esa-sceva/satcom-chunk-collection huggingface dataset:
# Experimental and Numerical Research on End-Wall Flow Mechanism of High-Loading Tandem Stators
## 1 Introduction
[19; 20; 21] numerically studied the tip clearance flow of a cantilever tandem stator with a large camber. The results indicated that the change in FB clearance had a greater influence on the performance of the cantilever tandem stator, while the change in RB clearance had little influence on the performance. [PERSON] et al. [22] compared two tandem cascades with different chord lengths of the FB and RB. The results showed that too small of a chord length of the FB increased the design load but reduced the range of positive incidence. The study of [PERSON] et al. [23] indicated that smaller FB corner separation was beneficial to reduce the end-wall loss at design and off-design points. [PERSON] et al. [24] measured the outlet flow field of tandem stators in a low-speed, single-stage test facility. The test results showed that the loss and blockage in the end-wall region were much higher than those in the mainstream area, and the flow between the FB and RB affected the size of the high-loss region in the end-wall area. [PERSON] et al. [25] compared a tandem-blade compressor stage and a conventional-blade compressor stage with the same loading coefficient of 0.46. The experimental results confirmed that tandem blades were able to improve the loading limit of compressors. Meanwhile, it was found that at high incidence, the complex interaction between the FB and the RB corner separation of tandem stators would cause significant deterioration of the flow field and had no advantage compared with conventional stators. The above research showed that the tandem stator in the compressor did not show obvious performance advantages like the two-dimensional tandem cascade due to the complex three-dimensional flow. At present, the research on three-dimensional flow of tandem stars was mostly based on cascade wind tunnels, and there was less research on real flow in compressor stage components. On the other hand, the complex flow mechanism in tandem blades was not fully revealed, especially the influence mechanism of the RB on the FB end-wall flow, the influence mechanism of the FB on the RB end-wall flow, and the corner stall in the tandem stators, which made it difficult to effectively improve the loading limit of compressors and limited the application of tandem stators in high-loading compressors. Therefore, the loss development and flow structure of tandem stators in a high-loading compressor with a loading factor of 0.46 (based on the tangential velocity of the rotor tip) were analyzed by means of experiment and numerical simulation, and the loss mechanism of tandem stators was revealed. The present research could provide support for the application of tandem stators in high-loading compressors.
## 3 Methodology
### Static Reconfiguration  
The non-uniformity in the sum of row irradiances is the main cause of mismatch issues of TCT configuration PV arrays. [PERSON] [42] pointed out that, to maximize the available power at the PV array output, it is desirable that none of the series-connected rows of parallel-connected PV modules limit the current flowing in a single string. If the total irradiance and current of each row are equal, the mismatch loss is minimized, and the actual output power is close to the theoretical output power. Hence, the criterion for static reconfiguration of TCT-configured PV arrays is to achieve power balance among the rows by adjusting the interconnection relationships of the PV modules.  
The shadows in terrestrial PV systems caused by local obstructions such as surrounding buildings and vegetation usually exhibit a concentrated distribution. This localized shading results in PV array's mismatch loss and significantly reduces the output power. The objective of PV array static reconfiguration is to evenly disperse concentrated shadows across the entire array, thereby reducing mismatch losses. Figure 5 illustrates the distribution of shadows before and after the static reconfiguration of terrestrial PV systems. Static reconfiguration does not require additional switches or actuators, nor does it necessitate consideration of the increased cable weight cost resulting from heightened complexity of the configuration [43]. For airship PV arrays, the shadows exhibit a regular distribution, requiring a design that considers this distribution characteristic. Simultaneously, the complexity of module interconnections must be considered to minimize additional cable weight costs.
# Hybrid Multi-Agent GraphRAG for E-Government: Towards a Trustworthy AI Assistant
## 2 Background
### Modularity, Explainability, and Methodological Foundations of GraphRAG
Modern GraphRAG architectures are modular, typically consisting of three stages: graph-based indexing, graph-guided retrieval, and graph-enhanced generation [17]. * Graph-based indexing involves converting raw corpora into text-attributed graphs using LLM-driven entity and relation extraction, as seen in GRAG [18] and StructuGraphRAG [14]. * Graph-guided retrieval may employ various techniques, ranging from rule-based reasoning, LM-based similarity scoring (e.g., KG-GPT), or GNN-based ranking (e.g., GNN-RAG, GraphRAG-FI) [29]. * Graph-enhanced generation integrates subgraphs into prompts using CoT-style or memory-based conditioning strategies, sometimes leveraging attention-based alignment or logits-based fusion to combine LLM's internal knowledge with retrieved content [14; 29]. Some frameworks, such as GraphRAG-FI and RoG, implement filtering and integration mechanisms to mitigate retrieval noise and overreliance on external sources. These models leverage internal model confidence (logits) and relevance scoring to balance between intrinsic and extrinsic knowledge sources [29].
## 5 Conclusions  
The surface subsidence of the Taibao lead-zinc mine was monitored utilizing Sentinel-1A imagery and PS-InSAR technology while analyzing the movement of overlying rock strata and surface before and after implementing various treatment methods in the goat. The obtained results indicate that:  
Reserved pillars fully support the roof of the closed goat. The surface subsidence negatively correlates with pillar stability and is highly susceptible to mining disturbances. The secondary equilibrium of rock mass stress requires a longer duration, resulting in extended surface subsidence cessation;  
The pillars play a crucial role in providing initial support to the roof during local goat filling treatment, and there exists a negative correlation between surface subsidence and stope span. The control of surface subsidence becomes more pronounced when the pillars are less stable and cover larger areas. As the filling materials near the pillars compact, surface subsidence gradually diminishes. In unfilled areas, the rate of surface subsidence remains relatively constant during the initial stage of treatment but gradually slows down until it ceases completely in later stages;  
The initial roof and pillar of the goat are the key factors in controlling surface settlement, and surface settlement is positively correlated with an unstable roof, unstable pillars, and mining depth; after the filler is compacted, the backfill controls the surface settlement, and surface settlement in an area with shallow mining depth and stable pillars tends to be stable at first, and the time needed for the surface settlement to stabilize gradually extends with increases in mining depth, unstable pillars, and the number of roofs.  
Conceptualization, H.L.; Investigation data analysis, X.H. and X.L.; Writing--original draft preparation, S.D. and Y.Y.; Writing--review and editing, H.D.; Visualization, W.X.; Supervision, X.H. and X.L. All authors have read and agreed to the published version of the manuscript. This research received no external funding.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The Sentinel-1 datasets can be acquired freely from Copernicus and ESA, [[https://search.asf.alaska.edu/#/](https://search.asf.alaska.edu/#/)]([https://search.asf.alaska.edu/#/](https://search.asf.alaska.edu/#/)) (accessed on 21 December 2022); optical imagery data can be obtained from Google Maps, [[http://www.gditu.net/](http://www.gditu.net/)]([http://www.gditu.net/](http://www.gditu.net/)) (accessed on 19 June 2020 and 11 December 2022); level monitoring data is obtained from Taibao.  
**Acknowledgments:** The authors would like to thank Taibao for providing free monitoring data on the level of the mine; the authors would like to thank the Copernicus program for free access to the Sentinel-1 images processed in this analysis; the authors would also like to thank Google for providing free optical imagery data of the mine.  
**Conflicts of Interest:** The authors declare no conflicts of interest.  
**Appendix A**
###### Abstract  
Next-generation passive optical networks (NG-PONs) are considered an essential solution for optical architectures, owing to the benefits of energy savings, service transparency, supporting several subscribers, and cost-effectiveness. In this work, a linearly polarized (LP [0,1]) modal bidirectional NG-PON using a graded-index multimode fiber (GIMMF) and free space optics (FSO) is realized. Four downlink/four uplink wavelengths are utilized under the impact of GIMMF nonlinearity, lens losses, and noise with a 100 m FSO link under clear air and weak turbulence. The results depict that a reliable 5.5 km range is obtained at an aggregate symmetric data rate of 40 Gbps. Also, the minimum focal length and lens reflectance of 0.085 m and 12-14.5% in the downlink as well as 0.08 m and 17-19% in the uplink are required, respectively, for a \(10^{-9}\) bit error rate over a 5 km range. It is also realized that the generated LP modes offer an optimum power fraction of 0.52 to \(\sim\)1 \(\times\)\(10^{-11}\) in the downlink and 0.53 to 1 \(\times\)\(10^{-10}\) in the uplink and phase values of 0.23 to 4.79 rad in the downlink and 0.96 to 5.81 rad in the uplink direction. Compared to other systems, the proposed design shows optimum performance and offers a \(-\)25.47 dB gain, a 28.84 dB noise figure, a \(-\)18.46 dBm output signal, and a 30.51 dB optical signal-to-noise ratio.  
references: 30 January 2025  
21 February 2025  
Accepted: 27 February 2025  
Published: 28 February 2025  
Citation: [PERSON]; [PERSON] Design and Investigation of Linearly Polarized Modal Next-Generation Passive Optical Network-Free Space Optics System Considering Fiber-Wireless Link Losses  
2025  
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# Quantum Key Distribution with Post-Processing Driven by Physical Unclonable Functions
## 2 Results and Discussion
### Large QKD networks
For the sake of clarity, we write the latter key as a concatenation of two smaller keys, i.e., \(\bar{k}_{\text{M,A}}||\kappa_{\text{M,A}}\). [PERSON] contacts the KDC and requests connection with [PERSON], who is already in the network. The key manager calculates \(\bar{k}_{\text{M,C}}\oplus\bar{k}_{\text{M,A}}\) and sends it to [PERSON] over a classical channel. The message is authenticated with the key \(\kappa_{\text{M,A}}\). Upon receipt of the message, [PERSON] confirms its origin, and she adds her key to the received message to obtain \(\bar{k}_{\text{M,A}}\oplus(\bar{k}_{\text{M,C}}\oplus\bar{k}_{\text{M,A}})= \bar{k}_{\text{M,C}}\). Hence, [PERSON] and [PERSON] share a common secret key, which can be expanded through QKD. It is worth emphasizing here that the realization of the ideas we have just presented does not require a QKD link between each user and the KDC. As shown in Figure 6, the manager and the user can agree on a common secret key by means of classical communication and local operations on their PUFs. The only requirement is for the manager to communicate a randomly chosen challenge to [PERSON] over a public channel. This allows a lot of flexibility with respect to the physical topology of the network, in the sense that there are no limitations associated with the transmission of quantum signals on the spatial separation between a user and the KDC. In the absence of QKD links between the KDC and the users, all the key material is provided only by the PUFs, and thus it is limited by the number of challenge-response pairs that can be supported by the PUFs under consideration. In this context, strong PUFs are preferable. However, even though a QKD link between [PERSON] and the KDC imposes limitations on the distance, at the same time it allows for the expansion of an initial key that has been obtained through PUFs. In this case, the network may become self-sustainable, with respect to the generation and the consumption of key material, and its operation is not expected to depend strongly on the type of used PUFs. Figure 7: Schematic representation of the procedure through which [PERSON] and [PERSON] can establish a common secret key, with a third party acting as a relay.
## 3 Results and Discussion
### Baseline Case Study of the Solar ORC System Performance  
The parameters of interest to this baseline study include the working fluid mixture components, mass fraction of each component, hot source temperature, and cold source temperature. The standard operating conditions are listed in Table 3.  
In order to accomplish the objective of implementing the ORC with a flat plate solar collector, hot and cold source temperatures at 85 \({}^{\circ}\)C and 25 \({}^{\circ}\)C, respectively are tested for each working fluid to determine the ORC's capacity to operate at these temperatures. An evacuated tube solar collector can be used to achieve temperatures up to 110 \({}^{\circ}\)C. Many of the working fluid mixtures do not yield results for overly high temperature above 85 \({}^{\circ}\)C and for low temperature below 25 \({}^{\circ}\)C, so it is necessary to find mean temperatures that would allow those mixtures to operate in solar ORC systems.  
Several parameters in the ORC model are adjusted to ensure that reasonable results can be derived. These parameters are listed in Table 4 for each working fluid mixture. The expander efficiency is assumed to be 80% and the superheating amount to be 5 \({}^{\circ}\)C; these are reasonable assumptions for the ORC performance analysis. The overall mass flow rate of the mixture is evaluated using the weighted linear interpolation method. For each component, the mass flow rate is considered to be the average of its minimum and maximum mass flow rates in Equation (19).  
\[\dot{m}_{mix}=x_{A}\dot{m}_{A}+x_{B}\dot{m}_{B} \tag{19}\]  
where \(\dot{m}_{mix}\) is the mass flow rate of the mixture, \(\dot{m}_{A}\) is the average mass flow rate of the first component of the mixture, \(x_{A}\) is the mass fraction of the first component, \(\dot{m}_{B}\) is the average mass flow rate of the second component of the mixture, and \(x_{B}\) is the mass fraction of the second component.  
Figure 4: Comparison between simulation and experimental results in ORC system using R245 fa/R123 working fluid mixtures for validation study.
## 5 Model-Based Predictive Control of the VSI
### Incremental Formulation
\begin{bmatrix}-\mathbb{I}_{6\times 6}&\mathbf{0}&\mathbf{0}& \cdots&\mathbf{0}\\ \mathbf{A}_{\mathbf{e}}&-\mathbb{I}_{6\times 6}&\mathbf{0}&\mathbf{B}_{\mathbf{e}}& \mathbf{0}\\ \mathbf{0}&\mathbf{A}_{\mathbf{e}}&-\mathbb{I}_{6\times 6}&\ddots&\mathbf{B}_{\mathbf{e}}\\ \vdots&\ddots&\ddots&\ddots&\ddots\\ \mathbf{0}&\cdots&\cdots&\cdots&\cdots\end{bmatrix} ,\ \mathbf{f}= \begin{bmatrix}-\Delta\mathbf{\tilde{x}}_{0}\\ \mathbf{0}\\ \mathbf{0}\\ \vdots\\ \mathbf{0}\end{bmatrix} . \tag{39}\]  
The constraint in (39) represents the current behavior of the system while forecasting its future dynamics over \(N\) steps to ensure optimal performance. The constraints on the LC filter current and the modulated voltage are formulated as the inequality constraints in (37), where  
\[\mathbf{P}= \begin{bmatrix}\mathbf{I}_{\mathbf{e}}&\mathbf{0}&\mathbf{0}& \mathbf{0}&\ldots&\mathbf{0}\\ \mathbf{0}&\ddots&\mathbf{0}&\mathbf{0}&\ldots&\mathbf{0}\\ \mathbf{0}&\mathbf{0}&\mathbf{J}_{\mathbf{e}}&\mathbf{0}&\ldots&\mathbf{0}\\ \mathbf{0}&\mathbf{0}&\mathbf{0}&\mathbf{E}&\ldots&\mathbf{0}\\ \vdots&\vdots&\vdots&\vdots&\ddots&\mathbf{0}\\ \mathbf{0}&\mathbf{0}&\mathbf{0}&\mathbf{0}&\mathbf{E}\end{bmatrix} ,\mathbf{a }= \begin{bmatrix}\Delta\mathbf{\tilde{x}}_{\min}\\ \Delta\mathbf{\tilde{x}}_{\min}\\ \Delta\mathbf{\tilde{u}}_{\min}\\ \Delta\mathbf{\tilde{u}}_{\min}\\ \Delta\mathbf{\tilde{u}}_{\max}\end{bmatrix} ,\mathbf{b}= \begin{bmatrix} \Delta\mathbf{\tilde{x}}_{\max}\\ \vdots\\ \Delta\mathbf{\tilde{x}}_{\max}\\ \Delta\mathbf{\tilde{u}}_{\max}\\ \vdots\\ \Delta\mathbf{\tilde{u}}_{\max}\end{bmatrix} . \tag{40}\]  
Solving the optimization problem (35), subject to the constraints (36) and (37), the algorithm computes the MPC output thought the OSQP solver using the RHC approach:  
\[\Delta\mathbf{\tilde{u}}_{0}=\text{OSQP}(\mathbf{H},\mathbf{h},\mathbf{F}, \mathbf{f},\mathbf{P},\mathbf{a},\mathbf{b}), \tag{41}\]  
where the control of the system is given by the following:  
\[\mathbf{u}_{t}=\Delta\mathbf{\tilde{u}}_{0}+\mathbf{u}_{t-1}+\Delta\mathbf{ \tilde{u}}_{s,t}. \tag{42}\]  
Interested readers are encouraged to consult [25] for more information on the OSQP solver. The proposed control strategy in (42) achieves reference tracking of the capacitor voltage in the VSL. Additionally, it accounts for operational constraints on the modulated voltage and physical limitations of the filter current through a QP approach. Including deviation variables in the MPC accelerates the system's steady-state convergence by feed-forwarding the steady-state operating point, thereby feeding forward the reference and the known disturbances and improving the system's time response. For embedded implementation, this work reformulates the equivalent optimization problem using the condensed approach for a more efficient implementation [35], achieving reduced computational costs and enabling average solution times of 70 \(\upmu\)s. Details of the condensed implementation are provided in Appendix A.
# Sustainable Support Material for Overhang Printing in 3D Concrete Printing Technology
## 4 Conclusions  
This study developed a temporary support material for the 3 DCP process, designed to support overhang sections during printing. Once the primary concrete hardens enough to be self-supporting, the temporary support can be easily removed. The material, made with non-reactive components like fly ash, recycled glass powder, and natural sand, remains in a paste form, ensuring easy removal even after the concrete has fully hardened. Below are the key conclusions drawn from this study:  
* Increased recycled glass content leads to higher dynamic and static yield stress.
* Higher recycled glass content improves buildability but reduces pumpability.
* Mixtures with up to 60% recycled glass were pumpable, but those with 65% and 70% content were not.
* Decreased flowability is caused by a higher amount of recycled glass due to particle interlocking.
* Increased fly ash content improves flowability due to the \"ball bearing effect\" of spherical particles.
* Higher recycled glass content enhances buildability by supporting more layers.
* The flow table test showed reduced flowability with higher recycled glass content.
* Uniaxial compression tests indicated increased compressive strength up to 65% recycled glass content, but a decrease at 70% due to shear cracking.
* Balanced optimization was achieved between flowability and buildability, resulting from a mixture with 60% recycled glass content.  
The optimized support material was successfully validated through the printing of a structure with a free-form opening and overhang section. While this study primarily focused on the immediate behavior of the support material under incremental stresses, it is acknowledged that incorporating time-dependent measurements of both creep and compressive strength would offer a more comprehensive understanding of material performance. Future research should address these aspects to evaluate the long-term stability  
Figure 17: Free-form overhang section after removal of support material.  
and deformation tendencies of the material under sustained loads, thereby enhancing the reliability and applicability of 3D concrete printing technologies. Nevertheless, this innovation enables 3 DCP to create complex free-form designs without the need for costly, labor-intensive external supports. Also, the material provides crucial stability during the printing of inclined walls, offering a higher degree of design freedom and enhancing the overall potential of 3D concrete printing in advanced architectural applications.  
The authors declare no conflict of interest.
# Design Options to Improve the Dynamic Behavior and the Control of Small H-Darrieus VAWTs
## 4 Discussion
### Variation of the \(G\) (Geometry) Index  
The index \(G\) collects several parameters as the rotor diameter \(D\) and its aspect ratio \(AR\). These are typical input parameters derived from early design considerations. The diameter can be deduced from the choice of a given swept area \(A_{D}=DH\), which is a direct consequence of the target AEP of the turbine; once \(A_{D}\) and \(AR\) are defined, the diameter can be deduced as follows:  
\[D^{2}=\frac{A_{D}}{AR}\]  
It is evident from the analysis of this index that low diameter VAWTs determine a drastic decrease in the inertia, but of course, the AEP is also correspondingly limited by adopting a reduced rotor aspect ratio [5]). Therefore, the target design considerations set this index as fixed and not negotiable.  
The number of the blade could be reduced, in principle, from the standard numbers (four or five) to three, or two, or even one, but this could lead to an increase in the torque ripple that may be unacceptable, both from the mechanical and the electrical point of view. Additionally, the noise emission can be affected by the blade reduction. Moreover, a reduction in the blade number can determine a reduction in the solidity: only if the chord length is increased by the corresponding ratio of blades reduction, there is no alteration. It follows, for instance, that by reducing from three to two blades, the WTI will increase by a factor of 1.5.  
The adoption of a well-designed internal spar can allow maximum increments from \(1^{2/3}=1\) of full square sections to \(10^{2/3}\approx 4.64\), or even \(100^{2/3}\approx 21.64\) of well-designed, structurally optimized open sections, indicating the need for an advanced structural design, possibly carried out with FEM tools. Squared or circular full sections are adopted only in very simple low technology projects and, typically, good designs already start from spar caps and shear web. In composite blades, the inner shear web connection is manufactured either with the spar caps built as part of the shell (and a separate shear web bonded between them) or by building the shear webs and spar caps together as a box spar (and thus glued into the shell). Alternatively, the shear web is directly extruded (in aluminum blades) or purtuded (in reinforced plastic blades). As a consequence, the room for improvement of WTI by operating on a spar and shell-type can in the order of about 4 to 5 times. Good knowledge of the material properties and the fabrication process is essential to reduce the safety factors, with a beneficial effect on WTI. This goal can be pursued by specific tests to characterize the safety factors to reduce the general guidelines given by the IEC norms [46], which can be reduced by a factor of about two, determining an increase in WTI of about 1.6 times.