• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.1-8
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• 2012

Multidisciplinary design optimization (MDO) for a suspension component of the vehicle front suspension was performed in this research. Shapes and thicknesses of the subframe were optimized to satisfy multi-disciplinary design requirements; weight, fatigue, crash, noise, vibration, and harshness (NVH), and kinematic and compliance (K&C). Analyses procedures of the performance disciplines were integrated and automated by using the process integration and design optimization (PIDO) technique, and the integrated and automated analyses environments enabled various types of analytic design methodologies for solving the MDO problem. We applied an approximate optimization technique which involves sequential sampling and metamodeling. Since the design variables for thicknesses should be dealt as discrete variables. the evolutionary algorithm is selected as optimization technique. The MDO problem was formulated three types of problems according to the order of priorities among the performance disciplines, and the results of MDO provided design alternatives for various design situations.

• Journal of Biomedical Engineering Research
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• v.28 no.3
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• pp.429-440
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• 2007

A coded excitation has been studied to improve the performance for ultrasound imaging in term of SNR, imaging frame rate, contrast to tissue ratio, and so forth. However, it requires a complicated arbitrary waveform transmitter for each active channel that is typically composed of a multi-bit Digital-to-Analog Converter (DAC) and a linear power amplifier (LPA). Not only does the LPA increase the cost and size of a transmitter block, but it consumes much power, increasing the system complexity further and causing a heating-up problem. This paper proposes an optimized 1.5bit fourth order sigma-delta modulation technique applicable to design an efficient arbitrary waveform generator with greatly reduced power dissipation and hardware. The proposed SDM can provide a required SQNR with a low over-sampling ratio of 4. To this end, the loop coefficients are optimized to minimize the quantization noise power in signal band while maintaining system stability. In addition, the decision level for the 1.5 bit quantizer is optimized for a given input waveform, which results in the SQNR improvement of more than 5dB. Computer simulation results show that the SQNR of a FM(frequency modulated) signal generated by using the proposed method is about 26dB, and the peak side-lobe level (PSL) of its compressed waveform on receive is -48dB.

• Korean Journal of Social Welfare
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• v.68 no.1
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• pp.53-71
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• 2016

This study, we analyzed the following in order to verify the effects of depression on suicidal ideation. First, correlations among depression, family solidarity and suicide variables were analysed. Second, the hierarchical regression analysis was conducted to examine the effects of suicidal ideation. Third, family solidarity Sobel-test was performed to investigate whether family solidarity mediates the link between depression and suicidal ideation. The data used in the study comes from the survey conducted by Hallym Aging Research Institute in 2014. Through stratified multi-stage random sampling, 2,034 individuals aged 65 and over and living in Chun-cheon city were analysed. The result with depression and family solidarity together shows the higher the level of depression is, the more suicide ideation is. which means depression has a direct impact on suicide ideation. In addition, it indicates the higher family solidarity is, the less suicide ideation is. Sobel-test which examines indirect effects of depression on suicidal ideation through family solidarity produces a statistically meaningful result. The result is family solidarity mediates the link between depression and suicidal ideation.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.5
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• pp.1913-1918
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• 2014

Background: The study is the first of its kind to be conducted in Saudi Arabia (KSA), aiming to analyze the effectiveness of an intervention program in improving the knowledge of oral cancer among the youth. Materials and Methods: A total of 1,051 young Saudis (57% males and 43% females with a mean age of $20.4{\pm}1.98$) were selected using multi-stage cluster sampling. Knowledge assessment was accomplished using a closed-ended questionnaire which was subjected to reliability tests. Prevalence of risk factors in relation to gender was analyzed using the chi-squared test. Effectiveness was calculated by comparing the pre- and post-intervention means, using the two-tailed paired t-test. Multiple logistic regression was employed in order to determine factors associated with awareness of risk habits, signs/symptoms and prevention of oral cancer. The significance level in this study was set at 0.05. Results: Females were seen to be more into the habit of sheesha smoking (3.3% rather than the use of other forms of risk factors. Prevalence of diverse risk factors such as cigarette smoking (20%), sheesha (15.3%), khat (27%) and shamma (9%) was seen among males. Gender and the use of modifiable risk factors among the study sample were significantly (p<0.001) associated with effectiveness of the intervention. The intervention program was highly effective (p<0.001) in improving the knowledge of oral cancer among the youth in Jazan, KSA. Multivariate analysis revealed that age and gender are the most significant factors affecting knowledge. Conclusions: The study gives a direction for further public health initiatives in this oral cancer prone region.

• Journal of Korea Multimedia Society
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• v.7 no.1
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• pp.44-53
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• 2004

This paper aims at presenting high quality at low resolution apply by a new antialiasing method for voxelized implicit surfaces. Implicit surfaces create a unique type of 3D-modeling. Some use of implicit surfaces are scientific and medical visualization, animation, medical simulation and interactive modeling. One of previous antialiasing methods for implicit surfaces presented by raytracing or texture mapping is making use of a stochastic sampling. But this method requires more calculation time and costs which is caused by complicated and difficult implicit functions. In the meanwhile, voxelized implicit surfaces generally use high resolution for good quality images but it costs to generate. In order to this problem, this paper suggests a shifted double Z-buffer which is very simple, more efficient and easy. Tn addition, there are applied box-filter and tent-filter to the double Z-buffer antialiasing method for better images. For results this method generate high quality image and it is easy to apply to various filters and is able to extend to multi Z-buffer.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.306-309
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• 2007

Japanese Ocean Flux Data Sets with Use of Remote Sensing Observations (J-OFURO) includes global ocean surface heat flux data derived from satellite data and are used in many studies related to air-sea interaction. Recently latent heat flux data version 2 was constructed in J-OFURO. In version 2 many points are improved compared with version 1. A bulk algorithm used for estimation of latent heat flux is changed from Kondo (1975) to COASRE 3.0(Fairall et al., 2005). In version 1 we used NCEP reanalysis data (Reynolds and Smith, 1994) as SST data. However, the temporal resolution of the data is weekly and considerably low. Recently there are many kinds of global SST data because we can obtain SST data using a microwave radiometer sensor such as TRMM/MI and Aqua/AMSR-E. Therefore, we compared many SST products and determined to use Merged satellite and in situ data Global Daily (MGD) SST provided by Japan Meteorological Agency. Since we use wind speed and specific humidity data derived from one DMSP/SSMI sensor in J-OFURO, we obtain two data at most one day. Therefore, there may be large sampling errors for the daily-mean value. In order to escape this problem, multi-satellite data are used in version 2. As a result we could improve temporal resolution from 3-days mean value in version 1 to daily-mean value in version 2. Also we used an Optimum Interpolation method to estimate wind speed and specific humidity data instead of a simple mean method. Finally the data period is extended to 1989-2004. In this presentation we will introduce latent heat flux data version 2 in J-OFURO and comparison results with other surface latent heat flux data such as GSSTF2 and HOAPS etc. Moreover, we will present validation results by using buoy data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12A
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• pp.1311-1319
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• 2007

This paper presents the VHDL implementation procedure of the passive RFID tag operating in Ultra High Frequency. The operation of the tag compatible with the EPCglobal Class1 Generation2(GEN2) protocol is verified by timing simulation after synthesis and implementation. Due to the reading range with relatively large distance, a passive tag needs digital processor which facilitates faster decoding, encoding and state transition for enhancement of an interrogation rate. In order to satisfy linking time, the pipe-line structure is used, which can minimize latency to serial input data stream. We also propose the sampling strategy to decode the Preamble, the Frame-sync and PIE symbols in reader commands. The simulation results with the fastest data rate and multi tags environment scenario show that the VHDL implemented tag performs faster operation than GEN2 proposed.

• Korean Journal of Biological Psychiatry
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• v.27 no.1
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• pp.9-17
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• 2020

Objectives The purpose of this study is to investigate the interest level, perception and attitude of suicide high-risk group toward the media's suicide report, and also to provide the fundamental data in order to strengthen both the standard and the recommendation of media coverage in Korea. Methods We analyzed the data from the 2013 The Korea National Suicide Survey. The study included 1500 participants aged between 19 and 75 years. The participants were selected through the regional multi-layer stratification method using the sampling frame of the 2010 Census. One-on-one face-to-face interviews investigated the interest level, opinions, and attitudes toward suicide reports and collected data on past suicide history and demographic data. The collected data were evaluated using multiple logistic regression analysis. A probability level of p < 0.05 was considered statistically significant. Results The suicide high risk groups with histories of suicidal ideations or attempts showed more interest in suicidal reports [suicidal thought odds ratio (OR) = 1.81, 95% confidence interval (CI) = 1.40-2.34 ; suicidal attempt OR = 3.21, 95% Cl = 1.52-6.78]. However, there was no difference among the groups in thought that suicide reports incite suicide (suicidal thought OR = 1.26, 95% Cl = 0.92-1.73 ; suicidal attempt OR = 0.96, 95% Cl = 0.44-2.09). The suicide high risk groups showed a positive attitude toward suicide reports, but it was not statistically significant (suicidal thought OR = 1.10, 95% Cl = 0.41-2.92 ; suicidal attempt OR = 1.10, 95% Cl = 0.76-1.59). Conclusions We suggest the need of careful attitude of media suicidal reports not to bring about copycat suicides. and also we offer suicide prevention campaign based on media leverage.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.501-506
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• 2001

Computer modeling is essential to evaluate possible design of suspension for a railway vehicles. By creating a simulation, the engineers are able to assess the feasibility of a given design and change the design factors to get a better design. But if one wishes to perform complex analysis on the simulation, such as railway vehicle dynamic, the computational time can become overwhelming. Therefore, many researchers have turned to surrogate modeling. A surrogate model is essentially a regression performed on a data sampling of the simulation. In the most general sense, metamodels(surrogate model) take the form $y(x)=f(x)+{\varepsilon}$, where y(x) is the true simulation output, f(x) is the metamodel output, and $\varepsilon$ is the error between the two. In this paper, a second order polynomial equation is partially used as a metamodel to represent the forty-six dynamic performances for high speed train. The number of factors as design variables of the metamodel is twenty-nine, which are composed the dynamic characteristics of suspension. This metamodel is used to search the optimum values of suspension characteristics which minimize the dynamic responses for high speed train. This optimization is a multi-objective problem which have many design variables. This paper shows that the response surface model which is made through the design of analysis of computer experiments method is very efficient to solve this complex optimization problem.

• Journal of the Korean Association of Geographic Information Studies
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• v.10 no.2
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• pp.71-81
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• 2007

One of the most important hydrologic components is evapotranspiration. It is a process by which water is evaporated from moist land surfaces and transpired into atmosphere by plants. There are many methods of estimating evapotranspiration rate and its potential such as the methods of soil-moisture sampling, lysimeter measurements, water balance, energy balance, groundwater fluctuations and evapotranspiration. But it is very difficult to estimate evapotranspiration in terms of regional discrete characteristics of topography and/or vegetation. The evapotranspiration is strongly affected by ground covering vegetation, and the degree of vegetation growth. In order to grasp vegetation condition over a vast study area, NDVI (Normalized Difference Vegetation Indices) calculated from the data obtained from NOAA/AVHRR were utilized. Through multi-regression analysis, we developed a model equation to estimate the evapotranspiration using NDVIs and temperature data.