Series Gap Research Articles

Comparison of eddy covariance CO<sub>2</sub> and CH<sub>4</sub> fluxes from mined and recently rewetted sections in a northwestern German cutover bog

Abstract. With respect to their role in the global carbon cycle, natural peatlands are characterized by their ability to sequester atmospheric carbon. This trait is strongly connected to the water regime of these ecosystems. Large parts of the soil profile in natural peatlands are water saturated, leading to anoxic conditions and to a diminished decomposition of plant litter. In functioning peatlands, the rate of carbon fixation by plant photosynthesis is larger than the decomposition rate of dead organic material. Over time, the amount of carbon that remains in the soil and is not converted back to carbon dioxide grows. Land use of peatlands often goes along with water level manipulations and thereby with alterations of carbon flux dynamics. In this study, carbon dioxide (CO2) and methane (CH4) flux measurements from a bog site in northwestern Germany that has been heavily degraded by peat mining are presented. Two contrasting types of management have been implemented at the site: (1) drainage during ongoing peat harvesting on one half of the central bog area and (2) rewetting on the other half that had been taken out of use shortly before measurements commenced. The presented 2-year data set was collected with an eddy covariance (EC) system set up on a central railroad dam that divides the two halves of the (former) peat harvesting area. We used footprint analysis to split the obtained CO2 and CH4 flux time series into data characterizing the gas exchange dynamics of both contrasting land use types individually. The time series gaps resulting from data division were filled using the response of artificial neural networks (ANNs) to environmental variables, footprint variability, and fuzzy transformations of seasonal and diurnal cyclicity. We used the gap-filled gas flux time series from 2 consecutive years to evaluate the impact of rewetting on the annual vertical carbon balances of the cutover bog. Rewetting had a considerable effect on the annual carbon fluxes and led to increased CH4 and decreased CO2 release. The larger relative difference between cumulative CO2 fluxes from the rewetted (13±6 mol m−2 a−1) and drained (22±7 mol m−2 a−1) section occurred in the second observed year when rewetting apparently reduced CO2 emissions by 40 %. The absolute difference in annual CH4 flux sums was more similar between both years, while the relative difference of CH4 release between the rewetted (0.83±0.15 mol m−2 a−1) and drained (0.45±0.11 mol m−2 a−1) section was larger in the first observed year, indicating a maximum increase in annual CH4 release of 84 % caused by rewetting at this particular site during the study period.

3-D-Printed High Data-Density Electromagnetic Encoders Based on Permittivity Contrast for Motion Control and Chipless-RFID

The 3-D-printed electromagnetic encoders based on permittivity contrast are presented and discussed in this article. The encoders, implemented using exclusively dielectric materials, are based on linear chains of dielectric inclusions. Two types of encoders are considered: 1) those where the inclusions are simple apertures made on a 3-D-printed dielectric plate (or substrate) and 2) those with inclusions made of high dielectric constant material 3-D-printed on a dielectric substrate (also 3-D-printed). In both cases, encoding is achieved by varying the dielectric constant of the substrate at predefined positions by means of the inclusions. For encoder reading, a microstrip line loaded with a slot resonator (etched in the ground plane) and a series gap is proposed. Such structure is very sensitive to short range dielectric constant variations, being able to detect the presence or absence of closely spaced inclusions when the encoder is displaced on top of the sensitive part of the reader, the slot resonator. For that purpose, the reader line is fed by a harmonic signal conveniently tuned, so that an amplitude-modulated (AM) signal containing the identification (ID) code is generated at the output port of the line. The proposed reader/encoder system is useful for motion control applications (linear displacement and velocity sensors) and for near-field chipless-radio frequency ID (RFID). Lower cost and major robustness against mechanical wearing are potential advantages of these encoders over other electromagnetic encoders based on a similar principle but based on metallic inclusions.

A New Ultracompact Narrow Bandpass Microstrip Filter Using Double-Negative Quasiplanar Cells

This paper presents a novel ultracompact narrow bandpass filter with high selectivity. The proposed filter is composed of cascading two basic cells. Each cell is basically a microstrip line loaded with a quasiplanar resonator and series gaps which can be fabricated using a standard multilayer printed circuit board technology. The structure is analyzed through an equivalent circuit and full-wave simulations. The simulation results are compared with experimental measurements demonstrating a good agreement between them. The measurement indicates that the realized bandpass filter at the center frequency of 1 GHz has a fractional bandwidth of 2.2%. Most importantly, in comparison with other similar recent works, it is shown that the proposed filter has the smallest size.

A compact dual‐band zeroth‐order resonator antenna loaded with meander line inductor

A novel zeroth-order resonator (ZOR) meta-material (MTM) antenna with dual-band is suggested using compound right/left handed transmission line as MTM. In this article, suggested antenna consists of patch through series gap, two meander line inductors, and two circular stubs. The MTM antenna is compact in size which shows dual-band properties with first band centered at 2.47 GHz (2.05-2.89 GHz) and second band is centered at 5.9 GHz (3.70-8.10 GHz) with impedance bandwidth of (S11 < − 10 dB) 34.69% and 72.45%, respectively. At ZOR mode (2.35 GHz), the suggested antenna has overall dimension of 0.197λo × 0.07λo × 0.011λo with gain of 1.65 dB for ZOR band and 3.35 dB for first positive order resonator band which covers the applications like Bluetooth (2.4 GHZ), TV/Radio/Data (3.700-6.425 GHz), WLAN (5-5.16 GHz), C band frequencies (5.15-5.35, 5.47-5.725, or 5.725-5.875 GHz) and satellite communication (7.25-7.9 GHz). The radiation patterns of suggested structure are steady during the operating band for which sample antenna has been fabricated and confirmed experimentally. It exhibits novel omnidirectional radiation characteristics in phi = 0° plane with lower cross-polarization values.

Approach to the recovery of geomagnetic data by comparing daily fragments of a time series with equal geomagnetic activity

Monitoring of geomagnetic field parameters and its variations is mainly carried out using ground-based magnetic observatories and variational stations. However, the imperfection of equipment used and the communication channels involved causes the presence of gaps in the time series of geomagnetic data, which, along with the spatial anisotropy of data sources, creates significant obstacles to their automated processing. In addition, the well-known methods for imputation of time series gaps provide the root-mean-square recovery error significantly exceeding the level acceptable for geophysical observations. Thus, the paper proposes a method for recovering geomagnetic data based on statistical methods for processing time series and machine learning principles using marked data and characterized by the fact that a pair of the time series fragments preceding and succeeding a missing fragment provide an indicative description of the time series fragment of interest, which together form a training sample to search for the missing fragment by a set of its attributes, followed by linear scaling to restore the original trend of an information signal. Analytical estimates of parameters of geomagnetic data time series are given, under which it is possible to apply the proposed method to recover both daily variations and several-minutes-long fragments.

Application of X-ray Detection Technology in Routine Tests of High Voltage Bushings and Arresters

The improper control of the production process can easily cause defects in the power equipment that cannot be found by routine tests. In this paper, X-ray detection technology was used to test high voltage porcelain bushings, high voltage composite bushings and metal oxide surge arresters polymeric with series gaps, which are prior to working. It is found that there are air gaps between the waterproof glue on the flange and the body of bushings, which will increase the vibration frequency of the porcelain bushings and will cause the bushings to be abnormally stressed. There is a misalignment or poor contact between the contact surface of internal valve pieces of the MOA, which will reduce the flow capacity of the series valve pieces. The above phenomena will reduce the reliability of the power grid operation. This paper believe that the current routine tests should be improved, X-ray detection technology should be used as a new routine test for high-voltage bushings and arresters to improve the reliability of equipment operation.

Design and band coalition of dual band microstrip filter using DGS, coupled line structures and series inductive metallic vias

An approach to design compact dual band BPF and technique to unite the two bands into a single wide band is presented in this paper. The novelty of the filter stands on the application of series of metallic vias which are used to merge the bands obtained using coupled line circuits and DGS structure. The coupled line filter and the coupled line filter integrated with DGS shows passband resonance at 4.5 GHz and 5.1 GHz within the microwave frequency of operation. Series metallic vias are used to merge the passbands into a single wider passband of bandwidth 1.6 GHz (3.5–5.1 GHz). The filter configurations are fed using stepped-impedance open stub technique to reduce cross coupling between adjacent structures. Moreover effects of several salient filter parameters like gap between edge of the microstrip coupled line resonator and via series GV and gap between mid-point of the open ended feed line and via row GM are studied to achieve greater isolation at higher frequencies. All simulated designs are fabricated and experimentally studied to vindicate the practical performance of all filter configurations.

Modeling of Graphene Coplanar Waveguide and its Discontinuities for THz Integrated Circuits Applications

Graphene, having extraordinary electronic and optical properties at THz frequencies, can be used in the design and development of miniaturized components, devices, and integrated circuits. Model of graphene-based transmission lines and their discontinuities play a crucial role in the realization of THz integrated circuits, which is not readily available in the literature. This paper reports the characteristics of graphene film deposited over a SiO2/Si wafer. Transmission line characteristics of graphene-based plasmonic coplanar waveguide (GPCPW) on SiO2/Si wafer have been determined from the electromagnetic modeling of the structure. Discontinuities in the GPCPW such as open end, series gap, and step junction have also been analyzed to obtain their lumped element electrical equivalent. Closed-form expressions are developed so that it can be used in the circuit design at later stage. It has been observed that GPCPW transmission lines have very high characteristic impedance values (∼1000–2500 Ω) which are not possible in non-graphene transmission line structures.

Multisite analysis of land surface phenology in North American temperate and boreal deciduous forests from Landsat

Abstract Forests play important roles in the Earth's climate system and global carbon cycle. Therefore, a critical need exists to improve our understanding of how the growing seasons of forests are changing, and by extension, how the composition and function of forests will respond to future climate change. Coarse spatial resolution satellite remote sensing has been widely used to monitor and map the phenology of terrestrial ecosystems at regional to global scales, and despite widespread agreement that the growing season of Northern Hemisphere forests is changing, the spatial resolution of these data sources imposes significant limitations on the character and quality of inferences that can be drawn from them. In particular, the spatial resolution afforded by instruments such as MODIS does not resolve ecologically important landscape-scale patterns in phenology. With this issue in mind, here we evaluate the ability of a newly developed Landsat phenology algorithm (LPA) to reconstruct a 32-year time series for the start and end of the growing season in North American temperate and boreal forests. We focus on 13 “sidelap” regions located between overlapping Landsat scenes that span a large geographic range of temperate and boreal forests, and evaluate the quality and character of LPA-derived start and end of growing season (SOS and EOS) dates using several independent data sources. On average, SOS and EOS dates were detected for about two-thirds of the 32 years included in our analysis, with the remaining one-third missing due to cloud cover. Moreover, there was generally better agreement between ground observations and LPA-derived estimates of SOS dates than for EOS across the 13 sites included in our study. Our results demonstrate that, despite the presence of time series gaps, LPA provides a robust basis for retrospective analysis of long-term changes in spring and autumn deciduous forest phenology over the last three decades. Finally, our results support the potential for monitoring land surface phenology at 30 m spatial resolution in near real-time by combining time series from multiple sensors such as the Landsat Operational Land Imager and the Sentinel 2 MultiSpectral Instrument.

A compact short‐ended zor antenna with gain enhancement using EBG loading

ABSTRACTA new compact CPW‐fed short ended antenna based on composite right/left handed (CRLH) resonant approach is presented in this article. The antenna is operated in series resonant mode and therefore zeroth order resonating (ZOR) frequency can be driven by series elements of the conventional CRLH‐TL. Proposed antenna is basically a symmetric ground plane CPW‐fed antenna, comprises of meandered line inductor, connected between patch and CPW ground planes. Series gaps are provided by means of an octagonal shaped interdigital capacitor. Proposed antenna shows ZOR property at 2.58–2.68 GHz with 2.74 dB gain at 2.64 GHz. It has been observed that high level of miniaturization leads to lowering the antenna gain, therefore EBG structures are employed on the signal patch to improve the antenna gain. Proposed antenna radiated omni‐directionally in xz‐ plane while bi‐directionally in yz‐ plane with cross polarization level is as low as −30 dB. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1194–1197, 2016

Miniaturized sharp band-pass filter based on complementary electric-LC resonator

In this paper, a novel application of complementary electric-LC (CELC) resonator as a basic element to synthesize miniaturized sharp band-pass filters is introduced. The proposed metamaterial band-pass filter is a three-stage CELC-based device, where two shunt short-circuited stubs are employed in the input and output stages and a series gap is etched in the middle stage. By these means, a high-selectivity prototype band-pass filter with 2 % fractional bandwidth in S band is designed and fabricated. The out-of-band attenuation is better than 40 dB, and the upper and lower transition bands are also quite sharp due to the presence of two transmission zeros (nearly 60 and 30 dB fall in 0.2 GHz at lower and upper edges, respectively). Moreover, the filter is substantially miniaturized with a size of effective region of 1.3 cm × 1 cm at 2.9 GHz, which is quite smaller relative to conventional designs with the same performance. The fabrication and measurement of the proposed filter configuration attest to its expected desirable features. Therefore, the application of CELC resonator is proposed for super-compact sharp band-pass filters.

Detection of Damaged Distribution Surge Arresters Using an Impulse Generator

SUMMARYDistribution surge arresters with an internal series gap have been installed on Japanese distribution lines at high density to reduce lightning‐related overvoltages. In contrast, surge arresters are sometimes damaged by direct lightning strokes, particularly in winter. Measurement of the insulation resistance between the terminals of the surge arrester and measurement of the dc discharge voltage of the surge arrester are generally adopted to detect damaged arresters. However, if metal‐oxide (MO) varistors are damaged and the internal series gap is not damaged, it is difficult to detect damaged arresters by the two conventional methods. Therefore, this paper presents a proposed detection method that can accurately detect damaged arresters. In the proposed method, first, the voltage between the terminals of the surge arrester is measured when the output of an impulse generator is applied to the surge arrester. Second, the damaged arrester is detected by comparison between its voltage waveform and the voltage waveform of the nondamaged arrester. The detection rate of damaged arresters by the proposed method is markedly higher than the rates of detection by the two conventional methods.

Nonlinear Frequency Characteristic of Multiple Series Gaps With Voltage-Dividing Network and Its Application in HVDC Circuit Breaker

This paper proposes an active resonance circuit based on multiple series gaps (MSG) with voltage-dividing network and self-charging trigger device. The working principle of active resonance circuit, MSG, and triggering device is described in detail. To determine the optimal parameter setting of MSG, the effects of the voltage frequency, equalizing resistance, and voltage-dividing capacitance on the voltage distribution of MSG are analyzed by simulation. To realize the interrupting process of short fault current and determine the operation requirements of the main devices of precharge direct current (dc) circuit breaker, a simulation model of interrupting short fault current is performed. Furthermore, an experiment of four-series gaps is presented to verify the turn-on characteristic of the MSG and an experiment of artificial current zero is set up to testify the feasibility of the active resonance circuit. The simulation and experimental results show that the active resonance circuit proposed in this paper can generate an artificial zero current and is suitable for precharge dc circuit breaker.

A compact very wideband amplifying filter based on RTD loaded composite right/left-handed transmission lines.

The composite right/left-handed (CRLH) transmission line (TL) is presented as a general TL possessing both left-handed (LH) and right-handed (RH) natures. RH materials have both positive permittivity and positive permeability, and LH materials have both negative permittivity and negative permeability. This paper aims to design and analyze nonlinear CRLH-TL transmission line loaded with resonant tunneling diode (RTD). The main application of this design is a very wideband and compact filter that amplifies the travelling signal. We used OrCAD and ADS software to analyze the proposed circuit. CRLH-TL consists of a microstrip line which is loaded with complementary split-rings resonators (CSRRs), series gaps, and shunt inductor connected parallel to the RTD. The designed structure possess a wide band that ranges from 5 to 10.5 GHz and amplifies signal up to 50 %. The proposed design is of interest to microwave compact component designers.

A compact CPW‐fed wideband metamaterial antenna using Ω‐shaped interdigital capacitor for mobile applications

ABSTRACTIn this article, a compact bandwidth enhanced CPW‐fed metamaterial antenna is presented. The band broadening is accomplished by combining the resonant modes (n = 0, 1, 2). The antenna is operated in series resonant mode, and therefore, resonant characteristics can be controlled effectively by varying series parameters. Coupling among patches are responsible for originating number of modes which is made nearer to the original mode (n = 0 mode) to enhance the bandwidth. Proposed antenna offers measured fractional bandwidth of 54.3% at 3. 41 GHz (center frequency). Ω (Ohm)‐shaped IDC is used to provide the series gap which improves impedance matching significantly. It is illustrated that the zeroth‐order resonating frequency depends on the series parameters by demonstrating the equivalent circuit model. The antenna has an average peak gain of 2.36 dB and average radiation efficiency of 92.81%, throughout the operating band (S11 &lt; −10 dB). The proposed antenna has the advantages of simple fabrication, compactness, and omnidirectional radiation pattern makes it suitable for modern wireless communication such as WLAN/Wi‐Fi (2.4–2.49 GHz), WiMAX (2.5–2.69 GHz, 3.4–3.6 GHz), Bluetooth (2.4–2.48 GHz). Furthermore, prototype of the antenna is fabricated and measured and is in good agreement with the simulated one. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2558–2562, 2015

Compact wideband antenna based on novel composite right/left handed transmission line

Based on a new type of composite right/left handed transmission line (CRLH TL), a novel compact wideband antenna is proposed. The CRLH TL is composed of a ground player with an etched complementary single split-ring resonator and a patch with two series gaps and two metal vias. Consistent simulated and measured results of the proposed antenna are shown that it operates at 3.46 GHz extended to 3.97 GHz (10 dB return loss bandwidth is 13.7%). The electrical size of the patch at the center frequency f = 3.72 GHz is only 0.25λ0 × 0.22λ0 × 0.01λ0, a 52.7% reduction in size comparing to the conventional patch antenna. The measured radiation efficiency was higher than 80% over the 10 dB return loss bandwidth. Additionally, the antenna attained a gain extended from 3.1 to 4.76 dB.

Effect of triphenylamine as electron-donor evenly spaced in 2, 4, 6 and 8 thiophene units of the main chain: synthesis and properties

Several poly(thiophene) derivatives containing triphenylamine (TPA) as electron-donor were synthesized by chemical homopolymerization in CHCl3 media using FeCl3 as oxidizing agent. Monomers containing TPA bonded by imine groups to terminal thiophene, bithiophene, terthiophene units allows polymerization to be performed in conditions similar to thiophene. TPA units are regularly spaced in 2, 4, 6 and 8 thiophenyl units in the main chain. TPA electron-donor effect on the polymers chains, as compared to poly(thiophene) was studied. Polymers, labeled as poly(TPA-Th), poly(TPA-biTh) and poly(TPA-Terth) were characterized by 1H-NMR, FT-IR and UV–visible spectroscopy, elemental analysis, thermal stability (TGA) intrinsic viscosity, differential scanning calorimetry (DSC) and electrochemically using cyclic voltammetry (CV). The characterizations are consistent with the proposed structures. The polymers exhibited different optical absorption. They exhibited low intrinsic viscosity, a different effective conjugation and high thermal stability. Moreover, the polymers displayed two redox processes with a redox potential lower than that of poly(thiophene). Highest Occupied Molecular Orbital (HOMO), Lowest Unoccupied Molecular Orbital (LUMO) and optical band gap (Eg) were measured and the obtained values were compared with those of poly(thiophene). The effect of the presence of TPA units in the thiophenyl chains on HOMO, LUMO, band gap, redox potential and on TGA is reported. To complete the series, HOMO/LUMO levels and band gap of a polymer containing TPA with 8 thiophenyl units in the chain were determined using theoretical calculations. The results proved that, with respect to poly(thiophene), it is possible to decrease HOMO and LUMO without changing the band gap, projecting itself as a potential polymer to be studied in organic photocells.

A Compact Zeroth-Order Resonating Wideband Antenna With Dual-Band Characteristics

In this letter, a compact zeroth-order resonating wideband antenna with dual-band characteristics is designed using composite metamaterial (MTM). Such composite MTM consists of patch with series gap, meander line inductor, and a radial stub. The proposed structure offers compact size with radiating element dimensions of $0.08{\lambda _o} \times 0.122{\lambda _o} \times 0.006{\lambda _o}$ . The proposed MTM antenna exhibits dual-band behavior with first band centered at 1.22 GHz while other band is centered at 3.97 GHz with an impedance bandwidth ( ${{\rm S}_{11}} ) of 5% and 59.9%, respectively. The proposed structure shows good radiation characteristics with an average peak gain of 1.82 dB and 2.15 dB for first and second band, respectively. The radiation patterns are consistent throughout the working band. The prototype structure has been fabricated and experimentally validated.

S-Shaped Complementary Split Ring Resonators and Their Application to Compact Differential Bandpass Filters With Common-Mode Suppression

This letter presents an S-shaped complementary split ring resonator (S-CSRR) for application in compact differential filters. The working principle of the proposed S-CSRR is explained and a circuit model is developed and validated through electromagnetic simulations. It is shown that an S-CSRR-loaded differential microstrip line with series gaps can be used in the design of compact differential bandpass filters (BPFs) with common-mode suppression. The filter design procedure is explained and the theoretical concept is validated through fabrication and measurement of a compact (0.09λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ×0.25 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ) third-order differential BPF with common-mode suppression.

Coplanar Waveguides Loaded with S-Shaped Split-Ring Resonators: Modeling and Application to Compact Microwave Filters

This letter studies the transmission characteristics of coplanar waveguides (CPWs) loaded with single-layer S-shaped split-ring resonators (S-SRRs) for the first time. Two structures are analyzed: 1) a CPW simply loaded with an S-SRR, and 2) a CPW loaded with an S-SRR and a series gap. The former exhibits a stopband functionality related to the resonance of the S-SRR excited by the contra-directional magnetic fluxes through the two connected resonator loops; the latter is useful for the implementation of compact bandpass filters. In both cases, a lumped-element equivalent circuit model is proposed with an unequivocal physical interpretation of the circuit elements. These circuits are then validated by comparing the circuit response with extracted parameters to full-wave electromagnetic simulations. The last part of the letter illustrates application of the S-SRR/gap-loaded CPW unit cell to the design of a bandpass filter. The resulting filter is very compact and exhibits competitive performance.