Attenuation Range Research Articles

Reverse Design of a Novel Coupling Strut for Vibration Attenuation in the Helicopter Cabin

Helicopter gearbox support strut is one of the main research objects in the field of vibration and noise control in helicopter cabins. Aiming to further widen the vibration attenuation range of traditional Bragg periodic struts, a novel type of Local resonance (LR)/Bragg coupling periodic strut with graded parameters as well as the reverse design method is proposed. Combined with the spectral element method (SEM) and the transfer matrix method (TMM), the analytical expression of the transform relationship of longitudinal vibrations through the coupling strut is yielded. The impacts of different parameters on the boundaries of bandgaps are explored according to the results of simulation analysis. On this basis, the gradient of parameters is determined, and then all unknown structural parameters can also be determined. Compared with the traditional Bragg periodic struts and the LR/Bragg coupling periodic strut with non-graded parameters, the presented strut has an obvious advantage of widening the low-frequency bandgaps below 500 Hz.

Enhancement of the vibration attenuation characteristics in local resonance metamaterial beams: Theory and experiment

Enhancing vibration isolation with local resonance metamaterials has attracted widespread attention due to the low-frequency band gap. However, the narrow band gaps limit its application. To improve vibration suppression properties over a wide frequency range under the constraints of space and mass in engineering, this paper presents the modeling techniques and design strategies for a local resonance elastic metamaterial beam with multiple resonators. The local resonance sub-system contains multi-degree-of-freedom resonators and is periodically mounted on the elastic beam. Two special cases, the elastic metamaterial beam with one-degree-of-freedom local resonator sub-system (1-DOF) and two-degree-of-freedom local resonator sub-system (2-DOF) are used to investigate the vibration attenuation characteristics in detail. Results are presented in the form of attenuation constant, which are calculated by the extended plane wave expansion (EPWE) method. The effects of frequency spacing, damping and mass ratio on the vibration attenuation characteristics of elastic metamaterial beams are comprehensively investigated. The results show that a wider and more stable attenuation range can be obtained by reasonably adjusting these three parameters. Finally, the comparison of experimental and simulation results demonstrates that the design strategies proposed in this paper can broaden the vibration attenuation regions. The theoretical approaches and design schemes can provide effective guidance for passive vibration control.

Skeletal muscle tissue composition ratio in patients with hip fracture: Comparison of fractured side and non-fractured side.

The extent of asymmetry in the muscle tissue composition ratios with hip fractures has not been clarified. To determine whether there is a difference in the muscle tissue composition ratios between the fractured and non-fractured sides of the trunk and thighs immediate measurement. Forty-four patients (84.6 ± 7.0 years) were included. Computed tomography images were used for measurements. The muscle tissue composition ratio was measured using muscle cross-sectional area (CSA) and attenuation coefficient (Hounsfield units; HU). Defined each HU attenuation range as follows: low-density muscle (LDM), low-quality muscle tissue with fat infiltration, normal-density muscle (NDM), muscle contractor tissue, and intramuscular adipose tissue (IMAT), fat infiltration tissue. The CSA of each muscle tissue was expressed as a percentage: %LDM, %NDM, and %IMAT. A paired t-test was performed for comparison. The %LDM on the fractured side was higher in the thigh and erector spinae. The %NDM on the fractured side was lower in the thigh. There was no significant difference in the %IMAT for all muscles. The thigh on the fractured side showed asymmetry with low %NDM and high %LDM. This characteristic captures a characteristic of muscle tissue that may have importance in hip fracture etiology.

Low Loss 16-Channel Photodetector Array Receiving Module With Fine Tuning Ability

A 16-channel photodetector array receiving module with good performance as low loss, fine tuning and high reliability is manufactured in our laboratory. The whole module was consisted with a silica arrayed waveguide grating chip (AWG), a thermo-optical type variable optical attenuator (VOA), a photodetectors (PDs) array with direct-current (DC) bias circuit, all components were integrated via 3D package method. In the article, the structure parameters of Y branch and edge couplers were optimized for lower loss. In order to realize excellent tuning ability, Titanium was selected as heating material for precisely tuning and its electric attenuation range could reach at a level more than 20 dB. Periodically segmented waveguide coupler designed in passive chips could minimize coupling loss less than 0.4 dB/coupling. The high-performance receiving module could effectively improve detection quality and significantly enlarge capacity in communication system.

A C/X/Ku/K-Band Precision Compact 6-Bit Digital Attenuator with Logic Control Circuits

This paper proposes a C/X/Ku/K band 6-bit digital step attenuator (DSA) which employs a variety of improved attenuation cells to achieve a wide bandwidth, stable amplitude variation, stable phase variation, and small area. In this paper, the improved T-type, π-type, and switched-path type topologies are analyzed theoretically and applied to different attenuation values to achieve the optimal attenuator performance. In addition, in order to reduce the complexity and to improve the stability of the overall radar system, the logic control circuit is integrated in the DSA chip in this paper. Finally, the proposed attenuator is implemented in 0.15μm GaAs technology, which has a maximum attenuation range of 31.5 dB with 0.5 dB steps. The proposed DSA exhibits a root-mean-square (RMS) attenuation error of less than 0.15 dB and an RMS phase error of less than 3°, at 4–24 GHz. The insertion loss (IL) and the area of the DSA are 4.3–4.5 dB and 1.5 mm × 0.4 mm, respectively. Benefiting from the improvements of the attenuation cells and the characteristic of GaAs technology with strong resistance to radiation and power processing capability, the proposed DSA is suitable for spaceborne radar systems.

Improved Model-Based Forest Height Inversion Using Airborne L-Band Repeat-Pass Dual-Baseline Pol-InSAR Data

This paper proposes an improved model-based forest height inversion method for airborne L-band dual-baseline repeat-pass polarimetric synthetic aperture radar interferometry (PolInSAR) collections. A two-layer physical model with various volumetric scattering attenuation and dynamic motion properties is first designed based on the traditional Random Motion over Ground (RMoG) model. Related PolInSAR coherence functions with both volumetric and temporal decorrelations incorporated are derived, where the impacts of homogenous and heterogeneous attenuation and dynamic motion properties on the performance of forest height inversion were investigated by the Linear Volume Attenuation (LVA), Quadratic Volume Attenuation (QVA), Linear Volume Motion (LVM), and Quadratic Volume Motion (QVM) depictions in the volume layer. Dual-baseline PolInSAR data were acquired to increase the degree of freedom (DOF) of the coherence observations and thereby provide extra constraints on the forest parameters to address the underdetermined problem. The experiments were carried out on a boreal forest in Canada and a tropical one in Gabon, where physical models with LVA + QVM (RMSE: 3.56 m) and QVA + LVM (RMSE: 6.83 m) exhibited better performances on the forest height inversion over the boreal and tropical forest sites, respectively. To leverage the advantages of LVA, QVA, LVM, and QVM, a pixel-wise optimization strategy was used to obtain the best forest height inversion performance for the range of attenuation and motion profiles considered. This pixel-wise optimization surpasses the best-performing single model and achieves forest height inversion results with an RMSE of 3.21 m in the boreal forest site and an RMSE of 6.48 m in the tropical forest site.

Attenuation band impedance matched BRF for measurements of electromagnetic noise

AbstractWireless communication devices such as wireless LANs and RFIDs are essential for smart home appliances and IoT (Internet of Things) devices in Smart Cities. When measuring the high‐frequency noise generated by devices, wireless signals of wireless communication devices and high‐frequency noise are measured at the same time. As a result, spectrum analyzers have insufficient dynamic range, or the excess signal from wireless communication devices causes harmonic distortion of the mixer inside the receiver, resulting in inaccurate measurements. Accordingly, a band rejection filter (BRF) is required to attenuate the radio signal. CISPR 16‐2‐3:2016+A1: 2019 assumes that impedances are matched for measurement, so if the impedance mismatch is large, the expanded uncertainty specified in CISPR 16‐4‐2:2011+A1:2014+A2:2018 increases. In this study, we propose a new BRF with impedance matching in the attenuation range and show its principle. As a result, the extended uncertainty could be reduced to 3.96 dB for the BRF of this study compared to 10.63 dB for the conventional BRF. In addition, the method comparison of CISPR 16‐2‐3:2016+A1: 2019 and vector network analyzer shows that the difference in attenuation of the conventional BRF was about −0.8 to 3.3 dB, whereas the BRF in this study were about −0.2 to 0.3 dB. The reduction of the expanded uncertainty and the good measurement results confirm the high usefulness of the CISPR 16‐2‐3 measurement system for the measurement of weak electromagnetic noise.

Epicardial adipose tissue volume and density is associated with cardiac dysfunction in asymptomatic people with type 2 diabetes

Abstract Background Type 2 diabetes (T2D) is associated with several perturbations of cardiac structure and function, which are precursors to the development of heart failure. Excess accumulation of epicardial adipose tissue (EAT) may contribute to cardiac dysfunction in individuals with T2D. Lipid-laden adipocytes have a lower computed tomography (CT) attenuation and can be readily identified using cardiac CT. Using a multimodality cardiac imaging approach, we aimed to assess the association of total and low attenuation EAT volume with early markers of cardiac dysfunction in people with T2D. Methods Prospective case-control study, in which participants with and without T2D and no known cardiovascular disease, underwent comprehensive cardiovascular phenotyping including multiparametric cardiac magnetic resonance imaging (MRI), echocardiography and non-contrast cardiac CT. EAT volume was measured from CT scans using a deep learning method and volumes indexed to body surface area. Total EAT was defined according to CT adipose tissue attenuation range of −30 to −190 Hounsfield Units (HU) and low attenuation EAT as −90 to −190 HU. Left ventricular (LV) volumes, function and strain measurements were derived from cardiac MRI images and diastolic function also assessed using echocardiography. Markers of early cardiac dysfunction in those with T2D were assessed for associations with EAT in T2D participants using multivariable linear regression analyses. Results Two hundred and fifty-four participants were included: demographic, anthropometric and imaging variables are displayed in Table 1. Subjects with T2D had increased LV concentric remodelling (higher LV mass/volume ratio), diastolic dysfunction (lower circumferential peak early diastolic strain rate (PEDSR) and average E/e') and reduced systolic function (global longitudinal strain, GLS) compared with controls. Total and low attenuation indexed EAT volumes were 1.6-fold and 2-fold higher, respectively, in participants with T2D compared to controls (Figure 1). After adjustment for age, gender, ethnicity, insulin resistance, systolic blood pressure and waist/hip ratio, total and low attenuation indexed EAT volume were independently associated with LV mass/volume ratio (total indexed EAT volume: β=0.002, p=0.02, low attenuation indexed EAT volume: β=0.004, p=0.01) and LV GLS (total indexed EAT volume: β=−0.02, p<0.01, low attenuation indexed EAT volume: β=−0.04, p=0.02) in subjects with T2D, but not indices of diastolic dysfunction. Conclusion Total and low attenuation EAT volumes are higher in individuals with T2D, and excess EAT accumulation is independently associated with early markers of cardiac dysfunction. Further studies into the underlying mechanisms of this interaction may facilitate the development of interventions targeted at EAT, which could mitigate against the development of heart failure in people with T2D. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): United Kingdom National Institute for Health Research

Performance of automatic exposure control on dose and image quality: comparison between slot-scanning and flat-panel digital radiography systems.

EOSedge™* (EOS Imaging, Paris, France) is an X-ray imaging system using automatic exposure control (AEC) with tube current modulation, in order to optimize dose deposition inpatients. This study aims at characterizing EOSedge organ dose deposition in comparison to a digital radiography (DR) system and the previous EOS system (EOS-1stgeneration), in relation to their respective image qualitylevels. Organ doses were measured in an anthropomorphic female adult phantom and a 5-year-old pediatric phantom using optically stimulated luminescence (OSL) dosimeters, which were carefully calibrated within the studied energy range. Organ doses were recorded on the EOSedge and the Fuji Visionary DRF (Fujifilm Medical Systems U.S.A., Inc, Lexington, MA). The resulting effective doses were compared to the EOS-1st-generation values present in the literature. Image quality assessment was carried out on end-user images. Quantitative image quality metrics were computed for all tested modalities on a quality assurance phantom. Qualitative assessment of EOSedge image quality was based on anthropomorphic phantom acquisitions against the EOS-1st-generation system, and on clinical images against the tested DRsystem. For a full-spine exam, and on the female adult phantom (respectively, the pediatric phantom), an effective dose of 92μSv (respectively, 32μSv) was obtained on EOSedge, and 572μSv (respectively, 179μSv) on the DR system; these values were compared to effective dose values of 290μSv (respectively, 200μSv) from the literature on EOS-1stgeneration, leading to an effective dose reduction factor of 6 with respect to the DR system, and of 3-6 with respect to EOS-1stgeneration. EOSedge provides the best compromise between contrast-to-noise ratio (CNR) and dose, with more consistent CNR values than the other tested modalities, in a range of attenuation from 10 to 40cm of poly(methyl methacrylate) (PMMA). Within this range, EOSedge is also comparable to DR for 10 and 20cm of PMMA, and better than DR for 30 and 40cm of PMMA, both in terms of spatial resolution and low-contrast detection. The anatomical landmarks of interest in the follow-up of spinal deformities can be detected in all testedmodalities. Results showed that EOSedge provides significant dose reduction factors for full spine imaging in both adults and children compared to the other tested modalities, without compromising image quality. We believe that this work could help raise awareness on the capabilities of modern X-ray systems, when equipped with appropriate AEC strategies, to perform ultra-low-dose, long-axisimages.

Double-beam metastructure with inertially amplified resonators for flexural wave attenuation

A new type of double-beam metastructure with periodically attached inertially amplified (IA) resonators is designed to attenuate the flexural wave propagation in the low-frequency range. An analytical approach based on the spectral element method (SEM) and the Wittrick-Williams algorithm is developed. The results of SEM show superior accuracy and an order of magnitude higher computational efficiency compared to the finite element method (FEM). Employing the developed approach, the wave attenuation behavior is presented as a function of the parameters including truss angle, beam thickness, IA mass, spring, and damper location to exhibit the perfect adjustability of bandgaps realized by the proposed structure. The local resonance bandgap frequencies are effectively lowered under the effect of inertial amplification. In addition, the damping amplification is also achieved by the IA structure, which is advantageous for extending the wave attenuation range. Finally, multibody dynamics numerical simulations are carried out to validate the reliability of the theoretical method and the rationality of simplifications used in the theoretical derivation. Furthermore, the formation mechanism of bandgaps is revealed by exploring the eigenmode shape on dispersion curves to obtain a thorough understanding of the structure.

Acoustic attenuation characteristics of the muffler phononic crystal with hybrid resonators

Aiming at achieving broadband and strong sound attenuation in the duct, this study proposes one compact and hybrid muffler phononic crystal. The two-dimensional (2D) transfer matrix method is applied to calculate the transmission loss (TL) of one unit cell validated by the numerical simulation and experiment. On this basis, the unit cell dispersion theory is employed to predict the bandgap properties of the infinite periodic mufflers. The sound reduction mechanism in the hybrid muffler is disclosed, while the effect of the period number on the acoustic performance is examined. It demonstrated that the acoustic resonant behaviors of the short-length mufflers are conducive to the continuous and superior attenuation band through the compact structure. The number of the TL domes and the boundary length of the short chamber could be evaluated by the cut-off frequency at the (0,1) radial mode and the first passing frequency for the muffler. Although each resonant-type component of the hybrid muffler is responsible for the TL peaks at different frequency ranges, via the coupling effect, they provide remarkably improved performance over a wide frequency range. The unit cell periodicity brings two types of bandgap, the locally resonant bandgap (LRG) and Bragg bandgap (BG), further enhancing the attenuation amplitude. Utilizing the different resonance mechanisms as well as the merging of the LRG and BG, the hybrid muffler phononic crystal is improved, which possesses a wide attenuation range with a tinier structure. The results develop new approaches for broadband and strong sound attenuation using the concept of the phononic crystal and offer a promising application in duct noise control.

Four-stage cascaded variable optical attenuator with large attenuation range for quantum key distribution

A four-stage cascaded variable optical attenuator (VOA) with a large attenuation range is presented. The VOA is based on a Mach–Zehnder interferometer (MZI) and fabricated in a silica-based planar lightwave circuit (PLC) platform. The thermo-optic effect is used to achieve intensity modulation. The measured maximum attenuation of the four-stage cascaded VOA is 88.38 dB. The chip is also tested in a quantum key distribution (QKD) system to generate signal and decoy states. The mean photon number after attenuation of the four-stage cascaded VOA is less than 0.1, which can meet the requirement of QKD.

A Wideband 6-Bit Digital Attenuator in a GaAs pHEMT MMIC

A low insertion loss, wideband 6-bit digital step attenuator is implemented in the 0.25-μm GaAs pHEMT process. Modified π- or T-type attenuator structures are adopted to expand the operation frequency bandwidth and reduce the insertion phase violation. Furthermore, the through-wafer via (TWV) is analyzed to reduce the influence of the parasitic effect on the high-frequency performance of the attenuator. The depletion mode single-gate switch transistors are used to control the on-off state of the attenuator, which provides low insertion loss and high isolation. The step of the attenuator is 0.5 dB, and the attenuation range is 31.5 dB. The measurement results show a maximum root mean square (RMS) attenuation error of 0.51 dB and RMS phase error of 6.6 degrees from DC-18 GHz. The chip area is 1.8 × 0.6 mm2.

Simulated Influence of Mountainous Wind Farms Operations on Local Climate

Renewable energy sources, especially wind power, were believed to be able to slow down global warming; however, evidence in recent years shows that wind farms may also induce climate change. With the rapid development of wind power industry, the number of wind farms installed in mountains has gradually increased. Therefore, it is necessary to study the impact of wind farms in mountainous areas on local climate. The Suizhou and Dawu wind farms in northern Hubei Province were chosen for the present study on the impact of wind farm operations on the local climate in mountainous areas. The mesoscale meteorological numerical model Weather Research and Forecasting Model (WRF) and the Fitch model, together with turbulence correction factor, were used to simulate wind farm operations and study their effects on local climate. The results showed the characteristics of wind speed attenuation in mountainous wind farms: the amplitude and range of wind speed attenuation were stronger in the nighttime than in the daytime, and stronger in summer than in winter. The surface temperature increased and became more significant in summer. However, a cooling variation was observed above the surface warming center. The height of this center was higher in the daytime than it was in the nighttime. The latent heat flux in the wind farms decreased at night, accompanied by an increase in sensible heat flux. However, these changes were not significant. Some differences were observed between the impact of wind farms on the climate in the plains and the mountains. Such differences are more likely to be related to complex terrain conditions, climate conditions, and the density of wind turbines. The present study may provide support for the development and construction of wind farms in mountainous areas.

Additively manufactured test phantoms for mimicking soft tissue radiation attenuation in CBCT using Polyjet technology

ObjectivesTo develop and validate a simple approach for building cost-effective imaging phantoms for Cone Beam Computed Tomography (CBCT) using a modified Polyjet additive manufacturing technology where a single material can mimic a range of human soft-tissue radiation attenuation. Materials and MethodsSingle material test phantoms using a cubic lattice were designed in 3-Matic 15.0 software . Keeping the individual cubic lattice volume constant, eight different percentage ratio (R) of air: material from 0% to 70% with a 10% increment were assigned to each sample. The phantoms were printed in three materials, namely Vero PureWhite, VeroClear and TangoPlus using Polyjet technology. The CT value analysis, non-contact profile measurement and microCT-based volumetric analysis was performed for all the samples. ResultsThe printed test phantoms produced a grey value spectrum equivalent to the radiation attenuation of human soft tissues in the range of −757 to +286 HU on CT. The results from dimensional comparison analysis of the printed phantoms with the digital test phantoms using non-contact profile measurement showed a mean accuracy of 99.07 % and that of micro-CT volumetric analysis showed mean volumetric accuracy of 84.80–94.91%. The material and printing costs of developing 24 test phantoms was 83.00 Euro. ConclusionsThe study shows that additive manufacturing-guided macrostructure manipulation modifies successfully the radiographic visibility of a material in CBCT imaging with 1 mm3 resolution, helping customization of imaging phantoms.

RADIOLOGIC CHARACTERISTICS OF COMPUTERIZED TOMOGRAPHY ATTENUATION IN RENAL CELL CARCINOMA

Background: Renal cell carcinoma (RCC) is the most common kidney cancer in adults. Computed Tomography (CT) with contrast study is used to diagnose RCC. The enhancement in the nephrogenic phase more than 15 Hounsfield units (HU) is suspected of RCCs. However, this threshold HU shows 15-20% false positive results for RCCs.
 Objectives: This study aimed to determine RCC enhancement in CT that was below the standard threshold and to analyze the attenuation range of RCCs in noncontrast CT. Methods: Patients with pathological RCC and undergoing CT with contrast study were retrospectively reviewed. An average of attenuation values of three regions of interest (ROI) were measured in noncontrast and nephrogenic phases, by avoiding foci of calcification and peritumoral region. ROI values were calculated for enhancement and range of attenuation values in the noncontrast CT.
 Results: A total of 152 pathologically RCCs were included in the study. Mean ± SD attenuation values were 32.54 ± 8.02 HU (range 13.3-57.23 HU) and 71.26 ± 33.1 HU (range 16.87-202.8 HU) for noncontrast and contrast CT, respectively. Thirty-one (20.4%) of RCCs did not reach 15 HU enhancement. Using multivariate analysis, significant differences among subtypes (p<0.001) and renal mass less than 7 cm (p<0.001) were observed. In noncontrast CT, using a range of 20-60 HU, 129 (84.9%) RCCs were entirely within this range. To improve the accuracy of RCC diagnosis, the combined use of both non-contrast attenuation group (<20 HU and >20 HU) and enhancement >15 HU could increase the accuracy to 96.7%.
 Conclusion: One-fifth of RCCs did not reach the standard enhancement threshold that were mostly found in nonclear cell subtype. Especially, when the mass was larger than 7 cm or involved nonclear cell RCCs, the enhancement threshold >15 HU must be carefully used for diagnosis. Using a noncontrast phase regardless HU combined with enhancement >15 HU could improve the accuracy of RCC diagnosis.

Small-Sized Absorbing Elements of Adaptol Attenuators for Surface Mounting

Promising topologies, methods of calculation and adjustment of parameters of small-sized absorbing elements of adaptoat-tenuators for surface mounting based on homogeneous and piecewise homogeneous resistive structures providing the implementation of a wide range of attenuations with specified values of input and output resistances are proposed. Topologies based on piecewise homogeneous structures have been studied, allowing not only to reduce the size of the absorbing elements, to ensure high values of the transformation coefficient (more than 200), but also to reduce the maximum values of the potential gradient and power density (on average by 1,5 and 3 times, respectively). The results obtained are especially important for the pulse mode of operation of adaptoattenuators. It is shown that the absorbing elements of the proposed topologies based on homogeneous resistive structures are not able to provide transformation coefficients of more than 3—3,5. The methods of calculation and adjustment of the parameters of absorbing elements, ratios and graphs showing the relationship of attenuation, transformation coefficient, reduction of the maximum values of the potential gradient and power density depending on the ratio of the sizes and resistivity of the resistive films used are given.

A Ku-Band Bi-Directional Transmit and Receive IC in 0.13 μm CMOS Technology

This paper presents a Ku-band transmit and receive IC in 0.13 µm CMOS technology for mobile satellite communication beamforming systems. A Ku-band transmit and receive IC is composed of a bi-directional amplifier, a 6-bit phase shifter, and a 6-bit digital step attenuator. The precise trimming bits are implemented in the phase shifter (2.8°) and digital step attenuator (0.5 and 1 dB) for the amplitude and phase error correction. The phase variation range of the phase shifter is 360° with a phase resolution of 5.625°. The attenuation range of 31.5 dB with an amplitude resolution of 0.5 dB is achieved. The gain of 2~5 dB and the input/output return losses of >10 dB are achieved from 12 to 16 GHz. The chip size is 2.5 × 1.5 mm2 including bonding pads. The DC power consumption is 216 mW.

Can the Digital Economy Facilitate Carbon Emissions Decoupling? An Empirical Study Based on Provincial Data in China.

The digital economy plays a dual role in the process of global carbon emissions decoupling; for this reason, its overall impact direction and mechanism are worth discussing. This paper attempts to answer the question of the role of the digital economy, based on a review of the existing literature. By constructing a panel smooth transition regression (PSTR) model, this paper empirically tests the effect of the digital economy on carbon emissions decoupling, based on panel data from 30 provinces in China from 2010 to 2019. In order to study the impact mechanism of the digital economy on carbon emissions decoupling, the mediating effect of industrial structure optimization is analyzed through a mediating effect model; the moderating effect is also explored by analyzing the network centrality characteristics of the digital economy. The core-periphery analysis method is adopted to group the samples to test the impact heterogeneity of the digital economy on carbon emissions decoupling. Based on this empirical analysis, the following conclusions are drawn. First, the digital economy has a promoting effect on carbon emissions decoupling, but this effect gradually weakens with the development of the digital economy. Second, the digital economy can promote carbon emissions decoupling through industrial structure optimization, and network centrality has a positive moderating effect on this mechanism. Third, heterogeneity exists in the promoting effect of the digital economy on carbon emissions decoupling, which is reflected in the different intensities of the promotion effect between the core nodes and the peripheral nodes in the network; the attenuation range of the promotion effect is also different when the regime switches.

Measuring Cryogenic Waveguide Loss in the Terahertz Regime

Waveguide attenuation due to conductor loss increases significantly in the terahertz regime. There are a variety of models to estimate this loss but the accuracy is unverified at cryogenic temperatures above 100 GHz. In this article, we present a new technique for measuring the conductor loss of these waveguides. The technique is based on measurements of a waveguide cavity resonator and uses a frequency- to distance-domain transform to isolate the different orders of transmission through the cavity. By calculating the relative loss between successive orders, we can estimate the loss of the resonator and calculate the waveguide attenuation constant. This technique is less susceptible to calibration errors and standing waves in the measurement system, making it suitable for cryogenic high-frequency measurements. For the purposes of this study, we measured the attenuation constant of several WR-2.8 and WR-3.0 waveguides made from aluminum, gold-plated aluminum, and tellurium copper. At room temperature, the measured attenuation constants were between 0.25 and 0.40 dB/cm in the 260- to 350-GHz frequency range. At cryogenic temperatures (4 K), the attenuation range reduced to between 0.18 and 0.26 dB/cm.