• Journal of Power Electronics
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• v.13 no.3
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• pp.349-361
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• 2013

As a result of the advantages such as high efficiency, continuous current and high stability margin, push-pull converter with continuous current (PPCWCC) is competitive for battery discharge regulator (BDR) which plays an important role in power conditioning unit (PCU). Leakage inductance yields current spike in low-ripple current of PPCWCCs. The operating modes are added due to leakage inductance. Therefore the steady state performance is affected, which is embodied in the spike of low-ripple current. PPCWCCs which are suitable for BDR can be separated into three types by current spike characteristics. Three representative topologies IIs1, IIcb2 and Is3 are analyzed in order to investigate the factors on the magnitude and duration of spike. Equivalent current sampling method (ECSM) which eliminates the sampling time delay and achieves excellent dynamic performance is adopted to prevent the spike disturbance on current sampling. However, ECSM reduces the sampling accuracy and telemetry accuracy due to neglecting the spike. In this paper, ECSM used in PPCWCCs is summarized. The current sampling error is analyzed in quality and quantity, which provides the foundation for offsetting and enhancing the telemetry accuracy. Finally, current sampling error rate of three topologies is compared by experiment results, which verify the theoretical analysis.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.97-108
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• 1996

A new type of passive samplers were designed and produced by authors. After evaluating the quality of activated carbon by measuring recovery rate of organic vapors and steadiness of sampling rate, activated carbon with 30 - 35 mesh produced by Company S in Korea was selected. In each passive sampler, an amount of 400 mg of the activated carbon was filled in 25-mm cassette and covered by fixed screen (or wire screen with 100 mesh). In addition to the fixed screen, a wind screen (or wire screen with 300 mesh) was also attached at outer face. The sampling rate of the new Korean passive samplers was estimated Conclusions obtained in the study are as follows. 1. Sampling rates of the newly developed Korean passive samplers were affected by sampling time. For n-hexane, sampling rates of 15- and 60-minute samples were 70.92 and 37.45 ml/min, respectively. Sampling rate of both 200- and 450-minute samples was 25.96 ml/min. It is concluded that, when passive samplers are used for measuring organic vapors, samples be collected longer than 60 minutes. 2. Sampling rate of the passive samplers was also affected by airborne concentration of organic vapors. Lower sampling rates were determined at level of 1/2 threshold limit values (TLVs) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH). It is recommended that sampling rate of the passive samplers be obtained at site by measuring concentrations using both the NIOSH Method and passive samplers simultaneously. 3. When the passive samplers, which collected organic vapors, were exposed to clean air for five hours, there was no significant loss of organic vapors due to reverse diffusion. 4. When samples were stored at room temperature ($21.8{\pm}0.7^{\circ}C$) and refrigerator ($3.8{\pm}0.7^{\circ}C$), there was no significant difference in the accuracy of results. For trichloroethylene and n-hexane, accuracies were within 25 % at both temperatures until seven days. However, poor accuracy exceeding 25 % was indicated in toluene from the first day. It is recommended that samples be stored at freezing temperature below $0^{\circ}C$. 5. Sampling efficiency was significantly affected by direction of the passive samplers. Results of samplers facing wind and down, respectively, were compared. Lower amount of organic vapors were collected when the sampler was oriented down. It is recommended that, when air velocity is low in plants, the passive samplers be oriented to the wind. However, when air velocity is high, the passive samplers be oriented down.

• Korean Journal of Human Ecology
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• v.19 no.5
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• pp.817-833
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• 2010

This study was dedicated to searching better course of low birth rate study in Korea by carefully analyzing past and present low birth rate researches. For this 179 studies(101 master thesis and 78 journal articles) from 1991 to 2009 were analyzed. Next, using SPSS Win 12.0, the research type, topic, participants, data collection and method of data analysis were compared to the studies' years of publication. The most frequently applied research approach, topic, sampling method, data collection procedure and data analysis method in the research was found to be a literature study, solution and prevention of low birth rate related policy, literature study, literacy analysis. In conclusion, low birth rate studies should become more diversified in terms of types of the research, data collection method, and data analysis. Additionally, research topics should become more realistic and specified. Moreover, research results should be verified before they are applied to the policy.

• Journal of Biomedical Engineering Research
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• v.16 no.3
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• pp.279-288
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• 1995

Ultrasonic Doppler systems for the purpose of estimating blood flow velocity, blood flow volume, and flow imaging are commonly used due to advantages of non-invasive and real time observation. Specially, the technical developments of color flow mapping (2-D Doppler) systems have made a relatively rapid progress. However, the 2-D Doppler systems have several problems, such as the range ambiguity, low signal to noise ratio, and slow frame rate. The slow frame rate problem is resolved by using the spatial average which is a method to acquire more data samples for mean frequency estimation. In this paper, spatial average method using the 2nd order sampling instead of quadrature sampling is proposed. The experimental results show that the proposed methods have good performance and easy application to the color flow mapping system.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.52-57
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• 2001

The passive ranging estimation techniques using a focused beamformer have been studied under the water. It is well known that the passive ranging estimation method using a focused beamformer is excellently evaluated. Among these, the passive ranging sonar is known to have a good performance under low signal-to-noise. ratio. However, its performance is degraded in multi-source environments. In this paper, we proposed the technique using dual focused beamformers to estimate the range. And when the sampling frequency is low, it is very difficult to steer the focused beam to the desired direction, as a result of this, the low performance occurs because of a distorted beam pattern. In this paper, we study the effect of sampling rate on passive ranging by using focused beamformer. And we verified the performance of the proposed method via computer simulation.

• Journal of Korea Society of Digital Industry and Information Management
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• v.16 no.1
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• pp.93-98
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• 2020

Research on underwater sensor networks is increasing due to such reasons as marine resource management, maritime disaster prediction and military protection. Many underwater sensor networks performs wireless communication using an acoustic sound wave band signal having a relatively low frequency. So the digital part of their modem can take charge of carrier band signal processing. To enable this, the sampling rate of the baseband band signal should be increased to a sampling rate at which carrier band signal processing is possible. In this paper, we designed a sampling rate increasing circuit based on a CIC interpolator for underwater sensor nodes. The CIC interpolator has a simple circuit structure. However, since the CIC interpolator has a large attenuation of the pass band and a wide transition band, an inverse sinc LPF is added to compensate for frequency response of the CIC interpolator. The proposed interpolator was verified in time domain and frequency domain using ModelSim and Matlab.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.27 no.2
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• pp.1-8
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• 2019

Optimal path planning refers to find the safe route to the destination at a low cost, is a major problem with regard to autonomous navigation. Sampling Based Planning(SBP) approaches, such as Rapidly-exploring Random Tree Star($RRT^*$), are the most influential algorithm in path planning due to their relatively small calculations and scalability to high-dimensional problems. $RRT^*$-Smart introduced path optimization and biased sampling techniques into $RRT^*$ to increase convergent rate. This paper presents an improvement plan that has changed the biased sampling method to increase the initial convergent rate of the $RRT^*$-Smart, which is specified as m$RRT^*$-Smart. With comparison among $RRT^*$, $RRT^*$-Smart and m$RRT^*$-Smart in 2 & 3-D environments, m$RRT^*$-Smart showed similar or increased initial convergent rate than $RRT^*$ and $RRT^*$-Smart.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.2C
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• pp.145-152
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• 2009

Ultra-wideband communication systems for impulse radio have merits that are possible for either high resolution ranging system or radio determination. Conventionally, in order to accomplish these functions, the rapid analog to digital convertor (ADC) is necessary to apply radio determination system operating in time domain. However, considering that low rate - wireless personal area network (LR-WPAN) aims to low-cost hardware implementation, the expensive ADC converting GHz sampling per second is not appropriate. So, this paper introduces the high resolution ranging system operating in frequency domain with using low sampling rate ADC, and a new non-coherent ranging scheme utilizing analog Frequency Modulation (FM) mode for the frequency domain transformation. To verify the superiority of the proposed ranging algorithm working in frequency domain, the suggested IEEE 802.15.4a TG channel model is used to exploit affirmative features of the proposed algorithm with conducting the simulation results.

• Journal of Environmental Health Sciences
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• v.35 no.6
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• pp.500-509
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• 2009

Passive samplers have been used for many years for the sampling of organic vapors in work environment atmospheres. Currently, all passive samplers used in domestic occupational monitoring are foreign products. This study was performed to evaluate variable parameters for the development of passive organic samplers, which include the geometry of the device and diffusive length for the sampler design. Four prototype diffusive lengths; A-1(4.5 mm), A-2(7.0 mm), A-3(9.5 mm), A-4(12.0 mm) were tested for adsorption performances to a chemical mixture (benzene, toluene, trichloroethylene, and n-hexane) according to the US-OSHA's evaluation protocol. A dynamic vapor exposure chamber developed and verified by related research was used for this study. The results of study are as follows. The results in terms of sampling rate and recommended sampling time test indicate that the most suitable model was A-3 (9.5 mm diffusive lengths on both sides) for passive sampler design in time weighted average (TWA) assessment. Sampling rates of this A-3 model were 45.8, 41.5, 41.4, and 40.3 ml/min for benzene, toluene, trichloroethylene, and n-hexane, respectively. The A-3 models were tested on reverse diffusion and conditions of low humidity air (35% RH) and low concentrations (0.2 times of TLV). These conditions had no affect on the diffusion capacity of samplers. In conclusion, the most suitable design parameters of passive sampler are: 1) Geometry and structure - 25 mm diameter and 490 $mm^2$ cross sectional area of diffusion face with cylindrical form of two-sided opposite diffusion direction; 2) Diffusive length - 9.5 mm in both faces; 3) Amount of adsorbent - 300 mg of coconut shell charcoal; 4) Wind screen - using nylon net filters (11 ${\mu}m$ pore size).

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.7
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• pp.3217-3238
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• 2018

In this paper, a depth image up-sampling method is put forward by using pixel classifying and jointed bilateral filtering. By analyzing the edge maps originated from the high-resolution color image and low-resolution depth map respectively, pixels in up-sampled depth maps can be classified into four categories: edge points, edge-neighbor points, texture points and smooth points. First, joint bilateral up-sampling (JBU) method is used to generate an initial up-sampling depth image. Then, for each pixel category, different refinement methods are employed to modify the initial up-sampling depth image. Experimental results show that the proposed algorithm can reduce the blurring artifact with lower bad pixel rate (BPR).