Gain Drop Research Articles

Upgrade of the NaI(Tl) crystal encapsulation for the NEON experiment

The Neutrino Elastic-scattering Observation with NaI(Tl) experiment (NEON) aims to detect coherent elastic neutrino-nucleus scattering (CEνNS) in a NaI(Tl) crystal using reactor anti-electron neutrinos at the Hanbit nuclear power plant complex. A total of 13.3 kg of NaI(Tl) crystals were initially installed in December 2020 at the tendon gallery, 23.7 ± 0.3 m away from the reactor core, which operates at a thermal power of 2.8 GW. Initial engineering operation was performed from May 2021 to March 2022 and observed unexpected photomultiplier-induced noise and a decreased light yield that were caused by leakage of liquid scintillator into the detector due to weakness of detector encapsulation. We upgraded the detector encapsulation design to prevent the leakage of the liquid scintillator. Meanwhile two small-sized detectors were replaced with larger ones resulting in a total mass of 16.7 kg. With this new design implementation, the detector system has been operating stably since April 2022 for over a year without detector gain drop. In this paper, we present an improved crystal encapsulation design and stability of the NEON experiment.

Spatial extension of the transient gain drop in a microchannel plate for a single-pulse irradiation

It is widely recognized that a microchannel plate gain drops temporarily after a particle initiates an electron avalanche and that a large amount of charge is extracted from the channel. Electron multiplication is expected to deplete the charges from the microchannel and produce depleted charges (wall charges), and this gain drop is known to persist until charges are replenished. In addition, it was reported that a gain drop occurs not only in the activated channels, where the electrons are multiplied, but also in the surrounding channels. A proposed mechanism for this phenomenon is suggested that the wall charges in the activated channels change the electric field in the surrounding channels, which affects the electron multiplications. In this study, the spatial extent of the gain drop of a chevron microchannel plate detector was evaluated by measuring gains as a function of distance from an activated channel. The experiment used two ultraviolet pulses with different beam sizes, which initially activated one channel and the six neighboring channels with carefully focused laser light, and then applied another light pulse to the surrounding 900 μm × 30 μm area. The gain of each channel was measured using a charge-coupled device camera, and the change in gain as a function of the output charge for the laser pulse was analyzed. A gain drop of 20% was observed at a channel located 110 μm far from the initial activated channel when the output charge was 4 pC. The obtained relationship between the radius of gain drop area and the output charge for the laser pulse was in good agreement with that predicted from the transverse electric field due to the wall charges by computational analysis.

A closely spaced two-port MIMO antenna with a radiation null for out-of-band suppressions for 5G Sub-6 GHz applications.

This paper presents the design and isolation enhancement of a filtering MIMO antenna with a radiation null for out-of-band suppressions suited for 5G sub-6 GHz communications. The MIMO antenna offers -10 dB impedance bandwidth functionality at the most prominent partial spectrum of the 5G NR n78 band for enabling wireless applications in base stations, ranging from 3.4 GHz to 3.61 GHz. To mitigate the redundancy of an RF filter and to achieve a strong filtering response, a radiation null is produced in the gain with four identical rectangular slots, which results in a significant gain drop of more than 8 dBi at the stopband. The geometrical design also allows 30 percent size reduction of single element. Subsequently, a closely spaced (0.11λ0) two-port MIMO antenna is implemented and with the utilization of the proposed rectangular shaped hollow stub parasitic element, the interelement isolation is significantly improved by more than 8 dB over the operational frequency range while retaining the filtering without any additional RF structure. The design simplification, peak gain of 5.4 dBi, near ideal response of diversity gain, ECC less than 0.03, congruency between simulated and measured results, and stable parameters make it a valuable choice for 3.5 GHz sub-6 GHz communications.

Sequentially rotated loop and spiral antenna arrays with a coplanar C‐figured feedline

AbstractUsing the moment method, two array antennas are investigated to reveal the effects of different radiation elements on the array characteristics. Each array comprises four elements sequentially rotated by 90° and excited by a coplanar C‐figured feedline above the ground plane. It is found that a loop element array has a 3 dB axial ratio bandwidth of 30%, 3.3 times as wide as that of an isolated loop without an array environment. In contrast, a spiral element array shows a 3 dB gain drop bandwidth of 62% (72% for the axial ratio bandwidth, wider than that of an isolated spiral by a factor of 3.0). Almost the same factors of 3.0 and 3.3 for the spiral and loop element arrays are then compared with those in similar studies. It is found that factors are classified into three groups by feedline types. The simulated results are verified by experimental work.

Automotive Lightweighting through novel Composite Materials

Abstract: The weight saving demand for motorcars has come more important, since the increase in the environmental issues. For boosting the energy frugality, maintaining safety and performance of ultramodern motorcars; featherlight compound accoutrements are essential. For acceleration of a lighter object, lower energy is needed as compare to acceleration of heavier one; so the featherlight compound accoutrements offer the great eventuality for adding vehicles effectiveness. Using lighter accoutrements in bus manufacturing improves vehicle project, acceleration, and continuity. Featherlight accoutrements are essential for boosting the energy frugality of ultramodern buses while maintaining their safety and performance. Because it takes lower energy to accelerate a lighter auto than a heavier one, featherlight accoutrements offer more implicit for both automakers and bus buyers. Composite accoutrements, similar as aluminium, magnesium and sword composites, have been proven to have better energy immersion than solid essence similar as sword alone, and therefore give further protection upon impact. Not only are featherlight vehicles energy effective, but they also enhance performance. drop in energy consumption gain by reduction in vehicle weight. By replacing sword & cast iron conventional factors with featherlight compound accoutrements similar as Mg & Al essence matrix compound, carbon & glass fiber corroborated polymer mixes can directly reduce the weight of the corridor of an automotive i.e. machine block and lattice and results in reduction of energy consumption by the vehicle. It can reduce the exhaust emigration and enhanced the energy frugality. By the use of light mixes in automotive can also carry fresh advanced emigration control system, safety bias, and integrated electronic system without increase in the overall weight of vehicles.

A Multipolarized Metal-Only Reflectarray Antenna

A multi-polarized metal-only reflectarray antenna (MPMORA) is proposed and investigated in this paper. The reflectarray is an all-metal planar structure and composed of unit-cells featuring perpendicularly placed size-variable slots carved in a metal sheet. Owing to negligible interactions between orthogonal slots of the unit-cell, a multi-polarized metal-only reflectarray with dual-linear and dual-circular operations can be realized by rotation of a linearly polarized feed with 0°, 45°, 90°, and 135°, respectively. For proof-of-concept, a prototype hosting 441 unit-cells and operating at X-band is manufactured and measured. The testing data reveals that the proposed design can achieve reasonable 1-dB gain drop bandwidths and peak aperture efficiencies for all polarizations, for instance, 15.3% and 45% in the case of right-hand circular polarization (RHCP). Moreover, the 3-dB axial ratio bandwidths for RHCP and left-hand circular polarization (LHCP) are also wide, which are 26% and 39%, respectively. These satisfactory behavior as well as the metal-only configuration make our design a competitive candidate for multi-polarization applications.

E-Plane-Focused Partial Maxwell Fish-Eye Lens Antenna for Multibeam Wide-Angle Scanning

This letter presents a multi-beam wide-angle scanning antenna based on the E-plane-focused partial Maxwell fish-eye (PMFE) lens operating in Ka-band. The gradient equivalent refractive index distribution of the lens is realized by the parallel plate waveguide (PPW) partially filled with dielectric material, which can support the E-plane focus. The lens is fed by a series of rectangular waveguides arranged along the straight cut line to realize the multiple beams. To improve the impedance matching, the dielectric wedges are loaded in the interface between the feeders and the lens. The E-plane broadening of waveguide feeding ports effectively alleviates the gain drop of wide-angle scanning. The measured results of the prototype show a beam scanning range more than ±90° with the aperture efficiencies between 57% and 85.7%. The good impedance matching is also obtained in the operating band. The proposed PMFE lens antenna has the application potential in the low-cost millimeter wave (MMW) multi-beam systems.

The Acoustic Response of Hydrogen/Ammonia Flames

Ammonia is a carbon-free fuel which could be used in gas turbines. Ammonia’s potential as a fuel can be improved when mixed with hydrogen. However, this could cause an increased propensity to thermoacoustic oscillations in the combustor. The acoustic response of hydrogen/ammonia flames was evaluated by calculating the flame transfer functions (FTFs). A local level set approach, combined with an incompressible velocity perturbation model, was used to calculate the flame front response to different frequencies of acoustic oscillations. The unsteady heat release rate was calculated from the flame front surface area, obtained by solving the G-equation, thereby calculating the gain and phase of the FTF. The unstretched flame speed, was obtained from experimental values and two chemical kinetic models: CRECK-NH3 and GRI-Mech3.0. The models’ accuracy was assessed by comparing the modelled to experimental values from literature. CRECK-NH3 was fitter for ammonia/hydrogen modelling, as it was always within 12% of experimental values, compared to GRI-Mech3.0 which always differed by over 35%. The FTFs suggested an increase in hydrogen enrichment led to an increase in the flame acoustic response, as the gain drop off occurred at a higher frequency with higher hydrogen content. The flame acts as a low-pass filter to acoustic waves and the bandwidth of this filter (the frequency at which the gain drops off) increases with hydrogen content. This was due to higher flame speeds with higher hydrogen content. These FTFs were also compared to those of hydrogen/methane flames and the non-linear response was briefly analysed.

Electromagnetically Controlled Beam-Steerable Reflectarray Antenna

A beam-steerable 2-bit reflectarray antenna with an electromagnetic control mechanism is presented in this communication. The phase reflection of the proposed 2-bit reflectarray unit elements is altered by moving two pins between a patch and the ground plane. In the suggested concept, the pins are moved with electromagnetism. To prove the concept, a prototype with manually turned screws is evaluated through measurements to verify the reflectarray performance. The prototype antenna is measured to have an impedance bandwidth of more than 5 GHz. The boresight realized gain is measured to be 20 dBi at 25 GHz and a gain bandwidth is more than 2 GHz. Measurements show that the prototype antenna is able to beam-steer in a 120-degree range with a gain drop of less than 3 dB.

Influence of pilot H[formula omitted] injection on methane-air swirled flame stabilization and acoustic response

Large Eddy Simulation is used to investigate the effect of localized pilot H2 injection on the Flame Transfer Function (FTF) of a premixed CH4-air swirled flame. The response of a perfectly premixed methane-air flame is compared to the one with an additional pilot hydrogen injection that supplies 10% of the original power. Numerical simulations are validated against experiments in terms of global FTF values at selected forcing frequencies, acoustic pressure and velocity signals, CH* flame images and flame root position dynamics. The unforced cases are first considered showing that, when H2 is injected in the center, the flame becomes slightly lifted with a localized diffusion front above the pilot injection. As in the experiments, LES retrieves that hydrogen pilot injection leads to a global redistribution of the heat release rate towards the flame root due to higher burning rates which translates to an overall FTF gain reduction over the entire frequency range explored. Then, the flame acoustic response for the two injection strategies is scrutinized at two distinct forcing frequencies: 240 Hz where the FTF gain difference is maximum, and 590 Hz where the FTF phase shift is maximum. LES reveals that, despite H2 pilot injection does not modify the dynamics of the large vortical structures shed in the external shear layer of the swiling jet which are synchronized by the acoustic forcing, the redistribution of the heat release rate towards the flame base weakens their interaction with the flame tip, explaining partly the FTF gain reduction at the two selected frequencies. In addition to that, a marked axial movement of the internal recirculation zone is observed at 240 Hz during the forcing cycle. For the pilot injection, it leads to an oscillation of the lifted flame root while, for the CH4-air case, the flame anchoring point is not affected. This additional oscillation leads for the pilot case to heat release rate fluctuations acting in phase opposition with respect to those observed at the flame tip, generating a further drop of the FTF gain at this specific frequency. The increased burning rate at the flame root and the flame length reduction of the pilot hydrogen flame also affect the characteristic time lag of the flame response. For both frequencies f = 240 Hz and 590 Hz, the phase shift between the two injection strategies is proportional to the flame length reduction caused by hydrogen injection. These simulations confirm that pilot hydrogen injection is an efficient way to reduce the acoustic response of swirled flames over a large frequency bandwidth.

A High-Efficiency SISL-Based Slot Antenna Array for Wireless Power Transmission Application

A high-efficiency slot antenna array based on substrate integrated suspended line (SISL) technology operating at 24 GHz is presented for wireless power transmission (WPT) application. Because of the feature of self-shielding and low loss of SISL technology, double-side SISL (DSISL) is used to further reduce substrate and conductor loss in antenna design. Besides, four radiating slots are etched on the top ground layer of DSISL and serially fed as a subarray without any extra feeding network. By utilizing DSISL and avoiding network loss, a high efficiency subarray is realized with simulated efficiency of up to 89% at 24 GHz. In addition, the subarray is fabricated and measured. The measured results of subarray show that the 10 dB impedance bandwidth is from 23.75 to 24.1 GHz, which covers the WPT band (24 GHz ± 100 MHz). The measured gain of 13.1 dBi and radiation efficiency of 83.5% is achieved at 24 GHz. Besides, the width of air cavities can be further reduced to 0.384λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free space wavelength at 24 GHz), benefiting from the basic mode tangential electromagnetic (TEM) mode of DSISL, which is good for wide scanning phased array design. Based on the subarray, a 1×8 phased array is designed and fabricated. The measured results show that |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | of −32 dB, isolation of 19 dB, and gain of 19.5 dBi is obtained at 24 GHz, while a wide scanning range of ±50°with gain drop less than 3.3 dB is achieved also at 24 GHz.

An All-Metal, Simple-Structured Reflectarray Antenna With 2-D Beam-Steerable Capability

An all-metal reflectarray (RA) element based on the variable-rotation technique is presented in this letter. The RA element, based on an elliptical inner conductor and a circular outer conductor, exhibits continuous 360° phase coverage with negligible element loss over a wide range of incident angles and frequencies. A 10 GHz prototype with 121 manually rotated elements was simulated, fabricated, and tested. The proposed RA antenna has two-dimensional beam-steerable capability up to 45° elevation angle. The measured results agree well with the simulated counterparts. For demonstration, four different steering cases are presented as examples by manually adjusting the rotation angle of the RA elements. The maximum measured antenna gain is 26.2 dBi, corresponding to an aperture efficiency of 66%. A 1.3 dB gain drop was measured during beam scanning from 0° to 40°.

Wide‐beam bent cross‐shaped DRA antenna for wide‐angle beam‐scanning phased array

AbstractIn the paper, a bent cross‐shaped dielectric resonator antenna element with wide half‐power beamwidth of 224.9° is proposed and applied for designing a 1 × 8 wide‐angle beam‐scanning linear phased array. To obtain small gain drop and reduce the mutual coupling of the scanning array, the dielectric wall loaded rectangular truncated slots are inserted. For validation, a prototype operating at 5.8 GHz is designed. Measurement results indicate that the main beam of the designed phased array can scan from −70° to +70° GHz with a gain drop of less than 1.75 dB and a sidelobe level of less than −5.08 dB.

X-Band Active Phased Array Antenna Using Dual-Port Waveguide for High-Power Microwave Applications

An X-band active phased array horn antenna with high power capacity and high peak power is proposed in this paper. At the horn aperture, the baffles are loaded to suppress higher-order modes and eliminate blind spots during beam scanning. Straight walls are added to improve impedance matching. Considering that the peak power that T/R modules can provide is very limited, the proposal of a dual-port waveguide breaks through the bottleneck of the power capacity of a single-port input for the first time. The proposed curved dual-port waveguide is used to connect the horn antenna and the T/R module, which is verified to improve the power capacity of the overall internal structure. Simulated and measured results show that VSWR ≤ 2 in the frequency range of 7.5–8.5 GHz. There is no grating lobe in the ±10° scanning range and the maximum gain drop does not exceed 0.4 dB. The power capacity of the proposed HPM array is 56.34 MW. The phased array antenna has the characteristics of flexible scanning, small size, and high gain, and can be applied in high-power microwave systems.

High Gain Monopulse Variable Inclination Continuous Transverse Stub Antenna for Satellite-Aided Vehicular Communications

This article presents a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band high gain monopulse variable inclination continuous transverse stub (VICTS) antenna for satellite-aided vehicular communications. The radiating part is divided into four regions and fed by an air-filled single-layer E-plane waveguide comparator cascaded with two groups of mirror-symmetric multiple-port excited linear source generators (LSGs). Two waveguide delay lines are carefully designed to compensate the phase difference between the adjacent radiating regions in the desired frequency band. Combined with the nonuniform slow-wave structure underneath the radiating slots, excitation signal with uniform phase distribution can be obtained, and then, the sum and difference patterns can be produced by using the comparator. For verification, a prototype operating at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band is designed and demonstrated. The experimental results show that the reflection coefficients for the sum and difference patterns are all lower than −10 dB within the frequency range of 19–21 GHz. The gain drop of the sum pattern is less than 5.7 dB within the beam scanning range of −1° to −62° at 21 GHz, while the amplitude imbalance and null depth of difference patterns are less than 4.5 and −20.6 dB, respectively. The proposed antenna can be a potential candidate for the future Internet of Vehicles.

Design of a Low temperature cofired ceramic wideband WideScan antenna array for millimetre‐wave applications

The design, fabrication, and measurement of a 7 × 7 mm-wave array antenna have been presented for 5G communications. The substrate integrated waveguide (SIW)-fed antenna element is formed of four parts: a rectangular radiating patch, a coupling slot cut onto the broadwall of the SIW, a transition layer, and a feeding layer at the bottom. The bandwidth and radiation efficiency has been improved by embedding an air cavity below the radiating patch, as the effective dielectric constant of the substrate is reduced. Moreover, a prototype has been fabricated and measured to verify the design principles. The finite array operating over 23–28 GHz has achieved active voltage standing wave ratios of less than 2 and 2.5 in the E- and H-planes while scanning up to 45° respectively. Compared with the theoretical ideal gain, the average gain drop of the measured embedded element gain is 0.73dB.

1-Bit Wide-Angle Folded Reflectarray Antenna at Ka-Band

This letter presents a folded reflectarray (FRA) capable of electrical beam steering in the Ka-band. The FRA consists of a low-profile feeding source, a dual-layer wire grid, and 36×36 polarization twisting reflective elements. An element of center shorted patch with two plated through holes is proposed where only two switches are required for polarization twisting and 1-bit encoding. A cavity is then introduced surrounding the element to improve the beam-steering performance. To verify the proposed element, two prototypes with 0° and 60° beam directions are designed and experimented where the metal stub and open circuit are used to model “ <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on/off</small> ” states of PIN diodes for simplification. The measured peak gain of 0°FRA is 27.5 dBi with 2 dB gain bandwidth of 28–32 GHz (13.3%). A measured gain drop of 3.25 dB is achieved by the 60°FRA, which verifies the wide-angle beam-steering ability. The measured reflection coefficient of the feeding source is less than −15 dB over the operating band. The proposed FRA has a good potential to realize beam-steering with real PIN diodes for the satellite communications.

Transport phenomena modeling of novel renewable natural gas reactors in various configurations

This paper presents a comparative assessment of several novel synthetic natural gas fixed-bed reactor designs and configurations. The four reactor concepts presented in the paper use the Sabatier reaction between carbon dioxide and hydrogen to produce methane. Due to the exothermic nature of the reaction and its pressure sensitivity, this study emphasizes the ability and potential of the reactor configurations to provide effective cooling, and minimize heat gain and pressure drops, so that the maximum methane yield and carbon dioxide conversion can be achieved. Out of four reactor designs, Concept 1 follows a conventional cylindrical fixed-bed reactor design; however, the bed is separated horizontally to promote inter-cooling. Concept 2 separates the bed into 2 segments vertically to facilitate cooling along the length of the reactor. Concept 3 follows a horizontal configuration in which the catalyst beds are separated into rectangular prisms. The different configurations of Concepts 1 to 3 were designed by varying the reactor dimensions and the number of catalyst beds. Most notably, Concept 4 using a unique helical design provides more effective cooling to the catalyst bed by increasing the surface area and decreasing the diameter of the reactor channel. However, the volumetric flow of this specific reactor model is significantly reduced. Furthermore, the inlet conditions of 200 °C and 30 bar help achieve a CH4 yield of approximately 85 % when considering Concept 1.

Joint clinical and socio-demographic determinants of CD4 cell count and body weight in HIV/TB co-infected adult patients on HAART

BackgroundTuberculosis is one of the most lethal communicable diseases in the world. In tuberculosis patients, HIV speeds up the course of the infection from latent to active illness. This study aimed to identify joint clinical and socio demographic determinant factors of CD4+ cell count and body weight in HIV/TB co-infected adult patients. MethodsFrom January 2013 to December 2019, 374 HIV/TB co-infected individuals were treated and had follow-ups. This study used descriptive data analysis, a linear mixed effects model for longitudinal data, and joint modeling of the two longitudinal outcome variables. ResultsIn this study, 51.1% of the 374 HIV-TB co-infected patients were women, 47.1% were rural dwellers, and 71.9% developed extra pulmonary TB. Females made up 54.3% of all patients who died. To detect the presence of correlation among repeated measured data, the AR (1) structure was chosen. The joint model was more appropriate for analysing and interpreting current data. ConclusionsBaseline age, follow-up time, baseline weight, place of residence, adherence level, educational background, functional status, WHO clinical stage, smoking status and type of TB developed were identified as significant joint factors in CD4 cell count and weight of HIV/TB co-infected patients from potential joint predictor variables. Therefore, the concerned bodies, specifically the FMOH and regional health staffs, should enhance public awareness about the factors that lead to a drop in CD4 count and weight gain, as well as an increased risk of death from HIV/TB co-infection. Furthermore, special attention should be paid to women and patients with poor adherence. Medication and treatment must be affordable and accessible to all co-infected patients in order to maximize their CD4 count and proportional body weight to their height, and to lengthen the lives of individuals who are co-infected.

Dual-Band Combined-Aperture Variable Inclination Continuous Transverse Stub Antenna With Consistent Beam Direction

This article presents a Tx/Rx dual-band combined-aperture variable inclination continuous transverse stub (VICTS) antenna for low-earth-orbit (LEO) satellite-on-the-move (SOTM) applications. The beam directions for the Tx and Rx bands are kept consistent during beam scanning, so that the antenna allows a duplex link. The topology of the combined-aperture VICTS antenna is derived from the requirement for consistent beam directions. Nonuniform slow wave structures (SWSs) are used to achieve the required phase difference and phase-changing rate (PCR) between the radiation slots in the two bands, while maximizing the antenna efficiency. Predeflection technique is applied to the radiation slots to reduce the gain drop at a wide beam scanning angle. A prototype operating at K- and Ka-bands is designed, fabricated, and measured. Experimental results show that the antenna has a consistent beam direction during scanning in the frequency ranges of 19–21 GHz (Rx band) and 29–31 GHz (Tx band). The maximum beam directions in Tx and Rx bands exceeds ±47° at a relative rotation angle of 40°, and the gain drop during the beam scanning is reduced within 2.3 and 3.5 dB.