery charging and discharging mechanism to extend the lifespan and effectively controls the LED discharge current according to battery charge state and lighting.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.9
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• pp.2003-2008
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• 2012

A drive system is necessary to operate LED by an LED illumination system. Because Switched Mode Power Supply (SMPS) is higher in efficiency in the large capacity than Linear Regulator, it is used mainly and controls this in an analog form or digital method. A MCU and a DSP of the digital control central processing unit were higher in a unit price than existing analog control chip, so that an approach was not easy for application of SMPS. But it can take the earnings by it lets you integrate various digital control features like an LED illumination system in one MCU, and realizing a whole system. In this paper, we suggest the algorithm that can improve LED driving current in applying such a digital control method using low-priced type MCU.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.283-288
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• 2004

The measurement of ultra low aspect ratio fluid film thickness is very crucial technique both for the verification of lubrication media characteristics and for the clearance design in many precision components such as MEMS, precision bearings and other slideways. Many technologies are applied to the measurement of ultra low aspect ratio fluid film thickness (i.e. elastohydrodynamic lubrication film thickness). In particular, in-situ optical interferometric method has many advantages in making the actual contact behaviors realized with the experimental apparatus. This measurement method also does the monitoring of the surface defects and fractures happening during the contact behavior, which are delicately influenced by the surface conditions such as load, velocity, lubricant media as well as surface roughness. Careful selection of incident lights greatly enhances the fringe resolutions up to $\~1.0$ nanometer scale with digital image processing technology. In this work, it is found that coaxial aligning trichromatic incident light filtering system developed by the author can provide much finer resolution of ultra low aspect ratio fluid film thickness than monochromatic or dichromatic incident lights, because it has much more spectrums of color components to be discriminated according the variations of film thickness. For the measured interferometric images of ultra low aspect ratio fluid film thickness it is shown how the film thickness is finely digitalized and measured in nanometer scale with digital image processing technology and space layer method. The developed measurement system can make it possible to visualize the contact deformations and possible fractures of contacting surface under the repeated loading condition.

• The KIPS Transactions:PartB
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• v.12B no.6 s.102
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• pp.631-636
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• 2005

Recently, research started to focus on Digital Multimedia Broadcasting(DMB), while the DMB service is already being launched to provide high quality audio, video and data broadcasting in Korea. Therefore, the demand for multimedia contents is also rose very sharply. In this paper, we introduced an MPEG-4 contents authoring system with mobile device for Digital Multimedia Broadcasting. Our system allows both single-handed and collaborative authoring modo. Further more, to overcome the delaytime for decoding the BIFS information, we also introduced an efficient algorithm to generate dynamic and light BIFS information.