Stopping Point Research Articles

Resource-Efficient Coverage Path Planning for UAV-Based Aerial IoT Gateway

Unmanned Aerial Vehicles (UAVs) have a lot of potential for developing new applications in a variety of fields, such as traffic monitoring, security, and military applications. In the vast nature of the Internet of Things (IoT) network, UAVs could work as Aerial Gateway (AG) for communications among low-powered and distributed ground IoT Devices (IDs). This research concentrates on the path planning and deployment system that may facilitate decisionmaking and guaranteed resource-efficient UAV mission assignment in serving ground IDs. Due to limited resources, it is essential to take into account several factors when designing such a system, including the AG flight time, the coverage radius, and the ground-to-air system's achievable data rate. As a result, the Energy Efficient Coverage Path Planning (EECPP) algorithm has been proposed. The EECPP is composed of two algorithms: the Stop Point Prediction Algorithm using K-Means, and Path Planning Algorithm using Particle Swarm Optimization. The outcome demonstrates that, in terms of total flight distance, EECPP outperforms Close Enough Traveling Salesman Problem (CETSP) by 19.99%. EECPP reduced energy usage by an average of 56.15% as opposed to Energy-Efficient Path Planning (E2PP). Due to its mobility nature with the addition of effective path planning, the AG is able to hover at each stop point, making it ideal for usage in crowded regions with high demand, emergency circumstances, and distant locations with no access to fixed base stations.

Constructing Coupling Model of Generalized B-Spline Curve and Crown (CMGBCC) to Explore the 3D Modeling of Chinese Fir Polymorphism

Crown simulation based on basis spline (b-spline) interpolation is a compatible method to simulate tree polymorphism at present. However, there are two problems when it simulates the crown: the first problem is that the derivative value at the top point needs to be given manually, and the second is that the type of value point needs to be collected equidistantly. To solve the above problems and realize convenient and accurate tree polymorphism simulation, this study took Chinese fir as the study object, set the crown morphological feature as the model value point, and constructed a coupling model of generalized B-spline curve and crown (CMGBCC) as the constraint condition of the crown shape to simulate the polymorphism in the process of a tree three-dimensional (3D) model. The position and size of the distribution on the 3D model of the branches were constrained by the curve, and the 3D modeling of a Chinese fir polymorphism was constructed. According to the collection of Chinese fir-type value points in the sample plot, the study realized the detailed types of value points’ precise simulation for three polymorphisms of the Chinese fir crown, including natural pruning, crown displacement, and crown shape difference. At the same time, the different withered existence states of the branches were considered preliminarily. Compared to the 3D model with the field survey data, indicating that constructed models could simulate the difference in tree crown morphology precisely, the branch models were separated by convenience to simulate the process of Chinese fir growth. In the process of construction, CMGBCC did not need to add the derivative value in a manual way and could collect the type of value points according to the characteristics of the crown morphological changes completely. Compared to the results of the crown curve constructed, which were based on generalized B-spline (GB-spline) interpolation and b-spline interpolation, it showed that the number of crown value points collected by the GB-spline interpolation method decreased by 18% on average. The precision of the crown shape constraint was improved by 7.63% compared to b-spline interpolation. The 3D modeling of tree polymorphism was combined with the relationship between tree morphology and environment. At the same time, it was convenient to simulate the behavior of forest management measures, such as pruning.

Qualitative Analysis of Tree Canopy Top Points Extraction from Different Terrestrial Laser Scanner Combinations in Forest Plots

In forestry research, for forest inventories or other applications which require accurate 3D information on the forest structure, a Terrestrial Laser Scanner (TLS) is an efficient tool for vegetation structure estimation. Light Detection and Ranging (LiDAR) can even provide high-resolution information in tree canopies due to its high penetration capability. Depending on the forest plot size, tree density, and structure, multiple TLS scans are acquired to cover the forest plot in all directions to avoid any voids in the dataset that are generated. However, while increasing the number of scans, we often tend to increase the data redundancy as we keep acquiring data for the same region from multiple scan positions. In this research, an extensive qualitative analysis was carried out to examine the capability and efficiency of TLS to generate canopy top points in six different scanning combinations. A total of nine scans were acquired for each forest plot, and from these nine scans, we made six different combinations to evaluate the 3D vegetation structure derived from each scan combination, such as Center Scans (CS), Four Corners Scans (FCS), Four Corners with Center Scans (FCwCS), Four Sides Center Scans (FSCS), Four Sides Center with Center Scans (FSCwCS), and All Nine Scans (ANS). We considered eight forest plots with dimensions of 25 m × 25 m, of which four plots were of medium tree density, and the other four had a high tree density. The forest plots are located in central Slovakia; European beech was the dominant tree species with a mixture of European oak, Silver fir, Norway spruce, and European hornbeam. Altogether, 487 trees were considered for this research. The quantification of tree canopy top points obtained from a TLS point cloud is very crucial as the point cloud is used to derive the Digital Surface Model (DSM) and Canopy Height Model (CHM). We also performed a statistical evaluation by calculating the differences in the canopy top points between ANS and the five other combinations and found that the most significantly different combination was FSCwCS respective to ANS. The Root Mean Squared Error (RMSE) of the deviations in tree canopy top points obtained for plots TLS_Plot1 and TLS_Plot2 ranged from 0.89 m to 14.98 m and 0.61 m to 7.78 m, respectively. The relative Root Mean Squared Error (rRMSE) obtained for plots TLS_Plot1 and TLS_Plot2 ranged from 0.15% to 2.48% and 0.096% to 1.22%, respectively.

Fishing Behavior Detection and Analysis of Squid Fishing Vessel Based on Multiscale Trajectory Characteristics

Accurate fishing activity detection from the trajectories of fishing vessels can not only achieve high-precision fishery management but also ensure the reasonable and sustainable development of marine fishery resources. This paper proposes a new method to detect fishing vessels’ fishing activities based on the defined local dynamic parameters and global statistical characteristics of vessel trajectories. On a local scale, the stop points and points of interest (POIs) in the vessel trajectory are extracted. Voyage extraction can then be conducted on this basis. After that, multiple characteristics based on motion and morphology on a global scale are defined to construct a logistic regression model for fishing behavior detection. To verify the effectiveness and feasibility of the method, vessel trajectory data, and fishing log data collected from Chinese ocean squid fishing vessels in Argentine waters in 2020 are integrated for fishing operation detection. Multiple evaluation metrics show that the proposed method can provide robust and accurate recognition results. Moreover, further analysis of the temporal and spatial distribution and seasonal changes in squid fishing activities in Argentine waters has been performed. A more refined assessment of the fishing activities of individual fishing vessels can also be provided quantitatively. All the results above can benefit the regulation of fishing activities.

Short-term bus travel time prediction for transfer synchronization with intelligent uncertainty handling

This paper presents two novel approaches for uncertainty estimation adapted and extended for the multi-link bus travel time problem. The uncertainty is modeled directly as part of recurrent artificial neural networks, but using two fundamentally different approaches: one based on Deep Quantile Regression and the other on Bayesian neural network. Both approaches use a recurrent neural network to predict multiple time steps into the future, but handle the time-dependent uncertainty estimation differently. We present a novel sampling technique in order to aggregate quantile estimates for link level travel time to yield the multi-link travel time distribution needed for a vehicle to travel from its current position to a specific downstream stop point or transfer site.To motivate the relevance of uncertainty-aware models in the domain, we focus on the connection protection application as a case study: An expert system to determine whether a bus driver should hold and wait for a connecting service, thus ensuring the connection, or break the connection and reduce its own delay. Our results show that the proposed quantile sampling method performs overall best for the 80%, 90% and 95% prediction intervals, both for a 15 min time horizon into the future (t+1), but also for the 30 and 45 min time horizon (t+2 and t+3), with a constant, but very small underestimation of the uncertainty interval (1–4 pp.). However, we also show, that the Bayesian model still can outperform the DQR for specific cases. Lastly, we demonstrate how a simple decision support system can take advantage of our uncertainty-aware travel time models to prioritize the difference in travel time uncertainty for bus holding at strategic points, thus reducing the introduced delay for the connection protection application.

Champa in the Medieval Islamic Sources

The establishment and spread of Islam have been associated with the continuity and development of long-distance trade. For a long time, merchants from the Islamic World dominated important trade routes in the Indian Ocean, and the Mediterranean connecting East-West trade. Hence, the information on ports and stopping points increased and contributed to the expanded knowledge of remote lands. On the way to China via the east half of the Indian Ocean, trading ships from the Islamic World anchored on several ports including Champa. So how was Champa described in the writings of the Islamic World? This article introduces central components of Islamic geographical imagination towards Champa and obstacles triggered by the worldview as well as the writing and copying process which we need to bear in mind to dig in further in detail for each toponym. As a case study, the article will analyze the description of Champa-related toponyms in Al-Mas’ūdī’’s Meadows of Gold and Mines of Gems (10th century) and the way those toponyms are mapped by Park Hyunhee- a modern historian.

Particle flow simulation of Brazilian splitting failure characteristics of layered shale

Shale reservoir is the research hotspot in the development of unconventional oil and gas resources. The properties of bedding plane have an important influence on the mechanical behavior of shale. According to the fracture characteristics of layered shale under Brazilian splitting load, the effects of bedding angle, bond strength ratio and natural fractures on the tensile strength and fracture pattern of layered shale in Brazilian splitting test were studied by particle flow code. The evolution mechanism of meso–macro fracture of shale is analyzed by combining the dynamic change process of particle mesoscopic force chain and crack. The results show that three types of fracture patterns are observed: splitting tensile failure of shale matrix, splitting tensile failure along bedding plane and tensile–shear composite failure along shale matrix and bedding plane. Mesoscopic cracks initiate at the top and bottom loading points of the disk. After the peak load, mesoscopic cracks propagate through and appear dense force chains until macroscopic failure occurs. The bond strength ratio of bedding plane affects the failure pattern and peak strength of the specimen. With the increase in bedding angle, the tensile strength decreases gradually. Considering the influence of natural fractures, the tensile strength of shale is lower, and the crack propagation is more complex. The research model and results provide theoretical basis for the mechanical properties evaluation and fracture pattern analysis of shale.

Study of the passengers average waiting time at public transport stops

When predicting public transport routes in cities, important indicators should be considered: the duration of stay on the bus route, passenger flow on the bus route, points of attraction and the passenger’s average waiting time at stops. These indicators are the basis for planning the operation of city transport. In particular, predicting the duration of traffic by studying the average passenger’s waiting time at stops is an important planning tool for transport companies. Therefore, this study can improve the quality of scheduled services by reducing the gap between actual and scheduled travel time. This article discusses this relevance and, based on experimental evidence, points to the benefit of using studies of average passenger waiting times, especially considering population groups. In fact, most of the factors which affect public transport operation, as had been proven by previous studies, follow a definite mathematical methodology. The analysis was performed using the data from field studies of passenger flow at bus stops (Lviv, Ukraine). The study of passengers at stopping points makes it possible to improve the quality of public transport services (calculate travel duration between stops and the duration of stay at them more accurately). The duration of stay at selected objects depending on a number of passengers was studied. Also, there are given the results of a study of the waiting time of public transport passengers at bus stops are given. A comparison of the dependence of the bus waiting time on population groups was obtained. After receiving this information, system operators can design and adjust the data according to the estimated trip duration. Nevertheless, it is necessary to carry out research at different types of stops in different parts of cities to clarify these data and for a more detailed analysis.

Monitoring mass movements using Network-RTK measurement technique and producing potential rockfall scenarios in a paleo-landslide area

Abstract Mass movements resulting from landslides cause significant losses in terms of lives and property. Periodic observations of these movements using geodetic measurement techniques help to prevent these losses. Network-RTK measurement technique produces real-time location with centimeter accuracy, based on phase observations using a network of reference stations. In this study, the paleo-landslide area in the Işıklar location of Trabzon province, Esiroğlu district, Turkey, was chosen as the application area. This study aims to measure the application area between 2019 and 2021, using the Network-RTK technique to determine the mass movements. Additionally, there is a rock block in an area with a steep slope. The possible movement of this rock block is a threat to infrastructure facilities, residential areas, agricultural areas, and life safety if the mass movement continues. Within this scope, the potential movement scenarios of the block were produced using RocPro3D software and UAV photogrammetry. Scenarios following an ongoing mass movements in the region triggering another mass movement are discussed. In the light of the results obtained, mass movements in the vertical direction of up to 28 cm were detected in the area where the rock block is located in the last 2 years. The periodic continuation of mass movements in the study area, declared a disaster-prone area, confirms the importance of the rock block in the region. In another phase of the study, possible movement scenarios of the rock block were examined using a rockfall analysis. In this context, with the help of an unmanned aerial vehicle, a digital elevation model and orthophoto map of the region where the rock block is likely to move was produced and a base map to be used in rockfall analysis was obtained. As a result of the rockfall analysis, maps showing the speed, energy, spread, possible impacts, and stopping points were produced. With the examination of these maps, it has been determined that residential areas, agricultural areas, and infrastructure facilities in the study area may be significantly damaged.

HTA26 Duration and Timing of Treatment Waning: Determining the Start and Stop Points Using Pembrolizumab in NSCLC As a Case Study

Treatment waning is an important uncertainty in health technology assessments (HTAs) when extrapolating immature data cuts of clinical trials.1 This research explored methods for determining the appropriate start and stop points of treatment waning, using mature overall survival (OS) data from KEYNOTE-024 as a case study.

Self-adaptive penalty approach as an alternative technique for lateral load analysis of framed type elevated water tank stagings

Elevated water tanks are vulnerable to lateral loads since heavy mass is concentrated at the top of the slender supporting staging. For the prediction of lateral loads due to earthquakes fundamental time period of tank stagings is essential because it influences the value of the acceleration coefficient from the response spectrum graph. Time period in turn depends on the lateral stiffness of the framed type tank staging. Staging in elevated water tanks is more flexible to lateral loads up to top panel and behaves rigidly above it due to rigid connection of heavy mass which is placed over top of the staging with massive ring girder and monolithic connection of side wall and bottom slab. This rigid behavior will establish kinematic relations among the top nodal points of the staging with container when subjected to lateral loads. The rigid nature of the container and its lateral movement can be stared with the lateral movement of the centre of gravity of the container. Hence, in order to obtain optimum ideal behavior of the staging, centre of gravity of the container connected with top panel top nodal points of the staging with rigid links in the mathematical model. In the current study, Stiffness of the staging is being evaluated by kinematic relations between the centre of gravity point and the top nodal points of the staging using the penalty function approach. Appropriate penalty parameters are identified and have been applied to the elevated water tank staging with different configurations. This approach is much more precise, and it may be employed to design elevated water tank staging.

Backtracking search algorithm with dynamic population for energy consumption problem of a UAV-assisted IoT data collection system

In recent years, collecting data from IoT devices by unmanned aerial vehicles (UAVs) has become a very hot research topic. This paper focuses on the energy consumption problem of a UAV-based IoT data collection system. To solve the considered energy consumption problem, this paper proposes a new population-based optimization algorithm called the backtracking search algorithm with dynamic population (BSADP), which can determine the optimal number and locations of stop points of the UAV simultaneously. In addition, BSADP has a simple framework, which consists of the proposed enhanced backtracking search algorithm (EBSA) and the designed population adjustment mechanism with opposition-based learning (PAMOBL). In the search process, the population is regarded as the entire deployment of the UAV. BSADP firstly generates the trail deployment of the UAV by EBSA and then the next generation deployment of the UAV is produced based on the trail deployment and PAMOBL. The performance of BSADP is investigated by two energy consumption formulations. Experimental results support the superiority of BSADP in optimizing the deployment of the UAV and prove the application value of BSADP in the real scenario. The source code of the proposed algorithm can be found from: https://github.com/jsuzyy/BSADP.

Математическое моделирование натекания водорода в гермзоне реакторного здания АЭС с ВВЭР-1200

Introduction. The patterns of hydrogen-air mixtures formation during the flow of hydrogen into the upper part of a large volume room in the initial moments of time are insufficiently studied. Therefore, the determination of regularities of formation of local explosive and fire-hazardous hydrogen-air mixtures when hydrogen flows into the lower part of the dome space of the reactor building is important. Goals and objectives. The purpose of the article is a theoretical study of occurrence of local fire and explosive zones of the hydrogen-air mixture generated during hydrogen leakage in the containment area of the reactor building in order to substantiate parameters of concentration sensors of the hydrogen concentration control system. To achieve it, a zone mathematical model of hydrogen concentration calculation in a pressurized room has been developed. Numerical experiments on regularities of hydrogen-air mixtures formation have been carried out. Theoretical basis. The generalized three-dimensional non-stationary differential equation of the laws of conservation of mass, momentum and energy is used to calculate local hydrogen concentration fields. The developed zone model makes it possible to determine hydrogen concentrations in the convective column and in the ceiling layer. Results and discussion. The characteristic fields of hydrogen mass concentrations in the volume of the dome space are obtained. It has been shown that at the initial stage of hydrogen leakage, a zone of the ceiling layer is formed under the ceiling of the dome space, which confirms the validity of the usage of the zone model. The hydrogen concentrations obtained by the field and zone models are compared. The distributions of hydrogen mass concentration along the convective column height at different Reynolds numbers in the hydrogen leakage hole have been obtained. It has been shown that hydrogen concentration sensors can detect a hydrogen leakage mode in the dome space only in a narrow area of Reynolds Re = 900–5,000. There is a leakage mode (Re = 3,358), in which the maximum hydrogen volume concentration is generated at the location of the concentration sensors at the maximum size of the fire and explosive hydrogen-air mixture zones in the room. Conclusions. The hydrogen concentration sensors used in the dome space of the NPP reactor building with water-­water reactors may not detect hydrogen at the top point of the dome at a sensitivity threshold of 2 % vol. In this case, in terms of the height of the convective column, hydrogen-air mixtures are formed within the fire and explosive concentration limits.

Identification of Stopping Points in GPS Trajectories by Two-Step Clustering Based on DPCC with Temporal and Entropy Constraints

The widespread adoption of intelligent devices has led to the generation of vast amounts of Global Positioning System (GPS) trajectory data. One of the significant challenges in this domain is to accurately identify stopping points from GPS trajectory data. Traditional clustering methods have proven ineffective in accurately identifying non-stopping points caused by trailing or round trips. To address this issue, this paper proposes a novel density peak clustering algorithm based on coherence distance, incorporating temporal and entropy constraints, referred to as the two-step DPCC-TE. The proposed algorithm introduces a coherence index to integrate spatial and temporal features, and imposes temporal and entropy constraints on the clusters to mitigate local density increase caused by slow-moving points and back-and-forth movements. Moreover, to address the issue of interactions between subclusters after one-step clustering, a two-step clustering algorithm is proposed based on the DPCC-TE algorithm. Experimental results demonstrate that the proposed two-step clustering algorithm outperforms the DBSCAN-TE and one-step DPCC-TE methods, and achieves an accuracy of 95.49% in identifying stopping points.

Bearing Habit of Sapindus mukorossi and the Relationship between the Shoot Characteristics of the Parent and Bearing Shoots and Yield

(1) Research Highlights: Sapindus mukorossi Gaertn has substantial economic and medicinal value as a high-quality raw material for energy, traditional Chinese medicine, and landscaping. However, few studies have focused on the bearing habit and shoot characteristics of S. mukorossi. (2) Background and Objectives: We aimed to investigate the bearing habit of “Yuanhua,” a selective breeding variety of S. mukorossi, and to identify the relationships among shoot characteristics, fruiting, and yield. (3) Materials and Methods: Ten healthy S. mukorossi trees were randomly selected to investigate the number of current-year shoots and bearing shoots. Eight-hundred-fifty current-year shoots of “Yuanhua” S. mukorossi were selected to investigate the number and position of the bearing and vegetative shoots. A total of 210 parent shoots and 145 bearing shoots of “Yuanhua” S. mukorossi were selected to investigate the characteristics. A generalized linear mixed model and a zero-inflated model were used for the analysis. (4) Results: (i) “Yuanhua” S. mukorossi has two types of current-year new shoots. After the new shoots produce leaves, if the growth points at the top continue to produce inflorescences that grow, bloom, and bear fruits, the new shoots are classified as bearing shoots. When the top growth points do not grow and do not produce inflorescences, the new shoots are termed vegetative shoots. The bearing shoots and vegetative shoots sprouted on the S. mukorossi parent shoots and developed into parent shoots in the following year, either developing from the bearing shoots or the vegetative shoots. (ii) The yield was affected by parent shoot characteristics. The type, length, diameter, and slenderness of parent shoots had significant effects on the number of current-year bearing shoots; the top diameter of the parent shoots and the number of current-year vegetative shoots had significant effects on parent shoot yield. (iii) The type of parent shoots, the length, and the top diameter of the current-year bearing shoots had significant effects on the single yield of a bearing shoot. (5) Conclusions: Selecting parent shoots with more bearing shoots and more fruit production according to the type, length, and thickness is a more efficient method for production management.

Multi-IRS and Multi-UAV-Assisted MEC System for 5G/6G Networks: Efficient Joint Trajectory Optimization and Passive Beamforming Framework

This article presents a multi-intelligent reflecting surface (IRS)- and multi-unmanned aerial vehicle (UAV)-assisted mobile edge computing (MEC) system for 5G/6G networks. In the studied system, multiple UAVs are integrated for providing services to large-scale user equipment (UEs) with the help of multiple IRSs. This article aims to minimize the overall cost including energy consumption, completion time, and maintenance cost of UAVs by jointly optimizing the trajectories of UAVs and phase shifts of IRSs. When solving this problem, one has to count in mind the deployment of stop points (SPs) of UAVs, and consider the association among UEs, and UAVs (i.e., which UE will send data to which UAV at which SP), the order of SPs, and the phase shifts of IRSs. Therefore, traditional optimization techniques may not solve the above-mentioned problem in an efficient way. To tackle the above-mentioned problem, this article proposes an algorithm called TPaPBA that consists of four phases. The first phase optimizes the SPs’ deployment via using a differential evolution algorithm having variable population size. As a result, all the SPs of UAVs can be obtained. Then, the second phase optimizes the association among UEs, SPs, and UAVs. Specifically, TPaPBA first adopts a clustering algorithm to optimize the SPs-UAVs association, and then a close criterion is introduced to optimize UEs-SPs association. Subsequently, third phase adopts a low-complexity greedy algorithm to optimize the order of SPs for UAVs. Finally, the phase shifts of IRSs are optimized to enhance the data rate between UEs and UAVs. The simulation results of TPaPBA on ten instances having UEs ranging from 100 to 1000, reveals that TPaPBA has significantly improved the system performance contribution and outperforms other approaches in terms of reducing the overall cost of UAVs.

RevGel-seq: instrument-free single-cell RNA sequencing using a reversible hydrogel for cell-specific barcoding

Progress in sample preparation for scRNA-seq is reported based on RevGel-seq, a reversible-hydrogel technology optimized for samples of fresh cells. Complexes of one cell paired with one barcoded bead are stabilized by a chemical linker and dispersed in a hydrogel in the liquid state. Upon gelation on ice the complexes are immobilized and physically separated without requiring nanowells or droplets. Cell lysis is triggered by detergent diffusion, and RNA molecules are captured on the adjacent barcoded beads for further processing with reverse transcription and preparation for cDNA sequencing. As a proof of concept, analysis of PBMC using RevGel-seq achieves results similar to microfluidic-based technologies when using the same original sample and the same data analysis software. In addition, a clinically relevant application of RevGel-seq is presented for pancreatic islet cells. Furthermore, characterizations carried out on cardiomyocytes demonstrate that the hydrogel technology readily accommodates very large cells. Standard analyses are in the 10,000-input cell range with the current gelation device, in order to satisfy common requirements for single-cell research. A convenient stopping point after two hours has been established by freezing at the cell lysis step, with full preservation of gene expression profiles. Overall, our results show that RevGel-seq represents an accessible and efficient instrument-free alternative, enabling flexibility in terms of experimental design and timing of sample processing, while providing broad coverage of cell types.

Investigation of the Gradient Properties of Samples Obtained by Direct Laser Deposition from a Mixture of Ni/Ti Elemental Powders

The research of deposition of a nitinol sample in an equiatomic ratio from a powder mixture of nickel and titanium 55Ni-45Ti (in wt.%) is aimed at studying the heterogenicity of the chemical composition in the cross-section of a thin-walled and multilayer (bulk) cylindrical sample. The main task of the study was to determine the presence or absence of the chemical composition deviation from layer to layer, and mechanical properties. Analysis on an optical microscope, EDS analysis, and microhardness measurement, a thin-walled sample was studied. A chemical gradient was detected in the sample from the base along with its entire height. An increase in the content of the Ti element and a decrease of the Ni element was detected with an increase in the number of layers and the height of the sample, and a change in the microstructure and hardness were found. The increase in hardness from the base to the top point of the sample reaches 50%. X-ray phase analysis (XRD) showed the presence of NiTi phases in the martensitic and austenitic state, the side phases of NiTi2 in a thin-walled sample, and the presence of the Ni4Ti3 phase and the TiO2 oxide phase in a cylindrical bulk sample. The chemical composition of the cylindrical bulk sample agrees with the chemical composition of the mixture loaded into the powder feeder 55:45 Ni and Ti in wt. %. To indirectly determine the shape memory effect of the final alloy, mechanical tests were carried out for compression of cylindrical samples with subsequent heating, which confirmed the presence of the shape memory effect with a degree of reversible deformation of about 40%.

Time–frequency signal analysis of flow pulsation in siphon outlet conduit based on HHT considering the pump‐conduit interaction

AbstractThe unsteady three‐dimensional numerical simulation calculation of the vertical axial flow pump device is performed based on CFD to examine the pressure pulsation and energy distribution features of the water flow within the siphon outlet conduit (SOC) under the hydraulic coupling of the pump and the flow conduit. The pressure pulsation signals (PPS) of monitoring points are decomposed using the Hilbert–Huang approach via empirical mode decomposition (EMD) and Hilbert spectrum analysis. The results show that the PPS of monitoring points of the SOC has no obvious periodicity. The low‐frequency range below 20 Hz serves as the primary frequency, and the energy ratio of the high‐frequency signal above 700 Hz is less than 1%. Under the condition of a small flow rate 0.3Qbep, there is obvious high‐frequency pulsation above 500 Hz at the inlet of the upstream section of the SOC, and there are periodic components distributed around 200 Hz. The energy of the pressure pulsation is primarily focused in the low‐frequency range below 40 Hz at the SOC outlet section. The PPS at the top and bottom monitoring points of the hump section are consistent, and the pressure pulsation energy (PPE) is mainly concentrated in the low frequency below 40 Hz. In both the big flow condition (1.2Qbep) and the optimal flow condition (1.0Qbep), the PPE of the monitoring points at the top of the hump section is distributed in the middle and low‐frequency band below 40 Hz, and the energy of monitoring points at the bottom of the hump section is concentrated in the low‐frequency band below 20 Hz, accounting for more than 70%. When the flow rate increases from 0.3Qbep to 1.2Qbep, the peak value of the pressure pulsation coefficient at the main frequency of each monitoring point at the top of the hump section changes little, and the peak value of the pressure pulsation coefficient at the main frequency of each monitoring point at the bottom increases first and then decreases. From the upstream section to the hump section of the SOC, the average frequency of each intrinsic mode function (IMF) of the PPS under different flow conditions shows an overall increasing trend. From the hump section of the SOC to its outlet, the average frequency of each IMF of the PPS decreases under the conditions of 1.0Qbep and 1.2Qbep, and there is no obvious change under the condition of 0.3Qbep.

Evaluating Characteristics of an Active Coastal Spreading Area Combining Geophysical Data with Satellite, Aerial, and Unmanned Aerial Vehicles Images

The northern region of the Maltese archipelago is experiencing lateral spreading landslide processes. This region is characterized by cliffs with a hard coralline limestone outcropping layer sitting on a thick layer of clay. Such a geological configuration causes coastal instability that results in lateral spreading which predispose to rockfalls and topplings all over the cliff slopes. The aim of this research was to develop a methodology for evaluating cliff erosion/retreat using the integration of geomatics and geophysical techniques. Starting from a 3D digital model of the Selmun promontory, generated by unmanned aerial vehicle (UAV) photogrammetry, it was possible to map the fractures and conduct geophysical measurements such as electrical resistivity tomography and ground penetrating radar for the identification and mapping of vertical fractures affecting the hard coralline limestone plateau, and to create a 3D geological model of the study area. In addition to this, high-accuracy orthophotos from UAV that were captured between 1957 and 2021 were georeferenced into a GIS and compared to aerial and satellite images. The movement and evolution of boulders and cracks in rocks were then vectorized to highlight, track and quantify the phenomenon through time. The results were used to derive a qualitative assessment of the coastal variations in the geometric properties of the exposed discontinuity surfaces to evaluate the volumes and the stop points of the observed rockfalls. The outcomes of this research were finally imported in a GIS which offers an easy approach for the collection and processing of coastal monitoring data. In principle, such a system could help local authorities to address social, economic and environmental issues of pressing importance as well as facilitate effective planning in view of a risk mitigation strategy.