Towards Dual-functional Radar-Communication Systems: Optimal Waveform Design

We focus on a dual-functional multi-input-multi-output (MIMO) radar-communication (RadCom) system, where a single transmitter communicates with downlink cellular users and detects radar targets simultaneously. Several design criteria are considered for minimizing the downlink multi-user interference. First, we consider both the omnidirectional and directional beampattern design problems, where the closed-form globally optimal solutions are obtained. Based on these waveforms, we further consider a weighted optimization to enable a flexible trade-off between radar and communications performance and introduce a low-complexity algorithm. The computational costs of the above three designs are shown to be similar to the conventional zero-forcing (ZF) precoding. Moreover, to address the more practical constant modulus waveform design problem, we propose a branch-and-bound algorithm that obtains a globally optimal solution and derive its worst-case complexity as a function of the maximum iteration number. Finally, we assess the effectiveness of the proposed waveform design approaches by numerical results.Comment: 13 pages, 10 figures. This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Simulation of ultrasonic vibration in a liquid aluminum bath for sapphire surface modification

Ultrasonic vibration has been found to play a significant role in promoting surface nano-crystallization of sapphire in a liquid aluminum bath. And the distribution of the vibration field is critical in controlling the modification procedure. Here, distribution of the ultrasonic vibration in a liquid aluminum bath was investigated by finite element method (FEM). Effects of shape of the ultrasonic horn and distance between the horn and the sapphire plates were investigated. It was found that the ultrasonic vibration density is high in the area adjacent to the ultrasonic horn. The distance between the horn and the plates significantly influence the vibration distribution. And the vibration density decreased significantly at the liquid/solid interface, indicating obvious energy absorption there. Vibration energy grads can be formed on sapphire surface. And this phenomenon shall be used to achieve different aims

Whole-body vibration training for children with neurological disabilities: A meta-analysis

Over the years, the concern over bone health deterioration in children with neurological disabilities (ND) has caught the interest of the research community. As the current traditional exercise methods are considered too challenging for children with ND, it is essential to seek effective rehabilitation programs with minimum difficulties and movement restrictions for children with disabilities, ultimately improving their muscle and bone health. Therefore, this study was performed to evaluate the potential application of whole-body vibration training (WBVT) as a beneficial and effective approach to improving bone mineral density (BMD), total body bone mineral content (BMC), and lean mass in children with ND. The impact of WBVT on children with ND was investigated using a systematic review and meta-analysis approach following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). A database search was conducted to screen and select previous literature sources published from January 2002 to July 2022 from EBSCO, PubMed, Scopus, and Web of Science databases that met the inclusion and exclusion criteria. Following the quality assessment (PEDro scale and NIH scale) and sensitivity analysis, the standardized mean difference (SMD) was conducted using the STATA 15.1 software with a 95% confidence interval (95% CI) (PROSPERO registration number: CRD42022343789). Eight studies (four randomized controlled trial [RCT] and four non-RCT studies) were selected, which involved 184 male and 130 female participants. Based on the PEDro scale, all RCT studies were classified as high methodological quality, while the NIH scale rated all non-RCT papers as “Good”. In addition, the meta-analysis results indicated that WBVT substantially enhanced femur BMD [(p<.01, z = 3.37), SMD (95% CI) = 0.47 (0.20, 0.74)], lumbar spine BMD [(p=.02, z = 2.32), SMD (95% CI) = 0.32 (0.05, 0.58)], total body BMC [(p<.01, z = 3.42), SMD (95% CI) = 0.29 (0.12, 0.46)] and lean mass [(p<.01, z = 2.80), SMD (95% CI) = 0.25 (0.07, 0.42)] of children with ND. However, the effect of WBVT was insignificant on the total body BMD of children with ND [(p=.22, z = 1.24), SMD (95% CI) = 0.14 (-0.08, 0.37)]. The meta-analysis demonstrated the significant effect of WBVT on the femur BMD, lumbar spine BMD, total body BMC, and lean mass in children with ND. Hence, WBVT can be suggested as a complementary treatment prescription for children with ND

Design and implementation of an RFID-based customer shopping behavior mining system

Shopping behavior data is of great importance in understanding the effectiveness of marketing and merchandising campaigns. Online clothing stores are capable of capturing customer shopping behavior by analyzing the click streams and customer shopping carts. Retailers with physical clothing stores, however, still lack effective methods to comprehensively identify shopping behaviors. In this paper, we show that backscatter signals of passive RFID tags can be exploited to detect and record how customers browse stores, which garments they pay attention to, and which garments they usually pair up. The intuition is that the phase readings of tags attached to items will demonstrate distinct yet stable patterns in a time-series when customers look at, pick out, or turn over desired items. We design ShopMiner, a framework that harnesses these unique spatial-temporal correlations of time-series phase readings to detect comprehensive shopping behaviors. We have implemented a prototype of ShopMiner with a COTS RFID reader and four antennas, and tested its effectiveness in two typical indoor environments. Empirical studies from two-week shopping-like data show that ShopMiner is able to identify customer shopping behaviors with high accuracy and low overhead, and is robust to interference.Department of Computing2016-2017 > Academic research: refereed > Publication in refereed journalbcr