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SPECTRAL PROPERTIES OF k-QUASI-2-ISOMETRIC OPERATORS
Junli Shen,Fei Zuo 한국수학교육학회 2015 純粹 및 應用數學 Vol.22 No.3
Let T be a bounded linear operator on a complex Hilbert space H. For a positive integer k, an operator T is said to be a k-quasi-2-isometric operator if T^{*k}(T^{*2}T^{2}-2T^{*}T+I)T^{k}=0, which is a generalization of 2-isometric operator. In this paper, we consider basic structural properties of k-quasi-2-isometric operators. Moreover, we give some examples of k-quasi-2-isometric operators. Finally, we prove that generalized Weyl's theorem holds for polynomially k-quasi-2-isometric operators
A comprehensive genetic algorithm for design optimization of Z-bar loader working mechanism
Junli Shen,Guoqiang Wang,Qiushi Bi,Junna Qu 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.11
The operation mechanism is generally considered as a key component of a wheel loader. Its working performance has great influence on the service life, stability, efficiency and economy of the loader. This paper establishes a mathematical model of Z-bar loader mechanism in polar coordinate with four-bar linkage and six-bar Watt linkage synthesis, investigates the working performance, such as mechanism transmission ratio, carry stability, parallelism, dumping in any position, bucket flat setting, maximum dig depth, extreme transmission angle and so on. Then we explore new design methods of joint-position of Z-bar loader linkage between tilt cylinder and loader frame to perfect some of the performance. A new method, comprehensive genetic algorithm, is presented to optimize non-linear equation with multi-constraints, and the results improve the multidisciplinary performance. Furthermore, a virtual prototype of the working mechanism is modeled to simulate and verify the optimization results.
Thermodynamic Investigation of Methanol and Dimethyl Ether Synthesis from CO2 Hydrogenation
Shen, Wen Jie,Jun, Ki Won,Choi, Ho Suk,Lee, Kyu Wan 한국화학공학회 2000 Korean Journal of Chemical Engineering Vol.17 No.2
The thermodynamics involved in the catalytic hydrogenation of CO₂ have been examined extensively. By assuming that methanol and dimethyl ether (DME) are the main products, two reaction systems each consisting of two pararell reactions were analyzed and compared in terms of the equilibrium yield and selectivity of the useful products, methanol and DME. The calculation results demonstrated that the production of DME allows much higher oxygenate yield and selectivity than that of methanol.
Evaluation of Various Escherichia coli Strains for Enhanced Lycopene Production
( Jun Ren ),( Junhao Shen ),( Thi Duc Thai ),( Min-gyun Kim ),( Seung Ho Lee ),( Wonseop Lim ),( Dokyun Na ) 한국미생물생명공학회 2023 Journal of microbiology and biotechnology Vol.33 No.7
Lycopene is a carotenoid widely used as a food and feed supplement due to its antioxidant, anti-inflammatory, and anti-cancer functions. Various metabolic engineering strategies have been implemented for high lycopene production in Escherichia coli, and for this purpose it was essential to select and develop an E. coli strain with the highest potency. In this study, we evaluated 16 E. coli strains to determine the best lycopene production host by introducing a lycopene biosynthetic pathway (crtE, crtB, and crtI genes cloned from Deinococcus wulumuqiensis R12 and dxs, dxr, ispA, and idi genes cloned from E. coli). The 16 lycopene strain titers diverged from 0 to 0.141 g/l, with MG1655 demonstrating the highest titer (0.141 g/l), while the SURE and W strains expressed the lowest (0 g/l) in an LB medium. When a 2 × YTg medium replaced the MG1655 culture medium, the titer further escalated to 1.595 g/l. These results substantiate that strain selection is vital in metabolic engineering, and further, that MG1655 is a potent host for producing lycopene and other carotenoids with the same lycopene biosynthetic pathway.
Shear Performance of Steel Thin Sheet-to-Thick Plate Bolted Connections
Shen Liu,Ruo-qiang Feng,Chang-jun Zhong 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.4
This paper presents a study on the bolted connections of cold-formed steel (CFS) sheets and hot-rolled steel (HRS) plates. The test strengths and failure modes were compared with the results predicted by the North American Specification (AISI S 100–16) and European Standard (EN1993-1–3) for CFS structures. Additionally, the influence of the fastener diameter and the thickness of the CFS sheets and HRS plates on the specimens were discussed. In addition, numerical modeling of the specimens was established to simulate the failure modes and load-deformation relationships. Finally, a modified equation for bearing strength is proposed, discussed, and verified by reliability analysis. The results showed that bearing failure, shear failure and net section failure were observed. The nominal strengths predicted by AISI S 100 and EN 1993–1-3 are generally conservative. The numerical models can predict the failure modes and load-deformation relationships of the specimens with good agreement. In addition, the proposed method for the bearing strength of the connections has better accuracy than the current specifications.
Jun Zhao,Fuqiang Shen,Chenzhe Si,Yuping Sun,Lu Yin 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.1
Experimental investigation on seismic performance of RC shear walls reinforced with CFRP bars in boundary elements to enhance the resilience was presented which is expected for stable resistance capacity and small residual deformation. Six RC shear walls reinforced with CFRP bars as longitudinal tensile materials in boundary elements were tested under reversed cyclic lateral loading while subjected to constant axial compression with different axial load ratios of 0.17, 0.26 and 0.33, respectively. Two forms of stirrups were used for each axial load ratio, which were rectangular and circular stirrups in boundary elements. A reference specimen, ordinary RC shear walls, was also introduced to certify the excellence of CFRP bars. The test results indicated that the walls utilizing CFRP bars had small residual deformations and residual crack widths. Lower crack propagation height and larger concrete crushing region, bearing capacity and equivalent viscous damping coefficient (EVDC) could be observed with the increase of axial load ratios. The effects of stirrup forms on experimental results had a relation to the axial load ratio. When the axial load ratio was small, the shear walls with circular stirrups had better energy dissipation than that with rectangular stirrups at a given drift level, while the cumulative energy dissipation (CED) were similar. With the increase of axial load ratio, the walls exhibited similar energy dissipation at the same drift level, however, the shear walls with rectangular stirrups had larger CED.
Shen, Haishan,Lee, Suhyeon,Kang, Jun-gu,Eom, Tae-Yil,Lee, Hoojeong,Kang, Chiwon,Han, Seungwoo Elsevier 2018 Journal of alloys and compounds Vol.767 No.-
<P><B>Abstract</B></P> <P>In this study, we investigated the effect of film thickness on the electrical and thermoelectric properties of bismuth-tellurium (Bi-Te) films. Bi-Te films of 1-, 4-, 10-, and 18-μm thicknesses were deposited via co-evaporation. Microstructural analyses using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy indicated columnar film growth, with a highly porous structure that increased with the film thickness. The electron mobility of the films decreased significantly as the film thickness increased, which may be explained by the film porosity. Given a fairly constant Seebeck coefficient, the power factor decreased significantly with film thickness: 2.8 mW/mK<SUP>2</SUP> for the 1-μm-thick film and 1.5 mW/mK<SUP>2</SUP> for the 18-μm-thick Bi-Te film.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We investigate the effects of the film thickness of Bi-Te films the electrical and thermoelectric properties. </LI> <LI> We deposit Bi-Te films with 1-, 4-, 10-, 18-μm thicknesses via co-evaporation. </LI> <LI> The electron mobility decreases significantly with the thickness increasing. </LI> <LI> With the Seebeck coefficient not changing much, the power factor decreases substantially with the thickness. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>