Cyclic p-y Curves of Monopiles in Dense Dry Sand Using Centrifuge Model Tests

In this study, centrifuge model tests were used to examine the lateral behavior of a monopile embedded in dry sand through cyclic lateral loading tests. The soil specimens used in the tests were dry Jumunjin sand with a relative density of 80% and a friction angle of 38°. A static loading test was performed once, and cyclic loading tests were performed four times using four magnitudes of cyclic load (30%, 50%, 80%, and 120% of static lateral capacity). The experimental cyclic p-y curve was obtained through the tests, and the maximum soil resistance points that were found for each load were used to find the cyclic p-y backbone curve for each depth. The two variables which are needed to define the cyclic p-y backbone curve, i.e., the initial modulus of subgrade reaction (kini) and ultimate soil resistance (pu), were suggested as functions of the soil’s physical properties and the pile. The cyclic p-y curve of the first cycle and the 100th cycle were formulated to present the upper limit and lower limit. The suggested cyclic p-y curve had an overestimated soil resistance compared with the existing API (1987) method, but the initial modulus of subgrade reaction was underestimated

Taming of random lasers

International audienc

Nanoscale mapping of noise-source-controlled hopping and tunneling conduction in domains of reduced graphene oxide

International audienc

Study on Dynamic Behavior of Bridge Pier by Impact Load Test Considering Scour

In this study, for the establishment of a safety evaluation method, non-destructive tests were performed by developing a full-scale model pier and simulating scour on the ground adjacent to a field pier. The surcharge load (0–250 kN) was applied to the full-scale model pier to analyze the load’s effect on the stability. For analyzing the pier’s behavior according to the impact direction, an impact was applied in the bridge axis direction, pier length direction, and pier’s outside direction. The impact height corresponded to the top of the pier. A 1-m deep scour was simulated along one side of the ground, which was adjacent to the pier foundation. The acceleration was measured using accelerometers when an impact was applied. The natural frequency, according to the impact direction and surcharge load, was calculated using a fast Fourier transform (FFT). In addition, the first mode (vibratory), second mode (vibratory), and third modes (torsion) were analyzed according to the pier behavior using the phase difference, and the effect of the scour occurrence on the natural frequency was analyzed. The first mode was most affected by the surcharge load and scour. The stability of the pier can be determined using the second mode, and the direction of the scour can be determined using the third mode

Lasing at topological edge states in a photonic crystal L3 nanocavity dimer array

International audienc

Anderson localizations and photonic band-tail states observed in compositionally disordered platform

International audienc

Centrifuge Tests On The Lateral Behavior Of Offshore Monopile In Saturated Dense Sand Under Cyclic Loading

In this study, the cyclic lateral behaviors of an offshore monopile in saturated dense sand under cyclic loading was investigated using centrifuge model tests. The soil used for testing was Jumunjin sand, which was deposited with a relative density of 80 %. A static loading test was carried out to obtain the static lateral capacity of the monopile, from which the magnitudes of cyclic load were determined at 30 %, 50 %, 80 %, and 120 % of the lateral capacity. A hundred cycles were applied to the pile head with the frequency of 0.125 Hz. Experimental cyclic p-y curves were obtained at 2, 5, and 7-m depths, from which equations for cyclic p-y curves for saturated dense sand were proposed. The proposed p-y curve was compared with the conventional p-y curves; it was found that the proposed equations overestimate the ultimate soil resistance compared with the conventional ones, whereas the initial modulus of subgrade reaction was only 35 % the conventional ones

A Highly Tunable and Fully Biocompatible Silk Nanoplasmonic Optical Sensor

Novel concepts for manipulating plasmonic resonances and the biocompatibility of plasmonic devices offer great potential in versatile applications involving real-time and in vivo monitoring of analytes with high sensitivity in biomedical and biological research. Here we report a biocompatible and highly tunable plasmonic bio/chemical sensor consisting of a natural silk protein and a gold nanostructure. Our silk plasmonic absorber sensor (SPAS) takes advantage of the strong local field enhancement in the metal–insulator–metal resonator in which silk protein is used as an insulating spacer and substrate. The silk insulating spacer has hydrogel properties and therefore exhibits a controllable swelling when exposed to water–alcohol mixtures. We experimentally and numerically show that drastic spectral shifts in reflectance minima arise from the changing physical volume and refractive index of the silk spacer during swelling. Furthermore, we apply this SPAS device as a glucose sensor with a very high sensitivity of 1200 nm/RIU (refractive index units) and high relative intensity change

Complex Growth Behavior of Li Dendrites in Al2O3 Nanoparticles-Driven Viscoelastic Electrolytes for Lithium Metal Batteries: Dynamic versus Quasistatic Rheology

Viscoelastic electrolytes have been focused as innovative electrolytes for Li metal batteries because of their unique mechanical and electrochemical properties compared to conventional Newtonian liquid electrolytes. However, the role of the mechanochemical properties of viscoelastic electrolytes in the electrochemical performance of Li metal has not been fully understood yet. In particular, dynamic rheology of viscoelastic electrolytes has not been considered one of significant factors accelerating Li dendrites growth. Herein, Al2O3 nanoparticles-driven viscoelastic electrolytes are introduced to improve the electrochemical performance of Li metal. In contrast to conventional Newtonian liquid electrolytes, viscoelastic electrolytes significantly suppress Li dendrites growth during cycling, resulting in excellent electrochemical performance, such as stable capacity retention over 400 cycles. Moreover, the complex growth mechanism of Li dendrites in viscoelastic electrolytes is demonstrated in terms of dynamic versus quasistatic rheology. Dynamic rheology prevails over quasistatic rheology as Al2O3 weight fraction and current density is increased in viscoelastic electrolytes. Dynamic rheology gives rise to spatial non-uniformity in the mechanical and rheological properties of viscoelastic electrolytes, leading to promoting Li dendrites growth due to the uneven distribution of local current density on the Li metal surface. These findings provide fundamental insights into strategies to design advanced electrolytes for Li metal batteries.