빔 구조물의 손상평가를 위한 임피던스 기술의 응용

홍동표,홍용,왕고평,김병진,김영문,이재정,김재열 한국공작기계학회 2006 한국공작기계학회 추계학술대회논문집 Vol.2006 No.-

This paper presents a primary study for a new method of enhancing measurement using impedance analysis method, which is widely used for structure health monitoring. Many of skyscrapers, bridges, tunnels, which have been built up several years, and nearly reached their operating life due to aging crack, material deterioration, and so on. therefore, the health monitoring technique has obtained considerable attention. The goal of this research is to show basic information to evaluate structural health condition using piezoelectric sensors. The piezoelectric materials have various merits. It is easy to shape various forms and can be embedded on the materials more conveniently. Moreover, the excitation frequency can be changed and the piezoelectric sensors cost less. All these features make the piezoelectric-based system applicable to structural healthy monitoring. This work presents a study for the development of a practical and quantitative technique for assessment of the structural health condition by piezoelectric impedance-based technique associated with longitudinal wave propagation. To estimate the damage condition numerically, we suggest the evaluation method Cov (Covariance) and CC (Correlation Coefficient) in this paper.

Exploiting Multi-Hop Relaying to Overcome Blockage in Directional mmWave Small Cells

Yong Niu,Chuhan Gao,Yongliang Ma,Li Su,Depeng Jin 한국통신학회 2016 Journal of communications and networks Vol.18 No.3

With vast amounts of spectrum available in themillimeter wave (mmWave) band, small cells at mmWave frequenciesdensely deployed underlying the conventional homogeneousmacrocell network have gained considerable interest fromacademia, industry, and standards bodies. Due to high propagationloss at higher frequencies, mmWave communications are inherentlydirectional, and concurrent transmissions (spatial reuse)under low inter-link interference can be enabled to significantlyimprove network capacity. On the other hand, mmWave linksare easily blocked by obstacles such as human body and furniture. In this paper, we develop a multi-hop relaying transmission(MHRT) scheme to steer blocked flows around obstacles by establishingmulti-hop relay paths. In MHRT, a relay path selectionalgorithm is proposed to establish relay paths for blocked flowsfor better use of concurrent transmissions. After relay path selection,we use a multi-hop transmission scheduling algorithm to computenear-optimal schedules by fully exploiting the spatial reuse. Through extensive simulations under various traffic patterns andchannel conditions, we demonstrate MHRT achieves superior performancein terms of network throughput and connection robustnesscompared with other existing protocols, especially under seriousblockage conditions. The performance ofMHRT with differenthop limitations is also simulated and analyzed for a better choiceof the maximum hop number in practice.

Research on bolt contour extraction and counting of locomotive running gear based on deep learning

Yong Zhang,Bo Long,Huajun Wang,Chunliang Gao 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.5

The detection of abnormal running gear is essential to a locomotive’s daily maintenance, with the posture and quantity of various small bolts being important indicators to judge whether the locomotive is running safely. Traditional detection algorithms are easily affected by light changes, stain coverage, and image distortion, which is difficult to meet the detection requirements. Thus this paper proposes a deep learning based on bolt detection method that is appropriate for locomotive running gears. First, a bolt segmentation network was developed based on an improved U-netthat compensates the image information loss after multiple cross fusions involving the fusion of front and back convolution layer feature images. Furthermore, the proposed network utilizes the PReLU activation function and employs the concept structure to optimize the convolution method. This strategy aims to improve further the model’s segmentation accuracy and convergence speed. On this basis, we exploited several morphological transformations to improve the contour detection accuracy and ensure the bolt counting accuracy. The experimental results on the mainline running train data highlight that, compared with U-net, the proposed network’s recall rate and the mean intersection over union value are increased by 5.38 and 14.3, respectively. Furthermore, the bolt counting method’s loss function and mean absolute errors are significantly reduced compared with the contour extraction algorithm.

Degradation of roller compacted concrete subjected to low-velocity fatigue impacts and salt spray cycles

Gao, Longxin,Lai, Yong,Zhang, Huigui,Zhang, Jingsong,Zhang, Wuman Techno-Press 2021 Advances in concrete construction Vol.12 No.5

Roller compacted concrete (RCC) used in the island reef airport runway will be subjected to the coupling actions of the fatigue impacts and the salt spray cycles, which will accelerate the deterioration of runway concrete and even threaten the flight safety. A cyclic impact testing machine and a climatic chamber were used to simulate the low-velocity fatigue impact and the salt spray cycles, respectively. The physical properties, the microstructures and the porosity of RCC were investigated. The results show the flexural strength firstly increases and then decreases with the increase of the fatigue impacts and the salt spray cycles. However, the decrease in the flexural strength is significantly earlier than the compressive strength of RCC only subjected to the salt spray cycles. The chlorine, sulfur and magnesium elements significantly increase in the pores of RCC subjected to 30000 fatigue impacts and 300 salt spray cycles, which causes the decrease in the porosity of RCC. The coupling effects of the fatigue impacts and the salt spray cycles in the later period accelerates the deterioration of RCC.

Study on the Crystalline Structure and the Thermal Stability of Silver-oxide Films Deposited by Using Direct-current Reactive Magnetron Sputtering Methods

Gao Xiao-Yong,Feng Hong-Liang,Zhang Zeng-Yuan,Ma Jiao-Min 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.4

Silver-oxide (AgxO) films were deposited on glass substrates by direct-current reactive magnetron sputtering at different oxygen flux ratios (OFR = [O2]/[Ar]) and substrate temperatures (Ts). An X-ray diffraction analysis indicates that the AgxO films are biphased (Ag + Ag2O) when deposited at low OFR values and that Ag2O-dominated AgxO film can only be synthesized at higher OFR values, as con¯rmed by X-ray photoelectron spectroscopy. This result may be due to the Ag2O phase being preferably produced at high OFR value. The AgO phase is thermodynamically unsta-ble compared with the Ag2O phase. In order to further offer deep insight into the ¯lm's thermal stability, Ag2O-dominated AgxO ¯lms were thermally treated by using a rapid thermal processing technique at different annealing temperatures for different annealing times. The Ag2O phase is thermodynamically stable at temperatures below the threshold of the thermal decomposition tem-perature which approaches 175 ±C. The domination of the Ag2O phase in the AgxO film may be attributed to the chain reaction AgO → Ag2O ↔ Ag + O, AgO + Ag → Ag2O.

Three-dimensional high-resolution velocity structure imaging and seismicity study of the Tangshan fault

Yong Ma,Lei Gao,Jinmeng Bi 한국지질과학협의회 2021 Geosciences Journal Vol.25 No.4

Based on the 4415 earthquakes body wave arrival times recorded by the 47 fixed and 33 temporary stations in Tangshan and its surrounding areas, the Tangshan fault’s area focal parameters and three-dimensional fine velocity structure model were inversed by using the consistency-constrained double-difference tomography method. The results revealed that the relocated earthquakes were roughly vertical to the fault’s strike, with the maximum depth exceeding 25 km. The Tangshan fault’s area Vp, Vs and Vp/Vs values demonstrate obvious inhomogeneity, and high speed bodies prone to the brittle fault are dominant on both sides of the fault in the upper crust. Small low velocity bodies appeared initially at the Ms7.8 Tangshan earthquake source in the 14–16 km range of the middle crust, followed by a gradual expansion of the low velocity area with an increase in depth. Variation in the velocity structure below the Tangshan earthquake source shows that the high temperature mantle source invading the crust has weakened the upper crust’s high-speed area, leading to stress accumulation in the local area, which is an important factor for the occurrence of earthquakes in the Tangshan region. The relationship between the regional seismic structure and Tangshan seismic sequence, causing migration of surrounding blocks and seismic activity in recent years was analyzed based on the Tangshan fault’s 3D highresolution velocity structure imaging. It is considered that the Tangshan area unique velocity structure not only plays a pivotal role in promoting horizontal tectonic stress during seismic activity, but is also the root cause of the aftershock evolution process and the fault’s morphological characteristics.

New Triterpenoids from the Fruits of Schisandra wilsoniana and Their Biological Activities

Gao, Xue-Mei,Li, Yun-Qi,Shu, Li-Dan,Shen, Yan-Qiong,Yang, Li-Ying,Yang, Liu-Meng,Zheng, Yong-Tang,Sun, Han-Dong,Xiao, Wei-Lie,Hu, Qiu-Fen Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.3

Investigation of an organic extract of the fruits Schisandra wilsoniana led to the isolation of two new highly oxygenated nortriterpenoids, named schilancidilactones V-W (1-2). Their structures were elucidated by spectroscopic evidence. Compounds 1-2 feature a double bond between C-7 and C-8 compared with related known nortriterpenoids isolated from the genus Schisandra. Compounds 1 and 2 were tested for their anti-HIV-1 activities and cytotoxicity. The results revealed that compounds 1 and 2 showed moderate anti-HIV-1 activities with $EC_{50}$ 3.05 and 2.87 ${\mu}g/mL$, respectively, and compound 1 showed high cytotoxicity against KB and MDA-MB-231 cell with $IC_{50}$ values of 3.18 and 5.22 ${\mu}M$, respectively.

Downregulation of Cdk1 and CyclinB1 Expression Contributes to Oridonin-induced Cell Cycle Arrest at G₂/M Phase and Growth Inhibition in SGC-7901 Gastric Cancer Cells

Gao, Shi-Yong,Li, Jun,Qu, Xiao-Ying,Zhu, Nan,Ji, Yu-Bin Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.15

Background: Oridonin isolated from Rabdosia rubescens, a plant used to treat cancer in Chinese folk medicine, is one of the most important antitumor active ingredients. Previous studies have shown that oridonin has antitumor activities in vivo and in vitro, but little is known about cell cycle effects of oridonin in gastric cancer. Materials and Methods: MTT assay was adopted to detect the proliferation inhibition of SGC-7901 cells, the cell cycle was assessed by flow cytometry and protein expression by Western blotting. Results: Oridonin could inhibit SGC-7901 cell proliferation, the $IC_{50}$ being $15.6{\mu}M$, and blocked SGC-7901 cell cycling in the $G_2/M$ phase. The agent also decreased the protein expression of cyclinB1 and CDK1. Conclusions: Oridonin may inhibit SGC-7901 growth and block the cells in the $G_2/M$ phase by decreasing Cdk1 and cyclinB1 proteins.

Ethanol but not Aqueous Extracts of Tubers of Sauromatum Giganteum(Engl.) Cusimano and Hett Inhibit Cancer Cell Proliferation

Gao, Shi-Yong,Li, Jun,Wang, Long,Sun, Qiu-Jia,Gong, Yun-Fei,Gang, Jian,Su, Yi-Jun,Ji, Yu-Bin Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.24

Background: Both alcohol and aqueous extracts of Sauromatum giganteum(Engl.) Cusimano and Hett, the dried root tuber of which is named Baifuzi in Chinese, have been used for folklore treatment of cancer in Northeast of China. However, little is known about which is most suitable to the cancer therapy. Materials and Methods: Serum pharmacology and MTT assays were adopted to detect the effects of ethanol and aqueous extracts of Sauromatum giganteum(Engl.) Cusimano and Hett, prepared by heat reflux methods, on proliferation of different cancer cells. Results: Cancer cells treated with medium supplemented with 10%, 20%, 40% serum(v/v) containing ethanol extract had a decline in viability, with inhibition rates of 7.69%, 21.8%, 41.9% in MCF-7 cells, 42.8%, 48.1%, 51.8% in SGC-7901 cells, 44.1%, 49.2%, 53.7% in SMMC-7721 cells, 6.8%, 15.2%, 39.8% in HepG2 cells, 7.57%, 16.3%, 36.2% in HeLa cells, 6.24%, 12.5%, 27.4% in A549 cells, and 7.20%, 17.5%, 31.3% in MDA-MB-231 cells, respectively. Viability in the aqueous extract groups was no different with that of controls. Conclusions: An ethanol extract of Sauromatum giganteum(Engl.) Cusimano and Hett inhibited the proliferation of SMMC-7721, SGC-7901 and MCF-7 cells, which supports the use of alcoholic but not aqueous extracts for control of sensive cancers, which might include hepatocarcinoma, gastric cancer and breast cancer.

Lyapunov-based Triggering Mechanisms for Event-triggered Control

Yong-Feng Gao,Liu Liu 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.6

In this paper, a new event-triggering scheme is proposed for a class of event-triggered control systems directly based on input-to-state stable Lyapunov functions. This class is characterized by a constructed decreasing function which is the upper bound of the suitably chosen ISS Lyapunov funtion. It is proven that, compared with the dynamic event-triggering mechanism reported in the literature, this new scheme can ensure a larger minimum interevent time with the same decay rate of the trajectory of the resultant closed-loop system, which is demonstratedthrough a numerical example.