esa-sceva/satcom-chunk-collection huggingface dataset:
# An Efficient Framework Model for Optimizing Routing Performance in VANETs
## 2 Related Work
They use Ant Colony Optimization to select the path at crossroad intersections, which enhances the network connectivity based on the tuned routing functionality pertaining some of the QoS metrics to adopt forward packet mechanisms. For a self-optimizing scheme to balanced routing resources in wireless sensor networks, the authors used Ant Colony Optimization to utilize and optimize network resources [34]. Most of these methods are adopted to enhance the paths with the best quality function, leading to a reduced packet loss, energy usage, and extended network lifetime. The disadvantages of these methods, however, is that the selection of the route is improved based on only two function qualities: the hop-count, and path quality. Another interesting study was proposed based on the automatic tuning method [35], which used a number of techniques to optimize the transmission time. The performance of the proposed protocol with the new configuration was compared to human configuration under different urban and highway scenarios. A heuristic method was used to tune the routing protocol parameters obtaining the configurations automatically to deal with the specific characteristic of VANETs [22]. However, this tuning only emphasized on enhancing the routing configuration parameters in terms of delay metric, only, without taking into consideration the remaining QoS metrics such as throughput. In summary, The primary objective of this work is to define the best parameter values for the routing protocol in VANET environments. These values are obtained by sensing the best response time for any change in the topology network, especially in terms of the overhead and end-to-end delay.
# Improvement of Porous GaN-Based UV Photodetector with Graphene Cladding
## 1 Introduction
Conventionally, such PDs are derived from Si-based sensors with photomultiplier tubes, which consisted of complex architecture. With the discovery of wide bandgap semiconductor materials such as GaN, its inherent thermal and chemical stability ensure stable performance [28, 29]. Despite the positive aspects of GaN, it faces several challenges in limiting its role as a PD. Due to the limited choice of substrates that matches with the lattice of GaN, defects such as dislocations would be formed during growth. Meanwhile, the intrinsic nature of GaN requires doping to achieve a reasonable conductivity. With low activation energy, a higher concentration of dopants would be introduced during growth to compensate for such losses. Consequently, this would reduce carrier mobility, thus leading to a slower response [28]. Application of graphene in optoelectronic devices was made possible since it is highly optically transparent (97.7% with monolayer) while retaining good electrical conductivity with charge mobility exceeding 100,000 cm\({}^{2}\)V\({}^{-1}\)s\({}^{-1}\)[30, 31]. In recent years, graphene was sought out as the potential material in further enhancing the performance of PDs. The was owed to the unique band structure of graphene, which can be described as the two vertices of inverted triangles meeting at a singular point known as the Dirac Point [32]. The lack of a notable bandgap infers broadband operation, i.e., it is capable of photodetection at a wider range of wavelengths. Next, due to the stable sp\({}^{2}\) hybridization of carbon atoms, graphene lacks dangling bonds that enable better charge mobility. In addition, the weak Fermi Level Pining (FLP) effect lowers the potential barrier at the heterojunction, which enables better sensing for PDs [33, 34, 35, 36]. This also infers that graphene heterojunctions would have rectifying behaviour in general. Examples of graphene heterojunction involvingsemiconductor material such as GaN, GaAs, and Si to make optical devices would be rectifying in nature [37; 38; 39; 40; 41]. Despite the numerous advantages of graphene/semiconductor heterojunction devices, they are susceptible to changes such as defects at the heterojunction. This necessitates studies to be conducted for such heterojunctions. In this work, a total of four UV photodetectors were fabricated and compared. They were categorized into two groups, with or without graphene cladding. The former consisted of two samples, i.e., as-grown and porous morphology GaN, which acted as control samples. On the other hand, the porous GaN in the latter group was cladded with graphene grown either using chemical vapour deposition or the electrochemical exfoliation method. The role of this graphene on the performance of a porous GaN-based UV photodetector is compared and evaluated.
## 6 Conclusions and Future Works  
This study proposed a deep learning-based framework for detecting and quantifying road damage using high-resolution pre- and post-disaster satellite imagery. Specifically, three change detection approaches (i.e., the overlay approach, difference-based approach, and Siamese-based approach) were evaluated under a strictly controlled experimental environment to identify the most effective strategy.  
Quantitative results of this study, validated over multiple runs, demonstrated that the difference-based model achieved the most effective and stable performance with the  
Figure 4: Example of road damage distribution map generated by the difference-based model.  
highest overall F1-score (\(F1_{s}\)). However, the detailed analysis revealed that even this best-performing model is constrained by a low detection recall for the 'damaged road' class. This highlights that the severe class imbalance inherent in such real-world datasets remains a critical and unresolved challenge for which standard training strategies are insufficient. Despite this limitation, the damage distribution maps generated by the framework can serve as a valuable tool for practical disaster response, enabling the prioritization of infrastructure restoration efforts.
###### Abstract  
This paper investigates the effect of a temperature shock on a small spacecraft with symmetrically arranged flexible elements. A two-dimensional thermoelasticity problem is posed. The disturbing effect of temperature shock on a small spacecraft has been determined. The assessment of the main disturbing factors arising from the temperature shock of flexible elements of a small spacecraft was carried out. Approximate dependences were obtained for the components of the displacement vector of the flexible element points. Numerical simulation was carried out for the symmetric scheme of the small spacecraft with two and four flexible elements. The dependence of the inertia force on temperature shock for the simulated small spacecraft at various initial deflections of the flexible element was constructed. Conclusions were drawn about the significance of the temperature shock influence on the dynamics of a small spacecraft. The results obtained were compared with the results of other studies and can be used in solving problems of remote sensing of the Earth and the implementation of gravity-sensitive processes on board small spacecraft.  
small spacecraft; temperature shock; disturbances; symmetrical scheme +
Footnote †: journal: Physics Letters A  
Arising from Temperature Shock with a Symmetrical Arrangement of Flexible Elements of a Small Spacecraft.
# Experimental and Numerical Analysis of an Innovative Combined String-Cable Bridge
## 2 Experimental Program
### Design of the Tested Model  
To achieve the goals of the experiment, a model of an innovative string-suspension bridge was designed. The string-cable structure model parameters were selected by performing a numerical analysis and considering the possible length of the real span of such a bridge, L = 50-70 m. According to the prepared drawings, the steel elements of the bridge model were made. The steel structures were manufactured according to the [49] production standard. In the laboratory of the faculty of civil engineering of Vilnius Gediminas technical university, this structure was assembled from separate elements. This bridge model consists of a pre-tensioned string supported through struts on a cable. This string, as the top element of the new combined steel structure, performs the function of the bridge's stiffness beam. The cable acts as the lower support chord of this combined structure. Strings and cable supports are designed to be immovable both vertically and horizontally and connected in one unit. The test model was designed in such a way that the string could easily be additionally tensioned. The string was continuous throughout the span and anchored at the ends with screws (see Figures 1 and 2). The string and cable in the supporting nodes can freely rotate around an axis perpendicular to the plane of the structure.  
The string-cable structure model parameters were as follows: model span L--5.0 m. The width of the bridge model (distance between two flat structures) is 0.5 m. The distance between the struts is the same and is 0.714 m (see Figure 1). The struts of the model are  
Figure 1: Experimental bridge model.  
Figure 2: Front view and intermediate nodes of the experimental bridge model.  
designed from rectangular cross-section profiles, RHS 40 \(\times\) 20 \(\times\) 2. Such cross-sectional dimensions of the struts were chosen to eliminate possible axial deformations of the struts and, at the same time, their effect on the behavior of the bridge model. The heights of the struts were chosen in such a way as to form the shape of the lower element (cable), which is in balance according to the acting axial forces of the struts. These cable coordinates allow the bridge system to deform evenly under a symmetrical load. The maximum height of the strut or cable sag is 0.490 m. The upper element (string) and lower element (cable) are designed from a 6 mm diameter round steel rod.
## 4 Optimization Analysis of the Waterproof Performance of the Waterstop
### Dimensional Optimization of the Waterstop  
The deformation state of the waterstop can be improved by optimizing the size of the waterstop. At present, there are many specifications for buried waterstops used in tunnels. To compare the influence of the size of the middle hole of the waterstop and the thickness of the waterstop on its deformation, various inner diameters of the middle hole are used for waterstop I. At the same time, specifications and engineering cases are referred to in order to select two types of waterstops. As shown in Figures 17 and 18, waterstop II is thinner than waterstop I, the thickness of waterstop III is the same as that of waterstop II, and the size of the mesopore of waterstop III is larger than that of waterstops I and II. The plane strain finite element models are established.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Conditions** & \(\rm P_{wl}^{st}\) **(MPa)** & \(\rm t_{c}\) **(mm)** & \(\rm Mises_{max}\) **(MPa)** & \(\rm t_{a}\) **(mm)** & \(\rm P_{wlmax}^{lt}\) **(MPa)** \\ \hline
1-1 & & 2.7 & 1.78 & 20.0 & 1.48 \\
1-2 & 0.101 & 4.7 & 1.82 & 10.0 & 0.53 \\
1-3 & & 2.0 & 2.05 & 29.5 & 6.92 \\
2-1 & & 3.1 & 1.75 & 20.0 & 1.45 \\
2-2 & 0.144 & 4.7 & 1.89 & 10.0 & 0.51 \\
2-3 & & 1.4 & 2.0  
Calculations show that: (1) When the middle hole has a specific outer diameter, increasing its inner diameter can improve the stress state during the deformation of the waterstop belt. The compression deformation is more obvious, and the maximum stress value is reduced by 71% when R = 9 compared to that when R = 1. (2) When the middle hole is a specific size, reducing the thickness of the waterstop belt can improve the stress state of the tensile deformation of the waterstop belt. At R = 9, the maximum stress value of waterstop II decreased by 13% compared with waterstop I. (3) Increasing the size of the hole in the waterstop belt can obviously improve the stress state during the deformation of the waterstop belt. Taking the settlement deformation as an example, the maximum stress value of waterstop III decreased by 34% compared with waterstop II.  
A waterstop is made of rubber, and if it is too thin, it will increase the risk of damage such as tearing and puncturing. The tunnel deformation joint has as designated width. On the premise of satisfying these two conditions, the above analysis shows that stress deformation can be improved by reducing the thickness of the waterstop and increasing the inner diameter and size of the hole in the waterstop. This will also reduce the damage to the bond between the waterstop and the concrete due to deformation, and reduce the risk of waterstop failure caused by excessive deformation.
## 4 Bond-Slip Relationship Model at High Temperature  
### Establishment of the Bond-Slip Relationship Model  
Many scholars have recently conducted research in relation to models of the bond-slip relationship between rebar and concrete. [PERSON] [26] used the rising section of the BPE model [27] to describe rebar and NC bond-slip curves, demonstrating that the predicated curves fit well with test results. [PERSON] [28] described the bond-slip curve between rebar and fiber concrete by modifying the concrete stress-strain relationship model of [PERSON] [29]. It was found that the modified model was in good agreement with the bond behavior between rebar and fiber concrete through the pullout test.  
Based on the bond-slip curves obtained from the tests in this study, the bond behavior between rebar and SFRC was found to be similar to that of the BPE model and the modified Guo model after comparison. Therefore, the parameters in the model were modified on the basis of the bond-slip relationship between rebar and NC. As shown in Figure 13, the rising section of the BPE model and the falling section of the Guo model were extended to SFRC. A model of the bond-slip relationship between rebar and SFRC is now proposed in which temperature and \(V_{f}\) are considered.  
The bond-slip curve equation can be expressed in a dimensionless way. As shown in Figure 13, OA is the rising section and the curve has a nonlinear upward trend. AB is a falling segment and the curve shows a nonlinear decreasing trend. The formulas are as follows.  
\[\text{Rising section }\ y=x^{\varphi}\ \ \ \ \ \ \ 0\leq x\leq 1 \tag{4}\] \[\text{Falling section }\ y=\frac{x}{\eta\left(x-1\right)^{2}+x}\ \ \ \ \ \ \ \ x\geq 1 \tag{5}\]  
Figure 13: Bond–slip relationship model.  
where \(\varphi\) and \(\eta\) are the fitting parameters determined from the experimental results, \(0\leq\varphi\leq 1\). The rising section (\(0\leq x\leq 1\)) and the falling section (\(x\geq 1\)) are continuous at the peak point of the curve.  
\[x=\frac{s}{s_{u}} \tag{6}\]  
\[y=\frac{\tau}{\tau_{u}} \tag{7}\]  
where \(\tau_{u}\) is the ultimate bond stress of the curve. \(s_{u}\) is the slip corresponding to ultimate bond stress.  
According to the characteristics of the curve, its mathematical expressions meet the requirements of the following geometric conditions.  
(1) \(x=0\), \(y=0\);  
(2) \(0\leq x<1\), \(\mathrm{d}^{2}y/\mathrm{d}x^{2}\)>0,  
slope of the curve (\(\mathrm{d}y/\mathrm{d}x\)) decreases monotonically, no inflection point;  
(3) \(x=1\), \(y=1\), \(\mathrm{d}y/\mathrm{d}x=0\);  
(4) \(x\)\(\rightarrow\)\(\infty\), \(\mathrm{d}y/\mathrm{d}x\)\(\rightarrow\)0;  
(5) \(x\geq 0\), \(0\leq y\leq 1\).
# A Survey of Internet of Things (IoT) Authentication Schemes +
## 5 Analysis of IoT Authentication Schemes
### Smart Homes  
Smart Homes are automated homes, where users will have the ability to control, monitor and access remotely ( using mobile phone (mobile application) or personal computer (web application)) climate systems (heating and air conditioning), appliances, lighting, TV, audio and video systems, etc. The authors of [66] developed a security scheme that can be deployed in smart homes. Such approach has the ability to overcome some security threats such as impersonation and replay attack [65], but it is still vulnerable to eavesdropping. The approach is based on OAuth 2.0 protocol. In [103], the authors introduced a new authentication scheme to authenticate the end devices deployed in smart homes, which is based on the combination of PUF and Physical Key Generation (PKG). The PUF provides the security of the system by generating a secure key based on the physical parameters of the end device ( the design of PUF depends on common circuit fabrication features that give it the ability to create unique secret key). Machine-to-Machine (M2M) communication is taking a lead in the IoT development, but it also has security challenges. In [104], the authors developed a scheme allowing a smart home network remote user to communicate with end devices. The scheme allows the mutual authentication between the communicating parties, besides establishing a secure connection to establish the confidentiality of data. The authors of [105] proposed a mutual authentication protocol for IoT end-devices (smart home use case) based on PUF. They introduced the concept of Object Life cycle (OLC) to describe the roadmap of the end-device from manufacture till the deployment in the IoT system and describing the security challenges during this roadmap.  
The authors of [106] developed a PUF-based authentication scheme for IoT devices to provide mutual authentication between the end device and the gateway by using the CRP data stored inside the gateway. It also provides a way for user (smart phone or wearable device) to authenticate itself with the gateway in order to have the ability to communicate with the end devices using session key generated between them. Timestamp data are used by the user to ensure security against replay attacks.  
The authors of [107] proposed a mutual authentication for IoT systems. The scheme is based on the lightweight features of Constrained Application Protocol (CoAP) as an application layer protocol for the communication between client and the server. The secure communication channel is provided by the advantage of Advanced Encryption Standard (AES) cipher. Both the client and the server challenge each other for mutual authentication by encrypting a payload from the message of size 256 bits, and then exchange payloads for verification. The authentication is done during the request-response interaction without the use of an extra layer (DTLS) which increases the communication and computation cost.
## 2 Construction of the Defocus and Tilt Compensation Theoretical Model
### Compensation Strategy and Process  
In the actual process of image plane adjustment, it is necessary to use a feedforward model to provide the required adjustment amount. Therefore, providing appropriate adjustment methods is indispensable.  
To achieve high-precision compensation, the compensation algorithm needs to be simple and efficient, avoiding the coupling of various parameters. Therefore, each parameter should ideally correspond to a unique image plane adjustment amount. The adjustment steps for surface deformation compensation are as follows:  
1. Calculate the rotation angle of the prism based on the tilt of the image plane. Using [PERSON]'s law to obtain the cosine of the direction of light rays, the rotation matrix can be obtained from the normal vectors before and after rotation, and then the rotation angle of the prism can be obtained through the formula. \[\overset{\rightarrow}{N_{3}}=R_{\omega}\overset{\rightarrow}{N_{3\omega}}\] (7) where \(\overset{\rightarrow}{N_{3}}\) is the normal vector of surface 3 after rotation, \(\overset{\rightarrow}{N_{3\omega}}\) is the normal vector of surface 3 before rotation, \(R_{\omega}\) is the rotation matrix.
2. Adjust the parameters to compensate for the image plane displacement in the x- and y-directions. Typically, two parallel plates tilted around the x- and y-axes are used in the exposure optical path to control lateral displacement. Therefore, this step can be optionally omitted based on practical requirements.
3. Adjust the parameters to compensate for the image plane movement in the z-direction. This adjustment is achieved through the oblique movement of the second wedge prism.
## 5 Experiment Measurement and Analysis
### Noise Measurement and Analysis  
The noise experiment of the stand fan is carried out in the semi-anechoic chamber to ensure low background noise and no significant reflection noise. There are three measuring points chosen to record the fan acoustic characteristics. The measurement point #1 is located at 1 meter away from the fan inlet while the other two points are separated with respect to a 45\({}^{\circ}\) angle from the axial direction, and placed at 1 meter downstream of the fan outlet. The noise testing result shows that (see Table 6) the optimal impeller can achieve higher performance, but its average noise level (50.8 dBA) is higher than that of the reference impeller (43.3 dBA) by 7.5 dBA. Apparently, 7.5 dB is a big noise increase; however, its flow rate enhancement of 54% is also a huge jump. Therefore, it is instructive to check the noise data for the optimal fan generating the same flow rate as the reference fan. With the aid of fan law, the rotating speed for the optimal fan can produce the same flow rate as the reference, i.e., 583 rpm. For convenient comparison, Table 6 also lists the acoustic data for both fans operating at 600 rpm. Clearly, under the same flow-rate operation, the noise generation for the optimal fan is roughly 1.5 dB lower than the reference fan. Hence, the optimal fan is able to provide the users two choices, which are the same flow with a silent environment and the huge air stream with a loud noise.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Case**} & \multicolumn{4}{c}{**900 rpm**} & \multicolumn{4}{c}{**600 rpm**} \\ \cline{2-7}  & \multicolumn{2}{c}{**Noise (dBA)**} & \multicolumn{2}{c}{**Avg. Noise (dBA)**} & \multicolumn{2}{c}{**Noise (dBA)**} & \multicolumn{2}{c}{**Avg. Noise (dBA)**} \\ \hline \multirow{3}{*}{Reference fan} & point 1 & 43.0 & & point 1 & 34.2 & \multirow{3}{*}{34.5} \\  & point 2 & 43.6 & 43.3 & point 2 & 34.8 & \\ \cline{1-1}  & point 3 & 43.3 & & point 3 & 34.5 & \\ \hline \multirow{3}{*}{Optimal fan} & point 1 & 49.6 & & point 1 & 40.8 & \multirow{3}{*}{42.0} \\  & point 2 & 51.7 & 50.8 & point 2 & 42.9 & \\ \cline{1-1}  & point 3 & 51.1 & & point 3 & 42.3 & \\ \hline \hline \end{tabular}
\end{table}
Table 6: Noise characteristics of the reference fan and the optimal fan at different rotating speeds.  
Figure 11: The experimental velocity distributions at the monitoring surface of the reference and optimal fans. (**a**) Reference fan; (**b**) optimal fan.