• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.735-741
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• 1986

An experimental study on the effects of exhaust pipe curvature on the performance of a diesel engine is presented. The experiments were carried out on a 4-cycle, 216 c.c diesel engine and two types of pipe curvature, circular arc and rectangle, were tested. The shaft output, shaft torque and specific fuel consumption were obtained by inserting bent pipes of different dimensions into the exhaust pipe at various engine operation conditions. It was found that the engine performance was decreased by the circular arc bent pipe and the effects were dominated by its arc angle. The decrease of engine performance was minimized by the arc angle of 180.deg.. By the rectangle pipes the performance was more decreased and the effects were little influenced by its dimensions.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.167-175
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• 1999

Many composite girder bridges have been constructed for about thirty five years. Nowadays they are aged or deteriorated because of the increase in traffic and vehicle loads. In this study, the effect of strengthening with glass fiber sheet is investigated to estimate the possibility for applying to damaged prestressed concrete bridges. One normal and eight cracked specimens which had been preloaded were tested. The cracked specimens were strengthened with either external prestressing or bonding glass fiber sheet, or using both methods. The results showed that the maximum loads are almost same for both methods. So it seems that the strengthening with glass fiber sheet can be used for strengthening damaged prestressed concrete girders. It is important that proper devices should be selected to prevent glass fiber sheet from premature bonding failure below its maximum load, which is similar to end anchorage problem in external prestressing method. It is proved that the devices proposed in this paper have sufficient anchoring capability to increase load carrying capacity.

• Journal of Advanced Navigation Technology
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• v.20 no.4
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• pp.344-351
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• 2016

In the present study, a dual-band multiple-input-multiple-output (MIMO) antenna covering WLAN frequency bands of 2.4 GHz (2.4 ~ 2.484 GHz) and 5 GHz (5.15 ~ 5.825 GHz) is newly presented to avoid use of decoupling structure for increasing isolation. The antenna consists of two L-shaped slots with n-shaped slots etched on the floating ground plane surrounded by open ended L-shaped slots which are placed in the left and right corner of PCB respectively. The proposed antenna is designed and fabricated on one side of FR4 substrate with dielectric constant of 4.3, thickness of 1.6 mm, and size of $50{\times}50mm2$. It has been observed that the measured impedance bandwidths ($S_{11}{\leq}-10dB$) are 0.3 GHz (2.28 ~ 2.58 GHz) in 2.4 GHz frequency band and 0.89 GHz (5.11 ~ 6 GHz) in 5 GHz frequency band respectively. In addition, It has been observed that the whole efficiency are more than 80 % in the whole operating frequency band and envelope correlation coefficient of the antenna is less than 0.05 as a very small value in spite of nothing of the decoupling structure.

• Journal of Korean Ophthalmic Optics Society
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• v.6 no.1
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• pp.13-29
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• 2001

A mathematical model was proposed to analyze the vibration of diaphragm, such as the contact lenses fitted on the eyes, being subjected to the external sinusoidal pressure. The model incorporates the differential equations and their numerical solution program, based on the wave equations. Turbo-C and graphic software, formulated to describe the dependence of the various parameters involved in the vibration. The model predicts the radial distribution of amplitude, frequency dependence of both average displacement amplitude and the power of diaphragm whose edge is being either simply supported or rigidly clamped in vibration. The effect of variables such as thickness, radius, damping coefficients on the vibration characteristics was illustrated by the computer simulation of the derived program. As the frequency of driving pressure increases above the certain value determined by the boundary conditions and parameters the wave shape or pattern changes from simple arc to belly or loops having double antinode. It seems that the effect of outer antinode progressively increases as the frequency increases. If this kind of phenomena occurs to the contact lens on the cornea in vivo, it may cause an abnormal correction power in the lenses or pull off the eye due the increased rise of outer part of the lens.

• Journal of the Korean Chemical Society
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• v.66 no.6
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• pp.493-508
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• 2022

Chemistry is the subject which includes properties, change, and composition of matter. Chemistry has the system which explains observable properties and change with microscopic level, it explains them using scientific theory and laws. In the national-level curriculum, the properties and changes of matter are continuously dealt with from elementary school to high school, and the curriculum are organized so that students could strengthen their understanding about matter. In other words, understanding of the properties and changes of matter is the base to explain everyday life with the view of chemistry, and these two are classified as domains of chemistry in the 2015 revised science curriculum. In this study, we confirmed students' understanding about properties of matter and change of matter, through the analysis about results of the National Assessment of Educational Achievement (NAEA). For that purpose, this study analyzed the 12 items about properties of matter, and 19 items about change of matter, which were used in the NAEA from 2015 to 2019. According to the results of classifying and analyzing questions according to the core concept, the understanding about the two domains significantly changed between the proficient achievement-level students and basic achievement-level students. Depending on the achievement-level, there was a difference in explaining the phenomenon by using the perspective of particles, and by associating scientific concepts and models, or there was a difference in understanding the inquiry related to these two domains. Based on this analysis, this study discussed some implications to be improved on teaching-learning for 'properties of matter', and 'change of matter'.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.6
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• pp.114-122
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• 2011

We propose an automatic localization technique based on Uniform Arc Length Sampling (UALS) of 360 degree range sensor data. The proposed method samples 3D points from dense a point-cloud which is acquired by the sensor, registers the sampled points to a digital surface model(DSM) in real-time, and determines the location of an Unmanned Ground Vehicle(UGV). To reduce the sampling and registration time of a sequence of dense range data, 3D range points are sampled uniformly in terms of ground sample distance. Using the proposed method, we can reduce the number of 3D points while maintaining their uniformity over range data. We compare the registration speed and accuracy of the proposed method with a conventional sample method. Through several experiments by changing the number of sampling points, we analyze the speed and accuracy of the proposed method.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.77-81
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• 2014

This paper propose a method to detect moving object and locating in real time from video sequence. first the proposed method extract moving object by differencing two consecutive frames from the video sequence. If the interval between captured two frames is long, it cause to generate fake moving object as tail of the real moving object. secondly this paper proposed method to overcome this problem by using doppler effects and HSV color model. finally the object segmentation and locating is done by combining the result that obtained from steps above. The proposed method has 99.2% of detection rate in practical and also this method is comparatively speed than other similar methods those proposed in past. Since the complexity of the algorithm is directly affects to the speed of the system, the proposed method can be used as low complexity algorithm for real time moving object detection.

• Analytical Science and Technology
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• v.30 no.6
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• pp.348-354
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• 2017

In this study, patterns of proteome expression were monitored and specifically expressed proteins in human milk were detected in collected human milk after 1 week, 3 weeks, and 6 weeks from delivery. A quantitative shotgun proteomic approach was used to identify human milk proteins and reveal their relative expression amounts. For each sample, two independent human milk samples from two mothers were pooled, and then three replicated shotgun proteomic analyses were carried out. Casein, which is a highly abundant protein in human milk, was removed, and then trypsin was treated to produce a digested peptide mixture. The peptides were loaded in the home-made reversed-phase C18 fused-silica capillary column, and then the eluted peptides were analyzed by using a linear ion-trap mass spectrometer. The relative quantitation of proteins was performed by the normalized spectral count method. For each sample, 81-109 non-redundant proteins were identified. The identified proteins consisted of glycoproteins, metabolic enzyme, and chaperon enzymes such as lactoferrin, carboxylic ester hydrolase, and clusterin. The comparative analysis for the 63 proteins, which were reproducibly identified in all three replications, revealed that 25 proteins were statically significant differentially expressed. Among the differentially expressed proteins, Ig lambda-7 chain C region and tenascin drastically decreased with the delivery time.

• Childhood Kidney Diseases
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• v.14 no.1
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• pp.51-61
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• 2010

Purpose : Previous studies have suggested that Chemokine (C-C motif) ligand-2 (CCL-2; also known as MCP-1) and CCL-5 (also known as RANTES) are possibly associated with the pathogenesis of various inflammatory and non-inflammatory renal diseases. The present study was conducted to investigate association of polymorphisms of CCL-2 and CCL-5 genes with childhood IgA nephropathy (IgAN). Methods : The authors analyzed six single nucleotide polymorphisms (SNPs) of CCL-2 and CCL-5 in 196 pediatric IgAN patients and in 285 healthy controls. We compared variations in SNPs between two several sets of IgAN subgroups, allocated by presence of proteinuria (>4 mg/$m^2$/hour), podocyte foot process effacement, and pathologically advanced disease markers, such as interstitial fibrosis, tubular atrophy, or global sclerosis. Results : Genotypic data of IgAN patients and controls showed no significant SNP frequency difference in both of of CCL-2 and CCL-5. Even though two linkage disequilibrium blocks were formed, there was no significance in the haplotype analysis. In the patient subgroup analysis, no SNP of CCL-2 and CCL-5 was found to be associated with the presence of proteinuria, podocyte foot process effacement, and pathologically advanced disease markers. Conclusion : Our data indicate that no association exists between CCL-2 and CCL-5 SNPs and childhood IgAN susceptibility, and presence of proteinuria, podocyte foot process effacement, and pathologic progression of IgAN.

• Elastomers and Composites
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• v.48 no.2
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• pp.148-155
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• 2013

The crosslinking density of polymer can be quantitatively calculated by the Flory-Rehner equation using the swelling experimental data and the lattice constant ${\beta}_1$ of interaction parameter (${\chi}$) in this equation should be chosen have used cautiously. This ${\beta}_1$ is the experimental data by rule of thumb, and researchers have used little different values respectively. Generally, the average molecular weight between crosslink points $M_c$ in the Flory-Rehner equation and the Mooney-Rivlin equation have the same value, and ${\beta}_1$ can be calculated when the $M_c$ in the Flory-Rehner equation is given. Therefore, in this research, firstly we calculated the $M_c$ using the selected ${\beta}_1$ (=0.34) and the swelling experimental data of 1,2,3-triazole polymer from the Flory-Rehner equation, secondly the $M_c$ from the Mooney-Rivlin equation is calculated by the tensile experimental data, and finally two $M_c$ were compared. As a result, two $M_c$ values were almost the same, and it was proved that the ${\beta}_1$ (=0.34) was selected properly.