A metal-dielectric coaxial (MDC) dual-mode resonator for bandpass filters is proposed in this work and is applied to various practical filter realizations in a compact in-line layout. Since the MDC ...resonator supports the TEM mode of the metal coaxial resonator and one of HE<inline-formula> <tex-math notation="LaTeX">_{11}</tex-math> </inline-formula> modes of a metal-loaded dielectric resonator (DR), both of which are dissimilar fundamental modes, the dual-mode resonator occupies a comparable volume that a conventional coaxial resonator can achieve. In addition to the basic properties of the dual-mode resonator, the mechanisms for controlling the couplings between various modes are also discussed in detail. The in-line realization of the cascaded quadruplet (CQ) and cascaded triplet (CT) sections using the MDC dual-mode resonator are particularly investigated for facilitating the design of practical filters with different filtering characteristics. To demonstrate the applicability of the proposed MDC dual-mode resonator, three six-pole bandpass filter prototypes in the in-line configuration are designed, fabricated, and tuned in the 3.5-GHz band with different transmission zero (TZ) arrangements. All experimental results affirm the unique features of the MDC dual-mode resonator and demonstrate its applicability to compact in-line bandpass filters with a wide range of symmetric/asymmetric filtering responses for future wireless base stations.
Fine particulate matter (PM2.5) is a severe air pollution
problem in China. Observations of PM2.5 have been available since 2013
from a large network operated by the China National Environmental ...Monitoring
Center (CNEMC). The data show a general 30 %–50 % decrease in annual mean
PM2.5 across China over the 2013–2018 period, averaging at −5.2 µg m−3 a−1. Trends in the five megacity cluster regions targeted by
the government for air quality control are -9.3±1.8 µg m−3 a−1 (±95 % confidence interval) for Beijing–Tianjin–Hebei,
-6.1±1.1 µg m−3 a−1 for the Yangtze River Delta, -2.7±0.8 µg m−3 a−1 for the Pearl River Delta, -6.7±1.3 µg m−3 a−1 for the Sichuan Basin, and -6.5±2.5 µg m−3 a−1 for the Fenwei Plain (Xi'an). Concurrent 2013–2018
observations of sulfur dioxide (SO2) and carbon monoxide (CO) show that
the declines in PM2.5 are qualitatively consistent with drastic
controls of emissions from coal combustion. However, there is also a large
meteorologically driven interannual variability in PM2.5 that
complicates trend attribution. We used a stepwise multiple linear regression
(MLR) model to quantify this meteorological contribution to the PM2.5 trends across China. The MLR model correlates the 10 d PM2.5
anomalies to wind speed, precipitation, relative humidity, temperature, and
850 hPa meridional wind velocity (V850). The meteorology-corrected
PM2.5 trends after removal of the MLR meteorological contribution can
be viewed as being driven by trends in anthropogenic emissions. The mean
PM2.5 decrease across China is −4.6 µg m−3 a−1 in the
meteorology-corrected data, 12 % weaker than in the original data, meaning
that 12 % of the PM2.5 decrease in the original data is
attributable to meteorology. The trends in the meteorology-corrected data
for the five megacity clusters are -8.0±1.1 µg m−3 a−1 for Beijing–Tianjin–Hebei (14 % weaker than in the original
data), -6.3±0.9 µg m−3 a−1 for the Yangtze River Delta
(3 % stronger), -2.2±0.5 µg m−3 a−1 for the Pearl River
Delta (19 % weaker), -4.9±0.9 µg m−3 a−1 for
the Sichuan Basin (27 % weaker), and -5.0±1.9 µg m−3 a−1 for the Fenwei Plain (Xi'an; 23 % weaker); 2015–2017 observations of
flattening PM2.5 in the Pearl River Delta and increases in the Fenwei
Plain can be attributed to meteorology rather than to relaxation of emission
controls.
The time-dependent density functional theory (TDDFT) method was carried out to investigate the hydrogen-bonded intramolecular charge-transfer (ICT) excited state of 4-dimethylaminobenzonitrile ...(DMABN) in methanol (MeOH) solvent. We demonstrated that the intermolecular hydrogen bond Cidentical withN···H---O formed between DMABN and MeOH can induce the Cidentical withN stretching mode shift to the blue in both the ground state and the twisted intramolecular charge-transfer (TICT) state of DMABN. Therefore, the two components at 2091 and 2109 cm⁻¹ observed in the time-resolved infrared (TRIR) absorption spectra of DMABN in MeOH solvent were reassigned in this work. The hydrogen-bonded TICT state should correspond to the blue-side component at 2109 cm⁻¹, whereas not the red-side component at 2091 cm⁻¹ designated in the previous study. It was also demonstrated that the intermolecular hydrogen bond Cidentical withN···H---O is significantly strengthened in the TICT state. The intermolecular hydrogen bond strengthening in the TICT state can facilitate the deactivation of the excited state via internal conversion (IC), and thus account for the fluorescence quenching of DMABN in protic solvents. Furthermore, the dynamic equilibrium of these electronically excited states is explained by the hydrogen bond strengthening in the TICT state.
Research in finance and macroeconomics has routinely employed multiple horizons to test asset return predictability. In a simple predictive regression model, we find the popular scaled test can have ...zero power when the predictor is not sufficiently persistent. A new test based on implication of the short-run model is suggested and is shown to be uniformly more powerful than the scaled test. The new test can accommodate multiple predictors. Compared with various other widely used tests, simulation experiments demonstrate remarkable finite-sample performance. We reexamine the predictive ability of various popular predictors for aggregate equity premium.
An efficient protocol for the synthesis of 3‐aminoquinoxalinones via the electrochemical dehydrogenative C‐3 amination of quinoxalin‐2(1H)‐ones was developed. With aliphatic amines and azoles as the ...nitrogen sources, a series of 3‐aminoquinoxalinones was obtained in up to 99% yield. This direct electrolytic method avoids the use of transition metals and external oxidants, and represents an appealing alternative for the synthesis of 3‐aminoquinoxalinones.
A decoupling technique for a symmetric four-element compact array is proposed. A dummy array terminated with optimum reactive loads is introduced to cancel the mutual couplings between the four ...radiating elements. A theory that leads to a general design procedure is developed. The technique is demonstrated by three practical design examples, including a compact and low-profile "cheese-cake" antenna array. Calculated channel capacities demonstrate that the performance of a 4-by-4 MIMO communication system that uses the cheese-cake array can be significantly improved as compared to the system using its coupled counterpart. This technique provides a promising approach to the design of a compact four-element array for a MIMO communication system.
Teachers' instructional practices are critical for guiding students' engagement in scientific practices within the classroom knowledge building community. In this study, we seek to understand how ...teachers' instructional supports of epistemic aspects involved in scientific modeling may influence students' meaningful engagement in the practice. In particular, we examine two upper elementary teachers' epistemological messages about modeling over the course of a model‐based unit and focus group conversations in consensus model activities to explore the relationship between teachers' instructional supports and students' practice. The results suggest that each teacher was sharing complex messages about various aspects of the modeling practice ranging from procedural to epistemic. Further, those messages were then reflected in students' work. Our findings indicate that teachers' (a) foregrounding of epistemological messages, (b) consistency in emphasizing those messages, and (c) unpacking of those messages may play an important role in how epistemological ideas about modeling are taken up by students. We conclude the paper by discussing implications for supporting teachers in meaningfully enacting modeling practice.
This paper is devoted to theoretical and practical issues concerning computer-aided tuning (CAT) of coupled-resonator diplexers with tapped wire T-junction. Special attentions are paid to the ...following aspects: 1) finding an appropriate circuit model to represent the tapped wire T-junction; 2) developing a legitimate transformation strategy to obtain the coupling matrix of the right form corresponding to the topology of the diplexer containing a tapped wire T-junction; and 3) proposing an adaptive CAT scheme that takes stray couplings into account in a dynamically optimized target coupling matrix. A conventional combline diplexer and a helical resonator diplexer are used as examples to demonstrate the circuit model extraction procedure and the adaptive CAT concept, showing the effectiveness and robustness of the proposed adaptive CAT method for practical applications.
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