esa-sceva/satcom-chunk-collection huggingface dataset:
# Simulation and Design of Three 5G Antennas
## 5 Design of an Eight-Element MIMO Array Antenna for Mobile Terminals with a Metal Frame
### Optimization of the Parameters for the Eight-Element MIMO Array Antenna
#### 5.2.1 Adding T-Type Decoupling Structures  
The coupling between antenna elements is primarily due to the interaction of currents between them. Typically, decoupling structures are added to antennas to suppress the transmission of coupled currents and improve antenna performance. To enhance the isolation between the \"ring-slot\" structures, this design improves isolation by etching a quarter-wavelength T-shaped structure in the gap between two \"ring-slot\" structures along the longer edge of the ground plane. To further investigate the decoupling mechanism of the T-type decoupling structure, simulations were conducted on the antenna currents.  
Figure 42a shows the current distribution diagram of the array antenna before adding the T-type decoupling structure, and Figure 42b shows the current distribution diagram after the T-type decoupling structure is added.  
From Figure 42, it can be observed that adding the T-type decoupling structure between the \"ring-slot\" structures along the longer edge effectively suppresses the transmission of coupled currents between the \"ring-slot\" structures and the ground plane, achieving a significant decoupling effect.  
Figure 41: The schematic diagram of the eight-element MIMO array antenna structure. (**a**) Front view, (**b**) back view and (**c**) side view.
## 4 Qualitative Discussion
### Other Properties of New LBAs  
#### 4.2.1 Influence on Setting Time and Air Entrainment  
Some of the recently developed LBAs were classified as set retarders [19; 78; 79]. [PERSON] et al. [19] evaluated a carboxymethylated Soda lignin as a cement set retarder admixture for oilwell application. As a result, the dosages of 4.7, 8.7, and 13.4 L/m\({}^{3}\) (liter per cubic meter) of the carboxymethyl lignin provided increases of 17, 66, and 104% in the setting time of the cement pastes, respectively. [PERSON] et al. [79] evaluated the retarding performance of diethanolamine-modified lignin. When added at a dosage of 0.05 wt.%, this admixture increased by approximately 50 and 70% the initial and final setting times of cement paste, respectively. The authors attributed this behavior to steric hindrance of molecular structure and electrostatic interactions of anchoring groups adsorbed on the cement particles during the hydration process, such as hydroxyl and amino groups [79].  
In another study, [PERSON] et al. [78] developed a set retarder modifying a sodium lignocellulosicate by a copolymerization process involving 2-acrylamide-2-methyl propane sulfonic acid and itaconic acid. The adsorption of the modified-lignosulfonate on the solid phases of the mixture contributed to the retarding effect enhancing the workability of modified phosphoaluminate cement pastes with a water/cement ratio of 0.5. In the study conducted by [PERSON] et al. [27], the black liquor investigated as a plasticizer was also classified as a set retarder. The incorporation of 30% of LBA in replacement of the water volume increased the initial and final setting times of the cement paste by 223% and 258%, respectively. The authors attributed the retarding performance of the black liquor to the high content of sugars in its composition [27].  
The air-entraining capacity of LBAs was also investigated. [PERSON] et al. [20] reported that amination-modified alkaline pulping black liquor act as an air-entraining admixture in ready-mixed wet mortars. According to the authors, the amino groups introduced into the lignin structure can form strong hydrogen bonds with water, which increases foam wall strength and provides stability and uniformity to the matrix [20]. Air entrainment propertieswere also observed in LBAs classified as plasticizers or superplasticizers. [PERSON] et al. [70] found that incorporating 0.4 wt.% of oxidized lignin led to matrices with an air content of up to 15%, while unmodified lignin matrices presented an air content of approximately 7%. Additionally, air-entraining properties were verified in sulfomethylated lignins [31], poly(ethylene oxide)-modified lignins [59], and unmodified lignins [86].
# Numerical Study on the Phase Sensitivity Variation in Low Frequency Primary Microphone Calibrations
## 5 Conclusions  
The low frequency phase characteristics of microphones are crucial for large-scale natural and artificial activity measurements, but their primary calibrations have been grossly overlooked. By means of the FEA technique, this paper studies the laser pistonphone-based primary calibration of microphones and finds that the generated sound pressures in both the pistonphone and microphone show an interesting phase lead (relative to the displacement excitation) at low frequencies due to the dominating pressure leakage loss. The diaphragm deformation of the microphone is then affected, and its sensitivity varies at low frequencies. Depending on whether its vent is inserted in the calibrating sound field or in the outside atmosphere, there are two very different phase sensitivity responses of the microphone. A phase lead limit of 90\({}^{\circ}\) will happen in vent in field calibrations, but the phase lead is almost unaffected in vent out field calibrations. Therefore, depending on whether the low-frequency sound in air or in duct is to be measured, the corresponding sensitivities of the microphone should be selected as the correction standard.  
Different from the in situ calibration and calibrator methods, which give only the phase consistencies of the microphones, the primary calibration-determined phase sensitivity of the microphone shows its intrinsic characteristics, and will not be affected by the installation change of the monitoring system. Therefore, it is recommended to obtain the primary phase sensitivity of the microphone before serving.  
Conceptualization, F.Z.; data curation, F.Z., D.L. and A.L.; methodology, F.Z. and D.L.; software, A.L.; validation, F.Z. and D.L.; writing--original draft, A.L.; writing--review and editing, F.Z., D.L., X.G. and L.L. All authors discussed the results and contributed to the final manuscript. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China, grant number (No. 51705298).  
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
## 1 Introduction
Over the years, researchers have conducted some studies concerning bearings of different geometries, aiming at the inclusion of additional effects, such as analysis of special lubricants, thermal and/or elastohydrodynamic analyzes and misalignment effects, among many others. Some of this research can be referred to in [19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29]. In this context, it is possible to observe that many of the previous research takes into account cylindrical journal bearings to study the behavior of nonlinear vibrations. Additionally, the works that aim to study multi-lobed bearings are concerned in introducing new effects, neglecting their inherent nonlinear behavior. Therefore, this paper expands the studies carried out in [17] on elliptical and trilobed bearings, with its main contribution is to analyze the nonlinear conditions introduced by these kinds of bearings, in the time and frequency domain, in a rotating system subject to severe loading conditions. For this a comparison between the linear and nonlinear approaches is performed. In addition, the vast majority of studies relating to nonlinearities in hydrodynamic bearings are concerned with the phenomenon of fluid induced instability. However, the idea here is to analyze the presence of these nonlinearities in operating conditions of the rotating system below the instability threshold, which are the most common cases found in industrial machines. The lubricant film is analyzed according to its dynamic characteristics, i.e., evaluating the pressure distribution and, consequently, the resulting hydrodynamic forces. The solution of the Reynolds equation through the finite volume method generates the pressure field inside the oil film, this method being widely used in the numerical simulation of problems for fluid dynamics and heat transfer. Regarding the severe operating conditions, high load cases are evaluated at low and high rotating speeds, representing situations where the shaft is closer to the bearing surface (low speeds) and situations above the first critical frequency (high speeds). Two different geometries, which are elliptical and three-lobe bearings, are analyzed. In addition, for each geometry, different levels of pre-load are tested. The analyses are made through evaluation of the temporal response for each system (shaft orbits) and of the spectrum response in the frequency domain (_fullspectrum_), as stated in [27]. Therefore, the results presented in this paper meet the needs of industry professionals, especially those who are knowledgeable and engaged in the mechanisms of how vibrations arise from rotor-bearing systems as well as in the reduction of these vibrations. Furthermore, the correct understanding of the vibration behavior is mandatory for fault identification in health monitoring of the rotating machinery.
###### Abstract  
To address the support problem of large-diameter drilling shafts in the west area of Zhangji coal mine, a thinner shaft lining structure composed of double layers of steel plate and high-performance concrete is proposed herein. Firstly, a series of tests of high-performance concrete preparation were carried out, and the optimized mix ratio of pumping concrete with 60-70 MPa strength for shaft lining of the drilled shaft was obtained. Then, shaft lining models were designed according to the similarity theory, and the mechanical properties of the shaft lining were experimentally studied by loading test. The test results showed that the stress state of concrete in the shaft was obviously improved, and the compressive strength of concrete was increased by 1.97-2.52 times. Finally, the results of the study were applied to a shaft in the control strata of the inlet shaft in the west area of Zhangji coal mine, which made it possible to use the drilling method to construct the shaft. The following field measurement showed that the annular strain of the shaft lining concrete was \(-487\)\(\mu\epsilon\), which is far less than the ultimate strain value of C65 concrete, and the shaft lining structure was kept safe and reliable.  
high-performance concrete; dual-steel-plate-confined; composite shaft lining structure; test study; engineering application
## 3 The Proposed Pattern Recognition Method
### Feature Ranking and Selection Based on Improved Laplacian Score Algorithm
The specific sample information is provided in Table 1.  
The weighting factors \(\alpha\) are set as 0.5, 1, and 0, and the corresponding feature selection methods are LFS, LS, and FS, which are used to rank the features of the two databases. The FCM clustering algorithm is used as the classifier and the classification results with different numbers of features are shown in Figure 2. In Figure 2, it can be clearly seen that the classification accuracies are significantly influenced by the feature ranking techniques. Compared with FS and LS, the LFS method has a superior ranking ability for the highest number of selected features, which may have a better purpose in terms of shear cutting status recognition. The reason for this is that LFS can comprehensively consider the power of locality preserving and global distinguishing capability, in order to evaluate the importance of a feature. Hence, the LFS method is utilized to rank the 28 features of vibration signals, and select an important feature vector for training the FCM clustering model. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Database** & \begin{tabular}{c} **Number of** \\ **Training Samples** \\ \end{tabular} & \begin{tabular}{c} **Number of** \\ **Testing Samples** \\ \end{tabular} & \
\begin{tabular}{c} **Number of** \\ **Categories** \\ \end{tabular} &
\begin{tabular}{c} **Number of** \\ **Features** \\ \end{tabular} \\ \hline Glass & 150 & 50 & 6 & 9 \\ WFRN & 500 & 100 & 4 & 24 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Statistical information of the two data sets. Figure 2: The classification results of different feature selection methods using the UCI database: (**a**) Glass; (**b**) WFRN.
## 2 Materials and Methods
### Pyrene Content of Py-PDMS Samples  
BPAA was employed to determine the pyrene content of the Py-PDMS samples. A solution of Py-PDMS was prepared with a known mass concentration (\(m\) in g\(\cdot\)L\({}^{-1}\)) in DMF, a solvent which was found to reduce H-bonding between the 1-pyreneacetamide labels of the Py-PDMS samples; see Figure 6D in Results and Discussion. The absorbance of the Py-PDMS solution in DMF at 344 nm (_Abs_(Py)), corresponding to the absorbance of the pyrene labels, was determined using a quartz cuvette with a 1 cm path length. The pyrene content (\(\lambda_{\mathrm{Py}}\) in mol\(\cdot\)g\({}^{-1}\)) was determined from the ratio \(Abs(\mathrm{Py})/[\epsilon_{\mathrm{Py}}\times m]\) where \(\epsilon_{\mathrm{Py}}\) is the molar extinction coefficient of BPAA. In turn, \(\lambda_{\mathrm{Py}}\) could be expressed according to Equation (1), which accounted for all pyrene species expected to be present in the Py-PDMS solution.  
\[\lambda_{Py}=\frac{[\mathrm{Py}-\mathrm{PDMS}]+[\mathrm{Py}-\mathrm{ODMS}]+[\mathrm{PA}]}{([\mathrm{Py}-\mathrm{PDMS}]+[\mathrm{Py}-\mathrm{ODMS}])M_{\mathrm{SiNY}}+[\mathrm{SiN}]M_{ \mathrm{SiN}}+[\mathrm{Me_{2}Si}]M_{\mathrm{Si}}+[\mathrm{PAA}]M_{\mathrm{ PAA}}} \tag{1}\]  
In Equation (1), ([Py-PDMS] + [Py-ODMS]), [SiN], [Me2 Si], and [PAA] are the molar concentrations of the (3-aminopropyl)methyl siloxane capped with 1-pyreneacetic acid of molar mass \(M_{\mathrm{SiNY}}\) (359.48 g\(\cdot\)mol\({}^{-1}\)), the acetyl capped (3-aminopropyl)methyl siloxane of molar mass \(M_{\mathrm{SiN}}\) (159.26 g\(\cdot\)mol\({}^{-1}\)), the dimethylsiloxane monomers of molar mass \(M_{\mathrm{Si}}\) (74.15 g\(\cdot\)mol\({}^{-1}\)), and 1-pyreneacetic acid of molar mass \(M_{\mathrm{PAA}}\) (260 g\(\cdot\)mol\({}^{-1}\)), respectively. Taking advantage of the fact that the PDMS sample contained 20.3 mol % of (3-aminopropyl)methylsiloxane units (as determined by titration of the amine groups with aqueous HCl [15]), and assuming that the pyrene contents of Py-PDMS and Py-ODMS are the sam, and that the GPC analysis yielded the molar fraction of PAA  
Figure 2: GPC absorbance traces for (**A**) Py(0.7)-PDMS; (**B**) Py(3.4)-PDMS; (**C**) Py(3.5)-PDMS; and (**D**) Py(5.2)-PDMS. The dashed line in Figure 2A represents the GPC trace for PAA while the dashed line in Figure 2C represents the GPC trace of the Py(3.5)-PDMS(f) sample after fractionation of Py(3.5)-PDMS through the GPC column.  
present in each Py-PDMS sample, the molar fraction \(x\) of structural units that were labeled with PAA could be determined precisely. A complete derivation for the determination of \(x\) can be found in the Supplementary Materials. Accordingly, the pyrene contents of the four Py-PDMS samples were 0.7, 3.4, 3.5, and 5.2 mol %.
# Trajectory Planning of Shape-Following Laser Cleaning Robot for the Aircraft Radar Radome Coating
## 2 Materials and Methods
### Measurement and Preprocessing of Point Cloud Data for Radar Dome Surfaces
#### 2.1.1 Measurement of Raw Point Cloud Data  
With the rapid development of 3D data acquisition technology, the utilization of 3D sensors for detecting the 3D profiles of objects has gained extensive application. In comparison to coordinate measuring machines (CMM) and articulated arm measuring machines, the advantages of 3D sensors are their non-contact measurement capability and wider detection range. In this study, measurements were performed using a 3D scanning sensor. Figure 3 presents a three-dimensional point cloud of an aircraft radome surface. The rotational symmetric radome was positioned with a base, as its vertical direction was aligned with the radome's vertical axis.
## 2 Antenna Configuration and Design Strategy  
### Antenna Design  
Figure 2 illustrates the design configuration of the proposed reconfigurable antenna. The antenna comprises a co-planar waveguide (CPW)-fed truncated-shaped radiator, which is further connected to an inverted L-shaped stub by means of an HPND-4005 diode D\({}_{1}\). Another meandered line stub is also connected to the top-right edge of the radiator by using a PIN diode D\({}_{2}\). A 100-pF surface-mounted (SMD) capacitor is placed at the node connecting both stubs to electrically separate them, so that each stub can work independently depending upon the switching state of the diode. The antenna offers a compact size of 15 \(\times\) 20 mm\({}^{2}\), whilst being easily accessible, and the cheap printed circuit-board material FR4, with a relative permittivity of 4.4 and thickness of 1.6 mm, is utilized  
Figure 1: Targeted applications of proposed reconfigurable antenna.  
as the substrate. The optimized dimensions of the proposed antenna and their respective values are as follow: a = 5; b = 6; c = 2; d = 2; e = 1.5; f = 0.5; g = 2.5; h = 0.5; i = 6; j = 6.4; k = 15; l = 20; m = 1.6, and r = 5.5 (unit is mm).
## 3 SRPC Mathematical Analysis  
### Circulating Current Analysis  
The MMC circulating currents are produced due to the inner DC-voltage differences between MMC SMs, then, Figure 4 shows the equivalent circuit of one of the MMC phases. As shown, the compensation current of phase \(x\), which should be injected by the SRPC, \(i_{rx}\), consists of two main components: the upper arm current, \(i_{rxu}\), and the lower arm current, \(i_{rxl}\). As presented in Equation (11), the upper arm current, \(i_{rxu}\), includes two main components: the circulating current component, \(i_{cirx}\), and the current related to the compensation current, \(i_{rx}\)/2. The circulating current flows through the whole MMC phase leg, circulates between the two dc-buses or/and among the MMC legs.  
\[i_{rxu}=\ i_{cirx}-\frac{i_{rx}}{2} \tag{11}\]  
As presented in Equation (12), the lower arm current, \(i_{rxl}\), also includes two main components: the circulating current component, \(i_{cirx}\), and the current related to the compensation current, \(i_{rx}\)/2.  
\[i_{rxl}=\ i_{cirx}+\frac{i_{rx}}{2} \tag{12}\]  
From Equations (11) and (12), the circulating current that flows through the MMC legs can be expressed as in (13), which is composed by two main parts: the double fundamental frequency component of 100 Hz and its even order harmonic contents and a direct current (DC) component results from the DC-link currents [13].  
\[i_{cirx}=\frac{i_{rxu}+i_{rxl}}{2} \tag{13}\]  
Figure 4: Equivalent circuit of one MMC leg of the SRPC system.  
By applying the [PERSON]'s voltage law on the equivalent circuit of Figure 4, it is possible to obtain the voltage equation of the upper and the lower loops as in Equation (14).  
\[\begin{array}{l}u_{x}=\ -L_{xu}\frac{d\dot{i}_{xuu}}{dt}-u_{xu}-i_{xu}\ R_{xu}\\ u_{x}=\ L_{xl}\ \frac{d\dot{i}_{xl}}{dt}+u_{xl}+i_{xxl}\ R_{xl}\end{array} \tag{14}\]
## 3 Signal Spatial Reconstruction Method for Relay Cooperative Networks  
Multi-satellite cooperative transmission is the key for remote sensing systems to realize global real-time observation and low-time delay remote sensing information transmission. In order to reduce the inter-beam interference and improve the system throughput, source satellite multiple modal transmission and the channel of relay transmission must be considered as a multidirectional relay channel for multibeam joint design. This can optimize transmission scheduling and intelligent information distribution. According to the channel characteristics, a co-channel transmission scheme for multiple unicast packets and multicast services is designed. This can save limited time-frequency resources and improve system transmission efficiency. By optimizing the signal space structure, orthogonal signal alignment directions are constructed. According to the difference in transmission channel quality, signal alignment order is determined to reduce the impact of transmission quality bottleneck in the system performance. In order to further improve the transmission efficiency of the system and increase the channel capacity, a constellation point remapping scheme is proposed for the fuzzy mapping problem of high order modulation in the physical layer network coding of relay node. The implementation framework of the method is shown in Figure 2.
# Evaluation of Antioxidant and Anticorrosive Activities of _Ceriops_ _tagal_ Plant Extract
## 3 Results and Discussion
### Antioxidant Studies
#### 3.2.3 Hydrogen Peroxide Free Radical Scavenging  
The reduction of hydrogen peroxide was as per the concentration of the extract, as shown in Figure 3c. The highest scavenging was observed at 1000 \(\mathrm{\SIUnitSymbolMicro g}\)/mL with 87% and the lowest was observed at 100 \(\mathrm{\SIUnitSymbolMicro g}\)/mL with 33%. Overall, a gradual increase in radical scavenging was observed from least to highest concentration, similar to the DPPH and nitric oxide assays. The antioxidant (for instance phenols and flavonoids) present in the extract actively reduces the reactive oxygen species (hydrogen peroxide) into water by donating electrons in a dose dependent manner [27]. The present results also show the same pattern as several previous studies that reported on _Heli chrysum longifolium_ [PERSON], _Newbouldia laevis_, and _Zizyphus jujuba_ [PERSON] [27; 42; 44].
## Materials and Methods
### Experimental Characterization
#### 2.2.1 Porosity  
Porosity \(\phi\) was experimentally measured using the air volume compression method [26] for a single apparent density \(\rho_{a}\), inserting the fibers of measured weight into a cylindrical specimen and measuring their thickness and therefore, the apparent volume.  
The method (Figure 4) involves the compression at constant temperature of the air inside a container in which the porous sample to be measured is positioned and is based on [PERSON]'s law for ideal gases. Since \(pV=\text{const.}\), by measuring the absolute pressure \(p_{0}\) before compression and the absolute pressure \(p_{1}\) at the end of the compression, when the compression volume \(\Delta V\) is known it is possible to calculate the volume of air present in the container as:  
\[V_{0}=\frac{\Delta Vp_{1}}{(p_{1}-p_{0})} \tag{7}\]The volume \(V_{0}\) thus calculated is equal to the difference between the known volume of the container \(V_{c}\) and the volume occupied by the fibers \(V_{m}\). Once \(V_{m}\) has been calculated, it is possible to calculate the density of the material constituting the fibers by dividing the total weight of the fibers \(M_{m}\) by the previously calculated volume \(V_{m}\):  
\[\rho_{m}=\frac{M_{m}}{V_{c}-\frac{\Delta Vp_{1}}{(p_{1}-p_{0})}} \tag{8}\]  
A fiber density of 1518 kg/m\({}^{3}\) was obtained from the pressure detected inside the device at the end of a compression of known air volume with (7) and (8).  
When the density of the fibers is known, it is possible to calculate the porosity for each bulk density using the following equation:  
\[\phi=1-\frac{\varrho_{a}}{1518} \tag{9}\]  
Figure 4: Schematic diagrams of the porosity measurement system based on the air volume compression method: (**a**) before the compression, (**b**) after the compression of know volume \(\Delta V\)[26].  
Figure 3: Schematic diagram of the procedure for the characterization of Posidonia fibers and acoustic modelling.  
The porosity values in the density range of the experimental measurements are shown in Figure 5.