• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1515-1527
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• 2016

With the growth of big data, machine learning, and cloud computing, the importance of storage that can store large amounts of unstructured data is growing recently. So the commodity hardware based distributed file systems such as MAHA-FS, GlusterFS, and Ceph file system have received a lot of attention because of their scale-out and low-cost property. For the data fault tolerance, most of these file systems uses replication in the beginning. But as storage size is growing to tens or hundreds of petabytes, the low space efficiency of the replication has been considered as a problem. This paper applied erasure coding data fault tolerance policy to MAHA-FS for high space efficiency and introduces VDelta technique to solve data consistency problem. In this paper, we compares the performance of two file systems, MAHA-FS and GlusterFS. They have different IO processing architecture, the former is server centric and the latter is client centric architecture. We found the erasure coding performance of MAHA-FS is better than GlusterFS.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.3
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• pp.307-313
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• 2018

The respiratory function is relevant to the craniofacial growth and orthodontic diagnosis. The size of the pharyngeal airway was measured in lateral cephalometric view in children visited Kyung Hee University Hospital from January 2015 to August 2017. A total of 74 healthy children (36 boys and 38 girls) aged 7 - 11 years (mean, 8.5 years) with a normodivergent facial pattern were divided into three groups according to anteroposterior jaw relation measuring A point-Nasion-B point (ANB) angle. Lateral cephalometric data were used to measure the airway dimensions. The dimensions of the middle airway were significantly lower, reducing the upper airway space, in large ANB angle group than in other children, suggesting that children with large ANB angle have narrower airway space than others.

• Journal of the Korean Institute of Landscape Architecture
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• v.35 no.1 s.120
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• pp.1-8
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• 2007

The purpose of this study is to suggest the minimum distance needed between landscape trees and apartment buildings. in order for the trees to grow soundly and maintain constant growth. Therefore, this study investigated and analyzed the present conditions of the green-spaces contiguous to apartment buildings and the trees inside the apartment complex. The following general problems were identified : (1) the tree growth conditions, (2) the planting intervals, and (3) the planting methods in the apartment complexes. The method of this study was to survey areas, measure the trees and analyze the results. Ten apartment complexes located in Seoul were randomly selected for this study. To analyze the greens contiguous to the building of each apartment complex, the greens were divided into three types, including the front greens, the side greens, and the rear greens. The study surveyed the width of all contiguous greens and the distance from trees to my given building. Four representative sites were specifically investigated to measure the crown widths, heights, and diameters of the trees. These investigations were carried out over 3 months from August to December 2006. According to the results of the study, it was found that the greens are narrower in width and the more closer to a building. The study identified a correlation between the tree and the passage of time after the completion of construction of an apartment complex, showing that the malformation of the trees worsened as time passed. As a result of measuring the right crown and left crown width with the tree trunk as the center, a broad difference was found between coniform trees and trees that tend to branch out more. For example, the ratio of the width of the Acer palmatum is 1:6. However, the ratio of the Metasequoia glyptostroboide is 1:1.7. Based on the overall analysis, it was concluded that the maintained minimum width must be greater than one meter over the green space according to the 'Landscape Standard 2000'. However, that is only applicable to cases such as apartment buildings that present no obstacles. In conclusion having greens placed within one meter of width to a building is not an appropriate environment for the healthy growth of trees. To create sound green spaces, sustainable, long-term growth rate and size should be considered. It is necessary to prepare new standards for the computation of planting trees and the measurement of square landscapes. Wall greenery and shrubberies could be an alternative in the case of a narrow-width green space.

• Progress in Superconductivity
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• v.13 no.2
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• pp.97-104
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• 2011

In the dielectric resonator method, which has been widely used for measuring the microwave surface resistance of superconductors, accuracies in the geometrical factors (G-factors) affect the uncertainty in the measured surface resistance. We compare the G-factors of short-ended sapphire resonator as obtained by using field analysis with those by using computer simulations: The former is obtained by using the analytic expressions for the electric and the magnetic field components inside the resonator, and the latter by using computer software. The G-factors as obtained by using the latter appear to be closer to those obtained by using the former as the resonator space is divided into larger number of sub-space, i.e., a tighter mesh, with a difference of ~8 % observed for a mesh of 14400 sub-spaces reduced to ~2 % for 114996 sub-spaces. Variations in the relative uncertainty in the surface resistance of typical $YBa_2Cu_3O_{7-\delta}$ superconductor films with those in the G-factors are studied, which provides an upper limit of the relative uncertainty in the G-factors required for realizing the target uncertainty in the surface resistance. These results could be useful in estimating the optimum number of meshes for obtaining the G-factors through computer simulations.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.271-287
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• 2013

In this study, more convenient model(S-model) for predicting ground surface settlement is developed through comparing field monitoring data of the domestic subway applied shield TBM method with conventional equation & numerical analysis. Sample stations are chosen from whole of excavation section and lateral & vertical ground surface settlement characteristic with excavation are analysed. Based on analysis result, through the comparison with actual monitoring data, the model that is possible to compute maximum surface settlement and settlement influence area is suggested with assumption that lateral surface settlement forms are composed relaxed zone and elastic zone. In addition, vertical ground surface settlement patterns with excavation are similar to cubic-function and S-model with assumption that coefficients are function of tunnel diameter and depth is suggested. Consequently, the ground surface settlement patterns are significantly similar to actual monitoring data and numerical method result. Thus, as a result, when tunnels are excavated using sheild TBM through rather soft weathered soil & rock layer, prediction of ground surface settlement with excavation using convenient S-model is practicable.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.11
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• pp.965-972
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• 2016

This paper presents results of flight experiments on a navigation algorithm including multiplicative extended Kalman filter for estimating attitude of the guided munition. The filter describes orientation of aircraft by data fusion with low-cost sensors where measurement update is done by multiplication, rather than addition, which is suitable for quaternion representation. In determining attitude from vector observations, the existing approach utilizes a 3-axis accelerometer as a 2-axis inclinometer by measuring gravity to estimate pitch and roll angles, while GNSS velocity is used to derive heading of the vehicle. However, during accelerated maneuvers such as coordinated flight, the accelerometer provides inadequate inclinometer measurements. In this paper, the measurement update process is newly defined to complement the vulnerability by using different vector observations. The acceleration measurement is considered as a result of a centrifugal force and gravity during turning maneuvers and used to estimate roll angle. The effectiveness of the proposed method is verified through flight experiments.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.2
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• pp.149-160
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• 2014

The objective of this study is the application of the harmony search (HS) algorithm and verification of the accuracy of inverse analysis to predict the location, thickness and electrical properties of anomalous zone ahead of tunnel face when utilizing the electrical resistivity survey using electrical resistivity of the ground. The relationship correlating the characteristic values of the anomalous zone with the electrical resistance values was derived using Gauss' laws and Ohm's laws. Inverse analysis program was developed to predict anomalous zone by using electrical resistivity based on HS algorithm. Electrical resistance measuring system is devised to obtain the electrical resistivity of the ground, and laboratory tests were performed on anomalies to verify the proposed HS algorithm. The test results show that the characteristics of the anomalies are predicted reasonably well resulting in less than 5% error when predicting the location and thickness of the anomaly.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.55-72
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• 2018

A method that can predict the mixed-ground condition ahead of a TBM tunnel face during tunnel construction utilizing electrical resistivity and induced polarization (IP) was proposed in this study. Effect of TBM advancement approaching the mixed-ground condition (composed of soil layer overlying rock layer) when currently running through soil zone on the electrical resistivity and IP measuring was assessed with laboratory-scale experiments. The resistivity and IP values were measured using four electrodes, by installing two electrodes on the tunnel face (at the cutterhead), and the other two electrodes on the segment lining. The test results showed that both of the measured resistivity and IP values were kept increasing as the TBM is approaching the soil-rock mixed-ground. Also, to get the more reliable results for predicting the mixed-ground condition, it was recommended that the measurement is made at the tunnel face utilizing 4-electrodes installed at the cutterhead as well as it is made utilizing the 2-electrodes installed at the segment lining along with the 2-electrodes installed on the tunnel face (at the cutterhead) so that two measured results are compared each other.

• Journal of Astronomy and Space Sciences
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• v.18 no.3
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• pp.239-248
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• 2001

Far-ultraviolet IMaging Spectrograph (FIMS) is the main payload of the first Korean scientific satellite, KAISTSAT-4, which will be launched in 2002. Among the optical parts, parabolic cylinder mirror does not have any heritage from previous astronomical missions, so the manufacturing and testing process itself is a challenging issue. We describe the method of manufacturing and measuring of the off-axis parabolic cylinder mirror and our initial experiments to establish the entire manufacturing process. Using the method, the profile error can meet the specification of $lambda$ per cm which is closely related with the astronomical performances. In case of the surface roughness, temperature controlled pitch polishing reduces $R_{q}$ under 1 nm implying that scattering in the entire spectral range of FIMS is less than 2% of the incident UV light.

• Journal of Oral Medicine and Pain
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• v.20 no.2
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• pp.361-376
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• 1995

The purpose of this study was to investigate the relationship between the head and neck postre and the cervical curvature, especially in forward head postrue(FHP). Sixty patients with craniomandibular disorders and thirty dental students without any signs and symptoms of craniomandibular disordres participated in this study as patient groups and sa control group, respectively. The author evaluated the head and neck posture of all subjects by plumb line and CROM( Cervical Ragne of Motion), and had taken cephaograph in natural head position. On the cephalograph the angle of cervical inclination formed by true horizntal plane and 4th cervical vertebra(C4) and the radius of cervical curvature from C1 to C5 were measured. A specially designed ruler was used for measuring cervical curvature. Occlusal contac number and force with T-scan system, electromygraphic activity of cervical muscles with Bio-EMG, and distance of freeway space with Bio-ECN were recorded, respectively. The collected data were processed by SAS/STAT progrm. The obtained results were as follows : 1. In subjects with longer radius which was less cervical curvature, head positioned more anteriorly than subjects with smaller radius, and they showed slightly straight cervical vertebra. 2. Between the patients and the control group, there were no differences in cervical curvature, in forward head position by plumb line and in CROM. But the patient group had a greater cervical inclination than the control group had. 3. There were positive correlation between cervical curvature and forward head position by plumbline,between forward head position y plumb line and that by CROM in patient group. The cervical inclination, however, had negative correlation with cervical curvature, and with forward head postion by plumb line, respectively. 4. In case of showing more cervical curvature and more forward head position by plumb line the head position was defined as forward head posture. In patient group, subjects without forward head posture showed greater posterior teeth contact force than subjects with forward head posture, but in control group, there were no difference between the two subjects. 5. There were higher electromyographic activity in almost all muscles and smaller freeway space in induced forward head posture than those in natural head position in subjects without forward head posture. In conclusion, head position of patients with craniomandibular disorders were not more anterior than that of normal control person, but they had tendency to head extension. From the result of this study, forward head posture could be defined as posterior rotation of upper cervical segment with a straight lower cercial segment due to loss of normal lordosis.