Variation Trend Research Articles

Investigation on damage-permeability model of dual-porosity coal under thermal-mechanical coupling effect

Understanding the permeability characteristics of coal under mining disturbance is crucial for ensuring coal mine safety and efficient gas extraction. Coal is a dual porosity medium consisting of matrix and fracture, and there are some differences in mechanics and permeability between matrix pores and fracture. However, research on the damage and gas seepage characteristics of dual-porosity coal is limited. In this paper, a coupled damage-permeability model considering matrix pores and fractures in coal is established, incorporating the influences of effective stress, gas adsorption, thermal expansion, and thermal cracking. And the reliability of the newly developed model was verified using experimental data of temperature and pressure variations under different stress boundary conditions. The results indicate that during the elastic stage, the total permeability and fracture permeability of coal exhibit a trend of decreasing and then increasing with pore pressure, while matrix permeability gradually increases. In the full stress-strain stage, the overall damage-permeability and fracture damage-permeability of coal exhibit an “S"-shaped variation trend with axial strain, while matrix damage-permeability shows a slow increasing trend. To accurately characterize the evolution of gas seepage in coal, contributions from matrix pores and fractures must be comprehensively considered, and the effects of gas adsorption, effective stress, thermal cracking, and thermal expansion on permeability cannot be ignored. Furthermore, through parameter sensitivity analysis, it is found that during the elastic stage, coal permeability decreases with an increase in the adsorption sensitivity coefficient and thermal expansion coefficient. In the full stress-strain process, coal permeability increases with an increase in the damage-permeability coefficient. The results of this study are of great significance for predicting the evolution of coal permeability in the working face ahead under mining disturbance.

Dimensional synthesis of an Inspection Robot for SG tube-sheet

To ensure the operational safety of nuclear power plants, we present a Quadruped Inspection Robot that can be used for many types of steam generators. Since the Inspection Robot relies on the Holding Modules to grip the tube-sheet, it can be regarded as a hybrid robot with variable configurations, switching between 4-RRR-RR, 3-RRR-RR, and two types of 2-RRR-RR, and the variable configurations bring a great challenge to dimensional synthesis. In this paper, the kinematic model of the Inspection Robot in multiple configurations is established, and the analytical solution is given. The workspace mapping is analyzed by the solution-space, and the workspace of multiple configurations is decomposed into the workspace of 2-RRR to reduce the analysis complexity, and the workspace calculation is simplified by using the envelope rings. The optimization problem of the manipulator is transformed into the calculation of the shortest contraction length of the swing leg. The switching performance of the Inspection Robot is evaluated by stride-length, turning-angle, and workspace overlap-ratio. The performance indexes are classified and transformed based on the proportions and variation trends of dimensional parameters to reduce the number of optimization objective functions, and Pareto optimal solutions are obtained using an intelligent optimization algorithm.

Integrating patch stability and network connectivity to optimize ecological security pattern

ContextDesigning and optimizing ecological security pattern (ESP) is an effective solution to formulate landscape planning. The commonly used network analysis for ESP optimization abstracts ecological sources and ecological corridors as homogeneous nodes and edges, ignoring the differentiated landscape pattern and patch stability.ObjectivesIt is aimed to construct ESP considering pattern and function, to explore the relationship of patch stability and network connectivity conservation objectives, and to optimize ESP with the integration of the two objectives.MethodsWe proposed a framework for constructing ESP based on ecosystem health and human footprint, and optimizing ESP with network robustness analysis. Land use conflict analysis and node/ edge removal method were further used to assess patch stability and network connectivity, respectively.ResultsESP of Ningxia was composed of 71 ecological sources covering an area of 10970.25 km2, and 150 ecological corridors covering an area of 3950.88 km2. The ecological sources and ecological corridors along the Yellow River had high patch stability but low network connectivity, while the largest ecological source had both high values of the two indicators. With the removal of nodes and edges, connectivity robustness, global efficiency, and equivalent connectivity of the ESP decreased from 1, 0.29, and 342.80 to 0, respectively. The variation trends of the three indicators under different removal scenarios were inconsistent. There was a distinct trade-off between the conservation objectives of patch stability and network connectivity.ConclusionsThis study highlighted how to balance different conservation objectives in landscape planning. Our framework can provide guidance for conservation planners to construct and optimize ESP without losing information due to the element abstraction in network analysis.

Crustal Apparent Density Variations in the Middle Segment of the North Tianshan Mountains and Their Tectonic Significance

In this study, we collected mobile gravity observations in the middle segment of the North Tianshan Mountains from August 2016 to July 2022 and carried out classical adjustment calculations under the constraint of the absolute gravity datum to obtain the spatiotemporal variation pattern of the local gravity field. We used equivalent source inversion to obtain the spatiotemporal variation characteristics of crustal apparent density. We also extracted the coseismic deformation field from SAR data, using the 2016 Hutubi earthquake as an example, and constructed a model of the seismogenic fault. The gravity monitoring network in the study area performed well in resolving the earthquake source parameters. Both the time-varying gravity field and equivalent apparent density variation pattern show prominent zoning characteristics with a smoothly evolving spatial distribution over time. The variation trends of the gravity field and equivalent apparent density are in line with the orientation of tectonic structures, and their anomalous signals can be detected before and after an earthquake. The constructed seismogenic structure of the 2016 Hutubi earthquake indicates a typical thrust earthquake, probably occurring on a north-dipping blind fault beneath a region with intense crustal deformation. The subsurface tectonic system reflected by this earthquake can be informatively extended to the entire middle segment of the North Tianshan Mountains by subsurface configuration. Our findings can serve as a reference for analyzing the source characteristics of the time-varying gravity field and interpreting anomalous pre-seismic signals, and aid in understanding earthquake preparation zones and the mode of crustal tectonic movements.

Experiment for the performance of a thin membrane inclined automatic wicking dew-point evaporative cooling device based on simulation results

The traditional indirect evaporative coolers necessitate a continuous operation of water pumps to ensure the wetting of wet channel walls. However, excessive water spraying can lead to a thickened water film, negatively impacting heat transfer efficiency and generating an additional pressure drop. Identifying suitable water supply strategies and exploring materials for the wet channel that possess good moisture retention and evaporation characteristics has drawn research attention over the years.In this study, an automatic wicking dew-point evaporative cooling device, whose structure was determined by corresponding optimal performance simulation research, was designed and manufactured. The thin film exhibits a certain inclination angle between the dry and wet channels to form a triangular channel to enhance support and increase heat transfer area. Utilizing the automatic water absorption characteristics of the membrane for water supply instead of spraying, makes the water more uniform and heat exchange more efficient. A comprehensive study was conducted on the effects of different operating parameters (working-to-intake air ratio, intake air velocity, water temperature, intake air temperature, and intake air humidity) on the performance of the device. The results indicate that the cooler performs best in high-temperature, low-humidity environments. When the inlet temperature, humidity, and velocity are within the range of 25–45 °C, 20–80 %, and 0.5–2.5 m/s, respectively, with a water temperature of 22 °C and an air-to-water flow rate ratio of 0.5, the maximum temperature drop can reach 14.8 °C, and the cooling capacity per unit area ranges from 13 to 150 W/m2. The wet-bulb efficiency and dew-point efficiency increased from 52.4 % and 33.6 % to 110.6 % and 88.5 %, respectively. When the air velocity increases from 0.5 m/s to 2.5 m/s, the product air temperature increases by 3.1 °C, and the wet-bulb efficiency and dew-point efficiency decrease by 25.1 % and 17.5 %, respectively. However, the variation trends of unit area cooling capacity and energy efficiency ratio (EER) are opposite. The optimal operating conditions are proposed with an air volume ratio of 0.5 and a water temperature range of 22–26 °C. Finally, the temperatures of the product air and water were observed during long-term operation testing to evaluate the stability of the device.

Investigation of decomposition and partial oxidation of mixed acid gas and methane for syngas production

Reaction processes of decomposition and partial oxidation of a mixture of acid gas (H2S and CO2) and methane (CH4) could enable the efficient production of valuable syngas resource (H2 and CO). In this work, the decomposition and partial oxidation of H2S–CH4–CO2 system was experimentally studied in a tube furnace. Effects of temperature, CH4 and CO2 addition, equivalence ratio and residence time were studied for syngas production and H2/CO variation. Extended temperature and pressure were then studied by equilibrium calculation for thermodynamic analysis in Aspen Plus software. The results showed the increasing temperature favored reactant conversion and syngas production. H2S decomposition was the dominant reaction at temperature below 1050 °C while threshold temperature for CH4 conversion over H2S was about 1100 °C. H2 was formed mainly via H2S decomposition at low temperatures. CH4 addition promoted H2 formation and conversely restrained H2S conversion. The introduction of O2 brought partial oxidation, favored the reaction rate, balanced H2/CO but reduced syngas production. H2/CO ratio also remained at an appropriate level at high CO2 addition since CO2 evidently adjusted the ratio via CO2+H2↔CO + H2O. However, this CO2 reactivity was only adequately expressed under high temperature and extended residence time. Equilibrium calculation confirmed experimental variation trends and revealed reducing pressure favored the syngas production. It could be inferred that extended residence time, higher temperature, suitable equivalence ratio, CH4 and CO2 addition and low pressure could enable improvement in both syngas production and H2/CO. This study revealed high syngas production and adjustment of H2/CO could be realized in H2S–CH4–CO2 system and this might be of great practical in industry.

Surface water-groundwater interactions drive the spatial variability of dissolved heavy metals and interfacial fluxes in mangrove intertidal zones

The intertidal aquifer is a crucial area that significantly influences the transport of heavy metals and the health of coastal environment. In this study, we used a 3-dimensional sampling method to analyze the spatial variability of heavy metals in the groundwater of the mangrove intertidal zone in China. The pollution level of heavy metals and their release processes into coastal waters through groundwater discharge were also explored. Our findings revealed high spatial heterogeneity of heavy metals occurred along the cross-shore, parallel-shore, and depth directions. Specifically, heavy metals exhibited inconsistent variation trends between the seawater infiltrated zone and groundwater discharge zone along the cross-shore direction. Fe, Cr, Cu, Zn, and Pb exhibited a similar variation trend along the cross-shore direction, but were opposite to that of Hg and As. In addition, most heavy metals showed higher concentrations in mangrove groundwater compared to inland pond water and coastal seawater, indicating that mangrove intertidal zone played a crucial role in sequestering heavy metals. The spatial variability of heavy metals can be attributed to different exchange types and magnitudes between the surface water and groundwater, as well as the complex biogeochemical reactions. Our study also identified a slight pollution level of Zn and Hg, and high groundwater discharge-derived fluxes of Hg and As compared with other study sites in the world. In addition, this study highlights the importance of considering different groundwater end-member, especially for redox sensitive heavy metals, when determining groundwater discharge-derived fluxes into the surface water in mangrove intertidal zone.

A text analytics approach for mining public discussions in online cancer forum: Analysis of multi-intent lung cancer treatment dataset

BackgroundOnline cancer forums (OCF) are increasingly popular platforms for patients and caregivers to discuss, seek information on, and share opinions about diseases and treatments. This interaction generates a substantial amount of unstructured text data, necessitating deeper exploration. Using time series data, our study exploits topic modeling in the novel domain of online cancer forums (OCFs) to identify meaningful topics and changing dynamics of online discussion across different lung cancer treatment intent groups. MethodsFor this purpose, a dataset comprising 27,998 forum posts about lung cancer was collected from three OCFs: lungcancer.net, lungevity.org, and reddit.com, spanning the years 2016 to 2018. ResultsThe analysis reflects the public discussion on multi-intent lung cancer treatment over time, taking into account seasonal variations. Discussions on cancer symptoms and prevention garnered the most attention, dominating both curative and palliative care discussions. There were distinct seasonal peaks: curative care topics surged from winter to late spring, while palliative care topics peaked from late summer to mid-autumn. Keyword analysis highlighted that lung cancer diagnosis and treatment were primary topics, whereas cancer prevention and treatment outcomes were predominant across multi-care contexts. For the study period, curative care discussions predominantly revolved around informational support and disease syndromes. In contrast, social support and cancer prevention prevailed in the palliative care context. Notably, topics such as cancer screening and cancer treatment exhibit pronounced seasonal variations in curative care, peaking in frequency during the summers (May to August) of the study period. Meanwhile, the topic of tumor control within palliative care showed significant seasonal influence during the winters and summers of 2017 and 2018. ConclusionOur text analysis approach using OCF data shows potential for computational methods in this novel domain to gain insights into trends in public cancer communication and seasonal variations for a better understanding of improving personalized care, decision support, treatment outcomes, and quality of life.

A comparison of next-generation turbulence profiling instruments at Paranal

ABSTRACT A six-night optical turbulence monitoring campaign has been carried at Cerro Paranal observatory in 2023 February and March to facilitate the development and characterization of two novel atmospheric site monitoring instruments – the ring-image next-generation scintillation sensor (RINGSS) and 24-h Shack Hartmann image motion monitor (24hSHIMM) in the context of providing optical turbulence monitoring support for upcoming 20–40 m telescopes. Alongside these two instruments, the well-characterized Stereo-SCIDAR and 2016-MASS-DIMM were operated throughout the campaign to provide data for comparison. All instruments obtain estimates of optical turbulence profiles through statistical analysis of intensity and wavefront angle-of-arrival fluctuations from observations of stars. Contemporaneous measurements of the integrated turbulence parameters are compared and the ratios, bias, unbiased root mean square error, and correlation of results from each instrument assessed. Strong agreement was observed in measurements of seeing, free atmosphere seeing, and coherence time. Less correlation is seen for isoplanatic angle, although the median values agree well. Median turbulence parameters are further compared against long-term monitoring data from Paranal instruments. Profiles from the three small-telescope instruments are compared with the 100-layer profile from the stereo-SCIDAR. It is found that the RINGSS and SHIMM offer improved accuracy in characterization of the vertical optical turbulence profile over the MASS-DIMM. Finally, the first results of continuous optical turbulence monitoring at Paranal are presented which show a strong diurnal variation and predictable trend in the seeing. A value of 2.65 arcsec is found for the median daytime seeing.

Evaluation of AquaCrop’s Ability to Simulate Water Stress Based on 2-Year Case Study of Maize Crop

To apply AquaCrop to the study of agricultural soil moisture in the North China Plain, a water-treatment experiment on summer maize was carried out at the Fengqiu experimental station of the Chinese Academy of Sciences from 2017 to 2018. A water treatment was used to achieve field water capacities of 20 (W1), 40 (W2), and 60 (W3) cm soil layers under irrigation, and a rain-fed treatment (W0) was added. The model parameters were calibrated using the measured data in 2017. Then, they were applied to 2018 to verify the ability of the model to simulate water stress. The results showed that the variation trends for crop yield, canopy coverage, total soil water content, and the curve in the growth cycle simulated via AquaCrop were consistent with the actual observations; the results of a discrete analysis showed that the values of b (regression coefficient), R2 (determination coefficient), and EF (efficiency) were close to 1, and the values of the RMSE (root mean square error) were close to 0, which proved that the model could simulate dynamic changes in summer maize yield, canopy coverage, and total soil water content well. AquaCrop had good applicability in the North China Plain and could be applied to the study of agricultural water consumption and water-use efficiency in this area. The simulated values obtained can serve as an easily obtainable source of long-term experimental data in areas with frequent non-extreme weather events.

Analysis of Factors Driving Subtropical Forest Phenology Differentiation, Considering Temperature and Precipitation Time-Lag Effects: A Case Study of Fujian Province

Subtropical forest phenology differentiation is affected by temperature, precipitation, and topography. Understanding the primary contributing elements and their interactions with forest phenology can help people better comprehend the subtropical forest growth process and its response to climate. Meanwhile, the temporal and spatial variations of phenological rhythms are important indicators of climatic impacts on forests. Therefore, this study aimed to analyze both a total area and different forest growth environments within the whole (i.e., coastal site areas (II, IV) and inland site areas (I, III)) as to spatiotemporal patterns associated with subtropical forests in Fujian Province, which is located at the boundary between the middle and south subtropical zones. Considering the asymmetric effects of climate and forest growth, this study chose pre-seasonal and cumulative temperature and precipitation factors and utilized the GeoDetector model to analyze the dominant drivers and interactions within phenology differentiation in Fujian Province. The results show the following: (1) All of the phenological parameters were advanced or shortened over the 19-year observation period; those of shrubland and deciduous broadleaf forests fluctuated greatly, and their stability was poor. (2) The phenological parameters were more distinct at the borders of the site areas. Additionally, the dates associated with the end of the growth season (EOS) and the date-position of peak value (POP) in coastal areas (i.e., II and IV) were later than those in inland areas (i.e., I and III). Among the parameters, the length of the growth season (LOS) was most sensitive to altitude. (3) Precipitation was the main driving factor affecting the spatial heterogeneity of the start of the growth season (SOS) and the EOS. The relatively strong effects of preseason and current-month temperatures on the SOS may be influenced by the temperature threshold required to break bud dormancy, and the relationship between the SOS and temperature was related to the lag time and the length of accumulation. The EOS was susceptible to the hydrothermal conditions of the preseason accumulation, and the variation trend was negatively correlated with temperature and precipitation. Spatial attribution was used to analyze the attribution of phenology differentiation from the perspectives of different regions, thus revealing the relationships between forest phenology and meteorological time-lag effects, the result which can contribute to targeted guidance and support for scientific forest management.

Research on the Reinforcement Effect and Bearing Characteristics of High-Pressure Jet-Grouting Piles on Covered Road Composite Ground in Landfill Sites

There is a notable difference between garbage pile foundations and general site foundations; due to their uneven particles, complex structure, and diverse composition, there are relatively few cases that can be used for reference. In this study, with the aim of renovating a landfill in Shenzhen, bearing-layer reinforcements were introduced in the overlying road of a garbage heap dominated by construction waste. The bearing capacity of a single-pile composite foundation was studied through a core-pulling test of high-pressure jet-grouting piles, a static load test of the bearing capacity of the single-pile composite foundation, design estimation, and numerical analysis. The results show that the obtained eigenvalue of the design estimate was 267.8 kPa, and the eigenvalue of the field test was between 182.58 kPa and 196.89 kPa, meeting the design requirement of an eigenvalue of no less than 175 kPa. The bearing capacity of the composite foundation of the single jet-grouting pile was analyzed using the ABAQUS numerical simulation software; the characteristic value of the bearing capacity of the single-pile composite foundation was 186.01 kPa, and the variation trend of its settlement–load curve was the same as that of the field test results, which met the design requirements. High-pressure jet-grouting pile technology has achieved remarkable results in the reinforcement of foundations that are mainly composed of construction waste.

Change trends of mean ice thickness, water level, and surface salinity in the Laptev Sea in winter-spring period under further climate warming conditions

he purpose of the paper is to identify the most likely trends in interannual changes of the ice cover thickness on sections of the Northern Sea Route in the Laptev Sea in the winter-spring months under conditions of further climate warming. A hypothesis that in the modern period such changes can be significantly impacted by melting of submarine permafrost layers located inside the sea shelf, — a process caused by their heat exchange with bottom sea waters, is put forward. To verify the hypothesis, trends in interannual changes in ice thickness are compared with trends in variations in sea level and surface salinity. As factual material, data from the global reanalysis GLORYS12v1 is used. The research methodology is based on the standard methods of mathematical statistics. A correlation between the trends of the above processes has been found. It allows us to confirm the hypothesis put forward. The results obtained indicate that, under the conditions of ongoing climate warming, there remains a high probability that the average thickness of the ice cover will not decrease, and the ice situation in the Laptev Sea in the winter-spring months will not improve significantly. The latter confirms the need and feasibility of further development of the Russian icebreaker fleet

Evaporation characteristics of cis-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(Z)) droplet in high pressure and temperature environments

Cis-1,1,1,4,4,4-hexafluoro-2-butene (R1336mzz(Z)) has emerged as an exceptionally promising low-global-warming-potential (GWP) refrigerant, ideal for spray cooling systems in the thermal management of electronic components. Research on the evaporation characteristics of an individual isolated cryogen droplet excludes uncertainties caused by droplet collisions and fusion, thereby laying the foundation for spray cooling. In this paper, a theoretical model for single R1336mzz (Z) droplet evaporation considering the effect of natural convection in a high pressure and temperature environment is proposed. The newly proposed model is validated by comparing the predicted results of the R1336mzz(Z) droplet evaporation with experimental data. Then, the effects of environmental temperature (323–523 K) and pressure (1–20 bar) on the R1336mzz(Z) droplet evaporation are investigated. The results reveal that the effect of increasing the ambient pressure on the droplet lifetime of R1336mzz(Z) undergoes a transition from deceleration to acceleration. Elevated temperature can promote droplet evaporation; however, the promoting effect of increasing the ambient temperature on droplet evaporation will be weakened in high-pressure cases. Increasing the ambient pressure and temperature both can enhance the heat transfer from the environment to the droplet through natural convection, while increasing the pressure greatly inhibits the molecular diffusion during droplet evaporation. Thus, the total evaporation rate depends on the competing effects of these two factors. In addition, the trend of the droplet temperature variation could differ based on droplet initial temperatures, ambient temperatures, and pressures. An increase in the ambient temperature or pressure corresponds to an increase in the droplet equilibrium temperature (Tequ). However, Tequ is almost independent of the droplet initial size and temperature.

National Variability in Pacemaker Implantation Rate Following TAVR: Insights From the STS/ACC TVT Registry

BackgroundAlthough permanent pacemaker (PPM) implantation is a common complication of transcatheter aortic valve replacement (TAVR), hospital variation and change in PPM implantation rates are ill defined. ObjectivesThe aim of this study was to determine hospital-level variation and temporal trends in the rate of PPM implantation following TAVR. MethodsUsing the American College of Cardiology/Society of Thoracic Surgeons TVT (Transcatheter Valve Therapy) Registry, temporal changes in variation of in-hospital and 30-day PPM implantation were determined among 184,452 TAVR procedures across 653 sites performed from 2016 to 2020. The variation in PPM implantation adjusted for valve type by annualized TAVR volume was determined, and characteristics of sites below, within, and above the 95% boundary were identified. A series of stepwise multivariable hierarchical models were then fit, and the median OR was used to measure variation in pacemaker rates among sites. ResultsFrom 2016 to 2020, the overall rate of PPM implantation was 11.3%, with wide variation across sites (range: 0%-36.4%); rates trended lower over time. Adjusted for annualized volume, there were 34 sites with PPM implantation rates above the 95th percentile CI and 28 with rates below, with wide variation among the remaining sites. After adjusting for patient-level covariates, there was variation among sites in the probability of PPM implantation (median OR: 1.39; 95% CI: 1.35-1.43, P < 0.001); although some of the variation was explained by the addition of valve type, residual variation in PPM implantation rates persisted in additional models incorporating site-level covariates (annualized volume, region, teaching status, hospital beds, etc). ConclusionsAlthough PPM implantation rates have decreased over time, substantial site-level variation remains even after accounting for observed patient characteristics and site-level factors. As there are numerous outlier sites both above and below the 95% confidence limit, dissemination of best practices from high-performing sites to low-performing sites and guideline-based education may be important quality improvement initiatives to reduce rates of this common complication.

Depth-dependent variations of physicochemical properties of sedimentary dissolved organic matter and the influence on the elimination of typical pharmaceuticals

Sedimentary dissolved organic matter (DOM) could exert a significant influence on the transformation of trace organic contaminants. However, the variations of sedimentary DOM properties with depth and their impact on trace organic contaminants biodegradation remain unclear. In this study, the qualitative changes in DOM properties with depth were assessed using spectral techniques. Specifically, within the sediment range of 0–30 cm, humic acid and fulvic acid fractions exhibited higher degrees of humification and aromatization at 10–20 cm, while hydrophilic fractions showed higher degrees of humification and aromatization at 20–30 cm. Furthermore, electrochemical methods were employed to quantitatively assess the electron transfer capacity of sedimentary DOM at different depths, which displayed consistent variation trend with humification and aromatization degree. The high degree of humification and aromatization, along with strong electron-accepting capability of DOM, significantly enhanced the biodegradation rates of tetracycline and ritonavir. To gain deeper insights into the influence of molecular composition of DOM on its properties, two-dimensional gas chromatography-quadrupole mass spectrometry analysis revealed that quinones and phenolic hydroxyl compounds govern the redox reactivity of DOM. Simulated experiment of DOM-mediated biodegradation of typical pharmaceuticals confirmed the role of quinones and phenolic hydroxyl groups in the redox reactivity of DOM.

Pre-mixed abrasive waterjet peening with post-low stress milling process and the effect of process parameters on the surface integrity of TC11 titanium alloy

Pre-mixed abrasive waterjet peening (PAWJP) is progressively gaining traction in enhancing metal materials’ surface integrity and mechanical behavior. To avoid the disadvantage of PAWJP in the application, a hybrid manufacturing method of pre-mixed abrasive waterjet peening with post-low stress milling (PAWJP-LSM) is proposed and studied experimentally. The principle of PAWJP-LSM was first introduced. Subsequently, the effect of the PAWJP-LSM parameters (i.e., abrasive type, traverse speed, nozzle inlet pressure, and removal amount) on the surface integrity of TC11 titanium alloy and its variation trend were systematically investigated. Results show that the specimen treated with PAWJP using different process parameters formed a PAWJP treatment area with a strengthening depth of 6–275 μm. The minimum surface roughness obtained by PAWJP was 0.727 μm. The maximum surface microhardness significantly increased to approximately 516.3 HV from 402.8 HV, with a maximum micro-hardness rate of 28.2 % and a maximum work hardening depth of 225 μm. The surface compressive residual stress (CRS) induced by PAWJP ranged from −97 to −322 MPa, with a maximum CRS exceeding −890 MPa and a maximum CRS layer thickness of 305 μm. The surface integrity of PAWJP-LSM is further enhanced compared to PAWJP, resulting in a 98.9 % reduction in minimum surface roughness and a 73.7 % reduction compared to the as-received surface roughness. Additionally, PAWJP-LSM exhibited a 98.9 % increase in surface CRS and a 19.4 % increase in maximum CRS. Moreover, the fatigue life was significantly improved by 69.4 %, which was 294.5 % higher than that of the as-received specimen. Nanocrystals with an average size of 27.3 nm were formed in the topmost surface. Overall, the PAWJP-LSM method demonstrated significant potential for engineering applications and exhibited substantial value in the surface treatment of TC11 alloy. This study validated the effectiveness of the proposed PAWJP-LSM method and provided a valuable reference for selecting optimized process parameters.

The Effect of a Liquified Wood Heavy Fraction on the Rheological Behaviour and Performance of Paving-Grade Bitumen

Biomass is one the most abundant renewable energy sources, and it can be processed through different thermochemical methods to obtain oils that can replace the petroleum bitumen used in road construction. For the construction industry to accept the bitumen replacement with bio-oil, it is necessary to know its properties and determine the applicability of conventional testing methods. This research utilized a liquified wood heavy fraction (bio-oil) obtained from waste wood through an innovative thermochemical liquefaction process. The aim was to investigate a kind of bio-bitumen produced by blending this bio-oil with paving-grade bitumen. The rheological behaviour in a wide temperature range, the performance relative to fatigue cracking and permanent deformation sensitivity, and the evolution with oxidative ageing were evaluated for the bio-bitumen and paving-grade bitumens. The bio-oil significantly affected the rheological behaviour of bitumen through an overall decrease in the phase angle and by failing the time–temperature superposition principle. The strong elastic response of the bio-bitumen improved resistance to fatigue and permanent deformation accumulation; however, resistance to oxidative ageing declined. Linear viscoelastic rheological indicators proposed in the literature to assess the material’s performance showed a similar trend of variation with oxidative ageing for bio-bitumen and paving-grade bitumen, though the indicators’ values could not be directly compared.

Contamination Status and Acute Dietary Exposure Assessment of Paralytic Shellfish Toxins in Shellfish in the Dalian Area of the Yellow-Bohai Sea, China

The Yellow-Bohai Sea is an important semi-enclosed continental shelf marginal seas with an intensive aquaculture industry in China. The current study analyzed the contamination status and the time variations of paralytic shellfish toxins (PSTs) in shellfish between 2019 and 2020 from the Yellow-Bohai Sea in the Dalian area and estimated the acute health risks to consumers in China. A total of 199 shellfish samples (including 34 Pacific oysters, 25 Mediterranean blue mussels, 34 Manila clams, 36 bay scallops, 34 veined rapa whelks and 36 bloody clams) were analyzed from four representative aquaculture zones around the Yellow-Bohai Sea in Dalian. Among the samples, scallops and blood clams were the shellfish species with the highest detection rate of PSTs (94.4%), and the highest level of PSTs was detected in scallops with 3953.5 μg STX.2HCl eq./kg (μg STX.2HCL equivalents per kg shellfish tissue), followed by blood clams with 993.4 μg STX.2HCl eq./kg. The contents of PSTs in shellfish showed a time variation trend, and autumn was the season of concern for PST contamination in Dalian. For general Chinese consumers, the probability of acute health risks to shellfish consumers from dietary exposure to PSTs was around 13%. For typical consumers in coastal areas of China, especially those with higher shellfish intake, there was an acute health risk associated with exposure to PSTs through shellfish consumption during the occurrence of harmful algal blooms. It is suggested that the government continue to strengthen the monitoring of the source of PSTs and the monitoring of harmful algal blooms and give reasonable advice on shellfish consumption for consumers in coastal areas, such as not eating scallop viscera.

Experimental study on a parallel optical fiber Sagnac loops-based sensor with the advantages of both high sensitivity and ultra-wide measurement range

The Vernier effect (VE) in optical interferometers has been used to improve the sensitivity in the measurements of strain, temperature, refractive index, etc. However, as the wavelength shifts beyond a free spectral range (FSR), it is difficult to determine the magnitude of the physical quantity and the measurement range is usually narrow. To overcome this problem, we constructed a fiber optic sensor combining two parallel Sagnac interferometers (PSIs) with a fiber Bragg grating (FBG). The sensitivity of temperature and strain measurements were enhanced about 5 times due to the VE effect in PSIs. FBG spectrum, which showed a monotonic and linear variation trend along with the variation of strain and temperature, was used to estimate the magnitude of the physical quantity beyond the FSR. Finally, an average strain sensitivity of −104.4 pm/µε was obtained in a wide measuring range of 0–5440 µε, while an average temperature sensitivity of 6.12 nm/°C was obtained in the temperature range of 2–58 °C. The measurement range has been extended 6 times and 4 times respectively compared to a single FSR. The integration of PSIs and FBG sensors offers not only high sensitivity, but also a wide measuring range. It can be used in many areas including medical equipment, automotive, and aerospace to make accurate strain and temperature measurements.