Switchable diurnal radiative cooling by doped VO2

This paper presents design and simulation of a switchable radiative cooler that exploits phase transition in vanadium di-oxide to turn on and off in response to...     

Stimuli-Responsive Dynamic Metaholographic Displays with Designer Liquid Crystal Modulators

Flat optics, realized by the artificially created 2D material platform called optical metasurfaces, is currently undergoing a science-to-technology transition. However, “real-time” active operations of such flat optical devices remain yet unresolved. Here, liquid crystals (LCs)-integrated metaholograms for ultracompact dynamic holographic displays are proposed. The anisotropic nature of the LCs allows facile and repeatable manipulation of the polarization of light. Specifically designed (“designer”) LCs and efficient helicity-encoded metaholograms are combined to realize stimuli-responsive dynamic displays. The designer LC modulators are used as switches that enable a variety of external stimuli (e.g., electric field, heat, surface pressure) to operate holographic images in real-time. Such a dynamic metaholographic platform will provide a path to external stimuli-driven “smart” sensing and display applications such as hologram labels for temperature/pressure/touch monitoring and interactive holographic displays with haptic motion recognition.     

Polypropylene/carbon nanotube composites prepared with a environmentally benign processes

Polypropylene (PP)/multiwalled carbon nanotube (MWNT) composites were prepared with an environmentally benign processes. The surface functionalization of the MWNTs was performed with water as a solvent, and the functionalized MWNTs were mixed with PP to form composites with a melt process. The effects of the MWNTs on the mechanical and thermal properties of the composites were studied. The tensile strength and modulus of the composites increased with the amount of MWNTs. The thermal stability was also improved by the reinforced MWNTs. The MWNTs also improved the oxidative stability of the composite on UV irradiation. Although pure PP degraded almost completely after 12 h of irradiation, the composite reinforced with MWNTs retained some level of mechanical strength after UV irradiation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Stiffness requirements for transverse stiffeners of rectangular CFT compression panels

This paper presents a more rational calculation of the minimum stiffness required for transverse stiffeners of stiffened concrete filled tube (CFT) compression panels. As longitudinal stiffeners are essentially compression members, transverse stiffeners are required to control the effective length. Both the longitudinal stiffener and transverse stiffener subdivide the compression panel in a grid pattern so the relatively thin plate can carry the induced compressive load in the most efficient manner. However, the provisions for the required rigidity of transverse stiffeners in the literature are inconsistent in general and in particular; do not exist in the case of the concrete filled compression panels. Here, the parameters that govern the behavior of the transverse stiffeners are identified theoretically using the column buckling approximation. In order to calibrate and quantify the analytical equations developed, incremental nonlinear analyses were performed on a large number of finite-element models. The numerically collected data were then used to validate the equations developed.     

Soil-Structure Interaction and Imperfect Trench Installations for Deeply Buried Concrete Pipes

The imperfect trench installation method is used to reduce earth pressure on buried concrete pipes. Few quantitative refinements to the imperfect trench installation method, however, have been added since the fundamental mechanics of the reverse arching action were proposed by Marston and Spangler. There have been limited research results published regarding, primarily, qualitative aspects of earth load reduction for imperfect trench conditions. This paper identifies variables that significantly affect earth loads, as well as the effects of bedding and sidefill treatments. An optimum geometry for imperfect trench installations with regard to a soft material zone is presented to maximize the earth load reduction effects. The optimization process was based on parametric studies of the geometry and location of the soft zone, bedding, and sidefill treatments to reduce earth pressures. Predictor equations for earth load reduction rates were formulated incorporating the optimum geometry for the soft zone and bedding and sidefill treatments.     

Top-down nanofabrication approaches toward single-digit-nanometer scale structures

Journal of Mechanical Science and Technology - Sub-10 nm nanostructures have received broad interest for their intriguing nano-optical phenomena, such as extreme field localization and enhancement,...     

Shear flow in thin-walled cellular sections

Frequently flexural members are made of single or multiple cellular sections due to a variety of reasons. Clearly, the superb torsional capacity of such sections is a major attraction for girders in horizontally curved alignments. However, the ease of maintenance and esthetic considerations favor the choice of such girders.     

An Immersive Augmented‐Reality‐Based e‐Learning System Based on Dynamic Threshold Marker Method

In recent years, augmented reality (AR) technologies have been the subject of great interest among many communities. In education applications, old‐fashioned materials (or textbooks) are still used, despite remarkable AR developments in the industrial area. We present an AR system for education. Our system consists of an authoring tool that can be used to create educational content, a viewer that plays that content, and an engine to manage the tool and viewer. In our system, a marker unit recognizes a marker printed on a plane or a cubic plane by adaptively adjusting the threshold to have an excellent recognition rate in diverse environments and acquires corresponding data of the marker. Based on the system, we test 142 elementary school students for increased educational benefits using our system.     

Unlocking the future of optical security with metasurfaces

The complex degrees of freedom of light, such as amplitude, phase, polarization, and orbital angular momentum, make it a prime candidate for use in optical secu...     

An augmented reality-based authoring tool for E-learning applications

In recent years, augmented reality technologies have been a subject of great interest among the scientific community. However, most studies have focused on hardware and software development without particular emphasis on the authoring phase. As a consequence, the authoring process of augmented reality applications is accomplished today through hard-coding of a specific application. This approach, however, requires operators. In the education applications, the hard-coding methods tend to be retained, despite remarkable technological developments in the industrial area. Textbooks are mainly used in educational systems and many educators are very passive about applying new materials. In this paper, we present an immersive authoring tool for education using augmented reality, where applications authorized by our tool interact with the user in order to increase the learner’s interest and reflect various desires of dynamic environment. Our authoring tool consists of a composing tool that can be used to create educational contents, a viewer that plays the content, and an engine to power the tool and viewer.