Performance Test and Thermal Insulation Effect Analysis of Basalt-Fiber Concrete

This paper examines the feasibility of applying inorganic thermal-insulating concrete in high geothermal roadways in underground coal mines. This innovative material is based on a mixture of ceramsite, glazed hollow beads, cement, and natural sand, enhanced with varying degrees of basalt fibers. Fibers were used as a partial substitute in the mixture, in the following volumes: 0% (reference specimen), 5%, 10%, 15%, and 20%. Their compressive strength, permeability resistance, and thermal conductivity were studied. A high content of fibers tends to entangle into clumps during mixing, resulting in a significant reduction in the mechanical properties of compressive strength. The appropriate amount of fiber content can improve impermeability, and the permeability height of 5% fiber concrete was reduced by 22.5%. Experiments on thermal behavior showed that an increase of basalt fibers leads to a significant reduction in thermal conductivity. For concrete containing 20% fiber, the thermal conductivity for the reference specimen (0%) in the wet state was reduced from 0.385 W/(m∙°C) to 0.098 W/(m∙°C). There was a slight increase in thermal conductivity when the temperature increased from 30 °C to 60 °C. Despite the reduced mechanical strength, the resulting concrete is well-suited for use in the insulation of underground roadways, as numerical simulations showed that insulating concrete with optimal fiber content (15%) can reduce the average temperature of the wind flow in a high ground temperature roadway of 100 m in length in a mine by 0.3 °C. The final cost-benefit analysis showed that insulating concrete has more economic benefits and broad development prospects when applied to high geothermal roadway cooling projects.     

Unveiling the Effect of CaF2 on the Microstructure and Transport Properties of Phosphosilicate Systems

As an effective flux, CaF₂ is beneficial in improving the fluidity of slag in the steel-making process, which is crucial for dephosphorization. To reveal the existence form and functional mechanism of CaF₂ in phosphosilicate systems, the microstructures and transport properties of CaO-SiO₂-CaF₂-P₂O₅ quaternary slag systems are investigated by molecular dynamics simulations (MD) combined with experiments. The results demonstrate that the Si-O coordination number does not vary significantly with the increasing CaF₂ content, but the P-O coordination number dramatically decreases. CaF₂ has a minor effect on the single [SiO₄] but makes the structure of the silicate system simple. On the contrary, F⁻ ions could reduce the stability of P-O bonds and promoted the transformation of [PO₄] to [PO₃F], which is beneficial for making the P element-enriched phosphate network structure more aggregated. However, the introduction of CaF₂ does not alter the tetrahedral character of the original fundamental structural unit. In addition, the results of the investigation of the transport properties show that the self-diffusion coefficients of each ion are positively correlated with CaF₂ content and arranged in the order of F⁻ > Ca²⁺ > O²⁻ ≈ P⁵⁺ > Si⁴⁺. Due to CaF₂ reducing the degree of polymerization of the whole melts, the viscosity decreases from 0.39 to 0.13 Pa·s as the CaF₂ content increases from 0% to 20%. Moreover, the viscosity of the melt shows an excellent linear dependence on the structural parameters.     

Detailed Molecular Interactions between Respiratory Syncytial Virus Fusion Protein and the TLR4/MD-2 Complex In Silico

Molecular interactions between respiratory syncytial virus (RSV) fusion protein (F protein) and the cellular receptor Toll-like receptor 4 (TLR4) and myeloid differentiation factor-2 (MD-2) protein complex are unknown. Thus, to reveal the detailed molecular interactions between them, in silico analyses were performed using various bioinformatics techniques. The present simulation data showed that the neutralizing antibody (NT-Ab) binding sites in both prefusion and postfusion proteins at sites II and IV were involved in the interactions between them and the TLR4 molecule. Moreover, the binding affinity between postfusion proteins and the TLR4/MD-2 complex was higher than that between prefusion proteins and the TLR4/MD-2 complex. This increased binding affinity due to conformational changes in the F protein may be able to form syncytium in RSV-infected cells. These results may contribute to better understand the infectivity and pathogenicity (syncytium formation) of RSV.     

Reduction of Cardiovascular Events and Related Healthcare Expenditures through Achieving Population-Level Targets of Dietary Salt Intake in Japan: A Simulation Model Based on the National Health and Nutrition Survey

Reducing population dietary salt intake is expected to help prevent cardiovascular disease and thus constrain increasing national healthcare expenditures in Japan’s super-aged society. We aimed to estimate the impact of achieving global and national salt-reduction targets (8, <6, and <5 grams/day) on cardiovascular events and national healthcare spending in Japan. Using published data including mean salt intake and systolic blood pressure from the 2019 National Health and Nutrition Survey, we developed a Markov model of a closed cohort of adults aged 40–79 years in 2019 (n = 66,955,000) transitioning among six health states based on the disease course of ischemic heart disease (IHD) and stroke. If mean salt intake were to remain at 2019 levels over 10 years, cumulative incident cases in the cohort would be approximately 2.0 million for IHD and 2.6 million for stroke, costing USD 61.6 billion for IHD and USD 104.6 billion for stroke. Compared with the status quo, reducing mean salt intake towards the targets over 10 years would avert 1–3% of IHD and stroke events and save up to 2% of related national healthcare costs. Attaining dietary salt-reduction goals among adults would yield moderate health economic benefits in Japan.     

BTO-Coupled CIGS Solar Cells with High Performances

In order to improve the power conversion efficiency (PCE) of Cu(In,Ga)Se₂ (CIGS) solar cells, a BaTiO₃ (BTO) layer was inserted into the Cu(In,Ga)Se₂. The performances of the BTO-coupled CIGS solar cells with structures of Mo/CIGS/CdS/i-ZnO/AZO, Mo/BTO/CIGS/CdS/i-ZnO/AZO, Mo/CIGS/BTO/CdS/i-ZnO/AZO, Mo/CIGS/CdS/BTO/i-ZnO/AZO, Mo/CIGS/BTO/i-ZnO/AZO, Mo/CIGS/CdS/BTO/AZO, and Mo/ CIGS/CdS(5 nm)/BTO(5 nm)/i-ZnO/AZO were systematically studied via the SCAPS-1D software. It was found that the power conversion efficiency (PCE) of a BTO-coupled CIGS solar cell with a device configuration of Mo/CIGS/CdS/BTO/AZO was 24.53%, and its open-circuit voltage was 931.70 mV. The working mechanism for the BTO-coupled CIGS solar cells with different device structures was proposed. Our results provide a novel strategy for improving the PCE of solar cells by combining a ferroelectric material into the p-n junction materials.     

Predicting Surface Residual Stress for Multi-Axis Milling of Ti-6Al-4V Titanium Alloy in Combined Simulation and Experiments

As one essential indicator of surface integrity, residual stress has an important influence on the fatigue performance of aero engines’ thin-walled parts. Larger compressive or smaller tensile residual stress is more prone to causing fatigue cracks. To optimize the state of residual stress, the relationship between the surface residual stress and the machining conditions is studied in this work. A radial basis function (RBF) neural network model based on simulated and experimental data is developed to predict the surface residual stress for multi-axis milling of Ti-6Al-4V titanium alloy. Firstly, a 3D numerical model is established and verified through a cutting experiment. These results are found to be in good agreement with average absolute errors of 11.6% and 15.2% in the σ_x and σ_y directions, respectively. Then, the RBF neural network is introduced to relate the machining parameters with the surface residual stress using simulated and experimental samples. A good correlation is observed between the experimental and the predicted results. The verification shows that the average prediction error rate is 14.4% in the σ_x direction and 17.2% in the σ_y direction. The effects of the inclination angle, cutting speed, and feed rate on the surface residual stress are investigated. The results show that the influence of machining parameters on surface residual stress is nonlinear. The proposed model provides guidance for the control of residual stress in the precision machining of complex thin-walled structures.     

Simulation and Experimental Substantiation of the Thermal Properties of Non-Autoclaved Aerated Concrete with Recycled Concrete Powder

Non-autoclaved aerated concrete (NAAC) is a two-phase material with a concrete matrix and air, exhibits good thermal insulation performance and shows good potential in the insulating construction industry. In this study, recycled concrete fine powder was used as an auxiliary cementing material, and the NAAC with different porosity and distribution was fabricated by the non-autoclaved method at different curing temperatures. The effect of porosity on the thermal conductivity and mechanical strength of NAAC is analyzed by experimental tests. A prediction method of thermal conductivity combining pore structure reconstruction and numerical simulation was proposed, which is established by two steps. Firstly, the pore size distributions of NAAC with different porosities were characterized by stereology image analyses. Secondly, the thermal conductivity prediction model based on the pore structure information was established by a COMSOL steady-state heat transfer module. The thermal conductivity results of COMSOL simulations were compared with the experiments and other theoretical models to verify the reliability of the model. The model was used to evaluate the effect of porosity, pore size distribution and the concrete matrix’s thermal conductivity on the thermal conductivity of NAAC; these are hard to measure when only using laboratory experiments. The results show that with the increase in curing temperature, the porosity of NAAC increases, and the number and volume proportion of macropores increase. The numerical results suggest that the error between the COMSOL simulations and the experiments was less than 10% under different porosities, which is smaller than other models and has strong reliability. The prediction accuracy of this model increases with the increase in NAAC porosity. The steady thermal conductivity of NAAC is less sensitive to the distribution and dispersion of pore size in a given porosity. With the increase in porosity, the thermal conductivity of NAAC is linearly negatively correlated with that of the concrete matrix, and the correlation is close to 1.     

Mechanical Properties Evaluation of Polymer-Binding C-S-H Structure from Nanoscale to Macroscale: Hydroxyl-Terminated Polydimethylsiloxane (PDMS) Modified C-S-H

Exploring and modifying the C-S-H structure at a micro–nano level is an effective solution to improve the performance of Portland cement. Compared with organics inserting C-S-H, the research on the performance of a polymer-binding C-S-H structure from nanoscale to macroscale is limited. In this work, the mechanical properties of a modified C-S-H, using hydroxyl-terminated polydimethylsiloxane (PDMS) as the binders, are evaluated. The PDMS-modified C-S-H structures are introduced into macro-defect-free cement to obtain stress–strain curves changes at a macro scale. The AFM–FM was adopted to measure the morphology and elastic modulus of C-S-H at a nano scale. The molecular dynamics (MD) simulation was performed to assess the toughness, tensile properties, and failure mechanism. The results show that the PDMS-modified C-S-H powders change the break process and enhance ductility of MDF cement. The elastic modulus of PDMS-modified C-S-H is lower than pure C-S-H. When PDMS molecules are located between the stacking crystal units, it can enhance the toughness of C-S-H aggregates. The PDMS-modified C-S-H stacking structure has better plasticity, and its tensile strains are higher than the pure C-S-H. PDMS molecules hinder the initial crack expansion, leading to the branching of the initial crack. In addition, the measurement of AFM–FM can identify and obtain the mechanical properties of basic units of C-S-H. This paper enhances the understanding of cement strength sources and modification methods.     

虚拟现实模拟培训在青年医师腹腔镜技能培训中的作用

目的 通过分析郑州大学附属郑州中心医院参加过腹腔镜技能培训的普外科青年医师的腹腔镜胆囊切除术学习曲线,探讨腹腔镜虚拟现实模拟培训的意义。方法 将青年外科医师50人分为两组,干预组参加虚拟现实模拟培训,对照组参加传统腹腔镜临床培训。培训完成后,在高年资拥有丰富腹腔镜手术经验医师的监督下完成30例腹腔镜胆囊切除术。应用CUSUM分析法,根据完成率、手术评分和手术时间绘制学员的手术学习曲线。x为手术例数,k为斜率。计算k=0时的x值,比较两组学员的手术学习曲线和术中评分。采用SPSS 23.00进行t检验和卡方检验。结果 干预组与对照组分别在x=19.24±0.39、x=21.72±0.73时跨过手术学习曲线,差异有统计学意义（P<0.01）;干预组与对照组显露胆囊部分得分分别为（10.82±2.73）、（9.71±2.69）（t=4.61,P<0.01）;解剖胆囊三角得分分别为（12.59±3.12）、（8.87±2.99）（t=6.21,P<0.01）;剥离胆囊得分分别为（10.69±3.38）、（8.80±3.55）（t=3.10,P<0.01）。结论 虚拟现实模拟培训可以促进腹腔镜培训的基本技能转化为临床操作技能,可促进普外科青年医师成长。     

达芬奇机器人手术系统模拟训练器在肝胆外科教学中的应用研究

目的 探讨达芬奇机器人手术系统模拟训练器在肝胆外科临床教学中的应用。方法 将来自重庆医科大学2019级临床医学专业的76名学生分为试验组和对照组。理论知识方面,两组采用相同的教学方法;实践操作方面,试验组采用达芬奇机器人手术系统模拟训练器（da Vinci robot surgical system simulation trainer,DVST）进行训练,对照组采用腹腔镜模拟训练器（laparoscopic simulation trainer,LST）进行训练。3个月后考核微创手术的两种基本技能：夹豆和缝合打结。采用SPSS 23.0进行独立样本t检验。结果 使用DVST考核,试验组拣豆（个/min）结果为（16.92±2.81）,对照组为（11.68±3.31）;试验组缝合打结（次/10 min）结果为（12.02±2.04）,对照组为（7.79±1.89）,试验组得分优于对照组（P<0.05）。使用LST考核时,试验组与对照组结果差异无统计学意义。问卷调查显示,试验组在提升对肝胆外科知识的学习兴趣、提升对肝胆外科手术系统的认识等5项问题的得分高于对照组（P<0.05）。结论 DVST运用于肝胆外科临床教学能显著提高学生微创手术技能,其仿真场景有助于激发学生自发进行训练的热情,有助于提高学生的临床思维能力。同时,在培养学生技能迁移能力方面,DVST明显优于LST。因此,DVST具有良好的教学应用价值,值得推广。