esa-sceva/satcom-chunk-collection huggingface dataset:
## 5 Conclusions  
A transient CFD simulation study was conducted on the communication port of a liquid launch vehicle gas-filled accumulator to investigate the impact of supply pipeline flow velocity, oscillatory flow velocity amplitude, and frequency on its impedance. The main conclusions are summarized as follows:  
(1) The linear resistance calculation results based on the quasi-steady assumption improve when the oscillation amplitude approaches zero and are further verified. The quasi-steady assumption is suitable for calculating the linear resistance of the communication  
Figure 13: Accumulator linear inertance under different conditions. (**a**) Frequency impact on linear inerance, (**b**) Fitting of frequency correction function.  
port when the oscillation frequency is less than 14.5 Hz. In this research, the deviation between calculation and simulation results is less than 3.2% at an oscillatory flow frequency of 1 Hz and less than 27% at 10 Hz. It also indicates that the linear resistance value at zero oscillatory flow amplitude can be used for the communication port design, as the deviation is less than 4% for small oscillations.  
(2) A linear frequency correction method on the impedance of the communication port is proposed, along with the formulae for calculating the communication port impedance, which can be used for the engineering design of gas-filled accumulators. After frequency modifications, the linear resistance of the communication port can be calculated up to 50 Hz, which is sufficient for covering the pogo frequency range. In this study, the deviation between calculation results and simulation results can be reduced to less than 26.5% within 5-50 Hz.  
(3) The formation of vortices downstream of the communication port is the main reason for its impedance reduction. Destroying or deferring the formation of this vortex may prevent high-frequency failure of the communication port and makes its resistance more stable within expected oscillatory flow velocity amplitude and frequency.  
Conceptualization, T.S., G.L., and Y.H.; methodology, T.S.; investigation, T.S.; writing--original draft preparation, T.S.; writing--review and editing, G.L. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The raw data supporting the conclusions of this article will be made available by the authors on request.  
This study was co-supported by the Beijing Institute of Astronautical Systems Engineering.  
The authors declare no conflicts of interest.
## 3 Principles of Infrared Spectroscopic Analysis Techniques
### Imaging and Mapping Spectroscopy
#### 3.3.3 Hyper Spectral Cube  
The huge amount of data assembled in especially imaging spectroscopy is collected in a hyper spectral cube. In this cube the sample is compartmented into small surface or volume areas (referred to as pixels), each of them representing a full spectrum. These cubes are mostly displayed as a three-dimensional (3D) matrix or data cube spanning two spatial dimensions x and y. The third dimension z corresponds to the individual wavelength/wavenumber (Figure 4).  
Figure 4: Schematic illustration of the hyperspectral cube principle.
###### Abstract  
In this study, the Ag\({}_{3}\)PO\({}_{4}\)/SnO\({}_{2}\) heterojunction on carbon cloth (Ag\({}_{3}\)PO\({}_{4}\)/SnO\({}_{2}\)/CC) was successfully fabricated via a facile two-step process. The results showed that the Ag\({}_{3}\)PO\({}_{4}\)/SnO\({}_{2}\)/CC heterojunction exhibited a remarkable photocatalytic performance for the degradation of Rhodamine B (RhB) and methylene blue (MB), under visible light irradiation. The calculated k values for the degradation of RhB and MB over Ag\({}_{3}\)PO\({}_{4}\)/SnO\({}_{2}\)/CC are 0.04716 min\({}^{-1}\) and 0.04916 min\({}^{-1}\), which are higher than those calculated for the reactions over Ag\({}_{3}\)PO\({}_{4}\)/SnO\({}_{2}\), Ag\({}_{3}\)PO\({}_{4}\)/CC and SnO\({}_{2}\)/CC, respectively. The enhanced photocatalytic activity could mainly be attributed to the improved separation efficiency of photogenerated electron-hole pairs, after the formation of the Ag\({}_{3}\)PO\({}_{4}\)/SnO\({}_{2}\)/CC heterojunction. Moreover, carbon cloth with a large specific surface area and excellent conductivity was used as the substrate, which helped to increase the contact area of dye solution with photocatalysts and the rapid transfer of photogenerated electrons. Notably, when compared with the powder catalyst, the catalysts supported on carbon cloth are easier to quickly recycle from the pollutant solution, thereby reducing the probability of recontamination.  
Keywords:Ag\({}_{3}\)PO\({}_{4}\)/SnO\({}_{2}\); heterojunction; carbon cloth; photocatalytic activity; visible light +
Footnote †: journal: Applied Physics Letters
## 5 Discussion
### The Ability of SIF Anomaly to Monitor Drought  
SIF is closely associated with vegetation photosynthesis and can serve as a valuable tool for monitoring the physiological status of vegetation and water stress conditions [65]. During drought events, water stress induces alterations in the physiological state of vegetation, consequently leading to changes in SIF [66]. In this study, we validated the applicability of SIF for drought monitoring using various approaches such as MODIS GPP, crop yield, and drought-affected areas. By establishing an SIF-based drought index, we successfully monitored drought occurrences in Henan Province.  
The occurrence of drought will exert an impact on crop growth, ultimately leading to a decrease in crop yield [13]. The SIF anomaly value had positive correlations with wheat and maize yield (Figure 8). The correlation coefficients were 0.93 and 0.89. Meanwhile, the SIF anomaly value had negative correlations with areas affected by drought, with a correlation coefficient of \(-0.58\) (Figure 9). The SIF anomaly index had a high correlation with the factors that characterized drought. It indicated that the SIF anomaly index was a useful factor for characterizing drought. Therefore, our study presents an alternative data source and selectable index for future regional drought monitoring and analysis.
# Low-Complexity Progressive MIMO-OFDM Receiver for Underwater Acoustic Communication
## 6 Conclusions  
This paper proposes two types of iterative receivers for MIMO-OFDM UWA communication systems. The first one is an ICI unaware iterative receiver, which uses soft information decision feedback based on a novel cost function threshold method. The receiver exploits the OMP channel estimation and LDPC coding scheme for MIMO-OFDM communication. The receiver is tested and compared with the non-iterative receiver as well as basic Turbo Iterative receiver with soft information  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Combined Hydrophone Number**} & **Value of \(D\)max** & **0** & **1** & **2** &
\begin{tabular}{c} **ICI-Unaware \\ **3 Iterations** \\ \end{tabular} \\ \hline
02 & 0.2333 & 0.1911 & 0.1911 & 0.1911 \\ \hline
03 & 0.1757 & 0.0587 & 0.0208 & 0.0156 \\ \hline
04 & 0.1276 & 0.0018 & 0.0006 & 0.0006 \\ \hline
05 & 0.0796 & 0.0006 & 0.0006 & 0.0006 \\ \hline \hline \end{tabular}
\end{table}
Table 2: BER comparison of iterative MIMO-OFDM receiver for different number of combined hydrophones in pool experiment.  
Figure 10: Doppler scaling factor estimation values for different hydrophones for eight OFDM symbols in one frame.  
feedback, where the channel estimation is kept outside the iteration loop. Simulations and experimental results prove the effectiveness of the proposed receiver.  
Secondly, we propose an ICI aware progressive iterative MIMO-OFDM receiver, which equalizes the ICI and adapts the ICI model according to the unknown channel conditions during the iterations. The value of D is progressively increased according to the level of the ICI present in the signal. The proposed receiver is compared with the non-progressive iterative receiver and its effectiveness is proved through simulations and pool experiment. Furthermore, both the receivers were compared in terms of complexity and an obvious reduction in complexity is noticed by the proposed progressive iterative receiver while equalizing the same level of ICI.  
Conceptualization, G.Q. and Z.B.; methodology, L.M. and F.Z.; software, X.L.; validation, L.M. and Z.B.; formal analysis, X.L.; investigation, L.M.; resources, G.Q. and F.Z.; data curation, Z.B. and X.L.; writing--original draft preparation, Z.B.; writing--review and editing, L.M.; visualization, X.L.; supervision, G.Q.; project administration, G.Q.; funding acquisition, G.Q.  
This research was supported by the National Natural Science Foundation of China under Grants 61431004, 61601136, 61601137, and 61771152, and the Fundamental Research Funds for the Central Universities of China under Grants HEUCF180501.  
The authors declare no conflict of interest.
# Integrated Photonics on Glass: A Review of the Ion-Exchange Technology Achivements
## 1 Introduction  
Unlike microelectronics where the CMOS technology emerged as the dominant platform, integrated optics or, as it is called nowadays, integrated photonics, does not rely on one single technological platform. Indeed, silicon photonics, III-V photonics, polymer photonics, LiNbO\({}_{3}\) photonics, and, last but not least, glass photonics co-exist in parallel, each of them presenting their own drawbacks and advantages.  
As for ion-exchange on glass, also called glass integrated optics, it is based on a material that has been known and used for centuries. Glass is easily available and can be easily recycled. The ion-exchange technique, although it is based on using microfabrication tools, can be considered as a relatively low-cost approach, which allows realizing waveguides with low propagation losses and a high compatibility with optical fibers. Glass photonics is not a platform that has been developed for a specific application. Therefore, Planar Lightwave Circuits (PLCs) realized by ion-exchange on glass are found in many fields with a wide range of applications.  
From its very beginning in 1972 [1], to products currently on the markets, thousands of papers have been published on this vivid topic. For this reason, making an extensive review of this technology is a cumbersome task. However, since excellent reviews have already been published in the past years [2; 3; 4; 5; 6; 7; 8; 9], we can skip the pioneering years when the basis of the technology was set by testing several glasses and ions and making multimode waveguides. In this paper, we will hence focus on devices made by ion-exchange on glass, their performances, and their applications.  
After a presentation of ion-exchanged waveguides, their realization process, their modelling, and their main characteristics, we will review devices made for telecommunication purpose. Then, we will review the use of ion-exchanged waveguides for the fabrication of optical sensors since these types of applications are taking a growing place in integrated photonics.
# AI-Enabled Intelligent Visible Light Communications: Challenges, Progress, and Future
## 3 Machine Learning in Physical Layer of IVLC
### Channel Equalization
#### 3.2.7 Postequalization LSTM-Equalizer  
High-speed VLC is limited by inherent nonlinear effects. Linear equalizers with limited taps seem powerless, and the Volterra series schemes suffer from high computational complexity when the high-order taps are required. With the rise of ML in solving nonlinear problems, long short-term memory (LSTM) networks are studied for VLC systems.  
In [61], researchers proposed a memory-controlled LSTM NN equalizer for both linear and nonlinear compensation, which outperforms the conventional Volterra-based and FIR-based equalizers. LSTM carries out channel equalization as a pattern classifier where the output of LSTM cells is activated by a specially designed function. Training data with high priority would be assigned by LSTM to the latest training sequence. The proposed LSTM equalizer in [61] contains an input layer, a logical hidden layer with long and short-term memory, a classification layer, and an output layer with a merge node. A standard LSTM cell structure is used for long/short-term memory links. Moreover, a batch random resequencing procedure is adopted to control the memory effect.  
Recently, the variants of LSTM have also drawn the attention of researchers because the simple LSTMs have a slow convergence speed. This is because the LSTM unit's inner parameters prolong the training period. A convolution-enhanced LSTM (CE-LSTM) equalizer, which extracts the features by using a convolutional layer, is proposed in [62] to shrink the complexity of the LSTM network and speed up the convergence progress. The experimental results also confirmed the feasibility of the proposed CE-LSTM equalizer.
# CEEMDAN-IHO-SVM: A Machine Learning Research Model for Valve Leak Diagnosis
###### Abstract  
Due to the complex operating environment of valves, when a fault occurs inside a valve, the vibration signal generated by the fault is easily affected by the environmental noise, making the extraction of fault features difficult. To address this problem, this paper proposes a feature extraction method based on the combination of Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) and Fuzzy Entropy (FN). Due to the slow convergence speed and the tendency to fall into local optimal solutions of the Hippocamp Optimization Algorithm (HO), an improved Hippopotamus Optimization (IHO) algorithm-optimized Support Vector Machine (SVM) model for valve leakage diagnosis is introduced to further enhance the accuracy of valve leakage diagnosis. The improved Hippopotamus Optimization algorithm initializes the hippopotamus population with Tent chaotic mapping, designs an adaptive weight factor, and incorporates adaptive variation perturbation. Moreover, the performance of IHO was proven to be optimal compared to HO, Particle Swarm Optimization (PSO), Grey Wolf Optimization (GWO), Whale Optimization Algorithm (WOA), and Sparrow Search Algorithm (SSA) by calculating twelve test functions. Subsequently, the IHO-SVM classification model was established and applied to valve leakage diagnosis. The prediction effects of the seven models, IHO-SVM. HO-SVM, PSO-SVM, GWO-SVM, WOA-SVM, SSA-SVM, and SVM were compared and analyzed with actual data. As a result, the comparison indicated that IHO-SVM has desirable robustness and generalization, which successfully improves the classification efficiency and the recognition rate in fault diagnosis.  
Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN); improved hippopotamus optimization (IHO); SVM; valve leakage +
Footnote †: journal: _Algorithms_
## 4 Our Methodology
### Transformer Models
#### 4.2.4 The ByT5 Model  
The ByT5 model [8] is a general-purpose pre-trained multilingual text-to-text model, based on its earlier predecessor, mT5 [101]. It completely disposes of SentencePiece [102] tokenizer, as it does not need any. The authors concentrated 3/4 of the parameters into the encoder by decoupling the depth of the encoder and the decoder. A small version of the ByT5 now has 12 encoder layers and four decoder layers.  
In the ByT5 model's case, the total vocabulary size is 384, consisting of: three special tokens (<_pad>_ for padding, 
 for the end of the sequence, and <_unk>_ for unknown), \(256=2^{8}\) values of the main eight-bit byte, and 125 extra sentinel tokens used only in the pre-training task. In the small version, the vocabulary accounts only for 0.3% of the total parameters, while in a similarly-sized mT5 model, the vocabulary took 85% of the total parameters. As a result, the small ByT5 model, working with fine-granularity tokens (bytes), outperforms mT5, which worked inefficiently due to its large granularity and its rarely-used vocabulary parts (subwords) which took up much parameter space.  
Due to its byte-level nature, the ByT5 model is slower to compute. More fine-grained tokenization produces more tokens for the same text and requires more time for the model to digest. However, the ByT5 model's authors showed that, for short-to-medium length text, the time increase is negligible. This is the case for diacritics restoration, as the input is composed of a single sentence.  
The sequence-to-sequence nature of the ByT5 model tackles the limitations of the latest state-of-the-art diacritics restoration model [46], which is based on the BERT. The latter system was an auto-encoding type, and it performed classifications for each token. That is, it had to predict the proper classes of each token correction, described by the position and diacritic sign type. This system is limited to its predefined instruction set (correction classes), which is highly language-dependent and involves the single task of restoring diacritics. On the other hand, our sequence-to-sequence ByT5 approach allows us to address multiple grammatical errors and learn to generate output sequences in a much more universal, language-independent approach.
# Non-Invasive Hydration Monitoring with a Graphene Dual Sweat Sensor
###### Abstract  
Maintaining optimal hydration is critical for physiological function, particularly during intense physical activities, in which dehydration or overhydration can impair performance and recovery. Traditional methods for monitoring hydration status, such as body weight changes, bioelectrical impedance, and urine specific gravity, are limited by inconvenience and lack of real-time capability. This study introduces a novel graphene-based dual-sensing electrochemical sensor for the rapid and non-invasive quantification of sodium and potassium concentrations in human sweat, key biomarkers of hydration status. Leveraging graphene's exceptional conductivity and functionalization potential, the sensor employs open-circuit potentiometry (OCP) to achieve high sensitivity and selectivity in detecting sodium and potassium. The sensor performance was validated against that of a commercial analyzer and ICP-OES, demonstrating a near-Nernstian response (61.93 mV/decade for sodium and 61.21 mV/decade for potassium detection) and a linear detection range spanning from 0.1 mM to 100 mM for both sodium and potassium monitoring in sweat. Sweat samples from an athlete during endurance exercise confirmed the sensor's reliability, with results closely matching those of ICP-OES and outperforming the commercial analyzer in regards to accuracy and sample efficiency. This work represents a cross-validated study of a sweat-based sensor with a second analytical technique, highlighting its potential as a real-time hydration monitoring tool for use in sports and beyond.  
s +
Footnote †: journal: applied sciences  
Article
# Wireless Energy Harvesting for Internet-of-Things Devices Using Directional Antennas
###### Abstract  
With the rapid development of the Internet of Things, the number of wireless devices is increasing rapidly. Because of the limited battery capacity, these devices may suffer from the issue of power depletion. Radio frequency (RF) energy harvesting technology can wirelessly charge devices to prolong their lifespan. With the technology of beamforming, the beams generated by an antenna array can select the direction for wireless charging. Although a good charging-time schedule should be short, energy efficiency should also be considered. In this work, we propose two algorithms to optimize the time consumption for charging devices. We first present a greedy algorithm to minimize the total charging time. Then, a differential evolution (DE) algorithm is proposed to minimize the energy overflow and improve energy efficiency. The DE algorithm can also gradually increase fully charged devices. The experimental results show that both the proposed greedy and DE algorithms can find a schedule of a short charging time with the lowest energy overflow. The DE algorithm can further improve the performance of data transmission to promote the feasibility of potential wireless sensing and charging applications by reducing the number of fully charged devices at the same time.  
Internet of Things; energy harvesting; beamforming; directional antenna +
Footnote †: journal:  
00 2023 by the authors. Liconse MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)]([https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/))).
## 2 Materials and Methods
### Material Properties  
The GFRP tubes are made of E-glass epoxy with the yield tensile strength of 27,500 psi following the ASTM D638 code. The yield tensile elongation of the epoxy has a nominal unit value of 0.4 to 6.7% based on the ASTM D638 standard. The composite full-scale GFRP tubes used in this research are constructed using the filament winding fabrication technique. This technique is appropriate for circular hollow components and is applied in this research based on the cylindrical shape of the piles. This method can be performed quickly and is a cost-effective approach for laying the material. The conversion procedure of fiber to fabric is eliminated in this method which in respect decreased the amount of needed fiber material. Moreover, due to the straight predetermined pattern of fabricated fibers in this method, structural properties of the fibers, such as FRP or GFRP are matched with the direction of the applied loads.  
The GFRP tubes are made of 7.5 mm structural wall thickness and the outer diameter of the test piles are between 227 mm and 241 mm. These GFRP tubes consist of three layers as inner, structural and protection laminates. In the test piles, fiber-oriented material is used with almost 40 degrees of longitudinal inclination from the horizontal axis of the pile. As is shown in Figure 1a, the GFRP tubes consist of three laminate layers which are asymmetrically rotated (+35/\(-\)86). The reinforces fibers orientated at 35\({}^{\circ}\) toward the longitudinal direction as they are oriented at 3\({}^{\circ}\) toward the hoop direction. Expansive additive materials in the tube enhanced the strength of the existing concrete against shrinkage and maintained the compression strength of the member. Regarding the used concrete mixture, three 150 mm \(\times\) 300 mm cylinder samples were tested following the ASTM C39-2015 standard.  
Figure 1b presents a schematic of the instrumenting used for conducting full-scale tests on the GFRP reinforced specimens. The strain gauges were set on the outer perimeter of the composite tubes to record hoop and longitudinal strain values. The midspan deflections were recorded using two 350  mm Linear Motion Transducers (LMTs). In addition, Dial Gauges were used to control small slips in the longitudinal direction between the composite tube and concrete. Two Position Indicator Gauges (PI Gauges) were installed in the midspan at both the top and bottom of the specimens to add more precision in measuring longitudinal displacements. The overhang region is designated for bending moment application during the tests.