Observation Platform Research Articles

Experimental study of a miniature organic Rankine cycle unit using ocean thermal energy

Miniature ocean thermal energy conversion (OTEC) unit is an attractive candidate for sustainable energy supply of autonomous ocean observation platforms. Due to the variability of power load, the OTEC remains susceptible to operation under off-design conditions. A miniature ORC-based OTEC unit was developed and constructed. The performance of the unit under design and off-design was experimentally examined. The effects of operating parameters (i.e., pump frequency and turbine frequency) on power generation and thermal efficiency were evaluate using response surface methodology. The results indicate that the unit can produce 0.917 kW net power with a thermal efficiency of 1.46% at 27 ℃ heat-source temperature and 6 ℃ cold-source temperature. Off-design steady-state assessment allows a wide operability range of working-fluid flow rate between 0.18 kg/s and 0.28 kg/s for R134a, corresponding to net power varying between −92 W and 166 W, as well as net thermal efficiency varying between −0.25% and 0.31%. Pump frequency is the primary operating variable affecting the unit performance, followed by turbine frequency. The optimal turbine frequency maximizing thermal efficiency increases with pump frequency, varying between 105 and 160 Hz. When the pump frequency is 32 Hz, the optimal turbine frequency is approximately 160 Hz, which corresponds to the maximum net output of 166 W. The current study offers experimental and theoretical supports for the design and operation of ORC-based OTEC unit.

Does mean sea level trend mask historical storm surge trend: evidence from tropical cyclones affecting Japan since 1980

Variability in storminess, storm surge, and mean sea level (MSL) can substantially alter coastal hazards associated with extreme sea levels (ESLs). However, the detection and attribution of the past changes in tropical cyclone (TC) activity and associated storm surges are hampered by the inhomogeneous TC records. In this study, we investigate spatiotemporal changes in storm surge levels in Japan from 1980 to 2019, a period when observational platforms including tide gauges and storm records are highly consistent. We find statistical evidence supporting the increase in surge annual maxima in several places including the bay area of Tokyo since 1980. This rate of change is comparable to that observed for MSL rise over the same period. These findings cast doubt on the current hypothesis underlying the flood adaptation plan, which assumes that future surge extremes will remain the same and only considers MSL changes. We demonstrate that the changes in ESL in the last 40 years cannot be explained by the rise of MSL alone. Rather, the northeastward shifting of TC landfall location along with intensifying and widening of TCs, might have altered the likelihood of ESL, including surge extremes. The substantial influence of these TC meteorological variables on surge levels combined with the rise of MSL, suggests that current coastal planning practices including critical heights for flood defenses might be inadequate in the future.

The Exploration of Ink Formulations in Binder Jet 3D Printing Drugs.

The application of binder jet 3D printing technology in the pharmaceutical field is developing rapidly. The properties of the ink are very important, affecting the stability of the ejection and the precision of the finished product, but there is a great lack of research on pharmaceutical inks. This study used solvents and excipients commonly used in pharmaceuticals to quantify the printability of inks using printability Z value theory, while using an ink-jet printing and observation platform to analyze the droplet ejection state of different composition inks from microscopic level. Studies have shown that compared to ethanol, the ejection effect of droplets was better when isopropanol was added to the ink, and the proportion added should not be greater than 40%; as the molecular weight of polyvinylpyrrolidone (PVP) increased, the concentration of PVP tolerated by the ink decreased; glycerin has a high ejection efficiency when the proportion is within 10%. In summary, a superior ink formulation of 40% aqueous isopropanol plus 0.1% PVP K30 and 4% glycerin was obtained. With this ink, levetiracetam dispersible tablets were prepared with a smooth printing process and the tablets had good appearance, good mechanical properties, and rapid release. This study provides a mutual validation of the Z value theory and the results of droplet ejection and tablet printing, while providing good ideas.

Dynamic modeling, motion analysis and fault diagnosis of underwater gliders with the loss of one wing

Underwater glider is one of the most promising ocean observation platforms and plays an important role in ocean observation and exploration because of its low energy consumption, long endurance and low cost. However, due to the complex and unpredictable ocean environment, many wing loss accidents of underwater gliders have been reported in recent years, which could not only lead to the uncontrollability of mission trajectory, but also cause the interruption of observation research. Therefore, this study explores the fault diagnosis of underwater gliders with the loss of one wing through dynamic modeling and motion analysis. First, a dynamic model of the Petrel underwater glider with the loss of one wing is established by considering the kinematic and dynamic theory, which is fundamentally different from the healthy prototypes. Then, the motion analysis of underwater gliders with the loss of one wing during the diving and climbing phases is performed using the proposed dynamic model, and the control strategy and parameter adjustment method are proposed for maintaining the target heading. Finally, three fault diagnosis methods of underwater gliders with the loss of one wing are proposed to timely and accurately detect the wing loss, which are verified by the massive sea trial data. Furthermore, the dynamic modeling, control strategy and fault diagnosis methods are also applicable to other underwater gliders.

Case Study of the Aerosol Optical Properties in the Atmosphere over Wuhan, China

The research on regional aerosol optical properties is of great significance for exploring climate regulation mechanisms and controlling atmospheric pollution. Based on the solar radiation observation platform, a three-month optical observation of atmospheric aerosols was conducted in Wuhan, China. The daily and monthly variation characteristics of aerosol optical depth (AOD550), Angstrom parameter (α440–870), and turbidity coefficient (β) were revealed, and the interrelations between the three optical parameters were fitted. Then, the potential relationships between atmospheric particulate matter (PM2.5, PM10) with AOD550 and β were discussed. The results show that the average values of AOD550, α440–870, and β in this case study are 0.42, 1.32, and 0.20, respectively. The frequency distribution patterns of the three optical parameters are all unimodal. AOD550 has a good linear correlation system with β, and the Pearson correlation coefficient reaches 0.94, while its correlation with α440–870 is not significant. The daily variation in AOD550 and β both show an increasing trend, and their monthly increases are more than 50%. However, the daily variation in α440–870 is relatively stable, and the fitted line is a nearly horizontal line with no significant monthly variation. The fluctuation of particulate matter concentration affects the aerosol optical properties to some extent, among which β has a prominent effect on the response to the change in PM2.5 concentration with a linear correlation coefficient of 0.861. As the concentration of particulate matter increases, the proportion of fine particulate matter in the atmosphere increases monthly, and the ratio of PM10 to PM2.5 concentrations decreases from 1.8:1 to 1.2:1. Atmospheric pollution conditions are frequent during this observation period, mainly at mildly turbid levels. Atmospheric turbidity shows an increasing trend month by month, and the concentration of particulate matter increases rapidly. The response of atmospheric aerosol optical properties to the changes in fine particulate matter concentration is significant, and controlling the particulate matter content in the atmosphere is an effective means to mitigate aerosol pollution.

Remote anomaly detection for underwater gliders based on multi-feature fusion

As an autonomous platform for long-term observation in the complex ocean environment beyond visual line of sight, the underwater glider (UG) may suffer from some anomalies during the mission. Thus, the anomaly detection of UGs appears to be particularly important for finding malfunction in time and avoiding loss of prototypes. This study considers the limitation of big data transmission in the ocean environment and proposes a remote detection method for Ug anomalies based on multi-feature fusion, which only requires a small amount of data. First, the failure analysis of UGs is performed, and eight characteristic parameters are selected to reflect the anomalies of UGs. Then, the principal component analysis is adopted to fuse the characteristic parameters, which can reduce the dimensions of variables and retain the characteristic information of the original variables to the greatest extent. Finally, the Density-Based Spatial Clustering of Applications with Noise Algorithm is adopted to reduce the false alarm rate of the method. The feasibility of the proposed remote anomaly detection method is verified by the massive historical data of multiple acoustic UGs. It relys on a small amount of data to detect all the abnormal profiles and achieve a decrease in false alarm rate after optimization, which reduce the operational overhead and misson cost.

Study on material removal mechanism and control strategy of multi-axis fast ED-milling

Diffuser-shaped film cooling holes, which have been used extensively in advanced aero-engines, are usually machined by electrical discharge machining (EDM) by means of drilling and die-sinking approaches in a sequence. However, this sequential machining on different types of machine tools suffers from low machining efficiency and accuracy severely. To cope with this problem, a multi-axis fast ED-milling method that uses tubular electrodes and high-pressure inner flush is proposed for various diffuser machining, such that the fabrication of diffusers can be realized on a single machine tool, is developed in this paper. However, the material removal mechanism and proper control strategies in this machining method are yet not fully investigated. To address this issue, with a dedicated observation platform, single-pulse discharge experiments were firstly carried out to achieve a better understanding of the gap discharge phenomena. The observation results imply that a high-pressure inner flushing can significantly promote the expelling of molten material from a molten pool as well as the evacuation of debris from a discharge gap. After that, characteristics of this machining method such as the electrode wear behavior and the gap discharge state variations were analyzed. Based on the analytical results, a dedicated electrode wear compensation strategy was proposed. Machining tests indicate that the new method guarantees rather higher machining efficiency and comparable surface quality in contrast with layer-by-layer fast ED-milling.

An early warning model for starfish disaster based on multi-sensor fusion

Starfish have a wide range of feeding habits, including starfish, sea urchins, sea cucumbers, corals, abalones, scallops, and many other marine organisms with economic or ecological value. The starfish outbreak in coastal areas will lead to severe economic losses in aquaculture and damage the ecological environment. However, the current monitoring methods are still artificial, time-consuming, and laborious. This study used an underwater observation platform with multiple sensors to observe the starfish outbreak in Weihai, Shandong Province. The platform could collect the temperature, salinity, depth, dissolved oxygen, conductivity, other water quality data, and underwater video data. Based on these data, the paper proposed an early warning model for starfish prevalence (EWSP) based on multi-sensor fusion. A deep learning-based object detection method extracts time-series information on the number of starfish from underwater video data. For the extracted starfish quantity information, the model uses the k-means clustering algorithm to divide the starfish prevalence level into four levels: no prevalence, mild prevalence, medium prevalence, and high prevalence. Correlation analysis concluded that the water quality factors most closely related to the starfish prevalence level are temperature and salinity. Therefore, the selected water quality factor and the number of historical starfish are inputted. The future starfish prevalence level of the starfish outbreak is used as an output to train the BP (back propagation) neural network to build EWSP based on multi-sensor fusion. Experiments show that the accuracy rate of this model is 97.26%, whose precision meets the needs of early warning for starfish outbreaks and has specific application feasibility.

A Review on Unmanned Aerial Vehicle Remote Sensing: Platforms, Sensors, Data Processing Methods, and Applications

In recent years, UAV remote sensing has gradually attracted the attention of scientific researchers and industry, due to its broad application prospects. It has been widely used in agriculture, forestry, mining, and other industries. UAVs can be flexibly equipped with various sensors, such as optical, infrared, and LIDAR, and become an essential remote sensing observation platform. Based on UAV remote sensing, researchers can obtain many high-resolution images, with each pixel being a centimeter or millimeter. The purpose of this paper is to investigate the current applications of UAV remote sensing, as well as the aircraft platforms, data types, and elements used in each application category; the data processing methods, etc.; and to study the advantages of the current application of UAV remote sensing technology, the limitations, and promising directions that still lack applications. By reviewing the papers published in this field in recent years, we found that the current application research of UAV remote sensing research can be classified into four categories according to the application field: (1) Precision agriculture, including crop disease observation, crop yield estimation, and crop environmental observation; (2) Forestry remote sensing, including forest disease identification, forest disaster observation, etc.; (3) Remote sensing of power systems; (4) Artificial facilities and the natural environment. We found that in the papers published in recent years, image data (RGB, multi-spectral, hyper-spectral) processing mainly used neural network methods; in crop disease monitoring, multi-spectral data are the most studied type of data; for LIDAR data, current applications still lack an end-to-end neural network processing method; this review examines UAV platforms, sensors, and data processing methods, and according to the development process of certain application fields and current implementation limitations, some predictions are made about possible future development directions.

Hydrodynamics of gas–liquid flow in a capillary at elevated pressure: Implications for the fixation of CO2 into propylene carbonate in microreaction systems

It is an effective method to capture and utilize carbon dioxide (CO2) by using a microreactor to fix CO2 into propylene carbonate (PC). It is important to investigate the hydrodynamics of gas–liquid flow in order to ensure that the CO2 fixation in microreactor is operated under suitable conditions to obtain efficient mass transfer performance. However, few studies have been concerned with PC-CO2 two-phase flow in microreactors, especially at elevated pressures. Therefore, a high-pressure microreactor observation platform is established in this work to explore the hydrodynamics of PC-CO2 two-phase flow at a pressure range of 0.5–3.0 MPa. Three typical patterns such as bubbly flow, slug flow, and slug-annular flow were observed, and the flow pattern diagram at different pressures was plotted using WeG and WeL. The influence of the pressure on flow pattern transition lines was further discussed. Moreover, the effects of pressure on bubble size, liquid film thickness, bubble frequency, and gas volume fraction were investigated, as well as the corresponding correlation models. This work may provide guidance for the operation of gas–liquid microreactor at elevated pressure, especially for the fixation of CO2 into PC.

Data collection optimization of ocean observation network based on AUV path planning and communication

The Ocean Observation Network (OON) is an ocean science and engineering observation platform which integrates underwater wireless sensors, acoustic buoys, submersible buoys, and sonars. The complex underwater environment makes it challenging to place the observation nodes flexibly. In this research, firstly, a novel OON data collection optimization scheme is proposed, which is based on Autonomous Underwater Vehicle (AUV) path planning and communication. By combining the Voronoi diagram and K-means algorithm, an optimized clustering algorithm (VorK-means) is proposed to optimize the location of junction boxes and reduce the losses in the transmission energy of submarine cables in the OON simultaneously. Subsequently, a computational algorithm for AUV data collection position is proposed based on Voronoi vertices and communication circles. Moreover, an improved Grey Wolf Optimization (GWO) algorithm, based on the Levy flight and dimension (LD) search strategy, is proposed and applied for the AUV path planning, which is named LD-GWO. The accuracy and efficiency are validated by applying the proposed algorithms to the Canadian North-East Pacific Time-series Underwater Networked Experiment (NEPTUNE). Compared with the K-means algorithm, the VorK-means algorithm can reduce the total length of submarine cables by nearly 14%, and compared with the GWO algorithm, LD-GWO can obtain shorter data collection paths under identical parameter settings.

College Mathematics Instructors’ Use of Recommended Pedagogical Practices

This study examined the extent to which college algebra instructors employ pedagogical practices previously found to assist students master difficult STEM content material and address their own previous math deficits. Faculty classroom behaviors were assessed with a modified version of the Generalized Observation and Reflection Platform (GORP). While it was not surprising that math faculty frequently lectured and wrote on the board, results also revealed that recommended practices were infrequently employed by instructors teaching college algebra. More specifically, faculty teaching introductory college algebra rarely addressed students’ misconceptions, made references to their students’ prior knowledge, or employed metacognitive teaching strategies. Moreover, while being observed, faculty never applied a mathematical concept to real life. Moreover, mathematics instructors rarely praised their students. The implications of these findings for professional development and hiring requirements are discussed and emphasized for college math department chairs and administrators generally. Results also highlighted the usefulness of the GORP assessment tool for assessing faculty classroom behaviors.

Design and Implementation of Inductively Coupled Power and Data Transmission for Buoy Systems

Moored buoys are important components of stereo platforms for ocean observation, which are crucial in underwater exploration. In complex marine environments, power supply and data transmission between moored buoys and underwater sensors are difficult. To solve these problems, an inductively coupled power and data transfer (ICPDT) scheme based on LCCL-S-LC hybrid compensation is proposed. The power transmission was analyzed by establishing an LCCL-S-LC compensation buoy ICPDT system model. The system efficiency and output power were analyzed when the load changed, and the optimal load resistor for maximum system efficiency was determined. A modulation and demodulation circuit used for data transmission was introduced, the compensation topology parameters of each loop of the buoy ICPDT system were deduced, and the crosstalk between power and data was analyzed and reduced. An ICPDT system prototype was built to verify the system’s feasibility and effectiveness when it was powered by 24 V. The LCCL-S-LC topology reduced the interference between data and power transmission. When the measured output power of the system was 61.5 W, the power transmission efficiency was 78.1%, and the data receiving end could achieve correct demodulation when the transmission rate was 100 kb/s.

A Review of Subsea AUV Technology

The observation and detection of the subsea environment urgently require large-scale and long-term observation platforms. The design and development of subsea AUVs involve three key points: the subsea-adapted main body structure, agile motion performance that adapts to complex underwater environments, and underwater acoustic communication and positioning technology. This paper discusses the development and evolution of subsea AUVs before proposing solutions to underwater acoustic communication and positioning navigation schemes. It also studies key technologies for the agile motion of subsea AUVs and finally gives an example of a solution for implementing underwater AUVs, i.e., the disk-shaped autonomous underwater helicopter (AUH). This paper will provide guidance for the design of subsea AUVs and the development of corresponding observation and detection technologies.

Research on image acquisition and contour extraction algorithm of partial discharge in oil

Abstract Partial discharge in oil paper insulation is an important reason for insulation breakdown. The study of partial discharge in transformer oil is of great significance for ensuring the reliability of transformers. In this paper, a comprehensive observation platform of partial discharge with needle plate electrode and oil-paper insulation is built, and the original shape image set of partial discharge is collected and established. Through multi-channel convolution processing of the true color image, gray level equivalent distribution of 3D section, segmentation stretching of threshold interval and binary neighborhood search, a general technical method suitable for processing a series of low brightness discharge images with background interference is finally obtained.

Winter and summer sedimentary dynamic process observations in the sea area off Qinhuangdao in the Bohai Sea, China

Sedimentary processes in marginal seas play an important role in the biology, physics, and geochemistry as well as ecology of coastal environments and contain abundant information about the material transfer from land to ocean and the regional circulation. Due to the huge sediment discharge of the Yellow River, the Bohai Sea, China is one of the areas with the highest suspended sediment concentration (SSC) in the world. Interestingly, the SSC at the west of the Bohai Sea is low all year round. Thus, it is of great significance to examine the sedimentary dynamic process in this area for better understanding the circulation structure, material exchange and regional environment of the Bohai Sea. Using seabed base observation platform measurements obtained in February 2017 and August 2019, this study examines the winter and summer hydrography and suspended sediment concentration in the sea area off Qinhuangdao located to the west of the Bohai Sea. In summer, the relatively weak residual currents flowed northeastward and showed little correlation with the wind field, especially in the middle layer of the water column. In winter, the residual currents were strengthened, flowing to the northeast during strong wind periods, and predominantly to the southwest during intermittent periods. Moreover, driven by the pressure gradient force associated with the wind-induced sea surface height variations, the winter current was closely related to the wind speed, with correlation coefficients ranging from 0.4 to 0.6 and a time lag of 10 h. The summer SSC was lower and mainly controlled by the tidal current, whereas in winter, owing to the enhanced Reynolds stress and turbulent kinetic energy, strong wind bursts triggered significant sediment resuspension and led to a higher SSC. For the suspended sediment flux (SSF), the advection terms contributed more than 80% in the winter and summer, while the vertical circulation terms contributed 13% in winter, and approximately half that much in summer. Generally, the suspended sediment is transported back and forth, with a little net northward and northeastward motions in winter and summer, respectively. This may explain the low SSC sustaining in coastal Qinhuangdao all year round. These results provide a reference for sedimentary studies conducted in other coastal waters, especially in monsoon-dominating shelf seas.

Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities.

Heat and carbon uptake in the Southern Ocean: the state of the art and future priorities.

A Periodically Updated Adaptive Sampling Framework for Marine Mobile Observation Platforms

Abstract While numerical models have been developed for several years, some of these have been applied to ocean-state sampling. Adaptive sampling deploys limited assets using prior information; then, observation assets are concentrated in areas of greater sampling value, which is very suitable for an extensive and dynamic marine environment. The improved resolution allows numerical models to be used on mobile platforms. However, the existing adaptive sampling framework for mobile platforms lacks regular interaction with the numerical model. And the observation scheme is easy to deviate from the optimal. This study sets up a closed-loop adaptive sampling framework for mobile platforms that realizes the optimization of model → sampling → model. Linking a coupled model with the sampling points of the mobile platforms, the adaptive method configures key sampling locations to determine when and where the sampling schemes are adjusted. With the aid of a coupled model, we selected an optimization algorithm for the framework and simulated the process under the twin experimental framework. This research provides theoretical technical support for the combination of model and mobile sampling platforms. Significance Statement The ocean is very difficult to observe because it is so vast. How to deploy observing assets is a question worth investigating. We designed an adaptive sampling framework for mobile observing platforms to improve the prediction accuracy of numerical models. This framework uses the prediction to design the observation scheme, then the observation to update the prediction, and then the updated prediction to adjust the sampling scheme, which achieves closed-loop optimization. We first selected an optimization algorithm for this framework by comparing experiments. Based on the optimization algorithm, we simulated the closed-loop optimization process. Simulation results show that this framework can significantly increase the efficiency of long-term ocean observations with mobile devices.

Suppression Measures of Partial Discharge at Rod–Plate Connection in Composite Tower

Rods and plates at the connections in composite insulating material towers are commonly fixed to each other by metal bolts, which may cause electrical field distortion at the connections. So, the rod–plate connections are prone to partial discharge under polluted and wet conditions, and the resulting electric field and temperature changes can affect the mechanical and electrical performance of the whole tower. In this paper, an artificial pollution test synchronous observation platform with an infrared and visible light imager, leakage current, and voltage measurement was built to observe the dry band formation and partial discharge at the simplified rod–plate connections in the composite towers. Then, the electric field simulation of the rod–plate connection specimen showed the current density distribution. When combining the test and the simulation, it was concluded that the cause of the partial discharge was the distortion of the current density and, thus, measures to suppress the partial discharge at the rod–plate connections were proposed. Finally, it was verified that the measures can improve the current density distortion phenomenon, delay dry band formation, and effectively suppress the partial discharge at the rod–plate connections under the same test conditions.

All-sky longwave radiation modelling based on infrared images and machine learning

Sky longwave radiation is an important input parameter for heat transfer and radiant energy balance calculations of the building envelope, and it has a significant effect on the accuracy of predictions of the energy consumption of buildings. The ability of the sky to emit longwave radiation needs to be accurately quantified under different weather conditions. In this study, a low-cost sky cloudiness observation platform based on an infrared imager was established, and an algorithm for calculating the cloudiness of the sky dome by stitching and processing infrared images was proposed. A machine learning model was developed by collecting local meteorological data; these data were then input into the synthetic minority oversampling technique algorithm. This model can estimate sky cloudiness based on conventional meteorological parameters. Nine different machine learning algorithms were tested, and a cloudiness prediction model based on the XGBoost algorithm was finally established, which had a prediction accuracy of 88.81%. Furthermore, an all-sky longwave radiation model was developed by introducing cloudiness parameters. The applicability of different longwave radiation models for clear and cloudy skies in subtropical climates was examined, and the coefficient values of the different models were modified. Finally, the formula applicable to subtropical climates was determined via a fitting method.