비만아 부모의 돌봄 경험: q 방법론

Annual review of condensed matter physics

Dynamics of Phononic Materials and Structures: Historical Origins, Recent Progress, and Future Outlook

Climate phenomena and their relevance for future regional climate change

The Randolph Glacier Inventory (RGI) is a globally complete collection of digital outlines of glaciers, excluding the ice sheets, developed to meet the needs of the Fifth Assessment of the Intergovernmental Panel on Climate Change for estimates of past and future mass balance. The RGI was created with limited resources in a short period. Priority was given to completeness of coverage, but a limited, uniform set of attributes is attached to each of the � 198 000 glaciers in its latest version, 3.2. Satellite imagery from 1999-2010 provided most of the outlines. Their total extent is estimated as 726 800 � 34 000 km 2 . The uncertainty, about � 5%, is derived from careful single-glacier and basin-scale uncertainty estimates and comparisons with inventories that were not sources for the RGI. The main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover. These errors appear not to be normally distributed, and quantifying them reliably is an unsolved problem. Combined with digital elevation models, the RGI glacier outlines yield hypsometries that can be com- bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers. The RGI has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume, and thus actual and potential contributions to sea-level rise.

https://www.eoas.ubc.ca/~vradic/Pfeffer_et_al2014.pdf

The Randolph Glacier inventory: a globally complete inventory of glaciers

Tailoring the dynamical behavior of wave-guide structures can provide an efficient and physically elegant approach for optimizing mechanical components with regards to vibroacoustic propagation. Architectured materials as pyramidal core kirigami cells combined with smart systems may represent a promising way to improve the vibroacoustic quality of structural components. This paper describes the design and modeling of a pyramidal core with auxetic (negative Poisson's ratio) characteristics and distributed shunted piezoelectric patches that allow for wave propagation control. The core is produced using a kirigami technique, inspired by the cutting/folding processes of the ancient Japanese art. The kirigami structure has a pyramidal unit cell shape that creates an in-plane negative Poisson's ratio macroscopic behavior. This structure exhibits in-plane elastic properties (Young's and shear modulus) which are higher than the out-of-plane ones, and hence this lattice has very specific properties in terms of wave propagation that are investigated in this work. The short-circuited configuration is first analyzed, before using negative capacitance and resistance as a shunt which provides impressive band gaps in the low frequency range. All configurations are investigated by using a full analysis of the Brillouin zone, rendering possible the deep understanding of the dynamical properties of the smart lattice. The results are presented in terms of dispersion and directivity diagrams, and the smart lattice shows quite interesting properties for the adaptive filtering of elastic waves at low frequencies bandwidths.

/pdf/a-piezo-shunted-kirigami-auxetic-lattice-for-adaptive-58kgv0in1k.pdf

A piezo-shunted kirigami auxetic lattice for adaptive elastic wave filtering

A negative capacitance shunt is a basic, analog, active circuit electrically connected to a piezoelectric transducer to control the vibrations of flexural bodies. The shunt circuit consists of a resistor and a synthetic negative capacitor to introduce a real and imaginary impedance on a vibrating mechanical system. The electrical impedance of the negative capacitance shunt modifies the effective modulus of the piezoelectric transducer to reduce the stiffness and increase the damping, which causes a decrease in amplitude of the vibrating structure to which the elements are bonded. To gain an insight into the electromechanical coupling and power output, the shunt and the electrical properties of the piezoelectric transducer are modeled using circuit modeling software. The power output of the model is validated with experimental measurements of a shunt connected to a piezoelectric transducer pair bonded to a vibrating aluminum cantilever beam. The model is used to select the passive components of the negative capacitance shunt to increase the efficiency and quantify the voltage output limit of the op-amp.

https://iopscience.iop.org/article/10.1088/0964-1726/22/6/065009/pdf

The power output and efficiency of a negative capacitance shunt for vibration control of a flexural system

Shape Memory Alloys (SMAs) are widely studied as new materials with potential for use in various passive or active vibration isolation systems. Up to now, few papers deal with a precise description of their proper dynamic behaviour. However, it is important to clearly understand the dissipation mechanisms in order to optimize the design of a structure. We present here a detailed characterization of a Cu–Al–Be beam. The stress induced phase transformation austenite → martensite produces a strongly nonlinear behaviour. The aim of this study is to confront experimental results to a rheological model of the beam. The experimental setup consists in a cantilever beam excited by a light electromagnetic actuator. The response is measured by an accelerometer fixed at the free end of the beam. Stepped sine measurements have been performed around the frequency of the first mode of the beam under different excitation levels. The obtained frequency response functions strongly depend on the global vibration amplitude. Then a specific finite element model has been designed, taking into account the geographic repartition of the two phases inside the beam. The simulations show a similar behaviour and allow the interpretation of the experimental observations.

Analysis of the behavior of a Shape Memory Alloy beam under dynamical loading

A substantial challenge in guiding elastic waves is the presence of reflection and scattering at sharp edges, defects, and disorder. Recently, mechanical topological insulators have sought to overcome this challenge by supporting back-scattering resistant wave transmission. In this paper, we propose and experimentally demonstrate a reconfigurable electroacoustic topological insulator exhibiting an analog to the quantum valley Hall effect (QVHE). Using programmable switches, this phononic structure allows for rapid reconfiguration of domain walls and thus the ability to control back-scattering resistant wave propagation along dynamic interfaces for phonons lying in static and finite-frequency regimes. Accordingly, a graphene-like polyactic acid (PLA) layer serves as the host medium, equipped with periodically arranged and bonded piezoelectric (PZT) patches, resulting in two Dirac cones at the K points. The PZT patches are then connected to negative capacitance external circuits to break inversion symmetry and create nontrivial topologically protected bandgaps. As such, topologically protected interface waves are demonstrated numerically and validated experimentally for different predefined trajectories over a broad frequency range.

https://www.pnas.org/content/pnas/117/28/16138.full.pdf

Manuel Collet

Papers

A piezo-shunted kirigami auxetic lattice for adaptive elastic wave filtering

The power output and efficiency of a negative capacitance shunt for vibration control of a flexural system

Analysis of the behavior of a Shape Memory Alloy beam under dynamical loading

Experimental realization of a reconfigurable electroacoustic topological insulator

Multi-mode wave propagation in ribbed plates. Part II: Predictions and comparisons