Transient Thermal Response of a Multilayered Geomaterial Subjected to a Heat Source

Lu Jun Wang,Zhi Yong Ai 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.9

The analysis of layered geomaterials thermo-mechanical coupling response is important in design and analysis of a nuclear waste repository. Conventional analytical approaches usually have some intrinsic faults of ill-conditioned matrices for thick layers or accumulative numerical errors for a great quantity of layers for containing positive exponential functions. This paper presents a stable computational approach with no positive exponential functions to study the transient thermal responses of a layered geomaterial subjected to a heat source. Based on the governing equations of thermo-mechanical coupling problems, the analytical layer elements for a finite layer and a half–space are derived by utilizing Laplace and Hankel transforms. The analytical layer elements are then assembled into the total stiffness matrix and solved in the transformed domain. Finally, the Laplace–Hankel transform inversion is employed to obtain an actual solution in the physical domain. Numerical computations indicate that the difference of geomaterial mass properties between layers shows obvious effects on thermal response of the layered system, and these results can be served as a benchmark solution for future analyses of stratified material.

Organocatalytic and Enantioselective Mannich Reaction of Dicyanoolefins with α-Amido Sulfones

Jun Lu,Wei-Yi Chen 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.10

Aprotic and Aqueous Li–O₂ Batteries

Lu, Jun,Li, Li,Park, Jin-Bum,Sun, Yang-Kook,Wu, Feng,Amine, Khalil American Chemical Society 2014 Chemical reviews Vol.114 No.11

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Application of softened truss model with plastic approach to reinforced concrete beams in torsion

Lu, Jun-Kai,Wu, Wen-Hsiung Techno-Press 2001 Structural Engineering and Mechanics, An Int'l Jou Vol.11 No.4

The present paper discusses the behavior of the reinforced concrete beams subjected to torsion by applying the endochronic plastic model in conjunction with the softened truss model. The endochronic constitutive equations are developed to describe the behavior of concrete. The mechanical behavior of concrete is decomposed into hydrostatic part and deviatoric part. New definition of the bulk modulus and the shear modulus are defined in terms of compressive strength of concrete. Also, new deviatoric hardening function is developed. Then, the endochronic constitutive equations of concrete are applied with the softened truss model for the behavior of the reinforced concrete beams subjected to torsion. The theoretical results obtained based on the present model are compared with the experimental data. The present model has shown the ability to describe the behavior of reinforced concrete beams subjected to torsion.

Magnetism in lithium-oxygen discharge product.

Lu, Jun,Jung, Hun-Ji,Lau, Kah Chun,Zhang, Zhengcheng,Schlueter, John A,Du, Peng,Assary, Rajeev S,Greeley, Jeffrey,Ferguson, Glen A,Wang, Hsien-Hau,Hassoun, Jusef,Iddir, Hakim,Zhou, Jigang,Zuin, Lucia Wiley-VCH 2013 ChemSusChem Vol.6 No.7

<P>Nonaqueous lithium-oxygen batteries have a much superior theoretical gravimetric energy density compared to conventional lithium-ion batteries, and thus could render long-range electric vehicles a reality. A molecular-level understanding of the reversible formation of lithium peroxide in these batteries, the properties of major/minor discharge products, and the stability of the nonaqueous electrolytes is required to achieve successful lithium-oxygen batteries. We demonstrate that the major discharge product formed in the lithium-oxygen cell, lithium peroxide, exhibits a magnetic moment. These results are based on dc-magnetization measurements and a lithium-oxygen cell containing an ether-based electrolyte. The results are unexpected because bulk lithium peroxide has a significant band gap. Density functional calculations predict that superoxide-type surface oxygen groups with unpaired electrons exist on stoichiometric lithium peroxide crystalline surfaces and on nanoparticle surfaces; these computational results are consistent with the magnetic measurement of the discharged lithium peroxide product as well as EPR measurements on commercial lithium peroxide. The presence of superoxide-type surface oxygen groups with spin can play a role in the reversible formation and decomposition of lithium peroxide as well as the reversible formation and decomposition of electrolyte molecules.</P>

Fatigue evaluation and CFRP strengthening of diaphragm cutouts in orthotropic steel decks

Lu Ke,Chuanxi Li,Jun He,Yongjun Lu,Yang Jiao,Yongming Liu 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.39 No.4

The cracking at the transverse diaphragm cutout is one of the most severe fatigue failures threatening orthotropic steel decks (OSDs), whose mechanisms and crack treatment techniques have not been fully studied. In this paper, full-scale experiments were first performed to investigate the fatigue performance of polished cutouts involving the effect of an artificial geometrical defect. Following this, comparative experimental testing for defective cutouts strengthened with carbon fiber-reinforced polymer (CFRP) was carried out. Numerical finite element analysis was also performed to verify and explain the experimental observations. Results show that the combinative effect of the wheel load and thermal residual stress constitutes the external driving force for the fatigue cracking of the cutout. Initial geometrical defects are confirmed as a critical factor affecting the fatigue cracking. The principal stress 6 mm away from the free edge of the cutout can be adopted as the nominal stress of the cutout during fatigue evaluation, and the fatigue resistance of polished cutouts is higher than Grade A in AASHTO specification. The bonded CFRP system is highly effective in extending the fatigue life of the defective cutouts. The present study provides some new insights into the fatigue evaluation and repair of OSDs.

Electro-Active Polymer Actuator by Employing Ionic Networking Membrane of Poly (styrene-alt-maleic anhydride)-Incorporated Poly (vinylidene fluoride)

Jun Lu(여군),Sang-Gyun Kim(김상균),Sunwoo Lee(이선우),Il-Kwon Oh(오일권) 한국소음진동공학회 2007 한국소음진동공학회 학술대회논문집 Vol.2007 No.11

Curcumin attenuates renal ischemia reperfusion injury via JNK pathway with the involvement of p300/CBP-mediated histone acetylation

Lu Yang,Xiaoxiang Chen,Zirong Bi,Jun Liao,Weian Zhao,Wenqi Huang 대한생리학회-대한약리학회 2021 The Korean Journal of Physiology & Pharmacology Vol.25 No.5

Apoptosis is proved responsible for renal damage during ischemia/reperfusion. The regulation for renal apoptosis induced by ischemia/reperfusion injury (IRI) has still been unclearly characterized to date. In the present study, we investigated the regulation of histone acetylation on IRI-induced renal apoptosis and the molecular mechanisms in rats with the application of curcumin possessing a variety of biological activities involving inhibition of apoptosis. Sprague–Dawley rats were randomized into four experimental groups (SHAM, IRI, curcumin, SP600125). Results showed that curcumin significantly decreased renal apoptosis and caspase-3/-9 expression and enhanced renal function in IRI rats. Treatment with curcumin in IRI rats also led to the decrease in expression of p300/cyclic AMP response element-binding protein (CBP) and activity of histone acetyltransferases (HATs). Reduced histone H3 lysine 9 (H3K9) acetylation was found near the promoter region of caspase-3/-9 after curcumin treatment. In a similar way, SP600125, an inhibitor of c-Jun N-terminal kinase (JNK), also attenuated renal apoptosis and enhanced renal function in IRI rats. In addition, SP600125 suppressed the binding level of p300/CBP and H3K9 acetylation near the promoter region of caspase-3/-9, and curcumin could inhibit JNK phosphorylation like SP600125. These results indicate that curcumin could attenuate renal IRI via JNK/p300/CBP-mediated anti-apoptosis signaling.

Molecular Cloning and Characterization of Two Brassica napus TTG1 Genes Reveal Genus-Specific Nucleotide Preference, Extreme Protein-Level Conservation and Fast Divergence of Organ-Specificity

Jun Lu,Jia Na Li,Bo Lei,San Gen Wang,You Rong Chai 한국유전학회 2009 Genes & Genomics Vol.31 No.2

Encoding a WD40 protein, Arabidopsis thaliana TRANSPARENT TESTA GLABRA1 (AtTTG1) regulates trichome and root hair differentiation as well as flavonoids and seed mucilage deposition in plants. Here, two Brassica napus TTG1 (BnTTG1) genes were isolated, and Southern hybridization also generated only two bands. The 1511-bp BnTTG1-1 and the 1555-bp BnTTG1-2 both have one intron, and show alternative sites for transcription start, polyadenylation and intron right border splicing. EST and GSS tags suggested that BnTTG1-1 was derived from B. rapa, while BnTTG1-2 from B. oleracea. Evidence implies that TTG1 was possibly triplicated in Brassiceae, but some triplicated members were lost soon, which might involve fragmental rearrangements. BnTTG1-1 shares 88.7% genomic and 95.7% mRNA identities with BnTTG1-2. Deduced BnTTG1-1 and BnTTG1-2 proteins both are 337 aa, differed only by substitution of a similar residue. They resemble AtTTG1 in WD40 domain and all conserved motifs. TTG1/AN11-type WD40 proteins are extremely conserved even across kingdoms. Homological and structural characterizations identified BnTTG1-1 and BnTTG1-2 to be orthologs of AtTTG1. Several non-coding motifs are conserved between AtTTG1 and BnTTG1. BnTTG1 coding regions tend to evolve high GC contents through T/A→C/G substitutions especially T→C transition, but AtTTG1 shows opposite base preference. BnTTG1 genes also evolve a GA-stretch in the leader sequence. RT-PCR detected complementation in organ-specificity between BnTTG1-1 and BnTTG1-2. BnTTG1-2 is more like AtTTG1 and is expressed in all major organs. BnTTG1-1 is more organ-specific with lower expression in seed and root, possibly withdrawing from regulating seed coat pigment/mucilage deposition and root hair formation.

Improved photocatalytic performance of Pd-doped ZnO

Jun bo Zhong,Jian zhang Li,Xi yang He,Jun Zeng,Yan Lu,Wei Hu,Kun Lin 한국물리학회 2012 Current Applied Physics Vol.12 No.3

ZnO and Pd-doped ZnO photocatalysts with different molar ratio of Pd/Zn (1/100, 2/100, 3/100 and 4/100) were prepared by a solegel method. The photocatalysts prepared were characterized by BET surface area, X-ray diffraction (XRD), UV/vis diffuse reflectance (DRS) and surface photovoltage spectroscopy (SPS), respectively. The results show that doping Pd into ZnO decreases the BET surface area. The XRD spectra of the Pd-doped ZnO catalysts calcined at 773 K show only the characteristic peaks of wurtzite-type. Doping Pd into ZnO increases the absorbance of ZnO in visible region and enhances the photoinduced charge separation rate. The photocatalytic activity of Pd-doped ZnO photocatalysts for decolorization of methyl orange (MO) solution was evaluated, of all the photocatalysts prepared, the Pddoped ZnO with 3/100 possesses the best photocatalytic activity. The results of further experiments show that increased adsorption ability of light and high separation rate of photoinduced charge carriers all play an important role in promotion of photocatalytic activity of Pd-doped ZnO nanostructure.