Effects of Quenching Methods and Aging Processes on the Crushing Properties and Microstructure of Al–Zn–Mg Alloy Thin-Walled Square Extrusions

Hui Guo,Jin Zhang,Cheng Wang,Yun‑lai Deng 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

In this study, the effects of different (online quenching and offline quenching) quenching methods and aging processes (T6and T73) on the crashworthiness and microstructural evolution of three Al–Zn–Mg alloys (G1–G3) were studied by conductingtensile test and axial compression tests at room temperature, combined with optical metallography, electron back scattereddiffraction, and transmission electron microscopy microstructural observations. The obtained results revealed that thecrushing properties of three different Al–Zn–Mg alloys subjected to different quenching methods and aging processes weresignificantly different. Their crushing energy absorption of are ranked as follows: G1 > G3 > G2. The highest total energyabsorption gap (between T6 and T73) is the G1 alloy, and the lowest one is the G3 alloy. The largest total energy absorptiongap between the two quenching methods is the G3 alloy, and the smallest one is the G1 alloy. The G2 alloy with the largesttotal amount of Zn + Mg has the highest number density of matrix precipitates, the largest precipitate gap (between T6 andT73) and the smallest precipitate gap between the two quenching methods. The G3 alloy with the largest Zn/Mg ratio hasthe smallest number density of matrix precipitates, the minimum precipitation gap (between T6 and T73) and the maximumprecipitation gap between the two quenching methods. The G1 alloy with the lowest Zn/Mg ratio has the smallest size ofgrain boundary precipitates and PFZ width, while their largest values are obtained for the G3 alloy with the maximum Zn/Mg ratio. As a crushing resistant structural material, the crushing properties is improved without reducing the strength. Theratio of Zn/Mg should be controlled within the range of 4.57–6.15, while the total amount of Zn + Mg should be controlledwithin the range of 6.18–7.01.

호이스트용 SRM의 구동시스템의 특성해석

이진국,이동희,안진우 경성대학교 공학기술연구소 2005 공학기술연구지 Vol.12 No.-

This paper presents a development of Switched Reluctance Motor (SRM) drive system for a hoist application. In the hoist system, smoothing start-up and braking are very important for a protection of goods. In order to improved a start-up and a stop performance of hoist system, the smoothing operation sequence of SRM using direct instantaneous torque control is proposed. The proposed Direct Instantaneous Torque Control (DITC) the instantaneous torque of SRM according to the switching sequence and hysteric band. In order to compare the reference and actual torque of SRM, pre-measured flux and torque look-up table are regulate used. The proposed SRM Drive system is verified by the simulation result.

4-레벨 인버터를 이용한 고속 SRM 구동시스템

이동희,이진국,안진우 경성대학교 공학기술연구소 2005 공학기술연구지 Vol.12 No.-

This paper proposes high speed SRM drive system for blower with a novel 4-level inverter and precise excitation position generator. In order to get a fast build-up and a demagnetization of excitation current, 4-level inverter system is proposed. The proposed 4-level inverter has additional charge capacitor, power switch and diode in the conventional asymmetric converter. The charged high voltage is supplied to the phase winding for fast current build- up, and demagnetization current is charged to additional capacitor of 4-level inverter. In addition, a precise excitation position generator can reduce turn-on and turn-off angle error according to sampling period of digital control system. The proposed high speed SRM drive system is verified by computer simulations and experimental results.

Synergistic Effects of Leflunomide and Benazepril in Streptozotocin-Induced Diabetic Nephropathy

Jin, Hua,Piao, Shang Guo,Jin, Ji Zhe,Jin, Ying Shun,Cui, Zhen Hua,Jin, Hai Feng,Zheng, Hai Lan,Li, Jin Ji,Jiang, Yu Ji,Yang, Chul Woo,Li, Can S.Karger 2014 The Nephron Journals Vol.126 No.3

<P>Abstract</P><P><B><I>Background:</I></B> Leflunomide (LEF) and benazepril have renoprotective effects on diabetic nephropathy (DN) through their anti-inflammatory and anti-fibrotic activities. This study investigated whether combined treatment using LEF and benazepril affords superior protection compared with the respective monotherapies. <B><I>Methods:</I></B> Diabetes was induced with streptozotocin (STZ, 65 mg/kg) by intraperitoneal injection in male Wistar rats. Two weeks after STZ injection, diabetic rats were treated daily for 12 weeks with LEF (10 mg/kg), benazepril (10 mg/kg), or a combination of both. Basic parameters (body weight, fasting blood glucose level, and 24 h urinary protein excretion), histopathology, inflammatory [inflammatory cell infiltration (ED-1), monocyte chemoattractant protein-1 (MCP-1), and Toll-like receptor-2 (TLR-2)] and glomerulosclerotic factors [transforming growth factor-β<SUB>1</SUB> (TGF-β<SUB>1</SUB>) and connective tissue growth factor (CTGF)], and oxidative stress (8-hydroxy-2'-deoxyguanosine, 8-OHdG) were studied. <B><I>Results:</I></B> Benazepril or LEF treatment significantly prevented body weight loss and 24 h urinary protein excretion induced by diabetes; combined treatment with LEF and benazepril further improved these parameters compared with giving each drug alone (all p < 0.01). Increased expression of inflammatory (MCP-1 and TLR-2) and glomerulosclerotic (TGF-β<SUB>1</SUB> and CTGF) factors in diabetic rat kidney was reduced by treatment with either LEF or benazepril and was further reduced by the combined administration of the two drugs (p < 0.01). These effects were accompanied by suppression of urinary 8-OHdG excretion. There was no significant between-group difference in blood glucose level. <B><I>Conclusions:</I></B> LEF treatment lessens DN, and combined treatment with LEF and benazepril provides synergistic effects in preventing DN.</P><P>© 2014 S. Karger AG, Basel</P>

Free Vibration of the Cracked Non-uniform Beam with Cross Section Varying as Polynomial Functions

Guo-jin Tan,Yang Liu,Yafeng Gong,Yangfan Shen,Ziyu Liu 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.11

This paper presents an approach for free vibration analysis of the cracked non-uniform beam with general boundary conditions, whose mass per unit length and bending moment of inertia varying as polynomial functions. Firstly, the general expression of mode shape function of the non-uniform beam with four undetermined coefficients is solved by a generalized power series method based on the Euler-Bernoulli beam theory. Then, the transfer matrix method is combined into the mode shape function of the non-uniform beam to improve the computational efficiency owe to the fewer segments divided by the cracks and joints at the different forms of variable cross-section. The massless rotational springs are adopted to simulate the cracks to derive the transfer relationship of the undetermined coefficients in the same segment. The four undetermined coefficients matrix is obtained by using equilibrium and continuity conditions between two adjacent segments, and then the characteristic equation of the entire cracked beam is formed. Finally, the correctness and reliability of the proposed method in this paper is verified by the methods presented by other published papers and the Finite Element Method (FEM). In addition, the crack parameters on the vibratory characteristics are investigated through the numerical examples.

On rings whose annihilating-ideal graphs are blow-ups of a class of Boolean graphs

Jin Guo,Tongsuo Wu,Houyi Yu 대한수학회 2017 대한수학회지 Vol.54 No.3

For a finite or an infinite set $X$, let $2^X$ be the power set of $X$. A class of simple graph, called strong Boolean graph, is defined on the vertex set $2^X\setminus \{X,\,\eset\}$, with $M$ adjacent to $N$ if $M\cap N=\eset.$ In this paper, we characterize the annihilating-ideal graphs $\mathbb{AG}(R) $ that are blow-ups of strong Boolean graphs, complemented graphs and pre-atomic graphs respectively. In particular, for a commutative ring $R$ such that $\mathbb{AG}(R)$ has a maximum clique $S$ with $3\le |V(S)| \leq \infty$, we prove that $\mathbb{AG}(R)$ is a blow-up of a strong Boolean graph if and only if it is a complemented graph, if and only if $R$ is a reduced ring. If assume further that $R$ is decomposable, then we prove that $\mathbb{AG}(R)$ is a blow-up of a strong Boolean graph if and only if it is a blow-up of a pre-atomic graph. We also study the clique number and chromatic number of the graph $\mathbb{AG}(R)$.

Synthesis and Characterization of Carbazole Core-based Small Molecular-Hole-transporting Materials for Red Phosphorescent OLEDs

Jin Guo Fan,김미진,Quynh Pham Bao Nguyen,Ramanaskanda Braveenth,고혜민,한지훈,김경우,권장혁,채규윤 대한화학회 2016 Bulletin of the Korean Chemical Society Vol.37 No.10

A series of carbazole core-based hole-transporting materials (HTMs) have been synthesized using Buchwald–Hartwig amination reaction. HTMs 7a and 7b exhibited high thermal decomposition temperatures of 400 and 380°C, respectively, without any crystalline features. Among the designed HTMs 7a–c, the device performance based on HTM 7a is the best and identical with that of the typical hole-transporting N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) material.

A Benzobisimidazolium-Based Fluorescent and Colorimetric Chemosensor for CO₂

Guo, Zhiqian,Song, Na Ri,Moon, Jong Hun,Kim, Myounwoo,Jun, Eun Jin,Choi, Jiyoung,Lee, Jin Yong,Bielawski, Christopher W.,Sessler, Jonathan L.,Yoon, Juyoung American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.43

<P>A new sensor for the fluorescent and colorimetric detection of CO<SUB>2</SUB> is described. The system utilizes fluoride to activate a tetrapropyl benzobisimidazolium salt and operates in the absence of an exogenous base. On the basis of spectroscopic and theoretical analyses, the mode of action of the present system is ascribed to the fluoride-induced formation of an N-heterocyclic carbene intermediate that reacts with CO<SUB>2</SUB> to form an imidazolium carboxylate.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-43/ja306891c/production/images/medium/ja-2012-06891c_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja306891c'>ACS Electronic Supporting Info</A></P>

Numerical study of rock-breaking performance of cutters in heterogeneous sand cobble ground

Jin Guo,Xiangwei Kong,Liu Cheng,Xueyi Li 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6

Further research into tunneling performance in heterogeneous sand cobble ground demands an accurate numerical model of actual formation. In this paper, the ground model composed of spherical sand and ellipsoidal cobble was constructed to study the rockbreaking performance by using the discrete element method. The shape and physical parameters of sand and cobble were obtained on the basis of field test data. Then, the ground model was constructed to simulate the rock-breaking process of the cutterhead. The results show that the center cutter has a high flat wear percentage. With the decrease in cobble content (CC), the cracks between cutters are not connected effectively, thereby resulting in lower rock-breaking quantity. Finally, the influences of CC on the optimal parameters and crack propagation were analyzed. The results indicate that the rock-breaking performance in the ground with a low CC can be improved by increasing penetration and reducing cutter spacing.

STRONG SHELLABILITY OF SIMPLICIAL COMPLEXES

Guo, Jin,Shen, Yi-Huang,Wu, Tongsuo Korean Mathematical Society 2019 대한수학회지 Vol.56 No.6

Imposing a strong condition on the linear order of shellable complexes, we introduce strong shellability. Basic properties, including the existence of dimension-decreasing strong shelling orders, are developed with respect to nonpure strongly shellable complexes. Meanwhile, pure strongly shellable complexes can be characterized by the corresponding codimension one graphs. In addition, we show that the facet ideals of pure strongly shellable complexes have linear quotients.