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Effects of stiffening rings on the dynamic properties of hyperboloidal cooling towers
Jun-Feng Zhang,Huai Chen,Yao-Jun Ge,Lin Zhao,Shi-Tang Ke 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.5
As hyperboloidal cooling towers (HCTs) growing larger and slender, they become more sensitive to gust wind. To improve the dynamic properties of HCTs and to improve the wind resistance capability, stiffening rings have been studied and applied. Although there have been some findings, the influence mechanism of stiffening rings on the dynamic properties is still not fully understood. Based on some fundamental perceptions on the dynamic properties of HCTs and free ring structures, a concept named “participation degree” of stiffening rings was proposed and the influence mechanism on the dynamic properties was illustrated. The “participation degree” is determined by the modal deform amplitude and latitude wave number of stiffening rings. Larger modal deform amplitude and more latitude waves can both result in higher participation degree and more improvement to eigenfrequencies. Also, this concept can explain and associate the pre-existing independent findings.
Jun-Feng Zhang,Yao-Jun Ge,Lin Zhao,Huai Chen 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.23 No.4
The influence mechanism of mean value components, noted as P0, on POD applications for complete random fields PC(t) and fluctuating random fields PF(t) are illustrated mathematically. The critical philosophy of the illustration is introduction of a new matrix, defined as the correlation function matrix of P0, which connect the correlation function matrix of PC(t) and PF(t), and their POD results. Then, POD analyses for several different wind pressure fields were presented comparatively as validation. It's inevitable mathematically that the first eigenmode of PC(t) resembles the distribution of P0 and the first eigenvalue of PC(t) is close to the energy of P0, due to similarity of the correlation function matrixs of PC(t) and P0. However, the viewpoint is not rigorous mathematically that the first mode represents the mean pressure and the following modes represent the fluctuating pressure when PC(t) are employed in POD application. When PC(t) are employed, POD results of all modes would be distorted by the mean value components, and it's impossible to identify P0 and PF(t) separately. Consequently, characteristics of the fluctuating component, which is always the primary concern in wind pressure field analysis, can only be precisely identified with P0 excluded in POD.
Zhang, Jun-Feng,Ge, Yao-Jun,Zhao, Lin,Chen, Huai Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.23 No.4
The influence mechanism of mean value components, noted as $P_0$, on POD applications for complete random fields $P_C(t)$ and fluctuating random fields $P_F(t)$ are illustrated mathematically. The critical philosophy of the illustration is introduction of a new matrix, defined as the correlation function matrix of $P_0$, which connect the correlation function matrix of $P_C(t)$ and $P_F(t)$, and their POD results. Then, POD analyses for several different wind pressure fields were presented comparatively as validation. It's inevitable mathematically that the first eigenmode of $P_C(t)$ resembles the distribution of $P_0$ and the first eigenvalue of $P_C(t)$ is close to the energy of $P_0$, due to similarity of the correlation function matrixs of $P_C(t)$ and $P_0$. However, the viewpoint is not rigorous mathematically that the first mode represents the mean pressure and the following modes represent the fluctuating pressure when $P_C(t)$ are employed in POD application. When $P_C(t)$ are employed, POD results of all modes would be distorted by the mean value components, and it's impossible to identify $P_0$ and $P_F(t)$ separately. Consequently, characteristics of the fluctuating component, which is always the primary concern in wind pressure field analysis, can only be precisely identified with $P_0$ excluded in POD.
Effects of stiffening rings on the dynamic properties of hyperboloidal cooling towers
Zhang, Jun-Feng,Chen, Huai,Ge, Yao-Jun,Zhao, Lin,Ke, Shi-Tang Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.5
As hyperboloidal cooling towers (HCTs) growing larger and slender, they become more sensitive to gust wind. To improve the dynamic properties of HCTs and to improve the wind resistance capability, stiffening rings have been studied and applied. Although there have been some findings, the influence mechanism of stiffening rings on the dynamic properties is still not fully understood. Based on some fundamental perceptions on the dynamic properties of HCTs and free ring structures, a concept named "participation degree" of stiffening rings was proposed and the influence mechanism on the dynamic properties was illustrated. The "participation degree" is determined by the modal deform amplitude and latitude wave number of stiffening rings. Larger modal deform amplitude and more latitude waves can both result in higher participation degree and more improvement to eigenfrequencies. Also, this concept can explain and associate the pre-existing independent findings.
Design, Modeling, and Analysis of a Railway Traction Motor With Independently Rotating Wheelsets
Oh, Ye Jun,Liu, Huai-Cong,Cho, Sooyoung,Won, Jun Hui,Lee, Hyungwoo,Lee, Ju IEEE 2018 IEEE transactions on magnetics Vol.54 No.11
<P>A conventional railway vehicle adopts the rigid-axle wheelset (RW) due to its inherently characteristics of automatic restoration capability without additional actuators or control. RW allows the railway vehicle to run to the center of the rail. However, there is no restoring force in independently rotating wheelsets (IRWs), if only traction torque control is applied as in RW. As a result, excessive wear and noise between the rail and the wheel are generated, and in severe cases a derailment may occur. In order for IRWs to generate restoring force, an active control strategy is needed that controls the left and right wheel torques independently. Because of this control characteristic, unlike the conventional traction motor of RW, fast torque response and precise torque control performance are required. In this paper, the design and modeling of an IRW traction motor were accomplished considering active restoring force control. A quasi-semi-closed slot structure is proposed to improve the power density and restoring torque control performance. In the next step, control simulation was performed using a static interior permanent magnet synchronous motor model considering slot harmonics. The validity of the proposed methods was verified through experiments using a dynamo.</P>
Optimal Tracking Performance of NCSs with Time-delay and Encoding-decoding Constraints
Jun-Wei Hu,Xi-Sheng Zhan,Jie Wu,Huai-Cheng Yan 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.4
In this paper, the tracking performance of networked control systems (NCSs) under energy constraints with time-delay and encoding-decoding is studied. Through spectral factorization and partial decomposition techniques, we can obtain the explicit representation of the optimal performance. It is shown that the optimal performance is affected by non minimum phase (NMP) zeros, unstable poles and other multiple communication constraints such as time-delay, encoding-decoding and additive white Gaussian noise (AWGN). At the same time, the obtained result shows that a two-parameter compensator is superior to a one-parameter compensator. In addition, it is found that time-delay, encoding-decoding and AWGN affected the tracking capability of NCSs. Finally, an example is given for verifying the correctness of the conclusions.
Effect of Material Characteristics on PMDC Motors based on the Grade of Electrical Steel Sheet
Jun-Young Kim,Dong-Woo Kang,Tae-Chul Jeong,Hyun-Soo Seol,Han Kim,Geo-Chul Jeong,Myung-Sik Jeong,Huai-Cong Liu,Ju Lee 한국자기학회 2019 Journal of Magnetics Vol.24 No.2
In this study, the effect of the material characteristics of electrical steel sheet on permanent magnet direct current (PMDC) motors is investigated using finite-element analysis. The motor design and test results are examined and verified through fabrication. The characterizations of brushless direct current (BLDC) motors according to the materials used in their cores have been actively studied. On the other hand, the effect of material characteristics on a PMDC motor consisting of brushes and commutators has not been studied as much. In the case of the PMDC motors, electrical steel sheets are infrequently used because this motor is relatively smaller than the BLDC motor. However, the iron loss characteristics, which are proportional to the frequency and the magnetic flux density, affect the efficiency even in small motors. Further, the output of the motor changes owing to saturation due to iron loss. The outcome presented in this study provides core materials selection guidelines to improve motor efficiency.
Optimal Slot Design of IPMSM in Railway With Independently Rotating Wheelsets
Liu, Huai-Cong,Lee, Ho-Joon,Seol, Hyun-Soo,Cho, Sooyoung,Lee, Ju,Oh, Ye Jun IEEE 2019 IEEE transactions on magnetics Vol.55 No.2
<P>This paper proposes a quasi-semi-closed (QSC) slot design method for an open-slot-type interior permanent magnet synchronous motor (IPMSM) for independently rotating wheelsets necessary to reduce the total harmonic distortion of no-load back-electromotive force and the torque ripple in the IPMSM. Four different slot-opening models were selected—the basic model, hairpin coil model, magnetic-wedge model, and QSC-slot model—and 2-D finite-element analysis was performed under open-circuit and load operations for each of the four models. Next, the relationships among the cogging torque, the torque ripple, and the saturation phenomenon in the core were analyzed. In addition, the manufacturing process, manufacturing cost, fill factor, end-winding resistance, copper loss, and efficiency were investigated. The experimental results verify the accuracy of the proposed method.</P>
Barrier 배치를 이용한 슈퍼프리미엄급 SynRM의 토크리플 저감 설계
유회총(Huai-cong Liu),이호준(Ho-Jun Lee),오세영(Se-Young Oh),유광현(Gwang-Hyeon Ryu),홍현석(Hyun-Seok Hong),김승주(Seung-Joo Kim),이주(Ju Lee) 대한전기학회 2013 대한전기학회 학술대회 논문집 Vol.2013 No.4
SynRM (Synchronous Reluctance Motor) is a high efficient motor. With a simple structure and more cheaper than induction Motor, However, the torque ripple of Synchrous Reluctance Motor is very large. This paper analyzes the SynRM output characteristics with a new rotor flux barriers arrangment design, since the stator of SynRM is similar as that of an induction motor. And compares a basic Model. By designed the relative positions between outer edges of flux barriers and slots correspond. As a result torque ripple can be reduced.