• Publications of The Korean Astronomical Society
• /
• v.24 no.1
• /
• pp.65-81
• /
• 2009

We present the performance test results of VLBI Correlation Subsystem (VCS) trial product which was being developed for 1 year from August 2007. It is a core component of Korea-Japan Joint VLBI Correlator (KJJVC). The aim for developing VCS trial product is to improve the performance of VCS main product to reduce the efforts and cost, and to solve the design problems by performing the preliminary test of the manufactured trial product. The function of VCS trial product is that it is able to process the 2 stations-1 baseline, 8 Gbps/station speed, 1.2 Gbps output speed with FX-type. VCS trial product consists of Read Data Control Board (RDC), Fourier Transform Board (FTB), and Correlation and Accumulation Board (CAB). Almost main functions are integrated in the FTB and CAB board. In order to confirm the performance of VCS trial product functions, the spectral analysis, delay compensation and correlation processing experiments were carried out by using simulation and real observation data. We found that the overflow problem of re-quantization after FFT processing was occurred in the delay compensation experiment. We confirmed that this problem was caused by valid bit-expression of the re-quantized data. To solve this problem, the novel method will be applied to VCS main product. The effectiveness of VCS trial product has been verified through the preliminary experimental results, but the overflow problem was occurred.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.2C
• /
• pp.306-314
• /
• 2004

Some receiver(and most transmit) beamforming algorithms with an array antenna at a cellular CDMA base stations require accurate internal and external calibrations. The external calibration, which usually needs to be done only once, determines the array manifolds, i.e. the complex response of each antenna as a function of DOA(Directions of Arrival). The internal calibrations are necessary because characteristics of RF/IF circuity of each receiver chain vary differently in response to temperature or humidity changes. We propose an iterative subspace-based calibration algorithm for an asynchronous CDMA-based antenna away in the presence of unknown gain and phase error is presented. We verify the subspace-based calibration algorithms by performing the experiment using measured data. Also, we propose an efficient algorithm using the simulated annealing technique. This algorithm overcomes the problem of the initial guessing in the subspace-based approach.

• Journal of the Korea Society of Computer and Information
• /
• v.23 no.6
• /
• pp.43-49
• /
• 2018

In this paper, we propose a taping therapy as effective intervention for patients with the back pain. The purpose of this study is to investigate the effects of taping intervention on the VAS evaluated score and he muscular activation degree among 119 paramedics with musculoskeletal injury. In order to achieve the purpose of the study, data was collected from 15 paramediecs in the paramedics department of 3 fire stations under J city's fire defense headquarters. The following results can be obtained by measuring the subjective, the back muscle strength and the buckling-anteflexion before and after the taping for 15 119 paramedics. Through the verification experiment of taping effect to paramedics during the stretcher lifting in this study the VAS evaluated score for the backache are $1.67{\pm}0.62$ before and $0.80{\pm}0.68$ after the application of taping which show statistically significant decrease(p<0.05). In the experimentof joint operation range the measured buckling anteflexion length are $14.62cm{\pm}4.89$ before and $16.41cm{\pm}4.11cm$ after the application of taping which show statistically meaningful difference(p<0.05). In the comparison of muscle activity about paramedics erector spinae(ES) shows the meaningful decrease and external obliques(EO) displays the significant increase. Erector spinae(ES) and internal obliques(IO) show the increasing trend in the muscle activity although they are not significant. the muscle activity for the erector spinae is lowered so that the contribution to the force required for the extensor during the stretcher lifting is resultingly reduced to have the effects of enhancing the activity of abdominal muscles.

• Nuclear Engineering and Technology
• /
• v.46 no.5
• /
• pp.633-640
• /
• 2014

In this research, the surface roughness affecting the pressure drop in a pipe used as the steam generator of a PWR was studied. Based on the CFD (Computational Fluid Dynamics) technique using a commercial code named ANSYS-FLUENT, a straight pipe was modeled to obtain the Darcy frictional coefficient, changed with a range of various surface roughness ratios as well as Reynolds numbers. The result is validated by the comparison with a Moody chart to set the appropriate size of grids at the wall for the correct consideration of surface roughness. The pressure drop in a full-scale U-shaped pipe is measured with the same code, correlated with the surface roughness ratio. In the next stage, we studied a reduced scale model of a U-shaped heat pipe with experiment and analysis of the investigation into fluid-structure interaction (FSI). The material of the pipe was cut from the real heat pipe of a material named Inconel 690 alloy, now used in steam generators. The accelerations at the fixed stations on the outer surface of the pipe model are measured in the series of time history, and Fourier transformed to the frequency domain. The natural frequency of three leading modes were traced from the FFT data, and compared with the result of a numerical analysis for unsteady, incompressible flow. The corresponding mode shapes and maximum displacement are obtained numerically from the FSI simulation with the coupling of the commercial codes, ANSYS-FLUENT and TRANSIENT_STRUCTURAL. The primary frequencies for the model system consist of three parts: structural vibration, BPF(blade pass frequency) of pump, and fluid-structure interaction.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.20 no.5
• /
• pp.127-133
• /
• 2020

The international cancer research institute under the WHO designated fine dust as a first-class carcinogen. Particular matter refers to dust that is small enough to be invisible and floating in the air. Particular matter is mainly emitted from the combustion process of fossil fuels such as coal and oil, and is a risk factor that can cause lung disease, pneumonia, and heart disease. The Ministry of Environment recently analyzed the output data of 10 fine dust measuring stations and, as a result, announced that about 60% had an error that the existing atmospheric measurement concentration was higher. In order to accurately predict fine dust, the wind direction and measurement position must be corrected. In this paper, in order to solve these problems, fuzzy rules are used to solve these problems. In addition, in order to calculate the fine particulate sensation index actually felt by pedestrians on the street, a computer simulation experiment was conducted to calculate the fine particulate sensation index in consideration of weather conditions, temperature conditions, humidity conditions, and wind conditions.

• Journal of the Korean Society for Railway
• /
• v.14 no.2
• /
• pp.167-173
• /
• 2011

This paper considers the problem of revising train departure time to reduce electric power consumption of mass rapid transit (MRT) railways. The motion of a train running between stations is divided into three phases: traction, coasting, and deceleration phases. The traction phase requires high electric power to operate MRT railways. In the coasting phase, the train moves stably by consuming little or no power. The deceleration phase is a braking mode and produces some electric power called regenerated brake power owing to inertia force for the train generated In the traction and coasting phases. The regenerative energy can be used by other accelerating trains within a specific range from the train and thereby the power consumptions of train can be reduced. We developed a mixed integer programming model to solve the problem. To validate the suggested model, a computational experiment was conducted using real data from Korea Metropolitan Subway.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.10
• /
• pp.1276-1283
• /
• 2016

The scale of financial damages on voice fishing has not been decreased despite of national and social efforts to reduce the amounts of voice fishing damage. One of these reasons is a sophisticated and vernacular speech style that makes it difficult to recognize the offenders. Furthermore, nowadays, young men have intensively been deceived by not only sophisticated and vernacular speech style which is used the employer of real public offices but also obtained personal information. As a result, this lead directly to the financial damages of younger people who has a stronger judgement than older. For this, we investigated the comparison and analysis between the criminals of voice fishing and the same generation younger people for identifying voice features. The experiment was carried out based on the pitch, bandwidth of pitch, energy, speech speed and voice color for searching the difference of voice characteristics between the criminals of voice fishing and the same generation younger people since 2011. The experimental result shows that there is a significant difference in energy and speech speed between the criminals of voice fishing and the same generation younger people.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.21 no.5
• /
• pp.615-627
• /
• 1997

An experiment was performed to local heat transfer coefficient and Nusselt number in the circular duct of 180.deg. bend for Re=6*10$^{4}$, 8*10$^{4}$ and 1*10$^{5}$ at swirling flow and non-swirling flow conditions. The test tube with circular section was made by stainless which has curvature ratio 9.4. The wall of test tube was heated directly by electrical power to 3.51 kw and swirling motion of air was produced by a tangential inlet to the pipe axis at the 180 degree. Measurements of local wall temperatures and bulk mean temperature of air are made at four circumferential positions in the 16 stations. The wall temperatures show particularly reduced distribution curve at bend for non-swirling flow but this effect does not appear for swirling flow. Nusselt number distributions for swirling flow which was calculated from the measured wall and bulk temperatures were higher than that of non-swirling flow. Average Nusselt number of swirling flow increased about 90 ~ 100% than that of non-swirling flow whole through the test tube. The Nu/N $u_{DB}$ values at the station of 90.deg. for non-swirling flow and swirling flow are respectively about 2.5 and 4.8 at Re=6*10$^{4}$. Also that is good agreement with Said's result for non-swirling flow. flow.

• Journal of Digital Convergence
• /
• v.19 no.9
• /
• pp.241-255
• /
• 2021

The purpose of this study was to verify the effects of the online lifelong education program which is a key words card production and demonstration on the job preparation skills for work for part-time developmental disabilities. The subjects of this study were three developmental disabilities workers working in a restaurant business on a part-time basis, and the experimental environment was composed of the home and subway stations where they reside. The study method used a single subject study, and the baseline, intervention, and maintenance were reflected as the design conditions of the experiment. As a result, the subjects of the study effectively acquired and maintained the job preparation skills for work work through the online lifelong education program for the production and demonstration of key words cards. Through the results of this study, it was possible to discuss and conclude that the significant functional relationship between the independent variables and the dependent variables is valid.

• Journal of the Korean Society of Safety
• /
• v.36 no.1
• /
• pp.64-71
• /
• 2021

Experimental and analytical investigations are performed to explore the explosion characteristics of a hydrogen-air mixture in open atmosphere. A hydrogen-air mixture tent of total volume of 27 m³, with 40% hydrogen volume, is used to observe overpressure at a distance from the ignition source. Vapor cloud explosion analyses are performed using the TNO multi-energy model and Baker-Strehlow-Tang model. The results of these analyses are compared with experiment done from this study and references. The experimental results with and without obstacles indicate that the overpressure values measured at a distance of 4.5-21.5 m from the ignition source are about 9.4-3.6 kPa and 6.5-2 kPa, respectively. This implies that the overpressure with obstacles is approximately 1.7 times greater than that without obstacles. Analytical observation indicates that the results obtained with the Baker-Strehlow-Tang model with M_f = 0.2-0.35 are in good agreement with those of most of the previous studies, including that obtained from this study. Moreover, the TNO multi-energy model with a volume of 27 m³ well predicts the overpressure obtained from this study. Further studies should considered explosions in semi-confined spaces, which is more suitable for hydrogen refueling stations.