• Structural Engineering and Mechanics
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• v.74 no.3
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• pp.381-394
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• 2020

The structural performance of cold-formed steel (CFS) built-up battened columns were numerically investigated in this paper. The built-up column sections were formed by connecting two-lipped channels back-to-back, with a regular spacing of battens plates, and have been investigated in the current study. Finite element models were validated with the test results reported by the authors in the companion paper. Using the validated models, the parametric study was extended, covering a wider range of overall slenderness to assess the accuracy of the current design rules in predicting the design strengths of the CFS built-up battened columns. The parameters viz., overall slenderness, different geometries, plate slenderness (b/t ratio) and yield stress were considered for this study. In total, a total of 228 finite element models were analyzed and the results obtained were compared with current design strength predicted by Effective Width Method of AISI Specifications (AISI S100:2016) and European specifications (EN1993-1-3:2006). The parametric study results indicated that the current design rules are limited in predicting the accuracy of the design strengths of CFS built-up battened columns. Therefore, a design equation was proposed for the AISI and EC3 specifications to predict the reliable design strength of the CFS Built-up battened columns and was also verified by the reliability analysis.

• Journal of Communications and Networks
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• v.5 no.1
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• pp.1-6
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• 2003

In this paper, we extend the derivation of the iterative soft-output Viterbi algorithm (SOVA) for partial response (PR) channels, and modify its decoding process such that it works consistently for arbitrary high code rates, e.g., rate 64/65. We show that the modified SOVA always outperforms the conventional SOVA that appears in the literature with a significant difference for high code rates. It also offers a significant cut down in the trace-back computations. We further examine its performance for parallel and serial concatenated codes on a precoded Class IC partial response (PR4) channel. Code rates of the form $\frac{k_0}{k_0+1}$($k_0$ = 4, 8, and 64) are considered. Our simulations indicate that the loss suffered by the modified SOVA, relative to the APP algorithm, is consistent for all code rates and is at most 1.2 dB for parallel concatenations and at most 1.6 dB for serial concatenations at $P_b$ = $10^{-5}$.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.388-394
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• 2010

In this paper the object recognition performance of a photon counting integral imaging system is quantitatively compared with that of a conventional gray scale imaging system. For 3D imaging of objects with a small number of photons, the elemental image set of a 3D scene is obtained using the integral imaging set up. We assume that the elemental image detection follows a Poisson distribution. Computational geometrical ray back propagation algorithm and parametric maximum likelihood estimator are applied to the photon counting elemental image set in order to reconstruct the original 3D scene. To evaluate the photon counting object recognition performance, the normalized correlation peaks between the reconstructed 3D scenes are calculated for the varied and fixed total number of photons in the reconstructed sectional image changing the total number of image channels in the integral imaging system. It is quantitatively illustrated that the recognition performance of the photon counting integral imaging system can be similar to that of a conventional gray scale imaging system as the number of image viewing channels in the photon counting integral imaging (PCII) system is increased up to the threshold point. Also, we present experiments to find the threshold point on the total number of image channels in the PCII system which can guarantee a comparable recognition performance with a gray scale imaging system. To the best of our knowledge, this is the first report on comparisons of object recognition performance with 3D photon counting & gray scale images.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.28 no.2
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• pp.117-131
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• 1992

A studies on the pattern of sea water circulation was carried out by using drogue experiments, tidal current measurement and hydrographic data in Kamak Bay which has two channels. At the flood, the water inflowed from the northern narrow channel flows mostly to the southward then the westward because Daekyung-island located at the flow path, at the same time the water from the southern channel of bay directed strongly to the north with a spine centered at around Gunnaeri. And these waters converged at the area between eng-Island and Deakyung-Island in the bigining of the flow, and placed at less southern part than the area at the late. The water of the north west inner bay having concave bottom topography inflows to Najin inlet with a spin of anti-clockwise. At the ebb, those waters in the bay turn back to two channels respectively, but most of waters directed to the southern channel of the bay. The directions of residual current of two channels are the southward mainly, and the current of inner area are influenced by the prevailing wind. The north-west inner bay which has the weak tidal current less than 10 cm/sec shows a similar upwelling by off-shore wind in winter, and the stratification in summer, respectively.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.34-37
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• 2017

This letter presents the signal processing of a CW radar (Continuous Wave or Doppler radar) sensor which enables the radar to detect the multiple targets' approaching and retreating using both I and Q channels. The proposed algorithm utilizes the phase change of the Quadrature signal, which occurs when targets move back and forth from the radar. The verification is carried out with the board containing a commercially available MMIC chip and an MCU by analyzing the received data from MMIC. Also the proposed algorithm is downloaded to MCU and the approaching and retreating movement is confirmed. The CW frequency is 24.125 GHz and the transmitter output power used is 7.2 dBm. Detectable distance is about 12 m.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10C
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• pp.946-954
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• 2009

General RFID system has assumed that the communication channel between reader and back-end database is secure channel. However, the reader can be communicated with the database through insecure channel like the communication channel between the reader and the tag according to application environment. In this paper, we propose a new secure RFID mutual authentication protocol based on open network channel which assumed that all communication channels between the database, the reader and the tag are insecure communication channels. The proposed protocol uses a secure one-way hash function to provide authentication and integrity against all communication messages which exchanged on the open channels. In addition, we designed that the proposed protocol can provide forward secrecy by performing the database and the tag update their old secret key with a new secret key after finished mutual authentication.

• Membrane Journal
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• v.18 no.4
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• pp.325-335
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• 2008

In this study, we used multi-channels ceramic membrane having larger permeate volume per unit time rather than tubular membrane. The hybrid process for advanced drinking water treatment was composed of granular activated carbons (GAC) packing between module inside and outside of multi-channels microfiltration membrane. Instead of natural organic matters (NOM) and fine inorganic particles in natural water source, modified solution was prepared with humic acid and kaolin. Kaolin concentration was fixed at 30mg/L and humic acid was changed as $2{\sim}10\;mg/L$ to inspect effect of organic matters. As a result, both resistance of membrane fouling ($R_f$) and permeate flux (J) were highly influenced by concentration of humic acid. Also, in result of water-back-flushing period (FT) effect, the shorter FT was the more effective to reduce membrane fouling and to enhance permeate flux because of frequent water-back-flushing. However, the optimal FT condition was 8 min when operating costs were considered. Then, the hybrid process using multi-channels ceramic membrane and GAC was applied to lake water treatment. As a result, average treatment efficiencies in our experiment using the hybrid process were 98.02% for turbidity, 75.64% for $UV_{254}$ absorbance, 7.18% for TDS and 84.73% for $COD_{Mn}$.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.2
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• pp.90-99
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• 2007

We demonstrate an 80km-reach 64-channel DWDM-PON based on wavelength-locked F-P LDs by changing the position of the C-band BLS for upstream channels from the CO to the RN. It mitigates the necessity of the high power C-band BLS and its handling problems. It also reduces back scattering induced penalty. We obtained less than $10^{-6}$ PLRs in all 128channels through 80km SMF. We also demonstrate a 240km-reach DWDM-PON based on wavelength-locked F-P LDs by adding a bidirectional erbium-doped fiber amplifier(EDFA). We show packet-loss-free transmission in all 128channels at 125 Mb/s per channel over 240km SMF We report the detuning effect of arrayed waveguide gratings(AWGs) and crosstalk effect in the implemented system. We Propose an architecture of a next generation defense wire communication system with the demonstrated long-reach DWDM-PON.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.89-91
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• 2004

In SCADA systems, an RTU is a device installed at a remote location that collects data, codes the data into a format that is transmittable and transmits the data back to a central station, or MTU. An RTU also collects information from the master device and implements processes that are directed by master device. RTUs are equipped with input channels for sensing or metering, output channels for control, indication or alarms and a communications port. In general, the data are transmitted via a wired communication infrastructure such as RS422 or RS485 between RTU and MTU. But, limited range of wired communication doesn't allow the system to cover remote areas over the limitation, and building a wired communication network is not easy in the circumstances. In this Paper, we design and implement a smart cost-effective Web-RTU that can communicate with MTU via Web. Web is of benefit to the Web-RTU, because it is not only free from the distance limitations, but also is built easily and cost-effectively wherever Internet resources are available. Additionally, Web can be easily applied to the SCADA system with the development of hardware and software for communications. The Web-RTU has a program memory, a data memory and a RAM inside, and uses Atmega128, low-cost 8 bit micro-processor with eight AI(Analog Input). It performs well enough to implement all existing roles of RTU.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.141-150
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• 2007

This paper presents a lumped model to predict crosstalk characteristics of thermally driven inkjet print heads. Using the lumped R-C model, heating characteristics of the head are predicted to be in agreement with IR temperature measurements. The inter-channel crosstalk is simulated using the lumped R-L network. The values of viscous flow resistance, R and flow inertance, L of connecting channels are adjusted to accord with the 3-D numerical simulation results of three adjacent jets. The crosstalk behaviors of a back shooter head as well as a top shooter head have been investigated. Predictions of the proposed lumped model on the meniscus oscillations are consistent with numerical simulation results. Comparison of the lumped model with experimental results identifies that abnormal two-drop ejection phenomena are related to the increased meniscus oscillations because of the more severe crosstalk effects at higher printing speeds. The degree of crosstalk has been quantified using cross-correlations between neighboring channels and a critical channel dimension for acceptable crosstalk has been proposed and validated with the numerical simulations. Our model can be used as a design tool for a better design of thermal inkjet print heads to minimize crosstalk effects.