Weakly np-Injective Rings and Weakly C2 Rings

Wei, Junchao,Che, Jianhua Department of Mathematics 2011 Kyungpook mathematical journal Vol.51 No.1

A ring R is called left weakly np- injective if for each non-nilpotent element a of R, there exists a positive integer n such that any left R- homomorphism from $Ra^n$ to R is right multiplication by an element of R. In this paper various properties of these rings are first developed, many extending known results such as every left or right module over a left weakly np- injective ring is divisible; R is left seft-injective if and only if R is left weakly np-injective and $_RR$ is weakly injective; R is strongly regular if and only if R is abelian left pp and left weakly np- injective. We next introduce the concepts of left weakly pp rings and left weakly C2 rings. In terms of these rings, we give some characterizations of (von Neumann) regular rings such as R is regular if and only if R is n- regular, left weakly pp and left weakly C2. Finally, the relations among left C2 rings, left weakly C2 rings and left GC2 rings are given.

On Rings Containing a Non-essential nil-Injective Maximal Left Ideal

Wei, Junchao,Qu, Yinchun Department of Mathematics 2012 Kyungpook mathematical journal Vol.52 No.2

We investigate in this paper rings containing a non-essential $nil$-injective maximal left ideal. We show that if R is a left MC2 ring containing a non-essential $nil$-injective maximal left ideal, then R is a left $nil$-injective ring. Using this result, some known results are extended.

Analysis of underwater explosion shock on ship shaft stern bearing lubrication characteristics under different bearing working conditions

Zhu Junchao,Wei Guangcheng,Peng Zilong,Xia Zhaowang,Zheng Liangyan,Zhu Hanhua 대한조선학회 2022 International Journal of Naval Architecture and Oc Vol.14 No.1

Warship always face the threat of underwater explosion shock, which may affect the ship stern tube bearing lubrication performance when the propeller shaft is bending. This paper builds the coupling model of shaft longitudinal vibration and bearing lubrication with consideration of shaft axial shock and misalignment. The performance of stern bearing under the influence of explosion shock was analyzed by solving the generalized Reynolds equation, shaft longitudinal vibration equation and explosion shock equation. The result shows that: the effect of underwater explosion shock on bearing lubrication performance is transient, and the effect will be more obvious when the bearing works at close quarter, larger misaligned angle, eccentricity and rotation speed. Moreover, the edge effect which caused by shaft bending will increase with the decrease of explosion distance and the increase of eccentricity.

Weakly Semicommutative Rings and Strongly Regular Rings

Wang, Long,Wei, Junchao Department of Mathematics 2014 Kyungpook mathematical journal Vol.54 No.1

A ring R is called weakly semicommutative ring if for any a, $b{\in}R^*$ = R\{0} with ab = 0, there exists $n{\geq}1$ such that either an $a^n{\neq}0$ and $a^nRb=0$ or $b^n{\neq}0$ and $aRb^n=0$. In this paper, many properties of weakly semicommutative rings are introduced, some known results are extended. Especially, we show that a ring R is a strongly regular ring if and only if R is a left SF-ring and weakly semicommutative ring.

Generalized Inverses and Solutions to Equations in Rings with Involution

Yue Sui,Junchao Wei 경북대학교 자연과학대학 수학과 2024 Kyungpook mathematical journal Vol.64 No.1

In this paper, we focus on partial isometry elements and strongly EP elements or a ring. We construct characterizing equations such that an element which both group invertible and MP-invertible, is a partial isometry element, or is strongly EP, exactly when these equations have solution in a given set.

An Active Voltage Doubling Rectifier with Unbalanced-Biased Comparators for Piezoelectric Energy Harvesters

Lianxi Liu,Junchao Mu,Wenzhi Yuan,Wei Tu,Zhangming Zhu,Yintang Yang 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

For wearable health monitoring systems, a fundamental problem is the limited space for storing energy, which can be translated into a short operational life. In this paper, a highly efficient active voltage doubling rectifier with a wide input range for micro-piezoelectric energy harvesting systems is proposed. To obtain a higher output voltage, the Dickson charge pump topology is chosen in this design. By replacing the passive diodes with unbalanced-biased comparator-controlled active counterparts, the proposed rectifier minimizes the voltage losses along the conduction path and solves the reverse leakage problem caused by conventional comparator-controlled active diodes. To improve the rectifier input voltage sensitivity and decrease the minimum operational input voltage, two low power common-gate comparators are introduced in the proposed design. To keep the comparator from oscillating, a positive feedback loop formed by the capacitor C is added to it. Based on the SMIC 0.18-μm standard CMOS process, the proposed rectifier is simulated and implemented. The area of the whole chip is 0.91×0.97 ㎟, while the rectifier core occupies only 13% of this area. The measured results show that the proposed rectifier can operate properly with input amplitudes ranging from 0.2 to 1.0V and with frequencies ranging from 20 to 3000 Hz. The proposed rectifier can achieve a 92.5% power conversion efficiency (PCE) with input amplitudes equal to 0.6 V at 200 Hz. The voltage conversion efficiency (VCE) is around 93% for input amplitudes greater than 0.3 V and load resistances larger than 20kΩ.

Anaerobic membrane bioreactors for wastewater treatment: mechanisms, fouling control, novel configurations, and future perspectives

Jiajia Li,Jinyuan Jiang,Junchao Li,Changjun He,Yong Luo,Lihong Wei 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.1

As the world focuses on reducing greenhouse gas emissions and recovering energy from sewage, technologies that can recover energy and reuse wastewater are becoming increasingly important. Anaerobic membrane bioreactor (AnMBR) technology has recently attracted attention, as it can achieve energy recovery and yields high-quality effluent. However, the large-scale commercial application of AnMBRs requires that certain barriers be overcome, including membrane pollution and dissolved methane recovery. In this review article, we summarize the basic principles of anaerobic wastewater digestion and discuss the excellent performance of AnMBRs for wastewater treatment. Various factors, membrane types, and pollution are discussed, and control strategies for dealing with membrane pollution are put forward. In addition, a variety of new AnMBRs are described that may better control membrane pollution. Finally, future research directions for AnMBRs are presented to promote the large-scale integrated application of AnMBRs for industrial wastewater treatment.

An Active Voltage Doubling Rectifier with Unbalanced-Biased Comparators for Piezoelectric Energy Harvesters

Liu, Lianxi,Mu, Junchao,Yuan, Wenzhi,Tu, Wei,Zhu, Zhangming,Yang, Yintang The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.3

For wearable health monitoring systems, a fundamental problem is the limited space for storing energy, which can be translated into a short operational life. In this paper, a highly efficient active voltage doubling rectifier with a wide input range for micro-piezoelectric energy harvesting systems is proposed. To obtain a higher output voltage, the Dickson charge pump topology is chosen in this design. By replacing the passive diodes with unbalanced-biased comparator-controlled active counterparts, the proposed rectifier minimizes the voltage losses along the conduction path and solves the reverse leakage problem caused by conventional comparator-controlled active diodes. To improve the rectifier input voltage sensitivity and decrease the minimum operational input voltage, two low power common-gate comparators are introduced in the proposed design. To keep the comparator from oscillating, a positive feedback loop formed by the capacitor C is added to it. Based on the SMIC 0.18-μm standard CMOS process, the proposed rectifier is simulated and implemented. The area of the whole chip is 0.91×0.97 mm², while the rectifier core occupies only 13% of this area. The measured results show that the proposed rectifier can operate properly with input amplitudes ranging from 0.2 to 1.0V and with frequencies ranging from 20 to 3000 Hz. The proposed rectifier can achieve a 92.5% power conversion efficiency (PCE) with input amplitudes equal to 0.6 V at 200 Hz. The voltage conversion efficiency (VCE) is around 93% for input amplitudes greater than 0.3 V and load resistances larger than 20kΩ.