Fatigue performance monitoring of full-scale PPC beams by using the FBG sensors

Licheng Wang,Jigang Han,Yupu Song 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.13 No.6

When subjected to fatigue loading, the main failure mode of partially prestressed concrete (PPC)structure is the fatigue fracture of tensile reinforcement. Therefore, monitoring and evaluation of the steelstresses/strains in the structure are essential issues for structural design and healthy assessment. The currentstudy experimentally investigates the possibility of using fiber Bragg grating (FBG) sensors to measure thesteel strains in PPC beams in the process of fatigue loading. Six full-scale post-tensioned PPC beams wereexposed to fatigue loading. Within the beams, the FBG and resistance strain gauge (RSG) sensors wereindependently bonded onto the surface of tensile reinforcements. A good agreement was found between therecorded results from the two different sensors. Moreover, FBG sensors show relatively good resistance tofatigue loading compared with RSG sensors, indicating that FBG sensors possess the capability forlong-term health monitoring of the tensile reinforcement in PPC structures. Apart from the above findings, itcan also be found that during the fatigue loading, there is stress redistribution between prestressed andnon-prestressed reinforcements, and the residual strain emerges in the non-prestressed reinforcement. Thisphenomenon can bring about an increase of the steel stress in the non-prestressed reinforcement.

Fatigue performance monitoring of full-scale PPC beams by using the FBG sensors

Wang, Licheng,Han, Jigang,Song, Yupu Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.13 No.6

When subjected to fatigue loading, the main failure mode of partially prestressed concrete (PPC) structure is the fatigue fracture of tensile reinforcement. Therefore, monitoring and evaluation of the steel stresses/strains in the structure are essential issues for structural design and healthy assessment. The current study experimentally investigates the possibility of using fiber Bragg grating (FBG) sensors to measure the steel strains in PPC beams in the process of fatigue loading. Six full-scale post-tensioned PPC beams were exposed to fatigue loading. Within the beams, the FBG and resistance strain gauge (RSG) sensors were independently bonded onto the surface of tensile reinforcements. A good agreement was found between the recorded results from the two different sensors. Moreover, FBG sensors show relatively good resistance to fatigue loading compared with RSG sensors, indicating that FBG sensors possess the capability for long-term health monitoring of the tensile reinforcement in PPC structures. Apart from the above findings, it can also be found that during the fatigue loading, there is stress redistribution between prestressed and non-prestressed reinforcements, and the residual strain emerges in the non-prestressed reinforcement. This phenomenon can bring about an increase of the steel stress in the non-prestressed reinforcement.

Mesoscale simulation of chloride diffusion in concrete considering the binding capacity and concentration dependence

Licheng Wang,Tamon Ueda 사단법인 한국계산역학회 2011 Computers and Concrete, An International Journal Vol.8 No.2

In the present paper, a numerical simulation method based on mesoscopic composite structure of concrete, the truss network model, is developed to evaluate the diffusivity of concrete in order to account for the microstructure of concrete, the binding effect of chloride ions and the chloride concentration dependence. In the model, concrete is described as a three-phase composite, consisting of mortar, coarse aggregates and the interfacial transition zones (ITZs) between them. The advantage of the current model is that it can easily represent the movement of mass (e.g. water or chloride ions) through ITZs or the potential cracks within concrete. An analytical method to estimate the chloride diffusivity of mortar and ITZ, which are both treated as homogenious materials in the model, is introduced in terms of water-tocement ratio (w/c) and sand volume fraction. Using the newly developed approaches, the effect of cracking of concrete on chloride diffusion is reflected by means of the similar process as that in the test. The results of calculation give close match with experimental observations. Furthermore, with consideration of the binding capacity of chloride ions to cement paste and the concentration dependence for diffusivity, the onedimensional nonlinear diffusion equation is established, as well as its finite difference form in terms of the truss network model. A series of numerical analysises performed on the model find that the chloride diffusion is substantially influenced by the binding capacity and concentration dependence, which is same as that revealed in some experimental investigations. This indicates the necessity to take into account the binding capacity and chloride concentration dependence in the durability analysis and service life prediction of concrete structures.

Mesoscale computational simulation of the mechanical response of reinforced concrete members

Licheng Wang,Jiuwen Bao 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.15 No.2

On mesoscopic level, concrete can be treated as a three-phase composite material consisting of mortar, aggregates and interfacial transition zone (ITZ) between mortar and aggregate. A lot of research has confirmed that ITZ plays a crucial role in the mechanical fracture process of concrete. The aim of the present study is to propose a numerical method on mesoscale to analyze the failure mechanism of reinforced concrete (RC) structures under mechanical loading, and then it will help precisely predict the damage or the cracking initiation and propagation of concrete. Concrete is meshed by means of the Rigid Body Spring Model (RBSM) concept, while the reinforcing steel bars are modeled as beam-type elements. Two kinds of RC members, i.e. subjected to uniaxial tension and beams under bending, the fracture process of concrete and the distribution of cracks, as well as the load-deflection relationships are investigated and compared with the available test results. It is found that the numerical results are in good agreement with the experimental observations, indicating that the model can successfully simulate the failure process of the RC members.

Georgenia faecalis sp. nov. isolated from the faeces of Tibetan antelope

Wang Xiaoxia,Yang Jing,Huang Yuyuan,Wu Xiaomin,Wang Licheng,Han Limei,Li Sha,Li Huan,Fu Xiaoying,Chen Hai,Zhu Xiong 한국미생물학회 2020 The journal of microbiology Vol.58 No.9

Two aerobic, Gram-stain-positive, non-motile, non-sporulating coccoid strains, designated ZLJ0423T and ZLJ0321, were isolated from the faeces of Tibetan antelope (Pantholops hodgsonii). Their optimal temperature, NaCl concentration and pH for growth were 28°C, 0.5% (w/v) NaCl and pH 7.5, respectively. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strains ZLJ0423T and ZLJ0321 were very similar to each other (99.8%) and had a sequence similarity of 97.0% with Georgenia satyanarayanai NBRC 107612T and Georgenia subflava CGMCC 1.12782T. Phylogenomic analysis based on 688 core genes indicated that these strains formed a clade with G. satyanarayanai NBRC 107612T and Georgenia wutianyii Z294T. The predominant cellular fatty acids were anteiso-C15:0, anteiso-C15:1 A and C16:0. The major menaquinone was MK-8(H4). The cell-wall amino acids consisted of alanine, lysine, glycine and aspartic acid, with lysine as the diagnostic diamino acid. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, phosphatidylinositol mannosides and two unidentified lipids formed the polar lipid profile. The DNA G + C content of both isolates was 73.9 mol%. The digital DNA–DNA hybridization value between strains ZLJ0423T and ZLJ0321 was 91.2%, but their values with closely related species and other available type strains of the genus Georgenia were lower than the 70% threshold. On the basis of polyphasic taxonomic data, strains ZLJ0423T and ZLJ0321 represent a novel species within the genus Georgenia, for which the name Georgenia faecalis sp. nov. is proposed. The type strain is ZLJ0423T (= CGMCC 1.13681T = JCM 33470T).

The Influence of Dispersion State of Graphene Sheets on the Microstructure and Thermal Conductivity of Free-Standing Reduced Graphene Oxide Films

Xiaorui Wang,Shuangling Jin,Rui Zhang,Yan Liu,Jiangcan Wang,Zhen Hu,Wangzhao Lu,Shuo Yang,Minglin Jin,Wenming Qiao,Licheng Ling 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.3

Reduced graphene oxide (rGO) aqueous dispersions were synthesized from GO suspensions with hydrazine as reducing agent via a microwave-hydrothermal process in ammonia solution. The rGO films were fabricated by vacuum filtration of above dispersions. When the weight ratio of hydrazine to GO (R N2H4/GO) increases from 0.125 to 9, the dispersion stability of rGO nanosheets in hydrazine/ammonia solution degrades gradually, the surfaces of resultant films become rough from smooth and large interspaces turn up in the transverse section. With the increasing of R N2H4/GO, the C/O atomic ratio and orientation degree of (002) plane of rGO films increase, and the in-plane thermal conductivity also increases, achieving a maximum value of 1056 W/m K when R N2H4/GO is 3.375, then decreases because large interspaces in the rGO film with higher reduction degree greatly limit the thermal transport due to the severe phonon scatterings at the sheets boundaries.

A Study of Leveraging Memory Level Parallelism for DRAM System on Multi-Core Architecture

Yuxuan Wang,Yingping Zhang,Xiaotian Zhang,Jian Yin,Licheng Chen 보안공학연구지원센터 2016 International Journal of Hybrid Information Techno Vol.9 No.4

DRAM system has been more and more critical on modern multi-core architecture where the Moore’s law has been made effect on increasing the number of cores integrated in a processor chip. The performance of DRAM system is usually measured in term of bandwidth and latency, which are regarded as inherently depending on Row Buffer Hit Rate (RBHR) according to previous studies. In this paper, we find that Memory Level Parallelism (MLP) exhibits a stronger correlation with the performance of DRAM system on multi-core/many-core architecture than RBHR, and promoting MLP significantly improves DRAM system performance. In order to exploit the MLP, we have evaluated various approaches including multi-bank, multi-row-buffers, multi-memory-controllers and the obsolete Virtual Channel Memory (VCM). The experimental results show that VCM is a better alternative to traditional DRAM chip on multicore/many-core architecture than the other three approaches because VCM has almost all the advantages of the others: 1) it can improve homogeneous workloads’ IPC by 2.21X on a 16-core system with 32 virtual channels due to leveraging unexploited MLP. 2) It can also promote Quality-of-Service (QoS) of DRAM system by removing unfairness while memory controllers serve memory requests. 3) It can save energy and has low area costs. Unfortunately, VCM, which was proposed in the late 1990s, faded away before multi-core/manycore became dominated. Therefore, we suggest memory chip vendors reconsider the VCM technology for multi-core architecture.

Grenville-age orogenic event along the northeastern margin of the Quanji massif, NW China: constraints from ~1.1 Ga migmatite

Zhouxuan Xiao,Licheng Ma,Wan Jiang,Ran Wang,Yuyan Yao,Jie Cai,Jingyu Lin,Lu Li 한국지질과학협의회 2020 Geosciences Journal Vol.24 No.3

Detailed petrologic, geochemical and geochronological investigation on migmatites provide key information on the tectonic-magmatic history of the Quanji Massif, NW China. The studied migmatites are mainly composed of granitic gneisses, with lenticular refractory residua spread along its foliation. Zircon U-Pb ages of 1129.2 ± 7.4 Ma (1σ, MSWD = 0.34, N = 31) and 1135.1 ± 9.5 Ma (1σ, MSWD = 0.05, N = 22) were determined for the granitic gneiss and refractory residue, respectively. Garnet grains from the refractory residue show no distinctive intra-crystalline zonation, and are rich in Fe and Mg, but poor in Ca and Mn, akin to those from metapelite. Samples from the granitic gneisses have high contents of SiO2 (from 67.92% to 69.89%), K2O (from 3.94% to 5.00%) and A/CNK (1.11–1.17), with LREE enrichment and distinctly negative Eu anomalies (Eu/Eu* = 0.49–0.53) in the chondrite-normalized REE patterns, and significantly negative Nb, Ta, Ti and Sr anomalies in the primitive mantle-normalized spider diagrams. Granitic gneisses samples have consistent Nd isotope compositions with negative εNd(t) values ranging from –1.06 to –6.04, and TDM model ages ranging from 1.83 to 2.23 Ga. These geochemical features suggest that the granitic rocks belong to the S-type granites, which were predominately derived from a late Paleoproterozoic crustal source. The granitic gneiss was probably formed by partial melting of the sediments which had been suffered graunlite-facies metamorphism. The components with low melting points (e.g., felsic minerals) might replace the sediments to form migmatites and migmatitic granites, and thus preserved the refractory residua. Therefore, the late Mesoproterozoic orogenic event is the coeval response of the global Grenvillian orogeny, indicating an important crustal remelting episode in the Quanji Massif.

Thermal history of the Jurassic marine sequences in the Qiangtang Basin, northern Tibetan Plateau: implication for the hydrocarbon preservation

Mingming Fei,Licheng Wang,Yalin Li,Yushuai Wei 한국지질과학협의회 2016 Geosciences Journal Vol.20 No.4

The Jurassic marine sequences of the Qiangtang Basin in the northern part of the Tibet Plateau have the best petroleum exploration prospect. The prototype basin has undergone multi-stage and complicated tectonic events since the Cretaceous, especially the mid-Cretaceous tectonic event and the Cenozoic uplift of Tibetan Plateau. However, little information about the impact of these tectonic events on petroleum preservation has been done. In this paper, the burial and thermal histories modeling using vitrinite reflectance (Ro) are used to characterize the impact. The results showed that there is a regional falling of palaeotemperature in the Qiangtang Basin during the mid-Cretaceous indicating a regional tectonic event caused by the collision between Lhasa and Qiangtang blocks. However, the Cenozoic tectonic event caused by the uplift of Tibetan Plateau since 30 Ma was only recorded in the Southern Qiangtang Depression and not obvious in the Northern Qiangtang Depression, which indicates that uplift-denudation caused by the mid-Cretaceous tectonic event was extensive in whole Qiangtang Basin and more significant to the hydrocarbon accumulation than those in the Cenozoic. The event could damage the previously formed hydrocarbon traps and caused the leaking of cap-rocks for the dramatically denudation especially in the Southern Qiangtang Depression. We speculated that the Northern Qiangtang Depression has the lower thickness of denudation and barely influenced by the Cenozoic tectonic events and thus is primary exploration target for gas or gas hydrate.

A (k,t,n) verifiable multi-secret sharing scheme based on adversary structure

( Jing Li ),( Licheng Wang ),( Jianhua Yan ),( Xinxin Niu ),( Yixian Yang ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.12

A (n,t,n) secret sharing scheme is to share a secret among n group members, where each member also plays a role of a dealer,and any t shares can be used to recover the secret. In this paper, we propose a strong (k,t,n) verifiable multi-secret sharing scheme, where any k out of n participants operate as dealers. The scheme realizes both threshold structure and adversary structure simultaneously, and removes a trusted third party. The secret reconstruction phase is performed using an additive homomorphism for decreasing the storage cost. Meanwhile, the scheme achieves the pre-verification property in the sense that any participant doesn`t need to reveal any information about real master shares in the verification phase. We compare our proposal with the previous (n,t,n) secret sharing schemes from the perspectives of what kinds of access structures they achieve, what kinds of functionalities they support and whether heavy storage cost for secret share is required. Then it shows that our scheme takes the following advantages: (a) realizing the adversary structure, (b) allowing any k out of n participants to operate as dealers, (c) small sized secret share. Moreover, our proposed scheme is a favorable candidate to be used in many applications, such as secure multi-party computation and privacy preserving data mining, etc.