• Imaging Science in Dentistry
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• v.31 no.4
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• pp.193-197
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• 2001

Purpose : To determine whether there is a relationship between abnormal temporomandibular joint radiographic findings and age or gender in a sample of preorthodontic patients. Materials and Methods : Individualized corrected sagittal tomographs of 188 temporomandibular joints in 94 preorthodontic patients, aged 11 to 29 years, were taken and viewed by an observer blinded to clinical records. The study population was divided into 2 aged groups (11-15 years and 16-29 years) for comparative purposes. Temporomandibular joint radiographic findings were classified as normal or abnormal. Results: There was no difference in ratio of abnormal to normal findings between the both aged groups. The frequency of osseous abnormalities was similar with that of abnormalities of condylar position. Abnormalities in CP and JS were most frequent in all aged groups. Conclusion : There is no significant difference between ages or genders for temporomandibular joint radiographic abnormalities.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.49-54
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• 2000

Korea Institute of Geology Mining and Materials(KIGAM) has been operating Korean Earthquake Monitoring System(KEMS) to archive the real-time data stream and to determine event parameters (epicenter origin time and magnitude)by the automatic processing and analyst review. To do this KEMS uses the Vindel Hue's velocity model which was derived from Wonju KSRS data. Because KIGAM now receives the real-time data from many stations including Wonju KSRS Cholwon seismo-acoustic array Uljin Wolsung Youngkwang Taejon Seoul Kimcheon Taegu etc. the proper velocity model should be established around the Korean peninsula, In this study P were velocity structures was derived from VELEST program using 69 events among the 835 events determined by KEMS in 1999 which were recorded by at least 5 stations. General trend of velocity structure was similar to Sang Jo Kim's model but velocity value was low in crust and high in upper mantle. Due to the sensitivity of inversion results to the initial input model the artificial short and blast data might be added.

• International Journal of Concrete Structures and Materials
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• v.2 no.1
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• pp.63-68
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• 2008

High performance concrete (HPC) is widely used in civil engineering due to its high durability and low permeability etc. Compared with ordinary concrete, HPC may develop much higher AS (autogenous shrinkage) at early age due to the relative low water cement (w/c) ratio and adding of mineral admixtures, which is one of the main reasons for early age micro-cracking of HPC structures. This paper studies the early age property of HPC columns under similar construction-site surroundings by embedded strain transducers. Results show that for HPC structure, early-age autogenous shrinkage especially within the first day after concrete pouring is pretty large. AS within the first day are 60% larger than those for 14 days in this research for all specimens. Therefore it should be taken into account for structure durability. By comparison of PHPC (plain HPC column) and RHPC (reinforced HPC column) specimens, the effects of reinforced bars on AS and temperature distribution have been analyzed. Also the influence of w/c ratio on AS is demonstrated.

• International Journal of Concrete Structures and Materials
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• v.6 no.2
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• pp.79-85
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• 2012

This paper presents the differences in growth of time-dependent strain values in reinforced cement concrete (RCC) and pre-stressed concrete (PSC) flexural members through experiment. It was observed that at any particular age, the time-dependent strain values were less in RCC beams than in PSC beams of identical size and grade of concrete. Variables considered in the study were percentage area of reinforcement, span of members for RCC beams and eccentricity of applied pre-stress force for PSC beams. In RCC beams the time-dependent strain values increases with reduction in percentage area of reinforcement and in PSC beams eccentricity directly influences the growth of time-dependent strain. With increase in age, a non-uniform strain develops across the depth of beams which influence the growth of concave curvature in RCC beams and convex curvature in PSC beams. The experimentally obtained strain values were compared with predicted strain values of similar size and grade of plane concrete (PC) beam using ACI 318 Model Code and found more than RCC beams but less than PSC beams.

• Journal of the Korean Wood Science and Technology
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• v.40 no.2
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• pp.101-109
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• 2012

Wood composites are a hygroscopic material and have ability to exchange its moisture content with air. This study investigated the formaldehyde emission and moisture content change of four wood composites (particleboard (PB), medium density fiberboard (MDF), high density fiberboard (HDF), laminated HDF (L-HDF)) as a function of bake-out temperature and time. The composites were baked out for 1, 3, 5, 7, 10, 14, 21, and 28 days at temperatures of $20{\pm}2$, $35{\pm}2$, and $50{\pm}2^{\circ}C$ in a dry oven. The moisture content change was used to determine the emission bake-out of the composites. Best bake-out time results were obtained with after 7 days all composites. Formaldehyde emission values of composites decreased with decreasing moisture content for both temperatures. The formaldehyde emission results of bake-out temperature 35 and $50^{\circ}C$ showed a similar tendency.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.2 s.233
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• pp.318-324
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• 2005

Theoretical efforts are performed to extend the formulation of NSLT(New Shear Lag Theory) for the prediction of the elastic modulus in short fiber composite. The formulation is based on the elastic stress transfer considering the stress concentration effects influenced by elastic modulus ratio between fiber and matrix. The composite modulus, thus far, is calculated by changing the fiber aspect ratio and volume fraction. It is found that the comparison with FEA(Finite Element Analysis) results gives a good agreement with the present theory (NSLT). It is also found that the NSLT is more accurate than the SLT(Shear Lag Theory) in short fiber regime when compared by FEA results. However, The modulus predicted by NSLT becomes similar values that of SLT when the fiber aspect ratio increases. Finally, It is shown that the present model has the capability to predict the composite modulus correctly in elastic regime.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.1
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• pp.133-143
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• 1997

Piezoelastic materials have recently attracted considerable attention because of their potential use in intelligent structural systems. In this paper, we treat a transient piezothermoelastic problem in a hexagonal plate of crystal class 6mm subjected to antisymmetric heating temperature. We analyze this problem by use of the potential function method. Numerical calculations are carried out for a cadmium selenide solid, and the results are presented graphically in comparison with those derived from the similar problem in a cadmium selenide plate subjected to symmetric heating temperature for a symmetry transient problem.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.416-421
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• 2005

Concrete are brittle materials and they are which come to brittle fracture rapidly by progress of cracks. Therefore, what the time for repairing the damage portion is understands importantly by such cracks. When they happened the glass pipe similar to concrete was used. Such a glass pipe can insert repair material in an inside, or can use it by switch. They are interested in the crack monitoring of structure using FM radio sensor and PZT sensor. In this study, the monitoring to a crack was studied using FM radio sensor and PZT sensor. Therefore, the purpose of this study is the fundamental research which detects damages of main members using the compound sensor which consisted of the radio sensors of resistance, PZT, and FM system.

• Journal of Magnetics
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• v.21 no.3
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• pp.364-373
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• 2016

The article presents the results and findings obtained through the assembly of opposing linear Halbach arrays from two magnet layers using large magnetic blocks from permanent NdFeB magnets, especially concerning the distribution of magnetic induction in an air gap. The use of these large blocks has led to a significant expansion of the area of magnetic field with a substantially higher value of magnetic induction in comparison with similar linear Halbach arrays composed of small magnets. The paper also discusses the determined dependences of magnetic induction on the parameters of the x, y, z coordinate system and indicates the possibilities of achieving an even stronger magnetic field in a larger volume of an air gap for application for instance in equipment for magnetic separation of raw materials, in instrument technologies and in other areas.

• Transactions on Electrical and Electronic Materials
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• v.16 no.6
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• pp.293-302
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• 2015

Degraded data stability, weaker write ability, and increased leakage power consumption are the primary concerns in scaled static random-access memory (SRAM) circuits. Two new SRAM cells are proposed in this paper for achieving enhanced read data stability and lower leakage power consumption in memory circuits. The bitline access transistors are asymmetrically gate-underlapped in the proposed SRAM cells. The strengths of the asymmetric bitline access transistors are weakened during read operations and enhanced during write operations, as the direction of current flow is reversed. With the proposed hybrid asymmetric SRAM cells, the read data stability is enhanced by up to 71.6% and leakage power consumption is suppressed up to 15.5%, while displaying similar write voltage margin and maintaining identical silicon area as compared to the conventional memory cells in a 15 nm FinFET technology.