The aim of this study was to investigate the prevalence of sleep problems, depression and anxiety symptoms among conscripted frontline nurses fighting coronavirus disease 2019 (COVID-19) in ...Wuhan.This study was a cross-sectional study conducted with 100 frontline nurses. Sleep quality, depression, and anxiety symptoms were measured using the Pittsburgh sleep quality index (PSQI), the Generalized Anxiety Disorder 7-Item Scale (GAD-7) and the Patient Health Questionnaire-9 (PHQ-9), respectively.Mean sleep duration was 5.71 hours (SD = 1.09) and mean sleep latency was 33.49 minutes (SD = 28.87). A total of 76%, 81%, 45%, and 19% reported difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS) or early morning awakening (EMA), nightmares and using hypnotics respectively. Among 100 participants in this study, 60 (60%) had poor sleep quality, 46 (46%) suffered depression symptoms and 40 (40%) reported anxiety symptoms. Sleep quality (OR = 3.16, 95% CI: 1.17-8.52) and anxiety symptoms (OR = 8.07, 95% CI: 2.92-22.33) were significantly associated with depression symptoms. Depression symptoms (OR = 7.92, 95% CI: 2.89-21.73) were related to anxiety symptoms. Similarly, depression symptoms (OR = 3.24, 95% CI: 1.19-8.79) were associated with poor sleep quality.Sleep disturbance, depression, and anxiety symptoms are very common among frontline nurses who treating patients with COVID-19 in Wuhan, China. Comprehensive measures that involve psychosocial and personal behaviors should be implemented to improve sleep quality and prevent depression and anxiety symptoms.
A wideband circularly polarized (CP) <inline-formula> <tex-math notation="LaTeX">4 \times 4 </tex-math></inline-formula> millimeter-wave antenna array composed of novel microstrip antenna elements is ...presented for IEEE 802.11 aj (45 GHz) application. Through introducing the L-shaped branches and truncated corners to the microstrip antenna element, an impedance bandwidth of 24.9% and a 3 dB axial ratio (AR) bandwidth of 17.3% are achieved. To clarify the effects of the L-shaped branches and truncated corners, the phase difference and amplitude ratios of the 180° and 90° electric field components at the point of (0,0,r) are extracted and analyzed. A simple and compact microstrip feeding network is designed to excite the CP antenna array, and two-layer PCB boards are used to implement the proposed array. The electromagnetic energy is coupled to the radiators from the feeding network through the aperture etched on the middle ground. The measured 3 dB AR bandwidth of the antenna array is 16% from 41.9 to 49.1 GHz, and the measured gain is all greater than 17 dBic within the band from 41 to 49 GHz.
A compact wideband circularly polarized (CP) millimeter-wave (mm-wave) antenna array using a three-layer segmented patches (SEP) element is presented in this letter. To achieve miniaturization and ...wideband feature, three-layer SEP with four L -shaped branches is first designed to generate three CP modes (AR minimum points) within a compact size. With the three CP modes, a broad AR bandwidth of 31.7% is achieved by the proposed CP element. Then, four metallic vias and an L -shaped feeding line are used to improve impedance matching. As a result, a wide impedance bandwidth of 33.1% is also obtained by the proposed CP element. Based on the proposed wideband CP element, a compact 4 × 4 CP antenna array fed by a simple full-incorporate microstrip network is designed. Measured results of the array show a 3 dB AR bandwidth of 29.7% from 30.1 to 40.6 GHz, an impedance bandwidth of 36.1% from 29.15 to 42.0 GHz, and a peak gain of 18.2 dBic, which is well suited for Q-band satellite communications.
A compact printed differential multiple-input- multiple-output (MIMO) antenna is presented for ultrawideband system applications with band-notched characteristic. The proposed MIMO antenna element ...consists of a differential U-shaped microstrip feedline and a stepped-shaped slot, printed on the bottom and top of the substrate, respectively. A half-wavelength resonant stub embedded in the stepped-shaped slot is exploited to obtain notched band, whose center frequency can be adjusted by the length of the stub. The staged slots among antenna elements are introduced to enhance the differential isolation. The final antenna has a compact size of 44 × 44 mm 2 . Measured results show that the proposed MIMO antenna achieves -10-dB impedance bandwidth from 2.95 to 10.8 GHz, isolation better than 15.5 dB over the whole operating band, and a notched band from 5.10 to 5.95 GHz.
Abstract
This paper presents a low‐profile and broadband pattern diversity microstrip antenna with quasiperiodic radiating patches fed by two slots. The thickness of the whole design is only 0.044λ
0
...(λ
0
is the free‐space wavelength of the center frequency), showing great potential in applications. The broadband property is realized by efficiently exciting TM
10
mode and antiphase TM
20
mode and forming two resonant frequencies in the target band. The antenna can generate a broadside or difference pattern by switching the input port of the broadband 180° hybrid coupling feed network. The measured results show that the coincident impedance bandwidth of the antenna working in the two pattern modes is 20.5% (3.20–3.93 GHz), and the maximum gain values are 6.85 dBi for the directional pattern and 5.80 dBi for the difference pattern.
This paper proposes a single‐layer filtering patch antenna array with simple differential feeding network. It is composed of a simple microstrip‐slot‐microstrip differential feeding network, four ...patch elements, two open‐ended lines and two U‐slots. Two gain nulls in the lower band and the upper band can be generated by introducing open‐ended microstrip lines and U‐shaped slots, respectively. Therefore, the selectivity of the gain curve is significantly improved. The proposed antenna array has an optimized dimension of 80 × 80 × 0.8 mm3 and a peak gain of 11.2 dBi. The measured impedance bandwidth (|Sdd11| < −10 dB) is 4.7% ranging from 5.01 GHz to 5.25 GHz. Additionally, the proposed antenna array also achieves common‐mode suppression in the whole band.
A dual-band antenna with wideband harmonic suppression based on dual-function slot structure is presented for the future microwave and millimeter-wave communication system in this letter. In the ...low-frequency band, the slot serves as the radiator, and both two parasitic patches and four slot-stubs are also introduced in the slot to increase the bandwidth. In the high-frequency band, this slot works as the feeding structure, which excites the 2 × 4 millimeter-wave patch array. Meanwhile, the wideband harmonic suppression between dual frequency bands is achieved by loading both four open-stubs on this slot and a T-stub in this slot. A prototype is fabricated and measured to validate the design, which covers a dual band of 5 and 27 GHz. Their measured -10 dB relatively impedance bandwidth is 21.9% and 13.7%, respectively. Moreover, the measured reflection coefficient is higher than -1 dB and the measured gain is lower than -10 dBi from 7 to 21.5 GHz, showing the characteristic of good harmonic suppression.
A dual-mode conjoint patch-pair is presented in this letter. Because the initial frequency ratio between the seventh and fifth modes of the proposed conjoint patch-pair is low, dual-mode ...characteristic can be easily achieved by further compressing the frequency ratio between these two modes. Through loading two metallized connection vias near the current nulls of the fifth mode, the resonant frequency of the seventh mode can be enormously reduced with little impact on that of the fifth mode, resulting in the realization of frequency-ratio compression. Based on the proposed dual-mode conjoint patch-pair, a broadband 4 × 4 patch antenna arrays is implemented. The measurements of the 4 × 4 array indicate that the achieved −10 dB impedance bandwidth is about 23.7% (23.8-30.2 GHz), which is wide enough to cover the 26 and 28 GHz bands at the same time.
This letter proposed a codesign of array-antenna decoupling surface (ADS) and crisscross-shaped dipole antenna (CSDA), with a wide low-band (LB) working bandwidth from 1.7 to 2.4 GHz and a wide ...high-band (HB) decoupling bandwidth from 3.3 to 4.2 GHz. The CSDA is electromagnetic transparent by introducing interdigital capacitors and high-impedance line, and operating together with four square parasitic units to form a wide LB bandwidth. For the HB antenna array, the spatial distance between each element is only 43 mm in x - and y -axes. The severe in-band coupling is suppressed by the combination of four units and a dielectric radome, acting as dual-layer ADS. With the codesign of ADS and CSDA, the mutual in-band and cross-band coupling is highly suppressed, which is valuable for dual-band antenna array decoupling.
To solve the bottleneck of the unstable accumulation of nitrite in the partial nitrification (PN)-anammox (AMX) in municipal wastewater treatment, a novel process called partial denitrification ...(PD)-AMX has been developed. PD-AMX, which is known for cost-efficiency and environmental friendliness, has currently exhibited a promising potential for the removal of biological nitrogen from municipal wastewater and has attracted much research interest regarding its process mechanisms, as well as its practical applications. Here, we review the recent advances in the PD process and its coupling to the anammox process, including the development, basic principles, main characteristics, and critical process parameters of the stable operation of the PD-AMX process. We also explore the microbial community and its characteristics in the system and summarize the knowledge of the dominant bacteria to clarify the key factors affecting PD-AMX. Then, we introduce the engineering feasibility and economic feasibility as well as the potential challenges of the process. The induction and implementation of partial denitrification and maintenance of mainstream anammox are critical issues to be urgently solved. Meanwhile, the implementation of a full mainstream anammox application remains burdensome, while the mechanism of partial denitrification coupled to anammox needs to be further studied. Additionally, stable operation performance and process control1 methods need to be optimized or developed for the PD-AMX system for better engineering practice. This review can help to accelerate the research and application of the PD-AMX process for municipal wastewater treatment.
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•PD-AMX provides a promising alternative for N removal from municipal wastewater.•Several strategies have been intensively developed to enrich PD and AMX microbes.•DO, pH, T, and C/N ratio are the main factors affecting PD-AMX process.•AMX biomass retention can be fulfilled by sludge granulation and biofilm formation.
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