Silver Nanoflower Decorated Graphene Oxide Sponges for Highly Sensitive Variable Stiffness Stress Sensors

Soft conductive materials should enable large deformation while keeping high electrical conductivity and elasticity. The graphene oxide (GO)‐based sponge is a potential candidate to endow large deformation. However, it typically exhibits low conductivity and elasticity. Here, the highly conductive and elastic sponge composed of GO, flower‐shaped silver nanoparticles (AgNFs), and polyimide (GO‐AgNF‐PI sponge) are demonstrated. The average pore size and porosity are 114 µm and 94.7%, respectively. Ag NFs have thin petals (8–20 nm) protruding out of the surface of a spherical bud (300–350 nm) significantly enhancing the specific surface area (2.83 m² g^?1). The electrical conductivity (0.306 S m^?1 at 0% strain) of the GO‐AgNF‐PI sponge is increased by more than an order of magnitude with the addition of Ag NFs. A nearly perfect elasticity is obtained over a wide compressive strain range (0–90%). The strain‐dependent, nonlinear variation of Young's modulus of the sponge provides a unique opportunity as a variable stiffness stress sensor that operates over a wide stress range (0–10 kPa) with a high maximum sensitivity (0.572 kPa^?1). It allows grasping of a soft rose and a hard bottle, with the minimal object deformation, when attached on the finger of a robot gripper.     

Thermal conductivity of CVD diamond films

Diamond films 60 and 170 µm in thickness were grown by PACVD (plasma-assisted chemical vapor deposition) under similar conditions. The thermal diffusivity of these freestanding films was measured between 100 and 300 K using AC calorimetry. Radiation heat loss from the surface was estimated by analyzing both the amplitude and the phase shift of a lock-in amplifier signal. Thermal conductivity was calculated using the specific heat data of natural diamond. At room temperature, the thermal conductivity of the 60 and 170 m films is 9 and 16 W-cm^–1. K^–1 respectively, which is 40–70% that of natural diamond, The temperature dependence of thermal conductivity of the CVD diamond films is similar to that of natural diamond, Phonon scattering processes are considered using the Debye model, The microsize of the grain boundary has a significant effect on the mean free path of phonons at low temperatures. The grain in CVD diamond film is grown as a columnar structure, Thus, the thicker film has the larger mean grain size and the higher thermal conductivity. Scanning electron microscopy (SEM) and Raman spectroscopy were used to study the microstructure of the CVD diamond films. In this experiment, we evaluated the quality of CVD diamond film of the whole sample by measuring the thermal conductivity.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Mobile-cloud assisted framework for selective encryption of medical images with steganography for resource-constrained devices

In this paper, the problem of outsourcing the selective encryption of a medical image to cloud by resource-constrained devices such as smart phone is addressed, without revealing the cover image to cloud using steganography. In the proposed framework, the region of interest of the medical image is first detected using a visual saliency model. The detected important data is then embedded in a host image, producing a stego image which is outsourced to cloud for encryption. The cloud which has powerful resources, encrypts the image and sent back the encrypted marked image to the client. The client can then extract the selectively encrypted region of interest and can combine it with the region of non-interest to form a selectively encrypted image, which can be sent to medical specialists and healthcare centers. Experimental results and analysis validate the effectiveness of the proposed framework in terms of security, image quality, and computational complexity and verify its applicability in remote patient monitoring centers.     

Transient temperature responses of hydronic radiant floor heating system by different pipe embedding depth and water supply condition

"Ondol" is a Korean unique heating system. It is a specific radiant floor heating system using combustion heat of briquette or timber in Korea. Such traditional "Ondol" is changed to radiant heating system with pipe-coil embedded in the floor or slab. This study has contributed to the understandings of the transient behaviours of Ondol-heated floor panels and enclosure exposed to this type of heating system. The result is that the water supply temperature had a large effect on the rate of increase in floor surface and room air temperature. But, in spite of a higher water supply temperature, the heat flow rate was not increased considerably. The shallow pipe embedding depths, of course, result in a low heat flow rate.     

A study on interfacial mechanisms and structure of poly(ethylene-co-methacrylic acid)/copper with reflection–absorption infrared spectroscopy

The interfacial mechanism and structure of poly(ethylene-co-methacrylic acid)/copper were investigated using reflection-absorption infrared spectroscopy (RAIR). Based on IR spectrum of EMAA/copper, a strong absorption peak appearing at approximate 1,600 cm⁻¹ is attributed to the asymmetric stretching vibration of COO^― (υCOO_as^―) and a relatively weak absorption band at 1,375 cm⁻¹ is assigned to the symmetric stretching vibration of COO^― (υCOO_s^―). Therefore, it can be determined that copper interacts with EMAA through a strong ionic interaction and carboxylate structure is formed in the interfacial regions. And, according to the band intensities of carboxylate stretching modes and different sensitivities of RAIR to perpendicular and parallel transition moments, it can be concluded that EMAA is absorbed onto a copper substrate with a configuration in which the twofold axis of the C_2υ point group for carboxylate group inclines certain degree from the normal to the surface. In addition, the interfacial carboxylate structure of EMAA/copper is confirmed to be a monodentate one through calculating the difference (Δυ)between the asymmetric carboxylate stretch (υCOO_as^―) and the symmetric stretch (υCOO_s^―).     

Effect of Multi-Wall Carbon Nanotubes on the Mechanical Properties of Natural Rubber

Multi-walled carbon nanotubes (MWNTs) were used to prepare natural rubber (NR) nanocomposites. Our first efforts to achieve nanostructures in MWNTs/NR nanocomposites were formed by incorporating carbon nanotubes in a polymer solution and subsequently evaporating the solvent. Using this technique, nanotubes can be dispersed homogeneously in the NR matrix in an attempt to increase the mechanical properties of these nanocomposites. The properties of the nanocomposites such as tensile strength, tensile modulus, elongation at break and hardness were studied. Mechanical test results show an increase in the initial modulus for up to 12 times in relation to pure NR. In addition to mechanical testing, the dispersion state of the MWNTs into NR studied by Transmission Electron Microscopy (TEM) in order to understand the morphology of the resulting system     

Physicochemical properties,antioxidant activity and inhibition of α‐glucosidase of a novel fermented pepper (Capsiccum annuum L.) leaves‐based vinegar

The aim of this study was to utilise by‐product pepper leaves for vinegar production due to its nutritional value. Changes in physicochemical and functional properties in four main process from raw material (leaves) to lactic acid (juice), alcohol (wine) and acetic acid (vinegar) fermentations were evaluated and compared. Their nutritional compositions were significantly different and particularly the wine and vinegar had higher total phenol content and their expanded diversity than the juice and then leaves (P < 0.05). Difference in values for phenolic compound was highly correlated with their α‐glucosidase inhibitory (AGI) and antioxidant capacities in DPPH and superoxide radical scavenging and reducing power assays (r = 0.919–0.981); vinegar ≥ wine > juice > leaves. Especially, AGI activity was greatly enhanced depending on fermentation steps beyond expectation. Thus, these data confirm that pepper leaves is a good functional source and the vinegar fermentation improved the functionality in stages.     

Saliency-weighted graphs for efficient visual content description and their applications in real-time image retrieval systems

The exponential growth in the volume of digital image databases is making it increasingly difficult to retrieve relevant information from them. Efficient retrieval systems require distinctive features extracted from visually rich contents, represented semantically in a human perception-oriented manner. This paper presents an efficient framework to model image contents as an undirected attributed relational graph, exploiting color, texture, layout, and saliency information. The proposed method encodes salient features into this rich representative model without requiring any segmentation or clustering procedures, reducing the computational complexity. In addition, an efficient graph-matching procedure implemented on specialized hardware makes it more suitable for real-time retrieval applications. The proposed framework has been tested on three publicly available datasets, and the results prove its superiority in terms of both effectiveness and efficiency in comparison with other state-of-the-art schemes.