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Imaoka Kouki,Yano Takuya,Yoshimitsu Masanori,Fukuhara Sotaro,Oshita Ko,Nakano Kanyu,Kunihiro Masaki,Idani Hitoshi,Okajima Masazumi 대한대장항문학회 2023 Annals of Coloproctolgy Vol.39 No.2
Purpose: Harvesting at least 12 lymph nodes (LNs) is recommended for adequate tumor staging in colon surgery. Although preoperative endoscopic tattooing has been used for primary localization of tumors, its impact on LN retrieval in colorectal surgery remains controversial. We aimed to investigate the relationship between preoperative tattooing and LN retrieval after laparoscopic rectal resection.Methods: We reviewed the records of 92 patients with rectal cancer who underwent laparoscopic resection from January 1, 2018 to December 31, 2019. Patients were categorized into 2 groups according to whether preoperative endoscopic tattooing was performed. The rate of adequate LN retrieval (≥12) was compared.Results: The tattooed and non-tattooed groups comprised 49 and 43 patients, respectively. In the tattooed and non-tattooed groups, the rates of adequate LN retrieval were 75.5% and 55.8%, respectively (P=0.046). Univariate analysis revealed that female sex, tattooing, LN metastasis status, pathological pathological stage (p-stage), and LN dissection were predictive factors for adequate LN retrieval. In the multivariate analysis, female sex (odds ratio [OR], 3.34; 95% confidence interval [CI], 1.15–9.73; P=0.027), tattooing (OR, 2.87; 95% CI, 1.03–7.94; P=0.043), and p-stage (OR, 3.34; 95% CI, 1.04–10.75; P=0.043) were independent predictive factors for adequate LN retrieval after surgery.Conclusion: This study revealed that preoperative endoscopic tattooing was statistically significantly associated with adequate LN retrieval in patients with rectal cancer who underwent laparoscopic rectal resection. Preoperative endoscopic tattooing should be considered to improve disease assessment and avoid stage migration.
J. Imaoka,Y. Ishikura,K. Ito,T. Aoki,M. Noah,M. Yamamoto 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Utilizing powder cores in many power electronics applications have been gaining much attention due to their attractive magnetic properties. However, it is quite challenging for the circuit designer to choose the proper core, as there are many kinds of magnetic powder cores available in the market. Therefore, due to the limitation of a single magnetic material property, it is often difficult to realize high power conversion efficiency within wide load ranges, including light and heavy load conditions. This paper proposes a novel design method of the multi-material inductor which combines multiple powder cores having different material properties. The aim of this work is to provide improved efficiency over the entire load range of power converters. The experimental results have proven that the inductor with multi-material powder cores can improve the efficiency over wide load range. The validity and effectiveness of the proposed magnetic design method are confirmed from theoretical analysis, simulation and experimental tests.
Analysis of Coupled-Inductor Configuration for an Interleaved High Step-Up Converter
Wilmar Martinez,Jun Imaoka,Yuki Itoh,Masayoshi Yamamoto,Kazuhiro Umetani 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
High step-up converters are widely used in sustainable energy systems and recently used in automotive applications due to their high voltage gain capability. Nevertheless, with the purpose of obtaining a higher voltage gain, in comparison with conventional boost converters, current high step-up converters often employ additional multiplier cells, which may lead to significant cost-up and low power density. Therefore, a novel two-phase interleaved high step-up converter is proposed in order to minimize additional circuit volume used to achieve large voltage gain. The proposed converter addresses the purpose by a particular coupled inductor where three windings are installed in one or two cores. As a result, the proposed converter can achieve higher voltage gain than the conventional topologies by adding a winding and two diodes to the interleaved two phase boost chopper, besides the coupled-inductor configuration. This paper evaluates two arrangements of the coupled-inductor configuration of the proposed high step-up converter: 1. Three windings integrated in only one core and 2. Two independent inductors with a shared winding. The result revealed that the proposed converter shows higher voltage gain than the normal boost converter and the magnetic integration in the coupled-inductor configuration further increases the voltage gain by 20%.
EMI Prediction and Reduction of Zero-Crossing Noise in Totem-Pole Bridgeless PFC Converters
Zhang, Baihua,Lin, Qiang,Imaoka, Jun,Shoyama, Masahito,Tomioka, Satoshi,Takegami, Eiji The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
In this study, a zero-crossing spike current issue in a totem-pole bridgeless power factor correction (PFC) converter is comprehensively investigated for the first time. Spike current occurs when input voltage crosses zero, becomes a noise source, and causes severe common mode emission issues. A generation mechanism for electromagnetic interference (EMI) is presented to investigate the EMI problem caused by zero-crossing issue, and a noise spectrum due to this issue is predicted by a theoretical analysis based on the Fourier coefficient of an approximate spike current waveform. Furthermore, a noise reduction method is proposed and then improved to reduce the spike current. Experimental measurements are implemented on a GaN-based totem-pole bridgeless PFC converter, and the spike current can be effectively suppressed through the proposed method. Furthermore, the noise spectrums measured without and with the reduced zero-crossing spike current are compared. Experimental results validate the analysis of the noise spectrum caused by the zero-crossing spike current issue.
EMI Prediction and Reduction of Zero-Crossing Noise in Totem-Pole Bridgeless PFC Converters
Baihua Zhang,Qiang Lin,Jun Imaoka,Masahito Shoyama,Satoshi Tomioka,Eiji Takegami 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
In this study, a zero-crossing spike current issue in a totem-pole bridgeless power factor correction (PFC) converter iscomprehensively investigated for the first time. Spike current occurs when input voltage crosses zero, becomes a noise source,and causes severe common mode emission issues. A generation mechanism for electromagnetic interference (EMI) is presentedto investigate the EMI problem caused by zero-crossing issue, and a noise spectrum due to this issue is predicted by a theoreticalanalysis based on the Fourier coefficient of an approximate spike current waveform. Furthermore, a noise reduction method isproposed and then improved to reduce the spike current. Experimental measurements are implemented on a GaN-basedtotem-pole bridgeless PFC converter, and the spike current can be effectively suppressed through the proposed method. Furthermore, the noise spectrums measured without and with the reduced zero-crossing spike current are compared. Experimental results validate the analysis of the noise spectrum caused by the zero-crossing spike current issue.
High reliable transformer-less deadtime less Inverter for Grid-connected Applications
Silumin Senanayake,Thilak Senanayake,Jun Imaoka,Masayoshi Yamamoto 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
This paper presents a transformer-less inverter topology that brings out the high-performance for grid connected inverters. The main advantages of this inverter eliminate the dead-time requirement, and allows both top and bottom switch from being on at same time, and thus shorting the DC bus supply to ground. This avoids the freewheeling diodes connected across the switches for loads other than purely resistive. Low output voltage distortion and low fundamental and common voltages losses result in high efficiency and high output power density. The input dc source and the output ac voltage share the same ground in proposed inverter, which effectively eliminates the leakage current caused by the DC source (PV panel, battery bank etc.). Analysis and simulation results are presented to demonstrate the effectiveness of the proposed inverter. Compared to the prior literature mentioned in this paper, 75- 86% reduction of semiconductor components is achieved with proposed inverter topology.
Experimental Verification of Maximum Operating Frequency for a SiC-MOSFET in Class-D ZVS inverter
Yi Xiong,Senanayake Thilak,Yu Yonezawa,Jun Imaoka,Masayoshi Yamamoto 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
This paper experimentally verified a previously proposed analytical model of maximum operating frequency of class-D ZVS inverter. The proposed model included the linearized drain-source parasitic capacitance and was usable at any duty ratio. The verification of the model was once conducted by simulation with a 650V/30A SiC-MOSFET spice model before, and in this paper the experimental verification was further conducted by PCB circuit, resulting in good consistency.
CO OBSERVATIONS AND STABILITY ANALYSIS OF B133 AND B134
Hong, S.S.,Kim, H.G.,Park, S.H.,Park, Y.S.,Imaoka, K. The Korean Astronomical Society 1991 Journal of The Korean Astronomical Society Vol.24 No.1
With the 14 m radio telescope at DRAO and the 4 m at Nagoya University, we have made detailed maps of $^{12}CO$ and $^{13}CO$ emissions from two Barnard objects B133 and B134 in the $J=1{\rightarrow}O$ rotational transition lines. Usual LTE analyses of the CO observations led us to determine the distribution of column densities over an entire area encompassing both globules. Total gas masses estimated from the column density map are $90\;M_{\odot}$ and $20\;M_{\odot}$ for B133 and B134, respectively. The radial velocity of B133 is red shifted with respect to B134 by $0.8\;km\;s^{-1}$, which is too lagre to bind the two clouds as a binary system. We have shown that the usual stability analysis based on the simplified version of virial theorem with the second time-derivative of the moment of inertia term $\ddot{I}$ being ignored could mislead us in determining whether a given cloud eventually collapses or not. The lull version of the scalar virial theorem with the $\ddot{I}$ term is shown to be useful in following up the time-dependent variations of the cloud size R and its streaming velocity $\dot{R}$ as functions of time. Results of our stability analysis suggest that B133 will eventually collapse in $(2{\sim}4){\times}10^6$ years.