• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2009.04a
• /
• pp.258-259
• /
• 2009

Pipe wall thinning is one of severe problems on structural safety in nuclear power plants. A guided wave can be a proper tool for the fast evaluation or monitoring. As for gradual wall thinnings, however, low sensitivity caused by the low reflection coefficient limits the use of the guided wave. In this work, instead of the guided wave reflection at the wall thinning, the variation of dispersion characteristics is concerned. SH waves were employed due to several advantages and the magnetostrictive patch transducers were used for the excitation and sensing of the SH waves. The proposed method were verified with some experiments and showed the feasibility as an effective tool for the inspection of gradual wall thinning.

• Journal of KSNVE
• /
• v.8 no.6
• /
• pp.1053-1061
• /
• 1998

In this paper. the power flow analysis(PFA) method is applied to the prediction of the vibrational energy density and intensity of coupled co-planar plates. To cover the energy transmission and reflection at the joint of the plates. the wave transmission approach is Introduced with the assumption that all the incident waves are normal to the joint. By changing the frequency ranges and internal loss factors. we have obtained the reliable PFA results. and compared them with the analytical exact solutions.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.23 no.2
• /
• pp.171-181
• /
• 2011

Recently, many studies have been attempted to save the cost of production and to build the ocean energy power generating system. The low-reflection structure with the wall-typed curtain which has a wave power generation system of OWC is known as the most effective energy conversion system. A three-dimensional numerical model was used to understand the characteristics of velocity of flows about compressed air and to estimate the pressure acting on the low-reflection structure due to the short-period waves. The three-dimensional numerical wave flume which is the model for the immiscible two-phase flow was applied in interpretation for this. The numerical simulation showed well about the changes in velocity of compressed air and the characteristics of pressure according to the change in the wave height and depth of the curtain wall. Additionally, the results found that there was the point of the maximum velocity of the compressed air when the reflection coefficient is at its lowest point.

• Journal of Navigation and Port Research
• /
• v.26 no.3
• /
• pp.289-294
• /
• 2002

The broadband high power 3-way combiner was designed and fabricated for the digital TV repeater. To achieve increase of the bandwidth and the high power capability, Wilkinson type power divider was adopted in our research. First of all, Wilkinson type power divider of equal-split and unequal-split were combined, and the characteristics of the four port in-phase power combiner was simulated for each thickness of dielectric substrates. As the results of simulation, the power combiner fabricated by using dielectric substrate of 120 mil-thickness has the characteristics as follows: insertion loss of less than -651 dB, reflection coefficient of less than -13 dB, isolation among the output ports of less than -15 dB, and pose difference among the output ports of smiler than 13$^{\circ}$. Therefore, this power combiner was possible to improve the limit of microstrip line width due to high impedance, the problem of power loss due to interaction between strip lines in a high power combiner and narrow bandwidth simultaneously. Furthermore, making broadband and high power could be achieved since the fabricated 3-way combiner has good characteristics of insertion loss, the reflection coefficient, separation between ports, and phase difference.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.7
• /
• pp.1160-1164
• /
• 2008

This paper presents an wideband stripline balun. And, the proposed balun is composed of one power divider and two phase converters on stripline substrate. The target characteristics of the proposed balun is the combination loss of below -0.05 dB, an amplitude imbalance of ${\pm}0.5\;dB$ and a phase imbalance of $180{\pm}10$ degrees, with the reflection coefficient(S11) of below -10 dB over frequencies ranging from 500 to 1500 MHz. The fabricated balun occupies the area of $12(W){\times}220(L){\times}2.3(T)\;mm3$. Experimental measurement shows that the fabricated balun has an amplitude imbalance of ${\pm}0.7\;dB$, a phase imbalance of $180{\pm}8$ degrees and an insertion loss of about -2 dB with the reflection coefficient(S11) of below -10 dB over frequencies ranging from 500 to 1,500 MHz.

• Journal of Korea Water Resources Association
• /
• v.53 no.10
• /
• pp.871-876
• /
• 2020

Understanding the wave characteristics near the outlet of coastal power plants for cooling water in the vicinity of the dredged areas is critically important for the construction and operation of the plants. By Employing the eigenfunction expansion method, in this study, we analyzed the reflection of monochromatic water waves over (1) shear currents near the outlet and (2) multi-arrayed trenches representing dredged areas. We firstly optimized the number of grids expressing shear currents and the number of evanescent modes based on a convergence test. We then analyzed the sensitivity of the reflection coefficients depending on (1) magnitude of shear currents, (2) width of shear currents, (3) a distance between adjacent trenches, and (4) a number of trenches. The results showed that the reflection coefficient was more sensitive to the number of trenches and the distance between trenches than the velocity of shear currents and the width of shear currents. We also found that even the effect of shear currents is relatively small, the effect is not negligible in a relative water depth from shallow to near shallow water waves (0.01 < kh ≦ 0.70).

• Journal of information and communication convergence engineering
• /
• v.11 no.1
• /
• pp.56-61
• /
• 2013

Modern integrated circuits (ICs) are becoming an integrated parts of analog, digital, and radio frequency (RF) circuits. Testing these RF circuits on a chip is an important task, not only for fabrication quality control but also for tuning RF circuit elements to fit multi-standard wireless systems. In this paper, RF test circuits suitable for embedded testing are introduced: RF power detectors, power control circuits, directional couplers, and six-port reflectometers. Various types of embedded RF power detectors are reviewed. The conventional approach and our approach for the RF power control circuits are compared. Also, embedded tunable active directional couplers are presented. Then, six-port reflectometers for embedded RF testing are introduced including a 77-GHz six-port reflectometer circuit in a 130 nm process. This circuit demonstrates successful calibrated reflection coefficient simulation results for 37 well distributed samples in a Smith chart. The details including the theory, calibration, circuit design techniques, and simulations of the 77-GHz six-port reflectometer are presented in this paper.

• Journal of Korean Critical Care Nursing
• /
• v.16 no.3
• /
• pp.87-98
• /
• 2023

Purpose : This descriptive survey investigated the effects of clinical nurses' critical reflection competency, professional pride, and person-centered care practices on patient safety management activities. Methods : The participants were 183 clinical nurses working at a tertiary hospital in South Korea. The questionnaires consisted of the Critical Reflection Competency Scale for Clinical Nurses Professional Pride the Person-Centered Nursing Assessment Tool and Patient Safety Management Activities. The collected data were analyzed using descriptive statistics, t-tests, ANOVA, Tukey's HSD, Pearson's correlation coefficient, and multiple regression using SPSS 29.0. Results : The mean score for patient safety management activities was 4.65±0.34 out of 5. There were significant differences in patient safety management activities according to age (F=3.90, p =.010), education level (t=-2.56, p =.013), total work experience (F=3.87, p =.010), and the number of healthcare accreditation system experiences (F=5.22, p =.006). Patient safety management activities were positively correlated with critical reflection competency (r=.337, p <.001), professional pride (r=.271, p <.001), and person-centered care practices (r=.399, p <.001). The results indicated that person-centered care practices affected patient safety management activities (𝛽=.358, p <.001) with the explanatory power of 22.5%. Conclusion : To improve clinical nurses' patient safety management activities, it is necessary to develop participatory educational programs that can integrate skills and attitudes based on conceptual knowledge of person-centered care. Intervention studies are needed to test the effect of person-centered care on patient safety when applied in clinical practice.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.8 no.6
• /
• pp.1158-1165
• /
• 2004

This paper describes the design of a two stage 1V power supply SiGe Low Noise Amplifier operating at 5.25㎓ for 802.lla wireless LAN application. The achieved performance includes a gain of 17㏈, noise figure of 2.7㏈, reflection coefficient of 15㏈, IIP3 of -5㏈m, and 1-㏈ compression point of -14㏈m. The total power consumption of the circuit was 7㎽ including 0.5㎽ for the bias circuit.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.04a
• /
• pp.236-238
• /
• 1997

A cellular power amplifier using an APCVD(Atmospheric Pressure Chemical Vapor Deposition)-grown SiGe base HBT of ETRI has been designed with a linear simulation CAD. The Si/SiGe HBT with an emitter area of 2$\times$8${\mu}{\textrm}{m}$$^2$typically has a cutoff frequency(f$_{T}$) of 7.0 GHz and a maximum oscillation frequency(f$_{max}$) of 16.1 GHz with a pad de-embedding A packaged power Si/SiGe HBT with an emitter area of 2$\times$8$\times$80${\mu}{\textrm}{m}$$^2$typically shows a f$_{T}$ of 4.7 GHz and a f$_{max}$ of 7.1 GHz at a collector current (Ic) of 115 mA. The power amplifier exhibits a Forward transmission coefficient(S21) of 13.5 dB, an input and an output reflection coefficients of -42 dB and -45 dB respectively. Up to now the III-V compound semiconductor devices hale dominated microwave applications, however a rapid progress in Si-based technology make the advent of the Si/SiGe HBT which is promising in low to even higher microwave range because of lower cost and relatively higher reproducibility of a Si-based process.ess.ess.