Thermal, electrical and mechanical properties of three-dimensional functional materials

Colloidal assembly is a dynamic phenomenon where the particulates dispersed in fluids, with the size over tens of nms to several μms, form into specific spatial organization resulting from the variations in the surroundings. The general hard sphere colloids with charged surfaces can be self-assembled into the periodic arrays during the drying process of the fluids. These static periodic arrays, namely, colloidal crystals do not possess any dynamic functionalities, but serve as a sacrificial template for the fabrication of various classes of 3D functional materials. On the other hand, some colloids themselves have their own dynamic functionalities, so that they can be directed-assembled in response to external triggering forces. These particles serve as an active element that offers dynamic changes in the properties of the material systems. The inorganic 3D functional meso/nanostructures were developed for the potential uses in thermal management applications using the self-assembled colloidal crystals as the template. Especially, the Fe3O4 was epitaxially grown through the complex 3D colloidal templates, after which the single crystal Fe3O4 3D porous structures were obtained. These materials have the multiple nanosized 3D interfaces to deter the phonon transport, and at the same time consist of the single crystals to enhance the electron transport. Through various kinds of analysis tools, we thoroughly characterized the materials, particularly focusing on the crystallinity, the density, the thermal conductivity, and the electrical conductivity. The epitaxial Fe3O4 nanoporous structures including the pores with 40 nm in diameter were identified to be thermally insulating and electrically conductive at the same time. The dynamically reconfigurable colloidal assembly in the viscoelastic fluids was investigated with the ultimate goals of the energy harvesting. As the first step, two different methods of integrating the colloids into the viscoelastic media were developed. The PNIPAM colloids, which intrinsically possess the thermo-responsive functionality, were synthesized by two kinds of polymerization routes, and then incorporated into the fibrin networks hydrogels using the method developed. The PNIPAM microgels/fibrin networks hydrogel composites demonstrated the reversibly switchable mechanical property, which is multifold jump in the storage modulus due to the strain-stiffening of fibrin networks, in response to the external temperature changes

Dynamic Duty-Cycle MAC Protocol for IoT Environments and Wireless Sensor Networks

This paper proposes a new protocol that can be used to reduce transmission delay and energy consumption effectively. This will be done by adjusting the duty-cycle (DC) ratio of the receiver node and the contention window size of the sender node according to the traffic congestion for various devices in the Internet of Things (IoT). In the conventional duty-cycle MAC protocol, the data transmission delay latency and unnecessary energy consumption are caused by a high collision rate. This is because the receiver node cannot sufficiently process the data of the transmitting node during the traffic peak time when the transmission and reception have the same duty-cycle ratio. To solve this problem, this paper proposes an algorithm that changes the duty-cycle ratio of the receiver and broadcasts the contention window size of the senders through Early Acknowledgment (E-ACK) at peak time and off/peak time. The proposed algorithm, according to peak and off/peak time, can transmit data with fewer delays and minimizes energy consumption. Document type: Articl

FEASIBILITY STUDY ON EFFECT OF STRUCTURAL FLEXIBILITY OF ASYMMETRIC PRE-SWIRL STATOR ON PROPULSION PERFORMANCE FOR KRISO CONTAINER SHIP (KCS)

The use of energy-saving devices is the most effective method for decreasing CO2 emissions, which is an increasingly concerning environmental issue. The asymmetric pre-swirl stator has been developed as an energy-saving device and has been successfully applied to various types of vessels. In the present study, a flexible material was applied to an asymmetric pre-swirl stator to determine the variation in the flow around stator and its efficiency. A fluid–structure interaction (FSI) analysis system was developed using the Star-CCM+ (fluid) and the Abaqus (structure). The proposed analysis system was validated by comparing the experimental results using a flexible plate in a flowing fluid. The flexible stator was applied to a 3,600 TEU KRISO Container Ship to determine the improvement in its performance compared to the previous optimum value achieved with a rigid stator. Although this application was conducted on a model scale and the deformation was small, the results of the flexible stator indicated the possibility of not only increasing the efficiency but also decreasing the vortex risk around stator blade

VALIDATION OF OPTIMALLY DESIGNED STATOR-PROPELLER SYSTEM BY EFD AND CFD

The development of energy-saving devices to lower the energy efficiency design index (EEDI) of ships has been actively researched worldwide. One such device is an asymmetric pre-swirl stator, which helps to improve the propulsion efficiency by recovering the rotational energy generated during propeller rotation. Determining the pitch angle is the most important factor in the design of an efficient asymmetric pre-swirl stator. To optimize the pitch angle of an asymmetric pre-swirl stator, this study deals with potential-flow, computational fluid dynamics, and model tests. The model delivered power at a design speed of 24 kt was compared by changing the pitch angle by ±2° with respect to the reference angle designed using a potential-flow program. The commercial code Star-CCM+ was used for the numerical analysis, and the model was also tested in a towing tank at Pusan National University. This study proposes an effective method for determining and verifying the optimal pitch angle of an asymmetric pre-swirl stator

Characteristics of DSSC Panels with Silicone Encapsulant

Dye-sensitized solar cells (DSSC) allow light transmission and the application of various colors that make them especially suitable for building-integrated PV (BIPV) application. In order to apply DSSC modules to windows, the module has to be panelized: a DSSC module should be protected with toughened glass on the entire surface. Up to the present, it seems to be common to use double glazing with DSSC modules, with air gaps between the glass pane and the DSSC modules. Few studies have been conducted on the characteristics of various glazing methods with DSSC modules. This paper proposes a paneling method that uses silicone encapsulant, analyzing the performance through experimentation. Compared to a multilayered DSSC panel with an air gap, the encapsulant-applied panel showed 6% higher light transmittance and 7% higher electrical efficiency. The encapsulant also prevented electrolyte leakage by strengthening the seals in the DSSC module

Metabolic determination of decursinol using human liver microsome

Purpose: To determine new metabolites of the main components of Angelica gigas known to give anti-inflammation and pain relief Methods: Decursinol and blank sample were metabolized in human liver microsomes. The metabolized samples were centrifuged and deproteinated by adding 3 mL acetonitrile. The acetonitrile layer was concentrated and reconstituted in methanol. Finally, the prepared sample was injected into the LC-Q- TOF-MS. Results: Four new metabolites of decursinol with m/z ranging from 263.0912 ~ 263.0920 were identified as hydroxylated forms of decursinol, and the hydroxylated position of each metabolite was characterized using TOF mass spectrum. Their error values of detected m/z were 0.38 ~ 2.29 ppm, which indicates high accuracy of analysis. Conclusion: Previously unreported decursinol metabolites have been identified in this study. The findings provide athe basis for further pharmaceutical studies and functional food development using decursinol

An efficient strategy for cell-based antibody library selection using an integrated vector system

BACKGROUND: Cell panning of phage-displayed antibody library is a powerful tool for the development of therapeutic and imaging agents since disease-related cell surface proteins in native complex conformation can be directly targeted. Here, we employed a strategy taking advantage of an integrated vector system which allows rapid conversion of scFv-displaying phage into scFv-Fc format for efficient cell-based scFv library selection on a tetraspanin protein, CD9. RESULTS: A mouse scFv library constructed by using a phagemid vector, pDR-D1 was subjected to cell panning against stable CD9 transfectant, and the scFv repertoire from the enriched phage pool was directly transferred to a mammalian cassette vector, pDR-OriP-Fc1. The resulting constructs enabled transient expression of enough amounts of scFv-Fcs in HEK293E cells, and flow cytometric screening of binders for CD9 transfectant could be performed simply by using the culture supernatants. All three clones selected from the screening showed correct CD9-specificity. They could immunoprecipitate CD9 molecules out of the transfectant cell lysate and correctly stain endogenous CD9 expression on cancer cell membrane. Furthermore, competition assay with a known anti-CD9 monoclonal antibody (mAb) suggested that the binding epitopes of some of them overlap with that of the mAb which resides within the large extracellular loop of CD9. CONCLUSIONS: This study demonstrates that scFv-Fc from mammalian transient expression can be chosen as a reliable format for rapid screening and validation in cell-based scFv library selection, and the strategy described here will be applicable to efficient discovery of antibodies to diverse cell-surface targets