• Proceedings of the KSRS Conference
• /
• 2004.10a
• /
• pp.646-649
• /
• 2004

LiDAR(Light Detection and Ranging) system can record intensity data as well as range data. Recently, LiDAR intensity data is widely used for landcover classification, ancillary data of feature extraction, vegetation species identification, and so on. Since the intensity return value is associated with several factors, same features is not consistent for same flight or multiple flights. This paper investigated correlation between intensity and range data. Once the effects of range was determined, the single flight line normalization and the multiple flight line normalization was performed by an empirical function that was derived from relationship between range and return intensity

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
• /
• v.10 no.2
• /
• pp.45-56
• /
• 2004

OBJECTIVE: The objective of this study was to know the effects of the postoperative lumbar extensor strengthening exercise program on back muscles strength and volume, pain, and the time of return to work. METHODS: A prospective controlled trial of lumbar extensor exercise program in patients who underwent microdiscectomy or percutaneous endoscopic discectomy for prolapsed lumbar intervertebral disc. Seventy-five patients were randomized into exercise group (20 male, 15 female) and non-exercise group (18 male, 22 female). Six weeks after surgery, patients in exercise group undertook a 12-week lumbar extension exercise (MedX) program. Assessment of spinal function was performed in all patients on postoperative 6 weeks, 18 weeks. The assessment included measures of lumbar extensor power, muscle mass of erector spinalis. All patients completed the visual analog scale (VAS) for evaluation of pain, and return to work. RESULTS: In muscle power, there were statistically significant improvements between pre and post test on muscle power in exercise group. But there were not statistically significant difference on muscle power in non-exercise group. In muscle mass, there were statistically significant difference between pre and post test on muscle mass in exercise group. But there were not statistically significant difference on muscle mass in non-exercise group. In the pain, there were statistically significant decrease between pre and post test on both group. But there were not statistically significant difference on fatty tissue and obesity in non-exercise group. The percentages of return to work in postoperative 4 months were significantly greater in the exercise group than in the non -exercise group. CONCLUSIONS: Postoperative lumbar extensor strengthening exercise program appears to be more beneficial to the patients who underwent operation for prolapsed lumbar intervertbral disc.

• Journal of Korea Water Resources Association
• /
• v.49 no.4
• /
• pp.275-282
• /
• 2016

The objective of this study is to propose a new method to determine the drought event and the design drought severity. In order to define a drought event from precipitation data, theory of run was applied with the cumulative rainfall deficit. When we have a large amount of rainfall over the threshold level, in this study, we compare with the previous cumulative rainfall deficit to determine whether the drought is relieved or not. The recurrence characteristics of the drought severity on the specific duration was analyzed by the conditional bivariate copula function and confidence intervals were estimated to quantify uncertainties. The methodology was applied to Seoul station with the historical dataset (1909~2015). It was observed that the past droughts considered as extreme hydrological events had from 10 to 50 years of return period. On the other hand, the current on-going drought event started from 2013 showed the significantly higher return period. It is expected that the result of this study may be utilized as the reliable criteria based on the concept of return period for the drought contingency plan.

• Journal of Institute of Control, Robotics and Systems
• /
• v.19 no.5
• /
• pp.416-422
• /
• 2013

This paper suggests a hybrid path planning method of multi-robots, where a path deviation prevention for maintaining a specific formation is implemented by using repulsive function, $A^*$ algorithm and UKF (Unscented Kalman Filter). The repulsive function in potential field method is used to avoid collision among robots and obstacles. $A^*$ algorithm helps the robots to find optimal path. In addition, error estimation based on UKF guarantees small path deviation of each robot during navigation. The simulation results show that the swarm robots with designated formation successfully avoid obstacles and return to the assigned formation effectively.

• Journal of Powder Materials
• /
• v.30 no.1
• /
• pp.29-34
• /
• 2023

A fixed-point iteration is proposed to integrate the stress and state variables in the incremental analysis of plastic deformation. The Conventional Newton-Raphson method requires a second-order derivative of the yield function to generate a complicated code, and the convergence cannot be guaranteed beforehand. The proposed fixed-point iteration does not require a second-order derivative of the yield function, and convergence is ensured for a given strain increment. The fixed-point iteration is easier to implement, and the computational time is shortened compared with the Newton-Raphson method. The plane-stress condition is considered for the biaxial loading conditions to confirm the convergence of the fixed-point iteration. 3-dimensional tensile specimen is considered to compare the computational times in the ABAQUS/explicit finite element analysis.

• Journal of Intelligence and Information Systems
• /
• v.23 no.2
• /
• pp.107-122
• /
• 2017

Volatility in the stock market returns is a measure of investment risk. It plays a central role in portfolio optimization, asset pricing and risk management as well as most theoretical financial models. Engle(1982) presented a pioneering paper on the stock market volatility that explains the time-variant characteristics embedded in the stock market return volatility. His model, Autoregressive Conditional Heteroscedasticity (ARCH), was generalized by Bollerslev(1986) as GARCH models. Empirical studies have shown that GARCH models describes well the fat-tailed return distributions and volatility clustering phenomenon appearing in stock prices. The parameters of the GARCH models are generally estimated by the maximum likelihood estimation (MLE) based on the standard normal density. But, since 1987 Black Monday, the stock market prices have become very complex and shown a lot of noisy terms. Recent studies start to apply artificial intelligent approach in estimating the GARCH parameters as a substitute for the MLE. The paper presents SVR-based GARCH process and compares with MLE-based GARCH process to estimate the parameters of GARCH models which are known to well forecast stock market volatility. Kernel functions used in SVR estimation process are linear, polynomial and radial. We analyzed the suggested models with KOSPI 200 Index. This index is constituted by 200 blue chip stocks listed in the Korea Exchange. We sampled KOSPI 200 daily closing values from 2010 to 2015. Sample observations are 1487 days. We used 1187 days to train the suggested GARCH models and the remaining 300 days were used as testing data. First, symmetric and asymmetric GARCH models are estimated by MLE. We forecasted KOSPI 200 Index return volatility and the statistical metric MSE shows better results for the asymmetric GARCH models such as E-GARCH or GJR-GARCH. This is consistent with the documented non-normal return distribution characteristics with fat-tail and leptokurtosis. Compared with MLE estimation process, SVR-based GARCH models outperform the MLE methodology in KOSPI 200 Index return volatility forecasting. Polynomial kernel function shows exceptionally lower forecasting accuracy. We suggested Intelligent Volatility Trading System (IVTS) that utilizes the forecasted volatility results. IVTS entry rules are as follows. If forecasted tomorrow volatility will increase then buy volatility today. If forecasted tomorrow volatility will decrease then sell volatility today. If forecasted volatility direction does not change we hold the existing buy or sell positions. IVTS is assumed to buy and sell historical volatility values. This is somewhat unreal because we cannot trade historical volatility values themselves. But our simulation results are meaningful since the Korea Exchange introduced volatility futures contract that traders can trade since November 2014. The trading systems with SVR-based GARCH models show higher returns than MLE-based GARCH in the testing period. And trading profitable percentages of MLE-based GARCH IVTS models range from 47.5% to 50.0%, trading profitable percentages of SVR-based GARCH IVTS models range from 51.8% to 59.7%. MLE-based symmetric S-GARCH shows +150.2% return and SVR-based symmetric S-GARCH shows +526.4% return. MLE-based asymmetric E-GARCH shows -72% return and SVR-based asymmetric E-GARCH shows +245.6% return. MLE-based asymmetric GJR-GARCH shows -98.7% return and SVR-based asymmetric GJR-GARCH shows +126.3% return. Linear kernel function shows higher trading returns than radial kernel function. Best performance of SVR-based IVTS is +526.4% and that of MLE-based IVTS is +150.2%. SVR-based GARCH IVTS shows higher trading frequency. This study has some limitations. Our models are solely based on SVR. Other artificial intelligence models are needed to search for better performance. We do not consider costs incurred in the trading process including brokerage commissions and slippage costs. IVTS trading performance is unreal since we use historical volatility values as trading objects. The exact forecasting of stock market volatility is essential in the real trading as well as asset pricing models. Further studies on other machine learning-based GARCH models can give better information for the stock market investors.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
• /
• v.11 no.1
• /
• pp.64-68
• /
• 2000

Background and Objectives : To assess the role of altered vocal function in transient voice change after short-term endotracheal intubation, we evaluated acoustic parameters, aerodynamic parameters, and laryngoscopic characteristics preoperatively and postoperatively. Materials and Methods : Vocal function of 10 patients undergoing tympanoplasty and mastoidectomy using general anesthesia and endotracheal intubation were studied preoperatively, at 1day and 7 days after extubation. Acoustic analysis, aerodynamic study, and telescopic examination were used to assess vocal function. Results : In acoustic parameters, there was no significant difference between preoperative and postoperative measures. However, in subglottic pressure, ere was a significant decrease at 1 day after extubation and this change was return to preoperative value at 7 days after extubation. MPT(Maximal Phonation Time), MER(Mean flow Ratio), and VC(Vital Capacity) were decreased 1 day after extubation but did not show statistically significant change. Three of 10 patients manifested a vocal fold edema and injection 1 day after extubation. Conclusions : Subglottic pressure revealed a significant decrease at 1 day after extubation. And this change was correlated with laryngeal morphologic change and decrement in pulmonary function.

• Proceedings of the IEEK Conference
• /
• 2002.06a
• /
• pp.183-186
• /
• 2002

In this paper, a microstrip Patch antenna with the T-shaped slits, which are employed to reduce the patch size. is proposed for GPS In order to analyze characteristics of the antennas are defined green function of the moment method. The microstrip Patch antenna and microstrip Patch with the T-shaped slits are fabricated. The numerical result of return loss and -10d13 bandwidth are compared with measured results.

• 한국초전도학회:학술대회논문집
• /
• v.10
• /
• pp.197-200
• /
• 2000

In this paper, we present a novel methodology for a wideband HTS antenna of finite length placed on a dielectric substrate. A methodology used in this work is based on a moment-method techniques with Green function singularity when the field point is in the source triangle. The designed resonance frequency of our HTS antenna is 11.85 GHz. The return loss is -26 dB. The bandwidth obtained is a significant 10.6 %. Experimental measurements for a HTS antenna designed in X-band are shown to agree well with the simulated prediction.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.26 no.5
• /
• pp.1-18
• /
• 2023

The Ecosystem Conservation Levy (formerly known as the Ecosystem Conservation Cooperation Fund) system has been in place for 20 years, and it can be said that it has now entered the settlement stage. Based on an analysis of publicly available project implementation data from 2014 to 2020, we found that: 1) As the number of return projects increases, the targets of restoration technologies are also strengthening, and it is necessary to frame a series of processes from application, creation, and monitoring for some detailed projects to improve the effectiveness and efficiency of utilizing the levy. 2) Most of the implemented projects are applied as micro-ecosystem creation, but there are many cases where the contents of the project can be seen as other project categories. This shows that the purpose of the return project needs to be approached more clearly and suggests that institutional complementation is needed from the project application stage. 3) The detailed technologies applied tend to be gradually expanding, but most of them are technologies that are not differentiated from general development projects. It is urgent to secure a more technical identity, such as a range and list of utilized technologies suitable for the characteristics and purposes of return projects. 4) It is necessary to establish a relevant evaluation system or framework to utilize the monitoring results of restoration projects. 5) There have been few cases of application of single restoration technologies since the beginning, but the content and scope of the complexity tend to expand in recent years. Even if the objectives are not comprehensive and diverse, it can be seen that many parts of the projects are oriented toward convergence, so it is necessary to conduct separate research on this. 6) As for the direction of improvement of the return project, it is possible to consider expanding the restoration and conservation focus to partially accommodate the complexity of the natural environment and human ecology. It seems that the expansion of restoration technologies that consider the role and function of humans in the natural environment should be explored.