• Journal of Drive and Control
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• v.18 no.2
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• pp.1-8
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• 2021

In this work, a circuit with a hydraulic power unit is formulated as a means of predicting the behavior of the prefill valve in the future. The behavior of the prefill valve can be examined by the measurements of the configured power unit, and the performance is determined by using hydraulic pumps, relief valves, and hydraulic hoses that make up the power unit. In particular, pressure/flow pulsation generated by hydraulic pumps can cause instability in the prefill valve and cause noise-induced degradation of the overall performance and reliability of the hydraulic system containing the prefill valve. Therefore, to study the behavior and performance of the prefill valve in a relatively accurate manner, the prediction of the characteristics of the hydraulic power unit driving the prefill valve is very important. In this study, the pulsation characteristics of the hydraulic pump were analyzed to theoretically demonstrate its relationship with different settings of the power unit, such as relief valve pressure settings and the presence/absence of the hose.

• Journal of dental hygiene science
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• v.23 no.2
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• pp.176-184
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• 2023

Background: Recently, a piezoelectric ultrasonic scaler based on a feedback control mechanism was introduced for pain relief. This study aimed to investigate the effects of a new ultrasonic scaler in reducing pain and discomfort in adults. Methods: A newly introduced ultrasonic scaler (Master 700^®) was used as the test device and a conventional ultrasonic scaler device (PIEZON^®) was used as the control device. Forty-one healthy adults visited the dental clinic for dental scaling but did not undergo scaling or periodontal treatment within 6 months. Intraoral examinations were performed before scaling and 3 months later; before scaling, both devices were randomly assigned on the left or right side of each dentition (split-mouth model) and scaling was performed by a registered dental hygienist. The levels of pain and discomfort during scaling were evaluated subjectively and objectively using the visual analog scale (VAS) and physiological monitoring of the heart rate (HR), respectively. Time was measured for each device. Results: All clinical indicators, except bleeding on probing, significantly improved with both devices. The treatment times were 7 minutes, 13 minutes (control) and 6 minutes, 59 minutes (test). VAS scores for pain were 4.89±2.12 (control) and 4.58±2.77 (test) points out of 10; for noise, these were 4.68±2.33 (control) and 4.55±2.55 (test), and for vibration, the values were 4.26±2.0 (control) and 4.18±2.48 (test). HR averages were 72.34±3.39 (control) and 75.97±9.78 (test) beats/min. No statistically significant differences were observed between the devices. Conclusion:The pain, discomfort levels, and scaling time of the new piezoelectric ultrasonic scaler did not differ from those of the conventional device. Further research and development are necessary for more prominent pain-relief effects of scaling devices.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1263-1269
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• 2016

Stress has become one of the largest health risk to shorten the life time of health. Accordingly, in order to increase the life time of health, stress relief can be very important. Many social expenses and economic commitment have been inputted for this purpose, but their effectiveness compared to the current situation is not very high. In this paper, we carried out an identification work of rain sound which is similar to the white noise that can stabilize the body and mind of the person by analyzing the variations of 3rd formant frequency bandwidth. Also, for relieving stress, the sounds of rain that is easily accessible at a relatively among the sounds of nature instead of consuming a lot of money and time were selected for solving these problems. In addition, we identified the effectiveness of the stress relief about the sound of rain and research on whether there is a difference between men and women in their 20's or not was performed. Finally, we discussed the personal - adjusted rain making to maximize the effectiveness of stress relief.

• Journal of Biomedical Engineering Research
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• v.35 no.3
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• pp.42-49
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• 2014

We propose an individual identification method using a single-lead electrocardiogram signal. In this paper, lead I ECG is measured from subjects in various physical and psychological states. We performed a noise reduction for lead I signal as a preprocessing stage and this signal is used to acquire the representative beat waveform for individuals by utilizing the ensemble average. From the P-QRS-T waves, features are extracted to identify individuals, 19 using the duration and amplitude information, and 16 from the QRS complex acquired by applying Pan-Tompkins algorithm to the ensemble averaged waveform. To analyze the effect of each feature and to improve efficiency while maintaining the performance, Relief-F algorithm is used to select features from the 35 features extracted. Some or all of these 35 features were used in the support vector machine (SVM) learning and tests. The classification accuracy using the entire feature set was 98.34%. Experimental results show that it is possible to identify a person by features extracted from limb lead I signal only.

• The Journal of the Korean dental association
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• v.37 no.6 s.361
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• pp.445-455
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• 1999

Arthrocentesis is a simple, less invasive, inexpensive, and highly efficient procedure for closed lock of the temporomandibular joint with regard to the lack of recurrence of symptoms during extended periods of follow-up and significiant improvement in pain and jaw function. It can be performed under local anesthesia. Arthrocentesis closed lock provide sustained normal joint function and marked pain relief. This study is the clinical outcome of arthrocentesis for closed lock of the temporomandibular joint. 160 patients(169 joints) who had experienced sudden-onset, persistent limited mouth opening were the subjects of this study. Arthrocentesis of the upper compartment of the affected TMJ was performed using normal saline. As results, at 3-60 months postarthrocentesis maximum mouth opening(MMO) had increased from mean of 27.7mm to 43.5mm, contralateral movements(CLM) from mean 5.74mm to 9.55mm, midline deviation during mouth opening from mean 3.04mm to 0.69mm. In 130 cases there was a history of joint noises, in 52 cases all noise had ceased after procedures.

• Journal of Drive and Control
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• v.18 no.3
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• pp.8-15
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• 2021

A rear axle steering (RAS) system is attached to the rear of medium and large commercial vehicles that transport large cargo. The existing RAS systems are driven by electro-hydraulic actuator (EHA), and most commercialized EHAs consist of electric motors, hydraulic pumps, relief valves, prefill valves and cylinders. The prefill valve required for such EHAs is a type of check valve with extremely low cracking pressure that should not allow RAS to have noise or vibration, and the prefill valve prevents system negative pressure as well as unstable operation. Most papers on this topic rely on experiments to predict valve performance, and theoretically detailed modeling of valves or pipelines is performed, but it is very rare to evaluate hydraulic vibration characteristics by analysing everything from hydraulic pumps to valves comprehensively. In this study, we proposed an experimental circuit that can predict the performance of the prefill valve. The study also analysed the pressure-flow pulsation that is transmitted to the valve through the pipeline, and how the transmitted pressure-flow pulsation affects the valve vibration.

• Journal of Korea Multimedia Society
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• v.16 no.7
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• pp.810-819
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• 2013

FCM (Fuzzy C-Means) clustering algorithm, a typical split-based clustering algorithm, has been successfully applied to the various fields. Nonetheless, the FCM clustering algorithm has some problems, such as high sensitivity to noise and local data, the different clustering result from the intuitive grasp, and the setting of initial round and the number of clusters. To address these problems, in this paper, we determine fuzzy numbers which project the FCM clustering result on the axis with the specific attribute. And we propose a model that the fuzzy numbers apply to FDT (Fuzzy Decision Tree). This model improves the two problems of FCM clustering algorithm such as elevated sensitivity to data, and the difference of the clustering result from the intuitional decision. And also, this paper compares the effect of the proposed model and the result of FCM clustering algorithm through the experiment using real traffic and rainfall data. The experimental results indicate that the proposed model provides more reliable results by the sensitivity relief for data. And we can see that it has improved on the concordance of FCM clustering result with the intuitive expectation.

• Korean Journal of Geomatics
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• v.2 no.1
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• pp.37-46
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• 2002

Accurate classification of water area is an preliminary step to accurately analyze the flooded area and damages caused by flood. This step is especially useful for monitoring the region where annually repeating flood is a problem. The accurate estimation of flooded area can ultimately be utilized as a primary source of information for the policy decision. Although SAR (Synthetic Aperture Radar) imagery with its own energy source is sensitive to the water area, its shadow effect similar to the reflectance signature of the water area should be carefully checked before accurate classification. Especially when we want to identify small flood area with mountainous environment, the step for removing shadow effect turns out to be essential in order to accurately classify the water area from the SAR imagery. In this paper, the flood area was classified and monitored using multi-temporal RADARSAT SAR images of Ok-Chun and Bo-Eun located in Chung-Book Province taken in 12th (during the flood) and 19th (after the flood) of August, 1998. We applied several steps of geometric and radiometric calculations to the SAR imagery. First we reduced the speckle noise of two SAR images and then calculated the radar backscattering coefficient $(\sigma^0)$. After that we performed the ortho-rectification via satellite orbit modeling developed in this study using the ephemeris information of the satellite images and ground control points. We also corrected radiometric distortion caused by the terrain relief. Finally, the water area was identified from two images and the flood area is calculated accordingly. The identified flood area is analyzed by overlapping with the existing land use map.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.4
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• pp.297-304
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• 2015

The change detection algorithms, based on remotely sensed satellite imagery, can be applied to various applications, such as the hazard/disaster analysis and the land monitoring. However, unchanged areas sometimes detected as the changed areas due to various errors in relief displacements and noise pixels, included in the original multi-temporal dataset at the application of unsupervised change detection algorithm. In this research, the object-based changed detection for the high-spatial resolution satellite images is applied by using the IR-MAD (Iteratively Reweighted- Multivariate Alteration Detection), which is one of those representative change detection algorithms. In additionally, we tried to increase the accuracy of change detection results with using the additional information, based on the cross-sharpening method. In the experiment, we used the KOMPSAT-2 satellite sensor, and resulted in the object-based IR-MAD algorithm, representing higher changed detection accuracy than that by the pixel-based IR-MAD. Also, the object-based IR-MAD, focused on cross-sharpened images, increased in accuracy of changed detection, compared to the original object-based IR-MAD. Through these experiments, we could conclude that the land monitoring and the change detection with the high-spatial-resolution satellite imagery can be accomplished efficiency by using the object-based IR-MAD algorithm.

• Land and Housing Review
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• v.13 no.4
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• pp.13-26
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• 2022

This study analyzes housing choice determinants of the youth and newlyweds households by using housing survey data in Incheon. A multinomial logit model is employed for analysis with the following variables: housing characteristics, housing market characteristics, and residential and neighborhood environment characteristics. The findings from the analysis are as follows. First, for the continued residence of the youth, the important factors were the relief assistance of housing maintenance costs. For the newlyweds, the important factors were the quality improvement of residential environments to ensure residential stability. Second, the housing choice factors to attract the youth were residential support for rent, maintenance costs, and relocation, and the improvements of residential environments such as security, noise levels, and medical facilities. For the newlyweds, the important factors were housing loan assistance for a home purchase or a cheonsei deposit and residential quality improvements for air pollution and parking facilities. Third, the youth were likely to move out due to high rental costs, and the newlyweds were likely to move out for the purchase of a new apartment or higher-quality housing.