다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Electromagnetic Metamaterials: Transmission Line Theory and Microwave Applications. By Christophe Caloz and Tatsuo Itoh.

Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.

IEEE Transactions on Microwave Theory and Techniques and Antennas and Propagation Announce a Joint Special Issue on Ultra-Wideband (UWB) Technology

Driver drowsiness and distraction are two main reasons for traffic accidents and the related financial losses. Therefore, researchers have been working for more than a decade on designing driver inattention monitoring systems. As a result, several detection techniques for the detection of both drowsiness and distraction have been proposed in the literature. Some of these techniques were successfully adopted and implemented by the leading car companies. This paper discusses and provides a comprehensive insight into the well-established techniques for driver inattention monitoring and introduces the use of most recent and futuristic solutions exploiting mobile technologies such as smartphones and wearable devices. Then, a proposal is made for the active of such systems into car-to-car communication to support vehicular ad hoc network's (VANET's) primary aim of safe driving. We call this approach the dissemination of driver behavior via C2C communication. Throughout this paper, the most remarkable studies of the last five years were examined thoroughly in order to reveal the recent driver monitoring techniques and demonstrate the basic pros and cons. In addition, the studies were categorized into two groups: driver drowsiness and distraction. Then, research on the driver drowsiness was further divided into two main subgroups based on the exploitation of either visual features or nonvisual features. A comprehensive compilation, including used features, classification methods, accuracy rates, system parameters, and environmental details, was represented as tables to highlight the (dis)advantages and/or limitations of the aforementioned categories. A similar approach was also taken for the methods used for the detection of driver distraction.

Driver Behavior Analysis for Safe Driving: A Survey

An approach to the design of a three-beam linearly-polarized microstrip antenna arrays has been proposed. The presented antenna arrays feature one broadside beam and two symmetrically scanned beams with respect to boresight direction generated with the use of a 3 × 3 Butler matrix as a feeding network. Such a Butler matrix allows to obtain equal power split and 0° −120°, and +120° differential phases at its outputs. The proposed concept has been experimentally verified by development and measurements of a three-element linear antenna array with uniform amplitude taper as well as a five-element linear antenna array with reduced sidelobe level, both operating at 2.5 GHz.

Three-beam microstrip antenna arrays fed by 3 × 3 Butler matrix

A broadband five-section symmetrical 3 dB directional coupler has been designed In order to improve the frequency characteristic of the coupler a recently proposed compensation technique has been used The developed coupler operates in 2–12 GHz frequency band and can be applied in a broadband 4×4 Butler matrix

https://ieeexplore.ieee.org/iel5/5523194/5540324/05540455.pdf

Compensated broadband five-section directional coupler for application in butler matrices

A novel method allowing for reduction of coupling between vertically placed radiating elements in antenna arrays has been proposed It has been shown, that appropriate offsetting the antenna array elements from the array symmetry axis allows to improve isolation between adjacent elements, which results in improvement of the obtained radiation pattern The theoretical investigation has been performed by means of electromagnetic calculations of an exemplary 1 x 4 wideband antenna array composed of Vivaldi type radiating elements operating within 2 - 10 GHz frequency range The designed antenna array has been manufactured and measured to experimentally verify the performance Obtained measurement results are in good agreement with the calculated ones, which proves the correctness and usefulness of the proposed approach

Approach to the design of wideband antenna arrays with reduced coupling between elements

In this paper a novel broadband ten-port reflectometer is proposed, which is composed of three classic 4 × 4 Butler matrices. It is shown that such a network provides an advantageous power distribution, which ensures the enhanced measurement accuracy. Performance of the proposed reflectometer has been examined by the reflection coefficient measurements in a broad frequency range 2 – 3 GHz. The measurement results are very close to the ones obtained using commercial VNA.

Broadband ten-port reflectometer with enhanced measurement accuracy

The problem of the realization of broadband quadrature directional couplers in UMS (United Monolithic Semiconductors) PH25 is thoroughly investigated. The limitations of the selected technology are discussed with respect to directional couplers’ design. It is shown that, in such technologies, two major problems have to be overcome to achieve the high-performance of the resulting integrated couplers, i.e., the realization of appropriate coupling together with appropriate characteristic impedances, and the equalization of inductive and capacitive coupling coefficients that are inherently different in inhomogeneous dielectric structures. Three different solutions that allow for achieving strong coupling in the selected UMS PH25 process were selected and experimentally investigated, showing the possibility of such circuits’ realization. In each of the presented integrated couplers, capacitive compensation techniques were applied for coupling coefficients’ equalization.

https://www.mdpi.com/2079-9292/8/12/1520/pdf

Slawomir Gruszczynski

Papers

Three-beam microstrip antenna arrays fed by 3 × 3 Butler matrix

Compensated broadband five-section directional coupler for application in butler matrices

Approach to the design of wideband antenna arrays with reduced coupling between elements

Broadband ten-port reflectometer with enhanced measurement accuracy

Realization of High-Performance Broadband Quadrature Directional Couplers in UMS PH25 Technology