• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.6 s.249
• /
• pp.497-504
• /
• 2006

A Coriolis mass flowmeter(CMF), which has U-Shaped unique measurins tube was developed fo. direct mass flow measurement. In order to convert the time difference between two measuring tubes motion into mass flowrate and flow quantity, a signal processing circuit, as a part of CMF, was also developed. The CMF was designed as the 15 mm nominal diameter of pipe connection and the 8 mm stainless steel(sus 316) pipe was used for measuring tube. To maximize the flow signal(time difference) from the measuring tubes, the natural frequency of measuring tube was adjusted as 220 Hz, which is same as the frequency of exciter. The maximum displacement at the end of the measuring tube was measured as 0.05 mm and the maximum time difference between two measuring tubes was observed as $20{\mu}s$, which was proper for discrimination and measuring range of CMF. The developed CMF was tested against the gravimetric flowmeter calibrator in the range of 3 kg/min and 30 kg/min. The results showed that the CMF has good linearity and repeatability in the tested flow range. Large size of CMF base on the current study experience will be developed.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1996.04a
• /
• pp.156-160
• /
• 1996

A vibrating angular rate sensor with tuning fork type resonator of microstructure (940*820 .mu. m$^{2}$) was designed and will be fabricated by polysilicon surface micromaching. The angular rate sensor is driven in a lateral direction by electrostatic force of comb drive electrodes, and vertical vibrations of the sensor, thich is detected capacitively, are produced by Coriolis forces due to an external angular rate. Mechanical Q factors and a difference between the frequencies of the two resonant modes, the driving mode and detecting mode, play a great role in increasing the sensitivity of the sensor. To be a highly sensitive sensor, it was designed to have as small frequency discrepancy of the two resonant modes as possible. Finite element method was used for the modal analysis. Several design parameters were selected and their contributions to the modal frequencies were investigated. A method was presented for tuning the detecting mode frequency by DC bias on the drive electrodes.

• Korean Journal of Community Nutrition
• /
• v.26 no.4
• /
• pp.296-306
• /
• 2021

Objectives: The objective of this study was to estimate the distribution of the usual dietary intake of foods with respect to the probability of consumption derived from the Food Frequency Questionnaire (FFQ) of the 2009 Korea National Health and Nutrition Examination Survey (KNHANES). Methods: The intake quantity and frequency of 63 food items were assessed from the 2009 KNHANES which was completed by 7,708 participants. The participants completed one or two 24-h dietary recalls and one FFQ. The usual intake distribution was estimated using the multiple source method (MSM), and the proportion of non-consumers was calculated through the usual intake distribution. This was then compared with the proportion of non-consumers from the 24-hour recall method. Results: The difference in the proportion of non-consumers ranged from 2% to 82.9%, indicating that there is a very large difference based on food groups. The food groups in which the proportion of non-consumers did not differ was composed of foods consumed daily, such as 'rice', 'cereal and barley', and 'Chinese cabbage and kimchi', or foods with distinct palatability such as 'coffee' and 'alcohol'. On the other hand, in the case of the food groups with a high difference in the proportion of non-consumers, most comprised fruits that emphasized seasonality. Conclusions: In the case of foods or food groups that are occasionally consumed, it is desirable to use 2 recalls with additional FFQ data by combining the consumption frequency and the quantity consumed.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.5
• /
• pp.109-114
• /
• 2009

An orthogonal frequency division multiplexing(OFDM) system is effective to bandwidth because of orthogonality of subcarriers and robust to multipath fading. However, if there is a frequency offset, we lose the orthogonality of subcarriers and that results in inter-carrier interference(ICI) which increases errors in the system. In this paper, we propose an algorithm that estimates the fine frequency offset using a correlation method in OFDM systems. This scheme compares two correlation values in different frequency offsets with opposite directions. From the difference between two correlation values we can derive a fine frequency offset estimation algorithm. Its performance is verified by computer simulations.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.5 no.4
• /
• pp.234-242
• /
• 2010

Two-way ranging methods such as TWR and SDS-TWR have been considered for many ranging systems because these methods are useful in the absence of synchronization. To estimate the location of a mobile node, complicated ranging procedures consisting of ranging frames between an anchor node and the mobile node are performed. Supporting multiple mobile nodes such as a few hundreds or thousands and several anchor nodes, the ranging procedures have the fatal disadvantage of processing delay and inefficient traffic bandwidth. On the other hand, the one-way ranging method is simple and fast, but susceptible to network synchronization. In this paper, we propose a method to modify asynchronous ranging equations to establish exact frequency or frequency offset, a method to estimate frequencies or frequency offsets, and a method to establish post-facto synchronization with anchor nodes. The synchronization for a node pair is adapted using instantaneous time information and corresponding difference of distances can be determined. We evaluate the performance of TWR, SDS-TWR and proposed ranging algorithms.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.167-172
• /
• 2007

The frequency-domain small-loop electromagnetic (EM) instruments are increasingly used for shallow environmental and geotechnical surveys because of their portability and speed. However, it is well known that the data quality is generally so poor that quantitative interpretation of the data is not justified in many cases. We present an inversion method that allows the correction for the calibration errors and also constructs multidimensional resistivity models. The key point in this method is that the data are collected at least at two different heights. The forward modeling used in the inversion is based on an efficient 3-D finite-difference method, and its solution was checked against 2-D finite-element solution. The synthetic and real data examples demonstrate that the joint inversion recovers reliable resistivity models from multi-frequency data severely contaminated by the calibration errors.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.9
• /
• pp.110-121
• /
• 2001

During hot pipe bending using induction heating, the wall of bending outside is thinned by tensile stress. In design requirement, the reduction of wall thickness is not allowed to exceed 12.5%. So in this study, two methods of bending, one is loading of reverse moment and the other is loading of temperature gradient, have been investigated to design pipe bending process that satisfy design requirements. For this purpose, finite element analysis with a bending radius 2Do(outer diameter of pipe) has been performed to calculate proper reverse moment and temperature gradient to be applied. Induction heating process has been analyzed to estimate influence of heating process parameters on heating characteristic by finite difference method. Then pipe bending experiments have been performed for verification of finite element and finite difference analysis results. Experimental results are in good agreement with the results of simulations.

• Journal of the Korean Institute of Telematics and Electronics T
• /
• v.35T no.3
• /
• pp.128-133
• /
• 1998

This paper is study on performance analysis of modulator using direct digital frequency synthesizer of Initial Clock Accumulating Method. It has been generally used for PLL or digital frequency synthesizing method to be synthesizd randomly chosen frequency state. In order to improve disadvantage of two methods, we constructed modulator system using DDFS of Initial Clock Accumulating Method. We also confirmed the coherence frequency hopping state and possibility of phase control. The results obtained from the experiments are as follows; First, the synthesized output frequency is proportional to the sampling frequency, according to index, K. Second, the difference of the gain between the basic frequency and the harmonic frequencies was more than 50 [dB], that is, this means facts that is reduced the harmonic frequency factor. Third, coherence frequency hopping state is confirmed by PN code sequence. Here, we confirmed the proposed method cut switching time, this verify facts that is the best characteristic of the frequency hopping. We also verified the fact that the phase varies as the adder is operated set or reset.

• Journal of Korean Clinical Nursing Research
• /
• v.25 no.1
• /
• pp.55-66
• /
• 2019

Purpose: This study was done to assess development and postnatal care interventions in postnatal care intervention records for maternity ward nurses in tertiary hospitals and women's hospitals in South Korea. Methods: This mixed-method research was a Time-Motion (TM) study. Data were collected through external observation of 12 nurses in 4 wards over 24 hours. Mann-Whitney U test and independent t-test were employed for the analysis of frequency and provision time of direct/indirect care activity. $x^2$ (Fisher's exact test) was utilized to determine the difference in frequency between two groups. IBM SPSS 22.0 statistical program was employed for calculation. All statistical significance levels were at ${\alpha}=.05$. Results: According to the KPCS-1 (Korean Patient Classification System-1), women's hospitals are group 3 and tertiary hospitals, group 4. With respect to time difference in direct care, tertiary hospitals showed 791 minutes and women's hospitals, 399 a difference of 392 minutes. For time difference in indirect care, women's hospitals had 2,415 minutes while tertiary hospitals, 2,080, a difference of 335 minutes for women's hospitals. No difference was found in the average total care workload between the two institutions. Individual time also showed no difference (p>.05). Conclusion: High-risk maternal care strength in tertiary hospitals and breast-feeding strength in women's hospitals need to be benchmarked with each other.

• Journal of Mechanical Science and Technology
• /
• v.20 no.6
• /
• pp.849-863
• /
• 2006

IBM (Immersed Boundary Method) with feedback momentum forcing was applied to stationary and moving bodies. The capability of IBM to treat the obstacle surfaces, especially with moving effect has been tested for two dimensional problems. Stationary and oscillating cylinders were simulated by using IBM based on finite volume method with Cartesian coordinates. For oscillating cylinder, lateral and vertical motions are considered, respectively. Present results such as time histories of drag and lift coefficients for both stationary and oscillating cases are in good agreement with previous numerical and experimental results. Also, the instantaneous wake patterns of oscillating cylinder with different oscillating frequency ratios well represented those of previous researches. More feasibility study for IBM has been carried out to two oscillating cylinders. Drag and lift coefficients are presented for two cylinders oscillating sinusoidally with phase difference of $180^{\circ}$.