• Journal of KSNVE
• /
• v.9 no.3
• /
• pp.593-599
• /
• 1999

A rotordynamic analysis is performed with a motor-bull gear rotor system supported on two partial bearings, which is intended to drive a high-speed turbo-chiller compressor impeller shaft through its built-in pinion gear. The motor-bull gear rotor system has a rated speed of 3,600 rpm, and is modeled utilizing the finite element method for analysis. As loadings on the bearings due to the gear action are significant in the system considered, each resultant bearing load is calculated statically by considering the generalized forces of the gear action as well as the rotor itself. The two support partial bearings are designed to take their varying loads along with their varying load angles, and they are also analyzed to give their rotordynamic coefficients. Then, a complex rotordynamic analysis of the motor-bull gear rotor-bearing system is carried out to evaluate its whirl natural frequencies and mode shapes and unbalance responses under various loading conditions. Results show that the bearings and entire rotor system are well designed regradless of operating conditions, i.e., loads and operating speeds.

• Communications of Mathematical Education
• /
• v.24 no.3
• /
• pp.709-730
• /
• 2010

The inverse function of a one-to-one correspondence is explained with a graph, a numerical formula or other useful expressions. The purpose of this paper is to know how low achieving students understand the learning contents needed reversible thinking about irrational functions. Low achieving students in this study took paper-pencil test and their written answers were collected. They made various mistakes in solving problems. Their error types were grouped into several classes and identified in this analysis. Most students did not connected concepts that they learned in the lower achieving students to think in reverse order in case of and to visualize concepts of functions. This paper implies that it is very important to take into account students' accommodation and reversible thinking activity.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.35 no.5
• /
• pp.277-286
• /
• 2022

The elastic and inelastic responses obtained from the experimental and analytical results of two RC building structures under the service level earthquake (SLE) and maximum considered earthquake (MCE) in Korea were used to weinvestigate the characteristics of the mechanisms resisting shear and torsional behavior in torsionally unbalanced structures. Equations representing the interactive effect of translational drift and torsional deformation on the shear force and torsional moment were proposed. Because there is no correlation in the behavior between elastic and inelastic forces and strains, the incremental shear forces and incremental torsional moments were analyzed in terms of their corresponding incremental drifts and incremental torsional deformations with respect to the yield, unloading, and reloading phases around the maximum edge-frame drift. In the elastic combination of the two dominant modes, the translational drift mainly contributes to the shear force, whereas the torsional deformation contributes significantly to the overall torsional moment. However, this phenomenon is mostly altered in the inelastic response such that the incremental translational drift contributes to both the incremental shear forces and incremental torsional moments. In addition, the given equation is used to account for all phenomena, such as the reduction in torsional eccentricity, degradation of torsional stiffness, and apparent energy generation in an inelastic response.

• Korea journal of population studies
• /
• v.22 no.2
• /
• pp.73-96
• /
• 1999

본 연구의 목적은 1980년대 중반부터 약 10여년 동안 현저한 출생시 성비불균형을 경험한 대구지역의 경산부들을 대상으로 아들을 낳기 위한 노력에 미치는 요인들을 밝히는데 있다. 1998년 4월부터 6월까지의 3개월동안 대구지역의 6개 종합병원에 내원한 임산부들 가운데 출산 경험이 있는 경산부를 대상으로 실시한 설문조사자료를 사용하였으며 경산부의 아들 낳기 노력에 영향을 미치는 요인들을 규명하기 위하여 로지스틱 회귀분석을 도입하였다. 연구결과에 따르면 대구지역의 경산부들은 여성에 대한 성차별을 많이 느끼고 있을 뿐만 아니라 아들 선호의식 역시 상당히 높은 것으로 나타났다. 연구대상자들의 24.7%는 임신 전 아들을 낳기 위한 노력은 한 경험이 있다고 응답하였으며 12.2%는 태아의 선별적 인공유산을 통하여 아들을 낳기 위한 노력을 시도한 경험이 있는 것으로 밝혀졌다. 로지스틱 회귀분석 결과에 따르면 여성에 대한 성차별, 아들선호의식, 자녀 가운데 아들이 없는 경우, 인공임신중절수술 및 연령 등의 요인들이 조사대상자들의 아들을 낳기 위한 노력에 통계적으로 유의미한 영향을 미치는 것으로 밝혀졌다. 이러한 결과로 미루어 보아 대구지역의 출생시 성비가 다른 지역보다 높은 이유는 아들을 선호하고 여성을 차별하는 의식의 기반이 되었던 과거 농경 중심사회의 오랜 전통이 상대적으로 많이 남아있는 보수적인 성향의 결과라 할 수 있다. 뿐만 아니라 이러한 성향이 소자녀관으로 변화된 현대에 있어도 아들 하나는 꼭 낳아야겠다는 강한 집념이 현대 의료기기의 발달 및 보급과 의료인들의 영리추구와 이해관계가 부합됨으로써 생겨난 결과로 볼 수 있다. 시설입소의 인종간 차이를 통제할 때 소수인종노인이 백인노인보다 쉽게 자녀동거에서 단독거주로 이행하는데 이는 소수인종에서 가족부양체계가 불안정함을 의미한다. 또한 빈곤시에 소수인종 노인은 백인노인에 비하여 쉽게 자녀와 떨어져 살게 된다. 이러한 결과는 소수인종 노인에 대한 가족의 지원은 그 가족의 경제적 제약속에서 매우 안정적이지 못함을 시사한다. 못함을 시사한다.로 판단된다.(가솔린, 등유, 경유)로 회수 가능하였다..01 (n=10), 4세포기배는 1.05$\pm$0.09 (n=10)를 나타냄으로써 수정란의 단계마다 $E_2$의 반응 결과가 차이가 남을 알 수 있었다. 4. $E_2$농도 곡선에서 PMSG 처리 후 $E_2$의 혈중농도는 계속적인 상승을 보이다가 배란시기에 최고치를 나타내었으며, 배란 후 다시 감소하여 8세포기에서는 급격한 감소현상이 나타났다. 이후 다시 상실기를 거쳐 배반포기 임신기간동안 $E_2$의 농도가 상승하였다. 5. $E_2$처리 후 세포내 $Ca^{2+}$ 농도변화의 결과로, $E_2$를 처리하지 않은 난자들의 세포내 $Ca^{2+}$ 농도는 836.4$\pm$131.2 (n=10), $E_2$를 처리한 난자들은 1736.4$\pm$192.0 (n=10)로써 유의한 (P<0.05) 차이를 보였다. 이상의 결과로부터 $E_2$처리에 의한 세포내

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.7
• /
• pp.761-768
• /
• 2010

This paper presents an effective method to achieve the wideband waveform for high resolution SAR(Synthetic Aperture Radar) using the frequency multiplication technique. And also this paper analyzes the root causes for the spectral regrowth due to 3rd-order intermodulation in chirp bandwidth expansion scheme using quadrature modulator and frequency multipliers. The amplitude and phase imbalance requirement are defined based on the simulation results in terms of quadrature channel imbalance. This minimizes the degradation of range resolution, peak sidelobe ratio and integrated sidelobe ratio. The wideband chirp generator using the frequency multiplier and memory map scheme was manufactured and the compensation technique was presented to reduce the spectral regrowth of SAR waveform by minimizing the amplitude and phase imbalance. After I and Q channel imbalance adjustment, the carrier level reduces －28.7 dBm to －53.4 dBm. Chirp signal with 150 MHz bandwidth at S-band expands to 600 MHz bandwidth at X-band. The sidelobe levels are reduced by about 8 to 9 dB by compensating the amplitude balance between I and Q channels.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.10a
• /
• pp.319-323
• /
• 1996

\ulcorner\ulcorner\ulcorner\ulcorner 80,000 rpm \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner(ultra-centrifuge)\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner(critical speed)\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner(separation margin)\ulcorner \ulcorner\ulcorner, \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner-\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner, \ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner(extra slender shaft)\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner, \ulcorner\ulcorner 1\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner(bumper ring) \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner(guide bearing)\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner. \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner(finite element method)\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner, \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner\ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner \ulcorner\ulcorner\ulcorner \ulcorner\ulcorner(damping)\ulcorner \ulcorner\ulcorner\ulcorner\ulcorner.

• Korean Journal of Culture and Social Issue
• /
• v.29 no.3
• /
• pp.275-304
• /
• 2023

This study aimed to examine the mechanisms underlying digital game usage behavior by applying the Theory of Planned Behavior and the Balance Theory. It investigated the influences of attitude, subjective norms, and perceived behavioral control on the intention to use digital games, as well as the differences in the application of the Theory of Planned Behavior model based on the balance state among individuals, significant others, and digital games. A total of 315 responses from adult PC game users were collected through an online survey conducted from October 21 to 25, 2021, and were analyzed using multiple regression analysis. The results revealed that attitude and perceived behavioral control had a significant positive impact on the intention to continue using digital games, while subjective norms did not exert a significant influence. By categorizing groups into balanced, unbalanced, and imbalance states based on the balance relationship, the application of the Theory of Planned Behavior model showed that in the unbalanced and imbalance groups, both perceived behavioral control and attitude had a positive impact on the intention to continue using digital games. However, in the balanced group, attitude only had a positive impact on the intention to continue game usage. This study contributes to understanding digital game users by examining both individual psychological factors and the influence of others on digital game usage behavior.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.42 no.12
• /
• pp.2049-2067
• /
• 2013

The purpose of this study is to present a more effective nutrition education activation plan. As a result of investigating the dietary education operating situation, 58.9% underwent direct education, and 89.5% underwent food life education through traditional food culture succeeding business operation. The results from investigating the recognition regarding dietary education are as follows. The activation level by education types was as low as 2.24 points, the necessity was as high as 4.54 points, the difficult point in performing food life education was 'overwork' with 4.43 points, and the teaching activity ability level was 'can effectively prepare a teaching guidance plan' at 2.96 points. As a result of investigating the nutrition consultation operating situations, 62.8% underwent it and all of the students as well as some parents and teachers performed it. The consumed time per consultation for effective nutrition consultation was 10~20 minutes, the required education equipment and data were 'consultation program' with 40.3%, and the important content during consultation was 'contents related to eating habits' with 70.5%, which was recognized as the most important.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.523-530
• /
• 2006

A rotordynamic analysis was performed with a dry vacuum pump, which is a major equipment in modern semiconductor and LCD manufacturing processes. The system is composed of screw rotors, lobes picking air, helical gears, driving motor, and support rolling element hearings of rotors and motor. The driving motor-screw rotor system has a rated speed of 6,300rpm, and was modeled utilizing a rotordynamic FE method for analysis, which was verified through the results of its 3-D finite element model. As loadings on the bearings due to the gear action were significant in the system considered, each resultant bearing load was calculated determinately and indeterminately by considering the generalized forces of the gear action as veil as the rotor itself. Each resultant hearing loading was used in calculating each stiffness of rolling element bearings. Design goals are to achieve wide separation margins of critical speeds and favorable unbalance responses of the rotor in the operating range. Then, a complex rotordynamic analysis of the system was carried out to evaluate its forward synchronous critical speeds, whirl natural frequencies and mode shapes, and unbalance responses under various unbalance locations. Results show that the entire system is well designed in the operating range. In addition, the procedure of rotordynamic analysis for dry vacuum pump rotor-bearing system was proposed and established.

• Tribology and Lubricants
• /
• v.28 no.6
• /
• pp.265-271
• /
• 2012

In the preceding Part I study, for improving the unbalance response vibration of a large PRT motor-generator rotor fundamentally by design, a series of design analyses were carried out for bearing improvement by retrofitting from original plain partial journal bearings, applied for operation at a rated speed of 1,800 rpm, to final tilting pad journal bearings. To satisfy evenly key basic lubrication performances such as the minimum lift-off speed and maximum oil-film temperature, a design solution of 5-pad tilting pad journal bearings and maximizing the direct stiffness by about two times has been achieved. In this Part II study, a detailed rotordynamic analysis of the large PRT motor-generator rotor-bearing system will be performed, applying both the original plain partial journal bearings and the retrofitted tilting pad journal bearings, to confirm the effect of rotordynamic vibration improvement after retrofitting. The results show that the rotor unbalance response vibrations with the tilting pad journal bearings are greatly reduced by as much as about one ninth of those with the plain partial journal bearings. In addition, for the tilting pad journal bearings there exist no critical speed up to the rated speed and just one instance of a concerned critical speed around the rated speed, whereas for the plain partial journal bearings there exist one instance of a critical speed up to the rated speed and two instances of concerned critical speeds around the rated speed.