UHF RFID Conductive Fabric Tag Design Optimization

This paper presents the design of a 920 MHz Ultra High Frequency (UHF) band radio frequency identification (RFID) conductive fabric tag antenna. The DC (Direct Current) resistance and impedance of the conductive fabric are measured by a DC multimeter and by a network analyzer at a UHF frequency band. The conductivities of the fabrics are calculated with their measured DC resistance and impedance values, respectively. The conductivities of the fabric are inserted into the CST simulation program to simulate the fabric tag antenna designs, and the results of the tag designs with two conductivities are compared. Two fabric UHF RFID tag antennas with a T-Matching structure, one with the name-tag size of 80 × 40 mm, and another with 40 × 23 are simulated and measured the characteristics of tag antennas. The simulated and measured results are compared by reflection coefficient S11, radar cross-section and reading range. The reading range of the 80 × 40 mm fabric tag antenna is about 4 m and 0.5 m for the 40 × 23 size tag. These fabric tags can be easily applied to an entrance control system as they can be attached to other fabrics and clothes.

Self-discharge rates in cells have a critical effect on the cycle life of parallel lithium-ion batteries

More than two parameters are adopted to sort lithium ion cells (LICs) for better performance in the production process, such as capacity, open-circuit voltage (OCV), direct current resistance (DCR), et al.

Pressure-sensitive properties of carbon nanotubes/bismuth sulfide composite materials

In this work, the pressure-sensitive properties of pure multi-walled carbon nanotubes and multi-walled carbon nanotubes/bismuth sulfide composite are investigated and compared. Composite was prepared by 50 wt% of each ingredient. Sandwich-type pressure-sensitive pellets (Ag/CNT/Ag and Ag/CNT-Bi2S3/Ag) of 2 mm in thickness and 15 mm in diameter were fabricated at a pressure of 6894.8 kNm−2 by Mortar and Pestle/Hydraulic Press technique. Both sides of the prepared samples were painted with silver paste to provide low resistance electrical contacts. Both the samples exhibited decrease in direct current resistance with the increase in the applied pressure (0–16.9 kNm−2). However, decrease in the resistance of multi-walled carbon nanotubes/bismuth sulfide composite was 1.2 times and sensitivity was 1.07 times higher than the pure carbon nanotubes. Experimental results were compared with simulated results that showed excellent agreement with each other.

Boiling Heat Transfer to Dilute Emulsions From a Vertical Heated Strip

Heat transfer measurements for nucleate pool boiling of a dilute emulsion on a short vertical surface are reported. The vertical surface is a thin steel ribbon of 1.35 mm height × 101 mm length. Direct current resistance heating produces boiling either on the surface or in the free convection boundary layer of dilute emulsions of pentane in water and FC-72 in water. Single phase and boiling heat transfer is measured for emulsions with a volume fraction of the dispersed component of 0.1% and 0.5% in a pool at approximately 25 °C. The dispersed component is created by a simple atomization process and no surfactants are employed to maintain the droplets of the dispersed phase in suspension. In free convection, the presence of the dispersed component somewhat impedes heat transfer, but when boiling commences enhancement of heat transfer is observed. Boiling is observed in the emulsions at lower surface temperatures than for water alone, and significantly more superheat is required to initiate boiling of the dispersed component than would be needed for a pool of the dispersed component alone. Consequently, a temperature over shoot is observed prior to initiation of boiling, and such an over shoot has been observed in several prior studies. Boiling heat fluxes are compared to recently published measurements of boiling in similar emulsions on a small diameter horizontal wire. Boiling generally occurs at a slightly higher degree of superheat of the dispersed component on the heated strip as compared to thin wires.