• Investigative Magnetic Resonance Imaging
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• v.6 no.1
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• pp.55-63
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• 2002

Purpose : We investigated the predictive values of relative CBV measured with perfusion MR imaging, and relative CBF measured with SPECT for tissue outcome in acute ischemic stroke. Material and Methods : Thirteen patients, who had acute unilateral middle cerebral artery occlusion, underwent perfusion MR imaging, and $^{99m}Tc-HMPAO$ SPECT within 6 hours after the onset of symptoms. Lesion-to-contralateral ratios of perfusion parameters were measured, and best cut-off values of both parameter ratios with their accuracy to discriminate between regions with and without evolving infarction were calculated. Results : Mean relative CBV ratios in regions with evolving infarction and without evolving infarction were $0.58{\pm}0.27$ and $0.9{\pm}0.17$ (p < 0.001), and mean relative CBF ratios in those regions were $0.41{\pm}0.22$ and $0.71{\pm}0.14$ (p < 0.001). The best cutoff values to discriminate between regions with and without evolving infarction were estimated to be 0.80 for relative CBV ratio and 0.56 for relative CBF ratio. The sensitivity, specificity and efficiency of each cutoff value were 80.6, 87.5, 82.7% for relative CBV ratio, and 72.2, 75.0, 73.0% for relative CBF ratio (p > 0.05 between two parameters). Conclusion Measurement of relative CBV and relative CBE may be useful in predicting tissue outcome in acute ischemic stroke.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1527-1533
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• 2002

When a mechanism transfers a motion to an intersected shaft, a cylindrical cam mechanism may be the best choice among the mechanisms. The cylindrical cam with a roller follower provides to transfer the motions to the intersect shafts simply without other connecting equipments of the intersect shafts. Typical example may be a roller-gear-cam mechanism. But the shape of the cam must be exactly defined in order to satisfy the conditions for the prescribed motion of the follower. This paper proposes a new method for the shape design of the cylindrical cams and also a CAD program is developed by using the proposed method. The relative velocity method calculates the relative velocity of the follower versus the cam at a center of roller, and then determines a contact point by using the geometric relationships and the kinematic constraints. The constraint used in the relative velocity method is that the relative velocity must be parallel to a common tangent line at the contact point of two independent bodies, i. e. the cam and the follower. Then, the shape of the cam is defined by the coordinate transformation of the trace of the contact points. Finally, this paper presents an example in order to prove the accuracy of the proposed methods in this paper and the application of the CAD program"CamDesign".

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.4
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• pp.508-516
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• 2016

When GPS signals are not available, a relative localization can be alternatively used to represent the topological relationship between mobile nodes. A relative location map of a network can be constructed by using the distance information between all the pairs of nodes in the network. If a network is large, a number of small local maps are individually constructed and are merged to obtain the whole map. However, this approach may result in a high computation and communication overhead. In this paper, we propose a reference-node selection scheme for relative localization map construction, which chooses a subset of nodes as a reference node that is supposed to construct local maps. The scheme is a greedy algorithm that iteratively chooses nodes with high degree as a reference node until the chosen local maps are successfully merged with a sufficient number of common nodes between nearby local maps. The simulation results indicate that the proposed scheme achieves higher localization accuracy with a reduced computational overhead.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.3
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• pp.100-107
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• 2002

The sea-surface winds during the passage of 64 typhoons for 1979-1999 were simulated using two different typhoon wind models, ie, typhoon parametric model(TPM) and primitive vortex model(PVM). The model hindcast winds were compared with the winds observed at JMA ocean buoys(22001 and 21002) and Kyushu ocean observation tower. The analysis of ms and relative errors between hindcast and observed winds was made to find the accuracy and sensitivity of the typhoon wind prediction models. Both hindcast winds of TPM and PVM underestimate the observed typhoon winds, but PVM winds are more closer to the observations with less rms and relative errors. Relative errors of two model winds were small within 200km from typhoon center, but TPM's relative errors increase up to 70% as the radial distance from typhoon center increases beyond > 200km although PVM's relative errors remain in 20% with less sensitive to the distance from typhoon centers.

• Particle and aerosol research
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• v.5 no.2
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• pp.53-62
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• 2009

In this study, the continuous monitoring of the concentration of PM-10 atmospheric particulate matter using beta ray attenuation method was compared with gravimetric method from September, 2006 to August, 2007. On the effects of the PM-10 concentration and mass difference by relative humidity and precipitation were considered. The result showed that the measurement error between beta ray method and gravimetric method are within -3~6% in average, which means PM-10 concentration data with beta ray method are relatively comparable. The current study also shows that the high PM-10 concentration events are mainly due to haze, Asian dust, and high relative humidity and the PM-10 mass concentration is closely related with relative humidity and precipitation events. Based on daily mean data, the PM-10 increases as relative humidity increases up to 70~80%, then decreases over 80% due to the precipitation. However, the distinct measurement discrepancy was not shown between beta ray method and gravimetric method based on current results. Consequently, this study shows that the collocated measurement in different instrument is essential in order to quantify the accuracy of PM-10. Furthermore, the more comprehensive and spatially distributed comparison is needed and this is remained for future study.

• The Journal of the Korea Contents Association
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• v.19 no.6
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• pp.179-191
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• 2019

It is not easy to predict the return on investment in the content business, and there is no index to evaluate cast & crew. The absolute number of TV ratings is steadily declining, but there is no substitute index yet. In this study, we tried to predict the relative popularity of the drama by designing the relative superiority of the individual drama viewership as the response variable and designing the relative superiority of the drama participants as the explanatory variables. We used various machine learning algorithms and added explanatory variables that were found to be useful in previous studies. As a result, with properly combined explanatory variables, a high prediction accuracy of 84% is obtained. In this study, we intend to promote the investment efficiency of the entire contents industry by predicting the relative popularity of the contents.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.626-635
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• 2012

Most of single frequency GPS receivers utilize low-quality crystal oscillators. If a lowquality crystal oscillator is utilized as the time reference of a GPS receiver, the receiver's clock bias grows very fast due to its inherent low precision and poor stability. To prevent the clock bias becoming too large, large clock jumps are intentionally injected to the clock bias and the time offset for clock steering purpose. The abrupt changes in the clock bias and the time offset, if not properly considered, induce serious accuracy degradation in relative differential positioning. To prevent the accuracy degradation, this paper proposes an efficient and systematic method to eliminate the undesirable clock jump effects. Experiment results based on real measurements verify the effectiveness of the propose method.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.2
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• pp.146-151
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• 2013

With the development of mobile internet, requirements of positioning accuracy for the LBS (Location Based Service) are becoming more and more higher. The LBS is based on the position of each mobile device. So, it requires a proper acquisition of accurate user's indoor position. Thus indoor positioning technology and its accuracy is crucial for various LBS. In general, RSSI (Received Signal Strength Indicator) measurements are used to obtain the position information of mobile unit under WLAN environment. However, indoor positioning error increases as multiple AP's configurations are becoming more complex. To overcome this problem, an enhanced indoor localization method by AP (Access Point) selection criteria adopting DOP (Dilution of Precision) is proposed.

• Journal of the Ergonomics Society of Korea
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• v.24 no.2
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• pp.45-49
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• 2005

The FSA(Force Sensitive Application) system measures hand force by using force resistance sensors. Compared to conventional hand force measurement systems such as Lafayette hand dynamometer and Jamar hydraulic hand dynamometer, the FSA system can be applied to analyze use of hand forces while the hand is manipulating objects for a task, However, the measurement performance of the FSA system has not been objectively evaluated. The present study tested the FSA system in terms of stability, repeatability, accuracy, and linearity. It is shown that the FSA system has good stability (CV$\leq$0.02) and linearity($R^2$=0.82), but has low repeatability(CV=$0.11{\sim}0.19$) and accuracy(22% of underevaluation on average). This performance result indicates that measurements from the FSA system should be used for relative comparison rather than for absolute comparison.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.35 no.4
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• pp.303-312
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• 2017

This paper indirectly created high density point cloud data using unmanned aerial vehicle image. Then, we tried to suggest new concept of classification technique where particular objects from point cloud data can be selectively classified. For this, we established the classification technique that can be used as search factor in classifying color information in point cloud data. Then, using suggested classification technique, we implemented object classification and analyzed classification accuracy by relative comparison with self-created proof resource. As a result, the possibility of point cloud data classification was observable using the image's information. Furthermore, it was possible to classify particular object's point cloud data in high classification accuracy.