• IEIE Transactions on Smart Processing and Computing
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• v.2 no.2
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• pp.45-56
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• 2013

The precise identification of vehicle positions, known as the vehicle localization problem, is an important requirement for building intelligent vehicle ad-hoc networks (VANETs). To solve this problem, two categories of solutions are proposed: stand-alone and data fusion approaches. Compared to stand-alone approaches, which use single information including the global positioning system (GPS) and sensor-based navigation systems with differential corrections, data fusion approaches analyze the position information of several vehicles from GPS and sensor-based navigation systems, etc. Therefore, data fusion approaches show high accuracy. With the position information on a set of vehicles in the preprocessing stage, data fusion approaches is used to estimate the precise vehicular location in the local map building stage. This paper proposes an efficient local map building scheme, which increases the accuracy of the estimated vehicle positions via V2V communications. Even under the low ratio of vehicles with communication modules on the road, the proposed local map building scheme showed high accuracy when estimating the vehicle positions. From the experimental results based on the parameters of the practical vehicular environments, the accuracy of the proposed localization system approached the single lane-level.

• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.50-56
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• 1999

This paper presents a new technique for generating precise clock delays. The technique can obtain finer timing resolution less than the gate delay of the delay chain by locking in multiple clock period. Using this technique, a 250ps of timing resolution could be achieved from a 750ps delay of the single delay stage in a DLL(Delay Locked Loop) structure. The delay chain of the proposed circuit is locked on three times of the clock period and a finer delay resolution than the absolute gate delay is achieved and verified through the simulation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.5
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• pp.385-393
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• 2004

This paper proposes a swing-arm type dual-stage actuator, which consists of a PZT actuator for fine motion and a VCM(voice coil motor) for coarse motion, for an SFF ODD(small form factor optical disk drive), in order to achieve fast access speed and precise track-following control. Over the past few decades there have been a lot of researches related to the VCM and dual-stage actuator. In this paper, we focus our attention on the design and control of the PZT actuator. Due to the dual cantilever structure. the PZT actuator can generate precise translational tracking motion at its tip to which an optical pickup is attached. and the effect of hysteric behavior of the PZT element is reduced. The dynamic model of the PZT actuator is derived by using the Hamilton's principle, and verified by comparing it with the experimental frequency response. The sliding mode control is designed in order to be robust against modeling uncertainties. Simulations and experimental results confirm the effectiveness of the suggested control scheme.

• Laser Solutions
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• v.12 no.1
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• pp.19-24
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• 2009

Because of its fast and precise welding performance, laser welding is becoming a new excellent welding method. However, the precise focusing and robust seam tracking are required to apply laser welding to the practical fields. In order to laser weld a type of T joint like a circular pipe on a square pipe, which could be met in the three dimensional structure such as an aluminum space frame, a visual sensor system was developed for automation of focusing and seam tracking. The developed sensor system consists of a digital CCD camera, a structured laser, and a vision processor. It is moved and positioned by a 2-axis motorized stage, which is attached to a 6 axis robot manipulator with a laser welding head. After stripe-type structured laser illuminates a target surface, images are captured through the digital CCD camera. From the image, seam error and defocusing error are calculated using image processing algorithms which includes efficient techniques handling continuously changed image patterns. These errors are corrected by the stage off-line during welding or teaching. Laser welding of a circular pipe on a square pipe was successful with the vision tracking system by reducing the path positioning and de focusing errors due to the robot teaching or a geometrical variation of specimens and jig holding.

• Journal of The Korean Society of Grassland and Forage Science
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• v.13 no.2
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• pp.132-138
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• 1993

Yield and plant constituent responses of forage sorghum cultivars have usually been compared in uniform defoliation management test. However the influence of harvest time on differential response of cultivars needs more precise definition. Therefore this study with sorghum-sorgo-sudan hybrid cv. NC+Sweet Leaf, and Super Su 22 and Sorghum-Sorghum hybrid cv. Pioneer 931 was carried out under two defoliation regimes, namely defoliation at heading stage of each variety and defoliation on the same calendar date in response to heading stage of early variety. The results are summarized as follows; 1. Three harvests were taken by early variety with 80 days and two harvests by late variety with 94 days from sowing to heading. 2. Dry matter and TDN yield tend to be higher when the plants are cut at ear emergence stage of late variety. 3. Crude protein content was similar for the same growth growth stage of 1st growth and 1st regrowth, and rather big different between varieties. 4. Considering only dry matter and TDN yield, it is recommendable to cut two times at ear emergence stage of late variety and also three times at ear emergence stage of early variety in view point of utilization period extension and distribution of forage products.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.1
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• pp.74-79
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• 2011

Alignment systems with multi-axis motions are applied to determine vertical arrangement of multilayer assembly such as LCD, PDP, and MLCC. This study reports the development of XY${\theta}$ alignment stage which is designed as thin-type structure and parallel actuations. The thin-type parallel XY${\theta}$ alignment stage is maintained below $1{\mu}m$ in repeatability error. The squareness and straightness also allow precise motion for the alignment by the developed stage. The measured error is ${\pm}6.25{\mu}m$ in the alignment experiment by the vision system on the parallel XY${\theta}$ alignment stage.

• Communications for Statistical Applications and Methods
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• v.28 no.5
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• pp.411-424
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• 2021

Inference following two-stage adaptive designs (also known as two-stage randomization designs) with survival endpoints usually focuses on estimating and comparing survival distributions for the different treatment strategies. The aim is to identify the treatment strategy(ies) that leads to better survival of the patients. The objectives of this study were to assess the performance three commonly cited methods for estimating survival distributions in two-stage randomization designs. We review three non-parametric methods for estimating survival distributions in two-stage adaptive designs and compare their performance using simulation studies. The simulation studies show that the method based on the marginal mean model is badly affected by high censoring rates and response rate. The other two methods which are natural extensions of the Nelson-Aalen estimator and the Kaplan-Meier estimator have similar performance. These two methods yield survival estimates which have less bias and more precise than the marginal mean model even in cases of small sample sizes. The weighted versions of the Nelson-Aalen and the Kaplan-Meier estimators are less affected by high censoring rates and low response rates. The bias of the method based on the marginal mean model increases rapidly with increase in censoring rate compared to the other two methods. We apply the three methods to a leukemia clinical trial dataset and also compare the results.

• Korean Journal of Remote Sensing
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• v.29 no.1
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• pp.69-79
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• 2013

This paper presents a two-stage geostatistical integration approach that aims at downscaling of coarse scale remote sensing data. First, downscaling of the coarse scale sedoncary data is implemented using area-to-point kriging, and this result will be used as trend components on the next integration stage. Then simple kriging with local varying means that integrates sparse precise observation data with the downscaled data is applied to generate thematic information at a finer scale. The presented approach can not only account for the statistical relationships between precise observation and secondary data acquired at the different scales, but also to calibrate the errors in the secondary data through the integration with precise observation data. An experiment for precipitation mapping with weather station data and TRMM (Tropical Rainfall Measuring Mission) data acquired at a coarse scale is carried out to illustrate the applicability of the presented approach. From the experiment, the geostatistical downscaling approach applied in this paper could generate detailed thematic information at various finer target scales that reproduced the original TRMM precipitation values when upscaled. And the integration of the downscaled secondary information with precise observation data showed better prediction capability than that of a conventional univariate kriging algorithm. Thus, it is expected that the presented approach would be effectively used for downscaling of coarse scale data with various data acquired at different scales.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.175-183
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• 2005

In recent years, as the demands of VBNS and VDSL increase, the development of kernel parts of optical communication such as PLC(Planar Light Circuit), Coupler, and WDM elements increases. The alignment and the attachment technology are very important in the fabrication of optical elements. In this Paper, the optical alignment characteristic of multi-axis ultra precision stage is studied. The alignment algorithms are studied for applying to the ultra precision multi-axis stage. The alignment algorithm is comprised of field search and peak search algorithms. The contour of optical power signals can be obtained by field search and the precise coordinate can be found out by peak search. Three kinds of alignments, such as 1 ch. input vs. 1 ch. output optical stack, 1 ch. input vs. 8 ch. output PLC stacks, and ferrule vs. ferrule, are performed for investigating the alignment characteristics.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.102-108
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• 2011

LQG/LTR control scheme is applied to the two axes stage using piezoelectric actuator for tracking reference input and suppressing hysteresis effect in this paper. The plant is combined with an integrator to improve the tracking ability. LQG/LTR controller is designed by making desirable target filter loop remove all poles except for an integrator included in new design plant model and loop transfer recovery. Decoupler in the shape of FIR filter is added to remove the coupling effect between the two axes motion and so feedback control loop is designed independently for the each axis motion.