esa-sceva/satcom-chunk-collection huggingface dataset:
## 3 SENDI: System for Detecting and Forecasting Natural Disasters Based on IoT
### Flash Flood Forecasting with the Use of ML  
This section describes the characteristics of the data used in the case study on flood forecasting and how the simple forecast models have been created. It should be stressed that these simple models are only used if there is a failure in communication with the _Cloud_ and the Tier 2 nodes, since this makes use of data from just one node. The WSN REDE is composed of 7 nodes, as shown in Figure 6, which are installed in the rivers of the city of Sao Carlos, Brazil. All the nodes use sensors which read the water pressure on the river bed and convert this value into the depth of the river, measured in centimeters, except in the case of the nodes where the sensor is a rain gauge that measures the volume of rain in the area. Another node that stands out from the others is the node installed in the mall of the town, which is also equipped with a camera that takes pictures of the monitored region. The data used for this study were collected between October 2013 and October 2014 from the node in the mall. The readings of the river level were taken at 1-min intervals and the area was the part of the town which experienced most frequent flooding.  
The readings selected to generate the models were only those which represent the times when the river levels rose or declined. These readings were separate from the others and formed the dataset shown in Figure 7. The models were generated by this dataset and through the implementation of the MLP (Multilayer Perceptron) that is present in the WEKA software [24].  
The parameters of the MLP for training were: learning rate = 0.3, 10-fold cross-validation as a test analysis and 1 hidden layer with 3 neurons. The inputs in the MLP are composed of the average of 5 readings. Two forecast models were generated for each node and, given the current time as \(t\), in one of the models the output of MLP is the forecast of the average river level from \(t+\tau\) to \(t+4+\tau\) (5 minuots in the future--used for generate red alerts), where the \(\tau\) parameter is detailed in the Section 4.2. The output of the other model is the forecast of the average of the river level from \(t+5+\tau\) to \(t+9+\tau\) (5 minuots in the future--used for generate red alerts). These parameters were defined on the basis of previous research, as in [19; 25].  
Figure 6: Example of a REDE node.  
Figure 7: River level dataset used to generate the forecast models.
# LDPC Codes on Balanced Incomplete Block Designs: Construction, Girth, and Cycle Structure Analysis
###### Abstract  
In this paper, we investigate the cycle structure inherent in the Tanner graphs of low-density parity-check (LDPC) codes constructed from balanced incomplete block designs (BIBDs). We begin by delineating the incidence structure of BIBDs and propose a methodology for constructing LDPC codes based on these designs. By analyzing the incidence relations between points and blocks within a BIBD, we prove that the resulting LDPC codes possess a girth of 6. Subsequently, we provide a detailed analysis of the cycle structure of the constructed LDPC codes and introduce a systematic approach for enumerating their short cycles. Using this method, we determine the exact numbers of cycles of lengths 6 and 8. Simulation results demonstrate that the constructed LDPC codes exhibit excellent performance.  
LDPC codes; balanced incomplete block designs (BIBDs); Tanner graph; cycle; girth 2020  
2
## 1 Introduction
According to TIA-942 [1], the environmental conditions of a datacenter are the dry bulb temperature being 18-27 \({}^{\circ}\)C, the maximum relative humidity being 60%RH, the maximum dew point being 15 \({}^{\circ}\)C, and the maximum temperature variation being no greater than 5 \({}^{\circ}\)C/h. However, in the regions of hot and wet environments, the formation of water condensate on the fin-and-tube heat exchangers in datacenters is common. Therefore, to meet the guidelines of GBT 19413-2010 [2], various studies using surface coating have been conducted. As examples, for wavy fins, [PERSON] et al. [3,4] showed that hydrophilic surface coating could reduce the pressure drop significantly due to the presence of film condensate. Similarly, [PERSON] and [PERSON] [5] also showed that increasing surface wettability could reduce the pressure drop significantly while not significantly reducing the heat transfer coefficient. [PERSON] and [PERSON] [6] also showed that hydrophilic coating would significantly reduce the airflow resistance, a larger reduction with a bigger inlet relative humidity. [PERSON] et al. [7] showed that by dry/wet cycling the contact angle of most commercial coatings increased with increasing numbers of dry/wet cycles, reaching the 55\({}^{\circ}\) to 65\({}^{\circ}\) range after 1000 cycles. Dry/wet cycling could also improve the wettability of the uncoated surface, believed to be due to surface oxidation and contamination. [PERSON] and [PERSON] [8] indicated that for the surfaces with a smaller contact angle, the generation of splash water and water bridging was less likely. [PERSON] et al. [9] showed that the critical air speed of water splash for completely wetted fin surfaces was twice that of partially wetted fin surfaces; moreover, for the prevention of water splash, the contact angles had to be smaller than 60\({}^{\circ}\). [PERSON] et al. [10] showed that for the uncoated fin surfaces, the pitch between the fins had to be greater than 3 mm to avoid water bridging; furthermore, hydrophilic fins could reduce the water splash situation without reducing the heat transfer rate of the fin-and-tube heat exchanger. In contrast, [PERSON] et al. [11] showed that the water droplet formation cycle shortened and the splashing droplet diameter reduced as the contact angle increased. Numerically, [PERSON] et al. [12] explored the bridging phenomena by adding gravity effects; whereas [PERSON] et al. [13] examined the dehumidifying behavior of water droplets which was validated by [PERSON] et al. [14]. It is clear that the reduction in both energy consumption and water splash is important to the equipment of datacenters. Therefore, this study focuses on these two aspects quantitatively by taking the fin density and airspeed as the controlling parameters to further substantiate the effects of hydrophilic surface coating explored in the literature.
# Monitoring the Capillary Jet Breakage by Vibration Using a Fast-Video Camera
## 4 Results and Discussion
### Selection of the Vibrated Membrane  
The encapsulator B-390 was initially designed based on the encapsulator Inotech. Both systems transmit the vibration using a polymer membrane. However, the magnet glued on the membrane tended to detach. It was observed that the breakage was not stable over time, forcing the operator to reset the frequency to maintain the correct breakage. [PERSON] has modified the system by introducing a metallic membrane. Both systems were compared by producing alginate beads using different nozzles.  
Finding the optimum conditions (i.e., conditions where the droplets seem immobile in front of the flashing LEDs) was generally more manageable with the metallic membrane. The droplet production was stable. The mean size and size distribution in optimum conditions were similar for both membranes (Figure 4A).  
Figure 4: Impact of frequency for metallic and polymer membrane while selecting optimum breakage conditions (see Section 4.1) (**A**) on droplet size (750 \(\upmu\)m nozzle, mean error 3%) (**B**) jet length before breakage for two different amplitudes of vibration (mean error 11%). (**C**) Droplet size dispersion (Nozzle 450 \(\upmu\)m, amplitude 4, mean error 6%).  
Before complete rupture, the droplets are connected by a liquid filament (Figure 2). The breakage of the filament itself may lead to tiny droplets called satellites. The number of satellites was lower than 1% of the droplets with both membranes, representing less than 1 ppm of the droplet volume.  
The main difference between the two types of membranes is observed in length before breakage (Figure 4B). The metallic membrane seems able to transfer the vibration more efficiently, leading to a faster breakage. The magnet is glued on the polymer membrane, while it is screwed on the metallic one. Several times it was needed to reattach the magnet on the polymer membrane, assuming that the connection was probably not strong enough over time. The vibration amplitude (Amp) seems to be important. The length of breakage increases with the frequency. As the total energy supplies to the system remain similar, the energy per rupture decreases as the frequency increases.  
The two alternatives to the Buchi encapsulator (Brace and Nisco) vibrate the support directly and not a membrane. It requires higher energy, which remains negligible. There is a higher risk of parasite vibrations, but some tests were done and showed that both systems overcome this problem. Buchi (2018) and Nisco encapsulators (Bucchi, 2019) are initially designed for lab scale, even though they have a multi-nozzle system. Buchi has a model developed specifically for biomedical applications. Brace (2018) is designed for industrial application with large-scale models.
# Simulation of the Cooling Effect of Porous Asphalt
###### Abstract  
Porous asphalt pavement shows lower internal temperature than does dense-graded asphalt pavement under high temperature conditions in summer. To study the cooling effect of porous asphalt pavement, the thermophysical properties of a dense-graded asphalt concrete (AC) mixture and a porous asphalt concrete (PAC) mixture were determined using a parallel model. Then, a laboratory-simulated sunshine experiment was carried out, and the convective heat transfer coefficients of specimens were inferred by virtual experiment. Lastly, the temperature field distribution simulation of PAC pavement was analyzed. The results show that the thermophysical properties of the PAC-13 mixture are lower than those of the AC-13 mixture; the larger the proportion of air voids, the greater the difference appears. Under windy conditions, the convective heat transfer coefficients of the PAC specimen surfaces are higher than those of AC specimens, and the convective heat transfer coefficient of the specimen surface shows an upward trend with increasing air voids. The cooling effect of the porous pavement increases with increasing proportion of air voids, and the cooling effect of the porous asphalt pavement is better than that of the dense-graded asphalt pavement. There is a good positive linear correlation between cooling effect and air voids, and mathematical models between them which can provide an important reference for PAC pavement design were fitted.  
Keywords:porous asphalt pavement; temperature field; air voids; cooling effect; simulation +
Footnote †: journal: Applied
###### Abstract  
The difference in heating or cooling to power ratio between required demands for district networks and the proposed tri-generation system is the most challenging issue of the system configuration and design. In this work, an adjustable, novel tri-generation system driven by geothermal resources is proposed to supply the thermal energies of a specific district network depending on ambient temperature in Germany. The tri-generation system is a combination of a modified absorption refrigeration cycle and a Kalina cycle using NH\({}_{3}\)-H\({}_{2}\)O mixture as a working fluid for the whole tri-generation system. A sensitive analysis of off-design conditions is carried out to study the effect of operational parameters on the system performances prior to optimizing its performance. The simulation show that the system is able to cover required heating and cooling demands. The optimization is applied considering the maximum exergy efficiency (scenario 1) and minimum total exergy destruction rate (scenario 2). The optimization results show that the maximum mean exergy efficiency in scenario 1 is achieved as 44.67% at the expense of 14.52% increase in the total exergy destruction rate in scenario 2. The minimum mean total exergy destruction rate in scenario 2 is calculated as 2980 kW at the expense of 8.32% decrease in the exergy efficiency in scenario 1.  
Keywords:tri-generation; off-design analysis; ammonia-water solution; geothermal; flexible demand production; optimization +
Footnote †: journal: Applied Sciences
# Authentication-Based Secure Data Dissemination Protocol and Framework for 5G-Enabled VANET
## 5 Performance Evaluation
### Communication and Storage Costs  
The communication cost is computed based on the total number of vehicles using different variables in the message transmission across the V2V communication area, as shown in Figures 5 and 6, for communication and storage costs, respectively. The storage cost is the overall memory required to store various factors. We are contemplated that the hash function is of 256-bit, a size of random number of 8-bytes, a timestamp is of 4 bytes, bi-linear combination of 128 bytes, symmetric and asymmetric encoder and decoder of 64 bytes, and signature of 128 bytes. Communication cost increases with increasing number of vehicles and the same is evident from the obtained results.  
Figure 6 shows the curve between storage cost and bytes stored. Storage cost is the amount of space required to store all the parameters. As it can be seen, storage cost is lowest for the proposed A-MAC protocol. This clearly justifies that the DCF of the A-MAC protocol is suitable for safety message dissemination under highly dense vehicular scenario. This is in line with the initial purpose for designing the protocols scheme, which decreases communication and storage costs.
# Vibration Properties of Dual-Rotor Systems under Base Excitation, Mass Unbalance and Gravity
###### Abstract  
Rotor systems installed in a transportation system or under seismic excitations are considered to have a moving base. Although extensive research has been conducted on the dynamic behavior of the single-rotor system under base motions, few studies have dealt with the dynamics of dual-rotor systems, especially the counter-rotating dual-rotor systems used in airplane engines. Moreover, mass unbalance and gravity are unavoidable excitations for most rotor systems. Therefore, the vibration properties of a counter-rotating dual-rotor system with the coupled effects of base motions, mass unbalance and gravity are investigated in this paper for the first time. Using the Lagrange principle associated with the finite element method, a general model for dual-rotor systems under base motions was established by using Timoshenko beam elements, leading to a detailed analysis of the natural properties and harmonic responses of the system. The results revealed that different whirling modes (backward, forward or both) may be mutually excited. This research can be helpful for the design and vibration analysis of dual-rotor systems concerned with base motion.  
vibration properties; dual-rotor systems; base motions; mass unbalance; gravity Article
## 4 Data-Driven Framework for Building Energy Consumption Prediction
### Model for Prediction
#### 4.4.7 Cnn  
CNNs were initially mainly applied in the field of image recognition, but in recent years, they have gradually been used in tasks of processing time-series data, such as building energy consumption prediction. CNN automatically extracts data features through components such as convolutional layers, pooling layers, and fully connected layers.  
When processing building energy consumption time-series data, the convolutional kernels in the convolutional layer can be regarded as small filters that slide over the data and extract local features in the data through convolution operations, such as the change patterns of energy consumption in different time periods. The pooling layer is used to reduce the data dimension, decrease the amount of calculation, and retain important features at the same time. After multiple layers of convolution and pooling operations, the data are input into the fully connected layer for the final prediction.  
For example, when predicting the energy consumption of residential buildings, CNN can predict future energy consumption by learning the local patterns in historical energy consumption data and related influencing factors (such as weather data). Compared with traditional machine learning algorithms, CNN can automatically learn the features in the data without the need for manual feature design, which has great advantages in processing complex building energy consumption data. In addition, CNN has translational invariance, has good adaptability to local feature changes in the data, and can more accurately capture the patterns in building energy consumption data. To better apply it to building energy consumption prediction, researchers will also improve the CNN structure, such as combining it with the Long Short-Term Memory network (LSTM) and so on, to better handle the long-term dependencies in time-series data.
## 7 Discussion
### Comparison of Different Algorithms  
To validate the superiority of the improved NSGA-II algorithm in solving the FPTLIR mission path energy-time optimization problem, a series of experiments was conducted using the improved NSGA-II algorithm, the standard NSGA-II algorithm, and the MOPSO algorithm to primarily compare their convergence, coverage, solution diversity, and computational efficiency. All algorithms were implemented in MATLAB with consistent basic parameter settings and runtime environment on a computer equipped with an Intel (R) Core (TM) i5-7300 HQ processor. During the experiment, each optimization algorithm was executed multiple times to calculate average values for relevant performance metrics. Common metrics such as Generational Distance (GD), which measures the distance between solutions generated by the algorithm and the true Pareto front, are used to assess convergence; the mean Hypervolume (HV), which considers both the distance and volume between solutions in the frontier, serves as a metric for characterizing coverage of the Pareto frontier; the size of the Pareto frontier indicates the number of solutions within it  
Figure 21: Relationship between power and forward velocities.  
and demonstrates solution diversity; runtime is used to measure computational efficiency. The performance metrics at different iterations are listed in Table 5.  
Comparing the results in Table 5, it can be seen that the improved NSGA-II algorithm has a lower GD value compared to both the standard NSGA-II algorithm and the MOPSO algorithm, indicating better convergence accuracy. Furthermore, based on the higher mean HV and Pareto front size values, it can be seen that the improved NSGA-II algorithm has a better uniformity and distribution quality of solutions in the objective space. Consequently, it is more suitable for multiobjective optimization problems with complex constraints, such as those presented in this paper. The comparison of running time shows that the improved NSGA-II algorithm requires a longer running time for the same number of iterations due to the increased complexity. However, despite this longer duration, its significant advantages compensate for this additional time cost when solving the complex multiobjective optimization problems discussed here. A comprehensive analysis of these results leads to the conclusion that the improved NSGA-II algorithm is not optimal in all cases, but it shows significant advantages when dealing with the complex multiobjective optimization problems discussed in this paper.
## 2 Hybrid Vibration Isolation System
### Structural Design  
The overall scheme of the hybrid vibration isolation system is shown in Figure 2. The electromagnetic actuator adopts a floating design; that is, the stator and the mover can float up and down along the housing. Such a design ensures that the actuator mover will not deviate up and down in the middle position relative to the stator under static loads. When assembling, the bolt must be connected to the mover locating ring through the positioning hole of the end cover so as to lock the stator and the mover. At this time, the mover of the electromagnetic actuator is located at the center of the stator. After the assembly is in place, a load is applied, under which the rubber vibration isolator is compressed under the load, and the mover and stator move down along the track of the housing as a whole. The relative positions of the mover and stator remain unchanged, as they are locked; the mover is still in the middle position of the stator. After the load is applied, the stator and the housing are bolted, and the locking bolt of the mover locating ring is removed to separate the mover from the stator. The stator housing bolts are threaded through with a series of iron wires to prevent loosening.  
Moreover, a sliding bearing structure is adopted between the mover output shaft and the upper cover to ensure the radial constraint between the mover and the stator, as shown in Figure 3 below. The lateral force of the upper load is directly transmitted to the housing through the mover output shaft instead of going down through the rubber vibration isolator. However, the problem is that the lateral stiffness of the mover and stator becomes larger. In order to enhance the lateral vibration isolation, a flexible rubber layer is set between the housing and the lower flange to ensure, to a certain degree, a self-aligning function of the housing. The thickness of the rubber layer can be adjusted using rubber with different degrees of hardness.  
Figure 1: Structural schematic diagram of the hybrid vibration isolation system.  
Figure 2: Cross-sectional view of the overall structure of the hybrid vibration isolation system.  
To further investigate the correlation between the thickness of the rubber and the lateral stiffness, a finite element simulation was carried out on the rubber layer based on the hyperelastic model of the COMSOL Multiphysics (version 5.4). solid mechanics module, and the curve was obtained, as shown in Figure 4 below.  
The results show that for rubber with a shore A hardness of 45, the lateral stiffness of the rubber layer was greater than 4000 N/mm when the thickness of the rubber layer was within 3 mm, which meets the requirements for resistance against lateral stiffness.