摘要：
Positron Emission Tomography (PET) image reconstruction remains a pivotal area in PET technology, critically influencing clinical diagnostic outcomes. Addressing the need for enhanced image quality, this study introduces a novel algorithm for PET image reconstruction. This algorithm integrates a penalty mechanism, morphological filtering, and the Maximum Likelihood Expectation Maximization (MLEM) algorithm, aiming to improve reconstructed image quality significantly. The operational process of the algorithm within each iteration encompasses two primary phases. Initially, image reconstruction is accomplished via the MLEM algorithm, followed by the application of a morphological filter to attenuate noise in the reconstructed image. Simulation experiments demonstrate that this algorithm effectively mitigates noise while preserving crucial details, such as image edges. Notably, this method presents the dual benefits of straightforward parameter configuration and ease of implementation. The results indicate a substantial enhancement in noise suppression and fine structure preservation in the reconstructed images, marking a significant advancement in PET image reconstruction techniques.
Positron Emission Tomography (PET) image reconstruction remains a pivotal area in PET technology, critically influencing clinical diagnostic outcomes. Addressing the need for enhanced image quality, this study introduces a novel algorithm for PET image reconstruction. This algorithm integrates a penalty mechanism, morphological filtering, and the Maximum Likelihood Expectation Maximization (MLEM) algorithm, aiming to improve reconstructed image quality significantly. The operational process of the algorithm within each iteration encompasses two primary phases. Initially, image reconstruction is accomplished via the MLEM algorithm, followed by the application of a morphological filter to attenuate noise in the reconstructed image. Simulation experiments demonstrate that this algorithm effectively mitigates noise while preserving crucial details, such as image edges. Notably, this method presents the dual benefits of straightforward parameter configuration and ease of implementation. The results indicate a substantial enhancement in noise suppression and fine structure preservation in the reconstructed images, marking a significant advancement in PET image reconstruction techniques.
期刊：
Proceedings of the Indian National Science Academy,2024年90(4):1029-1037 ISSN：0370-0046
通讯作者：
Yunshan Chen
作者机构：
National Demonstration Center for Experimental Civil Engineering Education, Hunan City University, Yiyang, China;Hunan Engineering Research Center of Structural Safety and Disaster for Urban Underground Infrastructure, Hunan City University, Yiyang, China;Grouting Engineering Technology Research Center, Hunan City University, Yiyang, China;[Yunshan Chen] Hunan Provincial Key Lab of Key Technologies of Digital Urban and Rural Spatial Planning, Hunan City University, Yiyang, China;Key Laboratory of Disaster Prevention and Mitigation Engineering and Protection Engineering in Colleges and Universities of Heilongjiang Province, Northeast Petroleum University, Daqing, China
通讯机构：
[Yunshan Chen] H;Hunan Provincial Key Lab of Key Technologies of Digital Urban and Rural Spatial Planning, Hunan City University, Yiyang, China
摘要：
In this investigation, we focused on geotechnical aspects concerning the static and dynamic slope stability analyses for a landfill during the final stages of construction under worst-case conditions. To ensure accuracy, we accounted for varying mechanical and physical characteristics of the buried wastes at different depths, which were determined through a combination of field investigation and literature data. For the dynamic analysis, we employed a Newark-type approach to calculate the permanent displacement of the buried wastes when subjected to a critical artificial earthquake. Subsequently, Newmark analyses were conducted to evaluate the sliding potential of the landfill cover and the critical wedge, enabling us to assess the yield acceleration and time history of permanent displacements. The comprehensive analysis outcomes have been instrumental in evaluating the landfill's overall static and seismic stability and assessing the adequacy of the design slopes. The study’s findings hold significant implications for ensuring the landfill’s safety and appropriateness under critical loading conditions.
作者机构：
[Luo, Qiao; Yu, Hongbing] Hunan City Univ, Coll Architecture & Urban Planning, Yiyang 413000, Peoples R China.;[Luo, Qiao; Yu, Hongbing] Hunan City Univ, Coll Architecture & Urban Planning, Lab Key Technol Digital Urban Rural Spatial Planni, Yiyang 413000, Peoples R China.;[Li, Yong] Chinese Acad Sci, Inst Atmospher Phys, State Key Lab Atmospher Boundary Layer Phys & Atmo, Beijing 100029, Peoples R China.;[Jiang, Shufang; Cao, Xueyou] Forestry Bur Yiyang City, Yiyang 410004, Peoples R China.
通讯机构：
[Li, Y ] C;Chinese Acad Sci, Inst Atmospher Phys, State Key Lab Atmospher Boundary Layer Phys & Atmo, Beijing 100029, Peoples R China.
关键词：
South Dongting Lake Nature Reserve;blue space;green space;precipitation;air temperature
摘要：
<jats:p>In recent years, the water level of the Dongting Lake (DTL) has been continuously low, and the wetland area and landscape pattern have changed significantly. Considering the obvious spatial heterogeneity of water regime changes in different waters of the DTL, this paper takes two core areas of the South Dongting Lake Nature Reserve (SDLNR) as study areas and analyzes the spatial distribution characteristics of the wetland blue–green landscape patterns by using remote sensing image data and hydrological and meteorological data. The multi-scale correlation between runoff, precipitation, temperature, and evapotranspiration in the SDLNR was studied via cross-wavelet transform analysis. The results show the following: (1) The change in the blue–green spatial patterns in different regions in different periods is inconsistent, and this inconsistency is related to the topography, climate, and human activities in each region; (2) there are seasonal fluctuations in precipitation, air temperature, and evapotranspiration in the SDLNR. Among them, the annual mean temperature shows a rising trend and passes the significance test with 95% confidence, while the annual mean precipitation and annual mean evapotranspiration show no significant change trend; and (3) our Pearson correlation analysis and cross-wavelet change results show that precipitation and temperature are strongly correlated with runoff, with a resonance period of 8–16 months, while the correlation between evapotranspiration and runoff is not significant. We recommend that policymakers establish an effective early warning system and make plans to store water through micro-terrain transformation in possible climate change treatments and strategies.</jats:p>
摘要：
<jats:p>Bamboo contains water-soluble saccharides and carboxylic acid which have an anticoagulation effect on Portland cement, and the anticoagulation ingredients can directly influence the hydration reaction extent. Hydration product varieties and hydration product-bamboo shaving binding interfaces of the Portland cement, and finally the mechanical properties of bamboo cement particle boards. In this paper, bamboo shavings are pretreated by carbonizing treatment, hydro-thermal treatment and alkali treatment; high performance liquid chromatography is adopted to analyze the influences of three different pretreatment methods on contents of water-soluble saccharides and carboxylic acid in the bamboo shavings; a Fourier infrared spectrometer and an X-ray diffractometer are respectively utilized to analyze the characteristic peak changes and crystallization property changes of chemical ingredients of the bamboo shavings before and after the three types of pretreatment. This paper discusses effects of three types of pretreatment methods in eliminating water-soluble saccharides and carboxylic acid in the bamboo shavings. Bamboo Portland cement particle boards was prepared using bamboo shavings, which are pretreated in three ways, and influences and mechanisms of different pretreatment methods on properties of the bamboo Portland cement particle boards were studied. Research indicates that the mechanical properties of the Portland cement particle board prepared from bamboo shavings pretreated with 3 % NaOH solution are superior to requirements of qualified products and superior products specified in the Standard.</jats:p>
摘要：
Tea waste contains various substances with phenolic hydroxyl groups, including lignin, tannins, tea polyphenols, etc., which are rarely utilized. In this study, tea waste was directly dispersed with graphene oxide to prepare tea waste/reduced graphene oxide (TW/rGO) hydrogel through a one-step hydrothermal method. The prepared hydrogel presented a continuous three-dimensional porous structure and exhibited good mechanical properties with a compressive strength of 53.4 ± 4.0 kPa. It also showed excellent electrochemical performance as an electrode material. Its specific capacitance reached 434.7 F g(-1) at a current density of 1 A g(-1), and its capacitance retention was 55.8% when the current density was increased to 100 A g(-1). In addition, an TW/rGO assembled all-solid-state supercapacitor demonstrated a superior specific capacitance of 372.8 F g(-1) and a competitive energy density of 12.9 Wh kg(-1) at 1 A g(-1).
关键词：
UAV-LiDAR;individual tree segmentation;forest stand volume estimation;Gaussian mixture model
摘要：
The main problems of forest parameter extraction and forest stand volume estimation using unmanned aerial vehicle light detection and ranging (UAV-LiDAR) technology are the lack of precision in individual tree segmentation and the inability to directly obtain the diameter at breast height (DBH) parameter. To address such limitations, the study proposed an improved individual tree segmentation method combined with a DBH prediction model to obtain the tree height (H) and DBH for calculating the volume of trees, thus realizing the accurate estimation of forest stand volume from individual tree segmentation aspect. The method involves the following key steps: (1) The local maximum method with variable window combined with the Gaussian mixture model were used to detect the treetop position using the canopy height model for removing pits. (2) The measured tree DBH and H parameters of the sample trees were used to construct an optimal DBH-H prediction model. (3) The duality standing tree volume model was used to calculate the forest stand volume at the individual tree scale. The results showed that: (1) Individual tree segmentation based on the improved Gaussian mixture model with optimal accuracy, detection rate r, accuracy rate p, and composite score F were 89.10%, 95.21%, and 0.921, respectively. The coefficient of determination R2 of the accuracy of the extracted tree height parameter was 0.88, and the root mean square error RMSE was 0.84 m. (2) The Weibull model had the optimal model fit for DBH-H with predicted DBH parameter accuracy, the R2 and RMSE were 0.84 and 2.28 cm, respectively. (3) Using the correctly detected trees from the individual tree segmentation results combined with the duality standing tree volume model estimated the forest stand volume with an accuracy AE of 90.86%. In conclusion, using UAV-LiDAR technology, based on the individual tree segmentation method and the DBH-H model, it is possible to realize the estimation of forest stand volume at the individual tree scale, which helps to improve the estimation accuracy.
摘要：
Depletion of fossil fuel resources at a high speed and increasing demand for energy supply for various purposes in today's life integrated with industry has led to collective contemplation for the optimal and maximum utilization of fossil fuels through the implementation of multigeneration systems. In the presented study, a multigeneration system for cooling, power, freshwater, and Hydrogen production is proposed and investigated from exergy, energy, and economic viewpoints through a specific scenario. A case study is performed, revealing that the system can deliver a net output power of 16,251.8 kW, a cooling load of 15,905.0 kW, produce freshwater at a rate of 3.891 kg/s, and generate hydrogen at 0.284 kg/h. The energy and exergy efficiencies of the system are 60.48 % and 32.55 %, respectively. An economic analysis shows a payback period of 0.474 years. A parametric evaluation is performed to perceive the system operation in various conditions. Subsequently, a multi-objective optimization using the MOPSO-LINMAP method is conducted to identify the optimal operating conditions for the system. The optimization results are compared with the case study findings, demonstrating further improvements in performance metrics. The optimized system achieves a slightly higher energy efficiency of 61.62 % and a lower payback period of 0.40 years, underscoring the benefits of the optimization process. This study highlights the potential of the proposed system to efficiently and economically meet the demands for power, hydrogen, cooling, and freshwater in various applications.
摘要：
This study prepared pomelo peel biochar (PBC) under different pyrolysis temperatures (T) (300-800 degrees C) and investigated the removal efficiency of tetracycline (TC) under the oxidative systems established by PBC and oxidants (hydrogen peroxide (H2O2), peroxymonosulfate (PMS), and peroxydisulfate (PDS)). The correlation between the properties of PBC and the removal efficiencies of TC was studied by Pearson analysis to clarify the critical properties of biochar in catalytic processes. The inorganic carbon (IC), ash, pH, basic functional groups (BFG), specific surface area (SSA), microporous surface area (S-micro), pore volume (PV), and graphitization degree (I-D/I-G) of PBC were positively correlated with the increase of T (p < 0.05). Notably, the SSA and PV of PBC increased from 4.294 m(2)/g and 0.002 cm(3)/g to 496.864 m(2)/g and 0.261 cm(3)/g as the pyrolysis temperature increased from 300 to 800 degrees C. In contrast, the yield, organic carbon (OC), and acidic functional groups (AFG) of PBC displayed negatively correlated with the increase of T (p < 0.05). R-ad, R-PBC/H2O2, R-PBC/PMS, and R-PBC/PDS represented the removal efficiencies of TC by PBC adsorption, PBC/H2O2, PBC/PMS, and PBC/PDS system. R-PBC/H2O2, R-PBC/PMS, and R-PBC/PDS showed a highly positive correlation to the R-ad (r = 0.965, 0.952, 0.946, p < 0.01). R-ad, R-PBC/H2O2, R-PBC/PMS, and R-PBC/PDS were positively correlated with K, Mg, ash, pH, BFG, and I-D/I-G (p < 0.01). There was no statistically significant correlation between persistent free radicals (PFRs) and the removal efficiencies of TC. Furthermore, SSA and PV showed positive relationships with the removal efficiencies of TC in the PBC/PMS and PBC/PDS systems, but no significant correlation with the removal efficiencies of TC in the PBC/H2O2 systems. Moreover, the catalytic behaviors and mechanisms were studied in the PBC-800 based oxidative systems. The quenching experiments and EPR spectra indicated that singlet oxygen (O-1(2)) was the main active species. Except for O-1(2), superoxide radical (O-2(center dot-)) also contributed to TC removal in the oxidative systems. From the changes in used PBC-800, the disordered sp(2) hybrid carbon, sp(3) C-C, and pyridinic-N were the main active sites in activation.
作者机构：
[Huang, Yonggang] College of Civil Engineering, Hunan City University, Yiyang, China;China Light Industry Changsha Engineering Co., Ltd., Changsha, China;[Wang, Guiyao] College of Civil Engineering, Changsha University of Science and Technology, Changsha, China;[Fu, Jingliang] China Light Industry Changsha Engineering Co., Ltd., Changsha, China<&wdkj&>College of Civil Engineering, Changsha University of Science and Technology, Changsha, China
通讯机构：
[Yonggang Huang] C;College of Civil Engineering, Hunan City University, Yiyang, China
关键词：
Vetiver root;Root–soil interface;Expansive soil;Pullout test
摘要：
Studying the pullout characteristics of roots can help to gain a deeper understanding of the interaction mechanism between plants and soil, and provide theoretical support and practical guidance for engineering applications. This paper aims to investigate the pulling characteristics of the root–soil interface in expansive soil reinforced by vetiver roots. For this purpose, the study focuses on exploring the correlation between the pullout force (PF) required to extract the roots and the pullout displacement caused by the extraction. The research also examines how the geometry of the roots affects the pulling characteristics of the root–soil using a pullout test. It is found that with increasing root diameter, root length segment (RLS), root volume, and root surface area (RSA), the maximum PF increases. The highest correlation coefficient was found between RSA and maximum PF, which explained 81.4% of the variation in maximum PF. Then, the functional relationship between RLS and PF is established. Using RSA to predict the maximum PF of vetiver root is relatively reasonable. The assessment of PF must consider RSA indicators. The increase in RSA due to a high number of roots results in the improvement of the PF of vetiver root. These findings could assist in enhancing the strength of expansive soils.
摘要：
Traditional model tests for soil and rock materials face challenges in observing the slurry diffusion within the soil mass, hindering the understanding of the relationship between grouting-induced ground deformation and grout diffusion. This study conducts grouting diffusion model tests using a self-developed experimental setup on both ordinary and transparent sand. We investigate cement slurry diffusion patterns, distribution characteristics, and temporal variations in ground uplift displacement during the grouting process. By leveraging a visualization grouting model and non-intrusive displacement measurements, we directly observe and verify the changes in cement slurry diffusion and ground displacement in transparent sand. The results indicate the following: during non-steady grouting in sand, slurry diffusion progresses from low-pressure infiltration to medium-pressure compaction, culminating in high-pressure fracturing; ground uplift displacement curves exhibit a consistent "step-like" increase with grouting time, featuring accelerated growth after each step; and visualization tests reveal a strong correlation between grouting pressure, slurry diffusion, and corresponding uplift displacement. Distinct features in the grouting pressure plot align with the acceleration phases of the displacement; at a water-cement ratio (w/c) of 0.8, the stratum's vertical deformation shows a symmetric "higher in the middle, lower on the sides" distribution. As the burial depth decreases, the stratum's uplift displacement tends to flatten horizontally, especially at w/c = 0.8 and 1.2.
