In this paper, we present a new location fingerprinting database comprised of Wi-Fi received signal strength (RSS) and geomagnetic field intensity measured with multiple devices at a multi-floor building in Xi'an Jiatong-Liverpool University, Suzhou, China. We also provide preliminary results of localization and trajectory estimation based on convolutional neural network (CNN) and long short-term memory (LSTM) network with this database. For localization, we map RSS data for a reference point to an image-like, two-dimensional array and then apply CNN which is popular in image and video analysis and recognition. For trajectory estimation, we use a modified random way point model to efficiently generate continuous step traces imitating human walking and train a stacked twolayer LSTM network with the generated data to remember the changing pattern of geomagnetic field intensity against (x, y) coordinates. Experimental results demonstrate the usefulness of our new database and the feasibility of the CNN and LSTMbased localization and trajectory estimation with the database.

To investigate the geological hazards caused by the action of drying-wetting cycle on rocks, we conducted a conventional triaxial compression test on sandstone under a high number of repeated drying-wetting cycles. By using the TAW-2000D microcomputer-controlled electro-hydraulic servo triaxial rock testing machine, this study investigated the influences of repeated drying-wetting cycles on the deformation and strength characteristics of sandstone. At the same time, the relationships among the strength, elastic modulus, and confining pressure of sandstone were analyzed. The results show that, when the drying-wetting cycles are relatively low, both the compressive strength and elastic modulus of the sandstone increase with the increase of the confining pressure, and the more drying-wetting cycles are, the more they increase. When the confining pressure imposed on the sandstone is constant and the drying-wetting cycles amount to 10-15 times, all the compressive strength, elastic modulus, cohesion, and internal friction angle significantly decrease. When the drying-wetting cycles exceed 15 times, the internal friction angle of the sandstone increases first and then gradually decreases. The fractures of the sandstone exhibit a transformation from brittle failure to ductile failure. Under the action of drying-wetting cycles, the sandstone is greatly influenced by the softening action of water soak at the initial stage. The conclusions provide favorable evidence for the analyses of the long-term stability of rock engineering.

Original scientific paper Rock generally contains various micro-cracks, fissures, pores, joints, and other defects. These defects affect the mechanical properties of rock. In order to clarify the influence of native fissures on rock deformation and failure modes, a laboratory study was carried out using the fissured dolomite, and acoustic wave velocity measurement and natural water absorption tests were conducted to determine the wave velocity and open porosity of the rock specimens. A series of uniaxial compression tests were conducted using the Rock Mechanics Rigidity Servo Testing System, and the strength and deformation characteristics and failure modes of the rock were analysed. The test results show that wave velocity, uniaxial compressive strength, and elastic modulus correlate well with open porosity by negative logarithm relations, and the correlation coefficients range from 0,699 to 0,848. When the stress reaches approximately 50 % of the uniaxial compressive strength, the number of acoustic emission increases substantially; when the stress reaches 10 MPa, the internal damage of the specimens begins to occur. The analysis of the post-failure morphology of the specimens suggest that three types of failure modes, i.e., tension, tension-shear mixed, and shear failures, are possible under uniaxial compression for the tested dolomite. The failure modes are closely related to the initial state of the fissure distribution in the rock. The conclusions obtained in this study provide significant reference for the stability analysis of fractured rock in rock engineering. Posljedica izvornih pukotina na mehaničko ponašanje stijene pod jednoosnim tlakomIzvorni znanstveni članak U stijeni uglavnom postoje različite mikro-pukotine, pukotine (duboke), pore, spojevi i druga oštećenja. Ta oštećenja utječu na mehanička svojstva stijene. Kako bi se razjasnilo djelovanje izvornih pukotina na deformacije i oštećenja stijene, provedeno je laboratorijsko istraživanje uporabom napukle stijene dolomita, a mjerenje brzine akustičkog vala i ispitivanje stupnja apsorpcije vode provedena su kako bi se ustanovila brzina vala i postojeća poroznost uzoraka stijene. Napravljen je niz ispitivanja jednoosne tlačne čvrstoće primjenom Rock Mechanics Rigidity Servo Testing System (sustava ispitivanja čvrstoće stijena) te su se analizirale karakteristike čvrstoće i deformacije i načini stvaranja oštećenja stijene. Rezultati ispitivanja pokazuju da su brzina vala, jednoosna tlačna čvrstoća i modul elastičnosti u korelaciji s otvorenom poroznošću primjenom negativnih odnosa logaritma, a koeficijent korelacije se kreće od 0,699 do 0,848. Kad naprezanje dostigne približno 50 % jednoosne tlačne čvrstoće, znatno se poveća broj akustičkih emisija; kad naprezanje dostigne 10 MPa, počinje se javljati unutarnje oštećenje uzorka. Analiza morfologije uzoraka nakon oštećenja pokazuje da su kod jednoosnog tlaka ispitivanog dolomita moguća tri načina nastajanja oštećenja, t.j. vlak, miješano vlak-smik i smik. Načini oštećenja su usko povezani s početnim sta...

No abstract