• Journal of the Korean GEO-environmental Society
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• v.15 no.4
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• pp.43-51
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• 2014

A Large-diameter drilled shaft of deep water depth composite foundation supporting a high rise pylon of the test designed super long span bridge was designed by allowable stress design method and failure probability through reliability analysis to bearing capacity was estimated. The allowable stress design results for the bearing capacity of a drilled shaft were analyzed by reliability analysis and the probability of failure shows 0.12 % in case of CFEM, 0.0002 % in case of Korea Highway Corporation criterion, and 0.003 % in case of structure foundation design criterion. In the allowable stress design, the bearing capacity of a large-diameter drilled shaft was obtained by applying to safety factor 3 and reliability analysis for the results was done. If the failure probability suggested by AASHTO(2007) specification is set to 0.02 %, the socketed length of a drilled shaft shows an increase of 25 % in CFEM, decrease of 60 % in KHCC, and decrease of 89 % in SFDC.

• Journal of Technologic Dentistry
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• v.45 no.2
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• pp.39-47
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• 2023

Purpose: This study aimed to confirm the applicability of gloss polishing using automatic barrel finishing with respect to three-dimensional (3D)-printed resin specimens. The surface roughness and grinding angle of the 3D-printed resin specimens were observed with respect to gloss polishing time using automatic dental barrel finishing. Methods: Herein, experiments were conducted on four types of 3D-printed resin specimens. The specimens, with a thickness of 100 ㎛ each, were printed using a 3D printer. Subsequently, light polymerization was performed on these specimens for 15 min. Post this surface treatment, the specimens underwent grinding for 25 min. This process was followed by gloss polishing at 5-min intervals for up to 25 min using automatic dental barrel finishing. The specimens were photographed using a 3D optical microscope, and their surface roughness and grinding angle were measured. Results: The Ra (centerline average roughness) values of all the specimens, except for crown & bridge 10 group and those in the control group that were not polished using automatic barrel finishing, were <0.2 ㎛. However, polishing time needs to be controlled to realize the desired surface roughness and grinding amount considering the hardness of the resin used. Conclusion: Gloss polishing of 3D-printed resin can be realized using automatic dental barrel finishing. However, polishing time needs to be controlled to realize the desired surface roughness and grinding amount considering the hardness of the resin used.

• Journal of Technologic Dentistry
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• v.45 no.2
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• pp.31-38
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• 2023

Purpose: This in vitro study aimed to compare the trueness of 3-unit fixed dental provisional prostheses (FDPs) fabricated by three different additive manufacturing and subtractive manufacturing procedures. Methods: A reference model with a maxillary left second premolar and the second molar prepped and the first molar missing was scanned for the fabrication of 3-unit FDPs. An anatomically shaped 3-unit FDP was designed on computer-aided design software. 10 FDPs were fabricated by subtractive (MI group) and additive manufacturing (stereolithography: SL group, digital light processing: DL group, liquid crystal displays: LC group) methods, respectively (N=40). All FDPs were scanned and exported to the standard triangulated language file. A three-dimensional analysis program measured the discrepancy of the internal, margin, and pontic base area. As for the comparison among manufacturing procedures, the Kruskal-Wallis test and the Mann-Whitney test with Bonferroni correction were evaluated statistically. Results: Regarding the internal area, the root mean square (RMS) value of the 3-unit FDPs was the lowest in the MI group (31.79±6.39 ㎛) and the highest in the SL group (69.34±29.88 ㎛; p=0.001). In the marginal area, those of the 3-unit FDPs were the lowest in the LC group (25.39±4.36 ㎛) and the highest in the SL group (48.94±18.98 ㎛; p=0.001). In the pontic base area, those of the 3-unit FDPs were the lowest in the LC group (8.72±2.74 ㎛) and the highest in the DL group (20.75±2.03 ㎛; p=0.001). Conclusion: A statistically significant difference was observed in the RMS mean values of all the groups. However, in comparison to the subtractive manufacturing method, all measurement areas of 3-unit FDPs fabricated by three different additive manufacturing methods are within a clinically acceptable range.

• International Journal of Highway Engineering
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• v.4 no.2 s.12
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• pp.1-8
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• 2002

Latex modified concrete(LMC) became to be applied as a new material for newly constructed bridge deck overlays in Korea due to its excellent bond strength, flexural strength and impermeability against water and chloride. However, it could not be adopted at repair job site because of its long curing time required. Thus, a research on latex modified concrete with rapid-setting cement(RSLMC) is necessary if it could develope the sufficient strength for early opening to traffic. This study focused on the durability of latex modified concrete with rapid-setting cement mainly on water permeable resistance and freeze-thaw resistance. The main experimental variables were latex contents(0, 5, 10, 15 and 20%) and antifoamer contents (0, 1.6, 3.2, 4.8 and 6.4%). Test results show that the permeability of RSLMC is very low indicating below 100 coulombs at 15% of latex contents at all antifoamer contents. The freeze-thaw resistance of RSLMC maintains above 90% of relative dynamic modulus at 3.2% of antifoamer content until 300 freezing-thawing cycles.

• Journal of Technologic Dentistry
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• v.19 no.1
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• pp.91-111
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• 1997

An aim of this study is to find out influenced factors of satisfaction degree on the clinical practice for the dental technology student and it can be provided the basic necessary data for the educational planning of the curriculum for the clinical practice. The target of study are selected form 7 junior health college students and colleges are located in around seoul form 14 junior health college throughout the nation. The questionnaries were distributed between 24th Feb to 30th July in 1997 to the 100 dental technicians who finished clinical practice and entered profession in 1997. All collected data were analysed by using SPSS/PC, Technical Statistic, One-Way ANOVA, Ttest, Person Correnlation Coefficient, Chrobach Alpha Coefficient and the result of the study is follow. 1) The satisfaction degree were classificated as 7 aspect and overall average score was 3.042. During that period satisfaction of personal relation aspect(M=3.737) shows highest level. Satsfiaction of clinical parctice(M=3.571) shows as second, Satisfiaction of environment(M=3.028), Satisfaction of guidance(M=2.915), satisfaction of subject are ordered of their scores. According to above study satisfaction's degree of subject show lowest level. 2) According to the result of verification of study. general character of student and satisfiaction degree has not much relation with sex, location of college, religion, period for enrolling college, teaching method of clinical practice. But the result show similar relation with following items. Satisfaction if subject and satisfaction of clinical practice(P=0.000), place of clinical practice and satisfaction of clinical practice(P=0.002), Academic record of college and satisfaction of clinical practice(P=0.000). 3) The relation of satisfaction(Subject, method of teaching, environment, period, rating, personal relation) of clinical practice and age of investigation's target Older student show higher satisfaction(P=0.040). Also method of teaching, environments, period, rating, personal relation has similarities with satisfaction. Therefore student who has higher satisfaction of clinical practice they also have higher rate for subject, environment, period, personal relation. 4) The result fo investigation, most interesting subject was crown & bridge and most difficult factor was too many simple-works to the student. One of ideal factor was discussing with counselor before they choose place for clinical practice. Third grade and first semester is most efficient time for clinical practice and 8 week is proper period for clinical practice. Clinical practice is absilutory mecessary and we find out most student rated positively. However we need more specific study about satisfcation of each subject. Because it shows lowest level and we need more pay attention for planning of clinical practice.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.145-150
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• 2004

In this study for the prosthesis of the spatial and directional sensation for the blind, an ultrasonic scale system and an electronic compass system were developed. The ultrasonic scale utilizes 40 ㎑ sound for the detection of distance to the barrier and the spatial information is transferred to the blind by various sound interval, which is proportional to the distance. The electronic compass utilizes a magnetoresistor bridge for the detection of the magnetic field strength of earth in horizontal plane. The information for the direction of the earth's north is transferred by tactile stimuli by a vibrating motor band around upper head. Detection distance of the ultrasonic scale is ranged from 0.065 to 3.26 meters, and the detection angle resolution of the electronic compass is about 22.5 degrees. The integrated system of the ultrasonic scale and the electronic compass was developed. Distance information is converted to the location of the tactile stimulation along the clockwise direction by a vibrating motor according to the distance installed around upper head of the blind. The intent of this article is to provide an practical prosthetic tool of spatial and directional sensation for the blind. Daily practice of this system will improve the usefulness of this system.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.1
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• pp.53-60
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• 2009

Isolated structures use devices such as high damping rubber bearings (HDRB) in order to dramatically reduce the seismic forces transmitted from the substructure to the superstructure. The laminated rubber bearing is the most important structural member of a seismic isolation system. The basic characteristics of rubber bearings have been confirmed through compression tests, compressive shearing tests and creep tests. This paper presents the results and analysis of a 1000hr, ongoing creep test conducted at 7.5MPa, 8.37MPa in our laboratory. The long-term behavior of bridge bearings, such as high-damping rubber bearings, will be discovered through a compression creep test subjected to actual environmental conditions. These tests indicated that the maximum creep deformation is about $0.3{\sim}1.92%$ of total rubber thickness.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1704-1710
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• 2010

The structure of a 2D grid-like copper(II) complex [Cu$(NCO)_2$(pyz)](pyz=pyrazine) (1) consists of 1D chains of Cu-pyz units connected by double end-on (EO) cyanato bridges. Each Cu(II) ion has a distorted octahedral coordination, completed by the four EO cyanato and two pyrazine ligands. Magnetic interactions through EO cyanato and pyrazine bridges in 1 are discussed on the basis of DFT broken-symmetry calculations at the B3LYP level. For model dicopper(II) complexes I (bridged by cyanato) and II (bridged by pyrazine), electronic structure calculations reproduce very well the experimental couplings for the S = 1/2 ferromagnetic and antiferromagnetic exchange-coupled 2D system: the calculated exchange parameters J are +1.25 $cm^{-1}$ and -3.07 $cm^{-1}$ for I and II, respectively. The $\sigma$ orbital interactions between the Cu $x^2-y^2$ magnetic orbitals and the nitrogen lone-pair orbitals of pyrazine are analyzed from the viewpoint of through-bond interaction. The energy splitting of 0.106 eV between two SOMOs indicates that the superexchange interaction should be antiferromagnetic in II. On the other hand, there are no bridging orbitals that efficiently connect the two copper(II) magnetic orbitals in I because the HOMOs of the basal-apical NCO bridge do not play a role in the formation of overlap interaction pathway. The energy separation in the pair of SOMOs of I is calculated to be very small (0.054 eV). This result is consistent with the occurrence of weakly ferromagnetic properties in I.

• PNF and Movement
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• v.17 no.3
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• pp.441-450
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• 2019

Purpose: This study identified the co-activation of quadriceps and hamstring muscles during hamstring strengthening exercises in healthy adults. Methods: Twenty-one participants were required for the present study design to achieve 80% power, 0.8 effect size (η2), and an alpha level of 0.05. Thus, this study recruited 21 healthy adults. All participants performed Nordic exercises, bridge exercises, and one-leg deadlifts randomly. The activity of the rectus femoris, vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (SM) were measured. In addition, the ratios of VM/VL and hamstring/quadriceps (HQ) were measured during the three hamstring strengthening exercises using electromyography. One-way ANOVA was used to compare the co-activation of quadriceps and hamstring muscles in the three exercises. Results: The activity of VM and VL during the performance of one-leg deadlifts was significantly higher than the other two exercises. The BF had significantly higher activity during the Nordic exercises compared to the other two exercises. In addition, the SM activation was significantly greater during Nordic exercises than one-leg deadlifts. Additionally, there was significant difference in HQ ratio among hamstring strengthening exercises. In specific, the one-leg deadlifts yielded a significantly lower HQ ratio. Conclusion: This study revealed that one-leg deadlifts are effective in rehabilitation for anterior cruciate ligament injury. In addition, Nordic exercises can be recommended to facilitate hamstring muscle activation.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.535-542
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• 2005

Two series of experiments on the performance of beam-column joints in High-Strength Reinforced concrete frames were carried out. Main experimental parameters were : concrete strength, column axial load and amount of joint hoop reinforcement. Test result showed that the ultimate shear strength of exterior joints increased of column axial compressive force and the amount of the joint hoop reinforcements. Through the regression analysis on the 24data, the following equation is obtained $jv_u=(2.935{\times}10-3\;{\rho}jw{\cdot}fy\;+\;0.365){\sqrt{f_{ck}}}$