• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4A
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• pp.586-591
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• 2000

In this paper, a PLHRO(Phase Locked Hair-pin Resonator Oscillator) for K-band is designed with the feedback property of PLL(Phase Locked Loop) using a new tuning mechanism. The proposed PLHRO generates the output power of -0.6 dBm at 24.42 GHz, and has the phase noise of -86.6 dBc/Hz at 100 KHz and -76.5 dBc/Hz at 10KHz offset from carrier frequency, and has suppression characteristics of -23 dBc and spurious noise of -65 dBc. Buffered 24.42 GHz PLHRO generates the output power of 5.6 dBm at 24.42 GHz and has the of a phase noise of -77.34 dBc/Hz at 100 KHz and -72 dBc/Hz at 100 KHz offset from carrier frequency.

• Journal of Powder Materials
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• v.24 no.3
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• pp.195-201
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• 2017

In this study, H13 tool steel sculptures are built by a metal 3D printing process at various laser scan speeds. The properties of commercial H13 tool steel powders are confirmed for the metal 3D printing process used: powder bed fusion (PBF), which is a selective laser melting (SLM) process. Commercial H13 powder has an excellent flowability of 16.68 s/50 g with a Hausner ratio of 1.25 and a density of $7.68g/cm^3$. The sculptures are built with dimensions of $10{\times}10{\times}10mm^3$ in size using commercial H13 tool steel powder. The density measured by the Archimedes method is $7.64g/cm^3$, similar to the powder density of $7.68g/cm^3$. The hardness is measured by Rockwell hardness equipment 5 times to obtain a mean value of 54.28 HRC. The optimum process conditions in order to build the sculptures are a laser power of 90 W, a layer thickness of $25{\mu}m$, an overlap of 30%, and a laser scan speed of 200 mm/s.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.9-16
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• 2018

Recently, the demand for eco-friendly parts has increased to reduce materials and parts that use fossil fuels. This has exacerbated the increase of energy prices and the enforcement of regulations by environmental agencies. Currently, polylactic acid (PLA) is a solution, as a common and eco-friendly material. PLA is a biodegradable material that can replace traditional petrochemical polymers. PLA has great advantages since it is resistant to cracking and shrinkage. When it is manufactured, there are few harmful byproducts. Improvement in the brittleness characteristics is another important task to be monitored throughout the production of industrial parts. Improvement in the brittleness property of products lowers the tensile strength and tensile elasticity modulus of the parts. This study focused on the mechanical properties of 3D-printed PLA parts. Tensile tests are performed while varying the infill print parameters to evaluate the applicability of PLA in several industrial areas.

• The Journal of Korea Robotics Society
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• v.11 no.3
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• pp.156-162
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• 2016

For the underwater localization, acoustic sensor systems are widely used due to greater penetration properties of acoustic signals in underwater environments. On the other hand, the good penetration property causes multipath and interference effects in structured environment too. To overcome this demerit, a localization method using the attenuation of electro-magnetic(EM) waves was proposed in several literatures, in which distance estimation and 2D-localization experiments show remarkable results. However, in 3D-localization application, the estimation difficulties increase due to the nonuniform (doughnut like) radiation pattern of an omni-directional antenna related to the depth direction. For solving this problem, we added a depth sensor for improving underwater 3D-localization with the EM wave method. A micro scale pressure sensor is located in the mobile node antenna, and the depth data from the pressure sensor is calibrated by the curve fitting algorithm. We adapted the depth(z) data to 3D EM wave pattern model for the error reduction of the localization. Finally, some experiments were executed for 3D localization with the fast calculation and less errors.

• Proceedings of the Korean Fiber Society Conference
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• 2007.11a
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• pp.395-396
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• 2007

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1349-1352
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• 2011

• Journal of applied mathematics & informatics
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• v.34 no.3_4
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• pp.221-225
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• 2016

For a connected graph G = (V, E), its inverse degree is defined as $\sum_{{\upsilon}{\in}{V}}^{}\frac{1}{d(\upsilon)}$. Using an upper bound for the inverse degree of a graph obtained by Cioabă in [4], we in this note present sufficient conditions for some Hamiltonian properties and k-connectivity of a graph.

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.301-304
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• 2014

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.151-151
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• 2012

A new plasma process, i.e., the combination of PIII&D and HIPIMS, was developed to implant non-gaseous ions into materials surface. HIPIMS is a special mode of operation of pulsed-DC magnetron sputtering, in which high pulsed DC power exceeding ~1 kW/$cm^2$ of its peak power density is applied to the magnetron sputtering target while the average power density remains manageable to the cooling capacity of the equipment by using a very small duty ratio of operation. Due to the high peak power density applied to the sputtering target, a large fraction of sputtered atoms is ionized. If the negative high voltage pulse applied to the sample stage in PIII&D system is synchronized with the pulsed plasma of sputtered target material by HIPIMS operation, the implantation of non-gaseous ions can be successfully accomplished. The new process has great advantage that thin film deposition and non-gaseous ion implantation along with in-situ film modification can be achieved in a single plasma chamber. Even broader application areas of PIII&D technology are believed to be envisaged by this newly developed process. In one application of non-gaseous plasma immersion ion implantation, Ge ions were implanted into SiO2 thin film at 60 keV to form Ge quantum dots embedded in SiO2 dielectric material. The crystalline Ge quantum dots were shown to be 5~10 nm in size and well dispersed in SiO2 matrix. In another application, Ag ions were implanted into SS-304 substrate to endow the anti-microbial property of the surface. Yet another bio-application was Mg ion implantation into Ti to improve its osteointegration property for bone implants. Catalyst is another promising application field of nongaseous plasma immersion ion implantation because ion implantation results in atomically dispersed catalytic agents with high surface to volume ratio. Pt ions were implanted into the surface of Al2O3 catalytic supporter and its H2 generation property was measured for DME reforming catalyst. In this talk, a newly developed, non-gaseous plasma immersion ion implantation technique and its applications would be shown and discussed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.443-446
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• 2005

As modern society needs to process of acquisition, storage and transmission of much information, the importance of signal processing is increasing and various digital filters are used in the two-dimensional signal such as image. And kinds of these digital filters are IIR(infinite impulse response) filter and FIR(finite impulse response) filter. And FIR filter which has the phase linearity, the easiness of creation and stability is applied to many fields. In design of this FIR filter, flatness property is a important factor in pass-band and stop-band. In this paper, we designed a 2-D Circular FIR filter using the Bernstein polynomial, it is presented flatness property in pass-band and stop-band. And we simulated the designed filter with noisy test image and compared the results with existing methods.