Channel Estimation for MmWave Massive MIMO with Hybrid Precoding Based on Log-Sum Sparse Constraints

Channel estimation is essential for millimeter-wave (mmWave) multiple-input multiple-output (MIMO) systems with hybrid precoding. However, accurate channel estimation is a challenging task as the number of antennas is huge, while the number of RF chains is limited. Traditional methods of compressed sensing for channel estimation lead to serious loss of accuracy due to channel angle quantization. In this paper, we propose a new iterative reweight-based log-sum constraint channel estimation scheme. Specifically, we exploit the structure sparsity of the mmWave channels by formulating the channel estimation problem as an objective optimization problem. We utilize the log-sum as a constraint, via optimizing an objective function through the gradient descent method, the proposed algorithm can iteratively move the channel estimated angle-ofarrivals (AOAs) and angle-of-departures (AODs) towards the optimal solutions, and finally improve the angle estimation performance significantly. In addition, to ensure the accuracy of channel estimation, we introduce a dynamic regularization factor to control the tradeoff between the channel sparsity and the data fitting error. Numerical experiments demonstrate that the proposed algorithm achieves better convergence behavior than conventional sparse signal recovery solutions

Assessing vaccine hesitancy using the WHO scale for caregivers of children under 3 years old in China

IntroductionVaccine hesitancy may increase infectious disease burden and impede disease control efforts, while few studies have measured such a phenomenon with a standardized tool in China. This study aimed to test the validation of the Vaccine Hesitancy Scale (VHS) developed by the WHO SAGE Working Group among caregivers and examine demographic characteristics associated with caregiver hesitancy in six provinces of China.MethodsUsing a multistage sampling design, this study was conducted in 36 immunization clinics in six provinces from December 2019 to August 2020. Caregivers of children aged 0–3  years were included. The VHS was used to assess vaccine hesitancy. The construct validity and internal consistency of the scale were assessed. Associations between caregivers’ characteristics and vaccine hesitancy were examined by simple and multiple linear regression models.ResultsOf the 3,359 participants included, a two-factor structure within the scale was identified, consisting of “lack of confidence” (1.89 ± 0.53) and “risks” (3.20 ± 0.75). Caregivers engaged in medical work expressed more confidence and were less concerned about risks compared to those of non-medical staff (p < 0.05). Participants with higher income levels were more confident (p < 0.05), while those surveyed after the COVID-19 pandemic, who were mothers, who had an older child, or who were raising a second or above birth child, had less concern about risks (p < 0.05).DiscussionWe found that the VHS had acceptable reliability and construct validity and caregivers’ hesitancy was driven more by concerns about risks than by the lack of confidence. Countering these concerns will be particularly important among non-medical staff, lower income, child’s fathers, having a younger child, or raising first-birth child groups

Comparison of ESWL and ureteroscopic holmium laser lithotripsy in management of ureteral stones.

BACKGROUND: There are many options for urologists to treat ureteral stones that range from 8 mm to 15 mm, including ESWL and ureteroscopic holmium laser lithotripsy. While both ESWL and ureteroscopy are effective and minimally invasive procedures, there is still controversy over which one is more suitable for ureteral stones. OBJECTIVE: To perform a retrospective study to compare the efficiency, safety and complications using ESWL vs. ureteroscopic holmium laser lithotripsy in management of ureteral stones. METHODS: Between October 2010 and October 2012, 160 patients who underwent ESWL or ureteroscopic holmium laser lithotripsy at Suzhou municipal hospital for a single radiopaque ureteral stone (the size 8-15 mm) were evaluated. All patients were followed up with ultrasonography for six months. Stone clearance rate, costs and complications were compared. RESULTS: Similarity in stone clearance rate and treatment time between the two procedures; overall procedural time, analgesia requirement and total cost were significantly different. Renal colic and gross hematuria were more frequent with ESWL while voiding symptoms were more frequent with ureteroscopy. Both procedures used for ureteral stones ranging from 8 to 15 mm were safe and minimally invasive. CONCLUSION: ESWL remains first line therapy for proximal ureteral stones while ureteroscopic holmium laser lithotripsy costs more. To determining which one is preferable depends on not only stone characteristics but also patient acceptance and cost-effectiveness ratio

Characteristics of the patients on both groups.

<p>Characteristics of the patients on both groups.</p

Rightureteral calculus (arrow) before ESWL.

<p>Rightureteral calculus (arrow) before ESWL.</p

Stone clearance rate according to ESWL sessions.

<p>ESWL1∶1^st session ESWL and so far.</p

Calculus-freeafter ureteroscopy.

<p>Calculus-freeafter ureteroscopy.</p