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Developing a compact circularly polarized (CP) antenna with good radiation characteristics for handheld radio frequency identification (RFID) readers is a very challenging task. Many compact CP antennas have been reported in the open literature, but most suffer from critical drawbacks of low gain and/or high back radiation. This paper presents a metasurface (MS) based CP antenna with compact size, high gain, and high front-to-back ratio characteristics. The compact size of the proposed design is achieved by using a 2 × 2 unit-cell MS, while the CP realization is accomplished through a coupling between the MS and a Y-shaped patch as a primary CP source. The final antenna has compact overall dimensions of 0.45λ × 0.45λ × 0.02λ, where λ is the guided wavelength at the center frequency. The operating bandwidth is about 2.0% (2.43-2.48 GHz) and the broadside gain is about 6.3 dBi. Besides, the front-to-back ratio (FBR) defined by the difference gain levels between the forward and backward directions is about 18 dB. Compared with the related compact CP antennas in the literature, the proposed design has the advantages of high gain and high FBR, making it suitable for compact RFID readers.

This paper proposes the $2.45~GHz$ planar Beam Steering Antenna Array for Indoor Positioning Systems. The antenna array consists of a phase shifter based on a $4\times 4$ Butler matrix, and an array of four dipole Yagi antennas. By choosing one of four beams using a switching controller, the main beam of the antenna can steer in four directions from +37°, −12°, +12° to −36°. The antenna has a narrow fan beam with a beamwidth in the azimuth plane of from +21.5° to +24.5° and in the elevation plane of approximately 90° which effectively minimizes multipath signals. These advantages are suitable for positioning systems to increase location accuracy. The antenna achieves a peak gain of from 9.1 to $9.8~dBi$ in four directions, a wide band of $400~MHz$ . The fully electronically steerable antenna prototype has been designed using CST software, simulated based on the finite element method, and fabricated on the RO4003C substrate as well as measured. The antenna is implemented in the Indoor Positioning System using three different location methods, including trilateration, triangulation, and fingerprinting, to highlight the antenna’s advantages in improving location accuracy with the ratio between the mean location error and area of 0.051, 0.033, and 0.023 respectively.

Knowledge about insulin pen storage significantly and directly affects treatment efficacy and quality for people with type 2 diabetes mellitus. Accurate and complete understanding and practice are vital for properly managing this chronic condition. However, studies on insulin pen use and storage have not been well-researched in Vietnam. This descriptive cross-sectional study aimed to assess the knowledge of people with type 2 diabetes regarding insulin pen use and storage. Data were collected through convenience sampling from 132 people with diabetes at a provincial hospital in Vietnam from September 2022 to May 2023. We developed the Vietnamese Insulin Pen Storage Knowledge Questionnaire (VIPSKQ) based on guidelines, Addendum 1: Forum for Injection Technique and Therapy Expert Recommendations, India 2021. Data were analyzed using descriptive statistics, the Chi-square test, and binary logistic regression. Results indicated that only 35.6% of participants had good knowledge of insulin pen storage, whereas 64.4% did not. Four factors that affected the participants' understanding of insulin-pen storage were age, education level, duration of diagnosis, and years of treatment for diabetes mellitus. Nurses need to educate people with diabetes to increase their knowledge and skills of insulin pen use and proper storage using various strategies, such as using videos, phone applications, and monitoring their practice regularly. Nurses must also keep abreast of the latest information on insulin treatment modalities and pen storage guidelines. Our questionnaire shows promise for use in practice but needs further testing in different settings with larger groups of individuals with type 2 diabetes. [ABSTRACT FROM AUTHOR]

In this paper, we consider a fundamental class of stochastic differential equations with time delays. Our aim is to investigate the weak convergence with respect to delay parameter of the solutions. Based on the techniques of Malliavin calculus, we obtain an explicit estimate for the rate of convergence. An application to the Carathéodory approximation scheme of stochastic differential equations is provided as well. [ABSTRACT FROM AUTHOR]