• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.318-323
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• 2005

To evaluate the accurate performance of turbomachinery, it is important to measure the unsteady flow phenomena downstream of the rotor blade. This paper presents the development of the fast-response total pressure probe for the measurement of the total pressure field at the exit of rotor and the result of measurement in a 1-stage axial turbine. The fast-response total pressure probe was fabricated by installing a fast-response pressure sensor near the head of a Kiel probe. And it measured the phase-lock averaged total pressure downstream of an 1-stage axial turbine. The developed probe successfully measured the accurate total pressure distribution at rotor exit and made possible to evaluate the loss distribution and the accurate performance of turbomachinery.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.2
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• pp.171-175
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• 1999

Morphological alteration of floral organ development in rice affected by chilling stress was examined. Three varieties of rice were grown under natural conditions and subjected to 12$^{\circ}C$ for 3 or 6 days starting from the ineffective tillering stage, before heading stage and returned to natural condition. Headings were delayed by a 6 day chilling treatment. After heading the panicles were collected and examined for any possible alteration in floral organ development. It appears that there were some differences in sensitivity to chilling stress and degree of injury depending on treatment stages and variety. Chuchungbyeo was the most frequent in producing abnormal flowers among the three varieties examined. Meiosis stage was shown to be the most vulnerable to chilling stress in both Chuchungbyeo and Ilpumbyeo and young panicle differentiation stage was the frequent stage to alter flower development in response to chilling stress only in Chuchungbyeo. It was confirmed that abnormalities occurred in pollen due to chilling stress is a major factor leading to low yield, but to some extent the alterations in carpel development may playa certain role in determining a total yield in response to chilling stress at the reproduction stage in rice. There were abnormalities like extra stigmata, extra lemma, double ovary as well as abnormal anther formation in response to chilling stress. Further studies of the phenocopy observed in rice floral development may be useful for an understanding of the resistance against chilling injury during reproductive stages in rice.

• The Korean Journal of Applied Statistics
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• v.23 no.3
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• pp.533-543
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• 2010

Asking sensitive questions by a direct survey method causes non-response bias and response bias. Non-response bias arises from interviewees refusal to respond and response bias arises from giving incorrect responses. To rectify these biases, Warner (1965) introduced a randomized response model which is an alternative survey method for socially undesirable or incriminating behavior questions. The randomized response model is a procedure for collecting the information on sensitive characteristics without exposing the identity of the respondent. Many survey researchers have proposed diverse variants of the Warner randomized response model and applied their model to collect the information of sensitive questions. Using an optimal allocation, we proposed three-stage stratified randomized response technique which is an extension of the Kim and Elam (2005) two-stage stratified randomized response technique. In this study, we showed that the estimator based on the proposed response model is more efficient than Kim and Elam (2005). But by adding one more survey step to the Kim and Elam (2005), our proposed model may have relatively less privacy protection compared to the Kim and Elam (2005) model.

• The Korean Journal of Applied Statistics
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• v.14 no.1
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• pp.103-110
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• 2001

This paper considers a multistage experiment. Response scales can be same or different from stage to stage. When variables are of nested structure, the response variable at each stage can be defined conditionally. For analysing such data with compound scales, this paper suggests a sequnce of dependence models and shows how to set up a sequence of models for the driver's liscense test data.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.6
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• pp.106-113
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• 2009

A 6-DOF precision stage was developed based on parallel kinematics structure with flexure hinges to eliminate backlash, stick-slip and friction and to minimize parasitic motion coupled with motions in the other-axis directions. For the stage, lever linkage mechanism was devised to reduce the height of system for the enhancement of horizontal stiffness. Frequency response comparison between experimental results and mathematical model extracted from dynamics of the stage was performed to identify the system parameters such as spring constants and damping coefficients of actuation modules, which cannot be calculated accurately by analytic methods owing to their complicated structures. This newly developed precision stage and its identified model will be very useful for precision positioning and control because of its high accuracy and non-coupled movement.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.5
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• pp.103-109
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• 2002

The paper investigates the change of frequency response characteristics on two-stage gear reduction servo system according to the variation of backlash amount of each gear reduction stage, under the condition that the backlash of total system is constant. It is shown that the frequency response characteristics of the system heavily depend on the contribution ratio which is defined as a ratio of the first backlash amount to the total backlash. It is also found that there is an optimal backlash combination to maximize the bandwidth of two-stage gear reduction servo system when the allowable total backlash is determined.

• Economic and Environmental Geology
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• v.39 no.3 s.178
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• pp.269-284
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• 2006

Aquifer responses to the river stage fluctuations were analyzed between the groundwater level and the river stage in an alluvial aquifer. The auto-correlation and cross-correlation as a time series analysis were applied. Study site is a floodplain in the Mangyeong river. Groundwater levels in each depth representing the silt and sand(SS), gravel and sand(GS), and weathered zone(WZ) layer were monitored. The groundwater levels were more sensitive to the river stage fluctuations than rainfall. Since the river stages are influenced by the gate operations downstream and tide, show periodic patterns, and the correlation coefficients with rainfall is low. Cross-correlation function between groundwater level in each depth do not show any delay time, then response time is very short to each depth. Cross-correlation analysis were performed to estimate the response time of groundwater levels to river stage fluctuations. Groundwater levels respond to the river stage within 30 minutes to 1 hour in wells near the stream. Short time lag between groundwater level and river stage indicates the quick response. A different response time imply the hydraulic inhomogeneity of the site, and a probable high permeability zone between river and aquifer can be inferred. Mangyeong-river in study site is a gaining stream normally, and river stage rising by gate operation or floods makes river water flow into groundwater. The auto-correlation and cross-correlation functions as a time series analysis can be a good tool to interpret the aquifer responses to stream stage fluctuation

• KOREAN JOURNAL OF CROP SCIENCE
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• v.64 no.3
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• pp.213-224
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• 2019

There is an increasing frequency in the occurrence of abnormal weather phenomena such as sharp increases and decreases in temperature. Under these weather conditions, the heading time of rice changes unexpectedly, which poses problems in agriculture. Therefore, we investigated the effect of temperature on the heading response at different growth stages in rice. During the period from transplanting to heading, the plants were subjected to different temperature treatments, each for a 9-day period, to observe the heading response. For the heading date analysis, "heading date" was defined as the number of days from transplanting to the appearance of the first spikelet. We found that the influence of temperature increased in the order of rooting stage, followed by meiosis, early tillering, spikelet differentiation, and panicle initiation stage in all ecological types and cultivars. In particular, unlike the results reported previously, the effect of temperature on heading during the photo-sensitive period was very small. Meanwhile, the influence of temperature on vegetative growth response at different growth stages was not consistent with heading response. These results can be used as basic data for predicting the variation in heading date owing to temperature variation at each growth stage. In addition, we propose that the concept of day length should be included in determining the influence of temperature on the photo-sensitive period.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.2
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• pp.65-72
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• 2004

Switching power supply systems are widely used in many industrial fields. Power factor correction (PFC) circuits have a tendency to be applied in new power supply designs. The input active power factor correction (APFC) circuits can be implemented in either the two-stage approach or the single-stage approach. The two-stage approach can be classified into boost type PFC circuit and dc/dc converter. The power factor correction circuit with a boost converter used as an input power source is studied in this paper. In a boost power factor correction circuit there are two feedback control loops, which are a current feedback loop and a voltage feedback loop. In this paper, the regulation performance of output voltage and compensator to improve the transient response presented at the continuous conduction mode (CCM) of the boost PFC circuit is analyzed. The validity of designed boost PFC circuit is confirmed by MATLAB simulation and experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.668-671
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• 2000

An aerostatic stage has frictionless behavior, so it has a advantage of investigation into driven mechanism such as ballscrew. In this paper, fur investigating positioning characteristic of ballscrew and feedback device in aerostatic stage, we compare the positioning characteristic between full-closed(laser scale) and semi-closed(encoder) system. Experimental results show that the aerostatic stage has a 10nm micro step response and repeatability is improved up to 1.00${\mu}{\textrm}{m}$ using laser scale. We confirm the laser scale compensate error motion of ballscrew, so acquire 1.12${\mu}{\textrm}{m}$ positioning accuracy.