• Transactions on Electrical and Electronic Materials
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• v.17 no.3
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• pp.172-177
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• 2016

Miller feedback compensation is introduced in a low dropout regulator (LDO) in order to obtain a capacitor-free regulator and improve the fast transient response. The conventional LDO has a limited bandwidth because of the large-size output capacitor and parasitic gate capacitance in the power MOSFET. In order to obtain a stable frequency response without the output capacitor, LDO is designed with resistor-capacitor (R-C) compensation and this is achieved with a connection between the gain-stage and the power MOS. An R-C compensator is suggested to provide a pole and zero to improve the stability. The proposed LDO is designed with the 0.35 μm CMOS process. Simulation testing shows that the phase margin in the Bode plot indicates a stable response, which is over 100^o. In the load regulation, the transient time is within 55 μs when the load current changes from 0.1 to 1 mA.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.1-15
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• 2004

The purpose of this study was to investigate the kinematic variables of the upper part of the body for 8 elderly men during walking. For this study, kinematic data were collected using a six-camera (240Hz) Qualisys ProReflex system. The room coordinate system was right-handed and fixed in space, with righted orthogonal segment coordinate systems defined for the head, trunk, and pelvis. Based on a rigid body model, reflective marker triads were attached on the 3 segments. Three-dimensional Cartesian coordinates for each marker were determined at the time of recording using a nonlinear transformation(NLT) technique with ProReflex software (Qualisys, Inc.). Coordinate data were low-pass filtered using a fourth-order Butterworth with cutoff frequency of 6Hz. Three-dimensional angles of the head, trunk, and pelvis segment were determined using a Cardan method. On the basis of each segment angle, angle-angle plot used to estimated the movement coordinations between segments. The conclusions were as follows; (1) During the support phase of walking, the elderly people generally kept their, head the flexional and abductional posture. Particularly, the elderly displayed little internal/external rotation. (2) The elderly people showed extensional and external rotation postures in the trunk movement. Particularly, It showed the change from adduction into abduction at the heel contact event of the stance phase. (3) The elderly people showed almost same pelvis movement from the flexion into extension, from the abduction into adduction, and from internal rotation into external rotation at the mid stance and toe off of the stance phase.

• Korean Journal of Medicinal Crop Science
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• v.7 no.2
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• pp.89-93
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• 1999

This study was carried out to investigate the effects of planting density, time and frequency of pinching on growth and yield of Lycium chinese Miller cultivated in vinyl house. This experiment was conducted at the experimental field of Cheong-yang Agriculture High School, Cheong-yang, Chung-nam province, in 1997 to 1998. The number of flowers, fruit setting number and dry weight of fruits per branch were increased as the spacings were wider, but the fruit yield per unit area was decreased up to the narrowest spacing plot of $60\;{\times}\;20cm$. The good results of growth status and fruit yield was obtained at the early pinching in May 5. As the more frequent pinching were treated, the more number of flowers and fruits per branch were produced, showing increase of fresh and dry yield, because of much more branches per plot.

• The Korean Journal of Applied Statistics
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• v.25 no.1
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• pp.15-27
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• 2012

We have studied the realized variance(RV) of intra-day returns and market microstructure noise based on high-frequency stock transaction data for the four largest companies in terms of market capitalization in the KOSPI. First, non-negligible biases are observed for the RV and for the bias-corrected realized variance($RV_{AC_1}$) which is constructed by adjusting RV for the first order autocorrelation in intra-day returns. Bias is more obvious for the RV and the $RV_{AC_1}$ when intra-day returns are sampled more frequently than every 2 minutes. Transaction Time Sampling(TTS) is shown to be better than Calendar Time Sampling(CTS) in terms of biases of the RV and the $RV_{AC_1}$ for the 4 companies. The analysis reveals that market microstructure noise is temporally dependent. Second, by using the Noise-to-Signal Ratio(NSR), we estimate sampling frequencies that are optimal in terms of the Mean Square Errors(MSE) of the RV and the $RV_{AC_1}$. The optimal sampling frequencies are around 200 for RV and is around 5000 for the $RV_{AC_1}$ for all the four stock prices. For the 6 hour transaction period of the Korean stock trading, these correspond to about 2 minutes and 6 seconds.

• Horticultural Science & Technology
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• v.33 no.3
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• pp.340-348
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• 2015

Mowing turfgrasses, especially fast growing species like perennial ryegrass, is one of the most time and money consuming tasks of their management. Trinexapac-ethyl (TE) is a popular plant growth regulator used to reduce mowing requirements, improve stress tolerance, and enhance turf quality. This study was conducted to investigate the effect of TE rate and frequency of applications on growth response and traffic tolerance of perennial ryegrass. The experiment was a split-plot laid out in a randomized complete block (RCB) design with three replications. TE was applied to main plots at 0.00, 0.25, and $0.50kg\;a.i.\;ha^{-1}$. Application pattern included an initial application, followed by two sequential applications at 6-wk intervals. Traffic treatment was applied to subplots with a cleated roller. Results demonstrated that TE consistently reduced vertical shoot growth, clippings dry weight, with maximum growth reduction of 59% and 65%, for 0.25 and $0.50kg\;a.i.\;ha^{-1}$, respectively, occurring at 2 weeks after initial TE treatment (WAT). Traffic also dramatically reduced vertical shoot growth and clippings dry weight. Overall, quality of perennial ryegrass was enhanced by sequential TE applications, however, turf quality and surface coverage reduced greatly under traffic, regardless of TE treatment. Total chlorophyll, chlorophyll a and chlorophyll b and total carbohydrates (TC) contents were also positively influenced following sequential TE application. Our results indicated that TE reduces mowing frequency and enhances turf quality rather than influencing traffic resistance.

• Asian Journal of Turfgrass Science
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• v.11 no.2
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• pp.105-115
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• 1997

Responses of 'Penncross' creeping bentgrass turf to various fairway cultural practices are not well-established or supported by research results. This study was initiated to evaluate the effects of irrigation frequency, clipping return or removal, and nitrogen rate on leaf and soil nitrogen con-tent in the 'Penncross' creeping bentgrass (Agrostis palustris Huds.) turf. A 'Penncross' creeping bentgrass turf was established in 1988 on a Sharpsburg silty-clay loam (Typic Argiudoll). The experiment was conducted from 1989 to 1991 under nontraffic conditions. A split-split-plot experimental design was used. Daily or biweekly irrigation, clipping return or removal, and 5, 15, or 25 g N $m-^2$ $yr-^1$ were the main-, sub-, and sub-sub-plot treatments, respectively. Treatments were replicated 3 times in a randomized complete block design. The turf was mowed 4 times weekly at a l3 mm height of cut. Leaf tissue nitrogen content was analyzed twice in 1989 and three times in both 1990 and 1991. Leaf samples were collected from turfgrass plants in the treatment plots, dried immediately at 70˚C for 48 hours, and evaluated for total-N content, using the Kjeldahl method. Concurrently, six soil cores (18mm diam. by 200 mm depth) were collected, air dried, and analyzed for total-N content. Nitrogen analysis on the soil and leaf samples were made in the Soil and Plant Analyical Laboratory, at the University of Nebraska, Lincoln, USA. Data were analyzed as a split-split-plot with analysis of variance (ANOVA), using the General Linear Model procedures of the Statistical Analysis System. The nitrogen content of the leaf tissue is variable in creeping bentgrass fairway turf with clip-ping recycles, nitrogen application rate and time after establishment. Leaf tissue nitrogen content increased with clipping return and nitrogen rate. Plots treated with clipping return had 8% and 5% more nitrogen content in the leaf tissue in 1989 and 1990, respectively, as compared to plots treated with clipping removal. Plots applied with high-N level (25g N $m-^2$ $yr-^1$)had 10%, 17%, and 13% more nitrogen content in leaf tissue in 1989, 1990, and 1991, respectively, when compared with plots applied with low-N level (5g N $m-^2$ $yr-^1$). Overall observations during the study indicated that leaf tissue nitrogen content increased at any nitrogen rate with time after establishment. At the low-N level treatment (5g N $m-^2$ $yr-^1$ ), plots sampled in 1991 had 15% more leaf nitrogen content, as compared to plots sampled in 1989. Similar responses were also found from the high-N level treatment (25g N $m-^2$ $yr-^1$ ).Plots analyzed in 1991 were 18% higher than that of plots analyzed in 1989. No significant treatment effects were observed for soil nitrogen content over the first 3 years after establishment. Strategic management application is necessary for the golf course turf, depending on whether clippings return or not. Different approaches should be addressed to turf fertilization program from a standpoint of clipping recycles. It is recommended that regular analysis of the soil and leaf tissue of golf course turf must be made and fertilization program should be developed through the interpretation of its analytic data result. In golf courses where clippings are recycled, the fertilization program need to be adjusted, being 20% to 30% less nitrogen input over the clipping-removed areas. Key words: Agrostis palustris Huds., 'Penncross' creeping bentgrass fairway, Irrigation frequency, Clipping return, Nitrogen rate, Leaf nitrogen content, Soil nitrogen content.

• Smart Structures and Systems
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• v.25 no.6
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• pp.719-732
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• 2020

Real-time hybrid simulation (RTHS) which combines physical experiment with numerical simulation is an advanced method to investigate dynamic responses of structures subjected to earthquake excitation. The desired displacement computed from the numerical substructure is applied to the experimental substructure by a servo-hydraulic actuator in real time. However, the magnitude decay and phase delay resulted from the dynamics of the servo-hydraulic system affect the accuracy and stability of a RTHS. In this study, a robust stability analysis procedure for a general single-degree-of-freedom structure is proposed which considers the uncertainty of servo-hydraulic system dynamics. For discussion purposes, the experimental substructure is a portion of the entire structure in terms of a ratio of stiffness, mass, and damping, respectively. The dynamics of the servo-hydraulic system is represented by a multiplicative uncertainty model which is based on a nominal system and a weight function. The nominal system can be obtained by conducting system identification prior to the RTHS. A first-order weight function formulation is proposed which needs to cover the worst possible uncertainty envelope over the frequency range of interest. Then, the Nyquist plot of the perturbed system is adopted to determine the robust stability margin of the RTHS. In addition, three common delay compensation methods are applied to the RTHS loop to investigate the effect of delay compensation on the robust stability. Numerical simulation and experimental validation results indicate that the proposed procedure is able to obtain a robust stability margin in terms of mass, damping, and stiffness ratio which provides a simple and conservative approach to assess the stability of a RTHS before it is conducted.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.1
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• pp.85-93
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• 2009

There are many curves in Seoul subway system. Therefore, the noise from subway system in curved line gives displeasure to passenger. The subway noise in curved line is affected not only by rail condition but also wheel condition and dynamic characteristics. The railway curving noise can be divided into 2 categories. The first is the noise due to stick-slip between wheel tread and rail head, and the second is one by wheel flange contact on rail side. Because of these phenomena - stick-slip and wheel flange contact - wheels are worn seriously. In this study the curving noise was reviewed by using eigen-mode of wheel and waterfall plot which shows noise level in time-frequency domain. And also those were reviewed in viewpoint of stick-slip noise and wheel flange contact noise. Finally, the relationship between curving noise and wheel wear was studied.

• International Journal of Highway Engineering
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• v.2 no.1
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• pp.147-156
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• 2000

Compaction is known to critically affect pavement performance. Due to its importance, a theoretical modelling of compacted density in the term of number of roller coverages is attempted by assuming compaction process essentially identical to pavement rutting. Excellent data fittings by the developed equation may prove the validation of assumptions made as well as justification of its use. According to the derived equation, a plot of density difference with respect to number of roller coverages in the logarithmic scale Produces a linear relationship. However, this linearity is turned out to be deviated by cooling effect, change of amplitude and frequency. Investigation of these three factors proposes a new generalized compaction density equation, which shows a promising future. By applying this general formula, the equations for the number of roller coverages required and the final compaction density obtained for a particular compaction project is derived first time in compaction research.

• Geophysics and Geophysical Exploration
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• v.12 no.1
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• pp.143-153
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• 2009

Using a discrete wavenumber method, we examine the effects on Logging-While-Drilling (LWD) logs when a mismatch exists between the amplitudes or generating times of the signals from individual monopoles in a LWD multipole source. An amplitude-mismatched LWD dipole/quadrupole source produces non-dipole/non-quadrupole modes as well as flexural and screw modes. The strongest of non-dipole/non-quadrupole modes is the Stoneley mode, whose amplitude increases with increasing mismatch. However, we can recover the flexural mode signals by A-C processing, and the screw mode by A-B+C-D processing, respectively. The Stoneley mode, which has the same amplitude at the same radial distance from the borehole axis, is cancelled out by A-C and A-B+C-D processing as long as the tool is placed at the centre of the borehole. The responses from a time-mismatched LWD multipole source look like the summation of responses by two or four monopole sources off the borehole axis. However, we can avoid the misinterpretation of the formation velocities by referring to the computed dispersion curves, which are independent of the arrival times of the modes, on the frequency semblance plot.