• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.24 no.2
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• pp.183-191
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• 2006

The accuracy of the upward continuation is assessed through the gravity modeling using an ultra-high degree spherical harmonic expansion. The difficulties in the numerical calculation of Legendre function with ultra-high degree, underflow and/or overflow, is successfully resolved in 128 bit calculation scheme. Using the generated Legendre function, the gravity anomaly with spatial resolution of $1'{\times}1'$ on the geoid is calculated. The generated gravity anomaly is degraded and extracted with various noise levels and data intervals, then upward continuation is applied to each data sets. The comparison between the upward continued gravity disturbances and the directly calculated from the spherical harmonics showed that the accuracy on the direct method was significantly better than that of Poisson method. In addition, it is verified that the denser and less noised gravity data on the geoid generates better gravity disturbance vectors at an altitude. Especially, it is found that the gravity noise level less than 5mGal, and the data interval less than 2arcmin is necessary for next generation precision INS navigation which requires the accuracy of 5mGal or better at an altitude.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.174-181
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• 2002

Dynamic deformation of the cylinder bore during actual engine operation has an important effect on the combustion gas sealing, oil consumption, friction and so on. The dynamic analysis using the finite element method is performed to investigate the dynamic deformation of the cylinder bore subjected to forced vibration under excitation of the combustion gas pressure. However, this analysis requires large computer memory and tremendous solving time. The pseudo-static analysis can be an alternative to the dynamic analysis at the expense of accuracy. Dynamic analysis and static analysis results are presented for both closed-deck block and open-deck block that are respectively combined with the cylinder block, cylinder head, transmission, and oil pan.

• The Korean Journal of Quaternary Research
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• v.3 no.1
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• pp.17-34
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• 1989

The distribution characteristics of incised meander river are analysed concerning topography, geology, stream order and altitude. Additionally geomorphological development of the Korean peninsular is considered with incised meander. The main findings are as follows: 1. The incised meander is intensively distributed on the west and north slope of T'aebak and Sobaek mountain range, but sparsely distributed on the opposite slopes. 2. Geologically, the occurrence rate of incised meander is high orderly as follows: Joseon supergroup, Pyeongan supergroup, Daedong supergroup metamorphic rock, Gyeongsang supergroup, and granite. The incised meander is developed well on the following conditions: hard rocks against weathering, stratified structure, geologic arrange across the river channel and contacting zone of geological formations. 3. The higher stream orders are, the higher occurrence of incised meander is. 4. Comparing the altitude of present river bed with the summit level of restored map, it is supposed that the incised meander rivers have been dissected about 300-500m down ward. 5. Considering the distribution characteristic of incised meander, it is suggested that not only T'aebak mountain range but Sobaek mountain range is the axis of asymmetrical up-warping in the Korean peninsular. 6. Considering the distribution characteristic of incised meander on the restored map and the stream order, it seems that present incised meander channel was inherited from antecedent meander river that had flowed on High and Middle level erosion surface. But the channel pattern has been modified.

• Journal of Korean Society for Geospatial Information Science
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• v.16 no.3
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• pp.117-126
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• 2008

Earth geopotential models were used to determine the reference surface in geoid modelling and many global geopotential models were developed after 1980's. Nowadays, EGM96 and EIGEN-GL04C geopotential models have been most widely used in the world, but what so called EGM2008 earth geopotential model were developed in 2008 by NGA. In this paper, we intended to compare the results of spherical harmonic analyses using the three geopotential model, EGM96, EIGEN-GL04C and EGM2008. So, the spherical harmonic analyses were performed up to degree and order 360(in case of EGM2008, up to degree and order 720, 1440, 2190 in addition), on each $1'{\times}1'$grid point in and around Korean peninsula. Geometric geoid were calculated at 464 GPS/leveling points for accuracy evaluation and then the results of three geopotential models were compared to geometric geoid. The results show that the accuracy of EGM2008 is improved considerablely compared to EGM96 and EIGEN-GL04C and it is possible to calculate geoidal heights within 14cm standard deviation and 5.5cm standard deviation after LSC fitting in and around Korean peninsula using EGM2008 geopotential model.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.846-853
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• 1995

In order to study electronic structures for locally disordered systems, we have developed a first-principle self-con-sistent-spin-polarized real space band method (TB-LMTO-R), which combines the tight-binding(TB) linear-muffin-tin orbital(LMTO) band rrethod and the recursion(R) rrethod. The TB-LMTO-R rrethod has been applied to fer-romagnetic bec Fe, hcp Co, and fcc Ni. With varying cluster sizes, recursion coefficients, and the order of the TB-Hamiltonian, we have calculated the local density of states(LDOS) and magnetic moments. It is found that the calculation with 5,000 atoms cluster, 40 continued fractions, and the second-order TB-Hamiltonian yields a conver¬gent result in agreement with those from the conventional LMTO. In this way, we have demonstrated a physical transparency of the TB-LMTO-R method as a real space description.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.10a
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• pp.648-651
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• 2018

흡연여부를 감별하는 지표가 있지만 반감기 등 여러 가지 요인에 따라 결과가 변한다는 단점이 있다. 그렇기 때문에 흡연여부 감별 시 외부요인에 영향을 덜 받는 지표가 필요하게 되었다. 그래서 흡연 여부 감별하는데 적합한 모형을 찾아 외부요인에 영향이 적은 지표를 개발에 도움이 될 것을 기대하며 연구를 진행하였다. 실험은 국민건강보험공단에서 제공한 건강검진정보데이터를 기반으로, SVM, Logistic Regression, KNN 등의 머신러닝 모델을 이용하여 흡연 여부를 감별하는 것을 진행한다. 이 실험은 속성에 따른 모형의 성능변화와 학습데이터 수에 따른 모형의 성능변화에 대한 2가지 측면에서 모델의 성능을 측정하였다. 모델의 평가는 정확도(accuracy), 정밀도(precision), 재현율(recall), 조화 평균(f1-score)으로 진행하였으며, 약 70퍼센트 정도의 정확도와, 60퍼센트 대의 재현율을 보인다. 실험 결과, SVM이 속성에 따른 모형의 성능 변화 실험에서는 63%의 재현율, 학습데이터 수에 따른 성능 변화 실험에서는 68%의 재현율을 보여, 흡연자 판별에 가장 좋은 성능을 보였다. 또한 재현율을 기준으로 실험 차수별로 가장 좋은 성능을 보인 모델과 가장 저조한 성능을 보인 모델의 차이를 비교한 결과, '속성에 따른 모형의 성능 변화 실험'에서는 최고 36%의 차이를 보였으며, '학습데이터 수에 따른 성능 변화 실험'에서 최고 42%의 차이를 보여 주었다. 이에 판별을 위한 속성도 중요하지만, 적합한 모형 선택 또한 중요하다는 것을 확인하였다.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.2
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• pp.447-452
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• 2019

The elder problem is very serious stage in the age of present. This paper carries out scientometric analysis based on keyword that effort of global researcher for this research field as viewpoint of ICT and healthcare in order to settle physical exercise and rehabilitation of elder. First, this paper performs analysis of linkage relation of keyword. Second this paper carries out the analysis of degree distribution and centrality analysis of network based on betweenness centrality, closeness centrality and harmony centrality. Through this process, this paper reviews research trend of present and future through core keyword in the field of ICT and healthcare.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.15 no.1
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• pp.131-139
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• 1997

Geopotential models were used to determine the reference surface in geoid modelling and until now, OSU91A model has been most widely used in the world. But what so called EGM96, GSFC/DMA geopotential model published in the latter half of the 1996 by GSFC/DMA project. In this paper, we intended to compare the results of spherical harmonic analyses using the both geopotential model and the spherical harmonic analyses performed up to degree and order 300 and the gravimetric geoidal heights considering gravity data on each $3'\times{3'}$ grid point in and around Korean peninsula. The results showed that the average geoidal height of study area computed from EGM96 is larger 0.40 m than that computed from OSU91A and the gravimetric geoidal heights us-ing EGM96 is larger 0.35 m than that using OSU91A model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.104-110
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• 1995

지반과 구조물의 동적 상호작용은 건설분야에서의 중요한 현상으로, 특히 지반을 통해 인근구조물로 전달되는 진동은 구조물 자체의 구조적인 문제 뿐 아니라 그 속에 거주하는 사람이나 설비에 대한 안전성 또는 사용성에 나쁜 영향을 야기할 수 있다. 본 논문에서는 이러한 진동을 저감시키기 위해, 지반내에 정상적인 진동전파를 방해하는 구조물을 시공하여 진동 저감효과를 만들어 내는 방법을 연구하였다. 이러한 연구의 발상은 다음과 같다. 충진지반에서의 지반진동의 진폭을 해석하면서 진동의 크기가 기저암의 위치에 따라 큰 영향을 받는 것을 알았고 이로부터 지반내에 인위적인 층을 만들수 있다면 지반진동의 크기를 변화시킬 수 있지 않을까라는 생각에서 본 연구를 시작하였다. 또한 지반 내에서의 정상적인 진동의 전파를 방해하기 위한 차진 구조물을 만드는 방법은 연약지반의 강도중대 또는 차수의 목적으로 주로 사용하고 있는 그라우팅공법의 사용이 가능할 것이므로, 기존의 그라우팅현장에서 만들어진 지반의 물성치들을 사용하여 경계요소법에 의한 수치해석적 방법을 택하였다. 본 연구에서는 그라우팅공법의 시공성에 관한 것은 포함되지 않는다. 본 논문에서는 지반의 구조를 경사구조와 수평지반구조라는 두가지 특징적인 경우에 대해 검토하였다. 이중 경사진 기저암층을 가진 지반의 경우에는 기저암에서 진동의 비대칭적인 반사에 의해 수평기저암에서와는 달리 기저암의 한쪽에서 다른쪽에 비해 큰 진동이 발생한다. 그라우팅층의 효과를 검토하기 위한 연구의 순서는 일정주파수의 조화진동에 대해 먼저 여러 가지 크기의 그라우팅층과 함께 블록으로 볼 수 있는 크기의 그라우팅층에 대해 진동저감효과를 해석하였고, 이를 통해 보강층의 소요크기 및 최적위치를 구하였다. 사용된 물성치는 실제 지하철 건설현장에서 나타난 지반물성치 및 그라우팅후의 지반강도 및 전단파전파속도를 이용하였다. 또한 마지막에서 검토된 기차하중에 대한 효과를 알아보기 위해 사용된 기차운행에 의한 지반가속도도 역시 측정된 값을 사용하였다. 그러나 당시의 기차운행속도가 낮아 정상적인 운행에서는 더 큰 값이 나올 것으로 판단되었으나 측정된 값을 그대로 사용하였다.

• Proceedings of the KSEEG Conference
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• 2001.05b
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• pp.42-63
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• 2001

The detail survey on the Songsanri tomb site including the Muryong royal tomb was carried out during the period from May 1 , 1996 to April 30, 1997. A quantitative analysis was tried to find changes of tomb itself since the excavation. Main subjects of the survey are to find out the cause of infiltration of rain water and groundwater into the tomb and the tomb site, monitoring of the movement of tomb structure and safety, removal method of the algae inside the tomb, and air controlling system to solve high humidity condition and dew inside the tomb. For these purposes, detail survery inside and outside the tombs using a electronic distance meter and small airplane, monitoring of temperature and humidity, geophysical exploration including electrical resistivity, geomagnetic, gravity and georadar methods, drilling, measurement of physical and chemical properties of drill core and measurement of groundwater permeability were conducted. We found that the center of the subsurface tomb and the center of soil mound on ground are different 4.5 meter and 5 meter for the 5th tomb and 7th tomb, respectively. The fact has caused unequal stress on the tomb structure. In the 7th tomb (the Muryong royal tomb), 435 bricks were broken out of 6025 bricks in 1972, but 1072 bricks are broken in 1996. The break rate has been increased about 250% for just 24 years. The break rate increased about 290% in the 6th tomb. The situation in 1996 is the result for just 24 years while the situation in 1972 was the result for about 1450 years. Status of breaking of bircks represents that a severe problem is undergoing. The eastern wall of the Muryong royal tomb is moving toward inside the tomb with the rate of 2.95 mm/myr in rainy season and 1.52 mm/myr in dry season. The frontal wall shows biggest movement in the 7th tomb having a rate of 2.05 mm/myr toward the passage way. The 6th tomb shows biggest movement among the three tombs having the rate of 7.44mm/myr and 3.61mm/myr toward east for the high break rate of bricks in the 6th tomb. Georadar section of the shallow soil layer represents several faults in the top soil layer of the 5th tomb and 7th tomb. Raninwater flew through faults tnto the tomb and nearby ground and high water content in nearby ground resulted in low resistance and high humidity inside tombs. High humidity inside tomb made a good condition for algae living with high temperature and moderate light source. The 6th tomb is most severe situation and the 7th tomb is the second in terms of algae living. Artificial change of the tomb environment since the excavation, infiltration of rain water and groundwater into the tombsite and bad drainage system had resulted in dangerous status for the tomb structure. Main cause for many problems including breaking of bricks, movement of tomb walls and algae living is infiltration of rainwater and groundwater into the tomb site. Therefore, protection of the tomb site from high water content should be carried out at first. Waterproofing method includes a cover system over the tomvsith using geotextile, clay layer and geomembrane and a deep trench which is 2 meter down to the base of the 5th tomb at the north of the tomv site. Decrease and balancing of soil weight above the tomb are also needed for the sfety of tomb structures. For the algae living inside tombs, we recommend to spray K101 which developed in this study on the surface of wall and then, exposure to ultraviolet light sources for 24 hours. Air controlling system should be changed to a constant temperature and humidity system for the 6th tomb and the 7th tomb. It seems to much better to place the system at frontal room and to ciculate cold air inside tombs to solve dew problem. Above mentioned preservation methods are suggested to give least changes to tomb site and to solve the most fundmental problems. Repairing should be planned in order and some special cares are needed for the safety of tombs in reparing work. Finally, a monitoring system measuring tilting of tomb walls, water content, groundwater level, temperature and humidity is required to monitor and to evaluate the repairing work.