• Journal of the Korean Society for Nondestructive Testing
• /
• v.26 no.1
• /
• pp.18-24
• /
• 2006

Reactor core and internal structures of a liquid metal reactor (LMR) can not be visually examined due to an opaque liquid sodium. The under-sodium viewing technique by using an ultrasonic wave should be applied far the visual inspection of reactor internals. In this study, an ultrasonic waveguide sensor with a strip plate has been developed for an application to the under-sodium viewing technique. The Lamb wave propagation of a waveguide sensor has been analyzed and the zero-order antisymmetric $A_0$ plate wave was selected as the application mode of the sensor. The $A_0$ plate wave can be propagated in the dispersive low frequency range by using a liquid wedge clamped to the waveguide. A new technique is presented which is capable of steering the radiation beam angle of a waveguide sensor without a mechanical movement of the sensor assembly The steering function of the ultrasonic radiation beam can be achieved by a frequency tuning method of the excitation pulse in the dispersive range of the $A_0$ mode. The technique provides an opportunity to overcome the scanning limitation of a waveguide sensor. The beam steering function has been evaluated by an experimental verification. The ultrasonic C-scanning experiments are performed in water and the feasibility of the ultrasonic waveguide sensor has been verified.

• Journal of the Society of Disaster Information
• /
• v.11 no.4
• /
• pp.570-580
• /
• 2015

In the study, planning indicator that should be considered in applying traffic calming technique was derived, and it was intended to analyze the importance of indicator that should most considered in planning traffic calming technique through AHP analysis on the basis of it. The result of planning indicator may be summarized by dividing into road section and crossing section. In road section, hump (0.35) for equipment stimulating reduction of speed, hump image/fort (0.31) for visual control equipment, and slalom type road (0.52) for chicane, and bollard (0.47) for blocking passing route are shown to be the most important and come before anything. In crossing section, signal indicator (0.33) for visual control equipment, rumble strip (0.44) for equipment stimulating reduction of speed, zigzag type road (0.65) for chicane, and blocking going straight at crossing (0.45) for blocking passing route are shown to be the most important and come before anything. The result of the study is judged to be used for basic material in applying traffic calming technique and establishing policy hereafter.

• The Journal of Korean Academy of Prosthodontics
• /
• v.36 no.6
• /
• pp.858-866
• /
• 1998

Soldering is the usual method used to correct an unstable fixed partial denture framework at patient's try-in; However, presoldering base metal alloys is technique-sensitve and results are unstable because it is difficult to maintain uniform heat distribution and to prevent oxidation of an alloy. A cast-joining technique has been developed by Weiss and Munyon for repair, correction and addition to base metal framework. This joining technique eliminates the problem with presoldering of non-precious frameworks. The object of this study was to 1) compare the relative flexure strength and the joining effectiveness of Ni-Cr-Be cast in two pieces and 'pre-soldered' versus in two pieces and 'cast-joined'. 2) determine the effect of increasing the number of retentive grooves on the face of the cast and 3) determine the effect of the relative matched position of groove patterns on flexure strength. The joining effectiveness can be expressed by the ratio of the mean flexure stress of soldered or cast-joined specimens to that of one-piece cast. Resin rods 3mm in diameter were used as pattern of specimens for one-piece casted, presoldered, and cast-joined groups. Cast-joined specimens had two different patterns of retentive grooves on the joined faces. Type A had cross-shaped grooves 1mm in depth. 0.6mm in width. Type B was the same except for the addition of one more retentive groove. In the experiment connecting cast-joined specimens, half of specimens with type A pattern had their patterns on the faces of paired casts matched with each other as mirror image. With the rest pairs, it was proceeded that one of paired casts turned 45 degrees so that the patterns crossed. Half of specimens with type B pattern also had the patterns matched as mirror image; However, here, one of paired casts turned 90 degrees with the other pairs. Retentive groove in this study lacked the intentional undercuts, in contrast with the suggestion of Weiss and Munyon. The specimens were subjected to four-point flexural loading in an Instron testing machine. The midspan flexural stress was calculated at the point of initial plastic strain as determined from a strip-chart recorder or at the point of failure if this occured at a lower stress level. Within the scope of this study, the following results were obtained. 1. The presoldered group showed flexural strength at least 2 times higher than the cast-joined groups. Its joining effectiveness was 82%. 2. In cast-joined groups, the flexural strength of joints with type B patterns exhibited 1.5 times that of joints with type A patterns. Joining effectivenesses were 38% for type B patterns, 25-26% for type A patterns. 3. The relative matched position of groove patterns did not have any significant effect on flexural strength of the cast-joined specimens with either type A patterns or type B patterns(p>.05).

• Journal of Chest Surgery
• /
• v.41 no.3
• /
• pp.320-328
• /
• 2008

Background: Numerous surgical devices for mitral repair have been used in the past with good results. In this study we describe a simple annuloplasty technique with using a new device ($Mitracon^{(R)}$). The aim of this study was to assess its efficacy and surgical results with using $Mitracon^{(R)}$. Material and Method: From May 2003 to October 2005, 46 patients (21 women and 25 men (mean age of $51.4{\pm}17.8$ years) with mitral regurgitation from various causes were treated with either the $Mitracon^{(R)}$ (the $Mitracon^{(R)}$ group) or the Capentier Edward rigid ring (the CE group). The median follow-up duration was 18.9 months. Result: The mean grade of mitral regurgitation before and immediately after surgery in the $Mitracon^{(R)}$ group and the CE group decreased from $3.2{\pm}0.8$ to $0.6{\pm}0.7$ and $3.4{\pm}0.7$ to $0.3{\pm}0.5$, respectively. There were no significant changes in the ejection fraction either between the two groups or before and immediately after surgery. No deaths were seen in either group. Early postoperative echocardiography of all 46 patients showed only trivial mitral regurgitation or none at all. Echocardiography at a median of 18.9 months also showed no progression in mitral regurgitation. The mean grade of mitral regurgitation in the $Mitracon^{(R)}$ group at this time point decreased from $3.2{\pm}0.8$ to $0.8{\pm}0.7$ (p<0.05). The CE group also showed a similar degree of decrease from $3.4{\pm}0.7$ to $0.3{\pm}0.6$ (p<0.05). The mitral valve area in the $Mitracon^{(R)}$ group at 1 year follow-up was $3.3{\pm}0.9cm^2$. The mitral valve area in the CE group was $2.7{\pm}0.6cm^2$. The mean mitral pressure gradient in the $Mitracon^{(R)}$ group at 1 year follow-up was $3.1{\pm}1.3$ mmHg. The mean pressure gradient in the CE group was $4.5{\pm}2.1$ mmHg, although any statistical significant difference for this between the groups was not reached. Conclusion: The present study showed the described technique to be safe and effective in the intermediate term. Because long term results are unavailable, a more extensive prospective randomized multicenter trial may be warranted to determine whether this procedure should be generally applied for repair of mitral valve disease.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.413-416
• /
• 2007

In general, by means of the electrodepositing technique, a copper foil sample was prepared with a high purity and a high density. But the mechanical properties of the electrodepositing copper foil was lower than it's the rolling copper foil. However, the production of copper foil with approximately 36 microns thick in rolling process was very difficult. This paper describes the outline of the high accuracy cold rolling in 6 high mill which was developed for the purpose of rolling very thin accurate gauge copper foil(36 micron thick), and give several rolling characteristic of 600 mm wide copper foil. a) Large strain can be accumulated pass by pass in industrial multi-pass rolling processing to overcome large critical strain for thickness accuracy through optimization of rolling schedule. b) Also, permissible tension for rolling 0.45 $\sim$ 0.036 mm thick copper strip stably in accordance with the each pass work had been established by FEM simulation results. c) During the plate rolling process, considerable values of the forces of material pressure on the tool occur. These pressures cause the elastic deformation of the roll, thus changing the shape of the deformation region. A numerical simulation of roll deflection during cold rolling is presented in the paper. d) The proposed pass schedule can roll very thin copper foil of 36 micron thickness to a tolerance of ${\pm}1$ microns. The validity of simulated results was verified into rolling experiments on the copper foil.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.12 no.1
• /
• pp.36-49
• /
• 1987

A planar waveguide model is presented for calculating dispersion characteristics of the normalized phase velocity and characteristic impedance with the frequency dependent effective dielectric constand and effective width in microstrip lines of the hybrid mode. Eeff(f) and Weff(f) are applied to a planar waveguide model by using an empirical relations and formula designed for CAD purposes as a function of frequency. A wide range of relative dielectric constants and the strip $h_{width}$strate height(W/h ratios), $0.5$\leq$W/h\leq2.5$ are used. These results are compared with static value, spectral domain analysis, and empirical results. As the result of a computer simulation, in the case of using a planar waveguide model, the frequency dependent normalized phase velocity is more closely approached to 1/ and characteristic impedance is more increased than the other method that has already been presented as the increasing of the frequency. And, the case of applying Eeff(f) designed for the purpose of CAD to this proposed model is show in better result than the case of using a empirical relations.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.1
• /
• pp.151-160
• /
• 1994

Recently, terrestrial photogrammetry has been applied effectively to data acquisition in GIS and to monitoring precise machinery for simulation test. Because 3-D coordinates of many object points can be quickly measured with constant accuracy and easy modeling by this method. In this study, the composition concerned with multi-camera system which simultaneously analyzes structure from multi-station using various cameras was developed. The errors of results were analyzed to investigate the accuracy of the system, error of unknown points and control points, convergent and strip adjustment for optimal network design also. As results of this study, the efficiency of multi-camera system developed here was proved through application to monitoring the entire area of the precise model ship. We could also acquire 3-dimensional coordinates with good accuracy by arranging pass points. Therefore, possibility of measurement of instantaneous deformation as well as precision analysis of structures can be suggested.

• Journal of the Society of Disaster Information
• /
• v.13 no.1
• /
• pp.81-88
• /
• 2017

In this paper, the behaviour of composite steel-CFRP members is studied experimentally and using FE-analysis. The use of advance composite materials in construction for repair and rehabilitation has become a frequent used method in the last decade. FRP composites have many advantages over the traditional technique of steel bonding for a number of reasons: 1. Composites add little or no additional weight to a building, eliminating the need for costly foundation strengthening. 2. FRP composites are very thin (1.2mm to 1.4mm). So there is no loss of floor space and negligible effect over the architectural aspect. 3. FRP composites do not corrode, this makes it long lasting. However, the method is yet to become a mainstream application due to a number of economical and design related issues. Brittle debonding failure, aging effect on bonding, broad based awareness and proper design guidelines are the main concern for future research works. This paper is focused on the ultimate load carrying capacity of the CFRP-strengthened beams and their effect on the deflection and failures modes by varying the amount of CFRP content.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.1
• /
• pp.8-13
• /
• 2010

In this paper, a new hairpin type strip-line BPF(Band Pass Filter) improving the suppression performance of unwanted frequency signal is studied. A modified hairpin filter is designed by classical hairpin filter design methodology and is realized by newly placing structure of designed filter. And a newly formed coupled-line effects between modified bilateral symmetry structures make the transmission zeros. Each transmission zeros can shift its frequency to wanted frequency by tuning a certain part of filter. To investigate the validity of this novel technique, an order-5 Chebyshev BPF centered at 9.2 GHz with a 15 % FBW(fractional bandwidth) were used. According to design and measurement results, a good performance of insertion loss of 0.8 dB and unwanted signal suppression of maximum 50 dB is achieved at full input/output ports.

• The Korean Journal of Physiology
• /
• v.29 no.2
• /
• pp.233-241
• /
• 1995

The nonapeptide bradykinin has been shown to exhibit an array of biological activities including relaxation/contraction of various smooth muscles. In order to investigate the effects of bradykinin on the contractility and the electrical activity of antral circular muscle of guinea-pig stomach, the isometric contraction and membrane potential were recorded. Also, using standard patch clamp technique, the $Ca^{2+}-activated$ K currents were recorded to observe the change in cytosolic $Ca^{2+}$ concentration. $0.4 {\mu}M$ bradykinin induced a triphasic contractile response (transient contraction-transient relaxation-sustained contraction) and this response was unaffected by pretreatment with neural blockers (tetrodotoxin, atropine and guanethidine) or with apamin. Bradykinin induced hyperpolarization of resting membrane potential and enhanced the amplitude of slow waves and spike potentials. The enhancement of spike potentials was blocked by neural blockers. Both the bradykinin-induced contractions and changes in membrane potential were reversed by the selective $B_2$-receptor antagonist $(N{\alpha}-adamantaneacetyl-_{D}-Arg-[Hyp, Thy,_{D}-Phe]-bradykinin)$. In whole-cell patch clamp experiment, we held the membrane potential at -20 mV and spontaneous and transient changes of Ca-activated K currents were recorded. Bradykinin induced a large transient outward current, consistent with a calcium-releasing action of bradykinin front the intracellular calcium pool, because such change was blocked by pretreatment with caffeine. Bradykinin-induced contraction was also blocked by pretreatment with caffeine. From these results, it is suggested that bradykinin induces a calciumrelease and contraction through the $B_{2}$ receptor of guinea-pig gastric smooth muscle. Enhancement of slow wave activity is an indirect action of bradykinin through enteric nerve cells embedded in muscle strip.