• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1218-1223
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• 2007

In this study, we experimentally investigate the equivalent ring theory for a slightly asymmetric ring. The slightly asymmetric ring has mode pair and frequency pair due to the small asymmetry and this mode pair generates beat in vibration and sound. In this paper, a slightly asymmetric ring is modeled as the equivalent ring, i.e., the assemblage of a symmetric ring and imperfect point masses. The equivalent ring has the same mode pair condition as that of the original asymmetric ring. Effect of the additional mass attachment is investigated by the equivalent ring theory and the result is compared with those of the measurement and the finite element analysis. It is confirmed that the original ring and the equivalent ring show the same change in frequency and mode under the various additional imperfection mass conditions. The equivalent ring theory explains how the asymmetric elements influence the mode characteristics and provides useful information to tune the beat property.

• Journal of electromagnetic engineering and science
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• v.4 no.1
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• pp.30-36
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• 2004

We determined equivalent circuit parameters of a 1.5 cell S-band RF gun cavity from the resonant characteristics of its decoupled cavities(half cell and full cell) using the code SUPERFISH. Equivalent circuit parameters of the 1.5 cell RF gun cavity resonated in the 0-mode were obtained easily from the circuit parameters of each decoupled cavities. In order to obtain equivalent circuit parameters for the $\pi$ -mode cavity, we calculated the differences of the resonant frequencies and the equivalent resistances between the 0- and $\pi$ -modes with slight variations of the radius and thickness of the coupling iris. From those differences, we obtained R/Q value and equivalent resistance of the $\pi$ -mode, which are directly related to the equivalent circuit parameters of the coupled cavity. Using calculated R/Q value, we can express equivalent inductance, capacitance and resistances of the RF gun cavity resonated in the $\pi$ -mode, which can be useful for analyzing coupled cavities in a steady state.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.516-519
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• 2012

This study proposes a method of an equivalent bell model in order to tune the beat period of a Korean bell. In a Korean bell having a slight asymmetry, each circumferential mode splits into a mode pair which has a slight difference in frequency, and the interaction of the mode pair makes a beat in vibration and sound. An equivalent bell model which consists of an axi-symmetric bell and an equivalent point mass, has the same mode property as in a real bell. The equivalent bell model is constructed by the finite element analysis based upon the theory of a revolutionary shell Using the equivalent bell model, the beat period is predicted when the bell thickness is locally decreased to improve the beat property. The predicted result is verified by experiment on a test bell. The proposed method is useful to save the time required for tuning the beat period of a large bell.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.25 no.2
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• pp.437-445
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• 1995

The purpose of this study was to evaluate the equivalent and effective dose, and estimate radiation risk to the critical organs of head and neck region from the use of adult and child mode in panoramic radiography. The results were as follows. 1. The salivary glands showed the highest equivalent and effective dose in adult and child mode. the equivalent and effective dose in adult mode were 837μSv and 20.93μSv, those in child mode were 462μSv and 11.54μSv, respectively. 2. Total effective doses to the critical head and neck organs were estimated 34.21μSv in adult mode, 20.14μSv in child mode. From these datas, the probabilities of stochastic effect from adult and child mode were 2.50x10/sup -6/ and 1.47x10/sup -6/. 3. The other remainder showed the greatest risk of fatal cancer. The risk estimate were 4.5 and 2.7 fatal malignancies in adult and child mode from million panoramic examinations. The bone marrow and thyroid gland showed about 0.1 fatal cancer in adult and child mode from these examinations.

• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.365-371
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• 2008

In this study, beat control method using an equivalent ring model is proposed to control beat period of a slightly asymmetric ring. Slight asymmetry in a ring generates mode pair and the interaction of the mode pair makes beat in vibration and sound. In a ring, as a simplified bell type structure, mode data are measured and an equivalent ring is determined so that the measured mode condition is satisfied. By the finite element analysis on the equivalent ring, changes of mode pair condition are predicted when local mass is attached or the local thickness is decreased. The predicted results are compared with the experimental result and the validity of the proposed method is verified.

• Nuclear Engineering and Technology
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• v.35 no.1
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• pp.1-13
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• 2003

In this study, an effective method to estimate the fundamental frequencies of co-axial cylinders immersed in fluid is proposed. The proposed method makes use of the equivalent mass or density that is derived from the added mass matrix caused by the fluid-structure interaction (FSI) phenomenon. The equivalent mass is defined from the added mass matrix based on a 2-D potential flow theory. The theory on two co-axial cylinders extended to the case of three cylinders. To prove the validity of the proposed method, the eigenvalue analyses upon coaxial cylinders coupled with fluid gaps are peformed using the equivalent mass. The analyses results upon various fluid gap is conditions reveal that the present method could provide accurate frequencies and be suitable for expecting the fundamental frequencies of fluid coupled cylinders in beam mode vibration.

• The Journal of the Acoustical Society of Korea
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• v.31 no.8
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• pp.561-568
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• 2012

This study proposes a method of an equivalent bell model in order to tune the beat period of a Korean bell. In a Korean bell having a slight asymmetry, each circumferential mode splits into a mode pair which has a slight difference in frequency, and the interaction of the mode pair makes a beat in vibration and sound. An equivalent bell model which consists of an axi-symmetric bell and an equivalent point mass, has the same mode property as in a real bell. The equivalent bell model is constructed by the finite element analysis based upon the theory of a revolutionary shell. Using the equivalent bell model, the beat period is predicted when the bell thickness is locally decreased to improve the beat property. The predicted result is verified by experiment on a test bell. The proposed method is useful to save the time required for tuning the beat period of a large bell.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1326-1335
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• 2019

Common mode (CM) chokes are a crucial part in EMI filters for mitigating the electromagnetic interference (EMI) of switched-mode power supplies (SMPS) and for meeting electromagnetic compatibility standards. However, the parasitic capacitances of a CM choke deteriorate its high frequency filtering performance, which results in increases in the design cycle and cost of EMI filters. Therefore, this paper introduces a negative capacitance generated by a negative impedance converter (NIC) to cancel the influence of equivalent parallel capacitance (EPC). In this paper, based on a CM choke equivalent circuit, the EPCs of CM choke windings are accurately calculated by measuring their impedance. The negative capacitance is designed quantitatively and the EPC cancellation mechanisms are analyzed. The impedance of the CM choke in parallel with negative capacitances is tested and compared with the original CM choke using an impedance analyzer. Moreover, a CL type CM filter is added to a fabricated NIC prototype, and the insertion loss of the prototype is measured to verify the cancellation effect. The prototype is applied to a power converter to test the CM conducted noise. Both small signal and EMI measurement results show that the proposed technique can effectively cancel the EPCs and improve the CM filter's high frequency filtering performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.2
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• pp.169-176
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• 2005

In this paper, a DC and small-signal AC modeling for the active-clamp, ful1-bridge boost converter is described. Based on the operation principle, the ac part of the converter can be replaced by a dc counterpart. Then, a conceptual equivalent circuit is derived by rearranging the switches. The equivalent circuit for this converter consists of CCM(Continuous conduction mode) boost and DCM(Discontinuous conduction mode) buck converter. The analyses for the equivalent CCM boost and DCM buck converter are done using the model of PWM switch. The theoretical modeling results are confirmed through experiment or SIMPLIS simulation.

• The Journal of the Acoustical Society of Korea
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• v.30 no.8
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• pp.436-445
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• 2011

In this paper, equivalent properties of 2-2 mode piezocomposites were studied. Variation of the properties of 2-2 mode piezocomposites was analyzed by the finite element method, and the result was compared with experimental measurement data to confirm the validity of the analysis. The equivalent properties of a single phase material to represent the piezocomposite composed of PZT-5H and polymer were derived by the asymptotic averaging method. Accuracy of the derived equivalent properties was enhanced by minimizing the discrepancy between the impedance spectra of full 2-2 piezocomposite and equivalent single phase material resonators of various vibration modes by the least square method. The equivalent properties of 2-2 piezocomposites derived in this study can be utilized to the design of diverse acoustic sensors.