• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1327-1336
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• 2012

In this paper, the dual-faced monopole antenna, which is arranged by numerous rectangular ring patches in sequence for the multi-bands is proposed. The ring type structure of the patch can be increased the bandwidth. Therefore the bandwidth and beam width are improved by using multiple arrayed patches. When the ring type patches are inserted serially, the resonance frequencies are occurred by the current flow from the first ring patch. It is possible because the gap between the patches is very narrow. In addition, if the patches are composed on the same plane as the feed-line, fabrication could be very difficult because the gap between the patches is extremely narrow. The thickness and permittivity of the antenna, moreover, are very important parameters because both sides of the substrate are used. We finally found the optimal thickness and permittivity to generate the coupling effect by simulation. All patches are consisted of 4-steps which the patch size was decreased 85 % by each step. In conclusion, the resonant frequency bands are 1.75~2.6 GHz(850 MHz), 3.24~3.46 GHz(220 MHz), 3.8~4.0 GHz(200 MHz), and 4.4~4.9 GHz(500 MHz).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.482-487
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• 2001

This paper introduces a Lorentz force type four-pole self-bearing motor, where the new pole arrangement of a stator is intended to function both as a synchronous PM motor and as a magnetic bearing. The Lorentz force type has some good points such as linearity of control force, freedom from flux saturation, and high efficiency unlike conventional self-bearing motors. Mathematical expressions of torque and radial force are derived to show that they can be separately controlled regardless of rotational speed and time. To verify the proposed theory, a prototype is made, where a ring-shape outer is actively controlled in two radial directions while the other motions are passively stable supposing the radial stability. Through some experiments, it is shown that the proposed scheme can provide high capability and feasibility for a small high-speed self-bearing motor.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.11
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• pp.1027-1033
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• 2010

A two-phase (gas-liquid) flow is a common phenomenon in fluidic systems, e.g., fluidic systems in the electro-magnetic or nuclear power generation industry and in the steel industry. The measurement of a two-phase flow is important for guaranteeing the safety of the system and for achieving the desired performance. The measurement of the void fraction, which is one of the parameters of the two-phase flow that determines the pressure drop and heat transfer coefficient, is very important. The time resolution achieved by employing the impedance method that can be used to calculate the void fraction from the impedance of the fluid is high because the electric characteristics are taken into account. Therefore, this method can be employed to accurately measure the void fraction without distortion of flow in real time by placing electrodes on the walls of the tubes. Coney analytically studied a ring-type impedance meter, which can be employed in a circular tube. The aim of this study is to experimentally verify the robustness of a three-ring impedance meter to variations in the electric conductivity of the fluid; this robustness was suggested by Coney but was not experimentally verified.

• Journal of Chest Surgery
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• v.9 no.2
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• pp.251-264
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• 1976

Forty three patients with disease of the aorta were admitted in this department during the period from beginning of 1956 to the end of 1976. They consisted of eighteen cases of aortic aneurysms, eight cases of Takayasu's arteritis, eight Leriche syndromes, six dissecting aneurysms, two aortic coarctations and one case of vascular ring. Of eighteen aortic aneurysms, twelve were operated resulting in eight survivors. Three of four mortalities were in shock preoperatively because of aneurysmal rupture. Among six dissecting aortic aneurysms, four were type III and two were type I according to DeBakey's classification. For the purpose of relief of acute arterial insufficiency in the lower extremities, a re-entry operation grafting a Y-shaped dacron vessel between abdominal aorta and common iliac arteries was performed. The patient regained consciousness soon after the operation and was well until postoperative second day, when severe convulsion developed abruptly and died. And in a chronic case of type III dissecting aneurysm, a dacron graft bypass shunt between ascending aorta and lower descending thoracic aorta with resection of the aneurysm was performed, but acute severe aortic insufficiency developed soon after the operation and fell into intractable heart failure resulting in death. The cause of the aortic insufficiency seems to be retrograde dissection from the proximal anastomosis site in the ascending aorta. Three cases were treated medically with Wheat's regimen. Two of them survived with relief of symptoms. Eight patients of Takayasu's arteritis were all females and aged between twenty and forty-four averaging twenty nine. Bypass graft operation between aortic arch and carotid arteries using Y-shaped nylon prostheses were performed in three patients resulting in death in two cases postoperatively due to severe cerebral arterial insufficiency during the procedure. All the patients with Leriche syndrome were males and over forty. In two cases, bypass graft with Y-shaped dacron vessel between terminal aorta and common iliac or femoral arteries were performed with good result. Thromboembolectomy or thromboendarterectomy was employed in three patients, of whom one was aggravated in sexual problem postoperatively. One out of two aortic coarctations and a vascular ring were treated surgically with excellent results.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.483-488
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• 2016

The present study proposes an economical embedded ring-sensor that can measure a strain behavior of cement paste and mortar in early age. Using the proposed ring-sensor, the experimental method is proposed that can measure the setting time of the cement paste and mortar conveniently. The experimental study has been conducted using the mixtures of which W/C are 0.30, 0.35, 0.40, and 0.45. From the test result, the setting times measured by convectional test methods such as vicat method and penetration resistance method are compared with the setting time proposed by this study. The result reveals that the proposed ring-sensor can effectively measure the early age behavior so that can evaluate the time when the contraction starts. In addition, the contraction starting time can be regarded as a rational setting time, which is similar to the initial setting of convectional test methods.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.4
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• pp.55-63
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• 2009

This paper reports on the theoretical and experimental study of the pressure ripples in a pressure unbalanced type vane pump which have widespread use in industry. Because they can infinitely vary the volume of the fluid pumped in the system by a control. Pressure ripples occur due to the flow ripples induced by geometry of side plate, leakage flow, reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume when the pumping chamber connected with the outlet volume. In this paper, we measured the pressure variation of a pumping chamber, reaction force on a cam ring, the mathematical model for analyzing the pressure ripples which included vane detachment and fluid inertia effects in notch area has been presented, and was applied to predict the level and the wave form of the pressure ripples according to operating conditions.

• Composites Research
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• v.22 no.6
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• pp.45-51
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• 2009

The marginal integrity at the composite resin-tooth interface has been analyzed in real time through acoustic emission (AE) monitoring during the polymerization shrinkage of composite resin subjected to the light exposure. It was found that AE signals were generated by the polymerization shrinkage. Most AE hit events showed a blast type signal having the principal frequency band of 100-200kHz. Bad bonding states were indicated by many hit events in the initial curing period of 1 minute with high contraction rate. The quantity of hit events for the human molar dentin specimen was much less than that for the steel ring specimen but more than that for the PMMA ring specimen. The better the bonding state, the less the AE hit events. The AE characteristics were related with the tensile crack propagation occurring in the adhesive region between the composite resin and the ring substrate as well as the compressive behavior of the ring substrate, which could be used for a nondestructive characterization of the marginal disintegrative fracture of the dental restoration.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.104-105
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• 2006

We succeeded the synthesis of new functional polymers by novel ring-opening addition reactions of bis(oxetane)s with diacyl chlorides, di(active ester)s, and di(carboxylic acid)s using quaternary onium salts as catalysts at appropriate conditions. Hyperbranched polyesters with many pendant hydroxy groups were also synthesized by the polyaddition of bis(oxetane)s with tricarboxylic acid, or by the self-polyadditions of $AB_2\;or\;A_2B$ type monomers containing oxetane group. The anionic ring-opening polymerization of (3-ethyl-3-hydroxymethyl)oxetane was examined using sodium tert-buthoxide to give hyperbranched poly(ether)s containing one oxetanyl group and many hydroxyl groups in the end of polymer chain.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.360-366
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• 2001

This paper show the designing, manufacturing and performance test procedure of a high speed, fixed ratio planetary roller type traction drive as a speed reducer. The arrangement and size design for sun roller, planetary rollers and ring roller are carried out and a proper pre-load mechanism are adopted. To improve transmitting power capacity and endurance limit, nitro-carburized bearing steel and a synthetic traction oil are used. The manufactured and assembled traction drive operated successfully under unloaded conditions. Further tests for various load and speed conditions are executing now to improve the performance of the traction drive.

• Journal of Chest Surgery
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• v.16 no.1
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• pp.3-9
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• 1983

Congenital mitral stenosis is a rare cardiac lesion which frequently associated with other congenital anomalies of the heart and great vessels. There are many difficulties in its preoperative diagnosis and choice of adequate treatment. We present two cases of congenital mitral stenosis who have had operated in this hospital at March 1981 and January 1983. One was 13 years old female with isolated, type III mitral stenosis who had mitral valve replacement with Ionescu-Shiley bioprosthetic valve, the other was 2 years and 3 months old female with supramitral ring associated with VSD and PDA who had operation of resection of supramitral ring and repair of associated lesions. Postoperative course of both cases is excellent except one episode of sudden supraventricular tachyar-rhythmia on latter case and it was controlled by medical treatment.