Novel Five-Level Three-Phase Hybrid-Clamped Converter with Reduced Components

Chen, Bin,Yao, Wenxi,Lu, Zhengyu The Korean Institute of Power Electronics 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

This study proposes a novel five-level three-phase hybrid-clamped converter composed of only six switches and one flying capacitor (FC) per phase. The capacitor-voltage-drift phenomenon of the converter under the classical sinusoidal pulse width modulation (SPWM) strategy is comprehensively analyzed. The average current, which flows into the FC, is a function of power factor and modulation index and does not remain at zero. Thus, a specific modulation strategy based on space vector modulation (SVM) is developed to balance the voltage of DC-link and FCs by injecting a common-mode voltage. This strategy applies the five-segment method to synthesize the voltage vector, such that switching losses are reduced while optional vector sequences are increased. The best vector sequence is then selected on the basis of the minimized cost function to suppress the divergence of the capacitor voltage. This study further proposes a startup method that charges the DC-link and FCs without any additional circuits. Simulation and experimental results verify the validity of the proposed converter, modulation strategy, and precharge method.

An Algorithm for Data Aggregation Scheduling with Long-lifetime and Low-latency in Wireless Sensor Networks

Zhengyu Chen,Geng Yang,Lei Chen,Jin Wang 보안공학연구지원센터 2012 International Journal of Future Generation Communi Vol.5 No.4

Co-DDTMA : Cooperative Distributed TDMA for Vehicular Networks

Zhen Chen,Zhengyu Liu,Jianghong Han,Songhua Hu,Yang Lu 보안공학연구지원센터 2016 International Journal of Future Generation Communi Vol.9 No.2

In recent years, Vehicular Ad Hoc Networks (VANET) has experienced a rapid development due to the advancement of wireless communication technologies, and now emerges as a promising way to provide road safety, traffic efficiency and infotainment applications. However, it is a challenge to design a reliable and efficient Medium Access Control (MAC) protocol for VANET due to its frequent topology changes and unreliable wireless links. Cooperative communication, on the other hand, can enhance the reliability of wireless links by exploiting the broadcast nature of the wireless communication. A cooperative scheme for MAC is proposed for VANET in this paper, referred to as Cooperative Distributed TDMA (Co-DTDMA). In the Co-DTDMA, neighboring nodes utilize its idle slots for cooperatively retransmitting a packet which has failed to reach the destination. Since the cooperative retransmission is conducted in node's own idle slot, the proposed scheme does not interrupt the normal transmission. Both theoretical analysis and simulation results demonstrate that the proposed scheme greatly increases the probability of successful packet transmission and decreases the packet transmission delay.

Novel Five-Level Three-Phase Hybrid-Clamped Converter with Reduced Components

Bin Chen,Wenxi Yao,Zhengyu Lu 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.6

This study proposes a novel five-level three-phase hybrid-clamped converter composed of only six switches and one flying capacitor (FC) per phase. The capacitor-voltage-drift phenomenon of the converter under the classical sinusoidal pulse width modulation (SPWM) strategy is comprehensively analyzed. The average current, which flows into the FC, is a function of power factor and modulation index and does not remain at zero. Thus, a specific modulation strategy based on space vector modulation (SVM) is developed to balance the voltage of DC-link and FCs by injecting a common-mode voltage. This strategy applies the five-segment method to synthesize the voltage vector, such that switching losses are reduced while optional vector sequences are increased. The best vector sequence is then selected on the basis of the minimized cost function to suppress the divergence of the capacitor voltage. This study further proposes a startup method that charges the DC-link and FCs without any additional circuits. Simulation and experimental results verify the validity of the proposed converter, modulation strategy, and precharge method.

Dark-Blood Computed Tomography Angiography Combined With Deep Learning Reconstruction for Cervical Artery Wall Imaging in Takayasu Arteritis

Su Tong,Zhang Zhe,Chen Yu,Wang Yun,Li Yumei,Xu Min,Wang Jian,Li Jing,Tian Xinping,Jin Zhengyu 대한영상의학회 2024 Korean Journal of Radiology Vol.25 No.4

Objective: To evaluate the image quality of novel dark-blood computed tomography angiography (CTA) imaging combined with deep learning reconstruction (DLR) compared to delayed-phase CTA images with hybrid iterative reconstruction (HIR), to visualize the cervical artery wall in patients with Takayasu arteritis (TAK). Materials and Methods: This prospective study continuously recruited 53 patients with TAK (mean age: 33.8 ± 10.2 years; 49 females) between January and July 2022 who underwent head-neck CTA scans. The arterial- and delayed-phase images were reconstructed using HIR and DLR. Subtracted images of the arterial-phase from the delayed-phase were then added to the original delayed-phase using a denoising filter to generate the final-dark-blood images. Qualitative image quality scores and quantitative parameters were obtained and compared among the three groups of images: Delayed-HIR, Dark-blood-HIR, and Dark-blood-DLR. Results: Compared to Delayed-HIR, Dark-blood-HIR images demonstrated higher qualitative scores in terms of vascular wall visualization and diagnostic confidence index (all P < 0.001). These qualitative scores further improved after applying DLR (Dark-blood-DLR compared to Dark-blood-HIR, all P < 0.001). Dark-blood DLR also showed higher scores for overall image noise than Dark-blood-HIR (P < 0.001). In the quantitative analysis, the contrast-to-noise ratio (CNR) values between the vessel wall and lumen for the bilateral common carotid arteries and brachiocephalic trunk were significantly higher on Darkblood- HIR images than on Delayed-HIR images (all P < 0.05). The CNR values were significantly higher for Dark-blood-DLR than for Dark-blood-HIR in all cervical arteries (all P < 0.001). Conclusion: Compared with Delayed-HIR CTA, the dark-blood method combined with DLR improved CTA image quality and enhanced visualization of the cervical artery wall in patients with TAK.

Cyclic AMP Responsive Element Binding Protein 3-like 4/AarF Domain Containing Kinase 5 Axis Facilitates Proliferation, Migration and Invasion of Lung Adenocarcinoma Cells by Modulating the TGFβ Pathway

Cheng Ai,Tenghao Rong,Zhengyu Chen,Wang Shen,Kaili Huang,Qiang Li,Jing Xiong,Wen Li 한국생물공학회 2023 Biotechnology and Bioprocess Engineering Vol.28 No.1

Cyclic AMP responsive element binding protein 3-like 4 (CREB3L4) has been reported as a transcription factor showing high expression in various cancers, whereas the mechanism of CREB3L4 in lung adenocarcinoma (LUAD) progression remains unclear yet. Expression levels of CREB3L4 and its downstream target gene AarF Domain Containing Kinase 5 (ADCK5) in LUAD tissues were analyzed by bioinformatics methods and were detected by real-time quantitative polymerase chain reaction at cellular level. The signaling pathways in which the downregulated ADCK5 enriched were analyzed via Gene Set Enrichment Analysis. The regulatory relationship between CREB3L4 and ADCK5 was identified by ChIP and dual luciferase reporter assay. CCK-8 and colony formation assays were utilized to evaluate LUAD cell proliferation. Transwell was utilized to measure migration and invasion of LUAD cells. Western blot was employed to check expression changes of CREB3L4, ADCK5, TGFβ pathway proteins and Epithelial- Mesenchymal Transition related proteins. Compared with paracancer tissues, CREB3L4 and ADCK5 were highly expressed in LUAD tissues, while silencing CREB3L4 could dramatically hinder invasion, proliferation and migration of LUAD cells. ADCK5 was the downstream target gene of CREB3L4, and CREB3L4 promoted the transcription of ADCK5. ADCK5 was markedly enriched in the TGFβ pathway, which stimulated the malignant development of LUAD cells by activating this pathway. In addition, the rescue assay verified that CREB3L4 regulated the TGFβ pathway by activating ADCK5, thereby accelerating LUAD cell malignant phenotypes. This study revealed the mechanism of CREB3L4/ADCK5 axis facilitating malignant phenotypes of LUAD cells, and bred new insights into the LUAD treatment.