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Wang, Zhaohui,Zhang, Junming,Sheng, Kuang The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3
With high penetration of renewable energies, power electronic transformers (PETs) will be one of the most important infrastructures in the future power delivery and management system. In this study, an isolated bidirectional modular multilevel DC/DC converter is proposed for PET applications. A modular multilevel structure is adopted as switching valves to sustain medium voltages to achieve modular design and high reliability. Only one high-frequency transformer is used in the proposed converter, which significantly simplifies the circuit and galvanic insulation design. A dual-phase-shift modulation strategy is proposed to regulate the output power and achieve a simple voltage balancing control. A down-scaled (2 kW/20 kHz) prototype is constructed to demonstrate the proposed converter and verify the control strategy. The experimental results comply with the theoretical analysis well, with the highest power efficiency reaching 97.6%.
Zhaohui Wang,Junming Zhang,Kuang Sheng 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3
With high penetration of renewable energies, power electronic transformers (PETs) will be one of the most important infrastructures in the future power delivery and management system. In this study, an isolated bidirectional modular multilevel DC/DC converter is proposed for PET applications. A modular multilevel structure is adopted as switching valves to sustain medium voltages to achieve modular design and high reliability. Only one high-frequency transformer is used in the proposed converter, which significantly simplifies the circuit and galvanic insulation design. A dual-phase-shift modulation strategy is proposed to regulate the output power and achieve a simple voltage balancing control. A down-scaled (2 kW/20 kHz) prototype is constructed to demonstrate the proposed converter and verify the control strategy. The experimental results comply with the theoretical analysis well, with the highest power efficiency reaching 97.6%.
Yet another Hybrid Strategy for Auto-tuning SpMV on GPUs
Zhaohui Wang,Xiaojie Qiu,Aimin Zhang,Yichao Cheng,Yi Peng,Sun Sun 보안공학연구지원센터 2015 International Journal of Software Engineering and Vol.9 No.5
Sparse matrix-vector multiplication (SpMV) is a key linear algebra algorithm and is widely used in many application domains. Besides multi-core architecture, there is also extensive research focusing on accelerating SpMV on many-core Graphics Processing Units (GPUs). SpMV computations have many indirect and irregular memory accesses, and load imbalance could occur while mapping computations onto single-instruction, multiple-data (SIMD) GPUs. SpMV is highly memory bandwidth-bound, though GPUs have massive computational resources, the performance of SpMV on GPUs is still unsatisfying. In this paper, we present a new hybrid strategy for auto-tuning SpMV on GPUs. Our strategy combines the advantages of row-major storage and column-major storage. Like many other strategies, we reordered a given sparse matrix according to row lengths in decreasing order. In order to be more adaptive and efficient, we proposed a new hybrid Blocked CSR and JDS (BCJ) format based on original CSR and JDS. BCJ splits a sparse matrix into a denser part and a sparser part after reordering and uses different kernels to process the corresponding part. And we proposed corresponding auto-tuning framework to help transforming matrix and launching kernels according to the sparsity characteristics of the matrix. A CUDA implementation of BCJ outperforms the original formats significantly on a broad range of unstructured sparse matrices.
Understanding Trump's Trade Policy with China: International Pressures Meet Domestic Politics
Zhaohui Wang 인하대학교 국제관계연구소 2019 Pacific Focus Vol.34 No.3
The trade confrontation between the United States and China has heightenedglobal concerns that a trade war between the two largest economies wouldhave serious consequences for the world economy. This article suggestsemploying a neoclassical realist framework to examine Trump’s trade policywith China as to best explain the US–China trade disputes since 2018. Itargues that Trump’s trade policy with China is fundamentally driven by theincreasingly competitive US–China relationship, which is influenced byTrump’s perception of China as America’s primary strategic competitor andconcern with the US trade deficit, and reinforced by the Trumpization of theRepublican Party under the US domestic polarization. The neoclassical real-ist analysis suggests that the trade tension embedded in the strategic compe-tition between the two countries is likely to continue for a considerable time.
Zhaohui Luan,Shuang Liu,Wei Wang,Kaige Xu,Shaosong Ye,Ruijue Dan,Hong Zhang,Zhenzhen Shu,Tongchuan Wang,Chaoqiang Fan,Malcolm Xing,Shiming Yang 한국생체재료학회 2022 생체재료학회지 Vol.26 No.4
Background: Wound closure in the complex body environment places higher requirements on suture’s mechanical and biological performance. In the scenario of frequent mechanical gastric motility and extremely low pH, single functional sutures have limitations in dealing with stomach bleeding trauma where the normal healing will get deteriorated in acid. It necessitates to advance suture, which can regulate wounds, resist acid and intelligently sense stomach pH. Methods: Based on fish swim bladder, a double-stranded drug-loaded suture was fabricated. Its cytotoxicity, histocompatibility, mechanical properties, acid resistance and multiple functions were verified. Also, suture’s performance suturing gastric wounds and Achilles tendon was verified in an in vivo model. Results: By investigating the swim bladder’s multi-scale structure, the aligned tough collagen fibrous membrane can resist high hydrostatic pressure. We report that the multi-functional sutures on the twisted and aligned collagen fibers have acid resistance and low tissue reaction. Working with an implantable “capsule robot”, the smart suture can inhibit gastric acid secretion, curb the prolonged stomach bleeding and monitor real-time pH changes in rabbits and pigs. The suture can promote stomach healing and is strong enough to stitch the fractured Achilles tendon. Conclusions: As a drug-loaded absorbable suture, the suture shows excellent performance and good application prospect in clinical work.
Modular Multilevel Power Electronic Transformer
Zhaohui Wang,Junming Zhang,Kuang Sheng 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
In this paper, a modular multilevel power electronic transformer structure for power distribution system is discussed. The proposed structure consists of two completely decoupled power stages. Modular multilevel converter is adopted as the front-end ac-dc stage to convert the medium ac voltage to medium dc voltage, or vice versa. Galvanic isolation and voltage conversion are realized by the cascaded dc-dc stage. Only one high frequency transformer is used in the dc-dc converter, which dramatically simplifies the circuit and galvanic isolation design. A dual phase shift control method is proposed to regulate the output and balance the submodule voltage in the dc-dc stage. To verify the effectiveness of the proposed converter and control method, a down-scaled prototype is constructed. The experimental results comply with the theoretical analysis very well.
High capacity ethidium bromide removal by montmorillonites
Lijuan Wang,Zhaohui Li,Xingrong Zhang,Guocheng Lv,Xisen Wang 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.12
Ethidium bromide (EtBr) is commonly used as a reagent to investigate DNA and RNA bonding in biochemistry. However, it is mutagenic and toxic; thus, its removal from the waste solution is of the top priority in lab safety practice. Although many products with high EtBr removal capacities are available on the market, developing new products with low material costs and high removal capacities is still an urgent priority. As the EtBr is in a cationic form Et+ balanced by counterion Br in aqueous solution, materials with high cation exchange capacity and large specific surface area may have great potential for efficient EtBr removal, Thus, several montmorillonites (MMTs) were evaluated for their EtBr removal capacity and methods of regeneration in this study. Results showed that both external and internal surfaces of MMTs were effective sorption sites for EtBr with a capacity up to 600mg/g. And the waste-laden materials could be regenerated or safely disposed after incineration at 500 oC for 2 h. As such, further tests on optimization and manufacturing kits or devices for practical EtBr removal in routine lab practice is of engineering priority, should MMTs be further explored as an effective material for EtBr removal.