• Journal of the Korean Geophysical Society
• /
• v.3 no.2
• /
• pp.77-90
• /
• 2000

Five electrical resistivity dipole-dipole and two seismic reflection surveys were performed in the southeastern margin of the Yongdong basin to delineate the shallow basin architecture. To investigate the intra-basin structure, twenty four resistivity sounding points and three dipole-dipole lines were selected especially in the vicinity of volcanic masses. The basin-fault boundaries are identified in electrical dipole-dipole resistivity section as high resistivity-contrast of approximately $1,500\;{\Omega}{\cdot}m$, characterized as a band of high standard-deviation. They are also effectively clarified in the seismic reflection data: amplitude and continuity contrasts in the common shot gather, first-arrival profiles, complex attribute plots. The intra-basin resistivity structures are constructed by interpolating vertical electrical sounding data and dipole-dipole profiles. The high-resistivity anomalies most likely originate from the northsouth-trending and northeast-dipping volcanic masses, which are to be further quantitatively investigated with geomagnetic and magnetotelluric surveys.

• Composites Research
• /
• v.28 no.4
• /
• pp.168-175
• /
• 2015

Recently, the applications of carbon fiber reinforced plastics (CFRPs) have become broader than ever when it comes to such industries as automotive, ships, aerospace and military because of their lightweight-ness and high mechanical properties. Thermosetting plastics like epoxy are frequently used as the binding matrix in CFRPs due to their high hardness, wetting characteristics and low viscosity. However, they cannot melted and remolded. For this reason, thermosetting plastic wastes have caused serious environmental problems with the production of fiber reinforced plastics. Thus, many studies have focused on the carbon fiber reinforced thermoplastics (CFRTPs) and recycling carbon fiber. In this study, recycled carbon fiber (RCF) was prepared from CFRPs using a pyrolysis method, which was employed to separate resin and carbon fiber. The degree of decomposition for epoxy resin was confirmed from thermal gravimetric analysis (TGA) and scanning electron microscope (SEM). The RCF was cut and ground to prepare a carbon fiber composite sheet (CFCS). CFCS was manufactured by applying recycled carbon fibers and various thermoplastic fibers. Various characterizations were performed, including morphological analyses of surface and cross-section, mechanical properties, and crystallization enthalpy of CFCS at different cooling conditions.

• Journal of the Korea Computer Graphics Society
• /
• v.22 no.5
• /
• pp.17-26
• /
• 2016

This paper presents an adaptive slicing method based on merging vertical layer polylines. Firstly, we slice the input 3D polygon model uniformly with the minimum printable thickness, which results in bounding polylines of the cross section at each layer. Next, we group a set of layer polylines according to vertical connectivity. We then remove polylines in overdense area of each group. The number of layers to merge is determined by the layer thickness computed using the cusp height of the layer. A set of layer polylines are merged into a single polyline by removing the polylines within the layer thickness. The proposed method maintains the shape features as well as reduces the printing time. For evaluation, we sliced ten 3D polygon models using our method and a global adaptive slicing method and measured the total length of polylines which determines the printing time. The result showed that the total length from our method was shorter than the other method for all ten models, which meant that our method achieved less printing time.

• The korean journal of orthodontics
• /
• v.38 no.1
• /
• pp.13-30
• /
• 2008

Objective: The objective of this study was to evaluate the displacement pattern and the stress distribution of the finite element model 3-D visualization during symphyseal widening according to the osteotomy position, osteotomy type, and distraction device. Methods: The kinds of distraction devices used were tooth-borne type, hybrid type, bone-borne type and tooth-borne type $30^{\circ}$ angulated, and the kinds of osteotomy design were vertical osteotomy line between the central incisors and step osteotomy line through the symphysis. Results: All reference points of the mandible including the condyles were displaced laterally irrespective of the osteotomy position, osteotomy method and distraction device. The anteroposterior or vertical displacements showed small differences between the groups. The widening pattern of the osteotomy line in the tooth-borne type of device was v shaped, and that of bone-borne type was a reverse v shape. However, the pattern in the hybrid type was parallel. The lateral displacement of the mandibular angle by the bone-borne device was more remarkable than the other types of devices. The displacement by the $30^{\circ}$ angulated tooth-borne type was different between the left and right sides in both the transverse and anteroposterior aspects. Conclusion: The design of the distraction devices and osteotomy line can influence the displacement pattern and the stress distribution during mandibular symphyseal distraction osteogenesis procedures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.299-299
• /
• 2007

후막형 무기 EL (electro-luminescence) 소자는 제조공정이 간단하고, 얇고, 가볍고, 유연한 동의 많은 장점들 때문에 휴대폰의 키패드 (key-pad) 및 광고용 back-light용으로 사용되고 있다. 이 무기 EL 소자는 비교적 손쉬운 스크린 프린팅 (screen-printing) 법으로 대면적을 제작할 수 있지만, LED (light emitting diode) 등과 비교하여 밝기가 낮아서 그 응용 분야가 제한되고 있다. EL 소자의 형광층은 전면 전극과 후면 전극 사이에 위치한다. EL은 이 형광층에 고 전기장이 걸릴 때, 전기장에 의해 가속된 전자가 형광층 내부에 첨가된 발광 중심의 전자를 여기시키고, 여기된 전자가 다시 바닥상태로 완화될 때 빛이 방출되는 현상이다. 즉, EL 소자는 이러한 전자 발광 현상을 이용한 소자로서, 전압 인가 시 발광 면 전체가 균일하게 발팡하는 평면 광원이다. 이러한 EL 소자에서 휘도의 증가는 후면 전극과 형광층 사이에 삽입되는 유전체 층의 특성과 밀접한 연관성이 있다. 본 연구에서는 고휘도 무기 EL 소자를 제작하기 위하여 이 유전체 층의 특성과 소자의 성능 사이의 관계를 알아보고자 하였다. 유전체 층에 사용하기 위해서 $BaTiO_3$-PVDF (polyvinylidene fluoride)의 복합체 필름을 제조하였다. 먼저 이 복합체 필름을 스크린 프린팅 (screen printing) 법으로 코팅하기 위한 페이스트 제작을 위해서, PVDF 수지를 용제에 녹였다. 그 다음, 일반 혼합기 및 삼단 롤밀 혼합기 (3-roll milling mixer) 등을 이용하여 $BaTiO_3$ 분말과 PVDF 용액을 다양한 비율로 혼합하여 페이스트를 제조하였다. ITO가 증착된 PET Film에 스크린 프린팅 법을 사용하여 형광층, 유전층, 배면 전극 등을 차례로 코팅하였다. $BaTiO_3$ (BT) 분말과 복합체 필름의 XRD 분석 결과, 분말 시료와 복합체 시료 모두 페로브스카이트 구조의 BT 회절선만 관찰되었다. 복합체의 단면 SEM 관찰에서는, BT 분말의 무게비가 증가할수록 더 치밀한 구조를 보여줌을 확인하였다. 또 EL소자의 유전상수와 휘도도 BT 분말의 혼합비가 증가할수록 증가하였다. 본 연구에서 제작한 무기 EL 소자의 최대 휘도는 약 $130\;cd/m^2$ 정도로 측정되었는데, 이는 휴대폰 키패드의 back-light용 광원으로 사용하기 충분하다고 판단되어진다.

• Pediatric Infection and Vaccine
• /
• v.25 no.3
• /
• pp.141-147
• /
• 2018

Purpose: Despite effectiveness and safety of maternal tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination, Tdap vaccination coverage during pregnancy remains quite low. We assessed the knowledge, attitude and practice on maternal Tdap vaccination among pregnant women. Methods: This study was a cross-sectional survey of pregnant women who visited tertiary obstetrics and gynecologic units in Seoul and Gyeonggi province of Korea. Individual questionnaires were administered to assess knowledge, attitude and practice on maternal immunization with Tdap. Results: The questionnaires were completed by 184 pregnant women; 158 (86%) had not received information from doctors about pertussis and Tdap, and 166 (90%) did not know the need for Tdap vaccination. Only 7% of pregnant women unlikely to receive Tdap vaccine during current pregnancy answered 3 or more of the 5 knowledge-based questions correctly. By logistic regression analysis, recommendation by doctor (adjusted odd ratio [OR], 236.2; 95% confidence interval [CI], 12.6-4,432), belief that the vaccine is effective (adjusted OR, 40.21; 95% CI, 2.35-687.7), and belief that the vaccine is safe (adjusted OR, 19.83; 95% CI, 1.54-255.9) were significantly important factors to respondents' intention to be vaccinated. Conclusions: Most pregnant women seem to be neither recommended nor adequately informed about Tdap vaccination. Information given by health care professionals is very important to increase Tdap coverage among pregnant women.

• Korean Journal of Heritage: History & Science
• /
• v.45 no.1
• /
• pp.218-231
• /
• 2012

A total of 126 fossil scaphopods (121 specimens from the Hagjeon Formation and 5 specimens from the Duho Formation) were found from the Cenozoic strata, Hagjeon and Duho Formations, Pohang Basin, Korea. Five species belonging two genera (Fissidentalium yokoyamai, F. sp. A, B, and Rhabdus sp. A, B) were classified: the most dominant species is Fissidentalium yokoyamai. The species of Fissidentalium yokoyamai is characterized by curved shell (accuration=3.90%) and very closely spaced longitudinal ribs on shell surfaces, while the species of Rhabdus is a nearly straight shell characterized by concentric growth lines without longitudinal ribs. Identification of two genera is somewhat easy due to such morphological differences but classification at generic level is hard because diagnostic features (e.g., cross section and apical structure) are lost in the most specimens. Consequently, except for Fissidentalium yokoyamai, the rest were classified temporarily as F. sp. A, B, and Rhabdus sp. A, B. Two types of preservation state were recognized: one is three-dimensionally preserved specimen (3D specimen) and the other is compressed specimen. Internal parts of the 3D specimen is filled with clastic sediments identical to the surrounding sediments of the shells, which is not observed in the compressed specimens. It is, thus, concluded that the 3D fossils were originally empty but internal cavity were immediately filled with the sediments, which may have protect from the compaction due to pressure during deposition of the gravelly to coarse sandstone of the Hagjeon Formation.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.2
• /
• pp.297-306
• /
• 2019

Since the centrifugal force acts on the flow in the curved channel, a transverse water surface gradient occurs and the thalweg is biased toward the outer bank. The submerged vanes may be used to solve various engineering problems of the curved channels. In order to analyze the influence of an attack angle and the distance between the vane arrays on the river bed variation and the superelevation in a bend, movable bed hydraulic experiments were conducted in a $90^{\circ}$ curved rectangular channel of a small-size gravel bed. Installing the submerged vanes in the bend increases the maximum scour depth. But if vanes are installed in a uniform obtuse angle, the scour depth may be reduced. If the flow rate in the channel bend with vanes equals to the channel forming discharge, the location of the maximum scour depth moved to the downstream and the superelevation increased. However if the flow rate is smaller than that, the location of the maximum scour depth moved upstream and the superelevation decreased. The channel bed change and the superelevation due to the installation of the submerged vanes have been dependent on the interaction of the attack angle, the flow rate, and the distance between the arrays.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.92-101
• /
• 2020

It is necessary to develop a rational method for evaluating the safety of bridges for the passage of inseparable crane vehicles exceeding the limit weight. In this study, the same method applied to the development of the recently introduced reliability-based highway bridge design code - limit state design method is applied to the calibration of the live load factor for the crane vehicle. Structural analysis was performed on the concrete bridge and the required strengths of the previous design code, the current design code and AASHTO LRFD were compared. When comparing the unfactored live load effect, the live load of the crane was greater than that of the current and previous design code. When comparing the required strength by applying the calibrated live load factor, the previous design code demands the largest strength and the current design code and the crane live load effect yields similar value. The results of safety evaluation of the actual bridges on the candidate route for the crane passage secured the same reliability as the target reliability index required by the design code and the strength of the cross section of the actual bridge is calculated greater than the required strength for the passage of the crane, which confirms the safety for the passage of the crane.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.2
• /
• pp.9-17
• /
• 2022

To take into account of the increasing speed of next generation high-speed trains, a new design code for the traffic safety of railway bridges is required. To solve dynamic responses of the bridge, this research offers a numerical analyses of PSC (Pre-stressed Concrete) box girder bridge, which is most representative of all the bridges on Gyungbu high-speed train line. This model takes into account of the inertial mass forces by the 38-degree-of-freedom and interaction forces as well as track irregularities. Our numerical analyses analyze the maximum vertical deflection and DAF (Dynamic Amplification Factor) between simple span and two-span continuous bridges to show the dynamic stability of the bridge. The third-order polynomial regression equations we use predict the maximum vertical deflections depending on varying running speeds of the train. We also compare the vertical deflections at several cross-sectional positions to check the influence of running speeds and the maximum irregularity at a longitudinal level. Moreover, our model analyzes the influence lines of vertical deflection accelerations of the bridge to evaluate traffic safety.