The homological properties of regular injective modules

Wei Qi,Xiaolei Zhang 대한수학회 2024 대한수학회논문집 Vol.39 No.1

Let $R$ be a commutative ring. An $R$-module $E$ is said to be regular injective provided that $\Ext_R^1(R/I,E)=0$ for any regular ideal $I$ of $R$. We first show that the class of regular injective modules have the hereditary property, and then introduce and study the regular injective dimension of modules and regular global dimension of rings. Finally, we give some homological characterizations of total rings of quotients and Dedekind rings.

THE u-S-GLOBAL DIMENSIONS OF COMMUTATIVE RINGS

Wei Qi,Xiaolei Zhang 대한수학회 2023 대한수학회보 Vol.60 No.6

Let $R$ be a commutative ring with identity and $S$ a multiplicative subset of $R$. First, we introduce and study the $u$-$S$-projective dimension and $u$-$S$-injective dimension of an $R$-module, and then explore the $u$-$S$-global dimension $u$-$S$-\gld$(R)$ of a commutative ring $R$, i.e., the supremum of $u$-$S$-projective dimensions of all $R$-modules. Finally, we investigate $u$-$S$-global dimensions of factor rings and polynomial rings.

Vasodilation Effect of 2-benzyl-5-hydroxy-6-methoxy-3, 4-dihydroisoquinolin- 1-one

Wei-Qi,Yong-Xiao Cao,Zhi-Zheng Xiong,Ting-Ting Chen,Xiao-Yan Gao,Hang Yu,San-Qi Zhang 대한약학회 2012 Archives of Pharmacal Research Vol.35 No.8

A 2-Benzyl-5-hydroxy-6-methoxy-3, 4-dihydroisoquinolin-1-one (ZC2) is a newly synthesized isoquinolinone compound. Its effect on vasodilation was evaluated in the present study. Isometric tension of rat artery rings was recorded by a sensitive myography system in vitro. The results showed that ZC2 relaxed rat mesenteric arteries pre-contracted by KCl, phenylephrine and 9, 11- dideoxy- 11α, 9α-epoxymethano-prostaglandin F2α (U46619), and abdominal aorta pre-contracted by KCl in a concentration-dependent manner. The ZC2-induced vasodilation was not affected by an endothelium denudation. ZC2 rightwards shifted the concentration-contraction curves, induced by KCl, phenylephrine, and 5-hydroxytryptamine (5-HT) in a non-parallel manner, which suggests that the vasodilation effects are most likely via voltage-dependent calcium channel (VDCC) and receptor-operated calcium channel (ROCC). Moreover, in Ca2+-free medium, ZC2 concentration-dependently depressed the vasoconstrictions induced by phenylephrine and CaCl2, and decreased a contractile response induced by caffeine, which indicates a role of extracellular Ca2+ influx inhibition through VDCC and ROCC, and intracellular Ca2+ release from Ca2+ store via the ryanodine receptors. Glibenclamide did not affect the vasodilation induced by ZC2, suggesting that ATP sensitive potassium channel is not involved in the vasodilation. The results indicate that ZC2 induces vasodilation by inhibiting the VDCC and ROCC, and receptormediated Ca2+ influx and release. The inhibition of intracellular Ca2+ release may be mediated via the ryanodine receptors.

미생물전기화학적 혐기성소화에서 벌크 및 전극에서의 메탄생성

( Weiqi Shi ),전항배 ( Hang-bae Jun ) 한국물환경학회 2020 한국물환경학회·대한상하수도학회 공동 춘계학술발표회 Vol.2020 No.-

미생물 전기화학적 혐기성소화조 bulk와 bio-film에서의 유기물 분해와 메탄생성 mechanism은 비교적 잘 정립이 되어있지만, 각 반응이 유기물분해 및 메탄생성에 기여하는 정량적인 분석에 대해서는 보다 심도 있는 연구가 필요하다. 미생물 전기화학적 혐기성소화조의 연구초기에는 lab-scale 규모의 비교적 작은 반응조에서 bio-film 내 microorganisms의 확보를 통하여 메탄발생 효율을 향상시키기 위한 연구에 초점을 맞추었다. 전극표면에 bio-film 형성을 극대화하기 위해 carbon brush나 activated carbon 등의 전극을 주로 사용하였고, 이는 bio-film에서의 메탄생성에 중요성이 부각되는 원인이 되었다. 하지만, A/V ratio의 최소화는 실용화를 위해 필연적이며, 낮은 A/V ratio에서 bulk sludge와 bio-film이 유기물분해 및 메탄발생에 기여하는 정량적인 기여도를 연구할 필요가 있다. 따라서, 본 연구에서는 낮은 A/V ratio (7.0 m²/m³)의 BEAD 미생물 전기화학적 혐기성소화조에서 음식물류폐기물로부터 메탄발생량을 분석하고, BEAD 반응조에서 bulk sludge와 bio-film이 메탄발생에 미치는 영향을 정량적으로 분석하였다. AD와 BEAD 반응조의 용량과 유효용량은 각각 25, 20 L이며, BEAD 반응조의 A/V ratio는 7.0 m²/m³이다. BEAD에 공급된 전압은 0.3 V이고, 환원전극으로 이어지는 도선 (Titanium wire) 사이에 1Ω의 외부저항과 함께 digital multi meter (DMM)를 설치하여 실제 전압를 측정하였다. Bulk 슬러지는 약 1,000일 동안 운전된 음식물류폐기물 중온혐기성소화조 내 슬러지를 사용하였으며, 기질은 음식물류폐기물 자원화시설로 유입되는 음식물류폐기물을 150㎛ sieve로 전처리한 후 OLR 8.0 kg/m³·d로 하여 1회/일 주입 및 배출시켰다. Bio-film은 음식물류 폐기물을 기질로 하여 약 1,000일 동안 운전된 미생물 전기화학적 혐기성소화조 내의 전극을 잘라식종하였다. BEAD에서 전체 메탄발생량 중 bulk sludge와 bio-film의 기여도는 각각 70.2, 29.8 %로 나타났으며, Bio-film 중 전류에 의한 직접적인 메탄발생은 전체 메탄발생량을 기준으로 약 8.7 %로 나타남으로서 bio-film 내에서 비전류적인 메탄의 생성 (약 21.1 %)이 우세하였다. BEAD 반응조의 bulk sludge, bio-film, and electrode가 메탄생성에 미치는 기여도는 각각 70.2, 29.8, 0 %이었다. Bulk sludge에 비해 bio-film의 높은 microorganism 활성도는 안정화 및 메탄발생속도 증가에 기여하였으며, 이는 bio-film의 생성 및 유지가 중요함을 나타낸다.

Hierarchical carrier‑based discontinuous PWM strategy for hybrid‑switch current source rectifier

Weiqi Wang,Xiangjian Meng,Xi Liang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.6

This paper proposes a hybrid-switch three-phase current source rectifi er (CSR) solution, which employs only one silicon carbide (SiC) switch and six traditional silicon (Si) switches. The corresponding hierarchical discontinuous pulse widthmodulation (HDPWM) strategy for the proposed CSR is also presented, which uses two parallel carrier-based discontinuous PWM branches to perform diff erentiated modulation operations on Si and SiC devices to endow the Si switches with zero current switching capability and conveniently make full use of the high-speed and low-loss advantages of SiC devices. Consequently, the proposed hybrid-switch CSR with HDPWM can even work as a full SiC device-switching converter with relatively lower costs, thus addressing the critical needs of effi ciency promotion of CSR applications. MATLAB simulations and experimental verifi cations were conducted to verify the performance of the proposed CSR solution.

Effects of Differences in Mechanical Parameters of Media on Mechanical Properties and Failure Form of Composite Samples

Weiqi Wang,Yicheng Ye,Qihu Wang,Xiaoyun Liu,Zhouhao Yuan,Pengcheng Li 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.2

The deformation and failure of composite rock masses at the contact zone can cause serious safety hazards in underground engineering. Therefore, uniaxial compression experiment and numerical studies of composite samples were conducted. Combined with theoretical analysis, the effects of differences in the mechanical properties of two media on the mechanical properties and failure form of composite samples were investigated. The results show that the difference in mechanical properties of two media weakened the strength and elastic modulus of the composite sample and resulted in complex failure form of the sample. Additionally, the peaks of the AE frequencies of the two media occurred successively after the peak stress of the sample. At the macrolevel, the two media failed successively. These effects are more pronounced as the degree of difference in the mechanical properties of the two media increased. The difference in mechanical properties of the two media resulted in uncoordinated deformation and constrained stress near the contact interface, and the difference in Poisson's ratio is the main factor. The influence (enhanced or weakened) of uncoordinated deformation on the mechanical properties of the composite sample is affected by differences in the elastic modulus and Poisson's ratios of the two media.

NaOH 용액과 폐 알루미늄의 반응에 의한 수소가스 생산

( Weiqi Shi ),( Thapa Ajay ),이범 ( Beom Lee ),전항배 ( Hang-bae Jun ) 한국폐기물자원순환학회(구 한국폐기물학회) 2020 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2020 No.-

신에너지 중 하나인 수소 에너지는 많은 에너지를 발생시키며, 다양한 방법을 통해 생성할 수 있어 주목을 받고 있다. 수소는 알칼리용액과의 반응으로써 생성할 수 있으며, 본 연구에서는 폐 알루미늄과 NaOH 용액의 반응에 의한 수소가스 생산을 관찰하였다. 알루미늄 생산 공장에서 공급받은 폐 알루미늄은 잘게 자른 형태(T 4.3 μm×L 0.5 mm×W 0.5 mm)로 준비되었고 NaOH용액은 1~5 M로 제작하였다. 용액의 용량에 따른 차이를 확인하고자 용액의 용량을 60 mL, 500 mL로 하였으며 500 mL의 멸균병 내에서 반응이 진행되었다. 5 g의 폐 알루미늄과 500 mL의 1 M, 3 M, 5 M의 NaOH 용액과의 반응 시 각각 5.7 L, 5.9 L, 6.2 L의 수소가 발생되었으며 발생속도는 각각 0.1 L-H₂/min·5gAl, 1 L-H₂/min·5gAl, 5.6 L-H₂/min·5gAl으로 나타났다. 이를 통하여 용액의 농도에 따라 수소가스의 총 발생량의 차이는 크지 않지만, 가스 발생속도에서는 농도의 영향을 받는 것을 알 수 있다. 또한 10g의 폐 알루미늄과 60 mL의 NaOH 5 M과 반응 시 총 발생량은 15.6 L로 나타났다. 따라서 본 연구를 통하여 용액의 용량이 가스 발생량에 미치는 영향은 미미하며, 수소 발생량은 폐 알루미늄의 양과 용액의 농도에 의해 결정됨을 확인하였다.

Effect of material mechanical differences on shear properties of contact zone composite samples: Experimental and numerical studies

Weiqi Wang,Yicheng Ye,Qihu Wang,Xiaoyun Liu,Fan Yang,Wenkan Tan 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.2

Aiming at the mechanical and structural characteristics of the contact zone composite rock, the shear tests and numerical studies were carried out. The effects of the differences in mechanical properties of different materials and the normal stress on shear properties of contact zone composite samples were analyzed from a macro-meso level. The results show that the composite samples have high shear strength, and the interface of different materials has strong adhesion. The differences in mechanical properties of materials weakens the shear strength and increase the shear brittleness of the sample, while normal stress will inhibit these effect. Under low/high normal stress, the sample show two failure modes, at the meso-damage level: elastic-shearing-frictional sliding and elastic-extrusion wear. This is mainly controlled by the contact and friction state of the material after damage. The secondary failure of undulating structure under normal-shear stress is the nature of extrusion wear, which is positively correlated to the normal stress and the degree of difference in mechanical properties of different materials. The increase of the mechanical difference of the sample will enhance the shear brittleness under lower normal stress and the shear interaction under higher normal stress.

How North Korea Views China: Quantitative Analysis of Korean Central News Agency Reports

( Weiqi Zhang ),( Dmitry Zinoviev ) 한국국방연구원 2018 The Korean Journal of Defense Analysis Vol.30 No.3

How does the North Korean government view China? This study examines North Korea’s foreign policy on China by analyzing the strategic options of North Korean leaders and applying sentiment analysis to Korean Central News Agency (KCNA) reports about China. It is found that North Korea’s generally positive attitude toward China contains nuanced types of sentiments and that North Korean leaders have managed the expression of these sentiments in the media to achieve political goals at domestic and international levels. Our findings also suggest that, first, China may not be the key to the solution of the Korean nuclear issue. Second, Kim Jong Un was not a weak leader from the beginning of his rule. Rather he had acquired a substantial amount of authority before Kim Jong Il passed away. Based on our findings, an analysis of the future development of the North Korea-China relationship is also provided.

Analysis of Rotor Noise Characteristics in Ground Effect

Weiqi Wang,Xi Chen,Qijun Zhao 한국전산유체공학회 2022 한국전산유체공학회 학술대회논문집 Vol.2022 No.10